Abstract: A method for forming dense ceramics, particularly a ceramic coating by a low temperature treatment is provided. The method for forming ceramics according to the invention is characterized in that a polysilazane having a number-average molecular weight of 100 to 50,000 or a modified polysilazane thereof is subjected to a heat treatment, then exposed to an atmosphere containing water vapor or immersed in distilled water containing a catalyst, or both, or is brought into contact with Pd.sup.2+ ions and water, the polysilazane having a skeleton comprising the unit represented by the following general formula (I): ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 each independently represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, a group other than the above and having a carbon atom directly attached to the silicon atom, an alkylsilyl group, an alkylamino group and an alkoxy group; with the proviso that at least one of R.sup.1, R.sup.2 and R.sup.3 is a hydrogen atom.

Abstract: A photocurable resin composition comprising (A) at least one urethane di- or triacrylate, which is a novel compound, (B) a radical polymeriable compound, and (C) a photopolymerization initiator, the weight ratio of the urethane acrylate (A) to the radical polymerizable compound (B) being 65/35 to 25/75; a method of producing a photo-cured object by photo-curing the above composition; a vacuum casting mold obtained by the above method; and a vacuum casting method using the above mold.

Abstract: An exposure apparatus for exposing a photomask pattern onto a photosensitive substrate via a plurality of optical systems includes a source of illumination for irradiating the photomask pattern with beams of light adapted to pass through the pattern and optical systems onto the substrate. A scanning mechanism for synchronously scanning the photomask pattern with the beams of light is included to transfer the pattern to the substrate. A plurality of illumination intensity measuring devices is provided for substantially simultaneously measuring the illumination intensities of the beams of light passing through the optical systems.

Abstract: In a helical-scan-type magnetic recording and playback method for forming diagonal tracks on a magnetic tape while recording and playing back digital data signals, the record and playback heads are installed on a rotating drum in a manner that enables the signal transfer delay associated with the record and playback signal processing of the digital data signal to be absorbed. The recording and playback is performed using a track pattern formed on the magnetic tape with the start and end points of the tracks located at distances of X and (L-X), respectively, from the lower edge of the tape, with L being the width of the tape, and X given by the equation:X=0.65+n.times.p.times.cos.theta.where n is the signal transfer delay time associated with the signal processing required to record and playback a digital data signal expressed as a number of tracks, p is the track pitch, and .theta. is the angle of inclination of the diagonal tracks relative to the lower edge of the tape.

Abstract: A sector mark detection apparatus detects a sector mark added to an arbitrary sector of an optical disk when seeking the arbitrary sector, where the optical disk has a predetermined recording format in which a predetermined number of sectors are arranged on the optical disk.

Abstract: A system and a method for the tertiary removal of oil from a well by introducing a fine water mist, subjecting it to an electric field to form a charged aerosol and changing the aerosol into steam to drive oil from the formation.