积和式的性质与应用

积和式的计算是组合矩阵理论中一个相当困难的问题,给出了积和式的一些基本性质,并进一步讨论了某些特殊矩阵的积和式的计算.     

法制建设是反腐败的治本之策

社会转型和体制转轨时期滋生的腐败是生长在我们国家肌体上的一颗毒瘤。干部人事制度、法制、权力监督制度等方面的缺陷是腐败现象滋生蔓延的深层次原因,对症下药地加强法制建设是反腐败的治本之策。     

表面磁钢永磁无刷电机电磁转矩的解析法分析

With the air gap magnetic field distribution of surface mounted permanent magnet (PM) motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis (FEA). In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy.     

基于Ansoft的自动门用永磁无刷直流电机的设计和分析

对用于自动门控制系统的永磁无刷直流电动机,采用基于等效磁路法的RMxprt软件和基于电磁场有限元分析法的Maxwell软件对样机进行设计、分析和计算,并用＂场路结合＂的设计思路,完成了一台12槽/8极无刷直流电机的电磁设计任务。     

1．5 MW直驱永磁风力发电机冗错技术的研究

为了提高大功率永磁风力发电机的运行可靠性,文章以额定功率1．5MW、78极324槽的直驱永磁风力发电机为例,阐述了两种直驱永磁风力发电机变流器拓扑结构的工作原理及特点,基于MATLAB/SIMULINK仿真技术,分析了直驱永磁风力发电机在缺相、变流器故障以及额定状态下的运行特点,通过仿真表明：采用容错技术,可使直驱永磁风力发电机在缺相、变流器故障时运行情况与正常运行情况基本相同,提高了电机在风力发电系统中的可靠性。     

一种基于正六面体划分的永磁球形电机

针对永磁球形电机的结构,结合应用永磁同步电机矢量控制方法和球面的正多面体均匀划分,提出一种基于正六面体改进型的永磁球形电机结构。通过对球面多面体划分,优化永磁球形电机转子的永磁体和定子的线圈位置,使永磁球形电机可以分别绕三个正交轴独立旋转,令传统的矢量控制可以直接应用于球形电机的控制系统中。本文给出了电机结构的三维图并阐述了该电机的控制方法。     

Measuring the Efficiency of Teachers by Standardized Tests

ABSTRACT

There have been strong calls to action in recent years to promote both school choice and the learning of science, technology, engineering, and mathematics (STEM). This has led to the burgeoning development of STEM-focused schools. Nine STEM-focused charter and 2 STEM-focused magnet schools that serve elementary-aged students were examined to assess the achievement of students who transfer to these schools, as compared to students transferring to non-STEM schools, in the content areas of mathematics, language arts, and reading. The achievement of students transferring to STEM-focused elementary schools was also evaluated after 3 years at their new school and compared both to students’ own prior achievement at their old school and to achievement of students comprising comparison groups. Results generally indicated no effect of STEM-focused magnet schools, but did indicate some positive effects of STEM-focused charter schools.     

Magnet Schools: Reform and Race in Urban Education

Popular film impacts the work of educators and education in a variety of ways. In this article, the authors examine popular films' portrayals of education and K-12 schooling and higher education instructors from a variety of perspectives. The authors also investigate how education provides a platform for the examination of contemporary cultural concerns. The authors and education graduate students offer recommendations for fruitful viewing. In addition, the authors provide some rationales for further study of education in popular film.     

基于ANSOFT的永磁同步电机电磁场分析

电机气隙是机电能量转换的重要区域,气隙中的磁通密度是电机设计的重要参数．对7．5kW永磁同步电机,通过有限元分析软件ANSOFT进行建模、定义材料属性和模型属性,经过剖分划网、加载边界条件和负载电流,求解偏微分方程组后,完成后处理,得到永磁同步电机气隙中的磁力线分布图和磁通密度分布图．分析结果为永磁同步电机的优化设计提供指导意义．     

我国PPI波动的长期驱动力与短期驱动力——基于Gonzalo-Granger分解的分析

根据我国PPI的7项分类指数的月度数据,运用Gonzalo和Granger(1995)以及Darrat和Zhong(2002)提出的检验协整系统中的长期驱动力和短期驱动力的方法,从PPI分类指数的视角分析了我国工业品出厂价格指数波动的长期驱动力和短期驱动力。研究结果显示,全部3项生产资料的分类指数(采掘工业、原料工业、加工工业)以及一般日用品类和耐用消费品类分类指数是我国PPI波动的长期驱动力,生活资料中的食品类、衣着类和耐用消费品类分类指数是短期驱动力。