布尔函数不交化的立方体算法

布尔函数的不交化是进行系统可靠度计算中的重要步骤。本文提出了一种进行布尔函数不交化的立方体算法。基于布尔函数的立方体表示法及不交代数,文中定义了立方体的有关运算法则,建立了立方体矩阵不交化算法,并用算例进行了说明。本算法的实现效率高,操作简便。     

多阶段任务系统可靠性分析的二元决策图模型

为了实现计算机自动生成多阶段任务系统的二元决策图可靠性模型,提出了二元决策图可靠性建模的通用方法。定义了嵌套的二元决策图数据结构BDD_Element,给出了二元决策图模型的描述和存储方法,提出了与门、或门和k/n表决门向二元决策图模型的自动转化算法。给出了建立多阶段任务系统二元决策图可靠性模型的2个步骤:基于逻辑门转化算法,将部件逻辑关系结构函数转化为阶段二元决策图模型;基于二元决策图布尔操作规则整合阶段二元决策图模型。卫星姿态调整任务的可靠性分析表明:该方法可以有效应用于多阶段任务系统的可靠性分析。     

The joint signature of coherent systems

We investigate the joint signature of $m$ coherent systems, under the assumption that the components have independent and identically distributed lifetimes. The joint signature, for a particular ordering of failure times, is an $m$‐dimensional matrix depending solely on the composition of the systems and independent of the underlying distribution function of the component lifetimes. The elements of the $m$‐dimensional matrix are formulated based on the joint signatures of numerous series of parallel systems. The number of the joint signatures involved is an exponential function of the number of the minimal cut sets of each original system and may, therefore, be significantly large. We prove that although this number is typically large, a great number of the joint signatures are repeated, or removed by negative signs. We determine the maximum number of different joint signatures based on the number of systems and components. It is independent of the number of the minimal cut sets of each system and is polynomial in the number of components. Moreover, we consider all permutations of failure times and demonstrate that the results for one permutation can be of use for the others. Our theorems are applied to various examples. The main conclusion is that the joint signature can be computed much faster than expected.     

多阶段任务系统可靠性分析的ROBDD算法

针对Markov方法分析多阶段任务系统(Phased-Mission System,PMS)可靠性时的状态空间爆炸问题,基于层次化建模思想,建立了PMS任务可靠性的顶层系统二维决策图(Binary Decision Diagram,BDD)模型和底层部件Markov模型。通过分析BDD中的同构节点和冗余节点,提出顶层模型构造过程中的同构节点合并策略和冗余节点删除策略。利用上述节点压缩策略生成简化模型,提高模型构造和存储效率。基于PMS部件排序规则,给出了层次化模型的递归求解方法,该方法的计算复杂度与顶层模型中的节点总数呈线性关系。通过算例分析,对比采用节点压缩策略前后的模型节点数,以及层次化方法与Markov方法的计算结果,验证了简化层次模型的正确性和有效性。     

Balancing perfectly periodic service schedules: An application from recycling and waste management

A national recycling and waste management company provides periodic services to its customers from over 160 service centers. The services are performed periodically in units of weeks over a planning horizon. The number of truck‐hours allocated to this effort is determined by the maximum weekly workload during the planning horizon. Therefore, minimizing the maximum weekly workload results in minimum operating expenses. The perfectly periodic service scheduling (PPSS) problem is defined based on the practices of the company. It is shown that the PPSS problem is strongly NP‐hard. Attempts to solve large instances by using an integer programming formulation are unsuccessful. Therefore, greedy BestFit heuristics with three different sorting schemes are designed and tested for six real‐world PPSS instances and 80 randomly generated data files. The heuristics provide effective solutions that are within 2% of optimality on average. When the best found BestFit schedules are compared with the existing schedules, it is shown that operational costs are reduced by 18% on average. © 2012 Wiley Periodicals, Inc. Naval Research Logistics 59: 160–171, 2012     

基于速度可控粒子群算法的航天测控系统任务可靠性分配

航天测控系统是一个典型的多阶段任务系统,讨论了可靠性分配时的约束条件和分配目标,构建了其任务可靠性分配模型,针对任务可靠性分配这类复杂的约束组合优化问题,提出了一种速度可控的粒子群优化算法.为克服粒子群算法的早熟问题,该算法引入了速度更新的方向控制规则和尺度控制规则用于增加群体的多样性,并根据两种控制规则,提出了种群粒子的速度更新策略.通过算例仿真,表明算法在用于航天测控系统任务可靠性分配问题时具有分配结果优、收敛速度快等优点.     

成败型产品的Bayes鉴定试验方案研究

利用可靠性增长模型给出了成败型产品鉴定试验的一种Bayes方法.提出了Bayes鉴定试验的最大后验风险准则,利用这种准则制定的鉴定试验方案综合了产品研制过程中的先验信息.在确保产品质量的前提下,与传统的鉴定试验方案相比,将大大节省试验时间.     

基于ExtendSim的系统可靠性建模

针对传统可靠性仿真模型建模繁琐,编程困难的问题,建立了基于Ex tendS im的可靠性模型,即串联、并联、旁联模型,相比传统方法具有建模直观、调试方便等优点,并以某混联系统为例与解析模型进行了对比验证,仿真结果表明,建立的可靠性模型是可信的,且此模型不依赖于单元寿命分布,相比解析模型具有更强的适应性。     

50000m~3油罐壁厚设计比较与分析

油罐的壁厚设计关系到油罐的经济性和可靠性,如何把握两者的辩证关系对油罐的设计与建设具有十分重要的意义。传统上大型油罐壁厚设计采用的是变点法;以可靠度理论为基础,以可靠性分析模型为核心,提出利用可靠度法求解大型油罐壁厚的新方法。以50 000 m3油罐为例,编程分析并计算以2种方法设计的壁厚。变点法设计的底圈罐壁厚度与圈数无关;以中心点可靠度法求解壁厚,可靠性指标一定时,底圈罐壁厚度同样与圈数无关。探讨可靠度法求解壁厚的可行性,验证变点法设计壁厚的可靠性。     

Shock model in Markovian environment

A Markov modulated shock models is studied in this paper. In this model, both the interarrival time and the magnitude of the shock are determined by a Markov process. The system fails whenever a shock magnitude exceeds a pre‐specified level η. Nonexponential bounds of the reliability are given when the interarrival time has heavy‐tailed distribution. The exponential decay of the reliability function and the asymptotic failure rate are also considered for the light‐tailed case. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005