2020-04-01T09:11:29Zhttps://dias.library.tuc.gr/oaiHandler
oai:dlib.tuc.gr:218112012-10-10T00:00:00Z28info:eu-repo/semantics/articleMainstream traffic flow control on freeways using variable speed limitsCarlson Rodrigo Castelan ()Παπαμιχαηλ Ιωαννης(http://users.isc.tuc.gr/~ipapa)Papamichail Ioannis(http://users.isc.tuc.gr/~ipapa)Παπαγεωργιου Μαρκος(http://users.isc.tuc.gr/~mpapageorgiou)Papageorgiou Markos(http://users.isc.tuc.gr/~mpapageorgiou)Traffic incident management,traffic congestion management,traffic incident managementhttp://purl.tuc.gr/dl/dias/CF2DBEC9-EA4E-4D15-931D-C8D5D903D71810.4237/transportes.v21i3.694Published at: 2014-09-25eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by-nc-nd/4.0/application/pdfIssued on: 2013Summarization: Mainstream Traffic Flow Control (MTFC), enabled via variable speed limits, is a control concept for real-time freeway traffic management. The benefits of MTFC for efficient freeway traffic flow have been demonstrated recently using an optimal control approach and a feedback control approach. In this paper, both control approaches are reviewed and applied to a freeway network in a simulation environment. The validated network model used reflects an actual freeway (a ring-road), fed with actual (measured) demands. The optimal and feedback control results are discussed, compared and demonstrated to improve significantly the system performance. In particular, the feedback control scheme is deemed suitable for immediate practical application as it takes into account operational requirements and constraints, while its results are shown to be satisfactory. In addition, the control system performance was not very sensitive to variations of the parameters of the feedback controller. This result indicates that the burden associated with fine tuning of the controller may be reduced in the field.ANPET - Associação Nacional de Pesquisa e Ensino em TransportesPresented on: Transportespeer-reviewedBibliographic citation: R.C. Carlson, I. Papamichail, M. Papageorgiou, "Mainstream traffic flow control on freeways using variable speed limits," Transportes, vol. 21, no. 3, pp. 56-65, 2013.
doi:10.4237/transportes.v21i3.694info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:229732012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectMotorway flow optimization in presence of vehicle automation and communication systemsRoncoli Claudio()Παπαμιχαηλ Ιωαννης(http://users.isc.tuc.gr/~ipapa)Papamichail Ioannis(http://users.isc.tuc.gr/~ipapa)Παπαγεωργιου Μαρκος(http://users.isc.tuc.gr/~mpapageorgiou)Papageorgiou Markos(http://users.isc.tuc.gr/~mpapageorgiou)The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 321132, project TRAMAN21.Motorway traffic controlTraffic flow optimisationQuadratic programminghttp://purl.tuc.gr/dl/dias/9BEA2A38-AFF2-49E1-B344-30E2C7BD34B5Published at: 2014-10-12eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by-nc-nd/4.0/application/pdfIssued on: 2014Summarization: This paper describes a novel approach for defining optimal strategies in motorway traffic flow control, considering that a portion of vehicles are equipped with vehicle automation and communication systems. An optimisation problem, formulated as a Quadratic Programming (QP) problem, is developed with the purpose of minimising traffic congestion. The proposed problem is based on a first-order macroscopic traffic flow model able to capture the lane changing and the capacity drop phenomena. An application example demonstrates the achievable improvements in terms of the Total Time Spent if the vehicles travelling on the motorway are influenced by the control actions computed as a solution of the optimisation problem.Παρουσιάστηκε στο: International Conference on Engineering and Applied Sciences OptimizationNational Technical University of AthensΒιβλιογραφική αναφορά: C. Roncoli, M. Papageorgiou, I. Papamichail, "Motorway flow optimization in presence of vehicle automation and communication systems," in Proceedings of the 1st International Conference on Engineering and Applied Science Optimization (OPT-i), 2014, pp. 519-529. full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:229692012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectOn microscopic modelling of adaptive cruise control systemsΝτουσακης Ιωαννης-Αντωνιος(http://users.isc.tuc.gr/~intousakis1)Ntousakis Ioannis-Antonios(http://users.isc.tuc.gr/~intousakis1)Νικολος Ιωαννης(http://users.isc.tuc.gr/~inikolos)Nikolos Ioannis(http://users.isc.tuc.gr/~inikolos)Παπαγεωργιου Μαρκος(http://users.isc.tuc.gr/~mpapageorgiou)Papageorgiou Markos(http://users.isc.tuc.gr/~mpapageorgiou)The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 321132, project TRAMAN21.Adaptive cruise controlTraffic flow modellingMicroscopic simulationhttp://purl.tuc.gr/dl/dias/F89B7182-6D1F-4179-A6D8-A875F09FD053Published at: 2014-10-12eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by-nc-nd/4.0/application/pdfIssued on: 2014Summarization: The Adaptive Cruise Control (ACC) system, is one of the emerging vehicle technologies that has already been deployed in the market. Although it was designed mainly to enhance driver comfort and passengers’ safety, it also affects the dynamics of traffic flow. For this reason, a strong research interest in the field of modelling and simulation of ACC-equipped vehicles has been increasingly observed in the last years. In this work, previous modelling efforts reported in the literature are reviewed, and some critical aspects to be considered when designing or simulating such systems are discussed. Moreover, the integration of ACC-equipped vehicle simulation in the commercial traffic simulator Aimsun is described; this is subsequently used to run simulations for different penetration rates of ACC-equipped vehicles, different desired time-gap settings and different networks, to assess their impact on traffic flow characteristics.Παρουσιάστηκε στο: International Symposium of Transport Simulation 2014ElsevierBibliographic citation: I.A. Ntousakis, I.K. Nikolos, M. Papageorgiou, "On Microscopic Modelling Of Adaptive Cruise Control Systems," in Proceedings of the 4th International Symposium of Transport Simulation (ISTS), 2014. full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:229682012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectStability investigation for simple PI-controlled traffic systemsKarafyllis Iason()Παπαγεωργιου Μαρκος(http://users.isc.tuc.gr/~mpapageorgiou)Papageorgiou Markos(http://users.isc.tuc.gr/~mpapageorgiou)The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 321132, project TRAMAN21.Systems, Nonlinear,nonlinear systems,systems nonlinearDES (System analysis),Discrete event systems,Sampled-data systems,discrete time systems,des system analysis,discrete event systems,sampled data systemsPI-regulatorhttp://purl.tuc.gr/dl/dias/A5DB2E56-C2C1-4AF6-A769-6BE271182E1C978-1-4799-2889-7 10.1109/ISCCSP.2014.6877846Published at: 2014-10-13eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by-nc-nd/4.0/application/pdfIssued on: 2014Summarization: This paper provides sufficient conditions for the Input-to-State Stability property of simple uncertain vehicular-traffic network models under the effect of a PI-regulator. Local stability properties for vehicular-traffic networks under the effect of PI-regulator control are studied as well: the region of attraction of a locally exponentially stable equilibrium point is estimated by means of Lyapunov functions.Παρουσιάστηκε στο: 6th International Symposium on Communications, Controls, and Signal ProcessingInstitute of Electrical and Electronics EngineersBibliographic citation: I. Karafyllis, M. Papageorgiou, "Stability investigation for simple PI-controlled traffic systems," in Proceedings of 6th International Symposium on Communications, Controls, and Signal Processing, 2014, pp. 186-189.full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:244732012-10-10T00:00:00Z28info:eu-repo/semantics/articleMicrosimulation analysis of practical aspects of traffic control with variable speed limitsΠαπαγεωργιου Μαρκος(http://users.isc.tuc.gr/~mpapageorgiou)Papageorgiou Markos(http://users.isc.tuc.gr/~mpapageorgiou)Muller Eduardo Rauh()Carlson Rodrigo Castelan()Kraus Werner()The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 321132, project TRAMAN21. The paper has been published by IEEE (http://ieeexplore.ieee.org/Xplore/defdeny.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D7006741&denyReason=-134&arnumber=7006741&productsMatched=null) and is IEEE copyrighted.Traffic volume,traffic flow,traffic volumeMainstream Traffic Flow ControlVariable Speed LimitsFreeway traffic controlhttp://purl.tuc.gr/dl/dias/1968E8C7-94C6-4EB3-A513-C686F3F12B7910.1109/TITS.2014.2374167Published at: 2015-03-26eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by-nc-nd/4.0/application/pdfIssued on: 2015Summarization: Mainstream traffic flow control (MTFC) with variable speed limits (VSLs) is a freeway traffic control method that aims to maximize throughput by regulating the mainstream flow upstream from a bottleneck. Previous studies in a macroscopic simulator have shown optimal and feedback MTFC potential to improve traffic conditions. In this paper, local feedback MTFC is applied in microscopic simulation for an on-ramp merge bottleneck. Traffic behavior reveals important aspects that had not been previously captured in macroscopic simulation. Mainly, the more realistic VSL application at specific points instead of along an entire freeway section produces a slower traffic response to speed limit changes. In addition, the nonlinear capacity flow/speed limit relation observed in the microscopic model is more pronounced than what was observed at the macroscopic level. After appropriate modifications in the control law, significant improvements in traffic conditions are obtained.Institute of Electrical and Electronics EngineersPresented on: IEEE Transactions on Intelligent Transportation Systemspeer-reviewedBibliographic citation: E.R. Müller, R.C. Carlson, W. Kraus Jr, M. Papageorgiou, "Microsimulation analysis of practical aspects of traffic control with variable speed limits," IEEE Transactions on Intelligent Transportation Systems, vol. 16, no.1, pp. 512-523, 2015.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:244752012-10-10T00:00:00Z28info:eu-repo/semantics/articleGlobal exponential stability for discrete-time networks with applications to traffic networksΚαραφυλλης Ιασων(http://users.isc.tuc.gr/~ikarafyllis)Karafyllis Iason(http://users.isc.tuc.gr/~ikarafyllis)Παπαγεωργιου Μαρκος(http://users.isc.tuc.gr/~mpapageorgiou)Papageorgiou Markos(http://users.isc.tuc.gr/~mpapageorgiou)The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 321132, project TRAMAN21. The paper has been published by IEEE (http://ieeexplore.ieee.org/Xplore/defdeny.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D6954406&denyReason=-134&arnumber=6954406&productsMatched=null) and is IEEE copyrighted.DES (System analysis),Discrete event systems,Sampled-data systems,discrete time systems,des system analysis,discrete event systems,sampled data systemsSystems, Nonlinear,nonlinear systems,systems nonlinearTraffic networkshttp://purl.tuc.gr/dl/dias/7837D167-81E0-4BB8-846D-67E9022A351010.1109/TCNS.2014.2367364 Published at: 2015-03-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by-nc-nd/4.0/application/pdfIssued on: 2015Summarization: This paper provides sufficient conditions for global asymptotic stability and global exponential stability, which can be applied to nonlinear, large-scale, uncertain discrete-time networks. The conditions are derived by means of vector Lyapunov functions. The obtained results are applied to traffic networks for the derivation of sufficient conditions of global exponential stability of the uncongested equilibrium point of the network. Specific results and algorithms are provided for freeway traffic models. Various examples illustrate the applicability of the obtained results.Institute of Electrical and Electronics EngineersPresented on: IEEE Transactions on Control of Network Systemspeer-reviewedBibliographic citation: I. Karafyllis, M. Papageorgiou, "Global exponential stability for discrete-time networks with applications to traffic networks," IEEE Transactions on Control of Network Systems, vol.2, no.1, pp.68-77, 2015.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:244792012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectModel predictive control for multi-lane motorways in presence of VACSRoncoli Claudio(http://users.isc.tuc.gr/~croncoli)Roncoli Claudio(http://users.isc.tuc.gr/~croncoli)Παπαμιχαηλ Ιωαννης(http://users.isc.tuc.gr/~ipapa)Papamichail Ioannis(http://users.isc.tuc.gr/~ipapa)Παπαγεωργιου Μαρκος(http://users.isc.tuc.gr/~mpapageorgiou)Papageorgiou Markos(http://users.isc.tuc.gr/~mpapageorgiou)The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 321132, project TRAMAN21.Vehicle automation and communication systemsVACShttp://purl.tuc.gr/dl/dias/E2D5690E-3ECA-464C-B283-A88327CEB21F10.1109/ITSC.2014.6957739 Published at: 2015-03-30eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by-nc-nd/4.0/application/pdfIssued on: 2014Summarization: A widespread use of vehicle automation and communication systems (VACS) is expected in the next years. This may lead to improvements in traffic management because of the augmented possibilities of using VACS both as sensors and as actuators. To achieve this, appropriate studies, developing potential control strategies to exploit the VACS availability, are essential. This paper describes a model predictive control framework that can be used for the integrated and coordinated control of a motorway system, considering that vehicles are equipped with specific VACS. Microscopic simulation testing demonstrates the effectiveness and the computational feasibility of the proposed approach.Παρουσιάστηκε στο: 17th International IEEE Conference on Intelligent Transportation SystemsInstitute of Electrical and Electronics EngineersBibliographic citation: C. Roncoli, I. Papamichail, M. Papageorgiou, "Model predictive control for multi-lane motorways in presence of VACS," in 17th International IEEE Conference on Intelligent Transportation Systems (ITSC 2014), Qingdao, China, 8-11 October 2014, pp. 501-507.full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:244852012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectAn optimisation-oriented first-order multi-lane model for motorway trafficRoncoli Claudio(http://users.isc.tuc.gr/~croncoli)Roncoli Claudio(http://users.isc.tuc.gr/~croncoli)Παπαγεωργιου Μαρκος(http://users.isc.tuc.gr/~mpapageorgiou)Papageorgiou Markos(http://users.isc.tuc.gr/~mpapageorgiou)Παπαμιχαηλ Ιωαννης(http://users.isc.tuc.gr/~ipapa)Papamichail Ioannis(http://users.isc.tuc.gr/~ipapa)The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 321132, project TRAMAN21.Macroscopic traffic flow modellingMulti-lane motorway trafficCapacity drophttp://purl.tuc.gr/dl/dias/27417F46-C51F-4D7E-90ED-067E7986E4AAPublished at: 2015-03-30eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by-nc-nd/4.0/application/pdfIssued on: 2015Summarization: Emerging vehicle automation and communication systems (VACS) may contribute to the mitigation of motorway traffic congestion on the basis of appropriate traffic control strategies. Based on appropriate VACS-based actuators, future traffic control may incorporate vehicle speed control and lane-assignment or lane-changing recommendations. To this end, an appropriate traffic flow model is needed, both for control strategy design and as a no-control base case for comparative evaluation studies. In this context, this paper presents a novel first-order multi-lane macroscopic traffic flow model for motorways which is mainly intended for use within a related optimal control problem formulation. The starting point is close to the well-known cell-transmission model (CTM), which is modified and extended to consider additional aspects of the traffic dynamics, such as lane changing and the capacity drop. The model has been derived with a view to combine realistic traffic flow description with a simple (piecewise linear) mathematical form, which can be exploited for efficient optimal control problem formulations. Although the model has been primarily derived for use in future traffic conditions including VACS, it may also be used for conventional traffic flow representation. In fact, the accuracy of the proposed modelling approach is demonstrated through calibration and validation procedures using conventional real data from an urban motorway located in Melbourne, Australia.Presented on: Transportation Research BoardBibliographic citation: C. Roncoli, M. Papageorgiou, I. Papamichail, "An optimisation-oriented first-order multi-lane model for motorway traffic," in 94th Annual Meeting of the Transportation Research Board (TRB), 11-15 January 2015, p.p 15-2905.full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:244832012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectAssessing the impact of a cooperative merging system on highway traffic using a microscopic flow simulatorΝτουσακης Ιωαννης-Αντωνιος(http://users.isc.tuc.gr/~intousakis1)Ntousakis Ioannis-Antonios(http://users.isc.tuc.gr/~intousakis1)Πορφυρη Καλλιρροη(http://users.isc.tuc.gr/~kporfyri)Porfyri Kalliroi(http://users.isc.tuc.gr/~kporfyri)Νικολος Ιωαννης(http://users.isc.tuc.gr/~inikolos)Nikolos Ioannis(http://users.isc.tuc.gr/~inikolos)Παπαγεωργιου Μαρκος(http://users.isc.tuc.gr/~mpapageorgiou)Papageorgiou Markos(http://users.isc.tuc.gr/~mpapageorgiou)The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 321132, project TRAMAN21.Microscopic flow simulatorhttp://purl.tuc.gr/dl/dias/2587B571-9241-4258-AD2D-26FD08C71DFE10.1115/IMECE2014-39850Published at: 2015-03-30eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by-nc-nd/4.0/application/pdfIssued on: 2014Summarization: Vehicle merging on highways has always been an important aspect, which directly affects the capacity of the highway. Under critical traffic conditions, the merging of main road traffic and on-ramp traffic is known to trigger speed breakdown and congestion. Additionally, merging is one of the most stressful tasks for the driver, since it requires a synchronized set of observations and actions. Consequently, drivers often perform merging maneuvers with low efficiency. Emerging vehicle technologies, such as cooperative adaptive cruise control and/or merging-assistance systems, are expected to enable the so-called “cooperative merging”. The purpose of this work is to propose a cooperative merging system and evaluate its performance and its impact on highway capacity. The modeling and simulation of the proposed methodology is performed within the framework of a microscopic traffic simulator. The proposed model allows for the vehicle-to-infrastructure (V2I) and vehicle-to-vehicle (V2V) communication, which enables the effective handling of the available gaps between vehicles. Different cases are examined through simulations, in order to assess the impact of the system on traffic flow, under various traffic conditions. Useful conclusions are derived from the simulation results, which can form the basis for more complex merging algorithms and/or strategies that adapt to traffic conditions.Presented on: American Society of Mechanical EngineersBibliographic citation: I. A. Ntousakis, K. Porfyri, I.K. Nikolos, M. Papageorgiou, "Assessing the impact of a cooperative merging system on highway traffic using a microscopic flow simulator," in ASME 2014 International Mechanical Engineering Congress and Exposition (IMECE2014), Montreal, Quebec, Canada, 14-20 November 2014, pp. V012T15A024.full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:244812012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectLocal ramp metering with distant downstream bottlenecks: a comparative studyWang Yibing()Kan Yuheng()Παπαγεωργιου Μαρκος(http://users.isc.tuc.gr/~mpapageorgiou)Papageorgiou Markos(http://users.isc.tuc.gr/~mpapageorgiou)Παπαμιχαηλ Ιωαννης(http://users.isc.tuc.gr/~ipapa)Papamichail Ioannis(http://users.isc.tuc.gr/~ipapa)The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 321132, project TRAMAN21.Express highways--Ramp metering,Expressway ramp metering,Freeway ramp metering,ramp metering traffic engineering,express highways ramp metering,expressway ramp metering,freeway ramp meteringALINEAPI-ALINEAhttp://purl.tuc.gr/dl/dias/9A613301-0261-49EC-85C0-1B6C7A3F01FD10.1109/ITSC.2014.6957782 Published at: 2015-03-30eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by-nc-nd/4.0/application/pdfIssued on: 2014Summarization: The well-known feedback ramp metering algorithm ALINEA can be applied for local ramp metering or included as a key component in a coordinated ramp metering system. ALINEA uses real-time occupancy measurements from the ramp flow merging area that may be at most few hundred meters downstream of the metered on-ramp nose. In many practical cases, however, bottlenecks with smaller capacity than the merging area may exist further downstream for various reasons, which suggests using measurements from those further downstream bottlenecks. Recent theoretical and simulation studies indicate that ALINEA may lead to a poorly damped closed-loop behavior in this case, but PI-ALINEA, a suitable Proportional-Integral (PI) extension of ALINEA, can lead to satisfactory control performance. This paper addresses the same local ramp-metering problem in the presence of downstream bottlenecks, with a particular focus on the general capacity of PI-ALINEA with three distinct types of bottleneck that may often be encountered in practice, i.e. (1) an uphill case; (2) a lane-drop case; (3) an un-controlled on-ramp case. Extensive simulation studies are conducted using a macroscopic traffic flow model to demonstrate that the performance of ALINEA indeed deteriorates in each of these bottleneck cases,
while significant improvement is obtained using PI-ALINEA in all cases. Moreover, with its control parameters appropriately tuned beforehand, PI-ALINEA is found to be universally applicable, with little fine-tuning required for field applications.Παρουσιάστηκε στο: 17th International IEEE Conference on Intelligent Transportation SystemsInstitute of Electrical and Electronics EngineersBibliographic citation: Y. Wang, Y. Kan, M. Papageorgiou, I. Papamichail, "Local ramp metering with distant downstream bottlenecks: a comparative study," in 17th International IEEE Conference on Intelligent Transportation Systems (ITSC 2014), Qingdao, China, 8-11 October 2014, pp. 768-773.full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:244602012-10-10T00:00:00Z28info:eu-repo/semantics/articleLearning model-free robot control by a Monte Carlo EM algorithm
Toussaint Marc()Kontes Georgios()Πιπεριδης Σαββας(http://users.isc.tuc.gr/~spiperidis)Piperidis Savvas(http://users.isc.tuc.gr/~spiperidis)Vlassis Nikos()Reinforcement learninghttp://purl.tuc.gr/dl/dias/5830B8CA-9579-4734-9AEE-DB24EA53FD55 10.1007/s10514-009-9132-0Published at: 2015-03-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2009Summarization: We address the problem of learning robot control by model-free reinforcement learning (RL). We adopt the probabilistic model of Vlassis and Toussaint (2009) for model-free RL, and we propose a Monte Carlo EM algorithm (MCEM) for control learning that searches directly in the space of controller parameters using information obtained from randomly generated robot trajectories. MCEM is related to, and generalizes, the PoWER algorithm of Kober and Peters (2009). In the finite-horizon case MCEM reduces precisely to PoWER, but MCEM can also handle the discounted infinite-horizon case. An interesting result is that the infinite-horizon case can be viewed as a ‘randomized’ version of the finite-horizon case, in the sense that the length of each sampled trajectory is a random draw from an appropriately constructed geometric distribution. We provide some preliminary experiments demonstrating the effects of fixed (PoWER) vs randomized (MCEM) horizon length in two simulated and one real robot control tasks.
Springer VerlagPresented on: Autonomous Robotspeer-reviewedBibliographic citation: N. Vlassis, M. Toussaint, G. Kontes, and S. Piperidis, "Learning model-free robot control by a Monte Carlo EM algorithm," Autonomous Robots, vol. 27, no. 2, pp. 123-130, 2009.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:246752012-10-10T00:00:00Z28info:eu-repo/semantics/articleModeling topsoil carbon sequestration in two contrasting crop production to set-aside conversions with RothC–Calibration issues and uncertainty analysisΝικολαιδης Νικολαος(http://users.isc.tuc.gr/~ninikolaidis)Nikolaidis Nikolaos(http://users.isc.tuc.gr/~ninikolaidis)S/N sequastrationAggregationParticulate OMRothC modelingCalibrationhttp://purl.tuc.gr/dl/dias/29A64EA8-C506-4D7B-B4D5-E961AABDFCD110.1016/j.agee.2012.11.010Published at: 2015-04-28eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2013Summarization: Model simulations of soil organic carbon turnover in agricultural fields have inherent uncertainties due to input data, initial conditions, and model parameters. The RothC model was used in a Monte-Carlo based framework to assess the uniqueness of solution in carbon sequestration simulations. The model was applied to crop production to set aside conversions in Iowa (sandy clay-loam soil, humid-continental climate) and Greece (clay-loam soil,
Mediterranean). The model was initialized and calibrated with particulate organic carbon data obtained by physical fractionation. The calibrated values for the Iowa grassland were 5.05 t C ha-1, 0.34 y-1, and 0.27 y-1 24 for plant litter input and decomposition rate constants for resistant plant material (RPM) and humus, respectively, while for the Greek shrubland these were 3.79
t C ha-1, 0.21 y-1, and 0.0041 y-126 , correspondingly. The sensitivity analysis revealed that for both sites, the total plant litter input and the RPM rate constant showed the highest sensitivity. The Iowa soil was projected to sequester 17.5 t C ha-1 and the Greek soil 54 tC ha- 28 1 29 over 100 years and the projected uncertainty was 65.6% and 70.8%, respectively. We
propose this methodology to assess the factors affecting carbon sequestration in agricultural soils and quantify the uncertainties.ElsevierPresented on: peer-reviewedBibliographic citation: F. E. Stamati, N. P. Nikolaidis, J. L. Schnoor, "Modeling topsoil carbon sequestration in two contrasting crop production to set-aside conversions with RothC–Calibration issues and uncertainty analysis," Agriculture, Ecosystems & Environment, vol. 165, pp. 190-200, Jan. 2013.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:246802012-10-10T00:00:00Z28info:eu-repo/semantics/articleNitrogen cycling and relationships between ammonia oxidizers and denitrifiers in a clay-loam soilΝικολαιδης Νικολαος(http://users.isc.tuc.gr/~ninikolaidis)Nikolaidis Nikolaos(http://users.isc.tuc.gr/~ninikolaidis)Παρανυχιανακης Νικολαος(http://users.isc.tuc.gr/~nparanychianakis)Paranychianakis Nikolaos(http://users.isc.tuc.gr/~nparanychianakis)Τσικνια Μυρτω(http://users.isc.tuc.gr/~mtsiknia)Tsiknia Myrto(http://users.isc.tuc.gr/~mtsiknia)Γιαννακης Γεωργιος(http://users.isc.tuc.gr/~gegiannakis)Giannakis Georgios(http://users.isc.tuc.gr/~gegiannakis)Καλογερακης Νικος(http://users.isc.tuc.gr/~nkalogerakis)Kalogerakis Nikos(http://users.isc.tuc.gr/~nkalogerakis)Ammonia oxidizing archaeaAmmonia oxidizing bacteriaNitrificationImmobilizationhttp://purl.tuc.gr/dl/dias/2908FD83-FCE7-4590-AD67-239BB280952D10.1007/s00253-013-4765-5Published at: 2015-04-29eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2013Summarization: This study investigated the effect of municipal solid waste (MSW) compost (0, 50, and 100 t/ha) on N cycling and the microorganisms involved in it, in a clay-loam soil. After a release of nitrates (NO3--N) in the first 6 days after compost incorporation, soil NO3--N content remained constant in all the treatments by day 62 suggesting immobilization of N. Then, soil NO3--N content increased, especially in the highest compost dose implying that the immobilization effect has been relieved, at least to some extent. amoA gene copies of ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) followed strictly the pattern of soil NO3--N content throughout the study providing evidence that both groups were involved in ammonia oxidation and changes in their population can be used as ‘indicator’ for predicting changes in soil nitrification status. Moreover, the strong correlation between AOA 12 and AOB amoA copies (R2: 0.94) and the high slope (13) of the curve suggest that AOA had probably a more important role on ammonia oxidation under conditions of low ammonia availability. Denitrifying genes (nirS, nirK, nosZ) also followed the general pattern of soil NO3–-N and they were strongly correlated with both groups of ammonia oxidizers, and particularly archaea, suggesting strong interrelationships among them. Losses of N through denitrification, as they were estimated from total nitrogen decrease, were inversely related to soil NO3--N content. Similar to ammonia oxidizers, denitrifying gene copies did not differ among compost treatments an effect that could be probably explained by the low availability of organic-C of the MSW compost and hence the competition with aerobic heterotrophs.Springer VerlagPresented on: peer-reviewedBibliographic citation: N. Paranychianakis, M. Tsiknia, G. Giannakis, N. P. Nikolaidis, N. Kalogerakis, "Nitrogen cycling and relationships between ammonia oxidizers and denitrifiers in a clay-loam soil," Applied microbiology and biotechnology, vol. 97, no. 12, pp. 5507-5515, Jun.2013.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:246782012-10-10T00:00:00Z28info:eu-repo/semantics/bookPartSoil organic matter dynamics and structureΝικολαιδης Νικολαος(http://users.isc.tuc.gr/~ninikolaidis)Nikolaidis Nikolaos(http://users.isc.tuc.gr/~ninikolaidis)Bidoglio G.()Soil carbonSoil nitrogenFeedback mechanicshttp://purl.tuc.gr/dl/dias/065FB389-C151-440C-A1D9-F6AF8DD375FE10.1007/978-94-007-5961-9_6Published at: 2015-04-28eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2013Summarization: Soil ecosystem functions have significantly deteriorated due to agricultural intensification with dramatic consequences on carbon loss, loss of soil biodiversity, erosion, compaction as well as unsustainable use of water and mineral resources. Sustainable agricultural practices are necessary if we are to face the challenge of food security while preserving the integrity of soil and aquatic ecosystems. Conservation agriculture which is comprised of zero or minimum tillage, carbon amendments and crop rotations holds great promise in delivering higher yields, using water and soil resources in a sustainable manner and increasing soil biodiversity. This paper presents a synthesis of current knowledge on soil ecosystem processes and modeling with a focus on carbon and nitrogen dynamics and their link to soil structure, and proposes a conceptual framework for model parameterization capable of predicting critical soil functions and potential shifts.
We reviewed the dynamics of carbon, nitrogen and soil structure with an emphasis in elucidating predominant state variables and the interaction with plants and food web dynamics. Existing models that simulate the dynamics of organic matter and structure in soils at various scales were evaluated for their ability to simulate the functions of soil ecosystem. Current modeling approaches treat carbon, nitrogen and soil structure for the most part separately without incorporating feedback mechanisms. The synergistic and antagonistic processes between bacteria and plants and fungi and plants are partially understood and more importantly the community lacks the knowledge to predict if and when these processes fail and any related potential ecosystem shift. A conceptual modeling framework is proposed, developed along the following three axes: incorporate emerging ecosystem state variables, account for the ecology of life in soils, and model processes from first principles. A synthesis of the carbon and nitrogen cycles is suggested in which the dynamics of the two cycles are interlinked. State variables in soil ecosystem models that link carbon and nitrogen dynamics with soil structure and the biological community are recommended. Plant feedback mechanisms with the physical, biochemical and biotic soil components and the symbiotic relationship between bacteria, fungi, and plants should be modeled using principles from the ecological succession theory that would relate the taxonomic structure with function and nutrient fluxes. A conceptual model of soil structure and soil stability is suggested that links the soil organic matter sub-model to an aggregation sub-model and a dynamic soil structure sub-model. The development of new generation soil ecosystem models is a necessary step to better quantify soil functions, assess possible soil tipping points, and develop methods to restore soil functions.Appearing in: Sustainable Agriculture ReviewsSpringer VerlagBibliographic citation: N. P. Nikolaidis, G. Bidoglio, "Soil Organic Matter Dynamics and Structure," in Sustainable Agriculture Reviews, vol. 12, Sustainable Agriculture Reviews, E. Lichtfouse, Ed., Dordrecht, Springer Science+Business Media, 2013, pp.175-199.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309022012-10-10T00:00:00Z28info:eu-repo/semantics/articleDissolution of a well-defined trichloroethylene pool
in saturated porous media:
Experimental design and aquifer characterization Χρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)A three-dimensional, bench-scale model aquifer was constructed
to study the dissolution of a TCE pool. The aquifer
consisted of medium-sized sand packing conveying steady, unidirectional
flow. A key aspect of the experimental design was a
mechanism by which a TCE pool of an ideal (circular) geometry
was placed and maintained in direct contact with the
bottom of the porous medium. The aqueous plume emanating
from this pool was monitored at several downgradient sampling
stations and analyzed using the analytical solution derived by Chrysikopoulos [1995]. All transport parameters required
by this solution, with the exception of the average mass
transfer coefficient (k*) for the pool, were estimated independently.
Of special note are the dispersion parameters, which
were estimated independently by fitting the results of a bromide
tracer test with a newly derived analytical solution describing
the transport of a conservative tracer in a homogeneous
aquifer of finite thickness.TCE Pool Dissolution Experiments,Column Experiment,Tracer Experiment,Experimental DesignThomas C. HarmonKenneth Y. Leehttp://purl.tuc.gr/dl/dias/86702C48-87CE-4344-AC4A-7ADE710FB328 10.1029/2000WR900082 Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2000Summarization: A unique three-dimensional bench-scale model aquifer is designed and
constructed to carry out dense nonaqueous phase liquid (DNAPL) pool dissolution
experiments. The model aquifer consists of a rectangular glass tank with internal
dimensions 150.0 cm length, 21.6 cm width, and 40.0 cm height. The formation of a welldefined
circular pool with a perfectly flat pool-water interface is obtained by a bottom
plate with a precise cutout to contain the DNAPL. The aquifer is packed with a wellcharacterized
relatively uniform sand. A conservative tracer is employed for the
determination of the longitudinal and transverse aquifer dispersivities. The dissolution
studies are conducted using a circular trichloroethylene (TCE) pool. The sorption
characteristics of TCE onto the aquifer sand are independently determined from a flowthrough
column experiment. Steady state dissolved TCE concentrations at specific
downstream locations within the aquifer are collected under three different interstitial
velocities. An appropriate overall mass transfer coefficient is determined from each data
set. The data collected in this study are useful for the validation of numerical and
analytical DNAPL pool dissolution models.University of California PressΠαρουσιάστηκε στο: WATER RESOURCES RESEARCH,peer-reviewedBibliographic citation: Constantinos V. Chrysikopoulos,Kenneth Y. Lee ,Thomas C. Harmon , "Dissolution of a well-defined trichloroethylene pool in saturated porous media:
Experimental design and aquifer characterization" , Water Resources Research. 2000, 36(7):1687-1696 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:313532012-10-10T00:00:00Z28info:eu-repo/semantics/articlePower Optimization of Wind Electric Conversion Systems Integrated into the Utility GridKalaitzakis K.C()Vachtsevanos, G.J(http://viaf.org/viaf/23660343)Δημοσίευση σε διεθνές περιοδικόWECS (Wind energy conversion systems),wind energy conversion systems,wecs wind energy conversion systemsElectric power pooling,Electric utility systems, Interconnected,Interties (Electric utilities),System interconnection, Electric power,Transmission line interconnection,interconnected electric utility systems,electric power pooling,electric utility systems interconnected,interties electric utilities,system interconnection electric power,transmission line interconnectionhttp://purl.tuc.gr/dl/dias/B7856E80-4C48-4A5B-A894-F27AF04E7517http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.01.pdfPublished at: 2015-09-23eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1982Περίληψη: This paper is concerned with the interconnected operation of WECS with the utility grid.Specifically ,it addresses problems of stability , protection and power flow optimization from the WECS to the power lines.
The approach followed contains both a theoritical and a experimental component.A variable-speed constant-frequency wind electric system utilizing a synchronous generator and line-commutated inverter provides experimental verification of computer simulation studies for the dynamic and steady-state performance of the interconnected system.
Simulation results indicate that the transient bahavior of the wind electric-power grid system is satisfactory with appropriate devices providing adequate protection to both the wind generator and the utility grid from a variety of fault conditions.
A maximum power tracking mechanism has been designed for the continuous matching of the wind-electric generator to the grid impedance characteristics.As a result,maximum electric power is transferred from the wind machine to the power lines.Computer simulation studies of this type of operation indicate the substantial improvement in power transfer that is achieved.
The proposed scheme tends to minimize equipment and maintenance costs while maximizing the energy transfer capabilities of the wind-electric conversion system and maintaining a high degree of reliability in overall system performance.Wind EngineeringΠαρουσιάστηκε στο: Wind Engineepeer-reviewedBibliographic citation: K.C. Kalaitzakis and G.J. Vachtsevanos, "Power Optimization of Wind Electric Conversion Systems Integrated into the Utility Grid," Wind Engineering, vol. 6, no. 1, pp. 24-36, 1982.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:301112012-10-10T00:00:00Z28info:eu-repo/semantics/articleΣυνέντευξη με τη Μαρία ΓούλαΧατζησαββα Δημητρα(http://users.isc.tuc.gr/~dchatzisavva)Chatzisavva Dimitra(http://users.isc.tuc.gr/~dchatzisavva)http://purl.tuc.gr/dl/dias/0E857A04-510F-42CC-BDBE-1CE55E5AEEBBPublished at: 2015-09-17elinfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2009Μη διαθέσιμη περίληψηNot available summarizationΤεχνικό Επιμελητήριο Ελλάδος. Τμήμα Κεντρικής ΜακεδονίαςΠαρουσιάστηκε στο: Τεχνογράφημαnon peer-reviewedΒιβλιογραφική αναφορά: Δ. Χατζησάββα, "Συνέντευξη με τη Μαρία Γούλα," Τεχνογράφημα, τομ. 372, σ.20-21, 2009.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318542012-10-10T00:00:00Z28info:eu-repo/semantics/articlePenetration of Wind Electric Conversion Systems into the Utility GridVachtsevanos, G.J(http://viaf.org/viaf/23660343)Kalaitzakis K.C()Δημοσίευση σε επιστημονικό περιοδικό Control systemsInterconnected systemsMesh generationPower generationPower system interconnectionPower system modelingPower system simulationSystem performanceWind energy generationWind power generationhttp://purl.tuc.gr/dl/dias/E8EDE09B-CE9E-4200-984B-134E9BD2412Ehttp://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.05.pdf 10.1109/TPAS.1985.319198Published at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1985Summarization: This paper is concerned with the development of appropriate models for the interconnected operation of wind generator clusters with an autonomous power system and simulation techniques for the study of the degree of penetration of such wind electric conversion devices when operating in parallel with the utility grid. The quality of the interconnected system performance is specified in terms of operational constraints and the resultant penetration strategy is implemented via a microprocessor-based control scheme. The strategy assures a satisfactory level of system performance while optimizing the available energy transfer from the wind generators to the utility grid.Institute of Electrical and Electronics EngineersΠαρουσιάστηκε στο: Power Apparatus and Systems, IEEE Transactions onpeer-reviewedBibliographic citation: G.J. Vachtsevanos, K.C. Kalaitzakis, "Penetration of Wind Electric Conversion Systems into the Utility Grid," Power Apparatus and Systems, IEEE Transactions on., vol.PAS-104, no. 7, pp. 1677-1683, Jul. 1985. doi: 10.1109/TPAS.1985.319198info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318572012-10-10T00:00:00Z28info:eu-repo/semantics/articleDesign and development of a new electronic sphygmomanometerVachtsevanos, G.J(http://viaf.org/viaf/23660343)Kalaitzakis K.C()Papamarkos, N(http://viaf.org/viaf/305652480)Δημοσίευση σε επιστημονικό περιοδικό Electronic designElectronic sphygmomanometerNoninvasive blood pressure measurementhttp://purl.tuc.gr/dl/dias/045541BB-1FC0-4068-8E91-2924DA46B00Bhttp://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.06.pdf 10.1007/BF02448933Published at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1985Summarization: The paper introduces a new technique for the indirect measurement of the systolic and diastolic blood pressure in humans. The technique is based upon a statistically consistent relationship between the amplitude of the pulsatile pressure waveform at the systolic and diastolic points and the amplitude of pulse signals detected when the artery is fully occluded. An adaptive measurement philosophy has been implemented in the design of an electronic sphygmomanometer which, in addition to a pressure transducer, contains suitable electronic instrumentation for processing and displaying the electronic signals. Verification of overall system accuracy is accomplished with direct comparison with manual auscultatory measurements. Clinical testing of a prototype indicates a satisfactory performance; measurement errors are maintained well within proposed standards for automated sphygmomanometers.Kluwer Academic PublishersPresented on: Medical and Biological Engineering and Computingpeer-reviewedBibliographic citation: G.J. Vachtsevanos, K.C. Kalaitzakis, and N.E, Papamarkos, "Design and development of a new electronic sphygmomanometer," Medical and Biological Engineering and Computing ., vol. 23, no. 5, pp. 453-458, Sep. 1985. doi:10.1007/BF02448933info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318622012-10-10T00:00:00Z28info:eu-repo/semantics/articleA Methodology for Dynamic Utility Interactive Operation of Dispersed Storage and Generation DevicesVachtsevanos, G.J(http://viaf.org/viaf/23660343)Kalaitzakis K.C()Δημοσίευση σε επιστημονικό περιοδικόComputational modelingControl equipmentDistributed power generationPower industryPower system dynamicsPower system interconnectionPower system modelingPower system simulationPower system stabilityReactive powerIEEE Power & Energy Societyhttp://purl.tuc.gr/dl/dias/9F28B8AF-438E-4A8A-B515-EC3C921B4986http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.07.pdf 10.1109/TPWRS.1987.4335072Published at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1987Summarization: This paper is introducing a new methodology for the dynamic integration of dispersed storage and generation devices into the electric utility distribution network operations. The dispersed source is viewed as an active device contributing towards the regulation of real and reactive power flows while improving the stability of the power system. Conceptual means are developed for an effective DSG-utility grid interface. Computer models of appropriate interconnection and control equipment are used in simulation studies to test the effectiveness of control strategies and optimize design parameters. Simulation results indicate that load frequency control and voltage regulation may be effectively accomplished with dispersed generators within a fraction of the time required for conventional regulating units. Appropriate modulation and conditioning of the DSG-output power can assist in damping out undesirable power oscillations. Implementation of the proposed policies may result in reduced load following requirements for conventional power generating units, increase the value and acceptability of new energy technologies, and improve power quality and stability of the interconnected system.Institute of Electrical and Electronics EngineersΠαρουσιάστηκε στο: Power Systems, IEEE Transactions onpeer-reviewedBibliographic citation: G.J. Vachtsevanos, K.C. Kalaitzakis, "A Methodology for Dynamic Utility Interactive Operation of Dispersed Storage and Generation Devices," Power Systems, IEEE Transactions on., vol. PWRS-2, no. 1, pp. 45-51, Feb. 1987. doi: 10.1109/TPWRS.1987.4335072info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318642012-10-10T00:00:00Z28info:eu-repo/semantics/articleA Hybrid Photovoltaic Simulator for Utility Interactive StudiesVachtsevanos, G.J(http://viaf.org/viaf/23660343)Kalaitzakis K.C()Δημοσίευση σε επιστημονικό περιοδικό Analog-digital conversionPhotovoltaic cellsPhotovoltaic energy systems,Photovoltaic facilities,Photovoltaic power plants,Photovoltaic solar generating plants,Power plants, Photovoltaic,Power systems, Photovoltaic,photovoltaic power systems,photovoltaic energy systems,photovoltaic facilities,photovoltaic power plants,photovoltaic solar generating plants,power plants photovoltaic,power systems photovoltaicPower system reliabilitySolar energySolar power generationSolar radiationSteady-stateTemperatureTestingIEEE Power & Energy Societyhttp://purl.tuc.gr/dl/dias/441E5DF3-F0CE-4185-94AE-701B6509F52Fhttp://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.08.pdf 10.1109/TEC.1987.4765834Published at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1987Summarization: An analog-digital photovoltaic (PV) array simulator is considered. The analog section is designed on the basis of an equivalent solar cell model while the digital section is constructed realizing the mathematical representation of the array. Fast time responses achieved by the analog section make this part suitable for the study of transient phenomena associated with the interconnected operation of PVs and the utility grid. Its digital counterpart is more appropriate for long-term experimental investigations due to its inherent accuracy and reliability. The combined hybrid simulator offers a versatile and flexible piece of apparatus capable of simulating the performance of any PV array under a variety of operating conditions. The device can be constructed with low-cost components in a compact arrangement offering transportability and ease of operation. Experimental results derived from a laboratory constructed prototype match closely the theoretically computed characteristics.Institute of Electrical and Electronics EngineersΠαρουσιάστηκε στο: Energy Conversion, IEEE Transactions onpeer-reviewedBibliographic citation: G.J. Vachtsevanos, K.C. Kalaitzakis, "A Hybrid Photovoltaic Simulator for Utility Interactive Studies," Energy Conversion, IEEE Transactions on ., vol. EC-2, no.2, pp. 227-231, Jun.1987. doi:10.1109/TEC.1987.4765834info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:327712012-10-10T00:00:00Z28info:eu-repo/semantics/articleDevelopment of a microprocessor-based adaptive technique for blood pressure measurements.Καλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Papamarkos, N(http://viaf.org/viaf/305652480)Vachtsevanos, G.J(http://viaf.org/viaf/23660343)Δημοσίευση σε επιστημονικό περιοδικό electronic sphygmomanometercardiac pressureDiagnostic tests, Noninvasive,Noninvasive diagnosis,Noninvasive diagnostic tests,diagnosis noninvasive,diagnostic tests noninvasive,noninvasive diagnosis,noninvasive diagnostic testshttp://purl.tuc.gr/dl/dias/64E62999-36F4-424B-8371-1D637A199941http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.10.pdfPublished at: 2015-09-28eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1989Summarization: The paper introduces a new microprocessor-based adaptive technique for the indirect measurement of the systolic and diastolic pressure in humans. The technique is based upon a statistically consistent relationship between the amplitude of the pulsative pressure waveform at the systolic and diastolic points and the amplitude of pulse signals detected when the artery is fully occluded. An adaptive measurement philosophy has been implemented in the design of an electronic analog-digital sphygmomanometer which, in addition to a pressure transducer, contains suitable electronic instrumentation for processing and displaying the electronic signals. A dedicated microprocessor is used to store statistical relations and control the operation of the device. Verification of overall system accuracy is accomplished via direct comparison with manual auscultatory measurements. Clinical testing of a prototype indicates satisfactory performance; measurement errors are maintained well within proposed standards for automated sphygmomanometers.
