摘要:

AbstractThe determination as to the cost‐effective number of spares for given types of items or equipment to be carried on board various types of ships is studied. This spare pool, known as the ship's COSAL, must provide prespecified levels of protection against stockouts for all uses of that item on board the given ship. This article derives and illustrates the methodology for optimally trading off the reduction in the ship's COSAL that can be gained by improving repair/resupply capabilities or by lowering the failure rate of the equipment through more or different types of preventive maintenance. A flexible class of preventive maintenance/repair response functions to cost is studied which are nonlinear and exhibit realistic diminishing returns. Two different types of assumptions are possible regarding the interdependencies of the resupply times across different ship types. A tractable budget allocation method is presented which can be used in a multiitem, multiship, multiechelon repair environment where there is one budget to cover all spares, all repair/resupply, and preventive maintenance activities. The technique incorporates different criticalities of shortages by type of ship and item. It can be used either in a budget building mode or a budget execution mod

ISSN:0028-1441    

DOI:10.1002/nav.3800300402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe classic transportation problem can be generalized with many carriers and one owner. From the formulation the competition in sense of game theory naturally appears. Here we present and solve this problem using a generalizedn‐person game. Besides the same composition properties about solutions and regarding zones, related results are considered. Finally, the problem in which there is a modification of the set of destinations assigned to the carriers is also studie

ISSN:0028-1441    

DOI:10.1002/nav.3800300403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThis article defines optimal replacement policies for identical components performing different functions in a given system, when more than one spare part is available. The problem is first formulated for two components and any number of spare parts and the optimal replacement timey(x)at timexis found to have a certain form. Sufficient conditions are then provided fory(x)to be a constanty* forx>y*, andy(x)=xforx>y* (single‐critical‐number policy). Under the assumption that the optimal policies are of the single‐critical‐number type, the results are extended to then‐component case, and a theorem is provided that reduces the required number of critical numbers. Finally, the theory is applied to the case of the exponential and uniform failure laws, in which single‐critical‐number policies are optimal, and to another failure law in which

ISSN:0028-1441    

DOI:10.1002/nav.3800300404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractIn this article we study the estimation of the average excess life θ in a two‐parameter exponential distribution with a known linear relationship between α (the minimum life) and θ of the form α =aθ, whereais known and positive. A comparison of the efficiencies of estimators which are linear combinations of the smallest sample value and the sample sum of deviations from the smallest sample value and the maximum likelihood estimators is made for various sample sizes and different values ofa. It is shown that these estimators are dominated in the risk by the minimum‐risk scale equivariant estimator based on sufficient statistics. A class of Bayes estimators for inverted gamma priors is constructed and shown to include a minimum‐risk scale equivariant estimator in it. All the members of this class can be compu

ISSN:0028-1441    

DOI:10.1002/nav.3800300405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe primary goal of this article is to extend the results of a previous article to the case where the effect of advertisement on sales lasts more than one period. Monotonicity of the optimal advertising and inventory policies in the various factors is investigated. Also, attention will be focused on the relationship between the fluctuations over time of the optimal policies and the variations over time of the factors involved, such as demand distributions and holding costs. For example, if over a finite interval the demand decreases from one period to the next, reaches a minimum, and then increases, then the optimal advertising policy will produce the opposite effect. The period of minimum demand never precedes that of maximum goodwill; moreover, the optimal inventory level decreases while the demand decreases. Finally, when demand distributions are just translates of one another, the results of this article can be extended to nonperishable goods.

ISSN:0028-1441    

DOI:10.1002/nav.3800300406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractConsider ak‐out‐of‐nsystem with independent repairable components. Assume that the repair and failure distributions are exponential with parameters {μ1, ⃛,μn} and {λ1, ⃛,λn}, respectively. In this article we show that if λi– μi= Δ for allithen the life distribution of the system is increasing

ISSN:0028-1441    

DOI:10.1002/nav.3800300407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe ordinary age replacement problem consists of finding an optimal age at which a unit, needed in a continuous production process, should be replaced in order to minimize the average long‐run cost per unit time. Bergman introduced a graphical procedure based on the total‐time‐on‐test (TTT) concept for the analysis of the age replacement problem. In this article, that idea is generalized to the situation of discounted costs. We also study a more general age replacement problem in which we have a form of imperfect

ISSN:0028-1441    

DOI:10.1002/nav.3800300408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThis article proposes a practical, data‐based statistical procedure which can be used to reduce or remove bias owing to artificial startup conditions in simulations aimed at estimating steady‐state means. We discuss results of experiments designed to choose good parameter values for this procedure, and present results of extensive testing of the procedure on a variety of stochastic models for which partial analytical results are available. The article closes with two illustrations of the application of the procedure to more complex statistical problems which are more representative of the kinds of purposes for which real‐world steady‐state simulation studies might be und

ISSN:0028-1441    

DOI:10.1002/nav.3800300409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThis note calls attention to a difficulty which arises frequently in the application of stress‐strength methods in reliability theory. This difficulty has led to unanticipated catastrophic failures in a number of application

ISSN:0028-1441    

DOI:10.1002/nav.3800300410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe notions of minimax paths, trees, and cut sets are defined for undirected graphs; and relationships between these entities are established. Simple solution procedures based on these relationships are presented.

ISSN:0028-1441    

DOI:10.1002/nav.3800300411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY