三峡水库蓄水后巴东地区波速比（Vp/Vs）研究     

陈俊华甘家思  李普丽薛军蓉  李峰李垠 《大地测量与地球动力学》2007,27(F06):12-14,42

采用固定台站法计算了三峡水库蓄水后湖北省巴东地区ML2.0以上地震的波速比值,并给出了各自的相关系数。结果显示,巴东地区地震波速比值变化与水库地震的震源浅,裂隙发育,水的渗入作用等有关,并存在扩容期间波速比降低,震前波速比回升的现象。  相似文献   

Study on the Bubble Growth and Departure with A Lattice Boltzmann Method     

CHEN Guo-qing  HUANG Xiao  WANG Shi-ping  KANG You-wei 《中国海洋工程》2020,(1):69-79

For the growth and departure of bubbles from an orifice, a free energy lattice Boltzmann model is adopted to deal with this complex multiphase flow phenomenon. A virtual layer is set at the boundary of the flow domain to deal with the no-slip boundary condition. Effects of the viscosity, surface tension, gas inertial force and buoyancy on the characteristics of bubbles when they grow and departure from an orifice in quiescent liquid are studied. The releasing period and departure diameter of the bubble are influenced by the residual gas at the orifice, and the interaction between bubbles is taken into consideration. The relations between the releasing period or departure diameter and the gravity acceleration show fair agreements with previous numerical and theoretical results. And the influence of the gas outflow velocity on bubble formation is discussed as well. For the bubbles growing in cross-flow field, effects of the cross-flow speed and the gas outflow velocity on the bubble formation are discussed, which is related to the application in ship resistance reduction. And optimal choice of the ship speed and gas outflow velocity is studied. Cases in this paper also prove that this high density ratio LBM model has its flexibility and effectiveness on multiphase flow simulations.  相似文献   

潮汐河口坝田长宽比对泥沙淤积特征影响试验研究     

张功瑾  罗小峰  路川藤  白一冰 《海洋工程》2020,38(4):29-36

在航道治理工程中,往往通过丁坝群来实现其稳定航槽等目的,而坝田作为缓流区,其与主槽的水沙交换主要取决于横向的紊动交换。基于长江口北槽丁坝群实测资料分析和物理模型水槽试验研究发现不同长宽比坝田内的流态、淤积形态、坝田与相邻河段水沙交换的机理均不同,在长江口北槽丁坝群坝田建成后的淤积初期阶段,长宽比为0.30～0.40的坝田内的平均淤积强度最大。水槽试验研究表明,长宽比为0.50的坝田内淤积的主要部位即为主环流所在位置(坝田外侧),而在副环流位置,则出现微淤或冲刷的趋势;而长宽比为0.33的坝田内的淤积分布相对比较均匀。长宽比为0.33的坝田内淤积速率明显大于长宽比为0.50的坝田,长宽比为0.33的坝田达到冲淤平衡的时间较长。坝田淤积强度与随坝田回流强度、坝田与主槽水沙交换系数的增加而增加。  相似文献   

Savonius型桨叶水动力特性研究     

吴映江  宋瑞银  郑堤  吴烨卿  陈炫光 《海洋工程》2020,38(2):143-150

Savonius桨叶是一种典型的垂直轴阻力型桨叶,在风力发电中广泛应用。这种桨叶具有在多风向作用下单向转动的特性。利用该特性,将其应用于捕获水质点运动方向发生周期性或非周期性改变的波浪能的相关研究。采用Fluent数值仿真软件并基于UDF二次开发技术建立桨叶三维数值模型,分析叶片重叠率、相对入水深度和开口率等参数对桨叶动转矩和功率等水动力特性的影响,搭建实验平台,开展物理模型对照试验。研究结果表明:叶片重叠率有助于减小S型桨叶负转矩;当桨叶在水面上高度与波幅相等时,其功率系数达到最大;在叶片上增加弹片阀开口,可以增大桨叶动转矩系数,当开口面积达到一半时,动转矩系数比未开口桨叶提高28.3%。  相似文献   

Multi-dimensional expansion of urban space through the lens of land use: The case study of Nanjing City,China     

