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近年来国际上研究地洼学说概况 总被引：1，自引：0，他引：1
周裕蕃 《大地构造与成矿学》1989,13(4):374-383
本文介绍了近五年来(1985—1989)国际上研究、评介和发展地洼学说的概况,对显生宙地洼区和前寒武纪原地洼区的特征作了归纳,并对各类地洼区作了比较。最后列举了当前国际上研究地洼学说和地洼成矿学的新动向。 相似文献
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Brian S. Duffield 《GeoJournal》1984,9(1):27-35
Conclusion This review must be seen alongside others which have attempted to explore the relationship between geography (and geographers) and the study of leisure and recreation (Coppock 1980, 1982a). It serves to confirm the wide-ranging and diverse contribution that geographers have made in this field and the ways in which the study of tourism has reflected developments in the wider discipline. It also confirms the very close and intimate connection between studies of tourism and social and economic policy in Britain and indicates the way in which geographers have attempted to shape policy and have in turn been influenced by the needs and demands of policymakers. The rewards of such interaction are clear and yet costs have also been incurred by the academic geographic community. Not the least of these costs is that tourism studies have been predominantly of an empirical nature and conceptual and theoretical advance has inevitably tended to lag behind these empirical investigations. It is to be hoped that the study of the geography of tourism, having now demonstrated its credentials to policymakers and decision-makers alike, can secure for itself a more central place within geographic teaching and research so that these lacunae can be remedied. 相似文献
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Geomorphology of desert sand dunes: A review of recent progress 总被引：2，自引：0，他引：2
Through the 1980s and 1990s studies of the geomorphology of desert sand dunes were dominated by field studies of wind flow and sand flow over individual dunes. Alongside these there were some attempts numerically to model dune development as well as some wind tunnel studies that investigated wind flow over dunes. As developments with equipment allowed, field measurements became more sophisticated. However, by the mid-1990s it was clear that even these more complex measurements were still unable to explain the mechanisms by which sand is entrained and transported. Most importantly, the attempt to measure the stresses imposed by the wind on the sand surface proved impossible, and the use of shear (or friction) velocity as a surrogate for shear stress also failed to deliver. At the same time it has become apparent that turbulent structures in the flow may be as or more important in explaining sand flux. In a development paralleled in fluvial geomorphology, aeolian geomorphologists have attempted to measure and model turbulent structures over dunes. Progress has recently been made through the use of more complex numerical models based on computational fluid dynamics (CFD). Some of the modelling work has also suggested that notions of dune ‘equilibrium’ form may not be particularly helpful. This range of recent developments has not meant that field studies are now redundant. For linear dunes careful observations of individual dunes have provided important data about how the dunes develop but in this particular field some progress has been made through ground-penetrating radar images of the internal structure of the dunes.
The paradigm for studies of desert dune geomorphology for several decades has been that good quality empirical data about wind flow and sand flux will enable us to understand how dunes are created and maintain their form. At least some of the difficulty in the past arose from the plethora of undirected data generated by largely inductive field studies. More recently, attention has shifted–although not completely–to modelling approaches, and very considerable progress has been made in developing models of dune development. It is clear, however, that the models will continue to require accurate field observations in order for us to be able to develop a clear understanding of desert sand dune geomorphology. 相似文献
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CaCl2-H2O体系人工合成流体包裹体研究 总被引：2，自引：9，他引：2
人工合成包裹体可以作为天然包裹体参照物,提高我们对天然包裹体各种形成作用的认识,并用来模拟天然包裹体以验证许多涉及流体包裹体研究假设的有效性。本文利用人工水晶裂隙愈合方式,在一定的温压条件下合成了具有特定组成的 CaCl_2-H_2O 体系流体包裹体,并对这些合成的包裹体样品进行了详细的测温学研究,结合倪培等(2003)研究结果,进一步证实了:人工合成包裹体与天然包裹体的相似性,以及流体包裹体中捕获流体是母溶液的真实代表性。因此,合成包裹体作为天然包裹体参照物,将在流体包裹体和地质流体研究领域具有十分广阔的应用前景。 相似文献
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数值模拟是一种利用电子计算机,通过数值计算和图像显示的方法,研究工程问题、物理问题乃至自然界各类问题的方法。随着高性能计算的不断发展,数值模拟方法在沉积盆地构造变形研究中的应用不断扩大,学术界和工业界将数值模拟方法广泛应用于盆地构造变形特征与变形机制的定量研究,取得了丰硕的成果。本文在系统分析前人数值模拟成果的基础上,阐述了有限元、有限差分、边界元和离散元四种常用数值模拟实验方法的特征和应用。同时,本文对近年来数值模拟方法在沉积盆地褶皱冲断构造变形中的研究进展进行了分类总结,重点介绍这一方法在构造特征与变形机制研究中取得的成果,为数值模拟方法在盆地构造变形领域应用的不断扩大和深入提供参考。最后,本文对数值模拟技术在目前应用中面临的问题和未来的发展方向提出了一些看法和建议。 相似文献
