共查询到20条相似文献，搜索用时 250 毫秒
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A. J. Christopher 《GeoJournal》1997,43(1):91-97
The revival of ethnic identities and the search for historical roots have been significant factors in re-shaping the map of the world in the late twentieth century. Multi-ethnic states have come under increasing strain throughout the century and undermining the concept of the nation-state. However, the successor states to the colonial empires in Africa exhibit the same strains as the often highly fragile successors to the European continental empires earlier in the century. The survival of these quasi-states has been dependent upon the support of the international community for over thirty years as a reaction to the era of colonialism. Anti-colonialism offers little practical support for states in a post-colonial, post-Cold War era. In some cases the result has been disintegration and the emergence of the collapsed state. The revived political movements aimed at democratisation and self-determination have unleashed forces which may be incompatible with the survival of the current state system. 相似文献
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《Geodinamica Acta》2013,26(1):49-50
New structural data and P–T estimates of syn-deformational assemblages within the Beni Bousera peridotites and their crustal envelope are used to explain their Alpine exhumation. The Beni Bousera peridotites occur as thin sheets within high grade crustal units of the lower Sebtides (inner Rif, Morocco) and are composed of weakly deformed spinel lherzolite in the core of the massif and garnet-spinel mylonite at the rim. The main foliation trajectories in both the peridotites and overlying crustal units show systematic rotation towards their mutual contact, indicating a kilometer-scale top to the NW shearing with a dextral component along this crust/mantle contact. Widespread top to the NW shear criteria within the crustal units overlying the peridotite support this feature. Available ages constrain the development of the main foliation in both the peridotites and crustal rocks between 25 and 20 Ma. New P–T data from the peridotites show that deformation occurs during decompression from ≈ 22 kbar, 1050°C to ≈ 9-15 kbar, 800°C. As a consequence, exhumation of the Beni Bousera peridotites takes place during the Oligo-Miocene lithosphere thinning in the footwall of a lithospheric extensional shear zone. The exceptional preservation of garnet within the mylonitic peridotites results from rapid cooling of the border of the massif due to the juxtaposition with colder crustal rocks along this shear zone. Uplifting of the hot mantle rocks simultaneously induces high temperature metamorphism in the overlying crustal units. These new findings allow us to reconstruct the deformation history of the Beni Bousera region and the Alboran domain in the framework of the western Mediterranean geodynamics during the last 40 Myrs. 相似文献
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在《地质学报》64卷2期和66卷2期上发表有这两个‘动物群’的重要论文。在长期有争议的清河镇群和下二台群中发现小壳化石固然非同小可,但笔者拜读了两文后,却感到有些困惑与失望。图版所示两个动物群的绝大多数(如果不是全部的话!)看来不象是小壳化石,而是人工处理样品时所形成的假化石。如果依据这样的‘化石’来确定地层,将会带来极大的混乱。 相似文献
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《水科学进展》《水利水电科技进展》《河海大学学报》编辑部 《水科学进展》1998,9(3):303-311
1998年长江和松花江出现了特大洪水,全国军民在党中央、国务院和中央军委领导下,进行了气壮山河的抗洪斗争。在取得抗洪斗争伟大胜利之后,“痛定思痛”,水利专家们开始对今年洪水的成因、孕灾机理、抢险经验,以及中国防洪战略和对策等问题进行深层次的思考。 相似文献
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1977年底，国务院批准在湖南中部设立一个全新的地级建制——涟源地区。次年，我国全面进入改革开放新时期。三十年风雨兼程，三十年春华秋实，如今，诞生于改革开放前夕的涟源地区，已随着改革开放的步履，茁壮成长为湖南中部一个朝气蓬勃的地级市——娄底市! 相似文献
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《Geoforum》2015
This article examines young Peruvians’ aspirations and the role of migration in their imagined futures, from a generational perspective. The data come from Young Lives, a long-term study of childhood poverty combining survey and qualitative approaches with children and their parents. The paper uses a biographical approach that sees migration as part of individual biographies as well as social structures and life course processes. The aim is to deepen understanding of the social contexts in which aspirations for and by children are generated, paying close attention to family migration histories, dynamic household contexts, and children’s migration networks. The analysis focuses on the time-spaces of migration aspirations, showing the way past, present and future are interconnected. It also emplaces aspirations by focusing on the way aspirations by and for children are constituted in and through particular places. The conclusion reflects on the role of poverty and argues that ‘aspirations’ are about much more than abstract ‘futures’; they orient actions in the present and say a great deal about young people’s current realities and relationships. 相似文献
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The paper examines the neighborhood council from the perspective of its contribution to town planning. Within the context
of planning in Israel, two distinct models of neighborhood council and their relationship to the municipal planning administration
in two different towns are considered. Their potential as a new arena of planning at the neighborhood level is evaluated,
including the ability to mediate between ‘bottom-up’ and ‘top-down’ planning processes, and to offer a planning framework
that combines local with professional knowledge. 相似文献
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C. J. Loupasakis B. G. Christaras G. Ch. Dimopoulos T. N. Hatzigogos 《Geotechnical and Geological Engineering》2009,27(1):71-80
The selection of the constitutive laws reproducing the response of geomaterials usually becomes a very complicated procedure;
especially during the analysis of geostructures containing coarse grained materials. The objective of this study, is the evaluation
of models based on the perfect and hardening plasticity theory, regarding their ability to analyze the behaviour of soil materials,
used for the construction of earth dams. The evaluated constitutive laws are the elastic–perfect plastic model based on the
Mohr–Coulomb failure criterion and the isotropic hardening CAP model based on the same criterion. The data used for the evaluation
of the models, originate from the body of the Sfikia earth dam. This dam is considered suitable, because of the specialized
laboratory tests’ available data, regarding the materials of every zone. The availability of those data, as well as the variety
of the construction geomaterials, allows the deduction of generalized conclusions, concerning the ability of the specific
models to simulate a variety of similar earth constructions. 相似文献