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S. A. Gil-Zepeda J. C. Montalvo-Arrieta R. Vai F. J. Snchez-Sesma 《Soil Dynamics and Earthquake Engineering》2003,23(1):77-86
A hybrid indirect boundary element – discrete wavenumber method is presented and applied to model the ground motion on stratified alluvial valleys under incident plane SH waves from an elastic half-space. The method is based on the single-layer integral representation for diffracted waves. Refracted waves in the horizontally stratified region can be expressed as a linear superposition of solutions for a set of discrete wavenumbers. These solutions are obtained in terms of the Thomson–Haskell propagators formalism. Boundary conditions of continuity of displacements and tractions along the common boundary between the half-space and the stratified region lead to a system of equations for the sources strengths and the coefficients of the plane wave expansion. Although the regions share the boundary, the discretization schemes are different for both sides: for the exterior region, it is based on the numerical and analytical integration of exact Green's functions for displacements and tractions whereas for the layered part, a collocation approach is used. In order to validate this approach results are compared for well-known cases studied in the literature. A homogeneous trapezoidal valley and a parabolic stratified valley were studied and excellent agreement with previous computations was found. An example is given for a stratified inclusion model of an alluvial deposit with an irregular interface with the half-space. Results are displayed in both frequency and time domains. These results show the significant influence of lateral heterogeneity and the emergence of locally generated surface waves in the seismic response of alluvial valleys. 相似文献
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????????С????????????????????ж???????????????????????????????????????????????????????????????????顣?????????????????С??????????????????????3.6??10????-5??ms????-2??????????????С???????????????????????????????????????????????????4.6??10????-5??ms????-2??????????????????????????????????????С?????????????????????????????п???????Ч????? 相似文献
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Watershed water quality models are increasingly used in management. However, simulations by such complex models often involve significant uncertainty, especially those for non-conventional pollutants which are often poorly monitored. This study first proposed an integrated framework for watershed water quality modeling. Within this framework, Probabilistic Collocation Method (PCM) was then applied to a WARMF model of diazinon pollution to assess the modeling uncertainty. Based on PCM, a global sensitivity analysis method named PCM-VD (VD stands for variance decomposition) was also developed, which quantifies variance contribution of all uncertain parameters. The study results validated the applicability of PCM and PCM-VD to the WARMF model. The PCM-based approach is much more efficient, regarding computational time, than conventional Monte Carlo methods. It has also been demonstrated that analysis using the PCM-based approach could provide insights into data collection, model structure improvement and management practices. It was concluded that the PCM-based approach could play an important role in watershed water quality modeling, as an alternative to conventional Monte Carlo methods to account for parametric uncertainty and uncertainty propagation. 相似文献
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The multiresolution character of collocation 总被引:3,自引:0,他引:3
C. Kotsakis 《Journal of Geodesy》2000,74(3-4):275-290
An interesting theoretical connection between the statistical (non-stochastic) collocation principle and the multiresolution/wavelet
framework of signal approximation is presented. The rapid developments in multiresolution analysis theory over the past few
years have provided very useful (theoretical and practical) tools for approximation and spectral studies of irregularly varying
signals, thus opening new possibilities for `non-stationary' gravity field modeling. It is demonstrated that the classic multiresolution
formalism according to Mallat's pioneering work lies at the very core of some of the general approximation principles traditionally
used in physical geodesy problems. In particular, it is shown that the use of a spatio-statistical (non-probabilistic) minimum
mean-square-error criterion for optimal linear estimation of deterministic signals, in conjunction with regularly gridded
data, always gives rise to a generalized multiresolution analysis in the Hilbert space L
2(R), under some mild constraints on the spatial covariance function and the power spectrum of the unknown field under consideration.
Using the theory and the actual approximation algorithms associated with statistical collocation, a new constructive framework
for building generalized multiresolution analyses in L
2(R) is presented, without the need for the usual dyadic restriction that exists in classic wavelet theory. The multiresolution and `non-stationary' aspects of the statistical collocation approximation
procedure are also discussed, and finally some conclusions and recommendations for future work are given.
Received: 26 January 1999 / Accepted: 16 August 1999 相似文献
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本文探讨了整体大地测量平差中的方差分量估计问题,给出了自适应最小二乘配置;不仅较好地解决了各类观测量权比的确定问题,而且能够确定信号的方差因子。此外,文章还对如何更好地确定局部地区扰动位及其泛函的协方差函数作了讨论;最后通过对一个实测网进行了整体平差,并与经典平差结果进行了比较。 相似文献
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Collocation-PECE�㷨�ڵ����Ǿ��ܶ����е�Ӧ�� 总被引:1,自引:1,他引:0
???????????У?PECE????????????????????????????Collocation????????????????幫??????????μ?PECE???????????????????ж??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????Adams-PECE????????PECE?????????????????????????????,???????????Collocation-PECE??????????????н???????????????Ч?? 相似文献
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In collocation applications, the prior covariance matrices or weight matrices between the signals and the observations should
be consistent to their uncertainties; otherwise, the solution of collocation will be distorted. To balance the covariance
matrices of the signals and the observations, a new adaptive collocation estimator is thus derived in which the corresponding
adaptive factor is constructed by the ratio of the variance components of the signals and the observations. A maximum likelihood
estimator of the variance components is thus derived based on the collocation functional model and stochastic model. A simplified
Helmert type estimator of the variance components for the collocation is also introduced and compared to the derived maximum
likelihood type estimator. Reasonable and consistent covariance matrices of the signals and the observations are arrived through
the adjustment of the adaptive factor. The new adaptive collocation with related adaptive factor constructed by the derived
variance components is applied in a transformation between the geodetic height derived by GPS and orthometric height. It is
shown that the adaptive collocation is not only simple in calculation but also effective in balancing the contribution of
observations and the signals in the collocation model. 相似文献