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## Network Problem (network + problem)
## Selected Abstracts## Solving generalized transportation problems via pure transportation problems NAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 7 2002Elsie Sterbin GottliebAbstract This paper investigates certain issues of coefficient sensitivity in generalized network problems when such problems have small gains or losses. In these instances, it might be computationally advantageous to temporarily ignore these gains or losses and solve the resultant "pure" network problem. Subsequently, the optimal solution to the pure problem could be used to derive the optimal solution to the original generalized network problem. In this paper we focus on generalized transportation problems and consider the following question: Given an optimal solution to the pure transportation problem, under what conditions will the optimal solution to the original generalized transportation problem have the same basic variables? We study special cases of the generalized transportation problem in terms of convexity with respect to a basis. For the special case when all gains or losses are identical, we show that convexity holds. We use this result to determine conditions on the magnitude of the gains or losses such that the optimal solutions to both the generalized transportation problem and the associated pure transportation problem have the same basic variables. For more general cases, we establish sufficient conditions for convexity and feasibility. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 666,685, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10034 [source] ## Approximation algorithm for the group Steiner network problem NETWORKS: AN INTERNATIONAL JOURNAL, Issue 2 2007Michal PennAbstract In this article we study the group Steiner network problem, which is defined in the following way. Given a graph G = (V,E), a partition of its vertices into K groups and connectivity requirements between the different groups, the aim is to find simultaneously a set of representatives, one for each group, and a minimum cost connected subgraph that satisfies the connectivity requirements between the groups (representatives). This problem is a generalization of the Steiner network problem and the group Steiner tree problem, two known NP-complete problems. We present an approximation algorithm for a special case of the group Steiner network problem with an approximation ratio of min {2(1 + 2x),2I}, where I is the cardinality of the largest group and x is a parameter that depends on the cost function. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 49(2), 160,167 2007 [source] ## Solution methods for the p -median problem: An annotated bibliography NETWORKS: AN INTERNATIONAL JOURNAL, Issue 3 2006J. ReeseAbstract The p -median problem is a network problem that was originally designed for, and has been extensively applied to, facility location. In this bibliography, we summarize the literature on solution methods for the uncapacitated and capacitated p -median problem on a network. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(3), 125,142 2006 [source] ## The 2-path network problem NETWORKS: AN INTERNATIONAL JOURNAL, Issue 3 2004Geir DahlAbstract Given a graph with nonnegative edge weights and a set D of node pairs, the 2- path network problem requires a minimum weight set of edges such that the induced subgraph contains a path with one or two edges connecting each pair in D. The problem is NP -hard. We present two integer programming models for the problem and study properties of associated polytopes, including cutting planes. Two approximation algorithms are suggested and analyzed. Some computational experience is reported. © 2004 Wiley Periodicals, Inc. [source] ## System aspects of 1100 kV AC transmission technologies in Japan IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 1 2009Eiichi Zaima Senior MemberAbstract This paper describes the system aspects of 1100 kV AC transmission technologies with the UHV transmission project in Japan. For realization of technical and economical optimization throughout the design of the transmission line and the substation, solutions for network problems and insulation coordination specific to UHV AC transmission systems were studied in Japan. They include fast multiphase reclosing systems by HSGS (High Speed Grounding Switch) and overvoltage control by the application of surge arresters and circuit breakers with closing/opening resistors. These sophisticated technologies provide highly reliable and economical 1100 kV substations and transmission lines. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] ## A framework for network quality monitoring in the VoIP environment INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 4 2007Ana Fląvia M. de LimaMonitoring speech quality in Voice over IP (VoIP) networks is important to ensure a minimal acceptable level of speech quality for IP calls running through a managed network. Information such as packet loss, codec type, jitter, end-to-end delay and overall speech quality enables the network manager to verify and accurately tune parameters in order to adjust network problems. The present article proposes the deployment of a monitoring architecture that collects, stores and displays speech quality information about concluded voice calls. This architecture is based on our proposed MIB (Management Information Base) VOIPQOS, deployed for speech quality monitoring purposes. Currently, the architecture is totally implemented, but under adjustment and validation tests. In the future, the VOIPQOS MIB can be expanded to automatically analyze collected data and control VoIP clients and network parameters for tuning the overall speech quality of ongoing calls. Copyright © 2006 John Wiley & Sons, Ltd. [source] ## Solving generalized transportation problems via pure transportation problems NAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 7 2002Elsie Sterbin GottliebAbstract This paper investigates certain issues of coefficient sensitivity in generalized network problems when such problems have small gains or losses. In these instances, it might be computationally advantageous to temporarily ignore these gains or losses and solve the resultant "pure" network problem. Subsequently, the optimal solution to the pure problem could be used to derive the optimal solution to the original generalized network problem. In this paper we focus on generalized transportation problems and consider the following question: Given an optimal solution to the pure transportation problem, under what conditions will the optimal solution to the original generalized transportation problem have the same basic variables? We study special cases of the generalized transportation problem in terms of convexity with respect to a basis. For the special case when all gains or losses are identical, we show that convexity holds. We use this result to determine conditions on the magnitude of the gains or losses such that the optimal solutions to both the generalized transportation problem and the associated pure transportation problem have the same basic variables. For more general cases, we establish sufficient conditions for convexity and feasibility. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 666,685, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10034 [source] |