Search Results (4 total)

A theoretical methodology promising improved design of vacuum insulation in high-voltage pulsed-power systems is described. It consists of shaping the electromagnetic fields within the system in such a way that charged particles which can in principle initiate vacuum surface breakdown are deflected away from the insulator surface, and secondary electrons, if emitted, are prevented from restriking the surface. Thus, vacuum surface breakdown is prevented before it is able to develop. Our methodology is presented here by a set of case studies.

Spherically symmetric time-dependent solutions are presented. One class of solutions could represent the interior of an incompressible sphere undergoing at its surface a process of condensation or evaporation. A large class of solutions of the equation T₂²=0 is also obtained. A generalization of the Oppenheimer-Snyder solution is found. Two solutions obeying an equation of state are described.

The question of the maximum amount of energy which can be radiated by a collapsing spherical star is reexamined. On Newtonian theory, gravitational energy is negative and unbounded below, so that unlimited amounts of energy can be released. It is shown that, in the relativistic collapse of a star with non-negative energy density, self-closure always takes place before the star can release 100% of its initially positive mass energy. Moreover, under physically reasonable restrictions on the pressure, the 100% upper limit can be approached only if the star happens to pass through a very special and improbable momentarily static configuration first considered by Zel'dovich. It is concluded that for normal spherical collapse the efficiency of energy release must be low.

A formal general solution of Einstein's equations in the static case containing an arbitrary function of r is obtained. A necessary and sufficient condition that the arbitrary function must satisfy in order that the solution be physically meaningful in the neighborhood of the center is established. A mapping from Newtonian solutions is indicated. The case of infinite pressure at the center is considered. New solutions are given as examples.