H∞ control for uncertain one‐sided Lipschitz nonlinear systems in finite frequency domain

The current article discusses the H_∞ disturbance attenuation control design problem for one‐sided Lipschitz systems in finite frequency domain. Models containing norm‐bounded parameter uncertainties, disturbances, and input nonlinearities are considered. By contrast to existing full frequency methods, the H_∞ controller is computed depending on the frequency ranges of disturbances. The finite frequency disturbance attenuation index is initially defined. Thanks to Finsler's lemma, sufficient and less conservative analysis conditions are also derived for the closed‐loop system. Then, synthesis conditions in the low, middle, and high frequency ranges as well as the whole frequency range, are formulated in terms of linear matrix inequalities. At last, to prove the effectiveness and the superiority of the proposed approach, a physical example is used and a comparative study is done.     

非规则梁桥伸缩缝处的碰撞对地震反应的影响

针对非规则梁桥在地震作用下伸缩缝处的碰撞现象,在建立考虑双边碰撞效应的简化动力分析模型的基础上,采用非线性地震反应时程分析方法,研究了纵向地震作用下非规则梁桥伸缩缝处的碰撞效应,并分析比较了双边碰撞与单边碰撞对桥梁结构位移的影响,研究结果对同类型的非规则梁桥的抗震设计具有一定的参考价值。     

LMI‐based adaptive output feedback fault‐tolerant controller design for nonlinear systems

This paper presents 2‐novel linear matrix inequality (LMI)‐based adaptive output feedback fault‐tolerant control strategies for the class of nonlinear Lipschitz systems in the presence of bounded matched or mismatched disturbances and simultaneous occurrence of actuator faults, including failure, loss of effectiveness, and stuck. The constructive algorithms based on LMI with creatively using Lyapunov stability theory and without the need for an explicit information about mode of actuator faults or fault detection and isolation mechanism are developed for online tuning of adaptive and fixed output‐feedback gains to stabilize the closed‐loop control system asymptotically. The proposed controllers guarantee to compensate actuator faults effects and to attenuate disturbance effects. The resulting control methods have simpler structure, as compared with most existing recent methods and more suitable for practical systems. The merits of the proposed fault‐tolerant control scheme have been verified by the simulation on nonlinear Boeing 747 lateral motion dynamic model subjected to actuator faults.     

On the existence,uniqueness and nature of Carathéodory and Filippov solutions for bimodal piecewise affine dynamical systems

In this paper, we deal with the well-posedness (in the sense of existence and uniqueness of solutions) and nature of solutions for discontinuous bimodal piecewise affine systems in a differential inclusion setting. First, we show that the conditions guaranteeing uniqueness of Filippov solutions in the context of general differential inclusions are quite restrictive when applied to bimodal piecewise affine systems. Later, we present a set of necessary and sufficient conditions for uniqueness of Filippov solutions for bimodal piecewise affine systems. We also study the so-called Zeno behavior (possibility of infinitely many switchings within a finite time interval) for Filippov solutions.     

小波极大模方法在旋转机械故障诊断中的应用研究

通过小波变换奇异性检测理论,利用连续小波变换提取极大模值线并求取Lipschitz指数,提取转子每转中Lipschitz指数的平均个数和全部Lipschitz指数的平均值作为转子故障振动信号的奇异性特征。通过BP神经网络对转子不平衡、不对中、油膜涡动、摩碰和无故障5种状态进行分类识别,取得了较好的效果。     

Functional Coefficient Autoregressive Models: Estimation and Tests of Hypotheses

In this paper, we study nonparametric estimation and hypothesis testing procedures for the functional coefficient AR (FAR) models of the form X_t = f ₁( X _{t − d} ) X _{t − 1}+ ... + f_p ( X _{t − d} ) X _{t − p} +ε _t , first proposed by Chen and Tsay (1993). As a direct generalization of the linear AR model, the FAR model is a rich class of models that includes many useful parametric nonlinear time series models such as the threshold AR models of Tong (1983) and exponential AR models of Haggan and Ozaki (1981). We propose a local linear estimation procedure for estimating the coefficient functions and study its asymptotic properties. In addition, we propose two testing procedures. The first one tests whether all the coefficient functions are constant, i.e. whether the process is linear. The second one tests if all the coefficient functions are continuous, i.e. if any threshold type of nonlinearity presents in the process. The results of some simulation studies as well as a real example are presented.     

Evaluating expectations about negative emotional states of aggressive boys using Bayesian model selection.

Researchers often have expectations about the research outcomes in regard to inequality constraints between, e.g., group means. Consider the example of researchers who investigated the effects of inducing a negative emotional state in aggressive boys. It was expected that highly aggressive boys would, on average, score higher on aggressive responses toward other peers than moderately aggressive boys, who would in turn score higher than nonaggressive boys. In most cases, null hypothesis testing is used to evaluate such hypotheses. We show, however, that hypotheses formulated using inequality constraints between the group means are generally not evaluated properly. The wrong hypotheses are tested, i.e.. the null hypothesis that group means are equal. In this article, we propose an innovative solution to these above-mentioned issues using Bayesian model selection, which we illustrate using a case study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

建筑评论与建筑设计之间

回顾30年来中国现代建筑评论理论发展历程及其标志性事件,认为总结和分析过去的经验,方能实现中国建筑评论理论与世界先进国家接轨.通过审视百多年来中国建筑的四个发展阶段,梳理出建筑评论理论与设计实践互为表里、互动互赢、共进共退的关系,并指出,只有真正实行“双百方针”,才能促进中国建筑业走向更大、更强.     

红外小目标小波多尺度相关检测方法

提出一种基于小波多尺度相关的目标检测方法.该方法通过二进小波对图像进行多尺度分析;利用边缘和噪声具有不同的Lipschitz指数造成它们的小波变换模在不同尺度下的不同传播特性,根据小波变换尺度相关性计算相邻大尺度模相关量用来增强信号,抑制噪声,提取粗略边缘图;并结合小尺度检测,具有定位精确的特点,将粗略边缘图与小尺度模图相与,寻找模极大值点,得到最终的检测结果.实验结果表明,该方法较传统的小波多尺度边缘检测方法能更加有效地进行红外小目标检测.