Abstract: An injector for injecting gas into a molten metal. The injector has a rotor that is rotatable about an axis of rotation, the rotor having a cylindrical projection-free side surface, a bottom surface, and a cavity for receiving molten metal located centrally of the rotor with respect to the axis of rotation. The rotor is provided with a plurality of openings in the side surface spaced around the rotor for ejecting molten metal and gas from the rotor upon rotation of the rotor about the axis of rotation. At least one opening in the bottom surface communicates with the cavity permitting entry of molten metal into the cavity, and a plurality of passages disposed in the rotor interconnect the cavity and the openings in the side surface. A gas passageway introduces gas into molten metal present within the rotor but lacks direct communication with the cavity, and is provided with at least one outlet opening into at least one of the plurality of passages to ensure regular and even gas distribution.

Abstract: Data sequences correspond to L different parameter sets (effective symbol length, guard interval length, the number of carrier waves) and transformed into parallel data by respective serial/parallel converters, which are allocated to respective carrier waves for OFDM and subjected to inverse discrete Fourier transform by inverse discrete Fourier transformers to produce sampled values for the transmission waveform in the time domain. The sampled values are transformed into serial sequences of sampled values by parallel/serial converters and then into a single temporal sampling sequence by a temporal sampling sequence switching unit. A frame synchronizing symbol is added to the temporal sampling sequence and then transformed into an analog base band OFDM signal before it is converted up to a transmission signal. The frequency bandwidth of the OFDM signal is made smaller than a predetermined value defined by the bandwidth of the available transmission channel.