Yokohama-shi, Japan
Yokohama-shi, Japan

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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.


Takano K.,Iwate University | Takahata J.,Iwate University | Takaki K.,Iwate University | Satta N.,Iwate University | And 2 more authors.
Electronics and Communications in Japan | Year: 2016

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 content of leaf blade is significantly increased (p < 0.01). © 2016 Wiley Periodicals, Inc.


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.


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.,Shishido Electrostatic Ltd. | Goto A.,Shishido Electrostatic Ltd. | Yamaguchi S.,Shishido Electrostatic Ltd. | Saito T.,Shishido Electrostatic Ltd. | And 2 more authors.
Electrical Overstress/Electrostatic Discharge Symposium Proceedings | Year: 2015

A perfectly balanced fan type electrostatic eliminator utilizing an intermittent pulse AC voltage power supply is developed. The short-term fluctuation range of the offset voltage (ion balance) is smaller than ±2 V without a sensor feedback system. The high performance is maintained in 2500 h continuous operation.


Iwabuchi M.,Iwate University | Wada K.,Iwate University | Takahashi K.,Shishido Electrostatic Ltd. | Takaki K.,Iwate University | Satta N.,Iwate University
IEEJ Transactions on Fundamentals and Materials | Year: 2015

Influence of pulse width and water conductivity on decolorization of organic dye by discharge inside bubble in water was investigated. Two types of pulsed power generator, a magnetic pulse compression circuit and an inductive-energy storage system using semiconductor opening switch, were used to generate high voltage pulses with various pulse widths. Indigo carmine was employed as a specimen to evaluate decolorization efficiency. Argon gas was used to identify the influence of hydroxyl radicals produced by the discharge on decolorization efficiency. Energy efficiency for the decolorization increased with decreasing the pulse width owing to the reduction of ohmic loss. © 2015 The Institute of Electrical Engineers.


Takaki K.,Iwate University | Nishimura J.,Iwate University | Koide S.,Iwate University | Takahashi K.,Shishido Electrostatic Ltd. | Uchino T.,Fukuoka University
IEEE Transactions on Plasma Science | Year: 2015

Ethylene (C2H4) gas promotes the aging of some kinds of fruits and vegetables such as persimmon, banana, and cucumber. Decomposition of ethylene using nonthermal plasma is effective for keeping freshness of fruits and vegetables in the transportation container. The ethylene was decomposed into gas stream using a dielectric barrier discharge (DBD) reactor driven by dual-polarity pulse generator that consisted of four insulated gate bipolar transistors and a pulse transformer. The output voltage of the pulse generator was 10 kV in amplitude, 1 kilopulse/s in repetition rate, and 50 μs in rectangular pulsewidth. The 200 ppm ethylene was diluted with dried air and was employed as simulated gas of the transportation container. The gas mixture was fed into the DBD reactor for the evaluation of the decomposition efficiency. The ethylene concentration decreased to less than 1 ppm after the DBD treatment at 30 J/L in input energy. The energy efficiency for ethylene decomposition was around 50 g/kWh and was almost independent of the initial ethylene concentration. The decomposition efficiency increased with increasing oxygen content of the background gas. The byproducts were analyzed by a Fourier transform infrared spectrometer. The results showed that the H2O and CO2 were mainly produced after the decomposition of the ethylene by the DBD plasma. © 2015 IEEE.


Takahashi K.,Shishido Electrostatic LTD. | Takahashi K.,Iwate University | Takaki K.,Iwate University | Satta N.,Iwate University
Journal of Advanced Oxidation Technologies | Year: 2012

In the present study, the degradation of organic contaminants by streamer discharge using a pulsed power generator under water is investigated. The experiments are conducted based on the decolorization of two dyes, Acid Red 1 and Acid Blue 74, and the decomposition of 1,4-dioxane. A gas-liquid separated reactor is developed and employed to achieve degradation with high energy efficiency. A tungsten wire electrode is placed in the gas phase, and a grounded 316 stainless steel wire is immersed in the water. The pulsed high voltage is generated by a magnetic pulse compression circuit and is applied to the wire electrode to generate streamer discharges in the gas region, which propagate into the bubble injected into the water. Oxygen and argon gases are injected to identify the dominant reactions of the degradation of organic contaminants. Acid Red 1 and Acid Blue 74 solutions are successfully decolorized by the discharges. The ozone produced by discharges in the gas region primarily decolorizes the dye solutions. The total organic carbon (TOC) of the 1,4-dioxane solution decreases due to discharge when argon is injected. The decrement rate of TOC does not increase through gaseous ozone injection or by discharges in the case of oxygen injection. These results show that the chemical species produced by discharges and by chemical reactions in the solution, such as hydroxyl and hydroperoxyl radicals, primarily decompose 1,4-dioxane. Iron ions dissolved by electrolysis enhanced the TOC decrement rate according to the Fenton reaction in acidic conditions. © 2012 Science & Technology Network, Inc.


Takahata J.,Iwate University | Takaki K.,Iwate University | Satta N.,Iwate University | Takahashi K.,Shishido Electrostatic Ltd. | And 2 more authors.
Japanese Journal of Applied Physics | Year: 2015

The effect of bubble discharge in water on the growth rate of plants was investigated experimentally for application to plant cultivation systems. Spinach (Spinacia oleracea), radish (Raphanus sativus var. sativus), and strawberry (Fragaria ' ananassa) were used as specimens to clarify the effect of the discharge treatment on edible parts of the plants. The specimens were cultivated in pots filled with artificial soil, which included chicken manure charcoal. Distilled water was sprayed on the artificial soil and drained through a hole in the pots to a water storage tank. The water was circulated from the water storage tank to the cultivation pots after 15 or 30 min discharge treatment on alternate days. A magnetic compressiontype pulsed power generator was used to produce the bubble discharge with a repetition rate of 250 pps. The plant height in the growth phase and the dry weight of the harvested plants were improved markedly by the discharge treatment in water. The soil and plant analyzer development (SPAD) value of the plants also improved in the growth phase of the plants. The concentration of nitrate nitrogen, which mainly contributed to the improvement of the growth rate, in the water increased with the discharge treatment. The Brix value of edible parts of Fragaria ' ananassa increased with the discharge treatment. The inactivation of bacteria in the water was also confirmed with the discharge treatment. © 2015 The Japan Society of Applied Physics.

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