中频接收机模拟测试台的可靠性设计与实现

依据原理框图建立可靠性模型;采用故障树模式,分析电子系统在工作时可能产生的潜在电路;对潜在电路的危害性进行定性分析,利用逻辑推理的方法找出截断或消除潜在电路的关键部位,依分析结果改进设计方案,画出改进后的原理框图进行可靠性设计,设计生产出的中频接收机模拟测试台一次成功,实例说明电子系统进行可靠性设计是保证产品质量的有效方法。     

大气折射引起的雷达定位误差模型

大气折射引起的雷达定位误差是限制雷达精度进一步提高的关键因素之一.针对目前只给出雷达测量参数的折射误差,不能明显给出实际应用中所需要的目标位置偏移误差现状.通过采用我国大气折射率的统计模型和目前公认的高精度的电波折射误差修正方法一射线描迹法,对大气折射引起的雷达定位误差进行了目标位置偏离的计算和拟合,建立了大气折射引起雷达测量目标的位置偏移误差模型,从而为雷达实际使用和精度评估奠定基础.     

数据挖掘在客户流失管理中的应用

客户流失是通信行业的难题。阐述了数据挖掘技术的数据分析、信息处理和预测功能,并举例介绍了数据挖掘在客户流失管理中的应用。     

无线Mesh网络中网络编码的文件共享模型

网络编码的基本思想是网络节点不仅参与数据转发,还参与数据处理,可大幅提高网络性能。传统文件传输系统存在文件分发时间的"瓶颈"问题,为此,提出一种在无线Mesh网络中网络编码的简化文件共享模型,采用理论分析和实验仿真的方法,研究节点间的4种合作机制。结果表明,在总分发时间上,基于网络编码转发机制比无网络编码的转发机制平均减少11.67%,显著地降低了文件传输系统的分发时间,从而提高了网络的吞吐量。     

人脸自动定位及其系统实现

人脸自动定位技术在智能视频通信、视频监控以及娱乐等领域有着广泛的应用。通过将基于肤色的人脸检测和基于人工神经网络的控制策略相结合,提出一种新的人脸自动定位算法。该算法简单有效,克服传统跟踪算法中需要利用帧间相关信息和需要标定摄像机的缺点,只需通过人脸检测程序给出人脸特征点在计算机图像中的坐标,就可直接得出摄像机水平调整量和垂直调整量,根据调整量控制摄像机运动即可将人脸自动定位在图像中心。最后利用面向对象的方法实现了系统,并且取得了满意的效果。     

自适应均衡技术在宽带微波传输中的应用

在微波视距通信中通常采用二径模型来描述信道,简要介绍了二径模型的频率响应、损伤参数以及多径时延与天线高度、通信距离的关系。自适应均衡器是对抗多径造成的频率选择性衰落的一种重要手段,简要介绍了自适应均衡器的原理以及设计思路,采用4种典型信道下均衡前后解调器的误码性能对自适应均衡器的抗二径损伤的效果进行评估。测试结果表明,自适应均衡器能有效地对抗二径造成的频率选择性衰落,该均衡器能满足工程使用要求。     

基于近似模型的电子封装散热结构优化设计

针对封装散热结构优化问题中存在的难点,提出了一种基于近似模型和随机模拟的快速全局优化方法.利用Kriging方法建立封装散热结构的近似模型,重构原始的优化问题,采用随机模拟对重构出的目标函数进行寻优,从而得到最优解.采用CVT试验设计,使Kriging模型的泛化预测能力达到最大程度的发挥;在随机模拟中采用Quasi-Monte Carlo法,有效地提高了寻优的效率.以方形扁平封装器件为例,应用该方法实现了封装散热结构的优化,结果表明所提出的方法有效地解决了设计变量中含有离散变量的问题,并且大大提高了随机模拟优化的计算效率.     

Web Services应用于电力GIS的探讨

近几年GIS在电力系统得到了广泛的应用。Web Services的出现,将改变在Web上进行软件设计的方法,也将引起电力GIS体系的变革。通过对电力GIS单个事例的剖析,给出一个基于Web Services的WebGIS三层系统构架模型并进行论述。基于Web Services开发的电力GIS具有系统扩展性强、代码重用度高的特点。其同时也是解决目前WebGIS系统所面临的问题的有效途径。     

一种网络学习资源的检索模型研究

首先介绍了四种网络学习模式,并探讨了这四种模式中的最流行的网络学习模式-个别化的网络学习模式的资源特征.然后对个别化的网络学习模式,构建了一种基于语义的检索模型,并对模型中各组成部分的主要作用和模型的检索过程进行了阐述.最后通过实验的验证,证明了模型的合理性和有效性.     

A BER-Based Partitioned Model for a 2.4GHz Vehicle-to-Vehicle Expressway Channel

Statistical channel models based on BER performance are presented for a frequency- and time-selective vehicle-to-vehicle wireless communications link in an expressway environment in Atlanta, Georgia, where both vehicles traveled in the same direction. The models are developed from measurements taken using the direct sequence spread spectrum (DSSS) technique at 2.45GHz. A collection of tapped delay line models, referred to as a “partitioned” model in the paper, is developed to attempt to capture the extremes of BER performance of the recorded channel. Overall and partition models are compared to the recorded channel in terms of the BER statistics obtained when the channels are inserted in a dedicated short range radio (DSRC) standard simulation system. The quality of the match between synthesized and recorded channel BER statistics is analyzed with respect to type of modulation (fixed or adaptive), the frame length, and the length of the interval over which the BER was calculated. Guillermo Acosta was born in Mexico City, Mexico, in 1962. He is a Ph.D. Candidate and a graduate research assistant in the School of Electrical and Computer Engineering at the Georgia Institute of Technology, in Atlanta, Georgia. He obtained his Bachelor of Engineering with Honors and Master of Engineering, both in Electrical Engineering, from Stevens Institute of Technology, Hoboken, New Jersey, in 1985 and 1987, respectively. He also obtained a Master of Business Administration with Honors from the Instituto Tecnologico Autonomo de Mexico (ITAM), Mexico City, Mexico, in 1996. Mr. Acosta has held technical and managerial positions in the recording, radio, and TV industries and in the Communications Ministry of Mexico. He has been an adjunct instructor in Electrical Engineering in the Instituto Tecnologico y Estudios Superiores de Monterrey Campus Estado de Mexico (ITESM-CEM) and the Universidad Iberoamericana. He is member of the IEEE, INCE, Tau Beta Pi, and Eta Kappa Nu. Mary Ann Ingram received the B.E.E. and Ph.D. degrees from the Georgia Institute of Technology, in Atlanta, Georgia, in 1983 and 1989, respectively. From 1983 to 1986, she was a Research Engineer with the Georgia Tech Research Institute in Atlanta, performing studies on radar electronic countermeasure (ECM) systems. In 1986, she became a graduate research assistant with the School of Electrical and Computer Engineering at the Georgia Institute of Technology, where in 1989, she became a Faculty Member and is currently Professor. Her early research areas were optical communications and radar systems. In 1997, she established the Smart Antenna Research Laboratory (SARL), which emphasizes the application of multiple antennas to wireless communication systems. The SARL performs system analysis and design, channel measurement, and prototyping, relating to a wide range of wireless applications, including wireless local area network (WLAN) and satellite communications, with focus on the lower layers of communication networks. Dr. Ingram is a Senior Member of the IEEE.