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Mathematics of Data/Image Coding, Compression, and Encryption V, with Applications

作者： Abdel-Gawad, Moez A. Belal, Ahmed A. Informatics Research Institute Mubarak City for Scientific Research Alexandria Egypt Dept. of Computer Science Faculty of Engineering Alexandria Egypt

In this paper, a new encryption mode, which we call the 2D-Encryption Mode, is presented. 2D-Encryption Mode extends ID-encryption modes, as ECB, CBC and CTR, to two dimensions. It has good security and practical properties. We first look at the type of problems it tries to solve, then describe the technique and its properties, and present a detailed mathematical analysis of its security, and finally discuss some practical issues related to its implementation.

关键词： Cryptography

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Behaviour investigation using simulation for redundant multicast transmission supporting adaptive QoS

Behaviour investigation using simulation for redundant multi...

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IEEE International Conference on Networks

作者： C. Bouras A. Gkamas A. Karaliotas K. Stamos Computer Engineering and Informatics Dept University of Patras Patras Greece Research Academic Computer Technology Institute Patras Greece

In this paper we describe a mechanism for redundant multicast transmission of multimedia data supporting adaptive QoS over the Internet and we investigate its behaviour using simulation. There are two major issues that have to be considered when designing and implementing such a mechanism, the fairness, which is the ability to cope with receiver heterogeneity, and the adaptation schemes. The proposed mechanism uses a friendly to the network users congestion control policy to control the transmission of the data. We evaluate the adaptive multicast transmission mechanism through a number of simulations in order to examine its behaviour to a heterogeneous group of receivers and its behaviour against TCP and UDP data streams. The main conclusion of the simulation was that the proposed mechanism has friendly behaviour against the dominant traffic types of today's Internet and treats a heterogeneous group of receivers with fairness.

关键词： Streaming media IP networks computer simulation Internet Quality of service Prototypes Computational modeling Data engineering informatics Bit rate

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Enhancing the DiffServ architecture of a simulation environment

Enhancing the DiffServ architecture of a simulation environm...

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International Workshop/Symposium on Distributed Simulation and Real-Time Applications (DS-RT)

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

Simulation has always been a valuable tool for experimentation and validation of models, architectures and mechanisms in the field of networking. In the case of the DiffServ framework, simulation is even more valuable, due to the fact that an analytical approach of mechanisms and services is infeasible because of the aggregation and multiplexing of flows. In this work, we have extended the functionality of a widely used simulation environment towards the direction of realistic traffic generation and a series of mechanisms defined by the DiffServ architecture. The modules created are being presented and a case study of a simulation scenario that exploits the functionality provided by them is described.

关键词： Diffserv networks Traffic control Computational modeling computer architecture computer simulation Aggregates computer networks Testing Communication system traffic control informatics

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Recent advances in wavelength routing 28th

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28th International Conference on Current Trends in Theory and Practice of informatics, SOFSEM 2001

作者： Kaklamanis, Christos Computer Technology Institute Dept. of Computer Engineering and Informatics University of Patras Rio26500 Greece

ISBN: (纸本)9783540429128

We study the problem of allocating optical bandwidth to sets of communication requests in all–optical networks that utilize Wavelength Division Multiplexing (WDM). WDM technology establishes communication between pairs of network nodes by establishing transmitter– receiver paths and assigning wavelengths to each path so that no two paths going through the same fiber link use the same wavelength. Optical bandwidth is the number of distinct wavelengths. Since state–of–the–art technology allows for a limited number of wavelengths, the engineering problem to be solved is to establish communication between pairs of nodes so that the total number of wavelengths used is minimized;this is known as the wavelength routing problem. In this paper we survey recent advances in bandwidth allocation in tree– shaped WDM all–optical networks. We present hardness results and lower bounds for the general problem and the special case of symmetric communication. We also survey various techniques that have been developed recently, and explain how they can be used to attack the problem. First, we give the main ideas of deterministic greedy algorithms and study their limitations. Then, we show how to use various ways and models of wavelength conversion in order to achieve almost optimal bandwidth utilization. Finally, we show that randomization can help to improve the deterministic upper bounds. © Springer-Verlag Berlin Heidelberg 2001.

