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91.
黄河三角洲潮滩发育时空谱系   总被引:3,自引:0,他引:3  
研究黄河三角洲潮滩发育的时空话系指出:在时间上,黄河三角洲潮滩系由不同时期河口滩发育而成,各段潮滩发育时间因素的差异在比较形态学上有清晰反映,在空间上,并存着处于不同发育阶段上的四种类型(阶段)。由此构成了黄河三角洲前沿所特有的湖滩形态时空体系。  相似文献   
92.
根据地质、地貌及地球物理资料分析,探讨展布于云南边陲哀牢山两侧的北西向断裂组成的红河断裂构造带,在东南亚的延伸特征。提出在该延伸带两侧沉积建造、构造活动,地球物理场和大地构造发展上均有显著差异。并进一步探讨该断裂构造带在大地构造上的意义。  相似文献   
93.
长江口三维潮流数值计算及动力分析   总被引:10,自引:1,他引:10  
采用三维动力学数学模型对长江口潮流场进行了计算,对长江口潮流流态在一个潮周期内逐时进行了分析,并对长江口南支盐水倒灌从动力学角度进行了初步探讨。计算结果表明:文中模型较好地重演长江口潮流场,可以用于大型复杂河口工程实际中的潮流场的计算和分析。  相似文献   
94.
河流对江苏海岸发育的影响   总被引:3,自引:0,他引:3  
赵全基 《海洋科学》1992,16(3):53-55
本文论述了江苏海岸发育的过程,探讨了长江、黄河、淮河等较大河流对海岸发育的影响。河流不仅能为海岸形态的塑造提供极为重要的物质基础,而且对于形成过程中的海洋动力作用产生一定影响。  相似文献   
95.
基于BP人工神经网络的水体遥感测深方法研究   总被引:5,自引:0,他引:5  
王艳姣  张鹰 《海洋工程》2005,23(4):33-38
利用Landsat7ETM+遥感图像反射率和实测水深值之间的相关性,建立了动量BP人工神经网络水深反演模型,并对长江口南港河段水深进行了反演.结果表明:具有较强非线性映射能力的动量BP神经网络模型能较好地反演出长江口南港河段的水深分布情况;由于受长江口水体高含沙量的影响,模型对小于5 m的水深值反演精度较高,而对大于10 m的水深值反演精度较低.  相似文献   
96.
下辽河平原—辽东湾的新构造运动   总被引:7,自引:0,他引:7  
通过地质、地貌及地球物理资料分析研究,发现下辽河平原—辽东湾的新构造运动的主要特征除了断裂发育、火山活动早期剧烈而晚期衰弱、现代地震活跃以及地壳差异和反差升降运动明显之外,还显示了:(1)深大断裂的控制性,(2)沉降中心的迁移性,(3)构造运动的阶段性和旋回性.  相似文献   
97.
渭河下游河道调整过程中的复杂响应现象   总被引:2,自引:1,他引:1  
许炯心 《地理研究》1989,8(2):82-90
应用系统复杂响应的原理研究三门峡水库上游渭河河道调整过程,表明上游河道河床形态对基面上升所作出的响应是复杂的,弯曲系数的变化为先减小而后增大,宽深比的变化是先增大后减小,比降由先减小而后增大,最后均趋于稳定.  相似文献   
98.
In an annual cycle from March 2005 to February 2006, benthic nutrient fluxes were measured monthly in the Dongtan intertidal flat within the Changjiang (Yangtze River) Estuary. Except for NH4^+, there always showed high fluxes from overlying water into sediment for other four nutrients. Sediments in the high and middle marshes, covered with halophyte and consisting of macrofauna, demonstrated more capabilities of assimilating nutrients from overlying water than the low marsh. Sampling seasons and nutrient concentrations in the overlying water could both exert significant effects on these fluxes. Additionally, according to the model provided by previous study, denitrification rates, that utilizing NO3- transported from overlying water (Dw) in Dongtan sediments, were estimated to be from -16 to 193 μmol·h^-1·m^-2 with an average value of 63 μmol·h^-1·m^-2 (n=18). These estimated values are still underestimates of the in-situ rates owing to the lack of consideration of DN, i.e., denitrification supported by the local NO3^- production via nitrification.  相似文献   
99.
We conducted ship-board incubation experiments to investigate changes in nutrient uptake of phytoplankton under different phosphate concentrations and irradiances in the Changjiang River Estuary and its adjacent waters in China. Under 100% natural irradiance the uptake rates of phosphate, silicate, and nitrate were accelerated at high phosphate levels (1.84 μM), while under low irradiance (about 50% natural irradiance) their uptake rates were restrained at the high but stimulated greatly at the intermediate phosphate concentrations (1.26 μM), as the growth of phytoplankton, changes in nitrite and ammonium uptake didn't follow an obvious pattern. Our results also showed that there were linear relationships between nitrate, silicate and phosphate uptake at different phosphate concentrations under low and high irradiances, and the growth period of phytoplankton was prolonged both at the high phosphate concentrations under high irradiance and at the intermediate concentrations under low irradiance, suggesting that the limitation of phytoplankton growth mainly reflected changes in its growth period, and because no such environment (low irradiance and low phosphate concentrations) actually existed in a high turbidity zone, phytoplankton blooms hardly occurred there. In the absence of irradiance, denitrification occurred readily and phytoplankton was kept decreasing, which resulted in phosphate regeneration.  相似文献   
100.
The northern margin of the Qaidam Basin is one of the main oil-gas exploration areas in western China, where source rocks are composed mostly of Middle and Lower Jurassic dark mud shale, carbargillite and coal. A large number of subsurface and outcrop samples differing in lithology with different types of organic matter were selected for resource evaluation, research and calculation. And among them, 13 samples were used for simulation experiment on hydrocarbon generating potential of various source rocks. At first, two kinds of heating modes were compared through simulation experiment, including single temperature-step heating and continual heating. Perhaps, the process of hydrocarbon generation and expulsion occurred naturally between a close system and an open system. In addition, the first heating mode was convenient, and all its reaction products were involved in the whole thermal evolution, and the final simulation experimental results were basically in consistency with the natural evolution trend Therefore, the first heating mode was adopted and the hydrocarbon yield of every sample was worked out. According to the type and lithology of organic matter and the hydrocarbon yield of samples for simulation experiment, hydrocarbon generation and expulsion mode with three kinds of lithology and five types of source rock has been established to provide the basis for hydrocarbon generation evaluation, research and resource calculation.  相似文献   
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