Antenna subset selection at multi‐antenna relay with adaptive modulation

In this paper, we proposed several antenna selection schemes for cooperative diversity systems with adaptive transmission. The proposed schemes were based on dual‐hop relaying where a relay with multiple‐antenna capabilities at reception and transmission is deployed between the source and the destination nodes. We analyzed the performance of the proposed schemes by quantifying the average spectral efficiency and the outage probability. We also investigated the trade‐off of performance and complexity by comparing the average number of active antennas, path estimations, and signal‐to‐noise ratio comparisons of the different proposed schemes. Copyright © 2011 John Wiley & Sons, Ltd.     

数字电视用户管理系统

课题实现了数字电视用户管理系统的设计与开发,以Oracle数据库作为后台数据库,以C Builder 6作为前台开发工具,包括表的设计与界面的设计.实现了数字电视用户管理系统基本功能,基本上满足了实际商业运营的需要.     

强激光驱动器能源系统瞬态特征实时测控系统研究

随着惯性约束核聚变研究的发展．强激光驱动器能源系统的研究备受关注。为了向激光驱动能源系统传输效率的研究提供可靠的实验数据．研究了强激光驱动器能源系统中氙灯瞬态放电特征数据进行实时检测的方法和测控系统结构。采用量化传输模式进行特征量的检测与传输，既实现了高压隔离，又避免了在远距离传输过程中受到干扰，确保测量精度。配合系统的模块化设计，采用多线程工作模式，对计算机系统的控制功能进行工作线程划分，提高了系统的实时性和协调性。实验表明，系统有效地实现了弱电系统对强电系统的远程控制．测量精度满足测量要求，已成功应用于能源系统的实验研究。     

PECVD法低温形成新型SiO_xN_y薄膜的界面特性研究

研究了等离子体增强化学气相淀积（PECVD）方法低温形成新型SIOxNy薄膜的界面特性。研究侧重于PECVDSiOxNy薄膜良好界面特性的控制，探索出界面特性与微观组份、衬底工作温度、反应室气压、退火致密、金属化后退火的相互关系。同时给出了获取界面等特性优良的PECVDSiOxNy薄膜的最优化工艺条件，并对实验结果进行了理论分析与讨论。     

一种模糊自适应BP算法的研究

本文在人工神经网络中引入模糊集理论，提出一种模糊自适应ＢＰ算法。通过奇偶校验和ＥＥＧ异常波形检测两上实例，验证了新算法在学习速度与性能上都优于传统的ＢＰ和虎法。     

互联网网络时延特征研究

互联网宏观拓扑结构下时延特征的研究对互联网结构与性能的理解具有重要作用。择取CAIDA Ark项目下分别位于4个不同地区的探测数据,提取网络时延与通信直径,发现网络时延与通信直径关系很小且超过70%的有效路径中存在支配时延。经分析,正是支配时延的存在影响了网络时延与通信直径的关系。对支配时延链路两端进行地理映射,发现支配时延以较高概率出现在同一国家同一城市某一链路传输之间。在此基础上,得出链路两端距离小于5 000 km的支配时延主要由排队时延组成,而链路两端距离大于5 000 km的支配时延主要由传播时延组成的结论。     

一种紧凑型宽带高功率微波驱动源

为实现对传输线开关振荡器或振荡天线进行快速充电,以提高其耐压能力和产生高频振荡信号的能量效率,本文研制了一种基于Tesla变压器的电容储能型脉冲驱动源。本文首先介绍该驱动源的工作原理和运行过程,接着利用等效电路方法分析了关键电路参数对负载充电过程的影响,然后介绍该驱动源的具体工程设计,最后介绍该驱动源初步测试结果以及将其应用于变压器油在10 ns量级脉冲下击穿特性研究的实验情况。实验表明,输出火花开关在中储电容器充电电压为-191 kV导通时,通过电感对等效电容为15 pF的传输线充电电压峰值为-224 kV,电压上升时间约10 ns。研究结果表明本文研究的驱动源能够满足对传输线开关振荡器等电容负载进行快速充电至数百kV高压的应用需求。     

FULL-RCMA: a high utilization EPON

This paper proposes an alternate solution for Ethernet passive optical networks. Our solution uses a novel protocol named full utilization local loop request contention multiple-access protocol to efficiently provide communications in passive optical networks. We study the physical layer implementation, as well as medium access control (MAC) layer protocol performance to illustrate the feasibility and benefit of our solution. The performance studies show that the MAC protocol is capable of offering 95% channel utilization under heavy load conditions. The performance results also indicate that delivery of multimedia traffic with a high quality-of-service can be achieved with our solution.     

In vivo Doppler shift measurements using multimode fiber-opticcatheters

A new fiber-optic catheter for in vivo blood-flow measurements has been developed. The catheter is designed to measure blood flow in both the forward (toward the catheter tip) and reverse (away from the catheter tip) flow directions. It consists of two multimode optical fibers with core diameter of 50 μm and cladding diameter of 125 μm. One fiber transmits the laser beam into blood and the other receives the backscattered light from the erythrocytes within the probe volume. In the flow experiment, it was found that the flow within the boundary layer is indeed laminar and, hence, the relationship between the Doppler shift frequencies and the flow velocities is linear, thereby making the linear calibration possible for predicting the free stream flow velocity. Plots of the maximum shift frequency (frequency at which the Doppler spectrum disappeared into the noise spectrum) against the flow velocities are found to be more linear in both the forward and reverse flow directions than that of the dominant shift frequency (frequency with the highest amplitude). These results were reaffirmed by the numerical flow simulation along the catheter side wall