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排序方式: 共有174条查询结果,搜索用时 15 毫秒
1.
Given a collection of n locations and a symmetric measure of distance (difference) between each pair of locations, we seek to identify (select) a subset of p locations so as to achieve two distinct objectives. The first objective is to use the selected locations as centers (medians) of p groups that would partition the entire collection and minimize the total distance between the locations and their respective group medians. The second objective is to maximize the minimum distance (diversity) among the selected locations themselves. We study this problem as a multi-objective optimization problem and propose an iterative algorithm to obtain its non-dominated frontier. At each iteration we construct and solve a 0–1 integer programming problem. Through a computational experiment we show that this algorithm is computationally effective for small to medium size instances of the problem. We also propose a Lagrangian heuristic algorithm for solving larger instances of this problem. 相似文献
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大中型水轮发电机的定子,因外形尺寸大,受到运输条件的限制,其定子机座采用分瓣制造运输,在安装现场进行组装焊接、铁芯堆积及定子下线。定子铁损试验是在定子铁芯冲片叠装、压紧后进行,通过测量铁损、温升及温差的方法检查定子铁芯冲片的制造及叠装整体质量,定子铁芯制造及安装质量好坏关系着机组的长期安全运行。文章对弄令电站1#发电机定子铁损试验的实施进行了研究分析。 相似文献
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求解VLSI 电路划分问题的混合粒子群优化算法 总被引:5,自引:0,他引:5
电路划分是VLSI物理设计过程中的一个关键阶段.该问题本质上是一个NP困难的组合优化问题.针对该问题,提出了一种带FM策略的混合粒子群优化算法.引入遗传算法的两点交叉算子和随机两点交换变异算子,保证了粒子在位置更新后依然可行;为了提高算法的局部搜索能力,将具有较强局部搜索能力的FM策略融入算法的位置更新;设计了种群多样性变异策略,提高了种群多样性,避免了易陷入局部最优的缺陷.对ISCAS89标准测试电路的仿真实验结果表明,所构造的算法是有效的. 相似文献
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Texture analysis provides a means to quantify complex changes in microscope images. We previously showed that cytoplasmic poly-adenylated mRNAs form mRNA granules in post-ischemic neurons and that these granules correlated with protein synthesis inhibition and hence cell death. Here we utilized the texture analysis software MaZda to quantify mRNA granules in photomicrographs of the pyramidal cell layer of rat hippocampal region CA3 around 1 h of reperfusion after 10 min of normothermic global cerebral ischemia. At 1 h reperfusion, we observed variations in the texture of mRNA granules amongst samples that were readily quantified by texture analysis. Individual sample variation was consistent with the interpretation that animal-to-animal variations in mRNA granules reflected the time-course of mRNA granule formation. We also used texture analysis to quantify the effect of cycloheximide, given either before or after brain ischemia, on mRNA granules. If administered before ischemia, cycloheximide inhibited mRNA granule formation, but if administered after ischemia did not prevent mRNA granulation, indicating mRNA granule formation is dependent on dissociation of polysomes. We conclude that texture analysis is an effective means for quantifying the complex morphological changes induced in neurons by brain ischemia and reperfusion. 相似文献
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一类离散事件系统的一步极大允许无冗余控制* 总被引:2,自引:0,他引:2
本文考虑用一般标识图模型描述的一类离散事件系统的禁止状态问题。在文[1]基础上,分析了允许控制策略对观测和控制时延的鲁棒性;给出了一步极大允许无冗余反馈控制策略的判据和搜索方法;导出了系统在一个并发活动序列发射后仍保持极大允许性的条件,即对应的并发活动序列的特征。 相似文献
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Solution techniques for Markov decision problems rely on exact knowledge of the transition rates, which may be difficult or impossible to obtain. In this paper, we consider Markov decision problems with uncertain transition rates represented as compact sets. We first consider the problem of sensitivity analysis where the aim is to quantify the range of uncertainty of the average per‐unit‐time reward given the range of uncertainty of the transition rates. We then develop solution techniques for the problem of obtaining the max‐min optimal policy, which maximizes the worst‐case average per‐unit‐time reward. In each of these problems, we distinguish between systems that can have their transition rates chosen independently and those where the transition rates depend on each other. Our solution techniques are applicable to Markov decision processes with fixed but unknown transition rates and to those with time‐varying transition rates. 相似文献
8.
Manbir S. Sodhi Alessandro Agnetis Ronald G. Askin 《International Journal of Flexible Manufacturing Systems》1994,6(4):287-310
The allocation of tools to machines determines potential part routes in flexible manufacturing systems. Given production requirements and a minimum feasible set of tools, the decision of how to fill vacant slots in tool magazines to maximize routing flexibility is shown to be a minimum cost network flow problem for the cases when routing flexibility is a function of the average workload per tool aggregated over tool types, or of the number of possible routes through the system. A linear programming model is then used to plan a set of routes for each part type so as to minimize either the material handling requirement or the maximum workload on any machine. The impact of these tool addition strategies on the material handling and workload equalization is investigated and computational results presented. The advantage of the overall approach is computational simplicity at each step and the ability to react to dynamic changes.This article is based upon work supported by the National Science Foundation under Grants No. DMC 85–44993 and DDM 92–15432.This work was done by the author while visiting the SIE Department of the University of Arizona. 相似文献
9.
In this paper, robust disturbance‐feedback strategies for finite time‐horizon problems are studied. Linear discrete‐time systems subject to linear control, state constraints, and quadratic objective functions are considered. In addition, persistent disturbances, which enter the system additively and are contained in a polytopic set, act on the system. The synthesis of robust strategies leads in the case of the traditional robust state‐feedback and open‐loop min–max strategies to, respectively, nonconvex problems or conservatism. However, robust disturbance‐feedback problems can easily be reformulated as convex problems and solved by tractable linear matrix inequalities. Hence this approach bypasses the nonconvexity issue while maintaining the advantages of feedback strategies. As a key result, it is shown that both sources of conservatism attributed to this approach, namely, the relaxation method and the affine parametrization, can be removed at the expense of an increase in computational effort. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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