Abstract: A heterojunction field effect transistor includes a carrier supplying layer comprising material which is not likely to produce a deep level even by doping. A channel layer comprises material which has the largest electron affinity among three types of semiconductor material constituting the heterojunction FET and has a high carrier mobility. A spacer layer is interposed between the channel layer and the carrier supplying layer and comprises material which enables the reduction of Coulomb interaction between two-dimensional carriers in the channel layer and ions in the carrier supplying layer. In addition, the spacer layer increases the effective conduction band energy discontinuity .DELTA.E.sub.c between the carrier supplying layer and the channel layer.

Abstract: A treatment chair assembly comprising a treatment chair and a chair base, the chair assembly being pivotally or swingably connected to a chair base, in which a chair elevating mechanism is housed, so that the chair can be turned upward from and downward to the chair base. With this treatment chair assembly, it is not necessary to separate the treatment chair from the chair base and move the treatment chair to a different place when the chair elevating mechanism and the instrument drive/control unit are maintained, checked or repaired. The treatment chair can be turned upward by pivoting or swinging without separating and moving the treatment chair. As a result, labor can be saved and no space is required to temporarily store the treatment chair. The space for a dental treatment room can be used effectively. Furthermore, since the chair is not separated or moved, less concern for staining or breaking the chair due to bumping against objects is necessary.

Abstract: Earth's crustal stress is measured by drilling a bore-hole in rock body, producing a longitudinal crack at a selected portion thereof with or without a natural traverse crack through intermittent application of hydraulic pressure thereat while measuring the pressure at different stages of crack production, producing an artificial traverse cracks through the use of a prenotch, determining orientations of the cracks thus produced by inspecting the bore-hole surface conditions, and numerically analyzing the crack orientations and the pressures at different stages of crack production.

Abstract: A device for controlling a headrest of a treatment equipment to be used for dental and medical treatment. The device comprises an arcuate support shaft connected to said headrest with the center of radius of curvature of the shaft positioned above said backrest, a guide sheath provided inside the top of said backrest, said sheath having an arcuate guide groove slidably receiving said support shaft, a lock mechanism for locking said support shaft in a suitable position in said guide groove, and lock releasing mechanism for unlocking said support shaft.

Abstract: A seat cover (1) mounted on a vehicle seat (A) is used as a heater in winter and as a ventilator in summer. A flexible main body (9, 9') has on its one side an electric heater (10) and on the other side a number of holes (13) through which air is discharged by a blower (32). The main body includes a core (22, 35) which defines therein a passage (8) for the air. The core consists of resilient material and includes a base plate (22b, 35a) which is provided with a number of projections (22a, 35c) projecting from at least one side of the base plate. The core improves flexibility of the seat cover to conform with both the user's body and the vehicle seat, while providing a sufficient rigidity to prevent closure of the air passage when the user's weight is applied thereto.

Abstract: A rotary vane type compressor having a rotor (8) mounted with a number of vanes (10) each accommodated in a vane groove (11) of a liner (12) made of anti-abrasive material and a boss (13) for fixing the liners (12) and the liners are fixed in position with respect to the boss by integrally casting the liners and the boss by placing them in the predetermined position using light weight alloy.

Abstract: A passage leads from a high pressure discharge zone of a vane pump to an interface defined between the surface of the rotor of the pump and an arcuate contact surface formed in the inner wall of the pump housing to supply fluid under pressure to the interface for lubricating same.

Abstract: According to this invention, useless exposure of a human being to X-ray is avoided and X-ray film is economically used by providing the X-ray generator of a dental X-ray apparatus with an X-ray intercepting means by which the size of the opening or slit for X-ray beams flow is easily controlled. The X-ray apparatus comprises an X-ray generator, an X-ray film, an arm for supporting the X-ray generator and the X-ray film in such a manner that the X-ray generator faces the X-ray film. When the arm is rotated at a predetermined angle around the X-ray film thereby causing the X-ray generator to be rotated proportionally, the X-ray generator emits X-ray beams through the vertically elongated slit disposed in the X-ray generator's head.

Abstract: An improved dental handpiece holder supports a handpiece in the region from the rear end of the grip portion to the tail-stock portion. A front gripping holder portion prevents movement in the horizontal direction, a rear gripping holder portion prevents a forward tipping moving, and the front and rear gripping portions co-act to prevent movement of the handpiece in the axial direction. The front gripping portion is provided with three separate portions, one on the left hand wall and two on its right hand wall. The two supporting portions on the right hand wall are spaced axially apart from one another, and the single supporting portion on the left hand wall is located in a axial position intermediate that of the opposing two portions. Right and left supporting portions in the rear gripping portion support the tail-stock of the handpiece.

Abstract: This disclosure relates to an assembly for paired face to face dental trainees designed to permit two trainees to receive training in dental treatment by seating them in an opposed relation with each other with the desk placed therebetween. The assembly is greatly contributable to a reduction in space, cost in that it comprises human head models and freely drawable and retractable instruments symmetrically mounted in the front and rear side of the desk assembly, drawing and retraction devices for the instruments housed in the upper and lower layers in the desk, a control unit and a piping unit each for a supply fluid housed in the desk, and side boxes attached to the same side on the front and the rear side of the desk and adapted to store treatment tools, utensils and the like therein.

Abstract: A combined magnetic tape head having a recording head and a reproducing head disposed in a side by side relationship with a recessed wedge shaped area therebetween. A shielding plate is interposed between the heads to reduce cross feed therebetween. The top portion of the shielding plate is bent into L-shape so that the bent tip confronts the recording head. The remainder of the wedge shaped area is covered with a resin material, or an auxiliary plate can be positioned over the plate extending between the heads. In order to maintain the combined head free from dust accumulation, the top portion of the L-shaped shielding plate or the auxiliary plate is tapered so that it has a substantially trapezoidal cross-section with either straight or curved inclining sides.

Abstract: An apparatus to control the air flow in an automobile comprises a box which is provided beneath a seat and has openings respectively formed in the upper wall and the front wall thereof, a fan which is mounted to the rear wall of the box and of which the rotation can be reversed, a switching plate which is provided in the box in such a way as to selectively close the opening formed in the upper wall and the opening formed in the front wall, and a means to drive the switching plate so as to selectively open either one of said openings in synchronism with the switching of the rotation of the fan, thereby the air is forcibly upwardly passed through the seat or the hot air from a heater or the cold air from a cooler provided in front of the seat is forcibly sent rearwardly through said box.

Abstract: An electronic air cleaner having therein an electrostatic precipitator and an ultraviolet sterilizing lamp is positioned close to an antenna of a radio receiver. A shielding cover lined with a thin metal film covers the lamp to block radiation of the electric noise waves generated by the lamp.

Abstract: An electrostatic dust precipitator as a gas cleaner in which a grounded, perforated metal filter is located at the gas inlet end of the space between a pair of grounded dust collecting electrodes having a discharge wire located therebetween so that electrostatic fields are developed not only between the discharge wire and the dust collecting electrodes but between the discharge wire and the metal filter.

Abstract: An electrostatic precipitator comprises at least a pair of parallel collecting plate electrodes between which is disposed an auxiliary plate electrode biased at an opposite potential to the potential applied to the collecting plate electrodes and a corona discharge electrode spaced predetermined distances from said collecting and auxiliary plate electrodes and biased at the same potential as that applied to the auxiliary plate electrode.