城镇化下流域不透水面扩张对洪峰的影响——以南京秦淮河为例     

孙延伟  许有鹏  高斌  王强  李升峰 《湖泊科学》2021,33(5):1574-1583

长江下游秦淮河流域近年来由于城市化崛起导致不透水面迅速扩张,改变了流域水文过程,导致暴雨洪水灾害风险增大.本文以南京秦淮河流域为例,基于1988—2015年间下垫面和水文气象资料建立了流域水文模型,通过不透水面扩张情景分析,探讨了 1988—2015年间不透水面空间扩张及对流域洪水过程的影响.研究结果表明:(1)秦淮河全流域1988—2015年不透水率从3.92%增长到19.11%,且不同区域扩张速度有所差异;(2)2006—2015年不透水面情景下的洪峰流量平均涨幅大于城市化初期;受流域上下游位置和下垫面地形条件的影响,流域溧水河和句容河两河源处的不透水面变化对洪峰的影响较流域下游出口处更显著;(3)秦淮河流域及不同位置的不透水面扩张情景下,小洪水的洪峰响应均大于大洪水,且不透水面扩张发生在下游主干河流域时的大、小洪水洪峰涨幅差距略大于河源流域.  相似文献   

基于软化拉-压杆模型的RC空间边节点抗剪承载力计算方法     

李振宝  郝娜  崔燕伟  宋坤 《震灾防御技术》2019,14(1):1-9

实际地震作用是多维的、随机的,框架节点在2个方向同时受力,其抗震能力相比于单向地震作用会降低。目前,对节点核心区在2个方向同时受力时抗剪承载力的研究尚未完善。在双向受力下,节点核心区2个方向传来的剪力形成合剪力作用面,在节点核心区内部形成不同于单向受力下的斜向斜压杆。本文基于软化拉-压杆模型,针对水平双向受力相同的空间边节点,在合剪力作用面内建立抗剪承载力计算模型,确定空间边节点核心区斜压杆以及钢筋拉杆的计算方法。利用有限元软件建立不同参数空间边节点模型,并收集部分空间节点试验数据,将剪力计算值与模拟值或试验值进行对比。结果表明,基于软化拉-压杆模型建立的双向受力下钢筋混凝土框架,其边节点抗剪承载力计算值与模拟值或试验值吻合良好。  相似文献   

Seasonal variability of tides in the deep northern South China Sea     

Zhao  Jiuqiang  Zhang  Yanwei  Liu  Zhifei  Zhao  Yulong  Wang  Meng 《中国科学:地球科学(英文版)》2019,62(4):671-683

Tides are the major energy source for ocean mixing, regulating the variation of oceanic circulation and sediment transport in the deep sea. Here twenty months of high-resolution current profiles, which were observed via a mooring system at a water depth of 2100 m in the northern South China Sea(SCS), are used to investigate seasonal variability in deep-sea tides.Spectral analysis shows that tides in this region are dominated by diurnal tide, and both diurnal and semidiurnal tide are vertical mode-1 dominant. Baroclinic diurnal tidal current exhibits pronounced seasonal variability, showing its kinetic energy was the strongest in summer, and the maximum depth-averaged value was up to 86.7 cm~2 s~(-2), which was about 1.5 times of that in winter and twice that in spring and autumn. In contrast, baroclinic semidiurnal tide displays no evident seasonal variability. Such seasonal variability in baroclinic tide was mainly modulated by the barotropic forcing from the Luzon Strait. On the other hand,two anticyclonic eddies and one cyclonic eddy, which originated off southwestern Taiwan in winter, crossed the mooring system.The cyclonic eddy had weak impact on current velocity in the deep sea, but the two deep-reaching anticyclonic eddies enhanced the current velocity through the full-water column by inducing strong subinertial flows. Consequently, the kinetic energy of tides was strengthened and the incoherent variance of baroclinic diurnal tide increased in winter, which contributed ～85% of the variability in diurnal tide. Meanwhile, the velocity of baroclinic diurnal tide was reduced in winter, which was attributed to the weakened stratification induced by the passage of anticyclonic eddies in the deep sea. The seasonal variability of tides in the deep northern SCS can provide a dynamic mechanism for interpreting sediment transport processes in the deep sea on different time scales.  相似文献   

Temporal and spatial evolution of a deep-reaching anticyclonic eddy in the South China Sea     

Meng WANG  Yanwei ZHANG  Zhifei LIU  Yulong ZHAO  Jianru LI 《中国科学:地球科学(英文版)》2019,(6)

