A theoretical model is presented that relates the ball-bat coefficient of restitution e to the ball coefficient of restitution e0 and dynamic stiffness k. The model is used to develop a technique to normalize e to values of e0 and k for a “standard ball.” The efficacy of this normalization technique is demonstrated by comparison with experimental data. It is shown to be vastly superior to a wid...

We propose a model for collisions between particles of a granular material and calculate the restitution coefficients for the normal and tangential motion as functions of the impact velocity from considerations of dissipative viscoelastic collisions. Existing models of impact with dissipation as well as the classical Hertz impact theory are included in the present model as special cases. We fin...

Here we address the old question in aeolian particle transport about the role of midair collisions. We find that, surprisingly, these collisions do enhance the overall flux substantially. The effect depends strongly on restitution coefficient and wind speed. We can explain this observation as a consequence of a soft bed of grains which floats above the ground and reflects the highest flying par...

Flow on an inclined plane is both one of the most common situations encountered in granular ows, as well as one of the most extensively studied geometries in their theoretical treatment. Nevertheless, so far there are very few systematic studies concerning the innuence of the (dissipative) material properties on the ow. Here, numerical simulations are presented where the focus is on the innuenc...

We calculate the coefficient of restitution, ǫ, starting from a microscopic model of elastic disks. The theory is shown to agree with the approach of Hertz in the quasistatic limit, but predicts inelastic collisions for finite relative velocities of two approaching disks. The velocity dependence of ǫ is calculated numerically for a wide range of velocities. The coefficient of restitution furthe...

The elusive riddle of ventricular fibrillation (VF) has been approached from many creative angles. The latest, presented by Wu et al in this issue of the journal [1], examines the effects of restitution properties on the “critical mass” i.e., the minimum size of cardiac tissue capable of sustaining fibrillation. What is noteworthy about this novel effort is that the very basis for the working h...

One of the main principles in hand surgery is the restitution of sensation in fingers which seems hard or impossible in extensive hand traumas especially in war injuries. In this article transfer of sensory branch of radial nerve to sensory branch of median (in 25 cases) and to sensory branch of ulnar nerve (for the first time in literature and in 12 cases) is reported. Operative technics and r...