A New Fault Location Method Based on Two Terminal Information of Self synchronous Rectification

In accordance with the high and extra high voltage long distance transmission line,this paper presents a fault location method based on two terminal information of self synchronous rectification.We adopt the long transmission line model,consider the effect of distribution capacity and can correct the sample phase angle difference in the real time btween two terminals.So that this method can avoid the fault location error owing to asynchronous message on the two terminals.Tested by a lot of simulations,the results are very satisfied.     

一类二阶非线性中立型方程的振动定理

利用Φ(t,s,r)型函数和Riecati技巧,建立了一类具有连续分布滞量的二阶非线性中立型微分方程的一些新的振动准则.     

Performance analysis and comparison of IEEE 802.11 distributed coordination function and improved schemes

To improve the media access control mechanism and enhance the performance of large scale wireless LANs, the distributed coordination function of IEEE802.11 standard and two typical improved schemes are studied extensively. Compared with the distributed coordination function, the fast collision resolution mechanism greatly enhances the throughput, but deteriorates the delay jitter and fairness of wireless LANs. The new self adaptive distributed coordination function markedly improves the delay jitter and fairness performance, while enhancing the throughput of wireless LANs to a certain degree. Hence, with further improvement, the new self adaptive distributed coordination function is more suitable for large scale wireless LANs for multimedia information transmission.     

Modeling and simulation of the conducted electromagnetic interference for permanent magnet direct current motors

A simulation model for evaluation of conducted electromagnetic interference(EMI) is developed based on analysis of the mechanism giving rise to conducted EMI. The simulation model includes high frequency effects associated with stray distributed parameter     

Simulation of dissolved nitrogen pollution in Xiaojiang river basin of Three Gorges reservoir

Xiao Jiang River is the largest tributary on the north of the middle part in Three Gorges reservoir area, because of predominant hilly cropland with purple soil, the dissolved nitrogen from surface and subsurface runoff caused by raining accounts for most part of the nitrogen pollution in water. This paper develops the annual pollution models based on the characteristics of topography and soil, etc., of the basin in order to study dissolved nitrogen pollution, and introduces a Semi distributed Land Use based Runoff Processes (SLURP) hydrological model into the surface and subsurface runoff simulation which is an important part of non point source pollution modeling. Integrated with the geography information system technology, the annual temporal spatial distribution of the dissolved nitrogen in the basin is simulated and the load at the watershed outlet is estimated from 2000 to 2007. The results show that the load from cropland is up to 68.3~76.8of the total load, in which over 85 from croplands and then rural settlement is 23.2~31.7.     

基于分布式无线网络的水质监控系统设计

为提高对水产养殖水质监控的实时性和测量精度,设计了一种基于无线传感器网络的水产养殖水质参数监控系统。该系统由水质参数采集终端、分布式传感器网络、传输控制中心基站、远程在线监控系统组成。参数采集终端采集水质参数并传输到中心基站,再通过GPRS发送给远程在线监控中心,根据用户向监控中心输入的参数实现水温、pH、溶氧(DO)的调节。参数测量过程中引入数字滤波算法提高测量精度,使用经过改进粒子群优化算法(PSO)整定的PID控制器实现水质参数的调节。结果显示:测量精度达到要求,温度、pH和DO的测量误差分别为2.1%、1.3%和3.6%,系统对温度、pH和溶氧调节的最大误差分别为1.9%、2.6%和3.1%。整个系统工作稳定可靠。     

空间数据对分布式水文模型SWAT流域水文模拟精度的影响

分布式水文模型的模拟精度受空间参数精度的影响.提升空间参数精度能较为精准描述流域空间特征,也会使空间数据量冗增,甚至影响模型运行效率.以分布式水文模型SWAT为例,分析DEM、子流域划分、土地利用、土壤、降水站点等空间数据精度对模型模拟精度的影响.结果表明:1)对不同对象(流量、泥沙、营养元素等)进行模拟时,大多数空间数据分辨率阈值不同,分辨率超出阈值可能降低模型模拟的精度;2)DEM分辨率降低,泥沙和总磷(TP)模拟结果的相对误差明显增加,而流量和硝态氮(NO3-N)模拟结果变化极小;3)DEM分辨率达到一定精度后,进一步提高并不会使地表径流模拟精度得到改善,低分辨率DEM获得的坡度较小,这会降低模型对流量的模拟,模拟的洪峰径流产生滞后现象;4)子流域划分对流域产流模拟影响较小,而对产沙模拟影响较大.子流域和水文响应单元的划分数量对流域上游产沙量影响较大,而对流域出口处泥沙荷载影响较小;5)土地利用和土壤图精度主要通过影响模型中HRU生成的数量而影响模拟结果;6)地表径流模拟上,能够体现对地表径流贡献较大的局地降水事件的分布式的降水数据要比利用气象站点获得的降水数据模拟结果的精度要高.研究结果可以为今后模型开发、利用、改进提供参考,提高模型模拟的精度.     

配送式水产品运输箱结构及监控系统的设计

通过分析水产品供应链的特点,提出水产品冷链物流监控及可追溯的方法,设计了可单独式鲜活水产品运输箱,实现保证存活率、温度监测、源头追溯等目的,从而保证水产品供应链各环节的有效衔接。通过配送式鱼箱结构及监控系统的设计与开发,达到水产品冷链物流监控及可追溯系统的实施。     

通过多元回归分析农村分布式可再生能源选择的行为研究

为了解决能源危机问题和中国农村低碳经济发展中遇到的问题,以农村户用沼气为典型的分布式可再生能源进行研究,对河北省高家庄的农村能源情况进行调研,以面谈的方式调查农户213户,总结有效问卷为152份,并在此基础上对农户基本情况及可再生能源(“三沼”)使用情况进行统计分析,利用多种回归分析方法来研究农村分布式可再生能源选择行为,分别分析了农民收入、文化程度、能源支出与沼气采用之间的关系,继而运用Logistic多元统计分析得出了农民收入和文化程度对农户可再生能源选择行为有显著性影响的结论,并对该地区未来沼气的采用情况进行了预测分析,以期为各种农村分布式可再生能源的推广提供一定的参考。     

适用于车辆动力的微小型燃气轮机技术

作为一种新型热机,微小型燃气轮机具有清洁、可靠、多用途等特点,近年来得到了广泛关注和快速发展。介绍微小型燃气轮机的技术特点,对以微小型燃气轮机为核心的分布式发电和车辆动力系统进行研究,并展望微小型燃气轮机的应用前景。