检索结果-内蒙古大学图书馆

A scalable exact algorithm for the vertex p-center problem

COMPUTERS & OPERATIONS RESEARCH 2019年 103卷 211-220页

作者： Contardo, Claudio Iori, Manuel Kramer, Raphael Univ Quebec Montreal ESG Dept Management & Technol Montreal PQ Canada UNIMORE Dipartimento Sci & Metodi Ingn Modena Italy

The vertex p-center problem consists in selecting p centers among a finite set of candidates and assigning a set of clients to them, with the aim of minimizing the maximum dissimilarity between a client and its associated center. State-of-the-art algorithms for the problem are based on the solution of a series of covering subproblems, and are particularly efficient when additional reduction rules are used to limit the size of the subproblems. In fact, these algorithms do not scale well when the cardinality of the dissimilarity matrix grows above a few million entries, as the time and space required to compute and store the matrix start dominating those required for solving the subproblems. We introduce a scalable relaxation based iterative algorithm that does not rely on the computation of the entire matrix, but rather relies on the computation of a typically much smaller sub-matrix that is only enlarged if deemed necessary. This method can solve to proven optimality p-center problems derived from the TSP library and containing up to one million clients for small but realistic values of p. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： p-center problem Clustering Facility location relaxation algorithm

来源：评论

学校读者我要写书评

暂无评论

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

引用

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

来源：评论

学校读者我要写书评

暂无评论

Non-cooperative game theory based energy management systems for energy district in the retail market considering DER uncertainties

引用

IET GENERATION TRANSMISSION & DISTRIBUTION 2016年第12期10卷 2999-3009页

作者： Marzband, Mousa Javadi, Masoumeh Luis Dominguez-Garcia, Jose Moghaddam, Maziar Mirhosseini Univ Manchester Sch Elect & Elect Engn Ferranti Bldg Manchester M13 9PL Lancs England Islamic Azad Univ Lahijan Branch Dept Elect Engn Lahijan Iran Islamic Azad Univ Guilan Sci & Res Branch Dept Elect Power Engn Rasht Iran Islamic Azad Univ Rasht Branch Dept Elect Power Engn Rasht Iran Catalonia Inst Energy Res IREC Jardins Dones de Negre 1 Barcelona 08930 Spain

In this study, a general framework for implementing a retail energy market based on the Nikaido-Isoda/relaxation algorithm is proposed as an electricity market structure with large distributed energy resources (DERs) penetration and demand side management of consumers. Moreover, the consumers are able to participate in the market as prosumers (i.e. producer and consumer at the same time). By considering the related uncertainties, the DERs can maximise their expected payoff or profit by undertaking strategies through the price bidding strategy, based on the proposed structure, considering Nash equilibrium. The results show the effectiveness and accuracy of the proposed framework in determining the optimal power set-points of players participating in the market to achieve the objectives.

关键词： energy management systems power markets game theory demand side management profitability pricing share prices noncooperative game theory based energy management systems energy district DER uncertainties distributed energy resources uncertainties retail energy market Nikaido-Isoda algorithm relaxation algorithm electricity market structure distributed energy resources penetration customer demand side management expected payoff maximisation expected profit maximisation price bidding strategy Nash equilibrium optimal power set-point determination

来源：评论

学校读者我要写书评

暂无评论

CHEMICAL GRAPH MATCHING USING TRANSPUTER NETWORKS

引用

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

来源：评论

学校读者我要写书评

暂无评论

MAXIMAL ACYCLIC SUBGRAPHS AND CLOSEST STABLE MATRICES

引用

SIAM JOURNAL ON MATRIX ANALYSIS AND APPLICATIONS 2020年第3期41卷 1167-1182页

作者： Cvetkovic, Aleksandar Protasov, Vladimir Yu GSSI I-67100 Laquila AQ Italy Univ LAquila DISIM I-67100 Laquila AQ Italy Natl Res Univ Higher Sch Econ Moscow 101000 Russia

We develop a matrix approach to the maximal acyclic subgraph (MAS) problem by reducing it to find the closest nilpotent matrix to the matrix of the graph. Using recent results on the closest Schur stable systems and on minimizing the spectral radius over special sets of nonnegative matrices, we obtain an algorithm for finding an approximate solution of the MAS problem. Numerical results for graphs from 50 to 1500 vertices demonstrate its fast convergence and give a rate of approximation larger than 0.6 in most cases. This method also gives the precise solution for the following weakened version of MAS: find the minimal r such that the graph can be made acyclic by cutting at most r incoming edges from each vertex. We also consider several modifications in the case when each vertex is assigned its own maximal number r(i) of cut edges, and some of the edges are "untouchable." Some applications are discussed.

