• Journal of the Korean Society of Industry Convergence
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• v.25 no.2_2
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• pp.309-314
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• 2022

The bonding strength [ISO22674] test was conducted by firing a dedicated ceramic powder on the surface of the dental titanium material treated with micro-arc oxidation. In the test group, an average result value of 34.34 MPa was obtained, and in the control group, a result value of 21.53 MPa was obtained. The bonding strength of the test group was higher than that of the control group by 12.81 MPa, resulting in a 37% improvement in durability of the dental artificial tooth ceramic restoration.

• 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%.

• Journal of Powder Materials
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• v.22 no.6
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• pp.426-431
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• 2015

Microstructural examination of the Nb-Si-B alloys at Nb-rich compositions is performed. The Nb-rich corner of the Nb-Si-B system is favorable in that the constituent phases are Nb (ductile and tough phase with high melting temperature) and $T_2$ phase (very hard intermetallic compound with favorable oxidation resistance) which are good combination for high temperature structural materials. The samples containing compositions near Nb-rich corner of the Nb-Si-B ternary system are prepared by spark plasma sintering (SPS) process using $T_2$ and Nb powders. $T_2$ bulk phase is made in arc furnace by melting the Nb slug and the Si-B powder compact. The $T_2$ bulk phase was subsequently ball-milled to powders. SPS is performed at $1300^{\circ}C$ and $1400^{\circ}C$, depending on the composition, under 30 MPa for 600s, to produce disc-shaped specimen with 15 mm in diameter and 3 mm high. Hardness tests (Rockwell A-scale and micro Vickers) are carried out to estimate the mechanical property.

• Journal of the Korean Vacuum Society
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• v.18 no.3
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• pp.236-243
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• 2009

Proton Engineering Frontier Project (PEFP) has supplied the metal ions to users by using an installed metal ion implanter of 120 keV. At present a feasibility study is being performed for a cobalt ion implantation. For a cobalt ion extraction we studied to sustain the high temperature($648^{\circ}C$) for metal ions vaporization from a cobalt chloride powder by using an alumina crucible in the ion source. The temperature condition of the crucible was satisfied with the plasma generation at the arc current of 120V and EHC power of 250W. The extracted beam current of $Co^+$ ions was dependent on the arc current in the plasma. The maximum beam current was $100{\mu}A$ at 0.18A of the arc current. The 3 peak currents of the extracted ions such as $Co^+$, $CoCl^+$ and $Cl^+$ were obtained by adjusting a mass analyzing magnet and the $Co^+$ ion beam peak current fraction as around 70% in the sum of the peak currents. The fluence of the implanted cobalt ions at the $10{\mu}A$ of the beam current and 90 minutes of the implantation time into an aluminum sample as measured around $1.74{\times}10^{17}#/cm^2$ by a quantitative analysis method of RBS (Rutherford Backscattering Spectrometry).

• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.216-225
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• 2006

This paper presents a new circuit topology of DC busline switch and snubbing capacitor-assisted full-bridge soft-switching PWM inverter type DC-DC power converter with a high frequency link for low voltage large current applications as DC feeding systems, telecommunication power plants, automotive DC bus converters, plasma generator, electro plating plants, fuel cell interfaced power conditioner and arc welding power supplies. The proposed power converter circuit is based upon a voltage source-fed H type full-bridge high frequency PWM inverter with a high frequency transformer link. The conventional type high frequency inverter circuit is modified by adding a single power semiconductor switching device in series with DC rail and snubbing lossless capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge inverter arms and DC busline can achieve ZVS/ZVT turn-off and ZCS turn-on commutation operation. Therefore, the total switching losses at turn-off and turn-on switching transitions of these power semiconductor devices can be reduced even in the high switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules is selected to be 60 kHz. It is proved experimentally by the power loss analysis that the more the switching frequency increases, the more the proposed DC-DC converter can achieve high performance, lighter in weight, lower power losses and miniaturization in size as compared to the conventional hard switching one. The principle of operation, operation modes, practical and inherent effectiveness of this novel DC-DC power converter topology is proved for a low voltage and large current DC-DC power supplies of arc welder applications in industry.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.12
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• pp.1048-1053
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• 2015

Ablative materials in a thermal protection system for atmospheric re-entry suffers from the most severe heat fluxes and temperatures, which induces surface recession in the thickness direction. In this paper, a 0.4MW arc-heated wind tunnel is operated to test for ablative materials, and a non-contact three-dimensional surface measuring system is used to evaluate the different surface characteristics of them. In particular, by postprocessing the three-dimensional image data, the surface roughness and recession of ablative materials can be calculated before and after the wind tunnel test. Moreover, the surface properties are analyzed quantitatively by comparing volume and mass losses of the test specimens.

