Flood frequency and routing processes at a confluence of the middle Yellow River in China

Floods cause environmental hazards and influence on socio‐economic activities. In this study, we evaluated the historic flood frequency at a confluence in the middle Yellow River, China. A non‐parametric, multivariate, empirical, orthogonal function matrix model, which consists of time correlation coefficients of flood discharge at different gauge stations and flood events was used for the analysis of flood frequency. The model addresses the characteristics of confluent floods such as frequency and the probability in multiple tributary rivers. Flood frequency analysis is often coupled with studies of hydrological routing processes that reduce the flood capacity of the rivers. Flood routing to the confluence were simulated using kinematic wave theory. Results of this flood frequency analysis showed that flooding frequency has intensified in the past 500 years, especially during the 19th century. Flooding in streams above the confluence was more frequent than in streams below the confluence. Over the last 2000 years, concurrent flooding in multiple tributary rivers accounted for 67.5% of the total flooding in the middle Yellow River. Simulation of flood routing processes shows that the decreased flooding capacity and elevated river bed of the shrunken main channel leads to an increased flood wave propagation time (24–52.3 h) in the study area after 1995. The model indicates that human activities, such as constructions of the Sanmenxia Dam, have changed flood routing boundary conditions and have contributed to the increased flood frequency at the confluence. Copyright © 2007 John Wiley & Sons, Ltd.     

充分灌与调亏灌溉条件下桃树滴灌的耗水量研究

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机电排灌工程管理之我见

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垂直腔激光器中弛豫振荡频率的优化控制

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二极管泵浦内腔倍频激光技术研究进展

评述了二极管泵浦内腔倍频激光技术的发展现状，对解决中小功率下‘绿光问题’的理论及实验方案进行了比较分析，对高功率内腔倍频系统亦进行了初步探讨。     

芯片AD9854在跳频通信系统中的应用

介绍了AD公司新推出的AD9854芯片的主要特性，讨论了将其应用于跳频通信系统中的优势。     

应用频率-初速法测试推算单桩承载力须解决的几个关键问题

本文对当前频率 -初速法应用中存在的一些问题阐述了作者的看法并着重探讨桩振初速度V0的计算方法、W0 的正确单位、如何使桩 -土体系明显震动、怎样从激振曲线中突出及分离出桩振曲线 ,从而获得正确的桩振频率f0 和首波峰 -峰值Ad、动静对比系数 βv 的选取     

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