Kluwer Academic PublishersPresented on: Medical progress through technologypeer-reviewedBibliographic citation: K.C. Kalaitzakis, N.E. Papamarkos, and G.J. Vachtsevanos, "Development of a microprocessor-based adaptive technique for blood pressure measurements," Medical Progress Through Technology, vol. 14, pp. 63-72, 1989info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:327912012-10-10T00:00:00Z28info:eu-repo/semantics/articleDesign of a Microprocessor-Based Sphygmomanometer.Καλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Papamarkos, N(http://viaf.org/viaf/305652480)Vachtsevanos, G.J(http://viaf.org/viaf/23660343)Δημοσίευση σε επιστημονικό περιοδικό microprocessorBlood--Pressure,blood pressuresphygmomanometerhttp://purl.tuc.gr/dl/dias/0ED259C0-EFC9-4BB5-B6A4-61BEDD8171EFhttp://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.11.pdfPublished at: 2015-09-28eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1990Summarization: This paper describes the implementation on a microprocessor of a new method for the indirect measurement and recording of the systolic and diastolic blood pressure in humans. The technique is based on a statistical analysis of the cardiac pulse pressure signal. Polynomial relations are derived between the amplitude of the pulsatile pressure waveforms at the systolic and diastolic points and the amplitude of pulse signals detected when the artery is fully occluded. With the dual objective of automating the measurement procedure and minimizing errors, an electronic analog-digital sphygmomanometer that contains suitable electronic instrumentation was developed. The functions of processing the pressure signal, automating the measurement, and recording the results are performed and controlled by a microprocessor. A laboratory prototype embodying this approach was constructed and its performance and reliability were verified using a series of clinical tests. The test results indicate that the device is accurate within acceptable bounds for automated blood pressure instruments.Biomedical Instrumentation and TechnologyPresented on: Biomedical instrumentation and technologypeer-reviewedBibliographic citation: K.C. Kalaitzakis, N.E. Papamarkos, and G.J. Vachtsevanos, "Design of a Microprocessor-Based Sphygmomanometer," Biomedical Instrumentation and Technology, vol. 24, pp. 31-36, Jan-Feb. 1990info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:328112012-10-10T00:00:00Z28info:eu-repo/semantics/articleOptimal PV system dimensioning with obstructed solar radiationΚαλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Δημοσίευση σε επιστημονικό περιοδικό Photovoltaic energy systems,Photovoltaic facilities,Photovoltaic power plants,Photovoltaic solar generating plants,Power plants, Photovoltaic,Power systems, Photovoltaic,photovoltaic power systems,photovoltaic energy systems,photovoltaic facilities,photovoltaic power plants,photovoltaic solar generating plants,power plants photovoltaic,power systems photovoltaicAbsorption, Atmospheric,Atmospheric absorption of solar radiation,Insolation,Radiation, Solar,Sun--Radiation,solar radiation,absorption atmospheric,atmospheric absorption of solar radiation,insolation,radiation solar,sun radiationhttp://purl.tuc.gr/dl/dias/E99D884A-12D6-4B3C-B464-3A43D6061A83http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.13.pdf 10.1016/0960-1481(95)00110-7Published at: 2015-09-28eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1996Summarization: This paper describes an analytical methodology for the optimised design of stand-alone photovoltaic (PV) systems installed at locations where the solar radiation is considerably shortened by obstacles, i.e. at the bottom of a gorge. A method for the computation of the real available solar energy incident on the PV panel is proposed, based on easily conducted measurements. The optimum tilt of the PV array, under such conditions, is obtained and a dimensioning procedure provides the optimal size of the PV-array/storage. The resulting system is tested by a verification routine. A case study, employing the complete algorithm proposed, is illustrated.ElsevierPresented on: Renewable Energypeer-reviewedBibliographic citation: K.C. Kalaitzakis, "Optimal PV system dimensioning with obstructed solar radiation," Renewable Energy, vol. 7, no. 1, pp. 51-56, 1996. doi:10.1016/0960-1481(95)00110-7info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:328312012-10-10T00:00:00Z28info:eu-repo/semantics/articleA fuzzy knowledge based method for maintenance planning in a power systemΣεργακη Αμαλια(http://users.isc.tuc.gr/~asergaki)Sergaki Amalia(http://users.isc.tuc.gr/~asergaki)Καλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Δημοσίευση σε επιστημονικό περιοδικό Inspection planningFuzzy relational databaseCriticality analysisDecision support systemshttp://purl.tuc.gr/dl/dias/57B31B37-7820-429C-A3FA-16971DC54738http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.21.pdf 10.1016/S0951-8320(02)00010-8Published at: 2015-09-28eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2002Summarization: The inspection planning in electric power industry is used to assess the safety and reliability of system components and to increase the ability of failure situation identification before it actually occurs. It reflects the implications of the available information on the operational and maintenance history of the system. The output is a ranked list of components, with the most critical ones at the top, which indicates the selection of the components to be inspected.
In this paper, we demonstrate the use of a fuzzy relational database model for manipulating the data required for the criticality component ranking in thermal power systems inspection planning, incorporating criteria concerning aspects of safety and reliability, economy, variable operational conditions and environmental impacts. Often, qualitative thresholds and linguistic terms are used for the component criticality analysis. Fuzzy linguistic terms for criteria definitions along with fuzzy inference mechanisms allow the exploitation of the operators' expertise.
The proposed database model ensures the representation and handling of the aforementioned fuzzy information and additionally offers to the user the functionality for specifying the precision degree by which the conditions involved in a query are satisfied.
In order to illustrate the behavior of the model, a case study is given using real inspection data.ElsevierPresented on: Reliability Engineering and System Safetypeer-reviewedBibliographic citation: A. Sergaki, K.C. Kalaitzakis, "A fuzzy knowledge based method for maintenance planning in a power system," Reliability Engineering & System Safety, vol. 77, no.1, pp. 19-30, Jul. 2002. doi:10.1016/S0951-8320(02)00010-8info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315242012-10-10T00:00:00Z28info:eu-repo/semantics/articleDevelopments in liquid-phase microextractionE Psillakis () N Kalogerakis()http://purl.tuc.gr/dl/dias/D349CD5D-7DEC-4B16-AAC4-129DE34610B510.1016/S0165-9936(03)01007-0Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2003Summarization: The development of faster, simpler, inexpensive and more environmentally friendly sample-preparation techniques is an important issue in chemical analysis. Recent research trends involve miniaturisation of the traditional liquid-liquid extraction (LLE) principle by greatly reducing the acceptor-to-donor phase ratio. One of the emerging techniques in this area is liquid-phase microextraction (LPME), where a hollow fibre impregnated with an organic solvent is used to accommodate or protect microvolumes of acceptor solution. This novel methodology proved to be an extremely simple, low-cost and virtually solvent-free sample-preparation technique, which provided a high degree of selectivity and enrichment by additionally eliminating the possibility of carry-over between runs. This article presents the different modes and hollow-fibre configurations of LPME, followed by an up-to-date summary of its applications. The most important parameters and practical considerations for method optimisation are also discussed. The article concludes with a comparison of this novel method with solid-phase microextraction (SPME) and single-drop microextraction (SDME).
ElsevierPresented on: peer-reviewedBibliographic citation: E. Psillakis, N. Kalogerakis , " Developments in liquid-phase microextraction ", Tr. in An. Chem.,vol. 22, no.9, pp. 565–574,2003.doi :10.1016/S0165-9936(03)01007-0info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315252012-10-10T00:00:00Z28info:eu-repo/semantics/articleDevelopments in single-drop microextractionE Psillakis()N Kalogerakis()http://purl.tuc.gr/dl/dias/EE539FDB-1AD8-46E1-9074-799EE8282A1010.1016/S0165-9936(01)00126-1Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2002Summarization: The continuous quest for novel sample preparation procedures has led to the development of new methods, whose main advantages are their speed and negligible volume of solvents used. The most recent trends include solvent microextraction, a miniaturisation of the traditional liquid–liquid extraction method, where the solvent to aqueous ratio is greatly reduced. Single-drop microextraction is a methodology that evolved from this approach. It is a simple, inexpensive, fast, effective and virtually solvent-free sample pretreatment technique. This article provides a detailed and updated discussion of the developments, modes and applications of single-drop microextraction, followed by a brief description of the theoretical background of the method. Finally, the most important parameters as well as some practical considerations for method optimisation and development are summarised.ElsevierPresented on: Trends in Analytical Chemistrypeer-reviewedBibliographic citation: E Psillakis, N. Kalogerakis , "Developments in single-drop microextraction " , Tr. in Anal.Chem., Volume 21, no. 1, pp. 54–64 ,2002.doi:10.1016/S0165-9936(01)00126-1info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:328722012-10-10T00:00:00Z28info:eu-repo/semantics/articleTXRF cation analysis by anionic membrane collectionΚαλλιθρακας Νικολαος(http://users.isc.tuc.gr/~nkallithrakas)Kallithrakas Nikolaos(http://users.isc.tuc.gr/~nkallithrakas)Χατζησταύρος Βασίλειος()Hatzistavros Vasilios()Total X -Ray Fluorescence (TXRF)http://purl.tuc.gr/dl/dias/DBACA891-F33C-4B2A-8A46-FB23170CCC5B10.1002/xrs.1156Published at: 2015-09-29eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2009Summarization: A new method for the determination of trace levels of cationic ions by anion selective membrane collection is presented. Anion selective membranes containing a few micrograms of different complexing reagents in polyvinyl chloride (PVC) matrix were produced in quartz reflectors. The membranes were immersed in water solutions with low concentrations of cationic metals, Cu, Co, Ni, Zn, and of anionic ligands (CN−, etc.). After the equilibration time the reflectors were left to dry and they were analyzed by Total X-Ray Fluorescence (TXRF). Many experimental parameters (pH effect, size of the membrane, volume sample) were examined. The minimum detection limits were estimated to be 1 ng/ml for all metallic cations even in seawater. The method needs less working labor than other enrichment procedures, the cations are collected directly on the TXRF reflector surface and very small chemical reagent consumption is needed. John Wiley and SonsΠαρουσιάστηκε στο: X-Ray Spectrometrypeer-reviewedBibliographic citation: V. Hatzistavros, N. Kallithrakas-Kontos, "TXRF Cation analysis by anionic membrane collection", X-. Ray Spectrometry, vol. 38, no. 3, pp. 229-233, Mar. 2009info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:328712012-10-10T00:00:00Z28info:eu-repo/semantics/articleA Simulation Model for the Reliable Integration of a 4.5MW Wind Farm into the Power Grid of the Crete IslandΚαλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Σταυρακακης Γεωργιος(http://users.isc.tuc.gr/~gstavrakakis)Stavrakakis Georgios(http://users.isc.tuc.gr/~gstavrakakis)Δημοσίευση σε διεθνές επιστημονικό περιοδικό simulation modelWECS (Wind energy conversion systems),wind energy conversion systems,wecs wind energy conversion systemsautonomous power systemshttp://purl.tuc.gr/dl/dias/54765A89-6067-4F9D-8F1D-1987562F6BAChttp://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.12.pdf 10.1080/01425919008941481Published at: 2015-09-29eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1990Summarization: This paper describes a computer simulation model which has been developed to study the effects of integrating wind energy conversion systems (WECS) into autonomous power systems. The quality of the interconnected system performance is specified in terms of operational constraints. Load-flow and power-system-stability studies were preformed in order to evaluate the penetration impact of a 4·5 MW wind farm on the local grid fo Sitia-Crete. The results show that the above wind energy penetration level will not cause any problem to the existing electric power grid.Taylor & FrancisPresented on: International Journal of Solar Energypeer-reviewedBibliographic citation: K.C. Kalaitzakis, and G.S. Stavrakakis, "A Simulation Model for the Reliable Integration of a 4.5MW Wind Farm into the Power Grid of the Crete Island," International Journal of Solar Energy, vol. 9, no. 3, pp. 137-146, 1990. doi:10.1080/01425919008941481
info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:330522012-10-10T00:00:00Z28info:eu-repo/semantics/articleSize optimization of a PV system installed close to sun obstacles.Καλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Σταυρακακης Γεωργιος(http://users.isc.tuc.gr/~gstavrakakis)Stavrakakis Georgios(http://users.isc.tuc.gr/~gstavrakakis)Δημοσίευση σε επιστημονικό περιοδικό solar radiationPV arraycase studyhttp://purl.tuc.gr/dl/dias/C34FACBD-CD09-41D5-A40C-BCBB5AFCAC6Fhttp://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.15.pdf 10.1016/S0038-092X(96)00101-6Published at: 2015-09-29eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1996Summarization: The assessment of the optimal size of a PV-array/battery-storage system, when the incident solar radiation is considerably obstructed, is presented in this article. An optimal dimensioning method is proposed based on a new procedure for the calculation of the actual solar radiation on the array surface, for installations located near obstacles. The optimum tilt of the PV array is also computed and the resulting optimal PV-array/battery-storage system is evaluated by an appropriate routine. The results of the application of the complete algorithm for a real case study inside a gorge are illustrated.ElsevierPresented on: Solar Energypeer-reviewedBibliographic citation: K.C. Kalaitzakis and G.S. Stavrakakis, "Size optimization of a PV system installed close to sun obstacles," Solar Energy, vol. 57, no. 4, pp. 291-299, Oct. 1996. doi:10.1016/S0038-092X(96)00101-6info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315532012-10-10T00:00:00Z28info:eu-repo/semantics/articleSingle drop microextraction for the analysis of organophosphorous insecticides in water Elefteria Psillakis()Triantafyllos A Albanis()Nicolas Kalogerakis()Dimitra A Lambropoulou()http://purl.tuc.gr/dl/dias/8FE96406-AFBF-4BE3-82B7-F165E1DE5E0210.1016/j.aca.2004.03.055Published at: 2015-09-24eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2004Summarization: A new method used for the extraction of 10 organophosphorous insecticides from water samples coupling single-drop microextraction with gas chromatography–mass spectrometry is presented here. Parameters, such as organic solvent, exposure time, agitation, organic drop volume and salt concentration were controlled and optimised. Overall, extraction was achieved by suspending a 1.5 μl toluene drop to the tip of a microsyringe immersed in a 5 ml donor aqueous solution containing 2.5% NaCl (w/v) and stirred at 800 rpm. The developed protocol was found to yield a linear calibration curve in the concentration range from 0.5 to 100 μg l−1 for all target analytes. Under selected ion monitoring mode, the limits of detection were found to be in the range between 0.010 and 0.073 μg l−1.Παρουσιάστηκε στο: Analytica chimica actapeer-reviewedBibliographic citation: D. A Lambropoulou, E.Psillakis, T. A Albanis, N. Kalogerakis, "Single drop microextraction for the analysis of organophosphorous insecticides in water ",Anal. ch.a act.,vol.516.no.1,pp.205-211, 2004.doi:10.1016/j.aca.2004.03.055info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315722012-10-10T00:00:00Z28info:eu-repo/semantics/articleComplexes of silver(I), thallium(I),lead(II) and barium(II) withbis[3-(2-pyridyl)pyrazol-1-yl]phosphinate: one-dimensional helicalchains and discrete mononuclear complexesElefteria Psillakis()Jon A McCleverty()John C Jeffery()Michael D War()http://purl.tuc.gr/dl/dias/C0B9FA77-3F06-485F-9BD7-5D363A53E93C10.1039/A700475CPublished at: 2015-09-24eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1997Summarization: Reaction of 3-(2-pyridyl)pyrazole with POBr 3 in toluene–NEt 3 afforded not the expected tris(pyrazolyl)phosphine oxide but the partially hydrolysed compound bis[3-(2-pyridyl)pyrazol-1-yl]phosphinate (as its triethylammonium salt). This compound has two potentially chelating N,N′-bidentate arms linked by an apical PO 2 - group. Reaction with AgNO 3 , Tl(O 2 CMe), Pb(NO 3 ) 2 or Ba(NO 3 ) 2 in dry MeCN followed by recrystallisation afforded crystals of the complexes [AgL]·2H 2 O, [TlL]·MeOH, [PbL 2 ]·H 2 O and [(BaL 2 ) 3 ]·6MeCN·2H 2 O respectively, all of which have been crystallographically characterised. The compound [AgL]·2H 2 O contains infinite helical chains (AgL) ∞ in which each ligand donates one N,N′-bidentate arm to each of two metals and each metal ion is four-co-ordinated by two arms from different ligands. The strands are held together in the crystal by a complex network of hydrogen bonds involving lattice water molecules and also by aromatic π-stacking interactions. The compound [TlL]·MeOH is likewise a one-dimensional helical polymer of TlL units, with each ligand bridging two metals and each Tl ion in a ‘2 + 3’ co-ordination geometry with two short bonds to ligands (<2.71 Å) and three longer, weak bonds (>2.87 Å): there is an obvious gap in the co-ordination sphere due to a stereochemically active lone pair. A combination of interstrand aromatic π-stacking interactions and hydrogen-bonding interactions involving the lattice MeOH molecule is present.Royal Society of ChemistryΠαρουσιάστηκε στο: Journal of the Chemical Society, Dalton Transactionspeer-reviewedBibliographic citation: E. Psillakis, J. C Jeffery, J. A McCleverty, M. D Ward , "Complexes of silver(I), thallium(I),lead(II) and barium(II) withbis[3-(2-pyridyl)pyrazol-1-yl]phosphinate: one-dimensional helicalchains and discrete mononuclear complexes " ,J. Chem. Soc., Dalton Trans., no.9, pp.1645-1651,2007.doi:10.1039/A700475Cinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315772012-10-10T00:00:00Z28info:eu-repo/semantics/articleSonochemical degradation of triclosan in water
and wastewaterElefteria Psillakis()Lucia Sanchez-Prado()Ruth Barro()Maria Llompart()Carmen Garcia-Jares()Marta Lores()Experimentalhttp://purl.tuc.gr/dl/dias/E9F87FF1-12ED-4633-A1B2-46873FE063DC10.1016/j.ultsonch.2008.01.007Published at: 2015-09-24eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2008Summarization: The sonochemical degradation of 5 lg l1 triclosan, a priority micro-pollutant, in various environmental samples (seawater, urban
runoff and influent domestic wastewater) as well as in model solutions (pure and saline water) was investigated. Experiments were conducted
with a horn-type sonicator operating at 80 kHz frequency and a nominal applied power of 135 W, while solid-phase microextraction
coupled with gas chromatography–electron capture detector (SPME/GC–ECD) was employed to monitor triclosan degradation.
The latter followed pseudo-first order kinetics with the rate constant being (min1): 0.2284 for seawater > 0.1051 for 3.5% NaCl in deionised
water > 0.0597 for centrifuged urban runoff 0.0523 for untreated urban runoff > 0.0272 for deionised water > 0.0063 for wastewater
influent. SPME/GC–ECD and SPME coupled with gas chromatography–mass spectrometry (SPME/GC–MS) were also used to
check for the formation of chlorinated and other toxic by-products; at the conditions in question, the presence of such compounds
was not confirmed.ElsevierΠαρουσιάστηκε στο: Ultrasonics sonochemistrypeer-reviewedΒιβλιογραφική αναφορά: L.Sanchez-Prado, R. Barro, C. G. Jares, M. Llompart, M. Lores, C. Petrakis, N.Kalogerakis, D. Mantzavinos, E.Psillakis , "Sonochemical degradation of triclosan in water and wastewater ",Ultras. Sonochemi. , vol . 15 ,no.5 ,pp. 689–694,2008.doi:10.1016/j.ultsonch.2008.01.007info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315792012-10-10T00:00:00Z28info:eu-repo/semantics/articleComplexes of a new bidentate chelating pyridyl/sulfonamide ligand with copper(II), cobalt(II) and palladium(II): crystal structures and spectroscopic propertiesElefteria Psillakis()Carl A Otter() Samantha M Couchman()John C Jeffery() Karen LV Mann()Michael D Ward()http://purl.tuc.gr/dl/dias/E9BDD35A-9831-42EE-A8AF-C163C729E75F10.1016/S0020-1693(98)00018-8Published at: 2015-09-24eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1998Summarization: Reaction of the bidentate ligand 2-(2-aminophenyl)pyridine with p-toluenesulfonyl chloride afforded the new bidentate ligand HL which contains potentially chelating pyridyl and (protonated) sulfonamide N-donor binding sites. The crystal structure of the ligand shows that the sulfonamide NH proton is involved in a hydrogen-bonding interaction with the pyridyl N atom, resulting in a near-coplanar arrangement of the pyridyl and phenyl rings.ElsevierΠαρουσιάστηκε στο: Inorganica chimica actapeer-reviewedBibliographic citation: C. A Otter, S. M Couchman, J. C Jeffery, K. LV Mann, E. Psillakis, M.D Ward , "Complexes of a new bidentate chelating pyridyl/sulfonamide ligand with copper(II), cobalt(II) and palladium(II): crystal structures and spectroscopic properties ", Inor.a chimica acta , vol. 278, no. 2, pp. 178–184 ,1998.doi:10.1016/S0020-1693(98)00018-8info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315852012-10-10T00:00:00Z28info:eu-repo/semantics/articleLanthanide complexes of the tetradentate N-donor liganddihydrobis[3-(2-pyridyl)pyrazolyl]borate and the terdentate N-donorligand 2,6-bis(1H-pyrazol-3-yl)pyridine: syntheses, crystalstructures and solution structures based on luminescence lifetime studiesElefteria Psillakis()Peter L Jones()Michael D Ward()David A Bardwell()http://purl.tuc.gr/dl/dias/09A3DF92-055B-4A2C-AC50-2493BDB0BFDB10.1039/A701297GPublished at: 2015-09-24eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1997Summarization: Lanthanide complexes of two polydentate N-donor ligands containing a mixture of pyridyl and pyrazolyl donors have been prepared. Dihydrobis[3-(2-pyridyl)pyrazolyl]borate (L 1 ) - is a tetradentate ligand with two bidentate chelating pyridyl/pyrazolyl arms linked by an apical BH 2 group; 2,6-bis(1H-pyrazol-3-yl)pyridine (L 2 ) is a terdentate chelating ligand reminiscent of terpyridine. Reaction of L 1 with lanthanide salts gave complexes of the type [M(L 1 ) 2 X] n+ ; the crystal structures of [Eu(L 1 ) 2 (dmf)][ClO 4 ]· 2.5CH 2 Cl 2 , [Tb(L 1 ) 2 (NO 3 )]·2CH 2 Cl 2 and [Tb(L 1 ) 2 (H 2 O)][L 1 ]· H 2 O·0.5CH 2 Cl 2 were determined and all contain two tetradentate ligands L 1 and an ancillary ligand X [dimethylformamide (dmf), nitrate or water] whose nature depends on the reaction/recrystallisation conditions to complete the co-ordination sphere. Luminescence studies of [Tb(L 1 ) 2 (NO 3 )] in water or D 2 O and MeOH or CD 3 OD showed that in methanol the solvation number q is ≈1.8, consistent with displacement of nitrate by the solvent; however in water q ≈ 4.5, indicating additional displacement of some of the N-donor heterocyclic rings of L 1 by co-ordinating water molecules. Reaction of L 2 with lanthanide salts afforded [M(L 2 ) 3 ] 3+ , all isolated as their hexafluorophosphate salts. The crystal structures of three of these (M = Eu, Gd or Ho) showed that they are isostructural and isomorphous, with tricapped trigonal-prismatic nine-co-ordinate geometries similar to that of [M(terpy) 3 ] 3+ (terpy = 2,2′:6′,2″- terpyridine). Royal Society of ChemistryΠαρουσιάστηκε στο: Journal of the Chemical Society, Dalton Transactionspeer-reviewedBibliographic citation: D. A Bardwell, J. C Jeffery, P. L Jones, J. A McCleverty, E. Psillakis, Z. Reeves, M.D Ward , "Lanthanide complexes of the tetradentate N-donor liganddihydrobis[3-(2-pyridyl)pyrazolyl]borate and the terdentate N-donorligand 2,6-bis(1H-pyrazol-3-yl)pyridine: syntheses, crystalstructures and solution structures based on luminescence lifetime studies " ,J. Chem. Soc., Dalton Trans.,no.12 , pp. 2079-2086, 1997.doi:10.1039/A701297Ginfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315872012-10-10T00:00:00Z28info:eu-repo/semantics/articleCopper(II)-templated assembly of tetranuclear grid-like complexesfrom simple pyridine–pyrazole ligands Elefteria Psillakis() Karen LV Mann()Jon A McCleverty() Claire M White()http://purl.tuc.gr/dl/dias/A71FF72D-711A-4221-8DEB-819568FAECC610.1039/A606827HPublished at: 2015-09-24eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1997Summarization: Reaction of Cu(O 2 CMe) 2 ·H 2 O with HL 1 [3-(2-pyridyl)pyrazole] or HL 2 [6-(3-pyrazolyl)-2,2′-bipyridine] and NH 4 PF 6 followed by crystallisation of the crude products from dmf–ether affords [Cu 4 L 1 6 (dmf) 2 ][PF 6 ] 2 1 and [Cu 4 L 2 4 (dmf) 4 ]- [PF 6 ] 4 2 respectively, in which the deprotonated pyrazolyl groups act as bridging ligands and the 2 × 2 grid–like architectures are a result of the preference of the Cu II ions for elongated square-pyramidal coordination geometries. Royal Society of ChemistryΠαρουσιάστηκε στο: Chemical Communicationspeer-reviewedΒιβλιογραφική αναφορά: J. C Jeffery, P.L Jones, K. LV Mann, E. Psillakis, J. A McCleverty, M. D Ward, C. M White , "Copper(II)-templated assembly of tetranuclear grid-like complexesfrom simple pyridine–pyrazole ligands ",Ch.Communicat.,vol. 2 ,pp.175-176,1997.doi : 10.1039/A606827H
info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:317142012-10-10T00:00:00Z28info:eu-repo/semantics/articleA dinuclear double-helical complex of potassium ions with acompartmental bridging ligand containing two terdentate N-donorfragmentsElefteria Psillakis()Johná C Jeffery()Joná A McCleverty()Michaelá D Ward()http://purl.tuc.gr/dl/dias/012693B1-F045-4C4F-87C7-7BE9D10DAD6D 10.1039/A607984IPublished at: 2015-09-24eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1997Summarization: Recently helicates have become a well known structural motif in supramolecular coordination
chemistry.1–4 They are of particular interest not just for their appealing structures but also because
of the processes of molecular recognition and self- assembly that are required for their
formation. Their formation requires (i) ligands which contain several discrete metal-ion binding
domains, and (ii) metal ions with specific preferences for particular coordination geometries that
match the ligand binding sites.Royal Society of ChemistryΠαρουσιάστηκε στο: Chemical Communicationspeer-reviewedBibliographic citation: J. C Jeffery, J. A McCleverty, M. D Ward ,E.Psillakis , "A dinuclear double-helical complex of potassium ions with acompartmental bridging ligand containing two terdentate N-donorfragments " ,Chem. Commun.,vol.5 , pp. 479-480, 1997.doi: 10.1039/A607984Iinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:317382012-10-10T00:00:00Z28info:eu-repo/semantics/articleSynthesis, crystal structure and some reactions of the ruthenacarborane complex [Ru(CO)2(MeC,CPh)(η5-7,8-C2B9H11]. Elefteria Psillakis()John C Jeffery()Paul A Jelliss()Gillian EA Rudd()F Gordon A Stone()http://purl.tuc.gr/dl/dias/BACF5449-143C-438E-B2AF-813C55CEE3E510.1016/S0022-328X(98)00363-5Published at: 2015-09-24eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1998Περίληψη: The alkyne complex [Ru(CO) 2 (MeC,CPh)(η 5 -7,8-C 2 B 9 H 11 ] (3c) has been prepared and its structure determined by X-ray crystallography. The ruthenium is co-ordinated on one side by the nido-7,8-C 2 B 9 H 11 fragment in a pentahapto manner, and on the other by the two CO molecules and the alkyne [Ru–C av. =2.305, C–C=1.228(3) Å. Treatment of 3c with PEt 3 and Ph 2 PCH 2 PPh 2 in CH 2 Cl 2 affords the ylid complexes [Ru{C(Me)C(Ph)PEt 3 }(CO) 2 (η 5 -7,8-C 2 B 9 H 11 )] (4b) and [Ru{C(Me)C(Ph)P(Ph) 2 CH 2 PPh 2 }(CO) 2 (η 5 -7,8-C 2 B 9 H 11 )] (4c), respectively. The structure of 4b was established by an X-ray diffraction study which revealed that the PEt 3 molecule was attached to the carbon atom of the CPh group. In contrast, reactions between 3c and the donor molecules AsPh 3 , SbPh 3 and Ph 2 P(S)CH 2 P(S)Ph 2 resulted in displacement of the alkyne and formation of the complexes [Ru(CO) 2 (L)(η 5 -7,8-C 2 B 9 H 11 )] (5a, L=AsPh 3 ; 5b, L=SbPh 3 ; 5c, L=Ph 2 P(S)CH 2 P(S)Ph 2 ). Treatment of 4c with the Ru(CO) 2 (η 5 -7,8-C 2 B 9 H 11 ) fragment yielded the diruthenium complex [Ru 2 (μ-Ph 2 PCH 2 PPh 2 )(CO) 4 (η 5 -7,8-C 2 B 9 H 11 ) 2 ] (6). The structure, based on the linking of two Ru(CO) 2 (η 5 -7,8-C 2 B 9 H 11 ) groups by the ligand Ph 2 PCH 2 PPh 2 , was determined by X-ray crystallography. NMR data for the new complexes are reported.ElsevierΠαρουσιάστηκε στο: Journal of organometallic chemistrypeer-reviewedΒιβλιογραφική αναφορά: J.C Jeffery, P. A Jelliss, E.Psillakis, G. EA Rudd, F G. A Stone, "Synthesis, crystal structure and some reactions of the ruthenacarborane complex [Ru(CO)2(MeC,CPh)(η5-7,8-C2B9H11] ",J. of organ. chem.,vol. 562,no.1,pp.17-27,1998.doi:10.1016/S0022-328X(98)00363-5info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:317392012-10-10T00:00:00Z28info:eu-repo/semantics/articleLow temperature SPME device: A convenient and effective tool for investigating photodegradation of volatile analytesElefteria Psillakis()Janusz Pawliszyn()Sanja Risticevic()Lucia Sanchez-Prado()http://purl.tuc.gr/dl/dias/6F00AA1A-0854-4E07-945D-35C8E6401EAF10.1016/j.jphotochem.2009.07.009Published at: 2015-09-24eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2009Summarization: Hexachlorobenzene (HCB), a model volatile compound, was exposed to UV irradiation (16 W, 254 nm) after being sorbed in an internally cooled or low temperature solid-phase microextraction (LT-SPME) fibre. Photolysis took place directly on the polydimethylsiloxane coating of the LT-SPME fibre, yielding an “in situ” generation of photoproducts. Maintaining the temperature of the cold fibre at 0 °C eliminated, for the first time, problems of analyte losses due to volatilisation, inherent to the conventional room temperature photo-SPME studies. During the present studies, nearly complete photoremoval of HCB could be achieved within 20 min of irradiation. Photoreduction through photodechlorination was shown to be the main decay pathway in which lesser chlorinated congeners were sequentially formed as intermediates. Accordingly, initial generation of pentachlorobenzene was followed in order from 1,2,3,5-tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene and 1,3,5-trichlorobenzene. ElsevierΠαρουσιάστηκε στο: Journal of Photochemistry and Photobiology A: Chemistrypeer-reviewedBibliographic citation: L.S.Prado, S. Risticevic, J. Pawliszyn, E. Psillakis , "
Low temperature SPME device: A convenient and effective tool for investigating photodegradation of volatile analyte ",J. of Photoch. and Phot. A: Ch.,vol.206, no.2,pp.227-230,2009. doi: 10.1016/j.jphotochem.2009.07.009info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:317712012-10-10T00:00:00Z28info:eu-repo/semantics/articlePhotolysis of 2,4-dinitrotoluene in various water solutions: effect of dissolved speciesElefteria Psillakis()Orestis Mihas()Nicolas Kalogeraki()http://purl.tuc.gr/dl/dias/90E78EB9-010C-4DC9-A829-B99A99C015C710.1016/j.jhazmat.2007.04.054Published at: 2015-09-24eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: This work investigates the photolysis of 2,4-dinitrotoluene (2,4-DNT) in the presence of different dissolved species. Initial experiments revealed that the direct photolysis of 2,4-DNT in deionized water solutions under sunlight and artificial light followed a pseudo-first order kinetic. Humic acids (HA) appeared to act as sensitizers in the aqueous photolysis of 2,4-DNT and the calculated half life was found to be approximately 2 h, which is faster than the half life calculated in the case of deionized water (∼4 h). The presence of salt (NaCl) in the deionized water solutions was found to have a more pronounced sensitizing effect upon the photolysis of 2,4-DNT, yielding half lives of the order of 1 h. Investigations on seawater and groundwater spiked with 2,4-DNT, revealed that photolysis is enhanced in the order seawater > groundwater∼deionized water.Παρουσιάστηκε στο: Journal of hazardous materialspeer-reviewedBibliographic citation: O. Mihas, N. Kalogerakis, E.Psillakis , "Photolysis of 2,4-dinitrotoluene in various water solutions: effect of dissolved species ",J. of hazar. mat.,vol.146,no.3,pp.535-539,2007. doi:10.1016/j.jhazmat.2007.04.054info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:317722012-10-10T00:00:00Z28info:eu-repo/semantics/articleNanofibrillar Cellulose-Chitosan Composite Film Electrodes: Competitive Binding of Triclosan, Fe(CN)63−/4−, and SDS SurfactantElefteria Psillakis()Kostoula Tsourounaki()Michael J Bonne()Matthew Helton()Anthony McKee()Frank Marken() Wim Thielemans()http://purl.tuc.gr/dl/dias/A6ECBF48-FB7D-4C31-99BD-01DFCCE5EECA10.1002/elan.200804338Published at: 2015-09-24eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2008Summarization: Glassy carbon electrodes are modified with a thin film of a cellulose-chitosan nanocomposite. Cellulose nanofibrils (of ca. 4 nm diameter and 250 nm length) are employed as an inert backbone and chitosan (poly-d-glucosamine, low molecular weight, 75–85% deacetylated) is introduced as a structural binder and “receptor” or molecular binding site. The composite films are formed in a solvent evaporation method and prepared in approximately 0.8 μm thickness. WILEY‐VCH VerlagΠαρουσιάστηκε στο: Electroanalysispeer-reviewedBibliographic citation: K. Tsourounaki, M. J Bonne, W. Thielemans, E. Psillakis, M. Helton, A. McKee, F. Marken, "Nanofibrillar Cellulose-Chitosan Composite Film Electrodes: Competitive Binding of Triclosan, Fe(CN)63−/4−, and SDS Surfactant ",Electroan.,vol.20, no.22, pp.2395-2402,2008.doi:10.1002/elan.200804338info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:317732012-10-10T00:00:00Z28info:eu-repo/semantics/articleThe coordination chemistry of mixed pyridine-phenol and phenanthroline-phenol ligands; The crystal structure of 2-(2-hydroxyphenyl)-1,10-phenanthroline (HL) and the crystal structure and properties of [FeL2][PF6]
Elefteria Psillakis()John C Jeffery()Charlotte SG Moore()Michael D Ward()Peter Thornton()http://purl.tuc.gr/dl/dias/1A6A82FD-4B5E-4A03-AF86-9AEF3B52B8BD10.1016/0277-5387(94)00281-IPublished at: 2015-09-24eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1995Summarization: The crystal structures of the N,N,O-terdentate ligand 2-(2-hydroxyphenyl)-1,10-phenanthroline (HL) and its Fe(III) complex [FeL2][PF6] (1) have been determined. In HL, an intramolecular OH … N hydrogen bond between the phenolic OH and the adjacent nitrogen atom of the phenanthroline fragment constrains these two donor atoms to be cisoid, with the proton ‘chelated’. The molecules of HL are associated into pairs in the crystal via a face-to-face aromatic π-stacking interaction. Complex 1 has a conventional distorted octahedral structure; sections of the aromatic ligands overlap between adjacent molecules to form an interleaved stack. It is high-spin down to 83 K, and its EPR spectrum (frozen glass at 77 K) is entirely typical of a rhombically distorted high-spin FeIII site.PergamonΠαρουσιάστηκε στο: Polyhedronpeer-reviewedBibliographic citation: J. C Jeffery, C. S. Moore, E. Psillakis, M. D Ward, P.Thornton , "The coordination chemistry of mixed pyridine-phenol and phenanthroline-phenol ligands; The crystal structure of 2-(2-hydroxyphenyl)-1,10-phenanthroline (HL) and the crystal structure and properties of [FeL2][PF6] ",Polyh.,vol.14,no.5,pp.599-604,1995.doi:10.1016/0277-5387(94)00281-Iinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318562012-10-10T00:00:00Z28info:eu-repo/semantics/articleIce photolysis of 2,2′,4,4′,6-pentabromodiphenyl ether (BDE-100): Laboratory investigations using solid phase microextractionElefteria Psillakis()Nicolas Kalogerakis()Maria Llompart()http://purl.tuc.gr/dl/dias/F4D57170-E8FF-4B13-B354-79AD2827056C10.1016/j.aca.2012.06.012Published at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2012Summarization: Here, we report for the first time a laboratory investigation into the photochemical degradation of 2,2′,4,4′,6-pentabromodiphenyl ether (BDE-100) in ice solid samples using an artificial UV light source. Solid phase microextraction (SPME) was used as a sensitive extraction technique for monitoring trace amounts of the hydrophobic pollutant and its photoproducts. The results showed that ice photolysis kinetics for BDE-100 is similar to the one observed in the aqueous counterpart. The eight photoproducts identified consisted of brominated diphenyl ethers with lower bromine content and polybrominated dibenzofurans, suggesting two important photodegradation pathways for BDE-100 in ice solid samples: (i) stepwise reductive debromination and (ii) intramolecular elimination of HBrElsevierΠαρουσιάστηκε στο: Analytica chimica actapeer-reviewedBibliographic citation: L.S. Prado, K. Kalafata, S. Risticevic, J. Pawliszyn, M. Lores, M. Llompart, N. Kalogerakis, E.Psillakis , "Ice photolysis of 2,2′,4,4′,6-pentabromodiphenyl ether (BDE-100): Laboratory investigations using solid phase microextraction " ,Anal. ch. acta., vol. 742,pp.90-96,2012.doi:10.1016/j.aca.2012.06.012info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318582012-10-10T00:00:00Z28info:eu-repo/semantics/articleComparison of pah levels and sources in pine needles from Portugal, Spain, and GreeceElefteria Psillaki()Arminda Alves()Damià Barceló()Nuno Ratola() José Manuel Amigo()Sílvia Lacorte()http://purl.tuc.gr/dl/dias/562877B5-FB06-4CDE-A35A-AD786A738FD310.1080/00032719.2011.649452Published at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2012Summarization: The main objective of this work was to assess and compare the levels, patterns, and sources of contamination of 16 polycyclic aromatic hydrocarbons (PAHs) between Portugal, Spain, and Greece (in the island of Crete). A total of 9 sampling sites were chosen (4 in urban and 5 in non-urban areas) in each country and pine needles from the Pinus pinea L. species were collected. Although the mean total PAH levels was similar in the three countries (279 ± 236 ng g−1 for Portugal, 294 ± 258 ng g−1 for Spain, 301 ± 253 ng g−1 for Greece, all dry weight) and, in general, 3-ring and 4-ring PAHs were predominant (being phenanthrene consistently the most abundant), there were some visible differences in the aromatic ring patterns and possible sources between the three regions. Source apportionment was done using PAH ratios (Phen/Ant and Flt/Pyr crossplots) and reflected mixed petrogenic and pyrogenic sources. Furthermore, Principal Component Analysis (PCA) clearly separated the urban and the non-urban sites and all three countries, which reinforces that the sources of contaminations vary in each case and the suitability of pine needles for trans-boundary biomonitoring of PAHs.Taylor & Francis GroupΠαρουσιάστηκε στο: Analytical Letterspeer-reviewedBibliographic citation: N. Ratola, J. M.Amigo, S. Lacorte, D. Barceló, E. Psillakis, A. Alves , "Comparison of pah levels and sources in pine needles from Portugal, Spain, and Greece",Anal. Let.,vol.45,no.5-6,pp.508-525, 2012.doi:10.1080/00032719.2011.649452info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318592012-10-10T00:00:00Z28info:eu-repo/semantics/articleRapid determination of octanol-water partition coefficient using vortex-sssisted liquid-liquid microextractionElefteria Psillakis()Antonio Canals()Konstantina Tyrovola()Anna Mastromichali()Iván P Román()EXPERIMENTALhttp://purl.tuc.gr/dl/dias/4DA97208-D579-452D-8655-FF32E7FC9B9310.1016/j.chroma.2014.01.003Published at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2014Summarization: Abstract Vortex-assisted liquid–liquid microextraction (VALLME) coupled with high-
performance liquid chromatography (HPLC) is proposed here for the rapid determination of
octanol–water partitioning coefficients (K ow). VALLME uses vortex agitation, a mild
emulsification procedure, to disperse microvolumes of octanol in the aqueous phase thus
increasing the interfacial contact area and ensuring faster partitioning rates. With VALLME, 2
min were enough to achieve equilibrium conditions between the octanolic and aqueous .ElsevierΠαρουσιάστηκε στο: Journal of Chromatography Apeer-reviewedBibliographic citation: I. P Román, A. Mastromichali, K. Tyrovola, A. Canals, E. Psillakis , "Rapid determination of octanol–water partition coefficient using vortex-assisted liquid–liquid microextraction ",J. of Chromat.,vol.1330, pp. 1–5,2014,doi:10.1016/j.chroma.2014.01.003info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318652012-10-10T00:00:00Z28info:eu-repo/semantics/articleSolid phase microextraction to determine the migration of phthalates from plastic ware to drinking water K Perdikea()N Kalogerakis()E Psillakis()http://purl.tuc.gr/dl/dias/E5219720-B6B4-4F89-8AFA-7EDCC557FBD3http://conferences.gnest.org/cest8/8cest_papers/abstracts_pdf_names/p118_Perdikea.pdfPublished at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2003Summarization: Overall, the results revealed that significant quantities of phthalates are expected to be
present in drinking water samples coming into direct contact with disposable plastic items at
elevated temperatures. The contamination level is higher when a prolonged exposure to
such temperatures is applied. Therefore, it is strongly advisable to control temperature
during the transfer, storage and/or handling of these materials. Key words: SPME, phthalate
esters, drinking water, water analysisΠαρουσιάστηκε στο: Proceedings of the 8th International Conference on Environmental Science and Technology peer-reviewedBibliographic citation: K. Perdikea, E. Psillakis, N. Kalogerakis .(2003,Sept.). Solid phase microextraction to determine the migration of phthalates from plastic ware to drinking water. Presented at the 8th International Conference on Environmental Science and Technology.[online]. Available :http://conferences.gnest.org/cest8/8cest_papers/abstracts_pdf_names/p118_Perdikea.pdfinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318672012-10-10T00:00:00Z28info:eu-repo/semantics/articleVacuum-assisted headspace solid phase microextraction of polycyclic aromatic hydrocarbons in solid samplesElefteria Psillakis()Nicolas Kalogerakis()Evangelia Yiantzi()http://purl.tuc.gr/dl/dias/2A1F1881-63AF-42FD-8DB0-8AE9E3C066F410.1016/j.aca.2015.05.047Published at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2015Summarization: For the first time, Vacuum Assisted Headspace Solid Phase Microextraction (Vac-HSSPME) is used for the recovery of polycyclic aromatic hydrocarbons (PAHs) from solid matrices. The procedure was investigated both theoretically and experimentally. According to the theory, reducing the total pressure increases the vapor flux of chemicals at the soil surface, and hence improves HSSPME extraction kinetics. Vac-HSSPME sampling could be further enhanced by adding water as a modifier and creating a slurry mixture. For these soil-water mixtures, reduced pressure conditions may increase the volatilization rates of compounds with a low KH present in the aqueous phase of the slurry mixture and result in a faster HSSPME extraction process. Nevertheless, analyte desorption from soil to water may become a rate-limiting step when significant depletion of the aqueous analyte concentration takes place during Vac-HSSPME. Sand samples spiked with PAHs were used as simple solid matrices and the effect of different experimental parameters was investigated (extraction temperature, modifiers and extraction time). Vac-HSSPME sampling of dry spiked sand samples provided the first experimental evidence of the positive combined effect of reduced pressure and temperature on HSSPME. Although adding 2 mL of water as a modifier improved Vac-HSSPME, humidity decreased the amount of naphthalene extracted at equilibrium as well as impaired extraction of all analytes at elevated sampling temperatures. Within short HSSPME sampling times and under mild sampling temperatures, Vac-HSSPME yielded linear calibration curves in the range of 1–400 ng g−1 and, with the exception of fluorene, regression coefficients were found higher than 0.99. The limits of detection for spiked sand samples ranged from 0.003 to 0.233 ng g−1 and repeatability from 4.3 to 10 %. Finally, the amount of PAHs extracted from spiked soil samples was smaller compared to spiked sand samples, confirming that soil could bind target analytes more strongly and thus decrease the readily available fraction of target analytes.ElsevierPresented on: Analytica Chimica Actapeer-reviewedBibliographic citation: E. Yiantzi, N. Kalogerakis, E. Psillakis , "Vacuum-assisted headspace solid phase microextraction of polycyclic aromatic hydrocarbons in solid samples ",Anal. Chim. Act. ,vol. 890, pp. 108–116,August 2015.doi:10.1016/j.aca.2015.05.047info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318742012-10-10T00:00:00Z28info:eu-repo/semantics/articleStochastic diagrammatic analysis of groundwater flow in heterogeneous porous mediaG. Christakos()D.T. Hristopulos()C.T. Miller()http://purl.tuc.gr/dl/dias/2E34F867-D8D9-401F-90BA-36FC80D9079B10.1029/95WR00733Published at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1995Summarization: The diagrammatic approach is an alternative to standard analytical methods for solving stochastic differential equations governing groundwater flow with spatially variable hydraulic conductivity. This approach uses diagrams instead of abstract symbols to visualize complex multifold integrals that appear in the perturbative expansion of the stochastic flow solution and reduces the original flow problem to a closed set of equations for the mean and the covariance functions. Diagrammatic analysis provides an improved formulation of the flow problem over conventional first-order series approximations, which are based on assumptions such as constant mean hydraulic gradient, infinite flow domain, and neglect of cross correlation terms. This formulation includes simple schemes, like finite-order diagrammatic perturbations that account for mean gradient trends and boundary condition effects, as well as more advanced schemes, like diagrammatic porous media description operators which contain infinite-order correlations. In other words, diagrammatic analysis covers not only the cases where low-order diagrams lead to good approximations of flow, but also those situations where low-order perturbation is insufficient and a more sophisticated analysis is needed. Diagrams lead to a nonlocal equation for the mean hydraulic gradient in terms of which necessary conditions are formulated for the existence of an effective hydraulic conductivity. Three-dimensional flow in an isotropic bounded domain with Dirichlet boundary conditions is considered, and an integral equation for the mean hydraulic head is derived by means of diagrams. This formulation provides an explicit expression for the boundary effects within the three-dimensional flow domain. In addition to these theoretical results, the numerical performance of the diagrammatic approach is tested, and useful insight is obtained by means of one-dimensional flow examples where the exact stochastic solutions are available.Παρουσιάστηκε στο: Water Resources Researchpeer-reviewedBibliographic citation: G. Christakos, D.T. Hristopulos and C.T. Miller , "Stochastic diagrammatic analysis of groundwater flow in heterogeneous porous Media ", Wat. Resour. Res.,vol. 31,no.7 ,pp. 1687-1703,1995.doi :10.1029/95WR00733info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318912012-10-10T00:00:00Z28info:eu-repo/semantics/articlePermissibility of fractal exponents and models of band-limited two-point functions for fGn and fBm random fields
