Helioseismology and the solar interior dynamics     

S. Vauclair 《Journal of Astrophysics and Astronomy》2000,21(3-4):323-329

The inversion of helioseismic modes leads to the sound velocity inside the Sun with a precision of about 0.1 per cent. Comparisoons of solar models with the “seismic sun” represent powerful tools to test the physics: depth of the convection zone, equation of state, opacities, element diffusion processes and mixing inside the radiative zone. We now have evidence that microscopic diffusion (element segregation) does occur below the convection zone, leading to a mild helium depletion in the solar outer layers. Meanwhile this process must be slowed down by some macroscopic effect, presumably rotation-induced mixing. The same mixing is also responsible for the observed lithium depletion. On the other hand, the observations of beryllium and helium 3 impose specific constraints on the depth of this mildly mixed zone. Helioseismology also gives information on the internal solar rotation: while differential rotation exists in the convection zone, solid rotation prevails in the radiative zone, and the transition layer (the so-called “tachocline”) is very small. These effects are discussed, together with the astrophysical constraints on the solar neutrino fluxes.  相似文献   

长江口外缺氧区沉积物中元素分布的氧化还原环境效应   总被引：4，自引：0，他引：4  

许淑梅  翟世奎  张爱滨  张怀静  卢海建 《海洋地质与第四纪地质》2007,27(3):1-8

对取自长江口外缺氧区及其邻近海域表层沉积物样品进行了粒度组成和元素(主要包括氧化还原敏感性元素和亲碎屑元素)丰度的分析与测试,对长江口外缺氧区缺氧环境对元素分布的影响进行了探讨,提出了长江口外缺氧区沉积物中氧化还原敏感性元素(Redox sensitive elements,简称RSE)分布的氧化还原环境效应。亲碎屑元素丰度的分布显示出明显的粒控效应,而氧化还原敏感元素的分布受粒度效应的制约很弱,主要受离岸缺氧区还原环境的制约,具有在缺氧区富集的特点。缺氧环境对RSE分布的影响超过了元素的粒控效应,从而使研究区RSE的分布呈现出典型的氧化还原环境效应。  相似文献   

顺序提取法探讨沉积物中主量元素在不同相态的分配特征   总被引：2，自引：0，他引：2  

邹亮  韦刚健 《海洋地质与第四纪地质》2007,27(2):133-140

在Tessier以及欧共体标准局BCR等前人顺序提取方法的基础上,采用一套改进的顺序提取法对海洋沉积物以及一些水系沉积物标准物质的主量元素进行逐步提取。利用ICP—AES、ICP—MS方法分析了各提取液中Ti、A1、Na、Mg、K、Ca、P、Fe、Mn的含量以及它们在不同相态的分配特征,同时,进一步探讨了酸去除沉积物中非陆源组分的效果,结果显示,最后经盐酸淋滤后的样品,沉积物中的生物、自生组分已经被溶解,而残留下来的剩余物质基本上可代表海洋沉积物的陆源碎屑组分。  相似文献   

长江和黄河入海沉积物不同粒级组分中稀土元素的比较   总被引：2，自引：0，他引：2  

乔淑卿  杨作升 《海洋地质与第四纪地质》2007,27(6):9-16

为探索区分黄、东海陆架沉积物中来自长江和黄河源的有效替代性指标,从长江和黄河河口区各取3个沉积物样品作为长江和黄河入海沉积物的端元样品。研究结果表明:长江和黄河沉积物不同粒级组分中REE的变化范围分别为145.49~256.77μg/g和121.22~135.56μg/g,随粒度由细变粗分别呈下倾的"双峰"型分布和倒"S"型分布;长江沉积物中REE约为黄河的1.5倍,最低值比黄河的最高值高出20%;8~16μm和2~4μm是凸显长江和黄河沉积物稀土元素差异的敏感粒级,REE、LREE/HREE和(La/Yb)n等稀土元素特征参数在这两个粒级组分中差异明显。本次实验结果大幅度地提高了两条河流REE差异的灵敏度和可信度,为建立区分长江与黄河入海沉积物物源实用的有效指标提供了可能。  相似文献   

波浪作用下孔隙海床-管线动力相互作用分析   总被引：1，自引：0，他引：1  

栾茂田  曲鹏  郭莹  杨庆  范庆来 《海洋工程》2007,25(2):43-51

波浪作用下海床中的孔隙水压力与有效应力是影响海底管线稳定性的主要因素。然而,在目前的海床响应分析中一般将管线假定为刚性,并不能合理地考虑海床与管线之间的相互作用效应,同时也没有考虑土体和管线加速度对海床动力响应的惯性影响,从而无法确定由此所引起的管线内应力。为此考虑管线的柔性,分别采用饱和孔隙介质的Biot动力固结理论和弹性动力学理论列出了海床与管线的控制方程,进而采用摩擦接触理论考虑海床与管线之间的相互作用效应,基于有限元方法建立了海床-管线相互作用的计算模型及其数值算法。通过变动参数对比计算讨论了管线几何尺寸、海床土性参数对波浪所引起的管线周围海床孔隙水压力和管线内应力的影响。  相似文献   

Towards a protocol for the trace element analysis of glass from rhyolitic shards in tephra deposits by laser ablation ICP‐MS          下载免费PDF全文

NICHOLAS J. G. PEARCE 《第四纪科学杂志》2014,29(7):627-640

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XFEM formulation with sub-interpolation,and equivalence to zero-thickness interface elements     

