气流中跃移颗粒的受力分析   总被引：14，自引：1，他引：13  

杨保  邹学勇  王周龙  董光荣  刘玉璋 《地理科学》1999,19(5):475-478

气流中颗粒跃移过程中受力分析及其运动机理的研究在发展风沙物理学理论方面具有重要的意义,长期以来,受实验条件和实验手段的限制,关于此方面的认识还不统一,采用高速频闪摄影技术,在计算跃移颗粒各运动参数的基础上,反推出跃移颗粒的阻力系数和升力系数,并将颗粒所受的阻力,升力和重力进行了比较,结果表明,阻力最重要,重力次之,升力也不可忽略,它占重力的２０％以上,利用数值计算方法,得出了颗粒的跃移运动轨迹,与  相似文献   

Magnetic properties of tidal flat sediments of the Yangtze Estuary and its relationship with particle size   总被引：6，自引：0，他引：6  

张卫国  俞立中 《中国科学D辑(英文版)》2003,46(9):954-966

Since the 1970s, environmental magnetism has found extensive applications in diverse research areas of geoscience[1]. In China, a lot of environmental magnetic studies have been carried out on loess, lake and marine sediments for the purpose of paleoclima…  相似文献   

Pore scale modeling of immiscible and miscible fluid flows using smoothed particle hydrodynamics     

Alexandre M. Tartakovsky  Paul Meakin 《Advances in water resources》2006

A numerical model based on smoothed particle hydrodynamics (SPH) was developed and used to simulate immiscible and miscible fluid flows in porous media and to study effects of pore scale heterogeneity and anisotropy on such flows.  相似文献   

Simulations demonstrating interaction between coarse and fine sediment loads in rain‐impacted flow     

P. I. A. Kinnell 《地球表面变化过程与地形》2006,31(3):355-367

Rain‐impacted flows dominate sheet and interrill erosion and are important in eroding soil rich in nutrients and other chemicals which may have deleterious effects on water quality. Erosion in rain‐impacted flow is associated with raindrop detachment followed by transport either by the combination of flow velocity and raindrop impact (raindrop‐induced flow transport, RIFT) or the inherent capacity of the flow to transport detached material. Coarse particles tend to be transported by RIFT, while fine particles tend to be transported without any assistance from raindrop impact. Because the transport process associated with coarse particles is not 100 per cent efficient, it generates a layer of loose particles on the soil surface and this layer protects the underlying soil from detachment. Simulations were performed by modelling the uplift and downstream movement of both fine and coarse particles detached from the soil surface by individual raindrop impacts starting with a surface where no loose material was present. The simulations produced a flush of fine material followed by a decline in the discharge of fine material as the amount of loose material built up on the bed. The decline in the discharge of fine material was accompanied by an increase in the discharge of coarse material. The relative amounts of coarse and fine material discharged in the flow varied with flow velocity and cohesion in the surface of the soil matrix. The results indicate that the discharge of various sized sediments is highly dependent on local soil, rain and flow conditions and that extrapolating the results from one situation to another may not be appropriate. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

长三角经济高速发展地区土壤pH时空变化及其影响因素   总被引：13，自引：0，他引：13  

邵学新  黄标  顾志权  钱卫飞  金洋  毕葵森  严连香 《矿物岩石地球化学通报》2006,25(2):143-149

通过调查和分析长三角地区张家港市2004年和第二次土壤普查时(1980)的土壤pH,探讨了该市近20年来基于经济高速发展影响下的土壤pH变化及影响因素。结果表明,自第二次土壤普查以来,该市土壤pH变化明显。南部人为土地区绝大部分土壤pH值都下降了一个单位,平均值由7.39降至6.33;北部雏形土区,两个时期的土壤pH值分别为7.92和7.98。土壤pH的降低可能同该地区长期施用化学肥料、酸雨及工业酸性“三废”排放的增加有关。此外,土地利用和田间管理也对土壤pH变化起着较为重要的作用,而土壤地球化学性质差异则是导致南北地区土壤pH变化不同的内在因素。  相似文献   

三维质点追踪模型及其在胶南海域的应用   总被引：2，自引：0，他引：2       下载免费PDF全文

张学庆  孙英兰 《水科学进展》2006,17(6):873-876

在已建立的变边界河口、陆架、海洋模型(ECOM)的基础上添加一个变边界质点追踪模块,研究胶东半岛南海域的物质输运特征,讨论了三维空间中,水质点在潮流作用下的迁移特点.该模型在近海海洋环境管理上具有实用价值.  相似文献   

多孔介质中水敏性应用的研究综述     

张晓辉  郑西来  林国庆  吴俊文  周骏 《水文地质工程地质》2006,33(4):81-84

水敏现象在石油、岩土和环境工程等领域广泛存在。有效地控制水敏现象的发生，不仅具有科学意义，还有一定的经济价值。本文在广泛查阅国内外研究成果的基础上，总结了水敏性在石油、岩土和环境工程方面应用的研究进展，并在此基础上提出了水敏性研究的发展方向。  相似文献   

An approximate analytical solution for the deposition of heavy particles released from an elevated line source   总被引：1，自引：1，他引：1  

T. Bouvet  J. D. Wilson 《Boundary-Layer Meteorology》2006,119(1):1-18

This work re-examines and further develops an analytical solution for the deposition swath of heavy particles released in the atmosphere from an elevated source over uniform terrain, correcting the particle diffusivity for the crossing trajectory effect. The revised (approximate) analytical solution proves to be accurate within 20% over a wide range of micrometeorological conditions and particle size, despite its neglect of the turbulence component of the deposition flux. It compares very satisfactorily with experimental data and with the simulations of a Lagrangian stochastic model, provided the variable U(H)/w _g ≤7 (ratio of the mean horizontal wind speed at source height to the particle settling velocity). In this domain of validity, simple formulae relating the statistics of the deposition swath to U(H)/w _g are derived.  相似文献   

纳米级微粒地球化学测量中异常重现性研究     

刘应汉  赵传东  孔牧  张华  张勤  任天祥 《物探化探计算技术》2007,(Z1)

纳米级微粒测量是寻找隐伏矿的新方法,选取实地模拟实验和在已知隐伏矿区,利用液态捕集剂和等离子体质谱分析测试样品,进行重复测量试验,研究结果表明,不同成矿元素,在地表形成异常的运移富集速率不同,其运移速率主要取决于纳米级微粒本身的地球化学性质,地下上升气流、断裂等裂隙有利于微粒的上升运移富集;纳米级微粒地球化学重复测量时,异常可具有良好的重现性,但异常重现较常规气体缓慢,通常需要2~3个月。  相似文献   

地幔流体的交代作用——来自碱性正长岩及其深源岩石包体的证据   总被引：2，自引：0，他引：2  

宋祥峰  刘显凡陶专卢秋霞  龙训荣 《岩石矿物学杂志》2007,26(4):310-314

滇西玉龙县小桥头硅化霓辉正长斑岩中,含有较多镁铁-超镁铁质深源包体岩石。经岩相学和电子探针及扫描电镜分析发现,伴随交代蚀变,寄主岩和各类镁铁-超镁铁质包体岩石中,普遍发育沿粒间和矿物晶体裂隙或解理纹贯入或穿插的黑色不透明物质,主要由微晶硅酸盐矿物和磁铁矿组成。本文研究认为,硅酸盐矿物与磁铁矿在背散射电子图像中表现为熔离特征,这种在透光显微镜下呈黑色不透明的微晶固体,是引发交代蚀变、具熔浆流体特点和超临界流体性质的地幔流体交代作用的一种微观表现。  相似文献