The statistical time lags at corona discharge inception of a point to plane gap for room air and dry air at a pressure of 750 Torr were measured automatically for about one thousand applications under the successive impulse with a pause time in the range 30-90s.
The aim of this paper is to determine the influence of successive discharges on the statistical time lag at corona inception which is associated with physical processes for the occurrence of initial electron.
The statistical distributions of the observed corona time-lag lead us to depend on the experimen- tal conditions such as the irradiation condition, the number of previous discharge, the pause time between two successive voltage applications and the nature of air involved with H2O. From the experimental results and their discussions, it was found that the negative ion O2- and discharge product O3 made by successive discharges play an important role in the behaviour of corona inception and the distribution of the corona time-lag can be related to the different number-density of O2- for each experimental condition.

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In recent years, various kinds of powder metal production methods have been developed. The plasma rotating electrode process (PREP) is a typical method but it needs a particular high-speed motor. Authors have proposed a metallic powder production method from an arc-discharge electrode vibrated in an ultrasonic frequency.
In this paper, we intend to make production time longer and to produce larger amount of metallic powder. We have adopted a metallic plate of 50×150×6mm in size as a processed ingot instead of a short cylindrical one in our previous trial. The iron plate is energized at its center by a 15kHz-600W ultrasonic power oscillator in this experiment. Both ends of the plate oscillate with amplitude of about 60μm. One end is now heated by an anode spot which is formed by an arc discharge established between the plate and another cathode. When the arc current is taken as 40 A, total processing time is attained to 2 min and 20g of iron powder is obtained. Diameter of the produced powder is distributed between 30 to 160μm with an average value of 67μm. Remarkable cooling effect is brought about by injecting, water drops at a rate of 1ml/s. Processing time as well as producing amount will be expected to be improved with larger arc current and larger plate associated with effective cooling.

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Fundamental properties of new types of high T, superconducting (SC) magnetic antennas of thin films (YBaCu-type), which were prepared by magnetron method (DC magnetron sputtering), were experimentally confirmed with the measurements of an increase of SC resistances under an application of magnetic fluctuations (f=1-550kHz). Improvements of the SC magnetic antennas were performed with the use of the SC thin films instead of bulktype superconductors.

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This paper presents the theoretical analyses of the equilibrium configuration of flux-core spheromaks (FCS) in a spheroidal conductive vessel. The Grad-Shafranov equation for force-free Taylor states is analytically solved. The solution is represented by a series expansion of the spheroidal function. The spheroidal function is expanded by Bessel functions, whose coefficients are refered in Stratton's table. As the boundary condition, the presence is assumed of a certain amount of external fluxes that axially penetrate the vessel through polar caps of the vessel. The equilibrium configuration is determined by flux functions assumed on the polar caps of a flux conserving vessel and a ratio of j to B. Classification is made of the FCS configurations in terms of appearance and location of null (X) points of the separatrix. Particularly, the conditions are parametrically searched for FCS configurations that have double null points at the rim of the center holes. In our numerical calculations, the number of expansion terms is limited by Stratton's table. Therefore, their accuracy is insufficient in strongly oblated configurations or configurations with small polar caps.

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Polypyrrole-PMMA composites have been prepared by the hot press of the mixture of non coated and coated PMMA spheres (1-2μm, 30μm, 50μm in diameter) with polypyrrole by chemical polymerization utilizing FeCl3. Higher electrical conductivity has been obtained in the compounds prepared by polypyrrole coated PMMA spheres of smaller diameter. Conductivity is enhanced by more than 17 orders of magnitude and its activation energy decreases in step wise when the concentration of polypyrrole coated PMMA sphere exceeds 10%. At this concentration electrodes are considered to be bridged by conducting path (polypyrrole). That is, this insulator-metal transition can be explained by a percolation model.
The application of this new technique for the use in semiconducting layer of cables is proposed.

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We proposed a new insulation diagnosis system which can detect partial discharge (PD) signals in power equipments in service rapidly and accurately.
The system is consist of a conventional wide range current probe for measurement of PD current on the grounding conductor, a high speed A/D converter and a computer system for application of digital signal processing techniques. The partial discharge signal is detected as a bast signal from these current signals on the grounding conductor by FFT and bandpass filtering. The beat signal is processed by the Hilbert transform for providing the envelope which includes amplitude, phase angle and frequency informations.
The envelope can be calculated as the magnitude |F(t)| by the detected current signal which can be viewed as the real component of a complex trace.
The degree of insulation degradation is judged by two methods. One is the method which evaluates the energy of PD from the value of envelope area and the other is the method which evaluates the repetition rate of the PD phenomena from the number of envelopes over the threshold relating to the insulating performance.

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Apparent neutralization due to the bipolar charging of polymer film occurs sometimes in the film processing. Such bipolar charging of the film is caused by contact with rollers, electrostatic discharge and charge elimination. The surface charges decrease very slowly because of the low conductivity of the materials.
Charge densities of about +23μC/m2 and -23μC/m2 are found respectively on the two sides of a PET film of 38μm thick at least one year after it was made. The potential of the outer surface of the film roll (6.5mm thick) is about -6kV. When the film is peeled from its roll electrostatic discharges occur. These phenomena occur probably in the following way. The surface potential of the film roll seems to be in proportion to the product of the bipolar charge density and the thickness of the roll. The high surface potential results in the charging of opposite sign on the roll's surface, and therefore the electrostatic discharges.

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