Dynamical approach to weakly dissipative granular collisions

Granular systems present surprisingly complicated dynamics. In particular, nonlinear interactions and energy dissipation play important roles in these dynamics. Usually, constant coefficients of restitution are introduced phenomenologically to account for energy dissipation when grains collide. The collisions are assumed to be instantaneous and to conserve momentum. Here, we improve on this phenomenology by introducing the dissipation through a viscous (velocity dependent) term in the equations of motion for two colliding grains. Using a first order approximation, we solve the equations of motion in the low viscosity regime. This approach allows us to calculate the collision time, the final velocity of each grain, and a coefficient of restitution that depends on the relative velocity of the grains. We compare our analytic results with those obtained by numerical integration of the equations of motion

Covariant spectator theory for the electromagnetic three-nucleon form factors: Complete impulse approximation

We present the first calculations of the electromagnetic form factors of $^3$He and $^3$H within the framework of the Covariant Spectator Theory (CST). This first exploratory study concentrates on the sensitivity of the form factors to the strength of the scalar meson-nucleon off-shell coupling, known from previous studies to have a strong influence on the three-body binding energy. Results presented here were obtained using the complete impulse approximation (CIA), which includes contributions of relativistic origin that appear as two-body corrections in a non-relativistic framework, such as "Z-graphs", but omits other two and three-body currents. We compare our results to non-relativistic calculations augmented by relativistic corrections of ${\cal O}(v/c)^2$.Comment: 30 pages, 13 figures, 6 table

Fast charging diversity impact on total harmonic distortion due to phase cancellation effect: Fast Charger's testing experimental results

Full charging cycles were performed in the studied chargers and THDV and THDI were observed. From the measurements it can be observed that the phase angles vary within a preferential range, i.e. remain within a range which is actually <90˚of amplitude. Two of the Chargers, working individually, failed to comply with the standards. Charger A barely makes it in terms of TDD and Charger C is out of the limit. In terms of individual harmonics also Charger A and Charger C are out of the limit of 4.5% for the 11th and 13th harmonics. The next step of the research will be to obtain the statistical distribution of each of the phase angles for all Chargers and perform simulations with different scenarios. Results so far suggest that stand alone Chargers with low short circuit values are recommended to have filters <13% THD.JRC.C.3-Energy Security, Distribution and Market