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Yokohama-shi, Japan

Takahashi K.,Shishido Electrostatic Ltd. | Yagi I.,University of Tokyo | Takaki K.,Iwate University | Satta N.,Iwate University
IEEE Transactions on Plasma Science | Year: 2011

The development of pulsed discharges inside a stationary air bubble in water was observed using an intensified charge-coupled device camera with high-speed gate. The discharges were ignited from a tungsten wire inserted into a glass tube, which was immersed in the purified water. The pulsed high voltage was applied to the wire by an inductive energy storage system pulsed-power generator. The streamer discharge was propagated into the bubble from the wire tip with a propagation velocity of 0.5 mm/ns. A back discharge was observed due to a charge accumulation on the water surface and the glass tube. © 2006 IEEE.

Soda Y.,University of Tokyo | Kodama T.,Shishido Electrostatic Ltd. | Oda T.,University of Tokyo
Conference Record - IAS Annual Meeting (IEEE Industry Applications Society) | Year: 2012

The GMR head in the tape recording is suffered from the corona discharge generated by tribo-electrification. In order to estimate the reliability of the head materials, the corona discharge using multi-pin electrodes was studied. The multi-pin electrodes were configured with maximum 15 pins. Each pin was distanced 5mm from neighbors and placed at 11mm over the Al plate. At negative voltage, the discharge started with isolated pulses. As the voltage increasing over -7kV, DC component appeared and increased. At positive voltage, the discharge was isolated pulses up to +10kV and DC component did not appeared. At 15-pins electrode, the period between the pulses was random and the peak values varied. Therefore, the corona discharges from the multi-pin electrodes occurred individually at each electrode. The mean current of 15-pins increased approximately five times at negative voltage and twenty times at positive voltage compared with that of single-pin. © 2012 IEEE.

Kawano S.,Iwate University | Wada K.,Iwate University | Kakuta T.,Iwate University | Takaki K.,Iwate University | And 2 more authors.
Journal of Physics: Conference Series | Year: 2013

Decolorization of an organic dye by discharge in high conductive water using a pulsed power generator and a discharge reactor was investigated. The discharge reactor consisted of a glass tube and a tungsten wire inserted into the glass tube, which was immersed in the water. Room air was injected into the glass tube to generate bubbles in the water. High voltage pulses were generated by an inductive-energy storage system using semiconductor opening switch (SOS) and by a magnetic pulse compression circuit. Fast recovery diodes were used as SOS diode in the inductive-energy storage system. The pulse width was changed in range from 10 to 1200 ns. The high voltage was applied to the tungsten wire. Indigo carmine was employed as a specimen to evaluate decolorization efficiency. Potassium nitrate was used to adjust the solution conductivity. The dye solution was successfully decolorized at 7 mS/cm conductivity. Energy efficiency for decolorization increased from 0.680 to 55.6 mg/Wh with decreasing the pulse width from 1200 to 10 ns owing to the reduction of ohmic loss.

Takahashi K.,Iwate University | Takahashi K.,Shishido Electrostatic Ltd. | Sasaki Y.,University of Tokyo | Mukaigawa S.,Iwate University | And 3 more authors.
IEEE Transactions on Plasma Science | Year: 2010

Water purification by streamer discharge using pulsed-power generator under a high-conductivity water containing pollutants has been investigated. A gasliquid separated reactor was developed to treat highly conductive solution. A wire electrode was placed in the gas phase and a plane electrode was immersed in the water. A pulsed high voltage generated by six stacked Blumlein lines was applied to the wire electrode to generate streamer discharge in the gas phase, which propagated into the air bubble injected into the water. Indigo carmine solution was employed as a specimen. Natrium chloride was used to adjust the solution conductivity in the range from 10 to 30000 μS/cm. A solution with 30000-μS/cm conductivity was successfully decolorized with energy efficiency of 75 μ/W · h. Some species of gas such as air, oxygen, nitrogen, and argon were injected to clarify dominant reactions of the decolorization. The result showed that the ozone produced by gas-phase discharges mainly contributed to the decolorization of the solution. The decolorization rate depended on the chloride ion supplied from the natrium chloride by scavenging of hydroxyl radical and on the copper ion eluted from the plane electrode by redox reactions such as Fenton reactions. © 2010 IEEE.

Takano K.,Iwate University | Takahata J.,Iwate University | Takaki K.,Iwate University | Satta N.,Iwate University | And 2 more authors.
IEEJ Transactions on Fundamentals and Materials | Year: 2015

An effect of discharge plasma irradiation to the circulating water in hydroponic cultivation system on plant growth rate was evaluated using Brassica rapa var. perviridis as specimen. The discharge plasma produced acids in the solution, which acts as a fertilizer. The Brassica rapa var. perviridis were cultivated in period of 42 days with the hydroponic system. The experimental result indicated that the growth rate of the Brassica rapa var. perviridis is improved drastically with the discharge treatment of the solution of hydroponic system, especially nitrogen content of leaf blade is significantly increased (P < 0.01). © 2015 The Institute of Electrical Engineers of Japan.

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