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Subrata K. Chakrabarti 《Ocean Engineering》1999,26(10):446
Breakwaters are often built in coastal waters to facilitate navigation and recreation, both inside and outside regions of the breakwater. This requires that the reflection and transmission characteristics of the structure be both minimized at the same time. This is achieved by a design that will allow dissipation of wave energy by multiple reflection. Such structures will need the knowledge of these characteristics in their design. Model tests were performed on a shallow water breakwater concept of this type to determine the reflection and transmission coefficients. The concept of the breakwater was to reduce both the reflection and transmission of waves. It was found that the breakwater design was effective at certain wave characteristics. Nondimensional loads and local pressures on the breakwater panels are also reported which will facilitate the structural design of such breakwaters. 相似文献
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对1∶250万重力异常向上延拓不同高度并分别计算135°方向水平导数,德尔布干断裂表现为北东向延伸的重力场分界线,采用基于DCT法欧拉反褶积对1∶10万高精度重磁数据向上延拓0~20 km追踪断裂轨迹,并进行1∶100万大地电磁测深反演和海拉尔盆地地震剖面解释,识别出德尔布干断裂具有向南东倾斜,切割深度至下地壳的特征.结合实测地质剖面和显微构造研究,认为德尔布干断裂的构造属性不是地块之间和不同时期造山带之间的拼接带,而是在晚侏罗世-早白垩世切割至下地壳北东向延伸的大型伸展变形带,也是晚中生代隆起区与根河-拉不大林-海拉尔盆地之间的控盆边界断裂带. 相似文献
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隧道地质超前预报在隧道施工开挖中起着关键性作用,同时也是工程地球物理界所面临的一大技术难题.本文回顾了我国主要隧道地质超前预报技术(隧道地震预报系统、水平声波剖面法、陆地声纳法、地质雷达法、红外探水法、超前钻探法和超前平导法)的历史,介绍了它们近年来的研究进展;分析了其现状及在几何结构成像、物性结构反演成像和复杂地质体结构探测中存在的不足;指出了当前亟待解决的基础理论研究、正反演研究、多参数综合利用、建立三维可视化的预测预警系统等问题并提出了解决这些问题的基本设想. 相似文献
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William Bosworth 《International Journal of Earth Sciences》1994,83(4):671-688
Large areas of north-east Africa were dominated by regional extension in the Late Phanerozoic. Widespread rifting occurred in the Late Jurassic, with regional extension culminating in the Cretaceous and resulting in the greatest areal extent and degree of interconnection of the west, central and north African rift systems. Basin reactivation continued in the Paleocene and Eocene and new rifts probably formed in the Red Sea and western Kenya. In the Oligocene and Early Miocene, rifts in Kenya, Ethiopia and the Red Sea linked and expanded to form the new east African rift system.This complex history of rifting resulted in failed rift basins with low to high strain geometries, a range of associated volcanism and varying degrees of interaction with older structures. One system, the Red Sea rift, has partially attained active seafloor spreading. From a comparison of these basins, a general model of three-dimensional rift evolution is proposed. Asymmetrical crustal geometries dominated the early phases of these basins, accompanied by low angle normal faulting that has been observed at least locally in outcrop. As rifting progressed, the original fault and basin forms were modified to produce larger, more through-going structures. Some basins were abandoned, others experienced reversals in regional dip and, in general, extension and subsidence became focused along narrower zones near the rift axes. The final transition to oceanic spreading was accomplished in the Red Sea by a change to high angle, planar normal faulting and diffuse dike injection, followed by the organization of an axial magma chamber. 相似文献
56.
During the evolution of continents, compressive tectonic phases can leave certain tectonic patterns in the lithosphere to be observed by reflection seismology. Also, in the area of the trans-European suture zone (TESZ) in the Baltic Sea, several relatively short, but occasionally strong, compressive phases have left their marks in the lithosphere in form of characteristic fault and thrust zones in the rigid parts of crust and mantle, especially clear and well investigated in some sediment troughs. At depth, interwedging processes seem to be generated by colliding tectonic units with different rheology, creating bi-vergent fault structures, possibly—but not necessarily—initiated by a previous subduction of intervening oceanic lithosphere. Near the surface, reactivation and inversion of previous faults are very selective. Transpressional processes and the reduced friction inside the faults are suggested to play a major role. It is assumed that the transfer of plate boundary stressed over long distances is performed mainly through the thick and rigid mantle lid, not through the thin, rigid, and heterogeneous upper crust. This assumption involves mechanisms of a vertical transfer of stresses from the mantle into the inversion area, and some signs of such a process are seen around the Tornquist Zone (TZ). Several examples of compressive transfer of stresses are shown. 相似文献
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Cobalt and its compounds have a broad field of application in Russian industries, being essential raw materials for metallurgy, medicine, and agriculture. That is why the production of cobalt is one of the key industries in Russia. Cobalt is produced from mineral raw materials as well as from secondary raw materials (for example, after processing of spent catalysts of oil refinery). It can also be obtained as a by‐product of nickel, manganese, and some other metals processing. That is the reason why the solutions of Ni and Mn industries contain up to 50 g/L of cobalt. obalt compounds are harmful for men’s heart, bloodvessel system, and thyroid gland. This fact explains the importance of the monitoring of cobalt concentrations in natural water and sewages. This task can be effectively achieved using the analytical sorption technique. The present work is focused on the preconcentration of cobalt and its determination by means of diffuse reflection spectroscopy. The preconcentration of cobalt was carried out using the macronetwork cation exchangers KB‐2M and KB‐2‐3T synthesized on the basis of methyl acrylate and long‐chain cross‐linking agents copolymers. Based on these collectors, a cobalt determination method in industrial solutions was worked out using solid‐phase spectroscopy. The colored surface compound to be determined was obtained by a preceding cobalt sorption on the resin and by subsequent treatment of the concentrate obtained with definite amount of nitroso‐R‐salt. The Co calibration curve is linear in the concentration range of 0.05...0.50 mg/L Co (sample volume is 50.0 mL) and the detection limit is 0.02 mg/L (1 μg absolute). 相似文献
60.
本文导出了一种由单程波方程利用反射/透射算子的可分表示方法模拟复杂介质中一次反射地震波的数值算法. 文中利用算子可分表示理论将反射/透射算子分解成适合于双域(空间域和波数域)运算的表达形式,使得本文得到的地震波数值模拟算法可适应于一定程度横向非均匀介质和界面起伏情况,在入射角小于45°时能够准确模拟振幅随入射角(AVA)的关系. 就模拟一次反射地震波而言,与前人研究的双程波动方程伪谱法地震波模拟相比,本文算法具有足够高的模拟精度,且计算效率成倍地提高. 相似文献