D.T. Hristopulos()http://purl.tuc.gr/dl/dias/B07C5CA5-0A02-4726-BA02-7C49A7B42F9810.1007/s00477-003-0126-8Published at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2003Summarization: The fractional Gaussian noise (fGn) and fractional Brownian motion (fBm) random field models have many applications in the environmental sciences. An issue of practical interest is the permissible range and the relations between different fractal exponents used to characterize these processes. Here we derive the bounds of the covariance exponent for fGn and the Hurst exponent for fBm based on the permissibility theorem by Bochner. We exploit the theoretical constraints on the spectral density to construct explicit two-point (covariance and structure) functions that are band-limited fractals with smooth cutoffs. Such functions are useful for modeling a gradual cutoff of power-law correlations. We also point out certain peculiarities of the relations between fractal exponents imposed by the mathematical bounds. Reliable estimation of the correlation and Hurst exponents typically requires measurements over a large range of scales (more than 3 orders of magnitude). For isotropic fractals and partially isotropic self-affine processes the dimensionality curse is partially lifted by estimating the exponent from measurements along fixed directions. We derive relations between the fractal exponents and the one-dimensional spectral density exponents, and we illustrate the relations using measurements of paper roughness.Springer-VerlagΠαρουσιάστηκε στο: Stochastic Environmental Research and Risk Assessmentpeer-reviewedBibliographic citation: D.T. Hristopulos, "Permissibility of fractal exponents and models of band-limited two-point functions for fGn and fBm random fields, Stoch. Envir. Res. and Risk Ass.,vol.17 ,no.3, pp. 191-216 ,2003.doi:10.1007/s00477-003-0126-8info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:318962012-10-10T00:00:00Z28info:eu-repo/semantics/articleSpatial random field models inspired from statistical physics with applications in the geosciencesD.T. Hristopulos()http://purl.tuc.gr/dl/dias/FFDF8219-E0EE-4E39-96D8-23B17CEC670110.1016/j.physa.2006.01.037Published at: 2015-09-25eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2006Summarization: The spatial structure of fluctuations in spatially inhomogeneous processes can be modeled in terms of Gibbs random fields. A local low energy estimator (LLEE) is proposed for the interpolation (prediction) of such processes at points where observations are not available. The LLEE approximates the spatial dependence of the data and the unknown values at the estimation points by low-lying excitations of a suitable energy functional. It is shown that the LLEE is a linear, unbiased, non-exact estimator. In addition, an expression for the uncertainty (standard deviation) of the estimate is derivedΠαρουσιάστηκε στο: Physica A: Statistical Mechanics and its Applicationspeer-reviewedBibliographic citation: D.T. Hristopulos, " Spartan spatial random field models inspired from statistical physics with applications in the geosciences " , Physi. A: Stati. Mech. and its Ap.,vol. 365,no. 1-2,pp. 211-216,2006.doi:10.1016/j.physa.2006.01.037info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:331312012-10-10T00:00:00Z28info:eu-repo/semantics/articleAdvanced fuzzy logic controllers design and evaluation for buildings’ occupants thermal–visual comfort and indoor air quality satisfactionΚολοκοτσα Διονυσια(http://users.isc.tuc.gr/~dkolokotsa)Kolokotsa Dionysia(http://users.isc.tuc.gr/~dkolokotsa)Tsiavos D.()Σταυρακακης Γεωργιος(http://users.isc.tuc.gr/~gstavrakakis)Stavrakakis Georgios(http://users.isc.tuc.gr/~gstavrakakis)Καλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Antonidakis E.()Δημοσίευση σε επιστημονικό περιοδικό fuzzy logicSelf-adaptive control systems,adaptive control systems,self adaptive control systemsReference model Energy consumptionBuilding users satisfactionhttp://purl.tuc.gr/dl/dias/9BAF1FA8-17BB-4D9C-8DFD-D039059C5CF4http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.18.pdf 10.1016/S0378-7788(00)00098-0Published at: 2015-09-29eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2001Summarization: The aim of this paper is to present and evaluate control strategies for adjustment and preservation of air quality, thermal and visual comfort for buildings’ occupants while, simultaneously, energy consumption reduction is achieved. Fuzzy PID, fuzzy PD and adaptive fuzzy PD control methods are applied. The inputs to any controller are: the PMV index affecting thermal comfort, the CO2 concentration affecting indoor air quality and the illuminance level affecting visual comfort. The adaptive fuzzy PD controller adapts the inputs and outputs scaling factors and is based on a second order reference model. More specifically, the scaling factors are modified according to a sigmoid type function, in such a way that the measured variable to be as closer as possible to the reference model. The adaptive fuzzy PD controller is compared to a non-adaptive fuzzy PD and to an ON–OFF one. The comparison criteria are the energy required and the controlled variables response. Both, energy consumption and variables responses are improved if the adaptive fuzzy PD type controller is used. The buildings’ response to the control signals has been simulated using MATLAB/SIMULINK.ElsevierPresented on: Energy and Buildingspeer-reviewedBibliographic citation: D. Kolokotsa, D. Tsiavos, G.S Stavrakakis, K. Kalaitzakis and E. Antonidakis, "Advanced fuzzy logic controllers design and evaluation for buildings’ occupants thermal–visual comfort and indoor air quality satisfaction," Energy and Buildings, vol. 33, no. 6, pp. 531-543, Jul. 2001. doi:10.1016/S0378-7788(00)00098-0info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:331712012-10-10T00:00:00Z28info:eu-repo/semantics/articleInterconnecting smart card system with PLC controller in a local operating network to form a distributed energy management and control system for buildingsΚολοκοτσα Διονυσια(http://users.isc.tuc.gr/~dkolokotsa)Kolokotsa Dionysia(http://users.isc.tuc.gr/~dkolokotsa)Καλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Antonidakis E.()Σταυρακακης Γεωργιος(http://users.isc.tuc.gr/~gstavrakakis)Stavrakakis Georgios(http://users.isc.tuc.gr/~gstavrakakis)Δημοσίευση σε επιστημονικό περιοδικό Control networksDistributed control Local networkCards, Smart,Chip cards,IC cards,Integrated circuit cards,Memory cards,smart cards,cards smart,chip cards,ic cards,integrated circuit cards,memory cards PLCFuzzy controlBuildings energy managementhttp://purl.tuc.gr/dl/dias/1E05DF61-B0D6-4F94-AB0C-7D76C6ECAC31http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.20.pdf 10.1016/S0196-8904(01)00013-9Published at: 2015-09-30eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2002Summarization: Distributed control and energy management for buildings is a viable solution, ensuring both indoor comfort for the occupants and reduction of energy consumption. The aim of this paper is to present the architecture of a distributed building energy management system that can be installed in new as well as in existing buildings, which are more energy inefficient. The system integrates a smart card unit, acting as a user machine interface, sensors, actuators, interfaces, a PLC controller that incorporates the fuzzy control algorithm, local operating network (LON) modules and devices and an optional PC which monitors the performance of the system. The distributed control architecture is based on the properties of the LON. The complete system is installed and tested in the Laboratory of Electronics of the Technical University of Crete.ElsevierPresented on: Energy Conversion and Managementpeer-reviewedBibliographic citation: D. Kolokotsa, K. Kalaitzakis, E. Antonidakis and G.Stavrakakis, "Interconnecting smart card system with PLC controller in a local operating network to form a distributed energy management and control system for buildings," Energy Conversion and Management, vol. 43, no. 1, pp. 119-134, Jan. 2002. doi:10.1016/S0196-8904(01)00013-9info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:331732012-10-10T00:00:00Z28info:eu-repo/semantics/articleShort-term load forecasting based on artificial neural networks parallel implementation.Καλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Σταυρακακης Γεωργιος(http://users.isc.tuc.gr/~gstavrakakis)Stavrakakis Georgios(http://users.isc.tuc.gr/~gstavrakakis)Anagnostakis E.()Δημοσίευση σε επιστημονικό περιοδικό Short-term load forecastingMoving window regression trainingGaussian encoding neural networksRadial basis networksReal time recurrent neural networkshttp://purl.tuc.gr/dl/dias/48FF40D6-9765-4A7F-80B1-78F0206E3D79http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.22.pdf 10.1016/S0378-7796(02)00123-2Published at: 2015-09-30eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2002Summarization: This paper presents the development and application of advanced neural networks to face successfully the problem of the short-term electric load forecasting. Several approaches including Gaussian encoding backpropagation (BP), window random activation, radial basis function networks, real-time recurrent neural networks and their innovative variations are proposed, compared and discussed in this paper. The performance of each presented structure is evaluated by means of an extensive simulation study, using actual hourly load data from the power system of the island of Crete, in Greece. The forecasting error statistical results, corresponding to the minimum and maximum load time-series, indicate that the load forecasting models proposed here provide significantly more accurate forecasts, compared to conventional autoregressive and BP forecasting models. Finally, a parallel processing approach for 24 h ahead forecasting is proposed and applied. According to this procedure, the requested load for each specific hour is forecasted, not only using the load time-series for this specific hour from the previous days, but also using the forecasted load data of the closer previous time steps for the same day. Thus, acceptable accuracy load predictions are obtained without the need of weather data that increase the system complexity, storage requirement and cost.ElsevierPresented on: Electric Power Systems Researchpeer-reviewedBibliographic citation: K. Kalaitzakis, G. Stavrakakis and E. Anagnostakis, "Short-term load forecasting based on artificial neural networks parallel implementation," Electric Power Systems Research, vol. 63, no. 3, pp. 185-196, Oct. 2002. doi:10.1016/S0378-7796(02)00123-2info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:330722012-10-10T00:00:00Z28info:eu-repo/semantics/articleLocal operating networks technology aiming to improve building energy management system performance satisfying the users preferencesΚολοκοτσα Διονυσια(http://users.isc.tuc.gr/~dkolokotsa)Kolokotsa Dionysia(http://users.isc.tuc.gr/~dkolokotsa)Καλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Σταυρακακης Γεωργιος(http://users.isc.tuc.gr/~gstavrakakis)Stavrakakis Georgios(http://users.isc.tuc.gr/~gstavrakakis)Sutherland George()Eftaxias George()Δημοσίευση σε διεθνές επιστημονικό περιοδικό Fuzzy PID controllerIntelligent building energy management systemCost function http://purl.tuc.gr/dl/dias/88B1E38B-3ED0-4AA9-B56E-4FE6A862CB43http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.16.pdf 10.1080/01425910108914372Published at: 2015-09-30eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2001Summarization: The available Building Energy Management Systems (BEMS), although they contribute to a significant reduction of energy consumption and improvement of the indoor environment, they can only be implemented in new buildings. Their installation in existing buildings is far from being cost effective due to the incompatibility of communication protocols between BEMS designed by various manufacturers and unavoidable modifications for data transmission. On the other hand, current research for energy efficient buildings has proved that although the design and the facilities including BEMS aim to satisfy the thermal and visual comfort plus the air quality demands while minimising the energy needs, they often do not reach their goals due to users interference. Latest trends in designing Intelligent Building Energy Management Systems (IBEMS) offer a Man Machine Interface that could store the users preferences and adapt the control strategy accordingly. The objectives of the present paper are to present the advantages of the use of a man machine interface based on a smart card terminal together with fuzzy control techniques in satisfying the users preferences plus to underline the capabilities that the LON network offers to the design. A fuzzy PID controller is developed to reach the first of the above objectives. The monitoring of the energy consumption along with satisfying the users preferences is achieved by the use of a suitable cost function for the whole system. All the above parameters as well as the cost function are kept between acceptable limits. The overall control system including the cost function is modeled and tested using MATLAB/SIMULINK. The implementation of the control system in an existing building requires interconnection of sensors and actuators installed across the building, is well served by the LonWorks technology due to its high standards and flexibility features.
Taylor & FrancisPresented on: International Journal of Solar Energypeer-reviewedBibliographic citation: D. Kolokotsa, K. Kalaitzakis, G. Stavrakakis, G. Sutherland and G. Eytaxias "'Local Operating Networks technology aiming to improve building energy management system performance satisfying the users preferences", Int.Journ. of So. Energy, vol. 21, no. 2-3, pp. 219-242, Jan. 2001, doi:10.1080/01425910108914372info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:331772012-10-10T00:00:00Z28info:eu-repo/semantics/articleGenetic algorithms optimized fuzzy controller for the indoor environmental management in buildings implemented using PLC and local operating networks.Κολοκοτσα Διονυσια(http://users.isc.tuc.gr/~dkolokotsa)Kolokotsa Dionysia(http://users.isc.tuc.gr/~dkolokotsa)Σταυρακακης Γεωργιος(http://users.isc.tuc.gr/~gstavrakakis)Stavrakakis Georgios(http://users.isc.tuc.gr/~gstavrakakis)Καλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Agoris D.()Δημοσίευση σε επιστημονικό περιοδικό Fuzzy controllerGenetic algorithms Control networksLocal operating networks Building indoor environment management systemhttp://purl.tuc.gr/dl/dias/B07042CA-08C8-482F-8853-4E7BA863AA40http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.24.pdf 10.1016/S0952-1976(02)00090-8Published at: 2015-09-30eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2002Summarization: In this paper, an optimized fuzzy controller is presented for the control of the environmental parameters at the building zone level. The occupants’ preferences are monitored via a smart card unit. Genetic algorithm optimization techniques are applied to shift properly the membership functions of the fuzzy controller in order to satisfy the occupants’ preferences while minimizing energy consumption. The implementation of the system integrates a smart card unit, sensors, actuators, interfaces, a programmable logic controller (PLC), local operating network (LON) modules and devices, and a central PC which monitors the performance of the system. The communication of the PLC with the smart card unit is performed using an RS 485 port, while the PLC-PC communication is performed via the LON network. The integrated system is installed and tested in the building of the Laboratory of Electronics of the Technical University of Crete.ElsevierPresented on: Engineering Applications of Artificial Intelligencepeer-reviewedBibliographic citation: D. Kolokotsa, G.S. Stavrakakis, K. Kalaitzakis and D. Agoris, "Genetic algorithms optimized fuzzy controller for the indoor environmental management in buildings implemented using PLC and local operating networks," Engineering Applications of Artificial Intelligence, vol. 15, no. 5, pp. 417-428, Sept. 2002. doi:10.1016/S0952-1976(02)00090-8info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:331792012-10-10T00:00:00Z28info:eu-repo/semantics/articleA survey of video processing techniques for traffic applications.Kastrinaki V.()Ζερβακης Μιχαλης(http://users.isc.tuc.gr/~mzervakis)Zervakis Michalis(http://users.isc.tuc.gr/~mzervakis)Καλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Δημοσίευση σε επιστημονικό περιοδικό Detection, Traffic,Monitoring, Traffic,Surveillance, Traffic,Traffic detection,Traffic surveillance,traffic monitoring,detection traffic,monitoring traffic,surveillance traffic,traffic detection,traffic surveillanceAutomatic vehicle guidanceAutomatic lane findingObject detectionDynamic scene analysishttp://purl.tuc.gr/dl/dias/2D869BA2-66D3-4936-9319-9680FCEE2DD3http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.25.pdf 10.1016/S0262-8856(03)00004-0Published at: 2015-09-30eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2003Summarization: Video sensors become particularly important in traffic applications mainly due to their fast response, easy installation, operation and maintenance, and their ability to monitor wide areas. Research in several fields of traffic applications has resulted in a wealth of video processing and analysis methods. Two of the most demanding and widely studied applications relate to traffic monitoring and automatic vehicle guidance. In general, systems developed for these areas must integrate, amongst their other tasks, the analysis of their static environment (automatic lane finding) and the detection of static or moving obstacles (object detection) within their space of interest. In this paper we present an overview of image processing and analysis tools used in these applications and we relate these tools with complete systems developed for specific traffic applications. More specifically, we categorize processing methods based on the intrinsic organization of their input data (feature-driven, area-driven, or model-based) and the domain of processing (spatial/frame or temporal/video). Furthermore, we discriminate between the cases of static and mobile camera. Based on this categorization of processing tools, we present representative systems that have been deployed for operation. Thus, the purpose of the paper is threefold. First, to classify image-processing methods used in traffic applications. Second, to provide the advantages and disadvantages of these algorithms. Third, from this integrated consideration, to attempt an evaluation of shortcomings and general needs in this field of active research.ElsevierPresented on: Image and Vision Computingpeer-reviewedBibliographic citation: V. Kastrinaki, M. Zervakis and K. Kalaitzakis, "A survey of video processing techniques for traffic applications," Image and Vision Computing, vol. 21, no. 4, pp. 359-381, Apr. 2003. doi:10.1016/S0262-8856(03)00004-0info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:324722012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectSequential decision making in repeated coalition formation under uncertainty Georgios Chalkiadakis()http://purl.tuc.gr/dl/dias/184802C9-8723-48FB-835B-8CF58392892Chttp://eprints.soton.ac.uk/id/eprint/265680Published at: 2015-09-26eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2008Μη διαθέσιμη περίληψηNot available summarizationΠαρουσιάστηκε στο: The Seventh International Conference on Agents and Multiagent Systems, Estoril, PortugalBibliographic citation: G. Chalkiadakis. (2008,May) .Sequential decision making in repeated coalition formation under uncertainty . Presentd at the Seventh International Conference on Agents and Multiagent Systems, Estoril, Portugal, 12 - 16 May 2008.[online].Available :http://eprints.soton.ac.uk/id/eprint/265680full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:325842012-10-10T00:00:00Z28info:eu-repo/semantics/articleMarketing solar thermal technologies: strategies in Europe, experience in GreeceΤσουτσος Θεοχαρης(http://users.isc.tuc.gr/~ttsoutsos)Tsoutsos Theocharis(http://users.isc.tuc.gr/~ttsoutsos)http://purl.tuc.gr/dl/dias/D29BF4F0-E3EA-457E-BC7C-FE686A552B1110.1016/S0960-1481(01)00096-9Published at: 2015-09-27eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2002Summarization: Solar thermal technologies (STTs) are mature in many EU Member States. However, in some EU regions solar applications, and especially the innovative ones (such as solar heating/cooling, solar drying, solar-powered desalination), remain at an early stage. The degree of development of each market does not depend on climate conditions (e.g., insolation) or on different technological developments. The major strengths, weaknesses, opportunities and threats of STTs are examined, in order to identify the most important actions that should be taken to reduce existing barriers, as opposed to RTD (Research and Technology Development) of the new STTs. These include financing schemes, publications, electronic dissemination tools, campaigns, events, creation of information centres, audits and studies.PergamonPresented on: Journal of Renewable Energypeer-reviewedBibliographic citation: T. D Tsoutsos ,"Marketing solar thermal technologies: strategies in Europe, experience in Greece ", Ren. Energ., vol. 26, no. 1,pp.33–46,May 2002.doi :00096info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:333332012-10-10T00:00:00Z28info:eu-repo/semantics/articleDesigning a new generalized battery management system.Chatzakis J.()Καλαϊτζακης Κωστας(http://users.isc.tuc.gr/~kkalaitzakis)Kalaitzakis Kostas(http://users.isc.tuc.gr/~kkalaitzakis)Voulgaris N.()Manias S.()Δημοσίευση σε επιστημονικό περιοδικό Battery management systemsDesign methodologyFault toleranceFault tolerant systemsbattery monitoringbattery protectionhttp://purl.tuc.gr/dl/dias/936C1BF1-6ED8-4C82-88B2-2968B1C852F7http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.28.pdf 10.1109/TIE.2003.817706Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2003Summarization: Battery management systems (BMSs) are used in many battery-operated industrial and commercial systems to make the battery operation more efficient and the estimation of battery state nondestructive. The existing BMS techniques are examined in this paper and a new design methodology for a generalized reliable BMS is proposed. The main advantage of the proposed BMS compared to the existing systems is that it provides a fault-tolerant capability and battery protection. The proposed BMS consists of a number of smart battery modules (SBMs) each of which provides battery equalization, monitoring, and battery protection to a string of battery cells. An evaluation SBM was developed and tested in the laboratory and experimental results verify the theoretical expectations.Institute of Electrical and Electronics EngineersPresented on: IEEE Transactions on Industrial Electronicspeer-reviewedBibliographic citation: J. Chatzakis, K. Kalaitzakis, N. Voulgaris, S. Manias, "Designing a new generalized battery management system," IEEE Trans. on Industrial Electronics, vol. 50, no. 5, pp. 990-999, Oct. 2003. doi:10.1109/TIE.2003.817706info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:334132012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectInvestigation of carbonate rocks appropriate for the production of natural hydraulic lime bindersΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)George Panagopoulos()Emmanouil Manoutsoglou()George Triantafyllou()http://purl.tuc.gr/dl/dias/0ED7E8DC-4393-4AB9-BC38-E85CB6C74412http://www.researchgate.net/publication/266078972_Investigation_of_carbonate_rocks_appropriate_for_the_production_of_natural_hydraulic_lime_bindersPublished at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2014Summarization: Cement industry is facing growing challenges in conserving materials and conforming to the demanding environ-mental standards. Therefore, there is great interest in the development, investigation and use of binders alternatives to Portland cement. Natural hydraulic lime (NHL) binders have become nowadays materials with high added value, due to their advantages in various construction applications. Some of them include compatibility, suitability, workability and the versatility in applications. NHL binders are made from limestones which contain sufficient argillaceous or siliceous components fired at relatively low temperatures, with reduction to powder by slaking with or without grinding. This study is focused in developing technology for small-scale production of cementitious binders, combining the knowledge and experience of geologists and mineral resources engineers. The first step of investigation includes field techniques to the study the lithology, texture and sedimentary structure of Neogene carbonate sediments, from various basins of Crete Island, Greece and the construction of 3D geological models, in order to determine the deposits of each different geological formation. Sampling of appropriate quantity of raw materials is crucial for the investigation. Petrographic studies on the basis of the study of grain type, grain size, types of porosity and depositional texture, are necessary to classify effectively industrial mineral raw materials for this kind of application. Laboratory tests should also include the study of mineralogical and chemical composition of the bulk raw materials, as well as the content of insoluble limestone impurities, thus determining the amount of active clay and silica components required to produce binders of different degree of hydraulicity. Firing of the samples in various temperatures and time conditions, followed by X-ray diffraction analysis and slaking rate tests of the produced binders, is essential to insure the beneficiation of their behavior. Beneficiation is defined as the implementation of the best available techniques to insure the production of an economically usable final product which combines both the hydraulicity of the silicates, aluminates and ferrites, as well as the reactivity of the calcium oxide amounts that are present.
Investigation of carbonate rocks appropriate for the production of natural hydraulic lime binders (PDF Download Available). Available from: http://www.researchgate.net/publication/266078972_Investigation_of_carbonate_rocks_appropriate_for_the_production_of_natural_hydraulic_lime_binders [accessed Oct 1, 2015].Παρουσιάστηκε στο: European Geisciences Union General Assembly, At Vienna, AustriaEuropean Geosciences UnionBibliographic citation: G.Triantafyllou ,G. Panagopoulos ,E. Manoutsoglou ,G.E. Christidis.(2014).Investigation of carbonate rocks appropriate for the production of natural hydraulic lime binders.European Geisciences Union General Assembly, At Vienna, Austria.[online]. Available:http://www.researchgate.net/publication/266078972_Investigation_of_carbonate_rocks_appropriate_for_the_production_of_natural_hydraulic_lime_bindersfull paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:334712012-10-10T00:00:00Z28info:eu-repo/semantics/articleA simple approach to the identification of trioctahedral smectites by X-ray diffractionΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)Eleni Koutsopoulou()http://purl.tuc.gr/dl/dias/D711D0B3-DDFD-4D9F-ADFB-96C7DFDC3EE910.1180/claymin.2013.048.5.22Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2013Summarization: A new method for identifying the trioctahedral smectites saponite, stevensite and hectorite is proposed in this study. The method is based on differences in the X-ray diffraction (XRD) patterns of the three smectites after (a) heating at 500°C for 90 min and (b) glycerol solvation of the Cs-forms of the smectites for 20 h. After heating at 500°C, well below the dehydroxylation temperature of the three smectites, saponite and hectorite re-expand upon ethylene glycol (EG) solvation, whereas stevensite layers remain collapsed. Saponite forms one-layer and hectorite two-layer complexes after Cs-saturation and glycerol solvation. Cs-stevensite displays a gradual increase in d 001 with increasing solvation time in glycerol vapours and forms two-layer glycerol complexes with prolonged solvation. Except for the individual Mg-smectites, the proposed method may be used to identify compositional heterogeneity that may exist in the smectites. Furthermore, it should be useful in identifying the individual trioctahedral Mg-smectites when present in mixtures, and in detecting interstratified layers of different Mg-trioctahedral smectites. Application of the method revealed that the SYnL-1 laponite (CMS Source Clay Project) is not homogeneous but consists of hectorite, stevensite and possibly mixed-layer hectorite/stevensite layers.Mineralogical SocietyPresented on: Clay Mineralspeer-reviewedBibliographic citation: G. Christidis, E. Koutsopoulou, " A simple approach to the identification of trioctahedral smectites by X-ray diffraction " ,C. Min., vo.48 ,no.5 ,pp. 687-696 ,2013.doi:10.1180/claymin.2013.048.5.22info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:334912012-10-10T00:00:00Z28info:eu-repo/semantics/articleCharacterization of El-Tih kaolin quality using mineralogical, geochemical and geostatistical analysesΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)Katsuaki Koike ()Alaa A. Masoud()http://purl.tuc.gr/dl/dias/3FF57102-486D-4AC7-A467-91677934E0BA10.1180/claymin.2013.048.1.01 Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2013Summarization: Detailed multi-scale characterization of the kaolin quality and the controlling depositional environment is crucial for optimal quality upgrading and for prioritizing potential exploitation areas. In the present work, the quality of El-Tih kaolin, Egypt, was investigated using the chemical/mineralogical characteristics as well as the field observations of the clay. Chemical analysis of major oxides was carried out using energy dispersive X-ray fluorescence (EDS-XRF) spectrometry. Mineralogical analyses were carried out using X-ray diffraction (XRD) and scanning electron microscopy coupled with wavelength-dispersive X-ray spectroscopy (SEM-WDS). Spatial heterogeneity of the quality was evaluated applying kriging geostatistical techniques and potential zones were identified.
Mineralogical SocietyPresented on: Clay Mineralspeer-reviewedBibliographic citation: A. A Masoud,G. Christidis, K. Koike, "Characterization of E1-Tih kaolin quality using mineralogical, geochemical and geostatistical analyses ", C. Min. ,vol.48 ,no. 1, pp.1-20 ,2013. doi:10.1180/claymin.2013.048.1.01 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:335312012-10-10T00:00:00Z28info:eu-repo/semantics/articleGeochemical characteristics of the alteration of volcanic and volcaniclastic rocks in the Feres Basin, Thrace, NE GreeceΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)I. Marantos()Th. Markopoulos() V. Perdikatsis()http://purl.tuc.gr/dl/dias/0206E902-F79B-4A81-A816-499AE42F7E8110.1180/claymin.2008.043.4.05 Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2008Summarization: The Tertiary basin of Feres consists of sedimentary rocks, andesitic-rhyolitic volcanic rocks of K-rich calc-alkaline affinities, rocks with calc-alkaline and shoshonitic affinities and volcaniclastic fall and flow deposits. Volcanic and volcaniclastic rocks have variable concentrations of LIL elements (Ba, Sr, Rb, Th) and HFS elements (Zr, V) due to their mode of origin. The pyroclastic flows frequently show more or less intense devitrification, vapour-phase crystallization and, in some cases, evidence of fumarolic activity, as is indicated by the presence of scapolite. The volcanic and volcaniclastic rocks display various types of alteration including formation of zeolites (clinoptilolite, heulandite, mordenite, and laumontite) and smectite, as well as hydrothermal alteration (development of silicic, argillic, sericitic and propylitic zones) associated with polymetallic mineralization. The behaviour of chemical elements during alteration varies. Some are immobile and their distribution is controlled by the conditions prevailing during parent-rock formation and emplacement, but others, such as Ba and Sr, are mobile and selectively fractionate in zeolite extra-framework sites. The formation of zeolite from alteration of volcanic glass is accompanied by an increase in Mg and Al content, and a decrease in Si and Na content, whereas Ca is not affected by alteration. In certain pyroclastic flows, there is a significant difference in K-content between incipient glass and altered rock, due to K-feldspar formation during devitrification and vapour-phase crystallization.
Presented on: Clay Mineralspeer-reviewedΒιβλιογραφική αναφορά: I. Marantos, Th. Markopoulos, G. E. Christidis ,V. Perdikatsis, " Geochemical characteristics of the alteration of volcanic and volcaniclastic rocks in the Feres Basin, Thrace, NE Greece",C. Min.,vol.43 ,no.4 ,pp.575-595 ,2008.doi:10.1180/claymin.2008.043.4.05 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:335712012-10-10T00:00:00Z28info:eu-repo/semantics/articleValidity of the structural formula method for layer charge determination of smectites: A re-evaluation of published dataΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)http://purl.tuc.gr/dl/dias/0722EAB5-73A1-473F-8B9F-42BBDE1876CF10.1016/j.clay.2008.02.002Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2008Summarization: The validity of the structural formula (SF) method for calculation of layer charge of smectites is examined through re-interpretation of
published data, which suggest that the SF method overestimates layer charge. The overestimation of layer charge by SF is based on assumptions
about the permanent CEC (CECperm) of smectites i) on the association of the molar mass of half unit cell (MHUC) with the CECperm of the smectitic
clay fraction and ii) on imbalanced SF calculated for a series of used smectites. The CECperm of smectites should not be determined at pH 4
because of competitive adsorption of H+ cations at exchangeable sites. This was verified by monitoring the pH of acidified smectite suspensions.
Instead the pH at the isoelectric point (iep) should be used for determination of permanent charge of smectites. Moreover it is suggested that the
equation of Lagaly [Lagaly, G., 1994. Layer charge determination by alkylammonium ions. In: Mermut, A.R. (Ed.), Layer Charge Characteristics
of 2:1 Silicate Clay Minerals. CMS Workshop lectures, vol. 6. The Clay Minerals Society, Boulder Colorado, pp. 2–46] which relates the smectite
content with layer charge may be used only if CECperm is calculated on a totally anhydrous basis, otherwise it may lead to significant
underestimation either of smectite content or of layer charge.ElsevierPresented on: Applied Clay Sciencepeer-reviewedBibliographic citation: G. E. Christidis ,"Validity of the structural formula method for layer charge determination of smectites: A re-evaluation of published data ", App. Cl. Sc.,vol. 42, no. 1-2,pp.1-7 ,2008. doi:10.1016/j.clay.2008.02.002info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:335782012-10-10T00:00:00Z28info:eu-repo/semantics/articleIon exchange equilibrium and structural changes in clinoptilolite irradiated with β- and γ-radiation. Part II: Divalent cationsDaniel Moraetis()Χρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gechristidis)Christidis Georgios(http://users.isc.tuc.gr/~gechristidis)Vasilios Perdikatsis()http://purl.tuc.gr/dl/dias/5E2C5A62-88B8-4046-AB03-269B333C6C7D10.1127/0935-1221/2008/0020-1802Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2008Summarization: Thermodynamic calculations of ion exchange for divalent cations were made for clinoptilolite in natural state and after
irradiation with three different doses of β-radiation (1012, 1015 and 3 × 1016 e/cm2) and γ-radiation (70 Mrad). The samples were
equilibrated with binary systems of divalent cations, namely Sr2+ ↔ 2Na+, Ca2+ ↔ 2Na+ and Mg2+ ↔ 2Na+ at 25 ◦C and total
solution normality of 0.025 N. The selectivity order Sr2+ > Ca2+ > Mg2+ was observed in non-irradiated clinoptilolite. After
irradiation with γ-radiation the affinity of clinoptilolite for Sr2+ increased and that for Mg2+ decreased, whereas the affinity for
Ca2+ remained unchanged. Irradiation with β-radiation influences selectivity order and clinoptilolite affinity decreases for Sr2+,
whereas it increases for Ca2+. For the sample irradiated with maximum dose of β-radiation the selectivity was almost identical
for Ca2+ and Sr2+. The crystallographic parameters and exchangeable cation site coordinates were refined for all samples with
the Rietveld method. The structure refinement of Sr2+-saturated samples yielded changes both in exchangeable sites and site
occupancy in channels A and B after irradiation with β-and γ-radiation. The cation sites Sr1 and Sr3 exhibit major changes both
in site coordinates and site occupancy after irradiation with β-radiation. In addition, irradiation with γ-radiation yielded major
changes in Sr1 occupancy, whereas coordinates changed only slightly. These structural modifications control the observed changes
in thermodynamic parameters after irradiation.E Schweizerbart Science PublishersPresented on: European Journal of Mineralogypeer-reviewedBibliographic citation: D. Moraetis,G.E. Christidis , V.Perdikatsis , "Ion exchange equilibrium and structural
changes in clinoptilolite irradiated with β- and γ-radiation. Part II: Divalent cations ",Eur. J. Mineral ,vol.20, no.4.,pp.603-620 ,2008. doi :10.1127/0935-1221/2008/0020-1802info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:335942012-10-10T00:00:00Z28info:eu-repo/semantics/articleWhite mica domain formation: A model for paragonite, margarite, and muscovite formation during prograde metamorphismΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)Kenneth J. T. Livi ()Péter Árkai ()David R Veblen()http://purl.tuc.gr/dl/dias/5AE54AF3-4930-460D-BBB0-BD992A0FDE6E10.2138/am.2008.2662Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2008Summarization: Scanning transmission electron microscopy images of the 00l white mica planes in crystals from
central Switzerland and Crete, Greece, reveal that domains of paragonite, margarite, and muscovite
are ordered within the basal plane. Energy dispersive X-ray analyses show that both cations in the
interlayer and in the 2:1 layer have ordered on the scale of tens to hundreds of nanometers. Domain
boundaries can be both sharp and crystallographically controlled or diffuse and irregular. A model
outlining the domain formation process is presented that is consistent with X-ray powder diffraction
and transmission electron microscopy data. The domain model incorporates aspects of a mixedlayered
and a disordered compositionally intermediate phase models. The main feature of the model
is the formation of mica species that segregate within the basal plane and contradict the notion of
homogeneous layers within mixed-layer phases. Implications for the formation of all diagenetic and
very low-grade metamorphic 2:1 sheet silicates are discussedPresented on: American Mineralogistpeer-reviewedBibliographic citation: J. T. Kenneth Livi ,G.E. Christidis ,Péter Árkai ,D. R Veblen , " White mica domain formation: A model for paragonite, margarite, and muscovite formation during prograde metamorphism ",Am. Mineral. ,vol. 93,no.4 pp.520-527 ,2008.doi :10.2138/am.2008.2662info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:336312012-10-10T00:00:00Z28info:eu-repo/semantics/articleIon exchange equilibrium and structural changes in clinoptilolite irradiated with β- and γ-radiation: Monovalent cationsΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)Daniel Moraetis ()Vassilis Perdikatsis()http://purl.tuc.gr/dl/dias/3A1CDB38-D940-4433-923A-C1A4D150BB4B10.2138/am.2007.2545Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2007Περίληψη: Thermodynamic calculations of ion-exchange reactions were applied for clinoptilolite in a natural
state and after irradiation with three doses of β-radiation (1012, 1015, 3 × 1016 e/cm2) and γ-radiation
(70 Mrad). Samples were equilibrated with binary systems of K+ ↔ Na+ and Cs+ ↔ Na+ at 25° and a
total normality of 0.025 N. Selectivity for K was not affected after β-radiation with doses of 1012 and
1015 e/cm2 (ΔG° = –6.37 kJ/equiv, lnKα = 2.58 for the original clinoptilolite), whereas it increased
considerably after 70 Mrad of γ-radiation (ΔG° = –7.88 kJ/equiv, lnKα = 3.18). Selectivity for Cs+
increased for the clinoptilolite irradiated with β-radiation (1012, 1015, 3 × 1016 e/cm2) and γ-radiation
(70 Mrad). ΔG° and lnKα for original sample and Cs+ ↔ Na+ were –7.33 kJ/equiv and 2.96,
respectively. Irradiated samples with β-radiation 1012, 1015, 3 × 1016 e/cm2 and 70 Mrad γ-radiation
yielded ΔG° and lnKα –7.41, –8.83, –8.60, –8.25 kJ/equiv and 2.99, 3.57, 3.47, 3.33 for Cs+ ↔ Na+,
respectively. Remarkable amorphization of clinoptilolite was observed after exposure at the highest
dose of β-radiation (3 × 1016 e/cm2) with a concomitant decrease in cation-exchange capacity (CEC).
Crystallographic parameters and especially exchangeable cation site coordinates were refi ned for all
samples with the Rietveld method. Cesium-saturated samples exhibited changes in the cation sites
Cs2 and Cs3, which are next to clinoptilolite channel walls with lower Al3+ for Si4+ substitution. The
observed changes include a shift in cation sites Cs2 and Cs3 toward channel walls and occupancy
decrease in site Cs2.Presented on: American Mineralogistpeer-reviewedBibliographic citation: D. Moraetis , G.E. Christidis ,V. Perdikatsis ," Ion exchange equilibrium and structural changes in clinoptilolite irradiated with - and -radiation: Monovalent cations ",Am. Min. ,vol. 92 , no. 10 , pp.1714–1730 ,2007.doi :10.2138/am.2007.2545info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:336332012-10-10T00:00:00Z28info:eu-repo/semantics/articleZeolitic alteration in the Tertiary Feres volcano-sedimentary basin, Thrace, NE GreeceΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)T. Markopoulos()T. Marantos()http://purl.tuc.gr/dl/dias/8C4DE11E-6080-4DCF-97BA-F3794F06D9AF10.1180/minmag.2007.071.3.327Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: The Tertiary volcano-sedimentary sequence of the Feres basin (Thrace, NE Greece), includes lavas of andesitic–rhyolitic composition as well as volcaniclastic rocks, pyroclastic flows and pyroclastic fall deposits principally of dacitic–rhyodacitic composition. The pyroclastic flow deposits frequently show intense devitrification, vapour-phase crystallization and evidence of fumarolic activity, which involves deposition of scapolite in pore spaces. The Feres basin can be subdivided on the basis of mineral alteration assemblages: (1) the Pefka region; characterized by intense hydrothermal alteration of the volcanic rocks and mineral zoning (silicic, arg illic, sericitic and propylitic zones) with polymetallic mineralization, and (2) the remainder of the basin; where the volcaniclastic rocks are characterized by the alteration of volcanic glass to zeolites (clinoptilolite, heulandite, mordenite, analcime), clay minerals (smectite, illite, celadonite, chlorite), SiO2 polymorphs (cristobalite, opal-CT, quartz), K-feldspar and calcite. Laumontite is also present as an alteration product of plagioclase, with stilbite sporadically occurring in veinlets. Locally, rhyolites are also altered to zeolites (clinoptilolite and/or mordenite). The zeolitization process has occurred rapidly with the depositional environment, temperature, rate of cooling (of the volcanic rocks), nature and temperature of the mineral-forming fluids and composition of the parent material controlling the formation of zeolites.
Presented on: Mineralogical Magazinepeer-reviewedBibliographic citation: I. Marantos, T. Markopoulos , G. E. Christidis ,"Zeolitic alteration in the Tertiary Feres volcano-sedimentary basin, Thrace, NE Greece ",Min.Mag. ,vol.71, no.3 , pp.327-345 ,2007. doi :10.1180/minmag.2007.071.3.327info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:336342012-10-10T00:00:00Z28info:eu-repo/semantics/articleGreek lignites as additives for controlling filtration properties of water–bentonite suspensions at high temperaturesΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)Vassilios C. Kelessidis()Christina Tsamantaki()Athanasios Michalakis()Pagona Makri()Kassiani Papanicolaou()Antonios Foscolos()http://purl.tuc.gr/dl/dias/48A28BC7-D491-49A4-ADC8-979E8475414710.1016/j.fuel.2006.10.009Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2007Summarization: The effectiveness of Greek lignites to control the filtration characteristics of water–bentonite suspensions and to minimize formation
damage at high temperatures was studied. Twenty-six lignite samples from various peat/lignite deposits in Greece were used together
with a commercial lignite product. The contents of humic and fulvic acids, humins, oxygen, ash and the cation exchange capacity of
lignite samples were examined with respect to fluid loss of these suspensions. The results show that most samples provided very good
filtration control of the water–bentonite suspensions after exposure to 177 C with some being superior to the commercial product. Better
performance was observed after addition of 3% w/v lignite. Total humic and fulvic acids as percentage of dry lignite matter and the
organic matter as lignite percentage showed a weak inverse correlation with the fluid loss volumes.
