Daniel C. Hong

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In the Brazil nut problem (BNP), hard spheres with larger diameters rise to the top. There are various explanations (percolation, reorganization, convection), but a broad understanding or control of this effect is by no means achieved. A theory is presented for the crossover from BNP to the reverse Brazil nut problem based on a competition between the(More)
The question of transport in a random two-component mixture is addressed. To this end, two models are precisely formulated that effectively extend to two-component mixtures the de Gennes ant model of one-component systems. We develop and test a scaling theory, and we solve some of the problems associated with the limit where one of the components is(More)
Starting from Enskog equation of hard spheres of mass m and diameter D under the gravity g, we first derive the exact equation of motion for the equilibrium density profile at a temperature T and examine its solutions via the gradient expansion. The solutions exist only when βµ ≤ µ o ≈ 21.756 in 2 dimensions and µ o ≈ 15.299 in 3 dimensions, where µ is the(More)
  • D C Hong
  • 2001
We present exact results for the density profile of a one dimensional array of N hard rods of diameter D and mass m under gravity g. For a strictly one dimensional system, the liquid-solid transition occurs at zero temperature, because the close-packed density straight phi(c) is 1. However, if we relax this condition slightly such that straight(More)
We present a detailed weakly nonlinear analysis, along with a solvability analysis, of a new instability in viscous ngering which we term the Surface-Tension-Driven instability. This instability occurs when the surface tension is modiied in proportion to the local curvature. It is an intrinsically nonlinear instability which always requires a nite-amplitude(More)
Molecular Dynamics simulations were carried out to test the thermodynamic theory of weakly excited, two-dimensional, granular systems [Hayakawa and Hong, Phys. Rev. Lett. 78, 2764(1997)], where granular materials are viewed as a collection of spinless Fermions. We first determine the global temperature T by fitting the steady state density profile to the(More)