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High-resolution manganese K-edge X-ray absorption near edge structure spectra were collected on a set of 40 Mn-bearing minerals.
The pre-edge feature information (position, area) was investigated to extract as much as possible quantitative valence and
symmetry information for manganese in various “test” and “unknown” minerals and glasses. The samples present a range of manganese
symmetry environments (tetrahedral, square planar, octahedral, and cubic) and valences (II to VII). The extraction of the
pre-edge information is based on a previous multiple scattering and multiplet calculations for model compounds. Using the
method described in this study, a robust estimation of the manganese valence could be obtained from the pre-edge region at
5% accuracy level. This method applied to 20 “test” compounds (such as hausmannite and rancieite) and to 15 “unknown” compounds
(such as axinite and birnessite) provides a quantitative estimate of the average valence of manganese in complex minerals
and silicate glasses.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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中国城市空间分布的双侧对称性 总被引:1,自引:1,他引:1
借助尺度归并和笛卡儿变换思想考察中国城市的宏观分布规律,发现中国城市在一定的空间和规模尺度上具有双重对称性:以秦岭—淮河为界,南方城市与北方城市呈现双侧对称特征;以呼和浩特—太原—郑州—武汉—广州沿线为轴,东部城市与西部城市形成双侧对称局势。中国城市的宏观对称性与地球公转和自转的方式有关,海陆差异、地表形态和水系构成是影响城市对称格局的重要因素。城市的对称分布属于广义的形态发育问题,对称形成的内在机制可能在于人类空间行为的自组织演化。 相似文献
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This article considers magnetic field generation by a fluid flow in a system referred to as the Archontis dynamo: a steady nonlinear MHD state is driven by a prescribed body force. The field and flow become almost equal and dissipation is concentrated in cigar-like structures centred on straight-line separatrices. Numerical scaling laws for energy and dissipation are given that extend previous calculations to smaller diffusivities. The symmetries of the dynamo are set out, together with their implications for the structure of field and flow along the separatrices. The scaling of the cigar-like dissipative regions, as the square root of the diffusivities, is explained by approximations near the separatrices. Rigorous results on the existence and smoothness of solutions to the steady, forced MHD equations are given. 相似文献
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针对我国地震监测预报中固定地点和固定观测装置及参数的视电阻率观测,给出了半空间倾斜各向异性介质中电阻率对称四极观测的理论探测深度,研究了地震前兆信息的检测深度问题,得到:(1)在强地震、孕震晚期阶段,在震中区及附近可检测到地壳近地表较深部介质的电阻率变化,其深度大于或远大于均匀介质之;(2)震级、震中距、观测方向不同或在不同的孕震阶段,探测深度存在差异,甚至存在大的差异,且是动态变化的.并依据理论探测深度讨论了地震视电阻率前兆变化的复杂性、地电台址电性条件等问题. 相似文献
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水系结构的分形和分维——Horton水系定律的模型重建及其参数分析 总被引:26,自引:3,他引:26
基于标准分形水系等级序列的镜象对称性,重建水系构成定律:从Horton第一,第二定律出发,导出关于河流长度与位序关系的三参数Zipf模型,从Horton第二,第三定律出发,导出广义的Hack定律;从Horton第一,第三定律出发,导出关于河流长度一流域面积关系的异速生长方程,根据上述数学变换结果建立了水系分维方程式,澄清了不同空间,不同类型的各种维数之间的数理关系。 相似文献
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