Nonlinear regression modeling via the lasso-type regularization

We consider the problem of constructing nonlinear regression models with Gaussian basis functions, using lasso regularization. Regularization with a lasso penalty is an advantageous in that it estimates some coefficients in linear regression models to be exactly zero. We propose imposing a weighted lasso penalty on a nonlinear regression model and thereby selecting the number of basis functions effectively. In order to select tuning parameters in the regularization method, we use a deviance information criterion proposed by Spiegelhalter et al. (2002), calculating the effective number of parameters by Gibbs sampling. Simulation results demonstrate that our methodology performs well in various situations.     

以数字社区为切入点建设和谐的社会生活共同体

把城乡社区建设成为管理有序、服务完善、文明祥和的和谐社会生活共同体是党的十七大提出的重大目标,利用互联网络及社区信息化平台建设现代化数字社区则对建设管理有序、服务完善、文明祥和的社会生活共同体有重要的推动作用。它是实现居民自治的硬件基础;是实现管理有序的依托平台;它为完善服务提供网络资源;为实现文明祥和、环境和谐提供精神保障。     

自愿性信息披露均衡机制探析

拥有私人信息的公司管理层,根据其报酬与业绩之间的敏感性水平,产生了不同的自愿性信息披露动机,在一定的金融微观市场结构条件下,公司管理层的自愿性信息披露均衡处于从完全披露到部分披露再到不披露的动态过程。     

社区作为“理性生态人”：内涵、结构和功能分析

“理性生态人”是指以实现包括人类在内的自然生态系统的和谐为目标而进行活动的人。社区作为“理性生态人”存在着三个维度的结构,即明确的社区生态文明意识,健全的社区生态管理制度和规范的社区生态管理行为。与此同时,社区作为“理性生态人”表现出三个层面的功能,即凸现社区的公共性质,促进社区管理改革的进程和丰富社区管理创新的内容。     

Modified quasi-profile likelihoods from estimating functions

We discuss higher-order adjustments for a quasi-profile likelihood for a scalar parameter of interest, in order to alleviate some of the problems inherent to the presence of nuisance parameters, such as bias and inconsistency. Indeed, quasi-profile score functions for the parameter of interest have bias of order O(1)$\mathrm{O}(1)$, and such bias can lead to poor inference on the parameter of interest. The higher-order adjustments are obtained so that the adjusted quasi-profile score estimating function is unbiased and its variance is the negative expected derivative matrix of the adjusted profile estimating equation. The modified quasi-profile likelihood is then obtained as the integral of the adjusted profile estimating function. We discuss two methods for the computation of the modified quasi-profile likelihoods: a bootstrap simulation method and a first-order asymptotic expression, which can be simplified under an orthogonality assumption. Examples in the context of generalized linear models and of robust inference are provided, showing that the use of a modified quasi-profile likelihood ratio statistic may lead to coverage probabilities more accurate than those pertaining to first-order Wald-type confidence intervals.     

Robust modified profile estimating function with application to the generalized estimating equation

We consider methods for reducing the effect of fitting nuisance parameters on a general estimating function, when the estimating function depends on not only a vector of parameters of interest, θ$\theta$, but also on a vector of nuisance parameters, λ$\lambda$. We propose a class of modified profile estimating functions with plug-in bias reduced by two orders. A robust version of the adjustment term does not require any information about the probability mechanism beyond that required by the original estimating function. An important application of this method is bias correction for the generalized estimating equation in analyzing stratified longitudinal data, where the stratum-specific intercepts are considered as fixed nuisance parameters, the dependence of the expected outcome on the covariates is of interest, and the intracluster correlation structure is unknown. Furthermore, when the quasi-scores for θ$\theta$ and λ$\lambda$ are available, we propose an additional multiplicative adjustment term such that the modified profile estimating function is approximately information unbiased. This multiplicative adjustment term can serve as an optimal weight in the analysis of stratified studies. A brief simulation study shows that the proposed method considerably reduces the impact of the nuisance parameters.     

Competitive and Cooperative Positioning in Supply Chain Logistics Relationships*

Cooperative logistics relationships require the sharing of information, which must be enabled by the integration of disparate information systems across partners. In this article, we theorize business‐to‐business logistics relationships should be managed using cooperative and competitive postures. Based on data from 91 dyadic relationships using interorganizational information technology (IT), we find that performance gains accrue when parties share strategic information and customize IT; mutual trust enables IT customization and strategic‐information flows and equitable relationship‐specific investments positively impact IT customization, mutual trust, and performance. Among other scholarly and practical implications discussed, partners should compete on resources for IT customization and cooperate to share strategic information. Managers tend to think of relationships with firms as polar opposites and view them as entirely cooperative or entirely competitive. Our results support active balancing and understanding of both competitive and cooperative stances. Such an approach enables conditions for participation symmetry that yields greater performance gains.     

Profile information matrix for nonlinear transformation models

For semiparametric models, interval estimation and hypothesis testing based on the information matrix for the full model is a challenge because of potentially unlimited dimension. Use of the profile information matrix for a small set of parameters of interest is an appealing alternative. Existing approaches for the estimation of the profile information matrix are either subject to the curse of dimensionality, or are ad-hoc and approximate and can be unstable and numerically inefficient. We propose a numerically stable and efficient algorithm that delivers an exact observed profile information matrix for regression coefficients for the class of Nonlinear Transformation Models [A. Tsodikov (2003) J R Statist Soc Ser B 65:759-774]. The algorithm deals with the curse of dimensionality and requires neither large matrix inverses nor explicit expressions for the profile surface.     

论虚拟图书馆

虚拟图书馆是信息网络化的产物 ,其含义是指基于计算机网络 ,特别是基于信息高速公路的多媒体信息管理系统。有信息资源数字化、网络的信息组织方式、网络化的传输及以用户为中心的服务模式四个方面的特征。虚拟图书馆从理论变为现实的发展过程中 ,遇到的障碍需克服 ,应采取对策。它的出现必将对人们的生活产生重大影响。     

西部信息产业的比较优势

本文是西部信息产业科技发展战略项目的研究结果之一.文章首先提出了界定西部信息产业比较优势的理论原则,在此基础上,研究了西部重点城市在IT领域的比较优势,并对其变化趋势做了动态分析.