In this paper a model that handles costs of turns in route planning is defined, investigated and discussed. Costs are traditionally attached to edges in a graph. For some important route planning problems other costs ...
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In this paper a model that handles costs of turns in route planning is defined, investigated and discussed. Costs are traditionally attached to edges in a graph. For some important route planning problems other costs can be identified, namely costs that appear when leaving one edge and entering the next. Examples are turn restrictions, the turning angle, or the simple necessity to turn. Such costs cannot be stored as attributes of nodes or edges in the graph, and they cannot be handled correctly by shortest path algorithms without modifications. Turn costs can be represented by a pseudo-dual graph in a way that shortest path algorithms run without modifications. Although the idea is not new, it has not found much interest in the literature. The pseudo-dual graph is defined here in a new way, it is systematically investigated, and some practical applications are shown. Concentrating strictly on topology, it turns out that the pseudo-dual graph is conceptually cleaner and more efficient in route planning than alternative, currently used ways to deal with turn costs. The discussed applications are from the field of pedestrian navigation, which gave rise to this research.
This paper presents an artificial neural network (ANN) based method for estimating route travel times between individual locations in an urban traffic network. Fast and accurate estimation of route travel times is req...
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This paper presents an artificial neural network (ANN) based method for estimating route travel times between individual locations in an urban traffic network. Fast and accurate estimation of route travel times is required by the vehicle routing and scheduling process involved in many fleet vehicle operation systems such as dial-a-ride paratransit, school bus, and private delivery services. The methodology developed in this paper assumes that route travel times are time-dependent and stochastic and their means and standard deviations need to be estimated. Three feed-forward neural networks are developed to model the travel time behaviour during different time periods of the day the AM peak, the PM peak, and the off-peak. These models are subsequently trained and tested using data simulated on the road network for the City of Edmonton, Alberta. A comparison of the ANN model with a traditional distance-based model and a shortest path algorithm is then presented. The practical implication of the ANN method is subsequently demonstrated within a dial-a-ride paratransit vehicle routing and scheduling problem. The computational results show that the ANN-based route travel time estimation model is appropriate, with respect to accuracy and speed, for use in real applications.
This paper deals with the problem of optimal dynamic routing in WDM optical networks with wavelength-changing facilities available at some of the nodes. The route may be either a lightpath (i.e., wavelength continuous...
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This paper deals with the problem of optimal dynamic routing in WDM optical networks with wavelength-changing facilities available at some of the nodes. The route may be either a lightpath (i.e., wavelength continuous channel) or a semi-lightpath (i.e., wavelength-converted channel). We attempt to estimate in this work the gain in blocking probability, when we move from lightpath routing to semi-lightpath routing, keeping the number of wavelengths fixed, in a given circuit switched network. We ensure optimal (minimum cost) routing in both the cases by using the algorithm of Banerjee et al. [7,8] (called algorithm-I in this paper) for lightpaths and that of Chlamtac et al. [6] (called algorithm-II) for semi-lightpaths. Our results indicate that, for both the algorithms, the blocking probability (P-B), as expected, increases with network load. At light load, P-B for algorithm-I is always larger than that for algorithm-II. But the rate of increase in P-B is slightly higher in case of algorithm-II, so that there is a crossover point where P-B for algorithm-II exceeds P-B for algorithm-I. This probably happens due to the irregularities in the semi-lightpaths at heavy loads when almost all routes are exhausted in the network. However, since this crossover phenomenon occurs at a very congested status of the network, it has little significance over the real life operation of a network. It only suffices to indicate that, under heavy load, both the algorithms are equally insufficient, and conversion does not improve the situation as might have been expected intuitively.
This paper introduces a graph-oriented representation of metabolism, and shows how to apply the shortest path algorithm to reconstruct metabolic pathways. Our metabolic model is constructed from molecular structures o...
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This paper introduces a graph-oriented representation of metabolism, and shows how to apply the shortest path algorithm to reconstruct metabolic pathways. Our metabolic model is constructed from molecular structures of compounds and reaction formulas of enzymes, and its output is all the logically possible pathways consisting of input reactions. We also show how to integrate putative reactions in the model. (C) 2000 Elsevier Science B.V. All rights reserved.
The Human Genome project has been considered "one of the great enterprises of 20th Century Science" [8]. The ultimate goal of many efforts in molecular biology, including the Human Genome Project, is to dete...
