The performance of cannibalization policies in a maintenance system with spares,repair, and resource constraints

This article presents the results of comparing the performance of several cannibalization policies using a simulation model of a maintenance system with spares, repair, and resource constraints. Although the presence of cannibalization has been incorporated into a number of maintenance system models reported in the literature, the questions of whether cannibalization should be done and what factors affect canibalization have received little attention. Policies tested include both no cannibalization and unlimited cannibalization as well as other based on the number of maintenance personnel available, the short-term machine failure rate at the time of cannibalization, and the relationship between the mean cannibalization and repair rates. The best policies found are those that allow cannibalization only when it can be done quickly relative to repair or when it can be done without delaying part repair actions. The policy of complete cannibalization (always cannibalize when it is possible) is found to perform poorly except when either average maintenance personnel utilization is very low or when mean cannibalization times are very short relative to mean repair times. The latter result casts doubts on the appropriateness of the assumption of complete cannibalization in many models in the literature.     

The reliability of multicomponent systems subject to cannibalization

A reliability model for multicomponent multistate systems is presented. This is a generalization of a model previously studied by Hirsch, Meisner, and Boll. In the earlier model, when a failure occurs for which no replacement spare is available, the locations using the same type of part as that having failed are “cannibalized” so as to allocate the shortages to locations where they are least detrimental to system performance. Here, we permit certain restrictions to be imposed upon the cannibalization procedure, and develop effective techniques for relating the probability laws governing the level of system performance to the system structure, cannibalization policy, kit of spare parts, and part reliabilities.     

有限维修能力下多级保障系统装备时变可用度评估及保障方案优化

备件库存和站点维修能力是影响备件维修周转的重要因素,制约着装备的使用效果。针对备件需求随任务阶段动态变化时装备保障方案的评估和优化问题,考虑站点维修能力对备件维修过程的影响,结合METRIC建模方法和动态排队理论,建立了有限维修能力下多级保障系统装备时变可用度评估模型。在评估模型基础之上,以保障费用为优化目标、装备可用度为约束条件,建立任务期内多级保障系统保障方案优化模型。以任务期内的最低可用度所对应的备件短缺数为观测值,分析各项资源的边际效益值,采用边际优化算法对各项资源进行优化计算。算例分析表明,评估模型能够计算多级保障系统任务期内各阶段装备可用度;保障方案优化模型和方法能够得到各项保障资源的优化配置方案。提出的模型和优化方法能够为装备保障人员制订合理的保障方案提供决策支持。     

有限维修能力下多级保障系统装备时变可用度评估及保障方案优化

备件库存和站点维修能力是影响备件维修周转的重要因素，制约装备使用效果。针对备件需求随任务阶段动态变化的装备保障方案评估和优化问题，考虑站点维修能力对备件维修过程的影响，结合METRIC建模方法和动态排队理论，建立了有限维修能力下多级保障系统装备时变可用度评估模型。在评估模型基础之上，以保障费用为优化目标，装备可用度为约束条件，建立了任务期内多级保障系统保障方案优化模型。以任务期内的最低可用度所对应的备件短缺数为观测值，分析了各项资源的边际效益值，采用边际优化算法对各项资源进行优化计算。算例分析表明，评估模型能够计算多级保障系统任务期内各阶段装备可用度；保障方案优化模型和方法能够得到各项保障资源的优化配置方案。提出的模型和优化方法能够为装备保障人员制定合理的保障方案提供决策支持。     

相控阵天线阵面两级备件优化配置模型

针对相控阵天线阵面备件配置存在的冗余性强、批量送修、多级维修等现实问题,综合考虑备件费用、维修能力以及库存策略之间的关系,建立了基于定期补给的两级备件优化配置模型。给出了系统的故障件维修周转过程和维修备件的定期补给过程,在分析备件、库存、维修能力之间关系的基础上,结合成批到达的排队理论,建立了系统的供应可用度模型。以备件配置费用最小为目标、以系统供应可用度为约束条件,建立了系统的备件优化配置模型,并通过边际效益分析法对模型进行了求解。通过算例仿真与分析对模型进行了验证。结果表明:构建的备件配置能够较好地解决相控阵天线阵面的备件配置问题,具有一定的优越性。     

随舰备件动态管理及备件数量计算模型

针对精确化保障的需要,提出了一种新的随舰备件动态管理策略.基于不同型号装备中相同型号的部件可以相互替换,开发了一个能综合考虑同型号部件具有不同寿命分布、任务要求的不同工作时间等特点的随舰备件数量计算模型.并以寿命服从正态分布的部件为算例进行了备件数量计算,验证了模型的可行性.     

