Constructal view of scaling laws of river basins   总被引：1，自引：0，他引：1  

A. Heitor Reis   《Geomorphology》2006,78(3-4):201-206

River basins are examples of naturally organized flow architectures whose scaling properties have been noticed long ago. Based on data of geometric characteristics, Horton [Horton, R.E., 1932. Drainage basin characteristics. EOS Trans. AGU 13, 350–361.], Hack [Hack, J.T., 1957. Studies of longitudinal profiles in Virginia and Maryland. USGS Professional Papers 294-B, Washington DC, pp. 46–97.], and Melton [Melton, M.A, 1958. Correlation structure of morphometric properties of drainage systems and their controlling agents. J. of Geology 66, 35–56.] proposed scaling laws that are considered to describe rather accurately the actual river basins. What we show here is that these scaling laws can be anticipated based on Constructal Theory, which views the pathways by which drainage networks develop in a basin not as the result of chance but as flow architectures that originate naturally as the result of minimization of the overall resistance to flow (Constructal Law).  相似文献   

Fault slip and rupture velocity inversion by isochrone backprojection     

Gaetano Festa  Aldo Zollo 《Geophysical Journal International》2006,166(2):745-756

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Dual simulations of fluid flow and seismic wave propagation in a fractured network: effects of pore pressure on seismic signature   总被引：1，自引：0，他引：1  

S. Vlastos  E. Liu  I. G. Main  M. Schoenberg  C. Narteau  X. Y. Li  B. Maillot 《Geophysical Journal International》2006,166(2):825-838

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Spherical Slepian functions and the polar gap in geodesy   总被引：4，自引：0，他引：4  

Frederik J. Simons  F. A. Dahlen 《Geophysical Journal International》2006,166(3):1039-1061

The estimation of potential fields such as the gravitational or magnetic potential at the surface of a spherical planet from noisy observations taken at an altitude over an incomplete portion of the globe is a classic example of an ill-posed inverse problem. We show that this potential-field estimation problem has deep-seated connections to Slepian's spatiospectral localization problem which seeks bandlimited spherical functions whose energy is optimally concentrated in some closed portion of the unit sphere. This allows us to formulate an alternative solution to the traditional damped least-squares spherical harmonic approach in geodesy, whereby the source field is now expanded in a truncated Slepian function basis set. We discuss the relative performance of both methods with regard to standard statistical measures such as bias, variance and mean squared error, and pay special attention to the algorithmic efficiency of computing the Slepian functions on the region complementary to the axisymmetric polar gap characteristic of satellite surveys. The ease, speed, and accuracy of our method make the use of spherical Slepian functions in earth and planetary geodesy practical.  相似文献   

S-wave velocity structure, mantle xenoliths and the upper mantle beneath the Kaapvaal craton   总被引：1，自引：0，他引：1  

Angela Marie Larson  J. Arthur Snoke  David E. James 《Geophysical Journal International》2006,167(1):171-186

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Towards a method for postcolonial development geography? Possibilities and challenges   总被引：2，自引：0，他引：2  

Parvati Raghuram  Clare Madge 《Singapore journal of tropical geography》2006,27(3):270-288

In this paper we explore the contours of a 'method' for postcolonial development geography, which makes it possible to imagine another 'world-picturing'. We suggest three steps towards such a method. First, we propose that a postcolonial method involves thinking about why we are doing research in the south in the first place; how we come to and produce our questions; and how we analyze and represent our findings based on our subject positionings. Second, that we need to recognize theorization as an inherent part of method, rethink how we currently theorize and reconfigure our methods of theorization to address wider political aims. Problematizing theorization helps challenge the universalism of Eurocentric theories, thus enabling development geography to move towards more decolonized versions and visions. Finally, that this must be accompanied by firmer recognition of our multiple investments – personal, institutional and geopolitical – and how they frame the possibilities for change. These are some possible steps that we think can reconfigure the 'scholarly track' that postcolonial development geographers traverse.  相似文献   

Surface wave tomography: finite-frequency effects lost in the null space   总被引：2，自引：1，他引：2  

Jeannot Trampert  Jesper Spetzler 《Geophysical Journal International》2006,164(2):394-400

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基于突变理论深埋硬岩隧道的失稳分析   总被引：3，自引：0，他引：3  

闫长斌  徐国元 《工程地质学报》2006,14(4):508-512

在分析隧道开挖引起围岩扰动和损伤的基础上,运用突变理论探讨了深埋硬岩隧道失稳的机理;基于势能原理,建立了深埋硬岩隧道失稳的尖点突变模型,导出了失稳的力学判据条件。结果表明:深埋硬岩隧道的失稳不仅受岩体特性及所受载荷的影响,而且与围岩中弹性区刚度和塑性区刚度的比值有关;开挖过程中,围岩受扰动和损伤程度越大,岩体完整性系数越小,力学参数指标弱化程度越高,塑性区范围越大,刚度比越小,围岩系统发生失稳的可能性就越大。工程实例分析表明,分析结果与实际经验基本一致;研究成果可为预防隧道失稳、采取合理的施工工艺和支护措施提供参考依据。  相似文献   

模糊理论在公路边坡稳定性分析中的应用   总被引：7，自引：0，他引：7  

许江  李克钢 《中国地质灾害与防治学报》2006,17(2):61-64

边坡工程是一个复杂的系统工程。边坡的稳定与否直接关系到其防护工作的程度。因此,如何有效、合理地判断边坡的稳定性对整个工程的经济与社会效益极为重要。影响边坡稳定的因素众多,判断其稳定与否应考虑各因素的综合效果。论文运用模糊理论中的多因素综合评判模型对某高速公路边坡的稳定性进行研究。通过全面考虑影响因素,建立相应的评判因素集及单因素评判矩阵,运用专家评判法和判断矩阵法确定出各因素的权重。最后通过多层次模糊评判得到该边坡的稳定性评判结果。研究证明,该法在边坡稳定性分析评判中是切实可行的。  相似文献   

Spatial assessment and redesign of a groundwater quality monitoring network using entropy theory, Gaza Strip, Palestine   总被引：3，自引：0，他引：3  

Y. Mogheir  V. P. Singh  J. L. M. P. de Lima 《Hydrogeology Journal》2006,14(5):700-712

Using entropy theory, a methodology was developed for the evaluation and redesign of groundwater quality monitoring wells in the Gaza Strip in Palestine. Essential to the methodology is the development of a Transinformation Model (TM) which yields the amount of information transfer and the dependency between the wells as a function of distance. The TM parameters, such as the minimum transinformation and the range, were employed for evaluating the network which revealed that most of the distances between wells were less than the range. It also indicated that a high percentage of redundant information existed in the network. Therefore, the network was reduced by superimposing a square pattern over the monitored area and selecting one well per square block in a stratified pattern. The methodology was tested using the chloride data collected from 1972–2000 from 417 groundwater quality monitoring wells in the Gaza Strip. The number of the groundwater quality monitoring wells in the Gaza Strip was reduced by 53%, while there was 26% redundant information based on the minimum existing distance between wells. This methodology is meant to help monitor the groundwater quality (salinity) in the Gaza Strip.  相似文献