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The Human Genome project has been considered "one of the great enterprises of 20th Century Science" [8]. The ultimate goal of many efforts in molecular biology, including the Human Genome Project, is to determine the entire sequence of human DNA and to extract genetic information from it. In this context an important step is to build restriction maps (location of certain identifiable markers) of portions of the DNA [8]. Optimal Mapping [24], [17], [21], a process that fixes elongated DNA molecules onto treated surfaces, is a very promising emerging technology for rapid production of ordered restriction maps. Our modeling and solution of detection, mass estimation, and extraction of ordered restriction maps of DNA molecules attempts to understand/answer questions of significant importance to geneticists, biologists, and chemists. In this paper we first describe the vision process that identifies the DNA molecules along with the restriction sites, and then model the restriction map problem and describe the algorithm that we use to extract the maps from the data. The input to the vision process is an image of the DNA molecules. We propose a simple Markov chain to model the DNA fragments, and use Single Source shortestpath (SSSP) algorithms to detect and measure the apparent length of the DNA fragments. This is at the heart of the imaging software in use at the laboratory for over 2 years: the practical implementation continues to undergo various fine-tuning processes. In the second part we model the ordered restriction map as a combinatorial problem which we call the Binary Flip Cut (BFC) problem. We prove hardness results for this and several of its variants and offer a practical solution using techniques from mean field annealing/EM algorithm and demonstrate its effectiveness in practice.
This paper presents a technique for smoothly blending some categories of three-dimensional polygonal objects. Polygon blending is usually considered a two-part process: generating vertex correspondences and interpolat...
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This paper presents a technique for smoothly blending some categories of three-dimensional polygonal objects. Polygon blending is usually considered a two-part process: generating vertex correspondences and interpolating between corresponding vertices to create the intermediate polygons. This paper considers the problem of automatic vertex correspondence determination. The proposed algorithm is based on the work of Sederberg and Greenwood [Computer, Graphics 26(2), 25-34, 1992]. The resulting solution tends to associate regions of the two objects which look alike. (C) 1998 Elsevier Science Ltd. All rights reserved.
Optical subscriber networks using wide bandwidth and low-loss fiber cables as infrastructures should be constructed promptly for providing ISDN services. From viewpoints of reliability and operability, the loop topolo...
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Optical subscriber networks using wide bandwidth and low-loss fiber cables as infrastructures should be constructed promptly for providing ISDN services. From viewpoints of reliability and operability, the loop topolo...
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Optical subscriber networks using wide bandwidth and low-loss fiber cables as infrastructures should be constructed promptly for providing ISDN services. From viewpoints of reliability and operability, the loop topology should be deployed as Ii cable distribution. Since considerable troublesome labor would be required for designing loop distribution networks, computer-aided design tools would be essential. This paper proposes the design method of the loop distribution based on the two shortestpaths and discusses the design method of optical cable loop distribution with respect to the fundamental networks based on the nationwide data of underground facilities. The loop distributions for subscriber networks based on the collected data are evaluated. As the results, the following points are clarified: (1) in case of a small number of assigned fibers, the number of hoops is small regardless of the regional conditions and the larger the number of assigned fibers, the larger the number of loops;(2) in small cities where large-scale future expansions are not expected, the loop structures remain almost unchanged and it is possible to install a large amount of fibers from the very beginning.
This paper describes an extension of the TNE algorithm, the objective of which is to increase its parallelism and to break the inter-processor deadlocks inherent with the use of TNE. The algorithm, which we call the S...
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ISBN:
(纸本)9780818671203
This paper describes an extension of the TNE algorithm, the objective of which is to increase its parallelism and to break the inter-processor deadlocks inherent with the use of TNE. The algorithm, which we call the SGTNE algorithm (Semi Global TNE), is executed over a cluster of processors as opposed to TNE, which is executed over a cluster of processes assigned to a single processor. SGTNE helps to break the inter-processor deadlocks by executing a shortest path algorithm over a snapshot of the LPs in a cluster of processors. This paper discusses the algorithm and its implementation and reports on the performance results of simulations of a partitioned FCFS queueing network model executed on the Intel Paragon A4 multiprocessor machine. We also examine the impact of partitioning on the efficient implementation of the SGTNE algorithm. The results obtained indicate that SGTNE yields good speedups and that a partitioning which makes use of a strongly connected component algorithm results in a reduction of 30% in the running time of a simulation when compared to simple partitioning strategies. The results also indicate that SGTNE outperforms TNE.
Let D subset-of R2 be a compact set, and let f be a continuous real-valued function on D. An algorithm is described that computes the distance (in the uniform norm parallel-to parallel-to on D) between f and the solut...
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Let D subset-of R2 be a compact set, and let f be a continuous real-valued function on D. An algorithm is described that computes the distance (in the uniform norm parallel-to parallel-to on D) between f and the solutions w of the wave equation partial derivative 2w/partial derivative s partial derivative t = 0. If, for some M > 0, W(M) subset-of C(D) is the set of solutions of the wave equation which are in the Lipschitz class Lip(M)1, the algorithm finds in W(M) a function of minimal distance from f.
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