Modeling and analysis of a mixed‐model assembly line with stochastic operation times

We consider a mixed‐model assembly line (MMAL) comprised a set of workstations and a conveyor. The workstations are arranged in a serial configuration. The conveyor moves at a constant speed along the workstations. Initial units belonging to different models are successively fed onto the conveyor, and they are moved by the conveyor to pass through the workstations to gradually generate final products. All assembling tasks are manually performed with operation times to be stochastic. An important performance measure of MMALs is overload times that refer to uncompleted operations for operators within their work zones. This paper establishes a method to analyze the expected overload times for MMALs with stochastic operation times. The operation processes of operators form discrete time nonhomogeneous Markov processes with continuous state spaces. For a given daily production schedule, the expected overload times involve in analyzing the Markov processes for finite horizon. Based on some important properties of the performance measure, we propose an efficient approach for calculating the expected overload times. Numerical computations show that the results are very satisfactory. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

Estimation of average backorders for an assemble‐to‐order system with random batch demands through extreme statistics

We investigate inventory management for a large‐scale multi‐product, multi‐component Assemble‐to‐Order system with general random batch demands. Results from extreme statistics theory are applied in developing approximation schemes for a widely used performance measure, customer backorders. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

一类多维双重时序 AR(1)-MA(q) 模型的平稳性

讨论了一类多维双重时序ＡＲ（１）－ＭＡ（ｑ）模型的二阶平稳性问题。通过导出一组线性方程组，给出了这类模型二阶平稳的显式充分条件和必要条件，为验证模型的二阶平稳性提供了一个可行的途径。     

环形区域极点/协方差约束下的模型简化设计

提出离散随机系统模型简化的一种新方法,即环形区域极点／协方差约束下的模型简化方法。这种设计方法的基本思路是构造指定维数的降阶模型,使其匹配给定的环形区域极点和稳态协方差参数,在系统的动态特性和稳态特性方面逼近给定的满阶模型。文中导出了期望的简化模型的存在条件及解析表达式,并提供了一个数值算例。     

浅析炮车比

本文以坦克发射时车体的角振幅和乘员所受加速度不超过一定值为基础,推导了炮车比极限值的理论公式;并对影响炮车比极值的因素进行了分析,最后,以59式坦克为例得出炮车比不超过1.71,该结论具有普遍意义.     

关于潜艇装备劳兰C导航仪技术问题的研究

本文提出了一种改善潜艇现有天线接收性能的方法,从而解决了在潜艇上安装使用劳兰C导航仪的关键技术问题。     

C~3I系统的决策时延分析

决策是C~3I 系统的核心问题之一。用Petri 网理论研究C~3I 系统的决策问题已取得了长足的进展。根据决策过程各阶段之所需时间具有随机性及不独立性的特点,以变迁发射时间不独立的随机Petri 网作为决策时延的建模与分析工具,并给出了这种随机Petri 网模型的一般分析方法。     

优序法在舰艇编队导弹攻击效能评估中的应用

导弹攻击是舰艇编队海上行动的主要作战样式,其导弹攻击效能的评估十分重要。首先建立了舰艇编队导弹攻击作战效能评价指标体系,然后介绍了评估舰艇编队导弹攻击效能的一种新方法——优序法,该方法应用简单,既可以处理定性问题,又能处理定量问题。最后给出了应用实例,验证了优序法比较适合于对舰艇编队导弹攻击效能进行评估。通过对舰艇编队导弹攻击效能的评估,可以有效地选用合适的舰艇编队样式。     

Volume discount decisions: Wealth maximization or EOQ approach?

A recent paper finds that when volume discounts are available, in some cases, reliance on the Economic Order Quantity (EOQ) model can induce purchasers to make wealth reducing decisions, and the Present Value (PV) approach should be preferred. While this finding is theoretically correct, the magnitudes of wealth reductions suggested by the paper's numerical examples seem to be questionable. Furthermore, the paper also finds that, in some other cases, a purchaser using the EOQ approach realizes a net increase in current wealth compared to a purchaser using the PV approach. Logic suggests that such a finding cannot be correct, since by its very definition, it is the PV approach that seeks to maximize the current wealth. We offer an alternative frame of comparison and a modified model to show that, under the paper's assumptions, the EOQ approach can never realize a net increase in current wealth compared to the current wealth generated by the PV approach. On the other hand, we also show that when typical values of the relevant parameters prevail, the additional costs imposed by the EOQ approach are not significant. Finally, we suggest that insofar as the PV approach requires greater administrative costs to implement, it may even be counterproductive to the goal of wealth maximization. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 377–389, 1998     

On lifetimes in random environments

For a component operating in random environment, whose hazard rate is assumed to be the realization of a suitable increasing stochastic process, conditions are found such that its lifetime is increasing in likelihood ratio (ILR). For the lifetimes of two components of the same kind some comparisons based on partial stochastic orders are presented. Some applications to the case of repairable components are finally provided. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 365–375, 1998