Mean square invariant forecasters for the weibull distribution

Many techniques of forecasting are based upon extrapolation from time series. While such techniques have useful applications, they entail strong assumptions which are not explicitly enunciated. Furthermore, the time series approach not based on an indigenous forecast principle. The first attack from the present point of view was initiated by S. S. Wilks. Of particular interest over a wide range of operational situations in reliability, for example, is the behavior of the extremes of the Weibull and Gumbel distributions. Here we formulate forecasters for the minima of various forms of these distributions. The forecasters are determined for minimization in mean square of the distance. From n original observations the forecaster provides the minimum of the next m observations when the original distribution is maintained. For each of the forecasters developed, tables of efficiency have been calculated and included in the appendix. An explicit example has been included for one of the forecasters. Its performance has been demonstrated by the use of Monte Carlo technique. The results indicate that the forecaster can be used in practice with satisfactory results.     

A dynamic nonlinear constrained optimal replacement model

A stochastically constrained optimal replacement model for capital equipment is constructed. Each piece of capital equipment, or machine, is characterized by its age and “utility” or “readiness” class. The readiness of a machine at any age is a stochastic function of its initial utility class and its age. The total discounted replacement cost of several replacement streams, each commencing with an initial machine, is minimized with respect to the replacement age and initial utility class of each machine, subject to a readiness constraint stating the lower bound on the expected number of machines in each utility class at any time. A general solution procedure is outlined and a specific case is solved in detail.     

B／S模式油料管理信息系统异构数据转换的实现

Internet的迅速发展和全军指挥自动化网的顺利建设使得油料管理信息系统由C／S模式向B／S模式发展成为需要,如何实现异构数据源的转换和备份是系统开发亟待解决的问题。提出了开发B／S模式油料管理信息系统时完成异构数据源转换的几种实现方法,重点介绍了如何设计程序将原始数据转换为SQL Server数据,如何以Access作为"中间层"实现SQL Senrer数据传递的问题,是Web环境下开发油料管理信息系统解决数据转换问题的一个有效方案。     

Book reviews

European Security in the New Political Environment by James H. Wyllie, London: Addison, Wesley Longman, 1997, ISBN 0-582-24403-X (pbk), £13.99

Russia and Europe: The Emerging Security Agenda edited by Vladimir Baranovsky, Oxford: Oxford University Press, SIPRI, 1997, ISBN 0-19-829201-5 (hbk), £45.00

The Defeat of Japan by David Rees, Westport, Connecticut and London: Praeger, ISBN 0-275-95955-4 (hbk), £46.50

The Collective Naval Defence of the Empire, 1900-1940 by Nicholas Tracy (ed.), London: Ashgate, for the Navy Records Society, 1997, ISBN 1859-284-027 (hbk), £59.50

Knights in White Armour The New Art of War and Peace by Christopher Bellamy, London: Pimlico Press, 1997, ISBN 0-7126-739-03 (pbk), £12.50

Regional Orders: Building Security in a New World by avid A. Lake and Patrick M. Morgan (eds), University Park: Penn State Press, 1997, ISBN 0-271-01703-i (hbk), £49.50/$55, ISBN 0-271-01704-X (pbk), £7.95/$19.95

Contested Social Orders and International Politics by David Skidmore (ed.), Nashville: Vanderbilt University Press, 1997, ISBN 0-8265-1284-4 (hbk), $32.95

The Politics of Threat: Minuteman Vulnerability in American National Security Policy by David H. Dunn. London: Macmillan Press, 1997, ISBN 0-333-67816-8 (hbk), £45.00

The Sociology of the Military by Guiseppe Caforio (ed.), Cheltenham: Edward Elgar, 1998, ISBN 1-85898-619-2, 704 pp., £150

The Nordic Nations in the New Western Security Regime by Ingemar Dorfer, Baltimore: Johns Hopkins University Press, 1997, ISBN 0-943875-83-8 (hbk), £27, ISBN 0-943875-82-X (pbk), £13     

On the solution of a stochastic bottleneck assignment problem and its variations

In this article, we study the stochastic version of the so-called bottleneck assignment problem. Our primary objective is to maximize the probability that the bottleneck value satisfies a specified target. Under general stochastic assumptions, we show that the solution in this case is easily obtained by solving a linear assignment problem. We next examine the situation where the target is to be minimized, given that the probability of satisfying the target exceeds a specified threshold. Finally, we address extensions to the original problem where a second objective is also considered.     

Due-date assignment and early/tardy scheduling on identical parallel machines

This article examines the problem of simultaneously assigning a common due date to a set of independent jobs and scheduling them on identical parallel machines in such a way that the costs associated with the due date and with the earliness or tardiness of the jobs are minimized. We establish that, for certain values of the due-date cost, an optimal schedule for this problem is also optimal for an early/tardy scheduling problem studied by Emmons. We discuss the solution properties for the two problems, and show that both problems are NP-hard even for two machines. We further show that these problems become strongly NP-hard if the number of machines is allowed to be arbitrary. We provide a dynamic programming solution for the problems, the complexity of which indicates that the problems can be solved in pseudopolynomial time as long as the number of machines remains fixed. Finally, we present the results of a limited computational study. © 1994 John Wiley & Sons, Inc.     

Cost analysis and extension of a simple maintenance-scheduling heuristic

Practitioners 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.