粒度Hough变换及其在遥感影像直线检测中的应用   总被引：1，自引：0，他引：1  

巫兆聪  万茜婷  梁静  周正 《武汉大学学报(信息科学版)》2007,32(10):860-863

在基于Hough变换的遥感影像直线检测的过程中引入粒度计算的概念,利用粒度计算具有多角度、多层次观察问题的能力,对遥感影像中的直线边缘特征进行不同粗细的粒度分析,建立粒度计算概念下的直线检测算法,实现对不同长短、粗细直线的识别。真实的IKONOS遥感影像机场跑道提取试验证明了该方法的有效性。  相似文献   

考虑岩土介质随机特性的工程场地地震动相干函数研究     

陈原  李杰 《世界地震工程》2007,23(3):1-6

将随机结构正交展开理论和随机振动分析的虚拟激励原理运用于场地波动有限元分析，形成了一种可以考虑岩土介质随机特性对工程场地地震动相干函数影响的分析方法。实例分析表明，非严格均匀分布的随机介质场地对场地表面的迟滞相干函数值有重要影响，这种影响可由场地的随机影响因子来衡量，在进行工程场地地震动随机场研究时应当考虑场地介质随机特性的影响。  相似文献   

Reflection/transmission laws for slowness vectors in viscoelastic anisotropic media     

V. Červený 《Studia Geophysica et Geodaetica》2007,51(3):391-410

The reflection/transmission laws (R/T laws) of plane waves at a plane interface between two homogeneous anisotropic viscoelastic (dissipative) halfspaces are discussed. Algorithms for determining the slowness vectors of reflected/transmitted plane waves from the known slowness vector of the incident wave are proposed. In viscoelastic media, the slowness vectors of plane waves are complex-valued, p = P + iA, where P is the propagation vector, and A the attenuation vector. The proposed algorithms may be applied to bulk plane waves (A = 0), homogeneous plane waves (A ≠ 0, P and A parallel), and inhomogeneous plane waves (A ≠ 0, P and A non-parallel). The manner, in which the slowness vector is specified, plays an important role in the algorithms. For unrestricted anisotropy and viscoelasticity, the algorithms require an algebraic equation of the sixth degree to be solved in each halfspace. The degree of the algebraic equation decreases to four or two for simpler cases (isotropic media, plane waves in symmetry planes of anisotropic media). The physical consequences of the proposed algorithms are discussed in detail. vcerveny@seis.karlov.mff.cuni.cz  相似文献   

Comment on the effect of anisotropy on the onset of convection in a porous medium     

D.A. Nield 《Advances in water resources》2007

The effect of anisotropy on the onset of convection in a saturated porous medium is discussed. In particular, the case of time-dependent density-driven convection is examined. The applicability of the value of an equivalent Rayleigh number as the criterion for the onset of convection is discussed.  相似文献   

Dynamic response of a piecewise circular tunnel embedded in a poroelastic medium   总被引：2，自引：0，他引：2  

Jian-Fei Lu  Dong-Sheng Jeng  Tsung-Lin Lee   《Soil Dynamics and Earthquake Engineering》2007,27(9):875-891

Recently, considerable efforts have been devoted to evaluation of seismic dynamic response of a circular tunnel. Conventional approaches have considered integral liners embedded in an elastic medium. In this study, we re-examine the problem with piecewise liners embedded in a porous medium. Surrounding saturated porous medium of tunnels is described by Biot's poroelastic theory, while the liner pieces and the connecting joints are treated as curved beams and characterized by curved beam theories. The scattered wave field in the porous medium is obtained by the wave function expansion method. The differential equations governing the vibration of a curved beam is discretized by the General Differential Quadrature (GDQ) method. The domain decomposition method is used to establish the global discrete dynamic equations for the piecewise tunnel. The surrounding soil and the tunnel are coupled together via the stress and the displacement continuation conditions which are implemented by the boundary collocation method. Numerical results demonstrate that the stiffness difference between the liner piece and the connecting joints has a considerable influence on the internal forces of the liner piece.  相似文献   

