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Efficient algorithms for the multicast trees under the packet-replication restrictions

IEICE TRANSACTIONS ON COMMUNICATIONS 2001年第9期E84B卷 2670-2680页

作者： Chung, SJ Hong, SP Chung, HS Seoul Natl Univ Seoul South Korea Chung Ang Univ Ansung South Korea

In this paper, we are concerned in obtaining multicast trees in packet-switched networks such as ATM nets, when there exist constraints on the packet (cell)-replication capabilities of the individual switching nodes. This problem can be formulated as the Steiner tree problem with degree bounds on the nodes, so we call it the Degree-Constrained Steiner Tree problem (DCST). Four heuristic algorithms are proposed: the first is a combined version of two well-known Steiner tree algorithms, heuristic Naive and the shortest path heuristic (SPH), and the second is a relaxation algorithm based on a mathematical formulation of the DCST, and the last two use a tree reconfiguration scheme based on the concept of 'logical link.' We experimentally compare our algorithms with the previous ones in three respects;number of solved instances, objective value or tree cost, and computation time. The experimental results show that there are few instances unsolved by our algorithms, and the objective values are mostly within 5% of optimal. Computation times are also acceptable.

关键词： multicasting degree-constrained steiner tree tree reconfiguration logical link relaxation algorithm

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relaxation algorithms to find Nash equilibria with economic applications

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ENVIRONMENTAL MODELING & ASSESSMENT 2000年第1期5卷 63-73页

作者： Krawczyk, JB Uryasev, S Victoria Univ Wellington Commerce & Adm Fac Wellington New Zealand Univ Florida Dept Ind & Syst Engn Gainesville FL 32611 USA

Recent theoretical studies have shown that a relaxation algorithm can be used to find noncooperative equilibria of synchronous infinite games with nonlinear payoff functions and coupled constraints. In this study, we introduce an improvement to the algorithm, such as the steepest-descent step-size control, for which the convergence of the algorithm is proved. The algorithm is then tested on several economic applications. In particular, a River Basin Pollution problem is considered where coupled environmental constraints are crucial for the relevant model definition. Numerical runs demonstrate fast convergence of the algorithm for a wide range of parameters.

关键词： computational economics Nash equilibrium coupled constraints relaxation algorithm

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Variation-based approach to image segmentation

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Science in China(Series F) 2001年第4期44卷 259-269页

作者：张永平郑南宁赵荣椿 DepartmentofMathematics ShaanxiNormalUniversityXi'an710062China TheInstituteofArtificialIntelligenceandRobotics Xi'anJiaotongUniversityXi'an710049China DepartmentofComputerScience NorthwestPolytechnicUniversity.Xi'an710072China

A new approach to image segmentation is presented using a variation framework. Re-garding the edge points as interpolating points and minimizing an energy functional to interpolate a smooth threshold surface it carries out the image segmentation. In order to preserve the edge informa-tion of the original image in the threshold surface, without unduly sharping the edge of the image, a non-convex energy functional is adopted. A relaxation algorithm with the property of global conver-gence, for solving the optimization problem, is proposed by introducing a binary energy. As a result the non-convex optimization problem is transformed into a series of convex optimization problems, and the problem of slow convergence or nonconvergence is solved. The presented method is also tested experimentally. Finally the method of determining the parameters in optimizing is also explored.

关键词： image segmentation variation optimization relaxation algorithm global convergence.

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Quantification and segmentation of brain tissues from MR images: A probabilistic neural network approach

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IEEE TRANSACTIONS ON IMAGE PROCESSING 1998年第8期7卷 1165-1181页

作者： Wang, Y Adali, T Kung, SY Szabo, Z Catholic Univ Amer Dept Elect Engn & Comp Sci Washington DC 20064 USA Georgetown Univ Sch Med Dept Radiol Washington DC 20007 USA Univ Maryland Baltimore Cty Dept Comp Sci & Elect Engn Baltimore MD 21250 USA Princeton Univ Dept Elect Engn Princeton NJ 08544 USA Johns Hopkins Med Inst Dept Radiol Baltimore MD 21205 USA

This paper presents a probabilistic neural network based technique for unsupervised quantification and segmentation of brain tissues from magnetic resonance images. Ht is shown that this problem can be solved by distribution learning and relaxation labeling, resulting in an efficient method that may be particularly useful in quantifying and segmenting abnormal brain tissues where the number of tissue types is unknown and the distributions of tissue types heavily overlap. The new technique uses suitable statistical models for both the pixel and context images and formulates the problem in terms of model-histogram fitting and global consistency labeling. The quantification is achieved by probabilistic self-organizing mixtures and the segmentation by a probabilistic constraint relaxation network. The experimental results show the efficient and robust performance of the new algorithm and that it outperforms the conventional classification based approaches.

