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通过分析海空重力测量系统误差的形成机理,我们发现海空重力仪格值标定误差是引起系统性测量偏差的主要因素之一.本文简要介绍了重力仪格值的标定方法,分析论证了格值标定的精度要求,提出了利用东西正反向重复测线检测校正海空重力仪格值的计算模型和补偿方法,分析讨论了该方法的校正精度及其适用条件,利用航空重力实际观测网数据对该方法的合理性和有效性进行了数值验证,证明该方法对消除海空重力测量系统性偏差具有显著作用. 相似文献
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Sign-constrained robust least squares, subjective breakdown point and the effect of weights of observations on robustness 总被引:3,自引:1,他引:3
Peiliang Xu 《Journal of Geodesy》2005,79(1-3):146-159
The findings of this paper are summarized as follows: (1) We propose a sign-constrained robust estimation method, which can
tolerate 50% of data contamination and meanwhile achieve high, least-squares-comparable efficiency. Since the objective function
is identical with least squares, the method may also be called sign-constrained robust least squares. An iterative version
of the method has been implemented and shown to be capable of resisting against more than 50% of contamination. As a by-product,
a robust estimate of scale parameter can also be obtained. Unlike the least median of squares method and repeated medians,
which use a least possible number of data to derive the solution, the sign-constrained robust least squares method attempts
to employ a maximum possible number of good data to derive the robust solution, and thus will not be affected by partial near
multi-collinearity among part of the data or if some of the data are clustered together; (2) although M-estimates have been
reported to have a breakdown point of 1/(t+1), we have shown that the weights of observations can readily deteriorate such results and bring the breakdown point of
M-estimates of Huber’s type to zero. The same zero breakdown point of the L
1-norm method is also derived, again due to the weights of observations; (3) by assuming a prior distribution for the signs
of outliers, we have developed the concept of subjective breakdown point, which may be thought of as an extension of stochastic
breakdown by Donoho and Huber but can be important in explaining real-life problems in Earth Sciences and image reconstruction;
and finally, (4) We have shown that the least median of squares method can still break down with a single outlier, even if
no highly concentrated good data nor highly concentrated outliers exist.
An erratum to this article is available at . 相似文献
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Yoko Ota Yu-Nung Nina Lin Yue-Gau Chen Nobuhisa Matsuta Takuya Watanuki Ya-Wen Chen 《Tectonophysics》2009,474(3-4):559-570
This study aims at the recent activity and development of an active wrench fault, the Touhuanping Fault in northwestern Taiwan. Northwestern Taiwan has been proposed in a current situation between the mature to waning collision in terms of tectonic evolution. The main drainage in this area, the Chungkang River, flows close to the trace of the fault mentioned above. We examined various types of deformation of fluvial terraces along the Chungkang River as a key to understanding the nature and rate of the late Quaternary tectonics. The E–W trending Touhuanping Fault has long been mapped as a geological boundary fault, but its recent activity was suspected. Field survey revealed that its late Quaternary activity is recorded in the offset fluvial terraces. Our result shows dextral slip and vertical offset with upthrown side on the south, and activated at least twice since the emergence of terrace 4 (older terrace 3 with OSL date of ca. 80 ka). Total amount of offset recorded in the Touhuanping terrace sequence is 15 m for dextral and 10 m for vertical offset. Estimated recurrence time of earthquake rupture may be a few tens of thousand years. Uplift on the upthrown side of the Touhuanping Fault also resulted in the formation of drowned valleys which were graded to terrace 4. Other deformation features, such as back-tilting, westward warping, and a range-facing straight scarp, were also identified. A second-order anticline roughly parallel to the Touhuanping Fault is suggested to be the origin of the northward tilting on terrace 3; it could have resulted from a flower structure on the Touhuanping Fault at shallow depth. This may demonstrate that the buried segment of the Touhuanping Fault has also been active since 80 ka. In the northern study area, the westward warping at terrace 2 probably represents late Quaternary activity of another NE–SW trending Hsincheng Fault. 相似文献
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Modelling of rutting of two flexible pavements with the shakedown theory and the finite element method 总被引:1,自引:0,他引:1
Cyrille Chazallon Georg Koval Pierre Hornych Fatima Allou Saida Mouhoubi 《Computers and Geotechnics》2009
This paper presents a finite element program, for the modelling of rutting of flexible pavements. In its present version, the program incorporates a permanent deformation model for unbound granular materials based on the concept of the shakedown theory developed by Zarka for metallic structures under cyclic loadings and has been used to estimate the permanent deformations of unbound granular materials (UGM) subjected to traffic loading. The calculation is performed in two steps: the first step consists in modelling the resilient behaviour of the pavement in 3D, using non-linear elastic models, to determine the stress field in the pavement. Then stress paths are derived and used to calculate the permanent deformations and the displacements, using a Drucker–Prager yield surface. An application to the prediction of the permanent deformations of experimental pavements with an unbound granular base, tested on the LCPC pavement testing facility is presented. 相似文献
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Seda Sendir Torisu Junichi Sato Ikuo Towhata Tsuyoshi Honda 《Soil Dynamics and Earthquake Engineering》2010
This paper concerns technological efforts for the general acceptance of performance-based seismic design principle of geotechnical structures. Among many problems to be solved, a particular emphasis was placed on the prediction of residual displacement that remains after a strong earthquake. Because of the complicated behavior of soils undergoing cyclic loading, the prediction is often either complicated/costly or not very accurate. The aim of this study is to examine the capability of existing prediction measures and propose some future scopes. To achieve these goals, shaking table model tests and laboratory shear tests were conducted by taking fill dams as an example target structure. It is concluded that performance-based design is possible if the necessary time and cost are spent and if the required accuracy of prediction is reasonable. 相似文献
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针对像素图数学基础变换问题 ,提出了一种间接变换思路 ,给出了具体的变换方法 ,包括整块变换和分块变换及拼接等问题 ,并作了相关的实验。 相似文献
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