Development of a recurrent Sigma-Pi neural network rainfall forecasting system in Hong Kong

At the moment, weather forecasting is still an art — the experience and intuition of forecasters play a significant role in determining the quality of forecasting. This paper describes the development of a new approach to rainfall forecasting using neural networks. It deals with the extraction of information from radar images and an evaluation of past rain gauge records to provide shortterm rainfall forecasting. All of the meteorological data were provided by the Royal Observatory of Hong Kong (ROHK). Preprocessing procedures were essential for this neural network rainfall forecasting. The forecast of the rainfall was performed every half an hour so that a storm warning signal can be delivered to the public in advance. The network architecture is based on a recurrent Sigma-Pi network. The results are very promising, and this neural-based rainfall forecasting system is capable of providing a rain storm warning signal to the Hong Kong public one hour ahead.     

江口水电站设计洪水分析研究

在分析芙蓉江流暴雨的洪水特性的基础上，采用多种方法插补展延了洪水资源系列，并充分利用历史洪水调查资料，使设计洪水分析计算采用的资料具有一定的代表性，可靠性，其中坝堤百年一遇设计洪水洪峰流量为12000m^3/s,72h洪量为10.2亿m^3，对江口水电站设计洪水成果，通过与上下游，干支流各站的设计洪水参数及与长江流域的部分大中型水利水电工程设计水成果比较，进行了合理性分析。     

An efficient reliable broadcasting protocol for wireless mobile ad hoc networks

The mobile ad hoc network (MANET) has recently been recognized as an attractive network architecture for wireless communication. Reliable broadcast is an important operation in MANET (e.g., giving orders, searching routes, and notifying important signals). However, using a naive flooding to achieve reliable broadcasting may be very costly, causing a lot of contention, collision, and congestion, to which we refer as the broadcast storm problem. This paper proposes an efficient reliable broadcasting protocol by taking care of the potential broadcast storm problem that could occur in the medium-access level. Existing protocols are either unreliable, or reliable but based on a too costly approach. Our protocol differs from existing protocols by adopting a low-cost broadcast, which does not guarantee reliability, as a basic operation. The reliability is ensured by additional acknowledgement and handshaking. Simulation results do justify the efficiency of the proposed protocol.     

基于广义预测控制的船舶编队

针对多船舶之间的编队合作问题,对船舶的编队控制进行研究。利用广义预测控制方法在船舶运行中对理想路径曲线进行预测,得出船舶的运动控制策略;通过运用领导-跟随者编队方法,在Cartesian坐标系下建立船舶编队控制模型,基于这种模型建立一系列船舶航迹约束,得到船队跟随者成员的控制策略。同时在船舶运行过程中,加入风浪的扰动,进行模拟仿真,得到船队的运行轨迹。     

风拖曳力系数和曼宁系数对风暴潮流模拟的影响

利用0205号威马逊台风期间实测风暴增水和风暴潮流数据,采用NCEP FNL和台风模型风场的融合风场作为驱动项,建立了覆盖东海的三维风暴潮流数值模型,研究风拖曳力系数和曼宁系数对风暴增水和风暴潮流的影响。计算结果表明:(1)风拖曳力系数取值应考虑随风速变化。表层风暴潮流受风拖曳力系数影响较大,中层和底层风暴潮流基本不受影响。(2)风暴潮流结构在一定程度上取决于曼宁系数;曼宁系数对中层和底层风暴潮流影响大于表层,曼宁系数越大,底摩擦阻力越大,风暴潮流垂向分层越明显。(3)风暴增水和风暴潮流对曼宁系数的响应不同,建立模型时,应同时率定风暴增水和风暴潮流。     

北京市雨水收集利用蓄水池容积计算与分析

基于北京市1984—2013年的日降雨资料,以北京林业大学林业楼及其周边绿地为研究区,设置3种用水情景(冲厕、绿地灌溉及冲厕+绿地灌溉),采用连续模拟法,分别绘制3种用水情景下雨水收集利用工程的雨水截留率、自来水替代率、供水保证率以及效益费用比变化曲线,并通过综合分析这些曲线的变化特征确定雨水蓄水池最佳设计容积(60~82 m3)。同时采用设计暴雨法计算1~5年不同重现期的蓄水池设计容积(77~248 m3)。结果表明,连续模拟法计算过程相对复杂,但可用于综合衡量雨水收集利用工程的雨洪管理效益,以及缓解水资源短缺效益、供水可靠性及经济可行性分析。     

交换网络中广播风暴的产生和生成树协议（STP）对其有效阻止

在交换网络环境中,物理环路可以提高网络的冗余,但容易产生双向的广播环,甚至形成广播风暴,使交换机瘫痪;通过生成树协议生成根网桥,根端口,指定端口和阻塞端口,在逻辑上断开该网段,形成一个无环网络,使网络中无法产生广播环和广播风暴;当其它链路出现故障时,阻塞的端口自动恢复,逻辑断开的线路又被连通,继续传输数据。     

宁夏一次（2009-04-23）区域性沙尘暴天气的热力、动力触发机制

利用NCAR/NCEP全球再分析资料,对宁夏一次（2009-04-23）区域性沙尘暴天气的环流背景及高、低空影响系统进行了分析,重点研究了触发和维持该次沙尘天气的热力及动力条件.结果表明,蒙古冷涡及其后部的横槽为该次沙尘天气提供了有利的环流背景;蒙古气旋及地面锋面是导致沙尘暴爆发的直接原因;水平和垂直方向上的高能量锋区为该次沙尘天气提供了强热力条件;高、低空急流的耦合是沙尘天气出现和维持的动力条件;次级环流的存在是沙尘天气维持和发展的动力保障.对沙尘暴天气过程的预报预警、防灾减灾具有重要的指导意义。     

特小流域暴雨洪水计算研究概述

浙江省地区丘陵地形分布较广,集雨面积为特小流域的情况普遍存在,而针对特小流域的洪水计算方法研究,对于小型水库、塘坝等小型水利工程的规划设计具有重要应用价值,同时对于探索流域产流汇流机理也具有重要的理论意义.简要概述了特小流域洪水计算的主要方法,包括经验公式法、推理公式法、瞬时单位线法等,同时对特小流域暴雨洪水计算的影响因素及特点进行了归纳总结.     

移动自组织网中基于最优距离的概率广播方案

广播是移动Adhoc网络提供路由发现、地址解析等网络功能的一项重要操作．为了减少了泛洪广播算法中的端到端延迟,有效利用有限的带宽资源,解决广播风暴问题,文中提出了一种距离感知的广播技术,即基于最优距离的概率广播方案．本方案通过结合概率算法和距离感知来解决广播风暴问题,以高可达率和低延迟在网络中传播广播数据包．仿真结果显示与主流的泛洪算法和概率广播算法相比,本方案在可到达率、端到端延迟及重播概率等方面的性能有所提高．