关键词： finite mixture models image segmentation information theoretic criteria model estimation probabilistic neural networks relaxation algorithm

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Stereo matching algorithm based on modified wavelet decomposition process

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PATTERN RECOGNITION 1997年第6期30卷 929-952页

作者： Kim, YS Lee, JJ Ha, YH KYUNGPOOK NATL UNIV DEPT ELECT ENGN TAEGU 702701 SOUTH KOREA DONGSEO UNIV DEPT COMP ENGN PUSAN 671716 SOUTH KOREA

Multiresolutional representation such as pyramidal structures is useful for stereo matching as coarse-to-fine strategy. However, conventional pyramidal structures using Gaussian or Laplacian filters lose much information due to their low-pass filtering characteristics and also cannot obtain any spatial orientation selectivity. The adoption of wavelet transform can remedy these problems, but at the time of image translation, it changes wavelet coefficients. In this paper, a pyramid using modified wavelet decomposition process is proposed to have translation invariance. The image transformed by the proposed method is converted into appropriate multiple features without loss of information. Since the importance of each feature is determined heuristically in the multiple feature-based stereo matching method, it is very difficult to fuse them adequately. In the proposed algorithm, the weight of each feature, that is, the relative importance of each feature, is decided from the similarity between the intensities in the local region of each left and right wavelet channels. Since the window size used for the decision of weight and disparity values greatly influences the processed result, the window is adaptively determined from the disparities estimated in the coarse resolution and low-varying channel of fine resolution. The window size must be large enough to obtain signal-to-noise ratio, but not too large as to induce the effects of projective distortion. Also, a new relaxation algorithm which can reduce false matches without blurring the disparity edge is proposed. By integrating adaptive weight variable window selection method, and relaxation process, an accurate and stable disparity map is obtained. Experimental results for various images show that the proposed algorithm has good performance even if the image has the unfavorable conditions. (C) 1997 Pattern Recognition Society.

关键词： stereo matching wavelet transform adaptive weights relaxation algorithm variable window selection method

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Many masses on one stroke: Economic computation of quark propagators

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INTERNATIONAL JOURNAL OF MODERN PHYSICS C 1995年第5期6卷 627-638页

作者： Frommer, A Nockel, B Gusken, S Lippert, T Schilling, K UNIV GESAMTHSCH WUPPERTAL DEPT PHYS D-42097 WUPPERTAL GERMANY FORSCHUNGSZENTRUM JULICH HLRZ DESY D-52425 JULICH GERMANY

The computational effort in the calculation of Wilson fermion quark propagators in Lattice Quantum Chromodynamics can be considerably reduced by exploiting the Wilson fermion matrix structure in inversion algorithms based on the non-symmetric Lanczos process. We consider two such methods: QMR (quasi minimal residual) and BCG (biconjugate gradients). Based on the decomposition M/kappa = 1/kappa-D of the Wilson mass matrix, using QMR, one can carry out inversions on a whole trajectory of masses simultaneously, merely at the computational expense of a single propagator computation. In other words, one has to compute the propagator corresponding to the lightest mass only, while all the heavier masses are given for free, at the price of extra storage. Moreover, the symmetry gamma 5 M = M(+) gamma 5 can be used to cut the computational effort in QMR and BCG by a factor of two. We show that both methods then become - in the critical regime of small quark masses - competitive to BiCGStab and significantly better than the standard MR method, with optimal relaxation factor, and CG as applied to the normal equations.

