A curtailed test for the shape parameter of the Weibull distribution

Summary A procedure is proposed in this paper for testing the shape parameter, of the Weibull distribution. The test statistic which is based on the extremal quotient, possesses a monotone property which makes it possible for rejection earlier than the last planned observation of the null hypothesis,H ₀: =₀ when the alternative hypothesis isH _a: <₀ and early acceptance ofH ₀ whenH _a: >₀. The test being scale-free, does not require the scale parameter to be known.     

Designs for estimating an extremal point of quadratic regression models in a hyperball

This paper is devoted to studying optimal designs for estimating an extremal point of a multivariate quadratic regression model in the unit hyperball. The problem of estimating an extremal point is reduced to that of estimating certain parameters of a corresponding nonlinear (in parameters) regression model. For this reduced problem truncated locally D-optimal designs are found in an explicit form. The result is a generalization of the results of Fedorov and Müller (1997) for onedimensional quadratic regression function in the unit segment. Received February 2002     

江西大型企业资本运作模式的现状及其改进对策研究

资本运作是一种有效配置资源、实现企业资本增殖的活动,其核心是产权制度创新。本文对江西大型企业资本运作模式的现状进行了分析,进而提出了一系列的合理的改进对策,以期提高起运作绩效。     

减少汽车业的浪费

汽车制造商和零件供应商可以节省巨大开支，但前提是双方要更为紧密地合作在一起麦肯锡的研究表明，北美汽车业每年在产品开发和组装过程中由于汽车生产商与供应商缺乏良好的计划和协调不当，造成了超过100亿美元的浪费。事实上．这只是较为保守的估算。因为我们的研究仅涵盖了供应商发生的成本，如：附加设计、生产工具最后改型和零件自身的附加成本。这还不包括因设计问题生产商需额外支付的改型费用、生产问题引发的车辆最终成本的增加或质保支出。这几项每年给汽车行业带来的浪费约为120亿美元。     

Inferences about the parameters of a time series model with changing variance

Summary We consider the problem of making inferences about the parameters of a time series model when there is the possibility of a discrete variance change at an unknown time point. For this we obtain the posterior distributions of the parameters and of the variance ratio.     

DISSIMILAR STRUCTURAL AND CONTROL PROFILES OF EDUCATIONAL AND TECHNICAL ORGANIZATIONS[1]

This article contrasts the characteristic structural and control profiles of educational organizations with those of technical organizations. A group of primary and secondary schools and the operating units of an industrial firm differed both in structural variables and in three activities of control: buffering, smoothing, and forecasting. the article suggests that educational organizations emphasize modes of control that operate on components peripheral rather than central to the organization's technical core.     

The Morishima gross elasticity of substitution

We show that the Hotelling–Lau elasticity of substitution, an extension of the Allen–Uzawa elasticity to allow for optimal output-quantity (or utility) responses to changes in factor prices, inherits all of the failings of the Allen–Uzawa elasticity identified by Blackorby and Russell [(1989) Am Econ Rev 79: 882–888]. An analogous extension of the Morishima elasticity of substitution to allow for output quantity changes preserves the salient properties of the original Hicksian notion of elasticity of substitution. We thank Paolo Bertoletti for drawing our attention to the issue addressed in this paper and for his comments on an earlier draft.     

Remaining life estimation of used components in consumer products: Life cycle data analysis by Weibull and artificial neural networks

Environmental awareness and legislative pressures have made manufacturers responsible for the take-back and end-of-life treatment of their products. To competitively exploit these products, one option is to incorporate used components in “new” or remanufactured products. However, this option is partly limited by a firm's ability to assess the reliability of used components. A comprehensive two-step approach is proposed. The first stage phase statistically analyzes the behavior of components for reuse. A well-known reliability assessment method, the Weibull analysis, is applied to the time-to-failure data to assess the mean life of components. In the second phase, the degradation and condition monitoring data are analyzed by developing an artificial neural network (ANN) model. The advantages of this approach over traditional approaches employing multiple regression analysis are highlighted with empirical data from a consumer product. Finally, the Weibull analysis and the ANN model are then integrated to assess the remaining useful life of components for reuse. This is a critical advance in sustainable management of supply chains since it allows for a better understanding of not only service requirements of product, but the remaining life in a product and hence its suitability for reuse or remanufacture. Future work should assess: (1) reduction in downtime of process equipment through the implementation of this technique as a means to better manage preventative maintenance; (2) reduce field failure of remanufactured product; (3) selling-service strategy through implementation of the proposed methodology.