多层介质膜光栅和介质膜反射镜抗激光损伤阈值研究

对多层介质膜光栅以及介质膜反射镜的激光损伤阈值进行了系统的研究。测试方法采用国际测试标准。测试结果表明,介质光栅的损伤阈值远低于未刻蚀的多层介质膜。对样品损伤形貌的扫描电镜照片分析发现,相比于未刻蚀的多层介质膜,介质膜光栅的初始损伤主要发生在光栅槽形的侧壁,且损伤主要是由驻波场的空间分布引起的本征吸收、制备过程中引入的杂质污染以及刻蚀过程中HfO2的化学计量机失衡引起的。     

两种多重签名方案的密码分析

对两种多重签名方案进行了深入的研究,提出了一种伪造攻击方法。在第一种方案中,该攻击使得群体中任一成员都能在不经其他成员同意的条件下代表整个群体生成有效签名,这说明该方案是不安全的。在第二种方案中,这种攻击使得指定的合成者能获取任何签名者的秘密密钥,从而可以生成有效门限签名,因此这个方案也是不安全的。分析了攻击成功的原因,为同行设计安全的新方案提供了有效借鉴。     

改进的阈值函数在心音信号消噪中的研究

为弥补传统阈值函数存在的不足、提高心音信号的消噪精度,提出了3种改进的阈值函数。试验中,首先对传统的软、硬阈值函数及3种改进的阚值函数进行去噪性能对比分析;其次,采用基于小波分析的频带局部能量特征提取法对消噪后的心音信号进行特征提取．并运用模糊Sammon映射算法将六维特征数据映射成二维以显示其散布特性。结果表明,改进的阈值函数二能更有效地消除噪声,其消噪后的心音信号特征向量较全面地反映了心音信号的特征。     

CO2激光辐照HgCdTe探测器的实验研究

采用CO2激光分别对PC型和PV型HgCdTe探测器进行干扰实验,得到了不同入射激光功率密度下的响应波形,给出了两种探测器的热效应干扰阈值和饱和阈值,并对实验结果进行了分析。     

卫星导航接收机抗干扰性能评估方法研究

卫星导航接收机的抗干扰是导航战研究的一项重要内容。合理的抗干扰性能评估方法是对接收机的抗干扰性能进行正确评估的基础,目前卫星导航接收机还没有建立统一的抗干扰性能评价方法。在吸取GPS系统抗干扰性能评估方法的合理性的基础上,提出一种在接收机输入端对抗干扰性能进行评估的方法,与传统的抗干扰性能评估方法相比,该方法更具有工程实际意义。     

Effect of the fabrication method on the electrical properties of poly(acrylonitrile-co-butadiene-co-styrene)/carbon black composites

Poly(acrylonitrile-co-butadiene-co-styrene) (ABS), an engineering plastic, was combined with carbon black (CB) to increase its conductivity. The ABS/CB composites were prepared using two different methods: dissolution of ABS in Butan-2-one and manual mixing of the constituent materials. These fabrication methods led to different microstructures, which led to vastly different electrical properties. The microstructures were acquired using scanning electron microscopy (SEM) and optical microscopy, while the electrical conductivity was obtained using impedance spectroscopy. The percolation threshold of the composites fabricated using the manual mixing method was found to be much lower (0.0054 vol.% CB) than that of the composites fabricated using the dissolution method (2.7 vol.% CB).     

Noise-Assisted Signal Reception in Threshold Neuron

1IntroductionSometi mes,noise can i mprove signal transmission orsignal processing in a nonlinear system.This phe-nomenonis the so-called Stochastic Resonance(SR)[1].Most studies of SRinvolve asubthresholdsignal througha single nonlinear systemand the non…     

A novel optical burst switching scheme—logical cascaded private subnet with start wavelength assignment policy

Many recent studies have convincingly demonstrated that network traffic exhibits a noticeable self-similar nature, which has a considerable impact on network performance, and most studies of optical burst switching (OBS) networks are under a fundamental assumption that full wavelength conversion is available throughout the network. In practice, however, economic and technical considerations are likely to dictate a more limited and sparse deployment of wavelength converters in the optical network. Therefore, we present a novel scheme for OBS networks, called logical cascaded private subnet (LCPN) with start wavelength assignment policy. We define the concept of canoe relative to cluster in self-similar traffic, and introduce a new device named payload segregator at the edge node as a gateway to the core node in OBS Networks. According to the changes in the edge node framework, we put forward the concept of cluster private subnet and canoe private subnet in the core node correspondingly. A new start wavelength assignment policy is proposed for the absence of (full) wavelength conversion capabilities in the core node of OBS Networks. The performance study indicates that, our new scheme is robust under self-similar traffic and wavelength continuity constraint.     

基于机器视觉的FPC智能对位系统的研究

针对传统对位装置对位精度低、速度慢的缺点, 设计并开发了基于机器视觉的柔性印刷电路(FPC)智能对 位装置。装置利用高分辨率工业CCD相机采集图像,配合机械和电气系统,控制运动控制卡 完成FPC智 能抓取、采集、处理和对位。在关键的定位算法中,通过改进的一维Otsu阈值分割方 法对FPC图像 进行阈值分割,利用提出的三椭圆平均拟合法提取定位圆圆心坐标,采用累计概率Hough直 线变换测量 旋转的角度;进而将计算的相对于标准位置的偏移量传送至运动控制卡,利用闭环反馈控制 伺服系统进行纠偏。在开发的样机上进行大量的在线实验结果表明,本文装置稳定性强, 对位精度高,对位误差不超过±0.06mm,角度误差不超过0.001rad。     

基于CT图像的肺实质分割技术研究

基于CT图像的肺实质分割不仅仅是后续图像处理最基础和最重要的技术,而且是一个典型的亟待解决的问题。基于CT图像的精确的肺实质分割是数学分析、计算机辅助分析和治疗的前提。本文明确了肺实质分割的概念及本质,以及肺实质分割在临床治疗中的重大意义。重点介绍了阈值法、区域生长法、主动轮廓模型和遗传算法,分析了它们的本质以及优缺点,并且列举大量实例说明。最后指出了基于CT图像的肺实质分割方法的发展趋势与面临的挑战。