气候变化国家评估报告(Ⅲ):中国应对气候变化对策的综合评价     

何建坤  刘滨  陈迎  Xu Huaqing  Guo Yuan  Hu Xiulian  Zhang Xiliang  Li Yu'e  Zhang Aling  Chen Wenying  Wei Zhihong  Duan Maosheng  Zhang Xiaohua  Lü Yingyun 《气候变化研究进展》2007,3(Z1):12-18

Climate change is increasingly becoming the hotspot issue of global attention. On the basis of review of the process responding to climate change of international community, this paper introduces the status of carbon emissions of the world and China, and the technology potential for China to mitigate carbon emissions. At the same time, this paper explores the macro-impacts of China's mitigation of carbon emissions, the equity of global mitigation of climate change, and the impacts of international cooperation in the field of climate change. Furthermore, this paper puts forward the ideas and countermeasures of mitigating climate change in China, indicating that China should positively adapt to the trends of international politics, economy and trade pattern changes and bring the strategies of mitigating climate change into national social and economic development strategy, planning to promote comprehensive, coordinated and sustainable development of national economy and society under the situation of global response to climate change.  相似文献   

土地可持续利用评价中GDP数据空间化方法的研究   总被引：7，自引：0，他引：7  

钟凯文  黎景良  张晓东 《测绘信息与工程》2007,32(3):10-12

分析了社会经济统计数据的空间化方法及GDP空间分布情况,提出了一种应用遥感和GIS技术,以土地利用类型为基础,结合面积权重与反距离加权的GDP数据空间化方法,实现了广东省韶关市GDP空间化.  相似文献   

论地球空间网格环境下的遥感产品虚拟化     

马洪超  徐宏根  狄黎平  邬建伟 《武汉大学学报(信息科学版)》2007,32(9):808-811,816

针对当前遥感产品获取存在的问题,基于网格技术、面向网络的服务技术等提出了遥感产品虚拟化的概念,并对它的定义、相关技术、特点和优点进行了讨论。认为地球空间网格环境下的遥感产品虚拟化需要建立在松散耦合型的计算模式上,需要借助于面向服务的构架。同时,为了完成网格环境下服务的发布、咨询、资源调度、服务控制、服务生命周期控制等一系列关键步骤,必须采用能够与基于服务的构架和理念相匹配的软件工程方法,提出了基于多智能体的软件工程方法学实现遥感产品虚拟化的构想,并指出了遥感产品虚拟化是面向网格计算环境的未来遥感数据处理系统的发展方向。  相似文献   

Taking into account general boundary conditions in upscaling absolute permeability     

T.?HontansEmail author  P.?Terpolilli 《Computational Geosciences》2005,9(4):219-245

Upscaling methods that need to solve local problems subject to boundary conditions are addressed in this article. We define a new upscaling method based on optimization problems, which can take into account general boundary conditions applied to local problems. The determination of upscaled permeability leads to minimizing the difference of dissipated energies (or averaged velocity) at fine and large scale. Using optimal control techniques, we obtain an effective computing algorithm that allows us to recover, with classical boundary conditions, the well-known results. The uniqueness issue is tackled for the optimization problems introduced in our approach. We show that the method is stable with respect to G-convergence, a property that establishes a link with homogenization theory, and finally, 2D numerical experiments are presented.  相似文献   

High density neighborhoods: Who enjoys them?     

Michal?MitranyEmail author 《GeoJournal》2005,64(2):131-140

To date, research into the subjective aspects of high density has focused mainly on the negative consequences of overcrowding. This study, in contrast, outlines some of the positive aspects of high density in neighborhoods, exploring the physical–spatial environment of two neighborhoods in the city of Haifa, Israel. It was found that while the relatively high residential density was similar in both neighborhoods (40 housing units per acre), this was more positively evaluated in one neighborhood as compared to the other. This can be attributed to some specific environmental and planning features. In particular, where physical planning enabled the potential advantages of high density to be realized, this was positively perceived and evaluated by local residents. Such advantages mainly comprised accessibility to a variety of services, more frequent public transportation, and access to open spaces within walking distance. Particularly advantageous were the increased opportunities for social gathering. At the same time, however, high density did not foster social relationships on the neighborhood level. The study further identified the gender and age groups that benefited most from the high density. Thus, women evaluated high density more positively than men. Young families with children and senior citizens (over 65) were also more likely to benefit, and to evaluate the high density environment more positively than other social groups.  相似文献