• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2181-2185
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• 2008

Fuel processing systems which convert HC fuel into $H_2$ rich gas (such as stream reforming, partial oxidation, auto-thermal reforming) need high temperature environment($600-1000^{\circ}C$). Generally, anode-off gas or mixture of anode-off gas and LNG is used as input gas of fuel reformer. In order to make efficient and low emission burner system for fuel reformer, it is necessary to elucidate the combustion and emission characteristic of fuel reformer burner. The purpose of this study is to develop a porous premixed flat ceramic burner that can be used for 1-5kW fuel cell reformer. Ceramic burner experiments using natural gas, hydrogen gas, anode off gas were carried out respectively to investigate the flame characteristics by heating capacity and equivalence ratio. Results show that the stable flat flames can be established for natural gas, hydrogen gas, anode off gas and mixture of natural & anode off gas as reformer fuel. For all of fuels, their burning velocities become smaller as the equivalence ratio goes to the lean mixture ratio, and a lift-off occurs at lean limit. Flame length in hydrogen and anode off gas became longer with increasing the heat capacity.

• KSBB Journal
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• v.25 no.5
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• pp.421-428
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• 2010

This paper reports on the experimental investigation carried out to evaluate the physical optimal conditions in the absorption column to remove odorous hydrogen sulfide gas. Hydrogen sulfide gas, as a highly undesirable contaminant, is most widely emitted from environmental treatment facilities. The absorbent mixed with natural second metabolites extracted from conifer trees and chemical absorbent of 2-aminoethanol was applied to remove it via chemical neutralization. The absorbent of natural second metabolites was achieved by a removal efficiency of 20-40% by itself depending on the treatment conditions, but the complex absorbent mixed with 0.1% amine chemical provides the removal efficiency of 98%. The optimal removal efficiencies have been examined against the two major parameters of temperature and pH. This study shows that the aqueous solution by natural second metabolites can be used as an appropriate absorbent in the column absorbed for the removal of hydrogen sulfide gas.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2197-2202
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• 2014

In this paper, we report on an investigation of highly sensitive sensing performance of a hydrogen sensor composed of palladium (Pd) nanowires. The Pd nanowires have been grown by electrodeposition into nanochannels and liberated from the anodic aluminum oxide (AAO) template by dissolving in an aqueous solution of NaOH. A combination of photo-lithography, electron beam lithography and a lift-off process has been utilized to fabricate the sensor using the Pd nanowire. The hydrogen concentrations for 2% and 0.1% were obtained from the sensitivities (${\Delta}R/R$) for 1.92% and 0.18%, respectively. The resistance of the Pd nanowires depends on absorption and desorption of hydrogen. Therefore, we expect that the Pd nanowires can be applicable for detecting highly sensitive hydrogen gas at room temperature.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.354-361
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• 2005

In high speed cutting process, due to the friction between the tool and workpiece, a temperature rise of contacting part is serious. It need to develop cutting tool for overcoming such a poor condition. So now, some studies, the optimization of tool shapes, the fine grains of tool material, multi-layer coating of tools are processing. If mirror finishing on the tool is processed, there is advantage of relation between chip and tool, because of less friction, and also tool's lift would be increased. As a result mirror like finishing is expected efficient enhancement of tool. Generally, it is too difficult to process by a general way for tools of complex shapes, it is required a new method to process such complex shape tools. The magnetic fluid polishing technique can polish the workpiece of complex shape, because the polishing method which polishes as compress the workpiece by the magnetism abrasives to arrange to the linear according to the line of magnetic force. In this paper, We polished the surface of the high speed cutting tool using the magnetic fluid polishing technique, to enhance the performance of the high speed cutting tool.

• Journal of Sensor Science and Technology
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• v.31 no.5
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• pp.348-352
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• 2022

Hydrogen gas (H₂) which is odorless, colorless is attracting attention as a renewable energy source in varions applications but its leakage can lead to disastrous disasters, such as inflammable, explosive, and narcotic disasters at high concentrations. Therefore, it is necessary to develop H₂ gas sensor with high performance. In this paper, we confirmed that H₂ gas detection ability of SnO₂ based H₂ gas sensor along with thermal treatment effect of SnO₂. Proposed SnO₂ based H₂ gas sensor is fabricated by MEMS technologies such as photolithgraphy, sputtering and lift-off process, etc. Deposited SnO₂ thin films are thermally treated in various thermal treatement temperature in range of 500-900 ℃ and their H₂ gas detection ability is estimatied by measuring output current of H₂ gas sensor. Based on experimental results, fabricated H₂ gas sensor with SnO₂ thin film which is thermally treated at 700 ℃ has a superior H₂ gas detection ability, and it can be expected to utilize at the practical applications.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2997-3009
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• 2023

The Passive containment Air-cooling System (PAS) can effectively remove the decay heat of the modular small nuclear reactor after an accident. The details of natural convection around the dome, which is a key part of PAS, were investigated numerically in the present study. The thermal dynamics around the dome were studied through the temperature, pressure and velocity contours and the streamlines. Additionally, the formation of the buoyant plume at the top of the dome was investigated. The results show that with the increase of Ra, the lift-off point moves toward the bottom of the dome, and the eddy under the buoyant plume grows larger gradually, which enhances the heat transfer. And the heat transfer along the dome surface with different truncation angles was investigated. As the angle increases, the heat transfer coefficient becomes stronger as well. Consequently, a newly developed heat transfer correlation considering the influence of truncation angle for the dome is proposed based on the simulated results. This study could provide a better understanding of natural convection around the dome of PAS and the proposed correlation could also offer more predictive value in the improvement of nuclear safety.

