The Internet shopping optimization problem arises when a customer aims to purchase a list of goods from a set of web-stores with a minimum total cost. This problem is NP-hard in the strong sense. We are interested in ...
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The Internet shopping optimization problem arises when a customer aims to purchase a list of goods from a set of web-stores with a minimum total cost. This problem is NP-hard in the strong sense. We are interested in solving the Internet shopping optimization problem with additional delivery costs associated to the web-stores where the goods are bought. It is of interest to extend the model including price discounts of goods. The aim of this paper is to present a set of optimization algorithms to solve the problem. Our purpose is to find a compromise solution between computational time and results close to the optimum value. The performance of the set of algorithms is evaluated through simulations using real world data collected from 32 web-stores. The quality of the results provided by the set of algorithms is compared to the optimal solutions for small-size instances of the problem. The optimization algorithms are also evaluated regarding scalability when the size of the instances increases. The set of results revealed that the algorithms are able to compute good quality solutions close to the optimum in a reasonable time with very good scalability demonstrating their practicability.
Printers usually generate a limited number of colors and lack the ability of producing continuous-tone color images. Traditional error-diffusion algorithms are used to solve this problem. Compared with other approache...
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Printers usually generate a limited number of colors and lack the ability of producing continuous-tone color images. Traditional error-diffusion algorithms are used to solve this problem. Compared with other approaches, the approaches of using error-diffusion in general can generate halftoned images of better quality. However, smeared edges and textures may occur in these halftoned images. To produce halftoned images of higher quality, these artifacts due to unstable images, dot-overlap, and error-diffusion must be eliminated or reduced. In this paper, we show that unstable images can be eliminated or reduced through using a proper color difference formula to select the reproduction colors even vector error-diffusion is performed in the RGB domain. We also present a method of using different filters to halftone different components of a color. This approach may have clearer and sharper edges for halftoned color images. Unexpected colors may be generated due to dot-overlap in the printing process. We have presented a method to eliminate this color distortion in the process of error-diffusion. Halftorting a color image by our proposed error-diffusion algorithm with edge enhancement has the following characteristics: the unstable images do not exist;the color-error caused by dot-overlap is corrected;and the smeared edges are sharpened. (C) 2003 Elsevier Inc. All rights reserved.
The Chinese postman problem on mixed networks (MCPP), is a practical generalization of the classical Chinese postman problem (CPP), which has many real-world applications. The MCPP has been shown to be NP-complete. Th...
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The Chinese postman problem on mixed networks (MCPP), is a practical generalization of the classical Chinese postman problem (CPP), which has many real-world applications. The MCPP has been shown to be NP-complete. Therefore, it is difficult to solve the problem exactly. For this reason, heuristic solution procedures have been proposed to solve the problem approximately. In this paper, we first review two existing solution procedures proposed by Edmonds and Johnson [Math. Progr. 5, 88-124 (1973)], and Frederickson [J. Assoc. Comput. Mach. 26, 538-554 (1979)], then introduce two new algorithms to solve the MCPP near optimally. The proposed new algorithms are tested and compared with the existing solution procedures. Computational results showed that the two new algorithms significantly outperformed the existing solution procedures.
Geomagnetic measurements are important in space weather and engineering applications of earth-orbiting satellites. This research presents an innovative algorithm that enables high-quality magnetic field measurements o...
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Geomagnetic measurements are important in space weather and engineering applications of earth-orbiting satellites. This research presents an innovative algorithm that enables high-quality magnetic field measurements on spacecraft without booms. The algorithm estimates the background field using multiple magnetometers and current telemetry on board a spacecraft. Results of a hardware-in-the-loop simulation showed an order of magnitude reduction in the magnetic effects of spacecraft onboard time-varying currents-from 300 nT to an average residual of 15 nT.
This paper summarises a study of terrain-scattered interference (TSI) mitigation techniques, focusing on joint TSI mitigation and monostatic clutter nulling for airborne radars. It begins with an overview of TSI pheno...
