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2008 3rd International Conference on Pervasive computing and Applications, ICPCA08

作者： Jinlan, Zhan Qingguo, Zhou Shuwei, Bai Li, Cuihual Bin, Hu Li, Lian Department of Computer Science Video and Image Processing Lab Xiamen University China Engineering Research Center of Open Source Software and Real-time System Ministry of Education Department of Information Science and Engineering Lanzhou University China Department of Computing University of Central England United Kingdom

ISBN: (纸本)9781424420209

In the paper, a new parallel LZW-Like algorithm, bidirectory LZW algorithm (BD-LZW) will be interpreted The new algorithm can be used in data compression/decompression system which runs on multi-microprocessor system, such as CELL, which the algorithm will be implemented on. Different from the conventional parallel LZW algorithm with one input directory, BD-LZW algorithm allows two threads reading characters from two ends of string. By this method, the data can be partitioned for compression/decompression loading between two threads fairly and easily. The most important is the compression performance can be improved by the new algorithm. Comparing running time, it's lower 10% than conventional parallel LZW (P-LZW) algorithm when there are two threads running on CELL architecture. © 2008 IEEE.

关键词： Compression algorithms Wireless sensor networks Yarn Partitioning algorithms image coding Data compression Video compression image processing computer science Open source software

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Outlier detection by weighted mercer-kernel based fuzzy clustering algorithm

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Iranian Journal of Electrical and computer Engineering 2005年第2期4卷 129-136页

作者： Shen, Hongbin Yang, Jie Dong, Yifei Wang, Shitong College of Computer and Information Engineering Hohai University Changzhou Jiangsu China Department of Image Processing and Pattern Recognition Jiaotong University Shanghai China School of Computer Science and Engineering University of New South Wales Australia School of Information Southern Yantze University Wuxi Jiangsu China Institute of Image Processing and Pattern Recognition Shanghai Jiaotong University China IEEE Institute of National Automation Department of Information Southern Yangtse University Polytechnic University of Hongkong Advanced Computing Research Center Bristol University United Kingdom

Outliers are data values that lie away from the general cluster of other data values. Detecting the outliers of a dataset is an important research topic for data cleaning and finding new useful knowledge in many research areas, i.e. data mining, pattern recognition, etc. In the past decades, many useful algorithms were proposed in the literature. In this paper, a new fuzzy kernel-clustering algorithm with outliers (FKCO) is presented to locate critical areas that are often represented by only a few outliers. Theoretic analysis also shows that FKCO can converge to a local minimum of the objective function. Finally, based on the information theory, a new criterion for finding outliers is also proposed. Simulations of different types of datasets demonstrate the feasibility of this new method. © 2005 JD.

关键词： Fuzzy control

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Meshless Isosurface Generation from Multiblock Data

Meshless Isosurface Generation from Multiblock Data

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6th Joint Eurographics - IEEE TCVG Symposium on Visualization, VisSym 2004

作者： Co, Christopher S. Porumbescu, Serban D. Joy, Kenneth I. Center for Image Processing and Integrated Computing Department of Computer Science University of California Davis United States

ISBN: (纸本)390567307X

We propose a meshless method for the extraction of high-quality continuous isosurfaces from volumetric data represented by multiple grids, also called "multiblock"data sets. Multiblock data sets are commonplace in computational mechanics applications. Relatively little research has been performed on contouring multiblock data sets, particularly when the grids overlap one another. Our algorithm proceeds in two steps. In the first step, we determine a continuous interpolant using a set of locally defined radial basis functions (RBFs) in conjunction with a partition of unity method to blend smoothly between these functions. In the second step, we extract isosurface geometry by sampling points on Marching Cubes triangles and projecting these point samples onto the isosurface defined by our interpolant. A surface splatting algorithm is employed for visualizing the resulting point set representing the isosurface. Because of our method's generality, it inherently solves the "crack problem"in isosurface generation. Results using a set of synthetic data sets and a discussion of practical considerations are presented. The importance of our method is that it can be applied to arbitrary grid data regardless of mesh layout or orientation. © The Eurographics Association 2004.

