航空摄影负片密度检测系统的研究与实现     

刘俊怡  方圣辉  王瑞幺 《测绘信息与工程》2005,30(6):12-13

利用了计算机系统的优势,改进了航空摄影负片的密度检测方法,实现了航空摄影负片密度检测系统,实验证明了该系统的可行性和实用性。  相似文献   

外空扰动引力计算方法的内在联系     

程芦颖  许厚泽 《测绘学院学报》2003,20(3):161-164

利用算子运算的方法，对求定外空扰动引力的Bjerhammar方法、虚拟点质量方法以及虚拟单层密度方法进行了系统地归纳；利用Possion核的再生特性及球谐函数的正交性质，给出了它们之间的换算关系；最后从两个方面分析了实用计算中各种方法的优劣。  相似文献   

人口密度模型与CA集成的城市化时空模拟实验   总被引：5，自引：1，他引：5  

罗平  杜清运  何素芳 《测绘科学》2003,28(4):18-21

有机地集成城市经典模型与元胞自动机 (CA)是一种有意义的理论实验。本文分无约束和有约束两种条件构建了城市化CA模型 ,推导出了基于均质地理背景和孤立城市的假设的城市人口密度时空模型 ,并进行了二者集成的实验研究 ,得出了如下结论 :(1)CA是城市化时空模拟的有效方法 ;(2 )经典的地理、城市模型可以有效地集成到城市化CA模型中 ,起到控制城市化轨迹的基本作用 ,在某种程度上能够弥补CA建模过于简单的不足。  相似文献   

Some Simple Statistical Models For Relative And Absolute Dispersion     

R. J. Munro  P. C. Chatwin  N. Mole 《Boundary-Layer Meteorology》2003,107(2):253-271

Observations of the dispersion of a contaminant plume in the atmospheric boundary layer, obtained using a Lidar, are analysed in the coordinate frame relative to the instantaneous centre of mass of the plume, as well as the absolute (or fixed) coordinate frame. The study extends the work presented in a previous article, which analysed the structure of the probability density function (pdf) of concentration within the relative coordinate frame. Firstly, the plume displacement component, or plume meander, is analysed and a simple parametric form for the pdf of the plume centreline position is suggested. This is then used to analyse the accuracy and applicability of absolute framework statistical quantities obtained by a convolution of the relative frame statistical quantity with the plume centreline pdf.  相似文献   

Local Log-Law-of-the-Wall in Neutrally-Stratified Boundary-Layer Flows     

S. Besio  A. Smazzino  C.F. Ratto 《Boundary-Layer Meteorology》2003,107(1):115-142

It is well known that in a neutrally-stratified turbulent flow in a deep constant-stress layer above a flat surface,the horizontal mean velocity varies logarithmically with height (the so-called `log-law-of-the-wall').More recently, the same logarithmic law has also been foundin the presence of non-flat surfaces, where it governs thedynamics of the areally-averagedvelocity and involves renormalized effective parameters.Here, we analyze wind profiles over two-dimensional sinusoidal hillsobtained both from numerical simulations performed with a primitiveequation model and from wind-tunnel measurements. We showthat also the local velocity profiles behave to a verygood approximation logarithmically, for a distance from the surface of the order of the maximum hill height almost to the top of the boundary layer. Such alocal log-law-of-the-wall involves effective parameters smoothly depending on theposition along the underlying topography.This dependence looks very similar to the topography itself.  相似文献   

On the three-dimensional oceanic density distribution in a millennium integration with an AO-GCM     

Jin-Song von Storch 《Ocean Dynamics》2003,53(1):11-20

 The three-dimensional time-mean density distribution in the ocean is determined not only by the time-mean fluxes of heat and freshwater at the sea surface, but also by time-mean vertical currents and time-mean density fluxes due to oceanic transients excited by fluctuating fluxes at the sea surface. The effects of these various processes on the global density fields are assessed using a balance equation of the variance of spatial density anomalies and a millennium integration with an atmosphere–ocean general circulation model. It is found that spatial density anomalies are generated by the time-mean heat fluxes at the sea surface and destroyed by the time-mean surface freshwater flux, by sinking of dense water and rising of less dense water, and finally by density fluxes associated with transients. The last two processes take place essentially in the oceanic interior. Since density fluxes of transient eddies act to reduce the existing density differences between the Atlantic/Southern Oceans and the other oceans, their presence could affect the global density balance, and from that the thermohaline circulation and the stability of this circulation. Received: 4 October 2001 / Accepted: 10 October 2002 Responsible Editor: Richard J. Greatbatch Acknowledgements I thank Ulrich Cubasch and his colleagues for providing me with the ECHAM3/LSG integration, Peter Müller and Richard Greatbatch for valuable suggestions.  相似文献   

Identification of parametric ground motion random fields from spatially recorded seismic data     

A. Zerva  J. L. Beck 《地震工程与结构动力学》2003,32(5):771-791

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地球主磁场的能量密度谱及其长期变化   总被引：6，自引：3，他引：6  

康国发  吴小平  文丽敏  胡家富 《地球物理学进展》2003,18(1):111-115

根据BJ地磁场模型和第8代国际地磁参考场(IGRF)模型，计算并分折了1690～2000年期间地球表面主磁场和分量的能量密度谱及其长期变化。结果表明1690～2000年期间主磁场的能量密度谱一直在减小，其主要原因是由于偶板子磁场的衰减产生的，而非偶板子磁场的能量密度谱在1690～1780年期间减小，1780～1890年增大，1890年以后快速增大。在地磁场总能谱的变化中，Z分量的贡献起主要作用。能量密度随谐波阶数的变化在半对数坐标中近似线性，非偶板子场的等效磁源深度位于核幔边界附近，n＝1，2谐波项的等效磁源位于地球内核边缘，其位置随时间变化。1780和1890年前后是地磁场变化的转折时期。能量密度谱的长期变化存在大约60a的周期规律。  相似文献   

中国海及邻域岩石圈三维密度分布     

方剑 《地球物理学进展》2003,18(2):306-311

利用中国海及邻域的 2 0× 2 0网格密度异常和 15′× 15′的网格平均布格重力异常 ,采用约束最小二乘方法反演 ,得到了中国海及邻域岩石圈内六个层面上 15′× 15′的密度分布结果 .反演结果表明 :(1)中国海及邻域岩石圈密度极不均匀 ,反映了区内强烈的构造活动特征 ;(2 )层内密度分布与大地构造有明显的相关性 ,不同的构造单元存在着密度差异 ,断裂带表现为密度异常梯级带 .  相似文献   

Fast practical evaluation of soil–structure interaction of embedded structures     

Izuru Takewaki  Noriko Takeda  Koji Uetani 《Soil Dynamics and Earthquake Engineering》2003,23(3):13-20

A simple and fast evaluation method of soil–structure interaction (SSI) effects of embedded structures is presented via a cone model. The impedances and the effective input motions at the bottom of an embedded foundation are evaluated by means of the cone model. Those quantities are transformed exactly to the corresponding values at the top of the foundation. The evaluated quantities are combined with the super-structure at the top of the foundation. The transfer function amplitude of the interstory drift of a single-degree-of-freedom super-structure is computed for various cases, i.e. no SSI, SSI without embedment, SSI with shallow embedment, SSI with deep embedment. Soil properties are also varied to investigate in more detail the SSI effects of embedded structures. It is found that, while the transfer function amplitude is reduced by the increase of embedment in general, the characteristics of the transfer function amplitude for a very small ground shear wave velocity and large embedment are irregular and complicated.  相似文献