Pulsed Electric Discharge Research Articles

Two Successive Shock Waves Generated by Underwater Pulse Electric Discharge for Medical Applications

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.

Impact of pulsed electric fields and high voltage electrical discharges on extraction of high-added value compounds from papaya peels

Extraction of the nutritionally valuable and antioxidant compounds from papaya peels using conventional aqueous extraction (E) (at 20°C, 50°C, and 60°C) and extraction assisted by pulsed electric field (PEF) or by high voltage electrical discharges (HVED) was studied. Increase of extraction temperature or extraction in basic media (pH=11) not always resulted in an increase of the yields or TEAC values. E.g., the concentration of proteins and TEAC values at pH=7 and pH=11 were noticeably smaller at 60°C as compared to those measured at 50°C. HVED-assisted technique showed a higher extraction efficiency of high-added value compounds compared to PEF-assisted extraction. E.g., the concentrations of proteins obtained for the HVED- or PEF-assisted extractions were 60mg/L and 20mg/L, respectively (pH=7 at 20°C and time of extraction of≈3/4h). The better efficiency of HVED-assisted extraction can reflect turbulation of suspension and fragmentation of pills provoked by electrical discharges. However, electrical discharges may produce chemical products of electrolysis and free reactive radicals, which can reduce the nutritional quality of high-added value compounds. Application of the two-stage method (PEF+supplementary aqueous extraction at 50°C) allowed a significant enhancement of the yields and antioxidant capacities of the extracted components from papaya peels even at neutral pH.

Solution of the nonlinear (radiative) thermal conductivity equation for pulsed high-current electric discharges in dense gases

A model of the initial expansion stage of cylindrical pulsed high-current electric discharges in dense gases in the approximation of radiative thermal conductivity is proposed. Based on the uniform distribution of the plasma pressure in the discharge channel and its constancy at this stage, the partial difference equations (continuity, Euler, and nonlinear thermal conductivity equations) of this model are reduced to ordinary differential equations. The space-time dependences of the plasma temperature and density in the channel on initial parameters were determined from the solutions to these equations. These dependences are consistent with experimental data within experimental error.

Pulsed evaporator of an electrodynamic disperse suspension of particles

We consider the technique for obtaining electrodynamic disperse suspension of metal (Al, W, Cu) and dielectric (semiconductor) particles (SiO2, Al2O3, CuO, Cu2O) and its evaporation with the help of a diffusive electric discharge. The time dependences of current and integrated luminescence intensity in a pulsed electric discharge in a tube containing a film of a substance (Cu) of the electrodynamic disperse suspension are measured.

Model of Pulsed Electrical Discharge Machining (EDM) using RL Circuit

This article presents a model of pulsed Electrical Discharge Machining (EDM) using RL circuit. There are several mathematical models have been successfully developed based on the initial, ignition and discharge phase of current and voltage gap. According to these models, the circuit schematic of transistor pulse power generator has been designed using electrical model in Matlab Simulink software to identify the profile of voltage and current during machining process. Then, the simulation results are compared with the experimental results.

Pulsed electrical discharge synthesis of red photoluminescence zinc oxide nanoparticles

Zinc oxide (ZnO) nanoparticles have been prepared using a pulsed electrical discharge in a liquid medium. The effects of the processing parameters, including liquid media, current, frequency of the electrical discharge and electrode gap distance exert significant effects on the characteristic and properties of ZnO nanoparticles. The synthesized ZnO nanoparticles are characterized using a combination of transmission electron microscopy (TEM), energy dispersive X-ray (EDS) and photoluminescence (PL) spectroscopy. The average size of ZnO nanoparticles varies between 10–25 nm depending on the processing parameters. It is found that an increase in the arc current plays a great role in particle growth and results in a significant increase in average particles size. Both frequency of discharge and electrode gap distance can influence the average particle size and distribution due to the variation in the cooling rate. The PL spectrum for all as-synthesized ZnO nanoparticles exhibits an ultraviolet emission (~3.4 eV) and a red visible emission (~1.98 eV). The blue shift is independent of the average size of the ZnO nanoparticles. However, the intensity of visible emission is significantly enhanced with the decrease of the particle sizes. The porous structure and irregular particle surface are suggested to contribute significantly to the visible red emission.

