It is necessary to increase the Jc values when developing practical MgB2 superconducting wire. High Jc values even in high magnetic fields were achieved using nanometer-sized Mg powder. The highly pure nanometer-sized Mg powder was fabricated using the thermal plasma method. In addition, doping with a small amount of SiC was tried for the purpose of enhancing Jc properties. The MgB2 superconducting wires were MgB2/Fe tapes prepared from a mixture of nanometer-sized Mg, commercial amorphous B and SiC, which were fabricated using the in-situ PIT method. The Jc values of the non-doped and 10 at% SiC-doped tapes reached 90 and 250 A/mm2 at 4.2 K and 10 T, respectively. In regard to the temperature dependence of Jc, it reached at 160 A/mm2 at 20 K and 4 T which nears the practical application level.
Thermoacoustic pheomena are classified into heat-pumping, prome-mover and dream-pipe including simple heat-conduction. Necessary conditions for thermoacoustic heat-engines are discussed using the first and second laws of thermodynamics and thermoacoustic theory. These conditions restirict possible regions of the temperature gradient and the phase difference between oscillations of pressure and displacement.