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Joint International Workshop on Adaptivity, Personalization and the Semantic Web, APS'06

作者： Rigou, Maria Sirmakessis, Spiros Tzimas, Giannis Computer Engineering and Informatics Department University of Patras Rio GR-26504 Department of Applied Informatics in Administration and Economy TEI of Messolonghi Nea Ktiria Messolonghi GR-30200 Research Academic Computer Technology Institute Patras University N. Kazantzaki Str. Rio GR-26500

ISBN: (纸本)1595934537

The paper introduces an algorithm for personalized clustering based on a range tree structure, used for identifying all web documents satisfying a set of predefined personal user preferences. The returned documents go through a clustering phase before reaching the end user, thus allowing more effective manipulation and supporting the decision making process. The proposed algorithm demonstrates increased applicability in semantic web settings, since they offer the infrastructure for the explicit declaration of web document attributes and their respective values, thus allowing for more automated retrieval. The proposed algorithm improves the k-means range algorithm, as it uses the already constructed range tree (i.e. during the personalized filtering phase) as the basic structure on which the clustering step is based, applying instead of the k-means, the k-windows algorithm. The total number of parameters used for modeling the web documents dictates the number of dimensions of the Euclidean space representation. The time complexity of the algorithm is O(log d-2n+v), where d is the number of dimensions, n is the total number of web documents and v is the size of the answer. Copyright 2006 ACM.

关键词： Cluster analysis

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A tool for extracting model clones from a conceptual schema

A tool for extracting model clones from a conceptual schema

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IASTED International Conference on Software engineering, as part of the 24th IASTED International Multi-Conference on applied informatics

作者： Faliagka, Evanthia Rigou, Maria Sirmakessis, Spiros Tzimas, Giannis Department of Computer Engineering and Informatics University of Patras Rio Campus 26504 Greece Research Academic Computer Technology Institute Patras University N. Kazantzaki str. Rio Campus 26500 Greece Department of Applied Informatics in Administration and Economy Technological Institution of Messolongi Nea Ktiria 30200 Greece

ISBN: (纸本)0889865744

In this paper the authors present an overview of techniques and tools that enable the effective evaluation and refactoring of a Web application's conceptual schema. Moreover, based on the introduction of the notion of model clones (in a previous work), as partial conceptual schemas that are repeated within a broader application model and the notion of model smells, as certain blocks in the Web applications model that imply the possibility of refactoring, this paper illustrates a methodology and a tool for detecting and evaluating the existence of potential model clones, in order to identify problems in an application's conceptual schema by means of efficiency, consistency, usability and overall quality. The methodology can be deployed either in the process of designing an application or in the process of reengineering it. Evaluation is performed according to a number of inspection steps. At first level the compositions used in the hypertext design are evaluated, followed by a second level evaluation concerning data manipulation and presentation to the user.

关键词： World Wide Web

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EST-Grid: An efficient scalable peer-to-peer infrastructure for Web Service discovery

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WSEAS Transactions on Communications 2006年第1期5卷 66-75页

作者： Sioutas, S. Drossos, L. Tsolis, D. Papatheodorou, T.S. Computer Engineering and Informatics Department University of Patras Building B University Campus 26500 Rion Patras Greece Technological Institute of Messolongi Department of Applied Informatics in Administration and Economics Technological Institute Campus 30200 Messolongi Greece

Web services are becoming an important enabler of the Semantic Web. In this paper, we present a new P2P infrastructure for Web Services discovery. Peers that store Web Services information, such as data item descriptions, are efficiently located using a scalable and robust data indexing structure for Peer-to-Peer data networks, EST-GRID (Exponential Search Tree). EST-GRID provides support for processing Exact match Queries of the form "given a key, map the key onto a node". EST-GRID adapts efficiently update queries as nodes join and leave the system, and can answer queries even if the system is continuously changing. Results from theoretical analysis show that the communication cost of the query and update operations scaling both in O(√log n) time where n the number of nodes.

