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The influence of waveforms of the applied voltage on hydrogen production from methane reforming using dielectric barrier discharge (DBD) is investigated. Three types of high voltage power generators with different pulse shape with widths of $50~\mu \text{s}$ –250 ns and voltage rise speeds of $7.6\times \,\,10^{4}$ – $5.2\times 10^{10}$ V/s of sinusoidal, bipolar pulses, and a nanosecond pulse voltage are used to control the waveform. The energy efficiency for hydrogen production in the case of nanosecond pulse is approximately 0.9 g/kW $\cdot \text{h}$ , much higher than those of sinusoidal and bipolar pulses, with approximately 0.5 g/kW $\cdot \text{h}$. This is due to that the voltage rise speed by the short pulse is much higher than those using the sine wave and the bipolar pulse, and so the discharge by the short pulse is uniformly generated. The hydrogen production increases and the energy efficiency decreases slightly with increasing pulse repetition rate. The hydrogen production efficiency is independent of the gas pressure within the ranges from 0.12 to 0.16 MPa. [ABSTRACT FROM AUTHOR]

Ethylene gas was decomposed using a dielectric barrier discharge (DBD) plasma reactor for the long-term preservation of fruits and vegetables with a focus on the influence of humidity on ethylene decomposition efficiency. DBD is actively used to produce nonthermal plasma, which is effective in converting C2H4 into CO2 and H2O, through an oxidization process with a high reaction rate because the nonthermal plasma in air contains a large number of chemically active species such as atomic oxygen radicals (O) and hydroxyl radicals (OH). This production of radicals depends on the level of humidity in the air. During the experiment, C2H4 gas was diluted by 200 ppm with an N2 and O2 gas mixture and was fed into the DBD reactor at a 3 L/min gas flow rate. The relative humidity (RH) of the gas was adjusted by the bubbling gas through water. The gas temperature was fixed at 25 °C. The experimental results showed that C2H4 decomposition efficiency was almost independent of RH. [ABSTRACT FROM AUTHOR]

In the microplasma generated by dielectric barrier discharge (DBD), a huge variety of discharge patterns are generated by self-organization. In this study, we experimentally observed variation in the hexagonal structures in capacity-coupled microgap DBD using a helium (He)/argon (Ar) mixture. The spatial distribution of the self-organized structure was revealed via a discharge experiment in which the equivalent barrier capacitance was continuously changed within the range of 56–1500 pF. The results demonstrate that the lattice spacing of the patterns can be continuously controlled within the range of 1.22–1.59 mm for an equivalent barrier capacitance of 56–172 pF. It is likely that an increase in external capacitance increases the discharge cell voltage. In contrast, the lattice constant remained unchanged with an increase in barrier capacitance within a range of 172–1500 pF. The lattice spacing of the patterns could be continuously controlled within a range of 0.66–0.74 mm for all He/Ar gas mixing ratios. [ABSTRACT FROM AUTHOR]

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]

An ac electric field (acEF) application technology has been reported as a principle technique for food preservation. With this method, conformational changes in the protein molecules of food materials may be induced. Conformational changes were experimentally examined using bovine serum albumin (BSA) as a model protein using an acEF technology. The amplitude of acEF was 66.7 kV/m. BSA with acEF (ac-BSA) and BSA without the ac field (n-BSA) were trypsinized under the same conditions. The derived peptides were compared by using sodium dodecyl sulfate polyacrylamide gel electrophoresis patterns. Formation of tryptic peptides was increased in n-BSA, and trypsin digestion was suppressed in ac-BSA. These results indicate that conformational changes in BSA molecules were induced by acEF application. [ABSTRACT FROM PUBLISHER]

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~\mu \texts 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. [ABSTRACT FROM PUBLISHER]

Water purification by streamer discharge using pulsed-power generator under a high-conductivity water containing pollutants has been investigated. A gas–liquid 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 30 000 \mu\S/cm. A solution with 30 000- \mu\S/cm conductivity was successfully decolorized with energy efficiency of 75 \mg/\W\cdot\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. [ABSTRACT FROM PUBLISHER]

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]