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E-learning and social networking services in the Greek School Network

E-learning and social networking services in the Greek Schoo...

IADIS International Conference e-Learning 2011, Part of the IADIS Multi Conference on computer Science and Information Systems 2011, MCCSIS 2011

作者： Paraskevas, Michael Stergatu, Helen Varvarigos, Emmanouel Research Academic Computer Technology Institute N.Kazantzaki str. GR-26504 Patras Greece Dept. of Computer Eng. and Informatics University of Patras GR-26504 Patras Greece

ISBN: (纸本)9789728939380

In this paper, we present the Greek School Network (GSN) and describe some of its advanced electronic services, designed to facilitate learning and collaboration. The main objective of the Greek School Network is to provide a network infrastructure for the interconnection of schools and the introduction of a wide range of telematic services to the educational community on a large scale. GSN is a safe educational network, whose services have received great acceptance and use by the school community. We present in detail the GSN electronic services (Web 2.0) related to elearning and social networking. We also provide statistical data that confirm the high use of the services. © 2011 IADIS.

关键词： E-learning

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A simulation study for optimizing the performance of Semi-layer delta networks

A simulation study for optimizing the performance of Semi-la...

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作者： Stergiou, Eleftherios Garofalakis, John Department of Informatics and Telecommunications Technology Technological Educational Institute of Epirus Arta Greece Department of Computer Engineering and Informatics University of Patras Patras Greece Research Academic Computer Technology Institute Rion Patras Greece

ISBN: (纸本)9789898425782

In this paper, a semi-layer multistage delta network is presented and exemplified considering various values of buffer size by using simulation. The proposed network configurations are evaluated and compared with each other. A performance evaluation was conducted via our simulator assuming uniform conditions and arrivals of Bernoulli type. Performance statistics were collected for the two most important performance indicators of the network that is throughput and packet latency. From this study emerges the appropriate configuration of single and semi-layer delta networks in terms of buffer size. The evaluation methodology can be applied to several network configurations, providing the basis for a fair comparison, and the necessary data for network engineering to optimize the performance of semi-layer delta networks.

关键词： Network layers

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Utilizing video encoding for power management over wireless networks

Utilizing video encoding for power management over wireless ...

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作者： Bouras, C. Stamos, K. Stroumpis, S. Zaoudis, G. Research Academic Computer Technology Institute Patras Greece Computer Engineering and Informatics Department University of Patras Patras Greece Technological Educational Institute of Patras Patras Greece

ISBN: (纸本)9789898425690

Power management is especially important in wireless networks because of the emergence of energy constrained mobile devices. This paper examines the ways that video encoding information can be used for more efficient power management. In particular, we propose and evaluate cross layer mechanisms that finetune transmission power depending on the video frame being encoded and we examine how this mechanism may be combined with algorithms that adjust transmission power based on feedback reports when TCP Friendly Rate Control (TFRC) is used as the transport protocol. Since typical video encoding uses frames of varying importance for the overall quality, this approach can improve received video quality and make better usage of available power.

关键词： Power management

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An improved GMPLS survivability mechanism using link delay-constrained algorithm

An improved GMPLS survivability mechanism using link delay-c...

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作者： Bikos, Anastasios Bouras, Christos Stamos, Kostas Research Academic Computer Technology Institute Patras Greece Computer Engineering and Informatics Department University of Patras Patras Greece Technological Educational Institute of Patra Patra Greece

ISBN: (纸本)9789898425690

It is widely accepted that GMPLS (Generalized MPLS) will be a key technology in the evolution of the next generation of reliable Internet Protocol (IP) backbone networks. Conventional GMPLS-based optical-switching network fault recovery only provides resiliency in terms of path segment selection instead of constraint-based calculation. This can create severe impact on the protocol's transport plane when a fault occurs to a link or path with many optical connections attached to it. This paper proposes the implementation of an improved GMPLS recovery algorithm based on the metric of optical link delay which is achieved through the pre or post selection of a safer and more stable protection path with fewer connections attached to it, and therefore with a lesser link delay metric compared to other possible paths. The improved recovery algorithm is evaluated using the network simulator ns-2 and more particularly a specialized simulator add-on for GMPLS, called ASONS (Automatically Switched Optical Network Simulator). The results indicate improved resiliency, increased fault avoidance, and reduced packet loss.

关键词： Simulators

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An adaptive tuning model for cognitive info-communication channels

An adaptive tuning model for cognitive info-communication ch...

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9th IEEE International Symposium on Applied Machine Intelligence and informatics, SAMI 2011

作者： Csapo, Adam Baranyi, Peter Dept. of Telecommunications and Media Informatics Budapest University of Technology and Economics Budapest Hungary Computer and Automation Research Institute Budapest Hungary

ISBN: (纸本)9781424474301

Cognitive infocommunication channels are abstract channels which use sensory substitution to convey structured perceptual information via any number of sensory modalities. Our goal is to develop engineering systems for the remote teleoperation of robots using sensory substitution to convey feedback information in meaningful ways. Such applications could help reduce the cognitive load for the user on the one hand, and help alleviate the effect of control instabilities and hidden parameters on the other. In this paper, we present a tensor algebraic approach for the compact representation of complete sensory substitution channels. Using HOSVD, we transform our representations into canonical, granular forms. Through a combination of rank-reduction and error compensation techniques, we propose an adaptive tuning model that can be used for iterative parameter space exploration, thus enabling users to explore the generated sensory substituted signals in a more intuitive fashion. © 2011 IEEE.

