地球物理中的反问题与不适定问题

本文讨论地球物理中的某些反问题与不适定问题。其内容如下:场的延拓与偏微分方程的不适定Cauchy问题;不适定问题稳定性的性态;线性不适定问题的正则化算法。     

Direct and inverse problems in local electromagnetic induction

Various methods of solving direct and inverse problems in local electromagnetic induction are presented. In the section dealing with direct problems some improvments are suggested in the finite difference method in the case of two-dimensional modeling. Two ways of dealing with inverse problems are presented, the first continous, the other parametric. Emphasis is laid upon algebraic aspects of dealing with one-dimensional inverse problems.     

我国环境问题与环境地球物理学

从环境和环境问题出发，简述了环境地球物理学的形成过程，并定义环境地球物理学为：应用地球物理学的理论和方法，研究解决环境保护、改善和治理方面问题的一门地球物理分支学科．文章叙述了全球和我国当前的主要环境问题，论述了环境地球物理学在解决这些问题中所起的重要作用；介绍了我国环境地球物理学在研究解决某些环境问题中的应用事例；并在分析我国对环境地球物理的需求以及满足这种需求的能力之后指出，我国环境地球物理工作者必将为我国和世界环境问题的解决及学科的发展做出应有的贡献．     

高层建筑抗拉隔震支座国内外研究现状

简要概述了传统隔震支座在高层及超高层应用中存在的不足及相应的解决对策,重点介绍抗拉隔震支座国内外的研究现状,最后指出目前抗拉隔震支座研究存在的问题。     

结构首次穿越失效研究的新进展

在结构首次穿越失效分析中,初始条件、成群穿越、结构的非线性及抗力退化等问题影响着分析方法的复杂性和分析结果的精确性。结合近年来的研究进展,本文讨论和分析了解决上述问题的新思路、新技术和新方法,同时,归纳了几个新的研究热点,以便为结构首次穿越失效的进一步理论和应用研究提供有益的参考。     

Parabolic Equation Techniques for Seismic Waves

— Parabolic equation techniques for solving seismic wave propagation problems are discussed. These techniques provide an excellent combination of accuracy and efficiency for problems involving laterally varying media. Due to recent improvements, the parabolic equation method is applicable to problems involving wide propagation angles, large variations in the properties of the medium, and all types of waves.     

A Wavelet Toolkit for Visualization and Analysis of Large Data Sets in Earthquake Research

— Wavelets have a wide range of useful functions that permit them to effectively treat problems such as data compression, scale-localization analysis, feature extraction, visualization, statistics, numerical simulation, and communication. We discuss their features and their use in an integrated manner to handle large-scale problems in earthquake physics and other nonlinear problems in the solid earth geosciences.     

From Bayes to Tarantola: New insights to understand uncertainty in inverse problems

Anyone working on inverse problems is aware of their ill-posed character. In the case of inverse problems, this concept (ill-posed) proposed by J. Hadamard in 1902, admits revision since it is somehow related to their ill-conditioning and the use of local optimization methods to find their solution. A more general and interesting approach regarding risk analysis and epistemological decision making would consist in analyzing the existence of families of equivalent model parameters that are compatible with the prior information and predict the observed data within the same error bounds. Otherwise said, the ill-posed character of discrete inverse problems (ill-conditioning) originates that their solution is uncertain. Traditionally nonlinear inverse problems in discrete form have been solved via local optimization methods with regularization, but linear analysis techniques failed to account for the uncertainty in the solution that it is adopted. As a result of this fact uncertainty analysis in nonlinear inverse problems has been approached in a probabilistic framework (Bayesian approach), but these methods are hindered by the curse of dimensionality and by the high computational cost needed to solve the corresponding forward problems. Global optimization techniques are very attractive, but most of the times are heuristic and have the same limitations than Monte Carlo methods. New research is needed to provide uncertainty estimates, especially in the case of high dimensional nonlinear inverse problems with very costly forward problems. After the discredit of deterministic methods and some initial years of Bayesian fever, now the pendulum seems to return back, because practitioners are aware that the uncertainty analysis in high dimensional nonlinear inverse problems cannot (and should not be) solved via random sampling methodologies. The main reason is that the uncertainty “space” of nonlinear inverse problems has a mathematical structure that is embedded in the forward physics and also in the observed data. Thus, problems with structure should be approached via linear algebra and optimization techniques. This paper provides new insights to understand uncertainty from a deterministic point of view, which is a necessary step to design more efficient methods to sample the uncertainty region(s) of equivalent solutions.     

北京国家地球观象台的管理

指出了北京国家地球观象台目前存在的一些问题,分析了出现这些问题的原因,并运用现代管理学的观点论述了解决这些问题的思路和方法。提出了把北京国家地球观象台建成监测、预测、科研三结合台站的管理目标,给出了实现这个目标应采取的管理方法和必要措施。     

The GeoClaw software for depth-averaged flows with adaptive refinement

Many geophysical flow or wave propagation problems can be modeled with two-dimensional depth-averaged equations, of which the shallow water equations are the simplest example. We describe the GeoClaw software that has been designed to solve problems of this nature, consisting of open source Fortran programs together with Python tools for the user interface and flow visualization. This software uses high-resolution shock-capturing finite volume methods on logically rectangular grids, including latitude-longitude grids on the sphere. Dry states are handled automatically to model inundation. The code incorporates adaptive mesh refinement to allow the efficient solution of large-scale geophysical problems. Examples are given illustrating its use for modeling tsunamis and dam-break flooding problems. Documentation and download information is available at www.clawpack.org/geoclaw.     