ElsevierPresented on: Fuelpeer-reviewedBibliographic citation: V.C. Kelessidis , C. Tsamantaki , A. Michalakis ,G. E. Christidis , P. Makri , K.Papanicolaou , A. Foscolos ,"Greek lignites as additives for controlling filtration properties of water–bentonite suspensions at high temperatures ", Fuel. ,vol.86, no. 7-8 ,pp.1112-1121 ,2007.doi:10.1016/j.fuel.2006.10.009info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:336362012-10-10T00:00:00Z28info:eu-repo/semantics/articleGelation of water-bentonite suspensions at high temperatures and rheological control with lignite additionΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)Vassilios C. Kelessidis()Pagona Makri()Vassiliki Hadjistamou()Christina Tsamantaki()Athanasios Mihalakis()Cassiani Papanicolaou()Antonios Foscolos()http://purl.tuc.gr/dl/dias/3FAEBE56-9AE6-4830-A528-25256B2B976110.1016/j.clay.2006.09.010Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2007Summarization: The effectiveness of lignite addition to prevent gelation of 6.42% w/w water–bentonite suspensions exposed to high
temperatures has been studied, using twenty six lignites from various basins in Greece with variable organic and inorganic contents
at concentrations of 0.5% and 3.0%. The lignite-free bentonite suspensions thickened considerably when heated at 177 °C for 16 h,
as was indicated by a two-fold increase of the yield stress, when compared to samples hydrated only at room temperature. However
plastic viscosity did not change appreciably. Full flow curves showed a Herschel–Bulkley behavior of all suspensions. Addition of
lignite maintained the stability of the suspensions exposed to high temperatures (177 °C) by keeping the yield stress low and did
not affect plastic viscosity. Some of the Greek lignites performed equally well with a commercial lignite product and improvements
of 80 to 100% of the stability of the suspensions, compared to lignite-free suspensions, have been found. Lignite addition also
lowered yield stresses for the hydrated samples. No specific trends have been identified between the effectiveness of lignites to
stabilize bentonite suspensions and their humic and fulvic acids and humins content. However, those lignites with highest humic
and fulvic acid contents have maximum stabilization capacity. Similarly, no specific trends have been observed between the
stabilization capacity of lignites and their inorganic components such as oxygen and ash content and also with the cation exchange
capacity. The effectiveness of the Greek lignites to stabilize bentonite suspensions is very high and the minor differences in the
efficiency of the different lignites cannot be attributed solely to any specific componentElsevierPresented on: Applied Clay Sciencepeer-reviewedBibliographic citation: V. C. Kelessidis , G. Christidis , P. Makri ,V.Hadjistamou , C. Tsamantaki , A. Mihalakis ,C.Papanicolaou, A. Foscolos ,"Gelation of water–bentonite suspensions at high temperatures and rheological control with lignite addition " ,Ap. Clay Sc.,vol. 36.no.4 ,pp.221-231 ,2007.doi :10.1016/j.clay.2006.09.010info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:336532012-10-10T00:00:00Z28info:eu-repo/semantics/articleInfluence of layer charge and charge distribution of smectites on the flow behaviour and swelling of bentonitesΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)Alex E. Blum()D.D. Eberl()http://purl.tuc.gr/dl/dias/5EFB42E1-A993-48AC-93A9-BA3DE365839710.1016/j.clay.2006.05.008Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2006Summarization: The influence of layer charge and charge distribution of dioctahedral smectites on the rheological and swelling properties of
bentonites is examined. Layer charge and charge distribution were determined by XRD using the LayerCharge program [Christidis,
G.E., Eberl, D.D., 2003. Determination of layer charge characteristics of smectites. Clays Clay Miner. 51, 644–655.]. The
rheological properties were determined, after sodium exchange using the optimum amount of Na2CO3, from free swelling tests.
Rheological properties were determined using 6.42% suspensions according to industrial practice. In smectites with layer charges
of −0.425 to −0.470 per half formula unit (phfu), layer charge is inversely correlated with free swelling, viscosity, gel strength,
yield strength and thixotropic behaviour. In these smectites, the rheological properties are directly associated with the proportion of
low charge layers. By contrast, in low charge and high charge smectites there is no systematic relation between layer charge or the
proportion of low charge layers and rheological properties. However, low charge smectites yield more viscous suspensions and
swell more than high charge smectites. The rheological properties of bentonites also are affected by the proportion of tetrahedral
charge (i.e. beidellitic charge), by the existence of fine-grained minerals having clay size, such as opal-CT and to a lesser degree by
the ionic strength and the pH of the suspension. A new method for classification of smectites according to the layer charge based on
the XRD characteristics of smecites is proposed, that also is consistent with variations in rheological properties. In this
classification scheme the term smectites with intermediate layer charge is proposed.ElsevierPresented on: Applied Clay Sciencepeer-reviewedBibliographic citation: G. E. Christidis , A. E. Blum , D.D. Eberl , "Influence of layer charge and charge distribution of smectites on the flow behaviour and swelling of bentonites ",Ap. Clay Sc.,vol. 34,no.1,pp.125-138 ,2006.doi :10.1016/j.clay.2006.05.008info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:337512012-10-10T00:00:00Z28info:eu-repo/semantics/articleInfluence of grinding on the structure and colour properties of talc, bentonite and calcite white fillersΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)Pagona Makri ()Vassilis Perdikatsis ()http://purl.tuc.gr/dl/dias/A9116B19-0E83-4F04-9C04-8D2474546AC110.1180/0009855043920128Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2004Summarization: The influence of grinding on colour and particle-size properties of talc and smectite
from a white bentonite were studied and compared with a fine-grained calcite from a chalk. Grinding
decreased the grain size of all three minerals. The crystallite size and structure of smectite was not
affected but the crystallite size of talc decreased. The Si–O–Mg and MgO bonds of talc were
disrupted and cation exchange capacity increased with increasing grinding. Delamination of talc
crystallites was observed in the initial stages of grinding, whereas with more intense treatment,
amorphous material was formed. Comminution improved the colour properties of all three minerals,
namely brightness, L* (lightness) and DE*ab (deviation from perfect white diffuser). Grinding time
exerts greater influence on the reflectance from calcite surfaces than from clay minerals. This
difference is attributed to continuous formation of progressively smaller diffuse reflection units
forming a smoother calcite surface. Decrease of grain size does not form considerably smaller diffuse
reflection units in clay minerals unless delamination takes place. With prolonged grinding,
amorphization forms additional diffuse reflection units and a smoother surface due to comminution.Mineralogical SocietyPresented on: Clay Mineralspeer-reviewedBibliographic citation: G.E. Christidis ,P. Makri ,V.Perdikatsis , " Influence of grinding on the structure and colour properties of talc, bentonite and calcite white fillers ",C. Min. ,vol.39, no.2 , pp.163-175 ,2004. doi:10.1180/0009855043920128info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:337912012-10-10T00:00:00Z28info:eu-repo/semantics/articleDetermination of layer-charge characteristics of smectitesΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)D. D. Eberl()http://purl.tuc.gr/dl/dias/D1E2FDA7-7BF7-462B-AAE8-9C22898E397F10.1346/CCMN.2003.0510607Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2003Summarization: A new method for calculation of layer charge and charge distribution of smectites is proposed.
The method is based on comparisons between X-ray diffraction (XRD) patterns of K-saturated, ethylene
glycol-solvated, oriented samples and calculated XRD patterns for three-component, mixed-layer systems.
For the calculated patterns it is assumed that the measured patterns can be modeled as random
interstratifications of fully expanding 17.1 A Ê layers, partially expanding 13.5 A Ê layers and non-expanding
9.98 AÊ layers. The technique was tested using 29 well characterized smectites. According to their XRD
patterns, smectites were classified as group 1 (low-charge smectites) and group 2 (high-charge smectites).
The boundary between the two groups is at a layer charge of –0.46 equivalents per half unit-cell. Lowcharge
smectites are dominated by 17.1 AÊ layers, whereas high-charge smectites contain only 20% fully
expandable layers on average. Smectite properties and industrial applications may be dictated by the
proportion of 17.1 AÊ layers present. Non-expanding layers may control the behavior of smectites during
weathering, facilitating the formation of illite layers after subsequent cycles of wetting and drying. The
precision of the method is better than 3.5% at a layer charge of –0.50; therefore the method should be
useful for basic research and for industrial purposes.Clay Minerals SocietyPresented on: Clays and Clay Mineralspeer-reviewedBibliographic citation: G. E. Christidis ,D. D. EBerl , "Determination of Layer-charge
Characteristics of Smectites ",Cl. and Clay Min. ,vol. 51, no. 6, pp. 644-655 ,2003.doi:10.1346/CCMN.2003.0510607info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:338312012-10-10T00:00:00Z28info:eu-repo/semantics/articleDecolorization of vegetable oils: A study of the mechanism of adsorption of b-carotene by an acid-activated bentonite from CyprusΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)Sotiria Kosiari()http://purl.tuc.gr/dl/dias/FC3CAC90-F034-4C23-BCED-6467F2152BC210.1346/CCMN.2003.0510309Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2003Summarization: The mechanism of decolorization of crude maize and sunflower oils was studied by means of
adsorption of b-carotene by a low-grade bentonite , containin g mixed-layered illite-smectite.
Decolorization depends on temperature and the time required for equilibrium decreases with increasing
temperature. The study of the kinetics of adsorption showed that decolorization of maize oil is a first-order
process which occurs in two steps: a first fast step with higher activation energy (25.6 kJ mol –1),
indicating the influence of a chemical interaction between the pigment and the clay surface, followed by a
second slow step with low activation energy (12.3 kJ mol –1), characteristic of physical adsorption on the
previously adsorbed molecules. Decolorization of sunflower oil is also a first-order process, described by a
single mechanism with intermediate activation energy (19.0 kJ mol –1). Adsorption isotherms of
decolorization of maize oil follow the Freundlich equation, indicating the existence of heterogeneous
adsorption sites on the solid’s surface. Heterogeneity is attributed both to different active centers on the
smectite surface (Bro¨ nsted and Lewis centers) and to the different phases present in bentonite, such as
illitic layers and clinoptilolite, which also have active centers on their surfaces.Clay Minerals SocietyPresented on: Clays and Clay Mineralspeer-reviewedBibliographic citation: G. E. Christidis, S. Kosiari , "Decolorization of vegetable oils: A
study of the mechanism of adsorption of B-Carotene by an acid-activated
bentonite from Cyprus ",Cl. and Clay Min, vol. 51, no. 3, pp.327–333, 2003.doi :10.1346/CCMN.2003.0510309info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:338332012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectEvaluation of an upper cretaceous limestone from the area of arta for
lime productionΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)George Triantafyllou ()Th. Markopoulos()http://purl.tuc.gr/dl/dias/DDB9F3C0-C5BC-4E22-A2EF-4093E227AC3EPublished at: 2015-10-01eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2001Summarization: Calciantion of an Upper Cretaceous limestone from the Ionian Unit ato 700-1100°C for 1-4 hours yielded very reactive lime end products. Lime formation was monitored by means of kinetic curves and TTT diagrams. Particle size seems to control th onset of lime crystallization at low temperatures, but it is of minor importance at higher temparatures. With the experimental setting used, lime formation was completed at 900°C. The specific surface area of the end products increases with firing temperature up to 800°C, decreasing thereafter. Decrepitation of lime increases gradually with firing temperature. Hydration temperature during slaking increases rapidly up to 900°C being constant thereafter. Sintering and production of fines during control the physical properties of lime.
Παρουσιάστηκε στο: 9th International Congress of the Geological Society of GreeceBibliographic citation: G.E. Christidis , G. Triantafyllou ,T. Markopoulos , " Evaluation of an Upper Cretaceous Limestone from the area of Arta for Lime Production " ,In 9th International Congress of the Geological Society of Greece",2001, pp.1169-1175.posterinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:338372012-10-10T00:00:00Z28info:eu-repo/semantics/articleIon exchange of zeolite Na-P(c) with Pb2+, Zn2+, and Ni2+ ionsΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)Ioannis Paspaliaris ()Aggeliki Moirou()http://purl.tuc.gr/dl/dias/438F10D2-C905-4957-8E6B-B8FF9189AB8110.1346/CCMN.2000.0480509Published at: 2015-10-01eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2000Summarization: This paper examines the ion-exchange properties of synthetic zeolite Na-P0, which was pro- duced from perlite-waste fines and has a SiO2:A1203 ratio of 4.45:1 and a cation-exchange capacity (CEC) of 3.95 meq g ~. Although equilibrium is attained rapidly for all three metals, exchange is incomplete, with At(max) (maximum equilibrium fraction of the metal in the zeolite) being 0.95 for Pb, 0.76 for Zn, and 0.27 for Ni. In both Na ~ ␣89 and Na --* ␣89 exchange, the normalized selectivity coefficient is virtually constant for :~A~(normalized equilibrium fraction of the metal in the zeolite) values of --<0.6, suggesting a pronounced homogeneity of the available exchange sites. The Gibbs standard free energy, AG~ of the Na ---)␣89 exchange calculated from the normalized selectivity coefficient is -3.11 kJ eq and, for the Na ~ 1/2Znexchange, it is 2.75 kJ eq ~.
Examination of the solid exchange products with X-ray diffraction (XRD) revealed a possible decrease in crystallinity of zeolite Pb-Pc as suggested by the significant broadening and disappearance of diffraction lines. This decrease is associated with a reduction of pore opening, as indicated from Fourier-transform infrared analysis (FTIR), which in turn results in a decrease of the amount of zeolitic water. Thermogra- vimetric-differential thermogravimetric (TG-DTG) analysis showed that water loss occurs in three steps, the relative significance of which depends on the type of exchangeable cation and subsequently on the type of complex formed with the cation and/or the zeolite channels. Zeolite Na-Pc might be utilized in environmental applications, such as the treatment of acid-mine drainage and electroplating effluents.Clay Minerals SocietyPresented on: Clays and Clay Mineralspeer-reviewedBibliographic citation: G.E. Christidis ,I. Paspaliaris ,A. moirou , "Ion exchange of zeolite Na-P(c) with Pb2+, Zn2+, and Ni2+ ions ",Cl. and Clay Min.,vol. 48,no.5, pp.563-571 ,2000.doi :10.1346/CCMN.2000.0480509info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:338712012-10-10T00:00:00Z28info:eu-repo/semantics/articlePhysical and chemical properties of some bentonite deposits of Kimolos Island, GreeceΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)http://purl.tuc.gr/dl/dias/5F00A0C3-EB40-4EEA-B820-B8EE16F63C76 10.1016/S0169-1317(98)00023-4Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1998Summarization: Bentonite deposits of Kimolos Island, Aegean, Greece were investigated in order to determine their physical and chemical properties. Testing included measurement of CEC (cation exchange capacity), swelling capacity, pH, rheological properties and some important foundry properties including green and dry compression strength, shatter index, wet tensile strength, compactability and permeability. The rheological and foundry properties are mainly influenced by the bentonite grade (smectite content) and the degree of disaggregation of the smectite quasicrystals due to the nature of the interlayer cation, the presence of mordenite and undevitrified glass shards, the degree of the oxidation of iron and the type of smectite–opal-CT interaction. Na-activation improves green compressive strength and especially wet tensile strength and decreases permeability, while its influence on the remaining foundry properties is unpredictable. Swelling properties are affected by bentonite grade, expressed by CEC, and the presence of characteristic phases (glass shards and opal-CT) decreases swelling, while zeolites increase CEC. The swelling capacity is closely related to the CEC, if smectite chemistry is controlled. It is shown that although the presence of zeolites like mordenite or small amounts of opal-CT may not affect rheological properties, the bonding properties always deteriorate. However, the presence of undevitrified glass reduces viscosity.
ElsevierPresented on: Applied Clay Sciencepeer-reviewedBibliographic citation: G. E. Christidis , "Physical and chemical properties of some bentonite
deposits of Kimolos Island, Greece ",Ap.Clay Sc. ,vol. 13.,no.2 ,pp.79-98 ,1998 .doi :10.1016/S0169-1317(98)00023-4info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:338732012-10-10T00:00:00Z28info:eu-repo/semantics/articleAcid activation and bleaching capacity of bentonites from islands of Milos and Chios, Aegean, GreeceΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)P.W. Scott()A.C. Dunham()http://purl.tuc.gr/dl/dias/6C4A2463-EE59-4824-955A-1B8289EA2B2F10.1016/S0169-1317(97)00017-3Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1997Summarization: Acid activation with HCl of two bentonites from the Aegean Islands of Milos and Chios, Greece, consisting of Chambers and Tatatilla-type and Otay-type montmorillonite, respectively, resulted in a 4 to 5-fold increase of the surface area of the raw materials. The activated materials have been rendered suitable for decolorization (bleaching) of rapeseed oil through removal of β-carotene. The optimum bleaching capacity is not associated with maximum surface area. Activation is characterized by destruction of the original smectite structure, removal of octahedral cations, uptake of OH− and formation of au amorphous Si-rich phase. Mg is the most readily removed element affecting the tendency for activation. The Otay-type montmorillonites are activated. more easily. Optimum conditions for activation are obtained using a variety of combinations of acid strength and residence time. The combination which is likely to be preferred on an industrial scale, is the least energy consuming. Therefore shorter treatments with more dilute acid are preferable.
ElsevierPresented on: Applied Clay Sciencepeer-reviewedBibliographic citation: G.E. Christidis ,P.W. Scott ,A.C. Dunham,"Acid activation and bleaching capacity of bentonites from the islands of Milos and Chios, Aegean, Greece,"Ap. Clay Sc.,vol. 12,no. 4,pp.329-347,1997.doi :10.1016/S0169-1317(97)00017-3info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:338912012-10-10T00:00:00Z28info:eu-repo/semantics/articleThe origin and control of colour of white bentonites from the Aegean islands of Milos and Kimolos, GreeceΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)P.W. Scott()http://purl.tuc.gr/dl/dias/3D06D166-E767-4D2E-B79D-63C61612C2B310.1007/s001260050092Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1997Summarization: Some of the Lower Pleistocene bentonites of Milos and Kimolos islands, Greece, are valued for their white colour and physicochemical
properties. They contain opal-CT and, sometimes, zeolite along with smectite, and have been derived from the alteration of
rhyolitic volcanic rocks. The Miloan white bentonites contain Tatatilla-type montmorillonite and beidellite. The Kimolian
ones have Chambers-type montmorillonite. The alteration process involved removal of alkalis and uptake of Mg, probably from
sea water. Si is either redistributed or partially removed. The Kimolian white bentonites have higher brightnesses, L* and whiteness index values, and lower yellowness index and ΔE*ab values compared with the Miloan ones. The variations in white colour are inversely related to the abundance of Fe oxides
and anatase, the occurrence of Fe in the smectite structure and its oxidation state. The presence of silica minerals is not
an important factor affecting colour, but is undesirable since it imparts high abrasiveness in commercial products. The formation
of white bentonites of high quality requires the removal of alkalis and silica during alteration of acid volcanics in order
to avoid crystallization of zeolites and opal-CT. Fe needs to be incorporated into the smectite structure. Such conditions
are rarely attained. Springer VerlagPresented on: Mineralium Depositapeer-reviewedBibliographic citation: G.E. Christidis , P.W. Scott ,"The origin and control of colour of white bentonites
from the Aegean islands of Milos and Kimolos, Greece ",Min. Dep., vol. 32.,no.3,pp.271-279 ,1997. doi :10.1007/s001260050092info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:304712012-10-10T00:00:00Z28info:eu-repo/semantics/articleDesign and analysis of a solar reactor for anaerobic wastewater treatmentΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)http://purl.tuc.gr/dl/dias/CC33FB5E-D063-4265-A872-E8643BF5D0DF10.1016/j.biortech.2008.01.067Published at: 2015-09-17eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2008Summarization: The aim of this research was to design a solar heated reactor system to enhance the anaerobic treatment of wastewater or biological
sludge at temperatures higher than the ambient air temperature. For the proposed reactor system, the solar energy absorbed by flat plate
collectors was transferred to a heat storage tank, which continuously supplied an anaerobic-filter reactor with water at a maximum temperature
of 35 C. The packed reactor was a metallic cylindrical tank with a peripheral twin-wall enclosure. Inside this enclosure was
circulated warm water from the heat storage tank. Furthermore, a mathematical model was developed for the prediction of the temperature
distribution within the reactor under steady state conditions. Preliminary results based on model simulations performed with meteorological
data from various geographical regions of the world suggested that the proposed solar reactor system could be a promising
and environmentally friendly approach for anaerobic treatment of wastewater and biological sludge.Παρουσιάστηκε στο: Bioresource Technologypeer-reviewedBibliographic citation: A.Ch. Yiannopoulos , I. D. Manariotis , C. V. Chrysikopoulos, "Design and analysis of a solar reactor for anaerobic wastewater treatment" ,biotech. technol.,vol. 99 ,pp.7742–7749.
Doi :10.1016/j.biortech.2008.01.067info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:308132012-10-10T00:00:00Z28info:eu-repo/semantics/articleAcoustically enhanced ganglia dissolution and mobilization in a monolayer of glass beadsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Eric T. Vogler()http://purl.tuc.gr/dl/dias/AF822548-BE39-4378-A952-A1C1F8E6296D10.1007/s11242-005-1525-8 Published at: 2015-09-19eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2006Summarization: A pore network consisting of a monolayer of glass beads was constructed
for experimental investigation of the effects of acoustic waves on the dissolution and
mobilization of perchloroethylene (PCE) ganglia. Dissolution experiments were conducted
with acoustic wave frequencies ranging from 75 to 225 Hz at a constant pressure amplitude
of 3.68 kPa applied to the inlet of the monolayer. Ganglia mobilization experiments
were conducted with a constant acoustic wave frequency of 125 Hz and acoustic pressure
amplitudes ranging from 0 to 39.07 kPa. Effluent dissolved PCE concentrations were
observed to increase in the presence of acoustic waves with the greatest increase (over
300%) occurring at the lowest frequency employed (75 Hz). Acoustic waves were also
observed to mobilize otherwise immobile PCE ganglia, break them apart, and further
enhance dissolution.Παρουσιάστηκε στο: Transport in Porous Mediapeer-reviewedBibliographic citation: C. V. Chrysikopoulos,E. T. Vogler,"Acoustically enhanced ganglia dissolution and mobilization in a monolayer of glass beads " ,trans.in por. media ,vol.64,no.1 ,pp.103–121,2006.doi:10.1007/s11242-005-1525-8 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306712012-10-10T00:00:00Z28info:eu-repo/semantics/articleDissolution of a multicomponent DNAPL pool in an experimental aquiferΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Kenneth Y. Lee()http://purl.tuc.gr/dl/dias/6997D60A-8495-4795-9EEF-C52EF7C3C96610.1016/j.jhazmat.2005.08.005Published at: 2015-09-17eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2006Summarization: This paper presents the results from a well-defined, circular-shaped, multicomponent dense nonaqueous phase liquid (DNAPL) pool dissolution
experiment conducted in a three-dimensional, bench scale model aquifer. The multicomponent pool is a mixture of tetrachloroethylene
(PCE) and 1,1,2-trichloroethane (1,1,2-TCA); PCE was the major component and 1,1,2-TCA was the minor component. Downgradient plume
concentrations were measured at five specific locations over time until the majority of the 1,1,2-TCA was depleted from the DNAPL pool
source. The experimental results suggest distinct spatial-temporal plume patterns for minor DNAPL components versus major DNAPL components.
The downgradient concentration varied over time for 1,1,2-TCA while a stable plume developed for PCE. A semi-analytical solution
for contaminant transport resulting from dissolution of multicomponent nonaqueous phase liquid pools successfully simulated the plume
structure and dynamics for both the major and minor DNAPL components.
© 2005 Elsevier B.V. All rights reserved.Παρουσιάστηκε στο: Journal of Hazardous Materialspeer-reviewedBibliographic citation: K. Y. Lee , C. V. Chrysikopoulos , " Dissolution of a multicomponent DNAPL pool in an experimental aquifer ",Jour. of Haza.Mater., pp 218–226.,2006, doi:10.1016/j.jhazmat.2005.08.005.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306742012-10-10T00:00:00Z28info:eu-repo/semantics/articleAcoustically enhanced multicomponent NAPL ganglia dissolution in water saturated packed columnsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Eric T. Vogler()http://purl.tuc.gr/dl/dias/FBD25A67-AD34-4BCA-99FE-3DC83D658CDC10.1021/es034665nPublished at: 2015-09-17eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2004Summarization: The impact of acoustic pressure waves on multicomponent
nonaqueous phase liquid (NAPL) ganglia dissolution in
water saturated columns packed with glass beads was
investigated. Laboratory data from dissolution experiments
with two and three component NAPL mixtures suggested
that acoustic waves significantly enhance ganglia dissolution
due to the imposed oscillatory interstitial water velocity.
The dissolution enhancement was shown to be directly
proportional to the acoustic wave frequency. Furthermore,
it was demonstrated that the greatest dissolution
enhancement in the presence of acoustic waves is
associated with the component of the NAPL mixture having
the smallest equilibrium aqueous solubility. Finally,
square shaped acoustic waves were shown to lead to
greater NAPL dissolution enhancement compared to
sinusoidal and triangular acoustic waves. The results of
this study suggested that aquifer remediation using acoustic
waves is a promising method particularly for aquifers
contaminated with NAPLs containing components with
very low equilibrium aqueous solubilities.Presented on: European Journal of Mechanical and Enviromental Engineeringpeer-reviewedBibliographic citation: C. V . Chrysikopoulos ,A . Vogler,"Acoustically Enhanced Multicomponent NAPL Ganglia Dissolution in Water Saturated Packed Columns " ,Environ. Sci. Technol. vol .38, pp. 2940-2945,2004.doi:10.1021/es034665ninfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306752012-10-10T00:00:00Z28info:eu-repo/semantics/articleDense colloid transport in a bifurcating fractureΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Scott C. James()http://purl.tuc.gr/dl/dias/7DFC9DB3-5E99-4559-9641-A9F234F6DB0910.1016/j.jcis.2003.09.033Published at: 2015-09-17eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2004Summarization: In this work, the transport of dense colloids through a water-saturated, bifurcating fracture is investigated using a constant spatial step
particle tracking technique. The size of the constituents of a colloid plume is an important factor affecting the partitioning of dense colloids
at the bifurcation. While neutrally buoyant colloids partition between daughter fractures in proportion to flow rates, dense colloids will
preferentially exit fractures that are gravitationally downgradient, notwithstanding that the majority of the interstitial fluid may flow through
the upper fracture. Comparison of the partitioning ratio between daughter fractures with the ratios of characteristic settling, diffusion, and
advection time reveal that these parameters control how colloids behave at fracture bifurcations.
Παρουσιάστηκε στο: Journal of Colloid and Interface Sciencepeer-reviewedBibliographic citation: S.C. James , C. V. Chrysikopoulos , "Dense colloid transport in a bifurcating fracture " ,Jour. of Coll. and Inter. Scien. ,vol.270,no.1 pp. 250–254,2004.doi:10.1016/j.jcis.2003.09.033info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306782012-10-10T00:00:00Z28info:eu-repo/semantics/articleEffective velocity and effective dispersion coefficient for finite-sized
particles flowing in a uniform fractureΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Scott C. James()http://purl.tuc.gr/dl/dias/28F948A0-F5B0-473F-8BFD-2EE5AB164E2F10.1016/S0021-9797(03)00254-6Published at: 2015-09-17eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2003Summarization: In this work we derive expressions for the effective velocity and effective dispersion coefficient for finite-sized spherical particles with
neutral buoyancy flowing within a water saturated fracture. We considered the miscible displacement of a fluid initially free of particles by
another fluid containing particles of finite size in suspension within a fracture formed by two semi-infinite parallel plates. Particle spreading
occurs due to the combined actions of molecular diffusion and the dispersive effect of the Poiseuille velocity profile. Unlike Taylor dispersion,
here the finite size of the particles is taken into account. It is shown that because the finite size of a particle excludes it from the slowest
moving portion of the velocity profile, the effective particle velocity is increased, while the overall particle dispersion is reduced. A similar
derivation applied to particles flowing in uniform tubes yields analogous results. The effective velocity and dispersion coefficient derived in
this work for particle transport in fractures with uniform aperture are unique and ideally suited for use in particle tracking models.Παρουσιάστηκε στο: Journal of Colloid and Interface Sciencepeer-reviewedBibliographic citation: S.C. James, C. V. Chrysikopoulos ,"Effective velocity and effective dispersion coefficient for finite-sized particles flowing in a uniform fracture " ,Journ. of Coll. and Interf. Sc.,vol. 263, no. 1 ,pp.288–295, 2003.doi :10.1016/S0021-9797(03)00254-6.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306812012-10-10T00:00:00Z28info:eu-repo/semantics/articleMass transfer coefficient and concentration boundary layer thickness for a dissolving NAPL pool in porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Kenneth Y. Lee()Marios M. Fyrillas()Pin-Yi Hsuan()Concentration boundary layer thickness,Time invariant average mass transfer coefficienthttp://purl.tuc.gr/dl/dias/88D7E4DA-0CA2-4C3F-884C-8183E089D3CA10.1016/S0304-3894(02)00264-9Published at: 2015-09-17eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2003Summarization: Analytical expressions for the time invariant, average mass transfer coefficient and the concentration
boundary layer thickness applicable to dissolving single-component nonaqueous phase liquid
(NAPL) pools in two-dimensional, saturated, homogeneous and isotropic porous formations are
derived. Good agreement between predicted and experimentally determined time invariant average
mass transfer coefficients is observed.Παρουσιάστηκε στο: Journal of Hazardous Materialspeer-reviewedBibliographic citation: C. V. Chrysikopoulos , P.Y.Hsuan,Marios M. Fyrillas , K. Y. Lee ,
"Mass transfer coefficient and concentration boundary layer thickness for a dissolving NAPL pool in porous media ",vol.97 ,no.1-3,pp.245-255,2003. doi: 10.1016/S0304-3894(02)00264-9info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306852012-10-10T00:00:00Z28info:eu-repo/semantics/articleRemoval of biocolloids suspended in reclaimed wastewater by injection into a fractured aquifer modelΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Rosanna La Mantia()Ioannis Manariotis()Costantino Masciopinto()Phenomenological Clogging Modelhttp://purl.tuc.gr/dl/dias/6E7DB66E-C37A-4B71-9274-E8AAA85E14EC10.1021/es902754nPublished at: 2015-09-17eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2010Summarization: Two pilot-scale fractured aquifer models (FAMs) consisting
of horizontal limestone slabs were employed to investigate the
removal of biocolloids suspended in reclaimed wastewater.
To better understand the behavior of real fractured aquifers,
theseFAMsintentionallywerenot “clean”.Thefracture apertures
were randomly spread with soil deposits, and both FAMs
were preflooded with reclaimed wastewater to simulate the
field conditions of the Nardo` fractured aquifer in the Salento area,
Italy, where fractures are not clean due to artificial groundwater
recharge. One of the FAMs was injected with secondary
effluent from a wastewater treatment plant collected prior to
the chlorination step and the other with exactly the same effluent,
which was further treated in a commercial membrane
reactor. Consequently, the organic and pathogen concentrations
were considerably higher in the secondary effluent than in
the membrane reactor effluent. Injected wastewater was
continuously recirculated. Pathogen removal was greater for
the secondary wastewater than the cleaner membrane reactor
effluent. A simple mathematical model was developed to
describe fracture clogging. The results suggest that the hydraulic
conductivity of FAMs can be significantly degraded due to
retention of viable and inactivated biocolloids suspended in
reclaimed wastewater.NRC Research PressΠαρουσιάστηκε στο: Environmental Science and Technology peer-reviewedBibliographic citation: C. V . Chrysikopoulos , C. Masciopinto , R. L. Mantia , I. D .Manariotis " Removal of biocolloids suspended in reclaimed wastewater by Injection into a fractured aquifer model " ,environ. sci. technol.,vol.44,no.3 , pp.971–977,2003. doi :10.1021/es902754n.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306872012-10-10T00:00:00Z28info:eu-repo/semantics/articleAnalysis of a ,model for contaminant transport in fracture media in the presence of colloidΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Assem Abdel-Salam()Analytical solution for colloid transporthttp://purl.tuc.gr/dl/dias/DA38DB3D-B8F0-489E-869B-A51B43CD17DE10.1016/0022-1694(94)02557-RPublished at: 2015-09-17eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1995Summarization: A mathematical model has been developed to study the cotransport of contaminants with colloids in saturated rock fractures. The contaminant is assumed to decay, and sorb on to fracture surfaces and on to colloidal particles, as well as to diffuse into the rock matrix; whereas, colloids are envisioned to deposit irreversibly on to fracture surfaces without penetration into the rock matrix. The governing one-dimensional equations describing the contaminant and the colloid transport in the fracture, colloid deposition on to fracture surfaces, and contaminant diffusion into the rock matrix are coupled. This coupling is accomplished by assuming that the amount of contaminant mass captured by colloidal particles in solution and the amount captured by deposited colloids on fracture surfaces are described by modified Freundlich reversible equilibrium sorption relationships, and that mass transport by diffusion into the rock matrix is a first-order process. The contaminant sorption on to fracture surfaces is described by a linear equilibrium sorption isotherm, while the deposition of colloids is incorporated into the model as a first-order process. The resulting coupled contaminant transport non-linear equation is solved numerically with the fully implicit finite difference method. The constant concentration as well as the constant flux boundary conditions have been considered. The impact of the presence of colloids on contaminant transport is examined. According to model simulations the results show that, depending on the conditions of the physical system considered, colloids can increase or decrease the mobility of contaminants.
Παρουσιάστηκε στο: Journal of Hydrologypeer-reviewedBibliographic citation: A. A. Salam,C. V. Chrysikopoulos ,"Analysis of a model for contaminant transport in fracture media in the presence of colloid ", J. of Hydrol.,vol. 165,no.1-4 , pp. 261-268 ,1995.doi:10.1016/0022-1694(94)02557-Rinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306892012-10-10T00:00:00Z28info:eu-repo/semantics/articleA three-dimensional steady-state atmospheric dispersion-deposition model for emissions from a ground-level area sourceΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)P. V. Roberts()L . M. Hildemman()Evaluation of Atmospheric disprersion model parametershttp://purl.tuc.gr/dl/dias/27DB26F8-81D1-4F27-9531-306AC4D10BA910.1016/0960-1686(92)90234-CPublished at: 2015-09-17eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1992Summarization: An analytical solution to the steady-state three-dimensional atmospheric dispersion equation
has been developed for the transport of non-buoyant emissions from a continuous ground-level area source.
The model incorporates power law profiles for the variation of wind speed and vertical eddy diffusivity with
height, represents the lateral eddy diffusivity as a function of wind speed and the crosswind dispersion
coefficient, and includes dry deposition as a removal mechanism. The model is well suited for accurate
prediction of emission concentration levels in the vicinity of an area source, as well as farther downwind,
under neutral or stable atmospheric conditions. The impact of the important model parameters on
contaminant dispersion is examined. The results from several simulations, compared with point and line
sources of equivalent source strength, indicate that at short downwind distances, predictions of contaminant
concentrations emitted from area sources may be unacceptably inaccurate unless the structure of the
source is properly taken into account.Παρουσιάστηκε στο: Atmospheric Environmentpeer-reviewedBibliographic citation: C. V. Chrysikopoulos ,L. M. Hildemann, P. V. Roberts, "A three-dimensional steady-state atmospheric dispersion-deposition model for emissions from a ground-level area source ",Atm. Envir, Vol. 26A, No. 5, pp. 747 -757, 1992.doi:10.1016/0960-1686(92)90234-C.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306912012-10-10T00:00:00Z28info:eu-repo/semantics/articleAnalytical solutions for one-dimensional colloid transport in saturated fracturesΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Assem Abdel-Salam()http://purl.tuc.gr/dl/dias/F8BDAA09-ADB9-4FF9-B398-9C94E0A57ACC10.1016/0309-1708(94)90032-9Published at: 2015-09-18eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1994Summarization: Closed-form analytical solutions for colloid transport in single rock fractures with
and without colloid penetration into the rock matrix are derived for constant
concentration as well as constant flux boundary conditions. A single fracture is
idealized as two semi-infinite parallel plates. It is assumed that colloidal particles
undergo irreversible deposition onto fracture surfaces and may penetrate into the
rock matrix, and deposit irreversibly onto rock matrix solid surfaces. The
solutions are obtained by taking Laplace transforms to the governing transport
equations and boundary conditions with respect to time and space. For the case
of no colloid penetration into the rock matrix, the solutions are expressed in terms
of exponentials and complimentary error functions; whereas, for the case of
colloid penetration into the rock matrix, the solutions are expressed in terms of
convolution integrals and modified Bessel functions. The impact of the model
parameters on colloid transport is examined. The results from several simulations
indicate that liquid-phase as well as deposited colloid concentrations in the
fracture are sensitive to the fracture surface deposition coefficient, the fracture
aperture, and the Brownian diffusion coefficient for colloidal particles penetrating
the rock matrix. Furthermore, it is shown that the differences between the two
boundary conditions investigated are minimized at dominant advective transport
conditions. The constant concentration condition overestimates liquid-phase
colloid concentrations, whereas the constant flux condition leads to conservation
of mass.
Παρουσιάστηκε στο: Advances in Water Resources peer-reviewedBibliographic citation: A. A. Salam, C. V. Chrysikopoulos, "Analytical solutions for one-dimensional colloid transport in saturated fractures ",Adv.n Wa. Res.,vol.17,no. 5,pp. 283- 296,1994.doi :10.1016/0309-1708(94)90032-9info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306932012-10-10T00:00:00Z28info:eu-repo/semantics/articleOne-dimensional virus transport in homogeneous porous media with time-dependent distribution coefficientΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Youn Sim()http://purl.tuc.gr/dl/dias/3EF28468-B1FE-495F-A12B-E50C7AD0EE0610.1016/0022-1694(95)02990-7Published at: 2015-09-18eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1996Summarization: A stochastic model for one-dimensional virus transport in homogeneous, saturated, semi-infinite porous media is developed. The model accounts for first-order inactivation of liquid-phase and adsorbed viruses with different inactivation rate constants, and time-dependent distribution coefficient. It is hypothesized that the virus adsorption process is described by a local equilibrium expression with a stochastic time-dependent distribution coefficient. A closed form analytical solution is obtained by the method of small perturbation or first-order approximation for a semi-infinite porous medium with a flux-type inlet boundary condition. The results from several simulations indicate that a time-dependent distribution coefficient results in an enhanced spreading of the liquid-phase virus concentration.
Παρουσιάστηκε στο: Journal of Hydrologypeer-reviewedBibliographic citation: C. V. Chrysikopoulos , Y. Sim , " One-dimensional virus transport in homogeneous porous media with time-dependent distribution coefficient " ,Jour. of Hydrol.,vol. 185 ,no. 1-4 ,pp.199-219,1996.doi:10.1016/0022-1694(95)02990-7info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306952012-10-10T00:00:00Z28info:eu-repo/semantics/articleAnalytical solutions for solute transport in saturated porous media with semi-infinite or finite thicknessΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Youn Sim()http://purl.tuc.gr/dl/dias/4CB55FC5-2C05-411B-93DA-91996139897710.1016/S0309-1708(98)00027-XPublished at: 2015-09-18eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1999Summarization: Three-dimensional analytical solutions for solute transport in saturated, homogeneous
porous media are developed. The models account for three-dimensional dispersion in
a uniform flow field, first-order decay of aqueous phase and sorbed solutes with
different decay rates, and nonequilibrium solute sorption onto the solid matrix of the
porous formation. The governing solute transport equations are solved analytically by
employing Laplace, Fourier and finite Fourier cosine transform techniques. Porous
media with either semi-infinite or finite thickness are considered. Furthermore,
continuous as well as periodic source loadings from either a point or an elliptic source
geometry are examined. The effect of aquifer boundary conditions as well as the
source geometry on solute transport in subsurface porous formations is investigated.Παρουσιάστηκε στο: Advances in Water Resourcespeer-reviewedBibliographic citation: Y. Sim , C. V. Chrysikopoulos , "Analytical solutions for solute transport in saturated porous media with semi-infinite or
finite thickness " ,Adv.in Wat. Res.Vol. 22, No. 5, pp. 507–519, 1999.doi:10.1016/S0309-1708(98)00027-X.info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:307092012-10-10T00:00:00Z28info:eu-repo/semantics/articleContaminant transport resulting from
multicomponent nonaqueous phase liquid pool
dissolution in three-dimensional subsurface formations Χρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Kenneth Y. Lee()http://purl.tuc.gr/dl/dias/3491D5AC-32B9-417E-89DB-F8CB6FF1915E10.1016/S0169-7722(97)00053-3 Published at: 2015-09-18eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1998Summarization: A semi-analytical method for simulating transient contaminant transport originating from the
dissolution of multicomponent nonaqueous phase liquid NAPL pools in three-dimensional,
saturated, homogeneous porous media is presented. Each dissolved component may undergo
first-order decay and may sorb under local equilibrium conditions. The NAPL pool dissolution
. process is envisioned to occur in a series of consecutive short intervals pulses . The mole
fraction, nonaqueous phase activity coefficient and aqueous solubility of every pool constituent are
estimated before the initiation of each pulse, and they are assumed to remain constant for the
duration of each interval. Individual component aqueous phase concentrations resulting from each
dissolution interval are estimated by existing analytical solutions applicable to single component
NAPL pools, and total concentration distributions of the same component are obtained by direct
superposition. The semi-analytical method is more efficient and less computationally demanding
than a finite-difference approximation. Furthermore, it is shown that neglecting the changes in
nonaqueous phase activity coefficients that occur during multicomponent NAPL pool dissolution
may result in erroneous predictions. The model presented in this work is useful for the design and
interpretation of experiments in laboratory bench scale aquifers, certain homogeneous subsurface
formations, and for the verification of complex numerical codes.Παρουσιάστηκε στο: Journal of Contaminant Hydrologypeer-reviewedBibliographic citation: C. V. Chrysikopoulos, K. Y. Lee "Contaminant transport resulting from multicomponent nonaqueous phase liquid pool dissolution in three-dimensional subsurface formations " ,J. of Cont. Hydrol.,vol. 31, no.1-2,pp.1–21,1998.doi:10.1016/S0169-7722(97)00053-3 .info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:307112012-10-10T00:00:00Z28info:eu-repo/semantics/articleAn efficient particle tracking equation with specified spatial step for the solution of the diffusion equationΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)ScottC.James()http://purl.tuc.gr/dl/dias/F7F6A630-5250-4584-9C75-1DF4F3C79AFE10.1016/S0009-2509(01)00344-X Published at: 2015-09-18eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2001Summarization: The traditional di(usive particle tracking equation provides an updated particle location as a function of its previous location
and molecular di(usion coe cient while maintaining a constant time step. A smaller time step yields an increasingly accurate, yet
more computationally demanding solution. Selection of this time step becomes an important consideration and, depending on the
complexity of the problem, a single optimum value may not exist. The characteristics of the system under consideration may be
such that a constant time step may yield solutions with insu cient accuracy in some portions of the domain and excess computation
time for others. In this work, new particle tracking equations speci%cally designed for the solution of problems associated with
di(usion processes in one, two, and three dimensions are presented. Instead of a constant time step, the proposed equations employ
a constant spatial step. Using a traditional particle tracking algorithm, the travel time necessary for a particle with a di(usion
coe cient inversely proportional to its diameter to achieve a pre-speci%ed distance was determined. Because the size of a particle
a(ects how it di(uses in a quiescent 8uid, it is expected that two di(erently sized particles would require di(erent travel times to
move a given distance. The probability densities of travel times for plumes of monodisperse particles were consistently found to
be log-normal in shape. The parameters describing this log-normal distribution, i.e., mean and standard deviation, are functions of
the distance speci%ed for travel and the di(usion coe cient of the particles. Thus, a random number selected from this distribution
approximates the time required for a given particle to travel a speci%ed distance. The new equations are straightforward and may be
easily incorporated into appropriate particle tracking algorithms. In addition, the new particle tracking equations are as accurate and
often more computationally e cient than the traditional particle tracking equationΠαρουσιάστηκε στο: Chemical Engineering Sciencepeer-reviewedBibliographic citation: S. C.James, C. V. Chrysikopoulos , "An e cient particle tracking equation with speci%ed spatial step for the solution of the diffusion equation ", Chem.Engin. Sc,.vol. 56,no.23 ,pp. 6535–6543, 2001.doi :10.1016/S0009-2509(01)00344-X info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:307132012-10-10T00:00:00Z28info:eu-repo/semantics/articleModeling of colloid and colloid-facilitated contaminant transport in a two-dimensional fracture with spatially variable apertureΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Assem Abdel-Salam()http://purl.tuc.gr/dl/dias/63774FC1-068D-456C-B4FA-5DD4140C6168 10.1007/BF01073172 Published at: 2015-09-18eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1995Summarization: Mathematical models are developed for two-dimensional transient transport of colloids, and cotransport of contaminant/colloids in a fracture-rock matrix system with spatially variable fracture aperture. The aperture in the fracture plane is considered as a lognormally distributed random variable with spatial fluctuations described by an exponential autocovariance function. Colloids are envisioned to irreversibly deposit onto fracture surfaces without penetrating the rock matrix; whereas, the contaminant is assumed to decay, sorb onto fracture surfaces and onto colloidal particles, as well as to diffuse into the rock matrix. The governing stochastic transport equations are solved numerically for each realization of the aperture fluctuations by a fully implicit finite difference scheme. Emphasis is given on the effects of variable aperture on colloid and colloid-facilitated contaminant transport. Simulated breakthrough curves of ensemble averages of several realizations show enhanced colloid transport and more pronounced fingering when colloids are subject to size exclusion from regions of small aperture size. Moreover, it is shown that an increase in the fracture aperture fluctuations leads to faster transport and increases dispersion. For the case of contaminant/colloids cotransport it is shown, for the conditions considered in this work, that colloids enhance contaminant mobility and increase contaminant dispersion.
Παρουσιάστηκε στο: Transport in Porous Mediapeer-reviewedBibliographic citation: C. V. Chrysikopoulos, A. Abdel-Salam "Modeling of colloid and colloid-facilitated contaminant transport in a two-dimensional fracture with spatially variable aperture " , Transp.in Por. Med. ,vol. 20,no.3,pp. 197-221, 1995.doi : 10.1007/BF01073172 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:307152012-10-10T00:00:00Z28info:eu-repo/semantics/articleModeling the transport of contaminants originating from the dissolution of DNAPL pools in aquifers in the presence of dissolved humic substancesΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Michael E. Tatalovich()Kenneth Y. Lee()http://purl.tuc.gr/dl/dias/F788FC1F-93AF-4B01-9947-8A3773EE0F6A10.1023/A:1006674114600 Published at: 2015-09-18eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1999Summarization:
A two-dimensional finite difference numerical model was developed to describe the
transport of dissolved organics originating from nonaqueous phase liquid (NAPL) pool dissolution in
saturated porous media in the presence of dissolved humic substances. A rectangular NAPL pool was
considered in a homogeneous porous medium with unidirectional interstitial groundwater velocity.
