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111.
缺位型铬尖晶石的存在是20世纪50年代才被认识的,因其高反射率并具磁性;长期以来被误认为磁铁矿,本文对比了它与正常型铬尖晶石化学结构式的差异;论证了其化学结构式的推导计算方法和鉴别特征,铬尖晶石的组成和结构是地质地球化学的重要信息。 相似文献
112.
113.
金刚石中晶格氢的UHF法计算分析 总被引:1,自引:0,他引:1
对金刚石中晶格氢进行了UHF法计算,结果表明,空穴吸引1~4个氢原子均可以稳定存在。空穴具有吸引较多氢原子在其周围的倾向,最多可以达到4个氢原子。当空穴吸引1个氢原子时,氢原子倾向于直接存在于碳晶格空穴中,不改变化学键的键长,即以顺磁性氢的状态存在时更为稳定。 相似文献
114.
就进一步探讨定向极小集理论(即定向极小映射β^φ)作了,给出并证明了定向极小映射保持和限并和连续格为完全分配格的一个充分条件。 相似文献
115.
A new simplified modelling strategy to simulate the non‐linear behaviour of reinforced concrete shear walls under dynamic loading is presented. The equivalent reinforced concrete (ERC) model is derived from the framework method and uses lattice meshes for concrete and reinforcement bars and uniaxial constitutive laws based on continuum damage mechanics and plasticity. Results show the capacity of the model to analyse structures having different slenderness and boundary conditions. For low reinforcement ratios however, results are sensitive to the angle formed by the diagonals of the concrete lattice and the horizontal bars. The method is compared with the shear multi‐layered beam model that uses Timoshenko multi‐layered 2D beam elements and biaxial constitutive laws. Comparisons for both models with experimental results of two research programs (one organized by NUPEC and the other by COGEMA and EDF) are provided. ERC is a simplified method that intends to save computer time and allows parametrical studies. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
116.
TEM and XRD determination of crystallite size and lattice strain as a function of illite crystallinity in pelitic rocks 总被引:2,自引:0,他引:2
W.-T. JIANG D. R. PEACOR P. ÁRKAI M. TÓTH & J. W. KIM 《Journal of Metamorphic Geology》1997,15(2):267-281
Average crystallite size and mean-square strain of illite in rock specimens and clay separates were measured independently in TEM images and by single-line Fourier (Voigt method) profile analysis of the c. 1 nm peak of XRD patterns for a prograde sequence of pelitic rocks (illite crystallinity indices=0.17–0.58°Δ2θ) from the Gaspé Peninsula, Quebec. The TEM-determined crystallite sizes in clay separates approximate those determined by Fourier profile analyses and those calculated from illite crystallinity indices by the Scherrer equation, with the exception of the diagenetic sample. The crystallite sizes and mean-square strains of illite in rock samples exhibit a trend similar to that determined by profile analyses, but the average crystallite sizes are up to five times larger than those measured for clay separates. TEM images show that all rock samples have a wide range of crystallite sizes, and the proportions of larger crystallites increase with metamorphic grade. The diagenetic illite is defect-rich, fine-grained (mean thickness by volume=c. 70 nm), 1Md material. Anchizonal illite tends to occur as separate aggregates of small 1Md and larger 2M1 crystals (c. 200 nm), comprising arrays of subparallel coalescing packets. The epizone sample has thick (c. 400 nm), defect-free crystals of muscovite occurring in stacks of parallel layers, or subhedral crystals intergrown with large-angle boundaries. Cleaved crystals that are free of intracrystalline layer terminations are dominant in clay separates of all samples, having ranges of smaller sizes with volume-average thicknesses of c. 43, 43, and 81 nm (c. 14, 28, 67 nm by the Voigt method), respectively, for the three zones. The results suggest that illite crystallinity indices do not provide a direct measure of a single microstructural state of illite in rocks, although they yield consistent limits for average crystallite sizes for the anchizone (23 & 48 nm here). Therefore, they serve as a general parameter of the degree of recrystallization on a relative basis, in part because the contributions of all peak-broadening variables (mixed layering, size and strain) decrease regularly with prograde regional metamorphism of pelites. The microstructural changes caused by rock disaggregation are probably a function of those variables as well. The data collectively demonstrate a trend from metastable, defect-rich, small crystals towards a stable assemblage of larger, defect-free crystals, through dissolution of strained crystals and neocrystallization, consistent with the Ostwald step rule. 相似文献
117.
There are two aspects in the study of irregular mixed-layer clay minerals: one is the kinds and ratios of their basic structural unit layers and the other is the junction probabilities of the unit layers. Irregular mixed-layer illite/smectite clay minerals (I/S) are widespread in nature. While studying the clay minerals from the Permian-Triassic (P/T) boundary bed, the authors found that I/S clay minerals are developed in all P/T boundary clay layers in areas from the northwest to southeast of China. Systematic mineralogical studies of the I/S clay minerals from Hunan, Hubei, Sichuan and Zhejiang were made by means of X-ray, infrared spectroscopic, electron microscopic and chemical analyses and a deepened study of the stacking sequences of their structural unit layers was conducted by the MacEwan one—dimentional direct Fourier transform. It was found that the stacking of the illite and smectite crystal layers along the c axis can be derived from Fibonacci sequences. Hence, the authors propose that such I/S clay minerals are possessed of two—dimentional crystal lattice and one—dimentional quasicrystal lattice. 相似文献
118.
Methods of calculating petrophysical properties from lattice preferred orientation data 总被引:13,自引:0,他引:13
We consider the theoretical problems of calculating the physical properties of an aggregate from the constituent crystal properties and the lattice preferred orientation. The notion of a macroscopically homogeneous sample with an internally varing distribution of stress and strain fields is introduced to explain why further efforts have to be made to improve on the physically based Voigt and Reuss bounds. It is shown that the Voigt and Reuss bounds become increasingly separated with inceasing anisotropy, emphasising the need for better methods. The problem of highly anisotropic minerals is illustrated with polycrystals of plagioclase feldspar and biotite. Biotite is used to illustrate the mean velocity, the geometric mean and the self-consistent methods. The self-consistent method, which is generally accepted to give the best estimate, is almost identical to geometric mean recently introduced by Matthies and Humbert (1993) and similar to the arithmetic mean of the Voigt and Reuss bounds (Hill, 1952). The geometric mean has the powerful physical condition that the aggregate mean is equal to the mean of the inverse property (e.g. mean elastic stiffness and compliance). Despite its lack of theoretical justification the Hill average remains a useful estimate. 相似文献
119.
凯威特型索承网壳结构的自振特性及参数分析 总被引:4,自引:0,他引:4
索承网壳结构是由单层球面网壳和去掉上层索的张拉整体结构组成的一种跨越能力大、经济合理的新型杂交空间结构。选用梁元、杆元和索元的混合有限元模型,采用分块Lanczos法,对凯威特型索承网壳结构的自振特性及其影响因素进行了系统分析研究,并与单层网壳结构进行比较,得出了可用于工程实践的结论,对其抗震、抗风性能分析研究以及工程应用有参考价值。 相似文献
120.