RELATIONSHIP BETWEEN VELOCITY PROFILE AND DISTRIBUTION OF SEDIMENT CONCENTRATION     

NI Jinren Professor  Dept. of Geography  Peking University HUI Yujia Professor  Dept. of Hydraulic Engineering  Tsinghua University 《国际泥沙研究》1993,(2)

I. ON THE INFLUENCING FACTORS OF THE SEDIMENT~LADEN FLOW VELOCITY PROFILEThe influence of sediment on the water--now structures must be considered when thevelocity profile of the sediment--laden now (or turbid flow) is studied. widely usedparameters for reflecting thoses influences are the sediment concentrahon and theffichardson number, where Ri represents the variation of the concentration gradient.Generally, the vertical distributions of sediment concentration and th…  相似文献   

An evaluation of surface-mine spoils area restoration in wyoming using rainfall simulation     

Gregg C. Lusby  Terrence J. Toy 《地球表面变化过程与地形》1976,1(4):375-386

A recently developed rainfall simulator was used to apply ‘rainstorms’ on restored spoils areas at two coal mining sites in Wyoming. Runoff and sediment yield were considerably greater from the reworked areas compared to similar measurements on nearby undisturbed areas. This may possibly be attributed to the fact that in the disturbed areas mean slopes were generally greater, there was more clay at the surface, and concentration of roots was not as great as in the undisturbed areas. The rainfall simulator appears to be a valuable tool in determining baseline data for later comparison with data form areas under rehabilitation.  相似文献   

长江流域夏季日面雨量精度与不同站数间关系研究     

匡晓为  王海军  严婧  王星宇  刘梦雨 《水文》2023,43(4):69-73

为探讨不同测量站配置数对统计长江流域夏季日面雨量精度的影响,选取金沙江下游、鄂东北、青弋水阳江3个流域作为研究对象,并挑选出不同站网分布,统计各站网分布计算的2016—2018年夏季日面雨量,运用平均绝对误差（MAE）、均方差（MSE）和相关系数（r）三个技术指标来评价各流域夏季日面雨量精度与站数之间的关系。结果表明：各流域夏季日面雨量精度均受站数变化的影响,MAE、MSE均随站数的增加而减小,但当站数增加到一定数量之后趋于稳定,r也有相同的变化规律,只是随站数增加而增大。同时,通过计算三个技术指标随站数平均变化值,定量揭示了以上变化规律并得到金下、鄂东北、青弋水阳江流域代表性站数分别为405站、293站、126站,与现有站数相比,分别减少25.1%、55.8%、56.6%,可为计算长江流域夏季日面雨量选用站数和站网布局提供参考。  相似文献   

城市街谷几何结构对街谷内流场及污染物浓度场影响的数值模拟   总被引：10，自引：3，他引：7  

吕萍  袁九毅  张文煜 《高原气象》2004,23(4):534-539

利用数值模拟方法研究了微尺度街道峡谷范围内街谷几何结构及街道两侧建筑物高度对称性对街谷内流场及机动车排放污染物扩散规律的影响。结果表明:当街道峡谷高宽比>2.1时,街谷内的流场结构由一个完整的垂直涡旋变为上下两个反向运动的强弱不同的垂直涡旋。各类型街谷内污染物扩散水平从强到弱依次为迎风面建筑物高度大于背风面建筑物高度的街道峡谷,迎风面建筑物高度小于背风面建筑物高度的街道峡谷;平行型街道峡谷。  相似文献   

海洋表层叶绿素浓度的激光雷达测量方法和海上实验   总被引：9，自引：0，他引：9  

陈卫标  吴东  张亭禄  刘智深 《海洋与湖沼》1998,29(3):255-260

依据激光感生荧光的原理和叶绿素分子的荧光谱特性,研制一套激发波长为532nm的海洋激光雷达系统,用于海洋表层叶绿素分子浓度的快速测量。应用该系统于1994年10－11月进行一次长距离的海上现场实验,对东海（2－32°N,122—129°E）21个站位的表层叶绿素浓度进行了测量,得到0．15μg/L-1．10μg／L范围的表层叶绿素分子的浓度分布。测量结果与水样的分光光度计测量结果相吻合。  相似文献   

IPCC emission scenarios: How did critiques affect their quality and relevance 1990–2022?     

《Global Environmental Change》2022

Long-term global emission scenarios enable the analysis of future climate change, impacts, and response strategies by providing insight into possible future developments and linking these different climate research elements. Such scenarios play a crucial role in the climate change literature informing the Intergovernmental Panel on Climate Change’s (IPCC) Assessment Reports (ARs) and support policymakers. This article reviews the evolution of emission scenarios, since 1990, by focusing on scenario critiques and responses as published in the literature. We focus on the issues raised in the critiques and the possible impact on scenario development. The critique (280) focuses on four areas: 1) key scenario assumptions (40%), 2) the emissions range covered by the scenarios and missing scenarios (25%), 3) methodological issues (24%), and 4) the policy relevance and handling of uncertainty (11%). Scenario critiques have become increasingly influential since 2000. Some areas of critique have decreased or become less prominent (probability, development process, convergence assumptions, and economic metrics). Other areas have become more dominant over time (e.g., policy relevance & implications of scenarios, transparency, Negative Emissions Technologies (NETs) assumptions, missing scenarios). Several changes have been made in developing scenarios and their content that respond to the critique.  相似文献   

江南造山带深部边界及成矿制约：来自综合地球物理的认识          下载免费PDF全文

严加永  吕庆田  张永谦  刘卫强  王栩  陈昌昕  徐峣  刘家豪 《岩石学报》2022,38(2):544-558

江南造山带位于组成华南大陆的扬子地块和华夏地块之间，是揭示华南陆块演化及其动力学过程、探索该地区大规模岩浆多金属成矿作用的关键窗口。前人在构造学、岩石学和矿床学等方面取得了诸多进展，但仍对江南造山带的深部结构认识不明，导致对其定义、边界范围、形成时代及演化过程等方面长期存在争议，故亟需开展综合地球物理探测工作，为解决上述争议问题提供约束。鉴于后期构造运动对上地壳大幅改造的影响，致使对于江南造山带的深部边界存在不同认识，本文以重力数据和航磁数据为主、辅以大地电磁测深结果、并与水系沉积物地球化学资料相结合，厘定江南造山带的深部边界。综合重磁多尺度边缘检测、深部电性结构及75种元素水系沉积物地球化学数据聚类分析结果，推测钦杭结合带可能为江南造山带东南侧深部边界，并推断了江南造山带北部可能的深部边界和周缘的断裂构造。基于上述结果和认识，分析了区域构造对金、铜矿床的控制作用，认为江南造山带深部边界及深部断裂扮演了成矿系统中“导矿通道”的角色，从深大断裂形成之初就提供了铜、金等幔源成分为主的矿物质，在合适位置就位成矿；后期复杂的构造运动，使得局部位置再次活化，成矿物质重新富集迁移，在次级断裂等有利...  相似文献