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The use of diary techniques in social surveys has been discouraged because of the difficulties which have often been associated with their implementation and the analysis of the results. This paper argues that given the use of proper safeguards, diary techniques may be employed to provide high quality data for behavioural analysis, particularly in rural studies. This view is supported by an examination of two case studies where a diary technique was successfully used. 相似文献
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L. Arenas M. OrtegaM.J. García-Martínez E. QuerolJ.F. Llamas 《Journal of Geochemical Exploration》2011
Linares (Jaen, Spain) has been subjected to an intense mining and metallurgic activity during 2500 years. Basically, lead and silver have been extracted from galena; as well as copper and zinc. Different studies have been conducted to evaluate trace element concentrations to obtain relationships with anthropogenic and geologic factors. The analytical results of these studies have been obtained with ICP-AES. This analytical technique is relatively expensive and inaccessible in zones with scarce economic means. In this study, XRF analyses have been conducted and the obtained results are presented, as well as a comparison with the previously obtained ICP results. In both cases, a cluster analysis has been made to try to identify the same relations in the target area. 5 groups have been identified, mainly related with lithology. Only 10 of the 122 grid squares (each one of 1 km2) are classified in different groups if the cluster analysis is conducted with XRF results or ICP results. ICP classifies better where these grid squares are located, mostly, in contact zones of different lithologies. 相似文献
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李四光教授是中国地热研究的倡导者,作者以中国科学院地质研究所地热室近20年来的研究工作为基础,从大地热流、深部地热、区域地温场、地热数学模拟、地热实验和分析测试系统、地热资源、矿山地热以及油田地热等八个方面阐述了我国地热研究的进展,以资缅怀和纪念李四光教授诞生100周年。 相似文献
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Earle R. Whipple 《Chemical Geology》1974,14(3):223-238
The chemical factors affecting the accuracy of Wilson's procedure for determination of ferrous iron in silicates have been investigated. This procedure utilizes pentavalent vanadium to oxidize ferrous iron as it is set free from the silicate by hydrofluoric acid. The quadrivalent vanadium produced is more resistant to oxidation by oxygen than ferrous iron, and conserves the reducing power of the silicate. The procedure is done at room temperature.Recovery of ferrous iron under various conditions has been studied to elucidate the chemical mechanisms of loss in the procedure. Some improvements have been made. The studies indicate that the procedure is of high accuracy.An effect resulting in loss of ferrous iron titre has been found, involving the chemical attack of solids by solutions containing oxygen and pentavalent vanadium. This loss does not appear to take place if all ion species are in solution. 相似文献
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X射线断层扫描技术在鲤鱼耳石对环境响应研究中的应用初探 总被引：1，自引：1，他引：0
作为生命矿物文石和球文石的载体,鱼耳石(fish otoliths)记载了鱼体生长过程中大量的环境信息。近30年来,其研究取得了很多成果,但利用医学技术的研究尚未见报道。文中尝试应用医学X射线断层扫描技术(CT)对取自河北白洋淀和北京密云水库的野生鲤鱼耳石进行分析研究。结果表明:白洋淀鲤鱼的星耳石和微耳石CT值均大于密云水库鲤鱼耳石相应的CT值,与白洋淀水体中的重金属元素含量明显高于密云水库水体中的重金属含量存在较好的相关性;同一水域星耳石与微耳石的CT值也存在明显差异,分析认为这种差异可能与元素的亲和性及占位方式有关。 相似文献
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《Gondwana Research》2010,17(3-4):370-400
A dense nationwide seismic network recently constructed in Japan has been yielding large volumes of high-quality data that have made it possible to investigate the seismic structure in the Japanese subduction zone with unprecedented resolution. In this article, recent studies on the subduction of the Philippine Sea and Pacific plates beneath the Japanese Islands and the mechanism of earthquake and magma generation associated with plate subduction are reviewed. Seismic tomographic studies have shown that the Philippine Sea plate subducting beneath southwest Japan is continuous throughout the entire region, from Kanto to Kyushu, without disruption or splitting even beneath the Izu Peninsula as suggested in the past. The contact of the Philippine Sea plate with the Pacific plate subducting below has been found to cause anomalously deep interplate and intraslab earthquake activity in Kanto. Detailed waveform inversion studies have revealed that the asperity model is applicable to interplate earthquakes. Analyses of dense seismic and GPS network data have confirmed the existence of episodic slow slip accompanied in many instances by low-frequency tremors/earthquakes on the plate interface, which are inferred to play an important role in stress loading at asperities. High-resolution studies of the spatial variation of intraslab seismicity and the seismic velocity structure of the slab crust strongly support the dehydration embrittlement hypothesis for the generation of intraslab earthquakes. Seismic tomography studies have shown that water released by dehydration of the slab and secondary convection in the mantle wedge, mechanically induced by slab subduction, are responsible for magma generation in the Japanese islands. Water of slab origin is also inferred to be responsible for large anelastic local deformation of the arc crust leading to inland crustal earthquakes that return the arc crust to a state of spatially uniform deformation. 相似文献
