BSS标准时钟系统

BSS标准时钟系统是应用GPS(全球定位系统)授时的标准时间显示和发送的系列装置。它的主要功用是: ·自动接收GPS(全球定位系统)授时并使系统时钟和GPS时间保持同步; ·每分钟在零秒时刻发送一次校时信号     

高性能同步相量测量装置守时钟研制

同步相量测量装置（PMU）可靠工作的关键是作为同步采样脉冲源的全球定位系统（GPS）的秒脉冲的可靠性。针对由于气候、故障及其他因素可能造成秒脉冲失效的情况，采用数字锁相环技术，利用复杂可编程逻辑器件（CPLD）及高精度晶振，研制了一种高性能的PMU守时钟。GPS信号正常时，守时钟跟踪输入的秒脉冲；秒脉冲失效时，守时钟则提供一定误差范围内与秒脉冲同步的替代信号。文中分析了其性能，通过仿真和实验进行了验证。     

GPS同步采样装置中防止干扰GPS秒脉冲信号的措施

为削弱和消除干扰对基于GPS同步采样装置的影响，在简要介绍GPS同步采样装置的基础上，根据秒脉冲总是位于2 s交界处的特点，提出了防止干扰GPS秒脉冲信号的软硬件措施。其中，软件鉴别法简单可行，适用于CPU内部资源充足的情况下；而硬件措施节约了CPU的片内资源，适用于CPU负担较重的应用场合。试验结果表明，该方法可有效地克服干扰信号对GPS同步采样装置的影响。     

提高测试精度的技巧

在水力机械模型试验中，常需要测量水头、流量、转速、力矩及真空压力等各种参数．这些参数会直接影响水轮机的效率．要提高这些测试参数的准确性，就必须使用精密的测试方法来减少其各种可能产生的误差．下面介绍的这种提高测试精度的技巧能解决上述问题．一套完整的数据采集系统装置具有各种功能板，包括模拟输人／输出板、数字输人／输出板、计数输人板及脉冲输出板等．这些功能板适当组合可用于测量各种电压信号、电流信号、脉冲信号和数字信号，也可用于各种过程控制．下面将分别讨论不同采集方式的情况．1分时采集情况分析在数据采集…     

新型移频式(FSK)远方跳闸信号传输装置的研究

本文介绍了YBX-Ⅱ型远方跳闸装置，装置由YBX-Ⅰ型机派生，采用载频直接移频(FSK)方式，以实现命令信号传输。装置采用有源鉴频器、接收导频独选方式，提高装置的安全可靠性；用反时限信杂比检测、高电平脉冲干扰检测和电平低落检测等信号，闭锁跳闸命令的输出，从而有效地抑制各种形式的干扰。     

龙滩水电工程大坝施工设备防碰撞预警系统的开发

该防碰撞预警系统利用GPS接收机作为信号采集装置，检测运动部件的位置，控制中心据此实时计算出各设备相关部件的位置及距离，判定是否有可能发生碰撞的设备，将警示指令发送给相关设备，提醒操作人员采取制动或避让等防撞措施，根据系统的特点布置检测装置及选定GPS接收机的精度等级，解决了立体布置且类型不同的设备间的防碰撞预警难题。     

基于数字锁相原理的GPS高精度同步时钟产生新方法

在分析时钟误差的基础上,根据全球定位系统（GPS）秒时钟无累计误差和晶振秒时钟无随机误差的特点,提出了一种利用GPS秒时钟同步晶振秒时钟实现高精度时钟的新方法。该方法根据数字锁相原理,通过测量GPS秒时钟与晶振秒时钟间的相位差来控制晶振秒时钟的分频系数,实时消除晶振秒时钟的累计误差,从而产生高精度秒时钟。实验结果表明,在GPS正常工作时能够保证其精度稳定在20 ns;GPS信号失效1 h的情况下,秒时钟精度仍能稳定在100 ns。根据此方法研制了具有较高性价比的高精度时钟发生装置,成功应用于行波定位系统中。     

洺河节制闸液压启闭机及闸控系统功能完善改造

针对洺河节制闸液压启闭机及闸控系统存在的主要问题,通过将行程检测装置由相对型行程检测装置改为绝对型行程检测装置,开度传感器输出信号由高速脉冲信号改为SSI信号,对存在安全隐患的油温加热装置及不易维护的液压元器件进行更换,增设用于安装SSI采集设备的通信柜,改造数据通信网络以调整PLC组网方式进行了改造。液压启闭机及闸控系统功能完善改造完成后,闸门开度等数据采集准确、高效、稳定,液压启闭机运行维护更加安全便捷,全面提升了闸门远程和现地控制的成功率。     

