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A tool for extracting model clones from a conceptual schema

A tool for extracting model clones from a conceptual schema

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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Modeling and evaluation of the effect of obstacles on the performance of wireless sensor networks

Modeling and evaluation of the effect of obstacles on the pe...

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Annual Symposium on Simulation

作者： I. Chatzigiannakis G. Mylonas S. Nikoletseas Computer Technology Institute CTI and Department of Computer Engineering and Informatics University of Patras Patras Greece

In this work, we propose an obstacle model to be used while simulating wireless sensor networks. To the best of our knowledge, this is the first time such an integrated and systematic obstacle model appears. We define several types of obstacles that can be found inside the deployment area of a wireless sensor network and provide a categorization of these obstacles, based on their nature (physical and communication obstacles), their shape, as well as their nature to change over time. In light of this obstacle model, we conduct extensive simulations in order to study the effects of obstacles on the performance of representative data propagation protocols for wireless sensor networks. Our findings show that obstacle presence has a significant impact on protocol performance. Also, we demonstrate the effect of each obstacle type on different protocols, thus providing the network designer with advice on which protocol is best to use.

关键词： Wireless sensor networks Wireless application protocol computer networks Contracts Fault tolerance Remote monitoring Temperature sensors Scattering informatics Computational modeling

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The influence of MIMO terminal user's hand on channel capacity

The influence of MIMO terminal user's hand on channel capaci...

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European Conference on Antennas and Propagation: EuCAP 2006

作者： Zervos, T. Alexandridis, A. Peppas, K. Lazarakis, F. Dangakis, K. Soras, C. Lindmark, B. Institute of Informatics and Telecommunications National Centre for Scientific Research Demokritos Athens Greece Department of Electrical and Computer Engineering University of Patras Patras Greece Department of Signals Sensors and Systems Royal Institute of Technology Stockholm Sweden

ISBN: (纸本)9290929375

In this paper the impact of user's hand holding a Multiple-Input-Multiple- Output (MIMO) terminal on the system performance is investigated. A 4×4 MIMO system is considered with a Personal Digital Assistant (PDA) terminal equipped with a compact array of 4 patch elements. The radiation patterns of the antenna elements are simulated in the presence of the other elements and in the presence of a user's hand. The obtained patterns are used to evaluate the covariance matrix of the receive antenna which is incorporated in a correlation-based MIMO channel model. MIMO channel capacity is calculated to demonstrate the capacity degradation caused by the user's hand.

关键词： Channel capacity

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A delay-based analytical provisioning model for a QoS-enabled service

A delay-based analytical provisioning model for a QoS-enable...

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IEEE International Conference on Communications (ICC)

作者： Christos Bouras Afrodite Sevasti RA Computer Technology Institute-RACTI Department of Computer Engineering and Informatics University of Patras Patras Greece Greek Research and Technology Network S. A. Athens Greece

Carefully designed and managed services are essential for quality-demanding traffic, especially in large-scale IP networks where the aggregation of flows and the variety of traffic types are extensive. Although individual mechanisms have been widely investigated, not much related work exists on integrated approaches to QoS provisioning that are also feasible to implement. This work presents a thorough approach to the design, dimensioning and provisioning of a high priority service for high-quality demanding traffic over an IP network. Our approach employs efficient scheduling and a dynamic admission control scheme while demonstrating novel characteristics in terms of the quality offered to IP flows.

关键词： Delay Analytical models Telecommunication traffic Traffic control IP networks Quality management Large-scale systems Quality of service Communication system traffic control Dynamic scheduling

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Equation based congestion control for video transmission over WCDMA networks

Equation based congestion control for video transmission ove...

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International Conference on Advanced Information Networking and Applications (AINA)

作者： A. Alexiou D. Antonellis C. Bouras Research Academic Computer Technology Institute Greece and Computer Engineering and Informatics Department University of Patras Greece

The scheme of real time streaming video is one of the newcomers in wireless data communication, raising a number of new requirements in both telecommunication and data communication systems. This scheme is applied when the user experiences real time multimedia content. rate control is an important issue in video streaming applications for both wired and wireless networks. A widely accepted rate control method in wired networks is equation based rate control. In this work, we focus on a mechanism for equation based congestion control for video transmission over WCDMA networks. With our mechanism, the sender explicitly adjusts its sending rate as a function of the measured rate of loss events, the round trip time and the packet size. Furthermore, we examine the performance of UMTS air interface for real time video transmission using real time protocols, through a number of experiments.

关键词： Equations Multiaccess communication Communication system control Telecommunication control Streaming media Data communication Telecommunication congestion control Real time systems Wireless communication Wireless networks

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Evaluating different one to many packet delivery schemes for UMTS

Evaluating different one to many packet delivery schemes for...

