منابع مشابه
Stirring two grains of sand*
Consider two unit balls in a d-dimensional flat torus with edge length r, for d ≥ 2. The balls do not move by themselves but they are pushed by a Brownian motion. The balls never intersect—they reflect if they touch. It is proved that the joint distribution of the processes representing the centers of the balls converges to the distribution of two independent Brownian motions when r →∞, assumin...
متن کاملGrain Size and Shape of Sand Grains in Ergs of Iran
Large areas of Iran are under the influence of wind erosion thus it is important that we recognize three zones ofremoval, transportation and deposition. The deposition zone is very important due to more damages and tangibleeffects. In this study we try to obtain a comprehensive idea to Persian desert with use of laboratory facilities, remotesensing, GIS and field surveying. We survey 28 ergs in...
متن کاملBiofilm origin of clay-coated sand grains
The presence of clay-sized particles and clay minerals in modern sands and ancient sandstones has long presented an interesting problem, because primary depositional processes tend to lead to physical separation of fineand coarse-grained materials. Numerous processes have been invoked to explain the common presence of clay minerals in sandstones, including infiltration, the codeposition of floc...
متن کاملPrecisely cyclic sand: self-organization of periodically sheared frictional grains.
The disordered static structure and chaotic dynamics of frictional granular matter has occupied scientists for centuries, yet there are few organizational principles or guiding rules for this highly hysteretic, dissipative material. We show that cyclic shear of a granular material leads to dynamic self-organization into several phases with different spatial and temporal order. Using numerical s...
متن کاملSome Observations on Electron Micrographs of Quartz Sand Grains
Electron micrographs of sand grains from southern Piedmont saprolites, temperate and polar glacial deposits, and the St. Peter Sandstone are presented. Sand-grain surface features of saprolite grains are described for the first time and from these some concept of the initial surface of a quartz sand grain is obtained. Micrographs of the sand grains from glacial deposits whose erosional history ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Nature
سال: 2007
ISSN: 0028-0836,1476-4687
DOI: 10.1038/449146a