Internal oxidation of dilute Cu–Al alloy powers with oxidant of Cu2O

The mechanisms responsible for the nucleation, growth and coarsening of Al₂O₃ particles in dilute Cu–Al alloys during internal oxidation have been investigated, and the alumina morphologies produced have been studied by electron microscopy using two-stage preshadowed carbon replica method. The alumina particle size has been observed to increase with increasing temperature of oxidation, with increasing time of oxidation, and with decreasing oxygen resource coefficient over the experimental range. These results indicate that the alumina particle size is determined by a competition between the rate of nucleation as the internal oxidation front passes and the subsequent growth and coarsening rates of the particles.     

Wide-band impedance characteristics of finite-ground uniform and stepped coplanar waveguides

Using the extended Heinrich equations for computing the per-unit-length resistance and inductance of coplanar waveguides (CPWs), we have studied the wide-band impedance characteristics of various finite-ground uniform and stepped CPWs. Finite-ground CPWs are frequently used in the design of CPW-based microwave and millimeter-wave devices. For various physical parameters, in particular the metallization thickness and its conductivity, we examined both resistance and inductance over a wide frequency range. Our work can serve as a basis for further study of the energy dissipation of the devices in the excitation of a high-power pulse.     

城市防灾空间系统规划初探

城市的防灾研究,不应只是重新检验并制订新版的建筑物防灾标准,还应该针对长期以来城市空间规划的缺陷,针对城市的各功能系统的空间分布及其与灾害环境的关系进行深入的探讨. 运用系统的观点,从宏观、中观、微观3 个层面提出了城市防灾空间的概念,并指出城市防灾空间系统规划应遵循的基本原则:与人的行为模式相结合;与城市建设、经济效益相结合;与环境保护相结合. 唯有如此,才能创造出可持续发展的城市空间.     

高线厂净循环水系统清洗预膜的实施

在高线厂净循环水系统投入运行之前，进行了管网及设备的清洗与预膜工作，使高线生产具备了良好的运行条件。     

Estimation of break location and size for loss of coolant accidents using neural networks

In this work, a probabilistic neural network (PNN) that has been applied well to the classification problems is used in order to identify the break locations of loss of coolant accidents (LOCA) such as hot-leg, cold-leg and steam generator tubes. Also, a fuzzy neural network (FNN) is designed to estimate the break size. The inputs to PNN and FNN are time-integrated values obtained by integrating measurement signals during a short time interval after reactor scram. An automatic structure constructor for the fuzzy neural network automatically selects the input variables from the time-integrated values of many measured signals, and optimizes the number of rules and its related parameters. It is verified that the proposed algorithm identifies very well the break locations of LOCAs and also, estimate their break size accurately.     

Corner block list representation and its application with boundary constraints

Floorplanning is a critical phase in physical design of VLSI circuits. The stochastic optimization method is widely used to handle this NP-hard problem. The key to the floorplanning algorithm based on stochastic optimization is to encode the floorplan structure properly. In this paper, corner block list (CBL)-a new efficient topological representation for non-slicing floorplan-is proposed with applications to VLSI floorplan. Given a corner block list, it takes only linear time to construct the floorplan. In floorplanning of typical VLSI design, some blocks are required to satisfy some constraints in the final packing. Boundary constraint is one kind of those constraints to pack some blocks along the pre-specified boundaries of the final chip so that the blocks are easier to be connected to certain I/O pads. We implement the boundary constraint algorithm for general floorplan by extending CBL. Our contribution is to find the necessary and sufficient characterization of the blocks along the boundary repre     

Feedback stabilization via designed planar centre manifold

This paper addresses the problem of local state feedback stabilization of a class of nonlinear systems, which have planar centre manifold. A new technique for designing centre manifold has been developed. Using this approach, a sufficient condition for stabilization of a class of nonlinear system is obtained. The approach has been specified for two particular critical cases: ‘zero centre’ with zero eigenvalue of multiplicity 2 and ‘oscillatory centre’ with a pair of pure imaginary eigenvalues. The control law, which stabilizes the overall system, is also presented. Some examples are presented to indicate how the present theorem may be implemented. Copyright © 2003 John Wiley & Sons, Ltd.     

PLC在华泰化工稀硝酸机组控制系统上的应用

针对硝酸机组的工艺特点及其技术要求，基于PLC可编程控制器技术，实现了化工机组生产过程监控的自动化撞制系统。讨论了由现场级、PLC控制级和HM1监控级3层结构组成的自动化控制系统的结构、功能和控制方法。用防喘振控制模式、启停车控制逻辑模式及PlD回路控制实现了机组控制的目标。所完成的控制系统成功地应用于安徽化工10^5t稀硝酸机组控制系统，实现了机组运行过程的实时监控、防喘振控制和启停车联锁逻辑等功能，取得了明显的成效。