基于GIS中电磁波传播路径特性的局放源定位方法

气体绝缘开关设备（GIS）中发生局部放电（以下简称局放）时，为查找绝缘缺陷，需对局放源进行准确定位。超高频（UHF）时差定位法由于原理简单、实现方便、定位精度高等优点获得了广泛应用，但当局放信号的初始脉冲较小而难以确定信号的起始脉冲时间时，UHF时差法将难以有效运用从而导致较大误差。为提高时差定位法的准确性，对局放电磁波在GIS中的传播路径特性进行研究，分析结果表明，局部放电产生的电磁波在GIS中的传播路径与局放源的位置、检测点的位置密切相关，据此提出了基于传播路径的脉冲时差定位法。实验结果表明，当局放源位于GIS外壳附近、电磁波信号初始脉冲很小、难以辨识时，用该方法可以准确定位。     

同步相量测量装置的一种异地校核方法

提出利用对晶振信号进行整数分频并结合GPS同步时钟生成相量测量装置（PMU）异地同步校核中基准信号的方法。通过分析可知，只要晶振频率足够高，生成的基准信号就有足够高的精度，而且信号的参量具有良好的可调节性。该方法可有效解决PMU测量网络中异地同步校核和自校核问题。     

Call for Papers

正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.     

库水波动下库岸边坡地下水浸润线解析解及误差分析

解析法是库岸边坡地下水浸润线计算中便于实际应用的方法,但该方法须基于若干假定并对潜水运动基本方程线性化后才能求解。针对各假定和线性化过程建立不同的地下水渗流数学模型,用解析法和有限元法解答上述数学模型,分析各误差大小及其规律。结果表明：库岸垂直处理带来的误差要小于方程线性化处理和不考虑非饱和渗流带来的误差,而且它们都随渗透系数变大而减小;在三峡库区库水调度情况下,假定库水位等速变化带来的误差对大多岸坡而言可以忽略;计算库岸边坡地下水浸润线时,解析法只适用于水位变化幅度相比含水层厚度较小,且几何边界规则、岩土结构简单、岩土体渗透性较好时的情况。     

Changes in Summer Irrigated Crop Area and Water Use in Southeastern Turkey from 1993 to 2002: Implications for Current and Future Water Resources

Changes in summer irrigated cropland acreage and related water use are estimated from satellite remote sensing and ancillary data in semi-arid Southeastern Turkey where traditionally dry agricultural lands are being rapidly transformed into irrigated fields with the help of water from the Euphrates-Tigris Rivers. An image classification methodology based on thresholding of Landsat NDVI images from the peak summer period reveals that the total area of summer irrigated crops has increased three-fold (from 35,000 ha to over 100,000) in the Harran Plain between 1993 and 2002. Coupled analysis of annual irrigated crop area from remote sensing and potential evapotranspiration based estimates of irrigation water requirements for cotton indicate a corresponding increase in agricultural water use from about 370 million cubic meters to over one billion cubic meters, a volume in accordance with the state estimates. These estimates have important implications for understanding the rapid changes in current agricultural withdrawals in Southeastern Turkey and form a quantitative basis for exploring the changes in future water demands in the region. For example, expansion of irrigated lands have led to a steady decrease in potential evaporation due to increased roughness and decreased humidity deficit in the Harran Plain. Assuming that the changes in future evaporation conditions will be of similar nature, water use for irrigation is expected to decrease over 40 percent in future irrigation sites. Incorporating this decrease in overall planning of the irrigation projects currently under construction should lead to improved management, and by extension, sustainability of water resources in the region.     

浅谈优化Vray渲染在制作三维场景的应用研究

用Vray三维渲染引擎来渲染三维场景,其质量和速度是由一些影响因素和参数设置决定的,不同的参数和因素,可以得出不同的三维渲染效果.因此,分析、优化三维渲染质量和速度的影响因素,正确、合理的选择参数对提高Vray最后渲染阶段的质量和速度非常重要.     

固结、渗流和沉积控制方程研究

本文从两相流体动力学的守恒方程出发，考虑固相、液相的相对运动，推导了可以考虑场的不均匀性和流体压缩性的统一形式的控制方程，并对方程所基于的物理概念和相互联系进行了必要的分析。通过对方程适当形式的表达，可导出用于大、小变形固结、渗流和沉积的简化方程，显示了在不同领域的三个理论存在一定的统一性。方程推导过程并未对本构关系加以限制，适用范围较广。依据实际问题的要求，作了不同形式的简化。     

四川省及重庆市中型水电站效益分析

该文分析了四川省及重庆市几座中型水电站的调查材料表明：四川省及重庆市中型水电站不仅在川渝主网和地方电网中起着很大的作用，并具有巨大的社会效益，同时还有综合利用效益，说明修建中型水电站的优越性．     

