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991.
992.
Using the superposition model in conjunction with our crystal field analysis package recently developed for 3d ions doped at arbitrary low symmetry sites in crystals, the energy levels and statevectors have been predicted within the whole 3d 3 configuration of Cr3+ at the four possible triclinic sites in kyanite (Al2O3∶SiO2). The values of the ground state zero-field splitting for each of the four Al sites are evaluated. The splittings of the lower excited state 2 E as well as the admixture of 4 T 2 state into 2 E have also been determined. The predicted results are compared with the available experimental data on the four possible, but so far not uniquely identified, substitutional Cr3+ sites in kyanite thus enabling correlation of the spectroscopic properties and substitutional sites. 相似文献
993.
994.
坨里组主要分布在北京西山坨里-大灰厂白垩纪沉积盆地的西部或西南部。是一套以砾岩为主的陆相碎屑沉积。含有丰富的动、植物及孢子花粉化石。孢粉组合是以Cicatricosisporites-Densois-porites-classopollis为代表,它们在组合中具有较高的含量,类型丰富多彩。根据组合中孢子和花粉的地层分布及国内外孢粉组合比较,定其时代为早白垩世早中期(凡兰吟—戈特里夫期)。气候为半干旱—干旱的热带。亚热带。 相似文献
995.
The existence of nonhydrostatic high-degree harmonics in the gravitational field of the earth has recently been determined using satellite and gravity observations. In this paper, we have applied the Goddard Space Flight Center GEM-8 gravity field model to calculate the small-scale mantle flow system under the Pacific plate. The resulting tectonic forces or stresses exerted by the flow currents show tensional forces under the Hawaiian Island chain and a system of latitudinal convection rolls under the East Pacific plate and are in agreement with geophysical theories. 相似文献
996.
Petrographic observations and analyses of CM matrices are consistent with their origin as in situ low temperature (<400°K) aqueous alteration products in a parent body regolith. At least four different phyllosilicates were tentatively characterized in Murray and Murchison meteorites, in addition to Fe- and Mg-serpentines in Nogoya. In comparison with bulk meteorite compositions, all phyllosilicates and bulk matrices show enrichment of K relative to Na. Possible loss of Na and possibly some Cl, with addition of H2O and CO2 and water-soluble organic compounds during alteration, indicates a partially open system during alteration. Poorly characterized phases (PCP) are fine-grained (< 1 μm) admixtures of variable proportions of phyllosilicates, carbonaceous matter and opaque oxides of sulfur with high Fe, Ni and Cr contents. Calcite and some magnetite show paragenetic overlap with PCP and phyllosilicates. Carbonaceous matter is largely associated with PCP in altered CM matrices. In the unaltered CV Allende, carbonaceous matter is concentrated on olivine surfaces as a micromounded coating, particularly in the dark haloes that surround some chondrules and aggregates. Precursive alteration material may have been analogous to similarly coated olivine mixed with smaller amounts of metal and sulfides.Synthesis of the water soluble organic compounds found in CM matrices may have occurred prior to or in the same environment as did aqueous alteration of the precursive phases. Preservation or partial preservation of this organic matter may reflect the degree of overlap in episodes of synthesis and alteration.Nogoya is 95% altered and has a bulk carbon content of 5.2 wt%, which is higher than any meteorite. In addition, it has the lowest measured ratio of any other carbonaceous chondrite, except for Karoonda. 相似文献
997.
An economical approach was developed to examine the effect of radiation damping on earthquake response of pilesupported offshore platforms. Parameteric studies were conducted to evaluate the effects of radiation damping on response. Various features of this effect were found for pile head stiffnesses, and responses of platforms subjected to harmonic and earthquake excitations. 相似文献
998.
999.
Equations are proposed which describe the diffusion of a plume of oil from chemically dispersed oil slicks into the oceanic water column and which yield estimates of oil concentration as a function of the volume of oil dispersed, time-varying plume area, depth, time, and as a function of a single adjustable parameter, vertical diffusivity. A ‘diffusion floor’ at any desired depth may be included. Experimental data were fitted to the equations to yield an estimate of this diffusivity. It is concluded that oil concentrations can be estimated with a mean error of a factor of three, this high value being attributable to the inherently variable nature of the oceanic diffusion processes. Implications for assessing the toxic effects of dispersed slicks are discussed. It may be possible to calculate acute median lethal water depths and volumes for given organisms subjected to given dispersed oil slicks. 相似文献
1000.
Mark K. Chang Jan W. Kwiatkowski Robert F. Nau Robert M. Oliver Karl S. Pister 《地震工程与结构动力学》1982,10(5):651-662
This paper outlines the use of discrete, autoregressive/moving-average (ARMA) models for identification and estimation of parameters in models derived from analysis of uniformly digitized earthquake ground motion acceleration data. Such models are of equal generality as compared to continuous-time models and have a number of significant advantages for purposes of digital analysis and simulation. The structure of ARMA models is briefly described, their relation to continuous models noted, and results of their application to a number of recorded accelerograms summarized. 相似文献