关键词： Distributed computer systems

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The dynamic monotone priority search tree (DMoPST): A new efficient 2-D spatial indexing scheme with optimal update time

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WSEAS Transactions on Systems 2006年第1期5卷 142-147页

作者： Drossos, L. Sioutas, S. Tsichlas, K. Ioannou, K. Technological Institute of Messolongi Department of Applied Informatics in Administration and Economics Technological Institute Campus 30200 Messolongi Greece Computer Engineering and Informatics Department University of Patras Building B University Campus 26500 Rion Patras Greece Wireless Telecommunication Laboratory Department of Electrical and Computer Engineering University of Patras Rion 26500 Patras Greece

For monotone generated points on the plane we present the Dynamic Monotone Priority Search Tree (DMoPST) in main/external memory with O(1) update time/O(1) block transfers in worst-case. The external version of the st... 详细信息

关键词： Database systems

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Location positioning techniques investigation in GSM networks

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WSEAS Transactions on Communications 2006年第6期5卷 1159-1168页

作者： Deligiannis, N. Louvros, S. Ioannou, K. Garmpis, A. Kotsopoulos, S. Wireless Telecommunication Laboratory Department of Electrical and Computer Engineering University of Patras Rion 26500 Patras Greece Department of Applied Informatics in Management and Economy Technical Education Institute of Messologi Greece

Positioning algorithms are of great importance in recent years, as the means of providing location based services (LBS) including wireless emergency services. Telecommunication engineers are frequently puzzled by the accuracy of the implemented technique in contrast with the cost. In this paper, we introduce a novel Time of Arrivals (TOA) location positioning method in GSM networks using three Base Stations (BSs). In order to implement the proposed solution an analytical explanation of the signaling flow is provided. The algorithm's accuracy is improved by introducing an additional weight coefficient reflecting the LOS/nLOS propagation. Finally, the cost function is simulated in a microcellular city centre environment and compared to Turin's. Moreover a reference is provided regarding the other methods of positioning.

关键词： Global system for mobile communications

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Low HRV entropy is strongly associated with myocardial infarction

Low HRV entropy is strongly associated with myocardial infar...

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作者： Lau, Stephan Haueisen, Jens Schukat-Talamazzini, Ernst G. Voss, Andreas Goernig, Matthias Leder, Uwe Figulla, Hans-R. Institute of Computer Science Friedrich Schiller University Jena Jena Germany Biomagnetic Center Jena Friedrich Schiller University Jena Jena Germany Department of Medical Engineering University of Applied Sciences Jena Jena Germany Institute of Biomedical Engineering and Informatics Technical University of Ilmenau Ilmenau Germany Clinic of Internal Medicine I Friedrich Schiller University Jena Jena Germany Biomagnetic Center Jena Friedrich Schiller University Jena Erlanger Allee 101 07747 Jena Germany

Heart rate variability (HRV) is a marker of autonomous activity in the heart. An important application of HRV measures is the stratification of mortality risk after myocardial infarction. Our hypothesis is that the information entropy of HRV, a non-linear approach, is a suitable measure for this assessment. As a first step, to evaluate the effect of myocardial infarction on the entropy, we compared the entropy to standard HRV parameters. The entropy was estimated by compressing the tachogram with Bzip2. For univariate comparison, statistical tests were used. Multivariate analysis was carried out using automatically generated decision trees. The classification rate and the simplicity of the decision trees were the two evaluation criteria. The findings support our hypothesis. The meanNN-normalized entropy is reduced in patients with myocardial infarction with very high significance. One entropy parameter alone exceeds the discrimination strength of multivariate standards-based trees. ©2006 by Walter de Gruyter.

关键词： Cardiology

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Experimental performance evaluation of the emerging WiMAX technology

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WSEAS Transactions on Information Science and Applications 2006年第2期3卷 322-327页

作者： Agapiou, G. Vali, D. Charalambakis, D. Georgiadis, P. Plakidis, E. Rorris, P. Ioannou, K. Garmpis, A. Mobile and Radio Communications Research Laboratories OTE S.A. Athens Greece Wireless Telecommunication Laboratory Department of Electrical and Computer Engineering University of Patras Rion 26500 Patras Greece Department of Applied Informatics in Management and Economy Technical Education Institute of Messologi Messologi Greece

The increasing demand for wireless broadband service offering in long distances is the major drive behind the emergence of the WiMAX technology. WiMAX is targeted to providing high bit data rates to the end users in a wireless manner, any time, in any location, even in harsh environmental conditions and at an acceptable quality. This paper presents the experimental results of a WiMAX system that follows the specifications of IEEE 802.16-2004 standard. Throughput and Bit Error Rate (BER) measurements, as well as voice and video service experiments are carried out, leading to useful conclusions for the performance evaluation of the WiMAX system under test and the WiMAX technology in general.

