Technical stability of stationary automatic control systems of variable structure with switched filters

Sufficient conditions for the technical stability in measure of a nonstationary control system with variable structure are established. The controller of the system has feedback-switched filters functioning together with shaper and actuator. It is assumed that the nonstationary parameters of the system vary within given ranges, at a finite rate, with appropriate control laws, with adjustment against mismatch signal, its derivatives of finite order, and all variable parameters of the filter. The parameters of the switching hyperplane remain constant. This approach for analysis of technical stability does not involve sliding mode conditions. Criteria of technical instability in measure for the control system under consideration are formulated using the properties of systems of comparison from below. The general criteria of technical stability and instability are applied to nonstationary filtered-control systems of variable structure of the third order. The comparison method based on normalized Lyapunov functions is used __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 6, pp. 110–127, June 2006.     

Prospective elementary teachers’ claiming in responses to false generalizations

When faced with a false generalization and a counterexample, what types of claims do prospective K-8 teachers make, and what factors influence the type and prudence of their claims relative to the data, observations, and arguments reported? This article addresses that question. Responses to refutation tasks and cognitive interviews were used to explore claiming. It was found that prospective K-8 teachers’ claiming can be influenced by knowledge of argumentation; knowledge and use of the mathematical practice of exception barring; perceptions of the task; use of natural language; knowledge of, use of, and skill with the mathematics register; and abilities to technically handle data or conceptual insights. A distinction between technical handlings for developing claims and technical handlings for supporting claims was made. It was found that prudent claims can arise from arguer-developed representations that afford conceptual insights, even when searching for support for a different claim.     

西康铁路远动系统改造设计

本文介绍了将西安至安康铁路牵引供变电设施纳入襄渝二线电力牵引远动系统实施实时数据采集和集中监控管理的改造设计,并明确了改造后达到的的调度系统功能及系统基本技术指标。     

中国智能家居专利分析

随着移动互联网的发展、智能终端的普及,以及人们生活水平的提高,智能家居将会是未来家居发展的趋势.对近年来国内智能家居领域的专利申请进行了整理和分析,从申请量趋势、技术领域分布、和重点申请人专利等角度进行专利分析,为智能家居的研究提供参考.     

IEC/TC29:电声学和全国电声学标委会标准动态(2008年9月～2011年6月)

给出了IEC/TC29自2008年9月～2011年6月的工作文件清单,以及IEC/TC29:电声学2009年～2011年6月发布的公告,介绍了IEC/TC29和全国电声学标准化技术委员会(SAC/TC23)目前标准和制修订情况.     

CMMB地面覆盖方案探讨

介绍了中国移动多媒体广播CMMB基本情况,对CMMB地面覆盖进行了初步探讨,对CMMB单频网的组建方式、建网要求等作了简要论述。     

信号隔离技术在某火控计算机中的应用

摘要：作为火控产品,可靠性的设计已成为决定该产品生命力的重要指标。为此,主要介绍了光电隔离和变压器隔离两种信号隔离技术在某型火控计算机中的应用,该技术的应用对提高产品的可靠性起到了良好的效果。     

CATV前端机房的标准化建设

建立完善的前端设备更换、安装、检修流程,建立完善的前端技术资料档案,使机房的技术人员能够快速熟悉机房设备和布线的变更,熟练掌握有线电视前端机房的各种新技术,对出现的故障能够迅速准确地判断并排除.     

数字转播车的维护调整与改造

电视转播车是电视台制作节目的重要设备,搞好数字转播车的维护调整和设备的更新改造,不仅能减少投入,而且可持久地为录制高质量的节目提供强有力的保障.从车体和技术系统两大方面讲述数字摄像机的调整与维护.     

CATV分支分配器隔离度及末端应用

了解分支、分配器反向隔离与相互隔离度以及在用户终端的正确使用，为减少用户的相互干扰。提高传输质量，应选用高标准的CATV器材，实现信号的反向隔离。