It was assumed that dissolved humic substances and aqueous phase contaminants may sorb onto the
solid matrix under local equilibrium conditions. The contaminant in the aqueous phase may undergo
first-order decay. Also, the dissolved contaminant may sorb onto humic substances. The transport
properties of dissolved humic substances are assumed to be unaffected by sorbing contaminants,
because dissolved humic macromolecules are much larger than dissolved contaminants and sorp-
tion of nonpolar contaminants onto humic substances do not affect the overall surface charge of
humic substances. The sorption characteristics of dissolved humic substances onto clean sand were
determined from column experiments. An effective local mass transfer rate coefficient accounting
for the presence of dissolved humic substances was developed. Model simulations indicate that
dissolved humic substances substantially increase NAPL pool dissolution, and consequently reduce
the required pump-and-treat aquifer remediation time. Παρουσιάστηκε στο: Transport in Porous Media peer-reviewedBibliographic citation: C. V. Chrysikopoulos ,K. Y. Lee ,M. E. Tatalovich ,"Modeling the transport of contaminants originating from the dissolution of DNAPL
pools in aquifers in the presence of dissolved humic substances" Trans. in Por.Med.,vol. 38,no.1 ,pp.93–115, 2000.doi:10.1023/A:1006674114600 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:307172012-10-10T00:00:00Z28info:eu-repo/semantics/articleThree-dimensional analytical models for virus Χρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Youn Sim()Comparison with Experimental Data,Model Simulations and Discussion,Model Developmenthttp://purl.tuc.gr/dl/dias/F76A8A02-C22F-4529-9C58-4DA2D99CAEAB10.1023/A:1006596412177Published at: 2015-09-18eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1998Summarization: Analytical models for virus transport in saturated, homogeneous porous media are developed.
The models account for three-dimensional dispersion in a uniform flow field, and first-order
inactivation of suspended and deposited viruses with different inactivation rate coefficients. Virus
deposition onto solid particles is described by two different processes: nonequilibrium adsorption
which is applicable to viruses behaving as solutes; and colloid filtration which is applicable to viruses
behaving as colloids. The governing virus transport equations are solved analytically by employing
Laplace/Fourier transform techniques. Instantaneous and continuous/periodic virus loadings from
a point source are examined.Παρουσιάστηκε στο: Transport in Porous Mediapeer-reviewedBibliographic citation: C. V. Chrysikopoulos , Y. Sim ,"Three-dimensional analytical models for virus " ,Tr. in por. me.,vol.30,no.1pp. 87–112, 1998.doi :10.1023/A:1006596412177info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:307312012-10-10T00:00:00Z28info:eu-repo/semantics/articleTransport of neutrally buoyant and dense
variably sized colloids in a two-dimensional
fracture with anisotropic apertureΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Scott C James()http://purl.tuc.gr/dl/dias/9E69919A-0EF0-4B7F-B354-22E20E18E0AD10.1023/A:1021952226861 Published at: 2015-09-19eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2003Summarization: The transport of monodisperse as well as polydisperse colloid suspensions in a twodimensional,
water saturated fracture with spatially variable and anisotropic aperture is investigated
with a particle tracking model. Both neutrally buoyant and dense colloid suspensions are considered.
Although flow and transport in fractured subsurface formations have been studied extensively by
numerous investigators, the transport of dense, polydisperse colloid suspensions in a fracture with
spatially variable and anisotropic aperture has not been previously explored. Simulated snapshots and
breakthrough curves of ensemble averages of several realizations of a log-normally distributed aperture
field show that polydisperse colloids exhibit greater spreading than monodisperse colloids, and
dense colloids show greater retardation than neutrally buoyant colloids. Moreover, it is demonstrated
that aperture anisotropy oriented along the flow direction substantially increases colloid spreading;
whereas, aperture anisotropy oriented transverse to the flow direction retards colloid movement.Παρουσιάστηκε στο: Transport in Porous Media peer-reviewedBibliographic citation: C. V. Chrysikopoulos, S. C. James, "Transport of neutrally buoyant and dense variably sized colloids in a two-dimensional
fracture with anisotropic aperture " ,Tran.in Por. Med.,vol. 51,no.2 ,pp.191–210, 2003.doi:10.1023/A:1021952226861info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:307352012-10-10T00:00:00Z28info:eu-repo/semantics/articleArtificial tracers for geothermal reservoir studiesΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Physicochemical tracer retention processeshttp://purl.tuc.gr/dl/dias/56FF26C7-002B-4E8C-A2DD-C10211B96DE810.1007/BF00775286 Published at: 2015-09-19eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1993Summarization: Safe disposal of thermally spent geothermal
brines that contain environmentally hazardous constituents
is commonly obtained by reinjection. The reinjection
process also serves to maintain reservoir pressure, enhance
thermal recovery, and eliminate possible compactional
subsidence. To avoid premature thermal breakthrough of
reinjected fluids, tracer tests are employed for detection
and evaluation of preferential path networks. In this paper
some promising tracers that have not received much attention
in geothermal reservoir studies are discussed, and a
comprehensive tabulation of field sites of artificial tracer
utilization is presented. Chemical and transport processes
responsible for tracer retention by the formation of reservoir
solids, as well as available tracer detection techniques,
are emphasized.Παρουσιάστηκε στο: Environmental Geologypeer-reviewedBibliographic citation: C. V. Chrysikopoulos , "Artificial tracers for geothermal reservoir
studiesb",Env. Geol.,vol.22 ,no.1 ,pp. 60- 70,1993.doi:10.1007/BF00775286 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:307372012-10-10T00:00:00Z28info:eu-repo/semantics/articleContaminant transport in a fracture with spatially variable aperture in the presence of monodisperse and polydisperse colloidsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Scott C. James()Tanya K. Bilezikjian()http://purl.tuc.gr/dl/dias/F36756C9-FC4E-4D68-AA2B-79D244EF1C73 10.1007/s00477-004-0231-3 Published at: 2015-09-19eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2005Summarization: A quasi-three-dimensional particle tracking
model is developed to characterize the spatial and temporal
effects of advection, molecular diffusion, Taylor
dispersion, fracture wall deposition, matrix diffusion,
and co-transport processes on two discrete plumes
(suspended monodisperse or polydisperse colloids and
dissolved contaminants) flowing through a variable
aperture fracture situated in a porous medium. Contaminants
travel by advection and diffusion and may
sorb onto fracture walls and colloid particles, as well as
diffuse into and sorb onto the surrounding porous rock
matrix. A kinetic isotherm describes contaminant sorption
onto colloids and sorbed contaminants assume the
unique transport properties of colloids. Sorption of the
contaminants that have diffused into the matrix is governed
by a first-order kinetic reaction. Colloids travel by
advection and diffusion and may attach onto fracture
walls; however, they do not penetrate the rock matrix. A
probabilistic form of the Boltzmann law describes filtration
of both colloids and contaminants on fracture
walls. Ensemble-averaged breakthrough curves of many
fracture realizations are used to compare arrival times of
colloid and contaminant plumes at the fracture outlet.
Results show that the presence of colloids enhances
contaminant transport (decreased residence times) while
matrix diffusion and sorption onto fracture walls retard
the transport of contaminantsΠαρουσιάστηκε στο: Stochastic Environmental Research and Risk Assessment peer-reviewedBibliographic citation: S.C. James,T. K. Bilezikjian ,C.V Chrysikopoulos"Contaminant transport in a fracture with spatially variable aperture in the presence of monodisperse and polydisperse colloids", Stoch. Environ. Res. Ris.k Assess ,vol.19,no.4 ,pp. 266–279,2005.doi :10.1007/s00477-004-0231-3 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:307712012-10-10T00:00:00Z28info:eu-repo/semantics/articleLocal mass transfer vorrelations for nonaqueous phase liquid pool dissolution in saturated porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Tae-Joo KIim()Formulation of Mass Transfer Correlationshttp://purl.tuc.gr/dl/dias/89C39575-0A11-478F-B693-AB8B73A8390E10.1023/A:1006655908240Published at: 2015-09-19eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1999Summarization: Local mass transfer correlations are developed to describe the rate of interface mass transfer
of single component nonaqueous phase liquid (NAPL) pools in saturated subsurface formations.
A three-dimensional solute transport model is employed to compute local mass transfer coefficients
from concentration gradients at the NAPL–water interface, assuming that the aqueous phase concentration
along the NAPL–water interface is constant and equal to the solubility concentration.
Furthermore, it is assumed that the porous medium is homogeneous, the interstitial fluid velocity
steady and the dissolved solute may undergo first-order decay or may sorb under local equilibrium
conditions. Power-law expressions relating the local Sherwood number to appropriate local Peclet
numbers are developed for both rectangular and elliptic/circular source geometries. The proposed
power law correlations are fitted to numerically generated data and the correlation coefficients are
determined using nonlinear least squares regression. The estimated correlation coefficients are found
to be direct functions of the interstitial fluid velocity, pool dimensions, and pool geometry.Παρουσιάστηκε στο: Transport in Porous Mediapeer-reviewedBibliographic citation: C. V. Chrysikopoulos,T.J. Kim, "Local mass transfer correlations for nonaqueous phase liquid pool dissolution insSaturated porous media",Transp. in Por. Media.,vol. 38 ,no.1 ,pp.167–187, 2000.doi :10.1023/A:1006655908240info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:308112012-10-10T00:00:00Z28info:eu-repo/semantics/articleEstimation of time dependent virus inactivation rates by geostatistical and resampling techniques: Application to virus transport in porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)E. T. Vogler() Virus transport in porous media, Poliovirus inactivationhttp://purl.tuc.gr/dl/dias/1D12D20F-0909-4549-AAB8-B5C8C5E0641C10.1007/s00477-003-0130-z Published at: 2015-09-19eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2004Summarization: A methodology is developed for estimating
temporally variable virus inactivation rate coefficients
from experimental virus inactivation data. The methodology
consists of a technique for slope estimation of
normalized virus inactivation data in conjunction with
a resampling parameter estimation procedure. The
slope estimation technique is based on a relatively
flexible geostatistical method known as universal kriging.
Drift coefficients are obtained by nonlinear fitting
of bootstrap samples and the corresponding confidence
intervals are obtained by bootstrap percentiles. The
proposed methodology yields more accurate time dependent
virus inactivation rate coefficients than those
estimated by fitting virus inactivation data to a firstorder
inactivation model. The methodology is successfully
applied to a set of poliovirus batch inactivation
data. Furthermore, the importance of accurate inactivation
rate coefficient determination on virus transport
in water saturated porous media is demonstrated with
model simulationsΠαρουσιάστηκε στο: Stochastic Environmental Research and Risk Assessmentpeer-reviewedBibliographic citation: C. V. Chrysikopoulos,E. T. Vogler, "Estimation of time dependent virus inactivation rates by geostatistical and resampling techniques: application to virus transport in porous media", Stoch. Environ.Res. ,vol. 18,no.2 ,pp. 67 – 78,2004.doi10.1007/s00477-003-0130-zinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:308152012-10-10T00:00:00Z28info:eu-repo/semantics/articleNonaqueous liquid pool dissolution in three-dimensional heterogeneous subsurface formationsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)E.T. Vogler()W.M.J. Bao()Mass transfer correlation,Comparison with analytical solutionhttp://purl.tuc.gr/dl/dias/75267210-1178-475D-9E01-354C7731A6C410.1007/s00254-002-0721-x Published at: 2015-09-19eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2003Summarization: A three-dimensional numerical flow and
contaminant transport model is developed to investigate
the effect of variable hydraulic conductivity on
average mass transfer coefficients associated with the
dissolution of dense nonaqueous phase liquid
(DNAPL) pools in heterogeneous, water-saturated
subsurface formations. Randomly generated, threedimensional
hydraulic conductivity fields are used to
represent a heterogeneous confined aquifer. Model
simulations indicate that the average mass transfer
coefficient is inversely proportional to the variance of
the log-transformed hydraulic conductivity. A power
law correlation relating the Sherwood number to the
variance of the log-transformed hydraulic conductivity
and appropriate Peclet numbers is developed.
A reasonable fit between predicted and numerically
determined mass transfer coefficients is observedΠαρουσιάστηκε στο: Environmental geologypeer-reviewedBibliographic citation: W.M.J. Bao, E.T. Vogler, C.V. Chrysikopoulos ,"Nonaqueous liquid pool dissolution in three-dimensional heterogeneous subsurface formations ",Envir. Geol.,vol. 43,no.8 ,pp.968–977,2003.doi :10.1007/s00254-002-0721-x info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:308172012-10-10T00:00:00Z28info:eu-repo/semantics/articleMonodisperse and polydisperse colloid transport in water-saturated fractures with various orientations: Gravity effectsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Scott C. James()http://purl.tuc.gr/dl/dias/BD0AACBA-B776-4111-A9A2-2D3E041F9D5A 10.1016/j.advwatres.2011.06.001 Published at: 2015-09-19eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2011Summarization: Numerical experiments are conducted to examine the effects of gravity on monodisperse and polydisperse
colloid transport in water-saturated fractures with uniform aperture. Dense colloids travel in
water-saturated fractures by advection and diffusion while subject to the influence of gravity. Colloids
are assumed to neither attach onto the fracture walls nor penetrate the rock matrix based on the assumptions
that they are inert and their size is larger than the pore size of the surrounding solid matrix. Both
the size distribution of a colloid plume and colloid density are shown to be significant factors impacting
their transport when gravitational forces are important. A constant-spatial-step particle-tracking code
simulates colloid plumes with increasing densities transporting in water-saturated fractures while
accounting for three forces acting on each particle: a deterministic advective force due to the Poiseuille
flow field within the fracture, a random force caused by Brownian diffusion, and the gravitational force.
Integer angles of fracture orientation with respect to the horizontal ranging from ±90 are considered:
three lognormally distributed colloid plumes with mean particle size of 1 lm (averaged on a volumetric
basis) and standard deviation of 0.6, 1.2 and 1.8 lm are examined. Colloid plumes are assigned densities
of 1.25, 1.5, 1.75 and 2.0 g/cm3. The first four spatial moments and the first two temporal moments are
estimated as functions of fracture orientation angle and colloid density. Several snapshots of colloid
plumes in fractures of different orientations are presented. In all cases, larger particles tend to spread
over wider sections of the fracture in the flow direction, but smaller particles can travel faster or slower
than larger particles depending on fracture orientation angleΠαρουσιάστηκε στο: Advances in Water Resourcespeer-reviewedBibliographic citation: S. C. James , C.V. Chrysikopoulos , "Monodisperse and polydisperse colloid transport in water-saturated fractures with various orientations: Gravity effects " ,Advanc. in Wat.Resou. ,vol.3,no.10, pp. 1249–1255,2011.doi : 10.1016/j.advwatres.2011.06.001 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:308322012-10-10T00:00:00Z28info:eu-repo/semantics/articleTransport of polydisperse colloids in a saturated fracture with spatially variable apertureΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Scott C. James()Algorithm Development,Fracture Generationhttp://purl.tuc.gr/dl/dias/A7D9F28D-166D-4430-935C-5C2786FC365E10.1029/2000WR900048 Published at: 2015-09-19eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2000Summarization: A particle tracking model is developed to simulate the transport of variably
sized colloids in a fracture with a spatially variable aperture. The aperture of the fracture
is treated as a lognormally distributed random variable. The spatial fluctuations of the
aperture are described by an exponential autocovariance function. It is assumed that
colloids can sorb onto the fracture walls but may not penetrate the rock matrix. Particle
advection is governed by the local fracture velocity and diffusion by the Stokes-Einstein
equation. Model simulations for various realizations of aperture fluctuations indicate that
lognormal colloid size distributions exhibit greater spreading than monodisperse
suspensions. Both sorption and spreading of the polydisperse colloids increase with
increasing variance in the particle diameter. It is shown that the largest particles are
preferentially transported through the fracture leading to early breakthrough while the
smallest particles are preferentially sorbed. Increasing the variance of the aperture
fluctuations leads to increased tailing for both monodisperse and variably sized colloid
suspensions, while increasing the correlation length of the aperture fluctuations leads to
increased spreading.Παρουσιάστηκε στο: Water Resources Researchpeer-reviewedBibliographic citation: S. C. James , C. V. Chrysikopoulos ,"Transport of polydisperse colloids in a saturated fracture with spatially variable aperture ",Wat.Resou.Res., vol. 36, no. 6, pp 1457–1465, Jun. 2000.doi :10.1029/2000WR900048 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:308922012-10-10T00:00:00Z28info:eu-repo/semantics/articleAnalytical models for one-dimensional virus transport in saturated porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Youn Sim()http://purl.tuc.gr/dl/dias/5889F740-AB98-4A55-9330-5C56E55EA85310.1029/95WR00199Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1995Summarization: Analytical solutions to two mathematical models for virus transport in
one-dimensional homogeneous, saturated porous media are presented, for
constant flux as well as constant concentration boundary conditions,
accounting for first-order inactivation of suspended and adsorbed (or
filtered) viruses with different inactivation constants. Two processes
for virus attachment onto the solid matrix are considered. The first
process is the nonequilibrium reversible adsorption, which is applicable
to viruses behaving as solutes; whereas, the second is the filtration
process, which is suitable for viruses behaving as colloids. Since the
governing transport equations corresponding to each physical process
have identical mathematical forms, only one generalized closed-form
analytical solution is developed by Laplace transform techniques. The
impact of the model parameters on virus transport is examined. An
empirical relation between inactivation rate and subsurface temperature
is employed to investigate the effect of temperature on virus transport.
It is shown that the differences between the two boundary conditions are
minimized at advection-dominated transport conditions.
Παρουσιάστηκε στο: Water Resources Researchpeer-reviewedBibliographic citation: C. V. Chrysikopoulos ,Y. Sim , "Analytical models for one-dimensional virus transport in saturated porous media , W. Resou. Res. ,vol. 31,no.5,pp.1429-1437,1995. doi :10.1029/95WR00199info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:308942012-10-10T00:00:00Z28info:eu-repo/semantics/articleUnsaturated flow in a quasi-three-dimensional fractured
medium with spatially variable aperture Χρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Assem Abdel-Salam()Numerical Formulationhttp://purl.tuc.gr/dl/dias/CAFE0EB4-83B0-4AB0-A7A0-478981E6123E 10.1029/96WR00656 Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1996Summarization: Transient moisture flow in a variably saturated quasi-three-dimensional
fracture-rock matrix system is investigated. The fracture is assumed to possess a spatially
variable aperture in its two-dimensional plane, whereas the rock matrix is treated as a
two-dimensional homogeneous and tight porous medium. The aperture fluctuations in the
fracture plane are described stochastically. Moisture exchange between the fracture and
the rock matrix is accounted for via an advective coupling term that governs the transfer
of moisture at the fracture-matrix interface and takes into account the effect of a fracturesurface
coating material. Although the variable aperture fracture is two-dimensional, the
coupling term between the fracture and the rock matrix accounts for the threedimensional
nature of the physical system. The stochastic nonlinear set of partial
differential equations is solved numerically by the Galerkin finite element method in
conjunction with the Picard iterative scheme and an automatic time step marching.
Simulations are performed to investigate phenomena which have been ignored in previous
studies. It is demonstrated that, for the case of no moisture exchange with the rock matrix,
the moisture follows preferential flow paths within the fracture plane and exhibits
pronounced fingering effects. Furthermore, it is shown that the larger the fracture
aperture fluctuations the more extended the moisture flow in the fracture. In addition, for
the case where there exists moisture exchange with the rock matrix, the movement of the
moisture front is considerably reduced, whereas fracture-surface coatings tend to slow
down moisture absorption by the rock matrix.Παρουσιάστηκε στο: Water resource researchpeer-reviewedBibliographic citation: A. A.Salam , C.V. Chrysikopoulos, "Unsaturated flow quasi-three-dimensional fractured medium with spatially variable aperture ", W.Resou.Resear ,vol.32,no.6,pp.1531-1540,1996.doi: 10.1029/96WR00656 .info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:308962012-10-10T00:00:00Z28info:eu-repo/semantics/articleOne-dimensional virus transport in porous media with time-dependent inactivation rate coefficientsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Youn Sim()Parameter Sensitivity Analysishttp://purl.tuc.gr/dl/dias/6DBD0025-8BE5-4818-BBAA-6DF29F0B540610.1029/96WR01496Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1996Summarization: A model for virus transport in one-dimensional, homogeneous, saturated
porous media is developed, accounting for virus sorption and inactivation of liquid phase
and adsorbed viruses with different time dependent rate coefficients. The virus inactivation
process is represented by a pseudo first-order rate expression. The pseudo first-order
approximation is shown to simulate available experimental data from three virus
inactivation batch studies better than the frequently employed constant rate inactivation
model. Model simulations indicated that the pseudo first-order approximation, compared
to the constant inactivation, leads to extended survival of viruses and, consequently, more
distant migration. Results from a parameter sensitivity analysis demonstrated that
estimation of pseudo first-order inactivation rate coefficients from field observations
requires data collection near the source of virus contamination during initial stages of
virus transport.Παρουσιάστηκε στο: Water resource researchpeer-reviewedBibliographic citation: Y. Sim , C. V. Chrysikopoulos,"One-dimensional virus transport in porous media with time-dependent inactivation rate coefficients ", Wa.resourc. res. , vol .32,no.8,pp.2607-2611,1996.doi:10.1029/96WR01496info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:308982012-10-10T00:00:00Z28info:eu-repo/semantics/articleAnalytical models for virus adsorption and inactivation in unsaturated porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Youn Sim()http://purl.tuc.gr/dl/dias/835E2A5D-7073-4169-9D47-A9240D81269410.1016/S0927-7757(99)00073-4 Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1999Summarization: Analytical models for virus adsorption and inactivation in batch systems of homogeneous, isothermal, unsaturated
porous media were developed. The models account for virus sorption onto liquid–solid as well as air–liquid interfaces
and inactivation of viruses in the liquid phase and at both interfaces. Mathematical expressions appropriate for virus
sorption onto liquid–solid and air–liquid interfaces were developed as functions of the soil moisture variation. The
models were solved analytically by Laplace transform procedures. The effects of soil moisture variation on virus
sorption at the liquid–solid as well as air–liquid interfaces were investigated. Available experimental data from virus
adsorption-inactivation batch studies were successfully simulated by one of the models developed in this work.
Παρουσιάστηκε στο: Colloids and Surfaces A Physicochemical and Engineering Aspectspeer-reviewedBibliographic citation: Y. Sim, C. V. Chrysikopoulos ,"Analytical models for virus adsorption and inactivation in unsaturated porous media ",Physicoch. and Engin. Aspects,vol. 155 , no.2-3 ,pp.189–197,1999.doi:10.1016/S0927-7757(99)00073-4 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:308992012-10-10T00:00:00Z28info:eu-repo/semantics/articleVirus transport in unsaturated porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Youn Sim()http://purl.tuc.gr/dl/dias/5091D7A3-C6E4-41CD-AED4-3FB32C2A1D33 10.1029/1999WR900302Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2000Summarization: A numerical model for one-dimensional virus transport in homogeneous,
unsaturated porous media was developed. The model accounts for virus sorption onto
liquid-solid and air-liquid interfaces as well as inactivation of viruses suspended in the
liquid phase and viruses attached at both interfaces. The effects of the moisture content
variation on virus transport in unsaturated porous media were investigated. In agreement
with previous experimental studies, model simulations indicated that virus sorption is
greater at air-liquid than liquid-solid interfaces. Available data from experiments of colloid
transport through unsaturated columns were successfully simulated by the virus transport
model developed in this study.Παρουσιάστηκε στο: Water resource researchpeer-reviewedBibliographic citation: Y. Sim, C. V. Chrysikopoulos , "Virus transport in unsaturated porous media ", Wat. Res.. Res.. ,vol. 36,no. 1,pp. 173-179,2000.doi : 10.1029/1999WR900302info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:339962012-10-10T00:00:00Z28info:eu-repo/semantics/articleOrigin of the bentonite deposits of eastern Milos, Aegean, Greece: Geological, mineralogical and geochemical evidencePeter W. Scott()T. Marcopoulos()Chemistry of the bentoniteshttp://purl.tuc.gr/dl/dias/5C2DF410-1B57-4941-8333-98DB1412287810.1346/CCMN.1995.0430108Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1995Summarization: The Lower Pleistocene bentonite deposits of Eastern Milos, Greece have been formed at the
expense of volcaniclastic rocks under submarine conditions. Systematic variation of the major chemical
elements reveals that the deposits were formed from different precursors which were erupted from different
volcanic centers belonging to at least two separate volcanic provinces. The volcanic eruptions were
probably subaqueous. The major authigenic phases are smectite, K-feldspar, opal-CT and the zeolites
mordenite and clinoptilolite. The deposits have a complex history and have been affected by hydrothermal
alteration.
The geological features ofbentonites coupled by the presence of abundant authigenic K-feldspar indicate
that alteration of the parent volcanoclastic rocks took place under low temperatures and is probably not
related to hydrothermal alteration, which is a separate event. Hydrothermal alteration has modified both
the mineralogical characteristics and the properties of bentonites. Alteration of the parent rocks to bentonites
was favoured by high water : wall rock ratios and fluid flow and is associated with leaching and
subsequent removal of Na, K and Ca. The source of Mg was the parent rocks and only small scale Mguptake
from the sea water has probably taken place. The formation of authigenic K-feldspar has probably
been favoured by a high K§ + activity ratio and high Si activity of the pore fluid. Such conditions
might have been favoured by the pH conditions and the cooling history of the parent rocks.Clay Minerals SocietyPresented on: Clays and Clay Mineralspeer-reviewedBibliographic citation: G. E. Christidis, P. W. Scott, T. Marcopoulos , "Origin of the bentonite deposits of eastern Milos, Aegean, Greece: Geological, mineralogical and geochemical evidence ,"Cl. and Clay Min. ,vol. 43 ,no.1,pp.63-67 ,1995.doi :10.1346/CCMN.1995.0430108info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:339912012-10-10T00:00:00Z28info:eu-repo/semantics/articleMechanism of illitization of bentonites in the geothermal field of Milos island
Greece: evidence based on mineralogy, chemistry, particle thickness and
morphologyΧρηστιδης Γεωργιος(http://users.isc.tuc.gr/~gchristidis)Christidis Georgios(http://users.isc.tuc.gr/~gchristidis)X-ray diffraction ,Electron microscopy http://purl.tuc.gr/dl/dias/050ED3BE-8E2C-4C22-80E2-5B910AF76B0110.1346/CCMN.1995.0430507Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1995Summarization: Hydrothermal alteration has caused illitization along a 40m vertical profile in the Tsantilis
bentonite deposit, Eastern Milos, Greece which consists principally of a Wyoming-type montmorillonite
and authigenic K-feldspar. The product K-bentonite which contains illite/smectite, kaolinite, K-feldspar,
quartz, sulphates and sulphides exhibits an unusual tendency for increase of expandability with depth.
Mineralogy and I/S textures were determined with X-ray diffraction and SEM and TEM methods
respectively and chemistry using X-ray fluorescence. Illitization is characterized by a 5- to 6-fold increase
of K and release of Si, Fe, Mg Na, and Ca from the parent rock, indicating a K-influx (K-metasomatism)
in the system.
The I/S particle morphology is characterized by both flaky and lath-like particles, the former dominating
in the range 100-50% expandable layers (R0 ordering) and the latter in the range 50-10% expandable
layers (R1 and R > 1 ordering). Flaky particles are also abundant in samples with R1 ordering and
abundant kaolinite, indicating that the latter might affect illitization. The I/S particles are classified in
populations with thickness multiples of 10 A, their thickness being probably smaller than the coherent
XRD domain. As the reaction proceeds, particles grow thicker and more equant. The distribution of I/S
particle dimensions forms steady state profiles showing log-normal distribution; however, sensu stricto
Ostwald ripening is unlikely. It seems that the reaction proceeds toward minimization of the surface free
energy of I/S, being affected principally by temperature and K-availability. The spatial distribution of
expandability implies that the heating source was probably a mineralized vein with T < 200~ directed
away from the bentonite, suggesting that illitization might be used as an exploration guide for mineral
deposits.Clay Minerals SocietyPresented on: Clays and Clay Mineralspeer-reviewedBibliographic citation: G.E. Christidis , "Mechanism of illitization of bentonites in the geothermal field of Milos island Greece: Evidence based on mineralogy, chemistry, particle thickness and morphology ", Cl. and Clay Min. ,vol. 43, no.5, pp.569-585 ,1995.doi :10.1346/CCMN.1995.0430507info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:340132012-10-10T00:00:00Z28info:eu-repo/semantics/articleThe Sparql2Xquery interoperability frameworkΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Nikos Bikakis()Chrisa Tsinaraki()Ioannis Stavrakantonakis()Nektarios Gioldasis()Basic XML Schema & OntologyXPath Setshttp://purl.tuc.gr/dl/dias/F2A524FF-3916-4571-8C7A-7A0C9B35672810.1007/s11280-013-0257-xPublished at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2015Summarization: he Web of Data is an open environment consisting of a great number of large inter-linked RDF datasets from various domains. In this environment, organizations and companies adopt the Linked Data practices utilizing Semantic Web (SW) technologies, in order to publish their data and offer SPARQL endpoints (i.e., SPARQL-based search services). On the other hand, the dominant standard for information exchange in the Web today is XML. Additionally, many international standards (e.g., Dublin Core, MPEG-7, METS, TEI, IEEE LOM) in several domains (e.g., Digital Libraries, GIS, Multimedia, e-Learning) have been expressed in XML Schema. The aforementioned have led to an increasing emphasis on XML data, accessed using the XQuery query language. The SW and XML worlds and their developed infrastructures are based on different data models, semantics and query languages. Thus, it is crucial to develop interoperability mechanisms that allow the Web of Data users to access XML datasets, using SPARQL, from their own working environments. It is unrealistic to expect that all the existing legacy data (e.g., Relational, XML, etc.) will be transformed into SW data. Therefore, publishing legacy data as Linked Data and providing SPARQL endpoints over them has become a major research challenge. In this direction, we introduce the SPARQL2XQuery Framework which creates an interoperable environment, where SPARQL queries are automatically translated to XQuery queries, in order to access XML data across the Web. The SPARQL2XQuery Framework provides a mapping model for the expression of OWL–RDF/S to XML Schema mappings as well as a method for SPARQL to XQuery translation. To this end, our Framework supports both manual and automatic mapping specification between ontologies and XML Schemas. In the automatic mapping specification scenario, the SPARQL2XQuery exploits the XS2OWL component which transforms XML Schemas into OWL ontologies. Finally, extensive experiments have been conducted in order to evaluate the schema transformation, mapping generation, query translation and query evaluation efficiency, using both real and synthetic datasets.Springer VerlagPresented on: World Wide Webnon peer-reviewedBibliographic citation: G.Skevakis , K.Makris , V.Kalokyri , P. Arapi , S.Christodoulakis ,"The SPARQL2XQuery Interoperability Framework ", w ,wide web ,vol. 18, no.2,pp.403-490 ,2015.doi :10.1007/s11280-013-0257-xinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:340512012-10-10T00:00:00Z28info:eu-repo/semantics/articleMetadata management, interoperability and linked data publishing support for natural history museumsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Giannis Skevakis()Konstantinos Makris()Varvara Kalokyri()Polyxeni Arapi()The Natural Europe CHOhttp://purl.tuc.gr/dl/dias/4B4D0432-4D79-48F7-92E2-F0A26EF7D57910.1007/s00799-014-0114-2Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2014Summarization: Natural history museums (NHMs) form a rich source of knowledge about Earth’s biodiversity and natural history. However, an impressive abundance of high-quality scientific content available in NHMs around Europe remains largely unexploited due to a number of barriers, such as the lack of interconnection and interoperability between the management systems used by museums, the lack of centralized access through a European point of reference such as Europeana and the inadequacy of the current metadata and content organization. The Natural Europe project offers a coordinated solution at European level that aims to overcome those barriers. In this article, we present the architecture, deployment and evaluation of the Natural Europe infrastructure allowing the curators to publish, semantically describe and manage the museums’ cultural heritage objects, as well as disseminate them to Europeana.eu and BioCASE/GBIF. Additionally, we discuss the methodology followed for the transition of the infrastructure to the Semantic Web and the publishing of NHMs’ cultural heritage metadata as Linked Data, supporting the Europeana Data Model.Springer VerlagPresented on: International Journal on Digital Librariespeer-reviewedBibliographic citation: G. Skevakis ,K.Makris ,V. Kalokyri ,P. Arapi S.Christodoulakis , "Metadata management, interoperability and linked data publishing support for natural history museums ",In.J. on Dig. Lib., vol.14, no.3-4 ,pp.127-140 ,2014. doi :10.1007/s00799-014-0114-2info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:340512012-10-10T00:00:00Z28info:eu-repo/semantics/articleMetadata management, interoperability and linked data publishing support for natural history museumsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Giannis Skevakis()Konstantinos Makris()Varvara Kalokyri()Polyxeni Arapi()The Natural Europe CHOhttp://purl.tuc.gr/dl/dias/4B4D0432-4D79-48F7-92E2-F0A26EF7D57910.1007/s00799-014-0114-2Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2014Summarization: Natural history museums (NHMs) form a rich source of knowledge about Earth’s biodiversity and natural history. However, an impressive abundance of high-quality scientific content available in NHMs around Europe remains largely unexploited due to a number of barriers, such as the lack of interconnection and interoperability between the management systems used by museums, the lack of centralized access through a European point of reference such as Europeana and the inadequacy of the current metadata and content organization. The Natural Europe project offers a coordinated solution at European level that aims to overcome those barriers. In this article, we present the architecture, deployment and evaluation of the Natural Europe infrastructure allowing the curators to publish, semantically describe and manage the museums’ cultural heritage objects, as well as disseminate them to Europeana.eu and BioCASE/GBIF. Additionally, we discuss the methodology followed for the transition of the infrastructure to the Semantic Web and the publishing of NHMs’ cultural heritage metadata as Linked Data, supporting the Europeana Data Model.Springer VerlagPresented on: International Journal on Digital Librariespeer-reviewedBibliographic citation: G. Skevakis ,K.Makris ,V. Kalokyri ,P. Arapi S.Christodoulakis , "Metadata management, interoperability and linked data publishing support for natural history museums ",In.J. on Dig. Lib., vol.14, no.3-4 ,pp.127-140 ,2014. doi :10.1007/s00799-014-0114-2info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:340712012-10-10T00:00:00Z28info:eu-repo/semantics/articleA crowdsourcing framework for the management of mobile multimedia nature observationsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Giannis Skevakis()Chrisa Tsinaraki()Ioanna Trochatou()The MoM-NOCS functionalityhttp://purl.tuc.gr/dl/dias/62F3A0DC-7766-427F-B606-73386366AE0410.1108/IJPCC-06-2014-0038Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2014Summarization: This paper aims to describe MoM-NOCS, a Framework and a System that support communities with common interests in nature to capture and share multimedia observations of nature objects or events using mobile devices. Design/methodology/approach – The observations are automatically associated with contextual metadata that allow them to be visualized on top of 2D or 3D maps. The observations are managed by a multimedia management system, and annotated by the same and/or other users with common interests. Annotations made by the crowd support the knowledge distillation of the data and data provenance processes in the system. Findings – MoM-NOCS is complementary and interoperable with systems that are managed by natural history museums like MMAT (Makris et al., 2013) and biodiversity metadata management systems like BIOCASE (BioCASE) and GBIF (GBIF) so that they can link to interesting observations in the system, and the statistics of the observations that they manage can be visualized by the software. Originality/value – The Framework offers rich functionality for visualizing the observations made by the crowd as function of time.EmeraldPresented on: International Journal of Pervasive Computing and Communicationspeer-reviewedBibliographic citation: G. Skevakis, .C Tsinaraki, I. Trochatou, S. Christodoulakis , "A crowdsourcing framework for the management of mobile multimedia nature observations ",Int. J.of Per. Compu. and Com.,vol. 10,no. 3,pp.216-238,2014 .doi:10.1108/IJPCC-06-2014-0038info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:341112012-10-10T00:00:00Z28info:eu-repo/semantics/articlePersonalised spatial knowledge management for pictures using ontologies and semantic mapsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Michalis Foukarakis() Lemonia Ragia()http://purl.tuc.gr/dl/dias/30E17CCA-6FA7-4C52-BD9B-3E04704311A010.1504/IJDCET.2009.02536Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2009Summarization: Cameras can provide integrated GPS and compass technology which makes them a powerful sensor for geographical context related images. They allow wireless connection to computers and the images can be automatically transferred to a PC or can be integrated into a GIS system. In this paper, we present an approach for personalised spatial information retrieval and visualisation for picture databases using ontologies and semantic maps. Ontologies are used in our case to describe domain knowledge in relation to spatial coordinates, to enhance image annotation, search capability and information visualisation. Individuals from the ontologies are represented by their footprint in semantic maps. Personalised semantic maps are constructed selecting ontologies, concept types or individuals that reflect the interests of the user. We describe a developed prototype system with a database design for ontologies and semantic maps. We demonstrate the automatic image annotation and the visualisation of the spatial queries. An application of the system targets the area of culture and tourism and provides a user friendly interface.Παρουσιάστηκε στο: International Journal of Digital Culture and Electronic Tourismpeer-reviewedBibliographic citation: S.Christodoulakis , M.Foukarakis, , L. Ragia , "Personalised spatial knowledge management for pictures using ontologies and semantic maps " ,In.J. of D.Cult. and El. Tour.,vol.4,no.1 ,2009. doi :10.1504/IJDCET.2009.02536info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:341332012-10-10T00:00:00Z28info:eu-repo/semantics/articleAn MPEG7 query language and a user preference model that allow semantic retrieval
and filtering of multimedia contentΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Chrisa Tsinaraki()MPEG-7 based multimedia content descriptionhttp://purl.tuc.gr/dl/dias/E5A4F869-DD04-4E8E-B39F-F5940B1BAC1F10.1007/s00530-007-0091-zPublished at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: We present in this paper the MPEG-7 Query Language (MP7QL), a powerful query language that we have developed for querying
MPEG-7 descriptions, as well as its compatible Filtering and Search Preferences (FASP) model. The MP7QL has the MPEG-7 as
data model and allows for querying every aspect of an MPEG-7 multimedia content description. It allows the users to express
the conditions that should hold for the multimedia content returned to them regarding semantics, low-level visual and audio
features and media-related aspects. The MP7QL queries may utilize the users’ FASP and Usage History as context, thus allowing
for personalized multimedia content retrieval. The FASP model supported is compatible with the MP7QL and has the model of
the standard MPEG-7 FASPs as a special case. The proposed FASPs essentially are MP7QL queries. Both the MP7QL and its compatible
FASP model allow for the exploitation of domain knowledge encoded using pure MPEG-7 constructs. In addition, they allow the
explicit specification of boolean operators and/or preference values in order to allow both the combination of the query conditions
according to the user intentions and the expression of the importance of the individual conditions for the users. The MP7QL
query results are represented as MPEG-7 documents, guaranteeing the closure of the results within the MPEG-7 space. The MP7QL
and the FASP model have been expressed using both XML Schema and OWL syntax. An implementation of the MP7QL, on top of an
XML Native Database is currently in progress. A real world-world evaluation study on the expressive power of the MP7QL shows
that it covers both general purpose and domain specific requirements in multimedia content retrieval. Springer VerlagPresented on: Multimedia Systemspeer-reviewedBibliographic citation: C. Tsinaraki , S. Christodoulakis ,"An MPEG-7 query language and a user preference model that allow semantic retrieval and filtering of multimedia content ",Mul. Sys., vol. 13,no.2,pp.131-153,2007.doi:10.1007/s00530-007-0091-zinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:341512012-10-10T00:00:00Z28info:eu-repo/semantics/articleInteroperability Support between MPEG-7/21 and OWL in DS-MIRFΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Chrisa Tsinaraki()Panagiotis Polydoros()The Web Ontology Languagehttp://purl.tuc.gr/dl/dias/7785DA17-FB8E-4CFE-B5EA-49304947CAE8 10.1109/TKDE.2007.33Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: In this paper, we focus on interoperable semantic multimedia services that are offered in open environments such as the Internet. The use of well-accepted standards is of paramount importance for interoperability support in open environments. In addition, the semantic description of multimedia content utilizing domain ontologies is very useful for indexing, query specification, retrieval, filtering, user Interfaces, and knowledge extraction from audiovisual material. With the MPEG-7 and MPEG-21 standards dominating the multimedia content and service description domain and OWL dominating the ontology description languages, it is important to establish a framework that allows these standards to interoperate. We describe here the DS-MIRF framework, a software engineering framework that facilitates the development of knowledge-based multimedia applications such as multimedia information retrieval, filtering, browsing, interaction, knowledge extraction, segmentation, and content description. DS-MIRF supports interoperability of OWL with the MPEG-7/21 so that domain and application ontologies expressed in OWL can be transparently integrated with MPEG-7/21 metadata. This allows applications that recognize and use the constructs provided by MPEG-7/21 to make use of domain and application ontologies, resulting in more effective retrieval and user interaction with the audiovisual material.Institute of Electrical and Electronics EngineersPresented on: IEEE Transactions on Knowledge and Data Engineeringpeer-reviewedBibliographic citation: C. Tsinaraki , P.Polydoros , S. Christodoulakis ,"Interoperability support between MPEG-7/21 and OWL in DS-MIRF ",iEEE Tran. on Knowl.e and Data Engin. ,vol.19,no.2 ,pp.219 - 232 ,2007.doi : 10.1109/TKDE.2007.33info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:341912012-10-10T00:00:00Z28info:eu-repo/semantics/articleSemantic, constraint & preference based authoring of multi-topic multimedia presentationsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)chrisa Tsinaraki()Adrea Perego()Panagiotis Polydoros()Athina Syntzanaki()Alessandro Martin()The SyMPA Authoring SystemThe DS-MIRF Frameworkhttp://purl.tuc.gr/dl/dias/1F3E3B3D-3E0B-4E0E-9FD9-2075A0750921http://www.researchgate.net/publication/201196629_Semantic_Constraint__Preference_Based_Multimedia_Presentation_AuthoringPublished at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2006Summarization: We present in this paper an integrated system that allows the management and annotation of multimedia objects stored in MPEG-7/21 repositories, and the specification and semi-automatic generation of multimedia presentations based on the content relationships that exist between the multimedia objects. This system is the outcome of the collaboration between the Technical University of Crete (TUC-MUSIC) and the University of Milan (UNIMI) in the CoCoMA (Content and Context Aware Multimedia Content Retrieval, Delivery and Presentation) project of the DELOS II European Network of Excellence on Digital Libraries. The resulting system is one of the main components of the CoCoMA infrastructure that aims to provide content- and context-aware rich interactive multimedia presentations by controlling data fusion and metadata reuse. The integrated system utilizes the SyMPA management and presentation authoring system developed by UNIMI and the DS-MIRF framework developed by TUC-MUSIC.Presented on: Journal of Digital Information Managementpeer-reviewedBibliographic citation: C.Tsinaraki, A. Perego, P. Polydoros, A. Syntzanaki,A. Martin, S. Christodoulakis.(2006).Semantic, constraint and preference based authoring of multi-topic multimedia presentations.Journal of Digital Information Management.[online].Available :http://www.researchgate.net/publication/201196629_Semantic_Constraint__Preference_Based_Multimedia_Presentation_Authoringinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:342122012-10-10T00:00:00Z28info:eu-repo/semantics/articleGraphonto: Owl-based ontology management and multimedia annotation in the ds-mirf frameworkΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Panagiotis Polydoros() Chrisa Tsinaraki()http://purl.tuc.gr/dl/dias/18D060DE-32C3-41B6-9408-E47A7D20D350http://www.dirf.org/jdim/v4i4a2.pdfPublished at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2006Summarization: We present here GraphOnto, a software component and an API that allow the definition and editing of both standard-based and domain OWL ontologies and their use in multimedia information system components. In our working environment an OWL Upper Ontology that captures the MPEG-7 MDS is utilized and OWL domain ontologies extend the upper ontology with domain knowledge. The ontologies imported in GraphOnto are parsed so that graphical ontology browsing and editing interfaces are automatically generated. The ontologies are used to guide the semantic multimedia annotation in a standardized manner. OWL Ontology mappings, expressed using OWL constructs, are supported and allow the definition of personalized ontologies. Personalization of the GraphOnto user interface on the application, task and user levels is provided. In addition, GraphOnto interoperates with an MPEG-7 Repository both for semantic entity reuse during multimedia content annotation and for semantic description storage. GraphOnto has been evaluated against Protégé and clearly outperforms it.Presented on: Journal of Digital Information Managementpeer-reviewedBibliographic citation: P. Polydoros, C. Tsinaraki, S. Christodoulakis .(2006).GraphOnto: 0wl-Based ontology management and multimedia annotation in the ds-mirf
framework.Journal of Digital Information Management.[online].Available :http://www.dirf.org/jdim/v4i4a2.pdfinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:343112012-10-10T00:00:00Z28info:eu-repo/semantics/article A natural language model for managing TV-anytime information in mobile environmentsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Anastasia Karanastasi()Fotis G. Kazasis()The Natural Language Model for the Digital TV Environmenthttp://purl.tuc.gr/dl/dias/404DEC92-FE04-481D-A88F-DF0D0771F72810.1007/s00779-004-0330-7 Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2005Summarization: The TV-Anytime standard describes structures of categories of digi-tal TV program metadata, as well as User Profile metadata for TV programs. We describe a natural language model for the users to interact with the TV-Anytime metadata and preview TV programs from their mobile devices. The language utilizes completely the TV-Anytime metadata specifications and it can accommodate future metadata extensions. The interaction model does not use clarification dialogues, but it uses the user profiles to rank the possible answers in case of ambiguities, as well as TV-Anytime Metadata information and on-tologies with information concerning digital TV. We describe an implementa-tion of the language that runs on a PDA and a mobile phone and manages the metadata on a remote TV-Anytime compatible TV set.Springer VerlagPresented on: Personal and Ubiquitous Computingpeer-reviewedBibliographic citation: A. Karanastasi, F.G. Kazasis, S. Christodoulakis ,"A natural language model for managing TV-Anytime information in mobile environments ",Pers. and Ubiqu. Comp.,vol.9 , no.4 , pp.262-272 ,2005.doi :10.1007/s00779-004-0330-7 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:343142012-10-10T00:00:00Z28info:eu-repo/semantics/articleOntology-based semantic indexing for MPEG-7 and TV-anytime audiovisual contentΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Chrisa Tsinaraki()Panagiotis Polydoros()Fotis Kazasis()http://purl.tuc.gr/dl/dias/0C365866-DC13-4B50-890E-A971C5D2135710.1007/s11042-005-0894-xPublished at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2005Summarization: In this paper, we describe a framework that we have developed for the support of ontology-based semantic indexing and retrieval of audiovisual content following the MPEG-7 and TV-Anytime standard specifications for metadata descriptions. Our work aims to provide a methodology to enhance the retrieval effectiveness of audiovisual content, while maintaining compatibility with the international multimedia standards.