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This paper summarises a study of terrain-scattered interference (TSI) mitigation techniques, focusing on joint TSI mitigation and monostatic clutter nulling for airborne radars. It begins with an overview of TSI phenomenology and two-dimensional space-time adaptive processing (STAP) techniques for cancelling TSI. Two approaches for mitigating combined TSI and clutter are then examined. In the first approach, a sequence of two-dimensional adaptive filters is used. The first of these filters cancels TSI, while the second filter cancels monostatic clutter. In the second approach, a single, three-dimensional pre-Doppler STAP algorithm is used to cancel clutter and TSI simultaneously. Performance results for a representative system are shown to illustrate the trade-offs inherent in designing a mitigation approach.
Very effective detection of spontaneous combustion or open fires in coal mines can be provided from calculations based on measurements of a few parts per million of carbon monoxide (CO) in the ventilating air, even in...
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Very effective detection of spontaneous combustion or open fires in coal mines can be provided from calculations based on measurements of a few parts per million of carbon monoxide (CO) in the ventilating air, even in the presence of CO from shotfiring, diesels and other sources. A project to develop automatic alarms is described. Forecasting/smoothing methods were abandoned in favour of the development of a model of normal conditions as a Markov process, with an associated sequential hypothesis test. Various approximations and assumptions allowed the derivation of algorithms to suit different circumstances, including both continuous and intermittent sampling of CO. In each case, the calculation of alarm levels for individual locations was an important part of the algorithm. The model allowed the most to be made of a minimal knowledge of rare events (i.e. heatings). The `quick and dirty' algorithms proposed are simple enough to allow an 8 bit micro to monitor 20 points while simultaneously revising alarm levels; yet being derived from a good model, they are effective, well behaved and adaptable.
This paper deals with the problem of sequencing robot activities for a robot-centered parallel-processor workcell where n jobs and m identical processors exist in the cell, and a robot is responsible for both loading ...
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This paper deals with the problem of sequencing robot activities for a robot-centered parallel-processor workcell where n jobs and m identical processors exist in the cell, and a robot is responsible for both loading and unloading activities. The objective of this paper is to determine the sequence of robot activities for minimizing the sum of completion times. A modified shortest processing time procedure based on the traditional shortest processing time sequencing rule in order to determine an upper bound has been proposed. A branch and bound algorithm to find an optimal sequence of robot activities has then been presented. A numerical example is illustrated and the computational results have been given.
The process of categorizing packets into "flows" in an Internet router is called pocket classification. All packets belonging to the same flow obey a predefined rule and are processed in a similar manner by ...
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The process of categorizing packets into "flows" in an Internet router is called pocket classification. All packets belonging to the same flow obey a predefined rule and are processed in a similar manner by the router. For example, all packets with the same source and destination IP addresses may be defined to form a flow. Packet classification is needed for non-best-effort services, such as firewalls and quality of service;services that require the capability to distinguish and isolate traffic in different flows for suitable processing. In general, packet classification on multiple fields is a difficult problem. Hence, researchers have proposed a variety of algorithms which, broadly speaking, can be categorized as basic search algorithms, geometric algorithms, heuristic algorithms, or hardware-specific search algorithms. In this tutorial we describe algorithms that are representative of each category, and discuss which type of algorithm might be suitable for different applications.
We initiate the study of the following problem: Given a non-planar graph G and a planar subgraph S of G, does there exist a straight-line drawing Gamma of G in the plane such that the edges of S are not crossed in Gam...
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We initiate the study of the following problem: Given a non-planar graph G and a planar subgraph S of G, does there exist a straight-line drawing Gamma of G in the plane such that the edges of S are not crossed in Gamma by any edge of G? We give positive and negative results for different kinds of connected spanning subgraphs S of G. Moreover, in order to enlarge the subset of instances that admit a solution, we consider the possibility of bending the edges of G not in S;in this setting we discuss different trade-offs between the number of bends and the required drawing area. (C) 2015 Elsevier BAT. All rights reserved.
Presents an evaluation of the algorithms that perform harmonic analysis using a corpus of excerpts of tonal music. Major tasks in harmonic analysis; Comparison of the labeling performance of algorithm using tie-breaki...
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Presents an evaluation of the algorithms that perform harmonic analysis using a corpus of excerpts of tonal music. Major tasks in harmonic analysis; Comparison of the labeling performance of algorithm using tie-breaking rules against its performance without the use of tie breaking; Classes that resulted from labeling errors.
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