基于抛物线方程的坐标拉伸τ-p变换的P-P、P-SV波分离

分离P-P波和P-SV波最常用的是τ-p变换法, 但是在τ-p域中, P-P波和P-SV波常有重叠部分, 不能很好分离。地震勘探中, 当炮检距小于界面深度时, P-P波和P-SV波的时距曲线方程都可近似为抛物线方程。针对这种情况, 提出了一种基于抛物线方程的坐标拉伸τ-p变换的P-P、P-SV 波分离方法, 该方法首先对地震记录沿空间方向上进行坐标拉伸, 再进行τ-p正变换, 在τ-p域中分离P-P波和P-SV波, 其次对P-P波和P-SV波分别进行τ-p反变换, 实现P-P波和P-SV波的分离。与常规τ-p变换法对比分析表明, 利用该方法能很好地将合成地震记录中的P-P波和P-SV波分离。     

A three‐point time discretization technique for parabolic partial differential equations

The Crank–Nicolson scheme has second‐order accuracy, but often leads to oscillations affecting numerical stability. On the other hand, the implicit scheme is free from oscillation, but it has only first‐order accuracy. In this work, a three‐point discretization scheme with variable time step is presented for the time marching of parabolic partial differential equations. The method proposed has second‐order accuracy, is unconditionally stable and dampens spurious oscillations of the numerical results. The application and effectiveness of the new method are demonstrated through several numerical examples. It is shown that, unlike the Crank–Nicolson method, the approach proposed produces no oscillatory response irrespective of the time step adopted. Copyright © 2010 John Wiley & Sons, Ltd.     

退化抛物型方程的广义T—周期解

本文证明了退化抛物型方程的边值问题     

Revision of the basic equations of wave distribution function analysis

The basic equations of wave distribution function analysis are rewritten in forms that treat the electric and magnetic fields of the waves in a more symmetrical way than the original equations do, and are slightly better for computing.     

Identification of the diffusion coefficient for a semi-linear hyperbolic-parabolic problem with discontinuous nonlinear terms

Numerical computations concerning geochemical processes in porous media require a knowledge of the values of the macroscopic parameters. In the context of the interpretation of leaching tests one such parameter is the apparent macroscopic diffusivity. In this paper, a mathematical model for dissolution in the presence of diffusion is considered. It is shown that the constant diffusion coefficient can be identifiable when the time integral of the flux is known. Moreover, a practical algorithm for computing the diffusion coefficient is proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Numerical Reliability for Mixed Methods Applied to Flow Problems in Porous Media

This paper is devoted to the numerical reliability and time requirements of the Mixed Finite Element (MFE) and Mixed-Hybrid Finite Element (MHFE) methods. The behavior of these methods is investigated under the influence of two factors: the mesh discretization and the medium heterogeneity. We show that, unlike the MFE, the MHFE suffers with the presence of badly shaped discretized elements. Thereat, a numerical reliability analyzing software (Aquarels) is used to detect the instability of a matrix-inversion code generated automatically by a symbolic manipulator. We also show that the spectral condition number of the algebraic systems furnished by both methods in heterogeneous media grows up linearly according to the smoothness of the hydraulic conductivity. Furthermore, it is found that the MHFE could accumulate numerical errors if large jumps in the tensor of conductivity take place. Finally, we compare running-times for both algorithms by giving various numerical experiments.     

空间直角坐标计算大地坐标的抛物线逼近法

采用抛物线逼近法求解大地纬度和大地高,先计算空间点在椭球面上的子午面坐标,然后求解点的大地纬度和大地高。     

煤层采动后甲烷运移与聚集形态分析

富含甲烷厚煤层经综采放顶煤方法开采后,甲烷运移通道和聚集空间随采场上覆岩层活动特征及导气裂隙带空间分布形态而不同。本文分析了煤层采动后采场覆岩关键层活动特征对导气裂隙带分布形态的影响,提出上覆岩层中破断裂隙和离层裂隙贯通后在空间形成椭抛带分布,阐述了卸压甲烷在椭抛带的升浮—扩散运移理论,为实现煤层与甲烷的安全共采提供了科学依据。      

抛物线型屈服面人工冻土蠕变本构模型研究

利用自行研制的W3Z-200型冻土三轴压缩蠕变仪,对淮南地区深表土冻土进行了三轴蠕变试验。根据试验结果,提出以标准黏弹塑性模型为基础,并耦合温度自由度,应用抛物线型屈服准则对模型中的黏塑性项进行改进,建立了新的本构模型来描述高围压复杂应力状态下冻土的蠕变变形特征。基于ADINA有限元软件平台,开发了冻土本构子程序。对淮南某冻结井筒开挖过程进行了数值模拟,计算结果验证了冻土抛物线型黏弹塑本构模型的正确性和合理性。     

结合抛物型缓坡方程计算波浪辐射应力

将波浪辐射应力与抛物型缓坡方程中的待求变量联系起来,提出了一种计算辐射应力的新方法,并用有限差分法对控制方程进行了数值求解。数值结果表明这种方法精度高、编程简单、求解快速,可用于实际大区域波浪辐射应力的计算。