Abstract: An induction heating device according to one embodiment includes a first coil portion and a second coil portion. A bar-shaped workpiece is placed between the first coil portion and the second coil portion. The first coil portion includes a pair of first narrow pitch portions formed in respective end portions thereof, a first wide pitch portion formed between the first narrow pitch portions, and a first medium pitch portion formed in the center. The second coil portion includes a pair of second narrow pitch portions formed in respective end portions, a second wide pitch portion formed between the second narrow pitch portions, and a second medium pitch portion formed in the center.

Abstract: An A/D converter for driving a plurality of delay units forming a pulse delay circuit by an analog input signal Vin and digitalizing the number of delay units through which a pulse signal passes in the pulse delay circuit at predetermined timings, provided with a plurality of pulse position digitalizing units used for A/D conversion and inputting delay pulses from the delay units of the pulse delay circuit to the pulse position digitalizing units through an inverter group comprised of inverters with different inversion levels (switching threshold level) by different input timings. The digital data obtained by the pulse position digitalizing units are added by an adder.

Abstract: An A/D converter for driving a plurality of delay units forming a pulse delay circuit by an analog input signal Vin and digitalizing the number of delay units through which a pulse signal passes in the pulse delay circuit at predetermined timings, provided with a plurality of pulse position digitalizing units used for A/D conversion and inputting delay pulses from the delay units of the pulse delay circuit to the pulse position digitalizing units through an inverter group comprised of inverters with different inversion levels (switching threshold level) by different input timings. The digital data obtained by the pulse position digitalizing units are added by an adder.

Abstract: A high-density and high-strength .beta.-type silicon carbide sintered body, in which crystal grains are made uniform and fine by adjusting the compounding ratio of the sintering aid and further taking a special means at the sintering step while suppressing the inclusion of .alpha.-SiC into the starting powder as far as possible during the production of the silicon carbide sintered body.

Abstract: A thermal storage unit has a thermal storage material which performs heat exchange through a fluid filled in a thermal storage body arranged within a vessel having an opening communicated to outside. The thermal storage body is a porous ceramic molding which contains the thermal storage medium.

Abstract: An electronic circuit substrate having excellent machinability and dimensional accuracy is disclosed, which comprises a porous ceramic sintered body having a three-dimensional network structure and contains permeable pores, and a resin filled into the permeable pores.

Abstract: This invention relates to a method of producing a silicon carbide substrate having desirable electrical insulation properties. The silicon carbide substrate is produced by applying to a surface of a silicon carbide plate a film-forming composition which consists essentially of at least one oxide or substance with produces an oxide by decomposition of an element selected from the group consisting of aluminum, phosphorus, boron, germanium, arsenic, antimony, bismuth, vanadium, zinc, lead, cadmium, sodium, potassium, lithium, beryllium, calcium, magnesium, barium and strontium and heating the silicon carbide body in an oxidizing atmosphere to form a eutectic oxide layer thereon.

Abstract: A silicon carbide substrate having excellent electrical insulation properties is disclosed. The silicon carbide substrate is produced by closely adhering to a surface of a silicon carbide plate body a eutectic oxide layer comprising SiO.sub.2 produced by partial oxidation of the plate body and at least one oxide selected from Al.sub.2 O.sub.3, P.sub.2 O.sub.5, B.sub.2 O.sub.3, GeO.sub.2, As.sub.2 O.sub.3, Sb.sub.2 O.sub.3, Bi.sub.2 O.sub.3, V.sub.2 O.sub.5, ZnO, PbO, Pb.sub.3 O.sub.4, PbO.sub.2, CdO, Na.sub.2 O, K.sub.2 O, BeO, CaO, MgO, BaO and SrO.