ADVANCES IN MEASURING TECHNIQUES OF BED LOAD     

ZHOU Gangyan ZOU Jiazhong 《国际泥沙研究》1997,(1)

I.m~UCrIONBedloadisthesedimentwhichmovesalongtheriverbedintheformofrolling,slidingandsaltation.BedloadmaycreatemanyproblemsintheoperationandmaintenanceofnavigationchannelandinthedevelOPmentofhydroelectricity.Dataofbedloaddischargearealsorequiredinthedesignofreservoir,inwhichtheinflowbedloadareallactuallytrapped.Thewaysofbedloadmotionaredifferentfordifferentsizes.Thus,itisextremelydifficulttodeterminethebedloaddischargeaccurately.Manyequationshavebeenproposedtocalculatethebedloaddischarge.H…  相似文献   

Discovery and analysis of ultra-micro grinding grain texture in slipping lamellae of ductile-brittle zone     

GE Heping  SUN Yan  LU Xiancai  ZHU Wenbin  GUO Jichun  LIU Deliang & Chi-yuen Wang . Department of Earth Sciences  Nanjing University  State Key Laboratory of Mineral Deposit  Nanjing  China  . Department of Earth  Space Sciences  University of Science  Technology of China  Hefei  China  . Department of Geology  Geophysics  University of California  Berkeley  CA  USA 《中国科学D辑(英文版)》2004,47(3)

In the 1990s of the 20th century, we participated in the research of the stress field in fissure tectonics of scientific deep bore cores for the Deep Observation and Sampling of the Earths Continental Crust (DOSECC for short). Spherical and enriched ul-tra-micro granular textures (nm size), which enriches Nb element (Wang & Sun, 1990; Sun & Wang, 1993)[1,2], were found during the observation of ul-tra-micro slipping lamellae of ductile and brittle oc-curring in Late Mesozoic granites us…  相似文献   

长江中下游旱涝中期预报方法及其业务应用   总被引：1，自引：1，他引：1  

金荣花  李月安  晁淑懿  任金声 《气象》2004,30(12):47-52

介绍了双层多因子综合相似的长江中下游旱涝中期预报模型。该模型引入了具有明确动力学和热力学意义的地转西风动量经向输送和经向温度梯度诊断量，同时强调了西太平洋副热带高压对长江中下游夏季降水的关键作用，并考虑了对流层中、低层500hPa高度和850hPa温度的大尺度环流背景场。与过去业务应用的单层相似预报模型相比较，不仅物理意义和天气学含义明确，而且更符合对具有复杂动力和热力机制的降水预报的考虑。5年的预报试验和业务应用结果表明，该方法对长江中下游地区旱涝的中期趋势预报有较好的预报能力。  相似文献   

信号传输的屏蔽措施与研究     

薄永进 《云南地理环境研究》2004,(Z1)

为了保证信息的正常传输,当布线环境有电磁干扰时,要相应地采用屏蔽系统。为了保证电子设备的正常工作,采用适当的屏蔽措施来阻挡或衰减电磁干扰。本文阐述了在现阶段雷灾中屏蔽的重要性以及屏蔽的具体施工,并对屏蔽的检验提出了一定的见解。  相似文献   

用GPS秒信号锁定高频振荡器的方法研究   总被引：1，自引：0，他引：1  

郭芳 《时间频率学报》2004,27(2):94-102

对用远距离传输的GPS秒信号锁定本地高频晶体振荡器的方法进行了探讨。介绍了高精度的时间数字转换器TDC(Time to Digital Converter)和对滤波的方法进行了探讨。为了降低成本又能够满足设计要求的精度，还考虑了双D／A转换的方法。有关的硬件系统已经通过了调试和一系列的测试和实验，在测量和控制精度方面，能达到设计的要求。此外，提出了这个系统有待解决的问题，如双D／A转换的非线性问题，Kalman滤波抗野值及继续提高精度的问题。  相似文献   

流动VLBI天线系统噪声温度及天线效率测量   总被引：1，自引：0，他引：1  

胡国军张继年  秦显平刘光明 《测绘学院学报》2004,21(1):14-16,20

我国自行研制的第一套流动VLBI系统——DCW—01型流动VLBI测量仪，目前已在国家重大科学工程“中国地壳运动观测网络”中投入使用。在流动VLBI的观测试验中，天线系统噪声温度和天线效率是观测前系统调试和检测的两项重要内容。天线系统噪声温度是衡量流动VLBI观测系统内部噪声程度的特性指标；天线效率反映了天线系统对到达天线能量的刊用率，在很多计算公式中是一个很重要的参数。因此，精确地测量它们的值是进行相关处理和计算的前提。文中结合我国流动VLBI观测站的研制与建设，介绍了流动VLBI测量仪的天线及接收机系统，并详细阐述了其天线系统噪声温度和天线效率的测量。  相似文献   

