• Journal of Korean Society of Environmental Engineers
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• v.30 no.12
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• pp.1268-1272
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• 2008

Low temperature plasma applied with partial oxidation is a technique to produce synthesis gas from methane. Low temperature plasma reformer has superior miniaturization and start-up characteristics to reformers using steam reforming or CO$_2$ reforming. In this research, a low temperature plasma reformer using GlidArc discharge was proposed. Reforming characteristics for each of the following variables were studied: gas components ratio (O$_2$/CH$_4$), the amount of steam, comparison of reaction on nickle and iron catalysts and the amount of CO$_2$. The optimum conditions for hydrogen production from methane was found. The maximum Hydrogen concentration of 41.1% was obtained under the following in this condition: O$_2$/C ratio of 0.64, total gas flow of 14.2 L/min, catalyst reactor temperature of 672$^{\circ}C$, the amount of steam was 0.8, reformer energy density of 1.1 kJ/L with Ni catalyst in the catalyst reactor. At this point, the methane conversion rate, hydrogen selectivity and reformer thermal efficiency were 66%, 93% and 35.2%, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.9
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• pp.949-954
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• 2006

The purpose of this paper is to develop water jet plasma reactor and investigate the optimal condition of the syngas production by reforming of hydrocarbon fuel. Fuel used was propane and plasma was generated by arc discharge on water jet surface. Discharge slipping over the water surface has a number of advantages such as a source of short-wave and UV radiation, and it can be used for biological and chemical purification of water. Parametric screening studies were conducted, in which there were the variations of power ($0.18{\sim}0.74$ kW), water jet flow rate($38.4{\sim}65.6$ mL/min), electrode gap($5{\sim}15$ mm) and treatment time($2{\sim}20$ min). When the variations were 0.4 kW, 53.9 mL/min, 10 mm and 20 min respectively, result of maximum $H_2$ concentration was 61.6%, intermediates concentration were 6.1% and propane conversion rate was 99.8%.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.433-445
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• 2021

Plasma blasting by high voltage arc discharge were performed in laboratory-scale soil samples to investigate the fluid penetration efficiency. A plasma blasting device with a large-capacity capacitor and columnar soil samples with a diameter of 80 cm and a height of 60 cm were prepared. Columnar soil samples consist of seven A-samples mixed with sand and silt by ratio of 7:3 and three B-samples by ratio of 9:1. When fluid was injected into A-sample by pressure without plasma blasting, fluid penetrated into soil only near around the borehole, and penetration area ratio was less than 5%. Fluid was injected by plasma blasting with three different discharge energies of 1 kJ, 4 kJ and 9 kJ. When plasma blasting was performed once in the A-samples, penetration area ratios of the fluid were 16-25%. Penetration area ratios were 30-48% when blastings were executed five times consecutively. The largest penetration area by plasma blasting was 9.6 times larger than that by fluid injection by pressure. This indicates that the higher discharge energy of plasma blasting and the more numbers of blasting are, the larger are fluid penetration areas. When five consecutive plasma blasting were carried out in B-sample, fluid penetration area ratios were 33-59%. Penetration areas into B-samples were 1.1-1.4 times larger than those in A-samples when test conditions were the same, indicating that the higher permeability of soil is, the larger is fluid penetration area. The fluid penetration radius was calculated to figure out fluid penetration volume. When the fluid was injected by pressure, the penetration radius was 9 cm. Whereas, the penetration radius was 27-30 cm when blasting were performed 5 times with energy of 9 kJ. The radius increased up to 333% by plasma blasting. All these results indicate that cleaning agent penetrates further and remediation efficiency of contaminated soil will be improved if plasma blasting technology is applied to in situ cleaning of contaminated soil with low permeability.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.557-575
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• 2020

