X-ray Microtomography Study Of The Compaction Process Of Rods Under Tapping

We present an x-ray microtomography study of the compactionprocess of cylindrical rods under tapping. The process is monitored bymeasuring the evolution of the orientational order parameter, local, andoverall packing densities as a function of the tapping number for differenttapping intensities. The slow relaxation dynamics of the orientationalorder parameter can be well ftted with a stretched-exponential law withstretching exponents ranging from0.9to1.6. The corresponding relaxationtime versus tapping intensity follows an Arrhenius behavior which isreminiscent of the slow dynamics in thermal glassy systems. We alsoinvestigated the initial random velocities of the rods and the averagecoordination number under tapping.