Qiao  Weifeng  Gao  Junbo  Guo  Yuanzhi  Ji  Qingqing  Wu  Ju  Cao  Min 《地理学报(英文版)》2019,29(5):749-761

Journal of Geographical Sciences - The study of multi-dimensional expansion of urban space (MEUS) addresses the laws of urban spatial expansion from all directions and angles. Using Nanjing as an...  相似文献   

氢氧化镁煅烧工艺和原料配比对氯氧镁水泥抗压强度的影响          下载免费PDF全文

阿旦春  肖学英  文静  董金美  郑卫新  常成功  刘盼  董飞  黄青 《盐湖研究》2020,28(3):85-92

以电石渣和MgCl_2制备的Mg(OH)_2为原料,制备氯氧镁水泥(MOC)用活性MgO,通过正交实验的方法观察煅烧温度、保温时间、活性MgO与MgCl_2摩尔比、H_2O与MgCl_2摩尔比对MOC试件抗压强度的影响。以3d、7d、28dMOC试件的抗压强度为评价指标,综合各因素对抗压强度的影响趋势发现:随煅烧温度及活性MgO与MgCl_2摩尔比的增加,MOC试件抗压强度呈增加趋势;保温时间大于30 min时,MOC试件的抗压强度随保温时间增加而降低;随H_2O与MgCl_2摩尔比的增大,试件的抗压强度逐渐减小。且不同龄期内,H_2O与MgCl_2摩尔比对试件抗压强度影响最为显著。当煅烧温度为600℃,保温时间为30 min,MgO与MgCl_2摩尔比为8,H_2O与MgCl_2摩尔比为13时,试件的抗压强度最佳。  相似文献   

LIFE CYCLE AND PRODUCTION OF CHIRONOMIDAE(DIPTERA) IN BIANDANTANG, A TYPICAL MACROPHYTIC LAKE (HUBEI, CHINA)   总被引：2，自引：0，他引：2  

阎云君 《中国海洋湖沼学报》2000,18(3):221-226

ＩＮＴＲＯＤＵＣＴＩＯＮＡｌｔｈｏｕｇｈｄｅｓｃｒｉｐｔｉｏｎｏｆｌｉｆｅｈｉｓｔｏｒｙａｎｄｅｓｔｉｍａｔｅｓｏｆａｎｉｍａｌｐｒｏｄｕｃｔｉｏｎｈａｖｅａｌｏｎｇｈｉｓｔｏｒｙ (Ｌｉｎ ｄｅｇａａｒｄ ,1 989) ,ｆｅｗｓｔｕｄｉｅｓｏｎｔｈｅｐｒｏｄｕｃｔｉｏｎｒａｔｅｏｆｂｅｎｔｈｉｃｍａｃｒｏｉｎｖｅｒｔｅｂｒａｔｅｓｗｅｒｅｃａｒｒｉｅｄｏｕｔｉｎＣｈｉｎｅｓｅｗａｔｅｒｓ (Ｌｉａｎｇ ,1 984 ) .Ｗｉｔｈｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｆｉｓｈｅｒｉｅｓａｎｄｔｈｅｄｅｔｅｒｉｏｒａｔｉｏ…  相似文献   

北京市住房价格和租金的空间分异与相互关系   总被引：1，自引：1，他引：1  

崔娜娜  古恒宇  沈体雁 《地理研究》2019,38(6):1420-1434

当前中国住房销售市场、住房租赁市场发展不平衡,研究住房价格、租金的空间分异与相互关系,对建立“租售并举”的住房制度具有重要参考价值。利用2016年北京市各住宅小区的住房价格、租金数据,及2006—2016年北京市逐月住房销售价格指数、住房租赁价格指数,从时空尺度剖析了住房价格、租金的空间分异与相互关系,并剖析了背后的差异机制。结果表明：① 北京市住房价格和租金的空间格局均呈多中心圈层递减结构,且南北差异明显,但租金的空间分异程度弱于住房价格。② 住房价格具有中等程度的空间相关性,受政策等随机性因素影响相对较大,而租金具有强烈的空间相关性,受区位交通等确定性因素影响相对较大。③ 住房价格和租金的价格剖面线并不相同,住房价格易受学区、大型公园等的影响,而租金更易受就业所在地、建筑年龄等的影响。售租比呈混乱斑驳、相对均质的扁平化分布特征,且小区越高档,售租比越高。④ 北京市住房销售市场和住房租赁市场基本相对独立发展,更符合双重市场的特征。产生上述差异的主要原因在于住房销售市场和住房租赁市场的市场特征、服务人群以及市场发育程度不同。  相似文献   

