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Proceedings - 18th International Conference on Advanced Information Networking and Applications, AINA 2004

作者： Koyama, Akio Barolli, Leonard Matsumoto, Kazunori Apduhan, Bernady O. Department of Informatics Yamagata University 4-3-16 Jonan Yonezawa Yamagata 992-8510 Japan Dept. of Information Engineering Fukuoka Institute of Technology 3-30-1 Wajiro-Higashi Higashi-ku Fukuoka 811-0295 Japan Department of Computer Software University of Aizu Tsuruga Ikki-machi Aizu-Wakamatsu 965-8580 Fukushima Japan Dept. of Intelligent Informatics Kyushu Sangyo University 2-3-1 Matsukadai Higashi-ku Fukuoka 813-8503 Japan

ISBN: (纸本)0769520510

The routing algorithms for multimedia communication should use for routing more than one QoS parameter. This is because new services such as video on demand and remote meeting systems require better QoS. However, the problem of QoS routing is difficult and to find a feasible route with two independent path constraints is NP-complete. Also, QoS routing algorithms for broadband networks must be adaptive, flexible, and intelligent for efficient network management. In this paper, we propose a multipurpose optimization method for QoS routing based on Genetic Algorithm (GA). The simulation results show that proposed method has a good performance and is a promising method for QoS routing.

关键词： Routers

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Bandwidth efficient transmission through sparse channels using a parametric channel estimation-based DFE

Bandwidth efficient transmission through sparse channels usi...

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IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC)

作者： A.A. Rontogiannis K. Berberidis Institute of Space Applications and Remote Sensing National Observatory of Athens Athens Greece Department of Computer Engineering & Informatics / R.A.C.T.I-Research and Development University of Patras Rio-Patras Greece

A novel equalization schemes based on parametric channel estimation is presented. The proposed scheme is appropriate for channels with long and sparse impulse response such as encountered in high definition digital video transmission systems. The main trait of the channel estimation part is that instead of seeking the whole channel impulse response (CIR), only the unknown time delays and attenuation factors of the physical channel multipath components are efficiently estimated. The equalization part comprises an adaptive decision feedback equalizer (DFE), whose initialization part is properly designed for sparse channels. The information needed in the initialization part is provided by the channel estimation part. The DFE converges much faster compared to the conventional DFE and the whole scheme utilizes a very short training sequence and hence a significant saving in bandwidth is achieved.

关键词： Bandwidth Channel estimation Decision feedback equalizers Delay effects Attenuation Adaptive equalizers Multipath channels HDTV Interference Observatories

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Image improvement in pinhole SPECT using complete data acquisition combined with statistical image reconstruction

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International Congress Series 2004年第C期1265卷 101-105页

作者： Zeniya, Tsutomu Watabe, Hiroshi Aoi, Toshiyuki Kim, Kyeong Min Teramoto, Noboru Hayashi, Takuya Sohlberg, Antti Kudo, Hiroyuki Iida, Hidehiro Department of Investigative Radiology National Cardiovascular Center Research Institute Suita Osaka 565-8565 5-7-1 Fujishiro-dai Japan Department of System Science Graduate School of Informatics Kyoto University Kyoto 606-8501 Yoshida-Honmachi Sakyo Japan Department of Clinical Physiology and Nuclear Medicine Kuopio University Hospital FIN-70211 Kuopio P.O. Box 1777 Finland Department of Computer Science Graduate School of Systems and Information Engineering University of Tsukuba Ibaraki 305-8573 1-1-1 Tennoudai Tsukuba Japan

Pinhole single-photon emission computed tomography (SPECT) with high spatial-resolution is suitable for small-animal imaging, but has limitations associated with spatial-resolution inhomogeneity or axial blurring. We have hypothesized that this blurring is due to incompleteness of projection data acquired by a single circular pinhole orbit. And we have developed a pinhole SPECT system with two circular orbits which satisfy Tuy's condition so as to provide complete data for 3D pinhole SPECT reconstruction within the whole field-of-view (FOV);a dedicated 3D ordered subsets expectation maximization (3D-OSEM) reconstruction method for two-orbit data. This study is aimed at evaluating accuracy and impact of this system. In this system, not the camera but the object rotates and the two orbits are 90° and 45° relative to object's axis. Experiments using a multiple-disk phantom filled with ^99mTc solution and a mouse bone scan using ^99mTc-labeled HMDP agent were carried out. The Feldkamp's filtered back-projection (FBP) method and the 3D-OSEM method were applied to these data sets. The axial blurring was apparent on images reconstructed by FBP for single-orbit data, while the 3D-OSEM using two-orbit data dramatically improved the resolution homogeneity and statistical noise property, and also demonstrated considerably better image quality in the mouse scan. © 2004 Elsevier B.V.

