Abstract: A III-V compound semiconducting single crystal is manufactured by a method using an encapsulant, which method comprises allowing the molten mass of a material for the crystal melted in advance under high pressure to be placed under a pressure lower than the pressure to be exerted during the work of pulling the crystal thereby causing the molten mass to generate bubbles and allowing the departing bubbles to entrain impurities from the molten mass, bringing a seed crystal into contact with the molten mass, applying a potential to the molten mass thereby determining the impurity concentration of the molten mass based on the results of the measurement and, after the impurity concentration of the molten mass determined as described above has reached a prescribed level, initiating the work of pulling the crystal from the molten mass.

Abstract: A composition of at least one member selected from the group consisting of sodium fluoride and calcium fluoride and optionally containing kaolin is powerful adhesive for ceramic articles which is used by interposing the adhesive intimately between the opposed surfaces for union of the ceramic articles and heating the adhesive to a temperature equal to or higher than the decomposition temperature of the fluoride used.

Abstract: A hydraulic servo-actuator has a casing embracing therein a hydraulic fluid chamber which is divided into two hydraulic drive chambers by a vane projecting from a first shaft. To each of the divided chambers are connected an oil feeding passage provided with a variable restrictor and intended for the feeding of pressurized oil and an oil discharge passage intended for the discharging of the pressurized oil. A second shaft is coaxially disposed relative to the first shaft, and the first and second shafts are correlated with each other in such a way that the relative rotary displacement occurring between the two shafts controls the aperture of the oil discharge passages communicating with the divided chambers. The difference between the static pressures which are consequently produced within the divided chambers because of the aperture of the oil discharge passages causes the vane to swing, making it possible to control the torque even when the vane is in the neighborhood of its neutral position.