Least squares estimation of varying‐coefficient hazard regression with application to breast cancer dose‐intensity data

To enhance modeling flexibility, the authors propose a nonparametric hazard regression model, for which the ordinary and weighted least squares estimation and inference procedures are studied. The proposed model does not assume any parametric specifications on the covariate effects, which is suitable for exploring the nonlinear interactions between covariates, time and some exposure variable. The authors propose the local ordinary and weighted least squares estimators for the varying‐coefficient functions and establish the corresponding asymptotic normality properties. Simulation studies are conducted to empirically examine the finite‐sample performance of the new methods, and a real data example from a recent breast cancer study is used as an illustration. The Canadian Journal of Statistics 37: 659–674; 2009 © 2009 Statistical Society of Canada     

Second-Order Approximations to Two Classes of Sequential Estimation Procedures

For the model considered by Chaturvedi, Pandey and Gupta (1991), two classes of sequential procedures are developed to construct confidence regions (which may be interval, ellipsoidal or spherical) of ‘pre-assigned width and coverage probability’ for the parameters of interest and for the minimum risk point estimation (taking loss to be quadratic plus linear cost of sampling) of the nuisance parameter. Second-Order approximations are derived for the expected sample size, coverage probability and ‘regret’ associated with the two classes of sequential procedures. A simple and direct method of obtaining the asymptotic distribution of the stopping time is provided. By means of examples, it is illustrated that several estimation problems can be tackled with the help of proposed classes of sequential procedures.     

浅析中国土族人口分布格局及其社会发展

人口分布格局,既是人在空间分布上呈现出来的地理状态,又是许多附着于分布环境上的社会人文变量的外在表现,因此对其进行研究具有探索自然和认识社会的双重意义。本文就中国土族人口的分布格局进行探讨,从历史和现实两方面分析了形成这种分布的原因,并在此基础上探讨了与人口分布格局密切相关的人口城市化、人口流动、人口素质提高、区域经济发展等社会热点问题,以期为政府政策的制定提供可靠的依据。     

MANAGED COMPETITION IN HEALTH INSURANCE

Rising healthcare costs have sparked debate about the best way to provide high‐quality affordable health insurance. We discuss the potential for regulated insurance markets to outperform single‐payer public insurance. We use as an example the private Medicare plans that now provide insurance to almost a third of seniors in the United States. The evidence suggests that private plans can limit costs and potentially appeal to enrollees, and that well‐designed risk adjustment can mitigate market failures due to adverse selection. However, fostering competition between insurers, especially in smaller markets, is difficult. We discuss how future research might illuminate the relative advantages of public and private health insurance.     

POLITICAL SELECTION IN CHINA: THE COMPLEMENTARY ROLES OF CONNECTIONS AND PERFORMANCE

Who becomes a top politician in China? We focus on provincial leaders—a pool of candidates for top political office—and examine how their chances of promotion depend on their performance in office and connections with top politicians. Our empirical analysis, based on the curriculum vitae of Chinese politicians, shows that connections and performance are complements in the Chinese political selection process. This complementarity is stronger the younger provincial leaders are relative to their connected top leaders. To provide one plausible interpretation of these empirical findings, we propose a simple theory in which the complementarity arises because connections foster loyalty of junior officials to senior ones, thereby allowing incumbent top politicians to select competent provincial leaders without risking being ousted. Our findings shed some light on why a political system known for patronage can still select competent leaders.     

THE FAILURE TO PREDICT THE GREAT RECESSION—A VIEW THROUGH THE ROLE OF CREDIT

Much has been written about why economists failed to predict the latest crisis. Reading the literature, it seems that this crisis was so obvious that economists must have been blind not to see it coming. We approach this failure by looking at one of the key variables in this analysis, the evolution of credit. We compare the conclusions reached in the recent literature with those that could have been drawn from an ex‐ante analysis. We show that the effect of credit on the business cycle cannot be exploited from a policymaker's point of view.     

中国优秀学术论文急速外流的原因及应对策略

通过对2014年中国SCI和SSCI学术论文外流情况的统计,当前学术论文外流的严重情况被全面和具体地呈现出来。通过系统梳理学术论文外流的相关研究,一方面从国家对论文外流缺乏宏观引导、科研考核机制刺激优秀论文外流、我国缺乏具有国际影响力的期刊以及国内期刊运作机制与国际化水平尚待提升4个方面揭示学术论文外流的具体原因;另一方面从宏观层面提出加强国家引导、集中优势资源打造国际顶级期刊、调整科研绩效考评政策、深化期刊体制改革、设立国内科技论文评奖机制5个方面的应对措施。     

多相感应电机任意非正弦气隙磁密的磁动势分析与应用

多相感应电机转矩密度的提高依赖于非正弦气隙磁密行波的合理构建,由于传统的电流相位、幅值控制策略无 法给出期望的非正弦磁密行波,因此文章研究了控制多相感应电机定子相电流中基波和谐波幅值、相位、频率的大小来 构建期望的气隙磁密波形的方法、首先基于单根载流导体产生的气隙磁动势波形,推导了任意相数、不对称、包含任意 高次谐波电流波形激励的具有典型绕组结构的多相感应电机的磁动势分布表达式。根据以上磁动势分析结论,多相电 机可通过变电流相序变极。针对气隙磁密行波逼近方波波形的案例,根据所提出的磁动势分析方法分析和预测了理想 空载励磁电流的波形。将预测波形和方波供电下的励磁电流波形进行了比较,从FFT分析结果来看,仍需微调各次谐波 电压相位,从而实现各次电流相位完全一致。