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A.-M.M. Abdel-Rahman 《Astrophysics and Space Science》2001,278(4):385-385
We investigate the effects of gravitational lensing in a modified generalrelativity flat cosmological model. We show that the predicted lensingprobability for low matter densities is larger than in the Einstein-deSitter model but considerably less than in constant- models. Wealso find that the optical depth at low density rises with the sourcered-shift more slowly than in constant- models and that the lensdistribution peaks at lower values of the lens red-shift. 相似文献
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A. Deif Azza Abed Kamal Abdel-Rahman Enayat Abdel Moneim 《Arabian Journal of Geosciences》2011,4(5-6):855-861
Recent and paleo seismicity indicate that moderate seismic activity is relatively large for Aswan area. This is a warning on the possibility of occurrence of earthquakes in the future too. No strong motion records are available in Aswan area for engineers to rely upon. Consequently, the seismological modeling is an alternative approach till sufficient instrumental records around Aswan become available. In the present study, we have developed new ground motion attenuation relationship for events spanning 4.0?≤? M w?≤?7.0 and distance to the surface projection of the fault up to 100 km for Aswan based on a statistically simulated seismological model. We generated suites of ground motion time histories using stochastic technique. The ground motion attenuation relation describes the dependence of the strength of the ground motions on the earthquake magnitude and distance from the earthquake. The proposed equation for peak ground acceleration (PGA) for the bed rock is in the form of: $ {\mathbf{log}}{\text{ }}\left( {{\mathbf{PGA}}/{\mathbf{gal}}} \right){\text{ }} = {\mathbf{1}}.{\mathbf{24}} + {\mathbf{0}}.{\mathbf{358}}{M_{\mathbf{w}}} - {\text{ }}{\mathbf{log}}\left( {\mathbf{R}} \right){\text{ }}-{\text{ }}{\mathbf{0}}.{\mathbf{008}}{\text{ }}{\mathbf{R}}{\text{ }} + {\text{ }}{\mathbf{0}}.{\mathbf{22}}{\text{ }}{\mathbf{P}} $ . Where PGA is the peak ground acceleration in gal (cm/s2); Mw, its moment magnitude; R is the closest distance between the rupture projection and the site of interest; and the factor P is a dummy variable. It is observed that attenuation of strong motion in Aswan is correlated with those used before in Egypt. 相似文献
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Yu-Shiu Chen Yu-Shu Kuo Wen-Chi Lai Yuan-Jung Tsai Shin-Ping Lee Kun-Ting Chen Chjeng-Lun Shieh 《山地科学学报》2011,8(4):571-581
Climate change has altered locally single-type disasters to large-scale compound disasters because of increasing intensity
and frequency of extreme rainfall events. The compound disasters can combine small-scale floods, debris flows, shallow landslides,
deep-seated landslides, and landslide lakes into a large-scale single disaster event. Although simulation models and evaluation
tools are available for single-type disasters, no single model is well developed for compound disasters due to the difficulty
of handling the interrelationship between two successive single-type disasters. This study proposes a structure for linking
available single-type simulation models to evaluate compound disasters and provides a useful tool of decision making for warning
and planning of disaster reduction. 相似文献
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Ashraf Emam Zakaria Hamimi Abdelhamid El-Fakharani Ezzat Abdel-Rahman Juan Gomez Barreiro Mohammed Y. Abo-Soliman 《Arabian Journal of Geosciences》2018,11(23):756
