Optimal H∞ scaling for sensitivity optimization of detection filters

The paper deals with the sensitivity optimization of detection filters in linear time‐varying (LTV) systems which are subject to multiple simultaneous faults and disturbances. The robust fault detection filter design problem as a scaled H_∞ filtering problem is considered. The effect of two different input scaling approaches to the optimization process is investigated. The objective is to provide the smallest scaled L₂ gain of the unknown input of the system that is guaranteed to be less than a prespecified level, i.e., to produce a filter with optimal disturbance suppression capability in such a way that sufficient sensitivity to failure modes should still be maintained. It is shown how to obtain bounds on the scaled L₂ gain by transforming the standard H_∞ filtering problem into a convex feasibility problem, specifically, a structured, linear matrix inequality (LMI). Numerical examples demonstrating the effect of the scaled optimization with respect to conventional H_∞ filtering is presented. Copyright © 2002 John Wiley & Sons, Ltd.     

基于Developer 2000环境下组合条件查询的实现

讨论了Oracle前端开发工具Developer/2000环境下任意组合条件查询的实现技术，并通过作者实际开发应用情况详细介绍了该技术的应用背景、应用效果及实例代码。     

应用Fuzzy使土地评估方法最优化

运用模糊数学理论 ,依据土地估价的原则 ,对估价师在评估土地价格时 ,如何选择估价方法的问题进行定量分析 ,将问题归结为用Fuzzy相似优先比进行排序择优 ,从而选出比较适合的估价方法     

Similarity solutions to a laminar boundary layer problem in power law fluids

A suitable similarity transformatiopn is introduced to reduce the laminar boundary layer equations of power law fluids to a class of singular nonlinear two-point boundary value problems.The skin friction and shear stress distributions for boundary layer flow over a moving flat plate are investigated by utilizing the shooting technique.Results indicate that for each fixed value of the power law exponent n or the velocity ratio parameter ξ,the skin friction and shear stress decrease with the increasing of n or ξ respectively.     

Experimental investigation on similarity between velocity and density profiles in density-stratified countercurrent flow in reactor horizontal leg

A density-stratified countercurrent flow was investigated to obtain data necessary to develop a physical model on a thermally stratified flow in a horizontal leg of a pressurized water reactor (PWR). The experiments were conducted at atmospheric pressure and temperature using fresh water and NaCl solution with a non-dimensional density ratio of up to 1.2. The emphasis was placed on measurements of velocity and concentration profiles near the interface between the two fluid layers. Measured mean velocity and concentration profiles were fitted consistently using the Monin–Obukhov similarity theory, which are well-known outcomes for stratified turbulent shear flow. The interfacial friction and entrainment coefficients obtained from the fitted profiles agreed well with existing results in literature, confirming the applicability of the Monin–Obukhov theory. Furthermore, a new empirical correlation was proposed for the prediction of a mixing layer thickness.     

化学反应和扩散引起的沿垂直平板层流自然对流的相似性解

本文应用无限小变换群理论,证明在壁面浓度与环境浓度之差,按x~(1/(3-2n))变化时,由于化学反应和扩散引起的沿垂直平板的定常层流自然对流是存在相似性解的。对相似性方程组在参数Sc=0.01,0.05,0.20,0.40,0.72;n=0,1.0,2.0;Q=0.5,1.0,2.0下,用Runge—Kutta方法进行了求解,得到了物理量随各参数变化的规律。     

Reasoning about Textual Similarity in a Web-Based Information Access System

The degree to which information sources are pre-processed by Web-based information systems varies greatly. In search engines like Altavista, little pre-processing is done, while in knowledge integration systems, complex site-specific wrappers are used to integrate different information sources into a common database representation. In this paper we describe an intermediate point between these two models. In our system, information sources are converted into a highly structured collection of small fragments of text. Database-like queries to this structured collection of text fragments are approximated using a novel logic called WHIRL, which combines inference in the style of deductive databases with ranked retrieval methods from information retrieval (IR). WHIRL allows queries that integrate information from multiple Web sites, without requiring the extraction and normalization of object identifiers that can be used as keys; instead, operations that in conventional databases require equality tests on keys are approximated using IR similarity metrics for text. This leads to a reduction in the amount of human engineering required to field a knowledge integration system. Experimental evidence is given showing that many information sources can be easily modeled with WHIRL, and that inferences in the logic are both accurate and efficient.     

Conceptual modeling of data base operations

A formalism adequate for the specification of behavioral properties of data bases is proposed. The formalism is a many-sorted first order predicate calculus, including a formalized notion of data base state. Both update and query requests are modeled through expressions by the use of predicates supplied in the language of the formal system, and are treated uniformly as a theorem proving process. The process consists of using the axioms defining the data base for either synthesizing a valid sequence of update operations (if such exists) or for answering the query.     

组合颜色、空间和纹理特征的图像检索

提出了一种组合颜色、空间信息和纹理特征的图像检索方法 .用颜色块直方图来表达图像的颜色特征 ;通过提取主颜色块的面积比、质心、分布方差等特征得到图像的空间特征 ;利用 Gabor滤波器组提取图像的纹理特征 .实验结果表明 ,基于组合特征的图像检索方法要优于单纯的基于颜色、空间或纹理特征的方法