Spontaneous stratification in granular mixtures

Article Abstract:

A size separation effect that occurs when granular mixture is poured between two vertical plates is described. The mixture's spontaneous stratification into alternating layers of small and large grains whenever the larger grains have larger angle of repose than the small grains is observed. Only spontaneous segregation, without stratification, is noted when the larger grains have smaller angle of repose than the small grains. A physical mechanism behind the observed stratification, which is related to the fact that a pair of layers, instead of only one, is formed in the course of each avalanche, is proposed.

Analysis, Separation (Technology), Granular materials

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Modelling urban growth patterns

Article Abstract:

A model for urban development based on the correlated percolation theory in presence of a density gradient, correctly reproduces the observed morphology of cities, area distribution of towns in an urban system and the urban growth dynamics. The model makes it possible to predict the global properties of urban morphologies. The developmental units are positioned with an occupancy probability, not at random. A study on cities indicates the large value of decentralization. Density gradient is the only factor of urban development which is affected by time.

Models, Observations, Cities and towns, City planning, Urban planning

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Self-similarity of complex networks

Article Abstract:

A variety of real complex networks are analyzed and the results are achieved by the application of a renormalization procedure that coarsegrains the system into boxes containing nodes within a given 'size'. A power-law relation between the number of boxes needed to cover the network and the size of the box is identified, defining a finite self-similar exponent.

United States, Science & research, Renormalization (Physics)

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