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

  相似文献   

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

  相似文献   

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

  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   

葛洲坝水利枢纽运行后泥沙冲淤变化分析   总被引：2，自引：1，他引：2       下载免费PDF全文

戴会超  何文社  袁杰  曹叔尤 《水科学进展》2005,16(5):691-695

对葛洲坝水利枢纽及其运行情况和河段特性进行了介绍。分析认为葛洲坝水利枢纽运行前后的入库水沙特性基本一致。探讨了库区冲淤变化特点、淤积量及其分布,冲淤过程及达到冲淤平衡的时间。对坝下游河床的冲淤过程、冲淤量、达到冲淤平衡的时间以及河床粗化,河底高程历年变化及同流量水位降低的原因、降低量及变化过程进行了分析总结。研究结果可为进一步探讨三峡水利枢纽与葛洲坝水利枢纽联合调度运用后水库泥沙淤积变化规律提供参考。  相似文献   

引黄水在北大港水库蓄存期水质咸化的研究   总被引：10，自引：0，他引：10       下载免费PDF全文

赵文玉  王启山  吴国平  吴立波  孙增峰  郑力燕 《水科学进展》2005,16(6):763-766

依据引黄水在北大港水库蓄存期水质咸化的事实以及传质理论,定性地分析了引黄水水质咸化的主要原因,包括盐碱土传质作用、蒸发浓缩作用以及风的扰动加速传质作用等.在北大港水库旁修建了一个模拟试验水池,进行了现场模拟试验研究.依据水量平衡和氯离子总量平衡的原理,分别定量地计算了传质作用和蒸发浓缩作用对水质咸化影响的比重.结果表明,在模拟水池蓄水后的30 d内,传质作用对水质咸化影响的比重有随时间增加而增长的趋势;30 d后,传质作用对水质咸化影响的比重稳定在80%,蒸发浓缩作用对水质咸化影响的比重稳定在20%,说明导致水质咸化的最主要因素是盐碱土传质作用.  相似文献   

Low-low satellite-to-satellite tracking: a comparison between analytical linear orbit perturbation theory and numerical integration   总被引：1，自引：0，他引：1  

P.N.A.M. Visser 《Journal of Geodesy》2005,79(1-3):160-166

Low-low satellite-to-satellite tracking (ll-SST) range-rate observations have been predicted by two methods: one based on a linear perturbation theory in combination with the Hill equations, and one based on solving the equations of motion of two low-flying satellites by numerical integration. The two methods produce almost equivalent Fourier spectra of the range-rate observations after properly taking into account a few resonant terms. For a typical GRACE-type configuration, where the two satellites trail each other at a distance of 300 km at an altitude of 460 km, and in the presence of the EGM96 gravity field model, complete to spherical harmonic degree and order 70, the agreement between the Fourier spectra is about 1 mm/s compared to a root-mean-square (RMS) value of more than 220 mm/s for the range-rate signal. The discrepancy of 1 mm/s can be reduced significantly when not taking into account perturbations caused by the J₂ term. Excluding the J₂ term, the agreement between the two methods improves to 0.4 mm/s compared to a RMS value of 6 mm/s for the range-rate signal. These values are 0.01 and 2.3 mm/s when ignoring the spectrum for frequencies below two cycles per orbital revolution, reducing the discrepancy even further to about 0.5% of the signal. The selected linear perturbation theory is thus capable of modeling gravity field induced range-rate observations with very high precision for a large part of the spectrum.  相似文献