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Numerous reports have elucidated different methods for treating dyeing wastewater using UV irradiation, ozonation, and chlorination. However, the high operational costs of these methods have necessitated the use of plasma. In this study, dielectric barrier discharge (DBD) was used to purify dyeing wastewater, generating ozone as a byproduct. An underwater DBD plasma system was designed to directly interact with water, thereby producing reactive oxygen species (ROS) and functioning as a powerful oxidizer. Additionally, UV, O3, and H2O2 are generated by the developed plasma system without using any other additives to produce OH radicals for purifying organic pollutants; therefore, this system circumvents the use of complex and advanced oxidation processes. A simulation test was performed, which revealed that methylene blue and rhodamine B were completely removed within 7 and 3 min, respectively. Therefore, the developed plasma system can be successfully applied for the purification of dyeing wastewater. [ABSTRACT FROM AUTHOR]

The empirical time-varying resistance model of the plasma channel $R_{\mathrm {pl}}(t) = \beta l^{2}/W_{\mathrm {in}}(t)$ in underwater discharge has been widely used, but the internal energy of the plasma channel $W_{\mathrm {in}}(t)$ is difficult to obtain and the discharge coefficient $\beta $ varies widely under different experimental conditions. This article introduces an improved empirical plasma channel resistance model $R_{\mathrm {pl}}(t) = \beta l^{2}/E_{\mathrm {pl}}(t)$ as well as a method for determining the discharge coefficient $\beta $. The effectiveness and the feasibility of the method are verified by comparing the simulation results and test results. The improved plasma channel resistance model and the method to determine the discharge coefficient can help guide the application of electrohydraulic shockwaves. [ABSTRACT FROM AUTHOR]

In this paper, we propose an innovative method for synthesizing copper nanoparticles (Cu-NPs) using underwater plasma. The proposed method using underwater plasma has advantages such as one-pot synthesis, fast reaction time, and high throughput. We obtained yields as high as 15 g of Cu-NPs powder from 25 g of copper hydroxide, for 10-min a reaction time. In addition, we confirmed that the Cu-NPs produced are spherical and range in size between 40 and 80 nm. We also verified that the synthesized Cu-NPs are almost pure Cu powder, close to 100 %, through high-resolution transmission electron microscopy and X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

In this paper, a new method of generation of an electrical discharge in water using plate electrodes is proposed. The electrical discharge in plate-to-plate configuration cannot be easily generated because of a low uniform electrical field. A nitrogen bubble is injected into one of the electrodes to create a favorable condition for electrical breakdown. The generated electrical discharge is studied using a high-speed framing camera. Two interesting effects have been observed. First, the discharge is preferentially initiated on the cathode. Second, the positive streamer reveals nontypical morphology. The physical mechanisms of discharge initiation and positive streamer propagation are discussed. [ABSTRACT FROM PUBLISHER]

This paper reports on analysis of two different types successive underwater shock waves generated by a device incorporating a compact shock-wave generator with a magnetic pulsed compression circuit. To generate shock waves, underwater pulsed electric discharges in high-impedance saline water were used. The saline water made possible underwater shock waves propagation in tissue with low reflection between the solution and tissue boundary, owing to their similar acoustic impedances. A cylindrical electrode holder and a semiellipsoidal shock-wave focusing reflector/generator were used in this paper. The diameter of the compact shock-wave reflector was 20 mm. Two kinds of successive underwater shock waves, one generated by electric discharge plasma expansion and the other by bubble collapse, were observed. The shock waves were studied by time-resolve high-speed visualization and direct pressure measurement using a fiber optic probe hydrophone pressure transducer. The former method elucidated propagation of underwater shock waves and behavior and collapse of the bubble near the electrodes, while the later measured two kinds of underwater shock waves pressures at different voltage amplitudes using the cylindrical electrode holder and the shock focusing generator. This paper clearly shows the importance of the secondary shock waves, their control, and damping, for effective and safe medical application of shock waves. [ABSTRACT FROM PUBLISHER]

Pulsed power, used to produce underwater discharges, has been the subject of numerous studies to elucidate its mechanisms and applications. This paper reports on observation by a high-speed camera of the production and progress of streamer discharges created using a magnetic pulse compression pulsed power generator with maximum output energy of 40 Joules per shot in the medium of both tap and distilled water. Bubble production along streamers, bubble collapse, generation of shock waves, and extinction of bubbles was also observed by a high-speed camera. [ABSTRACT FROM PUBLISHER]