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The paper presents the application of adaptive resonance theory of artificial neural networks (ANN) for classification of coal seams with respect to their proneness to spontaneous heating. In order to apply this technique, 31 coal samples have been collected from different Indian coalfields covering both fiery and non-fiery coal seams of varying ranks spreading over 8 different mining companies. The intrinsic properties of these samples have been determined by carrying out proximate, ultimate and petrographic analyses. The susceptibility indices of these samples have been studied by five different methods, viz. crossing point temperature, differential thermal analysis, critical air blast analysis, wet oxidation potential difference analysis and differential scanning calorimetric studies. Exhaustive correlation studies between susceptibility indices and the intrinsic properties have been carried out for identifying the appropriate spontaneous heating susceptibility indices and intrinsic properties to be used for classification of coal seams. The identified parameters are used as inputs and adaptive resonance theory of ANN has been applied to classify the coal seams into four different categories. This classification system will help the planners and practising mining engineers to take ameliorative measures in advance to prevent the occurrence of fire in mines. 相似文献
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Allen White 《Geoforum》2002,33(1):73-83
The growth in the global population of refugees over the last 20 years has been paralleled by the development and growth of refugee studies as a recognised discipline. However refugees do not comprise a naturally self-delimiting domain of scientific knowledge and have been constituted by refugee studies through discourses that emphasise humanitarian, apolitical and organic functionalist discourses that root refugee identities in particular places. This paper argues that the presently inadequate constitution of refugee identities in refugee studies has been compounded by geographic representations of regional refugee emergencies, stable conceptions of refugees and asylum seekers and dated and unproblematic understandings of space as inactive and not constitutive of social life. Using data collected in interviews held between 1995 and 1998 with representatives from refugee and asylum institutions and organisations this paper illustrates how discourses and funding policies that unproblematically assume community groups represent refugees asylum seekers ignore transnational differences and tensions that can exist in marginalised communities. However it should be pointed out that the discourses about place, nationality and identity and `natural' communities can also be used by the powerless to resist their marginalised and excluded positions. 相似文献
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Tourism in Spain has developed dramatically in recent decades but the growth of the tourist industry has not been experienced evenly throughout the country. Tourism is largely concentrated in a small number of essentially coastal and insular provinces. Analysis by principal components shows that significant regional variations occur in the demand for hotels from different national groups but, with the exception of the French, the spatial preferences of each nationality have remained remarkably constant in the period 1965–1980. However, as growth rates have differed from market to market, so the demand for hotels has developed at different rates from one province to another. Regional variations in the seasonality of demand also occur. These findings highlight the need for further geographical studies such as this to provide more spatial detail than is to be found in most national studies and at the same time to supply the synthesis which unrelated regional or local case studies lack. 相似文献
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国外对更新世末次冰期极盛期(LGM)以来环境演变的研究出现了一些新的趋势和特点。本文对此进行了归纳与分析，并指出它们对国内第四纪研究工作的启示意义。 相似文献