The temporal and spatial evolution of a deep-reaching anticyclonic eddy(AE) is studied using a combination of satellite measurements, moored observations and ocean model reanalysis data in the South China Sea(SCS). Three evolutionary stages in eddy's lifecycle are identified from changes in eddy dynamical characteristics estimated from satellite altimetry: birth(22 days), growth(64 days), and decay(47 days). Similar patterns are also distinguished from dynamic signals in HYCOM.Further, flows reversal and upwelling of cold water below 1500 m were captured by the in-situ records when this energetic,highly nonlinear and long-lived(over 19 weeks) AE passed by our mooring position. Its detailed vertical structure is examined through temperature anomalies, vertical shear of horizontal velocities, and horizontal streamlines estimated from ocean model reanalysis data. Results from the model reveal a mesoscale AE with first-mode baroclinic structure: a bowl-shaped anticyclonic flow in the upper ocean connected to a slant-cylinder cyclonic flow at depth, with a transition layer at depths between 400 and 700 m. It is in good agreement with moored observations but showing a shallower transition depth, suggesting a slight deficiency in the model due to limited deep-sea observations. Last, we estimate eddy heat transport at different depths and stages along the AE's path based on the model data. The result reveals that pronounced heat fluxes occur during growth stage(depths 400 m),counting for 73.03% of the total value. In the decay stage, major heat transport occurs at deeper depth(depths 700–1500 m).Dynamical characteristics suggest that the vertical structure and temporal evolution of the eddy play significant roles in basinscale movement and heat transferring. Considering that mesoscale eddies are ubiquitous in the SCS, our results support a recently-proposed mechanism, whereby upper ocean flows produce changes in the deep-sea circulation, potentially influencing boundary layer dynamics. For the first time to track and link an individual AE observed by satellite altimetry and ocean model,comparisons indicate that assimilative HYCOM outputs may be useful for examining the deep ocean properties within the SCS,especially under the impact of such an intensified surface-detected eddy.  相似文献   

鄂尔多斯盆地中部地区马家沟组断裂控制天然气运移方向的流体包裹体证据          下载免费PDF全文

冯艳伟  陈勇  赵振宇  刘听雨  雷静  钟升  王淼  李冠华  裴仰文 《地球科学》2021,46(10):3601-3614

为研究鄂尔多斯盆地中部地区马家沟组成藏期次和天然气运移方向与断裂活动的相关性,利用流体包裹体岩相学观察、激光拉曼光谱分析、均一温度和冰点温度的测定以及热力学PVT模拟方法对奥陶系马家沟组马五段储层的岩心样品进行了成分、温度和压力的测定与恢复.结果表明:构造裂缝脉体中充填的矿物为方解石、白云石和菱镁矿;脉体中共有4类流体包裹体,分别为富甲烷气体包裹体、含CO₂富甲烷气体包裹体、含甲烷盐水包裹体和盐水包裹体,这4类流体包裹体均存在于方解石脉体中;构造裂缝脉体和溶孔中含甲烷流体包裹体的均一温度在130.1~179.6 ℃之间,与含甲烷流体包裹体同期的盐水包裹体的均一温度范围为112.3~173.3 ℃.结合生排烃史和埋藏史,证明早白垩世是马家沟组天然气的主要成藏期.沿断裂分布的各井的捕获压力和压力系数呈现由西南向东北递减的趋势,早白垩世的构造运动在北东向的断层中产生大量构造裂缝,为天然气的运移提供了通道,证明含甲烷的流体沿北东向断裂运移并充注成藏.   相似文献   

粗骨料对混凝土界面过渡区氯离子扩散性能影响     

王元战  吕彦伟  龙俞辰  吴林键 《海洋工程》2018,36(2):73-82

通过室内干湿循环条件下混凝土中氯离子扩散试验,实测得到6种不同粗骨料体积分数的混凝土试件在不同时刻、不同深度处的氯离子浓度。经回归分析得到了不同粗骨料体积分数下混凝土的氯离子整体扩散系数,其值随粗骨料体积分数的增加而减小。同时,探讨了粗骨料的稀释、曲折和界面过渡区效应对混凝土中氯离子扩散的影响。在此基础上,同时考虑粗骨料体积分数Vf和界面过渡区厚度h的影响系数α(Vf,h),建立混凝土界面过渡区氯离子扩散系数模型,界面过渡区氯离子扩散系数随粗骨料体积分数的增大呈近乎线性地减小,随界面过渡区厚度的增大先显著减小而后逐渐趋于平稳。最后,将建立的界面过渡区氯离子扩散系数模型应用于混凝土中氯离子扩散的三维细观数模中。结果表明:细观数模计算结果与物理试验实测数据在变化趋势和数值大小上均能够吻合,可验证界面过渡区氯离子扩散系数模型的正确性与合理性。  相似文献   

