利用旋转平台模拟双河口羽流相互作用的研究     

戴娟娟  袁野平  宋浩宸 《海洋与湖沼》2020,51(5):1108-1117

本文通过旋转平台实验室实验的方法,探讨了双河口情况下两个羽流将如何发生相互作用。在研究中,提出了一种新颖的技术对河口羽流的各切面流场进行测量,来获得河口羽流多个平面的速度场及涡度场,并基于此模拟了双河口羽流系统的准三维结构。通过对不同入流速度下的双河口羽流流场演变过程和内部结构进行了一系列对比研究,以期揭示上游河流的入流如何影响下游河口涡旋的形成及在羽流相互作用情形下各个羽流的演变。实验结果表明:随着上游入流流量的增加,上游羽流形成的沿岸流对下游河口涡旋沿岸迁移的促进和离岸输运的抑制作用将更加显著。特别是在上游入流流量等于或大于下游入流流量的情况下,下游羽流河口涡旋的体积增长明显较单一河口情况放缓。在上游入流流量较大的情况下,下游原有河口涡旋被推向更下游位置,在远离河口的位置形成另一个河口涡旋。在垂直方向上,我们可以观察到高上游入流流量条件下的下游河口涡旋的深度较小,更有利于形成三层流体的情况。本研究对多河口近海流域的营养盐及污染物的输运情况等社会和生态问题的研究有着重要的意义。  相似文献   

GIS技术在房地产市场信息系统中的应用研究     

梁松  ;郝力  ;靖常峰 《测绘软科学研究》2009,(4):66-72

简要介绍了当前国内房地产现状、存在的问题,以及房地产市场信息系统（Real Estate Market Information System,以下简称REMIS）当前所处的发展背景,指出房产GIS在标准和应用上存在的一些问题。对房地产管理和REMIS对GIS的需求情况进行了分析。根据需求分析作者提出了GIS技术在REMIS中的几种应用模式,并指出基于楼盘表为核心的GIS应用模式将是未来房产GIS发展的方向。针对房产GIS应用的不同模式采用的几种关键技术也做了相应描述。  相似文献   

饱和砂土液化研究进展   总被引：7，自引：1，他引：6  

任红梅  吕西林  李培振 《地震工程与工程振动》2007,27(6):166-175

根据国内外文献资料,从三方面总结了饱和砂土的最新进展:饱和砂土液化判别方法、砂土液化的试验研究以及液化后分析,特别是探讨了液化对上部结构的影响。最后指出了存在的问题和今后的研究方向。  相似文献   

饱和粉土液化特性的大型振动台模型试验研究   总被引：3，自引：0，他引：3  

景立平  姚运生  郑志华 《地震工程与工程振动》2007,27(6):160-165

京沪高速铁路徐沪段路基的粉土粘粒含量少于1.5%、粉粒含量约为80%,在强烈地震作用下存在着液化可能性.为充分研究这一饱和粉土地层的液化特性,本文作者利用大型地震模拟振动台,进行了模拟自由场地饱和粉土的地震液化模型试验,试验结果再现了自然地震触发的粉土液化的各种宏观震害现象,揭示了饱和粉土的地震液化规律和特征。试验结果为京沪高速铁路徐沪段路基的抗震设计提供了参考依据。  相似文献   

Nonlinear aspects of energy dissipation in wood-panel joints   总被引：1，自引：1，他引：0  

Sara Casciati 《地震工程与工程振动(英文版)》2007,6(3):259-268

The joints connecting vertical and horizontal elements are the "weak link" in structural systems assembled from wood panels. If they are too weak, local failures may occur, resulting in performance that is significantly below expectations. If they are too resistant, the joints may be unable to dissipate energy during vibrations, thus possibly initiating a fast progressive failure. This paper re-processes and re-elaborates the results of shaking table tests previously carried out by the author and other co-workers. The goal is to assess the feasibility of a joint which is able to dissipate energy during vibration, without degrading the connection performance.  相似文献   

Performance of a base isolator with shape memory alloy bars   总被引：2，自引：1，他引：1  

Fabio Casciati  Lucia Faravelli  Karim Hamdaoui 《地震工程与工程振动(英文版)》2007,6(4):401-408

A new and innovative base isolation device is introduced in this paper based on extensive research carried out by the authors and their co-workers. A prototype of the device was built and experimentally tested on the shaking table. The new base isolation device consists of two disks, one vertical cylinder with an upper enlargement sustained by three horizontal cantilevers, and at least three inclined shape memory alloy (SMA) bars. The role of the SMA bars is to limit the relative motion between the base and the superstructure, to dissipate energy by their super-elastic constitutive law and to guarantee the re-centring of the device. To verify the expected performance, a prototype was built and tested under sinusoidal waves of displacement of increasing frequency with different amplitudes. It is shown that the main feature of the proposed base isolation device is that for cyclic loading, the super-elastic behavior of the alloy results in wide load-displacement loops, where a large amount of energy is dissipated.  相似文献   