地震台站采购困境与应对策略 ——以内蒙古自治区地震局所属台站为例

针对内蒙古自治区地震局所属台站在采购中存在的问题,以乌加河地震台、宝昌地震台在采购中存在的问题为研究对象,利用相关政策法规,结合近几年工作经验,提出几条合理建议,以便解决内蒙古自治区地震局所辖台站采购中存在的问题。     

关于地球物理中几个不适定问题的解的连续依赖性

本文讨论地球物理资料解释中三类典型的不适定问题,主要内容如下: 1.综述与三类典型不适定问题有关的问题及研究概况; 2.建立一个更接近物理实际的不适定问题的新提法; 3.给出三类典型不适定问题解的Hlder连续依赖性的估计式。     

Application of superposition with nonlinear head-dependent fluxes

While superposition is commonly used to address linear ground water problems, it can also be used to address certain nonlinear problems. In particular, it can be used to address problems with nonlinear head-dependent fluxes, where the problem can be separated conveniently into steady-state and transient-state components. Superposition can be used to simulate the transient-state head changes independently from the steady-state heads. The problems addressable by superposition include phreatophyte discharges, stream-aquifer interactions, spring discharges, and drain discharges. Each of these represents a nonlinear head-dependent flux, where the flux depends on the elevation of the land surface or some other feature. Superposition is applied by referencing elevations to the local steady-state water table and by imposing the negative of the steady-state flux on the transient-state problem.     

A displacement finite element modelling for convection-diffusion problems

The development of a displacement finite element formulation and its application to convective transport problems is presented. The formulation is based on the introduction of a generalized quantity defined as transport displacement. The governing equation is expressed in terms of this quantity and by using generalized coordinates a variational form of the governing equation is obtained. This equation may be solved by any numerical method, though it is of particular interest for application of the finite element method. Two finite element models are derived for the solution of convection-diffusion boundary value problems. The performance of the two element models is discussed and numerical results are given for different cases of convection and diffusion with two types of boundary conditions. The numerical results obtained show not only the efficiency of the numerical models in handling pure convection, pure diffusion and mixed convection-diffusion problems, but also good stability and accuracy. The applications of the developed numerical models are not limited to diffusion-convection problems but can also be applied to other types of problems such as mass transfer, hydrodynamics and wave propagation.     

On different numerical inverse Laplace methods for solute transport problems

Numerical inversion is required when Laplace transform cannot be inverted analytically by manipulating tabled formulas of special cases. However, the numerical inverse Laplace transform is generally an ill-posed problem, and there is no universal method which works well for all problems. In this study, we selected seven commonly used numerical inverse Laplace transform methods to evaluate their performance for dealing with solute transport in the subsurface under uniform or radial flow condition. Such seven methods included the Stehfest, the de Hoog, the Honig–Hirdes, the Talbot, the Weeks, the Simon and the Zakian methods. We specifically investigated the optimal free parameters of each method, including the number of terms used in the summation and the numerical tolerance. This study revealed that some commonly recommended values of the free parameters in previous studies did not work very well, especially for the advection-dominated problems. Instead, we recommended new values of the free parameters for some methods after testing their robustness. For the radial dispersion, the de Hoog, the Talbot, and the Simon methods worked very well, regardless of the dispersion-dominated or advection-dominated situations. The Weeks method can be used to solve the dispersion-dominated problems, but not the advection-dominated problems. The Stehfest, the Honig–Hirdes, and the Zakian methods were recommended for the dispersion-dominated problems. The Zakian method was efficient, while the de Hoog method was time-consuming under radial flow condition. Under the uniform flow condition, all the methods could present somewhat similar results when the free parameters were given proper values for dispersion-dominated problems; while only the Simon method, the Weeks method, and the de Hoog method worked well for advection-dominated problems.     

国家基本比例尺数字化地形图生产过程中地貌常见问题探讨

本文以1：10000单色数字化地形图为例，简述了国家基本比例尺数字化地形图生产过程中常见的与地貌相关质量问题。对部分产生质量问题的原因作了初步分析。以SCS多用途数字地形地籍测绘与管理系统软件和CASS5．1软件为例，对数字化地形图存在问题的修改方法进行了探讨。     

EROSION AND SEDIMENTATION PROBLEMS IN SOME ASIAN COUNTRIES

1 INTRODUCTIONFrom 1989 to 1993, as project managers of the UNDP/UNESCO project entitled Regional TrainingProgramme on Erosion and Sedimentation for Asia, the writers had the privilege of meeting manyoutstanding hydraulic engineers of this region and came to learn of some important erosion andsedimentation problems thereof. Some issues as noted by the writers are presented in the followingalong the some comments. These issues are mainly concerned with rivers. It should be stated tha…     

Coupling multiscale finite element method for consolidation analysis of heterogeneous saturated porous media

The multiscale finite element method is developed for solving the coupling problems of consolidation of heterogeneous saturated porous media under external loading conditions. Two sets of multiscale base functions are constructed, respectively, for the pressure field of fluid flow and the displacement field of solid skeleton. The coupling problems are then solved with a multiscale numerical procedure in space and time domain. The heterogeneities induced by permeabilities and mechanical parameters of the saturated porous media are both taken into account. Numerical experiments are carried out for different cases in comparison with the standard finite element method. The numerical results show that the coupling multiscale finite element method can be successfully used for solving the complicated coupling problems. It reduces greatly the computing effort in both memory and time for transient problems.     

Analytical solutions to global and local problems of electromagnetic induction in the earth

This review of analytic solutions is divided into two parts. The first part reviews electromagnetic induction in radially symmetric distributions of conductivity, and is appropriate to the study of global problems. In the second part, local problems of a specific nature are considered, the model being a half-space conductor with at least one lateral discontinuity separating regions of different uniform conductivities. In some problems, an approximate surface-boundary condition is used, and it is shown that the accuracy of the solutions has yet to be determined satisfactorily.