放牧制度对牧场入渗水文模型的影响

前言美国西部大量荒地用于放牧。虽然从最初殖民起就放牧牛羊,直到1930年以前并未作过水文影响的探讨。长期使用的破坏,特别是放牧对水文的影响所知极少。对于这类问题的应用水文技术还处在薄弱的初步阶段。现代放牧制度预期效益包括饲草的年生产量和长期产量及其品位,这种制度应适于依据牧场恢复而定的放牧管理计划,并能用于两个或多个牧场。特别缺乏这些放牧制度的水文影     

ONTOGENIC STUDY OF ISOZYMES IN GIANT TIGER PRAWN,PENAEUS MONODON (CRUSTACEA:DECAPODA)

The patterns of isozyme variation throughout the life cycle of the giant tiger prawn, Penaeusmonodon were described for ten enzyme systems (G3PD, MDH, LGG, GPI, MPI, FBP, PGM, LDH,PGD, and PROT). The zymograms showh little variation in the number of isozymic loci expressed duringlarval development compared with results reported for other penaeid prawns. There were specific ontogenicpatterns at some loci. As larvae developed beyond the embryonic stage, there was tendency for intensityof staining and complexity of banding patterns to increase.     

苏联经济地理学的发展

研究经济地理,必须同时研究这一学科的发展历史。在苏联,经济地理学的个别基本原理在一些古代俄罗斯的作品主要是游记中已经出现,这些基本原理往往与自然地理和民族志掺合在一起。十八世纪上半叶,伟大的俄国地理学家和旅游家И.К.基里洛夫(1689—1737)于1727年完成了著作《全俄罗斯的丰富物产》。这是俄国第一部在经济地理方面有系统统计资料的记述式作品。基里洛夫还于1734年绘制了第一本俄国地图册。     

The International Rosetta Mission

The European Space Agency (ESA) launched its science programme Horizon 2000 in themid eighties.this programme encompasses four big missions, the cornerstones,in addition tosmaller missions. The four cornerstones are:SOHO/Cluster a solary observatory and in situmeasurements of the Earth magnetosphere,XMM and X-ray observatory,Rosetta a comet ren-dezvous mission,and FIRST a far infrared observatory.SOHO was successfully launched in     

Effects of Sediment-induced Stratification on Floc Breakup in an Idealized Tidal Estuary： A Numerical Modelling Study

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.