模糊积分理论在图像融合效果评价中的应用

利用模糊积分、择近原则进行融合图像分析及效果评价,并以基于小波变换的图像融合方法为例,就医学中CT-MR图像融合的具体情况,对小波分解和重构层数不同的融合图像进行分析和评价.     

基于多个域的UML模型的一致性检测

任何模型的表示都是要有意义的、一致的，通常的解决办法是加强约束。给出了在当前软件开发过程中的解决方案。约束和语义的关系是一致性检测的基础。对建模过程中模型受到的各个域的约束进行分级：从专家系统的知识根基中引入即成建模规则并且用约束构造型定义了不一致性的类型、级别和严重程度，因此可以向用户发出警告并且帮助用户改正甚至完善模型。     

快速JPEG图像检索方法

本文给出了一种基于归一化化转动惯量(NormalizedMomentInertia,NMI)的JPEG图像快速检索方法,其特点是直接在压缩域中利用DCT系数进行块分类,每一类分块形成一个二值索引图,统计该索引图的NMI值作为该类的一个特征,所有类的NMI特征构成了图像的一个特征序列,以此进行图像检索。本方法不需要完全解压缩,降低了计算复杂度,对图像的平移,旋转和尺度变换有较好的鲁棒性。试验结果表明这种图像检索方法具有良好的检索性能。     

Some functional inequalities and inclusion relationships associated with certain families of integral operators

By making use of certain familiar integral operators, the authors introduce and investigate several new subclasses of starlike, convex, close-to-convex, and quasi-convex functions. Among other results presented here, the authors establish a number of inclusion relationships associated with some of these integral operators. Some of the results established in this paper would provide extensions of those given in earlier works.     

Hypermedia learning and prior knowledge: domain expertise vs. system expertise

Abstract Prior knowledge is often argued to be an important determinant in hypermedia learning, and may be thought of as including two important elements: domain expertise and system expertise. However, there has been a lack of research considering these issues together. In an attempt to address this shortcoming, this paper presents a study that examines how domain expertise and system expertise influence students' learning performance in, and perceptions of, a hypermedia system. The results indicate that participants with lower domain knowledge show a greater improvement in their learning performance than those with higher domain knowledge. Furthermore, those who enjoy using the Web more are likely to have positive perceptions of non-linear interaction. Discussions on how to accommodate the different needs of students with varying levels of prior knowledge are provided based on the results.     

Electromagnetic modeling of 2D electronic mode‐stirred reverberating chambers for electromagnetic compatibility and interference analysis and design

This research concentrates on developing a complete theoretical tool to analyze the electronic mode‐stirred reverberating chamber. A 2D modeling of the EM fields is performed, which can then readily be extended to a 3D analysis of the cavity. The finite‐difference time‐domain (FDTD) method is implemented to discretize the Maxwell's equations. With our newly proposed method, the electromagnetic‐field characteristics can be easily studied inside the reverberating chamber under a realistic circumstance, thus opening doors to the analysis of a large spectrum of problems related to both commercial and military applications. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

ON THE STABILITY AND STABILIZATION OF TIME‐VARYING NONLINEAR CONTROL SYSTEMS

Many stability and stabilization problems of nonlinear time‐varying systems lead to asymptotic behavior of (–K + L)‐type systems, which consist of a K‐function and an L‐function. The stability of these systems is of fundamental importance for a series of stabilization problems of time‐varying nonlinear control systems. Even though the asymptotical stability of such systems has been used widely and (in most cases) implicitly, we do not find a rigorous proof, in the literature, and the existing proof for a particular case is questionable. Under quite general conditions, we prove that the solution of these systems tends to 0 as t →. Some generalizations are also obtained. As an immediate consequence, a general theorem is obtained for the stabilization of time‐varying systems. Using the new framework, we examine several stability and stabilization problems. First of all, for cascade systems, two sets of sufficient conditions are obtained for uniformly asymptotical stability and globally asymptotical stability, respectively. Then we consider the stability of ISS and IISS systems. A new concept, namely, strong IISS, is proposed. Several stability properties for autonomous systems are extended to time‐varying systems. Finally, we consider stabilization via detection. A rigorous proof is given for a smooth state feedback time‐varying system with weak detectability to be stabilizable by means of an observer.     

一种时域解调激光干涉仪调制信号的方法

针对某低频水平振动校准设备的激光干涉仪,利用NI公司的多功能采集卡,采集激光干涉仪的调制信号及与其同相位的电容式位移传感器的输出信号.根据激光干涉仪调制原理,提出一种时域解调调制信号的方法.根据调制信号条纹的时域特性和它被限幅的实际特点,利用labview软件实现了信号的解调,并将电容位移传感器信号作为参考信号,还原解调后信号的相位,从而得到振动台高精度的振动波形.实验证明,此方法对连续振动信号的解调效果良好,具有较好的重复性和稳定性,精度可达到激光干涉仪发射激光波长的四分之一.     

基于小波包的数值积分误差分析及消除方法

在结构损伤识别的时域法研究中，数值积分的误差将直接影响反演参数结果的精度。积分初值的未知、消除数值积分引入的误差是结构损伤反演计算中信号处理的难题。针对积分初值、数值积分积累误差和数值积分引入的偏移误差进行了理论分析，得出此类误差均具有低频特性的性质，可作为信号低频噪声进行处理。根据数值计算误差的特点分析及小波包多尺度、高分辨的特性，设计了一种基于小波包的滤波器，较好地解决了消除数值积分计算引入误差的问题。通过四层剪切结构模型算例验证，结构刚度反演误差由73％-32．2％降低到0．6％-0．24％，获得了较理想的效果。该方法同样可以用于其它领域的数值处理。     

基于时域声辐射模态的结构噪声主动控制研究

以简支矩形板为例，提出了利用时域声辐射模态进行声辐射研究，并从物理和数学意义上对时域声辐射模态进行了解释。研究表明时域声辐射模态既与时间无关，也互相独立，使得计算和控制声功率得以简化。针对瞬时声功率主要由第一阶辐射模态的声功率所决定的特点，在时域里进行结构噪声的主动控制研究，通过抵消第一阶辐射模态的声功率使得总的声功率得以有效降低。在此基础上，建立基于最小二乘算法的自适应反馈控制系统，进行仿真计算，结果证明了主动控制策略是有效的。