• Korean Journal of Materials Research
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• v.7 no.1
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• pp.76-80
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• 1997

'4 NiAl coating process was applied on 316 stainless steel to retard the corrosion of the wet- seal area of separator for the molten carbonate fuel cell. The Nit11 phasc on the stainless steel substrate could be formed by pre-coating with Ni, plated with A1 and ther, heat treated at $800^{\circ}C$ for 3 hr in $H_2/N_2$ gas atmosphere. The corrosion protection behavior of YiAl coating layer was stuilied under immersion condition in molten cxhonate salt($62^{m}/_{o}Li_2CO_3-38^{m}/_{o}/K_{2}CO_{3}$) at $650^{\circ}C$. The NiAl coating layer ticposited on the AiSi 316 stainless steel had high corrosion resistance in molten carbor. dte salt. The corrosion resistance of XiAl (~~jpoared to be associated with the .A1 oxide formed on the surface of coating layer.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.116-122
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• 2012

The purpose of this study is to investigate the overall spray behavior characteristics for various injection conditions in a gasoline direct injection(GDI) injector with multi-hole. The spray characteristics, such as the spray penetration, the spray angle, and the injection quantity, were studied through the change of the injection pressure, the ambient pressure, and the energizing duration in a high-pressure chamber with a constant volume. The n-heptane with 99.5% purity was used as the test fuel. In a constant volume chamber, the injected spray was visualized by the spray visualization system, which consisted of the high-speed camera, the metal-halide lamp, the injector control device, and the image analysis system with the image processing program. It was revealed that the injection quantity was mainly affected by the difference between the injection pressure and the ambient pressure. For low injection pressure conditions, the injection quantity was decreased by the increase of the ambient pressure, while it nearly maintained regardless of the ambient pressure at high injection pressure. According to the increase of the ambient pressure in the constant volume chamber, the spray development became slow, consequently, the spray tip penetration decreased, and the spray area increased. In additions, the circular cone area decreased, and the vortex area increased.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.4
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• pp.101-107
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• 2007

This study investigated the wear of the valve and seat insert seating faces. A tester, an exhaust valve and a seat insert were used. Test variables were cycle numbers ($2{\times}10^6,\;4{\times}10^6,\;6{\times}10^6\;and\;8{\times}10^6$) and Hz (10Hz and 25Hz). The other test conditions such as temperature ($350^{\circ}C$), fuel (LPG) and load (1960N) were fixed. The 10Hz tests indicated that the average Rmax of the valve increased at the rate of $7.76{\mu}m/10^6$ cycles starting from $29.42{\mu}m$ at the $2{\times}10^6$ cycles and that of the seat insert increased at the rate of $8.57{\mu}m/10^6$ cycles starting from $34.19{\mu}m$ at the $2{\times}10^6$ cycles. The 25Hz tests indicated that the average Rmax of the valve increased at the rate of $1.58{\mu}m/10^6$ cycles starting from $74.2{\mu}m$ at the $2{\times}10^6$ cycles and that of the seat insert increased at the rate of $1.25{\mu}m/10^6$ cycles starting from $83.95{\mu}m$ at the $2{\times}10^6$ cycles. The tribochemical reaction product covered the two seating faces, preventing the wear of the seating faces. As cycle numbers became greater, the average Rmax of the seating faces became greater, but the increase rate varied significantly depending on the Hz. The wear mechanism of the two faces was investigated through the tribochemical reaction.

• Fire Science and Engineering
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• v.19 no.3 s.59
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• pp.13-19
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• 2005

An experimental study is presented for extinguishing characteristics of liquid fuel fire by water mist containing sodium acetate trihydrate. To evaluate the extinguishing performance of water mist containing an additive, the evaporation characteristics of a water droplet on a heated surface was examined. The evaporation process was recorded by a charge-coupled-device camera. Also, small-scale extinguishing tests were conducted for n-heptane pool fire in ventilated space to measure flame temperature variation. The average evaporation rate of a water droplet containing an additive was lower than that of a pure water droplet at a given surface temperature due to the precipitation of salt in the liquid-film and change of surface tension. In case of using an additive, the flame temperature was lower than that of pure water at a given discharge pressure and it was because the momentum of a water droplet containing an additive was increased reducing flame size. And also dissociated metal atoms, sodium, were reacted as a scavenger of the major radical species OH^-,\;H^+$ which were generated for combustion process. Moreover, at a high pressure of 4MPa, the fire was extinguished through blowing effect as well as primary extinguishing mechanisms.

