数字微波通信系统架构及传输体制选择

阐述数字微波通信的系统结构及数字微波通信系统的组成,并通过对PDH与SDH数字传输体制的比较分析来根据实际情况确定所要采用的传输模式,同时说明本站系统升级改造的必要性。     

基于半参数化SLC 的雷达目标识别

针对雷达目标高分辨距离像(HRRP)统计识别中SLC(基于累计量的随机学习算法)在小样本情况下概率密度估计准确度下降的问题,该文提出一种基于半参数化SLC 的雷达目标识别方法。该方法利用半参数化概率密度估计思想对SLC 非参数化概率密度估计进行修正,有效利用了HRRP 各距离单元幅值近似服从 Gamma 分布的经验知识,达到参数化方法和非参数化方法优劣互补以提高小样本情况下雷达目标识别率的目的。最后基于5 种飞机模型HRRP 数据的仿真实验证明了该方法的有效性。      

基于Pro/E二次开发的模型抽取技术

为了实现从复杂的装配体中抽取部分零部件进行CAE分析,同时保持被抽取零部件的空间位置关系不变。利用VC2005开发环境和Pro/E自带的Pro/ToolKit开发模块进行二次开发,在Pro/E非可视化的条件下将Pro/E模型导入内存,重新组合生成新装配体进行实时预览,并将预览合适的新装配体按照指定文件格式保存。结合虚拟火箭案例,验证了复杂模型抽取的可行性和实用性,提高了分析模型抽取、装配的效率和通用性。     

粉末冶金铁基阀板在烧结过程中的变形规律

利用粉末冶金法制备制冷压缩机用铁基阀板,研究阀板在生产过程中几何尺寸及平面度的变化规律。结果表明:烧结和整形工序使阀板的长度和宽度增加,阀板的厚度减小,长度和宽度的最大增加值分别为0.14mm和0.17mm,厚度最大缩小值为0.08mm,阀板的几何尺寸可以通过预成型来控制;烧结工序是导致阀板平面度增加的主要因素,烧结使阀板平面度的最大值为0.18mm,整形使阀板的平面度控制在0.04～0.08mm,仍不能满足使用要求。     

基于TMS320C642电子稳像算法的实现

介绍了一种解决视频图像抖动问题的电子稳像方法,系统利用灰度投影算法和德州仪器公司的定点数字信号处理器芯片TMS32ODM642实现电子稳像.文中提出了电子稳像性能的基本要求,介绍了稳像的基本原理,根据要求选择了稳像算法,从而设计了系统的硬件框图,并完成了算法的仿真.实验结果表明,该算法稳效果好,且达到准确性要求.     

The effect of the concentration of the majority charge carriers and irradiation intensity on the efficiency of radiation-defect production in <Emphasis Type="Italic">n</Emphasis>-Si crystals

The effect of the concentration of the majority charge carriers (n) and the electron-flux density (?) on the efficiency of radiation-defect production (η) in n-Si samples was studied. It is shown that the dependence η(?) features a maximum, which shifts to larger values of ? as n increases. This effect is explained by assuming that there is an optimal relation between the concentrations of primary defects produced per unit time and those of the free charge carriers, which charge these defects.     

Concept of multiorder multimode resonant optical filters

The idea of implementing optical filters by coupling evanescent waves from several diffracted orders into multiple leaky waveguide modes is studied theoretically. Using a dielectric thin-film structure consisting of a coupling grating placed between adjacent waveguides, guided-mode resonance filters exhibiting multiple reflection peaks within a specified wavelength range can be obtained. These peaks originate in the resonant waveguide modes that are excited by the diffracted waves dispersed by the grating. It is shown that this device can be used to realize multiwavelength as well as wide-band spectral filters.     

SOINMOSFET的双峰及辐射效应研究

通过对SOINMOFET的总剂量辐照试验,对器件辐照中的双峰效应进行研究。文中给出了双峰效应的表征。试验结果表明双峰的形状随辐照总剂量的增加而改变,并分析了具体的原因。另外,背栅晶体管对主要晶体管的耦合效应要远远大于其对寄生晶体管的作用。     

MOCVD growth of cubic GaN on 3C-SiC deposited on Si (100) substrates

The growth of cubic GaN on 3C-SiC/Si(100) by metal-organic chemical vapor deposition (MOCVD) under various growth temperatures, thicknesses of 3C-SiC, and V/III ratios was studied. The fractions of cubic and hexagonal phases in the films were estimated from the integrated x-ray diffraction intensities of the cubic (002) and hexagonal (1011) planes. A smooth SiC layer, a high growth temperature, and a moderate V/III ratio are three key factors for the nucleation of the cubic phase and its subsequent growth. Hexagonal GaN with its c-axis perpendicular to the substrate preferentially grows at the low temperature of 750°C. The inclusion of the cubic phase increases with increasing growth temperature. The optimum growth conditions for dominant cubic GaN formation were a growth temperature of 950°C, a 1.5 μm thick SiC layer, and a V/III ratio of 1500. With these growth conditions, a cubic GaN layer with the cubic component of 91% was obtained.     

A simple direct-torque neuro-fuzzy control of PWM-inverter-fedinduction motor drive

In this paper, the concept and implementation of a new simple direct-torque neuro-fuzzy control (DTNFC) scheme for pulsewidth-modulation-inverter-fed induction motor drive are presented. An adaptive neuro-fuzzy inference system is applied to achieve high-performance decoupled flux and torque control. The theoretical principle and tuning procedure of this method are discussed. A 3 kW induction motor experimental system with digital signal processor TMS 320C31-based controller has been built to verify this approach. The simulation and laboratory experimental results, which illustrate the performance of the proposed scheme, are presented. Also, nomograms for controller design are given. It has been shown that the simple DTNFC is characterized by very fast torque and flux response, very-low-speed operation, and simple tuning capability