关键词： Complete data acquisition Pinhole SPECT Small animal Statistical image reconstruction Tuy's condition

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Spatial, temporal and spatio-temporal databases - Hot issues and directions for PhD research

Spatial, temporal and spatio-temporal databases - Hot issues...

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作者： Roddick, John F. Egenhofer, Max J. Hoel, Erik Papadias, Dimitris Salzberg, Betty Sch. of Informatics and Engineering Flinders University GPO Box 2100 Adelaide SA 5001 Natl. Ctr. for Geogr. Info./Analysis University of Maine Orono ME 04469-5711 United States Research and Development Environ. Systems Research Institute 380 New York Street Redlands CA 92373 United States Department of Computer Science Hong Kong Univ. of Sci./Technology Clearwater Bay Hong Kong Hong Kong Coll. of Comp./Information Science Northeastern University Boston MA 02115 United States

Spatial and temporal database systems, both in theory and in practice, have developed dramatically over the past two decades to the point where usable commercial systems, underpinned by a robust theoretical foundation, are now starting to appear. While much remains to be done, topics for research must be chosen carefully to avoid embarking on impractical or unprofitable areas. This is particularly true for doctoral research where the candidate must build a tangible contribution in a relatively short time. The panel session at the Eighth International Symposium on Spatial and Temporal Databases (SSTD 2003) held on Santorini Island, Greece [7] in July 2003 thus took as its focus the question What to focus on (and what to avoid) in Spatial and Temporal Databases : recommendations for doctoral research. This short paper, authored by the panel members, summarizes these discussions.

关键词： Database systems

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Issues for the performance monitoring on networked virtual environments: The case of EVE 7

Issues for the performance monitoring on networked virtual e...

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7th International Conference on Telecommunications, ConTEL 2003

作者： Bouras, C. Giannaka, E. Tsiatsos, Th. Research Academic Computer Technology Institute Computer Engineering and Informatics Dept. Univ. of Patras Patra Greece

ISBN: (纸本)9531840520

The wide expansion and increasing demand for Networked Virtual Environments resulted in efforts for the optimization of these environments with the enhancement of advanced features, which offered extended functionality and created an improved sense of realism. However, the added functionality often creates resource overhead both in the system as well as in the network host, which results in performance reduction. This paper presents such a networked virtual environment and based on the system's architecture tries to trace down with the time and recourse consuming parameters and proposes models on which a networked virtual environment, like the one presented, could achieve optimization of its performance. © 2003, institute of Electrical and Electronics Engineers Inc. All rights reserved.

关键词： Virtual reality

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Offering open hypermedia services to the WWW: A step-by-step approach for developers 03

Offering open hypermedia services to the WWW: A step-by-step...

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12th International Conference on World Wide Web, WWW 2003

作者： Karousos, Nikos Pandis, Ippokratis Reich, Siegfried Tzagarakis, Manolis Research Academic Computer Technology Institute 26500 Rion Greece Dept. of Computer Engineering and Informatics University of Patras 26500 Rion Greece Salzburg Research Austria

ISBN: (纸本)1581136803

Hypermedia systems and more specifically open hypermedia systems (OHS) provide a rich set of implementations of different hypertext flavors such as navigational hypertext, spatial hypertext or taxonomic hypertext. Additionally, these systems offer component-based modular architectures and address interoperability between hypertext domains. Despite multiple efforts of integrating Web clients, a widespread adoption of OHS technology by Web developers has not taken place. In this paper it is argued that Web Services - which offer a component model for Web applications - can be integrated in OHSs. An architectural integration is proposed, a step-by-step process is outlined and an example of integration is provided. This very approach is aimed to benefit both worlds: the Web community with new rich hypermedia functionality that extends the current navigational hypermedia, and the OHS community by opening its tools and platforms to the many developer groups of the Web community.

