Characterization of indoor wireless channel at 5 GHz U-NII bands

The paper reports on the experiments undertaken at the University of Wollongong to characterise fading profiles and delay parameters of an indoor wireless channels at 5 GHz U-NII bands. The measurements were undertaken at different locations around the campus with results recorded for a post-processing to calculate the Rician K-factor, the level crossing rate and the average fade duration as well as mean excess delay, rms delay spread, and the coherence bandwidth of the channel. The presented measurement results can be useful in developing a Markov chain based model of the transport channel for IEEE802.11a or HYPRLAN-2 networks. The results also indicate scenarios where the coherence bandwidth of the channel is smaller than the width of the sub-carrier OFDM channels in either of the mentioned systems.     

Word prediction using a clustered optimal binary search tree

Word prediction methodologies depend heavily on the statistical approach that uses the unigram, bigram, and the trigram of words. However, the construction of the N-gram model requires a very large size of memory, which is beyond the capability of many existing computers. Beside this, the approximation reduces the accuracy of word prediction. In this paper, we suggest to use a cluster of computers to build an Optimal Binary Search Tree (OBST) that will be used for the statistical approach in word prediction. The OBST will contain extra links so that the bigram and the trigram of the language will be presented. In addition, we suggest the incorporation of other enhancements to achieve optimal performance of word prediction. Our experimental results showed that the suggested approach improves the keystroke saving.     

A parallel computing application of the genetic algorithm for lubrication optimization

This study investigated the performance of parallel optimization by means of a genetic algorithm (GA) for lubrication analysis. An air-bearing design was used as the illustrated example and the parallel computation was conducted in a single system image (SSI) cluster, a system of loosely network-connected desktop computers. The main advantages of using GAs as optimization tools are for multi-objective optimization, and high probability of achieving global optimum in a complex problem. To prevent a premature convergence in the early stage of evolution for multi-objective optimization, the Pareto optimality was used as an effective criterion in offspring selections. Since the execution of the genetic algorithm (GA) in search of optimum is population-based, the computations can be performed in parallel. In the cases of uneven computational loads a simple dynamic load-balancing scheme is proposed for optimizing the parallel efficiency. It is demonstrated that the huge amount of computing demand of the GA for complex multi-objective optimization problems can be effectively dealt with by parallel computing in an SSI cluster.     

公用车辆运行数据无线采集传输系统

针对公用车辆运行数据人工采集和录入效率低且不可靠等问题,提出了无线射频数据通信的设计。给出了采用SM5964单片机和NRF905单片射频收发器来实现车辆运行数据的无线采集传输的设计方案,包括车载机模块、无线发射和接收模块以及单片机和PC机之间的串行通信模块。该设计方案可推广应用于其他需要无线通信的数据采集系统。     

无线遥控液压爬行机器人的设计

无线遥控液压爬行机器人是一种用于大型构件滑移安装的新型施工装备.该机器人由爬行器、液压动力系统、传感检测和计算机无线遥控系统组成,通过自锁机构夹紧轨道形成反力推动构件.爬行器和液压系统采用了模块化设计,无线遥控通信设备采用了蓝牙数据收发器.机器人能应用于大型构件整体同步连续滑移的无线遥控作业,并且推力与速度可测可控.     

谐振式无线电能传输系统恒功率输出特性研究

在无线充电过程中,电池阻值的变化会引起输出功率的波动,从而减短电池寿命,影响充电安全。针对磁耦合谐振式无线电能传输变负载系统,通常是在接收端加入控制电路使输出功率稳定,但这增加了用电设备的体积。因此,文中提出了基于反射阻抗原理的2种恒功率控制策略：Sepic电路恒功率输出控制策略和移相控制恒功率输出控制策略。首先分析了负载电阻对输出功率的影响;然后分别推导了Sepic电路驱动信号的占空比、移相控制中驱动信号的移相角与输出功率的关系,给出了恒功率控制策略的原理;最后通过Matlab/Simulink搭建仿真模型,验证了文中理论分析及所提控制策略的正确性。仿真结果表明,2种控制策略均能有效实现恒功率输出。     

非规则、核外并行计算研究综述

非规则、核外计算既是大规模并行应用普遍存在的问题,也是影响大规模并行应用效率的关键问题.本文从并行处理模型、运行支持库实现和并行优化三个方面对非规则、核外计算技术进行了全面综述,并对典型研究成果的特点和不足进行了分析.如何充分利用系统结构的特点和应用数据本身的特点,寻求非规则、核外计算处理的优化是现有技术发展的共同思想.在此基础上,指出了处理两类问题的技术相关性以及在SMP集群系统结构和网络存储环境下,解决非规则、核外计算的新思路:一是从问题描述、编译优化、运行支持等多层次协同研究充分利用系统结构特点的优化技术,二是从应用问题出发,在并行粒度确定、并行范例选择等方面统一非规则、核外计算的处理,三是研究新的支持非规则通信的优化技术和动态负载均衡方法.     

基于无线网络车牌识别系统识别算法的研究

字符识别是智能车牌识别系统研究的核心问题,针对有线网络车牌识别系统的缺点,将BP算法应用在基于无线网络的车牌识别系统上,重点讨论了用改进的BP神经网络方法对车牌字符的识别;根据我国最新机动车号牌GA36-2007标准,设计出了用于车牌识别的3个神经网络,用MATLAB完成了对车牌字母部分识别的模拟,采用隐层节点22,动量因子0.8进行训练,最后得出实验结果,达到目标误差小于0.001的要求;证明这种方法应用在基于无线网络车牌识别系统上是高效的.     

云数据中心虚拟资源管理研究综述

云计算数据中心是数据中心架构和发展的方向,云数据中心的虚拟资源管理问题是当前的研究热点。总结了数据中心的发展历程,综述了云数据中心的虚拟化技术、虚拟资源提供与部署、资源调度模型与算法以及基于能量优化和负载均衡的虚拟机迁移技术的研究现状。最后展望了云数据中心虚拟资源管理领域有待进一步研究的方向。     

嵌入式无线家庭网关的设计与应用

智能家居是现代3C技术和信息家电结合的产物.智能家居离不开家庭网络,而家庭网络的关键是无线家庭网关.以S3C2440A处理器为核心,采用嵌入式和ZigBee技术,设计一个应用在智能家居中的无线家庭网关,并实现对家庭网络中智能设备的控制.