Stabilization of linear systems with input delay and saturation—A parametric Lyapunov equation approach

This paper studies the problem of stabilizing a linear system with delayed and saturating feedback. It is known that the eigenstructure assignment‐based low‐gain feedback law (globally) stabilizes a linear system in the presence of arbitrarily large delay in its input, and semi‐globally stabilizes it when the input is also subject to saturation, as long as all its open‐loop poles are located in the closed left‐half plane. Based on a recently developed parametric Lyapunov equation‐based low‐gain feedback design method, this paper presents alternative, but simpler and more elegant, feedback laws that solve these problems. The advantages of this new approach include its simplicity, the capability of giving explicit conditions to guarantee the stability of the closed‐loop system, and the ease in scheduling the low‐gain parameter on line to achieve global stabilization in the presence of actuator saturation. Copyright © 2009 John Wiley & Sons, Ltd.     

Structure damage diagnosis using neural network and feature fusion

A structure damage diagnosis method combining the wavelet packet decomposition, multi-sensor feature fusion theory and neural network pattern classification was presented. Firstly, vibration signals gathered from sensors were decomposed using orthogonal wavelet. Secondly, the relative energy of decomposed frequency band was calculated. Thirdly, the input feature vectors of neural network classifier were built by fusing wavelet packet relative energy distribution of these sensors. Finally, with the trained classifier, damage diagnosis and assessment was realized. The result indicates that, a much more precise and reliable diagnosis information is obtained and the diagnosis accuracy is improved as well.     

Performance-First Control for Discrete-Time LQG Problems

Performance-first control for discrete-time LQG is considered in this paper to minimize the probability that the performance index exceeds a preselected threshold via constructing a closed-loop feedback control law. This problem can be converted into a mean-variance control problem which can be solved by developing a nested form of the variance and using polynomial optimization as a solution scheme.     

Reachability determination in acyclic Petri nets by cell enumeration approach

Reachability is one of the most important behavioral properties of Petri nets. We propose in this paper a novel approach for solving the fundamental equation in the reachability analysis of acyclic Petri nets, which has been known to be NP-complete. More specifically, by adopting a revised version of the cell enumeration method for an arrangement of hyperplanes in discrete geometry, we develop an efficient solution scheme to identify firing count vector solution(s) to the fundamental equation on a bounded integer set, with a complexity bound of O((nu)^n−m), where n is the number of transitions, m is the number of places and u is the upper bound of the number of firings for all individual transitions.     

电子商务安全隐患及其对策

分析了电子商务的安全需求、面临的主要安全问题,并在对入侵行为进行分类研究的基础上,对电子商务活动流程的描述和脆弱点分析中研究了其安全对策.     

Robust guaranteed cost control for singular Markovian jump systems with time-varying delay

This paper is concerned with the guaranteed cost control for continuous-time singular Markovian jump systems with time-varying delay. Without using the free weighting matrices method, a delay-range-dependent condition is derived in terms of strict linear matrix inequality (LMI), which guarantees that the singular system is regular, impulse free and mean-square exponentially stable with an H(∞) performance. Based on this, the existence condition of the guaranteed cost state feedback controller is proposed. A numerical example is given to illustrate the effectiveness and less conservatism of the proposed design method.     

中文问句分类特征的研究

针对"不同的问句分类特征对问句分类的影响不相同,提取和处理这些特征的时间复杂度也不相同"的问题,提取问题疑问词、核心关键词(疑问词的一二级依存词和问句中心语)的主要义原、核心关键词的首义原、问句主谓宾的主要义原、命名实体、名词单(复)数等六种分类特征,采用支持向量机分类算法,对事实疑问句进行不同特征组合的分类对比实验,发现采用词义消岐技术提取的主要义原不仅对分类的准确率影响明显,而且大幅降低特征向量的维数,减少了处理时间。     

移动无线传感网络节点协同避障的改进方法

传统蜂拥控制模型在协同避障跟踪方面,目前有Reynolds和Tanner的蜂拥模型。笔者曾对其做出了改进,提出了与Steer to Avoid法则相结合的避障模型,该模型在跟踪过程中对凸形障碍有较高的避障效率。由于在Steer to Avoid的方向判断中,目标对节点具有引力,使节点群陷入凹形区域无法绕出。将协同避障模型引入凹形障碍环境中,对模型进一步改进,在Steer to Avoid转向判断时暂时取消目标对节点群的引力,让节点群在进入凹形后自行做出环境的判断并沿着障碍边缘不断搜索路径,最终绕出障碍到达目标。仿真实验结果表明：与传统两个模型相比,该模型在避障的平均速率和时间效率上有显著提高,适用于避开未知的凹形障碍。     

A low temperature preparation and photocatalytical activities of PDVB@TiO2 hybrid microspheres

The core/shell anatase TiO₂ encapsulated poly(divinylbenzene) (PDVB@TiO₂) hybrid microspheres were prepared by the two steps: (1) the copolymer particles (PDVB) were prepared by the radical precipitation copolymerization of divinylbenzene (DVB) and γ-[(methacryloxy)propyl]trimethoxysilane (KH-570); (2) tetrabutyl titanate (TBOT) was co-hydrolyzed with the trimethoxysilyl groups on the surfaces of the PDVB cores and then the amorphous TiO₂ shell obtained was phase transformed to anatase TiO₂ by acid peptization. The products were characterized by FT-IR, UV–vis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). Their photocatalytical activities were measured by the photo-degradation of methylene blue (MB). The polymer supported TiO₂ photocatalysts prepared at low temperature, had better repetition because of the coupled action of KH-570 between the PDVB core and TiO₂ shell. Furthermore, it could be easily separated from the solution by simple sedimentation.