• The Korean Journal of Mycology
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• v.25 no.4 s.83
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• pp.257-267
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• 1997

Fruit bodies similar to the Phellinus sp. residing on the mulberry were collected at Yang-yang in Kang-won-do province and one strain of Phellinus sp. was isolated from the fruit bodies. For mass production of the isolated mycelia in a submerged culture, the culture conditions, medium composition, and the effect of various culture systems on the mycelial growth, were investigated. The morphological characteristics of the fruit body were as follows: covered with blackish to black and rough, lower surface with yellowish-brown to dull-brown and smooth, 5-7 cm thick and hard woody. Also, the pure cultured mycelia showed yellowish-brown color, capability of purplish-brown pigment production on the PDA plate media, no-formation of clamp-connection, much binding branch, and enzyme activities such as laccase, tyrosinase and peroxidase. Therefore, pure cultured strain was identified to be Phellinus sp. In the flask culture, the optimum culture conditions for the mycelial production were obtained after cultivation of 8 days at inoculum level of 5%(v/v), media volume of 70 mL, 150 rpm, initial pH 6, and temperature of $30^{\circ}C$. Optimum medium composition from the response surface analysis were determined to be glucose 12.12 g/L, sucrose 12.12 g/L, yeast extract 11.15 g/L, malt extract 11.15 g/L, $KH_2PO_4$ 0.855 g/L and $CaCl_2$ 0.855 g/L. The production of the mycelia after 4 and 8 days of cultivation was 1.95 and 9.89 g/L, respectively. The maximum specific growth rate and productivity were $0.020\;hr^{-1}$ and 1.25 g/L/day, respectively. Among the three different culture systems for the growth of mycelia, the maximum mycelial dry weight of 7.5 g/L was obtained after cultivation of 4 days in the air-lift fermentor under aeration rate of 2.5 vvm. The maximum specific growth rate and productivity were $0.033\;hr^{-1}$ and 1.9 g/L/day, respectively, which were about 1.7 and 4.2 times higher than those of flask culture.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.309-319
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• 2011

We experimentally investigated lifted propane jet flames diluted with nitrogen to obtain flame-stability maps based on heat-loss-induced self-excitation. We found that heat-loss-induced self-excitations are caused by conductive heat loss from premixed flame branches to trailing diffusion flames as well as soot radiation. The conductive-heat-loss-induced self-excitation at frequencies less than 0.1 Hz is explained well by a suggested mechanism, whereas the oscillation of the soot region induces a self-excitation of lift-off height of the order of 0.1 Hz. The suggested mechanism is also verified from additive experiments in a room at constant temperature and humidity. The heat-loss-induced self-excitation is explained by the Strouhal numbers as a function of the relevant parameters.

• Elastomers and Composites
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• v.39 no.1
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• pp.71-76
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• 2004

4,4'-Methylenebis(2-chloroaniline)(MOCA) has been widely used as a crosslinking agent, but classified as a toxic chemical. Thus, its use will be limited in the near future. In this research, polyurethane coating films were prepared using 1,3-propanediolbis(4-aminobenzoate)(PDBA) as an alternative to MOCA. The base part was prepared by melting MOCA or PDBA in polyoxypropylene($M_n$=2000), followed by the addition of the various additives. The NCO-terminated toluene diisocyanate prepolymer was used as a curing agent. The polyurethane coating films were prepared by mixing the base part with the curing agent in an appropriate ratio at room temperature. The polyurethane coatings prepared using PDBA exhibited higher initial viscosity, but much longer pot lift, compared to those prepared using MOCA under the same conditions, due to lower reactivity of PDBA. The tensile strength and tear strength of the coating films were much weaker. However, the pot life, tensile strength, elongation, and tear strength of the coating films, prepared using PDBA in the presence of an increased amount of Pb(II)-octoate, were close to those of the coating films prepared using MOCA. Thus, it was concluded that PDBA can substitute MOCA in the preparation of polyurethane coatings as long as the reactivity of PDBA is enhanced using appropriate amounts of the catalyst or other appropriate catalyst.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.953-960
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• 2019

The Miller cycle is a diesel engine that has been developed in recent years that it can reduce NOx and improve fuel consumption by reducing the compression ratio through intake valve closing (IVC) time control. The Miller cycle can be divided into the early Miller method of closing the intake valve before the bottom dead center (BDC) and the late Miller method of closing the intake valve after the BDC. At low speeds, the late Miller method is advantageous as it can increase the volumetric efficiency; while at medium and high speeds, the early Miller method is advantageous because of the high internal temperature reduction effect due to the expansion of the intake air during the piston lowering from IVC to BDC. Therefore, in consideration of the ef ects of the early and late Miller methods, it is necessary to adopt the most suitable Miller method for the operating conditions. In this study, a two-stage turbo charge system was applied to four-stroke engines and the process of enhancing the Miller effect through a reduction of the intake and exhaust valve overlap as well as the valve change adjustment mechanism were considered. As a result, the ef ects of fuel consumption and Tmax reduction were confirmed by adopting the Miller cycle with a two-stage supercharge, a reduction of valve overlap, and an increase of suction valve lift.