摘要:

AbstractFor the case where the lifetime at a stress level has a Weibull distribution, statistically optimal and practical accelerated life test plans are developed under the assumptions of intermittent inspection and Type‐I censoring. For a statistically optimal plan the low stress level, the proportion of test units allocated, and the inspection times are determined such that the asymptotic variance of the maximum‐likelihood estimator of a certain quantile at the use condition is minimized. Although the practical plan adopts the same design criterion, it involves three rather than two overstress levels and easily calculated inspection schemes. Despite some loss in efficiency the practical plan has several advantages over the statistically optimal one. For instance, the practical plan can provide means for checking the validity of the assumptions made, may reduce the danger of extrapolation, and is more convenient to determine and implement. Computational experiments are conducted to evaluate the relative efficiency of a practical plan to the corresponding statistically optimal plan. Guidelines for selecting an appropriate practical plan are also described with an exam

ISSN:0894-069X    

DOI:10.1002/1520-6750(199102)38:1<1::AID-NAV3220380103>3.0.CO;2-3

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe present study considers the design of an optimal life test plan with Type I censoring in the case where only one testing machine is available and a machine tests items sequentially as seen in fatigue life tests of metallic materials. Under the condition that the life test is conducted in a fixed censoring time and with a fixed number of test items, a method for determining the censoring time and the number of test items is proposed from the Bayesian point of view. The proposed method is also applied to the Weibull life distribution with a known shape parameter.

ISSN:0894-069X    

DOI:10.1002/1520-6750(199102)38:1<23::AID-NAV3220380104>3.0.CO;2-V

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

年代:1991

数据来源: WILEY

摘要:

AbstractBounds forP(X 12+ X 22⩽k2σ 12) are given whereX1andX2are independent normal variables having zero means and variances σ 12, σ 22, respectively. This is generalized whenX1andX2are dependent variables with known cov

ISSN:0894-069X    

DOI:10.1002/1520-6750(199102)38:1<33::AID-NAV3220380105>3.0.CO;2-P

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn this article, we consider a situation in which a group of facilities need to be constructed in order to serve a given set of customers. However, the facilities cannot guarantee an absolute coverage to any of the customers. Hence, we formulate this problem as one of maximizing the total service reliability of the system subject to a budgetary constraint. For this problem, we develop and test suitable branch‐and‐bound algorithms and study the effect of problem parameters on solution difficulty. Some generalizations of this problem are also mentioned as possible extensi

ISSN:0894-069X    

DOI:10.1002/1520-6750(199102)38:1<41::AID-NAV3220380106>3.0.CO;2-L

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

年代:1991

数据来源: WILEY

摘要:

AbstractWe present an algorithm called the exact ceiling point algorithm (XCPA) for solving the pure, general integer linear programming problem (P). A recent report by the authors demonstrates that, if the set of feasible integer solutions for (P) is nonempty and bounded, all optimal solutions for (P) are “feasible 1‐ceiling points,” roughly, feasible integer solutions lying on or near the boundary of the feasible region for the LP‐relaxation associated with (P). Consequently, the XCPA solves (P) by implicitly enumerating only feasible 1‐ceiling points, making use of conditional bounds and “double backtracking.” We discuss the results of computational testing on a set of 48 problems taken from t

ISSN:0894-069X    

DOI:10.1002/1520-6750(199102)38:1<53::AID-NAV3220380107>3.0.CO;2-D

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

年代:1991

数据来源: WILEY

摘要:

AbstractModification of algorithms designed for scalar computing, to take advantage of vector processing, raises several challenges. This article presents the vectorization of the primal simplex based network algorithm and results in a 50% improvement in computational time. One of the major contributors to this improvement is the matching of the size of the pricing candidate list to the vector register size. The side constraints are relaxed into a single surrogate constraint. The single constraint network algorithm is vectorized and used as the basis for solving large‐scale constrained network problems. Computational experiments are presented which illustrate the vectorization of the network code as well as the ability of the surrogate constraint approach to deal with large constrained network problem

ISSN:0894-069X    

DOI:10.1002/1520-6750(199102)38:1<71::AID-NAV3220380108>3.0.CO;2-6

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn this article we present a stochastic model for determining inventory rotation policies for a retail firm which must stock many hundreds of distinctive items having uncertain heterogeneous sales patterns. The model develops explicit decision rules for determining (1) the length of time that an item should remain in inventory before the decision is made on whether or not to rotate the item out of inventory and (2) the minimum sales level necessary for retaining the item in inventory. Two inventory rotation policies are developed, the first of which maximizes cumulative expected sales over a finite planning horizon and the second of which maximizes cumulative expected profit. We also consider the statistical behavior of items having uncertain, discrete, and heterogeneous sales patterns using a two‐period prediction methodology where period 1 is used to accumulate information on individual sales rates and this knowledge is then used, in a Bayesian context, to make sales predictions for period 2. This methodology assumes that over an arbitrary time interval sales for each item are Poisson with unknown but stationary mean sales rates and the mean sales rates are distributed gamma across all items. We also report the application of the model to a retail firm which stocks many hundreds of distinctive unframed poster art titles. The application provides some useful insights into the behavior of the model as well as some interesting aspects pertaining to the implementation of the results in a “real‐world” si

ISSN:0894-069X    

DOI:10.1002/1520-6750(199102)38:1<87::AID-NAV3220380109>3.0.CO;2-V

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

年代:1991

数据来源: WILEY

摘要:

AbstractThis article deals with an inventory problem where the supply is available only during an interval of (random) lengthX. The unavailability of supply lasts for a random durationY. Using concepts from renewal theory, we construct an objective function (average cost/time) in terms of the order‐quantity decision variableQ. We develop the individual cost components as order, holding, and shortage costs after introducing two important random variables. Due to the complexity of the objective function whenXandYare general random variables, we discuss two special cases and provide numerical examples with sensitivity analysis on the cost and noncost parameters. The article concludes with a discussion of the comparison of the current model with random yield and random lead‐time models. Suggestions for further research are also provi

ISSN:0894-069X    

DOI:10.1002/1520-6750(199102)38:1<107::AID-NAV3220380110>3.0.CO;2-4

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

年代:1991

数据来源: WILEY

ISSN:0894-069X    

DOI:10.1002/1520-6750(199102)38:1<::AID-NAV3220380102>3.0.CO;2-9

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

年代:1991

数据来源: WILEY