有限水深Kelvin源格林函数及其导数的快速计算

应用线性船舶水动力学理论,将有限水深Kelvin移动兴波源格林函数分解成3部分:简单Rankine源集合、局部扰动项和波函数项。对各部分在亚临界和超临界航速时的快速计算分别作了讨论,其中对计算费时的局部扰动项采用了复数中的最陡下降积分法,加快了计算速度,进而引出各部分偏导数的计算。最后,比较了格林函数的差分值与偏导数值,计算了薄船兴波阻力与表面兴波,讨论了不同面元网格划分的收敛性,证实了亚临界、超临界航速兴波分别以横波、散波为主。     

Callable products with dependent demands

Capacity providers such as airlines often sell the same capacity to different market segments at different prices to improve their expected revenues. The absence of a secondary market, due to the nontransferability of airline tickets, gives rise to an opportunity for airlines to broker capacity between consumers with different willingness to pay. One way to broker capacity is by the introduction of callable products. The idea is similar to callable bonds where the issuer has the right, but not the obligation, to buy back the bonds at a certain price by a certain date. The idea of callable products was introduced before under the assumption that the fare-class demands are all independent. The independent assumption becomes untenable when there is significant demand recovery (respectively, demand cannibalization) when lower fares are closed (respectively, opened). In this case, consumer choice behavior should be modeled explicitly to make meaningful decisions. In this paper, we consider a general consumer choice model and develop the optimal strategy for callable products. Our numerical study illustrates how callable products are win-win-win, for the capacity provider and for both high and low fare consumers. Our studies also identify conditions for callable products to result in significant improvements in expected revenues.     

《地图学》教学的几点思考

《地图学》是地学领域各专业学生必须学习的一门专业基础课程,技术性强,应用广。由于学科比较抽象,理论性强,又较为枯燥,学生在学习过程中普遍反应难学。所以如何有效地组织教学,理清该学科的体系和架构,不仅能激发学生的学习兴趣,同时能让学生充分了解教材各章节的中的重点、难点,做到有的放矢。通过近二十年的地图教学实践,把地图教学分为理论、实验、应用和现代技术与地图学四个方面来实施教学,效果显著。     

考虑需求相关的可修复系统备件配置模型

对于一个拥有多台相同设备的可修复系统来说,一种备件的需求以及其对应的备件保障方案将影响着系统的可工作设备数量,从而影响着设备其他备件的需求,故假设备件需求相互独立且与系统自身备件保障方案无关而开展备件配置研究是不合理的.在考虑备件需求相关以及备件的保障方案对备件需求的影响的前提下,利用马尔可夫理论描述了备件需求规律,针对不串件拼修和串件拼修两种情况分别给出了可用度的计算方法,并在此基础上以备件配置费用作为优化目标,以可用度作为约束构建备件优化配置模型,给出了边际分析求解模型的方法.通过案例分析,验证了模型的正确性.     

On estimating survival for reliability models based on age-related stochastic comparisons

A new class of nonparametric reliability models is introduced and studied. A distribution is said to be better at age s than at age t (sBt) if the residual lifetime at age s is stochastically greater than or equal to the residual lifetime at age t. Applications to various forms of replacement policies, including the cannibalization of failed systems, are noted. For fixed s < t, the problem of estimating a survival curve assumed to belong to the sBt class is addressed using recursive methods. An sBt estimator is derived in closed form, and its uniform strong consistency at an optimal rate of convergence is demonstrated. A simulation study strongly supports the claim that the sBt estimator tends to outperform the empirical survivor function in small- and moderate-size samples. © 1993 John Wiley & Sons, Inc.     

多属性群决策理论的备件筛选方法

利用多属性群决策方法和多目标规划理论,建立了筛选武器装备维修备件的模型和方法.该方法首先按照多属性群决策方法对各种维修备件进行综合排序,然后再用多目标规划理论确定维修备件的选择方案.对该方法具体应用时的若干问题也进行了探讨.     

On some sequencing problems

The (mxn) sequencing problem may be characterized as follows: There are m machines which can produce a piece consisting of n parts. Each part has a determined order in which it is processed through the machines. It is assumed that each machine cannot deal with more than one part at a time and that the processing required for each part can be accomplished only on one machine. That is, the machines are all specialized so that alternate machines for the same processing on a part is not possible. The problem is to find the best production plan consisting in sequencing the different parts so as to make the whole amount of time from the beginning of work till the piece is completed the shortest possible. Such a plan is called an optimum one. In the first 4 sections of this paper, the problem (2xn) is solved for the (2xn) case in which the order in which parts come on the machine is not constrained by further assumptions. The remainder of the paper then takes up: 1) the (3xn) problem of Bellman-Johnson (viz. the technological processing order through the machine is the same for all parts) for several new special cases; 2) the 2xn problem of sequencing when delay times must also be considered; and, 3) some properties of an approximating method for solving (mxn) problems, including a delineation of cases when the approximating method will yield optimal solutions.     