A dc underwater discharge generated in gas bubbles (air, Ar, He, and \N2) in a \NaH2\PO4 \bullet 2 \H2\O solution is studied. It is shown that the maximal concentration of hydrogen peroxide produced in the discharge does not depend on gas composition. The energy efficiency of \H2\O2 production is, however, gas dependent, and the highest value of 2.95 g/kWh is obtained for air. The decomposition efficiency of the Direct Blue 106 dye, which is used as a model organic pollutant at an initial concentration of 20 mg/L, increases linearly with current in the investigated range (10–30 mA). A maximal dye decoloration of 65% is observed in a \N2 discharge after 20 min of treatment at a current of 30 mA. Different mechanisms of dye decoloration by plasma are proposed and discussed. [ABSTRACT FROM PUBLISHER]

Retrotransposons are mobile genetic elements which transpose via an RNA intermediate. Because the transposition of retrotransposons causes insertional mutagenesis in a genome, the activation of retrotransposons has been used for basic and applied genome studies in plant biology. Some retrotransposons were shown to be transcriptionally activated by biotic and abiotic stress factors, such as UV light, ozone, pathogens, wounding, and drought. A pulsed streamerlike discharge in water is known to generate physical phenomena, such as high electric fields, UV, ozone, other chemically active species, and shock waves. In this paper, an underwater pulsed discharge treatment was used as a new tool for the activation of retrotransposons in a Porphyra yezoensis genome. The results of reverse-transcription polymerase chain reaction for the discharge treatment of P. yezoensis showed that a copia-Iike retrotransposon, called PyRE1G1, was transcriptionally activated by the underwater pulsed discharge without cell damage. The effects of pulse parameters on the mRNA accumulation of PyRE1G1 showed that a certain charging voltage and larger applied pulse numbers gave sufficient results for the transcriptional activation of PyRE1G1. The maximum activation of the PyRE1G1 expression was induced 1 h after the discharge treatment. [ABSTRACT FROM AUTHOR]

A pulsed discharge produced underwater has been an attractive method to treat waste water. For the optimization and realization of the water treatment system utilizing underwater pulsed discharge, modeling analysis could be one of the essential works. However, there is still no simulation work about the underwater pulsed discharge due to the lack of knowledge about its characteristic parameters such as electron temperature, electron density, and so on. In this paper, the temperature and the electron density in a pulsed discharge plasma produced underwater are measured and presented. A magnetic pulse compressor (MPC) was developed and used to create the electrical discharge in water. The developed MPC is all-solid state and is, therefore, a maintenance-free generator. To define the temperature and the electron density in an underwater pulsed discharge plasma, two kinds of spectroscopic measurements, called the line-pair method and Stark broadening, were carried out. According to the experimental results, the temperature and the electron density in the pulsed discharge plasma between point-plane electrodes immersed in water are determined to be 15 000 K and 1018/cm³, respectively. [ABSTRACT FROM AUTHOR]

This paper is focused on providing a facile method for the production of underwater plasma by a capillary discharge in water. The underwater plasma is formed from a tungsten electrode inserted in a narrow dielectric capillary, showing the breakdown of water vapor in the capillary. This mainly produces atomic oxygen, atomic hydrogen, and hydroxyl radicals from the dissociation of water vapor, revealing different plasma species when the capillary electrode serves as the anode or the cathode. [ABSTRACT FROM AUTHOR]

A series of images of a generation process of an underwater secondary streamer from a developed primary streamer was visualized by an ultrahigh-speed camera with a microscope lens. The secondary streamer with a filamentary structure propagated with an average velocity of 30 km/s from one of the channel tips of the semispherical primary streamer with an average propagation velocity of 1.8 km/s. The synchronized current waveform showed that pulsed currents of about 100 mA were changed into a continuous current of about 300 mA when the secondary streamer started to propagate. This experiment was carried out by the application of a single-shot pulsed positive voltage to a needle-to-wire electrode system with a gap length of 6 mm. [ABSTRACT FROM PUBLISHER]