P2P网络资源多线程传输改进机制

该文提出了一种基于混合P2P网络的多线程传输优化机制,该机制由滑动窗口数据块动态调整策略和资源节点自适应选择策略组成,实现P2P网络节点下载任务分配合理化和网络负载均衡化。实验证明:该机制能够均衡网络负载,同时提高资源传输速率,增强传输节点网络稳定性。     

基于分布式认知无线电的非合作博弈频谱分配算法

基于博弈论的认知无线电频谱分配问题,是目前认知无线电领域的研究热点之一.分布式认知无线电系统的网络容错能力强,易于架设并且通信可靠性高.采用博弈论算法对认知无线电网络的频谱分配进行建模分析,可以很好的提高自适应算法的性能和收敛速度且降低了算法的复杂度.仿真结果表明,该分布式系统中的频谱分配算法收敛速度快、复杂度低并且具有很好的通信可靠性.     

新型无线防盗报警系统设计

介绍了一种新型无线防盗报警系统,该系统可实现多点监视,自动检测、报警,并通过PC机实时监控。系统采用AT89S52单片机作为控制器,无线发射、接收机选用NB5026/5027数字编解码器芯片,单片机与PC机采用USB接口通信,具有体积小、电路简单、可靠性高、传输距离远、用户操作界面友好等特点。从硬件电路和软件设计阐述了系统的组成与功能。     

基于nRF24LE1的无线数据传输系统实现

nRF24LE1是2.4 GHz ISM微波频段的低成本、高性能嵌入式微处理器智能射频收发器家族中的成员.设计了基于射频收发芯片nRF24LE1的无线数据传输系统,给出了射频收发系统主要部分的硬件电路图和软件收发程序流程图,重点探究了nRF24LE1在Enhanced ShockBurstTM收发模式下的无线数据收发过程和实现.室外测试实现了50 m以上的远距离无线数据传输,具有功耗低、传输距离远及性能稳定等优点,可广泛应用于多种无线数据传输的场合.     

超宽带传输参考接收机性能分析

在确定超宽带传输参考接收机模型的基础上,分析了基本TR接收机的误码性能,并在AWGN信道下进行了系统建模。仿真分析的结果表明,接收机的性能与脉冲对的重复数Ns、码元的积分时间以及接收机输入噪声带宽的大小之间均有规律可循,其适宜条件：Ns取3～5,标称积分时间等于脉冲宽度,噪声带宽应在保持正常接收时误码率为10-4或更低的水平选取。     

纳米碳管的非线性热电传输

利用Landauer-Büttiker公式对金属导线/单臂纳米碳管/金属导线结构的热电传输进行理论计算.在有限温度梯度下,利用迭代法计算非线性热电势和热电导,研究表明,热电势和热电导与系统电子的传输行为密切相关,热电势随系统化学势的变化而振荡,且可为正也可为负值,这种行为完全依赖于电子电导的变化.研究结果对分子器件热传输的实际应用有意义.     

分层码率控制策略在机器人遥操作中的应用

为实现卫星自维护遥操作系统中稳定可靠的视频反馈目标,提出一种基于分层码率控制的视频传输策略.利用实时探测到的带宽选择不同码率的视频流分层,使得视频传输对于不同的网络带宽具有自适应性.试验结果表明,该策略能够在波动带宽下给予遥操作者稳定流畅的视频反馈,有效地提高了遥操作系统的视觉临场感性能.     

基于红外原理的微型多气体检测系统的设计

为了解决目前煤矿瓦斯事故以及大量使用天然气的家庭安全、环境污染等问题,设计并开发了一种具有集成化、微型化的红外多气体检测系统,通过实验数据的测试对比和数据分析,这种系统达到了微功耗、微体积、宽量程、高分辨率等技术要求,且能集成多气体检测的微型检测系统.重点介绍了红外检测的光学原理,以及从单气体检测引入到集成多气体检测的设计思想和方法,并介绍了有关CAN总线的数据传输方式和无线数据通信方式在系统中的应用.     

Temperature rise of He Ⅱ forced flow and its negative Joule-Thomson effect

The temperature rise of He Ⅱ transfer system due to the negative Joule-Thomson(JT)effect is one of the major problems in the He Ⅱ forced flow system design.Negative Joule-Thomson effect of the He Ⅱ forced flow was analyzed and calculated in this paper.The temperature rise due to the heat leak along the transfer pipeline was calculated by the simplified equation and was modified by considering the negative Joule-Thomson effect.The modified results were compared with the temperature rise obtained by non-linear differential equations with consideration of the pressure gradient.The results show that the pressure gradient has strong effect on the temperature distribution.The modified results are in good agreement with the values calculated by the complicated equation,which verifies the effectiveness of the simplified equation in calculating the temperature rise when the negative JT effect of He Ⅱ is known.     

Wet friction performance of C/C-SiC composites prepared by new processing route

C/C-SiC composites with SiC island distribution were prepared via a new processing route. The fabrication process mainly included silicon infiltration by ultrasonic vibration, chemical vapor deposition (CVD), siliconizing, liquid phase impregnation and carbonization. The wear and friction properties were tested by an MM-1000 wet friction machine. The results show that SiC phases are mainly distributed between carbon fibers and pyrocarbons as well as among the pryocarbons. The dynamic friction coefficient of the composites decreases gradually from 0.126 to 0.088 with the increase of the surface pressure from 0.5 to 2.5 MPa at the same rotary speed. Furthermore, under the constant surface pressure, the dynamic friction coefficient increases from 0.114 to 0.126 with the increase of the rotary speed from 1 500 to 2 500 r/min. However, the coefficient decreases to 0.104 when the rotary speed exceeds 4 500 r/min. During the friction process, the friction coefficient of C/C-SiC composite is between 0.088 and 0.126, and the wear value is zero after 300 times brake testing. Foundation item: Project(2006CB600901) supported by the Major State Basic Research and Development Program of China; Project(0991015) supported by Guangxi Science Found, China; Project(200808MS083) supported by Guangxi Education Department Found