An (s,S) model for inventory with exponential lifetimes and renewal demands

Inventory control of products with finite lifetimes is important in many modern business organizations. It has been an important and difficult research subject. Here, we study the (s, S) continuous review model for items with an exponential random lifetime and a general renewal demand process through a Markov process. We derive a fundamental rate conservation theorem and show that all the other system performance measures can be obtained easily through the expected reorder cycle length. This leads to a simple expression for the total expected long run cost rate function in terms of the expected reorder cycle length. Subsequently, we derive formulas for computing the expected cycle lengths for the general renewal demand as well as for a large class of demands characterized by the phase type interdemand time distribution. We show analytically when the cost as a function of the reorder level is monotone, concave, or convex. We also show analytically that, depending on the behavior of the expected reorder cycle, the cost as a function of the order‐up level is either monotone increasing or unimodal. These analytical properties enable us to understand the problem and make the subsequent numerical optimization much easier. Numerical studies confirm and illustrate some of the analytical properties. The results also demonstrate the impact of various parameters on the optimal policy and the cost. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 39–56, 1999     

Efficient budget allocation strategies for elementary effects method in stochastic simulation

This paper focuses on extending the Morris' elementary effects method (MM) for sensitivity analysis/factor screening originated in the context of deterministic computer experiments to the stochastic simulation setting. Given a fixed simulation budget to expend, the main objective is to provide efficient and accurate estimates of main and interaction (or nonlinear) effects coined by the standard MM for characterizing the importance of each factor, despite the impact of simulation errors. Taking into account both the factor/input sampling uncertainty rooted in MM and the random errors inherent in a stochastic simulation, we develop efficient budget allocation strategies for implementing MM in this new context. Under each strategy proposed, we derive its corresponding optimal budget partition and optimal budget allocation rules. Numerical results corroborate the practical effectiveness of the proposed budget allocation strategies.     

Operations sequencing for a multi‐stage production inventory system

This article studies operations sequencing for a multi‐stage production inventory system with lead times under predictable (deterministic) yield losses and random demand. We consider various cases with either full or partial release of work‐in‐process inventories, for either pre‐operation or post‐operation cost structures, and under either the total discounted or average cost criteria. We derive necessary and sufficient criteria for the optimal sequence of operations in all cases. While the criteria differ in their specific forms, they all lead to the same principal: those operations with (1) lower yields, (2) lower processing costs, (3) longer lead times, and (4) lower inventory holding costs should be placed higher upstream in the system.Copyright © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 144–154, 2014     

张学良的军事思想

爱国救国是张学良军事思想的最主要内容,他先后提出过"息内战、御外侮",实现全国抗战、联共抗日等政治思想主张。为了将军队建设成一支能抗御外侮、保国卫民的武装力量,还提出了一系列建军治军的思想。张学良的爱国军事思想是他发动西安事变的重要驱动力,西安事变是张学良爱国军事思想的逻辑发展。     

按照新使命的需求深入推进军队建设转型

履行好我军新的历史使命,必须准确把握新世纪新阶段我军历史使命的科学内涵和时代背景,解决军队建设中的“两个不相适应”的主要矛盾,处理好军队建设转型与社会改革、军事斗争准备和国家经济建设的关系,加速推进军队建设转型,以满足国家对军队的新需求。     

基于Hill方程的编队卫星群运动分析与轨道设计

从Hill方程出发 ,研究了绕飞轨道的性质及编队卫星群的轨道设计方法。从三方面对绕飞轨道进行了描述 :坐标平面投影 ,与坐标平面的夹角 ,绕飞轨道根数。编队卫星群的轨道设计分两步进行 :先求基本环绕卫星的轨道根数 ;再求其它环绕卫星的轨道根数。仿真结果表明 ,此方法适用于编队飞行的初步设计     

基于谐波恢复方法的直升机声信号特征提取

在对直升机声信号特征进行分析之后,提出了一种基于谐波恢复的ESPRIT方法来提取直升机声信号谐波频率作为特征用以识别直升机声目标。同时对ESPRIT方法与其它方法在提取谐波能力方面作了比较。最后对实测的直升机声信号进行了谐波提取。各种结果均显示谐波恢复的ESPRIT方法在提取谐波频率方面较之其它方法更为优越,用它提取直升机声信号特征是十分有效的。     

一种用于声目标识别的小波变换去噪方法

根据受噪声污染信号的小波变换系数中对信号有贡献的仅占其很小一部分的事实,提出了一种基于系数门限值去噪的方法。对不同信号的仿真结果表明该方法去噪效果明显,运算量小,适合用于对声目标识别系统的噪声去除。这对于改善声目标识别系统的抗噪性能是十分有意义的。     

观瞄仪器微控MTF测量

为了全面客观地评价观瞄仪器成像质量,介绍采用光电探测原理和微机控制的信息处理技术,对观瞄仪器进行调制传递函数(MTF)测量的方法;用该方法全面评价观瞄仪器质量,具有操作简单,速度快,精度高,测量周期短的特点,适用于不同场合对各类观瞄仪器进行MTF(f)测量。     

试论军校课程管理的几个问题

论述了军校课程管理的地位、作用和任务,军校课程管理目标和管理范畴,以及军校课程管理的6项基本原则,并提出了加强军校课程管理的若干有效途径。