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本文简要回顾了二十世纪五、六十年代就矿找矿的历史,进而提出新一轮的就矿找矿。相比之下,新一轮就矿找矿具有新的特点。深部找矿实则是一种就矿找矿,地壳连续成矿理论、深部流体(成矿)作用理论、成矿台阶理论都为新一轮就矿找矿提供了理论依据。深部找矿在国内外初显成效,湘中地区亦有很多成功案例。本文从3个方面总结了深部找矿的一些经验标志,即矿种及矿种组合系列标志、花岗岩成矿专属性标志、幔源成因矿床的鉴别标志。此外,辨别成矿流体的深(幔)源标志、加强成矿规律研究、更新观念、引进新技术新方法,都是实际深部找矿工作中需要注意的。 相似文献
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Study on Probability Distributions of Multi-Timescale Aerosol Optical
Depth Using AERONET Data 下载免费PDF全文
The probability distribution analysis is per-formed for multi-timescale aerosol optical depth (AOD) using AErosol RObotic NETwork (AERONET) level 2.0 data.The maximum likelihood estimation is employed to determine the best-fit probability density function (PDF),and the statement that the fitting Weibull distribution will be light-tailed is proved true for these AOD samples.The best-fit PDF results for multi-site data show that the PDF of AOD samples with longer timescale in most sites tends to be stably represented by lognormal distribution,while Weibull distribution is a better fit for AOD samples with short timescales.The reason for this difference is ana-lyzed through tail characteristics of the two distributions,and an indicator for the selection between Weibull and lognormal distributions is suggested and validated.The result of this research is helpful for determining the most accurate AOD statistics for a given site and a given time-scale and for validating the retrieved AOD through its PDF. 相似文献
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Because a conventional isolation system with constant isolation frequency is usually a long‐period dynamic system, its seismic response is likely to be amplified in earthquakes with strong long‐period wave components, such as near‐fault ground motions. Seismic isolators with variable mechanical properties may provide a promising solution to alleviate this problem. To this end, in this work sliding isolators with variable curvature (SIVC) were studied experimentally. An SIVC isolator is similar to a friction pendulum system (FPS) isolator, except that its sliding surface has variable curvature rather being spherical. As a result, the SIVC's isolation stiffness that is proportional to the curvature becomes a function of the isolator displacement. By appropriately designing the geometry of the sliding surface, the SIVC is able to possess favorable hysteretic behavior. In order to prove the applicability of the SIVC concept, several prototype SIVC isolators, whose sliding surfaces are defined by a sixth‐order polynomial function, were fabricated and tested in this study. A cyclic element test on the prototype SIVC isolators and a shaking table test on an SIVC isolated steel frame were all conducted. The results of both tests have verified that the prototype SIVC isolators do indeed have the hysteretic property of variable stiffness as prescribed by the derived formulas in this study. Moreover, it is also demonstrated that the proposed SIVC is able to effectively reduce the isolator drift in a near‐fault earthquake with strong long‐period components, as compared with that of an FPS system with the same friction coefficient. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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