Determination of the Chapman- Jouguet Pressure of a High Explosive from One Single Test

Instead of evaluating the data of the surface velocities of adjacent metal foils of different thicknesses with reference to the high explosive charge, the shock wave velocity in a plexiglass block from one firing for one charge type was measured as a function of distance. If the high explosive charge is large enough, for example 64 mm diameter and 100 mm long, then the shock wave induced in the plexiglass gives, over the first 15 mm, a shock velocity which correlates with the detonation pressure or Chapman-Jouguet pressure. With the resolution inherent in this technique, an enhanced velocity over the first few millimeters, which would correspond to a von Neumann spike, could not be detected

Shaped Charge Optimization against ERA Targets

Abstract Shaped charges with different angles or/and different liner wall thicknesses have been tested against an explosive reactive armor sandwich. The reason was to find out if more robust shaped charges give more residual penetration against an ERA sandwich, compared to shaped charges with more penetration performance in RHA targets. It was thought, that the latter ones are more sensitive against disturbances. But the shaped charges with the higher perforation capability have typically higher jet tip velocities and this gives more residual penetration also against ERA targets. In other words the so-called more robust charges gave less performance against the ERA sandwiches than the shaped charges which have higher performance in RHA targets

Mott transitions in the multi-orbital systems

We investigate the Mott transitions in the two-orbital Hubbard model with different bandwidths. By combining dynamical mean field theory with the exact diagonalization, we discuss the stability of itinerant quasi-particle states in each band. We demonstrate that separate Mott transitions occur at different Coulomb interaction strengths in general, which merge to a single transition only under special conditions. In particular, it is clarified that the $xy$ and pair-hopping components of the Hund coupling play a key role to control the nature of the Mott transitions.Comment: 2 pages, 1 figure, submitted to SCES200

Orbital-selective Mott transitions in the degenerate Hubbard model

We investigate the Mott transitions in two-band Hubbard models with different bandwidths. Applying dynamical mean field theory, we discuss the stability of itinerant quasi-particle states in each band. We demonstrate that separate Mott transitions occur at different Coulomb interaction strengths in general, which merge to a single transition only under special conditions. This kind of behavior may be relevant for the physics of the single-layer ruthenates, Ca$_{2-x}$Sr$_x$RuO$_4$.Comment: 4 pages, 4 figure