Abstract: An underwater object positioning system comprises a workboat, an acoustic transmitter-receiver mounted on the workboat, first and second surface tow units towed by the workboat, an acoustic transducer that is mounted on the first surface tow unit, that is connected by a communication cable to the acoustic transmitter-receiver on the workboat and that is positioned by a radio positioning means; two acoustic receivers that are mounted on the second surface tow unit, that are connected by a communication cable to the acoustic transmitter-receiver on the workboat and that are positioned by a radio positioning means. An acoustic pulse transmitter is mounted on a submerged positioning target. A processor unit on the workboat calculates the location of the submerged target based on data showing the positions of the transducer and receivers, and the distances from the transducer and receivers to the acoustic pulse transmitter.

Abstract: This invention provides a manufacturing method and manufacturing apparatus, in which a nitridation reaction is caused to proceed in a vapor phase in the presence of a flame, wherein the desired aluminum nitride powder is manufactured by simultaneously controlling the following technical conditions: that are (1) forming of a highly dispersed and stable fluidized or aerosol state of a raw-material powder whose particle size is included within the range of 0.001 to 500 &mgr;m, (2) adjusting of the gas atmosphere in the flame, and utilizing of a direct nitridation method or a reduction nitridation method in which the high temperature of the flame is used as a driving force, and (3) controlling of the quantitative ratio of the raw material and the flame, or combining of heat treatment processes to be continued.

Abstract: This invention provides mesostructured oxide ceramics and a synthesizing method thereof, the synthesizing method employs a water-based solvent containing a metallic salt or metal complex as the ceramics precursor, template formed from an organic compound or the association thereof, and a precipitant, wherein mesostructured oxide ceramics are obtained from self-assembled oxide ceramics and organic substance by directly extracting oxide ceramics at a low temperature of 200° C. or less by utilizing a homogenous precipitation reaction from said ceramics precursor under the coexistence of a nanometer-sized template in the solvent, and separating and collecting the obtained precipitation, and mesostructured oxide ceramics is prepared by employing the synthesizing method described above.