区域生态地球化学评价核心与对策   总被引：30，自引：1，他引：30       下载免费PDF全文

杨忠芳  奚小环  成杭新  周国华  陈德友  张建新  袁晓军  冯海艳  陈家玮  刘爱华  汤奇峰  余涛 《第四纪研究》2005,25(3):275-284

生态地球化学是地学与土壤学、农业、环境学和生态学等多学科交叉融合产生的新学科,是地球化学领域新的发展方向。区域生态地球化学评价是在区域地球化学调查基础上,针对影响流域/区带生态系统安全性的元素异常而开展的一项评价和研究工作。多目标区域地球化学调查获得的海量高精度地球化学数据,可为环境质量评价提供背景值、为土地的质量和生态管护提供地球化学依据;调查还发现了一系列影响流域生态安全性的元素异常,针对异常元素分布特征,区域生态地球化学评价将开展异常元素追踪和成因甄别、生态效应评价和生态系统安全性的预警预测等项评价和研究工作。文章论述了区域地球化学调查成果,介绍了区域地球化学评价的思路,阐述了区域生态地球化学评价的主要问题与对策。  相似文献   

Investigation into the effect of fault properties on wave transmission          下载免费PDF全文

H.R. Mohammadi  H. Mansouri  M. Bahaaddini  H. Jalalifar 《国际地质力学数值与分析法杂志》2017,41(17):1741-1757

The estimation of wave transmission across the fractured rock masses is of great importance for rock engineers to assess the stability of rock slopes in open pit mines. Presence of fault, as a major discontinuity, in the jointed rock mass can significantly impact on the peak particle velocity and transmission of blast waves, particularly where a fault contains a thick infilling with weak mechanical properties. This paper aims to study the effect of fault properties on transmission of blasting waves using the distinct element method. First, a validation study was carried out on the wave transmission across a single joint and different rock mediums through undertaking a comparative study against analytical models. Then, the transmission of blast wave across a fault with thick infilling in the Golgohar iron mine, Iran, was numerically studied, and the results were compared with the field measurements. The blast wave was numerically simulated using a hybrid finite element and finite difference code which then the outcome was used as the input for the distinct element method analysis. The measured uplift of hanging wall, as a result of wave transmission across the fault, in the numerical model agrees well with the recorded field measurement. Finally, the validated numerical model was used to study the effect of fault properties on wave transmission. It was found that the fault inclination angle is the most effective parameter on the peak particle velocity and uplift. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Efficient DEM‐based overland flow routing using integrated recursive algorithms          下载免费PDF全文

Pin‐Chun Huang  Kwan Tun Lee 《水文研究》2017,31(5):1007-1017

Two primary concerns in performing watershed overland flow routing are the numerical instability and computational efficiency. The stability of executing an explicit scheme has to be maintained by observing the Courant–Friedrich–Lewy criterion, which is adopted to confirm that the numerical marching speed is larger than the wave celerity. Moreover, there is another criterion of time step devised in previous studies to avoid back‐and‐forth refluxing between adjacent grids. The situation of refluxing usually occurs on flat regions. In light of this, the selection of a small time increment to honor both restrictions simultaneously is believed to decrease the computational efficiency in performing overland flow routing. This study aims at creating a robust algorithm to relax both restrictions. The proposed algorithm was first implemented on a one‐dimensional overland plane to evaluate the accuracy of the numerical result by comparing it with an analytical solution. Then, the algorithm was further applied to a watershed for 2D runoff simulations. The results show that the proposed integrated algorithm can provide an accurate runoff simulation and achieve satisfactory performance in terms of computational speed.  相似文献   

基于温度植被干旱指数的电网输电线路走廊干旱分析     

孙洋杰  唐华林 《测绘与空间地理信息》2016,(10):94-97

以湖北省输电线路走廊地区作为研究区,利用2013年1~9月MODIS卫星影像数据,处理得到月尺度的归一化植被指数(Normalized Differential Vegetation Index,NDVI)与地表温度(Land Surface Temperature,LST)数据,构建NDVI-Ts特征空间,计算得到温度植被干旱指数(Temperature Vegetation Dryness Index,TVDI),用TVDI监测结果分析湖北省输电线路走廊区域2013年干旱时空分布情况。结果表明,湖北省输电线路走廊地区TVDI和土壤含水量之间存在显著的负相关,相关系数达到0.525(p0.05),由MODIS卫星影像计算得到TVDI影像可以有效表明湖北省输电线路走廊地区的土壤含水情况。  相似文献