To investigate purification characteristics of water containing surfactant by using an underwater plasma source with a porous glass membrane which functioned in bubble supply and the formation of micro-discharges, we first observed the bubble diameter, the ascent velocity of bubbles, and discharges. We also examined the influence of surfactant on the generation of OH radicals. It was found that the existence of surfactant made the sterilization effect higher and that B.subtilis spores could be effectively sterilized.

The fundamental electrical power generation experiment of a pulsed-laser-driven MHD generator with a divergent channel and segmented electrodes has been conducted with a rough estimate of gas heating efficiency of laser energy. The output energy is increased with the decrease in the initial filling gas pressure because of the increase in the gas velocity and the electrical conductivity with the gas temperature. The output power is surely improved in comparison with the previously examined generator with constant height channel and continuous electrode. About 70% of incident laser energy is absorbed and less than 20% is transferred to blast wave energy at low initial filling gas pressure in the present experimental set-up.

This paper shows that the influence of thickness of non-oriented electrical steels on the iron loss under PWM inverter excitation. It is already known that the iron loss under PWM inverter excitation is higher than the iron loss under sinusoidal excitation. We evaluated the iron loss of non-oriented electrical steels having various thicknesses under PWM inverter excitation in comparison to a sinusoidal excitation. The difference of the iron loss between inverter excitation and sinusoidal excitation is increased with the increase in material thicknesses. This tendency became marked in low carrier frequencies and low modulation factors. From the FFT analysis on flux waveforms, it was found that the high-harmonic component amplitudes in flux waveforms were increased with decreasing carrier frequencies and modulation factors, which resulted in the increase in eddy current losses, especially in thicker electrical steels.

Ca₃Co₄O₉ samples were made by the sintering method using the slurry consisted of Ca₃Co₄O₉ powder and Ca₃Co₄(OH)₁₈ hydroxide in binder solution. The preparation conditions for making the crack free samples were examined, and we found that using the slurry having a mixing ratio of Ca₃Co₄O₉ powder to 13 wt.% or 18 wt.% Ca₃Co₄(OH)₁₈ hydroxide in binder solution of 10:1.5, samples with a few crack could be prepared. From SEM observation, it was found that the void density in Ca₃Co₄O₉ samples could be controlled by the slurry sintering method. The electric conductivity (σ), Seebeck coefficient (S), and power factor (PF) of samples prepared by slurry sintering method at room temperature are 53 S/cm, 118 µV/K and 73.8 µWm^-1K^-2, respectively. The power factor (PF) at 600 °C was 173 µWm^-1K^-2.

This paper reports the temperature dependence of AC breakdown voltage (electric strength Fb) of vegetable-oil- based insulating fluid. We observed Fb of the soybean-oil-based insulating fluid, at the wide temperature regions (-50 to 100 [°C]). These results were shown as the following: (i) Fb showed the constant value between about -10 [°C] to room temperature. (ii) At low temperature region of -15 to -10 [°C], Fb increased with the decrease of the temperature. (iii) Fb dropped off with the decrease of the temperature below -15 [°C]. (iv) At high temperature region of over room temperature, Fb rose with the increase of the temperature.

Insulated copper wires for overhead distribution line could fracture because of stress corrosion cracking (SCC). In order to investigate the relationship between fracture time and tensile load of stranded copper wire, we observed the SCC of semi-hard drawn copper wire using an original accelerated SCC test. In this test stranded copper wire samples 60 mm² in size different from the tensile load were manufactured by changing the annealing condition tentatively. These samples, wound around PVC pipes 318 mm in diameter applying the prescribed tension, were exposed to vapor of HNO₃ solution in an airtight chamber controlled at 60±2℃. The fracture time of each sample was recorded by periodic visual observation. From the results the fracture time was remarkably prolonged with a decrease in the tensile load. Furthermore, it was shown that the fracture time of hard drawn stranded copper wire having the tensile load near the lower limit, i.e., 23.6 kN standardized in Japan was extended by 3 to 4 times compared with the conventional copper wire having that of about 26 kN. Thus, a new technique to control the annealing condition exactly for mass-production of hard drawn copper wire with high SCC durability is desired to be established.

To understand the electrical properties influenced by water absorption, the space charge measurement was performed for an epoxy (EP) / Boron nitride (BN) insulating composite that is expected to be applied as a higher thermal conductive insulating material. The negative space charge in absorbed EP/BN composite without silicone oil was observed just after the voltage application, and the negative charge amount in the vicinity of the anode increased with the increase of the time. On the other hand, the homo space charge in absorbed EP/BN composite with silicone oil was observed just after the voltage application and the distribution is the almost same until 600 s after the voltage application. The OH- content near the anode after the voltage application in absorbed EP/BN composite without silicone oil was also larger than that before the voltage application while the OH- content near the anode after the voltage application in absorbed EP/BN composite with silicone oil was smaller than that before the voltage application. The intermittent water pass over the electrodes caused by the addition of silicone oil led to the fixed space charge profiles in absorbed EP/BN composite with silicone oil.