Plasma blasting which is generated by high voltage arc discharge of electricity is applied to soil mass to improve permeability of soil and cleaning efficiency of oil contamination. A new high voltage generator was manufactured and three types of soil including silty sand, silty sand mixed with lime and silty sand mixed with cement were prepared. Small and large soil columns were produced using these types of soil and plasma blasting was performed within soil columns to investigate the variation of soil volume penetrated by fluid and permeability. Soil volume penetrated by fluid increased by 11~71% when plasma blasting was applied in soil. Although plasma blasting with low electricity voltage induced horizontal fracture and fluid penetrated along this weak plane, plasma blasting with high voltage induced spherical penetration of fluid. Plasma blasting increased the permeability of soil. Permeabilty of soils mixed with lime and cement increased by 450~1,052% with plasma blasting. Permeability of soil increased as discharge voltage increased when plasma blasing was applied once. However, several blastings with the same discharge voltage increase or decrease permeability of soil. Oil contaminated soil was prepared by adding diesel into soil artificially and plasma blasting was performed in these oil contaminated soil. Cleaning efficiency increased by average of 393% for soil located nearby the blasting and by average of 239% for soil located far from the blasting. Cleaning efficiency did not show any correlation with discharge voltage. All these results indicated that plasma blasting might be used for in-situ cleaning of oil contaminated soil because plasma blasting increased permeability of soil and cleaning efficiency.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.240-240
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• 2011

The first neutral beam injector (NBI-1) has been developed for the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. A first long pulse ion source (LPIS-1) has been installed on the NBI-1 for an auxiliary heating and current drive of KSTAR core plasmas. Performance of ion and neutral beam extractions in the LPIS-1 was investigated initially on the KSTAR NBI-1 system, prior to the neutral beam injection into the main plasmas. The ion source consists of a JAEA magnetic bucket plasma generator with multi-pole cusp fields and a set of KAERI prototype-III tetrode accelerators with circular apertures. The inner volume of plasma generator and accelerator column in the LPIS-1 is approximately 123 liters. Final design requirements for the ion source were a 120 kV/ 65 A deuterium beam and a 300 s pulse length. The extraction of ion beams was initiated by the formation of arc plasmas in the LPIS-1, called as an arc-beam extraction method. A stable ion beam extraction of LPIS-1 has been achieved up to an 100 kV/42 A for a 4 s pulse length and an 80 kV/25 A for a 14 s pulse length. Optimum beam perveance of 1.21 microperv has been found at an accelerating voltage of 80 kV. Neutralization efficiency has been measured by using a water flow calorimetry (WFC) method of calorimeter and an operation of bending magnet. The full-energy species of ion beams have been detected by using the diagnostic method of optical multichannel analyzer (OMA). An arc efficiency of the LPIS was 0.6~1.1 A/kW depending on the operating conditions of arc discharge.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2446-2452
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• 2009

A Ceramic Metal-halide lamp is achieved by adding multiple metals to a basic mercury discharge. Because the vapor pressure of most metals is very much lower than mercury itself, metal-halide salts of the desired metals, having higher vapor pressures, are used to introduce the material into the basic discharge. The metal compounds are usually polyatomic iodides, which vaporize and subsequently dissociate as they diffuse into the bulk plasma. Metals with multiple visible transitions are necessary to achieve high photometric efficiency and good color. Compounds of Sc, Dy, Ho, Tm, Ce, Pr, Yb and Nd are commonly used. The maximum visible efficacy of a Ceramic Metal Halide lamp, under the constant of a white light source, is predicted to be about 450lm/W. This is controlled principally by the chemical fill chosen for a particular lamp. Current these lamps achieve 130lm/W and these life time are the maximum 16,000[hr]. So factors of performance lower are necessary to improve lamp performance. In this paper, we analyzed factors of performance lower by accelerated deterioration test. The lamp was operated with short duration turn-on/turn-off procedure to enhance the effect due to electrode sputtering during lamp ignition. The tested lamp that was operated with a longer turn-on/off(20/20 minutes) showed blackening, changed distance between electrodes and lowered color rendering & color temperature by losses of Dy at 421.18nm, I at 511nm, T1 at 535nm and Na at 588nm compared with the new lamp.

