Scheduling a maintenance activity on parallel identical machines

We study a problem of scheduling a maintenance activity on parallel identical machines, under the assumption that all the machines must be maintained simultaneously. One example for this setting is a situation where the entire system must be stopped for maintenance because of a required electricity shut‐down. The objective is minimum flow‐time. The problem is shown to be NP‐hard, and moreover impossible to approximate unless P = NP. We introduce a pseudo‐polynomial dynamic programming algorithm, and show how to convert it into a bicriteria FPTAS for this problem. We also present an efficient heuristic and a lower bound. Our numerical tests indicate that the heuristic provides in most cases very close‐to‐optimal schedules. © 2008 Wiley Periodicals, Inc. Naval Research Logistics 2009     

基于集对分析的维修保障系统效能评估

在分析维修保障系统效能影响因素的情况下,应用集对分析方法建立了维修保障系统效能多指标评估模型,以定量的结果对维修保障系统效能进行综合评估,并与层次分析法和突变评价法的结果进行比较,结论一致.为维修保障系统效能评估问题寻求出一种新的方法,其评估结果可为决策提供定量依据.     

基于数据的故障诊断更新问题分析及应用

机内测试被广泛应用于故障诊断,装备健康管理与预测等领域。本文针对机内测试设备在设计和升级时遇到的分类器更新,样本数量不平衡,硬件条件限制问题,提出了初步解决方案。首先,利用基于密度的聚类和人工免疫的方法处理原始数据,然后提出了基于代表样本点的混合学习方法,最后利用支持向量机和仿真案例验证了本文所提方法。结果表明本文所提方法能够解决上述问题,有助于基于数据的机内测试设备设计与升级。     

Maintaining systems with heterogeneous spare parts

We consider the problem of optimally maintaining a stochastically degrading, single‐unit system using heterogeneous spares of varying quality. The system's failures are unannounced; therefore, it is inspected periodically to determine its status (functioning or failed). The system continues in operation until it is either preventively or correctively maintained. The available maintenance options include perfect repair, which restores the system to an as‐good‐as‐new condition, and replacement with a randomly selected unit from the supply of heterogeneous spares. The objective is to minimize the total expected discounted maintenance costs over an infinite time horizon. We formulate the problem using a mixed observability Markov decision process (MOMDP) model in which the system's age is observable but its quality must be inferred. We show, under suitable conditions, the monotonicity of the optimal value function in the belief about the system quality and establish conditions under which finite preventive maintenance thresholds exist. A detailed computational study reveals that the optimal policy encourages exploration when the system's quality is uncertain; the policy is more exploitive when the quality is highly certain. The study also demonstrates that substantial cost savings are achieved by utilizing our MOMDP‐based method as compared to more naïve methods of accounting for heterogeneous spares.     

Praying for Rain? Water Scarcity and the Duration and Outcomes of Civil Wars

Recent anecdotal evidence from the civil wars in Somalia and Yemen suggest that water scarcity may shape the dynamics of civil wars. While a considerable body of research has examined the connection between water scarcity (such as low rainfall) and the onset of civil war, very little research has examined how water scarcity may shape the duration and outcomes of civil wars. Looking specifically at rainfall, this paper argues that changes in access to water play a key role in the duration of civil wars. As rainfall declines, there is a reduction in resources available to both the government and the rebel group, leading to a stalemate in fighting. Furthermore, this paper argues that declines in rainfall are felt more acutely by rebel groups who seek to challenge the government through conventional warfare. This paper tests these propositions using hazard models. The results provide robust support for the propositions.     

基于二元语义和模糊理论的舰员级维修绩效评估方法

针对舰员级维修工作的特点,建立了绩效评估指标体系,将二元语义和模糊理论相结合,提出了一种舰员级维修绩效评估方法,并通过实例进行了计算和验证。该方法可以有效解决语言评价信息集结和运算中出现的信息丢失和扭曲,提高评估精度,为绩效管理的各环节工作提供了依据。     

基于SOA的网络化维修保障信息系统体系结构研究

随着信息技术的迅猛发展,网络化维修模式将会成为未来武器装备维修模式变革的潮流,而面向服务的体系架构即SOA(Service-Oriented Architecture),可以有效地解决传统的维修信息系统中所面临的"信息孤岛"和"功能孤岛"的问题,是实现网络化维修保障的重要基础之一。分析介绍面向服务架构SOA的概念、体系架构、技术实现,并结合网络化维修保障的具体需求,提出了一个基于SOA的网络化维修保障体系框架。     

军用航空机务维修人员安全知识结构评价研究

随着军用航空装备复杂性、安全性的提升,对广大机务维修人员安全知识结构提出了更高的要求。以某机务部队现状为依据,研究航空机务维修人员安全知识结构评价问题。利用工作分析法对航空机务维修人员的工作进行了深入分析,建立了航空机务维修人员安全知识结构指标体系,通过构建基于熵权的改进BP神经网络模型对建立的知识体系结构进行评价。以某单位实际调研数据为基础,利用MATLAB仿真实现了模型的训练和测试,对机务维修人员的安全知识结构进行量化分析,为机务人员的安全知识能力培养提供决策依据和参考。     

基于CCA/DEA的装备维修保障绩效评价

运用典型相关分析方法(CCA)和数据包络法(DEA),从纯技术效率、规模效率和综合效率3方面对空军飞行团维修保障绩效进行计算分析,结果表明,飞行团维修费使用效益方面经费配置效率整体不高,特别是对于中修费和维修器材购置费,须采取管控措施提高经费利用效率。     

相控阵雷达维修方案优选方法研究

针对相控阵雷达维修方案的选择问题,确定了维修方案的决策属性,并提出一种基于改进TOPSIS法的相控阵雷达维修方案优选方法。该方法通过引入Vague集来处理维修方案选择中存在的模糊信息,并采用博弈论综合赋权法来确定决策属性的综合权重。通过计算各备选方案与正、负理想方案的灰色关联度,得到了维修方案的灰色关联相对贴近度,进而实现对维修方案的排序和选择。最后,通过算例应用与分析,对提出的方法进行了验证。