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东海内陆架沉积物敏感粒级构成及其地质意义 总被引:2,自引:0,他引:2
沉积物粒级包含了大量的沉积环境信息,在古环境恢复和重建中被广泛应用。基于采自东海内陆架的三根沉积物岩芯,作者利用激光粒度分析方法研究了沉积物的粒度组成,确定了敏感性粒级,探讨了搬运机制及其环境意义。研究表明:东海内陆架现代沉积物含有大致相同的三个敏感性粒级,分别是粒级1(12μm)、粒级2(12—225μm)和粒级3(225μm)。从北到南敏感粒级具有逐渐细化的趋势,该趋势与长江入海沉积物向南搬运过程中发生的沉积分异作用有关。粒级1和粒级2分别由均匀悬浮次总体和递变悬浮次总体构成,而粒级3则由生物过程产生。结合该区的海洋动力特征,作者认为,粒级2可较好地用来指示冬季海洋动力强度,并具有揭示东亚冬季风强度的潜在意义。 相似文献
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Human-machine interactive visiting and fixed-route visiting are currently the main roaming modes in digital three-dimensional (3D) scenes. However, in general, when a person visits an attraction area, s/he does not follow a fixed path, but instead wander about according to his/her interests. Here, we propose a new roaming mode, called autonomic visiting. That is, in a digital 3D scene, a user selects several interest spots, then a route connecting these spots can be automatically determined and 3D scene can be seen along this route. This study presents a technical approach that enables the realization of autonomic visiting in 3D scenes. Firstly, Delaunay triangular meshes for the terrain in 3D scene are established. Secondly, a plane-growth algorithm and a line-connection algorithm are introduced to automatically mend the broken parts of these triangular meshes. Thirdly, the triangular meshes are then merged and differently weighted according to different layers. Finally, a progress-zone transmission algorithm is presented to optimal the shortest route, which is derived from A-Star (A*) algorithm. Digital 3D campus of Nanjing University, China, is taken as the experimental materials. The experimental results prove the effect of the proposed approach. 相似文献
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Sediment source and transport trends are influenced by various hydrodynamic factors, and thus play important roles in sedimentary evolution and coastal stability. To examine sediment transport trends around the abandoned Yellow River delta promontory and its erosion mechanism, we employ empirical orthogonal function (EOF) analysis to study sedimentary characteristics and transport trends of the abandoned Yellow River delta in northern Jiangsu Province, China. The results showed that: (1) the main sediment source in the abandoned Yellow River delta is the submarine coastal slope and both sides of the abandoned Yellow River Delta; (2) the main hydrodynamics controlling sediment transport is the current that runs along the shore, coupled with waves, especially southward currents; (3) the sediment of the study area was redistributed under hydrodynamics; coarse sediments were eroded and broadly transported to the south. Therefore, it is concluded that the sediment sources and transport have important influence on coastal evolution: the sediment source area shows mass loss of deposits and erosion; deposits in the submarine coastal slope provide the source and were continuously eroded to provide materials to other places as a sediment source. 相似文献
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Cheng Yinhe Zhou Shengqi Wang Dongxiao Lu Yuanzheng Huang Ke Yao Jinglong You Xiaobao 《中国海洋湖沼学报》2016,34(3):619-628
The observed characteristics of lower atmospheric ducts over the South China Sea(SCS) were analyzed based on Global Position Systerm(GPS) radiosonde data collected four times daily during autumn open cruises from 2006 to 2012.Duct occurrence,thickness,and strength over the SCS were about 40%,150-m thick,and 8 M units,respectively,which were larger than during the summer monsoon period.Most ducts occurred at heights 1 500 m and these ducts easily trap electromagnetic wave clusters with wavelengths 2 m.Diurnal variation of the SCS ducts appeared evident.They occurred more often at midnight at higher altitudes(about 1 100 m),with a thickest layer of about 145 m and less frequently during the evening at lower altitudes(about 800 m),with a thinnest layer of about 125 m.Moreover,ducts during the daytime at a mean height of about 900 m,with the greatest strength of about 10 M units.Furthermore,all duct variables observed over the SCS in autumn decreased from north to south.These findings are useful not only in the design of radar and communication systems,but also for evaluating possible effects of anomalous propagation on meteorological radar and military applications. 相似文献
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The mean velocity of debris flow is one of the most important parameters in the design of mitigation structures and in quantitative risk analysis. This study develops a model to predict the mean debris flow velocity observed in the field by applying the incomplete similarity argument. An equation for estimating the Darcy-Weisbach resistance coefficient for debris flows with a volumetric sediment concentration larger than 0.19 is accordingly derived using 128 sets of observation data from nine Chinese gullies, in which both the effect of the volumetric sediment concentration and channel slope on resistance are considered. The derived equation is then verified and compared against five previously published equations by using 61 sets of published observation data from six gullies located in four countries. The applications of the proposed equation are discussed, and the improvements made using the proposed equation are clearly very significant when compared with the previously published equations. 相似文献