• Journal of IKEEE
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• v.19 no.2
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• pp.265-270
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• 2015

In this paper, we proposed a dual-directional SCR (silicon-controlled rectifier) based ESD (electrostatic discharge) protection circuit. In comparison with conventional SCR, this ESD protection circuit can provide an effective protection against ESD pulses in the two opposite directions, so the ESD protection circuit can be discharged in two opposite direction. The proposed circuit has a higher holding voltage characteristic than conventional SCR. These characteristic enable to have latch-up immunity under normal operating conditions as well as superior full chip ESD protection. it was analyzed to figure out electrical characteristics in term of individual design parameters. They are investigated by using the Synopsys TCAD simulator. In the simulation results, it has trigger voltage of 6.5V and holding voltage increased with different design parameters. The holding voltage of the proposed circuit changes from 2.1V to 6.3V and the proposed circuit has symmetrical I-V characteristic for positive and negative ESD pulse.

• Journal of IKEEE
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• v.21 no.1
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• pp.7-12
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• 2017

This paper proposed the ESD protection circuit for the high-voltage applications with latch-up immunity and high area efficiency. The proposed circuit has high holding voltage compared to the conventional SCR by inserting the floating regions and applying the segmentation layout. It has the area efficiency is more higher due to the segmentation layout. The proposed circuit has the higher holding voltage of the 21.67V than the 3.39V of the conventional SCR. The electrical characteristics of the proposed circuit was investigated by TCAD simulator, and was proved through the fabrication by using the 0.18 BCD process.

• Journal of the Korea Society of Computer and Information
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• v.28 no.1
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• pp.121-127
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• 2023

In this study, the design conditions and CFD analysis results are compared and reviewed in SCR that can optimally reduce nitrogen compounds. To this end, it was analyzed and compared using CFD to see if the design criteria were satisfied for the shell and tube areas of the boiler. In the SCR system, the analysis area is the gas/air heat exchanger on the shell side, and eight tubes of the gas/air heat exchanger on the tube side. Through CFD analysis, the gas velocity distribution on the primary catalyst side of the SCR system was designed to be 2.4%, and the NH3/NOx molar ratio distribution was 3.7%, which satisfied the design criteria. In addition, the uniformity of the temperature distribution was confirmed and the required condition of 260℃ or higher was satisfied. The angle of the gas entering the catalyst met the design conditions at 2.9 degrees, and the pressure loss that occurred also satisfied the design requirements. Through this CFD analysis, it was confirmed that it was designed and operated by satisfying the design conditions required for each area.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.119-123
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• 2012

This study presents the effect of oxygen on the $NH_3$ selective catalytic reduction (SCR) by Mn/$TiO_2$ catalyst. The lattice oxygen of catalysts is participate in the low temperature SCR, and the gaseous oxygen directly takes part in the rexoidtion of reduced catalyst. These redox properties of oxygen an play important role in SCR activity and the available capability of lattice oxygen depends on the manganese oxidation state of the catalyst surface. $MnO_2$ species has a higher redox property than that of $Mn_2O_3$ species on deposited $TiO_2$ surface and these manganese oxide states strongly depend on the $TiO_2$ surface area.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.154-161
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• 2009

This study is a part of project of urea-SCR system development for an in-use medium duty diesel engine. This study shows the effect of ammonia oxidation catalyst and SCR volume on $NO_X$ reduction performance. When AOC(Ammonia Oxidation Catalyst) is not used, the urea injection should be controlled accurately to prevent $NH_3$ slip. However, it is found that the accurate $NH_3$ slip control is not easy without AOC in real engine operating conditions, because $NH_3$ and $NO_X$ reaction characteristics change with many factors such as exhaust gas temperature and $NH_3$ absorbance on SCR. SCR volume is also one of important design parameters. This study shows that $NO_X$ reduction efficiency increases with increase of SCR volume especially at high space velocity and low exhaust gas temperature conditions. Additionally, this paper shows the emissions of EURO-2 medium duty diesel engine can be improved to the level of EURO-5 with a DPF and urea-SCR system.