Laura Crusat  Ignacio Carol  Daniel Garolera 《国际地质力学数值与分析法杂志》2019,43(1):45-76

This paper describes a particular formulation of the extended finite element method (XFEM) specifically conceived for application to existing discontinuities of fixed location, for instance, in geological media. The formulation is based on two nonstandard assumptions: (1) the use of sub-interpolation functions for each subdomain and (2) the use of fictitious displacement variables on the nodes across the discontinuity (instead of the more traditional jump variables). Thanks to the first of those assumptions, the proposed XFEM formulation may be shown to be equivalent to the standard finite element method with zero-thickness interface elements for the discontinuities (FEM+z). The said equivalence is theoretically proven for the case of quadrangular elements cut in two quadrangles by the discontinuity, and only approximate for other types of intersections of quadrangular or triangular elements, in which the XFEM formulation corresponds to a kinematically restricted version of the corresponding interface plus continuum scheme. The proposed XFEM formulation with sub-interpolation, also helps improving spurious oscillations of the results obtained with natural interpolation functions when the discontinuity runs skew to the mesh. A possible explanation for these oscillations is provided, which also explains the improvement observed with sub-interpolation. The paper also discusses the oscillations observed in the numerical results when some nodes are too close to the discontinuity and proposes the remedy of moving those nodes onto the discontinuity itself. All the aspects discussed are illustrated with some examples of application, the results of which are compared with closed-form analytical solutions or to existing XFEM results from the literature.  相似文献   

Strategic elements in the Fort Cooper Coal Measures: potential rare earth elements and other multi-product targets     

J. H. Hodgkinson  M. Grigorescu 《Australian Journal of Earth Sciences》2020,67(3):305-319

Abstract

Mineral matter in coals has been found to host valuable elements including germanium, lithium and rare-earth elements (REE), but such content of Australian coals remains under-explored. The aim of this paper is to provide a proof-of-concept study that determines elemental concentrations in the mineral matter of the high-ash, Fort Cooper Coal Measures (FCCM), Bowen Basin, Queensland. Coal in the FCCM has good coking properties but has not been extensively explored owing to its high ash content. This study performs a preliminary assessment of the elements from the coal portion that would typically become waste after washing or combustion. Given that the needs for industrial extraction methods will change over time, cataloguing and documenting the elemental composition of coal may assist future development of multiple products for the benefit of both the coal and mineral industries. This preliminary study has revealed similar elevations of REE and higher-than-average crustal concentrations of lithium, bismuth and scandium in some of the samples. Further analyses will be required on a larger dataset to better understand elemental associations and explore spatial patterns of elemental content that may indicate localised enrichments. Understanding the potential of valuable elements in the FCCM may stimulate interest in multiple-product-coal (or elemental-coal) mining in this under-exploited resource and further encourage the reduction of waste from other Australian coals at the wash-plant stage.  相似文献   

新疆且末县米特河地区1:5万水系沉积物地球化学特征及找矿意义          下载免费PDF全文

张中欣 《山东国土资源》2020,36(6):34-42

根据1:5万水系沉积物地球化学测量工作成果,对采集的3138件样品中Cu,Pb,Zn,Au,Ag,W,Sn,Mo,Bi,As,Sb,Cr,Co,Ni共14种元素进行分析测试。研究结果表明,Au,Ag,Cu,Ni是区内最有找矿潜力的成矿指标元素;聚类分析所划分的4类元素簇群,主要与中低温成矿元素、阿尔金南缘断裂、蛇绿混杂岩相关,通过因子分析得到Ni-Cr-As-Sb-Cu-Bi,W-Bi-As-Cu,Bi-W,As,Ag-Zn-Pb,Cu-Bi-As共6类元素组合。其中Cr,Ni,Sb,Cu,As,Bi组合反映出与低温热液活动和断裂构造活动有关;Cr,Ni元素的富集主要与研究区内叶桑岗蛇绿混杂岩带关系密切;Ag,Pb,Zn组合则与地层低温热液元素局部富集和断裂构造活动密切相关。在综合异常分析和查证的基础上,结合区域成矿地质条件、区内矿产地质特征,圈定、划分出2个找矿远景区,并指出了研究区内以金、铜、银、镍为主要优势矿种,铅、锌为潜力矿种。  相似文献   

Influence of Lode angle‐dependent failure criteria on shear localization analysis in sand          下载免费PDF全文

Mitul Sisodiya  Arghya Das 《国际地质力学数值与分析法杂志》2018,42(8):979-998

Geotechnical experiments show that Lode angle‐dependent constitutive formulations are appropriate to describe the failure of geomaterials. In the present study, we have adopted one such class of failure criteria along with a versatile constitutive relationship to theoretically analyze the effects of Lode angle on localized shear deformation or shear band formation in loose sand for both drained and undrained conditions. We determine the variation in the possible stress states for shear localization due to the introduction of Lode angle by considering the localized deformation as a bifurcation problem. Further, similar bifurcation analysis is performed for the stress states along a specific loading path, namely, plane strain compression at the constitutive level. In addition, the plane strain compression tests have been simulated as a boundary value finite element problem to see how Lode angle affects the post‐localization response. Results show that the inclusion of a Lode angle parameter within the failure criterion has considerable effects on the onset, plastic strain, and propagation of shear localization in loose sand specimens. For drained condition, we notice early inception of shear localization and multiple band formation when the Lode angle‐dependent failure criterion is used. Undrained localization characteristics, however, found to be independent of Lode angle consideration.  相似文献