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J A Both

Publications and source records attributed to J A Both.

2 recordsLinked to original sources

Density-functional theory of hard-sphere condensation under gravity.

The onset of condensation of hard spheres in a gravitational field is studied using density-functional theory (DFT). We find that the local density approximation yields results identical to those obtained previously using the kinetic theory [Physica A 271, 192, (1999)], and a weighted density-functional theory gives qualitatively similar results, namely, that the temperature at which condensation begins at the bottom scales linearly with the weight, diameter, and number of layers of particles. We find also that the different DFT approaches give quantitatively different results for the density profiles at low temperatures. In particular, the weighted density-functional approach reveals the layering of hard spheres in the solid regime.

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Surface instability in windblown sand.

We investigate the formation of ripples on the surface of windblown sand based on the one-dimensional model of Nishimori and Ouchi [Phys. Rev. Lett. 71, 197 (1993)], which contains the processes of saltation and grain relaxation. We carry out a nonlinear analysis to determine the propagation speed of the restabilized ripple patterns, and the amplitudes and phases of their first, second, and third harmonics. The agreement between the theory and our numerical simulations is excellent near the onset of the instability. We also determine the Eckhaus boundary, outside which the steady ripple patterns are unstable.

Journal Article↗