In our framework, domain-specific ontologies guide the definition of both the application-specific metadata and the instance-description metadata that describe the contents of audiovisual programs and/or their segments. The ontologies are also used in order to provide compatible descriptions in both audiovisual content standards (MPEG-7 and TV-Anytime) for the same content. This approach allows indexing compatibility and interoperability of TV-Anytime and digital library applications.
We describe the design and implementation of a system supporting this framework. The components of the system include a segmentation tool for segmenting audiovisual information, which also provides ontology-based semantic indexing capabilities, and an appropriate API for semantic query support. An application testbed for the domain of soccer games has been developed on top of this system. An ontology for soccer games has been defined and used for indexing and retrieval of soccer games that have been stored in the system database.
The methodology we developed opens up a wide opportunity for the creation of MPEG-7 and TV-Anytime services offering structured domain-specific ontologies that can be integrated to these standards for enhancing audiovisual content retrieval performance. Kluwer Academic PublishersPresented on: Multimedia Tools and Applicationspeer-reviewedBibliographic citation: C. Tsinaraki, P.Polydoros, F. Kazasis, S. Christodoulakis, "Ontology-based semantic indexing for MPEG-7 and TV-anytime audiovisual content ,"Mult.Tools and Appl. ,vol .26,no.3,pp. 299-325, 2005.doi:10.1007/s11042-005-0894-xinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:343312012-10-10T00:00:00Z28info:eu-repo/semantics/articleOptimal data placement on disks: a comprehensive solution for different technologiesΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)P. Triantafillou()C. A. Georgiadis()http://purl.tuc.gr/dl/dias/7EDD9BAA-8BB6-4ED5-BC77-FC9130291A4F10.1109/69.842270Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2000Summarization: The problem of optimally placing data on disks (ODP) to maximize disk-access performance has long been recognized as important. Solutions to this problem have been reported for some widely available disk technologies, such as magnetic CAV and optical CLV disks. However, important new technologies such as multizoned magnetic disks, have been recently introduced. For such technologies no formal solution to the ODP problem has been reported. In this paper, we first identify the fundamental characteristics of disk-device technologies which influence the solution to the ODP problem. We develop a comprehensive solution to the problem that covers all currently available disk technologies. We show how our comprehensive solution can be reduced to the solutions for existing disk technologies, contributing thus a solution to the ODP problem for multizoned disks. Our analytical solution has been validated through simulations and through its reduction to the known solutions for particular disksIEEEPresented on: IEEE Transactions on Knowledge and Data Engineeringpeer-reviewedBibliographic citation: C. A. Georgiadis ,P. Triantafillou , C. A. Georgiadis,"Optimal data placement on disks: A comprehensive solution for different disk technologies ", vo.12,no.2 ,pp.324 - 330 ,2000.doi: 10.1109/69.842270info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:343522012-10-10T00:00:00Z28info:eu-repo/semantics/articleResearch and development issues for large-scale multimedia information systemsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis) Peter Triantafillou ()http://purl.tuc.gr/dl/dias/942C14E4-FCFB-4CE7-8CDC-25225A9B7B6E10.1145/234782.234793Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1995Μη διαθέσιμη περίληψηNot available summarizationPresented on: ACM Computing Surveyspeer-reviewedBibliographic citation: P.Triantafillou , S. Christodoulakis , "Research and development issues for large-scale multimedia information systems ",CM Comp. Surv.,vol. 27 ,no.4 ,pp.576-579,1995.doi: 10.1145/234782.234793info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:343912012-10-10T00:00:00Z28info:eu-repo/semantics/articleOptimal histograms for limiting worst-case error propagation in the size of join results.Χριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Yiannis E. Ioannidis()Asymptotically optimal serial histogramshttp://purl.tuc.gr/dl/dias/A0E77513-A9A3-47D9-9553-601A84B1B52210.1145/169725.169708Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1993Summarization: Many current relational database systems use some form of histograms to approximate the frequency distribution of values in the attributes of relations and on this basis estimate query result sizes and access plan costs. The errors that exist in the histogram approximations directly or transitively affect many estimates derived by the database system. We identify the class of serial histograms and its subclass of end-btased histograms; the latter is of particular interest because such histograms are used in several database systems. We concentrate on equality join queries without function symbols where each relation is joined on the same attribute(s) for all joins in which it participates. Join queries of this restricted type are called t-cllque queries. We show that the optimal histogram for reducing the worst-case error in the result size of such a query is always serial. For queries with one join and no function symbols (all of which are vacuously t-clique queries), we present results on finding the optimal serial histogram and the optimal end-biased histogram based on the query characteristics and the frequency distributions of values in the join attributes of the query relations. Finally, we prove that for t-clique queries with a very large number of joins, h~gh-bzased h zstograms (which form a subclass of end-biased histograms) are always optimal. To construct a histogram for the join attribute(s) of a relation, the values in the attribute(s) must first be sorted based on their frequency and then assigned into buckets according to the optimality results above.
Presented on: ACM Transactions on Database Systemspeer-reviewedBibliographic citation: Y. Ioannidis , S. Christodoulakis , " Optimal histograms for limiting worst-case error propagation in the size of join results",ACM Trans. on Datab. Syst. , vol. 18 ,no. 4 ,pp. 709-748,1993 .doi : 10.1145/169725.169708
info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:344112012-10-10T00:00:00Z28info:eu-repo/semantics/articlePrinciples of storage and retrieval of multimedia dataΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Jim Gemmell()http://purl.tuc.gr/dl/dias/5FFF5B4A-80DB-43B2-8D8E-7284C174840D10.1145/128756.128758Published at: 2015-10-02eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1992Summarization: This paper establishes some fundamental principles for the retrieval and storage of delay-sensitive multimedia data. Delay-sensitive data include digital audio, animations, and video. Retrieval of these data types from secondary storage has to satisfy certain time constraints in order to be acceptable to the user. The presentation is based on digital audio in order to provide intuition to the reader, although the results are applicable to all delay-sensitive data. A theoretical framework is developed for the real-time requirements of digital audio playback. We show how to describe these requirements in terms of the consumption rate of the audio data and the nature of the data-retrieval rate from secondary storage. Making use of this framework, bounds are derived for buffer space requirements for certain common retrieval scenarios. Storage placement strategies for multichannel synchronized data are then categorized and examined. The results presented in this paper are basic to any playback of delay-sensitive data and should assist the multimedia system designer in estimating hardware requirements and in evaluating possible design choices.Association for Computing MachineryPresented on: ACM Transactions on Information Systemspeer-reviewedBibliographic citation: J. Gemmell ,S. Christodoulakis ,"Principles of delay-sensitive multimedia data storage retrieval ",ACM Trans. on Info. Syst. ,vol. 10,no.1 ,pp. 51-90,1992.doi:10.1145/128756.128758info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:344312012-10-10T00:00:00Z28info:eu-repo/semantics/articleFile organizations with shared overflow blocks for variable length
objectsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Yannis Manolopoulos()http://purl.tuc.gr/dl/dias/C9997B6B-4949-4EB0-92E5-77E82D6CC16D10.1016/0306-4379(92)90028-LPublished at: 2015-10-02eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1992Summarization: Traditional file organizations for records may also be appropriate for the storage and retrieval of objects. Since objects frequently involve diverse data types (such as text, compressed images, graphics, etc.) as well as composite structures, they may have a largely variable length. In this paper, we assume that in the case of composite objects their components are clustered together and that object file organizations have overflows. The blocks of the main file are grouped so that they share a common number of overflow blocks. For this class of file organizations we present and analyze the performance of three different overflow searching algorithms. We show that the third algorithm gives very significant performance advantages under certain circumstances.
Presented on: Information Systemspeer-reviewedBibliographic citation: Y. Manolopoulos , S, Christodoulakis ,File organizations with shared overflow blocks for variable length objects ", Inf. syst. vol. 17,no. 6 ,pp.491-509,1992.doi:10.1016/0306-4379(92)90028-Linfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:345712012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectCOLearn and open discovery space portal alignment: A case of enriching open learning infrastructures with collaborative learning capabilitiesΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)N. Mourmoutzis()P. Arapi()M. Mylonakis()G. Stylianakis()http://purl.tuc.gr/dl/dias/656642AA-8362-4A90-8F97-75345B8ABDD710.1109/IMCTL.2014.7011142 Published at: 2015-10-03eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2014Summarization: In this paper we present COLearn platform which can be seen as a shell, easily integrated on top of existing open learning infrastructures (such as LMSs and OER repositories) to enrich their capabilities by offering functionality to design rich learning activities and learning workflows. COLearn run-time environment is used to enact these activities and workflows. This way, COLearn leverages the power of the underlying infrastructures, provides structure to the groups of learners that participate in learning workflows, dynamically adapts the workflows during their enactment, monitors their evolution to facilitate assessment and provides feedback to the learners. COLearn employs an intuitive graphical representation exploiting the BPMN standard. As an internal representation and interoperability model it uses IMS LD thus offering effective sharing and remixing to realize the vision of open educational practices. This is an important aspect as it makes explicit the, otherwise tacit knowledge pertaining to the design of learning experiences.Παρουσιάστηκε στο: International Conference on Interactive Mobile Communication Technologies and Learning (IMCL) 2014 IEEEBibliographic citation: G. Stylianakis , N. Moumoutzis , P. Arapi , M. Mylonakis , S. Christodoulakis ,"COLearn and open discovery space portal alignment: A case of enriching open learning infrastructures with collaborative learning capabilities ",In the Int. Conf. on Inter. Mob. Com. Techn. and Learn. (IMCL) ,pp.252 - 256.doi :
10.1109/IMCTL.2014.7011full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:345712012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectCOLearn and open discovery space portal alignment: A case of enriching open learning infrastructures with collaborative learning capabilitiesΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)N. Mourmoutzis()P. Arapi()M. Mylonakis()G. Stylianakis()http://purl.tuc.gr/dl/dias/656642AA-8362-4A90-8F97-75345B8ABDD710.1109/IMCTL.2014.7011142 Published at: 2015-10-03eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2014Summarization: In this paper we present COLearn platform which can be seen as a shell, easily integrated on top of existing open learning infrastructures (such as LMSs and OER repositories) to enrich their capabilities by offering functionality to design rich learning activities and learning workflows. COLearn run-time environment is used to enact these activities and workflows. This way, COLearn leverages the power of the underlying infrastructures, provides structure to the groups of learners that participate in learning workflows, dynamically adapts the workflows during their enactment, monitors their evolution to facilitate assessment and provides feedback to the learners. COLearn employs an intuitive graphical representation exploiting the BPMN standard. As an internal representation and interoperability model it uses IMS LD thus offering effective sharing and remixing to realize the vision of open educational practices. This is an important aspect as it makes explicit the, otherwise tacit knowledge pertaining to the design of learning experiences.Παρουσιάστηκε στο: International Conference on Interactive Mobile Communication Technologies and Learning (IMCL) 2014 IEEEBibliographic citation: G. Stylianakis , N. Moumoutzis , P. Arapi , M. Mylonakis , S. Christodoulakis ,"COLearn and open discovery space portal alignment: A case of enriching open learning infrastructures with collaborative learning capabilities ",In the Int. Conf. on Inter. Mob. Com. Techn. and Learn. (IMCL) ,pp.252 - 256.doi :
10.1109/IMCTL.2014.7011full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:345722012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectThe ALICE experience: A learning framework to promote gaming literacy for educators and its refinementΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)N.Moumoutzis ()M.Christoulakis ()A. Pitsiladis ()G.Sifakis ()I.Maragoudakis ()http://purl.tuc.gr/dl/dias/7D7A9F99-149D-4E99-84BE-82FFDF346967 10.1109/IMCTL.2014.7011143 Published at: 2015-10-03eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2014Summarization: Educators are facing the challenge to use the learning potential of games from several complementary objectives. Above all, they need to develop their own competencies and critical thinking on games. The overarching framework for a fruitful answer to this challenge could be structured around a particular type of literacy, the so-called gaming literacy. This new type of literacy seeks to provide a firm ground for cultivating a new type of thinking about the world that is more close to the children's way of thinking: “What does the world look like from the point of view of gaming?” To enable educators effectively move towards this direction, it is important to formalize the professional knowledge and skills they need to develop, offer new learning opportunities for them (either pre-service or in-service) and build communities of practice within which they could exchange their experiences and continue their professional development. We present our work towards this direction, the underlying learning framework, its initial conception, the first pilot implementation and directions of further developments focusing on mobile games.Παρουσιάστηκε στο: International Conference on Interactive Mobile Communication Technologies and Learning (IMCL) 2014 IEEEBibliographic citation: N.Moumoutzis , M.Christoulakis , A.Pitsiladis , G. Sifakis, I. Maragoudakis, S.Christodoulakis ,"The ALICE experience: A learning framework to promote gaming literacy for educators and its refinement ",In the International Conference on Interactive Mobile Communication Technologies and Learning (IMCL) ,pp. 257 - 261 .doi :
10.1109/IMCTL.2014.7011143full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:345952012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectCoLearn: Real time collaborative learning environmentΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Nektarios Moumoutzis()Polyxeni Arapi()George Stylianakis()http://purl.tuc.gr/dl/dias/D1897FC8-8C48-400C-9F64-DBBA0CD4FE3F10.1109/ICeLeTE.20Published at: 2015-10-03eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2013Summarization: Computer Supported Collaborative Learning hasbecome an important part of e-learning providing interactivityand accessibility to learning resources either synchronouslyor asynchronously among users. In order to develop an elearning environment that supports collaborative learningone should cope with learning content, communication andcollaboration facilities, technological infrastructure, and runtime execution (i.e. learning process). Collaboration scripts areemployed to specify the components of the learning processincluding collaboration and interaction patterns within groupsof participants. In this paper we present a Computer SupportedCollaborative Learning platform which includes a collaborationscript authoring tool based on the Business Process ModelingNotation as the model for the graphical representation of scripts.Collaboration scripts are parsed and transformed to IMSLearning Design Level C learning flows. The second importantcomponent of the platform is the run time environment whichis based on the Copper Core Engine that executes the IMSLearning Design learning flows and a Message OrientedMiddleware which is built over the Extensible Messagingand Presence Protocol. This middleware layer enables groupmanagement and social interaction among participants. Theplatform integrates external learning tools by implementingthe IMS Learning Tool Interoperability specification. The IMSLearning Tool Interoperability specification is used to enable thedynamic integration of external tools through services.Παρουσιάστηκε στο: The Second International Conference on E-Learning and E-Technologies in Education (ICEEE2013), Sept. 23-25 Poland 2013Institute of Electrical and Electronics EngineersBibliographic citation: G. Stylianakis, P. Arapi, N.Moumoutzis, S. Christodoulakis ,CoLearn: Real time collaborative learning environment ", In 2013 Int.Conf on E-Lea. and E-Tech. in Educ., pp.13 - 18.doi : 10.1109/ICeLeTE.2013.6644340full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:345952012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectCoLearn: Real time collaborative learning environmentΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Nektarios Moumoutzis()Polyxeni Arapi()George Stylianakis()http://purl.tuc.gr/dl/dias/D1897FC8-8C48-400C-9F64-DBBA0CD4FE3F10.1109/ICeLeTE.20Published at: 2015-10-03eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2013Summarization: Computer Supported Collaborative Learning hasbecome an important part of e-learning providing interactivityand accessibility to learning resources either synchronouslyor asynchronously among users. In order to develop an elearning environment that supports collaborative learningone should cope with learning content, communication andcollaboration facilities, technological infrastructure, and runtime execution (i.e. learning process). Collaboration scripts areemployed to specify the components of the learning processincluding collaboration and interaction patterns within groupsof participants. In this paper we present a Computer SupportedCollaborative Learning platform which includes a collaborationscript authoring tool based on the Business Process ModelingNotation as the model for the graphical representation of scripts.Collaboration scripts are parsed and transformed to IMSLearning Design Level C learning flows. The second importantcomponent of the platform is the run time environment whichis based on the Copper Core Engine that executes the IMSLearning Design learning flows and a Message OrientedMiddleware which is built over the Extensible Messagingand Presence Protocol. This middleware layer enables groupmanagement and social interaction among participants. Theplatform integrates external learning tools by implementingthe IMS Learning Tool Interoperability specification. The IMSLearning Tool Interoperability specification is used to enable thedynamic integration of external tools through services.Παρουσιάστηκε στο: The Second International Conference on E-Learning and E-Technologies in Education (ICEEE2013), Sept. 23-25 Poland 2013Institute of Electrical and Electronics EngineersBibliographic citation: G. Stylianakis, P. Arapi, N.Moumoutzis, S. Christodoulakis ,CoLearn: Real time collaborative learning environment ", In 2013 Int.Conf on E-Lea. and E-Tech. in Educ., pp.13 - 18.doi : 10.1109/ICeLeTE.2013.6644340full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:306832012-10-10T00:00:00Z28info:eu-repo/semantics/articleDissolution of a well-defined trichloroethylene pool in saturated porous media: Experimental results and model simulationsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Kenneth Y. Lee()Experimental mass transfer correlation,TCE dissolution datahttp://purl.tuc.gr/dl/dias/4AEE9A8D-B6D3-47FB-AAC7-95D61340555D10.1016/S0043-1354(02)00097-0Published at: 2015-09-17eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2002Summarization: An experimental mass transfer correlation was developed for trichloroethylene (TCE) pools dissolving in watersaturated
porous media. A three-dimensional, bench-scale model aquifer previously designed by Chrysikopoulos et al.
(Water Resour. Res. 36(7) (2000) 1687) was employed for collection of the experimental dissolution data. The unique
aspect of the model aquifer design is the formation of a well-defined, circular TCE pool at the bottom of the model
aquifer. Steady-state dissolved TCE concentrations at specific downstream locations within the aquifer were collected
for each of the seven interstitial velocities considered in this study. For each interstitial velocity, a corresponding time
invariant overall mass transfer coefficient was determined by fitting the experimental data to an analytical solution
applicable to nonaqueous phase liquid (NAPL) pools (Water Resour. Res. 31(4) (1995) 1137). Subsequently, a
correlation relating the time invariant overall Sherwood number to appropriate overall Peclet numbers was developed.
Relatively good agreement between the newly developed correlation and experimental data was observed. r 2002
Elsevier Science Ltd. All rights reserved.Παρουσιάστηκε στο: Water Researchpeer-reviewedBibliographic citation: K. Y. Lee , C. V. Chrysikopoulos, "Dissolution of a well-defined trichloroethylene pool in saturated porous media: experimental results and
model simulations " , Wat. Re.,vol. 36 ,no.15 ,pp.3911–3918,2002.doi:10.1016/S0043-1354(02)00097-0info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309042012-10-10T00:00:00Z28info:eu-repo/semantics/articleExperimental investigation of acoustically enhanced solute transport in porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Eric T. Vogler()Mathematical Formulationhttp://purl.tuc.gr/dl/dias/3D10F298-D271-4B31-9AC3-D6E64322FECC10.1029/2002GL015304Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2002Summarization: The effect of acoustic waves on the transport of a
conservative tracer in a water saturated column packed with
glass beads was investigated. It was observed from the
experimental data that the addition of acoustic waves, in the
frequency range between 60 to 245 Hz, to a steady
background pressure gradient, enhances solute transport
compared to the base case consisting of only a background
pressure gradient. Furthermore, it was found that the effective
velocity of the solute is approximately inversely proportional
to the frequency of the acoustic wave.Παρουσιάστηκε στο: Geophysical Research Letters peer-reviewedBibliographic citation: E.T. Vogler , C. V. Chrysikopoulos, "Experimental investigation of acoustically enhanced solute transport in porous media ", Geoph.Res. Let.,vol. 29,no. 15,pp.1710,2002.doi:10.1029/2002GL015304info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309062012-10-10T00:00:00Z28info:eu-repo/semantics/articleEarly breakthrough of colloids and bacteriophage MS2 in a water-saturated sand columnΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Arturo A. Keller ()Sanya Sirivithayapakorn()http://purl.tuc.gr/dl/dias/818810E1-D836-40C7-9427-AD8677B6BFFF10.1029/2003WR002676 Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2004Summarization: We conducted column-scale experiments to observe the effect of transport velocity
and colloid size on early breakthrough of free moving colloids, to relate previous
observations at the pore scale to a larger scale. The colloids used in these experiments
were bacteriophage MS2 (0.025 mm), and 0.05- and 3-mm spherical polystyrene beads, and
were compared with a conservative nonsorbing tracer (KCl). The results show that early
breakthrough of colloids increases with colloid size and water velocity, compared with the
tracer. These results are in line with our previous observations at the pore scale that
indicated that larger colloids are restricted by the size exclusion effect from sampling all
paths, and therefore they tend to disperse less and move in the faster streamlines, if they
are not filtered out. The measured macroscopic dispersion coefficient decreases with
colloid size due to the preferential flow paths, as observed at the pore scale. Dispersivity,
typically considered only a property of the medium, is in this case also a function of
colloid size, in particular at low Peclet numbers due to the size exclusion effect. Other
parameters for colloid transport, such as collector efficiency and colloid filtration rates,
were also estimated from the experimental breakthrough curve using a numerical fitting
routine. In general, we found that the estimated filtration parameters follow the clean bed
filtration model, although with a lower filtration efficiency overall.Παρουσιάστηκε στο: Water resource researchpeer-reviewedBibliographic citation: C. V. Chrysikopoulos,A. A. Keller ,S. Sirivithayapakorn , "Early breakthrough of colloids and bacteriophage MS2 in a water-saturated sand column", Wat.Resourc. Re.,vol.40,no. 8,2004.doi :10.1029/2003WR002676 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309082012-10-10T00:00:00Z28info:eu-repo/semantics/articleAnalysis of one-dimensional solute transport through porous media with spatially variable retardation factorΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Peter K. Kitanidis()Analytical small-perturbation solutionhttp://purl.tuc.gr/dl/dias/0C06BAC6-0CD9-417E-96F9-1E7B4F6AD0AE10.1029/WR026i003p00437Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1990Summarization: A closed-form analytical small-perturbation (or first-order) solution to the one-dimensional advection-dispersion equation with spatially variable retardation factor is derived to investigate the transport of sorbing but otherwise nonreacting solutes in hydraulically homogeneous but geochemically heterogeneous porous formations. The solution is developed for a third- or flux-type inlet boundary condition, which is applicable when considering resident (volume-averaged) solute concentrations, and a semi-infinite porous medium. For mathematical simplicity it is hypothesized that the sorption processes are based on linear equilibrium isotherms and that the local chemical equilibrium assumption is valid. The results from several simulations, compared with predictions based on the classical advection-dispersion equation with constant coefficients, indicate that at early times, spatially variable retardation affects the transport behavior of sorbing solutes. The zeroth moments corresponding to constant and variable retardation are not necessarily equal. The impact of spatially variable retardation increases with increasing Péclet number.
Παρουσιάστηκε στο: Water Resources Researchpeer-reviewedBibliographic citation: C. V. Chrysikopoulos ,P. K. Kitanidis , P.V. Roberts, "Analysis of one-dimensional solute transport through porous media with spatially variable retardation factor" , Wa. resourc. researc.,vol. 26, no. 3 ,pp.437-446,1990.doi :10.1029/WR026i003p00437info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309102012-10-10T00:00:00Z28info:eu-repo/semantics/articleOne-dimensional solute transport in porous media with partial well-to-well recirculation: Application to field experimentsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Paul V. Roberts()http://purl.tuc.gr/dl/dias/8F501104-DAEC-4549-B85B-4AD81266ACFF10.1029/WR026i006p01189Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1990Summarization: A solute transport model incorporating well-to-well recirculation was developed to facilitate the interpretation of pilot-scale field experiments conducted for the evaluation of a test zone chosen for in situ restoration studies of contaminated aquifers, where flow was induced by recirculation of the extracted fluid. A semianalytical and an approximate analytical solution were derived to the one-dimensional advection-dispersion equation for a semi-infinite medium under local equilibrium conditions, with a flux-type inlet boundary condition accounting for solute recirculation between the extraction-injection well pair. Solutions were obtained by taking Laplace transforms to the equations with respect to time and space. The semianalytical solution is presented in Laplace domain and requires numerical inversion, while the approximate analytical solution is given in terms of a series of simple nested convolution integrals which are easily determined by numerical integration techniques. The applicability of the well-to-well recirculation model is limited to field situations where the actual flow field is one dimensional or where an induced flow field is obtained such that the streamlines in the neighborhood of the monitoring wells are nearly parallel. However, the model is fully applicable to studies of solute transport through packed columns with recirculation under controlled laboratory conditions.
Παρουσιάστηκε στο: Water Resources Researchpeer-reviewedBibliographic citation: C. V. Chrysikopoulos ,P. V. Roberts,P. K. Kitanidis , " One-dimensional solute transport in porous media with partial well-to-Well recirculation: Application to field experiments ", Wat. resour. res.,vol. 26, no. 6,pp.1189-1195,1990.doi:10.1029/WR026i006p01189info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309122012-10-10T00:00:00Z28info:eu-repo/semantics/articleThree-dimensional analytical models of contaminant transport from nonaqueous phase liquid pool dissolution in saturated subsurface formationsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)http://purl.tuc.gr/dl/dias/6747F86D-5AAD-4B80-B52F-0E38E3F3F2A610.1029/94WR02780 Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1995Summarization: Closed form analytical solutions are derived for three-dimensional transient contaminant transport resulting from dissolution of single-component nonaqueous phase liquid pools in saturated porous media. The solutions are suitable for homogeneous porous media with unidirectional interstitial velocity. The dissolved solute may undergo first-order decay or may sorb under local equilibrium conditions. The solutions are obtained for rectangular and elliptic as well as circular source geometries, assuming that the dissolution process is mass transfer limited, by applying Laplace and Fourier transforms. Although the solutions contain integral expressions, these integrals are easily evaluated numerically. These solutions are useful for verifying the accuracy of numerical solutions to more comprehensive models and for design and interpretation of experiments in laboratory-packed beds and possibly some field studies. The results of several simulations indicate that for short downstream distances, predictions of contaminant concentrations are sensitive to the source structure and orientation with respect to the direction of interstitial flow .
Παρουσιάστηκε στο: Water Resources Research peer-reviewedΒιβλιογραφική αναφορά: C. V. Chrysikopoulos , " Three-δimensional αnalytical μodels of contaminant transport from nonaqueous phase liquid pool dissolution in saturated subsurface formations " , Wat. Res. Res.,vol.31,no.4,pp.1137-1146,1995. doi :10.1029/94WR02780 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309142012-10-10T00:00:00Z28info:eu-repo/semantics/articleFate and transport of pathogens in a fractured aquifer in the Salento area, ItalyΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Costantino Masciopinto()Rosanna La Mantia()All the necessary parameters
required for accurate description of the aquifer were determined
by two tracer tests and 34 pumping tests. The spatial
variability of the mean fracture aperture was evaluated with
well-established geostatistical procedures. A numerical flow
model was developed to determine the distribution of the
piezometric heads throughout the aquifer for each realization
of the fracture aperture field. Furthermore, a finite
difference transport model was developed for the simulation
of pathogen migration in the fractures based on the piezometric
head distributions provided by the flow model. The
pathogen concentration data, collected at sampling locations
Well #1 and Well #2 during the winter of 2002 were
adequately fitted by the transport model. The fitted model
parameters include the longitudinal and transverse coefficients,
the initial inactivation rate, and the pathogen resistivity
coefficient.http://purl.tuc.gr/dl/dias/1DDF20B6-2C65-4AF8-8EFE-64E4D288F07610.1029/2006WR005643 Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2008Summarization: This study investigates the fate and transport of pathogens introduced by artificial
groundwater recharge at the Nardo` fractured aquifer in the Salento area, Italy. Wastewater
effluents from a municipal treatment plant with known pathogen concentrations were
injected into a sinkhole and the migration of pathogens in the fractured aquifer was
monitored at six sampling wells. The fate of pathogens was quantified by a mathematical
model describing colloid transport in a set of three-dimensional, parallel fractures with
spatially variable aperture. The number of parallel fractures and their average fracture
aperture were determined from appropriate field pumping and tracer tests. The aperture
spatial distribution was described by an experimental semivariogram developed from
available field data obtained from two tracer tests and 34 pumping tests. The experimental
results suggest that for the municipal wastewater injected into the Nardo` aquifer the
required most conservative set back distance for drinking wells should be over 8000 m.Παρουσιάστηκε στο: Water Resources Researchpeer-reviewedBibliographic citation: Masciopinto, C., R. La Mantia, C. V. Chrysikopoulos, "Fate and transport of pathogens in a fractured aquifer in the Salento area, Italy ", Water Resources Research (Impact Factor: 3.71). 01/2008; 440(1). info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309162012-10-10T00:00:00Z28info:eu-repo/semantics/articleTransport of biocolloids in water saturated columns packed with sand: Effect of grain size and pore water velocityΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Vasiliki I. Syngouna()http://purl.tuc.gr/dl/dias/9FFC4207-467D-4206-BD51-98C89BDA30A0 10.1016/j.jconhyd.2011.09.007Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2011Summarization: The main objective of this study was to evaluate the combined effects of grain size and pore
water velocity on the transport in water saturated porous media of three waterborne fecal indicator
organisms (Escherichia coli, MS2, and ΦX174) in laboratory-scale columns packed with
clean quartz sand. Three different grain sizes and three pore water velocities were examined
and the attachment behavior of Escherichia coli, MS2, and ΦX174 onto quartz sand was evaluated.
The mass recoveries of the biocolloids examined were shown to be highest for Escherichia
coli and lowest for MS2. However, no obvious relationships between mass recoveries and
water velocity or grain size could be established from the experimental results. The observed
mean dispersivity values for each sand grain size were smaller for bacteria than coliphages, but
higher for MS2 than ΦX174. The single collector removal and collision efficiencies were quantified
using the classical colloid filtration theory. Furthermore, theoretical collision efficiencies
were estimated only for E. coli by the Interaction-Force-Boundary-Layer, and Maxwell approximations.
Better agreement between the experimental and Maxwell theoretical collision efficiencies
were observed.Παρουσιάστηκε στο: Journal of Contaminant Hydrologypeer-reviewedBibliographic citation: V. I. Syngouna, C.V. Chrysikopoulos , "Transport of biocolloids in water saturated columns packed with sand: Effect of grain size and pore water velocity ", J. of Cont. Hydro.,vol.126 ,no.3-4 ,pp. 301-314,2011.doi : 10.1016/j.jconhyd.2011.09.007info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309182012-10-10T00:00:00Z28info:eu-repo/semantics/articleCotransport of Pseudomonas putida and kaolinite particles through
water-saturated columns packed with glass beadΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Ioanna A. Vasiliadou ()http://purl.tuc.gr/dl/dias/35D47210-FD6B-4905-9F6A-8D5C3DDB90D2 10.1029/2010WR009560Published at: 2015-09-20eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2011Summarization: This study is focused on Pseudomonas putida bacteria transport in porous media in the
presence of suspended kaolinite clay particles. Experiments were performed with bacteria
and kaolinite particles separately to determine their individual transport characteristics in
water-saturated columns packed with glass beads. The results indicated that the mass
recovery of bacteria and clay particles decreased as the pore water velocity decreased.
Batch experiments were carried out to investigate the attachment of Pseudomonas putida
onto kaolinite particles. The attachment process was adequately described by a Langmuir
isotherm. Finally, bacteria and kaolinite particles were injected simultaneously into a
packed column in order to investigate their cotransport behavior. The experimental data
suggested that the presence of clay particles significantly inhibited the transport of bacteria
in water-saturated porous media. The observed reduction of Pseudomonas putida recovery
in the column outflow was attributed to bacteria attachment onto kaolinite particles, which
were retained onto the solid matrix of the column. A mathematical model was developed to
describe the transport of bacteria in the presence of suspended clay particles in onedimensional
water-saturated porous media. Model simulations were in good agreement with
the experimental results.Παρουσιάστηκε στο: Water resource researchpeer-reviewedΒιβλιογραφική αναφορά: I. A. Vasiliadou, C. V. Chrysikopoulos, "Cotransport of Pseudomonas putida and kaolinite particles through water-saturated columns packed with glass beads " , Waτ. Res.Resea., vol.47,no. 2,2011.doi : 10.1029/2010WR009560info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309712012-10-10T00:00:00Z28info:eu-repo/semantics/articleBiosorption of Cu 2+ and Ni 2+ by Arthrospira platensis with different biochemical compositionsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Dimitris Georgakakis()Hüseyin Bozkurt()Abuzer Çelekli()Dimitris Mitrogiannis()Giorgos Markou()This study employed for the first time carbohydrate-enriched
dry and living biomass of A. platensis as biosorbent for copper or
nickel ions. The results show that the various biomass compositions
of A. platensis obtained from cultivation under different phosphorus
concentrations had a diverse effect on Cu2+ and Ni2+
biosorption capacity. The experiments with dry biomass show that
the accumulation of carbohydrates slightly improved the biosorption
capacity for nickel, but significantly improved the biosorption
capacity for copper. In contrast, the experiments with living biomass
show that the accumulation of carbohydrates decreased the
biosorption capacity for both metals. A. platensis showed greater
biosorption capacity for Ni2+ than for Cu2+. For all biomass types
investigated, the pseudo-second order kinetics model fitted better
the experimental data, but underestimated slightly the early time
data (first 15 min). It was observed that the intra-particle diffusion
was not a limited process, and that intra-particle diffusion model
described well the experimental data for the first 15 min. Also, it
was observed that the Freundlich model represents better the
biosorption onto living biomass due to the presence of possible
bioaccumulation, whereas, the Langmuir model fits better the
experimental data with dry biomass. The results show that the
main sorption mechanisms involved were ion exchange and
complexation. In general, the carbohydrate-enriched biomass contributed
to a weak ion-exchange sorption.http://purl.tuc.gr/dl/dias/AF1459A4-47B3-49DA-AD36-57B6AF50D31710.1016/j.cej.2014.08.037 Published at: 2015-09-21eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2015Summarization: This study is focused on copper and nickel biosorption onto Arthrospira platensis biomass of different biochemical
compositions. Four types of A. platensis were employed, namely: (1) typical dry biomass (TDB),
(2) carbohydrate-enriched dry biomass (CDB), (3) typical living biomass (TLB), and (4) carbohydrateenriched
living biomass (CLB). The CDB was produced using a cultivation mode where phosphorus was
the limiting nutrient. The biosorption of both metals investigated was shown to be very fast. Most of
the metal sorption capacity of the biomass was filled within 15–30 min, and equilibrium was achieved
within 30–60 min. The cultivation conditions (nutrient repletion or depletion) did not affect the pattern
of copper and nickel biosorption kinetics. The capacity for copper ions biosorption was significantly positively
affected by the accumulation of carbohydrates in the dry biomass, but was negatively affected by
the accumulation of carbohydrates in the living biomass. For nickel ions, the alteration of biomass had a
little but positive effect on the dry biomass, and a greater negative effect (about 30% lower biosorption
capacity) on the living biomass. Living biomass exhibited a higher biosorption capacity than dry biomass,
for both metals. The biosorption of copper and nickel onto A. platensis biomass occurred mainly due to the
mechanisms of ion exchange and complexation, and less to physical adsorption.Παρουσιάστηκε στο: Chemical Engineering Journalpeer-reviewedBibliographic citation: G.Markou , D. Mitrogiannis , A. Çelekli , H. Bozkurt , D. Georgakakis ,C. V. Chrysikopoulos , "Biosorption of Cu 2+ and Ni 2+ by Arthrospira platensis with different biochemical compositions "Che.Engin. J.,vol. 259, pp. 806–813,2015.doi 10.1016/j.cej.2014.08.037 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309732012-10-10T00:00:00Z28info:eu-repo/semantics/articleEffect of gravity on colloid transport through water-saturated columns packed with glass beads: modeling and experimentsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Vasiliki I. Syngouna()http://purl.tuc.gr/dl/dias/E1EF74A3-9A9D-40EE-846D-2FA0D982DE0010.1021/es501295nPublished at: 2015-09-21eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2014Summarization: The role of gravitational force on colloid
transport in water-saturated columns packed with glass beads
was investigated. Transport experiments were performed with
colloids (clays: kaolinite KGa-1b, montmorillonite STx-1b).
The packed columns were placed in various orientations
(horizontal, vertical, and diagonal) and a steady flow rate of Q
= 1.5 mL/min was applied in both up-flow and down-flow
modes. All experiments were conducted under electrostatically
unfavorable conditions. The experimental data were fitted with a newly developed, analytical, one-dimensional, colloid transport
model. The effect of gravity is incorporated in the mathematical model by combining the interstitial velocity (advection) with the
settling velocity (gravity effect). The results revealed that flow direction influences colloid transport in porous media. The rate of
particle deposition was shown to be greater for up-flow than for down-flow direction, suggesting that gravity was a significant
driving force for colloid depositionΠαρουσιάστηκε στο: Environmental Science and Technology peer-reviewedBibliographic citation: C. V. Chrysikopoulos, . V. I. Syngouna, "Effect of gravity on colloid transport through water-saturated columns packed with glass beads: Modeling and experiments " , Envir. Scien. and Tech.,vol. 48 ,no. 12,2014.doi :10.1021/es501295ninfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309752012-10-10T00:00:00Z28info:eu-repo/semantics/articleExperimental investigation of acoustically enhanced colloid transport in water-saturated packed columnsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)J. Matthew Thomas()http://purl.tuc.gr/dl/dias/7BBE3DCD-1C65-46E0-9DF6-CEE442A320FA10.1016/j.jcis.2006.12.062 Published at: 2015-09-21eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2007Summarization: The effects of acoustic wave propagation on the transport of colloids in saturated porous media were investigated by injecting Uranine (conservative
tracer) as well as blue and red polystyrene microspheres (colloids of different diameters; 0.10 and 0.028 μm, respectively) into a column
packed with glass beads. Experiments were conducted by maintaining the acoustic pressure at the influent at 23.0 kPa with acoustic frequencies
ranging from 30 to 150 Hz. The experimental results suggested that colloid size did not affect the forward and reverse attachment rate coefficients.
The acoustic pressure caused an increase in the effective interstitial velocity at all frequencies for the conservative tracer and colloids of both sizes,
with maximum increase at 30 Hz. Furthermore, acoustics enhanced the dispersion process at all frequencies, with a maximum at 30 Hz.
© 2007 Elsevier Inc. All rights reserved.Παρουσιάστηκε στο: Journal of Colloid and Interface Sciencepeer-reviewedBibliographic citation: J. M. Thomas , C. V. Chrysikopoulos , "Experimental investigation of acoustically enhanced colloid transport in water-saturated packed columns " , J. of Col. and Interf. Scienc. ,vol. 308 ,no. 1, pp. 200-207,2007.doi :10.1016/j.jcis.2006.12.062 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309912012-10-10T00:00:00Z28info:eu-repo/semantics/articleNon-invasive in situ concentration determination of fluorescent or color tracers and pollutants in a glass pore network modeΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Vasileios E. Katzourakis()Christina C. Plega()http://purl.tuc.gr/dl/dias/6596003E-C7C7-4186-A7C5-6B4AC957A7F210.1016/j.jhazmat.2011.10.042 Published at: 2015-09-21eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2011Summarization: This study presents a non-invasive imaging method for in situ concentration determination of conservative
tracers and pollutants in a two-dimensional glass pore network model. The method presented is
an extension to the work by Huang et al. [1], and Thomas and Chysikopoulos [2]. The method consists of
fabricating the glass pore network model using a photolithography technique, conducting flowthrough
contaminant transport experiments, taking digital photographs at various times of the two-dimensional
pore network under ultraviolet or visible light source, and determining the spatially-distributed pollutant
concentrations by measuring the color intensity in the photographs with comparative image
analysis. Therefore, the method is limited to fluorescent or colored pollutants and tracers. The method
was successfully employed to in situ concentration determination of uranine and red color tracers.Παρουσιάστηκε στο: Journal of hazardous materialspeer-reviewedBibliographic citation: C. V. Chrysikopoulos, Ca C. Plega, V. E. Katzourakis , "Non-invasive in situ concentration determination of fluorescent or color tracers and pollutants in a glass pore network model " J. of hazar. materia. ,vol.198, pp. 299-306,2011.doi:10.1016/j.jhazmat.2011.10.042 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:309932012-10-10T00:00:00Z28info:eu-repo/semantics/articleGeneralized TaylorAris moment analysis of the transport of sorbing solutes through porous media with spatiallyperiodic retardation factorΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Paul V. Roberts()Peter K. Kitanidis()Rate-limited sorbing solute transport,Effective macroscopic coefficientshttp://purl.tuc.gr/dl/dias/CC2244A6-14C0-4741-9EB2-6F3B42C2521E10.1007/BF00647395 Published at: 2015-09-21eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1992Summarization: Taylor-Aris dispersion theory, as generalized by Brenner, is employed to investigate the macroscopic behavior of sorbing solute transport in a three-dimensional, hydraulically homogeneous porous medium under steady, unidirectional flow. The porous medium is considered to possess spatially periodic geochemical characteristics in all three directions, where the spatial periods define a rectangular parallelepiped or a unit-element. The spatially-variable geochemical parameters of the solid matrix are incorporated into the transport equation by a spatially-periodic distribution coefficient and consequently a spatially-periodic retardation factor. Expressions for the effective or large-time coefficients governing the macroscopic solute transport are derived for solute sorbing according to a linear equilibrium isotherm as well as for the case of a first-order kinetic sorption relationship. The results indicate that for the case of a chemical equilibrium sorption isotherm the longitudinal macrodispersion incorporates a second term that accounts for the eflect of averaging the distribution coefficient over the volume of a unit element. Furthermore, for the case of a kinetic sorption relation, the longitudinal macrodispersion expression includes a third term that accounts for the effect of the first-order sorption rate. Therefore, increased solute spreading is expected if the local chemical equilibrium assumption is not valid. The derived expressions of the apparent parameters governing the macroscopic solute transport under local equilibrium conditions agreed reasonably with the results of numerical computations using particle tracking techniques.
