Theory and application research development of semi-solid forming in China

In order to adapt to the trend of “energy saving and emission reduction” and impel the practical application of semi solid processing (SSP) in China, the progress and application of semi-solid theory in China have been reviewed briefly and systematically. It was emphasized on basic theories, such as formation of globular grains, rheology, high pressure solidification and plastic deformation and applications, such as material design, preparation of semi-solid billets (slurries), thixoforming and application status, which are based on the advantage of semi-solid processing. The results show that the gap of SSP between world level and China exists, especially in application technologies, including market recognition, application fields exploiting, developing of billets (slurries) preparation technologies with low cost and special equipments. The prospect of semi-solid forming development path in China is presented. And we hope that application of SSP has great new breakthrough and development and China will be changed from a large metal processing country to a powerful metal processing country.     

Multi-model parameter estimation scheme for self-tuning controllers

A multi-model parameter estimation scheme (MMPES) based on a modification of the gaussian sum approach is proposed and its application in self-tuning it-incremental controllers is presented. As shown in the simulation examples, the MMPES gives a fast retuning of the estimated parameters when there is a parameter change; and by preserving the optimal model, it avoids the corruption of the estimated parameters when there is a load change. Thus it is more robust than existing techniques such as the variable forgetting factors. The only penalty in the MMPES is the increase in computing load, yet the proposed MMPES requires substantially less computing effort than that proposed by Andersson (1985).     

Failure detection and isolation by model cost analysis

A new concept for solving failure detection and isolation (FDI) problems in a linear system, called the parity-cost algorithm, is developed. A parity function is used to generate the residual of the measurement system by projecting the redundancy data from the measurement domain onto an orthogonal space. The decision-making process is done by using model cost analysis through the energy concept. The concept developed has three merits: (a) both direct and analytical redundancy systems can be handled easily; (b) FDI problems of combined sensors and actuators can be solved simultaneously; and (c) the parity-cost process can be quantified and multiple failures isolated quickly.     

钢筋销栓模型及其在深梁分析中的应用

本文提出了一个用于有限元分析的钢筋销栓作用模型。该模型采用分布模式来处理钢筋的横向销栓力和横向变形,以便与钢筋的整体式模型和混凝土的分布裂缝模型相协调。在有限元分析中采用了位移控制的割线刚度迭代法,可以进行荷载位移曲线下降段的分析计算。对深梁试件的分析表明,本文提出的钢筋混凝土模型可以准确分析试件的荷载变形特性。同时发现,纵向主筋的销栓作用对深梁的承载力和变形能力都有重要的影响。     

高功率因数三相脉冲宽度调制整流器的研制

三相整流器可以实现单位功率因数运行和低谐波含量,可以有效减少电力电子设备对电网的干扰,而且有利于大功率场合应用。以TMS320F2812为控制芯片,介绍了一款14 kW三相电压型脉冲宽度调制整流器的研制,并给出试验结果。     

Flexural strength–ductility performance of flanged beam sections cast of high‐strength concrete

Flanged sections are often used for long‐span concrete beams to maximize their structural efficiency. However, although for the same sectional area a flanged section could render a higher flexural strength, it would also lead to a lower flexural ductility, especially when heavily reinforced. Thus, when evaluating the flexural performance of a beam section, both the flexural strength and ductility need to be considered. In this study, the post‐peak flexural behaviour of flanged sections is evaluated by means of an analytical method that uses the actual stress–strain curves of the materials and takes into account strain reversal of the tension reinforcement. From the numerical results, the flexural strength–ductility performance of flanged sections is investigated by plotting the strength and ductility that could be simultaneously achieved in the form of design graphs. It is found that (1) at the same overall dimensions and with the same amount of reinforcement provided, a flanged section has lower flexural ductility than a rectangular section; (2) at the same overall dimensions, a flanged section has inferior strength–ductility performance compared to a rectangular section; and (3) at the same sectional area, a flanged section has better strength–ductility performance compared to a rectangular section. Copyright © 2003 John Wiley & Sons, Ltd.     

Membership function learning in fuzzy classification

A novel three-layer fuzzy neural network (FNN) is proposed which possesses ihe structure and learning ability of artificial neural networks, and the classification ability of fuzzy algorithms for pattern classification problems. During learning, the proposed FNN learns the membership function of each fuzzy class from training samples and adaptively organizes its hidden layer. The learning and recall times of the FNN are fast. Simulation results are also presented.     

基于.NET的网络化测控平台的设计开发

介绍一种基于.NET的通用网络化测控平台硬件方案和软件系统功能设计,给出了测控平台在某电力系统的实例应用。该测控平台具有良好的灵活性、适应性和扩展性。