关键词： Hypermedia systems

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Evaluation of teleteaching services over ATM and IP networks

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Telematics and informatics 2003年第1期20卷 1-18页

作者： Bouras, Ch. Gkamas, A. Kapoulas, V. Tsiatsos, Th. Computer Technology Institute Riga Feraiou 61 GR-26221 Patras Greece Computer Engineering and Informatics Department University of Patras Riga Feraiou 61 GR-26221 Patras Greece

This paper presents the components of a synchronous teleteaching application, their underlying technology and their interaction with network services. In addition, it presents the architecture and design of a synchronous teleteaching application used over the public ATM network in Greece. This paper presents various teleteaching scenarios over an ATM network infrastructure with the use of native ATM and IP over ATM. In each scenario we present the standards used, the logical components, the resource demands (network and equipment) and its special characteristics. For each scenario we give detailed information about the transmission and frame rates and the video delay. The main result of our experiments is that broadband networks offer many capabilities for high quality teleteaching, and generally speaking, high quality telematic services. © 2002 Elsevier Science Ltd. All rights reserved.

关键词： computer aided instruction

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Multi-user layer in the EVE distributed virtual reality platform

Multi-user layer in the EVE distributed virtual reality plat...

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International Conference on Distributed Computing Systems Workshop

作者： C. Bouras D. Psaltoulis C. Psaroudis T. Tsiatsos Computer Engineering and Informatics Department University of Patras Greece Research Academic Computer Technology Institute Greece

In this paper, we present the design and implementation of a VRML97 multi-user layer, which is introduced in the EVE distributed virtual reality platform. Main consideration of our multi-user extension is the ease of transforming single-user virtual worlds to multi-user virtual worlds, as well as the conformity with any standard VRML97 browser. Furthermore, we present the EVE's communication platform, which can be used in order to support Collaborative Virtual Environments (CVEs). Main issues regarding the effective network communication as well as the initialization of the 3D scene are discussed in this paper.

关键词： Virtual reality Distributed computing informatics Virtual environment Design engineering Layout Space technology Collaboration User interfaces Web sites

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Issues for the performance monitoring on networked virtual environments: the case of EVE

Issues for the performance monitoring on networked virtual e...

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International Conference on Telecommunications (ConTEL)

作者： C. Bouras E. Giannaka Th. Tsiatsos Research Academic Computer Technology Institute Computer Engineering and Informatics Department University of Patras Patras Greece

The wide expansion and increasing demand for networked virtual environments resulted in efforts for the optimization of these environments with the enhancement of advanced features, which offered extended functionality and created an improved sense of realism. However, the added functionality often creates resource overhead both in the system as well as in the network host, which results in performance reduction. This paper presents such a networked virtual environment and based on the system's architecture tries to trace down with the time and recourse consuming parameters and proposes models on which a networked virtual environment, like the one presented, could achieve optimization of its performance.

关键词： computer aided software engineering Virtual environment computer networks Condition monitoring Virtual reality computerized monitoring informatics Computational modeling computer simulation System performance

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Competitive video on demand schedulers for popular movies

Competitive video on demand schedulers for popular movies

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作者： Bouras, Christos Kapoulas, Vaggelis Pantziou, Grammati Spirakis, Paul Research Academic Computer Technology Institute 2 Riga Feraiou 61 262 21 Patras Greece Department of Computer Engineering and Informatics University of Patras 265 00 Rion-Patras Greece Department of Informatics Technological Education Institute of Athens Ag. Spyridonos Str. 122 10 Egaleo-Athens Greece

In this paper we investigate the online video on demand problem, namely having to accept or reject a request for a movie without knowing the future requests. We present online movie-scheduling schemes that implement the principles of refusal by choice and delayed notification. A novel way to schedule movies that exploits the knowledge of the distribution of the preference of requests for movies, is shown to have a competitive ratio that outperforms all the previously known schemes in practical situations. In fact, our scheduler has a competitive ratio bounded above by a constant, independent of the number of the users, channels, or movies, in the case that a large fraction of the requests tends to concentrate in a small number of movies. We extend our approach by presenting an "adaptive" randomized scheduler which initially is not aware of the movie popularities but it adapts to it, and achieves the same asymptotic competitive ratio. © 2002 Elsevier Science B.V. All rights reserved.

关键词： Competitive ratio Online scheduling algorithm Probability distribution Video on demand

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