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971.
用一个高分辨率的 f平面正压涡度方程模式 ,实施了时间积分为 36h的 2 1组试验 ,研究相邻中尺度涡旋与台风涡旋的相互作用。结果指出 :这种相互作用能否导致台风加强 ,取决于两类因子 :一是台风涡旋最大风速的取值以及圆形基流切变的强弱 ;二是切变基流中的中尺度涡旋的自身条件 ,包括中尺度涡旋的分布、尺度、强度和结构。台风强度与初始中尺度涡旋的尺度、强度之间存在着非线性的联系 相似文献
972.
A fully coupled finite element code based on mixture theory is developed. Prévost's multi-surface constitutive model is tailored to three-dimensional loads and used to predict effective stresses. A new viscous boundary is implemented to avoid wave reflections towards the structure. In contrast to traditional methods, this boundary is able to absorb the two dilatational waves and the shear wave.Two soil deposits and two dams, with different slopes, composed by loose and dense sands have been subjected to the Pacoima accelerogram. Results show how the liquefaction propagates in the soil deposits and earth dams. The importance of the coupling between dilatancy–contractancy and filtration is highlighted by a parametric investigation. Phenomena such as liquefaction and cyclic mobility are reproduced, indicating the robustness of the constitutive model and finite element simulations. As an outcome of the parametric analysis, the seismic stability of dams cannot be improved by decreasing the upstream or downstream slopes. 相似文献
973.
Nobuyuki Kinoshita 《Boundary-Layer Meteorology》2003,106(1):61-91
Turbulent flow data of wind velocity and temperature in the unstably stratifiedatmospheric boundary layer, derived from steel tower observations in the field and wind-tunnel experiments were used to study the relationship between the plumes and the small-scale eddies in the inertial subrange. Flow visualisation experiments in the wind tunnel were also conducted to observe the structure of the flow in the plumes, and time series data were analysed by using wavelet transforms. The results show that variances of velocity and temperature due to the small-scale eddies are large in the plumes and small outside of the plumes, and that the momentum and heat fluxes due to the small-scale eddies follow the same tendency as found in the variances. The ratios of the variances caused by the small-scale eddies in the plumes to the whole of the variances caused by the small-scale eddies in and out the plumes increase with non-dimensional height -z/L in which L is the local Obukhov length. Similar ratios of the fluxes caused by the small-scale eddies also show the same tendency. These ratios can be expressed as functions of -z/L for results based on field observationand the wind tunnel experiments. This relation hardly changes even if the wavelet function is changed. The flow visualisation experiments show that the plumes have a complicated structure in which mushroom type flows are stacked on top of each other. This characteristic structure seems to increase the energy of the small-scale eddies in the plumes. 相似文献
974.
975.
洛阳盆地地热资源与龙门地热田的关系 总被引:6,自引:1,他引:6
龙门地热田的形成是其特殊地质构造制约地下水运动的结果,F1,F2为龙门地热田的控热构造,F41为地热田的导水构造,∈3为龙门地热储层,上覆数百米的二叠,三叠系则成为龙门地热田的盖层,龙门地热田之北邻洛阳盆地为凹陷区,但地温梯度却为3.1℃/100m,明显高于龙门及其它相邻地区,经对洛阳盆地地热背景及控热条件分析认为:延伸并隐伏于洛阳盆地中的龙门控热构造F1,F2断层,仍具有导热性质,F1,F2断层虽被F3错开,还仍具有导水作用,经F1,F2排入洛阳盆地的热水,不但提高了洛阳盆地的地温,而且也是洛阳盆地热储层,下第三系砂,砾岩含水层的主要补给水源,故根据龙门地热勘探情况,选择洛阳盆地的地热开发目标区应为F1构造带上和隐伏的北东向断裂带上,取水层段应为下第三系上部的断裂带附近。 相似文献
976.
GIS中几何对象之间的空间关系 总被引:2,自引:0,他引:2
几何对象之间的空间关系是GIS研究的重要理论问题之一,在分析ArcInfo和OpenGIS对空间关系描述的基础上,运用基于维数扩展的9交模型,得到在实际应用中基本的空间关系分类,并对空间关系的进一步研究提出了展望。 相似文献
977.
G.M. Tarekul ISLAM M.R. KABIR Ainun NISHAT Institute of Flood Control Drainage Research Bangladesh University of Engineering Technology Dhaka Bangladesh E-mail: tarek@ifcdr.buet.ac.bd Department of Water Resources Engineeri 《国际泥沙研究》2002,17(2)
1 INTRODUCTION Bifurcations are typical features in alluvial rivers as well as in estuaries. In braided rivers confluence and bifurcation occur regularly (Fig.1). A bifurcation occurs when a river splits into two branches (Fig. 2). This happens when a middle bar forms in a channel or a distributary carries flow from the main river. In estuaries when the direction of tidal flow turns around an island, a confluence becomes bifurcation and vice versa. A braided river in the upstream end o… 相似文献
978.
Attenuation relations for horizontal peak ground acceleration and response spectrum in northeastern Tibetan Plateau region 总被引:1,自引:0,他引:1
Introduction Developing local attenuation relations of ground motion is one of the key steps in seismic hazard assessment. Because of inadequate strong ground motion records in China, the attenuation relations used in China are usually developed by using the transforming method (Hu, Zhang, 1983; HU, ZHANG, 1984). To use this method, we need to have both the attenuation relation of seismic intensity for the studied region and the attenuation relations of seismic intensity and ground mo-tion… 相似文献
979.
Micropiles are being increasingly utilized in foundation rehabilitation and seismic retrofitting projects. The function of
the micropiles in these projects is to enhance the foundation ultimate capacity as well as reduce foundation deflection. This
paper focuses on an analytical model for micropile load-displacement behavior subjected to compressive as well as tensile
loading. The soil-micropile interaction is considered explicitly in the model development. Furthermore, to keep the model
simple and accessible to designers, the micropile-soil interface is assumed to be linearly elastic-perfectly plastic and homogeneous
with depth. Closed form expressions of micropile deformation as a function of applied load are presented. These expressions
are used to study the effect of model parameters on micropile yield behavior. Micropile strain distribution and the load transfer
behavior calculated by the model are discussed. The model calculations are compared with the field measured load-displacement
curves. The measured micropile load-displacement data available in the literature are analyzed to evaluate the model parameters.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
980.