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31.
G. de Weisse 《Mineralium Deposita》1967,2(4):349-356
Résumé L'exploitation récente d'un gisement de bauxite près de Mégare (Grèce) a fait apparaître sur les calcaires de base une concentration verte d'oxyde de nickel relativement élevée. La présence dans le gisement d'argiles rouges, renfermant de fortes proportions d'oxyde de fer avec des teneurs relativement faibles en alumine et des traces d'oxyde de nickel, induit à penser qu'il s'agit d'un produit latéritique dérivé d'une roche ultrabasique et transporté ultérieurement sur la région calcaire karstifiée avec ses remplissages bauxitiques. L'étude se termine par une hypothèse sur la genèse de ce gîte singulier.
The recent mining of a bauxite deposit near Megara (Greece) has shown on the footwall limestone a relatively high concentration of a green nickel oxide. The occurrence in the same deposit of red clays with a rather high percentage of iron oxide and a low content of alumina, together with some traces of nickel, induces to think that this material is composed of a lateritic soil derived from an ultrabasic rock and subsequently transported on karstified limestone with its bauxitic fillings. — The study ends with an hypothesis on the genesis of this unusual deposit.相似文献
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The longitudinal strength of the high-speed ferry was investigated by subjecting the ship's hull girder to long-term loads obtained from a frequency-domain panel code. Prior to the statistical analysis, linearly computed transfer functions were corrected for nonlinear effects, yielding two sets of transfer functions valid for different wave amplitudes. One set corresponded to the hogging condition; the other set, to the sagging condition. Two regular equivalent design waves were specified that resulted in loads representing the most severe global design load conditions. The still-water loading condition, yielding a still-water vertical bending moment in hogging, was superimposed on the wave-induced loads to obtain the total (design) loads in hogging. For the sagging condition only, additional impact-related loads were superimposed to obtain the total (design) loads in sagging. A finite element model of the ship's structure was subjected to pressure distributions according to the two regular design waves. For comparison with classification society rule values, a simple beam theory strength analysis of the ship's midship section was performed first, and then another finite element analysis was carried out, whereby the imposed loads were tuned to the rule values of vertical bending moments. Rule-based magnitudes of nominal maximum longitudinal stress deviated significantly (25–39%) from comparable stresses obtained by the panel code based finite element analysis. However, stresses obtained from the rule-based finite element analysis agreed more favorably, especially in hogging. In the uppermost deck, for example, the panel code based compressive stress was only 9% larger than the comparable stress from the rule-based finite element analysis. 相似文献
34.
Georg Irion Jens Müller Jose Nunes de Mello Wolfgang J. Junk 《Geo-Marine Letters》1995,15(3-4):172-178
The Quaternary history of the Amazon lowlands is characterized by deposition of sediments of Andean provenance and by the influences of changing sea levels. Areas well above the present water tables were not reached by Pleistocene high-water stages. These areas have been intensively weathered since the Tertiary, forming hard lateritic weathering horizons. These weathering horizons are best explained by the relatively constant, humid tropical climate throughout the Quaternary. In the western Amazonian Lowland, flood plains corresponding to the different Pleistocene sea-level heights were formed. During low sea level, erosion in the drainage areas increased and the water levels of the central Amazon River system were lowered. Valleys drowned and lakes formed in the lower reaches of rivers and creeks during high sea-level stages. These lakes (ria lakes) remained in the valleys with rivers having a low sediment load. Seismic profiling (3.5 kHz) in some of these lakes clearly showed deposits of the three last periods of Quaternary high sea-level stages. 相似文献
35.
Numericalsimulationofthree-dimensionaltidalcurrentintheBobalSea¥DenZhenxing;YangLianwu;andJoseOzer(ReceivedMay1,1993;accepted... 相似文献
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Uwe?LangrockEmail author Ruediger?Stein Marcus?Lipinski Hans-Jürgen?Brumsack 《Geo-Marine Letters》2003,23(1):34-42
The late Volgian (early "Boreal" Berriasian) sapropels of the Hekkingen Formation of the central Barents Sea show total organic carbon (TOC) contents from 3 to 36 wt%. The relationship between TOC content and sedimentation rate (SR), and the high Mo/Al ratios indicate deposition under oxygen-free bottom-water conditions, and suggest that preservation under anoxic conditions has largely contributed to the high accumulation of organic carbon. Hydrogen index values obtained from Rock-Eval pyrolysis are exceptionally high, and the organic matter is characterized by well-preserved type II kerogen. However, the occurrence of spores, freshwater algae, coal fragments, and charred land-plant remains strongly suggests proximity to land. Short-term oscillations, probably reflecting Milankovitch-type cyclicity, are superimposed on the long-term trend of constantly changing depositional conditions during most of the late Volgian. Progressively smaller amounts of terrestrial organic matter and larger amounts of marine organic matter upwards in the core section may have been caused by a continuous sea-level rise. 相似文献
38.
赤潮生物种类特征光谱获取技术 总被引:1,自引:0,他引:1
较为系统地研究了赤潮生物水体反射率曲线获取方法。通过对 2类反射率反演方法得出的反射率曲线与实际反射率曲线进行比较 ,得出在不具备大气环境参数的情况下 ,经验线性法的反演结果与实际反射率曲线最接近的结论 ,并进一步对正常海水和赤潮生物水体的光谱特性进行分析 ,提取出赤潮生物水体的特征光谱。这是进行赤潮监测和识别的重要前提 相似文献
39.
Trends in biomass, density and diversity of North Sea macrofauna 总被引:6,自引:2,他引:6
40.
M. B. de Groot H. den Adel T. P. Stoutjesdijk C. J. van Westenbrugge 《Coastal Engineering》1995,26(3-4)
Flow slides may affect the stability of dikes. A flow slide is an instability of a submerged slope caused by liquefaction of loose, (medium) fine sand. Whether a flow slide will occur depends on the properties of the sand, which are a function of its density, and the geometry of the slope, as determined by wave and current induced scour and sedimentation. The influence of sand properties and the geometry parameters on the risk of flow slides are discussed. The application of a flow slide prediction method to an example and a risk analysis is briefly discussed. 相似文献