• Journal of the Korean institute of surface engineering
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• v.44 no.5
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• pp.173-178
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• 2011

Separator of stack in polymer electrolyte membrane fuel cell (PEMFC) is high cost and heavy. If we make it low cost and lighter, it will have a great ripple. In this study, low carbon steel is used as base metal of separator because the cost of low carbon steel is very cheaper commercial metal material than stainless steels, which is widely used as separator. Low carbon steel has not a good corrosion resistance. In order to improve the corrosion resistance and electrolytic conductivity, low carbon steel needs to be surface treated. We made Chromium electroplated layer of $5{\mu}m$, $10{\mu}m$ thickness on the surface of low carbon steel and it was nitrided for 2 hours at $1000^{\circ}C$ in a furnace with 100 torr nitrogen gas pressure. Cross-sectional and surface microstructures of surface treated low carbon steel are investigated using SEM. And crystal structures are investigated by XRD. Interfacial contact resistance and corrosion tests were considered to simulate the internal operating conditions of PEMFC stack. The corrosion test was performed in 0.1 N $H_2SO_4$ + 2 ppm $F^-$ solution at $80^{\circ}C$. Throughout this research, we try to know that low carbon steel can be replaced stainless steel in separator of PEMFC.

• Journal of Aquaculture
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• v.21 no.3
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• pp.125-132
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• 2008

Seed production of olive flounder Paralichthys olivaceus was performed in a pilot RAS. The growth of juvenile olive flounder and changes in water quality were monitored for the entire production period. The pilot RAS consisted of 8 circular culture tanks($4.0mD{\times}1.0mH$), 2 trickling biofilters($1.7mD{\times}2.0mH$), 2 protein skimmers ($0.8mD{\times}2.5mH$), and 4 sedimentation chambers($0.7mD{\times}1.5mH$). The culture surface area was about $100.5m^2$ and the actual working volume was about $106.9m^3$. As many as 300,000 fertilized olive flounder eggs were initially distributed into 2 culture tanks with the water temperature at $19.0^{\circ}C$. Live feeds such as rotifers and Artemia nauplii were fed until the 32nd day after hatching, and a commercial diet was fed from the 19th day to the end of the experiment. After 70 days, 150,256 juveniles with a body length of $65.8{\pm}3.9mm$ were produced in the RAS, with a daily growth rate for body length of 4.7%/day. At this time, the final culture density was 1,495 individuals $m^{-2}$, and 13.6 L of makeup water, 0.071 kW of electricity and 0.025 L of diesel fuel were used to produce a juvenile olive flounder. During metamorphosis of the larvae, the TAN concentration increased to 0.99 mg/L, which made the larvae sensitive to result in some mortality. However no more massive mortality occurred at the juvenile stage after metamorphosis even at a TAN concentration of 4.25 mg/L and a ${NO_2}^{-}-N$ concentration of 2.45 mg/L.

• Transactions on Electrical and Electronic Materials
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• v.5 no.5
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• pp.204-207
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• 2004

In this work, we present the electrochemical properties of Al bipolar plate, which can be re-searched for the application of PEMFC system. Bulk resistance of the plate was measured with a four-point probe method. The electrical conductivity of noble metal coated Al plate was 4.40 x 10$^4$ S/cm. On the other hand, the electrical interfacial resistance of the noble metal coated Al plate valued at 0.15 mΩ-$\textrm{cm}^2$ and that of graphite was 0.26 mΩ-$\textrm{cm}^2$ under the holding pressure of 140 N/$\textrm{cm}^2$ at the applied current of 5 A. And the performance of Al bipolar plate for PEMFC was evaluated at various conditions. The single cell performance was more than 0.43 W/$\textrm{cm}^2$ (0.47 Wig) for noble metal coated Al bipolar plate at 5$0^{\circ}C$ under atmospheric pressure in external humidified hydrogen and oxygen condition. As the present results, we could show the results that the noble metal coated Al bipolar plates were favorable in the aspect of electrical properties compared with those of the commercialized resin-impregnated graphite plates.

