Multivariate analysis of trace elements in shallow groundwater in Fuchu in western Tokyo Metropolis,Japan     

Dang Quoc Thuyet  Hirotaka Saito  Takeshi Saito  Shigeoki Moritani  Yuji Kohgo  Toshiko Komatsu 《Environmental Earth Sciences》2016,75(7):559

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Modes,hydrodynamic processes and ecological impacts exerted by river–groundwater transformation in Junggar Basin,China     

Wenke Wang  Zhan Wang  Rongzhe Hou  Longyao Guan  Yan Dang  Zaiyong Zhang  Hao Wang  Lei Duan  Zhoufeng Wang 《Hydrogeology Journal》2018,26(5):1547-1557

The hydrodynamic processes and impacts exerted by river–groundwater transformation need to be studied at regional and catchment scale, especially with respect to diverse geology and lithology. This work adopted an integrated method to study four typical modes (characterized primarily by lithology, flow subsystems, and gaining/losing river status) and the associated hydrodynamic processes and ecological impacts in the southern part of Junggar Basin, China. River–groundwater transformation occurs one to four times along the basin route. For mode classification, such transformation occurs: once or twice, controlled by lithological factors (mode 1); twice, impacted by geomorphic features and lithological structures (mode 2); and three or four times, controlled by both geological and lithological structures (modes 3 and 4). Results also suggest: (1) there exist local and regional groundwater flow subsystems at ~400 m depth, which form a multistage nested groundwater flow system. The groundwater flow velocities are 0.1–1.0 and?<0.1 m/day for each of two subsystems; (2) the primary groundwater hydro-chemical type takes on apparent horizontal and vertical zoning characteristics, and the TDS of the groundwater evidently increases along the direction of groundwater flow, driven by hydrodynamic processes; (3) the streams, wetland and terminal lakes are the end-points of the local and regional groundwater flow systems. This work indicates that not only are groundwater and river water derived from the same source, but also hydrodynamic and hydro-chemical processes and ecological effects, as a whole in arid areas, are controlled by stream–groundwater transformation.  相似文献   

一种改进的多基线相位展开方法     

谢家朝  谢先明  许华夏  王健  曾庆宁 《测绘科学》2018,(1):117-123

针对最大似然估计的多基线InSAR相位解缠算法对噪声比较敏感且难以解缠低信噪比干涉图的缺点,该文提出一种多基线迭代与最大似然估计相结合的多基线相位展开方法。首先利用多基线迭代法得到最长基线干涉图粗略的干涉相位;然后在以此粗略相位为中心的相位区间里,利用多基线最大似然估计得到最长基线干涉图的干涉相位精确估计值。该文采用仿真的金字塔场景、多山场景以及城市场景干涉图进行相位解缠实验。实验表明,该方法的相位展开精度比多基线迭代法和最大似然估计法都有了不同程度的提高。  相似文献   

Evaluating the performance of an explicit dynamic relaxation technique in analyzing non-linear geotechnical engineering problems     

Hoang K. Dang  Mohamed A. Meguid 《Computers and Geotechnics》2010,37(1-2):125-131

Explicit dynamic relaxation is an efficient tool that has been used to solve problems involving highly non-linear differential equations. The key feature of this method is the ability to use explicit dynamic algorithms in solving static problems. Few attempts have been made to date to apply this technique in conventional geotechnical engineering. In this study, an algorithm that incorporates the application of a stiffness dependent time step scheme is proposed. The algorithm has been successfully used to solve 2D and 3D non-linear geotechnical engineering problems. To calibrate the developed algorithm, numerical simulations have been conducted for a strip and square footings supported by Mohr–Coulomb material. Performance of four different types of brick elements used in collapse load calculation is examined in terms of convergence speed and accuracy. In addition, the role of employing adaptive time steps in reducing the number of iterations needed for convergence is also evaluated.  相似文献   

Mechanical Behavior of Light-Weight Soil Under Consolidated Drained Shear Condition     

Tian-Shun Hou  Wei Wang  Ya-Sheng Luo  Jin-Qian Dang  Xiu-Juan Yang 《Marine Georesources & Geotechnology》2013,31(3):264-276