关键词： lattice QCD relaxation algorithm parallel computer

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ACCELERATING WILSON FERMION MATRIX INVERSIONS BY MEANS OF THE STABILIZED BICONJUGATE GRADIENT algorithm

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INTERNATIONAL JOURNAL OF MODERN PHYSICS C-PHYSICS AND COMPUTERS 1994年第6期5卷 1073-1088页

作者： FROMMER, A HANNEMANN, V NOCKEL, B LIPPERT, T SCHILLING, K UNIV GESAMTHSCH WUPPERTAL DEPT PHYSD-42097 WUPPERTALGERMANY

The stabilized biconjugate gradient algorithm BiCGStab recently presented by van der Vorst is applied to the inversion of the lattice fermion operator in the Wilson formulation of lattice Quantum Chromodynamics. Its computational efficiency is tested in a comparative study against the conjugate gradient and minimal, residual methods. Both for quenched gauge configurations at beta = 6.0 and gauge configurations with dynamical fermions at beta = 5.4, we find BiCGStab to be superior to the other methods. BiCGStab turns out to be particularly useful in the chiral regime of small quark masses.

关键词： LATTICE QCD relaxation algorithm PARALLEL COMPUTER

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DETECTING MYOCARDIAL BOUNDARIES OF LEFT-VENTRICLE FROM A SINGLE FRAME 2DE IMAGE

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PATTERN RECOGNITION 1990年第7期23卷 799-806页

作者： CHOU, WS WU, CM CHEN, YC HSIEH, KS NATL TSING HUA UNIV INST ELECT ENGN HSINCHU 30043 TAIWAN VET GEN HOSP SHIH PAI DEPT PEDIAT CARDIOL SECT TAIPEI 112 TAIWAN

A new method for detecting myocardial boundaries of the left ventricle from a short-axis viewed, two-dimensional echocardiographic (2DE) image is presented. The method extracts the outer boundary based on an ideal echo-intensity image model and relaxation algorithm, while the endocardial border is detected by the principle employed by Klingler et al. with some modifications. The only a priori information needed in this method is to assign the approximated contraction center of the left ventricle. Neither the searching limits used in the radial search method nor information about rough positions of myocardial borders used in a plan-based detection scheme is required. Practical examples are given and illustrated. Methods for the generalization of the proposed method are discussed.

关键词： Two-dimensional echocardiography relaxation algorithm Binary morphology Border detection Model-based detection system

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DYNAMIC ESTIMATION OF OPTICAL-FLOW FIELD USING OBJECTIVE FUNCTIONS

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IMAGE AND VISION COMPUTING 1989年第4期7卷 259-267页

作者： ZHAO, WZ QI, FH YOUNG, TY SHANGHAI JIAO TONG UNIV INST IMAGE PROCSHANGHAIPEOPLES R CHINA

Optical flow (image velocity) fields are computed and interpreted from an image sequence by incorporating knowledge of object kinematics. Linear and quadratic objective functions are defined by considering the kinematics, and the function parameters are estimated simultaneously with the computation of the velocity field by relaxation. The objective functions provide an interpretation of the dynamic scenes and, at the same time, serve as the smoothness constraints. The computation is initially based on measured perpendicular velocity components of contours or region boundaries which, due to the ‘aperture problem’, are theoretically not the true perpendicular velocity components. This difficulty is alleviated by introducing a dynamic procedure for the measurement of the perpendicular components. Experiments on using objective functions for synthetic and real images of translating and rotating objects generated velocity fields that are meaningful and consistent with visual perception.

关键词： optical flow image velocity field objective function dynamic estimation relaxation algorithm motion analysis

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CHEMICAL GRAPH MATCHING USING TRANSPUTER NETWORKS

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PARALLEL COMPUTING 1988年第1-3期8卷 295-300页

作者： BRINT, AT GILLET, VJ LYNCH, MF WILLETT, P MANSON, GA WILSON, GA UNIV SHEFFIELD DEPT COMP SCISHEFFIELD S10 2TNS YORKSHIREENGLAND

This paper discusses the use of networks of transputers for the matching of the labelled graphs which are used to represent chemical structures in computer-based chemical information systems; in particular, the implementation of a relaxation algorithm for chemical substructure searching is described. Tests with a doubly-linked chain of transputers suggest that near-linear speedups can be obtained by a partitioning of the database which is to be searched; lesser speedups are obtained with other network configurations. Current work is described involving the exploitation of an alternative level of parallelism in the relaxation algorithm and the parallel implementation of an algorithm for the identification of the maximal substructures common to a pair of chemical compounds.

关键词： Chemical graph maximal common substructure relaxation algorithm subgraph isomorphism substructure searching transputer network

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