• Journal of the Korean Applied Science and Technology
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• v.37 no.4
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• pp.723-732
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• 2020

The spent RHDS (Residue HydroDeSulfurization) catalyst is deactivated mainly by deposition of various contaminants such as coke, sulfur and vanadium on the surface of catalyst. To eliminate those contaminants, the following remanufacturing process was conducted. The first, heavy oil on the surface of the spent RHDS catalyst was removed by kerosene and dehydrated. The second, the high temperature incineration was carried out to eliminate coke and sulfur components deposited on the surface of spent RHDS catalyst. The third, the excessive quantity of Vanadium deposited on the surface of catalyst was removed by leaching process as follows: ultrasonic agitation was carried out at 50℃, for 10 seconds with 0.5% and 1% oxalic acid solution. The purpose of this process is to find out regenerated RHDS catalyst can be used as SCR catalyst for NOx reduction by controlling the vanadium residual content of the regenerated RHDS catalyst through leaching process. The composition of regenerated RHDS catalyst was analyzed by XRF and the NOx reduction efficiency was also measured by continuous catalytic fixed bed reactor. As the result, regenerated catalyst, with 0.5% oxalic acid, ultrasonic agitation in 10 seconds, showed the most stable NOx reduction efficiency. Also, in comparison with commercial SCR catalyst, the NOx reduction performance of regenerated catalyst was similar to that of commercial SCR catalyst at the temperature 375℃ and higher whereas was lower than commercial SCR catalyst at the temperature range between 200~250℃. Therefore, it was confirmed that the regenerated catalyst as powder form wash coated on the surface of metal corrugated substrate can be used for commercial SCR catalyst.

• Resources Recycling
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• v.21 no.6
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• pp.65-73
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• 2012

Selective catalytic reduction(SCR) catalysts are obtained from de-NOx system of thermoelectric power plant. A process was developed for valuable metals such as vanadium and tungsten recovery from spent SCR catalyst by using soda roasting followed by water leaching. Spent SCR catalyst having $V_2O_5$(1.23 mass %) and $WO_3$(7.73 mass %). For getting soluble metal forms of the targeted metals like vanadium and tungsten soda roasting process was implemented. In soda roasting process, sodium carbonate added 5 equivalent ratio at roasted temperature $850^{\circ}C$ with 120 min roasted time for $544{\mu}m$ particle size of spent SCR catalyst. After soda roasting process moved to water leaching for roasted spent catalyst. Before leaching process the roasted spent catalyst was grinded up to $-45{\mu}m$ size. The leaching time is 30 min at $40^{\circ}C$ temperature, 10 % pulp density. The final leaching efficiency obtained 46 % of vanadium and 92 % of tungsten from present process.

• Honam Mathematical Journal
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• v.21 no.1
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• pp.157-169
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• 1999

For a k-connected inverse system $({\scr{X}},\;*)=((X_{\lambda},\;*),p_{{\lambda}{{\lambda}}^{\prime}},\;{\Lambda})$ of pointed topological spaces and pointed preserving weak fibrations, inducting epimorphic chain maps, over a directed set, we show that the homotopy group ${\pi}_k(lim{\scr{X}},\;*)$ of the inverse limit is isomorphic to the integral homology group $$H_k(lim{\scr{X}};\mathbb{Z})$. Using the result of S. $Marde{\check{s}}i{\acute{c}}$, we prove that the group of pure extension $Pext(colimH^n({\scr{X}},\;A)$ is isomorphic to the group of extension $Ext({\Delta}({\lambda}),\;Hom(H^n({\scr{X}}),\;A))$.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.125-126
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• 2012

The key issues for the reduction technologies of the exhaust gas from diesel engine being developed are to reduce particulate matters and NOx. Performance of NOx removal in SCR process depends on such various factors as catalyst factors(catalyst composition, shape, velocity, etc.), exhaust gas temperature and velocity distribution. In this study checked flow uniformity with the flow characteristics in the SCR reactor by using STAR CCM+. The pressure drop of experiment and simulation had similar result more than 90% at catalytic Cell. Also, flow uniformity calculated about 0.9036 ant 1st catalytic ind SCR reactor.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.700-704
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• 2009

A simulation study on SCR(steam carbon dioxide reforming) in gas-to-liquid(natural gas to Fischer-Tropsch synthetic fuel) process was carried out in order to find optimum reaction conditions for SCR experiment. Optimum operating conditions for SCR process were determined by changing reaction variables such as temperature and $CH_4/steam/CO_2$ feed ratio. Simulation was carried out by Aspen Plus. During the simulation, overall process was assumed to proceed under steady-state conditions. It was also assumed that physical properties of reaction medium were governed by RKS(Redlich-Kwong-Soave) equation. Optimum simulation variables such as temperature and feed ratio were determined by considering $H_2/CO$ ratio for FTS(Fischer-Tropsch synthesis), $CH_4$ conversion, and $CO_2$ conversion. Simulation results showed that optimum reaction temperature and $CH_4/steam/CO_2$ feed ratio in SCR process were $850^{\circ}C$ and 1.0/1.6/0.7, respectively. Under optimum temperature of $850^{\circ}C$, $CH_4$ conversion and $CO_2$ conversion were found to be 99% and 49%, respectively.