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The runoff of the Huanghe contains a great amount of suspended load and forms the high-density underflows (hyperpycnal currents) at the river mouth. The sediments over the subaqneous delta are mainly transported by the underflow. The sediment texture gradually get fining seawards, which relates to the attenuation of the hyperpycnal currents and hypopycnal plumes. Being hydraulically equivalent to the medlum-silt-sized quartz, which is the dominant component in the sediments, the clastic mica concentrates on the delta. The maximum thickness of the subaqueous delta is about 16m and the period of accumulation lasted from 12 to 16 years, therefore its sedimentary rate ranges from 110 to 130 cm/a. 相似文献
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为了精确分析经纬仪主镜的面形均方根,对主镜支撑连接球绞的仿真方法进行研究.建立了主镜支撑系统的有限元模型,对比了刚性连接、约束节点自由度和接触边界条件三种球绞的仿真方法.采用接触边界条件方法仿真得到的主镜面形均方根值为16.37nm,应用干涉仪检测得到主镜在径向支撑状态下的面形均方根值为17.53nm,仿真结果与实验结果的偏差为6.62%.实验结果显示三种方法中,接触边界条件法能较准确地获得主镜面形均方根值,用此方法对主镜径向支撑结构进行了参数化分析,获得径向支撑位置、长度和宽度对主镜面形的影响规律,可以为主镜面形的精确分析及主镜支撑结构设计提供参考. 相似文献
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黄河水下三角洲的动力沉积特征 总被引:4,自引:0,他引:4
本文根据1985—1988年期间进行的综合海上调查及室内研究结果确定,黄河径流在口门处形成高密度潜流,是水下三角洲沉积物的主要搬运营力.由口门向外沉积物发生结构递变,与潜流及表层羽体流的逐渐衰减有关.水下三角洲堆积体的最大厚度为16m,堆积时间为12—15a,沉积速率达110—130cm/a. 相似文献
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