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排序方式: 共有354条查询结果,搜索用时 15 毫秒
31.
Marta Dolealov 《国际地质力学数值与分析法杂志》1994,18(1):1-24
Overestimation of displacements in numerical calculations can occur if some requirements are not met by the constitutive relations. Along with consideration for small strain behaviour of soils1 the stiffening effects of unloading in shear should be taken into account. The latter problem is analysed in the paper using embankment dams as a typical example. Strain and stress paths in their cores and shells were derived from field measurement results and frequent path direction changes during seemingly monotonic loading process were discovered. Proportional loading test results of isotropically and anisotropically consolidated sand allowed interpretation of the in situ paths by the incremental theory of plasticity and distinction between the sections where unloading and reloading in shear develop. Furthermore, the analysis of these tests showed a marked stiffening of the soil due to unloading as well as neutral loading in shear. The strain redistribution due to material inhomogeneity, either inherent or introduced by the loading process, was identified as a common reason for the frequent occurrence of this phenomenon. Consequently, overestimations in displacement calculations can be brought about by neglecting this important effect by the constitutive model used. Accordingly, the unit response envelopes of some typical constitutive laws have been checked from this special point of view, and the models properly describing this phenomenon selected. 相似文献
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Solar Physics - We present simplified models for the region where Lα is formed, in the boundary between prominences and corona. The models were calculated by solving the radiation transfer in... 相似文献
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Bioremediation and toxicity determination of natural seawater polluted with weathered crude oil by salt-tolerant consortia in a SBR 总被引:1,自引:0,他引:1
The aim of this research was to compare the bioremediation treatment of seawater polluted with two different concentrations of weathered crude oil (0.2 for experiment (a) and 1.14% for experiment (b), v/v) by salt-tolerant consortia enriched from the sludge of a refinery wastewater treatment facility, in a SBR. The use of a commercial bioremediation stimulant (S200) was also evaluated as an alternative to the traditional nitrogen and phosphorus supplement. 相似文献
35.
Alvarez-Salgado XA Herrera JL Gago J Otero P Soriano JA Pola CG García-Soto C 《Marine pollution bulletin》2006,53(5-7):239-249
Hydrographic data collected during the cruise HIDROPRESTIGE were combined with meteorological and dynamic data provided by remote sensors and drifting/moored buoys, to describe the surface circulation of the Northern Iberian basin in March-April 2003. Sea surface winds transported the floating Prestige oil slicks from the sinking area to the continental slope off the Rías Baixas in 1/2 month: the surface current intensity was 2% of the wind intensity and it was rotated clockwise 5 degrees from the wind direction. Mesoscale cyclonic and anticyclonic structures west of 10 degrees W increased the residence time of oil patches in the Northern Iberian basin, as compared with the expected southwards flow of the Iberian current (IC). On the other hand, the Iberian poleward current (IPC) formed a marked surface front with coastal waters, preventing the entry of fuel oil into the rías. PAHs in the surface layer during the cruise were <0.5 microgL(-1), except in the Galicia bank (approximately 1 microg L(-1); where the Prestige tanker was still leaking) and the vicinity of Cape Fisterra (approximately 1.5 microg L(-1); where the convergence front between the IPC and coastal waters vanished). 相似文献
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Palma Orlović-Leko Zlatica Kozarac Božena Ćosović Slađana Strmečki Marta Plavšić 《Journal of Atmospheric Chemistry》2010,66(1-2):11-26
Characterization of atmospheric surfactants in bulk precipitations was carried out by adsorption study at the mercury electrode/solution interface using phase sensitive AC voltammetry. The structure and permeability of the adsorbed organic films at the mercury electrode was tested using the redox processes of lead and cadmium ions as electrochemical tools. The effects of organic matter from the bulk precipitations (rainwater and melted snow) were compared to those obtained for aqueous solutions of model substances: aromatic hydrocarbon (naphtalene), anionic surfactant (sodium dodecylbenzene sulfonate, NDBS), protein (albumine) and selected model substances suggested to be representative of water soluble organic compounds (WSOC) in atmospheric water (monocarboxylic, dicarboxylic, and polyacidic compounds and levoglucosan). It was found that substances like humic acid and 3-hydroxybutanoic acid may play an important role in atmospheric heterogeneous chemistry because of their surface active potential. 相似文献
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Archaeological surface surveys have located open‐air sites on cropland in the Sierra de Atapuerca (Burgos, Spain). To what degree agricultural disturbances have impacted archaeological site integrity is poorly defined and may greatly affect interpretations of prehistoric land use. This paper presents the results of three experiments concerned with the effects of tillage on artifact distribution, focusing specifically on lateral and vertical artifact displacement. We demonstrate highly variable horizontal displacement of artifacts by plowing and overall downward movement of lithic materials within the soil. This results in an expansion of site boundaries and reduction of surface artifact density, yielding a biased and unrepresentative picture of past human activity. More experimental studies are needed to better define agricultural disturbances to surface archaeological assemblages. © 2008 Wiley Periodicals, Inc. 相似文献
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Alluvial fans and shallow carbonate lakes interfered in the Teruel half‐graben during the Late Miocene–Pliocene. Tectonic influence is recorded in alluvial and lacustrine–palustrine successions, with long‐term climate changes being recorded in detail in the isotopic signatures of carbonates. Episodes of tectonic activity induced alluvial fan progradation and lake retraction in the whole basin. Three lacustrine stages have been identified, which support the idea that climate also exerted an important control on sedimentation. The transition between stages 1 and 2 occurred during a tectonically calm episode due to an increase in aridity in the Early Turolian; small fans with source areas next to the lake margin prograded, inducing lake‐shore retraction. The transition from stage 2 to 3 was caused by the superimposition of increasing tectonic activity and aridity effects. Our study demonstrates that discrimination of allogenic factors controlling sedimentation in continental closed basins is possible using sequence stratigraphy in combination with other techniques such as geochemistry of carbonates. 相似文献