Abstract: A process for preparing a carbon black which can control the particle size distribution and aggregate size distribution of the carbon black. This apparatus comprises a combustion chamber, a cylindrical throat more contracted than the combustion chamber, which is adapted for forming a plug flow of the hot gas, downstream of said throat, an expanding venturi portion downstream of said throat, and a carbon black reaction chamber; and a process comprising forming a plug flow of the hot gas in at least the cylindrical throat and the expanding venturi portion; and feeding a hydrocarbon material from hydrocarbon material spraying nozzles provided at two or more axially separate sites in the expanding venturi portion.

Abstract: A power supply circuit for discharge machining comprising a first switching means for supplying a d-c power voltage to a discharge gap between a discharge machining electrode and a workpiece, a first energy consumption circuit having a second switching means provided on the output side of the first switching means, and a second energy consumption circuit having a third switching means provided in the vicinity of the discharge gap in parallel therewith, in which the second switching means of the first energy consumption circuit and the third switching means of the second energy consumption circuit are caused to conduct after the first switching means is turned off.

Abstract: A discharge machining apparatus adapted to permit the supply of discharge current to be cut off without increasing electrode consumption. Arrangements are made to gradually increase the level of discharge current, rather than maintaining the current level of discharge pulse. By doing so, electrode consumption becomes independent of the pulse width of the discharge pulse, so the discharge current can be cut off immediately after an abnormal state such as short circuiting or an instantaneous interruption of the discharge current occurs, eliminating the danger of deteriorating the quality of the machining surface of a workpiece.

Abstract: The direction-variable speaker system has first and second speaker cases containing speaker units for different reproduction bands, respectively, and an intermediate case interposed between those two speaker cases. The first speaker case and the intermediate case are connected by a first pivotal shaft pivotally of each other and are given tendency to pull each other. Between the first speaker system and the intermediate case is provided a rising angle setting mechanism including a first gear cam secured to one of these cases and a stopper member secured to the other for meshing engagement with the first gear cam. The second speaker case and the intermediate case are connected by second pivotal shaft pivotally of each other and are given tendency to pull each other.