酸洗法测定海洋沉积物有机碳和无机碳含量的致命缺陷   总被引：2，自引：0，他引：2  

凌晨  刘志飞  张靖雯  赵玉龙  张艳伟  Fernandez Adrian R. 《海洋学报(英文版)》2020,39(8):96-102

Organic and inorganic carbon contents of marine sediments are important to reconstruct marine productivity,global carbon cycle, and climate change. A proper method to separate and determine organic and inorganic carbons is thus of great necessity. Although the best method is still disputable, the acid leaching method is widely used in many laboratories because of its ease-of-use and high accuracy. The results of the elemental analysis of sediment trap samples reveal that organic and inorganic carbon contents cannot be obtained using the acid leaching method, causing an infinitely amplified error when the carbon content of the decarbonated sample is 12%±1% according to a mathematical derivation. Acid fumigation and gasometric methods are used for comparison, which indicates that other methods can avoid this problem in organic carbon analysis. For the first time, this study uncovers the pitfalls of the acid leaching method, which limits the implication in practical laboratory measurement, and recommends alternative solutions of organic/inorganic carbon determination in marine sediments.  相似文献   

大连市内部地域结构转型与郊区化   总被引：29，自引：7，他引：22  

曹广忠  柴彦威 《地理科学》1998,18(3):234-241

在回顾大连城市内涪地域结构形成发展的基础上,分析了８０年代以来大连城市土地利用结构的总体变化趋势,并尝试提出了大连市内部地域结构模式图。８０年代期间,大连市内部地域结构已开始由单中心集聚型向多中心集聚与扩散并存型转型,而这种转型是大连市效区化现象在城市地域上的空间反映。  相似文献   

Estimation of eddy viscosity on the South China Sea shelf with adjoint assimilation method   总被引：2，自引：0，他引：2  

ZHANGYanwei  TIANJiwei  XIELingling 《海洋学报(英文版)》2009,28(5):9-16

The eddy viscosity of the ocean is an important parameter indicating the small-scale mixing process in the oceanic interior water column.Ekman wind-driven current model and adjoint assimilation technique are used to calculate the vertical profiles of eddy viscosity by fitting model results to the observation data.The data used in the paper include observed wind data and ADCP data obtained at Wenchang Oil Rig on the SCS (the South China Sea) shelf in August 2002.Different simulations under different wind conditions are analyzed to explore how the eddy viscosity develops with varying wind field.The results show that the eddy viscosity endured gradual variations in the range of 10^-3-10^-2 m²/s during the periods of wind changes.The mean eddy viscosity undergoing strong wind could rise by about 25% as compared to the value under weak wind.  相似文献   

中国人文地理学研究进展与展望   总被引：6，自引：1，他引：5  

方创琳  周尚意  柴彦威  陆玉麒  朱竑  冯健  刘云刚 《地理科学进展》2011,30(12):1470-1478

本文重点总结了近年来人地关系论、文化地理学、行为地理学、社会地理学和政治地理学等人文地理学的特色分支学科和新兴分支学科的发展现状、研究进展及未来发展展望。通过对国内大量的文献分析和与国外相关研究进展的比较分析后认为,中国人文地理学在理论创新、研究方法、手段革新和实践应用等方面均取得了丰硕的研究成果。表现为：人地关系论作为地理学研究核心的地位得到进一步提升;文化地理研究视野更为开阔,并在转向新文化地理学;行为地理学进入了重要的研究转向与繁荣发展新阶段;政治地理学顺应地缘政治战略需求开始由低迷走向回暖;社会地理学伴随和谐社会建设蓬勃发展。未来中国人文地理学研究的总体趋势是,面向国家战略需求,树立人地和谐的科学发展观,紧跟中国经济社会发展的时代步伐,在力所能及地解决国家发展中若干新问题的同时,重点深化人地关系理论及研究方法,加强人地系统调控机理与过程、格局与节律及其示范应用的研究,加强人地系统演进过程中的全球问题、全球变化及其区域响应的研究;顺应国家文化产业大发展和建设文化强国的战略要求,加强文化地理研究与国家文化产业振兴的融合研究,建设中国“本土化”的文化地理学学科体系;进一步拓展行为地理学研究广度与深度,加强实验性研究;关注新地缘政治学、都市政治地理和地方政治地理的研究,依托“六普”数据推动社会地理学研究实现新的跨越。通过上述研究,进一步推动中国人文地理学健康持续稳定发展。  相似文献