Lithological discrimination of Neoproterozoic rocks occupying Nugrus-Hafafit area, South Eastern Desert of Egypt, has been carried out using Operational Land Imager (OLI) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensors’ imagery data. The applicable processing enhancement techniques include optimum index factor (OIF), band ratioing, principal component analysis (PCA), and minimum noise fraction (MNF) transform. The area comprises varieties of low-grade metamorphosed ophiolitic mélange and island-arc rocks, thrusting over high-grade metamorphic gneissic core complexes, and intruded by syn-, late-, and post-tectonic granitoids. The OLI band ratio 6/7 discriminates clearly the ophiolitic serpentinites-talc-carbonate rocks, while 4/5 ratio image is able to separate between mafic and felsic rocks. Moreover, the ASTER band ratio 6/8 is used to distinguish the amphibole-bearing rocks, including amphibolite and hornblende gneiss. The OLI and ASTER second principal component (PC2) images reflect the contrast spectral behavior of ophiolitic mélange rocks through visible-near-infrared (VNIR) and shortwave (SWIR) regions. The OLI-PC3 shows the ability to delineate the Fe-rich rocks, including amphibolite and metamafics, while ASTER-PC3 is effective for quartz-feldspathic granites and psammitic gneisses. Visual interpretation and integration of processed data with petrography and field investigation resulted in complete differentiation for the different lithologies and creation of a new detailed geological map of Nugrus-Hafafit area. 相似文献
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依据水平风矢量场的分解思路,应用调和-余弦的二维风场分解方法,对水平风场的加速度迁移项也进行调和-余弦的分解,引入加速度迁移项位势概念,用加速度迁移项对应的位势分量部分对东移高原低涡及登陆台风系统的演变过程进行分析.结果表明:加速度迁移项位势对东移高原低涡系统有较好的描述作用.利用加速度迁移项位势追踪东移的高原低涡系统比常用的500 hPa位势高度场对低涡进行追踪更为清晰.此外,加速度迁移项位势在登陆台风Bilis的分析中也有较好的应用,可用以指示台风系统,判断台风中心的位置以及表示台风强度的变化.由于加速度迁移项位势可反映出水平风场平流的辐合辐散特征,因此对低涡及台风等与平流场的辐合辐散关系密切的天气系统的动力结构有较好的识别能力,可以作为一个新的动力诊断变量来诊断示踪天气系统的演变. 相似文献
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2006年7月19-24日,东北地区出现一次明显的冷涡发展导致强降水的过程.对这次东北冷涡过程的天气形势分析表明,该东北冷涡的维持和发展与冷涡东部阻塞高压的建立与消亡有关.本文根据500 hPa环流形势演变特征,将东北冷涡发生发展过程分为4个阶段,并借助调和-余弦谱展开方法,对东北冷涡各阶段850 hPa水平风和水汽通量进行无辐散和无旋转分量分解,分析各阶段无旋转风动能和无辐散风动能之间的能量转化.研究结果表明,分解得到的无辐散风及其水汽通量清楚地展现出了东北冷涡的大尺度环流和水汽输送通道及水汽来源,而从无旋转风及其水汽通量上则可以直观地看到冷涡低层的中小尺度风场及水汽辐合辐散区,为分析东北冷涡内部对流提供帮助.东北冷涡发展的不同阶段其水汽来源有所不同,初始阶段的水汽主要来自黄海和渤海地区,发展阶段水汽主要来自日本海,而到成熟阶段和减弱阶段,水汽输送通道被破坏,冷涡的水汽供应大大减少,与同时期暴雨减弱一致.同时,无旋转风辐合强值区和无旋转风水汽通量大值区的重合区域有利于强对流的发生发展,表现为重合区与TBB(Temperature of Black Body,黑体辐射温度)强对流云带的形状和位置对应良好,与降水落区也较为一致,可为预报东北冷涡引发的强降水落区这一预报难点问题提供参考.从动能转化上看,无旋转风和无辐散风的动能转化项能很好地反映东北冷涡整个生命史过程中各阶段强度的变化特点,对冷涡强度预报具有一定的指示意义. 相似文献
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利用气候倾向率、标准偏差方法,划分基准年研究1952-2010年辽宁西部地面、耕作层温度变化特征。结果表明：辽宁西部年平均地面温度、农作物生长季地面和耕作层温度呈升高趋势,气候倾向率分别为0.395℃/10a、0.304℃/10a、0.206℃/10a。冬季、春季对年平均地面温度升高贡献最大,气候倾向率为0.535℃/10a、0.521℃/10a;夏季、秋季贡献较小,气候倾向率为0.223℃/10a、0.291℃/10a。第Ⅲ基准年升温最剧烈。研究结果可为该地区农业生产结构调整、生态环境治理等提供参考。 相似文献
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Kamal Abdel-Rahman Abd El-Aziz Khairy Abd El-Aal S. M. El-Hady A. A. Mohamed Enayat Abdel-Moniem 《Arabian Journal of Geosciences》2012,5(4):653-661
The horizontal-to-vertical spectral ratio technique has applied to detect the fundamental frequency at the sites of ambient noise recordings for New Domiat city. Noise measurements are acquired at 90 of sites for 1?h of continuous recording with a sampling rate of 100?Hz. Then, these data are processed following to SESAME project scheme. The presence of deep sedimentary basin in the Nile Delta suggests that the site response should be important. Consequently, the obtained fundamental frequency has lower values (0.2?C0.6?Hz). However, low-frequency ground motions attenuate more gradually with distance and can excite vibrations in large engineered structures, such as tall buildings and long bridges. There is hazardous threat even from the distant earthquakes originated from Mediterranean convergence zone for the structures in the city. It is recommended that the results of this study must be taken into consideration from civil engineering point of view before construction of civil engineering structures at this part. 相似文献