关键词： Wireless telecommunication systems

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Throughput and interference measurements in copper wires of xDSL type modems

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WSEAS Transactions on Information Science and Applications 2006年第2期3卷 352-357页

作者： Agapiou, G. Doukoglou, T. Georgiadis, P. Georgakopoulos, G. Plakidis, E. Rorris, P. Ioannou, K. Ioannou, A. Garmpis, A. Mobile and Radio Communications Research Laboratories OTE S.A. Athens Greece Wireless Telecommunication Laboratory Department of Electrical and Computer Engineering University of Patras Rion 26500 Patras Greece Department of Applied Informatics in Management and Economy Technical Education Institute of Messologi Messologi Greece

Crosstalk is an important factor that needs to be considered and study its effects in copper wires, especially when voice communication takes place. Its presence has proven to be an impaired factor in the performance of communication services. This paper measures the isolation losses and the crosstalk losses as a function of the frequency and the length of the copper wires. It also presents throughput results from modems designed in the context of an EU financed project that can provide a symmetric 100 Mbps over two pairs for reach up to 500m (5 times the existing reach of 100-BASE-T systems).

关键词： Modems

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Efficient SIE/VIE scattering analysis of ferroelectric inhomogeneous materials with high permittivity for microwave applications

Efficient SIE/VIE scattering analysis of ferroelectric inhom...

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European Conference on Antennas and Propagation: EuCAP 2006

作者： Avdikos, Georgios K. Zervos, Theodore Anastassiu, Hristos T. Uzunoglu, Nikolaos K. School of Applied Mathematics and Physics National Technical University of Athens Heroon Polytechniou 9 GR-15780 Zografou Greece Institute of Informatics and Telecommunications National Centre for Scientific Research Demokritos Athens 15310 Greece Hellenic Aerospace Industry Communications and Networks Design and Development Dept. PO Box 23 Schimatari - Tanagra Viotia Greece School of Electrical and Computer Engineering National Technical University of Athens Heroon Polytechniou 9 GR-15780 Zografou Greece

ISBN: (纸本)9290929375

Ferroelectric materials have been gaining much interest over the last decades due to the unique operational characteristics they demonstrate, when a dc electric field is applied. This paper investigates the scattering analysis of electromagnetic waves from materials with high permittivity that follows a linear spatial variation along one axis. The Surface Integral Equation (SIE) and Volume Integral Equation (VIE) methods are invoked to compute the currents and the radar cross section (RCS). The number of unknowns for the VIE is, as expected, larger than for the SIE method. The RCS and the induced current are associated in such a way that one can approximate the linear variation with relatively few elements (unknowns).

关键词： Ferroelectric materials

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Efficient SIE/VIE scattering analysis of ferroelectric inhomogeneous materials with high permittivity for microwave applications

Efficient SIE/VIE scattering analysis of ferroelectric inhom...

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European Conference on Antennas and Propagation, EuCAP

作者： Georgios K. Avdikos Theodore Zervos Hristos T. Anastassiu Nikolaos K. Uzunoglu School of Applied Mathematics and Physics National and Technical University of Athens Zografou Greece National Centre for Scientific Research Demokritos Institute of Informatics and Telecommunications Athens Greece Communications and Networks Design & Development Department Hellenic AeroSpace Industry SA Viotia Greece School of Electrical and Computer Engineering National and Technical University of Athens Zografou Greece

Ferroelectric materials have been gaining much interest over the last decades due to the unique operational characteristics they demonstrate, when a dc electric field is applied. This paper investigates the scattering analysis of electromagnetic waves from materials with high permittivity that follows a linear spatial variation along one axis. The surface integral equation (SIE) and volume integral equation (VIE) methods are invoked to compute the currents and the radar cross section (RCS). The number of unknowns for the VIE is, as expected, larger than for the SIE method. The RCS and the induced current are associated in such a way that one can approximate the linear variation with relatively few elements (unknowns).

关键词： Ferroelectric materials Permittivity Electromagnetic scattering Radar scattering Integral equations Electromagnetic analysis Radar cross section Linear approximation Dielectric materials Microwave antenna arrays

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