共查询到20条相似文献，搜索用时 15 毫秒
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地球科学发展的生命之翼——地球科学文化建设初探 总被引：6，自引：0，他引：6
从人类社会发展的历史来看,文化产业在人类社会作为一个重要产业出现,是社会文明进步的标志。据报道,20世纪90年代末某些发达国家的文化产业产值已超过了制造业产值,有些国家还明确提出“将科技作为文化,作为人们的社会活动”[1]。地球科学文化产业很可能作为一个分支产业而活跃在社会发展的舞台上,因为拯救地球将成为21世纪世界的主旋律。拯救地球是人类面临的一项庞大的综合的系统性的社会工程。地球上人的生存、发展需要地球科学文化,需要以地球科学思想、科学方法和科学精神为内涵的文化推进人类社会向前迈进。江泽民同志在党的十六大报… 相似文献
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A. F. Trendall 《Australian Journal of Earth Sciences》2013,60(3):287-311
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离心模型试验中微型土压力盒土压力测定 总被引：1，自引：0，他引：1
土压力作为离心模型试验中重要的测试参数,受土压力盒的性能、离心机数据采集系统稳定性及外部环境等诸多因素的影响,准确地测量土压力较为困难。土压力盒作为土压力测试元件,其性能对土压力测量准确性有直接影响。为获得较为准确的土压力测试数据,结合离心机数据采集系统,选择两种常见的电阻应变式土压力盒。通过标定试验得出两种土压力盒砂标系数均小于出厂标定系数,Ⅰ型偏小64.75%,Ⅱ型偏小18.77%,Ⅱ型土压力盒与出厂数据的重合度比Ⅰ型好;在研究墙高10～30 m类扶壁式挡墙侧向土压力分布的离心模型试验中,与Ⅱ型土压力盒相比,Ⅰ型存在按出厂系数测得数据失真、灵敏度低和稳定性差的缺点。标定试验和离心试验结果表明,接入自行组建的数据采集系统的Ⅱ型土压力盒比接入静态应变数据采集系统的Ⅰ型土压力盒性能更佳。 相似文献
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Plan curvature and landslide probability in regions dominated by earth flows and earth slides 总被引：4，自引：0，他引：4
Damaging landslides in the Appalachian Plateau and scattered regions within the Midcontinent of North America highlight the need for landslide-hazard mapping and a better understanding of the geomorphic development of landslide terrains. The Plateau and Midcontinent have the necessary ingredients for landslides including sufficient relief, steep slope gradients, Pennsylvanian and Permian cyclothems that weather into fine-grained soils containing considerable clay, and adequate precipitation. One commonly used parameter in landslide-hazard analysis that is in need of further investigation is plan curvature. Plan curvature is the curvature of the hillside in a horizontal plane or the curvature of the contours on a topographic map. Hillsides can be subdivided into regions of concave outward plan curvature called hollows, convex outward plan curvature called noses, and straight contours called planar regions. Statistical analysis of plan-curvature and landslide datasets indicate that hillsides with planar plan curvature have the highest probability for landslides in regions dominated by earth flows and earth slides in clayey soils (CH and CL). The probability of landslides decreases as the hillsides become more concave or convex. Hollows have a slightly higher probability for landslides than noses. In hollows landslide material converges into the narrow region at the base of the slope. The convergence combined with the cohesive nature of fine-grained soils creates a buttressing effect that slows soil movement and increases the stability of the hillside within the hollow. Statistical approaches that attempt to determine landslide hazard need to account for the complex relationship between plan curvature, type of landslide, and landslide susceptibility. 相似文献
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Four moldavites and one sample each of an australite, billitonite, indochinite, philippinite, thailandite, Ivory Coast tektite, bediasite and a georgianite were analyzed using neutron activation analysis for La, Ce, Sm, Eu, Tb, Yb and Lu. The REE abundances resemble those of sedimentary rocks. Most of the tektites display a depletion of Eu, a characteristic feature of mature Phanerozoic continental sedimentary rocks. However, the Ivory Coast tektite and georgianite are relatively enriched in Eu, possibly due to the presence of plagioclase-rich source rocks. 相似文献
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离子型稀土矿中离子稀土的ICP-AES测定方法研究 总被引：2，自引：0，他引：2
稀土作为一种不可再生的国家重要战略资源,具有优异的磁、光、电性能。离子吸附型稀土矿,是我国特有的新型稀土矿物,以风化淋积型稀土矿床形式存在,一般直接就地采用电解质溶液溶浸即可获得混合稀土氧化物,文中选取了稀土含量呈高中低分布的三个样品考察了浸提时间、浸提剂浓度、以及液固比对浸提效果的影响,确定了最佳的浸提方法,应用电感耦合等离子体光谱仪上机测定,通过加标回收检验方法准确度,其回收率在90-110%之间。该方法操作简单,灵敏度高(检出限为0.10~0.4μg/g),可用于大批量离子型稀土矿中浸出型稀土含量的测定。 相似文献
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Methods recommended for calculating the probability of failure of earth slopes, as distinct from factor of safety, are discussed. In particular the ‘Level II’ and ‘Level II’ approaches as defined by the Joint Committee of Structural Safety (J.C.S.S.) are referred to; these are set forth in C.I.R.I.A. Report No. 631 and attention is drawn to the contributions therein by M. J. Baker and M. Horne, and to how these considerations affect this particular problem. The mechanical model used throughout is Bishop's simplified method2. 相似文献
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Passive earth pressure calculations in geotechnical analysis are usually performed with the aid of the Rankine or Coulomb theories of earth pressure based on uniform soil properties. These traditional earth pressure theories assume that the soil is uniform. The fact that soils are spatially variable leads to two potential problems in design: do sampled soil properties adequately reflect the effective properties of the entire soil mass and does spatial variability in soil properties lead to passive earth pressures that are significantly different from those predicted using traditional theories? This paper combines non-linear finite element analysis with random field simulation to investigate these two questions. The specific case