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81.
82.
V. Pereyra 《Pure and Applied Geophysics》1996,148(3-4):345-386
We describe an integrated forward and inverse three-dimensional modeling system that can deal with complex geological structures. The system has been designed to handle large-scale problems by using a distributed approach. It uses seismic ray tracing for forward simulation, time-to-depth mapping, and nonlinear travel-time inversion.A novel decomposition method is our tool to attack large-scale problems in a parallel approach. The system is fully implemented and we demonstrate its performance with synthetic examples.This research was partially supported by the National Science Foundation under SBIR Grant III-9300992. 相似文献
83.
从亥姆霍兹方程出发,导出了自聚焦光纤中传导模在圆柱坐标系中的场分布形式,并给出了几个低阶模的分布图。 相似文献
84.
1962—1986年JYD1968.0地极坐标的均匀化及其与BIH的比较 总被引:2,自引:0,他引:2
本文研究了1962-1986年JYD1968.0地极坐标均匀中星表系统差,章动系列的变动和光行星常数变动的影响,并将经过改正后的JYD1968.0地极坐标系统和BIH系统作了比较。 相似文献
85.
《地震学报(英文版)》1993,6(3):619-629
In the present study the long period surface wave records of 238 wave-paths from 79 earthquakes within China and its adjacent
regions received by 30 seismic network stations are measured by using the improved match-filtering frequency-time analysis
technique and the grid dispersion inversion method to obtain the rayleigh pure-path dispersion values for 147 slant grids
of 4° × 4° in this area, then a three-dimensional shear wave velocity model of the crust and upper mantle beneath south China
area to a depth of 170 km is inversed.
It is found that there are obvious differences among the main structural units, and there are also certain differences among
the subordinate elements even in the individual unit. The crustal thickness of this area is ranging from 30 to 43 km, and
is getting thicker gradually from the east to the west. The average shear velocity of crust is ranging form 3.48 to 3.68 km/s
with the lowest in the northeast part and highest in the west part. No obvious crustal low velocity layer of large scale is
detected. There exist upper mantle low velocity zones in the most of south China area with the starting depth ranging from
75 to 106 km. The lowest shear velocity within the low velocity zones is about 4.28–4.38 km/s. Despite of the existing of
upper mantle low velocity zones beneath the most of south China area, the interfaces between the important layers are quite
clear, the variation of the bedding surfaces is very gentle, and the lateral changes measured in a larger scale of the underground
structure are rather small. It may indicate that the crustal and upper mantle structure of the main part of south China area
belongs to the relatively stable structure of the continental blocks except for the fringe areas such as the fold-faulted
region in the west part and the fault system along the southeastern coast which may belong to the tectonically active area.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 159–167, 1993.
This subject is supported by the National Science Foundation of China. 相似文献
86.
半拉格朗日、半隐式欧拉方程组大气数值模式研究 总被引:2,自引:1,他引:1
介绍了一个具有较高时间积分效率的三维弹性大气数值模式。其中,控制方程为能够描述大气非静力及可压缩性的欧拉方程组,时间积分采用了高效率的“半拉格朗日、半隐式”方案。通过引用一个简化的“云物理过程”参数化方案,针对大气中深厚湿对流过程的若干问题进行了数值试验,结果表明,模式能够对该过程中的一些基本和复杂现象进行有效地模拟。试验结果还表明,动力学框架具有很好的稳定性,能够实现高效率的时间积分,它还具有较好的频散特性,保证了空间计算的精度,从而完好地描述了风暴的形态。 相似文献
87.
Decoupling of the coupled poroelastic equations for quasistatic flow in deformable porous media containing two immiscible fluids 总被引:1,自引:0,他引:1
The study of the poroelastic behavior of sedimentary materials containing two immiscible fluids in response to either applied stress or pore pressure change in a quasistatic limit, i.e., negligible second time-derivatives, is of great importance to many hydrogelogical problems, e.g., land subsidence caused by withdrawal of subsurface fluids. The poroelasticity models developed for analyzing these problems feature partial differential equations that are coupled in the terms describing viscous damping and strain field. To determine closed-form analytical solutions for induced volumetric strain (dilatation) of the solid framework and its interaction with fluid flows, the choice of normal coordinates whose transformation can be performed to decouple these poroelastic equations is highly desirable. In this paper, we show that normal coordinates for decoupling these equations are real-valued and equal to three different linear combinations of the dilatations of the solid and the fluids (or equivalently, three different linear combinations of two individual fluid pressures and solid dilatation). In contrast to fully saturated porous media, it is found that the viscous damping effect must be represented in normal coordinates in the presence of the second fluid. The resulting decoupled equations representing independent motional modes are a Laplace equation and two diffusion equations, which can be solved analytically under a variety of initial and boundary conditions. Thus, after inverse transformation of normal coordinates is performed, the closed-form analytical solutions for induced solid volumetric strain and excess pore fluid pressures can be obtained simultaneously from our decoupled partial differential equations. 相似文献
88.
针对当前复杂环境水流模拟的需求,建立了新型的基于特征型高分辨率数值算法的三维非结构网格浅水动力模型。模型采用有限体积法离散sigma坐标下的三维浅水方程,运用Roe黎曼近似解评估水平界面通量。模型网格拟合边界能力强,可根据需要局部加密;格式数值性能优良,具有守恒性、单调迎风性、高数值分辨率等特性。同时,应用干湿判别法处理动边界,以适应浅滩地形漫/露过程模拟的需要。封闭水池内部风生环流、干河床上溃坝过程和长江口实际潮流场的模拟从不同侧面展示了模型的特点,结果表明它能够准确地预测水流的三维流动结构,而且计算简单高效,具有良好的数值稳定性。 相似文献
89.
90.
地图数字化中基于点位坐标的统一平差模型 总被引:3,自引:0,他引:3
探讨了地图数字化过程中采用平差方法来建立坐标计算的统一模型。将测得的角度、边长等数据化为方向、距离观测值列立误差方程,通过调用统一的平差迭代计算程序来计算未知点坐标及精度。详细给出了基于平差的11种常用坐标计算方法,并通过实例进行了说明。 相似文献