Communication channels within ethnic groups

Major channels of communication are examined for two major functions: providing news of the ethnic community, and linking ethnics to the “mother country.” The four major channels are: interpersonal channels (friends and neighbors), radio, local metropolitan daily newspapers, and ethnic-language newspapers. Size of ethnic group is linked to channel preference, and greater ethnicity is related to a preference for ethnic media for both functions. Lower SES ethnics lend to rely more on interpersonal communication and ethnic media, while higher SES ethnics turn more to metro media and magazines. Channel preference as indicated by respondents is also linked to actual usage patterns.     

A historical overview of educational psychology

A historical review of educational psychology might improve understanding of current status and problems. Before American development of the field, the Greeks, Juan Vives in the 16th century, and Pestalozzi and Herbart in the 19th century applied psychological views to educational problems. Despite the absence of scientific psychology in 19th century America, normal schools offered courses purporting to be psychological in content; these courses were supported by textbooks on the subject. James began, and Thorndike developed, the discipline that by the mid-1920s had assumed much of its current form. Journals and academic departments appeared in the first quarter of the century also. The continuing search through the middle of the century for a satisfying professional organization reflected educational psychology's difficulties in establishing an identity. It is not clear even today that the field has “crystallized,” as one writer described it in the 1920s.     

自抗扰控制技术在铝电解过程控制中的应用

针对铝电解控制系统的大滞后、大惯性以及动态特性随工况变化的不确定性等特点,本文提出了ADRC技术的氧化铝浓度控制方案。该控制方案能使铝电解过程很快进入稳态,超调量较小,提高了铝电解过程的动态和稳态性能。     

美国环境与健康管理体制对我国的启示

通过介绍美国环境与健康的管理和科研相关工作,为我国环境与健康的管理提供借鉴。     

中国男篮参加第15届世界男篮锦标赛比赛状况研究

通过观看参加第15届男篮世锦赛的中国男篮的所有比赛,结合国际篮联提供的比赛数据进行分析,对参加此次比赛的中国男篮进行客观评价,查找与世界强队的差距,发现问题所在,为今后的训练和比赛提供理论参考。     

美国的州立图书馆及其作用——美国图书馆的管理和运营概述之一

文章介绍了美国州立图书馆在美国图书馆系统中的作用和在美国图书馆发展中,在执行美国有关图书馆法的过程作所起的作用。通过对州图书馆发展的历史回顾,州图书馆在州政府的行政隶属关系,以及美国法律中对州图书馆职能的规定等方面的讨论,可以看出州图书馆及其作用的形成有其历史、政治和法律的原因。在此基础上,文章进一步讨论州图书馆对公众,州内各级政府以及各类图书馆所提供的服务。最后介绍州图书馆按《美国图书馆服务和技术法案》规定,在执行联邦政府图书馆法和监管政府图书馆基金时必须进行的图书馆服务计划的制定和评估过程。     

Independent force and position control for cooperating manipulators

The problem of independent force and position control of multitask cooperating manipulators is studied. Each manipulator is in a non-singular configuration and the object can be driven by the contact forces exerted by the end effectors of the manipulators. The design requirement is to control each coordinate of the position of the object as well as each component of the “rest” forces, except the moving forces that are determined uniquely from the object's position. The present design requirement has been proved to be always satisfied together with asymptotic and BIBO stability. A class of controllers solving the above simultaneous problem is analytically determined. The proposed state feedback controller does not depend upon the specific object dynamics and thus the resulting closed-loop multimanipulator system performs as required, not only when handling various objects but also when the dynamics of the objects are unknown or hard to compute or disturbed by external forces.     

曹魏行政体制中的州郡

曹魏时期三级行政体制似仍在发展之中,州作为高层政区似并不完整,中央仍对郡国实行直接控制,而且民政重心仍在郡国。     

Output regulation for a class of positive switched systems

In this paper, a complete procedure for the study of the output regulation problem is established for a class of positive switched systems utilizing a multiple linear copositive Lyapunov functions scheme. The feature of the developed approach is that each subsystem is not required to has a solution to the problem. Moreover, two types of controllers and switching laws are devised. The first one depends on the state together with the external input and the other depends only the error. The conditions ensuring the solvability of the problem for positive switched systems are presented in the form of linear matrix equations plus linear inequalities under some mild constraints. Two examples are finally given to show the performance of the proposed control strategy.     

交流异步电机状态变量观测及其优化控制

采用维持磁通始终恒定的方法对电机转矩直接控制，可解决交流异步电机控制精度和系统复杂性之间的矛盾，在电机状态变量观测及位置控制中应用了现代控制理论，和传统的矢量控制方法相比，在相同的性能指标下，该系统便于用微机来完成实时控制。