Regression Analysis of Restricted Mean Survival Time Based on Pseudo-Observations

Regression models for survival data are often specified from the hazard function while classical regression analysis of quantitative outcomes focuses on the mean value (possibly after suitable transformations). Methods for regression analysis of mean survival time and the related quantity, the restricted mean survival time, are reviewed and compared to a method based on pseudo-observations. Both Monte Carlo simulations and two real data sets are studied. It is concluded that while existing methods may be superior for analysis of the mean, pseudo-observations seem well suited when the restricted mean is studied.     

Comparisons of Test Statistics Arising from Marginal Analyses of Multivariate Survival Data

We investigate the properties of several statistical tests for comparing treatment groups with respect to multivariate survival data, based on the marginal analysis approach introduced by Wei, Lin and Weissfeld [Regression Analysis of multivariate incomplete failure time data by modelling marginal distributians, JASA vol. 84 pp. 1065–1073]. We consider two types of directional tests, based on a constrained maximization and on linear combinations of the unconstrained maximizer of the working likelihood function, and the omnibus test arising from the same working likelihood. The directional tests are members of a larger class of tests, from which an asymptotically optimal test can be found. We compare the asymptotic powers of the tests under general contiguous alternatives for a variety of settings, and also consider the choice of the number of survival times to include in the multivariate outcome. We illustrate the results with simulations and with the results from a clinical trial examining recurring opportunistic infections in persons with HIV.     

Choice of Parametric Accelerated Life and Proportional Hazards Models for Survival Data: Asymptotic Results

We discuss the impact of misspecifying fully parametric proportional hazards and accelerated life models. For the uncensored case, misspecified accelerated life models give asymptotically unbiased estimates of covariate effect, but the shape and scale parameters depend on the misspecification. The covariate, shape and scale parameters differ in the censored case. Parametric proportional hazards models do not have a sound justification for general use: estimates from misspecified models can be very biased, and misleading results for the shape of the hazard function can arise. Misspecified survival functions are more biased at the extremes than the centre. Asymptotic and first order results are compared. If a model is misspecified, the size of Wald tests will be underestimated. Use of the sandwich estimator of standard error gives tests of the correct size, but misspecification leads to a loss of power. Accelerated life models are more robust to misspecification because of their log-linear form. In preliminary data analysis, practitioners should investigate proportional hazards and accelerated life models; software is readily available for several such models.     

人口与环境可持续发展

人口环境系统是人口、资源、环境组成的对立统一的自然社会系统 ,是高度融合的有机整体。人口环境系统动因包括人口环境运动的推动、关系的调整和规律的作用。地球环境系统被人口压力突破后表现出矛盾的滞后性、影响的多重性和经济陷于衰退。人口过多、素质偏低和老龄化加快三症并发 ,成为中国人口与环境发展的独特现象。环境的作用包括给人类提供自然资源、自净功能或环境容量 ,提供舒适性环境的精神享受。环境问题的实质是人类索取超过资源本身、排污超过环境自净能力、自然资源耗竭超过极限便不可逆转。中国传统工业是一柄双刃剑 ,高投入、高消费求得增长 ,物耗和污染代价巨大。环境污染的主因是决策者和建设者缺乏可持续发展意识。可持续发展是实现人口与环境协调发展的科学、合理的社会结构范式。可持续发展可形象地比作人类发展坐标轴 :纵坐标是时间上的连续性 ,即兼顾当代与后代 ,控制人口 ,提高素质 ,珍惜资源 ,保护环境 ;横坐标是空间上的立体性 ,即精神文明、物质文明、社会文明、生态文明并举 ;轴心是人口与环境关系的良性互动。     

"自然人"的制度功能与内部结构

"自然人"作为现代民法中首要的民事主体,其本身的建构以及与其他制度的相互联系,无不体现文明的法治对人的终极关怀.故从普遍人性中的合理因素入手,探讨自然人制度建构对维护人性的的应有功能是有意义的.     

Marginal Regression of Gaps Between Recurrent Events

Recurrent event data typically exhibit the phenomenon of intra-individual correlation, owing to not only observed covariates but also random effects. In many applications, the population may be reasonably postulated as a heterogeneous mixture of individual renewal processes, and the inference of interest is the effect of individual-level covariates. In this article, we suggest and investigate a marginal proportional hazards model for gaps between recurrent events. A connection is established between observed gap times and clustered survival data with informative cluster size. We subsequently construct a novel and general inference procedure for the latter, based on a functional formulation of standard Cox regression. Large-sample theory is established for the proposed estimators. Numerical studies demonstrate that the procedure performs well with practical sample sizes. Application to the well-known bladder tumor data is given as an illustration.     

语言教学的“粗料输入”

在语言教学中 ,教师经常面对的一项选择是如何为学习者安排难度适当 ,份量适中的语言材料。作者认为 ,借助克拉申的语言输入 -输出假设不妨为一个行之有效的方法。语言教学中的粗料输入在内化学习者语言知识、提高语言能力方面能起到独到的作用     

Absorptive and transformative capacities in nanotechnology innovation systems

We identify managerial challenges offered by an emergent nanotechnology innovation system in which knowledge is dispersed, asymmetric and contested. We argue the proposed models of knowledge absorption and transformation enhance existing theories of knowledge and emergent technology by recognizing how and why knowledge flows among the actors in emergent technology innovation system. We base our argument on combined research evidence from a Delphi study concerning the future of European manufacturing, from which a selected statement has been analyzed, and from analysis of the NanoManufacturing Institute at Leeds University, UK; specifically its work in building ties between different actors associated with nanotechnology. We conclude our paper with suggestions for future research.     

考虑通行约束和运力限制的灾后应急物资联合调度优化研究

考虑到灾后路网受损难以运输应急物资，本文研究了应急响应中车辆-直升机联合调度的路径优化问题。针对受灾地区的实时路况，通往灾区的救援工具受到数量以及装载量的约束，本文将受灾点等待救援的平均时间最短以及应急网络总费用最低设为目标，构建运力受限条件下带通行约束的救援物资联合运输多目标优化模型，然后根据随机邻域搜索变异和分级交叉的思想构建出一种带精英策略的非支配排序混合进化算法（NSHEA-II）得到模型的解，并利用算例分析对该算法进行可行性检验。结果发现，本文构建的NSHEA-II算法相对NSGA-II算法能够得到较好的结果且波动性较小，这为决策者制定救援物资的配送方案提供有效的技术支撑。     

供应链中具有产能限制的竞争企业中的信息共享研究

本文研究由一个供货商和两个制造商组成的二级供应链中，制造商之间的横向信息共享策略和供应商的定价问题。在模型中，上游供应商同时为下游两家制造商提供价格相同的原材料，下游制造商生产具有替代性的商品进行数量竞争，并受到相同的产能限制。以Cournot博弈为研究手段，求解了制造商的均衡订货决策和信息共享策略，分析比较了在不同的信息共享策略下制造商的利润、供应商的利润和批发价格。本文在研究制造商的信息共享策略时考虑了上游供应商的批发价格的影响。研究表明，当均衡解受到产能约束时，制造商的信息共享策略会反向。在某些情况下，完全信息共享和完全信息不共享都可能成为博弈的占优策略。上游供应商通过调整批发价格可以影响制造商的信息共享决策。该模型为上游供应商提供了一种最优定价策略，也为下游制造商提供了求解自身最优订货量和信息共享决策的方法。