• Journal of ILASS-Korea
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• v.25 no.1
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• pp.21-26
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• 2020

The objective of this work is to numerically reveal the effect of equivalence ratio change on the simultaneous reduction of NO_X and soot emissions from the simulated-EGR compression ignition engine containing CO₂. An experiment was conducted by using a single-cylinder common-rail injection system engine, an intake control system, and exhaust emissions analyzers. The numerical analysis results were validated under the same experimental conditions. To investigate the effect of equivalence ratio by simulated-EGR containing CO₂, the O₂, N₂, and CO₂ mole fraction were changed in the initial air conditions to the cylinder. The results were analyzed in terms of peak cylinder pressure, indicated mean effective pressure, indicated specific nitrogen oxide, and indicated specific soot. It was revealed that ignition delay characteristics and heat release rate (ROHR) characteristics were not significantly different according to the equivalence ratio. However, as the equivalence ratio increased from 0.68 to 0.83, the maximum combustion pressure and IMEP decreased by about 6.5% and 9.4%, respectively. In the case of ISFC, as is well known, the trend is opposite of IMEP. In the case of ISNO, as the equivalence ratio increased, less NO was generated, and as the equivalence ratio increased by 0.05, the ISSoot value of about 10% increased.

• Nuclear Engineering and Technology
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• v.47 no.1
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• pp.11-25
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• 2015

The accident at Japan's Fukushima Daiichi nuclear power plant in March 2011, caused by an earthquake and a subsequent tsunami, resulted in a failure of the power systems that are needed to cool the reactors at the plant. The accident progression in the absence of heat removal systems caused Units 1-3 to undergo fuel melting. Containment pressurization and hydrogen explosions ultimately resulted in the escape of radioactivity from reactor containments into the atmosphere and ocean. Problems in containment venting operation, leakage from primary containment boundary to the reactor building, improper functioning of standby gas treatment system (SGTS), unmitigated hydrogen accumulation in the reactor building were identified as some of the reasons those added-up in the severity of the accident. The Fukushima accident not only initiated worldwide demand for installation of adequate control and mitigation measures to minimize the potential source term to the environment but also advocated assessment of the existing mitigation systems performance behavior under a wide range of postulated accident scenarios. The uncertainty in estimating the released fraction of the radionuclides due to the Fukushima accident also underlined the need for comprehensive understanding of fission product behavior as a function of the thermal hydraulic conditions and the type of gaseous, aqueous, and solid materials available for interaction, e.g., gas components, decontamination paint, aerosols, and water pools. In the light of the Fukushima accident, additional experimental needs identified for hydrogen and fission product issues need to be investigated in an integrated and optimized way. Additionally, as more and more passive safety systems, such as passive autocatalytic recombiners and filtered containment venting systems are being retrofitted in current reactors and also planned for future reactors, identified hydrogen and fission product issues will need to be coupled with the operation of passive safety systems in phenomena oriented and coupled effects experiments. In the present paper, potential hydrogen and fission product issues raised by the Fukushima accident are discussed. The discussion focuses on hydrogen and fission product behavior inside nuclear power plant containments under severe accident conditions. The relevant experimental investigations conducted in the technical scale containment THAI (thermal hydraulics, hydrogen, aerosols, and iodine) test facility (9.2 m high, 3.2 m in diameter, and $60m^3$ volume) are discussed in the light of the Fukushima accident.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.1
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• pp.131-140
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• 2005

To investigate secondary carbonaceous species within PM$_{10}$ and PM$_{2.5}$ in Seoul urban Metropolitan Area (SMA), Korea. atmospheric particulate matters samples were collected at two sites of SMA at UOS (The University Of Seoul station) sites and IHU (InHa University of Incheon station) during the period of 4 to 14 January and 12 to 22 May, 11 to 15 August 2004, and their characteristics were qualitatively discussed. during January and May and August of 2004. Daily average mass concentration 0.095 mg/㎥ in PM$_{10}$ and 0.053 mg/㎥ in PM$_{2.5}$ for mass respectively. were observed in SMA. The concentrations of carbonaceous species contributed 18.4% and 16.4% of PM$_{2.5}$ and PM$_{10}$ during the sampling period, respectively, of which OC accounted for 68% and 52% more of the total carbon (TC). OC and EC concentrations and their mass percentages were higher in PM$_{2.5}$ than in PM$_{10}$ which could be attributed to generation process. Organic aerosols would constitute up to 38% of PM$_{2.5}$ based on the evaluation of 1.6 for the ratio of OC to organic particulate. Secondary organic carbon (SOC) were estimated to be more than 13% and up to 68% of total OC based on the minimum OC/EC ratio of 1.06/1.11 using least square method. Comparisons of OC and EC with trace elements. As results of carbonaceous species analysis, the dominant factor in view of fine particle (PM$_{10}$/PM$_{2.5}$) is primary emission source such as mobile, fossil fuel combustion etc. during winter time in SMA. But in summer periods, remarkable fine particle increasing factor was secondary organic carbon dependent to photochemical reaction. reaction.n. reaction.