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WANG Guixian WANG Xingkui GUO Jiachao Professor Sediment Research Laboratory Dept. of Hydraulic Engineering Tsinghua University Beijing China. Associate Professor Dept. of Hydraulic Engineering Tsinghua University. Assistant Dept. of Hydraulic Engineering Tsinghua University. 《国际泥沙研究》1993,(3)
I. INTRODUCTIONResistance to flow in alluvial streams is one of the crucial problems in fluvial hydraulics. Despite that large amount of studies have been conducted for centuries, no perfectmethod describing and calculating the resistance to flow in alluvial streams is availablehll now. Investigation on bed forms and resistance properties of light--weight bed materials is even more scarce. USWES (1936) has conducted systematic experiments onlight--weight materials in a flume & m long an… 相似文献
63.
陈高云 《成都信息工程学院学报》1999,(4):11
说明了用图形方式展现C程序运行情况的必要性和可行性;介绍了用图形演绎C程序运行的总设计思想;详细介绍了图形界面设计要求和程序模块的功能要求。 相似文献
64.
我国"入世"后,外国跨国公司必然会进入我国的地质市场.对比,本文指出了国内地勘单位与跨国公司相比,在技术力量、资本和管理水平等方面存在的问题,以及它们的介入所带来的不利影响和机遇,针对这些问题提出了具体的对策及所采取的措施. 相似文献
65.
山西义兴寨金矿床金矿物颗粒的产出及其成矿动力学意义 总被引:1,自引:0,他引:1
山西义兴寨金矿床的金主要呈包体金和裂隙金两种产出状态.文章根据成矿地球化学动力学理论,论证了金元素在含矿断裂发生脆性破裂和脆-韧性扩张活动中析出的化学反应类型,以及受反应动力学条件的制约,形成矿石中金不同产出状态的规律.指出热液矿床中普遍存在的包体金为热液成矿早期阶段断裂发生脆性破裂和成矿流体沸腾,导致快速反应结晶的产物;而裂隙金和晶隙金为成矿晚期金等矿质在流体中残余富集,同时成矿断裂再次发生脉动破裂,即成矿热力学演化与有利的构造动力学因素耦合作用的结果.得出金矿物颗粒的产出状态具有成矿动力学意义的结论. 相似文献
66.
Bank erosion rates and processes across a range of spatial scales are poorly understood in most environments, especially in the seasonally wet tropics of northern Australia where sediment yields are among global minima. A total of 177 erosion pins was installed at 45 sites on four sand‐bed streams (Tributaries North and Central, East Tributary and Ngarradj) in the Ngarradj catchment in the Alligator Rivers Region. Bank erosion was measured for up to 3·5 years (start of 1998/99 wet season to end of 2001/02 wet season) at three spatial scales, namely a discontinuous gully (0·6 km2) that was initiated by erosion of a grass swale between 1975 and 1981, a small continuous channel (2·5 km2) on an alluvial fan that was formed by incision of a formerly discontinuous channel between 1964 and 1978, and three medium‐sized, continuous channels (8·5–43·6 km2) with riparian vegetation. The bank erosion measurements during a period of average to above‐average rainfall established that substantial bank erosion occurred during the wet season on the two smaller channels by rapid lateral migration (Tributary Central) and by erosion of gully sidewalls due to a combination of within‐gully flows and overland flow plunging over the sidewalls (Tributary North). Minor bank erosion also occurred during the dry season by faunal activity, by desiccation and loss of cohesion of the sandy bank sediments and by dry flow processes. The larger channels with riparian vegetation (East Tributary and Ngarradj) did not generate significant amounts of sediment by bank erosion. Deposition (i.e. negative pin values) was locally significant at all scales. Bank profile form and channel planform exert a strong control on erosion rates during the wet season but not during the dry season. Copyright © 2006 Commonwealth Government of Australia. 相似文献
67.
The feasibility and efficiency of a seismic retrofit solution for existing reinforced concrete frame systems, designed before the introduction of modern seismic‐oriented design codes in the mid 1970s, is conceptually presented and experimentally investigated. A diagonal metallic haunch system is introduced at the beam–column connections to protect the joint panel zone from extensive damage and brittle shear mechanisms, while inverting the hierarchy of strength within the beam–column subassemblies and forming a plastic hinge in the beam. A complete step‐by‐step design procedure is suggested for the proposed retrofit strategy to achieve the desired reversal of strength hierarchy. Analytical formulations of the internal force flow at the beam–column‐joint level are derived for the retrofitted joints. The study is particularly focused on exterior beam–column joints, since it is recognized that they are the most vulnerable, due to their lack of a reliable joint shear transfer mechanism. Results from an experimental program carried out to validate the concept and the design procedure are also presented. The program consisted of quasi‐static cyclic tests on four exterior, ? scaled, beam–column joint subassemblies, typical of pre‐1970 construction practice using plain round bars with end‐hooks, with limited joint transverse reinforcement and detailed without capacity design considerations. The first (control specimen) emulated the as‐built connection while the three others incorporated the proposed retrofitted configurations. The experimental results demonstrated the effectiveness of the proposed solution for upgrading non‐seismically designed RC frames and also confirmed the applicability of the proposed design procedure and of the analytical derivations. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
68.
Numerical and analytical solutions are presented for the elastic and inelastic response of single‐degree‐of‐freedom yielding oscillators to idealized ground acceleration pulses. These motions are typical of near‐fault earthquake recordings generated by forward rupture directivity and may inflict damage in the absence of substantial structural strength and ductility capacity. Four basic pulse waveforms are examined: (1) triangular; (2) sinusoidal; (3) exponential; and (4) rectangular. In the first part of the article, a numerical study is presented of the effect of oscillator period, strength, damping, post‐yielding stiffness and number of excitation cycles, on inelastic response. Results are presented in the form of dimensionless graphs and regression formulas that elucidate the salient features of the problem. It is shown that conventional R–µ relations may significantly underestimate ductility demand imposed by near‐fault motions. The second part of the article concentrates on elastic‐perfectly plastic oscillators. Closed‐form solutions are derived for post‐yielding response and associated ductility demand. It is shown that all three ground motion histories (i.e. acceleration, velocity, and displacement) control oscillator response—contrary to the widespread view that ground velocity alone is of leading importance. The derived solutions provide insight on the physics of inelastic response, which is often obscured by the complexity of numerical algorithms and actual earthquake motions. The model is evaluated against numerical results from near‐field recordings. A case study is presented. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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针对三维激光测高拟合问题,本文采用BP神经网络进行拟合,该方法可以有效地消除或减弱数据中的系统误差影响,提高计算精度。实际算例证明,在数据无粗差情况下,BP神经网络的内符合与外符合精度优于传统的二次曲面拟合的精度。 相似文献