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981.
Light transmission data collected from June to July 1987 and from February to March 1997 by the R/V Kexue 1 in the East China Sea were used to analyze its distribution characteristics and its relation to the sediment transport in this sea. Some results obtained were: (1) The Taiwan Warm Current flowing northwards seemed to be a barrier preventing suspended matter discharged from the Changjiang River Estuary from continuously moving southeastward and causing the suspended matter to flow along a path near 123°30′E in summer and 123°00′E in winter. (2) Suspended matter in the area adjacent to the Changjiang River Estuary could not be transported southward along the coast in summer due to opposing offshore currents including the Taiwan Warm Current flowing northward and the Changjiang Diluted Water turning northeastward. (3) The thermocline and temperature front bar suspended matter from crossing through. 相似文献
982.
Cooper Creek is characterized by an exceptionally wide floodplain and a complex system of anastomosing channels which together can accommodate a large range of highly variable flows. In consequence flood frequency curves are unusually steep. With minimal tributary contribution over the two study lengths — Currareva-Nappa Merrie (> 400 km) and Nappa Merrie-Innamincka (32 km) — downstream output is largely controlled by upstream input, so that similar flow regimes and hydrograph forms can be maintained despite transmission losses and the variable activation of channels. Input-output relationships defined in terms of total flow volume and peak discharge suggest that, above a threshold flow of about 25% duration, transmission losses exceed 75% on average over the Currareva-Nappa Merrie length. The large difference in absorption between primary channels on the one hand and subsidiary channels and the floodplain surface on the other means that transmission losses vary non-linearly with stage. They are relatively low when flow is confined to the primary channels, but increase at higher stages as lesser channels and the floodplain are activated. Early levels do not recur until flows of < 0.5% duration are attained when output/input ratios increase rapidly with discharge. The influences of seasonality and background flow on output discharge are small relative to that of input discharge. Despite the long river distance, peak flows at Currareva and Nappa Merrie are well correlated. However, over the shorter Nappa Merrie-Innamincka length with its more confined system of channels, correlations are better and transmission losses less. They vary from 60% just above the threshold discharge to <10% at flows below 20% duration. Over this length outflow hydrographs can be effectively estimated by the three parameter Muskingum procedure, at least on an event by event basis, but further application must await additional records to understand fully how the parameters vary in an environment where streamflow is transmitted through a highly variable system of channels. 相似文献
983.
本文详细地讨论了正在建设中的我国地震信息系统卫星通信网的总体规划、组网方案、网络功能和系统配置,并且详细地讨论了各种数据的通信方式,认为由V-NET系统构成的地震信息卫星通信网具有传输地震数据、声码话音、图文传真、计算机数据的综合数据通信能力,能够为地震信息系统提供高速、可靠且价廉的数据传输服务。 相似文献
984.
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???????????????е????·?????????????????????????????????????????????????????????????????????????????????????????Σ????????α????????????????????????????????????????????????????????????μ???????????????????????????????????????????????????????? 相似文献
985.
A simplified process-based approach for evaluating onshore sandbar migration is presented in this study. This approach takes wave-averaged parameters as input and computes sediment transport processes using a reconstructed intra-wave orbital velocity signal. The proposed method guarantees good predictive skills for multiple onshore sandbar migration cases without an ad hoc calibration for each scenario. The study differs from previous onshore sandbar migration models, where calibration and testing are performed on just one or few events, and model assessment for uncalibrated realizations is rarely carried out. The present version of the model only addresses onshore sandbar migrations. For the onshore migration cases analyzed, the model has better predictive skills than state-of-the-art morphodynamic models (XBeach and Unibest-TC). 相似文献
986.
利用2017年10月26日—2018年3月14日期间,乌鲁木齐机场跑道视程≤600 m时跑道25方向大气透射仪和前向散射仪的跑道视程数据,以及跑道25方向大气透射仪和中间段大气透射仪跑道视程数据进行对比分析,得到以下结论:(1)大气透射仪的跑道视程数据大于等于前向散射仪的跑道视程数据的比例为96%,跑道视程≤400 m时,两种设备相互替代性较好;(2)相比于黑夜,白天情况下前向散射仪的跑道视程数据更接近25方向大气透射仪的跑道视程数据;(3)相比于跑道中间段大气透射仪,跑道25方向前向散射仪跑道视程数据更接近25方向的大气透射仪跑道视程数据。 相似文献
987.
988.
989.
发展城市轨道交通是解决城市交通问题的有效措施,所产生的振动和噪声形成环境问题,成为发展的“瓶颈”.文中以北京城轨道交通13号线霍营-回龙观段的观测振动信号作为输入,选择6层、10层和16层钢筋混凝土结构以及5层砌体结构,建立土结相互作用三维有限元模型,计算结构各层振动响应以及傅氏谱,从这两方面分析结构响应随距离的变化关... 相似文献
990.
随着医学应用和工业应用对X射线剂量、三维物体的成像速度的要求越来越严格,三维CT成像已经成为必然趋势,因此有必要对三维CT系统性能进行研究。本文首先建立三维CT图像噪声的理论估计方法,接着提出了基于FDK算法的三维CT系统性能评估的4种解析计算方法,使用高斯差模型作为通道函数。通过实验我们验证了本文提出的三维CT系统性... 相似文献