Analysis of solute transport with a hyperbolic scale-dependent dispersion model

An empirical hyperbolic scale-dependent dispersion model, which predicts a linear growth of dispersivity close to the origin and the attainment of an asymptotic dispersivity at large distances, is presented for deterministic modelling of field-scale solute transport and the analysis of solute transport experiments. A simple relationship is derived between local dispersivity, which is used in numerical simulations of solute transport, and effective dispersivity, which is estimated from the analysis of tracer breakthrough curves. The scale-dependent dispersion model is used to interpret a field tracer experiment by nonlinear least-squares inversion of a numerical solution for unsaturated transport. Simultaneous inversion of concentration-time data from several sampling locations indicates a linear growth of the dispersion process over the scale of the experiment. These findings are consistent with the results of an earlier analysis based on the use of a constant dispersion coefficient model at each of the sampling depths.     

Flow and transport through two-dimensional isotropic media of binary conductivity distribution. Part 2: NUMERICAL simulations and comparison with theoretical results

In the present part the results of numerical simulations of flow and transport in media made up from circular inclusions of conductivity K that are submerged in a matrix of conductivity K ₀, subjected to uniform mean velocity, are presented. This is achieved for a few values of =K/K ₀ (0.01, 0.1 and 10) and of the volume fraction n (0.05, 0.1 and 0.2). The numerical simulations (NS) are compared with the analytical approximate models presented in Part 1: the composite elements (CEA), the effective medium (EMA), the dilute system (DSA) and the first-order in the logconductivity variance (FOA). The comparison is made for the longitudinal velocity variance and for the longitudinal macrodispersivity. This is carried out for n<0.2, for which the theoretical and simulation models represent the same structure of random and independent inclusions distribution. The main result is that transport is quite accurately modeled by the EMA and CEA for low , for which _L is large, whereas in the case of =10, the EMA matches the NS for n<0.1. The first-order approximation is quite far apart from the NS for the values of examined . This material is based upon work supported by the National Science Foundation under Grant No. 0218914. Authors also wish to thank the Center of Computational Research, University at Buffalo for assistance in running numerical simulations.     

我国最近4次7级以上地震前1年的平静特征

我国最近4次7级以上地震前的地震活动图象表明,7级地震前1年,地震所在地区出现在中强地震活动水平较高背景下的大范围5级以上地震的平静特征。它可能是岩石在应力作用下的变形特性改变的表现。这一特征对我国大陆7级地震的中期预报与7级地震的发生地区的判定具有很现实意义。     

有耗媒质中脉冲响应的研究

本文详细论述了一维有耗媒质中脉冲响应的正演理论及其模拟技术。深入研究了导电率、介电常数对脉冲响应的影响。以平面脉冲电磁波在一维介质中的传播理论为基础，编制脉冲响应的仿真模拟软件。最后，用实际模型验证了该模拟技术的正确性和可靠性。     

层状岩体的Cosserat介质理论中第二剪切模量G^c的研究

针对层状结构岩体，从建立一个标量出发，推导出二维平面应变状态下，Ｃｏｓｓｅｒａｔ介质理论中第二剪切模量Ｇｃ值。最后通过算例，分析了Ｇｃ对计算结果的影响。     

Computation of large-scale parameters for dispersion in fissured porous medium using finite-volume method

In this work, we are interested in solute transport in fissured porous media. The medium is considered as a special case of a two-region system, and a two-equation model previously obtained from a volume averaging technique is used to derive large-scale dispersion coefficients. These coefficients are obtained as solutions of a set of closure problems and the main objective of this work is to present an efficient method to solve these closure problems. The method makes use of an unstructured grid and special techniques to take into account the fissure network. Results are compared with other existing methods on simple fissured media. Finally, the technique is applied to a complex structure.     

水文地质研究新动向

由于日益增长的社会发展的需要，水文地质研究正在产生巨大变化。人们对各种工农业活动所产生的诸多环境污染问题的关注，以及对“高放”放射性废物和毒性液体的地下深层埋设的安全评价需求，致使水文地质研究产生许多新的生长点。无论是在水文地质研究的学科发展领域，还是在解决重大社会问题方向，水文地质学家均面临着巨大的挑战和机遇。     

1995年夏季T63L16中期预报效果检验

为了考证Ｔ６３模式的性能与产品的质量，对１９９５年夏季造成我国暴雨的环流形势和主要影响系统Ｔ６３的预报结果进行天气学检验和评估，其结果表明，Ｔ６３较Ｔ４２有了显著改进。     

云南武定6.5级地震前的大形势及发震过程分析

１９９６年１０月２４日武定６．５级地震是滇东地区近１０年来的最大地震事件。本文首先论述了该地区的长期缺震现象及周边强震持续活跃对它的牵动影响；进而通过多种地球物理量的时空分析，发现震前１年震区地表荷载突然出现剧烈加载，震区地下介质亦变得很不稳定；最后，６．５级地震恰在有多个“天文奇点”会集的１０月２４日爆发，受调性质极为显著。     

四川地区Sn波偏振

本文分析了１９９４年、１９９５年成都遥测地震台网实时处理系统记录的５０多个ＭＬ３．０～４．０级地震的Ｓｎ波偏振，研究这一地区地壳介质的各向异性．结果表明，在短周期三分向地震图上，对来自不同传播方向的，有可靠到时的Ｓｎ波偏振是一致的，其优势取向与其它方法观测的这一地区最大水平主压应力方向相同。这意味着，这一地区地壳介质存在地震波各向异性。