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991.
The Problem of studying eomPlex multicomPonent systems without seParation of theeomPonents 15 well known.Generally,the situation arises whenever interaetions betweeneomPonents are essential in determining the funetion of the system,notably in biochemiealsystems and in eatalysis.In eases sueh as these,the ultimate aim 15 to deduee the role of eaehof the eomPonents as well as the interaetions between them by 相似文献
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X.H.Wang 《中国海洋大学学报(英文版)》2004,3(2):115-122
Floc breakup dynamics are studied by a sediment transport numerical model in an idealized tidal estuary that has a constant water depth and rapid flocculation of cohesive sediments. The focus is placed on the effects of boundary layer stratification induced by a bottom nepheloid layer on floc breakup and size distribution in the water column. In a neutrally stratified estuary, the floc size distribution follows a parabolic function with maximum values at the surface and bottom. The sediment-induced stratification in the bottom boundary layer increases the median floc sizes. Furthermore, sediment-voided convection caused by the settling lutocline generates significant turbulent kinetic energy dissipation and reduces floc size at the depth where the convective mixing happens. Below that depth, a weak local maxima in the floc size is predicted due to presence of the lutocline. The effect of sediment-stratified bottom boundary layer on the floc breakup can be consistently approximated by a linear regression between the maximal floc size and flux Richardson number. 相似文献
995.
广东肇庆第四纪岩石地层划分 总被引:1,自引:0,他引:1
粤西肇庆内陆地盆地第四纪堆(沉)积物,从下而上具有粗→细→很细或粗→细→很粗的变化,根据沉积物的物质成分,成因类型及其所处的地貌部位,将其划分为黄岗组,大湾镇组,睦岗组,北岭组等4个岩石地层单位,其时代为中一-晚更新世至中一晚全新世。 相似文献
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We have used a 2-D microphysics model to study the effects of atmospheric motions on the albedo of Titan's thick haze layer. We compare our results to the observed variations of Titan's brightness with season and latitude. We use two wind fields; the first is a simple pole-to-pole Hadley cell that reverses twice a year. The second is based on the results of a preliminary Titan GCM. Seasonally varying wind fields, with horizontal velocities of about 1 cm sec-1 at optical depth unity, are capable of producing the observed change in geometric albedo of about 10% over the Titan year. Neither of the two wind fields can adequately reproduce the latitudinal distribution of reflectivity seen by Voyager. At visible wavelengths, where only haze opacity is important, upwelling produces darkening by increasing the particle size at optical depth unity. This is due to the suspension of larger particles as well as the lateral removal of smaller particles from the top of the atmosphere. At UV wavelengths and at 0.89 micrometers the albedo is determined by the competing effects of the gas the haze material. Gas is bright in the UV and dark at 0.89 micrometers. Haze transport at high altitudes controls the UV albedo and transport at low altitude controls the 0.89 micrometers albedo. Comparisons between the hemispheric contrast at UV, visible, and IR wavelengths can be diagnostic of the vertical structure of the wind field on Titan. 相似文献
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MacDermott AJ Barron LD Brack A Buhse T Drake AF Emery R Gottarelli G Greenberg JM Haberle R Hegstrom RA Hobbs K Kondepudi DK McKay C Moorbath S Raulin F Sandford M Schwartzman DW Thiemann WH Tranter GE Zarnecki JC 《Planetary and Space Science》1996,44(11):1441-1446
A characteristic hallmark of life is its homochirality: all biomolecules are usually of one hand, e.g. on Earth life uses only L-amino acids for protein synthesis and not their D mirror images. It is therefore suggested that a search for extra-terrestrial life can be approached as a Search for Extra-Terrestrial Homochirality (SETH). A novel miniaturized space polarimeter, called the SETH Cigar, is described which could he used to detect optical rotation as the homochiral signature of life on other planets. Moving parts are avoided by replacing the normal rotating polarizer by multiple fixed polarizers at different angles as in the eye of the bee. It is believed that homochirality will be found in the subsurface layers on Mars as a relic of extinct life. 相似文献
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