Optimal joint preventive maintenance and production policies

We study joint preventive maintenance (PM) and production policies for an unreliable production‐inventory system in which maintenance/repair times are non‐negligible and stochastic. A joint policy decides (a) whether or not to perform PM and (b) if PM is not performed, then how much to produce. We consider a discrete‐time system, formulating the problem as a Markov decision process (MDP) model. The focus of the work is on the structural properties of optimal joint policies, given the system state comprised of the system's age and the inventory level. Although our analysis indicates that the structure of optimal joint policies is very complex in general, we are able to characterize several properties regarding PM and production, including optimal production/maintenance actions under backlogging and high inventory levels, and conditions under which the PM portion of the joint policy has a control‐limit structure. In further special cases, such as when PM set‐up costs are negligible compared to PM times, we are able to establish some additional structural properties. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005.     

Some order relations in closed networks of queues with multiserver stations

Consider a closed network of queues of the “product-form” type, where each station has s servers (s ≥ 1 is identical for all stations). We show that the throughput function of the network is Schur concave with respect to the loading of the stations and arrangement increasing with respect to the assignment of server groups. Consequently, different loading/assignment policies can be compared under majorization/arrangement orderings and their relative merits decided according to the yields of throughput. The results can be used to support planning decisions in computer and production systems which are modeled as closed networks of queues.     

植物油交联共聚阻尼材料的研究

为扩大阻尼材料的原料来源,降低成本,提高阻尼性能,研究以植物油(蓖麻油、棉子油、桐油)为原料,合成环氧植物油及桐油酸酐,将桐油酸酐与环氧植物油进行本体聚合,制得了一系列 AB—交联共聚物。对试样进行动态力学测试,结果表明,该共聚物具有较高的阻尼因子(tanδ最高在1以上),较宽的阻尼温域。在40～60℃时,tanδ值持续大于0.3,是一类成本低廉、阻尼性能良好的新型阻尼材料。     

离聚体乳胶IPN的合成及相容性的研究

本文介绍了一种新型高分子材料—离聚体乳胶IPN的合成,并利用动态力学粘弹谱对其阻尼性能及相容性进行了研究。结果表明该体系不但可以设计为热力学上的增容体系,还具有动力学上的强迫增容效果,合成的新材料表现了组分之间良好的协同作用,因而具有宽广的有效阻尼温域。     

■AB■_n型嵌段聚氨酯软硬段间的相容性与动态力学谱

本文讨论了■A—B■_n丢嵌段聚氨酯软硬段间的相容性对其动态力学谱(tanσ曲线)的影响,指出:相容性对tanσ曲线的影响的本质是相间过渡区的性质。对■A—B■_n型嵌段聚氨酯体系,当其由完全不相容向完全相容(或由完全相容向完全不相容)变化时,tanσ曲线形状的变化为窄→宽→窄。通过tanσ曲线的变化可定性分析其相容性变化。     

某型导弹弹翼静力分析的一种数学模型

应用有限元方法,建立了变厚度薄板三角形单元刚度矩阵,给出了变厚度薄板三角形单元形心上的应力和位移计算的数学模型。通过对某型反坦克导弹弹翼进行静力分析和实验比较,表明采用这种模型进行分析合乎结构设计精度要求。     

离散滑模变结构控制稳定性分析

对流行的离散变结构控制的两种方案——K.Furuta方案和Wang氏方案进行了研究,发现Wang氏方案中的稳定性定理不能成立,其证明不充分。并通过仿真,给出了反例。文章指出控制结构在A区和B区交替变换过程中,系统状态运动的一个循环过程所对应的转移矩阵A_i~*的谱半径小于1,系统才是渐近稳定的。     

态势估计中一种基于贝叶斯估计的统计时间推理方法

统计时间推理是态势估计中的一个重要组成部分。Ｋｉｒｉｌｏｖ的基于极大似然估计（Ｍａｘｉ－ｍｕｍＬｉｋｅｌｉｈｏｏｄＥｓｔｉｍａｔｉｏｎ,ＭＬＥ）的推理方法将未知时间变量看作常数,估计方差较大。文中建立的已知时间信息和未知时间变量之间的关系模型,将未知时间变量扩展为随机变量,将贝叶斯估计（ＢａｙｅｓＥｓｔｉｍａｔｉｏｎ,ＢＥ）引入时间推理。经过对两种推理算法的性能进行分析和比较,发现在一定范围内,基于ＢＥ的方法性能优于基于ＭＬＥ的方法。     

潜载/舰载作战系统的对抗效能分析

首先分析了潜艇与水面舰艇对抗时的相对效能,然后强调了潜艇隐蔽作战方式的重要性．最后,对提高潜载作战系统效能关键技术的发展提出了建议．     

陀螺马达驱动信号的数字化测量与失真度分析

简要介绍陀螺马达驱动信号的数字化测量方法及失真度分析的数学原理 ,给出了一个实例 .实践证明 ,该方法电路结构简单、参数测量准确、程序编写方便 ,具有较好的实时性能 .