百叶型太阳能集热墙集热效率实验研究

提出建立了在现有Trombe墙的空气夹层中悬挂百叶窗帘的百叶型太阳能集热墙,搭建了带有百叶型集热墙的可对比热箱实验平台,对百叶型集热墙的集热效率进行了测试和分析,实验结果显示,在冬季时,百叶型集热墙的瞬时集热效率最高能达41％,平均集热效率在30％左右,该研究表明新型百叶型集热墙能显著的提高室内环境温度,改善室内热环境,降低室内制热负荷.     

Drivers of change in agricultural water productivity and its improvement at basin scale in developing economies

We approach the issue of water productivity in agriculture by identifying five sets of drivers of change. We find that irrigation efficiencies at the field level can result in real water savings under certain conditions, but that small farmers in most of South Asia and Africa have little incentive to adopt the appropriate measures. Although water productivity improvement and water savings at the regional level are possible through a shift to economically efficient crops, such changes may be constrained by concerns with respect to domestic and regional food security, rural employment, and farming system resilience.     

Roll Waves in High Gradient Channels

Abstract

Vedernikov's number quantifies the allowable capacity that can be sustained as a stable uniform flow in a high gradient channel, but it does not provide any guidance to the design of freeboard when roll waves exist. Without considering roll waves, high gradient channels are undersized using the uniform flow approach and fail to maintain design integrity. This paper presents revised design curves to determine the stability of flow in high gradient channels. When the design condition exceeds the limiting condition, roll waves should be considered in design. This study applies the model of moving hydraulic jump to simulate roll waves. It provides estimations for wave heights when Froude number is greater than 1.50.     

Irrigation infrastructure development in the Limarí Basin in Central Chile: implications for adaptation to climate variability and climate change

One option to deal with climate variability in agriculture is to build irrigation infrastructure, although this may lead to the overdevelopment of water resources, leading to ‘basin closure’. The Limarí Basin, in central north Chile, has relied on irrigation infrastructure over the last 30 years to increase water supply reliability and extend irrigated acreage, especially for permanent crops. This situation has reduced adaptation opportunities in the basin, which is currently experiencing a severe drought that, according to climate change projections, is expected to persist in the future, with important consequences for the sustainability of agriculture production.     

亭子口缆机运行效率提高的工作研究

根据缆机浇筑混凝土的工艺特性,将缆机浇筑混凝土过程中的车辆运输及缆机吊运程序进行作业流程分解,将缆机吊运作业周期划分为9个操作单元,采集缆机吊运混凝土过程中卸料和浇筑全周期各单元的50个工作样本数据进行统计分析,找出需改进的关键点,针对性地提出了6项改进措施.改进作业方案后缆机吊运混凝土的效率提高了约20％.     

基于水联网及智慧水利提高水资源效能

针对水资源供需系统的“动态性、关联性、预期性、不确定性”,以信息技术当前快速发展和应用的物联网理论与技术为基础,提出了水联网及智慧水利概念：其总体架构是集物理水网、虚拟水网和市场水网一体的现代化水资源系统;其核心特征是实时感知、水信互联、过程跟踪、智能处理;其关键技术是基于云技术的监测、计算和服务,基于多水源高效能的智慧调度,基于多通道优拓扑的精准投递;其核心目标准确预报、精准配送和高效管理,全面提高水资源效能,促进我国水资源高效利用水平的跨越式提升。     

显热回收装置及其系统应用于北京办公建筑的可适应性

以北京地区办公建筑为重点研究对象,结合实测方法,选取北京地区办公建筑中应用较为广泛的板翅式及转轮式显热回收装置及其系统为实测对象,分析了室外温度、风速等因素对热回收装置的热效率、降低新风能耗的贡献率以及全年运行能耗的综合影响.分析结果表明,板翅式显热换热器在北京地区冬季采暖期使用时,当迎面风速vy1.5 m/s,显热效率η=60%～70%,可降低新风能耗50%以上;而板翅式及转轮式显热回收装置在北京地区夏季的可适应性较差,绝大多数时间η低于《公共建筑节能设计标准》要求的60%.     

近场无线能量传输系统的效率研究

对于近场无线能量传输系统,输入信号的波形及平均功率发生变化,可能会对信号能量的传输效率产生一定的影响。针对该问题通过理论分析与实验验证相结合的方式,研究了近场无线能量传输系统的输入信号波形及平均功率的变化对信号能量传输效率所产生的影响。提出了选择方波、正弦波和三角波三种典型波形的信号作为输入信号,进行横、纵向全面分析的方法,得出了同一种波形的输入信号的能量传输效率是相同的,不随信号输入功率的变化而发生改变;不同波形输入信号的能量传输效率是不同的,且方波、正弦波、三角波三种波形信号的无线能量传输效率比为2.622∶1.768∶1。     

PS基于身份数字签名算法的改进

PS（Paterson and Schuldt）算法直接利用两组独立的Waters身份处理函数分别处理用户身份和签名消息,该算法的安全归约效率很低。为此,改进了Waters身份处理函数的参数选择方法,并将其应用于PS签名算法安全证明的改进,使新的基于身份数字签名算法安全归约效率大大提高,从PS方案的O（（qkn）^-2）提高到O（（qkn√n））^-1）,从而使新算法更加安全、可信。     

基于啮合效率下斜齿圆柱齿轮设计参数的选择

斜齿轮因具有传动平稳和承载能力高等优点而被广泛用于高速、重载传动中。目前对于斜齿轮的设计多以满足齿面接触强度、轮齿弯曲强度和齿面抗胶合承载能力为准则,未考虑设计参数对啮合效率的影响,易造成能源浪费和经济损失。在影响齿轮啮合效率的因素中,滑动摩擦功率损失占主要地位。因此,本文从计算斜齿轮滑动摩擦功率损失入手,通过计算啮合点处的滑动摩擦功率损失并沿啮合线积分,得到斜齿轮啮合效率的表达式,从中揭示出设计参数对啮合效率的影响规律,进而提出在满足齿面接触强度、轮齿弯曲强度和齿面抗胶合承载能力的前提下斜齿轮设计参数的选择原则。