Multi-item service constrained (s,S) policies for spare parts logistics systems

Many organizations providing service support for products or families of products must allocate inventory investment among the parts (or, identically, items) that make up those products or families. The allocation decision is crucial in today's competitive environment in which rapid response and low levels of inventory are both required for providing competitive levels of customer service in marketing a firm's products. This is particularly important in high-tech industries, such as computers, military equipment, and consumer appliances. Such rapid response typically implies regional and local distribution points for final products and for spare parts for repairs. In this article we fix attention on a given product or product family at a single location. This single-location problem is the basic building block of multi-echelon inventory systems based on level-by-level decomposition, and our modeling approach is developed with this application in mind. The product consists of field-replaceable units (i.e., parts), which are to be stocked as spares for field service repair. We assume that each part will be stocked at each location according to an (s, S) stocking policy. Moreover, we distinguish two classes of demand at each location: customer (or emergency) demand and normal replenishment demand from lower levels in the multiechelon system. The basic problem of interest is to determine the appropriate policies (s_i S_i) for each part i in the product under consideration. We formulate an approximate cost function and service level constraint, and we present a greedy heuristic algorithm for solving the resulting approximate constrained optimization problem. We present experimental results showing that the heuristics developed have good cost performance relative to optimal. We also discuss extensions to the multiproduct component commonality problem.     

Inventory pooling games for expensive,low‐demand spare parts

We consider several independent decision makers who stock expensive, low‐demand spare parts for their high‐tech machines. They can collaborate by full pooling of their inventories via free transshipments. We examine the stability of such pooling arrangements, and we address the issue of fairly distributing the collective holding and downtime costs over the participants, by applying concepts from cooperative game theory. We consider two settings: one where each party maintains a predetermined stocking level and one where base stock levels are optimized. For the setting with fixed stocking levels, we unravel the possibly conflicting effects of implementing a full pooling arrangement and study these effects separately to establish intuitive conditions for existence of a stable cost allocation. For the setting with optimized stocking levels, we provide a simple proportional rule that accomplishes a population monotonic allocation scheme if downtime costs are symmetric among participants. Although our whole analysis is motivated by spare parts applications, all results are also applicable to other pooled resource systems of which the steady‐state behavior is equivalent to that of an Erlang loss system. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012     

按保障度最大配置备件模型

考虑了备件资源有限,有多个需求单位的条件下,依据装备数量、零部件、元器件的故障率,单装用数、平均更换时间、各级维修机构领取备件的平均时间,建立了两级备件保障度的模型,并在备件总资源量一定的条件下,按保障度最大给出了两级备件配置的程序、方法和示例.模型举例说明了模型输出结果的特征和敏感性.模型应用可减少备件的积压,降低备件的短缺,提高备件的保障效果.     

基于Bayes理论的装备维修性验证方法

针对装甲装备关键部件维修性验证中出现的小子样问题,提出了基于Bayes理论的小子样维修性验证,重点针对对数正态分布下维修性指标验证的验后似然比验证方法进行了深入研究。通过对装甲装备某关键部件的试验数据的实例分析,验证了该方法在减少样本容量及试验费用方面的有效性和合理性。     

通用军械装备维修备件合同商保障方式研究

提出了备件合同商保障的概念,给出了备件合同商保障内容和维度,分析了备件合同商保障的特征,着重从备件的存储方式和供应方式两个方面进行了定性分析,为实施备件合同商保障奠定了理论基础．     

不确定需求下多级备件库存系统优化模型

针对现实中备件需求量的不确定性,论文首先用模糊随机变量描述不确定需求,并通过灰集以及期望值理论表示出备件期望短缺数,然后对多级备件库存系统在不确定需求环境下的优化问题作了研究,提出了不确定性可用度的区间估计,并利用边际分析法建立了备件库存优化模型,进而对其进行优化仿真,最后对系统可用度进行区间估计,得到了不确定需求下的最优费效比曲线。该方法能够为解决不确定需求下备件库存优化问题提供新的途径。     

随舰备件需求分析中维修策略问题

分析了面向任务保障性工程理论指导下的舰船随舰备件配置问题,就最大、最小两种维修策略下随舰备件配置问题进行了研究,给出了面向任务的随舰备件需求分析仿真模型框架,结合算倒,研究了最大维修策略与最小维修策略的适用时机:在任务确定且任务结构函数明确条件下,应采用最小维修策略;否则采用最大维修策略.