Abstract: A permanent magnet rotor wherein a rotary shaft has an orthogonal cross a sectional shape orthogonal in a longitudinal direction of the rotary shaft, a plurality of circular-arc portions which are around the axis of rotation of the rotary shaft, and rectilinear portions which connect the adjacent circular-arc portions with straight lines having no curved portion. Respective permanent magnets, equal in number to the circular-arc portions, are fixed extending over the circular-arc portions and the rectilinear portions. The surface of each permanent magnet remote from the rotary shaft has a cross sectional contour orthogonal to the longitudinal direction of the rotary shaft, forming a circular arc which protrudes outward.

Abstract: A fixed slit plate and a rotary slit plate which is secured to a rotating shaft are provided between two photoconductive elements and a light emitting element, and the two photoconductive elements provide two outputs which have the phase difference .pi. therebetween. These two outputs thus provided are added to extract the dc component, thereafter exerting feedback control over the light emitting element such that this dc component is maintained at a constant level.

Abstract: Hydrazine is added to low-level radioactive waste, and the waste is contacted with an iron hydroxide-cation exchange resin so that its radioactive concentration may be lowered. The resin is a strongly acid cation exchange resin treated with ferric chloride and aqueous ammonia and containing a product of hydrolysis of ferric ions.

Abstract: When driving an AC motor with a PWM inverter, the width of a speed command signal is modulated by a carrier to produce width modulated pulses for controlling main switching elements. The width modulated pulses are liable to be attended with impulses which cause magnetic vibrations in the AC motor, resulting in noises. The generation of these impulses can be suppressed by changing the amplification factor of an amplifier for the speed command signal or the amplitude of the carrier on the basis of the rate of change of the speed command signal. Noises which would be attendant on low speed running of the AC motor can be reduced by changing the amplification factor of the amplifier and the amplitude of the carrier on the basis of detected frequency of the speed command signal or revolution of the AC motor during low speed running.

Abstract: This invention relates to a dental handpiece including turbine blades to be driven by a high-speed fluid under pressure to a turbine rotor chucking a cutting shaft, and blades are provided with openings or cutout portions located at both outside ends in a thrust direction of the blades so as to provide flange portions between the openings and the end portions of the blades and the peripheral width of the blades is larger than that of the high-speed fluid supply apperture.

Abstract: A method of lubricating a dental hand-piece wherein a small-sized lubricating oil sealed oiler is detachably mounted in a position adjacent to the rotor side of a rotor driving air passageway of a dental hand-piece device, the lubricating oil from said oiler is continuously mixed into rotor driving air to atomize said oil by utilizing the pressure and flow rate of said rotor driving air when said hand-piece is in use, and the mist oil thus obtained is supplied together with said air to said rotor to thereby continuously lubricate the rotor; and a novel small-sized oiler used in the method; are disclosed.

Abstract: This invention relates to a driving mechanism of an air bearing journaled handpiece for dental treatment, the mechanism being improved in that even when a load contrary to the direction of rotation of a tool shaft such as cutting of the teeth acts upon the tool shaft in a dental operation, rotation of the tool shaft does not stop because of load resistance but enables the heretofore, unmaterialized medium-speed cutting (hereinafter referred to as "extension to medium-speed rotation") and makes it possible to obtain improved torque during high-speed rotation in addition to the extension to medium-speed rotation.

Abstract: A cartridge-type chuck for use in a dental handpiece wherein a substantially cylindrical cartridge case incorporates within itself at least a friction-type chuck body and a stopper provided with a square hole of a smaller diameter than the inner diameter of said chuck body, said cartridge case being formed at its front part into truncated cone by tapering the outer circumferential surface and is provided at its thickened rear part with a threaded interface on the circumference, is disclosed. This cartridge-type chuck is able to be loaded and unloaded for the purpose of replacing it with ease in relation to the rotor disposed in the inside of a dental hand-piece, into which the dental cutting tool can be inserted by a single step, and whose holding power is strong enough to be free from occurrence of the center whirling of the spindle of said cutting tool.

Abstract: Particulate polycondensates of thiourea, thiosemicarbazide, or thiocarbazide with aldehydes and phenolic or amine constituents adsorb heavy metals from aqueous solutions of their compounds, also mercury from its vapors.