The corona and breakdown characteristics of pure N2 and mixture (SF6/N2), in high-field needle-to-plane gaps with short gap length, were examined under positive polarity with various wave fronts of microseconds. Although a small addition of SF6 gas to N2 gas showed a slight increase in the corona onset voltage, the breakdown voltage was extremely high compared with that of pure N2 gas. The breakdown voltage increased on increasing the wave fronts in the region of μs and reduced on further increase of wave fronts. In order to make clear the mechanism of the corona initiated breakdown, the corona properties under various pulse waveforms were observed with an optical technique such as an image intensifier tube. In the high nonuniform field under the pulse voltage of μs region, it was found that corona stabilization is enhanced effectively by a small addition of SF6 gas to N2 gas and' that the development of the corona is dependent on the wavefront time of the pulse voltage.
It cannot be said that the unsteady flow of non-Newtonian fluid in a pipe has been sufficiently studied. This paper describes the results of the comparison between the analytical calculations and experimental observations of the pendulation of a pseudo-plastic fluid column in an open vertical U-tube. The method is to estimate the values of the coefficient K and index n of the pseudo-plastic flow equation of Ostwald de Waeles model. It is found that the parameters K and n can be estimated with an accuracy of 1% and 2%, respectively, by choosing their values so that the oscillating motion of the fluid calculated analytically using these values come closest to the motion observed experimentally.