Titanium carbonitride coating by pulsed electrical discharge in an aqueous solution of ethanolamine

Titanium carbonitride (TiCN) coating is prepared by electrical discharge machining using a titanium tool electrode and a carbon and nitrogen containing dielectric media of ethanolamine. The composition, morphology and microstructure of the TiCN coating are characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, electron probe micro-analyzer and X-ray photoelectron spectroscopy. Its microhardness and interfacial adhesion strength against 45# carbon steel substrate are also investigated. The results reveal that a 15μm thick layer mainly composing of TiC0.3N0.7 phase with fine-grain structure is created and it metallurgically bonds with the steel substrate. Such unique microstructure results in an improved hardness of 1780HV and bonding strength of TiCN coating is 4 times higher than TiN coating obtained by magnetron sputtering.

Bipolar Pulsed Electrical Discharge for Synthesis of Tungsten Nanoparticles in the Aqueous Solutions

ABSTRACTThe liquid phase plasma reduction method was applied to prepare the tungsten nanoparticles from the solu-tion of tungsten chloride using bipolar pulsed electrical discharge system. The liquid phase plasma providesextremely rapid reactions caused by activated chemical species. The OH radicals produce H 2 O 2 and the hydro-gen radicals are used for the reduction process to generate W nanoparticles. While spherical tungsten nanopar-ticles were mostly observed, triangular and hexagonal-shaped nanoparticles were also observed occasionallyin the plasma treated reactant solution. The anionic surfactant of SDS was shown to exhibit a large in”uenceon the particle generation procedure.KEYWORDS: Tungsten, Nanoparticle, Liquid Phase Plasma, Surfactant, Emission Spectra. 1. INTRODUCTION Nanotechnology has gained a considerable importance,in the recent times. Tungsten nanoparticles are used asfunctional materials. 1 These particles exhibit peculiar ther-mal behavior that was thought to be associated with storedinternal energy.

Research on Electrical Characteristics of Metal Rubber

Metal rubber is a new type of elastic damping material. It’s often used in all kinds of instruments and equipment to vibration isolation and buffer. The internal of metal rubber is mesh structure in space formed with wires. The contact points of the crossed wires aren’t solid collusion. Although the compressive strength of metal rubber is very good, but the structure of metal rubber would become loosly and destroyed under tensile load. Literature [1] put forward that the pulse discharge sintered to metal rubber can make the contact point transform to solid collusion. The method is based on the theory of resistance welding to the contact points between sintering metal wires in metal rubber. The research and analysis to the electricity characteristics of the metal rubber has important significance to optimize parameters of electrical pulse discharge experiment and improve the quality of sinter.

Experimental characterization of plasma formation and shockwave propagation induced by high power pulsed underwater electrical discharge.

High power pulsed electrical discharges into liquids are investigated for new industrial applications based on the efficiency of controlled shock waves. We present here new experimental data obtained by combination of detailed high speed imaging equipments. It allows the visualization of the very first instants of plasma discharge formation, and then the pulsations of the gaseous bubble with an accurate timing of events. The time history of the expansion/compression of this bubble leads to an estimation of the energy effectively transferred to water during the discharge. Finally, the consecutive shock generation driven by this pulsating bubble is optically monitored by shadowgraphs and schlieren setup. These data provide essential information about the geometrical pattern and chronometry associated with the shock wave generation and propagation.

Nanosecond Pulsed Electric Discharge Synthesis of Carbon Nanomaterials in Helium at Atmospheric Pressure from Adamantane

Nanosecond pulsed discharges in a helium-adamantane mixture at atmospheric pressure were used for the synthesis of carbon nanomaterials, using the smallest diamondoid, adamantane, as a precursor. The discharges were generated using a point-to-plane electrode with a gap distance of 1–2 mm, at room temperature, 373 and 473 K. Scanning electron microscopy of the electrodes showed the formation of carbonaceous deposits with different morphologies, while micro-Raman spectra of the deposits covering the electrodes contained features characteristic of carbon structures of varying order. To study the effect of the temperature conditions on the plasma characteristics, time-resolved optical emission spectroscopy measurements were carried out at room temperature and 456 K. The optical emission spectra showed that at room temperature the afterglow has a duration of about several microseconds, whereas at 456 K, the plasma decay is on the order of only 1 \({\mu }\) s. This may be an indication that the carbon nanomaterials are predominantly formed in the afterglow of the nanosecond pulsed discharge, with the presence of hydrogen radicals facilitating the formation of carbonaceous materials.