• Resources Recycling
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• v.26 no.4
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• pp.19-25
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• 2017

The ways of producing metal silicon include a carbon reduction method, a plasma reduction method, and a thermite reaction method. The carbon reduction process produces metal silicon by metallurgical refining. The carbon reduction method is produced by adding a raw material mixed with quartz and coke to an electric arc furnace which is for carbon reduction. The cost of high energy costs and environmental protection facilities is an issue when producing metal silicon using electric arc furnaces. For this reason, there is no metal silicon production facility in Korea yet. Therefore, the optimal manufacturing conditions by the carbon reduction method are being studied through the experimental facilities by the companies and research institutes. The present study investigated the change of metal silicon purity according to the purity of silicon when extracting metal silicon using the thermit reaction, which has a relatively lower manufacturing cost than the carbon reduction method.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.205-209
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• 2015

CCU (Carbon Capture & Utilization) has a potential technology for the reduction and usage of carbon dioxide which is greenhouse gas emitting from a fossil fuel buring. To decompose the carbon dioxide, a three phase gliding arc plasma-catalytic reactor was designed and manufactured. Experiments of carbon dioxide reduction was performed by varying the gas flow rate with feeding the $CO_2$ only as well as the input power, the catalyst type and steam supply with respect to the injection of the mixture of $CO_2$ and $CH_4$. The $CO_2$ decomposition rate was 7.9% and the energy efficiency was $0.0013L/min{\cdot}W$ at a $CO_2$ flow rate of 12 L/min only. Carbon monoxide and oxygen was generated in accordance with the destruction of carbon dioxide. When the injection ratio of $CH_4/CO_2$ reached 1.29, the $CO_2$ destruction and $CH_4$ conversion rates were 37.8% and 56.6% respectively at a power supply of 0.76 kW. During the installation of $NiO/Al_2O_3$ catalyst bed, the $CO_2$ destruction and $CH_4$ conversion rates were 11.5% and 9.9% respectively. The steam supply parameter do not have any significant effects on the carbon dioxide decomposition.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.4
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• pp.593-599
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• 2003

The purposes of this study were to evaluate the microleakage of class V composite resin restorations utilizing the different curing lights, to assess the flowable resin, $Filtek^{TM}Flow$(3M Dental Products, USA) and composite resin, $Filtek^{TM}Z250$(3M Dental Products, USA) which need 20s curing time for halogen light could replace $Z100^{TM}$ Restorative(3M Dental Products, USA) for the microleakage, and to evaluate the effect of adhesive resin on marginal microleakage. Light curing units used in this study were conventional halogen light, XL3000(3M Dental Products, USA) and plasma arc light, Flipo(Lokki, France). Class V cavities were prepared and each cavity was filled with each composite resin. After being filled, the teeth were stored in distilled water, polished, thermocycled and soaked in 1% methylene blue solution. Following results were obtained from evaluation of the sectioned surface. 1. There was no statistically significant difference in microleakage of $Filtek^{TM}Flow$ and $Filk^{TM}Z250$ between two kinds of curing units(p>0.05). 2. Flowable resin, $Filtek^{TM}Flow$ showed more microleakage than Z100 and $Filtek^{TM}Z250$ regardless of curing units(p<0.05). 3. Adhesive resin reduced the microleakage of composite resin in both halogen light and plasma arc light(p<0.05).

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.499-503
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• 2004

This application-oriented paper describes an automated welding carriage system to weld a thin corrugated workpiece with welding seam tracking function. Hyundai Heavy Industries Corporation has developed an automatic welding carriage system, which utilizes pulsed plasma arc welding process for corrugated sheets. It can obtain high speed welding more than 2 times faster than traditional TIG based welding system. The aim of this development is to increase the productivity by using automatic plasma welding carriage systems, to track weld seam line using vision sensor automatically, and finally to provide a convenience to operator in order to carry out welding. In this paper a robust image processing and a distance based tracking algorithms are introduced for corrugated workpiece welding. The automatic welding carriage system is controlled by the programmable logic controller(PLC), and the automatic welding seam tracking system is controlled by the industrial personal computer(IPC) equipped with embedded OS. The system was tested at actual workpiece to show the feasibility and performance of proposed algorithm and to confirm the reliability of developed controller.