A nonlinear minimization approach to multiobjective and structured controls for discrete‐time systems

In this paper, a nonlinear minimization approach is proposed for multiobjective and structured controls for discrete‐time systems. The problem of finding multiobjective and structured controls for discrete‐time systems is represented as a quadratic matrix inequality problem. It is shown that the problem is reduced to a nonlinear minimization problem that has a concave objective function and linear matrix inequality constraints. An algorithm for the nonlinear minimization problem is proposed, which is easily implemented with existing semidefinite programming algorithms. The validity of the proposed algorithm is illustrated by comparisons with existing methods. In addition, applications of this work are demonstrated via numerical examples. Copyright © 2004 John Wiley & Sons, Ltd.     

DISCRETE WAVELET TRANSFORM FOR DENOISING RAMAN SPECTRA OF HUMAN SKIN TISSUES USED IN A DISCRIMINANT DIAGNOSTIC ALGORITHM

In this work, we applied the discrete wavelet transform (DWT) method as a denoising tool for dispersive Raman spectra of skin samples, and we compared the results obtained with the low-order polynomial fitting in a discriminating model based on principal components analysis (PCA). We used a set of 50 Raman spectra of skin tissue fragments diagnosed as normal (N) (25 spectra) and basocellular cell carcinoma (BCC) (25 spectra). A denoising procedure using DWT and its inverse was employed, and the resulting spectra were compared to denoising using low-order polynomial fitting and adjacent averaging smoothing. The tissue spectral profile showed changes in the intensity of bands below 1400 cm^?1 for DWT compared to the denoising by polynomial and smoothing. By applying PCA and Mahalanobis distance in both groups processed, we verified that the filtering method does not alter significantly the discrimination of N and BCC tissues. However, the DWT denoising presented an interesting result, which showed the main components after decomposition of the Raman signal used in the reconstruction.     

基于磁晶格的机械构件线应变在线检测技术

介绍了基于等间距磁晶格在线检测机械构件线应变的基本原理；提出了检测信号处理与波形转换方法；将机械构件线应变的检测转换为对检测信号波形高低电平持续时间的计测，并推导出时间计测值与构件线应变之间的数学关系式。为实现机械构件线应变的非接触式实时在线定量检测提供新的技术与方法。     

间隙对磁流体密封水介质的影响规律

为提供磁流体密封水的应用技术支持,研制了磁流体密封的试验装置,提出了新的试验方法来验证和解释理论分析和推导的正确性。试验中采用不同的密封间隙,以确定磁流体密封能力与密封间隙之间的关系。试验结果表明,磁流体的密封能力随密封级数的增加而提高;在一定范围内随密封间隙的增大而减小;密封间隙在0.05-0.20 mm时,效果较好,同时密封级数有一个最佳值;但是在特别小的时候,与所有文献报道不同的是密封能力不是提高而是在减小。     

制造系统建模中Petri网的工具和方法

本文概述了Ｐｅｔｒｉ网研究方面的一些最新研究结果，讨论了基于Ｐｅｔｒｉ网的一些建模工具，这些工具特别适合于制造系统的建模，性能分析，实时控制、系统可靠性系统等，文中还介绍了实际应用中所获得的某些结果，最后，提出了Ｐｅｔｒｉ网在制造系统建模中需解决的若干问题。     

3104铝合金的流变应力行为与动态再结晶

对3104铝合金在350-500℃以0．005-0．1s^-1的形变速率进行压缩，真应变为50％，随后立即水冷。采用真应力一真应变曲线和TEM研究其高温压缩变形中的流变应力行为和它的动态再结晶过程。结果表明：3104铝合金为正应变速率敏感材料，具有稳态流变的特征。流变应力随着变形速率的增加而增加，随着变形温度的升高而降低。在低形变温度(350℃)和低形变速率(0．035s^-1)下，该合金发生动态再结晶。     

应变模态在框架结构节点损伤诊断中的应用研究

通过对某7层钢制框架结构节点损伤的数值模拟和模型试验，利用应变模态在结构损伤前后的相对变化进行框架结构节点损伤的诊断。结果表明，一阶应变振型对损伤及其位置敏感，高阶应变振型节点的存在使得依据高阶应变模态进行损伤诊断时容易造成误判。因此，利用一阶应变振型在损伤前后的相对变化可以对框架结构节点的损伤进行诊断。     

EMS磁悬浮列车悬浮间隙传感器关键技术研究

以所研制的磁悬浮列车悬浮间隙传感器样机为背景，系统介绍了利用电涡流效应测量悬浮电磁铁和轨道间隙的原理、间隙传感器各部分组成。通过选用特殊的谐振电路和采取其他措施，解决了在线圈谐振和信号解调方面存在的关键问题。测试结果表明样机具备了测量间隙的基本功能，并且在常用测量段范围内有较好的线性度。     

利用位移测量推估梁及桥梁动态应变的方法研究

桥梁损伤检测是桥梁工程的一个重要课题。梁的应力应变参数与其刚度存在直接关系，因而应变模态测量可望用于桥梁损伤检测。动态应变测量可通过位移测量实现，但对位移传感器提出了特定的要求。对位移测量方法的误差分析表明传感器的相频一致性对测试精度有较大影响。在此分析基础上，利用特制的DP传感器进行了工字钢梁的模拟实验，实验结果验证了测量方法的可行性。     

Quantitative analysis of microstructure refinement in ultrafine-grained strips of Al6063 fabricated using large strain extrusion machining

Abstract

In present research work, ultrafine-grained strips of Al-6063 alloy were fabricated using hybrid extrusion machining technique known as “large strain extrusion machining (LSEM).” Fabrication of strips was done using the customized HSS tools of different rake angles varying from 0° to 10° under different machining conditions. Microstructural and mechanical characterizations of these strips were done to ascertain the effect of different parameters on their properties. From the results of hardness measurement of strips, it was concluded that hardness of the strips increased by 34–97% of the base material as of the refinement of grain size occurred. Surface lay was improved by 30% with higher cutting velocity and rake angle. Crystallite size was found to decrease with increase in the rate of strain. The shear strain was increased as chip compression ratio increased and rake angle decreased. Fabrication ability of strips increased due to increase in strain hardening exponent and it may result in the large scope of their applications. Nano-hardness of the strips was found to be more than bulk alloy. These above said results showed that ultrafine strips fabricated using LSEM process can become a good choice for future material fabrication.