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401.
中国泛滥平原沉积物中铂,钯丰度值及地球化学省的初步研究 总被引:29,自引:5,他引:24
根据中国泛滥平原沉积物中Pt、Pd的分析结果,求得泛监平原沉积物中的Pt、Pd近似丰度值分别为0.46ng/g和0.40ng/g。据泛监平原沉积物中Pt、Pd的空间分布模式初步圈出滇黔Pt、Pd地球化学省,新疆Pt、Pd地球化学省和西藏雅布江Pt、Pd地球化学省。 相似文献
402.
403.
黔西南铊矿床(点)赋矿地层中成矿元素的若干地球化学问题研究 总被引:11,自引:0,他引:11
本文以地球化学过程基本定律为指导,根据区域和矿区外围八条剖面169件样品的分析数据,采用柯尔莫各洛夫非参数正态检验法,对黔西南铊矿床(点)赋矿地层中成矿元素Tl、Au、Hg、Sb、As、Pb、Zn的丰度值进行了研究。 相似文献
404.
研究了GIS技术在城市雨水管网设计中的应用问题,建立了雨水管网设计的相关模型,重点分析了两类直接影响雨水管网工程的计算模型——水力优化计算与指标再优化模型 相似文献
405.
The Barrell and Sears and Edlen formulae use the Sellmeier form away from resonances, which gives a “smooth” dependence within
the visible and near-infrared spectra. All known atlases indicate numerous resonances in these regions, which cause local
disturbance of the dispersion curve. Anomalous dispersion may be estimated from an absorption by the Kramer-Kronig ratios.
It gives a change of phase refractive index of air in a range from several ppt to 1 ppb within narrow optical regions, causing
large local dispersions. Computation of the group refractive index with the use of Rayleigh's ratio shows that the influence
of resonance effects may be more than several ppm. For example, the error of the group refractive index for high-precision
EDM using HeNe lasers (633 nm) varies between 0.2 and 0.7 ppm, depending on the laser stability.
Received: 17 July 1996 / Accepted: 27 March 1997 相似文献
406.
The following equation is proposed in this paper to estimate the crustal growth rate of the North China Platform on the basis
of mass equilibrium between the crust and the mantle:
相似文献
407.
ZHONG Ningning Lu Shuangfang HUANG ZHILONG Zhang Yousheng XUE Haitao PAN Changchun 《中国科学D辑(英文版)》2004,47(Z2)
Through geological observation, simulation in laboratory and numerical modeling, the factors that control the changes in total organic content (TOC) of source rock have been studied. When the formula DTOC=(TOC0-TOC)/TOC0 (original organic carbon content in the rock) is used to measure the TOC (total organic carbon content) changes in the source rock through geological time, the degrees and directions of such changes are determined by losses and relative amounts both of organic and inorganic matter in the source rock. The DTOC equation, which is used to calculate the loss rate in the process of maturation for the source rock, is therefore obtained by analyzing the mass balance relations. For a certain type of source rock with a certain maturation history, the changes of its TOC respond only to the rates of hydrocarbon generation and expulsion. In actual cases of geological entities, DTOC generally ranges from -0.05 to 0.2, while the calculated reconversion coefficient (k) for organic carbon content remains between 0.90 and 1.25. Only in an ideal situation where there are extremely high rates of hydrocarbon generation and expulsion can the DTOC value experience significant changes, with k reaching up to 2.5. It is concluded, therefore, that the criterion for carbonates source rock assessment, based on reconverting the TOC to the value of its original state, may have overestimated the course of the "carbon-reduction", which is likely in many cases to make a poor source rock sound better. 相似文献
408.
Ribera P. Gimeno L. Gallego D. García-Herrera R. Hernández E. de la Torre L. Nieto R. Calvo N. 《Studia Geophysica et Geodaetica》2004,48(2):447-458
Two different groups of indices have been defined to analyze the evolution of global temperature between 1958 and 1998. All the indices were evaluated at three different levels (850, 500 and 200 hPa), and averaged indices were calculated using the whole globe, continental areas and oceanic areas. The first group of indices analyzes the area of the world covered with higher and lower than normal temperatures, detecting a slight cooling in the 200 hPa level. The second group of indices studies the annual frequency of extreme events, and again, it is at 200 hPa where the most intense variation is detected. Finally, an analysis is performed to determine the regions most sensible to variations in the occurrence of extreme events. Tropical areas are mostly responsible of the variations detected in the second group of indices. 相似文献
409.
利用历史天气图资料,统计1960~2002年共42a桂林市10月暴雨天气过程,分析其影响天气系统环流特征及演变规律,分类建立预报模式指标,为10月暴雨实时预报业务提供一些参考。 相似文献
410.
Fragility curves are found to be useful tools for predicting the extent of probable damage. They show the probability of highway structure damage as a function of strong motion parameters, and they allow the estimation of a level of damage probability for a known ground motion index. In this study, an analytical approach was adopted to develop the fragility curves for highway bridges based on numerical simulation. Four typical RC bridge piers and two RC bridge structures were considered, of which one was a non‐isolated system and the other was an isolated system, and they were designed according to the seismic design code in Japan. From a total of 250 strong motion records, selected from Japan, the United States, and Taiwan, non‐linear time history analyses were performed, and the damage indices for the bridge structures were obtained. Using the damage indices and ground motion parameters, fragility curves for the four bridge piers and the two bridge structures were constructed assuming a lognormal distribution. It was found that there was a significant effect on the fragility curves due to the variation of structural parameters. The relationship between the fragility curve parameters and the over‐strength ratio of the structures was also obtained by performing a linear regression analysis. It was observed that the fragility curve parameters showed a strong correlation with the over‐strength ratio of the structures. Based on the observed correlation between the fragility curve parameters and the over‐strength ratio of the structures, a simplified method was developed to construct the fragility curves for highway bridges using 30 non‐isolated bridge models. The simplified method may be a very useful tool to construct the fragility curves for non‐isolated highway bridges in Japan, which fall within the same group and have similar characteristics. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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