考虑非线性退化与随机失效阈值的剩余寿命预测

针对广泛存在的非线性退化设备,现有方法尚未考虑随机失效阈值对剩余寿命预测结果的影响。因此,通过对设备性能退化过程进行分析,提出了一种综合考虑非线性退化与随机失效阈值的剩余寿命预测方法。基于Wiener过程构建了考虑个体差异与测量误差的非线性退化模型;基于卡尔曼滤波算法建立状态空间模型以实现对退化状态的在线更新;基于极大似然法估计失效阈值分布系数估计方法,得到随机失效阈值的概率分布;基于随机失效阈值推导出剩余寿命的概率分布,实现对剩余寿命的在线预测。算例研究表明,所提方法可以有效地提升剩余寿命预测的准确性,具备一定工程应用价值。     

On the reduction of total‐cost and average‐cost MDPs to discounted MDPs

This article provides conditions under which total‐cost and average‐cost Markov decision processes (MDPs) can be reduced to discounted ones. Results are given for transient total‐cost MDPs with transition rates whose values may be greater than one, as well as for average‐cost MDPs with transition probabilities satisfying the condition that there is a state such that the expected time to reach it is uniformly bounded for all initial states and stationary policies. In particular, these reductions imply sufficient conditions for the validity of optimality equations and the existence of stationary optimal policies for MDPs with undiscounted total cost and average‐cost criteria. When the state and action sets are finite, these reductions lead to linear programming formulations and complexity estimates for MDPs under the aforementioned criteria.© 2017 Wiley Periodicals, Inc. Naval Research Logistics 66:38–56, 2019     

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.     

装备保障方案综合评价系统的分析与设计

为了科学合理地对装备保障方案进行权衡分析和优化筛选，从装备保障方案综合评价的具体需求出发，提出了装备保障方案综合评价系统的总体结构，基于 OU（组织单元）与 BOU（基本组织单元）的组织建模法构建了装备保障方案综合评价的组织结构模型，设计了系统的角色和各功能模块，并给出系统运作的一般流程和具体事例，验证了该系统的可行性和有效性。     

Planning gamma accelerated degradation tests with two accelerating variables

Gamma accelerated degradation tests (ADT) are widely used to assess timely lifetime information of highly reliable products with degradation paths that follow a gamma process. In the existing literature, there is interest in addressing the problem of deciding how to conduct an efficient, ADT that includes determinations of higher stress‐testing levels and their corresponding sample‐size allocations. The existing results mainly focused on the case of a single accelerating variable. However, this may not be practical when the quality characteristics of the product have slow degradation rates. To overcome this difficulty, we propose an analytical approach to address this decision‐making problem using the case of two accelerating variables. Specifically, based on the criterion of minimizing the asymptotic variance of the estimated q quantile of lifetime distribution of the product, we analytically show that the optimal stress levels and sample‐size allocations can be simultaneously obtained via a general equivalence theorem. In addition, we use a practical example to illustrate the proposed procedure.     

灰色层次分析决策方法在坦克评估中的应用

给出了利用灰色层次分析决策方法进行评估的一般步骤,并以坦克为例,构建了基于坦克的机动性、防护性、火力性、信息性、可靠性的评估模型。     

基于FAHP的岸防炮兵雷达作战效能评估分析方法

针对岸防炮兵雷达的特点和作战任务,从探测能力、定位能力、数据处理能力、目标识别能力、抗干扰能力、可用性、可靠性和生存能力8个指标层,建立岸防炮兵雷达作战效能评估的层次结构体系,并确定了指标体系综合指标的随机性和模糊性,运用模糊层次分析法对雷达效能进行综合评估,给出了确立各因素权重的方法.为该雷达作战使用提供了辅助决策的依据.     

考虑多类资源的多任务并行维修过程Petri网建模

针对基本Petri网在建立多种任务共享多类资源情况下的复杂并行维修过程时存在的结构复杂化问题,应用网抽象原理,由简入繁,将库所变迁网模型逐步转化为常量弧有色网和有色网模型,由单类任务/单类资源、单类任务/多类资源模型逐步建立了考虑多类资源的多任务并行维修过程模型。采用Petri网仿真分析工具ExSpect对有色网模型进行了实例研究。结果表明：模型具有通用性,便于仿真实现。     

控制不等式的改进

讨论了随机过程控制关系产生的不等式,对这个不等式给出了一个新系数,改进了以前的结果,并将其应用于局部平方可积鞅.     

电磁发射系统改进FAHP-神经网络健康评估方法

准确定量评估电磁发射系统发射前的健康状态意义重大。针对模糊层次分析方法(Fuzzy Analytic Hierarchy Process, FAHP)在评估电磁发射系统串行结构同级元素健康值时存在较大偏差,且无法适用系统非线性变权重需求的缺陷,提出改进FAHP-神经网络方法。通过在计算同级元素健康指数时构造能够满足串行结构健康评估的非线性函数进行计算,并在数学上证明该方法的有效性；通过引入神经网络系统,在已有的系统先验信息和测量数据的基础上训练模型解决系统健康评估非线性变权重需求。基于电磁发射系统脉冲成形网络系统建立健康评估模型,开展评估试验。结果表明,提出的方法健康评估精度较高,在各种系统健康状态下,评估结果均符合系统实际的健康状况；对比传统的FAHP,提出的改进方法评估精度大幅提升,且在评估试验中没有出现故障误报和漏报的情况,从而验证了提出方法的可行性和工程实用价值。