摘要:

AbstractDefense contractors retain engineers for two reasons. First, engineers work on current‐period production contracts. Second, engineers conduct independent research and development (IR&D) and write bids and proposals (B&P) for future contracts. The amount of IR&D/B&P activity, however, understates the amount of effort devoted to learning that reduces the cost of future production. Even some engineers who work on current‐period production may engage in learning, as a by‐product of their efforts. This article develops and implements a model for estimating the volume of learning activity undertaken by four large manufacturers of military aircraft. © 1994 John Wiley&Son

ISSN:0894-069X    

DOI:10.1002/1520-6750(199412)41:7<853::AID-NAV3220410702>3.0.CO;2-8

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe strategic trade‐offs between acquiring new capacity and subcontracting (or leasing) capacity are explored for service environments characterized by rapid technological improvement or highly seasonal demand. Reflecting the focus on service‐sector organizations, it is assumed that demand cannot be met from inventory. Furthermore, the critical impact that subcontracting has on a firm's competitive pricing policy is examined. The analysis presented is of particular relevance for firms in price‐competitive industries such as telecommunications, information services, or health care, because subcontracting capacity represents an alternative to acquiring costly new capacity which may soon become obsolete or unnecessary. It is shown that the optimal price charged is based on the higher of the two operating costs incurred (internal unit cost or unit cost of subcontracting). It is also shown that as a consequence of subcontracting to maximize profit, the optimal price charged is never reduced and may increase. © 1994 John Wiley&Son

ISSN:0894-069X    

DOI:10.1002/1520-6750(199412)41:7<875::AID-NAV3220410703>3.0.CO;2-Y

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

年代:1994

数据来源: WILEY

摘要:

AbstractComponent grouping problems, a type of set‐partitioning problem, arise in a number of different manufacturing and material logistics application areas. For example, in circuit board assembly, robotic work cells can be used to insert components onto a number of different types of circuit boards. Each type of circuit board requires particular components, with some components appearing on more than one type. The problem is to decide which components should be assigned to each work cell in order to minimize the number of visits by circuit boards to work cells. We describe two new heuristics for this problem, based on so‐called greedy random adaptive search procedures (GRASP). With GRASP, a local search technique is replicated many times with different starting points. The starting points are determined by a greedy procedure with a probabilistic aspect. The best result is then kept as the solution. Computational experiments on problems based on data from actual manufacturing processes indicate that these GRASP methods outperform, both in speed and in solution quality, an earlier, network‐flow‐based heuristic. We also describe techniques for generating lower bounds for the component grouping problem, based on the combinatorial structure of a problem instance. The lower bounds for our real‐world test problems averaged within 7%‐8% of the heuristic solutions. Similar results are obtained for larger, randomly generated problems. © 1994 John Wil

ISSN:0894-069X    

DOI:10.1002/1520-6750(199412)41:7<893::AID-NAV3220410704>3.0.CO;2-R

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

年代:1994

数据来源: WILEY

摘要:

AbstractWe consider a single‐machine scheduling problem with the objective of minimizing the mean (or equivalently, total) tardiness and earliness when due dates may differ among jobs. Some properties of the optimal solution are discussed, and these properties are used to develop both optimal and heuristic algorithms. Results of computational tests indicate that optimal solutions can be found for problems with up to 20 jobs, and that two of the heuristic procedures provide optimal or very near optimal solutions in many instances. © 1994 John Wiley&Sons, I

ISSN:0894-069X    

DOI:10.1002/1520-6750(199412)41:7<913::AID-NAV3220410705>3.0.CO;2-A

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

年代:1994

数据来源: WILEY

摘要:

AbstractA pursuer (P) pursues an evader(E), with each party choosing a speed in ignorance of the other's choice. Going extremely fast is not wise for either party because doing so would quickly exhaust available energy. The situation is modeled as a two‐person zero‐sum game. The game may or may not have a saddle point, depending on the energy ratio and tactical parameters. © 1994 John Wiley&Sons,