Kluwer Academic PublishersΠαρουσιάστηκε στο: Transport in Porous Media peer-reviewedBibliographic citation: C. V. Chrysikopoulos ,P. K. Kitanidis, P.V. Roberts ,"Generalized TaylorAris moment analysis of the transport of sorbing solutes through porous media with spatiallyperiodic retardation factor ", Transp. in Po.Media ,vol. 7 ,no.2 , pp.163-185, 1992.doi:10.1007/BF00647395 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:310312012-10-10T00:00:00Z28info:eu-repo/semantics/articleTransport of pseudomonas putida in a 3-D bench scale experimental aquiferΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Vasileios E. Katzourakis()Ioanna A. Vasiliadou()Vasiliki I. Syngouna()http://purl.tuc.gr/dl/dias/5BAF6094-BD73-4BD3-AB12-B9B9E0A3F5C810.1007/s11242-012-0015-z Published at: 2015-09-21eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2012Summarization: This study is focused on the transport of Pseudomonas (P.) putida bacterial cells
in a 3-D model aquifer. The pilot-scale aquifer consisted of a rectangular glass tank with
internal dimensions: 120 cm length, 48 cm width, and 50 cm height, carefully packed with
well-characterized quartz sand. The P. putida decay was adequately represented by a firstorder
model. Transport experiments with a conservative tracer and P. putida were conducted
to characterize the aquifer and to investigate the bacterial behavior during transport in water
saturated porous media. A 3-D, finite-difference numerical model for bacterial transport in
saturated, homogeneous porous media was developed and was used to successfully fit the
experimental data. Furthermore, theoretical interaction energy calculations suggested that
the extended-DLVO theory seems to predict bacteria attachment onto the aquifer sand better
than the classical DLVO theory.Παρουσιάστηκε στο: Transport in Porous Mediapeer-reviewedBibliographic citation: C.V. Chrysikopoulos , V. I. Syngouna ,I. A. Vasiliadou ,V. E. Katzourakis, "Transport of pseudomonas putida in a 3-D bench scale experimental aquifer " Transp. in Por Media , vol. 94 ,no.3, pp. 617-642 ,2012.doi:10.1007/s11242-012-0015-z info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:310512012-10-10T00:00:00Z28info:eu-repo/semantics/articleCotransport of clay colloids and viruses in water saturated porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Vasiliki Syngouna ()http://purl.tuc.gr/dl/dias/B9212025-20C5-4AE6-8DA2-539E98EE68BD10.1016/j.colsurfa.2012.10.018Published at: 2015-09-21eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2013Summarization: This study examines the cotransport of clay colloids and viruses in laboratory packed columns. Bacteriophages
MS2 and X174 were used as model viruses, kaolinite (kGa-1b) and montmorillonite (STx-1b)
as model clay colloids, and glass beads as model packing material. The combined and synergistic effects
of clay colloids and pore water velocity on virus transport and retention in porous media were examined
at three pore water velocities (0.38, 0.74, and 1.21 cm/min). The results indicated that the mass recovery
of viruses and clay colloids decreased as the pore water velocity decreased; whereas, for the cotransport
experiments no clear trend was observed. Temporal moments of the breakthrough concentrations suggested
that the presence of clays significantly influenced virus transport and irreversible deposition onto
glass beads. Mass recovery values for both viruses, calculated based on total virus concentration in the
effluent, were reduced compared to those in the absence of clays. The transport of both suspended and
attached onto suspended clay-particles viruses was retarded, compared to the tracer, only at the highest
pore water velocity. Moreover both clay colloids were shown to hinder virus transport at the highest pore
water velocity. ElsevierΠαρουσιάστηκε στο: Colloids and Surfaces A Physicochemical and Engineering Aspects peer-reviewedBibliographic citation: V. I. Syngouna, C. V. Chrysikopoulos , "Cotransport of clay colloids and viruses in water saturated porous media " , Coll. and Surf. a Physicoche. and Engin. Aspec. vol.416 ,no.1 ,pp. 56-65, 2013.doi:10.1016/j.colsurfa.2012.10.018info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:310712012-10-10T00:00:00Z28info:eu-repo/semantics/articleModeling colloid transport and deposition in saturated fracturesΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Assem Abdel-Salam()http://purl.tuc.gr/dl/dias/FA32814D-7592-44DE-8005-44A5613824C310.1016/S0927-7757(96)03979-9 Published at: 2015-09-21eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1997Summarization: A model is developed to describe the transport of colloids in a saturated fracture with a spatially variable aperture, accounting for colloid deposition onto fracture surfaces under various physicochemical conditions. The fracture plane is partitioned into unit elements with different apertures generated stochastically from a log-normal distribution. The model also accounts for colloid size exclusion from fracture elements with small apertures. Both equilibrium and kinetic colloid deposition onto fracture surfaces are investigated. Colloid surface exclusion is incorporated in the dynamics of kinetic deposition. The impact of deposited colloids on further colloid deposition is described by either a linear or a non-linear blocking function. The resulting system of governing partial differential equations is solved numerically using the fully implicit finite difference method. Model simulations illustrate the presence of preferential colloid transport in the fracture plane. It is shown that size exclusion increases the dispersion of colloids and leads to earlier breakthrough, especially for large-size particles. Furthermore, it is demonstrated that surface exclusion enhances colloid transport, and the assumption of clean-bed media may underestimate liquid-phase colloid concentrations.
Presented on: Colloids and Surfaces A: Physicochemical and Engineering Aspectspeer-reviewedBibliographic citation: C. V. Chrysikopoulos ,A. A.Salam , "Modeling colloid transport and deposition in saturated fractures ", Col.and Surf. a Physico. and Engin. Aspect. ,vol.121 ,no.2 pp. 189-202,1997.doi :10.1016/S0927-7757(96)03979-9 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:310912012-10-10T00:00:00Z28info:eu-repo/semantics/articleMeasuring and modeling the dissolution of nonideally shaped dense nonaqueous phase liquid pools in saturated porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Thomas C. Harmon()Brian K. Dela Barre()Physical Aquifer Model System and Sampling Protocols,DNAPL Pool Dissolution Theoryhttp://purl.tuc.gr/dl/dias/C60C6E4F-AE21-44A9-99F5-4BF898A2DC6510.1029/2001WR000444Published at: 2015-09-21eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2002Summarization: A three-dimensional physical aquifer model was used to study the dissolution of a
dense nonaqueous phase liquid (DNAPL) pool. The model aquifer comprised a packing of
homogeneous, medium-sized sand and conveyed steady, unidirectional flow.
Tetrachloroethene (PCE) pools were introduced within model aquifers atop glass- and
clay-lined aquifer bottoms. Transient breakthrough at an interstitial velocity of 7.2 cm/h,
and three-dimensional steady state concentration distributions at velocities ranging from
0.4 to 7.2 cm/h were monitored over periods of 59 and 71 days for the glass- and claybottom
experiments, respectively. Pool-averaged mass transfer coefficients were obtained
from the observations via a single-parameter fit using an analytical model formulated with
a second type boundary condition to describe pool dissolution [Chrysikopoulos, 1995].
Other model parameters (interstitial velocity, longitudinal and transverse dispersion
coefficients, and pool geometry) were estimated independently. Simulated and observed
dissolution behavior agreed well, except for locations relatively close to the pool or the
glass-bottom plate. Estimated mass transfer coefficients ranged from 0.15 to 0.22 cm/h,
increasing weakly with velocity toward a limiting value. Pool mass depletions of 31 and
43% for the glass- and clay-bottom experiments failed to produce observable changes in
the plumes and suggested that changes in pool interfacial area over the period of the
experiment were negligible. Dimensionless mass transfer behavior was quantified using a
modified Sherwood number (Sh*). Observed Sh* values were found to be about 2–3
times greater than values predicted by an existing theoretical mass transfer correlation,
and 3–4 times greater than those estimated previously for an ideally configured
trichloroethene (TCE) pool (circular and smooth). It appeared that the analytical model’s
failure to account for pore-scale pool-water interfacial characteristics and larger scale pool
shape irregularities biased the Sh* estimates toward greater valuesΠαρουσιάστηκε στο: Water Resources Research peer-reviewedBibliographic citation: B. K. Dela Barre, T. C. Harmon,C. V. Chrysikopoulos, "Measuring and modeling the dissolution of nonideally shaped dense nonaqueous phase liquid pools in saturated porous media " , Wat. Resour.Rese.,vol. 38 ,no.8 pp. 1133,2002.doi :10.1029/2001WR000444info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:311112012-10-10T00:00:00Z28info:eu-repo/semantics/articleMacrodispersion of sorbing solutes in heterogeneous porous formations with spatially periodic retardation factor and velocity fieldΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Peter K. Kitanidis()http://purl.tuc.gr/dl/dias/34B0EDC9-7777-408B-9E34-ADA8D92B812710.1029/92WR00010 Published at: 2015-09-21eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1992Summarization: Expressions for the macroscopic velocity vector and dispersion tensor for sorbing solute transport in heterogeneous porous formations whose hydrogeologic properties are repeated at intervals were derived via Taylor-Aris-Brenner moment analysis. An idealized three-dimensional porous formation of infinite domain with spatially periodic retardation factor, velocity field, and microdispersion coefficients in all three directions was considered. Sorption was assumed to be governed by a linear equilibrium isotherm under local chemical equilibrium conditions. The analytical expressions presented are based on a perturbation method where all of the spatially periodic parameters employed were assumed to have ``small'' fluctuations. It was shown that the effective velocity vector is given by the volume-averaged interstitial velocity vector divided by the volume-averaged retardation factor, and the effective dispersion dyadic (second-order tensor) is given by the volume-averaged microdispersion dyadic divided by the volume-averaged dimensionless retardation factor plus a dyadic expressing the increase in solute spreading caused by the spatial variability of the parameters.
Παρουσιάστηκε στο: Water Resources Researchpeer-reviewedBibliographic citation: C. V. Chrysikopoulos ,P. K. Kitanidis,.P. V. Roberts ,"Macrodispersion of sorbing solutes in heterogeneous porous formations with spatially periodic retardation factor and velocity field ", Wat.resour. rese., vol. 28 ,no.6 ,pp.1517-1529, 1992.doi:10.1029/92WR00010 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:311512012-10-10T00:00:00Z28info:eu-repo/semantics/articleVirus fate and transport during artificial recharge with recycled waterΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Robert Anders()http://purl.tuc.gr/dl/dias/9BDE8C30-C8A4-4699-9A00-CB1A38F74A8C10.1029/2004WR003419 Published at: 2015-09-21eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2005Summarization: A field-scale experiment was conducted at a research site using bacterial viruses
(bacteriophage) MS2 and PRD1 as surrogates for human viruses, bromide as a
conservative tracer, and tertiary-treated municipal wastewater (recycled water) to
investigate the fate and transport of viruses during artificial recharge. Observed virus
concentrations were fitted using a mathematical model that simulates virus transport in
one-dimensional, homogeneous, water-saturated porous media accounting for virus
sorption (or filtration), virus inactivation, and time-dependent source concentration. The
fitted time-dependent clogging rate constants were used to estimate the collision
efficiencies for bacteriophage MS2 and PRD1 during vertical fully saturated flow.
Furthermore, the corresponding time-dependent collision efficiencies for both
bacteriophage asymptotically reached similar values at the various sampling locations.
These results can be used to develop an optimal management scenario to maximize the
amount of recycled water that can be applied to the spreading grounds while still
maintaining favorable attachment conditions for virus removal.Παρουσιάστηκε στο: Water Resources Researchpeer-reviewedBibliographic citation: R. Anders,C. V. Chrysikopoulos, "Virus fate and transport during artificial recharge with recycled wate", Wa. Res. Resear. ,vol.10 , no.41, 2005. doi :10.1029/2004WR003419 info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:313312012-10-10T00:00:00Z28info:eu-repo/semantics/articleMathematical modeling of colloid and virus cotransport in porous media: Application to experimental dataΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Vasileios E. Katzourakis()http://purl.tuc.gr/dl/dias/AFF1F989-E0C3-47C5-A986-F5D4C0A0DEB110.1016/j.advwatres.2014.03.001Published at: 2015-09-22eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2014Summarization: A conceptual mathematical model was developed to describe the simultaneous transport (cotransport) of
viruses and colloids in three-dimensional, water saturated, homogeneous porous media with uniform
flow. The model accounts for the migration of individual virus and colloid particles as well as viruses
attached onto colloids. Viruses can be suspended in the aqueous phase, attached onto suspended colloids
and the solid matrix, and attached onto colloids previously attached on the solid matrix. Colloids can be
suspended in the aqueous phase or attached on the solid matrix. Viruses in all four phases (suspended in
the aqueous phase, attached onto suspended colloid particles, attached on the solid matrix, and attached
onto colloids previously attached on the solid matrix) may undergo inactivation with different inactivation
coefficients. The governing coupled partial differential equations were solved numerically using
finite difference methods, which were implemented explicitly or implicitly so that both stability and
speed factors were satisfiedΠαρουσιάστηκε στο: Advances in Water Resourcespeer-reviewedBibliographic citation: V. E. Katzourakis , C. V. Chrysikopoulos , Mathematical modeling of colloid and virus cotransport in porous media: Application to experimental data " Advanc. in Wat. Resour.,vol. 68, pp. 62–73,2014 .doi :10.1016/j.advwatres.2014.03.001info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:313522012-10-10T00:00:00Z28info:eu-repo/semantics/articleDegradation of PAHs by high frequency ultrasoundΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Hrissi K. Karapanagioti()Ioannis D. Manariotis()http://purl.tuc.gr/dl/dias/EAFA24A9-0477-490D-B663-170E4CCC5EC910.1016/j.watres.2011.02.009Published at: 2015-09-22eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2011Summarization: Polycyclic aromatic hydrocarbons (PAHs) are persistent organic compounds, which have
been reported in the literature to efficiently degrade at low (e.g. 20 kHz) and moderate (e.g.
506 kHz) ultrasound frequencies. The present study focuses on degradation of naphthalene,
phenanthrene, and pyrene by ultrasound at three different relatively high frequencies
(i.e. 582, 862, and 1142 kHz). The experimental results indicate that for all three frequencies
and power inputs 133 W phenanthrene degrades to concentrations lower than our
experimental detection limit (<1 mg/L). Phenanthrene degrades significantly faster at
582 kHz than at 862 and 1142 kHz. For all three frequencies, the degradation rates per unit
mass are similar for naphthalene and phenanthrene and lower for pyrene. Furthermore,
naphthalene degradation requires less energy than phenanthrene, which requires less
energy than pyrene under the same conditions. No hexane-extractable metabolites were
identified in the solutions.ElsevierΠαρουσιάστηκε στο: Water Research peer-reviewedBibliographic citation: I. D. Manariotis , H.K. Karapanagioti , C.V. Chrysikopoulos , "Degradation of pahs by high frequency ultrasound ", wat. resear .,vol. 45, no.8, pp. 2587- 2594,2011.doi :10.1016/j.watres.2011.02.009info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:314112012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectTransport of TiO2 nanoparticles through water saturated packed columnsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)I.D. Manariotis()D. Vassilopoulos()http://purl.tuc.gr/dl/dias/FC6D9680-4723-4C28-9EA4-003A9D890248http://www.researchgate.net/publication/262335999_Transport_of_TiO2_nanoparticles_through_water_saturated_packed_columnsPublished at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2014Summarization: In this work, various TiO2 NP suspensions were prepared using different preparation techniques.
Rutile-anatase and anatase TiO2 NPs were used for the preparation of aquatic NP suspensions at
various concentrations. Measurements of particles size and zeta potential were performed in order
to investigate the effect of sonication and aging on nanoparticle agglomerates. Finally, transport
experiments of TiO2 NP solutions in packed columns were performed for varying TiO2
concentrations. The concentration and size of the NPs were measured at the outlet of the column. It
was observed that a substantial percentage of the NPs injected into the experimental column were
retained in the column packing.Παρουσιάστηκε στο: 12th International Conference on Protection and Restoration of the Environment, At Skiathos GreeceBibliographic citation: V. Sygouni,D. Vassilopoulos , I.D. Manariotis , C.V. Chrysikopoulos .(2014). .Transport of TiO2 nanoparticles through water saturated packed columns .Presented at 2th International Conference on Protection and Restoration of the Environment At Skiathos Greece. [onlive].Available :http://www.researchgate.net/publication/262335999_Transport_of_TiO2_nanoparticles_through_water_saturated_packed_columnsfull paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:314512012-10-10T00:00:00Z28info:eu-repo/semantics/articleVirus inactivation by high frequency ultrasound in combination with visible lightΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Ioannis D. Manariotis()Vasiliki I. Syngouna()http://purl.tuc.gr/dl/dias/964270B5-4ECC-4F30-A47F-77EB8E8FA35910.1016/j.colsurfb.2013.01.038Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2013Summarization: In this study, the effects of high frequency ultrasound (US) and visible light (VL) on virus inactivation
were investigated. The bacteriophages X174 and MS2 were used as model viruses. The experiments
were performed at room temperature at three different, relatively high US frequencies (i.e., 582, 862, and
1142 kHz) with and without the use of VL, and different initial virus concentrations. The two bacteriophages
were diluted in phosphate-buffered saline solution to a titer of 103–104 pfu/mL. The experimental
virus inactivation data were satisfactorily represented by a simple first-order kinetic expression. Virus
inactivation was faster at the lower frequencies (582 and 862 kHz). Furthermore, it was observed that
MS2 was inactivated faster than X174. The simultaneous use of US and VL was found to be more effective
than US alone for MS2 inactivation, indicating the existence of a synergistic effectElsevierPresented on: Colloids and Surfaces B: Biointerfacespeer-reviewedBibliographic citation: C. V. Chrysikopoulos, I.D. Manariotis, V. I. Syngouna, "Virus inactivation by high frequency ultrasound in combination with visible light ",Col. and Surf. B: Biointerf., vol. 107 ,pp. 174– 179,2013.doi: 10.1016/j.colsurfb.2013.01.038info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:314722012-10-10T00:00:00Z28info:eu-repo/semantics/articleTransport of Viruses Through Saturated and Unsaturated Columns Packed with SandΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Vasileios E. Katzourakis()Ioanna A. Vasiliadou()Vasiliki I. Syngouna()Bacteria–Quartz Sand Interactionshttp://purl.tuc.gr/dl/dias/DB659C03-8621-417A-A83E-83B7AE8670080.1007/s11242-008-9239-3Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2008Summarization: This study is focused on the transport of Pseudomonas (P.) putida bacterial cells
in a 3-D model aquifer. The pilot-scale aquifer consisted of a rectangular glass tank with
internal dimensions: 120 cm length, 48 cm width, and 50 cm height, carefully packed with
well-characterized quartz sand. The P. putida decay was adequately represented by a firstorder
model. Transport experiments with a conservative tracer and P. putida were conducted
to characterize the aquifer and to investigate the bacterial behavior during transport in water
saturated porous media. A 3-D, finite-difference numerical model for bacterial transport in
saturated, homogeneous porous media was developed and was used to successfully fit the
experimental data. Furthermore, theoretical interaction energy calculations suggested that
the extended-DLVO theory seems to predict bacteria attachment onto the aquifer sand better
than the classical DLVO theory.SpringerΠαρουσιάστηκε στο: Transport in Porous Mediapeer-reviewedBibliographic citation: C. V. Chrysikopoulos , V.I. Syngouna ,I. A. Vasiliadou ,V. E. Katzourakis , "Transport of Pseudomonas putida in a 3-D Bench Scale
Experimental Aquifer ",Trans. in Por. Media ,vol.76 ,no.1 ,pp. 121-138,2008. doi:0.1007/s11242-008-9239-3info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:314742012-10-10T00:00:00Z28info:eu-repo/semantics/articleVirus attachment onto quartz sand: Role of grain size and temperatureΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Andriana F. Aravantinou()http://purl.tuc.gr/dl/dias/CEA5AFED-FC37-420D-9DF9-2E1E15C7A1F610.1016/j.jece.2014.01.025Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2014Summarization: Virus transport in groundwater is controlled mainly by attachment onto the solid matrix and
inactivation. Therefore, understanding how the various parameters affect virus attachment can lead to
improved virus transport predictions and better health risk evaluations. This study is focused on the
attachment of viruses onto quartz sand under batch experimental conditions. The bacteriophages
FX174 and MS2 were used as model viruses. Three different sand grain sizes were employed for the
static and dynamic experiments. The batch sorption experiments were performed under static
conditions at 4 8C and 20 8C and dynamic conditions at 4 8C. The experimental data were adequately
described by the Freundlich isotherm. It was shown that temperature significantly affects virus
attachment under static conditions. The attachment of both MS2 and FX174 onto quartz sand was
greater at 20 8C than 4 8C. Higher virus attachment was observed under dynamic than static conditions,
and in all cases, the affinity of MS2 for quartz sand was greater than that of FX174. Furthermore, in most
of the cases considered, bacteriophage attachment was shown to decrease with increasing quartz sand
size.Παρουσιάστηκε στο: Journal of Environmental Chemical Engineeringpeer-reviewedBibliographic citation: C. V. Chrysikopoulos , A. F. Aravantinou , "Virus attachment onto quartz sand: Role of grain size and temperature " ,J. of Envir. Ch. Eng.,vol. 2 ,no.2 ,pp. 796–801,2014.doi:10.1016/j.jece.2014.01.025info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:314762012-10-10T00:00:00Z28info:eu-repo/semantics/articleNumerical modeling of three-dimensional contaminant migration from dissolution of multicomponent NAPL pools in saturated porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)K. Y. Lee()http://purl.tuc.gr/dl/dias/3A081F23-9B45-4538-82E1-D39F065BE7BF10.1007/BF00768737Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1995Summarization: A three-dimensional model for contaminant
transport resulting from the dissolution of multicomponent
nonaqueous phase liquid (NAPL) pools in threedimensional
saturated subsurface formations is developed.
The solution is obtained numerically by a finite-difference
scheme, and it is suitable for homogeneous porous media
with unidirectional interstitial velocity. Each dissolved
component may undergo first-order decay and may sorb
under local equilibrium conditions. It is also assumed that
the dissolution process is mass transfer limited. The nonaqueous
phase activity coefficients of the NAPL pool
components are evaluated at each time step. The model
behavior is illustrated through a synthetic example with
a NAPL pool consisting of a mixture of TCA (1,1,2-
trichloroethane) and TCE (trichloroethylene). The numerical
solution presented in this work is in good agreement
with a recently developed analytical solution for the special
case of a single component NAPL pool. The results
indicate the importance of accounting for the necessary
changes in the organic phase activity which significantly
affects the equilibrium aqueous solubilityΠαρουσιάστηκε στο: Environmental Geologypeer-reviewedBibliographic citation: K. Y. Lee , C. V. Chrysikopoulos, "Numerical modeling of three-dimensional contaminant migration from dissolution of multicomponent NAPL pools
in saturated porous media " ,Environ. Geo. ,vol. 26,no.3, pp.157-165,1995.doi:10.1007/BF00768737info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:314782012-10-10T00:00:00Z28info:eu-repo/semantics/articleBootstrap estimation of the mass transfer coefficient of a dissolving nonaqueous phase liquid pool in porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Pin-Yi Hsuan()Marios M. Fyrillas()Estimation of Mass Transfer Coefficients,NAPL Pool Dissolution and Contaminant Transporthttp://purl.tuc.gr/dl/dias/4614432E-42FC-434B-B4D9-6EA39F8BD5E110.1029/2001WR000661Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2002Summarization: A new method for confidence interval estimation of mass transfer coefficients suitable for
dissolving dense nonaqueous phase liquid pools in homogeneous, water-saturated porous media is
developed. The method is based on the bootstrap resampling technique in conjunction with a least
squares regression procedure. The method is successfully applied to experimental data collected
from bench scale trichloroethylene pool dissolution experiments. INDEX TERMS: 1829
Hydrology: Groundwater hydrology; 1831 Hydrology: Groundwater quality; 1832 Hydrology:
Groundwater transport; KEYWORDS: NAPL pool dissolution, mass transfer coefficient, bootstrap,
estimation, contaminant transportΠαρουσιάστηκε στο: Water Resources Researchpeer-reviewedBibliographic citation: M. M. Fyrillas ,C. V. Chrysikopoulos , P.Y. Hsuan, " Bootstrap estimation of the mass transfer coefficient of a dissolving nonaqueous phase
liquid pool in porous media " Wat Resour Resear, Vol. 38, No. 3, pp.1026 , 2002.doi :10.1029/2001WR000661info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:314802012-10-10T00:00:00Z28info:eu-repo/semantics/articleMass transfer correlations for nonaqueous phase liquid pool dissolution in saturated porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Tae-Joon Kim()Development of Mass Transfer Correlationshttp://purl.tuc.gr/dl/dias/03630E29-C6AF-44A3-83A3-5B7EB82852CC 10.1029/1998WR900053Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1999Summarization: Correlations describing the rate of interface mass transfer from singlecomponent
nonaqueous phase liquid (NAPL) pools in saturated subsurface formations are
developed. A three-dimensional contaminant transport model is employed to obtain
overall mass transfer coefficients computed from concentration gradients at the NAPLwater
interface. The model assumes that the porous medium is homogeneous, the
interstitial fluid velocity is steady, and the dissolved solute may sorb under local
equilibrium conditions. Furthermore, it is assumed that the dissolved concentration along
the NAPL-water interface is equal to the solubility concentration. Power law correlations
relate the overall Sherwood number to the appropriate overall Peclet numbers. Both
rectangular and elliptic/circular source geometries are considered. The proposed
relationships are fitted to numerically determined mass transfer coefficients, and the
correlation coefficients are determined by nonlinear least squares regression. Good
agreement between predicted and available experimentally determined overall mass
transfer coefficients is observedΠαρουσιάστηκε στο: Water Resources Researchpeer-reviewedBibliographic citation: T.J. Kim , C.V. Chrysikopoulos , "Mass transfer correlations for nonaqueous phase liquid pool dissolution in saturated porous media " ,Wat. Resour.Res. ,vol. 35,no.2,pp.449-459, 1999.doi: 10.1029/1998WR900053info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:314822012-10-10T00:00:00Z28info:eu-repo/semantics/articleRemoval of mercury from aqueous solutions by malt spent rootletsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Vasileios A. Anagnostopoulos()Ioannis D. Manariotis()Hrissi K. Karapanagioti()http://purl.tuc.gr/dl/dias/E1EBDB72-07D0-4CDB-86A9-CF2E6AD1571310.1016/j.cej.2012.09.074Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2012Summarization: Mercury poses a severe threat to environment due to its toxicity, even at low concentrations. Biosorption
is a promising, low cost, and environmentally friendly clean up technique. Malt spent rootlets (MSR), a
brewery by-product, were used as sorbents for the removal of mercury from aquatic systems. The effect
of the solution pH, contact time between sorbent, solid to liquid ratio, and initial mercury concentration
on mercury removal were investigated experimentally. It was found that the optimum pH for the mercury
sorption onto MSR was approximately 5. Sorption kinetic experiments revealed that mercury sorption
is a relatively rapid process, where film diffusion and intra-particle diffusion play an important role.
The kinetic data were successfully described by both the pseudo-second-order and Elovich models. The
isotherm data were adequately fitted by the Langmuir model determining a monolayer capacity qmax
equal to 50 mg/g and suggesting a functional group-limited sorption process. MSR were capable of
removing significant amounts of mercury, mainly due to the carboxyl and phosphonate groups of their
surfaces.Παρουσιάστηκε στο: The Chemical Engineering Journalpeer-reviewedBibliographic citation: V. A. Anagnostopoulos , I. D. Manariotis , H. K. Karapanagioti ,
C.V. Chrysikopoulos , "Removal of mercury from aqueous solutions by malt spent rootlets " ,Chemi. Engin. J. ,vol. 213 ,pp. 135–141,2012.doi:10.1016/j.cej.2012.09.074info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:314842012-10-10T00:00:00Z28info:eu-repo/semantics/articleAttachment of Pseudomonas putida onto differently structured kaolinite minerals: A combined ATR-FTIR and H-1 NMR studyΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Georgios Papavassiliou()Michael Fardis()Eleni Karakosta()Ioanna A. Vasiliadou()Dionisios Panagiotaras()Dimitris Papoulis()http://purl.tuc.gr/dl/dias/E509AED8-110D-4C75-9769-A4970E1E770410.1016/j.colsurfb.2011.01.026Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2011Summarization: The attachment of Pseudomonas (P.) putida onto well (KGa-1) and poorly (KGa-2) crystallized kaolinitewas
investigated in this study. Batch experiments were carried out to determine the attachment isotherms of
P. putida onto both types of kaolinite particles. The attachment process of P. putida onto KGa-1 and KGa-2
wasadequately described by a Langmuir isotherm. Attenuated Total Reflection Fourier Transform Infrared
Spectroscopy and Nuclear Magnetic Resonance were employed to study the attachment mechanisms of P.
putida. Experimental results indicated that KGa-2 presented higher affinity and attachment capacity than
KGa-1. It was shown that electrostatic interactions and clay mineral structural disorders can influence
the attachment capacity of clay mineral particles.Παρουσιάστηκε στο: Colloids and surfaces B: Biointerfaces peer-reviewedΒιβλιογραφική αναφορά: I.A. Vasiliadou, D. Papoulis, C. V. Chrysikopoulos,
D.Panagiotaras, .Ε, Karakosta, M. Fardis, G. Papavassiliou , "Attachment of Pseudomonas putida onto differently structured kaolinite
minerals: A combined ATR-FTIR and 1H NMR study " , Col. and Surf. B: Biointerf.,vol. 84,no. 2 , pp.354–359,2011.doi :10.1016/j.colsurfb.2011.01.026info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:314852012-10-10T00:00:00Z28info:eu-repo/semantics/articleAn experimental study of acoustically enhanced NAPL dissolution in porous mediaΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Eric T. Vogler()http://purl.tuc.gr/dl/dias/4ACA8244-7E4E-499C-9265-FC3F4FB99EF810.1002/aic.10221Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2004Summarization: The effects of acoustic waves on the dissolution of dense nonaqueous phase liquids in
water saturated porous media are investigated. Experiments of trichloroethylene (TCE)
ganglia dissolution within a water saturated column, packed with glass beads, are
conducted. Acoustic waves with pressure amplitudes ranging from 0 to 1625 Pa and
frequencies ranging from 0 to 285 Hz are employed to the interstitial fluid at the inlet of
the packed column. Effluent dissolved TCE concentrations are observed to increase up to
120% in the presence of acoustic pressure waves compared to the case where TCE
dissolution without acoustic waves is monitored. The observed effluent dissolved TCE
concentration increase is attributed to enhanced mass flux at the TCE-water interface,
caused by acoustic waves. Highest dissolution rates occur at discrete frequencies suggesting
resonance effects or the presence of standing waves. Although acoustic waves
enhance TCE dissolution, they dissipate almost exponentially with distance from the
acoustic sourceΠαρουσιάστηκε στο: AIChE Journalpeer-reviewedBibliographic citation: E. T. Vogler, C. V. Chrysikopoulos ," An Experimental Study of Acoustically Enhanced NAPL Dissolution in Porous Media " ,A. J. ,vol.50 ,no.12 ,pp.3271 - 3280,2004.doi:10.1002/aic.10221info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:314872012-10-10T00:00:00Z28info:eu-repo/semantics/articleSorption of Pseudomonas putida onto differently structured kaolinite mineralsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Maria I. Bellou()Maria A. Tselepi()Vasiliki I. Syngouna()Petros A. Kokkinos()Apostolos Vantarakis()Spyros C. Paparrodopoulos()http://purl.tuc.gr/dl/dias/4B0C01C5-535D-459F-8C2C-21EDA89873B110.1016/j.scitotenv.2015.02.036Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2015Summarization: Human adenoviruses (hAdVs) are pathogenic viruses responsible for public health problems worldwide. They
have also been used as viral indicators in environmental systems. Coliphages (e.g., MS2, ΦX174) have also
been studied as indicators of viral pollution in fecally contaminated water. Our objective was to evaluate the
distribution of three viral fecal indicators (hAdVs, MS2, and ΦΧ174), between two different phyllosilicate clays
(kaolinite and bentonite) and the aqueous phase. A series of static and dynamic experiments were conducted
under two different temperatures (4, 25 °C) for a time period of seven days. HAdV adsorption was examined
in DNase I reaction buffer (pH=7.6, and ionic strength (IS)=1.4 mM), whereas coliphage adsorption in phosphate
buffered saline solution (pH=7, IS=2 mM). Moreover, the effect of IS on hAdV adsorption under static
conditions was evaluated. The adsorption of hAdVwas assessed by real-time PCR and its infectivitywas tested by
cultivation methods. The coliphages MS2 and ΦΧ174 were assayed by the double-layer overlay method. The
experimental results have shown that coliphage adsorption onto both kaolinite and bentonite was higher for
the dynamic than the static experiments; whereas hAdV adsorption was lower under dynamic conditions. The
adsorption of hAdV increased with decreasing temperature, contrary to the results obtained for the coliphages.
This study examines the combined effect of temperature, agitation, clay type, and IS on hAdV adsorption onto
clays. The results provide useful new information on the effective removal of viral fecal indicators (MS2,
ΦX174 and hAdV) from dilute aqueous solutions by adsorption onto kaolinite and bentoniteΠαρουσιάστηκε στο: Science of the Total Environmentpeer-reviewedBibliographic citation: M. I. Bellou ,V. I. Syngouna , M. A. Tselepi , P. A. Kokkinos , S. C. Paparrodopoulos ,A. Vantarakis , C. V. Chrysikopoulos , "Interaction of human adenoviruses and coliphages with kaolinite
and bentonite " ,Scien. of the Tot. Envir.,vol. 517 ,pp.86–95,2015.doi:10.1016/j.scitotenv.2015.02.036info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315022012-10-10T00:00:00Z28info:eu-repo/semantics/articleAttachment of bacteriophages MS2 and ΦX174 onto kaolinite and montmorillonite: Extended-DLVO interactionsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Vasiliki I. Syngouna()http://purl.tuc.gr/dl/dias/1987F07F-34F8-4E41-814D-ECBFC58A226A10.1016/j.colsurfb.2011.11.028Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2011Summarization: This study aims to gain insights into the interaction of virus particles with clay colloids. Bacteriophages
MS2 and X174 were used as model viruses and kaolinite (KGa-1b) and montmorillonite (STx-1b) as
model colloids. The experimental data obtained from batch experiments of MS2 and X174 attachment
onto KGa-1b and STx-1b suggested that virus attachment is adequately described by the Freundlich
isotherm equation. Both MS2 and X174 were attached in greater amounts onto KGa-1b than STx-1b
with MS2 having greater affinity than X174 for both clays. Furthermore, extended-DLVO interaction
energy calculations explained that the attachment of viruses onto model clay colloids was primarily
caused by hydrophobic interaction. The theoretical and experimental results of this study were found to
be in good agreement with previous findings.Παρουσιάστηκε στο: Colloids and surfaces B: Biointerfaces peer-reviewedBibliographic citation: C. V. Chrysikopoulos, V.I. Syngouna, "Attachment of bacteriophages MS2 and X174 onto kaolinite and montmorillonite: Extended-DLVO interactions " ,Col. and Surf.B: Biointerf.,vol. 92 ,pp. 74– 83,2011.doi :10.1016/j.colsurfb.2011.11.028info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315062012-10-10T00:00:00Z28info:eu-repo/semantics/articleTransport of polydisperse colloid suspensions in a single fractureΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Scott C. James()http://purl.tuc.gr/dl/dias/67C7237E-4CA4-459C-816C-B51D5071600Ahttp://www.researchgate.net/publication/258223723_Transport_of_polydisperse_colloid_suspensions_in_a_single_fracturePublished at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 1999Summarization: The transport of variably sized colloids (polydisperse) in a fracture with
uniform aperture is investigated by a particle-tracking model that treats colloids as
discrete particles with unique transport properties while accounting for either matrix
diffusion or irreversible colloid deposition. For the special case of a monodisperse colloid
suspension the particle-tracking model is in perfect agreement with predictions based on
an existing analytical solution. It is shown that lognormal colloid size distributions exhibit
greater spreading than monodisperse suspensions. Increasing the fracture porosity of the
solid matrix leads to higher matrix diffusion, which in turn delays particle breakthrough
for both the monodisperse and variably sized colloid suspensions. The smallest particles of
a distribution are more greatly affected by matrix diffusion whereas the largest particles
are transported faster and further along a fracture. Both perfect sink and kinetic colloid
deposition onto fracture surfaces are examined. Kinetic deposition accounts for colloid
surface exclusion by either a linear or nonlinear blocking function. For both cases the
smallest colloid particles tend to preferentially deposit onto the fracture wall. Both matrix
diffusion and surface deposition tend to discretize colloid distributions according to
particle size so that larger particles are least retarded and smaller particles are more
slowly transported. Furthermore, it is shown that the rate of colloid deposition is inversely
proportional to the fracture aperture.Παρουσιάστηκε στο: Water Resources Researchpeer-reviewedBibliographic citation: S.C. James , C. V. Chrysikopoulos.(March, 1999).Transport of polydisperse colloid suspensions in a single fracture . Water Resources Research.[online].pp. 707–718. Available: http://www.researchgate.net/publication/258223723_Transport_of_polydisperse_colloid_suspensions_in_a_single_fractureinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315082012-10-10T00:00:00Z28info:eu-repo/semantics/articleTransport of human adenoviruses in water saturated laboratory columnsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)P. Kokkinos()V. I. Syngouna()M. A. Tselepi()M. Bellou()Apostolos Vantarakis()http://purl.tuc.gr/dl/dias/FF8FF44D-BA2C-464B-A8C4-64592A483A98 10.1007/s12560-014-9179-8Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2015Summarization: Groundwatermay be contaminated with infective
human enteric viruses from various wastewater discharges,
sanitary landfills, septic tanks, agricultural practices, and
artificial groundwater recharge. Coliphages have been widely
used as surrogates of enteric viruses, because they share many
fundamental properties and features.Although a large number
of studies focusing on various factors (i.e. pore water solution
chemistry, fluid velocity, moisture content, temperature, and
grain size) that affect biocolloid (bacteria, viruses) transport
have been published over the past two decades, little attention
has been given toward human adenoviruses (hAdVs). The
main objective of this study was to evaluate the effect of pore
water velocity on hAdV transport in water saturated laboratory-
scale columns packed with glass beads. The effects of
pore water velocity on virus transport and retention in porous
media was examined at three pore water velocities (0.39, 0.75,
and 1.22 cm/min). The results indicated that all estimated
averagemass recovery values forhAdVwere lower than those
of coliphages, which were previously reported in the literature
by others for experiments conducted under similar experimental
conditions.Παρουσιάστηκε στο: Food and Environmental Virologypeer-reviewedBibliographic citation: P. Kokkinos , V. I. Syngouna , M. A. Tselepi ,M. Bellou ,C. V. Chrysikopoulos ,
A.Vantarakis, "Transport of human adenoviruses in water saturated
laboratory columns ",F. and Envi. Virolo. ,vol. 7 ,no. 2, 2015.doi: 10.1007/s12560-014-9179-8info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315102012-10-10T00:00:00Z28info:eu-repo/semantics/articleVirus inactivation in the presence of quartz sand under static and dynamic batch conditions at different temperaturesΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Andriana F. Aravantinou()http://purl.tuc.gr/dl/dias/C68C7E26-08BA-420E-B83B-478400185CA110.1016/j.jhazmat.2012.07.002Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2012Summarization: Virus inactivation is one of the most important factors that controls virus fate and transport in the
subsurface. In this study the inactivation of viruses in the presence of quartz sand was examined. The bacteriophages
MS2 and X174 were used as model viruses. Experiments were performed at 4 ◦C and 20 ◦C,
under constant controlled conditions, to investigate the effect of virus type, temperature, sand size, and
initial virus concentration on virus inactivation. The experimental virus inactivation data were satisfactorily
represented by a pseudo-first order expression with time-dependent rate coefficients. Furthermore,
the results indicated that virus inactivation was substantially affected by the ambient temperature and
initial virus concentration. The inactivation rate of MS2 was shown to be greater than that of X174.
However, the greatest inactivation was observed for MS2 without the presence of sand, at 20 ◦C. Sand
surfaces offered protection against inactivation especially under static conditions. However, no obvious
relationship between sand particle size and virus inactivation could be established from the experimental
data. Moreover, the inactivation rates were shown to increase with decreasing virus concentrationΠαρουσιάστηκε στο: Journal of Hazardous Materialspeer-reviewedΒιβλιογραφική αναφορά: C.V. Chrysikopoulos, A. F. Aravantinou, "Virus inactivation in the presence of quartz sand under static and dynamic batch conditions
at different temperatures ",J. of Hazar. Maτ. ,vol.233– 234 ,pp. 148– 157,2012.doi:10.1016/j.jhazmat.2012.07.002info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315122012-10-10T00:00:00Z28info:eu-repo/semantics/articleAnalytical solutions for monodisperse and polydisperse colloid transport in uniform fracturesΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Scott C. James()http://purl.tuc.gr/dl/dias/D10A5D54-5F47-4763-9DE0-36AAAF86D05310.1016/S0927-7757(03)00316-9Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2003Summarization: Analytical solutions are derived describing the transport of suspensions of monodisperse as well as polydisperse colloid
plumes of neutral buoyancy within a fracture with uniform aperture. Various initial and boundary conditions are considered.
It is shown that both the finite colloid size and the characteristics of the colloid diameter distribution significantly affect the
shape of colloid concentration breakthrough curves. Furthermore, increasing the standard deviation of the colloid diameter
enhances colloid spreading and increases the number of attached colloids when colloid–wall interactions are taken into account.
Excellent agreement between available experimental data and the analytical solution for the case of an instantaneous release of
monodisperse colloids in a natural fracture is observed.Παρουσιάστηκε στο: Colloids and Surfaces A Physicochemical and Engineering Aspectspeer-reviewedBibliographic citation: S. C. James , C. V. Chrysikopoulos , "Analytical solutions for monodisperse and polydisperse colloid transport in uniform fractures " ,Col. and Surf. A: Physico. Eng. Asp.,vol. 226, no.1-3,pp.101–118,2003.doi:10.1016/S0927-7757(03)00316-9info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315132012-10-10T00:00:00Z28info:eu-repo/semantics/articleContaminant transport in a variable aperture fracture in the presence of monodisperse colloidsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Scott C. James()Tanya K. Bilezikjian()http://purl.tuc.gr/dl/dias/57E1F283-287C-4694-B2CE-589E8457176B10.1007/s00477-004-0231-3Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2005Summarization: A quasi-three-dimensional particle tracking
model is developed to characterize the spatial and temporal
effects of advection, molecular diffusion, Taylor
dispersion, fracture wall deposition, matrix diffusion,
and co-transport processes on two discrete plumes
(suspended monodisperse or polydisperse colloids and
dissolved contaminants) flowing through a variable
aperture fracture situated in a porous medium. Contaminants
travel by advection and diffusion and may
sorb onto fracture walls and colloid particles, as well as
diffuse into and sorb onto the surrounding porous rock
matrix. A kinetic isotherm describes contaminant sorption
onto colloids and sorbed contaminants assume the
unique transport properties of colloids. Sorption of the
contaminants that have diffused into the matrix is governed
by a first-order kinetic reaction. Colloids travel by
advection and diffusion and may attach onto fracture
walls; however, they do not penetrate the rock matrix. A
probabilistic form of the Boltzmann law describes filtration
of both colloids and contaminants on fracture
walls. Ensemble-averaged breakthrough curves of many
fracture realizations are used to compare arrival times of
colloid and contaminant plumes at the fracture outlet.
Results show that the presence of colloids enhances
contaminant transport (decreased residence times) while
matrix diffusion and sorption onto fracture walls retard
the transport of contaminants. Model simulations with
the polydisperse colloids show increased effects of cotransport
processes.Παρουσιάστηκε στο: Stochastic Environmental Research and Risk Assessmentpeer-reviewedBibliographic citation: S. C. James ,T. K. Bilezikjian , C. V. Chrysikopoulos , "Contaminant transport in a fracture with spatially variable aperture
in the presence of monodisperse and polydisperse colloids " ,Stoch. Environ. Res. Risk. Assess ,vol.19 pp. 266–279,2005.doi:10.1007/s00477-004-0231-3info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315152012-10-10T00:00:00Z28info:eu-repo/semantics/articleTransport of viruses in water saturated columns packed with sand: Effect of pore water velocity, sand grain size, and suspended colloidsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Vasileios E. Katzourakis()http://purl.tuc.gr/dl/dias/718D1ADB-0182-42A9-AF4E-3A678B0826F310.1016/j.advwatres.2014.03.001Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2014Summarization: A conceptual mathematical model was developed to describe the simultaneous transport (cotransport) of
viruses and colloids in three-dimensional, water saturated, homogeneous porous media with uniform
flow. The model accounts for the migration of individual virus and colloid particles as well as viruses
attached onto colloids. Viruses can be suspended in the aqueous phase, attached onto suspended colloids
and the solid matrix, and attached onto colloids previously attached on the solid matrix. Colloids can be
suspended in the aqueous phase or attached on the solid matrix. Viruses in all four phases (suspended in
the aqueous phase, attached onto suspended colloid particles, attached on the solid matrix, and attached
onto colloids previously attached on the solid matrix) may undergo inactivation with different inactivation
coefficients. The governing coupled partial differential equations were solved numerically using
finite difference methods, which were implemented explicitly or implicitly so that both stability and
speed factors were satisfied. Furthermore, the experimental data collected by Syngouna and Chrysikopoulos
[1] were satisfactorily fitted by the newly developed cotransport model.Παρουσιάστηκε στο: Advances in Water Resourcespeer-reviewedBibliographic citation: V. E. Katzourakis , C. V. Chrysikopoulos , "Mathematical modeling of colloid and virus cotransport in porous media: Application to experimental data" ,Advanc. in Wat. Resour.,vol. 68,pp. 62–73,2014.doi:10.1016/j.advwatres.2014.03.001info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315192012-10-10T00:00:00Z28info:eu-repo/semantics/articleLongitudinal interpolation of parameters characterizing channel geometry by piece-wise polynomial and universal kriging methods: effect on flow modelingΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Interpolation of parameters characterizing the geometry
of channel beds is needed to support flow modeling
at varying grid resolutions. Three methods of interpolating
geometric parameters between survey stations
were described including piece-wise linear interpolation,
monotone piece-wise-cubic Hermitian interpolation,
and universal kriging. The latter gives parameter estimates
that minimize the mean square error of the interpolator
and therefore is considered the most accurate
method. Based on the application of these methods to
a dataset describing cross-sectional properties at 283 stations,
piece-wise linear interpolation gave parameter
estimates that very closely track universal kriging estimates.
