基于类复向量原理的机器人位置和姿态分析

介绍了双实部类复向量的有关原理,建立了机器人位置的类复向量方程,并以6R机械手为例,论述机器人位置和姿态分析的类复向量方法。本文的方法与现行坐标变换矩阵法相比,变换次数和被变换的向量个数明显减少,从而使计算过程大大简化。     

IV估计框架下模型设定检验问题的讨论

 IV估计框架下各种统计量的良好性质依赖于相应的模型设定,如果这些模型设定未能得到数据的支持,其统计推断结论将是不可靠的。如判定计量经济模型是否存在内生性的Hausman检验,实证研究中同一问题的检验结果可能大相径庭。如何通过合理的模型设定检验程序来获得模型参数科学、可靠的估计结果和检验结论呢？本文讨论了工具变量估计框架下的各种模型设定检验问题,明确了各个检验统计量的适用条件及其逻辑联系,给出了工具变量估计框架下模型设定检验的一般步骤。     

Using plausible values in secondary analysis in large-scale assessments

Plausible values are typically used in large-scale assessment studies, in particular, in the Trends in International Mathematics and Science Study and the Programme for International Student Assessment. Despite its large spread, there are still some questions regarding the use of plausible values and how such use affects statistical analyses. The aim of this paper is to demonstrate the role of plausible values in large-scale assessment surveys when multilevel modeling is used. Different user strategies concerning plausible values for multilevel models as well as means and variances are examined. The results show that some commonly used user strategies give incorrect results while others give reasonable estimates but incorrect standard errors. These findings are important for anyone wishing to make secondary analyses of large-scale assessment data, especially those interested in using multilevel models to analyze the data.     

双语服务——大学图书馆的新选择

“双语服务”对大学图书馆的服务创新具有重要意义。图书馆实现双语服务,应该在环境视觉感官双语对照、日常接待礼仪用语、馆藏建设资源保障、参考咨询工作服务、人力资源管理、团队外语素质目标等方面的双语服务进行全面的设计与实施,以提升大学图书馆的信息服务水平。     

Immigrant children in the age of educational reform

Abstract

Immigrant children are the fastest growing subgroup among United States schoolchildren today. This paper explores how the new testing movement affects these students, many of which are English language learners.The passage of new federal laws mandating that all students be tested within one year of entrance into a U.S. school is refuted by long standing research. Studies have demonstrated that it takes five to seven years for students to attain the academic language necessary to achieve success in educational settings.This paper explores the instructional program options for immigrant students and advocates for changes in the current testing protocol for them.     

Exact solutions to the Behrens–Fisher Problem: Asymptotically optimal and finite sample efficient choice among

The problem of testing the equality of two normal means when variances are not known is called the Behrens–Fisher Problem. This problem has three known exact solutions, due, respectively, to Chapman, to Prokof’yev and Shishkin, and to Dudewicz and Ahmed. Each procedure has level alpha and power beta when the means differ by a given amount delta, both set by the experimenter. No single-sample statistical procedures can make this guarantee. The most recent of the three procedures, that of Dudewicz and Ahmed, is asymptotically optimal. We review the procedures, and then compare them with respect to both asymptotic efficiency and also (using simulation) in finite samples. Of these exact procedures, based on finite-sample comparisons the Dudewicz–Ahmed procedure is recommended for practical use.     

ASME Risk-Based Inservice Inspection and Testing: An Outlook to the Future

Significant research work has been completed in the development of risk-based inservice inspection (ISI) and testing (IST) technology for nuclear power plant applications through the ASME Center For Research and Technology Development. This paper provides technology that has been developed for these engineering applications. The technology includes risk-based ranking methods, beginning with the use of plant probabilistic risk assessment (PRA), for the determination of risk-significant and less risk-significant components for inspection and the determination of similar populations for pumps and valves for inservice testing. Decision analysis methods are outlined for developing ISI and IST programs. This methodology integrates nondestructive examination data, structural reliability/risk assessment results, PRA results, failure data, and expert opinion to evaluate the effectiveness of ISI programs. Similarly, decision analysis uses the output of failure mode and causes analysis in combination with data, expert opinion, and PRA results to evaluate the effectiveness of IST programs. Results of pilot applications of these ASME methods to actual nuclear plant systems and components are summarized. The results of this work are already being used to develop recommended changes in ISI and IST requirements by the ASME Section XI and the ASME Operation and Maintenance Code organizations. A perspective on Code and regulatory adoption is also outlined. Finally, the potential benefits to the nuclear industry in terms of safety, person-rem exposure, and costs are summarized.     

微量元素与人体健康关系研究的回顾与展望

目前,已有大量的基础医学实验研究和临床观察资料表明,人体患有各种疾病时体内的某些微量元素含量存在着显著的异常,这一现象已引起了国内外学者的广泛关注。本文根据近年国外的文献报道 概述了微量元素的生理作用及与人体健康关系的研究进展,并报道了应用各种仪器测定微量元素的方法。     

Towards a theory of point optimal testing

This paper puts the case for the inclusion of point optimal tests in the econometrician's repertoire. They do not suit every testing situation but the current evidence, which is reviewed here, indicates that they can have extremely useful Small-sample power properties. As well as being most powerful at a nominated point in the alternative hypothesis parameter space, they may also have optimum power at a number of other points and indeed be uniformly most powerful when such a test exists. Point optimal tests can also be used to trace out the maxemum attainable power envelope for a given testing problem, thus providing a benchmark against which test procedures can be evaluated. In some cases, point optimal tests can be constructed from tests of simple null hypothesis against a simple alternative. For a wide range of models of interst to econometricians, this paper shows how one can check whether a point optimal test can be constructed in this way. When it cannot, one may wish to consider approximately point optimal tests. As an illustration, the approach is applied to the non-nested problem of testing for AR(1) distrubances against MA(1) distrubances in the linear regression model.