主动变刚度-阻尼系统预测最优控制的理论与试验研究     

谭平  阎维明  周福霖 《地震工程与工程振动》2007,27(4):139-146

介绍了一种具有自主知识产权的新型开关控制型半主动控制系统——主动变刚度.阻尼(AVS.D)系统的减振控制机理,建立了AVS.D结构振动控制体系的运动方程。为了合理补偿AVS.D系统实时控制过程中不可避免地存在着的控制时滞,本文提出一种预测最优控制算法,推导了其开关控制律。为了检验AVS.D系统的减震控制效果及预测最优控制算法的有效性,我们设计研制出AVS.D装置,编制了AVS.D系统预测最优控制的实时控制软件,在某单层钢框架模型上进行了AVS.D系统的模拟地震振动台试验,比较了不同控制方式时的减震效果。研究结果表明,本文所提出的预测最优控制算法是非常有效的,可推广应用于所有开关控制型半主动控制系统。AVS.D系统具有反应放大功能,经济可靠、安全有效,可望有较好的工程应用前景。  相似文献   

Screening the current soil drainage class map of Flanders (Belgium) for its predictive quality     

J. Van de Wauw  P.A. Finke 《水文研究》2012,26(20):3003-3011

The predictive quality of the current drainage class map of Flanders was evaluated using data from two monitoring networks: one with good spatial coverage but poor temporal coverage and another with better temporal but poor spatial coverage. We combine both networks to obtain 1678 point predictions for mean highest water (MHW) and mean lowest water (MLW) tables by applying time series modelling and total least squares regression. The resulting MHW and MLW point data set was used to evaluate the currency of the existing map and to identify regional differences. The quality of the current map is moderate, and large differences occur between regions. Especially the Campine region shows large and systematic differences, whereas the southeastern hills and chalk–loam region is relatively accurate. If more weight is given to errors in the wetter drainage classes, about 50% of the area of Flanders would benefit from remapping. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Impact of soil and water conservation measures on catchment hydrological response—a case in north Ethiopia     

Jan Nyssen  Wim Clymans  Katrien Descheemaeker  Jean Poesen  Ine Vandecasteele  Matthias Vanmaercke  Amanuel Zenebe  Marc Van Camp  Mitiku Haile  Nigussie Haregeweyn  Jan Moeyersons  Kristine Martens  Tesfamichael Gebreyohannes  Jozef Deckers  Kristine Walraevens 《水文研究》2010,24(13):1880-1895

Impact studies of catchment management in the developing world rarely include detailed hydrological components. Here, changes in the hydrological response of a 200‐ha catchment in north Ethiopia are investigated. The management included various soil and water conservation measures such as the construction of dry masonry stone bunds and check dams, the abandonment of post‐harvest grazing, and the establishment of woody vegetation. Measurements at the catchment outlet indicated a runoff depth of 5 mm or a runoff coefficient (RC) of 1·6% in the rainy season of 2006. Combined with runoff measurements at plot scale, this allowed calculating the runoff curve number (CN) for various land uses and land management techniques. The pre‐implementation runoff depth was then predicted using the CN values and a ponding adjustment factor, representing the abstraction of runoff induced by the 242 check dams in gullies. Using the 2006 rainfall depths, the runoff depth for the 2000 land management situation was predicted to be 26·5 mm (RC = 8%), in line with current RCs of nearby catchments. Monitoring of the ground water level indicated a rise after catchment management. The yearly rise in water table after the onset of the rains (ΔT) relative to the water surplus (WS) over the same period increased between 2002–2003 (ΔT/WS = 3·4) and 2006 (ΔT/WS >11·1). Emerging wells and irrigation are other indicators for improved water supply in the managed catchment. Cropped fields in the gullies indicate that farmers are less frightened for the destructive effects of flash floods. Due to increased soil water content, the crop growing period is prolonged. It can be concluded that this catchment management has resulted in a higher infiltration rate and a reduction of direct runoff volume by 81% which has had a positive influence on the catchment water balance. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

地形图符号库的设计   总被引：15，自引：0，他引：15  

陈顺清 《测绘学报》1993,22(1):56-64

本文吸取了美国地图数据库软件INFORMAP Ⅲ、地理信息系统软件ARC/INFO等的符号库设计思想，给出了地形图符号的分类和定义，阐述了适合于微型计算机的装配式符号的构成及“表格驱动式”符号库设计的方法。为方便面状符号的绘制，引入了封闭线结点数数组法来描述多边形的数据结构，介绍了笔者设计的基于微机上的CARDS/Symbols符号库系统。实践表明，本文提出的原理和方法适用于一切工程制图的符号库设计。最后还指出了CG、CAD技术对地形图符号规范的新要求。  相似文献