基于主动相位控制的脉冲激光相干合成技术

提出并验证了基于随机并行梯度下降(SPGD)算法的主动相位控制脉冲激光相干合成方案.利用低通滤波器滤除脉冲激光光强变化导致的性能评价函数起伏,提取出相位噪声导致的性能评价函数变化,然后将这个低通滤波后的性能评价函数用于SPGD算法的极值寻优过程,从而实现脉冲激光的锁相.对该方案进行了理论分析和数值模拟,并进行了两路脉冲激光相干合成实验.实验结果表明,当系统从闭环到开环时,系统性能评价函数均值提高到开环的1.6倍,干涉条纹长曝光对比度从0提高到0.43.在该方案中,通过增加合成脉冲激光路数,并在各路脉冲激光中引入多级功率放大器,能够得到更高的合成功率输出.     

Coordinated pricing and inventory control problems with capacity constraints and fixed ordering cost

This article addresses a single‐item, finite‐horizon, periodic‐review coordinated decision model on pricing and inventory control with capacity constraints and fixed ordering cost. Demands in different periods are random and independent of each other, and their distributions depend on the price in the current period. Each period's stochastic demand function is the additive demand model. Pricing and ordering decisions are made at the beginning of each period, and all shortages are backlogged. The objective is to find an optimal policy that maximizes the total expected discounted profit. We show that the profit‐to‐go function is strongly CK‐concave, and the optimal policy has an (s,S,P) ‐like structure. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012     

具有战时随机延误与损耗的多配送中心路径优化

建立了具有战时随机延误与损耗的多配送中心配送路径安排模型,给出了基于随机模拟的蚁群算法。算法通过给定残存率、用时与置信度阈值,把多目标问题作为单目标来处理。用随机模拟的方法来求路径的置信度,并以此为基础搜索转移策略的临域与判断未遍历点的插入位置。算法设计了符合问题特点的从虚拟点出发的转移策略与对两类路段不同的信息素更新策略,确保算法的实现。最后,通过算例说明了该方法的可行性与有效性。     

Properties of the geometric and related processes

Some properties of the geometric process are studied along with those of a related process which we propose to call the α‐series process. It is shown that the expected number of counts at an arbitrary time does not exist for the decreasing geometric process. The decreasing version of the α‐series process does have a finite expected number of counts, under certain conditions. This process also has the same advantages of tractability as the geometric process; it exhibits some properties which may make it a useful complement to the increasing geometric process. In addition, it may be fit to observed data as easily as the geometric process. Applications in reliability and stochastic scheduling are considered in order to demonstrate the versatility of the alternative model. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005     

Failure profiles of coherent systems

In this paper we first introduce and study the notion of failure profiles which is based on the concepts of paths and cuts in system reliability. The relationship of failure profiles to two notions of component importance is highlighted, and an expression for the density function of the lifetime of a coherent system, with independent and not necessarily identical component lifetimes, is derived. We then demonstrate the way that failure profiles can be used to establish likelihood ratio orderings of lifetimes of two systems. Finally we use failure profiles to obtain bounds, in the likelihood ratio sense, on the lifetimes of coherent systems with independent and not necessarily identical component lifetimes. The bounds are relatively easy to compute and use. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004     

Deterministic and stochastic scheduling with teamwork tasks

We study a class of new scheduling problems which involve types of teamwork tasks. Each teamwork task consists of several components, and requires a team of processors to complete, with each team member to process a particular component of the task. Once the processor completes its work on the task, it will be available immediately to work on the next task regardless of whether the other components of the last task have been completed or not. Thus, the processors in a team neither have to start, nor have to finish, at the same time as they process a task. A task is completed only when all of its components have been processed. The problem is to find an optimal schedule to process all tasks, under a given objective measure. We consider both deterministic and stochastic models. For the deterministic model, we find that the optimal schedule exhibits the pattern that all processors must adopt the same sequence to process the tasks, even under a general objective function GC = F(f₁(C₁), f₂(C₂), … , f_n(C_n)), where f_i(C_i) is a general, nondecreasing function of the completion time C_i of task i. We show that the optimal sequence to minimize the maximum cost MC = max f_i(C_i) can be derived by a simple rule if there exists an order f₁(t) ≤ … ≤ f_n(t) for all t between the functions {f_i(t)}. We further show that the optimal sequence to minimize the total cost TC = ∑ f_i(C_i) can be constructed by a dynamic programming algorithm. For the stochastic model, we study three optimization criteria: (A) almost sure minimization; (B) stochastic ordering; and (C) expected cost minimization. For criterion (A), we show that the results for the corresponding deterministic model can be easily generalized. However, stochastic problems with criteria (B) and (C) become quite difficult. Conditions under which the optimal solutions can be found for these two criteria are derived. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004     

加权随机模拟的时变可靠性分析方法

针对结构时变可靠性的随机模拟分析方法计算代价大的问题,在极值方法的基础上提出基于加权随机模拟的时变可靠性分析策略。时变可靠性分析需要计算在不同时间处的失效概率,通常需要进行多次可靠性分析,计算代价巨大。所提方法通过对常规静态可靠性的随机模拟方法进行改进拓展,运用加权策略分别发展了加权蒙特卡洛法和加权重要抽样法,使之能够高效分析计算时变可靠性问题。所提方法仅需一次常规可靠性分析模拟,即可得到时变失效概率函数估计。采用管状悬臂梁和十杆桁架两个算例进行验证。结果表明,基于加权思想的分析方法在能确保精确度的前提下能够大幅度减小计算量,提高计算效率。     

反潜直升机吊声搜潜效能的建模仿真

从直升机使用吊放声纳(简称吊声)的搜潜过程入手,通过仿真环境假设,吊声搜潜效能描述,建立了吊声搜潜效能的蒙特卡洛法模型。介绍了常用搜索方法,并建立了其搜索要素表。根据模型编制了仿真程序,实现了不同搜索方法的仿真计算,为研究不同战术条件下如何合理选择有效的搜索方法奠定了基础。     

舰载直升机反潜搜索最佳方案优选模型及应用

目前,舰载直升机已成为现代水面舰艇搜潜反潜的重要力量,为了提高作战效率,对舰载直升机在反潜搜索中的战斗使用进行了研究,建立了搜索力的最优配置模型,解决了在已知目标分布的条件下舰载直升机反潜搜索中选择初始探测点、确定搜索路径、确定搜索次数以及搜索效率评估等问题,并在几种常见的目标分布下对最佳搜索方案作了实例演示,为舰载直升机的反潜战斗使用提供了依据。     

A search game with a protector

A classic problem in Search Theory is one in which a searcher allocates resources to the points of the integer interval [1, n] in an attempt to find an object which has been hidden in them using a known probability function. In this paper we consider a modification of this problem in which there is a protector who can also allocate resources to the points; allocating these resources makes it more difficult for the searcher to find an object. We model the situation as a two‐person non‐zero‐sum game so that we can take into account the fact that using resources can be costly. It is shown that this game has a unique Nash equilibrium when the searcher's probability of finding an object located at point i is of the form (1 − exp (−λ_ix_i)) exp (−μ_iy_i) when the searcher and protector allocate resources x_i and y_i respectively to point i. An algorithm to find this Nash equilibrium is given. © 2000 John Wiley & Sons, Inc. Naval Research Logistics 47:85–96, 2000