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431.
本文对地震逆散射的研究,旨在于为抑制层间多次波和地震波场多重散射对一次反射干扰效应提供理论依据.这对薄互层地层滤波的高频恢复、保幅弹性反演、衍射地震勘探及海洋地震勘探中的干扰消除皆具重要意义.本文基于上下行波分解及弹性波互易定理,导出横向变速介质条件下线性预测算子的表达式和反射数据的广义谱分解方程. 文中先由上覆地层广义反射透射矩阵的元素定义线性预测算子,并将其表示成一系列单程波算子的线性组合,之后将横向变速介质条件下线性预测方程表达为反射数据与线性预测算子及其逆的乘积. 对该方程的求解可获得上覆地层的线性预测算子,从而可借以求出相应的反射透射算子. 本文先将水平层状介质条件下垂直入射的一维线性预测方程推广到斜入射的情况,以此为参照,导出横向非均匀介质条件下反射数据的地震逆散射广义谱分解方程.文中也揭示了单程波地震逆散射算子、反射透射算子的性态.本文还针对水平层状介质条件,给出斜入射的数值结果. 相似文献
432.
文中提出的EVPP(Extended Velocity Plan Processing)方法是根据风场连续及局部分片光滑的性质,假定在一很小的分析窗内风矢量保持线性变化关系,使得在分析窗内反演得到的风场在矢径上的投影与实际观测的多普勒雷达径向速度场之间的误差达到最小,并利用零速度线这一特点对问题的求解做出约束,使得所得解尽可能达到全局最优,即:(1)利用变分的思想求出水平风速的大小及方向;(2)利用风场局部分片光滑,对风的方向做出矫正。虽然由于风场受到线性假设这一限制,使得其使用的范围得到了局限,但是在本文中利用零速度线这一特征使得反演的结果得到了进一步的提高。文中利用模拟的理想个例和实际观测到的个例分别进行了研究分析。为了证明其理论的可行性,首先我们利用三维冰雹云模式模拟了辽宁2005年7月8日的一次冰雹云过程,考虑到个例的代表性,我们选择了辐合、辐散、旋转以及均匀风场等4种类型的流场结构进行了模拟分析,同时为了验证该种方法对于资料质量的依赖性以及噪声的敏感性,我们在理想质量中加入了随机噪声。从对模拟风场的反演,证明了该方法理论上的可行性,而且噪声对其结构的影响不大。然后针对台风、飑线、强对流等实际天气过程作了进一步分析。最后对反演结果进行了误差分析,结果表明这一方法能较好地反演出中尺度系统的水平流场结构。 相似文献
433.
根据地震波场的线性叠加原理,提出了对地震共炮道集及其震源进行线性叠加的一般方案——广义地震数据合成的方法.利用这个方法,可以根据不同的地质情况和要求得到各种不同的人工合成地震数据道集和震源,如平面波数据道集和震源、局部平面波(束)数据道集和震源以及面向目标的人工合成地震数据道集和震源.对于人工合成地震数据道集的偏移成像可应用单平方根方程实现.不同的合成地震数据道集具有不同偏移成像特性:平面波数据道集具有很高的计算效率,局部平面波数据道集具有很好的方向性,面向目标的合成地震数据道集具有很好的面向目标特性. 相似文献
434.
Shen Jun Wang Yipeng Song Fangmin Yu Weixian Cao Zhongquan Shen Xuhui Hou Xueying and Li ZhixiangInstitute of Geology SSB Beijing ChinaInstitute of Earthquake Engineering Seismological Bureau of Yunnan Province Kunming China 《中国地震研究》1998,(2)
The data of the strike-slip offset along the Xiaojiang active fault can be obviously grouped.The groups of small orders of magnitude data within 100 m show clear linear characteristics of increments between 8 m and 12 m,which indicates that the segments of the Xiaojiang active fault is of characteristic seismicity and the distribution of the values of each group indicates that there are smaller earthquakes and creep between two large earthquakes along each segment of the Xiaojiang active fault.The interval between two characteristic large earthquakes can be calculated with the increments for two groups of slip data and the slip rate of the fault.Furthermore,the frequency of smaller earthquakes can also be estimated by comparing the distributions of the displacements of the large earthquakes with the distributions of the values of each group of data.The groups of large slip displacements show that there is close relationship between the records of the displacements of the fault and the changes of the cli 相似文献
435.