关键词： Computational mechanics

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Reversible n-bit to n-bit integer Haar-like transforms

Reversible n-bit to n-bit integer Haar-like transforms

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Data Compression Conference (DCC)

作者： J. Senecal M. Duchaineau K.I. Joy Center for Image Processing and Integrated Computing Computer Science Department University of California Davis USA Center for Applied Scientific Computing Lawrence Livemore National Laboratory USA

Methods of producing reversible n-bit to n-bit integer transforms is presented in this paper. Such methods are particularly suited for hardware-based implementations, as keeping the coefficients to n bits simplifies the design of custom hardware and makes it easier to use these approaches on preexisting hardware with limited channel width. One of our methods, called table-lookup Haar (TLHaar) is an approximation of the Haar integer wavelet transform (Haar IWT). The Haar IWT takes two integer data values A and B and using averaging and differencing produces a low-pass value L and a high-pass value H, both integers. The lookup tables are created by initializing each with an identity transform. TLHaar executes up to 44% faster. Compression results are mixed, and depend on the compression method used and the image type.

关键词： image coding Table lookup Scientific computing Hardware Laboratories image processing computer science Wavelet transforms Equations Convergence

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Squeeze: Numerical-precision-optimized volume rendering

Squeeze: Numerical-precision-optimized volume rendering

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作者： Bitter, Ingmar Neophytou, Neophytos Mueller, Klaus Kaufman, Arie E. Clinical Image Processing Services Department of Radiology National Institutes of Health United States Computer Science Center for Visual Computing State University of New York Stony Brook United States

ISBN: (纸本)3905673150

This paper discusses how to squeeze volume rendering into as few bits per operation as possible while still retaining excellent image quality. For each of the typical volume rendering pipeline stages in texture map volume rendering, ray casting and splatting we provide a quantitative analysis of the theoretical and practical limits for the required bit precision for computation and storage. Applying this analysis to any volume rendering implementation can balance the internal precisions based on the desired final output precision and can result in significant speedups and reduced memory footprint. © The Eurographics Association 2004.

关键词： Volume rendering

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Length-limited variable-to-variable length codes for high-performance entropy coding

Length-limited variable-to-variable length codes for high-pe...

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Data Compression Conference (DCC)

作者： J. Senecal M. Duchaineau K.I. Joy Institute for Scientific Computing Research Lawrence Livemore National Laboratory USA Center for Image Processing and Integrated Computing Computer Science Department University of California Davis USA Center for Applied Scientific Computing Lawrence Livemore National Laboratory USA

Arithmetic coding achieves a superior coding rate when encoding a binary source, but its lack of speed makes it an inferior choice when true high-performance encoding is needed. This paper presents the practical implementation of fast entropy coders for binary messages utilizing only bit shifts and table lookups. To limit code table size the proposed code lengths is limited with a type of variable-to-variable (VV) length code created from source string merging. This is referred to as "merged codes". With merged codes it is possible to achieve a desired level of speed by adjusting the number of bits read from the source at each step. The most efficient merged codes yield a coder with a worst-case inefficiency of 0.4%, relative to the Shannon entropy. Using a hybrid Golomb-VV bin coder the compression ratio that is competitive with other state-of-the-art coders, at a superior throughput is achieved.

关键词： Entropy coding image coding Table lookup Throughput Computational modeling Scientific computing Laboratories Degradation Arithmetic image processing

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Improving topological segmentation of three-dimensional vector fields

Improving topological segmentation of three-dimensional vect...

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5th Joint Eurographics - IEEE TCVG Symposium on Visualization, VisSym 2003

作者： Mahrous, Karim M. Bennett, Janine C. Hamann, Bernd Joy, Kenneth I. Center for Image Processing and Integrated Computing Department of Computer Science University of California Davis DavisCA95616-8562 United States

ISBN: (纸本)3905673010

We present three enhancements to accelerate the extraction of separatrices of three-dimensional vector fields, using intelligently selected .sample. streamlines. These enhancements reduce the number of needed sample streamlines and their propagation length. Inflow/outflow matching supports the simultaneous extraction of topologically significant inflow and outflow separatrices in a single pass. An adaptive sampling approach is introduced and used to seed streamlines in a more meaningful and efficient manner. Cell-locking is a new concept that isolates regions of a data set that do not contain separatrices. This concept makes streamline propagation more efficient as streamlines are not propagated through cells that do not influence or contain separatrices. These enhancements enable us to perform separatrix construction for three-dimensional vector field data requiring less overall computation. © 2003 Eurographics Association. All rights reserved.

