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IEEE Conference and Exhibition on Global Telecommunications (GLOBECOM)

作者： F. Farahmand Qiong Zhang J.P. Jue Department of Computer Electronics and Graphics Technology Central Connecticut State University New Britain CT USA Mathematical Sciences and Applied Computing Arizona State University USA Department of Computer Science University of Texas Dallas Richardson TX USA

In this paper we describe a rate-based OBS network architecture in which core switch nodes send explicit messages to edge nodes requesting them to reduce their transmission rate on congested links. Within this framework, we introduce a new contention avoidance mechanism called proportional control algorithm with explicit reduction request (PCwER). Through source rate control, PCwER proactively attempts to prevent the network from entering the congestion state. Basic building blocks and performance trade-offs of PCwER are the main focus of this paper. In addition, through a simple fluid model we analyze the characteristics of the algorithm. Our simulation results show that the proposed contention avoidance techniques improve the network utilization and reduce the packet loss probability

关键词： Optical control Optical fiber networks Optical feedback Optical network units Optical packet switching Optical losses Optical buffering computer networks Optical computing Switches

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Data burst grooming in optical burst-switched networks

Data burst grooming in optical burst-switched networks

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International Conference on Broadband Networks (BroadNets)

作者： F. Farahmand Q. Zhang J.P. Jue Department of Computer Electronics and Graphics Technology Central Connecticut State University New Britain CT USA Mathematical Sciences and Applied Computing Arizona State University USA Department of Computer Science University of Texas Dallas Richardson TX USA

In this paper we address the problem of data burst grooming in optical burst-switched (OBS) networks. In OBS networks IP packets with the same edge node destination are assembled into larger packets called data bursts. Depending on the core node's switching technology, data bursts are required to have a minimum length. On the other hand, each IP packet in a burst has a time delay constraint, called maximum end-to-end delay, which determines the upper time limit before which the packet must reach its destination. Thus, a data burst cannot wait indefinitely until sufficient number of IP packets are assembled and the minimum burst length requirement is met. In order to satisfy the packet maximum end-to-end delay requirement, many bursts will be timed out and released before they reach the minimum length requirement. Under such circumstances, padding overhead must be added to these short bursts, called sub-bursts. Excessive padding results in high overhead and high data burst blocking probability. One approach to minimize the amount of padding overhead, while maintaining the end-to-end delay requirement of IP packets, is to groom multiple sub-bursts together. That is, sub-bursts with different destinations are aggregated together at the edge node and transmitted as a single burst until they are separated at some downstream node. In this paper we present an edge node architecture enabling burst grooming capability. We also develop two basic grooming approaches, namely no-routing-overhead (NoRO) and minimum-total-overhead (MinTO). Through a comprehensive simulation study we show that, in general, our proposed grooming algorithms can significantly improve the performance compared to the case of no grooming. However, careful considerations must be given to network loading condition and the number of sub-bursts allowed to be groomed together. We show that although simple greedy algorithms can reduce network overhead, they may alter the traffic characteristics and increase it

关键词： Intelligent networks Optical fiber networks Assembly Optical network units Delay effects Optical packet switching computer networks Optical computing Telecommunication traffic Bandwidth

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Ship hull fitting using NURBS

Ship hull fitting using NURBS

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International Conference on computer graphics, Imaging and Visualization, CGIV

作者： A.S. Wen S.M.H. Shamsuddin Y. Samian Department of Graphics and Multimedia Faculty of Computer Science and Information System Universiti Teknologi Malaysia Malaysia Department Of Marine Technology Faculty of Mechanical Engineering Universiti Teknologi Malaysia Malaysia

Ship hull form module is the main module in ship design. The problem of creating fair ship hull surface is of major importance in computer aided ship design environment. The fairness of these surfaces is generally considered a subjective notion depending on the judgment of the designers (e.g. visually pleasing, devoid of unnecessary bumps or wiggles, satisfying certain continuity requirements). One of the restriction in ship hull design is that the existing details of a ship design on paper or a ship that already been constructed physically couldn't be reconstructed accurately and concisely in a ship hull design software. This problem can take on many different characteristics, depending on the goal of the reconstruction, the origin of the offset, and tools or methods available to tackle the job. All of these must be taken into account in developing the best approach to solving the problem in the most efficient manner. In this research, the implementation of NURBS method is used because it brings the most convincing results.