• Journal of Powder Materials
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• v.18 no.2
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• pp.112-121
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• 2011

This study investigated the effect of solvent on the fabrication of Ni-free Fe-based alloy nano powders by employing the PWE (pulsed wire evaporation) in liquid and compared the alloy particles fabricated by three different methods (PWE in liquid, PWE in Ar, plasma arc discharge), for high temperature oxidation-resistant metallic porous body for high temperature soot filter system. Three different solvents (ethanol, acetone, distilled water) of liquid were adapted in PWE in liquid process, while X-ray diffraction (XRD), field emission scanning microscope (FE-SEM), and transmission electron microscope (TEM) were used to investigate the characteristics of the Fe-Cr-Al nano powders. The alloy powder synthesized by PWE in ethanol has good particle size and no surface oxidation compared to that of distilled water. Since the Fe-based alloy powders, which were fabricated by PWE in Ar and PAD process, showed surface oxidation by TEM analysis, the PWE in ethanol is the best way to fabricate Fe-based alloy nano powder.

• Tribology and Lubricants
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• v.32 no.4
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• pp.125-131
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• 2016

In recent years, thick ta-C coating has attracted considerable interest owing to its existing and potential commercial importance in applications such as automobile accessories, drills, and gears. The thickness of the ta-C coating is an important parameter in these applications. However, the biggest problems are achieving efficient coating and uniformity over a large area with high-speed deposition. Feasibility is confirmed for the ta-C coating thickness of up to 9.0 µm (coating speed: 3.0 µm/h, fixed substrate) using a single FCVA cathode. The thickness was determined using multiple coating cycles that were controlled using substrate temperature and residual stresses. In the present research, we have designed a coating system using FCVA plasma and produced enhanced thick ta-C coating. The system uses a specialized magnetic field configuration with stabilized DC arc plasma discharge during deposition. To achieve quality that is acceptable for use in automobile accessories, the magnetic field, T-type filters, and 10 pieces of a multi-cathode are used to demonstrate the deposition of the thick ta-C coating. The results of coating performance indicate that uniformity is ±7.6 , deposited area is 400 mm, and the thickness of the ta-C coating is up to 5.0 µm (coating speed: 0.3 µm/h, revolution and rotation). The hardness of the coating ranges from 30 to 59 GPa, and the adhesion strength level (HF1) ranges from 20 to 60 N, depending on the ta-C coating.

• Journal of the Korean institute of surface engineering
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• v.36 no.1
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• pp.79-84
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• 2003

$WC-Ti_{1}$ -xA $l_{x}$ N multilayered coatings are performed by their periodically repeated structures of lamellae of WC-Ti/$WC-Ti_{1}$ -xA $l_{x}$ Nmaterials. The $WC-Ti_{1}$ -xA $l_{x}$ N coatings with variable Al content were deposited onto AISI D2 steel by cathodic arc deposition (CAD) method. The electrochemical behavior of multilayered $WC-Ti_{1}$ -xA $l_{x}$ N coatings with different phases (WC- Ti$0.6/Al_{0.4}$ N, $WC-Ti_{0.53}$$Al_{0.47}$N, $WC-Ti_{0.5}$ $Al_{0.5}$ N and $WC-Ti_{ 0.43}$$Al_{0.57}$ N) was investigated in deaerated 3.5% NaCl solution at room temperature. The corrosion behaviors for the multilayered coatings were investigated by electrochemical techniques (potentiodynamic polarization) and surface analyses (X-ray diffraction (XRD), scanning electron microscopy (SEM), and glow discharge optical emission spectroscopy (GDOES)). In the petentiodynamic polarization test, the corrosion current density of $WC-Ti_{0.5}$$Al_{0.5}$N was lower than others.

• Applied Microscopy
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• v.45 no.4
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• pp.242-248
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• 2015

In this paper, three carbon sources, i.e., solid graphite, gaseous CH4 and liquid ethanol, and one solid silicon source were employed to synthesize SiC/C nanocomposite powders by arc-discharge plasma. The processing conditions such as the component ratios of raw materials, atmospheric gases, etc. were adjusted for controllable synthesis of the nanopowders. It is indicated that both of solid graphite and silicon can be co-evaporated and reacted to form nanophases of cubic ${\beta}$-SiC with ~50 nm in mean size and a little free graphite; the carbon atoms decomposed from gaseous $CH_4$ favor to combine with the evaporated silicon atoms to form the dominant SiC nanophase; liquid carbon source of ethanol can also be used to harvest the main ${\beta}$-SiC and minor 6H-SiC phases in the assembly of nanoparticles. The as-prepared SiC/C nanocomposite powders were further purified by a heat-treatment in air and their photocatalytic performances were then greatly improved.