Optimal sample size allocation for tests with multiple levels of stress with extreme value regression

In this article, we discuss the optimal allocation problem in a multiple stress levels life‐testing experiment when an extreme value regression model is used for statistical analysis. We derive the maximum likelihood estimators, the Fisher information, and the asymptotic variance–covariance matrix of the maximum likelihood estimators. Three optimality criteria are defined and the optimal allocation of units for two‐ and k‐stress level situations are determined. We demonstrate the efficiency of the optimal allocation of units in a multiple stress levels life‐testing experiment by using real experimental situations discussed earlier by McCool and Nelson and Meeker. Monte Carlo simulations are used to show that the optimality results hold for small sample sizes as well. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

Churchill's naval holiday: Arms control and the Anglo‐German naval race, 1912–1914

Brian Johnson, The Secret War. London: BBC, 1978. Pp. 352; £6.50.

R. V. Jones, Most Secret War: British Scientific Intelligence 1939–45. London: Hamish Hamilton, 1978. Pp. xx + 556; £7.95.

Solly Zuckerman, From Apes to Warlords 1904–46. London: Hamish Hamilton, 1978. Pp. 00 (Information not available from publisher); £8.50.

Adrian Preston, ed., General Staffs and Diplomacy before the Second War. London: Croom Helm, 1978. Pp. 138; £5.95.

W. G. F. Jackson. ’Overlord’: Normandy 1944. London: Davis Poynter, 1978. Pp. 250; £6.75.

Richard K. Betts, Soldiers, Statesmen, and Cold War Crises. Cambridge, Mass. and London: Harvard University Press, 1977. Pp. 292 + index + appendices; Np.

Gerard J. Mangone, Marine policy for America—The United States at Sea. Lexington, Mass.: Lexington Books, 1977. Pp. 370, £17.50.

F. M. Richardson, Fighting Spirit. London: Leo Cooper, 1978. Pp. 189 + xv; £7.50.

Allen R. Millet, Ed., A Short History of the Vietnam War. London &; Bloomington: Indiana University Press, 1978. Pp. 169; £2.75.

Robert P. Berman, Soviet Airpower in Transition. Washington: Brookings, 1978. Pp. 82; $2.95 (Paper).     

采用空气轴承的大行程快速刀具伺服系统

随着对结构化超精密部件需要的不断增加,出现了加工具有高的表面光洁度以及形状精度的非旋转对称镜片的新技术。根据现有的快速刀具伺服系统,研制出了最大行程为16mm的新型快速刀具伺服系统(图1)。以前的快速刀具伺服系统采用了弹性导向机构,而现在的快速刀具伺服系统则采用了空气轴承,并且用了一个高频直线电机来驱动这个系统。由于采用了一个新的功率放大器,使得这个系统能够最高达到100Hz的频率以及1mm的振动幅度。这篇文章给出了这种新型快速刀具伺服系统的技术细节。     

Comparative evaluation of prior versus progressive articulation of preference in bicriterion optimization

Procedures for solving multiple criteria problems are receiving increasing attention. Two major solution approaches are those involving prior articulation and progressive articulation of preference information. A progressive articulation (interactive) optimization approach, called the Paired Comparison Method (PCM) is compared to the prior articulation approach of a priori utility function measurement in a quality control decision environment from the perspective of the decision maker. The three major issues investigated included: (1) the ease of use of each method, (2) the preferences of solutions obtained, and (3) the insight provided by the methodology into the nature and structure of the problem. The problem setting involved management students who were rquired to determine an acceptance sampling plan using both methods. The PCM provided the most preferred solutions and was considered easier to use and understand. The prior articulation of preference method was found to give more insight into the problem structure. The results suggest that a hybrid approach, combining both prior preference assessment and an interactive procedure exploiting the advantages of each, should be employed to solve multiple criteria problems.     

Responding to the failed state: The need for strategy

Given the challenges posed by failed and failing states, and the likelihood that such failure will continue well into the new millennium, the need for a strategic approach appears evident. Should we respond? If so, how and with what expectations? Answers to such questions require an underlying set of strategic guidelines. This article contributes to developing that strategy by examining common manifestations of state failure and some possible response objectives. It concludes by arguing that careful and tough analysis must guide our choices about where and when to respond, and how ambitiously we set our objectives.     

Estimating moments of the minimum order statistic from normal populations—a bayesian approach

Let Yⁱ ∽ N(θⁱ, σ), i = 1, …, p, be independently distributed, where θⁱ and σ are unknown. A Bayesian approach is used to estimate the first two moments of the minimum order statistic, W = min (Y¹, …, Y^p). In order to compute the Bayes estimates, one has to evaluate the predictive densities of the Yⁱ'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 Wiley & Sons, Inc.     

Spares stocking policies for repairable items with dependent repair times

This paper analyzes the problem of determining desirable spares inventory levels for repairable items with dependent repair times. The problem is important for repairable products such as aircraft engines which can have very large investment in spares inventory levels. While existing models can be used to determine optimal inventory spares levels when repair times are independent, the practical considerations of limited repair shop capacity and prioritized shop dispatching rules combine to make repair times not independent of one another. In this research a simulation model of a limited capacity repair facility with prioritized scheduling is used to explore a variety of heuristic approaches to the spares stocking decision. The heuristics are also compared with use of a model requiring independent repair times (even though that assumption is not valid here). The results show that even when repair time dependencies are present, the performance of a model which assumes independent repair times is quite good.     

The Hungarian method for the assignment problem

This paper has been presented with the Best Paper Award. It will appear in print in Volume 52, No. 1, February 2005.