investigated is a two-dimensional frictionless passive wall with a cohesionless drained soil mass. The wall is designed against sliding using Rankine's earth pressure theory. The unit weight is assumed to be constant throughout the soil mass and the design friction angle is obtained by sampling the simulated random soil field. For a single sample, the friction angle is used as an effective soil property in the Rankine model. For two samples, an average of the sampled friction angles is used. Failure is defined as occurring when the Rankine predicted passive resistance acting on the wall, modified by a factor of safety, is greater than that computed by the random finite element method. Using Monte Carlo simulation, the probability of failure of the traditional design approach is assessed as a function of the factor of safety using and the spatial variability of the soil. 相似文献
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《Earth》2009,92(1-4):1-26
Passive margins have existed somewhere on Earth almost continually since 2740 Ma. They were abundant at 1900–1890, 610–520, and 150–0 Ma, scarce at ca. 2445–2300, 1600–1000, and 300–275 Ma, and absent before ca. 3000 Ma and at 1740–1600. The fluctuations in abundance of passive margins track the first-order fluctuations of the independently derived seawater 87Sr/86Sr secular curve, and the compilation thus appears to be robust. The 76 ancient passive margins for which lifespans could be measured have a mean lifespan of 181 m.y. The world-record holder, with a lifespan of 590 m.y., is the Mesoproterozoic eastern margin of the Siberian craton. Subdivided into natural age groups, mean lifespans are 186 m.y. for the Archean to Paleoproterozoic, 394 m.y. for the Mesoproterozoic, 180 m.y. for the Neoproterozoic, 137 m.y. for the Cambrian to Carboniferous, and 130 m.y. for the Permian to Neogene. The present-day passive margins, which are not yet finished with their lifespans, have a mean age of 104 m.y. and a maximum age of 180 m.y. On average, Precambrian margins thus had longer, not shorter, lifespans than Phanerozoic ones—and this remains the case even discounting all post-300 Ma margins, most of which have time left. Longer lifespans deeper in the past is at odds with the widely held notion that the tempo of plate tectonics was faster in the Precambrian than at present. It is entirely consistent, however, with recent modeling by Korenaga [Korenaga, J., 2004. Archean geodynamics and thermal evolution of Earth. Archean Geodynamics and Environments, AGU Geophysical Monograph Series 164, 7–32], which showed that plate tectonics was more sluggish in the Precambrian. The abundance of passive margins clearly tracks the assembly, tenure, and breakup of Pangea. Earlier parts of the hypothesized supercontinent cycle, however, are only partly consistent with the documented abundance of passive margins. The passive-margin record is not obviously consistent with the proposed breakup of Nuna (Columbia), the assembly of Rodinia, or the assembly or breakup of the putative Pannotia. An alternative model is put forth involving (a) formation of two or more supercratons during the late Paleoproterozoic, (b) a Mesoproterozoic interval dominated by lateral accretion of arcs rather than by continental breakup and dispersal, (c) wholesale collision to form Rodinia by the end of the Mesoproterozoic, and (d) staged breakup of Rodinia through much of the Neoproterozoic. 相似文献
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G. P. Eaton 《Environmental Geology》1994,24(4):309-311
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We studied the states of rare earth elements in ore of the Xianglushan rare earth deposit. Rare earth ore samples were tested and examined by scanning electron microscope, electron probe, and chemical leaching. No independent rare earth minerals were detected by scanning electron microscope. Elements detected by the electronic probe for the in situ micro-zone of the sample included: O, Al, Si, Ca, Mg, Fe, Ti, K, Na, S, Cl, C, Cu, Cr, V, and Pt. Rare earth elements were not detected by electron probe. (NH4)2SO4, (NH4)Cl, NaCl, and H2SO4 were used as reagents in chemical leaching experiments that easily leached out rare earth elements under the action of 10% reagent, indicating that the rare earth elements in ore are mainly in the ionic state rather than present as rare earth minerals. 相似文献
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A simple and reliable method for predicting the relationship between lateral displacement and earth pressure for rigidly framed earth retaining structures (RFERS) was developed. Closed‐form equations were derived such that if one value of displacement or pressure is known (or assumed) the other can be computed for hydrostatic, seismic, uniform, and semi‐elliptical earth pressure distributions. Additionally, the general form of the equations can be used to predict the magnitude of the lateral force even if the shape of the earth pressure is unknown, with a reasonable degree of accuracy. The expressions for deflection were derived by treating the structure as an equivalent cantilever beam and calibrating the resulting expression using the finite element method (FEM). A parametric FEM analysis, of 42 000 different RFERS configurations, was performed to calibrate the expressions, using multivariate non‐linear regression between the derived expressions and FEM. A Weibull statistical analysis was performed for each equation and determined that the equations had better than 80% probability to yield deflections that are within 25% of the value computed using FEM. Furthermore, there is a 98% certainty that each equation will yield a deflection that is within 50% of that computed using FEM. