Dynamic routing of prioritized warranty repairs

Recent years have seen a strong trend toward outsourcing warranty repair services to outside vendors. In this article we consider the problem of dynamically routing warranty repairs to service vendors when warranties have priority levels. Each time an item under warranty fails, it is sent to one of the vendors for repair. Items covered by higher priority warranty receive higher priority in repair service. The manufacturer pays a fixed fee per repair and incurs a linear holding cost while an item is undergoing or waiting for repair. The objective is to minimize the manufacturer's long‐run average cost. Because of the complexity of the problem, it is very unlikely that there exist tractable ways to find the optimal routing strategies. Therefore, we propose five heuristic routing procedures that are applicable to real‐life problems. We evaluate the heuristics using simulation. The simulation results show that the index‐based “generalized join the shortest queue” policy, which applies a single policy improvement step to an initial state‐independent policy, performs the best among all five heuristics. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

一种克服火控系统假定误差的方法

阐述了假定误差是当前高炮火控系统的最大误差 ,也是最难克服的误差 ,借鉴航空火控的热线原理 ,利用人对机动目标的模糊预测能力 ,提出了一种人机结合的火控系统工作原理。这是高炮火控系统克服假定误差的一种途径     

卫星移动通信信道模型及仿真

对移动卫星通信的三种典型信道进行了完整的理论分析.通信信号在不同的信道参数条件下,经过瑞利(Rayleingh)信道、莱斯(Rician)信道和阻挡效应下的莱斯信道(Rician/Lognormal)进行了计算机仿真,得到了仿真结果.经分析比较发现,信道参数不同,得到的误码率曲线不同.信道的性能主要取决于信道参数,各种因素的影响可以归结到这些参数的影响,理论分析和仿真实验结果一致.     

虚拟电流注入法在线补偿转子位置估算误差

旋转高频注入法能估计永磁同步电机零速和低速时的转子位置,但在转子磁极位置解调过程中滤波器的使用会带来较大估算误差.提出虚拟电流注入法来在线补偿转子位置误差,基于估算的转速,构造与负序响应电流同频率的虚拟电流,经过与负序电流完全相同的解调,得到的虚拟电流相位与解调前相位的差值补偿估算的转子位置.分析比较了注入旋转电压导致...     

Approximate dynamic programming methods for an inventory allocation problem under uncertainty

We propose two approximate dynamic programming methods to optimize the distribution operations of a company manufacturing a certain product at multiple production plants and shipping it to different customer locations for sale. We begin by formulating the problem as a dynamic program. Our first approximate dynamic programming method uses a linear approximation of the value function and computes the parameters of this approximation by using the linear programming representation of the dynamic program. Our second method relaxes the constraints that link the decisions for different production plants. Consequently, the dynamic program decomposes by the production plants. Computational experiments show that the proposed methods are computationally attractive, and in particular, the second method performs significantly better than standard benchmarks. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006     

Optimal pricing and inventory control policy in periodic‐review systems with fixed ordering cost and lost sales

This paper studies a periodic‐review pricing and inventory control problem for a retailer, which faces stochastic price‐sensitive demand, under quite general modeling assumptions. Any unsatisfied demand is lost, and any leftover inventory at the end of the finite selling horizon has a salvage value. The cost component for the retailer includes holding, shortage, and both variable and fixed ordering costs. The retailer's objective is to maximize its discounted expected profit over the selling horizon by dynamically deciding on the optimal pricing and replenishment policy for each period. We show that, under a mild assumption on the additive demand function, at the beginning of each period an (s,S) policy is optimal for replenishment, and the value of the optimal price depends on the inventory level after the replenishment decision has been done. Our numerical study also suggests that for a sufficiently long selling horizon, the optimal policy is almost stationary. Furthermore, the fixed ordering cost (K) plays a significant role in our modeling framework. Specifically, any increase in K results in lower s and higher S. On the other hand, the profit impact of dynamically changing the retail price, contrasted with a single fixed price throughout the selling horizon, also increases with K. We demonstrate that using the optimal policy values from a model with backordering of unmet demands as approximations in our model might result in significant profit penalty. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2006     

A multilevel passenger screening problem for aviation security

Passenger prescreening is a critical component of aviation security systems. This paper introduces the Multilevel Allocation Problem (MAP), which models the screening of passengers and baggage in a multilevel aviation security system. A passenger is screened by one of several classes, each of which corresponds to a set of procedures using security screening devices, where passengers are differentiated by their perceived risk levels. Each class is defined in terms of its fixed cost (the overhead costs), its marginal cost (the additional cost to screen a passenger), and its security level. The objective of MAP is to assign each passenger to a class such that the total security is maximized subject to passenger assignments and budget constraints. This paper shows that MAP is NP‐hard and introduces a Greedy heuristic that obtains approximate solutions to MAP that use no more than two classes. Examples are constructed using data extracted from the Official Airline Guide. Analysis of the examples suggests that fewer security classes for passenger screening may be more effective and that using passenger risk information can lead to more effective security screening strategies. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006     

直升机超视距主动引导定位误差分析

针对用直升机引导超视距导弹攻击目标的需求,对直升机超视距引导定位的误差来源进行探讨,利用微分原理求解三角形误差的方法,建立惯导大地法、航姿大地法、双向定位法三种不同引导定位方法的误差求解模型。利用误差来源数据进行编程解算模型,最后得出定位误差分析结论,为舰载反舰导弹精确超视距攻击提供有益的参考。     

复合制导防空导弹中末制导交班问题研究

根据防空导弹武器系统发展趋势,分析了中末制导交班问题的来源和研究的必要性,然后分析了影响中末制导交班的主要误差源,并计算了方位和俯仰平面导引头指向误差,讨论了不同条件下的交班问题。     

动态教学法在《政治学原理》课程教学中的运用

政治学原理课程在授课过程中存在着教材内容的确定性和稳定性,而无论从国际国内形势还是从政治学研究而言,政治学所关注的范围和内容又都处于动态的不断发展变化的。笔者以为,只有在授课中具体运用动态教学法,通过联系学生自身、联系社会现实、联系国家大事、联系国际政治等实际,才能使政治学原理课程在马克思主义基本原则的指导下,更富有时代特征和生活气息,使学生真正学有所获。