Optical diagnostics for high power pulsed underwater electrical discharge characterization

In order to evaluate the behavior of a high power pulsed underwater electrical discharge, and especially characterize the pressure generated by such a discharge, we implemented several optical diagnostics. We first observed directly the expansion of the plasma produced by the dielectric breakdown of the water between the electrodes and the resulting gaseous pulsating bubble. This observation led to an estimate of the pressure inside the bubble with respect to time. We then visualized the propagation of the pressure wave generated by the discharge with shadowgraph and Schlieren setup. The obtained velocity was then used to evaluate the theoretical maximum pressure at the pressure front. Finally, we measured the velocity induced by the pressure wave on a thin aluminum disk with a heterodyne velocimeter and used numerical simulation to obtain a temporal form of pressure. These methods and results can be used to develop and assess performances of processes using underwater electrical discharges to generate pressure waves such as electrohydraulic forming.

Behavior of AISI SAE 1020 Steel Implanted by Titanium and Exposed to Bacteria Sulphate Deoxidizer

A hybrid technology to treat solid surfaces with the pulse high voltage and electric arc discharges of low pressure with a three-dimensional ion implantation technique (3DII) is applied. This technology is used to protect AISI SAE 1020 steel against a microbiological corrosion. The titanium ion implanted steel samples (coupons) are subjected to a medium of bacteria sulphate deoxidizer (BSD) which are very typical of the hydrocarbon industry and are potentially harmful for structures when are in contact with petroleum and some of its derivatives.The used technology aims to find an effective hybrid procedure to minimize the harmful effects of bacteria on AISI SAE 1020 steel. The hybrid technology efficiency of superficial titanium implantation is estimated through the measurements of the point corrosion characteristics obtained after testing both the treated and non-treated coupons. The three-dimensional surface structures of the samples are reconstructed with help of a confocal microscope.

Development of a pulsed power system using MOSFETs and underwater pulsed electric discharge

Development of a pulsed power system using MOSFETs and underwater pulsed electric discharge

Development of Multi-Wire Electric Discharge Machining for SiC Wafer Processing

In order to slice the larger size ingot toward 6 inch of silicon carbide (SiC), we are developing Multi-wire Electric Discharge Machining (EDM). To prevent wire break during slicing, we have developed the electric discharge pulse control system. So far, with 10 multi-wires, we have succeeded in slicing of 4 inch SiC balk single crystal without wire break. High quality slicing surface (e.g. small value of around 10 μm of SORI for 3 inchi wafer) was also achieved. By polishing methode, EDM-sliced wafer was estimated to have the uniform thickness of damaged layer over the entire surface. We confirmed that the wafer sliced by EDM can be processed in the later process, by grinding the 3 inch wafer. And it was confirmed that 6 inch ingot can be sliced with 10 multi-wire EDM, by slicing the boule of SiC poly crystal. For the larger diameter ingot than 4 inch, Multi-wire EDM will be practically used by the effective removal of machining chips from the machining clearance between the wire and work.

Influences of Pulsed Electric Fields on the Gene Expression of Pathogenic Bacteria

In the biological and medical fields, sterilization using pulsed electric fields or discharges and electroporation have been studied actively in recent years. It is clear that a pulsed electric field has some sort of effect on an organism. At present, however, it is not sufficiently clear what effect occurs and how the mechanism of a pulsed electric field acts on the organism. The effects of pulsed electric fields on ribonucleic acid RNA expression in biological cells were studied with the objective of elucidating the bioelectric mechanism. A pulsed electric field was applied to Vibrio parahaemolyticus, a pathogenic bacteria, and the expression of RNAs, specifically thermostable direct hemolysin TDH, VP1680, and VP1699, which represent pathogenic agents, were analyzed using the polymerase chain reaction PCR method. The level of expression of VP1680 increased when a pulsed electric field was applied, and the effect was at a peak when the electric field strength was 14i¾?kV/cm. The electric field strength barely affected the expression of TDH and VP1699. It was found that the effects of the electric field were different among the RNAs. The expression level varied with time when expression was analyzed. These results suggest the possibility of selective control of gene expression by using pulsed electric fields and possible new applications such as the development of functional foods.