关键词： Design automation Surface fitting Curve fitting Computational geometry

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Geometric spanners for routing in mobile networks

Geometric spanners for routing in mobile networks

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作者： Gao, Jie Guibas, Leonidas J. Hershberger, John Zhang, Li Zhu, An Department of Computer Science Stanford University Stanford CA 94305 United States Ctr. for the Math. of Information California Institute of Technology Pasadena CA 91125 United States Mentor Graphics Corporation Wilsonville OR 97070 United States Compaq Systems Research Center Palo Alto CA Information Dynamics Laboratory Hewlett Packard Laboratories Palo Alto CA 94304 United States

We propose a new routing graph, the restricted Delaunay graph (RDG), for mobile ad hoc networks. Combined with a node clustering algorithm, the RDG can be used as an underlying graph for geographic routing protocols. This graph has the following attractive properties: 1) it is planar;2) between any two graph nodes there exists a path whose length, whether measured in terms of topological or Euclidean distance, is only a constant times the minimum length possible;and 3) the graph can be maintained efficiently in a distributed manner when the nodes move around. Furthermore, each node only needs constant time to make routing decisions. We show by simulation that the RDG outperforms previously proposed routing graphs in the context of the Greedy perimeter stateless routing (GPSR) protocol. Finally, we investigate theoretical bounds on the quality of paths discovered using GPSR.

关键词： Telecommunication networks

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INTERNATIONAL JOURNAL OF ELECTRONIC COMMERCE 2004年第4期8卷 115-129页

作者： Zeng, C Xing, CX Zhou, LZ Zheng, XH Computer science Tsinghua University Beijing Associate professor of computer science and technology Tsinghua University Professor and dean Department of Computer Science and Technology Tsinghua University Librarian Tsinghua University library

Collaborative filtering is used in recommender systems and e-commerce both to help customers find items they want to buy and to help businesses prepare goods they will offer. The k-Nearest Neighbor (KNN) method plays a central role in collaborative filtering by finding the k-nearest neighbors for a given user and employing them to predict the user's interests. This method suffers from problems of sparsity and nonscalability due to the sparseness of the user-item data set and the entire scan of such a data set in search of neighbors. These problems are solved with a matrix conversion method for compressing items into classes and an instance-selection method to narrow the scope of neighbor searching. The matrix conversion method avoids the "cold start" problem and makes predictions more accurate. The instance-selection method improves the performance of prediction without sacrificing accuracy. Combining these two methods results in better accuracy and performance.

关键词： collaborative filtering instance selection similarity measure

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Blue-c API: A multimedia and 3D video enhanced toolkit for collaborative VR and telepresence

Blue-c API: A multimedia and 3D video enhanced toolkit for c...

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Proceedings VRCAI 2004 - ACM SIGGRAPH International Conference on Virtual Reality Continuum and its Applications in Industry

作者： Naef, Martin Staadt, Oliver Gross, Markus Computer Graphics Laboratory Swiss Fed. Institute of Technology Zurich Switzerland Computer Science Department University of California Davis United States

ISBN: (纸本)1581138849

In this paper we present the blue-c application programming interface, a software toolkit for media-rich, collaborative, immersive virtual reality applications. The blue-c API provides easy to use interfaces to all blue-c technology, including immersive projection, live 3D video acquisition and streaming, audio, tracking, and gesture recognition. The integration of multimedia data, including 2D video, 3D video, and animation, into the scene graph is presented. We emphasize on our performance-optimized 3D video handling and rendering pipeline, which is capable of rendering 3D video inlays consisting of up to 30,000 fragments updated at 10 Hz in real-time, enabling remote users to meet inside our virtual environment.

关键词： Virtual reality

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Framework for real time cloud rendering

Framework for real time cloud rendering

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International Conference on computer graphics, Imaging and Visualization, CGIV

作者： M.A. Rana M.S. Sunar M.N.N. Hayat S. Kari A. Bade Department of Computer Graphics and Multimedia Faculty of Computer Science and Information System University Technology of Malaysia Skudai Johor Malaysia

computer graphics (CG) is a key technology for producing visual contents. Currently computer generated imagery techniques are being developed and applied, particularly in the field of virtual reality applications, film production, training and flight simulators, to provide total composition of realistic computer graphic images. Clouds are an integral feature of the sky without them synthetic outdoor scenes seems unrealistic. Modeling and animating clouds is a difficult task. Most systems are difficult to use, as they require adjustment of numerous, complex parameters, and are noninteractive. This paper presents an intuitive, interactive system to artistically model, animate, and render visually convincing clouds using modern graphics hardware. A high-level interface models clouds through the visual use of cubes. Clouds are rendered as textured billboards by making use of hardware accelerated API - OpenGL. The resulting interactive design and rendering system produces perceptually convincing cloud models that can be used in any interactive system.

