[en] More complex moving boundary problems, nonequilibrium problems, both one and two phase in one dimension are considered and reviewed. (author). 9 refs

[en] Dielectric barrier discharge in helium at atmospheric pressure was studied by taking fast images of the discharge during one current pulse using an intensified charge couple device. It was observed that there appears a weakly luminous layer close to the anode at the very beginning of the discharge, then the luminous area gradually expands into the entire gap as the anode layer moves toward the cathode, and finally a highly luminous layer forms close to the cathode at the time around the maximum of the current pulse. The evolution of the discharge pattern indicates a transition from Townsend discharge to glow discharge

[en] A dielectric barrier discharge in nitrogen at atmospheric pressure was investigated by means of the electrical measurement, the fast photography and the time-resolved spectroscopy. By addition of a nitrogen flow, a stable homogeneous discharge was produced in a gap not longer than 3 mm and it was identified with a Townsend discharge. It was found that the discharge was extinguished while the voltage of the gas gap continued to increase. This extraordinary manner of discharge extinction was explained by the limited number of trapped electrons on the dielectric surface that could not provide a long-lasting Townsend discharge with sufficient secondary electrons. Due to the 'memory effects' the lowest breakdown voltage for a Townsend discharge in a 2 mm gap is only 4.9 kV in contrast to the streamer breakdown voltage of 8.2 kV. The working domain of the Townsend discharge is dependent on the frequency and the amplitude of the applied voltage. When the flow velocity increases from 0 to 140 cm s^-1, the discharge current decreases from 2.9 to 2.3 mA and the breakdown voltage increases from 5.3 to 5.9 kV, which is attributed to the nitrogen pressure in the gap increasing with the flow velocity. With the gas flow, the intensities of the spectral lines from the second positive system of N₂ are almost unchanged, whereas those from NO_γ systems are significantly reduced. From this phenomenon, it may be inferred that the density of oxygen as impurity in the discharge gap decreases with the gas flow. This result is in agreement with the existing theory that less oxygen leads to more metastables N₂(A) surviving to produce more seed electrons for initiating a Townsend discharge in nitrogen at atmospheric pressure.

[en] Based on the diagnostic techniques of electrical measurement, emission spectroscopy and fast photography, the effects of the helium flow in dielectric barrier discharge of atmospheric helium were investigated. It was shown that the nitrogen molecules as impurity in the discharge gap are reduced by a helium flow through the gap. As nitrogen molecules are very efficient quenchers of helium metastables, the introduction of the helium flow may induce an increase in the density of helium metastables after discharge and thus an enhanced contribution of these metastables to the next breakdown of helium gap at a lower voltage. The area of the higher density of He metastables after discharge moves from upstream to downstream as the flow velocity increases, leading to the area of starting discharge moving from upstream to downstream. It seems that the nitrogen molecules as the impurity in helium play more important roles in influencing the behaviour of helium discharge than the products etched from the dielectric surface by discharge.

[en] In the process of water treatment by bipolar pulsed discharge plasma, there are not only the chemical effects such as the cold plasma, but also the physical effects such as the optical radiation. The energy of the optical radiation can be used by photocatalyst. Therefore, the effect of the photocatalyst to the degradation of the organic pollutant was investigated using a packed bed reactor by bipolar pulsed discharge in the air-liquid-solid mixture. The nanoparticle TiO₂ photocatalyst was obtained using the sol-gel method and the typical dye solution Indigo Carmine was chosen as the degradation target to test the catalytic effect of the nanoparticle TiO₂ photocatalyst. Experiment results proved that the degradation efficiency of the Indigo Carmine solution was increased by a certain extent with the TiO₂ photocatalyst. It was totally decolorized within 3 minutes by bipolar pulsed discharge in the condition that the peak voltage was 30 kV and the air flow was 1.0 m³ h⁻¹.

[en] A special design for the multi-jets electrospinning system is presented. In this work, a 6 (g/ml) % polyethylene oxide (PEO) water solution was electrified and pushed by air pressure through a spinneret. The spinnerets were built-up with needles with a regular hexagon distribution and each 3 needles have been designed as a regular triangle distribution. The outside needles modified the electrical field to uniform the electrical field strength on the inside nozzles and restrict the path of the inside jets. A coaxial iron ring was used in order to uniform the electrical field strength on the outside nozzles and restrict the collection area. In this paper, a 7 cm diameter ring was used in the 7 needles system, a 9 cm diameter ring was used in the 19 needles system and a 1lcm diameter iron ring was used in the 37 needles system test. The results demonstrated that the special design setup can produce uniform nanoscale fibres and the spinning process is insensitive with the atmosphere disturbance. The distribution of needles shows a possibility design for improving the production rate of nanofibres manufacturing.

[en] The recovery of the gas density and the hold-off voltage of a spark gap after breakdown were investigated with Mach-Zehnder interferometry and two-pulse method, respectively. It was shown that the gas density in a 2.7 mm gap filled with atmospheric nitrogen almost fully recovers at t=50 ms but the breakdown voltage of the gap only recovers to its static hold-off voltage, about 21.4% of its original overvolted breakdown voltage. The mechanisms for the delayed recovery of the ability to be overvolted were discussed.

[en] Removal of amaranth, a commercial synthetic azo dye widely used in the dye and food industry, was examined as a possible remediation technology for treating dye-contaminated water. Effects of various parameters such as gas flow rate, solution conductivity, pulse repetition frequency, etc., on decolorization kinetics were investigated. Experimental results show that an aqueous solution of 24 mg/l dye is 81.24% decolorized following 30 min plasma treatment for a 50 kV voltage and 0.75 m³/h gas flow rate. Decolorization reaction of amaranth in the plasma reactor is a pseudo first order reaction. Rate constant (k) of decolorization increases quickly with increasing the applied voltage, pulse repetition frequency and the gas flow rate. However, when the applied voltage is beyond 50 kV and increases further, increase rate of k decreases. In addition, k decreases quickly when the solution conductivity increases from 200 to 1481 μS/cm. The decolorization reaction has a high rate constant (k = 0.0269 min^-1) when the solution pH is beyond 10. Rate constant k decreases with the decrease of pH and reaches minimum at a pH of about 5 (k _min = 0.01603 min^-1), then increases to 0.02105 min^-1 when pH decreases to 3.07. About 15% of the initial TOC can be degraded only in about 120 min non-thermal plasma treatment