11 research outputs found
Current reversal with type-I intermittency in deterministic inertia ratchets
The intermittency is investigated when the current reversal occurs in a
deterministic inertia ratchet system. To determine which type the intermittency
belongs to, we obtain the return map of velocities of particle using
stroboscopic recording, and numerically calculate the distribution of average
laminar length . The distribution follows the scaling law of , the characteristic relation of type-I
intermittency.Comment: 4 pages, 7 figure
Pattern Formation in Laser Induced Melting
A laser focussed onto a semiconductor film can create a disordered lamellae
pattern of coexisting molten-solid regions. We present a continuum model based
on the higher reflectivity of the molten regions. For large latent heat, this
model becomes equivalent to a model of block copolymers. The characteristic
wavenumber of the lamellae is that marginally stable to slow variations in the
orientation (the zig-zag instability) and is obtained via systematic expansions
from two limits. The lamellae can also be unstable to the zig-zag instability
and Eckhaus instability simultaneously. This instability is a signal of dynamic
steady states. We numerically study the behaviour after a quench. The lamellar
size agrees with the analytic results and experiments. For shallow quenches,
locally parallel stripes slowly straighten in time. For deep quenches, a
disordered lamellae forms. We construct the director field and determine the
orientational correlation length. Near onset the correlation is fixed by the
system size. Far from onset the correlation length saturates at a finite value.
We study the transition to the time-dependent asymptotic states with decreasing
latent heat. postScript figures available on requestComment: 44 pages, revtex 3.
Apparent wall slip in non-Brownian hard-sphere suspensions
We analyze apparent wall slip, the reduction of particle concentration near the wall, in hard-sphere suspensions at concentrations well below the jamming limit utilizing a continuum level diffusion model. The approach extends a constitutive equation proposed earlier with two additional potentials describing the effects of gravitation and wall-particle repulsion. We find that although both mechanisms are shear independent by nature, due to the shear-rate-dependent counter-balancing particle migration fluxes, the resulting net effect is non-linearly shear dependent, causing larger slip at small shear rates. In effect, this shows up in the classically measured flow curves as a mild shear thickening regime at the transition from small to intermediate shear rates