Abstract: A vector quantizer and a vector quantization method are provided, which do not allow the embedding position of the watermark information to be identified easily, and thus enable unfair use of the vector quantized information to be accurately found out. Waveform extraction is performed on input signal data to output extracted waveform data. Index data are generated based on the output extracted waveform data. As index data to be generated based on predetermined extracted waveform data in which no watermark information is to be embedded, out of the output extracted waveform data, index data is randomly selected, which corresponds to the predetermined extracted waveform data from a plurality of index data which, when decoded, have amounts of errors falling within a predetermined range with respect to the predetermined extracted waveform data before decoding.

Abstract: A method for polymerizing or copolymerizing .alpha.-olefin in a vapor phase condition by supplying to a reactor a catalyst composed of a solid catalyst component containing at least titanium and/or vanadium as well as magnesium and an organic aluminum compound wherein the current due to the electric charge transferred from polymer particles electrified to an electrode disposed at a position where sheet-like polymers will be produced in a reactor, as a result of contact of the polymer particles in the reactor with the electrode is determined, and the polymerization or copolymerization is carried out under such condition where the mean value of current is zero or a positive value. As a result, it becomes possible to prevent production of sheet-like polymers and to stably continue the reaction for polymerization.

Abstract: In the polymerization of olefins with a vapor phase fluidized bed reactor, the improvement comprises the steps of feeding seed polymer particles and the reaction is then started after feeding an organoaluminum compound on a prescribed basis, thereby avoiding the formation of sheet-like polymer in the initial period of the reaction and the lowering of the bulk density of the product polymer.

Abstract: In the preparation of polyolefin in a vapor phase polymerization using catalysts comprising a solid catalyst component containing titanium and/or vanadium; and magnesium and an organoaluminum compound, when the reaction is stopped for a certain period of time, the restarting of reaction is possible by feeding in the first place an organoaluminum compound into the reaction system with retaining of polymer particles in the reactor.