Site modelling methods for detecting hydrologic alteration of flood frequency and flood duration in the floodplain below the carlyle dam,lower Kaskaskia River,Illinois, USA

Reports concerning the influence of dams on river hydrology vary among researchers, interest groups and government agencies. These often contradicting statements may occur because changes in hydrology caused by dams are distinct for each dam and river watershed. The objective of this research was to use site specific techniques to determine if the 1967 installation of the Carlyle Dam, lower Kaskaskia River, Illinois, altered flood frequency and duration within the forested floodplain located below the dam. Results indicated a decrease in flood duration and frequency, and a decrease in annual flood frequency variation at a site 6.4 km below the dam. Pre‐dam versus post‐dam differences in flood frequency and duration at the site 32.2 km below the dam were related to climate rather than dam effects. Although dam impacts are a concern, this research shows that distance downstream from the dam and downstream tributary and watershed characteristics should be considered before assuming that the dam has changed hydrologic parameters for portions of rivers. This research also indicates that areas of the lower Kaskaskia River may still maintain hydrologic ecological integrity, and could be targeted for restoration and adaptive management purposes. Hydrologic modelling combined with river gage and on‐site well measurement techniques presented in this study could provide detailed flood frequency and duration information for land use, sociological and geomorphological questions in focus areas within river floodplains. Copyright © 2008 John Wiley & Sons, Ltd.     

Statistical tools for thermal regime characterization at segment river scale: Case study of the Ste‐Marguerite River

Suitable thermal fish habitats are constrained by both maximum and minimum temperature tolerances. A multivariate and geostatistical approach was developed to estimate stream thermal characteristics at the river segment scale. Data from 22 temperature‐monitoring stations during summer 2007 were used to estimate monthly maximum temperature as well as thermal characteristics such as the number of events, the cumulative degree–days and the associated duration over specific temperature thresholds of 19 and 21°C. The probability of exceeding these temperature thresholds has also been interpolated. The methodology relies on the construction of a multivariate space using physiographic and hydrological characteristics of gauging stations as inputs in a canonical correlation analysis (CCA). A geostatistical interpolation technique, ordinary kriging, was subsequently used to perform interpolation in the physiographical space constructed using CCA. Results from this study were obtained for thermal characteristics estimated into two different interpolation spaces: (1) a 7 metrics space, and (2) an 8 metrics space. Cross‐validation technique has been performed and satisfactory results were obtained. Kriging thermal characteristics (magnitude and duration) into the 7 metric space for a 19°C threshold exceedance leads to best results with Relative Root Mean Square Error (RRMSE) ranging between 9.66 and 15.08%. The study shows that kriging in a multivariate space is a promising tool for water resources managers, especially in cases where risk mapping for lethal or sub‐lethal temperature thresholds may be required for a specific fish species. Copyright © 2010 John Wiley & Sons, Ltd.     

掺MgO混凝土的宏细观试验研究

利用MgO膨胀剂的延迟微膨胀效应能显著提高大体积混凝土的力学性能,产生的预压应力还能有效提高大体积混凝土抵抗温度开裂的能力,但目前对其微观机理研究不多。采用宏观与微观相结合的方式,研究了不同活性指数、不同掺量的MgO混凝土的力学性能,利用SEM/EDS微观分析手段揭示了MgO对混凝土性能影响的作用机理。试验结果表明：MgO取代部分水泥掺入混凝土中,混凝土的力学性能降低;掺量为4%~5%时,活性指数为100s的MgO混凝土的膨胀率大于活性指数为50 s的MgO混凝土;MgO混凝土的膨胀特性与Ca,Si,Mg,Al等元素的分布情况有关,掺入的MgO将改变界面区Ca,Si,Mg元素的富集特性,Ca元素和Mg元素更易于在界面区富集,导致混凝土宏观力学性能的降低。     

基于MIDAS软件探讨施工工序对深基坑稳定性的影响

基于武汉地铁名都站深基坑工程与水文地质勘察资料,建立了三维工程地质仿真计算模型。依据名都站深基坑开挖支护方案,利用有限元软件MIDAS的摩尔-库仑本构模型,对武汉地铁名都站深基坑施工过程中,不同施工工序下每步开挖之后,基坑的变形情况做仿真模拟计算,并对比分析其对基坑稳定性的影响。结果表明：基坑围护结构的变形情况与施工工序有很大的关系,施工工序越合理,上部土体变形越小,反之越大。因此,在基坑工程的施工过程中,要注重施工步骤的划分与合理安排,从而保证基坑工程的安全。研究成果为以后武汉地区基坑工程的施工设计提供了值得借鉴的经验。