改进的局域均值分解在机械故障诊断中的应用

为了准确地提取出故障特征,把局域均值分解算法应用于机械故障振动信号的特征提取中.然而在对信号进行局域均值分解时,由于端点的趋势无法预知,在分解时会污染到整个信号序列,而且滑动平均造成了信号的过平滑处理,导致故障特征不能准确地提取.采用波形匹配解决端点处信号的走势,之后再利用线性插值求得信号的局域均值函数与包络函数,通过在Matlab环境下仿真调幅信号验证了该算法在端点处能很好的保持原有信号的特征;并采用实际的机械振动信号进行实验验证,引入端点效应评价指标,根据分解后的生产函数与原信号的相关系数验证了改进的局域均值分解更能准确地提取故障特征.     

无线技术是RTU发展的方向之一

监控系统信号传送方式的发展过程的特点是：信号传送类型从多种数据类型、统一模拟信号到统一数字信号;信号传送介质从有线、总线到无线。无线传送技术代表了监控系统信号传送的发展方向,国内一部分RTU生产厂商已经率先在RTU的应用中推出了无线技术的产品,以无线技术作为RTU有线通信技术的补充,但其使用的无线技术存在一些局限性。作者认为,无线技术是RTU发展的方向之一,RTU应优先采用符合流程行业的三大无线国际标准的无线产品。     

江苏省地震前方指挥车应急数据信息通信方式的实现

前方指挥车是在有地震灾害事件发生时,能够立即响应,并快速到达地震震中所在地,立即开展现场信息汇集与共享、地震灾情动态评估和修正、辅助决策建议及时生成、现场资源调度和管理,实现前方指挥部与现场工作人员、国家指挥部、区域指挥部的不同应用系统之间的数据信息的共享和传递.本文主要介绍前方指挥车两种不同应急通信方式,并讨论各自的优缺点.     

数字化高校一卡通的建设模式分析

校园一卡通是数字化高校校园建设的重要组成部分和核心部分,而且已经应用到广大高校校园管理、金融服务和生活服务等方面中,取得了十分显著的成效.本文通过介绍数字化高校和校园一卡通,进而分析了数字化高校架构下校园一卡通的建设模式,之后还探讨了现阶段数字化高校一卡通建设模式的应用实践.     

Stochastic stability of semi‐Markovian jump systems with mode‐dependent delays

Semi‐Markovian jump systems, due to the relaxed conditions on the stochastic process, and its transition rates are time varying, can be used to describe a larger class of dynamical systems than conventional full Markovian jump systems. In this paper, the problem of stochastic stability for a class of semi‐Markovian systems with mode‐dependent time‐variant delays is investigated. By Lyapunov function approach, together with a piecewise analysis method, a sufficient condition is proposed to guarantee the stochastic stability of the underlying systems. As more time‐delay information is used, our results are much less conservative than some existing ones in literature. Finally, two examples are given to show the effectiveness and advantages of the proposed techniques. Copyright © 2013 John Wiley & Sons, Ltd.     

On adaptive sliding mode control without switching gain overestimation

This paper presents some further results on adaptive sliding mode control (ASMC) for a class of nonlinear systems with bounded uncertain parameters. Given a large initial tracking error, current ASMC design generally produces an unnecessarily large switching gain, consequently leading to a serious chattering problem or a large‐amplitude control jump for the continuous counterpart. To solve such an overadaptation problem, the switching gain adaptation mechanism is first analyzed in this paper, and the adaptation induced by the initial tracking error is suggested to be removed. Then, by exploiting the global sliding mode feature of time‐varying sliding mode control and integral sliding mode control, we present two effective methodologies for ASMC design. The proposed ASMC algorithms ensure that there is no overestimation of the switching gain and the system response is not slowed down when a small switching gain is generated. The validity of the proposed methods is verified by both theoretical analysis and simulation results. Copyright © 2012 John Wiley & Sons, Ltd.     

A generalized robust H ∞ filtering for singular Markovian jump systems and its applications

In this paper, a generalized robust H _∞ filtering method is proposed for a class of singular Markovian jump systems, whose generality is mainly embodied that the desired filter could bear perturbances in terms of uncertainties on its parameter matrices. Firstly, an LMI condition of robust mode‐dependent filter is developed. Based on the given result, a new approach to mode‐independent H _∞ filter is presented, which establishes a direct connection between mode‐dependent and mode‐independent filters. Secondly, when the transition rate matrix is with elementwise bounded uncertainties or partially unknown, sufficient conditions of such robust mode‐dependent and mode‐independent filters are all developed within LMI frameworks. Finally, a numerical example is used to demonstrate the effectiveness of the proposed methods. Copyright © 2013 John Wiley & Sons, Ltd.     

电子商务模式的多维分类体系研究

电子商务模式的开展是实现电子商务应用的重要问题之一.为充分探讨电子商务模式的体系建立,在总结已有成果基础上,本文基于电子商务模式的分类讨论十大类基本的电子商务模式,分析构建多维电子商务模式分类体系.     

高校计算机机房管理模式的探讨

高校的计算机机房为学生提供日常授课、特殊考试、自主上机等服务,是高校开展信息教育的重要场所.机房的建设与管理工作水平直接体现了高校的信息化水平,也直接影响了计算机相关教学的教学质量.本文对传统的机房管理模式进行了分析,探讨了其优点与不足,并且提出了一种新型的机房专职管理教师与学生协同的管理模式,具有一定的参考价值.     

制造任务分解与制造单元级资源配置协同优化

针对网络化制造环境下制造任务分解与资源配置脱节的问题,提出了制造任务逐层分解与制造单元级资源配置协同优化的方法,建立了协同优化流程.在对制造任务特点进行分析的基础上,建立了制造任务模型和制造单元资源模型,建立了多目标优化模型和目标的综合评价体系,利用在遗传算法求解搜索过程中所获得的动态信息进行综合评价,并随着求解搜索过程的深入对变异幅度进行调整,以达到全局优化和加快收敛速度的目的.最后以实例验证了该方法的可行性与有效性.