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181.
In this note we describe a local-search heuristic (LSH) for large non-unicost set-covering problems (SCPs). The new heuristic is based on the simulated annealing algorithm and uses an improvement routine designed to provide low-cost solutions within a reasonable amount of CPU time. The solution costs associated with the LSH compared very favorably to the best previously published solution costs for 20 large SCPs taken from the literature. In particular, the LSH yielded new benchmark solutions for 17 of the 20 test problems. We also report that, for SCPs where column cost is correlated with column coverage, the new heuristic provides solution costs competitive with previously published results for comparable problems. © 1995 John Wiley & Sons, Inc. 相似文献
182.
In this article we apply perturbation analysis (PA), combined with conditional Monte Carlo, to obtain derivative estimators of the expected cost per period with respect to s and S, for a class of periodic review (s, S) inventory systems with full backlogging, linear holding and shortage costs, and where the arrivals of demands follow a renewal process. We first develop the general form of four different estimators of the gradient for the finite-horizon case, and prove that they are unbiased. We next consider the problem of implementing our estimators, and develop efficient methodologies for the infinite-horizon case. For the case of exponentially distributed demand interarrival times, we implement our estimators using a single sample path. Generally distributed interarrival times are modeled as phase-type distributions, and the implementation of this more general case requires a number of additional off-line simulations. The resulting estimators are still efficient and practical, provided that the number of phases is not too large. We conclude by reporting the results of simulation experiments. The results provide further validity of our methodology and also indicate that our estimators have very low variance. © 1994 John Wiley & Sons, Inc. 相似文献
183.
Michael H. Clemmesen 《Defense & Security Analysis》2019,35(1):96-97
The article outlines the essential role of free play elements in various types of exercises for the development of in-depth and practical military professionalism. It thereafter argues why such use of free play contradicts the military science founded Russian Way of War. 相似文献
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Michael S. Curl 《Arms and Armour》2019,16(1):27-55
Despite the lance’s status and the amount of attention the couched lance has received in historiography, study of its martial art has been neglected. The various lance types and techniques used by western European cavalry have only recently begun to receive scholarly attention. Additionally, Medieval European lance use has too often been studied in isolation, without an adequate understanding of the idiosyncratic and asymmetrical dynamics of mounted combat. Although the charge with the couched lance was a valid tactic, it was only one of many. Light and heavy lances were used in one hand or two to trip, block, unhorse, and wrestle. These techniques were governed by the harsh laws of distance, speed, impact, iron, and asymmetry. By utilizing the surviving Fechtbücher and several Peninsular and Near Eastern sources, a brief foray into the diverse techniques of lance use and their purposes has been attempted here. 相似文献
186.
Clustering problems are often difficult to solve due to nonlinear cost functions and complicating constraints. Set partitioning formulations can help overcome these challenges, but at the cost of a very large number of variables. Therefore, techniques such as delayed column generation must be used to solve these large integer programs. The underlying pricing problem can suffer from the same challenges (non‐linear cost, complicating constraints) as the original problem, however, making a mathematical programming approach intractable. Motivated by a real‐world problem in printed circuit board (PCB) manufacturing, we develop a search‐based algorithm (Rank‐Cluster‐and‐Prune) as an alternative, present computational results for the PCB problem to demonstrate the tractability of our approach, and identify a broader class of clustering problems for which this approach can be used. © 2009 Wiley Periodicals, Inc. Naval Research Logistics 2009 相似文献
187.
Why are some countries prone to ethno-nationalist conflict, whereas others are plagued by class conflict? This is a question that has seldom been raised and rarely been examined empirically. This paper presents a social-structural theory to account for the variable incidence of these two forms of political instability. These two types of conflict result from distinct principles of group solidarity – ethnicity and class – and since each individual is simultaneously a member of an ethnic group (or many such groups) and a particular class, these two principles vary in the degree to which they are mutually exclusive or cross-cutting. The degree of economic stratification between groups and economic segmentation within them shapes the relative salience of each principle of group solidarity in any society and is associated with a characteristic form of political mobilization. In places where between-group inequalities are high, and within-group inequalities low, ethnicity should be the dominant principle of group solidarity and serve as the primary basis of group conflict. By contrast, in countries where between-group inequalities are low, and within-group inequalities high, class is more likely to serve as the dominant principle of group solidarity, and conflicts along class lines are more likely. We test these conjectures with data in over 100 countries on cross-cutting cleavages, ethnic war, and class conflict. The results are supportive of the theory, and provide evidence that how groups are stratified and segmented in societies shapes the type of civil war. 相似文献
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James Dingley Shima Keene Michael Smith David Pinder 《Defense & Security Analysis》2009,25(3):313-320
190.