Variable water‐saturated areas and streamflow generation in the small Ringelbach catchment (Vosges Mountains,France): the master recession curve as an equilibrium curve for interactions between atmosphere,surface and ground waters          下载免费PDF全文

Bruno Ambroise 《水文研究》2016,30(20):3560-3577

In the small Ringelbach research catchment, where studies on the water cycle components in a granitic mountainous environment have been conducted since 1976, the water‐saturated areas that are hydraulically connected to the outlet play a major role in the streamflow generation, as it is here that complex interactions between atmosphere, surface and ground waters take place. During baseflow recession periods, which may last several months between two groundwater recharge events, the atmospheric inputs of water and energy on these contributing areas only explain the streamflow fluctuations observed around the master recession curve, which defines the groundwater contribution: fluctuating above it in the case of precipitation input on these areas, below it in the case of evaporation output from these areas. Streamflow may therefore largely deviate from the master recession curve in the case of long, hot, dry spells. Detailed mapping has shown that their variable extent is well related to baseflow by a loglinear curve. On the other hand, a synthetic master recession curve, well fitted by a second‐order hyperbolic function, has been obtained from numerous pure recession periods. Both based on these two curves, a simple procedure and a simple model have been used to (i) validate the hypothesis that the connected saturated areas are the only permanent variable contributing areas and (ii) simulate the daily streamflow volumes over long baseflow recession periods by a water balance of the aquifer below these areas only. The storm runoff ratio for small to moderate rainfall events is indeed corresponding to the catchment saturated fraction at that time. The volume of daily streamflow oscillations is indeed corresponding to the evaporation at the potential rate from the saturated areas only. In both cases, streamflow naturally tends towards the master recession curve after the end of any atmospheric perturbation. Introducing these findings into TOPMODEL led to significantly improved simulation results during baseflow recession periods. The master recession curve may therefore be considered as a dynamic equilibrium curve. Together with the relationship between saturated extent and baseflow, it provides the main characteristics necessary to understand and model the interactions at this complex interface and the resulting daily streamflow variations during baseflow recession periods in this type of catchment. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Comparison of methods for quantifying surface sublimation over seasonally snow‐covered terrain          下载免费PDF全文

Graham A. Sexstone  David W. Clow  David I. Stannard  Steven R. Fassnacht 《水文研究》2016,30(19):3373-3389

Snow sublimation can be an important component of the snow‐cover mass balance, and there is considerable interest in quantifying the role of this process within the water and energy balance of snow‐covered regions. In recent years, robust eddy covariance (EC) instrumentation has been used to quantify snow sublimation over snow‐covered surfaces in complex mountainous terrain. However, EC can be challenging for monitoring turbulent fluxes in snow‐covered environments because of intensive data, power, and fetch requirements, and alternative methods of estimating snow sublimation are often relied upon. To evaluate the relative merits of methods for quantifying surface sublimation, fluxes calculated by the EC, Bowen ratio–energy balance (BR), bulk aerodynamic flux (BF), and aerodynamic profile (AP) methods and their associated uncertainty were compared at two forested openings in the Colorado Rocky Mountains. Biases between methods are evaluated over a range of environmental conditions, and limitations of each method are discussed. Mean surface sublimation rates from both sites ranged from 0.33 to 0.36 mm day^?1, 0.14 to 0.37 mm day^?1, 0.10 to 0.17 mm day^?1, and 0.03 to 0.10 mm day^?1 for the EC, BR, BF and AP methods, respectively. The EC and/or BF methods are concluded to be superior for estimating surface sublimation in snow‐covered forested openings. The surface sublimation rates quantified in this study are generally smaller in magnitude compared with previously published studies in this region and help to refine sublimation estimates for forested openings in the Colorado Rocky Mountains. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献