Traction image method for irregular free surface boundaries in finite difference seismic wave simulation

In this study, we propose a new numerical method, named as Traction Image method, to accurately and efficiently implement the traction-free boundary conditions in finite difference simulation in the presence of surface topography. In this algorithm, the computational domain is discretized by boundary-conforming grids, in which the irregular surface is transformed into a 'flat' surface in computational space. Thus, the artefact of staircase approximation to arbitrarily irregular surface can be avoided. Such boundary-conforming gridding is equivalent to a curvilinear coordinate system, in which the first-order partial differential velocity-stress equations are numerically updated by an optimized high-order non-staggered finite difference scheme, that is, DRP/opt MacCormack scheme. To satisfy the free surface boundary conditions, we extend the Stress Image method for planar surface to Traction Image method for arbitrarily irregular surface by antisymmetrically setting the values of normal traction on the grid points above the free surface. This Traction Image method can be efficiently implemented. To validate this new method, we perform numerical tests to several complex models by comparing our results with those computed by other independent accurate methods. Although some of the testing examples have extremely sloped topography, all tested results show an excellent agreement between our results and those from the reference solutions, confirming the validity of our method for modelling seismic waves in the heterogeneous media with arbitrary shape topography. Numerical tests also demonstrate the efficiency of this method. We find about 10 grid points per shortest wavelength is enough to maintain the global accuracy of the simulation. Although the current study is for 2-D P-SV problem, it can be easily extended to 3-D problem.     

A simple hypoplastic model for normally consolidated clay

The paper presents a simple constitutive model for normally consolidated clay. A mathematical formulation, using a single tensor-valued function to define the incrementally nonlinear stress–strain relation, is proposed based on the basic concept of hypoplasticity. The structure of the tensor-valued function is determined in the light of the response envelope. Particular attention is paid towards incorporating the critical state and to the capability for capturing undrained behaviour of clayey soils. With five material parameters that can be determined easily from isotropic consolidation and triaxial compression tests, the model is shown to provide good predictions for the response of normally consolidated clay along various stress paths, including drained true triaxial tests and undrained shear tests.     

张家口地下热水资源成因探讨

张家口地热资源丰富，通过对区内地热成矿机制，成矿规律的分析认为，以祁吕系为主的多构造体系复合部位控制了本区地下热水的形成与分布，本区地下热水是大气降水经深循环而成，经计算深循环的深度达为2600m，张家口南部地区有很多个热水异常点，是具有远景意义的地热区。     

吉尔嘎朗图凹陷宝饶洼槽下白垩统层序地层与沉积体系

运用高分辨率层序地层学原理和方法,通过对钻井和地震资料的综合分析,在二连盆地吉尔嘎朗图凹陷下白垩统中识别出1个超长期基准面旋回(二级层序)SSC1和5个长期基准面旋回(三级层序):LSC1,LSC2,LSC3,LSC4,LSC5,分析了各旋回的发育特征。识别出五种类型的沉积体系:滨浅湖近岸水下扇、较深水湖浊积扇、滨浅湖扇三角洲、滨浅湖辫状河三角洲和河流沉积体系,并在等时地层格架内分析了各基准面旋回的沉积体系构成和储层砂体的发育情况。综合分析生、诸、盖条件后认为,在垂向上,LSC3旋回为本区最有利的储集层段,在平面上,本区的油气勘探应主要寻找宝饶构造带辫状河三角洲前缘砂体,主要储层砂体类型为前缘分流水道砂和前缘席状砂。     

邻苯二酚螯合树脂的合成及水样中铝的测定

合成并表征了新螯合树脂———邻苯二酚螯合树脂(XAD-2-Catechol),研究了XAD-2-Catechol吸附铝的特性和茜素红-铝的显色反应,在pH4.5的HAc-NaAc缓冲介质中,茜素红和铝(Ⅲ)反应生成红色络合物,λm ax=500 nm,铝的含量在0-50μg/25 mL内符合比耳定律。建立了邻苯二酚螯合树脂分离/富集-茜素红分光光度法测定天然水样中铝的新方法,对水样中铝形态进行测定,结果满意。     

REE/trace element characteristics of sandstone-type uranium deposits in the Ordos Basin

1 Introduction The Ordos Basin is the second largest sedimentary basin in China. During the last 10 years, a great progress has been achieved in the aspects of tectonic evolution, dynamics process, inner and outer geological processes during Mesozoic-Cen…     

单斜构造岩溶含水层及其岩溶渗漏条件分析--以湖北水江坪河水电站河湾地块为例

通过对湖北水江坪河水电站河湾地块寒武系下统龙王庙组上段(∈21l)单斜岩溶含水系统的水动力、温度、水量均衡以及岩溶发育特征分析,提出在单斜岩层中存在2层岩溶结构和2层岩溶水系统,上层岩溶水系统的水位高于正常蓄水位(475m),而深层岩溶水系统的水位低于正常蓄水位(475m).在建库条件下,库水可通过深层岩溶水系统向河湾下游径流排泄,即河湾地块存在岩溶渗漏问题.该结论已得到深孔勘探以及钻孔彩色录像初步查证.     

基于本体与LDAP的空间信息网格资源管理机制

为了在网格计算中满足空间信息系统在语义方面的特殊要求，克服传统网格研究的数据格式很少涉及信息资源的语义内容的缺陷，把本体和轻量目录访问协议结合到一起，建立了基于语义的空间信息网格资源管理系统，使多源异构的地理信息系统组成了一个虚拟统一的逻辑组织，有效地实现了基于语义的空间信息系统集成和互操作。     

高光谱遥感数据三次光滑样条滤噪

分析了高光谱遥感数据噪声滤波的作用和现状，实现了一种基于三次光滑样条函数的高光谱遥感数据噪声滤波算法，解决了目前高光谱遥感数据噪声滤波算法自适应效果不理想的问题。通过对AVIRIS数据试验，证明此方法简单易行，计算精度高，具有良好的局部自适应拟合能力，并能有效地滤除数据中的噪声，改善数据质量。     

北京市地下水动态监测示范工程的建设和应用

北京市地下水动态监测示范工程是北京市科委的重大项目,从1999年开始建设,到2004年4月全面完成.本文详细介绍了该项目的建设及开发内容,以及在北京市地下水动态监测工作中的应用情况.