Piece-wise-cubic interpolation, including monotone
piece-wise-cubic Hermitian interpolation and
cubic spline interpolation, gave parameter estimates that
did not track as wellBrett F. Sandershttp://purl.tuc.gr/dl/dias/03A5CB4E-49DE-4126-8E6F-A74E4202F2B610.1016/j.advwatres.2004.08.010Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2004Summarization: Channel geometry often is described by a set of longitudinally varying parameters measured at a set of survey stations. To support
flow modeling at arbitrary resolution, three methods of parameter interpolation are described including piece-wise linear interpolation,
monotone piece-wise-cubic Hermitian interpolation, and universal kriging. The latter gives parameter estimates that
minimize the mean square error of the interpolator, and therefore can be used as a standard against which the accuracy of polynomial
methods can be assessed. Based on the application of these methods to a dataset describing cross-sectional properties at 283
stations, piece-wise linear interpolation gives parameter estimates that closely track universal kriging estimates and therefore this
method is recommended for routine modeling purposes. Piece-wise-cubic interpolation gives parameter estimates that do not track
as well. Differences between cubic and kriging estimates were found to be 2–10 times larger than differences between linear and kriging
parameter estimates. In the context of one-dimensional flow modeling, the sensitivity of steady state water level predictions to
the channel bed interpolator is comparable to a 5% change in the Manning coefficient.Παρουσιάστηκε στο: Advances in Water Resourcespeer-reviewedBibliographic citation: Brett F. Sanders , Constantios V. Chrysikopoulos , "Longitudinal interpolation of parameters characterizing channel geometry by piece-wise polynomial and universal
kriging methods: effect on flow modeling " , Advances in Water Resources 27 (2004) 1061–1073, info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315212012-10-10T00:00:00Z28info:eu-repo/semantics/articleDissolution of nonaqueous
phase liquid pools in anisotropic
aquifersΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)E .T Vogler()http://purl.tuc.gr/dl/dias/715B4B5F-FB4F-4482-BAED-47F87D7152A310.1007/PL00009787Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2001Summarization: A two-dimensional numerical transport model is developed to determine the effect of aquifer anisotropy and heterogeneity
on mass transfer from a dense nonaqueous phase liquid (DNAPL) pool. The appropriate steady state groundwater flow equation
is solved implicitly whereas the equation describing the transport of a sorbing contaminant in a confined aquifer is solved
by the alternating direction implicit method. Statistical anisotropy in the aquifer is introduced by two-dimensional, random
log-normal hydraulic conductivity field realizations with different directional correlation lengths. Model simulations indicate
that DNAPL pool dissolution is enhanced by increasing the mean log-transformed hydraulic conductivity, groundwater flow velocity,
and/or anisotropy ratio. The variance of the log-transformed hydraulic conductivity distribution is shown to be inversely
proportional to the average mass transfer coefficient.
Παρουσιάστηκε στο: Stochastic Environmental Research and Risk Assessmentpeer-reviewedBibliographic citation: E. T. Vogler ,C. V. Chrysikopoulos, "Dissolution of nonaqueous phase liquid pools in anisotropic aquifers " ,Stoch. Environ.Research and Risk Ass. ,vol.15, no.1, pp. 33-46,2001.doi :10.1007/PL00009787info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315002012-10-10T00:00:00Z28info:eu-repo/semantics/articleInteraction between viruses and clays in static
and dynamic batch systemsΧρυσικοπουλος Κωνσταντινος(http://users.isc.tuc.gr/~cchrysikopoulos)Chrysikopoulos Constantinos(http://users.isc.tuc.gr/~cchrysikopoulos)Vasiliki I . S yngouna()http://purl.tuc.gr/dl/dias/4AC83DC2-6750-417C-AE24-3E8FA13E0E0910.1021/es100107aPublished at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2010Summarization: Bacteriophage MS2 and ΦX174 were used as surrogates for
human viruses in order to investigate the interaction between
viruses and clay particles. The selected phyllosilicate clays
were kaolinite and bentonite (>90% montmorillonite). A series
of static and dynamic experiments were conducted at two
different temperatures (4 and 25 °C) to investigate the effect
of temperature and agitation (dynamic experiments) on virus
adsorption onto clays. Appropriate adsorption isotherms were
determined. Electrokinetic features of bacteriophages and
clays were quantified at different pH and ionic strength (IS).
Moreover, interaction energies between viruses and clays were
calculated for the experimental conditions (pH 7 and IS ) 2
mM) by applying the DLVO theory. The experimental results
shown that virus adsorption increases linearly with suspended
virus concentration. The observed distribution coefficient (Kd)
was higher for MS2 than ΦX174. The observed Kd values were
higher for the dynamic than static experiments, and increased
with temperature. The results of this study provided basic
information for the effectiveness of clays to remove viruses by
adsorption from dilute aqueous solutions. No previous study
has explored the combined effect of temperature and agitation
on virus adsorption onto clays.Παρουσιάστηκε στο: Environmental Science and Technology peer-reviewedBibliographic citation: V . I . Syngouna
C . V . Chrysikopoulos , "Interaction between viruses and clays in static and dynamic batch systems ",Environ. Sci. Technol. ,vol.44, no.12 pp. 4539–4544,2010.doi:10.1021/es100107ainfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315262012-10-10T00:00:00Z28info:eu-repo/semantics/articleEnhancement of biodegradability of industrial wastewaters by chemical oxidation pre-treatment. Elefteria Psillakis()Dionissios Mantzavinos()Coupling chemical and biological treatmenthttp://purl.tuc.gr/dl/dias/72CAAFE3-A529-4FB8-A8F7-7EA0C9508A2E10.1002/jctb.1020Published at: 2015-09-23eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2004Summarization: Chemical oxidation technologies are often employed for the treatment of complex industrial
effluents that are not amenable to conventional biological methods. The role of chemical oxidation depends
on the treatment objectives andmay vary from partial remediation to complete mineralization. In the case
of partial treatment, chemical oxidation aims at the selective removal of the more bioresistant fractions
and their conversion to readily biodegradable intermediates that can subsequently be treated biologically.
Coupling chemical pre-oxidation with biological post-treatment is conceptually beneficial as it can lead
to increased overall treatment efficiencies compared with the efficiency of each individual stage. This
paper reviews recent developments and highlights some important aspects that need to be addressed when
considering such integrated schemes.John Wiley & Sons, Ltd.Παρουσιάστηκε στο: Journal of Chemical Technology and Biotechnologypeer-reviewedBibliographic citation: D.Mantzavinos, E. Psillakis , "Enhancement of biodegradability of industrial wastewaters by chemical oxidation pre-treatment ", J. Chem. Techno.l Biotechnol.,vol . 79,pp. 431–454 ,2004. doi:10.1002/jctb.1020info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315292012-10-10T00:00:00Z28info:eu-repo/semantics/articleAnion-templated assembly of a supramolecular cage complexElefteria Psillakis()Michael D Ward()Jon A McCleverty()John C Jeffery()Charles‐Antoine Carraz()Karen LV Mann()James S Fleming()http://purl.tuc.gr/dl/dias/EF6B6050-2017-4952-B1CA-B6A1D3D97B8C10.1002/(SICI)1521-3773(19980518)37:9<1279::AID-ANIE1279>3.0.CO;2-QPublished at: 2015-09-23eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 1998Summarization: THe templating effect of the tetrafluoroborate ion leads to assembly of four CoII ions and six bridging ligands around this anion to give a tetrahedral complex with a bridging ligand along each edge and the anion trapped in the central cavity (shown below). Surprisingly under identical conditions but with NiII a simpler dinuclear complex forms.
Wiley‐vch verlag gmbhPresented on: Angewandte Chemie International Editionpeer-reviewedBibliographic citation: J. S Fleming, K. LV Mann, C.A.Carraz, E.Psillakis, J. C Jeffery, J. A McCleverty, M.D Ward , "Anion-Templated Assembly of a Supramolecular Cage Complex ",Ang. chem. interna. edit.,vol.37,no.9 ,pp.1279-1281,1998.doi:10.1002/(SICI)1521-3773(19980518)37:9<1279::AID-ANIE1279>3.0.CO;2-Qinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315362012-10-10T00:00:00Z28info:eu-repo/semantics/articleElectrochemical oxidation of olive oil mill wastewatersElefteria Psillakis()Marina Gotsi()Nicolas Kalogerakis()Petros Samaras() Dionissios Mantzavinos()http://purl.tuc.gr/dl/dias/E5CAF8E2-60C6-46EB-9071-411FB80ECC9F10.1016/j.watres.2005.07.037Published at: 2015-09-24eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2005Summarization: The electrochemical oxidation of olive oil mill wastewaters over a titanium–tantalum–platinum–iridium anode was
investigated. Batch experiments were conducted in a flow-through electrolytic cell with internal recycle at voltage of 5, 7
and 9V, NaCl concentrations of 1%, 2% and 4%, recirculation rates of 0.4 and 0.62 L/s and initial chemical oxygen
demand (COD) concentrations of 1475, 3060, 5180 and 6545 mg/L. The conversion of total phenols and COD as well as
the extent of decolorization generally increased with increasing voltage, salinity and recirculation rate and decreasing
initial concentration. In most cases, nearly complete degradation of phenols and decolorization were achieved at short
treatment times up to 60 min; this was accompanied by a relatively low COD removal that never exceeded 40% even
after prolonged (up to 240 min) times. The consumption of energy per unit mass of COD removed after 120 min of
treatment was found to be a strong function of the operating conditions and was generally low at high initial
concentrations and/or reduced salinity. The acute toxicity to marine bacteria Vibrio fischeri decreased slightly during
the early stages of the reaction and this was attributed to the removal of phenols. However, as the reaction proceeded
toxicity increased due to the formation of organochlorinated by-products as confirmed by GC/MS analysis. The
toxicity to Daphnia magna increased sharply at short treatment times and remained quite high even after prolonged
oxidation.PergamonΠαρουσιάστηκε στο: Water Researchpeer-reviewedBibliographic citation: M. Gotsi, N. Kalogerakis, E. Psillakis, P. Samaras, D. Mantzavinos , "Electrochemical oxidation of olive oil mill wastewaters " ,Wat. Resear.,vol. 39,no.17 ,pp. 4177–4187,2005.doi:10.1016/j.watres.2005.07.037info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315402012-10-10T00:00:00Z28info:eu-repo/semantics/articleVortex-assisted liquid-liquid microextraction of octylphenol, nonylphenol and bisphenol-AElefteria Psillakis()Evangelia Yiantzi() Konstantina Tyrovola()Nicolas Kalogerakis()http://purl.tuc.gr/dl/dias/2C190A94-F49C-4D26-95DA-2151C92E59C810.1016/j.talanta.2009.11.005Published at: 2015-09-24eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2010Summarization: A new and fast equilibrium-based solvent microextraction technique termed vortex-assisted
liquid–liquid microextraction (VALLME) has been developed and used for the trace analysis of octylphenol,
nonylphenol and bisphenol-A in water and wastewater samples. According to VALLME, dispersion of
microvolumes of a low density extractant organic solvent into the aqueous sample is achieved by using
for the first time vortex mixing, a mild emulsification procedure. The fine droplets formed could extract
target analytes towards equilibrium faster because of the shorter diffusion distance and larger specific
surface area. Upon centrifugation the floating extractant acceptor phase restored its initial single microdrop
shape and was used for high-performance liquid chromatographic analysis. Different experimental
parameters were controlled and the optimum conditions found were: 50l of octanol as the extractant
phase; 20 ml aqueous donor samples; a 2 min vortex extraction time with the vortex agitator set at a
2500rpm rotational speed; centrifugation for 2 min at 3500 rpm; no ionic strength or pH adjustment.
The calculated calibration curves gave high levels of linearity yielding correlation coefficients (r2) greater
than 0.9935. The repeatability and reproducibility of the proposed method were found to be good and
the limits of the detection were calculated in the low g l−1 level ranging between 0.01 and 0.07g l−1.
Matrix effects were determined by applying the proposed method to spiked tap, river water and treated
municipal wastewater samples.ElsevierΠαρουσιάστηκε στο: Talantapeer-reviewedBibliographic citation: E. Yiantzi, E. Psillakis , K. Tyrovola, N. Kalogerakis , "Vortex-assisted liquid–liquid microextraction of octylphenol, nonylphenol and
bisphenol-A " ,Tal.,vol. 80,no.5 ,pp.2057–2062,2010.doi:10.1016/j.talanta.2009.11.005info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:315422012-10-10T00:00:00Z28info:eu-repo/semantics/articleAn ionic liquid as a solvent for headspace single drop microextraction of chlorobenzenes from water samplesElefteria Psillakis()Lorena Vidal()Nuria Grané()Frank Marken()Antonio Canals()http://purl.tuc.gr/dl/dias/628BB734-289F-47B4-A709-B4519375955910.1016/j.aca.2006.10.053Published at: 2015-09-24eninfo:eu-repo/semantics/openAccessLicense: http://creativecommons.org/licenses/by/4.0/application/pdfIssued on: 2007Summarization: A headspace single-drop microextraction (HS-SDME) procedure using room temperature ionic liquid and coupled to high-performance liquid
chromatography capable of quantifying trace amounts of chlorobenzenes in environmental water samples is proposed. A Plackett–Burman design
for screening was carried out in order to determine the significant experimental conditions affecting the HS-SDME process (namely drop volume,
aqueous sample volume, stirring speed, ionic strength, extraction time and temperature), and then a central composite design was used to optimize
the significant conditions. The optimum experimental conditions found from this statistical evaluation were: a 5 L microdrop of 1-butyl-3-
methylimidazolium hexafluorophosphate, exposed for 37 min to the headspace of a 10mL aqueous sample placed in a 15mL vial, stirred at
1580 rpm at room temperature and containing 30% (w/v) NaCl. The calculated calibration curves gave a high level of linearity for all target
analytes with correlation coefficients ranging between 0.9981 and 0.9997. The repeatability of the proposed method, expressed as relative standard
deviation, varied between 1.6 and 5.1% (n = 5). The limits of detection ranged between 0.102 and 0.203 gL−1. Matrix effects upon extraction
were evaluated by analysing spiked tap and river water as well as effluent water samples originating from a municipal wastewater treatment plant.ElsevierΠαρουσιάστηκε στο: Analytica chimica actapeer-reviewedBibliographic citation: L. Vidal , E. Psillakis , C. E. Domini ,
N. Grane, F. Marken , A. Canals , "An ionic liquid as a solvent for headspace single drop microextraction of chlorobenzenes from water samples " ,Anal. chim. acta ,vol. 584,no.1, pp. 189–195,2207.doi :10.1016/j.aca.2006.10.053info:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:346512012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectFederating natural history museums in natural EuropeΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Konstantinos Makris()Giannis Skevakis()Varvara Kalokyri()Polyxeni Arapi()John Stoitsis()Nikos Manolis()Sarah Leon Rojas()http://purl.tuc.gr/dl/dias/599A70CA-61E3-4427-9FA2-E26A59BC93E910.1007/978-3-319-03437-9_35Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2013Summarization: An impressive abundance of high quality scientific content about Earth’s biodiversity and natural history available in Natural History Museums (NHMs) around Europe remains largely unexploited due to a number of barriers, such as: the lack of interconnection and interoperability between the management systems used by museums, the lack of centralized access through a European point of reference like Europeana, and the inadequacy of the current metadata and content organization. To cope with these problems, the Natural Europe project offers a coordinated solution at European level. Cultural heritage content is collected from six Natural History Museums around Europe into a federation of European Natural History Digital Libraries that is directly connected with Europeana.eu. This paper presents the Natural Europe Cultural Digital Libraries Federation infrastructure consisting of: (a) The Natural Europe Cultural Environment (NECE), i.e. the infrastructure and toolset deployed on each NHM allowing their curators to publish, semantically describe, manage and disseminate the Cultural Heritage Objects (CHOs) they contribute to the project, and (b) the Natural Europe Cultural Heritage Infrastructure (NECHI) interconnecting NHM digital libraries and further exposing their metadata records to Europeana.eu.
Παρουσιάστηκε στο: 7th Metadata Semantics and Research Conference (MTSR) 2013 Springer VerlagBibliographic citation: Ko. Makris, G. Skevakis, V. Kalokyri, P. Arapi, S.Christodoulakis, J. Stoitsis, Ni Manolis, S. L. Rojas ,"Federating Natural History Museums in Natural Europe ", In 2013 the Meta Sem and Res Conf (MTSR) ,pp.361-372.doi :10.1007/978-3-319-03437-9_35posterinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:346512012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectFederating natural history museums in natural EuropeΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Konstantinos Makris()Giannis Skevakis()Varvara Kalokyri()Polyxeni Arapi()John Stoitsis()Nikos Manolis()Sarah Leon Rojas()http://purl.tuc.gr/dl/dias/599A70CA-61E3-4427-9FA2-E26A59BC93E910.1007/978-3-319-03437-9_35Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2013Summarization: An impressive abundance of high quality scientific content about Earth’s biodiversity and natural history available in Natural History Museums (NHMs) around Europe remains largely unexploited due to a number of barriers, such as: the lack of interconnection and interoperability between the management systems used by museums, the lack of centralized access through a European point of reference like Europeana, and the inadequacy of the current metadata and content organization. To cope with these problems, the Natural Europe project offers a coordinated solution at European level. Cultural heritage content is collected from six Natural History Museums around Europe into a federation of European Natural History Digital Libraries that is directly connected with Europeana.eu. This paper presents the Natural Europe Cultural Digital Libraries Federation infrastructure consisting of: (a) The Natural Europe Cultural Environment (NECE), i.e. the infrastructure and toolset deployed on each NHM allowing their curators to publish, semantically describe, manage and disseminate the Cultural Heritage Objects (CHOs) they contribute to the project, and (b) the Natural Europe Cultural Heritage Infrastructure (NECHI) interconnecting NHM digital libraries and further exposing their metadata records to Europeana.eu.
Παρουσιάστηκε στο: 7th Metadata Semantics and Research Conference (MTSR) 2013 Springer VerlagBibliographic citation: Ko. Makris, G. Skevakis, V. Kalokyri, P. Arapi, S.Christodoulakis, J. Stoitsis, Ni Manolis, S. L. Rojas ,"Federating Natural History Museums in Natural Europe ", In 2013 the Meta Sem and Res Conf (MTSR) ,pp.361-372.doi :10.1007/978-3-319-03437-9_35posterinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:346742012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectBringing environmental culture content into the Europeana.eu portal: The natural Europe digital libraries federation infrastructureΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Konstantinos Makris() Giannis Skevakis() Varvara Kalokyri()Nektarios Gioldasis()Fotis G. Kazasis()http://purl.tuc.gr/dl/dias/FCBF445A-BCFC-4E1B-9A6F-CB970E62A3C310.1007/978-3-642-24731-6_40Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2011Summarization: The aim of the Natural Europe project [1] is to improve the availability and relevance of environmental culture content for education and life-long learning use, in a multilingual and multicultural context. Cultural heritage content related with natural history, natural sciences, and nature/ environment preservation, is collected from six Natural History Museums (NHMs) around Europe into a federation of European Natural History Digital Libraries that is directly connected with Europeana.eu. We present here the Natural History Digital Libraries Federation infrastructure along with the appropriate tools and services that (a) allow the participating NHMs to uniformly describe and semantically annotate their content according to international standards and specifications, (b) interconnect their digital libraries, and (c) expose metadata records for Natural History cultural heritage objects to Europeana.eu.Παρουσιάστηκε στο: 5th International Conference, MTSR 2011, Izmir, Turkey, October 12-14, Springer VerlagBibliographic citation: K. Makris, G.Skevakis, V. Kalokyri, N. Gioldasis, F.G. Kazasis, S. Christodoulakis ," Bringing environmental culture content into the Europeana.eu portal: The natural Europe digital libraries federation infrastructure ",In 2011 5th Int. Conf. (MTSR) , pp. 400-411.doi : 10.1007/978-3-642-24731-6_40full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:346912012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectMapping MPEG-7 to CIDOC/CRMΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Anastasia Angelopoulou()Chrisa Tsinaraki()The MPEG72CIDOC Mapping ModelMPEG-7 to CIDOC/CRM Transformationhttp://purl.tuc.gr/dl/dias/245914D9-7432-4A1C-ADC0-E092005B5E1C10.1007/978-3-642-24469-8_6Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2011Summarization: The MPEG-7 is the dominant standard for multimedia content description; thus, the audiovisual Digital Library contents should be described in terms of MPEG-7. Since there exists a huge amount of audiovisual content in the cultural heritage domain, it is expected that several cultural heritage objects, as well as entities related with them (i.e. people, places, events etc.), have been described using MPEG-7. On the other hand, the dominant standard in the cultural heritage domain is the CIDOC/CRM; consequently, the MPEG-7 descriptions cannot be directly integrated in the cultural heritage digital libraries.
We present in this paper a mapping model and a system that allow the transformation of the MPEG-7 descriptions to CIDOC/CRM descriptions, thus allowing the exploitation of multimedia content annotations in the cultural heritage digital libraries. In addition, the proposed mapping model allows linking MPEG-7 descriptions to CIDOC/CRM descriptions in a Linked Data scenario.Παρουσιάστηκε στο: International Conference on Theory and Practice of Digital Libraries, TPDSpringer VerlagBibliographic citation: A.Angelopoulou, C. Tsinaraki, S. Christodoulakis , "Mapping MPEG-7 to CIDOC/CRM ", In 2011 In. Conf. on Th. and Pr. of Dig. Libr., (TPDL) ,pp.40-51.doi:10.1007/978-3-642-24469-8_6full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:347552012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectMobile multimedia event capturing and visualization (MOME)Χριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Amalia Panteli()Chrisa Tsinaraki()Lemonia Ragia()Fotis Kazasis()The conceptual model http://purl.tuc.gr/dl/dias/4AD5DEEB-6B7B-40F7-9265-438BF1A3E4F110.1109/MUE.2011.29 Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2011Summarization: Capturing Multimedia Events such as natural disasters, accident reports, building damage reports, political events, etc., are expensive functionalities due to the number and training of the people required, as well as the time involved in the capturing and post-processing of multimedia. In addition, the captured multimedia content often fails to give the viewer a comprehensive understanding of the event captured in context. We present a model and a mobile system for multimedia event capturing by a one-man-crew. The system supports: (a) the real time capturing of complex multimedia events of different types, (b) the recording of the capturing process and the metadata associated with the events, (c) the visualization of the events and the capturing process, and (d) the learning and preparation of the one-man-crew that will do the multimedia event capturing.
Παρουσιάστηκε στο: n the proceedings of the FTRA MUE 2011 Conference 28-30 JuneIEEEBibliographic citation: A. Panteli, C. Tsinaraki#, L. Ragia, F. Kazasis, S.Christodoulakis , "Mobile multimedia event capturing and visualization (MOME) ", In 2011 proc. of the FTRA MUE Con. ,pp.101 - 106.doi : 10.1109/MUE.2011.29full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:347912012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectTransforming teaching and learning: Changing the pedagogical approach to using educational programming languagesΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Petros Lameras()David Smith()Nektarios Moumoutzis() Emanuela Ovcin()Στυλιανακης Γεωργιος(http://users.isc.tuc.gr/~gstylianakis)Stylianakis Georgios(http://users.isc.tuc.gr/~gstylianakis)http://purl.tuc.gr/dl/dias/74D7141A-EFA7-4239-A96F-2F00EEAA5378http://www.virtuelleschule.at/fileadmin/reports/konferenzbeitraege/transform_learning_2010a.pdfPublished at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2010Summarization: Within the context of a European project exploring the development of programming skills in secondary education by means of modern educational programming languages, this paper proposes certain pedagogical methods, approaches and frameworks for enhancing the development of programming skills, and thereby increasing the number of students studying computer science both at school and university level. In particular, the aim of this paper is to explore the issues surrounding curriculum design for computer courses with a special focus on programming. It has been argued that the utilisation of learning activities that demonstrate specific pedagogic approaches (inquiry-based learning, collaborative learning, cognitive constructivism or activity based) is limited suggesting that teachers are not fully aware of how to apply different pedagogical considerations to their actual practice. This is more apparent in programming courses because of the increased level of abstraction which may cause certain difficulties in teaching and learning. The creation of curricula based on pedagogically-rich teaching and learning activities, and the introduction of Educational Programming Languages (EPLs) designed for teachers to teach students how to develop computer programs, may generate powerful learning opportunities. The main purpose of this paper is to outline the theoretical underpinning of teaching and learning EPLs, and to argue that, to be comprehensive, curriculum design for programming courses must consider important perspectives, each of which leads to specific ways of teaching programming. The paper starts by surveying the current state of computer science curriculum in the participating countries in the context of curriculum design, before looking at learning theories and EPLs that may be used to support informed decisions for pedagogically-driven programming course design. Each decision requires different approaches to teaching programming which are necessary for aligning theory and practice within a viable educational model. The paper concludes by proposing that information and communication technology (ICT) tools may provide a framework to design and structure teaching and learning activities for programming courses.Παρουσιάστηκε στο: hort paper presented at the ALT-C conference, Nottingham, UK, 7-9 SeptembeBibliographic citation: P. Lameras , D. Smith , N. Moumoutzis ,S. Christodoulakis , E. Ovcin , G. Stylianakis .( 2010 , Sept. ) .Presented at the ALT-C conference, Nottingham, UK, 7-9 September, 2010.[online].Available :http://www.virtuelleschule.at/fileadmin/reports/konferenzbeitraege/transform_learning_2010a.pdffull paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:348312012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectQuerying XML data with SPARQL Χριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Nikos Bikakis()Nektarios Gioldasis()Chrisa Tsinaraki()Mapping OWL to XML SchemaThe Query Translation Processhttp://purl.tuc.gr/dl/dias/14745BDE-923B-46A7-9B8E-E14A54112D2510.1007/978-3-642-03573-9_32Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2009Summarization: SPARQL is today the standard access language for Semantic Web data. In the recent years XML databases have also acquired industrial importance due to the widespread applicability of XML in the Web. In this paper we present a framework that bridges the heterogeneity gap and creates an interoperable environment where SPARQL queries are used to access XML databases. Our approach assumes that fairly generic mappings between ontology constructs and XML Schema constructs have been automatically derived or manually specified. The mappings are used to automatically translate SPARQL queries to semantically equivalent XQuery queries which are used to access the XML databases. We present the algorithms and the implementation of SPARQL2XQuery framework, which is used for answering SPARQL queries over XML databases.Παρουσιάστηκε στο: In the proceedings of the 20th International Conference on Database and Expert Systems Applications DEXASpringer VerlagBibliographic citation: N. Bikakis, N. Gioldasis, C. Tsinaraki, S. Christodoulakis ,"Querying XML data with SPARQL " in 2009 Int. Conference on Data.and Expert Sys. ap. DEXA , pp.372-381.doi: 10.1007/978-3-642-03573-9_32full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:348512012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectTowards a mediator based on owl and SPARQLΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Konstantinos Makris()Nikos Bikakis()Nektarios Gioldasis()Chrisa Tsinaraki()SPARQL Query Reformulationhttp://purl.tuc.gr/dl/dias/CC2C42DF-763D-4896-8CF2-821394650FB810.1007/978-3-642-04754-1_34Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2009Summarization: We propose a framework that supports a federated environment based on a Mediator Architecture in the Semantic Web. The Mediator supports mappings between the OWL Ontology of the Mediator and the other ontologies in the federated sites. SPARQL queries submitted to the Mediator are decomposed and reformulated to SPARQL queries to the federated sites. The evaluated results return to the Mediator. In this paper we describe the mappings definition and encoding. We also discuss briefly the reformulation approach that is used by the Mediator system that we are currently implementing.Παρουσιάστηκε στο: In the Proceedings of the 2nd World Summit on the Knowledge Society, Crete, GreeceSpringer VerlagBibliographic citation: K. Makris, N.Bikakis, N. Gioldasis, C. Tsinaraki, S. Christodoulakis, " Towards a mediator based on owl and SPARQL " In 2009 the Proc. of the 2nd World Sum. on the Knowl. Soc., Crete, Greece ,pp.326-335.doi :10.1007/978-3-642-04754-1_34full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:349112012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectSemantic based access over XML dataNikos Bikakis()Χριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Nektarios Gioldasis()Chrisa Tsinaraki()SPARQL Graph Pattern NormalizationMapping OWL to XML Schemahttp://purl.tuc.gr/dl/dias/5D4355EF-8E47-4CC7-9AC8-45C8B06BE0A310.1007/978-3-642-04754-1_27Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2009Summarization: The need for semantic processing of information and services has lead to the introduction of tools for the description and management of knowledge within organizations, such as RDF, OWL, and SPARQL. However, semantic applications may have to access data from diverse sources across the network. Thus, SPARQL queries may have to be submitted and evaluated against existing XML or relational databases, and the results transferred back to be assembled for further processing. In this paper we describe the SPARQL2XQuery framework, which translates the SPARQL queries to semantically equivalent XQuery queries for accessing XML databases from the Semantic Web environment.Παρουσιάστηκε στο: In the Proceedings of the 2nd World Summit on the Knowledge Society, Crete, GreeceSpringer VerlagBibliographic citation: N. Bikakis, N.Gioldasis, C. Tsinaraki, S. Christodoulakis ,"Semantic based access over XML data ",In 2009 the Pro. of the 2nd World Sum. on the Knowl. Soc., Crete, Greece,pp. 259-267.doi :10.1007/978-3-642-04754-1_27full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:349322012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectRich metadata and context capturing through CIDOC/CRM and mpeg-7 interoperabilityΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Alexandros Ntousias()Nektarios Gioldasis()Chrisa Tsinaraki()CIDOC/CRM TO MPEG-7http://purl.tuc.gr/dl/dias/280E76B1-C64D-41E5-B12A-221E7CF1A76910.1145/1386352.1386377Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2008Summarization: It is now accepted that powerful retrieval of multimedia data can be achieved with the integration of semantic and contextual metadata that relate to multimedia objects. In the case of objects related to culture and history there is a wealth of related information stored in Digital Libraries. CIDOC/CRM is a new, rapidly adopted standard in the field of cultural heritage that provides a very powerful model for encoding cultural heritage knowledge. In this paper we propose that knowledge is extracted and encoded in MPEG-7 multimedia object descriptions in an automatic manner so that the multimedia objects are augmented with very rich metadata descriptions coming from Digital Libraries. We analyze the mapping problem between CIDOC/CRM and MPEG-7 and we present the algorithms and a software system that supports this mapping.Παρουσιάστηκε στο: In the Proceedings of the ACM International Conference on Image and Video Retrieval (CIVR), Niagara Falls, Canada, July 7-9Association for Computing MachineryBibliographic citation: A.Ntousias,N. Gioldasis , C.Tsinaraki , S. Christodoulakis , "Rich metadata and context capturing through CIDOC/CRM and MPEG-7 interoperability ", In 2008 Proc. of the ACM Int. Conf. on Image and Video Retrieval (CIVR), pp.151-160 .doi :10.1145/1386352.1386377full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:349712012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectSpatial information retrieval from images using ontologies and semantic mapsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Michalis Foukarakis()Lemonia Ragia()http://purl.tuc.gr/dl/dias/D3245414-B2F2-4148-96F9-F789DB1A730F10.1007/978-3-540-87781-3_59Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2008Summarization: Cameras provide integrated GPS technology which makes them a powerful sensor for geographical context related images. They allow wireless connection to computers and the images can be automatically transferred to a PC or can be integrated into a GIS system. In this paper we propose an approach for spatial information retrieval from images using the concept of ontologies and semantic maps. The term of ontology is used in our case to describe spatial domain knowledge to enhance the search capability and image annotation. The objects are represented by their location in semantic maps. We describe a developed prototype system with a database design for ontologies and semantic maps. We demonstrate the automatic image annotation and the visualization of the spatial queries. The system is oriented to the area of culture and tourism and provides a user friendly interface.Παρουσιάστηκε στο: 1st World Summit on the Knowledge Society. 24-28 September 2008, Athens, GreeceSpringer VerlagBibliographic citation: S. Christodoulakis, M.Foukarakis , L.Ragia , "Spatial information retrieval from images using ontologies and semantic maps ", In 2008 1st World Sum. on the Knowl. Soc. , pp.549-556.doi :10.1007/978-3-540-87781-3_59full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:350112012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectSupport for interoperability between owl based and XML schema based applicationsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Chrisa Tsinaraki()The XS2OWLhttp://purl.tuc.gr/dl/dias/248ACC70-28CC-4A5E-960A-4DA51E16A44EPublished at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: We present in this paper a framework that provides support for interoperability between XML
Schema based and OWL based applications. In particular, we describe how the information
exchange between such applications is achieved, through the transformations of XML
documents to OWL/RDF descriptions and of OWL/RDF descriptions to (parts of) valid XML
documents. This functionality is built on top of OWL ontologies that fully capture the semantics
of the XML Schemas. These ontologies are the outcome of the application of the XS2OWL
mapping model that we have developed on an XML Schema. This way, the work reported here
integrates and extends our previous work on the XS2OWL mapping model to take into account,
in addition to the transformation of XML Schemas to OWL-DL ontologies, the transformation
of XML documents to OWL/RDF descriptions and vice versa.Παρουσιάστηκε στο: 2nd DELOS Conference On Digital Libraries, Tirrenia, Italy, DecemberBibliographic citation: C.Tsinaraki, S. Christodoulakis ,"Support for interoperability between owl based and XML schema based a pplications " presented at 2nd DELOS Conference On Digital Libraries, Tirrenia, Italy, December 2007.posterinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:350322012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectInteroperability of XML schema applications with owl domain knowledge and semantic web toolsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Chrisa Tsinaraki()XS2OWL Modelhttp://purl.tuc.gr/dl/dias/06C2AD45-6FC9-4DDC-9700-103A18B2478410.1007/978-3-540-76848-7_57Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: Several standards are expressed using XML Schema syntax, since the XML is the default standard for data exchange in the Internet. However, several applications need semantic support offered by domain ontologies and semantic Web tools like logic-based reasoners. Thus, there is a strong need for interoperability between XML Schema and OWL. This can be achieved if the XML schema constructs are expressed in OWL, where the enrichment with OWL domain ontologies and further semantic processing are possible. After semantic processing, the derived OWL constructs should be converted back to instances of the original schema. We present in this paper XS2OWL, a model and a sys-tem that allow the transformation of XML Schemas to OWL-DL constructs. These constructs can be used to drive the automatic creation of OWL domain ontologies and individuals. The XS2OWL transformation model allows the cor-rect conversion of the derived knowledge from OWL-DL back to XML con-structs valid according to the original XML Schemas, in order to be used trans-parently by the applications that follow XML Schema syntax of the standards.Παρουσιάστηκε στο: In the proceedings of the 6th International Conference on Ontologies, DataBases, and Applications of SemanticsSpringer VerlagBibliographic citation: C.Tsinaraki, S. Christodoulakis ,Interoperability of XML schema applications with owl domain knowledge and semantic web tools " ,In 2007 proc. of the 6th Int.l Conf. on Ontologies, DataB. and Ap. of Semantics , pp.850-869 .doi :10.1007/978-3-540-76848-7_57full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:350722012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectXS2OWL: A Formal model and a system for enabling XML schema applications to interoperate with OWLDL domain knowledge and semantic web toolsΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Chrisa Tsinaraki()http://purl.tuc.gr/dl/dias/0ECE7655-21C5-4512-A32A-E660759F684610.1007/978-3-540-77088-6_12Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: The domination of XML in the Internet for data exchange has led to the development of standards with XML Schema syntax for several application domains. Advanced semantic support, provided by domain ontologies and se-mantic Web tools like logic-based reasoners, is still very useful for many appli-cations. In order to provide it, interoperability between XML Schema and OWL is necessary so that XML schemas can be converted to OWL. This way, the semantics of the standards can be enriched with domain knowledge encoded in OWL domain ontologies and further semantic processing may take place. In or-der to achieve interoperability between XML Schema and OWL, we have de-veloped XS2OWL, a model and a system that are presented in this paper and enable the automatic transformation of XML Schemas in OWL-DL. XS2OWL also enables the consistent transformation of the derived knowledge (individu-als) from OWL-DL to XML constructs that obey the original XML Schemas.Παρουσιάστηκε στο: In the proceedings of the 1st DELOS Conference,Springer VerlagBibliographic citation: C.Tsinaraki , S. Christodoulakis , "XS2OWL: A Formal model and a system for enabling XML schema applications to interoperate with OWLDL
domain knowledge and semantic web tools ",In 2007 proc. of the 1st DELOS Conf., pp. 124-136 .doi :10.1007/978-3-540-77088-6_12full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:351312012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectQuerying MOF repositories: The design and Implementation of the query metamodel language (QML)Χριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)F. Kazasis ()G. Kotopoulos ()http://purl.tuc.gr/dl/dias/22523810-6649-47B1-8637-FBB3B72E3C7810.1109/DEST.2007.372001 Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: In a Digital Business Ecosystem (DBE) information on the businesses and the services they provide may be described in terms of models and data which are used to semantically discover partners and services. The Object Management Group (OMG) defines a four layered modelling architecture, the Model Driven Architecture (MDA), which provides mechanisms for rapid development of modelling languages addressing domain problems using the Meta Object Facility (MOF). MOF incorporates object oriented concepts and is a subset of UML. Furthermore, as users typically don’t know how to make requests, the system has to be tolerant. The Query Metamodel Language (QML) is a language that ex-ploits the Object Constraint Language (OCL) (which is very closely associated with UML and therefore MOF) to provide powerful query support on model repositories. This paper presents the motivation for QML along with its abstract syn-tax. It also introduces the framework for QML processing that incorporates information retrieval functionality and is used to formulate fuzzy queries using the extended boolean model. It describes how QML is integrated in the MOF architecture and how semantic expansion of queries and evaluation can be done in an effective way.Presented on: IEEEBibliographic citation: G. Kotopoulos , F. Kazasis ,S. Christodoulakis , "Querying MOF repositories: The design and Implementation of the query metamodel language (QML) " ,in 2007 Int. Conf. on Digital Ecos. and Techn. ,pp.373 - 378 , doi: 10.1109/DEST.2007.3720full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:351532012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObject A Framework and an architecture for supporting interoperability between digital libraries and eLearning applications Χριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Polyxeni Arapi()Nektarios Moumoutzis()Manolis Mylonakis()The METS/SCORM transformation componenthttp://purl.tuc.gr/dl/dias/CEB5EDA6-51C9-4506-96E5-35126142A46E10.1007/978-3-540-77088-6_13Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: One of the most important applications of Digital Libraries (DL) is learning. However, DLs and their standards have been developed independently on eLearning applications and their standards, raising interoperability issues between digital libraries and eLearning applications. In order to enable the development of eLearning applications that easily exploit DL contents it is crucial to bridge the interoperability gap between digital libraries and eLearning applications. For this purpose, a generic interoperability framework has been developed that could also be applied to other types of applications which are built on top of digital libraries, although this paper focuses on the detailed requirements of the eLearning applications. In this context, a framework and an algorithm for supporting personalization in elearning applications has been developed that performs automatic, on-demand, creation of personalized learning experiences using reusable (audiovisual) learning objects, taking into account the learner profiles and a set of abstract training scenarios (pedagogical templates). From a technical point of view, all the framework components have been organized into a service-oriented Architecture that Supports Interoperability between Digital Libraries and ELearning Applications (ASIDE). A prototype of the ASIDE Framework has been implemented.Παρουσιάστηκε στο: In the Proceedings of the DELOS Conference on Digital Libraries, Tirrenia, Pisa, Italy, February 2007 Springer VerlagBibliographic citation: P. Arapi, N. Moumoutzis, M. Mylonakis, S. Christodoulakis , "A framework and an architecture for supporting interoperability between digital libraries and eLearning applications ", in 2007 Delos Con. on Digital Libr., pp.137-146. doi :10.1007/978-3-540-77088-6_13full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:351532012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObject A Framework and an architecture for supporting interoperability between digital libraries and eLearning applications Χριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Polyxeni Arapi()Nektarios Moumoutzis()Manolis Mylonakis()The METS/SCORM transformation componenthttp://purl.tuc.gr/dl/dias/CEB5EDA6-51C9-4506-96E5-35126142A46E10.1007/978-3-540-77088-6_13Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: One of the most important applications of Digital Libraries (DL) is learning. However, DLs and their standards have been developed independently on eLearning applications and their standards, raising interoperability issues between digital libraries and eLearning applications. In order to enable the development of eLearning applications that easily exploit DL contents it is crucial to bridge the interoperability gap between digital libraries and eLearning applications. For this purpose, a generic interoperability framework has been developed that could also be applied to other types of applications which are built on top of digital libraries, although this paper focuses on the detailed requirements of the eLearning applications. In this context, a framework and an algorithm for supporting personalization in elearning applications has been developed that performs automatic, on-demand, creation of personalized learning experiences using reusable (audiovisual) learning objects, taking into account the learner profiles and a set of abstract training scenarios (pedagogical templates). From a technical point of view, all the framework components have been organized into a service-oriented Architecture that Supports Interoperability between Digital Libraries and ELearning Applications (ASIDE). A prototype of the ASIDE Framework has been implemented.Παρουσιάστηκε στο: In the Proceedings of the DELOS Conference on Digital Libraries, Tirrenia, Pisa, Italy, February 2007 Springer VerlagBibliographic citation: P. Arapi, N. Moumoutzis, M. Mylonakis, S. Christodoulakis , "A framework and an architecture for supporting interoperability between digital libraries and eLearning applications ", in 2007 Delos Con. on Digital Libr., pp.137-146. doi :10.1007/978-3-540-77088-6_13full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:352312012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectOntology-driven semantic ranking for natural language disambiguation in the ontoNL frameworkΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Anastasia Karanastasi()The OntoNL Semantic Disambiguation Algorithmhttp://purl.tuc.gr/dl/dias/E8C78940-8BA8-4986-AF22-2101D5989FDC10.1007/978-3-540-72667-8_32Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: The measurement of the semantic relatedness has many applications in natural language processing, and many different measures have been proposed. Most of these measures use WordNet as their central resource and not domain ontologies of a particular context. We propose and evaluate a semantic relatedness measure for OWL domain ontologies that concludes to the semantic ranking of ontological, grammatically-related structures. This procedure is used to disambiguate in a particular domain of context and represent in an ontology query language, natural language expressions. The ontology query language that we use is the SPARQL. The construction of the queries is automated and also dependent on the semantic relatedness measurement of ontology concepts. The methodology has been successfully integrated into the OntoNL Framework, a natural language interface generator for knowledge repositories. The experimentations show a good performance in a number of OWL ontologies.
Παρουσιάστηκε στο: Ιn the Proceedings of the 4th European Semantic Web Conference (ESWC), Innsbruck, Austria, 3-7 JuneSpringer VerlagBibliographic citation: A. Karanastasi , S. Christodoulakis , "Ontology-driven semantic ranking for natural language disambiguation in the ontoNL framework ", in 2007 4th Eur. Sem. Web Conf. (ESWC) ,pp.443-457 .doi :10.1007/978-3-540-72667-8_32full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
oai:dlib.tuc.gr:352512012-10-10T00:00:00Z28info:eu-repo/semantics/conferenceObjectSemantic processing of natural language queries in the OntoNL frameworkΧριστοδουλακης Σταυρος(http://users.isc.tuc.gr/~schristodoulakis)Christodoulakis Stavros(http://users.isc.tuc.gr/~schristodoulakis)Anastasia Karanastasi()The OntoNL Semantic Relatedness Measurehttp://purl.tuc.gr/dl/dias/528BC460-BA5C-4D16-9ABD-469A02EC2E8710.1109/ICSC.2007.36Published at: 2015-10-04eninfo:eu-repo/semantics/openAccessΌροι χρήσης: Μη διαθέσιμοLicense: http://creativecommons.org/licenses/by/4.0/Issued on: 2007Summarization: The OntoNL Framework provides an architecture and
re-usable components for automating as much as possible
the building of natural language interfaces to information
systems. In addition to the syntactic analysis components,
OntoNL has semantic analysis components which exploit
domain ontologies to provide better disambiguation of the
user input. We present in this paper the algorithms used
for semantic processing of the natural language queries, as
well as an ontology-driven semantic relatedness measure
developed for this purpose. We also present extensive evaluation
results with different ontologies using human subjects.Presented on: Bibliographic citation: A. Karanastasi , S. Christodoulakis , "Semantic processing of natural language queries in the ontoNL framework ", in 2007 IEEE Int. Conf. on Sem. Comp. (IEEE ICSC) .doi :10.1109/ICSC.2007.36full paperinfo:eu-repo/grantAgreement/EC/FP7/246686
1585732293449:828