关键词： acyclic graph nonnegative matrix spectral radius relaxation algorithm closest stable matrix spectrum of a graph

来源：评论

学校读者我要写书评

暂无评论

Computer simulation of random sphere packing in an arbitrarily shaped container

引用

CMC-COMPUTERS MATERIALS & CONTINUA 2008年第2期7卷 109-118页

作者： Li, S. X. Zhao, L. Liu, Y. W. Peking Univ State Key Lab Turbulence & Complex Syst Study Coll Engn Beijing 100871 Peoples R China Chinese Acad Sci Inst Mech Beijing 100080 Peoples R China

Most simulations of random sphere packing concern a cubic or cylindric container with periodic boundary, containers of other shapes are rarely studied. In this paper, a new relaxation algorithm with pre-expanding procedure for random sphere packing in an arbitrarily shaped container is presented. Boundaries of the container are simulated by overlapping spheres which covers the boundary surface of the container. We find 0.4 similar to 0.6 of the overlap rate is a proper value for boundary spheres. The algorithm begins with a random distribution of small internal spheres. Then the expansion and relaxation procedures are performed alternately to increase the packing density. The pre-expanding procedure stops when the packing density of internal spheres reaches a preset value. Following the pre-expanding procedure, the relaxation and shrinking iterations are carried out alternately to reduce the overlaps of internal spheres. The pre-expanding procedure avoids the overflow problem and gives a uniform distribution of initial spheres. Efficiency of the algorithm is increased with the cubic cell background system and double link data structure. Examples show the packing results agree well with both computational and experimental results. Packing density about 0.63 is obtained by the algorithm for random sphere packing in containers of various shapes.

关键词： sphere packing random packing computer simulation relaxation algorithm containers

来源：评论

学校读者我要写书评

暂无评论

DYNAMIC ESTIMATION OF OPTICAL-FLOW FIELD USING OBJECTIVE FUNCTIONS

引用

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

来源：评论

学校读者我要写书评

暂无评论

Fast, on-line learning of globally consistent maps

引用

AUTONOMOUS ROBOTS 2002年第3期12卷 287-300页

作者： Duckett, T Marsland, S Shapiro, J Univ Orebro Dept Technol S-70182 Orebro Sweden Univ Manchester Dept Comp Sci Manchester M13 9PL Lancs England

To navigate in unknown environments, mobile robots require the ability to build their own maps. A major problem for robot map building is that odometry-based dead reckoning cannot be used to assign accurate global position information to a map because of cumulative drift errors. This paper introduces a fast, on-line algorithm for learning geometrically consistent maps using only local metric information. The algorithm works by using a relaxation technique to minimize an energy function over many small steps. The approach differs from previous work in that it is computationally cheap, easy to implement and is proven to converge to a globally optimal solution. Experiments are presented in which large, complex environments were successfully mapped by a real robot.

关键词： simultaneous localization and mapping concurrent map-building and self-localization relaxation algorithm Gibbs sampling learning and adaptation

来源：评论

学校读者我要写书评

暂无评论

Stereo matching algorithm based on modified wavelet decomposition process

引用

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

来源：评论

学校读者我要写书评

暂无评论

Efficient numerical method for linear stability analysis of solitary waves

引用

COMPUTER PHYSICS COMMUNICATIONS 2011年第12期182卷 2479-2485页

作者： Alexandrescu, Adrian Salgueiro, Jose R. Univ Vigo Dept Fis Aplicada Area Opt Orense 32004 Spain

In this paper we use a numerical relaxation algorithm to improve and generalize the obtainment of the perturbation eigenstates of nonlinear systems. As a model problem we consider the linear stability analysis of the vortex eigenstates of the cubic-quintic nonlinear Schrodinger equation. It is shown by numerical calculations that the relaxation algorithm permits accurate tracing of complex perturbation eigenvalues. (C) 2011 Elsevier B.V. All rights reserved.

关键词： Nonlinear waves Linear stability Complex eigenvalues relaxation algorithm

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：