关键词： Surveys

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Architectures and protocols for educational virtual environments

Architectures and protocols for educational virtual environm...

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2001 IEEE International Conference on Multimedia and Expo, ICME 2001

作者： Bouras, Ch. Tsiatsos, Th. Computer Technology Institute Greece Computer Engineering and Informatics Dept. Univ. of Patras Greece

ISBN: (纸本)0769511988

Shared or networked virtual environments are one of the most promising uses of the virtual reality technology. While a lot of research has been done in the area of multi-user virtual environments corresponding to the sharing of events very few research has been done on specific services and functionality. However both the requirements and the kind of the offered services affect significantly the design of a system. In this paper we present the main issues in the design of a platform to support the distant education process using networked virtual environments. We also introduce the term Educational Virtual Environments and their basic requirements. According to these requirements of the educational virtual environments we propose both a suitable architecture and a protocol for the interaction between the components of this architecture.

关键词： Network architecture

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Randomized path coloring on binary trees 3

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3rd International Workshop on Approximation Algorithms for Combinatorial Optimization, APPROX 2000

作者： Auletta, Vincenzo Caragiannis, Ioannis Kaklamanis, Christos Persiano, Pino Dipartimento di Informatica ed Applicazioni Università di Salerno Baronissi84081 Italy Computer Technology Institute Dept. of Computer Engineering and Informatics University of Patras Rio26500 Greece

ISBN: (纸本)9783540679967

Motivated by the problem of WDM routing in all–optical networks, we study the following NP–hard problem. We are given a directed binary tree T and a set R of directed paths on T. We wish to assign colors to paths in R, in such a way that no two paths that share a directed arc of T are assigned the same color and that the total number of colors used is minimized. Our results are expressed in terms of the dept. of the tree and the maximum load l of R, i.e., the maximum number of paths that go through a directed arc of T. So far, only deterministic greedy algorithms have been presented for the problem. The best known algorithm colors any set R of maximum load l using at most 5l/3 colors. Alternatively, we say that this algorithm has performance ratio 5/3. It is also known that no deterministic greedy algorithm can achieve a performance ratio better than 5/3. In this paper we define the class of greedy algorithms that use randomization. We study their limitations and prove that, with high probability, randomized greedy algorithms cannot achieve a performance ratio better than 3/2 when applied to binary trees of dept. Ω(l), and 1.293 −o(1) when applied to binary trees of constant dept.. Exploiting inherent properties of randomized greedy algorithms, we obtain the first randomized algorithm for the problem that uses at most 7l/5 +o(l) colors for coloring any set of paths of maximum load l on binary trees of dept.o(l1/3), with high probability. We also present an existential upper bound of 7l/5 +o(l) that holds on any binary tree. In the analysis of our bounds we use tail inequalities for random variables following hypergeometrical probability distributions which may be of their own interest. © Springer-Verlag Berlin Heidelberg 2000.

关键词： Binary trees

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A virtual reality system for hand acupuncture

A virtual reality system for hand acupuncture

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8th Annual Meeting of Medicine Meets Virtual Reality, MMVR 2000

作者： Kim, K.H. Choi, Y.K. Lee, E.T. Ryou, W.B. Electronics and Telecommunications Research Institute Korea Republic of Dept. of Computer Engineering Korea University of Technology and Education Korea Republic of Dept. of Computer Science Kwang-Woon University Korea Republic of

ISBN: (纸本)1586030140

A virtual reality system for the hand acupuncture treatment is proposed. The hand acupuncture, called sujichim, is mostly conducted at home and many people try to learn and apply it to the health care of their family. Using our system, a novice can easily perform the acupuncture by himself to improve his body condition. According to the experiments, our system is proved to be very effective and easy to use.

关键词： Acupuncture

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POS disambiguation and unknown word guessing with decision trees 9

POS disambiguation and unknown word guessing with decision t...

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9th Conference of the European Chapter of the Association for Computational Linguistics, EACL 1999

作者： Orphanos, Giorgos S. Christodoulakis, Dimitris N. Computer Engineering and Informatics Dept. Computer Technology Institute University of Patras Rion Patras26500 Greece

This paper presents a decision-tree approach to the problems of part-of-speech disambiguation and unknown word guessing as they appear in Modern Greek, a highly inflectional language. The learning procedure is tag-set independent and reflects the linguistic reasoning on the specific problems. The decision trees induced are combined with a high-coverage lexicon to form a tagger that achieves 93,5% overall disambiguation accuracy. © EACL 1999. All rights reserved.

