SOC系统中C到VHDL的转换

近年来,SOC设计方法学的研究越来越引起人们的注意。C语言适合对系统进行高层次的描述。C语言的系统描述经过软硬件划分之后,要求将硬件实现部分转换为适合于综合的VHDL语言。文章通过分析两种语言的区别,提出并实现了适于表达C语言描述内容的VHDL结构形式,并对几种C语言结构提出合理的转换方案。实验表明,文章提出的方案是正确的和有效的。     

Finite element recovery techniques for local quantities of linear problems using fundamental solutions

We show that local quantities of interest such as displacements or stresses of a FE–solution can be calculated with improved accuracy if fundamental solutions are employed. The approach is based on Bettis theorem and an integral representation of the local quantities via Greens function. The unknown Greens function is split into a regular part and a fundamental solution so that only the regular part must be approximated on the finite element ansatz space. Some numerical studies for linear elasticity will illustrate our approach.     

21世纪中叶西南国际诸河水能资源开发设想

西南国际诸河包括澜沧江、怒江、红河和伊落瓦底江,4大流域在我国境内总流域面积约41万km^2,本文论述诸流域水能资源量分布特点及其开发利用条件,开发程度,根据化、西南地区各（区）21世纪中叶经济发展,电力规划和区域电网结构设计的可能性,开发西部水能资源,实现了“西电东送”的目标,提出分阶段水电开发设想,重点是21世纪前20年。西南国际诸河水能资源丰富,根据初步复核的技术可开发装机容量为5298．17万KW,年发电量2577．44亿KW.h。装机容量按河流分澜沧江57．71％,怒江占30．38％、红河和伊洛瓦底河两江仅占11．91％,至1995年开发程度仅为4．93％,说明西南国际诸河尚有大量的水能资源待开发。为加快我国西南部地区经济的发展,促进东西部经济共同繁荣,必须加大西南国际诸河的水能资源开发利用,这也符合目前国家的西部开发策略。     

Quality measure of color images based on properties ofvision psychology and color distortion in MPEG-21

In this article, a new way to evaluate the quality of color images is proposed, in which the properties of human vision psychology, objective fidelity, edge information, and color distortion will be combined through utilizing 3-D matrix transform. There exists color redundancy and structural similarity between three different frames of a color image, the definition of vision properties will be measured by 3-D submatrix integration transform (SIT), in which three color components are integrated into one model and color redundancy can be exploited fully. The simulation results show that the measure index is very effective and objective in accord with vision properties.     

基于DAB及DAB系列系统的单频网切换方案设计与仿真

《30 MHz~3000 MHz地面数字音频广播系统技术规范》即通常所说的DAB(数字音频广播)中国标准虽然是针对于音频的,但是考虑到基带部分是信源透明的,所以完全可以作为手机电视的传输网络。文中在兼容DAB标准的情况下提出了一种单频网切换的方案,以实现服务的平滑过渡。通过对ETSI协议的相关补充并采用二级检索的机制保证了接收机在地域切换时信号的连续性,最后通过软件仿真的方法从视觉直观上验证了该方法的效果,从而确定了该方案的可行性。     

基于超声波的八路巡检流量计设计

在流量测量中,超声波测流量以其非接触测量方式、智能化以及测量范围广等优点被广泛应用。针对超声波流量测量的优点,该设计开发了一套八路巡检的超声波时差法流量测量装置,该测量装置采用了主控制器STM32和高精度计时芯片TDC-GP21,通过对信号的升压发射处理和八路测量通道的切换,用以测量小管径、低流速、单向流体的管道内流量。该测量装置采用高压驱动超声波换能器,提高了装置的抗干扰能力,大大减少了使用成本,并且通过软件的方法有效地抑制了流量装置的零点漂移,提高了测量装置的计量精度。     

Microstructural evolution of AS21X HPDC alloy during thermal treatment

Abstract

The microstructure of a High Pressure Die Cast Magnesium (HPDC) AS21X alloy was investigated after various heat treatments. The material, supplied in the as cast state, consisted of Mg-α grains separated by intermetallic particles such as Mg₁₇Al₁₂, Mg₂Si and Al–Mn. The alloy was subjected to solution treatment at 415° C for times ranging from 0.5 to 48 h and to aging to assess grain growth stability and precipitation hardening. Light microscopy showed that Mg-α grains increase slightly in size whereas intermetallic particles do not disappear but assume a more rounded shape. Static precipitation and/or dissolution were followed by electrical conductivity, hardness measurements and X-ray diffractometry. Tensile properties at room temperature were evaluated on both the as cast and solution treated samples. Density was used as an indicator of porosity to explain the scatter in elongation to fracture data. Study of the fracture surfaces revealed the morphology of porosity and the otherwise ductile fracture failure mechanism.     

Cross-sectional distortion behaviors of thin-walled rectangular tube in rotary-draw bending process

The cross-sectional distortion usually appears during rotary-draw bending process of thin-walled rectangular tube with small bending radius.To study the cross-sectional distortion of the tube,a three-dimensional finite-element model of the process was developed based on ABAQUS/Explicit code and its reliability was validated by experiment.Then,the cross-sectional distortion behaviors of the tube were investigated.The results show that a zone of larger circumferential stress appears on the tube when bending angle reaches 30°.And in the larger circumferential stress zone,the sagging phenomenon is produced obviously.The maximum cross-sectional distortion is located in the larger circumferential stress zone and the angle between the plane of maximum cross-sectional distortion and the bending reference plane is about 50°.The position of the maximum cross-sectional distortion keeps almost unchanged with the variation of the clearances between dies and tube.     

氧—乙炔火焰钎焊在LF21铝合金上的应用

从铝钎焊机及具体工艺操作方面进行阐述，解决了LF21防锈铝用氧－乙烯火焰作为热源进行钎焊的工艺问题。     

NAM模型与水资源配置模型耦合研究

选取汉江作为示范流域,基于MIKE BASIN软件构建了汉江流域水资源配置模型,介绍了该系统的重要特征,探讨了系统内部各组成部分间相互联系;将所建模型与NAM模型的预测结果进行耦合,并分析了2006年皇庄以上汉江流域水资源供需平衡.结果表明:汉江流域内(至皇庄)生活用水、工业用水基本满足要求;农业灌溉、河道内生态用水缺水率为35.8%、25.7%,整体缺水率为22.2%.