ISSN:0894-069X    

DOI:10.1002/1520-6750(199412)41:7<935::AID-NAV3220410706>3.0.CO;2-#

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

年代:1994

数据来源: WILEY

摘要:

AbstractPractitioners of maintenance scheduling sometimes use a simple analytic formula, derived based on inspection scheduling, as a heuristic to determine the length of the preventive maintenance period. The sensitivity of this heuristic solution is analyzed and the cost penalties are calculated compared to the exact solution that utilizes the lifetime distribution in the derivation of the optimal preventive maintenance period. A simple extension of the heuristic is suggested to improve the approximation with a slightly increased computational effort. The sensitivity and cost analysis of the improved heuristic are discussed as well. © 1994 John Wiley&Sons, Inc

ISSN:0894-069X    

DOI:10.1002/1520-6750(199412)41:7<945::AID-NAV3220410707>3.0.CO;2-U

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn this article we study the problem of scheduling independent tasks, each of which requires the simultaneous availability of a set of prespecified processors, with the objective of minimizing the maximum completion time. We propose a graph‐theoretical approach and identify a class of polynomial instances, corresponding to comparability graphs. We show that the scheduling problem is polynomially equivalent to the problem of extending a graph to a comparability graph whose maximum weighted clique has minimum weight. Using this formulation we show that in some cases it is possible to decompose the problem according to the canonical decomposition of the graph. Finally, a general solution procedure is given that includes a branch‐and‐bound algorithm for the solution of subproblems which can be neither decomposed nor solved in polynomial time. Some examples and computational results are presented. © 1994 John Wiley&Son

ISSN:0894-069X    

DOI:10.1002/1520-6750(199412)41:7<959::AID-NAV3220410708>3.0.CO;2-K

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn many routing‐location models customers located at nodes of a network generate calls for service with known probabilities. The customers that request service in a particular day are served by a single server that performs a service tour visiting these customers. The order of providing service to customers for each potential list of calls is uniquely defined by some a priori fixed basic sequence of all the customers (a priori tour). The problems addressed in this article are to find an optimal home location or an optimal basic sequence for the server so as to minimize the expectation of a criterion. The following criteria are considered: the total waiting time of all the customers, the total length of the tour, the maximal waiting time of a customer, the average traveled length per customer, and the average waiting time per customer. We present polynomial‐time algorithms for the location problems. For the routing problems we present lower bounds that can be calculated efficiently (in polynomial time) and used in a branch‐and‐bound scheme. © 1994 John Wiley&S

ISSN:0894-069X    

DOI:10.1002/1520-6750(199412)41:7<973::AID-NAV3220410709>3.0.CO;2-H

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn this article we propose new sequential sampling inspection plans with screening indexed by LTPD and AOQL, in which the alternative of accepting or rejecting a lot is decided by the results of sequential sampling plans, based on the minimal lattice paths. It is illustrated that the average total inspection can be economized by using both of the proposed sequential sampling inspection plans, with screening indexed by LTPD and AOQL, respectively. © 1994 John Wiley&Sons, Inc

ISSN:0894-069X    

DOI:10.1002/1520-6750(199412)41:7<991::AID-NAV3220410710>3.0.CO;2-2

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

年代:1994

数据来源: WILEY

摘要:

AbstractLetYi∽N(θi, σ i2),i= 1, …,p, be independently distributed, where θiand σ i2are unknown. A Bayesian approach is used to estimate the first two moments of the minimum order statistic,W= min (Y1, …,Yp). In order to compute the Bayes estimates, one has to evaluate the predictive densities of theYi's conditional on past data. Although the required predictive densities are complicated in form, an efficient algorithm to calculate them has been developed and given in the article. An application of the Bayesian method in a continuous‐review control model with multiple suppliers is discussed. © 1994 John

ISSN:0894-069X    

DOI:10.1002/1520-6750(199412)41:7<1007::AID-NAV3220410711>3.0.CO;2-#

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

年代:1994

数据来源: WILEY