Large-Sample Variance of Fleiss Generalized Kappa

Cohen’s kappa coefficient was originally proposed for two raters only, and it later extended to an arbitrarily large number of raters to become what is known as Fleiss’ generalized kappa. Fleiss’ generalized kappa and its large-sample variance are still widely used by researchers and were implemented in several software packages, including, among others, SPSS and the R package “rel.” The purpose of this article is to show that the large-sample variance of Fleiss’ generalized kappa is systematically being misused, is invalid as a precision measure for kappa, and cannot be used for constructing confidence intervals. A general-purpose variance expression is proposed, which can be used in any statistical inference procedure. A Monte-Carlo experiment is presented, showing the validity of the new variance estimation procedure.     

卷绕系统中的张力递减控制

分析了张力递减控制原理，简要介绍了采用磁粉离合器传动的张力递减控制系统，以及该系统应用于玻纤布验卷设备的实例。     

直流电路中产生交流电的实验分析

通过创新思维,将力学、电磁学理论应用于直流电路和感应器,从直流电路中产生出交流电．此研究对于开发具有广阔市场前景的交直流同时供电的发电设备具有重要的理论和实践意义．     

三相交流调压电路的分析与仿真

在分析单相交流调压电路运行原理和工作方式的基础上,深入研究了三相交流调压电路的调压规律和调压效果,并在Matlab／simulink仿真平台上对三相星形无中线交流调压电路的理论部分进行了验证,结果表明：三相交流调压电路的分析是正确的．     

二苯并噻吩加氢脱硫催化剂NiMo/Al2O3和NiMo/AC的对比研究

通过N2吸附、X-射线衍射（XRD）和程序升温还原（TPR）等技术对载体和相应催化剂进行表征,考察了NiMo/Al2O3和NiMo/AC催化剂的加氢脱硫性能.结果表明,催化剂NiMo/AC上活性组分在载体活性炭表面高度分散,且活性组分与载体之间的相互作用较弱,催化剂表面的Ni,Mo活性相易于还原.在相同活性评价条件下,当以NiMo作为活性组分时,以氧化铝为载体的催化剂活性在低温时高于以活性炭为载体的催化剂,在较高温度时,两者活性相差不大.     

AG4自动变速器换档过程分析

自动变速器是车辆传动系统的主要部件,换档质量是反应其性能的重要指标.将自动变速器中的行星传动机构简化为等效杠杆,利用等效杠杆的受力平衡图和转速关系图可以直观判断单向离合器的接合或分离、换挡执行元件的工作状态以及动力传递路线.采用模拟杠杆法对AG4的行星齿轮变速器动力学进行分析,建立了该变速器通用的动力学运动方程,并就1-2档和2-3的升降档过程进行了分析.     

基于智能型AC—SSR的三相交流电机正反转控制及应用

在铁制网状纸篓成型的生产过程中,要求控制三相交流电动机正反转,采用交流接触器组成的控制电路。因其正反转频繁而造成交流接触器的触点很快损坏。使用交流固态继电器组成的控制电路,切换速度快,使用寿命长。尤其是采用智能型三相交流电动机正反转固态继电器组成的控制电路,接线简单,实际运行稳定可靠。     

AC48304语音处理器在嵌入式IP-PBX中的应用

IP-PBX（Internet Protocol-Private Branch Exchange,基于因特网协议的专用交换机）的数字中继基于AC48304语音处理器,采用ARM处理器及嵌入式Linux操作系统,实现了较低成本的嵌入式IP-PBX的VOIP中继.     

Application of direct torque control to electric screw presses for speeding up torque response and reducing starting current

Fast response and stable torque output are crucial to the performance of electric screw presses. This paper describes the design of a direct torque control （DTC） system for speeding up torque response and reducing the starting current of electric screw presses and its application to the J58K series of numerical control electric screw presses with a dual-motor drive. The DTC drive system encompasses speed control, torque reference control, and switching frequency control. Comparison of the DTC dual-AC induction motor drive with corresponding AC servo motor drive showed that for the J58K-315 electric screw press, the DTC drive system attains a higher maximum speed （786 r/min） within a shorter time （1.13 s） during a 250 nun stroke and undergoes smaller rise in temperature （42.0 ℃） in the motor after running for 2 h at a 12 min-1 strike frequency than the AC servo motor drive does （751 r/min within 1.19 s, and 50.6 ℃ rise）. Moreover, the DTC AC induction motor drive, with no need for a tachometer or position encoder to feed back the speed or position of the motor shaft, enjoys increased reliability in a strong-shock work environment.     

AC元数据研究

本文从定义,元素,应用等多个方面介绍了一种新的元数据格式AC。指出定义专门的“元数据的元数据”格式而不再将元数据管理信息混杂在内容元数据信息中是资源描述的一个发展趋势。