关键词： Clouds Rendering (computer graphics) computer graphics Animation Interactive systems Hardware Character generation Image generation Virtual reality Application software

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Robust watermarking of point-sampled geometry

Robust watermarking of point-sampled geometry

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International Conference on Shape Modeling and Applications

作者： D. Cotting T. Weyrich M. Pauly M. Gross Computer Graphics Laboratory Swiss Federal Institute of Technology Zurich Switzerland Computer Science Department University of Stanford Stanford CA USA

We present a new scheme for digital watermarking of point-sampled geometry based on spectral analysis. By extending existing algorithms designed for polygonal data to unstructured point clouds, our method is particularly suited for scanned models, where the watermark can be directly embedded in the raw data obtained from the 3D acquisition device. To handle large data sets efficiently, we apply a fast hierarchical clustering algorithm that partitions the model into a set of patches. Each patch is mapped into the space of eigenfunctions of an approximate Laplacian operator to obtain a decomposition of the patch surface into discrete frequency bands. The watermark is then embedded into the low frequency components to minimize visual artifacts in the model geometry. During extraction, the target model is resampled at optimal resolution using an MLS projection. After extracting a watermark from this model, the corresponding bit stream is analyzed using statistical methods based on correlation. We have applied our method to a number of point-sampled models of different geometric and topological complexity. These experiments show that our watermarking scheme is robust against numerous attacks, including low-pass filtering, resampling, affine transformations, cropping, additive random noise, and combinations of the above.

关键词： Robustness Watermarking Geometry Clustering algorithms Partitioning algorithms Frequency Solid modeling Additive noise Spectral analysis Algorithm design and analysis

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Citeseer: Past, present, and future 2nd

Citeseer: Past, present, and future

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2nd International Atlantic Web Intelligence Conference, AWIC 2004

作者： Lee Giles, C. School of Information Sciences and Technology professor Computer Science and Engineering Supply Chain and Information Systems eBusiness Research Center The Pennsylvania State University University ParkPA United States

ISBN: (纸本)9783540246817

CiteSeer, a computer science digital library, has been a radical departure for scientific document access and analysis. With nearly 600,000 documents, it has over a million page views a day making it one of the most popular document access engines in computer and information science. CiteSeer is also portable, having been extended to ebusiness (eBizSearch) and more recently to academic business documents (SMEALSearch). CiteSeer is really based on two features: actively acquiring new documents and automatic tagging and linking of metadata information inherent in an academic document’s syntactic structure. We discuss methods for providing new tagged metadata and other data resources such as institutions and acknowledgements. © Springer-Verlag Berlin Heidelberg 2004.

关键词： Digital libraries

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GPU-assisted z-field simplification

GPU-assisted z-field simplification

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International Symposium on 3D Data Processing Visualization and Transmission

作者： A. Bogomjakov C. Gotsman Center of Graphics and Geometric Computing Computer Science Department Technion-Israel Institute of Technology Haifa Israel

Height fields and depth maps which we collectively refer to as z-fields, usually carry a lot of redundant information and are often used in real-time applications. This is the reason why efficient methods for their simplification are necessary. On the other hand, the computation power and programmability of commodity graphics hardware has significantly grown. We present an adaptation of an existing real-time z-field simplification method for execution in graphics hardware. The main parts of the algorithm are implemented as fragment programs which run on the GPU. The resulting polygonal models are identical to the ones obtained by the original method. The main benefit is that the computation load is imposed on the GPU, freeing-up the CPU for other tasks. Additionally, the new method exhibits a performance improvement when compared to a pure CPU implementation.

关键词： Hardware Rendering (computer graphics) Concurrent computing computer graphics computer science Application software computer aided instruction Throughput Physics computing Pipelines

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