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选取中国东部1961—2012年夏季5—9月无缺测429站逐日降水资料,利用广义帕雷托分布(GPD)拟合,研究中国东部52 a以及El Nio发展年和衰减年极端降水的统计特征,并分析其成因。结果表明:1)中国东部降水阈值呈由东南向西北递减的态势,且基本为线性增加趋势。2)华南地区尺度参数最大,出现极端降水的概率大。黄河以南地区尺度参数变化趋势正值较多,出现极端降水的概率增加。3)El Nio发展年夏季,西太平洋上有气旋环流异常,中国东南部受气旋西侧的异常偏北气流影响,多地阈值偏小,只有福建东南部及黑龙江中西部易发生破纪录的极端降水。4)El Nio衰减年夏季,西太平洋上为异常反气旋环流,中国东南部受反气旋西侧的异常偏南气流影响,多地阈值偏大,广东中东部及皖鄂赣交界处发生洪涝灾害的可能性增大。 相似文献
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Based on the theory of gravity‐driven groundwater flow systems, we have developed a complex Flow System Sand‐Box Model (FSM). It enables the visual observations of the development and characteristics and temporal evolution of complex Tóthian flow systems in the laboratory. The configuration of the regional, intermediate and local flow systems can be controlled and observed; hydraulic head, flow direction and travel time can be measured; and the scale and shape of the sub‐flow systems as well as the path lines and flow lines can be observed directly. The experiments demonstrate the Tóthian flow systems in a small basin with multiple sources and sinks. Greater local topographic (water table) undulation will lead to larger local flow systems. Greater regional and less local topographic undulation will enhance the development of intermediate and regional flow systems. In homogeneous media, increasing fluid‐potential differences between source and sink increase the spatial scale of the generated flow systems. The FSM is a useful teaching aid and experimental device to study and develop an intuitive insight into gravity‐driven groundwater flow systems. It helps to visualize and understand the hydraulic properties and controlling factors of Tóthian flow systems and may be used to study problems related to the chemical and temperature characteristics of the flow systems as well. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Re–Os and U–Pb Geochronology of Porphyry and Skarn Types Copper Deposits in Jilin Province,NE China 下载免费PDF全文
Yong Zhang Shu–Wen Xing Quan–Heng Song Yan Wang Zheng–Tao Yu Xiao–Hui Du Yu–Bo Ma Zeng–Jie Zhang 《Resource Geology》2015,65(4):394-404
Jilin Province in NE China lies on the eastern edge of the Xing–Meng Orogenic Belt. Mineral exploration in this area has resulted in the discovery of numerous large, medium, and small sized Cu, Mo, Au, and Co deposits. To better understand the formation and distribution of both the porphyry and skarn types Cu deposits of the region, we examined the geological characteristics of the deposits and applied zircon U–Pb and molybdenite Re–Os isotope dating to constrain the age of the mineralization. The Binghugou Cu deposit yields a zircon U–Pb age for quartz diorite of 128.1 ± 1.6 Ma; the Chang'anpu Cu deposit yields a zircon U–Pb age for granite porphyry of 117.0 ± 1.4 Ma; the Ermi Cu deposit yields a zircon U–Pb age for granite porphyry of 96.8 ± 1.1 Ma; the Tongshan Cu deposit yields molybdenite Re–Os model ages of 128.7 to 130.2 Ma, an isochron age of 129.0 ± 1.6 Ma, and a weighted mean model age of 129.2 ± 0.7 Ma; and the Tianhexing Cu deposit yields molybdenite Re–Os model ages of 113.9 to 115.2 Ma, an isochron age of 114.7 ± 1.2 Ma, and a weighted mean model age of 114.7 ± 0.7 Ma. The new ages, combined with existing geochronology data, show that intense porphyry and skarn types Cu mineralization was coeval with Cretaceous magmatism. The geotectonic processes responsible for the genesis of the Cu mineralization were probably related to lithospheric thinning. By analyzing the accumulated molybdenite Re–Os, zircon U–Pb, and Ar–Ar ages for NE China, it is concluded that the Cu deposits formed during multiple events coinciding with periods of magmatic activity. We have identified five phases of mineralization: early Paleozoic (~476 Ma), late Paleozoic (286.5–273.6 Ma), early Mesozoic (~228.7 Ma), Jurassic (194.8–137.1 Ma), and Cretaceous (131.2–96.8 Ma). Although Cu deposits formed during each phase, most of the Cu mineralization occurred during the Cretaceous. 相似文献
995.
金刚石生长阶段所捕虏的不纯净组分,能够提供大量地幔流体的信息。本文从金刚石的成因研究,表征地幔流体的固体包裹体、流体包裹体及流体的制药因素等方面讨论了金刚石不纯净组分与地幔流体的关系。 相似文献
996.
Maritime network dynamics before and after international events 总被引:1,自引:0,他引:1
Investigating the influence of international events on global maritime networks is a challenging task that must comprehensively incorporate geographical, political, and maritime sciences. Understanding global maritime network dynamics is an initial and critical step in this investigation. This study proposes an automatic identification system (AIS)-based approach to understanding maritime network dynamics before and after international events. In this approach, a spatiotemporal modeling method is introduced to measure the similarity in shipping trends before and after international events. Then, a spatiotemporal analytic framework is proposed to understand the maritime network dynamics by grouping similar situation, and assessing possible indirect effects within a network. Finally, three case studies of international events, military conflict, lifted economic sanctions, and government elections, were used to investigate the observed network dynamics possibly affected by international events. The results indicate that container, tanker, and bulk shipping between India and its connected countries all declined more than 69% after military conflicts between India and Pakistan in August 2015. Tanker shipping between Iran and the United Arab Emirates increased 51% after economic sanctions on Iran were lifted. Container shipping between Sri Lanka and Singapore, Malaysia, and India increased more than 74% after the general election in Sri Lanka. These investigations demonstrate the feasibility of the proposed approach in assessing the possible effects of international events on maritime network dynamics. 相似文献
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