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371.
In this article we have generalized previous models on multiechelon recoverable inventory systems to cover the cases of batch ordering and shipment policy, and when items can either be repaired or condemned. The batch ordering and shipment policy is appropriate when the setup cost for shipment and order and/or the demand rates of the items are relatively high. The operating characteristics of such a system have been studied. Specifically, the probability distribution of backorder levels at the bases are analyzed for different repair-time distributions. An approximation scheme is proposed for this distribution, and is evaluated using extensive simulation results. The results indicate that the scheme is very effective in providing near-optimal stocking levels in such a system. 相似文献
372.
The orienteering problem involves the selection of a path between an origin and a destination which maximizes total score subject to a time restriction. In previous work we presented an effective heuristic for this NP-hard problem that outperformed other heuristics from the literature. In this article we describe and test a significantly improved procedure. The new procedure is based on four concepts—center of gravity, randomness, subgravity, and learning. These concepts combine to yield a procedure which is much faster and which results in more nearly optimal solutions than previous procedures. 相似文献
373.
Resource-constrained project scheduling with cash flows occurs in many settings, ranging from research and development to commercial and residential construction. Although efforts have been made to develop efficient optimal procedures to maximize the net present value of cash flows for resource-constrained projects, the inherent intractability of the problem has led to the development of a variety of heuristic methods to aid in the development of near-optimal schedules for large projects. This research focuses on the use of insights gained from the solution of a relaxed optimization model in developing heuristic procedures to schedule projects with multiple constrained resources. It is shown that a heuristic procedure with embedded priority rules that uses information from the revised solution of a relaxed optimization model increases project net present value. The heuristic procedure and nine different embedded priority rules are tested in a variety of project environments that account for different network structures, levels of resource constrainedness, and cash-flow parameters. Extensive testing with problems ranging in size from 21 to 1000 activities shows that the new heuristic procedures dominate heuristics using information from the critical path method (CPM), and in most cases outperform heuristics from previous research. The best performing heuristic rules classify activities into priority and secondary queues according to whether they lead to immediate progress payments, thus front loading the project schedule. © 1997 John Wiley & Sons, Inc. Naval Research Logistics 44: 365–381, 1997 相似文献
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优选科学合理的作战方案,是指挥员作战决策的关键。根据作战实际情况,运用五标度和六标度法量化了各因素对作战决策方案的影响指标,建立了基于多人层次分析法(GAHP)理论的优选作战决策方案数学模型,以从方案中选出作战效益最好、付出代价最小且最具可行性的方案,作为决策的具体行动依据。最后通过实例验证了模型的可操作性。GAHP方法能很好地运用不同决策者对方案的不同评价,形成最终决策,对作战指挥决策有一定的现实意义。 相似文献
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讨论一类二阶微分方程x¨+εf(x,x.)x.+g(x)=0的Poincar分岔极限环的不存在性,利用一阶Mel’nikov函数直接从整体上进行分析讨论,得出了若干充分条件和判别准则。 相似文献
378.
讨论了一类广义Linard方程x¨+f1(x)x.2+εf2(x)x.+g(x)=0的Poincar分岔极限环的唯一性和不存在性。将不对Abel积分进行分项,而是利用一阶Mel′nikov函数直接从整体上进行分析讨论,得出了若干判别准则和充分条件。 相似文献
379.
A fundamental difficulty in developing effective production planning models has been accurately reflecting the nonlinear dependency between workload and lead times. We develop a mathematical programming model for production planning in multiproduct, single stage systems that captures the nonlinear dependency between workload and lead times. We then use outer linearization of this nonlinear model to obtain a linear programming formulation and extend it to multistage systems. Extensive computational experiments validate the approach and compare its results to conventional models that assume workload‐independent planning lead times. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009 相似文献
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