An Estimation Method of the Pair Potential Function for Gibbs Point Processes on Spheres

An estimation method for pairwise interaction potential of a stationary Gibbs point process is introduced by considering the case of observations located on a sphere. It is based both on Fourier decomposition of the potential and on minimum contrast estimation. It is defined when many independent realizations of the process are available. Consistency and asymptotic normality are proved for the resulting estimators. The method enables derivation of the choice of the potential function by embedded hypotheses testing. The method is applied to independent observations of root locations on internodes around stem of maize roots. The internodes are described as circles and we focus on the interaction function associated with the potential. Since a model with too many components seems to fail, we choose a sequential procedure based on embedded hypotheses testing to build a simpler model.     

Equilibrium Wage Dispersion with Worker and Employer Heterogeneity

We construct and estimate an equilibrium search model with on–the–job–search. Firms make take–it–or–leave–it wage offers to workers conditional on their characteristics and they can respond to the outside job offers received by their employees. Unobserved worker productive heterogeneity is introduced in the form of cross–worker differences in a “competence” parameter. On the other side of the market, firms also are heterogeneous with respect to their marginal productivity of labor. The model delivers a theory of steady–state wage dispersion driven by heterogenous worker abilities and firm productivities, as well as by matching frictions. The structural model is estimated using matched employer and employee French panel data. The exogenous distributions of worker and firm heterogeneity components are nonparametrically estimated. We use this structural estimation to provide a decomposition of cross–employee wage variance. We find that the share of the cross–sectional wage variance that is explained by person effects varies across skill groups. Specifically, this share lies close to 40% for high–skilled white collars, and quickly decreases to 0% as the observed skill level decreases. The contribution of market imperfections to wage dispersion is typically around 50%.     

地方国有邮电通信企业偿债能力的综合分析与评价

应用因子分析法对地方国有邮电通信企业偿债能力进行了多因素下的综合分析与评价，介绍了分析与评价过程。     

Information Systems Management Issues: Reporting and Relevance*

Reports of key information systems issues have been published over the last two decades in many journals. Leading IS journals (e.g., MIS Quarterly, Information & Management, among others) have published key IS management issue reports every three or four years over the last 15 years, and will probably continue to provide such reports in the future. Although these reports claim to provide decisional guidance to practitioners, researchers, consultants, etc., the authors in their experience have noted concerns about their usefulness. While not questioning the validity of the methods and analysis conducted in these studies, we address two important questions in this article: the manner of reporting of the key issue results (which might be misleading), and the relevance of the results (are they providing what they intended to?). We hope that our discussion will provide new perspectives in making resource allocation decisions to both readers and authors of key issue articles.     

Selection of linear mixed-effects models for clustered data

We consider model selection for linear mixed-effects models with clustered structure, where conditional Kullback–Leibler (CKL) loss is applied to measure the efficiency of the selection. We estimate the CKL loss by substituting the empirical best linear unbiased predictors (EBLUPs) into random effects with model parameters estimated by maximum likelihood. Although the BLUP approach is commonly used in predicting random effects and future observations, selecting random effects to achieve asymptotic loss efficiency concerning CKL loss is challenging and has not been well studied. In this paper, we propose addressing this difficulty using a conditional generalized information criterion (CGIC) with two tuning parameters. We further consider a challenging but practically relevant situation where the number, $m$, of clusters does not go to infinity with the sample size. Hence the random-effects variances are not consistently estimable. We show that via a novel decomposition of the CKL risk, the CGIC achieves consistency and asymptotic loss efficiency, whether $m$ is fixed or increases to infinity with the sample size. We also conduct numerical experiments to illustrate the theoretical findings.     

快速成形件精度的影响因素及对策

快速成形是现代制造业快速响应市场必备的过程--快速成形前处理、分层叠加成形、后处理,对影响快速成形所制作的模型(快速成形件)精度的影响因素作了全面的分析.最后提出了提高快速成形件精度的对策.