线性和非线性横波型不稳定的数值研究 总被引:8,自引:0,他引:8
本文应用一个准二维的非线性非静力数值模式研究了线性和非线性横波型不稳定的中尺度模态的发展、演变和结构特征。结果表明:Richardson数对横波型不稳定的发展和演变有影响。Ri数越小,不稳定增长越快,且增长率最大的波的波长就越短。非线性横波型不稳定在其发展初期,可以用线性理论作很好的近似;随着不稳定的进一步发展,扰动增强,非线性作用增强,其扰动结构与线性情况相比发生了很大变化,扰动结构最后演变成以顺时针环流为主的结构。 相似文献
436.
437.
本文根据线状要素地理信息表达的需要,对线状符号进行了分类.在分析了线状符号的视觉变量之后,给出了其图案单元的数据结构。最后结合线状符号的分解、组合特性提出了线状符号的配置方法。 相似文献
438.
Elongation and migration of sand dunes 总被引:3,自引:0,他引:3
Two distinct processes are known to act on dynamic dunes, the process of migration by erosion on the windward side and deposition on the lee side, typical for transverse dunes, and the process of elongation typical for linear dunes. These two processes are determined by wind direction relative to the dune alignment. This article reviews the assertion that linear dunes experience lateral displacement in addition to elongation. Fieldwork on vegetated linear dunes (VLDs) and GIS work on seif dunes indicates no lateral migration for these dunes. Linear dunes can shift laterally only when a slip face, formed on the lee side, reaches the plinth of the dune. The winds from both sides of the seif dune are never symmetric; usually winds from one direction are more dominant and effective. The outcome is the formation of peaks and saddles along the dune. The strongest winds create a slip face on the lee side of the peak segments of the dune, oblique to the dune alignment, which reaches the base of the dune and displaces the peak downwind along the dune alignment. The internal structure of the seif dune is formed mostly by this dominant wind direction and gives the impression that the dune has shifted laterally. On the other hand, there are cases in which the wind directions relative to dune alignment fall between those of transverse and seif dunes. In such cases, both processes act on the dune, which subsequently experiences migration as well as elongation. 相似文献
439.
J. Marshall 《Journal of Geodesy》2002,76(6-7):334-344
Several pre-analysis measures which help to expose the behavior of L
1 -norm minimization solutions are described. The pre-analysis measures are primarily based on familiar elements of the linear
programming solution to L
1-norm minimization, such as slack variables and the reduced-cost vector. By examining certain elements of the linear programming
solution in a probabilistic light, it is possible to derive the cumulative distribution function (CDF) associated with univariate
L
1-norm residuals. Unlike traditional least squares (LS) residual CDFs, it is found that L
1-norm residual CDFs fail to follow the normal distribution in general, and instead are characterized by both discrete and
continuous (i.e. piecewise) segments. It is also found that an L
1 equivalent to LS redundancy numbers exists and that these L
1 equivalents are a byproduct of the univariate L
1 univariate residual CDF. Probing deeper into the linear programming solution, it is found that certain combinations of observations
which are capable of tolerating large-magnitude gross errors can be predicted by comprehensively tabulating the signs of slack
variables associated with the L
1 residuals. The developed techniques are illustrated on a two-dimensional trilateration network.
Received: 6 July 2001 / Accepted: 21 February 2002 相似文献
440.
Jean H.P. Paelinck 《Journal of Geographical Systems》2002,4(4):371-383
Links between socio-economic units have been studied by means of various techniques. This study analyses networks that take
on a permanently growing importance in evolutionary economics. The analysis is conducted in a sequential way on matrices picturing
the intensities of certain relations; the technique used is linear assignment. The latter is first applied to matrices of
socio-economic relations set up for the Netherlands and Portugal; the various types of “networking” present could be revealed
and compared. Medical activities, taken in their socio-economic setting, rest also on various networks ; available matrices
for the Netherlands are submitted to the above method of analysis. Moreover, a classical input-output matrix for the United
Kingdom is used as a last test for the validity of the method.
Received: 1 March 2002 / Accepted: 19 November 2002 相似文献