To reveal the influence of material composition on mechanical properties of light-weight soil, stress-strain -volumetric strain characteristics and Poisson's ratio of mixed soil were researched by consolidated drained shear tests. The results show that light-weight soil is a kind of structural soil, so its mechanical properties are affected by mixed ratio and confining pressure, and mixed soil possesses structural yield stress. When confining pressure is less than the structural yield stress, strain softening occurs; when confining pressure is more than the structural yield stress, strain hardening is observed. There are two kinds of volume change behavior: shear contraction and shear dilatancy. Shear dilatancy usually leads to strain softening, but there isn't an assured causal relationship between them. Poisson's ratio of mixed soil is a variational state parameter with the change of stress state, it decreases with increased confining pressure, and it increases with increased stress level. When axial strain is near 5%, Poisson’ ratio is gradually close to a steady value. The main range of Poisson's ratio is 0.25～0.50 when confining pressure changes from 50 to 300 kPa. When unconfined compressive strength of mixed soil is less than 328 kPa, its stress-strain-volumetric strain characteristics can be predicted very well by Duncan-Chang model (E-B model). However, when the range of unconfined compressive strength is [328 kPa, 566 kPa], the model can't predict stress-strain characteristics accurately when confining pressure is under 200 kPa, and it also can't predict the strong shear dilatancy phenomenon of mixed soil under low confining pressure.  相似文献   

Linear inversion of seismic moment tensors of general point source by using generalized ray theory     

Rui-Feng Liu  Jing-Ping Dang  Shao-Dong Fang  Pei-Shan Chen 《地震学报(英文版)》1997,10(2):253-259

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地理信息系统图例库的研究   总被引：7，自引：1，他引：6  

党安荣  乔彦友 《地理科学》1996,16(4):370-376

图例库是地理信息系统（ＧＩＳ）的有机组成部分,开发灵活实用的图例库是研制ＧＩＳ软件的重要内容之一,关系到ＧＩＳ成果图形表达的科学性。借鉴ＩＮＴＥＲＧＲＡＰＨ／ＩＧＤＳ的图例库设计思想,引入“符合集合”及“操作函数”的概念,从图例库的基本内涵、实体内容及主要操作等几方面论述了作者对图例库的研究成果。  相似文献   

链子崖危岩体勘查中物探技术的应用     

郭建强  彭成  孙党生 《水文地质工程地质》2003,30(3):54-57

三峡链子崖危岩体防治工程之前进行了大量的调查和勘探工作,为开展整治工程奠定了基础,其中物探技术发挥了重要作用。本文简要介绍了音频大地电场法、甚低频电磁法、电测深法、高密度电阻率法、浅层地震法、声波跨孔法等物探技术探测隐伏裂缝、煤洞、岩溶以及堆积物厚度等方面的应用成果和一些经验。  相似文献   

中国钴资源及其开发利用概况   总被引：14，自引：0，他引：14  

丰成友  张德全  党兴彦 《矿床地质》2004,23(1):93-100

文章概述了中国钴矿床的类型、时空分布、最新研究进展及开发利用现状，指出世界上共(伴)生主要钴矿床类型在中国均已发现，可归纳为4大类，其中以岩浆型Ni—Cu—Co硫化物矿床、热液及火山成因钴多金属矿床最为重要；中国钴矿的形成可分为6个重要成矿期，划分出7个重要成矿带；尽管钴多以伴生组分产在镍、铜、铁等矿床中，但近年来中国先后发现了一些不同元素组合、不同成因类型的独立钴矿床。鉴于中国当前钴资源比较紧缺和钴消费快速增长，建议既要充分利用好国内外资源，又要加大钴资源勘查及开发利用力度，以满足国民经济发展的需要。  相似文献   

大地测量反演模型优化问题的研究     

党亚民  陈俊勇  晁定波 《大地测量与地球动力学》1998,(2)

在大地测量反演中,由于观测数据的不足或由于对模型空间了解的匮乏,总会出现病态问题,因此在进行反演解算之前对反演模型空间进行优化是很有必要的。利用矩阵扰动的理论研究了大地测量反演中的病态问题,并提出了模型优化的两种方法。  相似文献