Hypersonic Flow over a Cylinder with a Nanosecond Pulse Electrical Discharge

A computational study of Mach 5 airflow over a cylinder with a dielectric barrier discharge actuator was performed. The actuator was pulsed at nanosecond time scales and it rapidly added thermal energy to the flow, creating a shock wave that traveled away from the pulse source. As the shock wave traveled upstream, it interacted with the standing bow shock, and temporarily increased the bow shock standoff distance. This phenomenon was also observed experimentally through phase-locked schlieren photography. This paper aims to reproduce flow phenomena observed in the experiment using high-fidelity computations in order to provide additional insight into the shock–shock interaction, and subsequent effect on the cylinder, through a reduced-order phenomenological model of the actuator. A three-dimensional simulation of the experiment was able to accurately capture the complex cylinder/tunnel-sidewall interaction, and to replicate the changes in the flow produced by the nanosecond dielectric barrier discharge. The results show that the device was very effective at moving the standing bow shock for a minimal energy budget.

Oxidation of S(IV) in Seawater by Pulsed High Voltage Discharge Plasma with TiO2/Ti Electrode as Catalyst

Oxidation of S(IV) to S(VI) in the effluent of a flue gas desulfurization(FGD) system is very critical for industrial applications of seawater FGD. This paper reports a pulsed corona discharge oxidation process combined with a TiO2 photocatalyst to convert S(IV) to S(VI) in artificial seawater. Experimental results show that the oxidation of S(IV) in artificial seawater is enhanced in the pulsed discharge plasma process through the application of TiO2 coating electrodes. The oxidation rate of S(IV) using Ti metal as a ground electrode is about 2.0×10−4 mol · L−1 · min−1, the oxidation rate using TiO2/Ti electrode prepared by annealing at 500°C in air is 4.5×10−4 mol · L−1 · min−1, an increase with a factor 2.25. The annealing temperature for preparing TiO2/Ti electrode has a strong effect on the oxidation of S(IV) in artificial seawater. The results of in-situ emission spectroscopic analysis show that chemically active species (i.e. hydroxyl radicals and oxygen radicals) are produced in the pulsed discharge plasma process. Compared with the traditional air oxidation process and the sole plasma-induced oxidation process, the combined application of TiO2 photocatalysts and a pulsed high-voltage electrical discharge process is useful in enhancing the energy and conversion efficiency of S(IV) for the seawater FGD system.

Morphological and electrophysiological field observations on electric freshwater fish of the genus Mormyrops Müller 1843 (Teleostei: Mormyridae) from West and southern Africa

Different specimens of Mormyrops anguilloides (Linnaeus 1758) were reported to display electric organ discharge (EOD) pulses of either initially head-positive or initially negative polarity, a hypothetical sex difference that has not been substantiated to date. The morphology and EODs of M. anguilloides of both sexes and a sexually mature size from the Comoé and Bandama rivers, Côte d'Ivoire, and the Lower and Middle Zambezi, Mozambique, displayed initially positive EODs. The morphologically similar M. breviceps Steindachner 1895 of both sexes and a sexually mature size from the Bandama River displayed initially head-negative EODs of biphasic waveform and long duration (0.93–1.15 ms) in the very-low-frequency spectral range. Mormyrops anguilloides from the Comoé and Bandama rivers were differentiated in caudal peduncle depth and in EOD waveform, pulse duration and spectral energy content. The former samples displayed a biphasic, lower-frequency EOD pulse of up to 0.42 ms duration, the latter a tetraphasic, high-frequency EOD of up to 0.33 ms. It is suggested that reports of EODs of both polarities in M. anguilloides indicate the presence of an unrecognised species.

Перспективы получения мелкодисперсных порошков с помощью импульсного электрического разряда в жидкости

Перспективы получения мелкодисперсных порошков с помощью импульсного электрического разряда в жидкости