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The influence of the electric parameters, applied voltage, and pulse repetition rate on the energy efficiency for hydroxyl radical production from pulsed discharge inside of a bubble is investigated in this paper, as a possible application for waste water treatment. To evaluate the energy efficiency, indigo carmine, a common dye, is used as a chemical probe of hydroxyl radicals. Argon is injected into water through a vertically positioned glass tube, into which high-voltage wire electrode is placed to generate plasmas at low applied voltage. The energy efficiency increases with the decreasing pulse repetition rate and output voltage with the same indigo carmine concentration. The results show that the energy efficiency for the hydroxyl radical production increases with the decreasing amount of energy input into the solution per unit time because of the decrease in the recombination reaction of the hydroxyl radicals in the solution. The impedance between the electrodes decreases with the increasing output voltage, which increases the ohmic losses in the solution but does not contribute to the production of hydroxyl radicals. [ABSTRACT FROM AUTHOR]

SUMMARY 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). [ABSTRACT FROM AUTHOR]

A review of mainly the past two years is undertaken of the industrial applications of pulsed power. Repetitively operated pulsed power generators with a moderate peak power have been developed for industrial applications. These generators are reliable and have low maintenance. Development of the pulsed power generators helps promote industrial applications of pulsed power for such things as food processing, medical treatment, water treatment, exhaust gas treatment, ozone generation, engine ignition, ion implantation and others. Here, industrial applications of pulsed power are classified by application for biological effects, for pulsed streamer discharges in gases, for pulsed discharges in liquid or liquid-mixture, and for material processing. [ABSTRACT FROM AUTHOR]

Pulsed electric fields (PEFs), which are generated by pulsed power technologies, are being tested for their applicability in food processing through protein conformational change and the poration of cell membranes. In this article, enzyme activity change and the permeabilization of agricultural products using pulsed power technologies are reviewed as novel, nonthermal food processes. Compact pulsed power systems have been developed with repetitive operation and moderate output power for application in food processing. Firstly, the compact pulsed power systems for the enzyme activity change and permeabilization are outlined. Exposure to electric fields affects hydrogen bonds in the secondary and tertiary structures of proteins; as a result, the protein conformation is induced to be changed. The conformational change induces an activity change in enzymes such as α-amylase and peroxidase. Secondly, the conformational change in proteins and the induced protein functional change are reviewed. The permeabilization of agricultural products is caused through the poration of cell membranes by applying PEFs produced by pulsed discharges. The permeabilization of cell membranes can be used for the extraction of nutrients and health-promoting agents such as polyphenols and vitamins. The electrical poration can also be used as a pre-treatment for food drying and blanching processes. Finally, the permeabilization of cell membranes and its applications in food processing are reviewed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An inductive energy storage system pulsed power generator using semiconductor opening switch (SOS) diodes was employed to drive a co-axial cylinder plasma reactor for ozone synthesis with high yield. Fast recovery diodes were used as SOS diodes in the inductive energy storage system pulsed power generator to produce short-pulse high-voltage with high-repetition rate. The high-voltage pulse was applied to a 1 mm diameter center wire electrode in the reactor. The copper cylinder of 19 mm inner diameter was used as outer electrode and was connected to a ground. Oxygen and dry air were used as source gases and were injected into the plasma reactor with 2 L/min. gas flow rate. The synthesized ozone concentration increased in proportion to pulsed voltages repetition rate under oxygen gas condition. The ozone yield of about 230 g/kWh was obtained in oxygen gas and was independent of circuit parameter. The ozone yield decreased from 230 to 100 g/kWh by changing the source gas from oxygen to dry air. The ozone yield depended on circuit parameters such as capacitance of the primary energy storage capacitor and inductance of the secondary energy storage inductor under dry air condition. [ABSTRACT FROM AUTHOR]

The development of discharge inside a bubble in water is observed using high-speed gated ICCD cameras. A tungsten wire is inserted into a glass tube, which is immersed in water. Argon gas is injected into the glass tube through a solenoid valve to generate bubbles at the tip of the glass tube. The pulsed high voltage is generated using an inductive energy storage system pulsed power generator driven by a SI-thyristor. Two ICCD cameras with optical axes perpendicular to each other are used to take two orthogonal images, and an ICCD camera that is capable of taking 12 consecutive photographs used to evaluate the propagation velocity of the discharge. The discharge propagates into the bubble from the tip of the wire in the glass tube. Then, the discharge propagates along the bubble surface. The propagation velocity is almost independent of water conductivity and 2.7–3.6 × 105 m/s. The average maximum length of the discharge propagation decreases from approximately 8.9 to 5.4 mm with increasing water conductivity from 7 to 1000 μS/cm. Indigo carmine, a commonly used organic dye, was used as the chemical probe of the active species produced by the discharge inside the bubble. The amounts of indigo carmine decomposition with 120 min of treatment is 0.24–0.26 μmol and independent of water conductivity. Meanwhile, the energy efficiency for the indigo carmine decomposition in water decreases from 18 to 7.3 μmol/Wh with increasing water conductivity from 7 to 1000 μS/cm. The amount of hydrogen peroxide production by the treatment increases from 2.0 to 3.1 μmol with increasing the conductivity. These results show that the amount of active species consumed in loss reactions such as their recombination increases with decreasing length of discharge propagation. • The discharge inside argon bubble in water is observed using high speed gated ICCD cameras. • Discharge propagates along the bubble surface with the propagation velocity of 2.7–3.6 105 m/s. • Hydroxyl radical supply to water decreases with increasing conductivity because of increase of recombination reaction. [ABSTRACT FROM AUTHOR]