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881.
882.
C. J. Soares S. Guedes R. Jonckheere J. C. Hadler S. M. Passarella A. N. C. Dias 《Geological Journal》2016,51(5):805-810
This work presents fission‐track ages and thermal history modelling of apatite samples from two Brazilian alkaline formations: Alto Paranaíba and Ponta Grossa Arches. The apatite fission‐track ages obtained for Alto Paranaíba Arch agree with those determined by other radiometric dating methods presenting higher closure temperatures. The ages given by the fission‐track thermochronometer suggest that no strong tectonic event has occurred after Alto Paranaíba Formation during Upper Cretaceous. This event is also supported by thermal history modelling of this arch, which is characterized by fast cooling followed by residence at lower temperatures. On the other hand, apatite fission‐track ages from Ponta Grossa Arch are systematically lower than other radiometric ages, suggesting that at least one tectonic event occurred after Ponta Grossa Formation, around 130 Ma. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
883.
根据台风路径数据,通过计算评价单元内不同强度台风灾害发生频数和路径长度,综合表征台风孕灾环境敏感性的大小。结果表明:1)在四个强度台风条件下,敏感性最高的区域位于海南省、广东省沿海、福建省和浙江省沿海,随着台风灾害强度增强,影响范围呈现向北、向内陆延伸、扩展的趋势;2)台风灾害强度达到中度时,高敏感性的区域减少,低敏感性的区域面积大幅度增加,同时,台风路径东移明显,福建所受影响加重,海南和广东影响有所减小。 相似文献
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885.
An objective prediction approach to the 6 h-144 h track and intensity of tropical cyclones over the northwestern Pacific is proposed. On the basis of both analog deviation technique and completed historical sample curve library, the track or intensity prediction for each forecast period are determined respectively through the optimum weighted superposition of displacement or intensity change of the cases, with different number and weighted coefficient corresponding to minimal analog deviation, from different tropical cyclone or different stage of the same cyclone. so that the prediction results for both forecast period and entire process are optimal. The verification suggests that the approach exhibits better forecast performance than other previous forecast methods by having remarkable decreasing forecast errors in short-and medium-range forecast of both track and intensity,and that the approach can also be used to predict effectively the decay process of tropical cyclone and is able to predict anomalous track and tropical depression. 相似文献
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The uplifting process of the Bogda Mountain during the Cenozoic and its tectonic implication 总被引:1,自引:0,他引:1
The Tianshan Mountains have undergone its initial orogeny, extension adjusting and re-orogeny since the Late Paleozoic. The re-orogeny and uplifting process of the orogeny in the Mesozoic and Cenozoic are two of most important events in the geological evolution of Euro-Asian continent, which resulted in the formation of the present range-and-basin pattern in topography of the Tianshan Mountains and its adjacent areas. Thermochronology results by the method of fission-track dating of apatite suggest three obvious uplifting stages of the Bogad Mountain Chain re-orogeny during the Cenozoic, i.e. 5.6-19 Ma, 20-30 Ma, and 42-47 Ma. The strongest uplifting stage of the mountain is the second one at 20 -30 Ma, when the mountain uplifted as a whole, and the beginning of re-orogeny was no less than 65 Ma. Furthermore, our studies also show that the uplifting types of the mountain are variable in the dif-ferent time periods, including uplifting of mountain as a whole and differential uplifting. The apparently diversified uplifting processes of the mountain chain are characterized by the migration (or transfor-mation) of the uplifting direction of the mountain from west to east and from north to south, and the main process of mountain extending is from north to south. 相似文献
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890.
Dynamic response of high-speed ballasted railway tracks: 3D periodic model and in situ measurements 总被引:2,自引:0,他引:2
A three-dimensional (3D) model for the soil–railway track system is proposed. It is based on a geometrical periodic hypothesis. The dynamic soil–structure interaction is taken into account. This representation is used for the case of a ballasted railway track subjected to high-speed moving loads and a new formulation of dynamic responses of the system is proposed. Moreover, recent in situ measurements performed in a high-speed line of the North of France are presented. Lateral and vertical accelerations in several locations of the railway track have been measured and the periodic model is confronted with these records. 相似文献