关键词： Error compensation

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Modelling the MOS Device Conductance Using an Extended Tunnelling Model and Subsequent Determination of Interface Traps.

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MRS Online Proceedings Library (OPL) 2011年第1期864卷 E4.25-E4.25页

作者： N. Konofaos Computer Engineering and Informatics Dept. & Research Academic Computer Technology Institute Building B University Campus Patras Greece. email: nkonofao@ceid.upatras.gr

The contribution of the AC conductance on admittance spectroscopy measurements on Metal-Insulator-Semiconductor (MIS) devices allows the calculation of the interface traps density and the relevant time constant. Two equivalent model approaches can be applied in order to explain the experimental results. One model is the statistical model based on the Shockley- Read-Hall (S-R-H) recombination statistics and the other one is a model based on the quantum tunneling effect. Recent evidence suggest that the tunneling model can be equivalent to the statistical one if a continuum of states is also considered in the modeling, creating an extended tunneling model. In the present paper, a further investigation on the extended model is attempted. Admittance spectroscopy data were collected for various Insulator/Si combinations, such as SrTiO3 and BaTiO3 deposited on Si. Both the S-R-H based and the extended tunneling models were used to analyze the data. The results showed that the extended tunneling can model the conductance of the device successfully and can calculate the interface states density and the traps time constant.

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AN IMPROVED GMPLS SURVIVABILITY MECHANISM USING LINK DELAY-CONSTRAINED ALGORITHM

AN IMPROVED GMPLS SURVIVABILITY MECHANISM USING LINK DELAY-C...

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International Conference on Data Communication Networking

作者： Anastasios Bikos Christos Bouras Kostas Stamos Computer Engineering and Informatics Department University of Patras Research Academic Computer Technology Institute

ISBN: (纸本)9789898425690

关键词： GMPLS Link failure probability Link delay-constrained Algorithm LSP routing Path protection

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Building a Platform-Agnostic Wireless Network of Interconnected Smart Objects

Building a Platform-Agnostic Wireless Network of Interconnec...

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Panhellenic Conference on informatics (PCI)

作者： Orestis Akribopoulos Vasileios Georgitzikis Anastasia Protopapa Ioannis Chatzigiannakis Research Academic Computer Technology Institute (RACTI) and Computer Engineering and Informatics Department University of Patras Greece

In this work, we present a platform-agnostic framework for integrating heterogeneous Smart Objects in the Web of Things. Our framework, consists of 4 different hardware platforms, Arduino, SunSPOT, TelosB, iSense. These hardware platforms are the most representative ones, as used by the relevant research community. A first contribution of our work is a careful description of the necessary steps to make such a heterogeneous network interoperate and the implementation of a network stack, in the form of a software library, named mkSense, which enables their intercommunication. Moreover, we describe the design and implementation of software library which can be used for building "intelligent software" for the Web of Things.

关键词： computer architecture IEEE 802.15 Standards Software Hardware Wireless sensor networks Color Logic gates

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A TCP Prediction Scheme for Enhancing Performance in OBS Networks

A TCP Prediction Scheme for Enhancing Performance in OBS Net...

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IEEE International Conference on Communications (ICC)

作者： Kostas Ramantas Kyriakos Vlachos Computer Engineering and Informatics Department & Research Academic Computer Technology Institute University of Patras Rio Greece

The efficient transmission of TCP traffic over OBS networks is a challenging problem, due to the high sensitivity of TCP congestion control mechanism to losses. In this paper, a traffic prediction scheme is proposed that exploits TCP traffic dynamics to optimize the performance of TCP transmission over OBS networks. Due to the TCP flow control mechanism, traffic dynamics can be accurately predicted in at least one RTT-long prediction window. In the proposed scheme, the prediction process is tightly coupled with the burst assembly process since the edge node is capable of inspecting incoming TCP traffic, keeping traffic statistics in parallel to the assembly process. These statistics are then used for traffic predictions. In this way burst size can be predicted and thus in advance reserve the appropriate resources. In this paper, we detail the traffic prediction mechanism and we also provide simulation results to assess its performance.

关键词： Histograms Throughput Assembly Fluid flow measurement Protocols Accuracy Bandwidth

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Using a nature inspired technique to train a dynamic IA-RWA algorithm

Using a nature inspired technique to train a dynamic IA-RWA ...

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International Conference on Telecommunications (ICT)

作者： Konstantinos Manousakis Emmanouel Varvarigos Computer Engineering and Informatics Department Research Academic Computer Technology Institute University of Patras Patra Greece

In this work we add a training phase to an Impairment Aware Routing and Wavelength Assignment (IA-RWA) algorithm so as to improve its performance. The initial IA-RWA algorithm is a multi-parametric algorithm where a vector of physical impairment parameters is assigned to each link, from which the impairment vectors of candidate lightpaths are calculated. The important issue here is how to combine these impairment parameters into a scalar that would reflect the true transmission quality of a path. The training phase of the proposed IA-RWA algorithm is based on an optimization approach, called Particle Swarm Optimization (PSO), inspired by animal social behavior. The training phase gives the ability to the algorithm to be aware of the physical impairments even though the optical layer is seen as a black box. Our simulation studies show that the performance of the proposed scheme is close to that of algorithms that have explicit knowledge of the optical layer and the physical impairments.

关键词： Particle swarm optimization Heuristic algorithms Training Mathematical model Physical layer Equations Optimization

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