关键词： Extraction

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Detecting critical regions in scalar fields

Detecting critical regions in scalar fields

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5th Joint Eurographics - IEEE TCVG Symposium on Visualization, VisSym 2003

作者： Weber, Gunther H. Scheuermann, Gerik Hamann, Bernd Ag Graphische Datenverarbeitung und Computergeomterie Fb Informatik Universität Kaiserslautern Germany Center for Image Processing and Integrated Computing Department of Computer Science University of California Davis United States

ISBN: (纸本)3905673010

Trivariate data is commonly visualized using isosurfaces or direct volume rendering. When exploring scalar fields by isosurface extraction it is often difficult to choose isovalues that convey .useful. information. The significance of visualizations using direct volume rendering depends on the choice of good transfer functions. Understanding and using isosurface topology can help in identifying .relevant. isovalues for visualization via isosurfaces and can be used to automatically generate transfer functions. Critical isovalues indicate changes in topology of an isosurface: The creation of new surface components, merging of surface components or the formation of holes in a surface component. Interesting isosurface behavior is likely to occur at and around critical isovalues. Current approaches to detect critical isovalues are usually limited to isolated critical points. Data sets often contain regions of constant value (i.e., mesh edges, mesh faces, or entire mesh cells). We present a method that detects critical points, critical regions and corresponding critical isovalues for a scalar field defined by piecewise trilinear interpolation over a uniform rectilinear grid. We describe how to use the resulting list of critical regions/points and associated values to examine trivariate data. © 2003 Eurographics Association. All rights reserved.

关键词： Transfer functions

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Iso-splatting: a point-based alternative to isosurface visualization

Iso-splatting: a point-based alternative to isosurface visua...

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Pacific Conference on computer Graphics and Applications

作者： C.S. Co B. Hamann K.I. Joy Center for Image Processing and Integrated Computing (CIPIC) Department of Computer Science University of California USA

We present a new approach to isosurface visualization that we call "iso-splatting." We use point primitives for representing and rendering isosurfaces. The method consists of two steps. In the first step, point samples are generated throughout the volumetric domain of a scalar function. In the second step, these points are projected onto the isosurface of interest. We render the resulting point set using a surface splatting algorithm. The method can be extended to out-of-core or parallel environments. Our results show that this method can offer much greater time and space efficiency when compared with standard triangle-based methods, thereby supporting higher levels of interactivity. Parts of the algorithm can be accelerated using graphics hardware. One key advantage of this approach is that, since extraction computations are divided into two smaller phases, work can be distributed to exploit all available resources.

关键词： Isosurfaces Visualization Rendering (computer graphics) Computational geometry Fuels image processing computer science Acceleration Graphics Hardware

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Using graphs for fast error term approximation of time-varying datasets

Using graphs for fast error term approximation of time-varyi...

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5th Joint Eurographics - IEEE TCVG Symposium on Visualization, VisSym 2003

作者： Nuber, C. LaMar, E.C. Pascucci, V. Hamann, B. Joy, K.I. Center for Image Processing and Integrated Computing Department of Computer Science University of California Davis DavisCA95616-8562 United States Center for Applied Scientific Computing Lawrence Livermore National Laboratory LivermoreCA94550-9234 United States

ISBN: (纸本)3905673010

We present a method for the efficient computation and storage of approximations of error tables used for error estimation of a region between different time steps in time-varying datasets. The error between two time steps is defined as the distance between the data of these time steps. Error tables are used to look up the error between different time steps of a time-varying dataset, especially when run time error computation is expensive. However, even the generation of error tables itself can be expensive. For n time steps, the exact error look-up table (which stores the error values for all pairs of time steps in a matrix) has a memory complexity and pre-processing time complexity of O(n2), and O(1) for error retrieval. Our approximate error look-up table approach uses trees, where the leaf nodes represent original time steps, and interior nodes contain an average (or best-representative) of the children nodes. The error computed on an edge of a tree describes the distance between the two nodes on that edge. Evaluating the error between two different time steps requires traversing a path between the two leaf nodes, and accumulating the errors on the traversed edges. For n time steps, this scheme has a memory complexity and pre-processing time complexity of O(nlog(n)), a significant improvement over the exact scheme;the error retrieval complexity is O(log(n)). As we do not need to calculate all possible n2 error terms, our approach is a fast way to generate the approximation. © 2003 Eurographics Association. All rights reserved.

关键词： Errors

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