Dependent masking and system life data analysis: Bayesian inference for two-component systems

Data from field operations of a system is often used to estimate the reliability of components. Under ideal circumstances, this system field data contains the time to failure along with information on the exact component responsible for the system failure. However, in many cases, the exact component causing the failure of the system cannot be identified, and is considered to be masked. Previously developed models for estimation of component reliability from masked system life data have been based upon the assumption that masking occurs independently of the true cause of system failure. In this paper we develop a Bayesian methodology for estimating component reliabilities from masked system life data when the probability of masking is dependent upon the true cause of system failure. The Bayesian approach is illustrated for the case of a two-component system of exponentially distributed components.     

ANALYSIS OF DOUBLY CENSORED DATA AND THE HIV INCUBATION PERIOD DISTRIBUTION IN WESTERN AUSTRALIA

The paper analyses the distribution of times from HIV seroconversion to the first AIDS defining illness for a subcohort of the Western Australian HIV Cohort Study for whom the seroconversion date is known to fall within a calendar time window. The analysis is based on a generalised gamma model for the incubation times and a piecewise constant distribution for the conditional times of seroconversion given the seroconversion windows. This allows flexible hazard shapes and also allows comparison of goodness of fit of the gamma and Weibull distributions which are often used for modelling incubation times. Computational issues are discussed. In these data, neither age at seroconversion, nor calendar time of seroconversion, nor the identification of a seroconversion illness appears to afFect incubation distributions. The Weibull distribution appears to provide a reasonable fit. The distribution of times from seroconversion to an HIV-related death is also briefly considered.     

Recursive procedures for multiple decisions: finite time memory and stepwise maximum likelihood procedure

A version of the multiple decsion problem is studied in which the procedure is based only on the current observation and the previous decision. A necessary and sufficient condition for inconsistency of the stepwise maximum likelihood procedure is shown to be the boundedness of the likelihood ratios. In the case of consistency the (typically slow) rate of convergence to zero of the error probabilities is determined.     

早期酋长制群体的聚落形态比较研究——以内蒙古东部、安第斯山北部和美洲中部三个地区为例

对内蒙古东部、安第斯山北部和美洲中部三个地区的早期酋长制群体的聚落形态进 行的比较研究表明,尽管这三个地区的发展过程大致相当,但在这三个地区中,大体类似的转变 却以不同的方式发生,从而导致了三个各具特色的等级社会的出现。最初的、大规模的、以等级 制度原则组织起来的酋长制群体出现后,其发展轨道的早期阶段明显地为后来的、较大的、更复 杂的政治实体即国家的出现创造了条件。通过地域性聚落分析,可以发现这三个地区在不同规模 层次上的人口和社会组织的异同,其中在赤峰和奥哈卡(Oaxaca)地区都存在的小型群体却不见 于马格达雷那高地(AltoMagdalena)的现象,需要进行更深入的研究,才能进一步揭示出在马 格达雷那高地是什么样的社会交流把这些家庭联合成更大的社会团体。     

Metropolitan influences on migration into poor and nonpoor neighborhoods

Data from the Panel Study of Income Dynamics and three decennial US censuses are used to examine the influence of metropolitan-area characteristics on black and white households’ propensity to move into poor versus nonpoor neighborhoods. We find that a nontrivial portion of the variance in the odds of moving to a poor rather to a nonpoor neighborhood exists between metropolitan areas. Net of established individual-level predictors of inter-neighborhood migration, black and white households are more likely to move to a poor or extremely poor tract rather than to a nonpoor tract in metropolitan areas containing many poor neighborhoods and a paucity of recently-built housing in nonpoor areas. Blacks are especially likely to move to a poor tract in metropolitan areas characterized by high levels of racial residential segregation and in which poor tracts have a sizeable concentration of blacks. White households are more likely to move to a poor than to a nonpoor tract in metropolitan areas that have comparatively few African Americans.     

抗病苹果品种在M.26、M.27和Mark砧木上的生长和结果习性

对以M .2 7EMLA、M .2 6EMLA和Mark为砧的Liberty、NY7541 4— 1、NY74 82 8— 1 2、NY6570 7— 1 9和McShay等苹果品种的生长、早熟性、产量和果实大小等项目进行的研究表明 ,Liberty、McShay、NY74 82 8— 1 2的树体大于NY7541 4— 1、NY6570 7— 1 9的树体最小。就砧木而言 ,以Mark为砧的苹果品种树体大于以M .2 6为砧的 ,以M .2 7为砧的树体最小。本文中的品种和砧木对树体的生长的影响没有交互作用。NY74 82 8— 1 2在定植后第 3、4年花量最大 ,NY6570 7— 1 9的最少。 1 993年时以Mark为砧的树花量比以M .2 6的为最多 ,以M .2 7为砧的开花量最少。Liberty、NY7541 4— 1和NY74 82 8— 1 2的累计产量比McShay和NY6570 7— 1 9的高。以Mark为砧的树累计产量多于以M .2 6为砧的 ,以M .2 7为砧的品种产量最低。NY6570 7— 1 9果形最大 ,NY74 82 8— 1 2的最小。以M .2 7为砧的树所结果实比以M .2 6和Mark为砧的小。NY7541 4— 1的树势中庸 ,早熟 ,高产 ,产量效率高 ,果实大小适度。NY74 82 8— 1 2在本试验中的表现也较好 ,但它对苹果黑星病只具Vm抗性而不具Vf抗性 ,故不可能作为新品种定名。在这些抗病品种中 ,根据早熟性、树势、产量和果形大小来看 ,Liberty和NY7541 4— 1具最佳的商品生产潜力。以     

中国基层政府与农村社区协同发展论析

农村社区作为一种具有较强认同感的社会生活共同体,承担着联系国家和农村社会的作用.通过对农村社区进行有效治理,中国基层政府在向农村社区居民传输国家方针政策的同时,也可以实现政府行政管理和农村社区自身发展的有效衔接和互构.本文通过对不同时期国家公权体系下的农村社区治理模式进行回顾梳理,对农村社区运行过程中的"治理失灵"、"信任式微""财权弱化"等现实问题进行了积极的反思.在此基础上,提出了理顺基层政府权责、培育公民文化环境、拓展利益诉求渠道等几种衔接思路,这样有助于中国基层政府与农村社区协同发展体系的构建.     

The differential contributions of teen drinking homophily to new and existing friendships: An empirical assessment of assortative and proximity selection mechanisms

Alcohol use is pervasive in adolescence. Though most research is concerned with how friends influence drinking, alcohol is also important for connecting teens to one another. Prior studies have not distinguished between new friendship creation, and existing friendship durability, however. We argue that accounting for distinctions in creation–durability processes is critical for understanding the selection mechanisms drawing drinkers into homophilous friendships, and the social integration that results. In order to address these issues, we applied stochastic actor based models of network dynamics to National Longitudinal Study of Adolescent Health data. Adolescents only modestly prefer new friendships with others who drinker similarly, but greatly prefer friends who indirectly connect them to homophilous drinkers. These indirect homophilous drinker relationships are shorter lived, however, and suggest that drinking is a social focus that connects adolescents via proximity, rather than assortativity. These findings suggest that drinking leads to more situational and superficial social integration.