Experiment and analysis of the effect of fine tracking system on the unstable platform in laser communication

Atmospheric turbulence and platform vibration in the space optical communication can cause the offset and jitter of beam, which further result in the fluctuations of received optical power. To resist this effect, a communication system with fine tracking systems in the receiver and transmitter is designed. The system is used in the experiment of laser communication between high-rise buildings over a distance of 3.5 km. After adding a vibration source to the transmitter, the centroids of spots captured by the camera of the transmitter and the optical power of receiver are recorded for the purpose of analysis. When the vibration source works at the designated frequency, a peak appears at the corresponding frequency in the spectrum of the spot centroids and the optical power of receiver. Then the peak disappears once the fine tracking system begins to work. Compared with the condition without the fine tracking system, the minimum value of the optical power of receiver is increased by 5 dB, and the standard deviation is decreased by 30%.     

飞秒激光烧蚀镍的数值模拟

为了研究金属镍的飞秒脉冲激光烧蚀特性,利用三维双温模型和采用有限差分法,对飞秒激光烧蚀镍的三维温度场进行数值模拟,计算得到了单脉冲烧蚀阈值、单脉冲烧蚀半径及烧蚀深度等。通过改变激光能量,研究了电子品格耦合时间随脉冲能量变化的规律以及脉冲能量对烧蚀半径、烧蚀深度、烧蚀速率的影响。模拟结果表明,随着飞秒脉冲激光能量的增加,材料烧蚀引起的喷射出现的越早,完成烧蚀所用时间越长,烧蚀速率越大,同时材料烧蚀孔半径、深度增加,最终趋于饱和。     

Toward a Game Theoretic View of Secure Computation

We demonstrate how Game Theoretic concepts and formalism can be used to capture cryptographic notions of security. In the restricted but indicative case of two-party protocols in the face of malicious fail-stop faults, we first show how the traditional notions of secrecy and correctness of protocols can be captured as properties of Nash equilibria in games for rational players. Next, we concentrate on fairness. Here we demonstrate a Game Theoretic notion and two different cryptographic notions that turn out to all be equivalent. In addition, we provide a simulation-based notion that implies the previous three. All four notions are weaker than existing cryptographic notions of fairness. In particular, we show that they can be met in some natural setting where existing notions of fairness are provably impossible to achieve.     

用计算机VGA显示器复现指定颜色的研究

如能用计算机控制在普通ＶＧＡ显示器上准确地显示出指定的颜色，那么计算机显示系统就将成为色度学、彩色视觉、印刷、印染等领域方便的、价格低廉的研究手段，为此要对计算机显示系统的颜色空间进行标定，这时遇到的主要困难是显示器显示特性的非线性，以及Ｒ、Ｇ、Ｂ三个通道之间的交联作用，我们通过对几种不同瑾显示的研究，对Ｒ、Ｇ、Ｂ三角交联规律作了探索并提出了存在三色交联时的显示特性表示公式和参数标定方法，从而实现     

一种特征消除的SAR盲移频干扰方法

针对传统移频干扰存在移频干扰特征和无法对抗波形捷变合成孔径雷达(SAR)信号的缺点,文中提出了特征消除的SAR盲移频干扰方法。首先,对接收到的两路SAR信号分别进行延时和2倍频谱扩展;然后,将两路信号进行共轭相乘产生干扰信号,从而将频谱扩展后的信号恢复成原来的SAR回波信号样式,并引入移频干扰相位调制项,可在SAR距离向产生前移、滞后假目标干扰。该方法不仅消除了移频干扰特征,而且能够有效对抗波形捷变SAR雷达信号,是一种盲移频干扰方法。理论分析和仿真实验证明了该方法的可行性和有效性。     

一种采用多天线的OFDM超宽带通信系统的性能分析

本文首先研究了在典型室内信道下基于OFDM技术的超宽带（UWB）通信系统的性能，并提出了一种接收能量模型。在此基础上，推广到多天线的情况，得到了基于该系统的误码率表达式。最后，通过仿真验证了分析结果。结果表明本文的分析方法是准确合理的，天线的数目对系统性能有较大的影响     

AlGaN/GaN型气敏传感器对于C0的响应研究

研究了基于AlGaN/GaN型结构的气敏传感器对于C0的传感性.制备出AlGaN/GaN型气敏传感器器件,并测试得到了器件在50℃时对于不同浓度(1%,9000,8000,5000和1000ppm)的C0的响应情况;测试并分析了1%CO在50和100℃下响应度的差异,计算了通人1%CO前后器件的肖特基势垒高度的变化和灵敏度随电压的分布关系.结果表明,器件的灵敏度强烈依赖于器件的工作温度和通入的气体浓度,随着温度和浓度的增加,器件的灵敏度呈单调增加,器件在100℃空气气氛中表现出了良好恢复性能.     

基于粒子滤波的行人跟踪研究及其性能分析

智能监控系统中的行人跟踪功能在很大程度上能够减轻工作人员的大量眼力工作,通过智能的方式自主地跟踪用户感兴趣的目标。在视频监控环境的基础上,利用改进的粒子滤波器,设计了一个行人跟踪系统,并使其具有系统性能分析的功能。通过使用Mean Shift算法进行目标位置的预估计和多特征融合的方式使该系统在视频背景复杂的情况下能够实现对行人的稳定跟踪。并在实际应用中,分析了在遮挡情况下,行人跟踪效果差的原因,并予以改进。在Visualc＋＋集成开发环境中,基于OpenCV和MATLAB编程实现了系统,能够实时地对目标进行跟踪,并对跟踪结果进行反馈。     

WDM PON中新型组播技术的研究

实现有效的组播传输是WDM PON实用化的关键技术之一,介绍了我们提出并实验验证了其可行性的几种WDM PON新型组播模式,为WDM PON技术的进一步发展和实际应用提供了参考与可选的业务组播方案.     

Infrared Radiance Simulation and Application under Cloudy Sky Conditions Based on HIRTM

An algorithm based on hyperspectral infrared cloudy radiative transfer model (HIRTM) is introduced and a simulation method for infrared image of the generation geostationary meteorological satellite is proposed. Based on the parameters from weather research and forecast (WRF), such as the water content, atmospheric temperature, and humidity profile, the simulation data for the advanced Himawari imager (AHI) infrared radiative (IR) channels of Himawari-8 are obtained. Simulated results based on HIRTM agree well with the observed data. Further, the movement, development, and change of the cloud are well predicated. And the simulation of IR cloud image for the weather forecast has been obtained. This paper provides an improved method for evaluation and improvement of regional numerical model for weather forecast.