Modeling of covariance structures of random effects and random errors in linear mixed models

Abstract

In this paper, we discuss how to model the mean and covariancestructures in linear mixed models (LMMs) simultaneously. We propose a data-driven method to modelcovariance structures of the random effects and random errors in the LMMs. Parameter estimation in the mean and covariances is considered by using EM algorithm, and standard errors of the parameter estimates are calculated through Louis’ (1982 Louis, T.A. (1982). Finding observed information using the EM algorithm. J. Royal Stat. Soc. B 44:98–130. [Google Scholar]) information principle. Kenward’s (1987 Kenward, M.G. (1987). A method for comparing profiles of repeated measurements. Appl. Stat. 36:296–308.[Crossref], [Web of Science ®] , [Google Scholar]) cattle data sets are analyzed for illustration,and comparison to the literature work is made through simulation studies. Our numerical analysis confirms the superiority of the proposed method to existing approaches in terms of Akaike information criterion.     

Estimating survival curves with left truncated and interval censored data via the ems algorithm

It is well-known that the nonparametric maximum likelihood estimator (NPMLE) of a survival function may severely underestimate the survival probabilities at very early times for left truncated data. This problem might be overcome by instead computing a smoothed nonparametric estimator (SNE) via the EMS algorithm. The close connection between the SNE and the maximum penalized likelihood estimator is also established. Extensive Monte Carlo simulations demonstrate the superior performance of the SNE over that of the NPMLE, in terms of either bias or variance, even for moderately large Samples. The methodology is illustrated with an application to the Massachusetts Health Care Panel Study dataset to estimate the probability of being functionally independent for non-poor male and female groups rcspectively.     

坩埚热导率对晶体生长温度场的影响

本文通过有限元数值方法计算了坩埚热导率对晶体生长温度场的影响,指出当坩埚热导率大于晶体材料的热导率时,生长区域的纵向温梯会有大幅度减小,反之,温梯变化较小。并且认为当坩埚侧面与环境的热交换系数很大时,坩埚热导率的影响作用变小。并指出坩埚热导率可以通过热处理及其他手段予以调节。     

A Note on Inconsistency of NPMLE of the Distribution Function from Left Truncated and Case I Interval Censored Data

We show that under reasonable conditions the nonparametric maximum likelihood estimate (NPMLE) of the distribution function from left-truncated and case 1 interval-censored data is inconsistent, in contrast to the consistency properties of the NPMLE from only left-truncated data or only interval-censored data. However, the conditional NPMLE is shown to be consistent. Numerical examples are provided to illustrate their finite sample properties.     

阿洪王国的历史与变迁——印度东北部侗台语民族研究之一

十三世纪至十九世纪印度东北部的历史当属阿洪王国的历史.阿洪王国是十三世纪上半叶由侗台语民族之一支的阿洪人在布拉马普特拉河上游地区建立的国家.阿洪人的先民属中国古代"百越"族群,与云南傣族、缅甸的掸族有直接的族源关系.与周边的山地民族相比,阿洪人拥有先进的稻耕农业技术,并由于文字、宗教、政治、军事体制等因素,使其得以稳定和发展.但是由于人口比例、交流与融合方面的变迁以及内部斗争的消耗,加上英、缅等外部势力的入侵,终于让延续了六百年的王国灭亡了.本文在探求阿洪王国历史的同时也对阿洪人的语言、文化等方面的变迁进行分析,审视他们是融入还是脱离印度的主流文化的趋势.     

"双泛"与"三个主义"--兼析新疆周边的安全局势

本文简要地讨论了两个方面的问题一,关于"双泛"、"三个主义"的一些理论问题;二,关于新疆周边安全形势的评估.     

天津市青年农民受教育现状调查

农民教育问题是关系到农民整体素质的提高,加快实现农业现代化,以及加快农村富裕劳动力转移的进程。我国农村教育问题,特别是青年农民的教育问题比较紧迫,亟待我们解决。本文通过对天津市五区一县1200户农民综合情况的问卷调查,分析了青年农民受教育程度现状及特点等方面的问题。     

工会推进产业工人队伍建设的探索研究

产业工人是工人阶级的主体,在国民经济发展建设中发挥支撑作用。工会作为代表广大工人阶级利益的群众组织,在推进产业工人队伍建设改革中肩负着不可推卸的责任和重担。在目前新形势和时代变革下,我国产业工人队伍建设的现状还不能很好地适应经济转型中出现的新情况和新问题。对工会推进产业工人队伍建设的情况进行研究,在借鉴制造业强国经验的基础上,从思想政治引领、搭建发展平台、打造能力提升工程、利用“互联网+”和完善保障体系五个方面进行探索建设,从而为工会组织持续打造高素质产业工人队伍工作提供政策借鉴。