成型阴极脉冲电化学光整加工在轧辊上的应用

采用成型阴极对冷轧丝杠轧辊进行脉冲电化学光整加工.文章介绍了该方法的基本原理,给出了实验装置,在一定的工艺条件下,对轧辊进行了脉冲电化学光整加工.结果表明,该方法能将轧辊表面粗糙度从0.3μm减小至0.06μm.     

拓宽调速范围的微机PWM变频传动系统

本文对单CPU结构的PWM变频调速系统做了一些探讨。为解决系统中存在的微机计算速度偏低和硬件复杂性问题,较好地处理软件和硬件的配合问题,本文提出了在较少的硬件结构基础上,通过在线设置辅助数据表,实现计算和存贮相结合的PWM方式:在设计中,利用了微机键盘和显示器实现系统管理。为解决电动机低速运行时机械特性变软这一问题,本文提据电动机定子电压和频率的协调控制原则,实现以电动机基波电流和功率因数为反馈信号的协调控制。实验结果表明,所设计的变频调速系统具有较宽的调频范围、较高的电压及频率分辨率,低速带负载能力大为改善,操作灵活方便。     

脉宽调制器单粒子效应测试系统研制

本文在分析脉宽调制器(PWM)单粒子效应主要失效模式的基础上,研制了具备频率异常测试、占空比异常测试和参考电压测试功能的PWM单粒子效应测试系统,并在中国原子能科学研究院HI-13串列加速器上开展了单粒子效应试验。试验结果表明:单粒子效应会导致PWM输出信号的脉冲丢失和占空比改变,脉冲丢失时间和占空比改变的持续时间有时可达数ms;UC1825AJ型PWM的单粒子效应LET阈值约为4.4MeV·cm2·mg-1,UC1845AJ型PWM的抗单粒子性能受工艺批次的影响较大。     

High-speed ground moving target detection research using triangular modulation FMCW

The frequency modulated continuous wave (FMCW) radar has the characteristics of low probability of interception, good hidden property and the ability to counter anti-radiation missiles. This paper proposes a new method for high-speed ground moving target detection (GMTD) using triangular modulation FMCW. According to the characteristic of the opposite range shift induced by the upslope and downslope modulation FMCW, the upslope and downslope are imaged, respectively. After compensation of continuous motion of the platform and time difference between upslope and downslope signals for imaging, the moving target can be detected through displaced phase center antenna (DPCA) technology. When the moving target is detected, the moving target image is extracted, and correlation processing is used to obtain the range shift, which can be used to estimate the target radial velocity, and further to find the real position of the target. The effectiveness of this method is verified by the result of computer simulation. __________ Translated from Journal of Xidian University, 2008, 35(4): 586–591 [译自: 西安电子科技大学学报(自然科学版)]     

Modeling and finite element analysis of rod and wire steel rolling process

Two thermomechanical coupled elastic-plastic finite element （FE） models were developed for predicting the 12-pass continuous rolling process of GCrl 5 rod and wire steel. The distances between stands in the proposed models were set according to the actual values, and the billets were shortened in the models to reduce the calculation time. To keep the continuity of simulation, a technique was developed to transfer temperature data between the meshes of different models in terms of nodal parameters by interpolation functions. The different process variables related to the rolling process, such as temperature, total equivalent plastic strain, equivalent plastic strain rate, and contact friction force, were analyzed. Also, the proposed models were applied to analyze the reason for the occurrence of an excessive spread in width. Meanwhile, it was also utilized to assess the influence of the roll diameter change on the simulated results such as temperature and rolling force. The simulated results of temperature are found to agree well with the measured results.     

男西装袖窿结构参数的研究

对男西装袖窿结构中的重要结构参数——衣片的袖窿宽及衣袖的袖山高进行分析与研究，提出了合理有效的设计方法，即用比例法确定衣片的袖窿宽及用制图法确定衣袖的袖山高．该方法将对男西装的结构设计与工艺制作提供有益的参考．     

音频DFT域量化水印性能研究

为研究基于量化音频DFT域的水印算法性能,分析了该算法的原理,给出了一种简便的嵌入和提取公式,重点分析了算法的透明性、鲁棒性等性能,指出了算法的缺陷。首先,利用均方误差定义得出了嵌入失真公式,认为透明性与量化步长的平方成正比,而且当载体系数较小时容易引起听觉失真;其次,依据信息提取原则推导了加性高斯白噪声和幅度规整攻击下的误比特率,认为算法抗噪性能只与量化步长有关,而算法抵抗幅度规整攻击的性能很差;最后,通过仿真实验验证了以上公式的正确性。     

一种无线电信号的模拟调制参数测量系统设计

无线电信号的模拟调制参数测量在无线电检测定位、通信发射机测试校准,民用船舶的导航通信等领域都有广泛应 用。设计实现了一种基于超外差结构的无线电信号模拟调制参数的测量系统,以STM32F4 系列单片机作为控制核心,包括 的主要硬件电路模块有本振信号源、混频器、LC无源滤波器、锁相环、低噪声放大器、包络检波电路、鉴频电路等。系统可自 动识别普通调幅波、调频波、未调制的单频载波等模拟调制类型,完成无线电信号解调输出的同时自动测量出载波频率、调制 信号频率、调幅指数、调频指数等主要调制参数。实测结果表明,系统对调制类型识别正确,调幅或调频信号的解调波形信噪 比高、无明显失真,载波频率测量的相对误差小于10-5,主要调制参数测量的相对误差均小于5%。     

多弧离子镀与磁控溅射共沉积TiN/TiCN多层膜的高温抗氧化性能

TiN/TiCN多层膜的高温抗氧化性研究对于扩大其应用领域具有重要作用,但目前鲜见相关报道。采用多弧离子镀与磁控溅射技术以不同调制周期在304不锈钢表面共沉积TiN/TiCN多层膜。采用XRD、XPS、倒置显微镜及高温氧化试验研究了多层膜的高温抗氧化行为。结果表明:TiN/TiCN多层膜表面光滑平整、均匀致密,薄膜主要为具有Ti-(C,N)键的fcc-TiN结构;随着调制周期的减小,TiN/TiCN多层膜生长取向发生转变,且具有(111)晶面生长织构;随着氧化温度的升高,多层膜的显微硬度逐渐降低,氧化增重速率不断增大,且在700℃之后变化速率较快,薄膜的开始氧化温度约为750℃;随着调制周期的减小,多层膜TiN与TiCN界面层数量增多,促使晶粒细化,提高了其致密性,还隔断了缺陷贯穿薄膜的连续性,显著降低了薄膜的孔隙率,致使O原子扩散困难,增强了薄膜的高温抗氧化性能。