一类Kermack—Mckandrick方程组初值问题

本文研究描述传染病现象的一类Kermack—Mekandrick方程组初值问题光滑解整体存在唯一性及渐近性质。     

Path(ological) Dependency? Core Competencies from an Organizational Perspective

The development of the 'resource-based theory of the firm' has helped to reorient the field of strategic management towards a focus on the organizational processes and structures which produce 'core competencies'. By challenging previous assumptions of market determinism this approach seems to open up the prospect of a greater dialogue with the theories and concerns of organization studies. This paper aims to determine the scope of such a dialogue by developing an appreciation and critique of the core competencies framework from an organizational perspective. In this context, the key feature of resource-based theories is seen to be their focus on organizational knowledge rather than decision-making processes as the engine of competitive performance. This focus has a powerful resonance with studies of knowledge in organizations, particularly those forms of knowledge which are linked to product and process design.
However, despite the important shift towards a knowledge-based view of competition, the core competencies approach fails to follow the logic of its own argument as far as the organizational appropriation of knowledge is concerned. In their pursuit of an ontological model of competitive performance –defining the essential causes of firm competitiveness – resource-based approaches neglect the socially embedded qualities of organizational knowledge. As a result, the social construction of knowledge, encompassing the dilemmas posed by the employment relationship and the pitfalls of institutionalization, is neglected. Instead, a smoothly linear model is developed linking skills, competence and competitiveness. This mechanistic view is further reinforced by reliance on a command and control model of the management process. Organizational knowledge is not a biddable resource at the disposal of top management.     

深圳十年规划建设理论与实践初探

本文根据深圳十年规划与建设经验,对市场经济条件下的城市规划理论、乡镇城市化、开放型城市的交通与电讯网络、城市生态环境的保护、投资软硬环境的建设,以及如何提高城市规划的科学水平等问题作了探讨。     

Aalen's Linear Model for Sampled Risk Set Data: A Large Sample Study

Borgan and Langholz (1997) describe a method for estimating the parameter functions in Aalen's linear hazard regression model from sampled risk set data. Using a counting process formulation and the martingale central limit theorem, we provide a study of the asymptotic distributional properties of the estimator. The results are applied to study the efficiencies of the nested case-control and counter-matched designs relative to a full cohort analysis.     

A Nonparametric Test for the Parallelism of Two First-Order Autoregressive Processes

A nonparametric testing procedure for the parallelism of two first-order autoregressive processes is presented. This paper discuss the Mann–Whitney statistic, its natural competitor two-sample t -test, and the bootstrap method. It studies the asymptotic efficacies of the studentized Mann–Whitney statistic and the t -test statistic with their relative efficiency. Simulation results for comparing the powers of these test statistics are also presented.     

静电电子回旋脉塞的单粒子理论

本文用单粒子理论研究了静电电子回旋脉塞。通过对静电电子回旋脉塞中的电子运动的分析,导出了电子与波互作用的非线性摆方程。文中用二阶扰动方法求解非线性摆方程,得到了TE_(mn)和TM_(mn)两种工作模式的静电电子回旋脉塞不稳定性线性增益公式,进一步证实了静电电子回旋脉塞不稳定性是存在的。     

A BAYESIAN INTERPRETATION OF MULTIPLE POINT ESTIMATES

Consider a large number of econometric investigations using different estimation techniques and/or different subsets of all available data to estimate a fixed set of parameters. The resulting empirical distribution of point estimates can be shown - under suitable conditions - to coincide with a Bayesian posterior measure on the parameter space induced by a minimum information procedure. This Bayesian interpretation makes it easier to combine the results of various empirical exercises for statistical decision making. The collection of estimators may be generated by one investigator to ensure the satisfaction of our conditions, or they may be collected from published works, where behavioral assumptions need to be made regarding the dependence structure of econometric studies.     

A Multiple Imputation Approach to Linear Regression with Clustered Censored Data

Weextend Wei and Tanner's (1991) multiple imputation approach insemi-parametric linear regression for univariate censored datato clustered censored data. The main idea is to iterate the followingtwo steps: 1) using the data augmentation to impute for censoredfailure times; 2) fitting a linear model with imputed completedata, which takes into consideration of clustering among failuretimes. In particular, we propose using the generalized estimatingequations (GEE) or a linear mixed-effects model to implementthe second step. Through simulation studies our proposal comparesfavorably to the independence approach (Lee et al., 1993), whichignores the within-cluster correlation in estimating the regressioncoefficient. Our proposal is easy to implement by using existingsoftwares.     

Simplified Estimating Functions for Diffusion Models with a High-dimensional Parameter

We consider estimating functions for discretely observed diffusion processes of the following type: for one part of the parameter of interest we propose to use a simple and explicit estimating function of the type studied by Kessler (2000); for the remaining part of the parameter we use a martingale estimating function. Such an approach is particularly useful in practical applications when the parameter is high-dimensional. It is also often necessary to supplement a simple estimating function by another type of estimating function because only the part of the parameter on which the invariant measure depends can be estimated by a simple estimating function. Under regularity conditions the resulting estimators are consistent and asymptotically normal. Several examples are considered in order to demonstrate the idea of the estimating procedure. The method is applied to two data sets comprising wind velocities and stock prices. In one example we also propose a general method for constructing diffusion models with a prescribed marginal distribution which have a flexible dependence structure.     

Non-parametric Estimation of the Residual Distribution

Consider a heteroscedastic regression model Y = m ( X ) +σ( X )ε, where the functions m and σ are smooth, and ε is independent of X . An estimator of the distribution of ε based on non-parametric regression residuals is proposed and its weak convergence is obtained. Applications to prediction intervals and goodness-of-fit tests are discussed.