立方相GaN的持续光电导

研究了金属有机物化学气相外延 (MOVPE)方法生长的非故意掺杂的立方相 Ga N的持续光电导效应 .在六方相 Ga N中普遍认为持续光电导效应与黄光发射有关 ,而实验则显示在立方 Ga N中 ,持续光电导效应与其中的六方相 Ga N夹杂有关系 ,而与黄光发射没有关系 .文中提出 ,立方相 Ga N与其中的六方相 Ga N夹杂之间的势垒引起的空间载流子分离是导致持续光电导现象的物理原因 .通过建立势垒限制复合模型 ,解释了立方相 Ga N的持续光电导现象的物理过程 ,并对光电导衰减过程的动力学作了分析 .对实验数据拟合的结果证明以上的模型和推导是与实验相符的 .     

用二次离子质谱和扩展电阻探针技术测量硅中注入硼的深度分布及扩展电阻探针技术分辨率的估算

利用二次离子质谱和扩展电阻探针技术测量了硅中注入硼的深度分布 .在适当的测量深度 ,用扩展电阻探针技术测得的结果对二次离子质谱技术测量的结果进行了标定 ,从而得到硅片中硼原子的深度分布 .用近似模型估算了扩展电阻探针针尖半径对测试分辨率的影响 .若探针针尖半径为r0 ,测量斜面的角度为 ξ ,在用扩展电阻探针技术测量载流子浓度的深度分布时 ,可以近似认为深度分辨率为 7 86r0 sinξ.还定性讨论了样品表面耗尽层对扩展电阻探针技术的影响.     

基于计算机视觉的油管螺纹非接触智能检测

针对传统接触式油管螺纹参数测量方法的缺点,开发了基于计算机视觉的油管螺纹非接触智能检测系统。在简述非接触智能检测测量原理和测量系统组成的基础上,详细介绍了利用非接触智能检测系统对油管螺纹参数进行测量的方法,其中包括图像的采集及预处理,图像的锐化,螺纹边缘轮廓的检测与提取,螺纹尺寸的测量计算与对比分析。     

PBA/PMMA核壳结构乳胶粒子粒径分析

采用种子乳液聚合制备出了PBA/PMMA核壳结构乳胶粒子，研究并分析了MMA在3种不同投料方式（间歇法、半间歇法和平衡溶胀法）下粒子粒径变化情况。实验发现第二单体采用间歇法投料可获得较理想的核壳结构乳胶粒。     

SF6气体绝缘电容式电压互感器研制

本文介绍西容公司新研制的一种完全无油化的SF6气体绝缘电容式电压互感器,提出了关键技术问题解决方案和产品绝缘结构的设计思路.并介绍了研制成功的110kV和220kV系列产品的结构、技术参数、性能指标、试验考核情况和产品特点.     

基于数学形态学的红外图像小目标检测

针对红外成像跟踪系统的低信噪比、背景和噪声干扰严重的小目标图像,以及后续的目标识别处理需要目标的灰度信息的特点,设计了一种基于数学形态学的红外灰度图像小目标检测算法,并用FPGA硬件实现。实验表明,数学形态学滤波能够大大提高目标的信噪比,去除背景和噪声干扰,保留目标的灰度信息,满足系统实时性要求,是一种有效的红外灰度图像小目标检测算法。     

Cutoff rate and outage probability performance comparisons between DVB-T and DMB-T systems under mobile multipath channels

As an effective technique for combating multipath fading and for high-bit-rate transmission over wireless channels, orthogonal frequency-division multiplexing (OFDM) is extensively used in modern terrestrial digital television broadcasting systems to support high performance bandwidth-efficient multimedia services. Cutoff rate and outage probability are two important criteria to evaluate the performance of a practical communication system in radio engineering. In this paper, the cutoff rate and outage probability performance are compared between two important terrestrial digital television broadcasting systems, the cyclic prefix OFDM based DVB-T system and the time domain synchronous OFDM based DMB-T system, under different mobile multipath channel conditions. The DVB-T system and the DMB-T system are summarily introduced. The cutoff rate and outage probability expressions are developed, and simulation results are given for both the DVB-T system and the DMB-T system.     

Effects of Electric Field Gradient on an Anti-Plane Crack in Piezoelectric Ceramics

An anti-plane, semi-infinite crack in polarized ceramics is analyzed using the theory of elastic dielectrics with electric field gradient. The effects of electric field gradient on electromechanical fields around the crack is examined.     

A push mechanism for GPRS supporting private IP addresses

The General Packet Radio Service (GPRS) provides a packet switched data service for mobile users. However, the existing GPRS specification does not provide the push mechanism and it is difficult to support GPRS services such as call termination (incoming call) for wireless voice over IP (VoIP). Based on the short message service, this paper proposes a push mechanism for GPRS supporting private IP addresses. Our approach does not need to modify the existing GPRS structure.