Cost models for evaluating virtual design strategies in multicycle product families

Rapid technological change and increased competition are forcing firms to compress the time it takes to develop product families and rapidly realize innovations among successive family members (models). Competition in rapidly changing high-variety markets requires effective management of design information across successive generations of products as well as in the same product generation. This paper considers two complementary approaches to design information management: virtual design and modular design. Virtual design describes the abstraction hierarchy used to represent product function. Modular design describes the hierarchy of physical realizations of the product and leads to a group technology approach to manufacturing. An analytical model is used to describe the impact of design management strategy characterized by investment in tools and infrastructure for virtual design and group technology on product development costs. This model provides insight into the impacts on costs of the mix of standard and revised parts in a product family. Virtual design has greatest impact on cost when there is a large proportion of parts revision, while group technology has most impact on cost when large numbers of standard parts are re-used. Effective management strategy for high variety rapidly changing products should combine both of these approaches and emphasize compatible organizational methods and technology integration.     

拟周期算子的均质化过程

本文研究具振荡拟周期系数的均质化过程,首先得到了拟周期函数的一些有趣性质,然后证明了拟周期算子的一个均质化定理.     

Relative efficiency of first difference estimator in panel data regression with serially correlated error components

We consider the pooled cross-sectional and time series regression model when the disturbances follow a serially correlated one-way error components. In this context we discovered that the first difference estimator for the regression coefficients is equivalent to the generalized least squares estimator irrespective of the particular form of the regressor matrix when the disturbances are generated by a first order autoregressive process where the autocorrelation is close to unity.     

Convergence rates of change-point estimators and tail probabilities of the first-passage-time process

In the classical setting of the change-point problem, the maximum-likelihood estimator and the traditional confidence region for the change-point parameter are considered. It is shown that the probability of the correct decision, the coverage probability and the expected size of the confidence set converge exponentially fast as the sample size increases to infinity. For this purpose, the tail probabilities of the first passage times are studied. General inequalities are established, and exact asymptotics are obtained for the case of Bernoulli distributions. A closed asymptotic form for the expected size of the confidence set is derived for this case via the conditional distribution of the first passage times.     

上海股市价格聚集现象及影响因素研究

选取上证50指数成份股半年的高频分笔数据，实证研究了上海股市的价格聚集现象。结果显示，上海股市存在显著的价格聚集现象，且开盘阶段价格聚集程度显著高于其余时间的日内效应。同时对价格聚集的影响因素进行了回归分析，发现股价大小、股价波动性和每笔交易额对价格聚集有显著的正影响，而股票的流通市值和每天交易笔数的影响显著为负。最后，对限价指令薄的价格聚集现象进行研究，并做了进一步的分析。     

Perturbation analysis for an orthogonal least-squares estimator

Coordinate measuring machines (CMMs) are used to check the geometric integrity of component parts. The geometric constraints to which a part must conform, as defined e.g., by The American National Standards Institute, assume the use of some type of gauging system when inspecting the part. Statistical issues arise in interpretting CMM data in the inspection of part tolerances. We consider a set of n planar regions on the surface of a part. The unit vector normal to each plane is estimated by orthogonal least squares. The small-sample density of this estimator (on the unit sphere S²) is determined asymptotically as the variance of the CMM error approaches 0. To a first-degree approximation, this density is Fisher-von Mises. Diagnostics are reviewed to test the geometric constraint that the n planar regions are oriented correctly with respect to one another, and to test the flatness of planar regions.     

Likelihood Ratio Confidence Bands in Non–parametric Regression with Censored Data

Let ( X , Y ) be a random vector, where Y denotes the variable of interest possibly subject to random right censoring, and X is a covariate. We construct confidence intervals and bands for the conditional survival and quantile function of Y given X using a non-parametric likelihood ratio approach. This approach was introduced by Thomas & Grunkemeier (1975 ), who estimated confidence intervals of survival probabilities based on right censored data. The method is appealing for several reasons: it always produces intervals inside [0, 1], it does not involve variance estimation, and can produce asymmetric intervals. Asymptotic results for the confidence intervals and bands are obtained, as well as simulation results, in which the performance of the likelihood ratio intervals and bands is compared with that of the normal approximation method. We also propose a bandwidth selection procedure based on the bootstrap and apply the technique on a real data set.     

割圆术与穷竭法

阐述了中国古代“割圆术”与古希腊“穷竭法”的联系与差异 .“割圆术”包含近代极限思想 ,其过程是一个无限过程 ,可以创造崭新结果 ;而“穷竭法”适用范围更广 ,是一个有限过程 ,结合归谬法可以推论预期的结果     

A New Family of BAN Estimators for Polytomous Logistic Regression Models based on ϕ- Divergence Measures

In this paper we study polytomous logistic regression model and the asymptotic properties of the minimum ϕ-divergence estimators for this model. A simulation study is conducted to analyze the behavior of these estimators as function of the power-divergence measure ϕ_(λ) Research partially done when was visiting the Bowling Green State University as the Distinguished Lukacs Professor     

Buehler confidence limits and nesting

The Buehler 1 –α upper confidence limit is as small as possible, subject to the constraints that its coverage probability is at least 1 –α and that it is a non‐decreasing function of a pre‐specified statistic T. This confidence limit has important biostatistical and reliability applications. Previous research has examined the way the choice of T affects the efficiency of the Buehler 1 –α upper confidence limit for a given value of α. This paper considers how T should be chosen when the Buehler limit is to be computed for a range of values of α. If T is allowed to depend on α then the Buehler limit is not necessarily a non‐increasing function of α, i.e. the limit is ‘non‐nesting’. Furthermore, non‐nesting occurs in standard and practical examples. Therefore, if the limit is to be computed for a range [α_L, α_U]of values of α, this paper suggests that T should be a carefully chosen approximate 1 –α_L upper limit for θ. The choice leads to Buehler limits that have high statistical efficiency and are nesting.