干扰抵消型多用户检测器性能分析

用模块化的方法描述了 ＳＩＣ、ＭＳＳＩＣ、ＰＩＣ和ＰＳＩＣ干扰抵消多用户检测算法，给出算法的实现结构图，并且在渐近有效性、抗远近效应、系统容量和实现复杂度诸方面进行了性能比较分析。分析表明需要进行功率排序的ＭＳＳＩＣ、ＰＳＩＣ和ＳＩＣ算法比ＰＩＣ算法具有更好的抗远近效应的性能，ＭＳＳＩＣ和 ＰＳＩＣ算法在渐近有效性和系统容量方面要显著强于ＳＩＣ和ＰＩＣ算法。     

基于软件芯片的快速原型制造系统软件设计方法

本文把软件芯片的概念引入快速原型制造（RPM）系统的软件设计之中,根据RPM系统软件结构的特点,对其进行了软件芯片划分,并论述了每个软件芯片的功能。以数控语言解释器软件芯片为例,详细地介绍了RPM系统软件芯片的研制过程。研究了如何用软件芯片构造RPM系统软件。     

基于软件芯片的可重构远程故障诊断系统*

提出了一种具有充分柔性与可重构性的远程故障诊断系统的结构模型,利用软件芯片技术对系统中的各功能模块进行封装,并描述了系统的运行原理。根据应用设备的不同要求,通过系统数据组织、诊断芯片适配和运行结构设计,可以快速重构出不同的诊断系统。     

Joining of Cf/SiC composite to Ti alloy using composite filler materials

Abstract

C_f/SiC was successfully joined to Ti alloy with Ag–Cu–Ti–W, Ag–Cu–Ti–SiC and Ag–Cu–Ti–TiC mixed powders by some suitable brazing parameters. Microstructure and shear strengths of the preformed joint were investigated. The results showed that the W particulate and reaction products can uniformly distribute in the brazing layer of the performed joint. These composite brazing layers relaxed the thermal stress of the joint effectively. These characteristics were beneficial to the joint, which had shear strengths that were significantly higher than the optimal shear strengths of the joint brazed with pure Ag–Cu–Ti at room temperature and 500°C.     

陶瓷材料在滑动接触中的裂纹扩展模拟

对刚性柱面和SIC陶瓷材料平面产生滑动接触进行了有限元数值分析,以有限元软件ABAQUS作为分析平台,以扩展有限元方法(XFEM)和最大主应力判定准则对整个滑动接触过程中裂纹扩展的行为进行了模拟,得出了裂纹尖端单元的最大主应力及裂纹扩展路径和裂纹张开角,为生产实际过程中的无损探伤提供理论的测量视角。     

Coarsening of particulate silicon in aluminium based matrices

Abstract

Published measurements of the coarsening parameter K = (r³2r³_o)/t of particulate silicon in Al – Si alloy base matrices are compared with values predicted for volume diffusion control according to the LSW model corrected for finite volume fraction. While some measurements are within a factor of 10 of LSW predictions, others exceed these by factors as high as 10³ to 10⁴. Possible reasons for such large apparent enhancements of coarsening rate are discussed.     

一种改进的码分多址通信系统的多用户干扰抵消接收机

在码分多址通信系统中,由于许多用户占用同一信道进行通信,传统的单用户检测策略和最佳的多用户检测策略不是很实用。本文对直接序列－码分多址系统的多用户检测策略和次最优检测策略进行了分析和阐述,讨论了一种改进的多级并行干扰抵消接收策略,最后给出了几种模拟结果。     

Comments on “Transient stability of an a.c. generator by Lyapunov's direct method”

A matrix method is presented for the determination of the response sequences of discrete time-invariant linear systems for a large range of deterministic input sequences.

Using the z-transform formulation the transfer function of the discrete system is defined and, assuming that the input sequence is a linear combination of a certain set of basic sequences, it is demonstrated that an explicit formulation of the output sequence may be obtained by purely matrix operations. This approach not only simplifies the application of the z-transform technique but can also be used as the basis of a digital computer programme.

Examples are given to illustrate the use of the method including its application to the solution of general nth-order difference equations     

Investigation on compressibility of Al–SiC composite powders

Abstract

The consolidation behaviour of particulate reinforced metal matrix composite powders during cold uniaxial compaction in a rigid die was studied. Al–SiC powder mixtures with varying SiC particle size, ranging from nanoscale (50 nm) to microscale (40 µm), at different volume fractions up to 30% were used. Based on the experimental results, the effect of the reinforcement particles on the densification mechanisms, i.e. particle rearrangement and plastic deformation, was studied using modified Cooper–Eaton equation. It was found that by increasing the reinforcement volume fraction or decreasing its size, the contribution of particle rearrangement on the densification increases while the plastic deformation becomes restricted. In fact, when percolation network of the ultrafine reinforcement particles is formed, the rearrangement could be the dominant mechanism of consolidation. It was also shown that at tap condition and at the early stage of compaction where the particle rearrangement is dominant, the highest density is achieved when the reinforcement particle size is properly lower than the matrix (0˙3<the size ratio<0˙5) and the fraction of hard particles is relatively low (<10%). At high compaction pressures, the reinforcement particles significantly influence the yield pressure of composite powders, thereby retarding the densification.     

两级过滤去除地下水中铁锰的试验研究

通过锰砂和硅碳素两级过滤的方式,研究了含锰、含铁及高铁低锰三种水质条件下铁锰的去除效果,进一步探讨了不同水质中铁锰的去除方法。结果表明,对于单独含锰的水质,可仅采用二级硅碳素滤柱去除;对于单独含铁的水质,可仅采用一级锰砂滤柱去除;对于高铁低锰的水质,可通过两级过滤同时去除铁锰。锰砂和硅碳素两级过滤处理含铁锰地下水是可行的,根据不同的水质,可以采用不同的处理方法。