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IEEE International Symposium on World of Wireless Mobile and Multimedia Networks (WoWMoM)

作者： A. Alexiou D. Antonellis C. Bouras Computer Engineering and Informatics Department University of Patras Greece Research Academic Computer Technology Institute Greece

It is known that multicasting is an efficient method of supporting group communication as it allows the transmission of packets to multiple destinations using fewer network resources. Thus, service providers are increasingly interested in supporting multicast communications over wireless networks and in particular over UMTS. Multicasting is a more efficient method of supporting group communication than unicasting or broadcasting, as it allows transmission and routing of packets to multiple destinations using fewer network resources. In this paper the three above mentioned methods of supporting group communication are analyzed in terms of their performance

关键词： 3G mobile communication Performance analysis Multicast protocols Ground penetrating radar computer networks Wireless networks Routing Circuits Multimedia communication Costs

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Knowledge-Based Adaptive Assessment in a Web-Based Intelligent Educational System

Knowledge-Based Adaptive Assessment in a Web-Based Intellige...

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International Conference on Advanced Learning Technologies (ICALT)

作者： I. Hatzilygeroudis C. Koutsojannis C. Papavlasopoulos J. Prentzas Department of Computer Engineering & Informatics School of Engineering University슠of슠Patras Greece Department of Informatics and Computer Technology Technological Educational Institute of Lamia Greece

In this paper, we present an adaptive and intelligent Web-based educational system that uses AI techniques for personalized assessment of the learners. More specifically, we focus on a mechanism for on-line creation of a user-adapted test, which can be used alongside the predetermined test. The user can ask for such a test any time he/she is willing to do so, even if he/she has not studied all predetermined concepts of a learning goal. A small rule base is used by an expert system inference engine for making decisions on the difficulty level of the exercises to be included in the test. This is based on the evaluation of the learner during concept studying. Adaptive assessment of the learner can be repeatedly used until there is no further need. Another small rule-base is used for deciding on whether a new test is suggested or not. This is based on the learner's previous test assessment results. Preliminary experimental results show that the users need less time to study a learning goal when using the adaptive assessment capability of the system

关键词： Intelligent systems System testing Artificial intelligence Expert systems Adaptive systems informatics Educational technology World Wide Web Education Engines

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Discovering regularities in biosequences: Challenges and applications

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Journal of Computational Methods in Sciences and engineering 2006年第3期5卷 189-199页

作者： Makris, C.H. Perdikuri, K. Tsakalidis, A. Computer Engineering and Informatics Department University of Patras 26500 Patras Greece Research Academic Computer Technology Institute 61 Riga Feraiou Street 26221 Patras Greece

Computational methods on molecular sequence data are at the heart of computational molecular biology. Identification of known or unknown DNA and RNA motifs or regions involved in various biological processes such as initiation of transcription, gene expression and translation, or the discovery of various types of repeats are some of the applications of major concern. An accurate identification and localization of such elements will allow biologists to perform deeper studies of the structure, function and evolution of genomes. This requires the development of faster and more complex mathematical models and computer algorithms. In this work we discuss current techniques to cope with string problems in molecular sequence data. We focus on Weighted Sequences and Sequences with “don't care characters”, explaining the open problems and their relevance to biological applications.

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Resubmissions and Partly Defined Requests in an Adaptive Admission Control Algorithm for Bandwidth Brokers

Resubmissions and Partly Defined Requests in an Adaptive Adm...

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International Conference on Systems and International Conference on Mobile Communications and Learning Technologies, (ICN/ICONS/MCL) International Conference on Networking

作者： Ch. Bouras K. Stamos Computer Engineering and Informatics Department University of Patras Patras Greece Research Academic Computer Technology Institute Patras Greece

The purpose of this paper is to examine the issues related to the efficiency and adaptability of the admission control module of a Bandwidth Broker. The proposed architecture is able to handle situations such as the resubmission of previously rejected requests and offer a fair treatment for requests in an environment where a subset of these requests do not specify their ending time. We describe the proposed mechanisms for such cases which aim at solving the additional problems of fairly prioritizing resubmitted requests and efficiently handle requests which do not specify ending times. We also provide experimental evaluations of the proposed algorithms and the conclusions they lead us to.

关键词： Programmable control Adaptive control Admission control Bandwidth computer architecture Diffserv networks Routing Quality of service Resource management informatics

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Modeling and Simulation of Submicron MOSFETs with Alternative Gate Dielectrics for DraM Cells

Modeling and Simulation of Submicron MOSFETs with Alternativ...

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International Conference on Microelectronics, MIEL

作者： N. Konofaos G.Ph. Alexiou Computer Engineering & Informatics Department University of Patras Patras Greece Research Academic Computer Technology Institute Patras Greece

In this study, we designed and simulated MOS devices having alternative gate dielectrics and examined their electrical behaviour as well as their effectiveness on the performance of a DraM cell containing them. The devices under test had gate dielectrics of SrTiO 3 , (Ba 1-x Sr x )TiO 3 , TiO 2 , Ta 2 O 5 , Y 2 O 3 and (Pb 1 La x )TiO 3 . Equivalent oxide thicknesses were derived between 0.95 and 4 nm. Among the candidate materials, SrTiO 3 was the most promising when data retention is required, while Y 2 O 3 depicted the best I-V behavior. An increased cell capacitance resulted to higher memory refreshing times, improving substantially the device reliability

关键词： MOSFETs random access memory High-K gate dielectrics Leakage current Circuit testing Dielectric materials High K dielectric materials MOS devices Dielectric devices Inorganic materials

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