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Tremendous volumes of data have been captured, archived and analyzed. Sensors, algorithms and processing systems for transforming and analyzing the data are evolving over time. Web Portals and Services can create transient data sets on-demand. Data are transferred from organization to organization with additional transformations at every stage. Provenance in this context refers to the source of data and a record of the process that led to its current state. It encompasses the documentation of a variety of artifacts related to particular data. Provenance is important for understanding and using scientific datasets, and critical for independent confirmation of scientific results. Managing provenance throughout scientific data processing has gained interest lately and there are a variety of approaches. Large scale scientific datasets consisting of thousands to millions of individual data files and processes offer particular challenges. This paper uses the analogy of art history provenance to explore some of the concerns of applying provenance tracking to earth science data. It also illustrates some of the provenance issues with examples drawn from the Ozone Monitoring Instrument (OMI) Data Processing System (OMIDAPS) (Tilmes et al. 2004) run at NASA’s Goddard Space Flight Center by the first author. 相似文献
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The younger granites in Finland contain more REE than the older ones. In the youngest, postorogenic rapakivi granites, the total REE concentration is highest, the light REE are more enriched, and the negative Eu anomaly is more pronounced than in the older granites. The enrichment of the light REE, the anomalous behavior of the extreme elements (La, Ce, and Lu) in normalized graphs, and the depletion of Eu indicate the degree of differentiation the rock has undergone. These features are usually more pronounced in large, homogeneous granites than in metamorphic or volcanogenic rocks. Silicic vein rocks usually contain less REE than the granites proper; the distribution pattern in many is as in granites, but in some the heavy elements are more enriched. The positive Eu anomaly in Precambrian metamorphic rocks is tentatively attributed to metamorphic differentiation and to the secretion of silicic material from the host rock. 相似文献
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F.J. Flanagan 《Geochimica et cosmochimica acta》1974,38(12):1731-1744
A revised list of reference samples of interest to geoscientists has been extended to include samples for the agronomist, the archaeologist and the environmentalist. In addition to the source from which standard samples may be obtained, references or pertinent notes for some samples are included.The number of rock reference samples is now almost adequate, and the variety of ore samples will soon be sufficient. There are very few samples for microprobe work. Oil shales will become more important because of the outlook for world petroleum resources. The dryland equivalent of a submarine basalt might be useful in studies of sea-floor spreading and of the geochemistry of basalts.The Na- and K-feldspars of BCS (British Chemical Standards—Bureau of Analysed Samples), NBS (National Bureau of Standards), and ANRT (Association Kationale de la Recherche Technique) could serve as trace-element standards if such data were available. Similarly, the present NBS flint and plastic clays, as well as their predecessors, might be useful for archaeological pottery studies. The International Decade for Ocean Exploration may stimulate the preparation of ocean-water standards for trace elements or pollutants and a standard for manganese nodules. 相似文献
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Three-dimensional reliability analysis of earth slopes 总被引：2，自引：0，他引：2
Reliability of cohesive soil slopes is assessed using a three-dimensional (3D) probabilistic stability analysis algorithm. Spatial variability of soil properties is represented by an anisotropic random field. Parametric studies are performed for a typical earth structure. The influence of the model parameters, including expected value, variance and correlation distance of soil shear strength, on the reliability associated to particular failure mechanisms is evaluated. The effect on reliability of the dimensions and shape of potential slip surfaces for a given random field is also assessed. It is shown that the mechanisms that contribute most significantly to global probability of failure of the slope may be quite different from those identified as critical by standard deterministic evaluations assuming soil homogeneity. Some practical implications of this fact are discussed. 相似文献