This paper proposes a macroscopic arc model applicable to the transient d. c. arc axially blasted by impulsive compressed air. Its presure as well as the blasted velocity are higher than those adopted in modern power circuit breakers. Thermal dissipation out of the arc column is well estimated by a slightly modified heat transfer relationship derived for a solid cylinder in forced convection. The exponentially decaying d. c. current produced in an inductance-free RC circuit is stronly suppressed when a switching arc is axially blasted by the impulsive compressed air induced by explosin of a detonator. The calculated suppressed current waveforms coincide with those actually obtained experimentally under the following various conditions: the recovery voltage from 1.5 to 6 kV, the pressure of the blasted compressed air from 0.77 to 1.47 MPa and the velocity from 730 to 1130 m/s.
Anthracene single crystals are grown by the Bridgman method under various conditions, and the quality estimation of the crystals is made from their triplet lifetime. The growth conditions for crystals with least defect are experimentally investigated. The best class of crystal is obtaiued when Ceq, which is defined by three main parameters, namely, temperature difference between an upper furnace and a lower one, down velocity of the ampoule, and cross section of the ampoule, and cross section of the ampoule, has the value of 180. It is suggested that the temperature difference is a more appropriate factor for determining growth condition rather than the temperature gradient.