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81.
82.
通过详查评价,提高了对矿床地质特征的研究程度。在继续肯定矿床的成矿严格受张堰花浆长岩体与金群的接触带控制的同时,对矿床的主要赋矿地层即外接带金山群的分层,构造其各类岩性组成在矿过程中的作用进行了详尽的厘定。 相似文献
83.
Recently discovered dinosaur bones in submerged near-shore deposits of southwest Istria include one vertebra, one femur, and two rib fragments. They all show well-developed vascularization. The large amounts of primary bone tissue in the vertebral and femoral compacta as well as in one rib fragment suggest that they belong to sub-adult animals which were growing rapidly. The structure of a second rib fragment differs in that it consists of secondary bone. The absence of lines of arrested growth is evident in all investigated bones. This suggests a sustained manner of bone deposition. 相似文献
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85.
57Fe-Mössbauer spectra of eleven Fe-Mg-bearing staurolite samples, synthesized at 5, 20 and 25 kbar and 680°C, ranging in composition from xFe?=1.00 to xFe?=0.15, and of two Zn-Fe-bearing staurolite samples, synthesized at 20 kbar and 700°C with xFe?=0.10 and xFe?=0.32 were collected at room temperature. The spectra reveal that about 80% of Fetot (in case of Fe-Mg-bearing staurolite) and about 70% of Fetot (in case of Fe-Zn-bearing staurolite) are located as Fe2+ at the three subsites Fe1, Fe2 and Fe3 of the tetrahedral T2-site. The refinement of the spectra results in almost identical values for the isomer shift (IS) (±1.0 mm/s) but significantly different values for the quadropole splitting (QS) for the three subsites which is in accordance with the different distortions of these sites. About 8% of Fetot (in case of Fe-Mg-bearing staurolite) and 13% of Fetot (in case of Fe-Zn-bearing staurolite) are located as Fe2+ at the octahedral M4 site, while the remainder percents of Fetot indistinguishably occur as Fe2+ at the octahedral M1 and M2 sites of the kyanite-like part of the structure. Within the whole Fe-Mg-staurolite solid solution series the Mössbauer parameters QS of the sites M4 and (M1, M2) vary systematically with composition whereas IS remains constant. There is a high negative correlation of the total Mg-content with Fe-occupation of all the Fe-bearing sites indicating a continuous substitution of Fe2+ by Mg on all these sites. Synthetic Fe-staurolites show no increasing occupation of the octahedral sites by two-valent cations with pressure, as was assumed by several authors. 相似文献
86.
龙门山国家地质公园飞来峰成因的新证据 总被引:1,自引:0,他引:1
近来发现四川彭州(原称彭县)、什邡一带的飞来峰是第四纪冰川作用形成的。笔者等在塘坝子、葛仙山等飞来峰的底界及周边,多次发现飞来峰是压在早更新世的冰水堆积层之上。葛仙山北寨门、丁家湾,什邡大垭口等剖面的地质现象,充分说明塘坝子、葛仙山等飞来峰是第四纪中更新世时“飞”来,压盖上去的。同时可见飞来峰与第四系之间是“冷接触”,找不到确切的断层证据。笔者等还用现有的区域地质调查资料及新的地质成果,编制了1:10万更新世时的彭县至汶川的地质剖面图,并设想了冰雪层掩盖情况。那时岷江尚未剥蚀下切,按现在标高计的5000m处,即在光光山、太子城之上约1000m的“天”上。当时应在该处出露的石炭系-二叠系石灰岩,就是塘坝子、葛仙山飞来峰的根部。塘坝子、葛仙山就是从那里被冰川作用剪切、从母体分离的石灰岩,滑动、随冰川固体流,滑移到彭县来的。笔者还从理论上阐述了塘坝子、尖峰顶、天台山等如此巨大的山体,能被冰川作用拔起、挖掉、推走的原因和根据。从而解释了飞来峰“飞”行的过程。顺理成章,合乎自然,揭开了飞来峰之迷。 相似文献
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88.
Elsa DaCosta 《Geoforum》2007,38(1):190-206
Central Vi?t Nam is one of the most vulnerable areas in the country to natural disasters. In 1985 a major typhoon hit the Tam Giang Lagoon coastal area in the province of Th?a Tiên-Hu?, Central Vi?t Nam, with severe impacts on the sampan dwellers who lived there on boats and fished for their livelihoods. Since then, the government has attempted to resettle them on land in order to decrease their vulnerability to such events. Consequently, this process has changed the livelihood options as well as the social networks of the sampan dwellers. This study of the resettlement village of Th?y ?i?n analyses the social networks and different forms of social capital being utilised by the resettled sampan dwellers as part of their changing livelihoods and questions whether the social capital formed will indeed lead to a long term decrease in vulnerability. It is found that while bonding and linking social capital have been newly formed, the trust required for bridging social capital formation is still missing, and this in turn is hindering the possibilities of sustainable livelihood formation. 相似文献
89.
Influence of surface roughness of the Teflon plates on kinetics of the bubble attachment was studied. Phenomena occurring during collisions of the air bubble, rising in clean water, with Teflon plates, differing only in their surface roughness, were recorded and analysed using a high-speed camera. Variations of the local velocity of the bubble during the collisions and the time of the bubble attachment were determined. It was found that the Teflon surface roughness was the parameter of a crucial importance for the attachment time of the colliding bubble. Depending on degree of the surface roughness the time of the attachment varied by over order of magnitude (from 3 to over 80 ms). In the case the Teflon surfaces having roughness below 1 μm there were recorded four to five “approach–bounce” cycles prior to the bubble attachment. Moreover, after the first collision the rapid pulsations of the bubble shape (within fraction of millisecond) were recorded. For surfaces of roughness ca. 50 μm and larger the attachment always occurred during the first collision—there was no bouncing observed and the time of the attachment was below 3 ms. It was documented that presence of a micro-bubble at the surface facilitated attachment of the colliding bubble. 相似文献
90.
从极限平衡理论角度对刚性桩复合地基中垫层作用机理进行分析,提出桩顶垫层厚度、垫层材料内摩擦角等参数对桩土应力分担的控制公式,推导出在已知表面应力情况下考虑桩土共同作用的桩土沉降计算公式,在此基础上提出一种桩土应力比的迭代计算方法。编制程序实现对算例的计算,总结分析计算结果并与实测值进行对比验证。 相似文献