The relationship between lifetime health trajectories and socioeconomic attainment in middle age

A large literature demonstrates the direct and indirect influence of health on socioeconomic attainment, and reveals the ways in which health and socioeconomic background simultaneously and dynamically affect opportunities for attainment and mobility. Despite an increasing understanding of the effects of health on social processes, research to date remains limited in its conceptualization and measurement of the temporal dimensions of health, especially in the presence of socioeconomic circumstances that covary with health over time. Guided by life course theory, we use data from the British National Child Development Study, an ongoing panel study of a cohort born in 1958, to examine the association between lifetime health trajectories and socioeconomic attainment in middle age. We apply finite mixture modeling to identify distinct trajectories of health that simultaneously account for timing, duration and stability. Moreover, we employ propensity score weighting models to account for the presence of time-varying socioeconomic factors in estimating the impact of health trajectories. We find that, when poor health is limited to the childhood years, the disadvantage in socioeconomic attainment relative to being continuously healthy is either insignificant or largely explained by time-varying socioeconomic confounders. The socioeconomic impact of continuously deteriorating health over the life course is more persistent, however. Our results suggest that accounting for the timing, duration and stability of poor health throughout both childhood and adulthood is important for understanding how health works to produce social stratification. In addition, the findings highlight the importance of distinguishing between confounding and mediating effects of time-varying socioeconomic circumstances.     

Random effects regression mixtures for analyzing infant habituation

Random effects regression mixture models are a way to classify longitudinal data (or trajectories) having possibly varying lengths. The mixture structure of the traditional random effects regression mixture model arises through the distribution of the random regression coefficients, which is assumed to be a mixture of multivariate normals. An extension of this standard model is presented that accounts for various levels of heterogeneity among the trajectories, depending on their assumed error structure. A standard likelihood ratio test is presented for testing this error structure assumption. Full details of an expectation-conditional maximization algorithm for maximum likelihood estimation are also presented. This model is used to analyze data from an infant habituation experiment, where it is desirable to assess whether infants comprise different populations in terms of their habituation time.     

Windows2000下数控系统运动控制器的应用研究

通过对自行研制的GD102运动控制器特性的研究,将其驱动程序划分为内核支持层、寄存器读写层、基本命令层和应用层;分析了各层次的功能和实现原理及各层次间的通信机制。在分析Windows2000下内核模式驱动程序的构成和I/O请求处理流程的基础上,以DriverWorks为工具开发了运动控制器的驱动程序,并对驱动程序开发中的一些关键问题进行了论述。该驱动程序已被成功地应用到实际开放式数控系统项目,并取得了良好的效果。     

冗余度机器人的运动规划碰撞算法

在考虑了操作机的关节极限、自碰撞和静态障碍物的情况下,从给定的初始位形出发,发现一条到末端效应器目标位置和姿态的相连可到达路径。方法给出了机器人操作机点到点逆运动学问题求解算法,利用碰撞算法实现了冗余度机器人运动规划,仿真验证了该方法的有效性,并表明了该方法具有较大的实用价值。     

论速度变化对标枪成绩的影响

本文就网络英语教学目前存在的认识上的误区、大学英语网络教学目前可采用的基本模式以及大学英语网络教学的优越性和目前存在的问题进行探讨     

Fuzzy K-means clustering models for triangular fuzzy time trajectories

We focus our attention on the classification of fuzzy time trajectories with triangular membership function, described by a given set of individuals. To this purpose, we adopt a fullyinformational approach, explicitly recognizing the informational nature shared by the ingredients of the classification procedure: the observed data (Empirical Information) and the classification model (Theoretical Information). In particular, by supposing that the informational paradigm has a fuzzy nature, we suggest three fuzzy clustering models allowing the classification of the triangular fuzzy time trajectories, based on the analysis of the cross sectional and/or longitudinal characteristics of their components (centers and spreads). Two applicative examples are illustrated.     

机械运动方案的模糊综合评价

机械运动方案的设计 ,最终要求通过分析比较确定最优的方案 .用实例介绍了模糊综合评价法在机械运动方案设计中的应用     

卧式椭圆轨迹振动筛的自定中心问题研究

当振动筛筛箱各点作长轴平行于筛面的椭圆轨迹运动时,这种振动筛的胶带轮不可能只作定轴转动(即自定中心)。如果恰当地选择胶带轮几何中心的偏心值,胶带轮的摆动幅度将减小,因此,胶带的工作情况仍将得到改善。     

论当前影视霸权与文学尴尬生存的悖论性处境——以铁凝作品的影视改编为例

90年代以来消费主义文化的蓬勃兴起和媒介权力的空前膨胀,传统意义上的当代文学格局已经发生了深刻的变迁,而影视文化的强势崛起是造成文学影响力削弱的重要因素。本论文通过对铁凝作品的影视改编过程的解读和阐释,具体的剖析影视与文学之间从共荣、疏离、蚕食、反抗的深切关联,直接关涉到我们对影视时代文学尴尬的生存方式的感知和变迁时代的文化症候。     

试论英语词汇语义上的动态发展

任何一种语言都是活的语言,它随着人类社会文明的不断发展和变化在人们实际生活中变化着.英语词语亦如此.本文试图通过透视"英语词汇语义上的动态发展",引起我们对词义变化的足够重视,从而更好地掌握和使用英语词汇.