Transitions in the Horizontal Transport of Vertically Vibrated Granular Layers

Motivated by recent advances in the investigation of fluctuation-driven ratchets and flows in excited granular media, we have carried out experimental and simulational studies to explore the horizontal transport of granular particles in a vertically vibrated system whose base has a sawtooth-shaped profile. The resulting material flow exhibits novel collective behavior, both as a function of the number of layers of particles and the driving frequency; in particular, under certain conditions, increasing the layer thickness leads to a reversal of the current, while the onset of transport as a function of frequency occurs gradually in a manner reminiscent of a phase transition. Our experimental findings are interpreted here with the help of extensive, event driven Molecular Dynamics simulations. In addition to reproducing the experimental results, the simulations revealed that the current may be reversed as a function of the driving frequency as well. We also give details about the simulations so that similar numerical studies can be carried out in a more straightforward manner in the future.Comment: 12 pages, 18 figure

Adsorption sites in zeolites A and X probed by competitive adsorption of H{sub 2} with N{sub 2} or O{sub 2}: Implications for N{sub 2}/O{sub 2} separation

The authors determine details of the adsorption of O{sub 2} or N{sub 2} in Li{sup +} exchanged zeolites by way of their effect on coadsorbed H{sub 2} molecules using inelastic neutron scattering (INS) techniques. The results clearly show, for example, the absence of type III cations in Li-A and the expected stronger binding of N{sub 2} (compared with O{sub 2}) and thereby provide insight into the relative efficacy of Li-X for O{sub 2}/N{sub 2} separation