Interpretation of tracer tests performed in fractured rock of the Lange Bramke basin, Germany

 Two multitracer tests performed in one of the major cross-fault zones of the Lange Bramke basin (Harz Mountains, Germany) confirm the dominant role of the fault zone in groundwater flow and solute transport. Tracers having different coefficients of molecular diffusion (deuterium, bromide, uranine, and eosine) yielded breakthrough curves that can only be explained by a model that couples the advective–dispersive transport in the fractures with the molecular diffusion exchange in the matrix. For the scale of the tests (maximum distance of 225 m), an approximation was used in which the influence of adjacent fractures is neglected. That model yielded nearly the same rock and transport parameters for each tracer, which means that the single-fracture approximation is acceptable and that matrix diffusion plays an important role. The hydraulic conductivity of the fault zone obtained from the tracer tests is about 1.5×10^–2 m/s, whereas the regional hydraulic conductivity of the fractured rock mass is about 3×10^–7 m/s, as estimated from the tritium age and the matrix porosity of about 2%. These values show that the hydraulic conductivity along the fault is several orders of magnitude larger than that of the remaining fractured part of the aquifer, which confirms the dominant role of the fault zones as collectors of water and conductors of fast flow. Received, April 1997 Revised, January 1998, August 1998 Accepted, August 1998     

用长周期面波波形拟合及P波初动方向估计中等地震的震源机制

提出利用周期范围４５-１００ｓ间的面波波形拟合与Ｐ波初动符号相结合,估计中小地震震源机制的方法．给出两个倾滑为主和三个走滑为主的震例．其中最小的是１９９６年１２月１６日北京顺义ＭＬ４．５级地震.比较了１９９６年２月５日云南丽江Ｍｓ６．０级余震的机制解与美国哈佛大学ＣＭＴ结果的相似程度,各震例记录图与理论图的相似程度,以及初动分布与主压力轴Ｐ和主动力轴Ｔ分布区的一致程度．从比较结果看,得到的震源机制解有参考价值,开发的软件有可用性．     

Elastic waves in nonhomogeneous media under 2D conditions: II. Numerical implementation

The purpose of this work is to present three methods of analysis for elastic waves propagating in two dimensional, elastic nonhomogeneous media. The first step, common to all methods, is a transformation of the governing equations of motion so that derivatives with respect to the material parameters no longer appear in the differential operator. This procedure, however, restricts analysis to a very specific class of nonhomogeneous media, namely those for which Poisson's ratio is equal to 0.25 and the elastic parameters are quadratic functions of position. Subsequently, fundamental solutions are evaluated by: (i) conformal mapping in conjunction with wave decomposition, which in principle allows for both vertical and lateral heterogeneities; (ii) wave decomposition into pseudo-dilatational and pseudo-rotational components, which results in an Euler-type equation for the transformed solution if medium heterogeneity is a function of one coordinate only; and (iii) Fourier transformation followed by a first order differential equation system solution, where the final step involving inverse transformation from the wavenumber domain is accomplished numerically. Finally, in the companion paper numerical examples serve to illustrate the above methodologies and to delineate their range of applicability.     

Second-Order Solutions for Random Interfacial Waves Under Steady Uniform Currents

1.Introduction Owingtothesimilaritiesbetweenthesurfacewaveandtheinterfacialwave,itisnaturaltoapply themethodsdevelopedforsurfacewavestothestudyofinterfacialwavesasreviewedbyUmeyama (1998;2000).Recently,Song(2004)derivedsecond ordersolutionsforrandominterfacialwavesat aconstantdepthinatwo layerfluidsystemwitharigidlidusinganexpansiontechnique,analogousto thatusedbyLonguet Higgins(1963)andSharmaandDean(1979),tostudyrandomsurfacewaves. Inthispaper,Song’sresultsareextendedtoamoregeneralcaseoft…     

KNO3溶液结构:密度泛函理论和分子动力学研究

基于密度泛函理论,采用ωB97XD方法和6-311++G(d,p)基组,系统研究了[K(H₂O)_n]⁺,[NO₃(H₂O)_n]-和KNO₃(H₂O)_n水合团簇的结构和性质;并结合经典分子动力学、OPLS-AA全原子力场以及SPC/E水模型模拟了不同水盐比(WSR) KNO₃溶液,目的在于深入理解KNO₃溶液中K⁺和 NO-₃的微观水合结构,以及K⁺-NO-₃离子间缔合作用特征。研究发现,对于KNO₃(H₂O)_n (n=6,8,10和12)水合团簇,K⁺第一水合层稳定结构为四、五和六水合结构,其中五水合结构最稳定。K⁺和NO-₃主要以溶剂共享离子对形式存在。随着团簇尺寸减小,直接接触离子对(CIP)物种出现。同时,分子动力学模拟证实KNO₃溶液中形成了直接接触K⁺-NO-₃离子对,且随着溶液浓度增加,CIP物种形成需越过更大能垒。以上结果表明在KNO₃稀溶液中主要存在物种为水合K⁺和NO-₃,随浓度增大,单齿直接接触离子对(MCIP)逐渐出现。在高浓溶液或过饱和溶液中,K⁺-NO-₃离子缔合主要以单齿CIP和少量双齿CIP结构存在。     

工程测量观测误差的形成原因及解决方法

工程测量中不可避免地会产生观测误差,主要来自仪器设备、自然条件及人为因素的影响。若要提高测绘成果的精准性,就要从这3个方面进行分析并加以完善。     

Dependence of upper atmosphere photochemistry on the shape of the diurnal cycle of the photolysis rates

A photochemical model of the atmosphere constitutes a non–linear, non–autonomous dynamical system, enforced by the Earth’s rotation. Some studies have shown that the region of the mesopause tends towards non–linear responses such as period-doubling cascades and chaos. In these studies, simple approximations for the diurnal variations of the photolysis rates are assumed. The goal of this article is to investigate what happens if the more realistic, calculated photolysis rates are introduced. It is found that, if the usual approximations—sinusoidal and step fiunctions—are assumed, the responses of the system are similar: it converges to a 2–day periodic solution. If the more realistic, calculated diurnal cycle is introduced, a new 4–day subharmonic appear.     

Exact solutions to Kaluza-Klein cosmologies

We consider general methods to find exact solutions of Kaluza-Klein cosmologies with phenomenological matter and show some general conclusions about factorwise homogeneous and isotropic models.     

New solutions in linearized R+R2 gravity

A general method is proposed to solve in the linear approximation the fourth-order gravitational equations, which stem from Lagrangians $ \text{Q} = 1 ‐ g\left( {R + \frac{1}{2}aR^2 + bR_{av} R^{av} } \right) ‐ x\text{Q}. $ The metric of a static spherically symmetric body and the metric of a straight infinitely thin cosmic string are given.     

Deviation of circular geodesics in static spherically symmetric space-times

For static spherically symmetric space-times the equations of geodesic deviation are solved for circular geodesics. We discuss the connection between the obtained solutions and the stability behaviour of the geodesics. The perihelion shift for test bodies moving on nearly circular geodesics is also derived.