关键词： Decision trees

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Edge coloring of bipartite graphs with constraints 24th

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24th International Symposium on Mathematical Foundations of computer Science, MFCS 1999

作者： Caragiannis, Ioannis Kaklamanis, Christos Persiano, Pino Computer Technology Institute and Dept. of Computer Engineering and Informatics University of Patras Rio26500 Greece Dipartimento di Informatica ed Appl Università di Salerno Baronissi84081 Italy

ISBN: (纸本)3540664084

It is a classical result from graph theory that the edges of an l-regular bipartite graph can be colored using exactly l colors so that edges that share an endpoint are assigned different colors. In this paper we study two constrained versions of the bipartite edge coloring problem. Some of the edges adjacent to a pair of opposite vertices of an l-regular bipartite graph are already colored with S colors that appear only on one edge (single colors) and D colors that appear in two edges (double colors). We show that the rest of the edges can be colored using at most max{min{l+D,3/l2},l+S+D/2} total colors. We also show that this bound is tight by constructing instances in which max{min{l+D,3/l2},l+S+D/2} colors are indeed necessary. Some of the edges of an l-regular bipartite graph are already colored with S colors that appear only on one edge. We show that the rest of the edges can be colored using at most max{l + S/2, S} total colors. We also show that this bound is tight by constructing instances in which max{l + S/2, S total colors are necessary. © Springer-Verlag Berlin Heidelberg 1999.

关键词： Color

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Healthcare informatics Society of Ireland

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Irish Journal of Medical Science 1999年第4期168卷 276-282页

作者： Rigby, M. Sheridan, A. Draper, R. Stephens, G. Gaffney, P. Grimson, J. Avalos, G. Comerford, F. R. Kanagaratnam, B. Dineen, B. Hamilton, I. Jung, B. Felton, E. Berry, D. Grimson, W. Rice, D. H. Healy, M. Bruce, A. Kelly, J. Carroll, T. Grogan, A. Hurl, G. A. Hyland, D. Roberts, J. Brazil, J. Callanan, I. Devitt, A. O’Brien, T. O’Sullivan, U. M. Peyton, K. Wilson, M. J. Collins, R. Crawley, L. Foley, D. Strachan, H. McBrearty, P. Murnane, R. Murphy, E. Keane, V. Mulvany, F. Sweeney, P. D. Kenny, D. O’Connell, P. R. Balfe, P. Minogue, G. Centre for Health Planning & Management Keele University Keele Staffordshire Britain St. John of God Hospital Stillorgan Hospitaller Order of St. John of God Stillorgan Dept. of Computer Science Trinity College Dublin Clinical Chemistry Laboratory Tallaght Hospital Tallaght Dublin 24 Department of Experimental Medicine Faculty of Medicine National University of Ireland Galway Department of Health Promotion Faculty of Medicine National University of Ireland Galway School of Control Systems & Electrical Engineering Dublin Institute of Technology Ireland Shared Medical Systems Malvern USA Healy Services Dublin Universal Learning Systems Ltd. Dublin The Rotunda Hospital Dublin Mater Misericordiae Hospital Dublin Institute for Healthcare Informatics Dublin First Consulting Group Macclesfield Britain Virus Reference Laboratory UCD Belfield Dublin 4 Cappagh Orthopaedic Hospital Dublin Ireland Southern Health Board Cork Mater Misericordiae Hospital Dublin 7 DSS Dublin Ltd. Ireland University College Dublin Ireland Mary Aikenhead School of Nursing St. Vincent’s Hospital Dublin Blackrock Clinic Dublin Borders Community Health Services NHS Trust Britain James Connolly Memorial Hospital Blanchardstown Dublin 15 Kildare and West Wicklow Mental Health Service for People with A Learning Disability Eastern Health Board Dublin Health Research Board Dublin General Practice Research Unit The Medical Centre Dungloe Dept. of Clinical Biochemistry Our Lady’s Hospital for Sick Children Crumlin Dublin 12

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