• Journal of the Korean Society of Combustion
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• v.16 no.3
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• pp.33-40
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• 2011

Combustion experiments were conducted at three different fuels ($CH_4$, $C_2H_4$ and $C_3H_8$) to investigate the effects of combustor pressure (30 ~ -30 kPa) on combustion charateristics and reaction zone structure. Regardless of the fuels, emission index of CO (EICO) increased with decreasing combustor pressure, and EICO of $C_2H_4$ was mostly affected by changing combustor pressure at subatmospheric pressure. In order to observe reaction zone, $OH^*$, $CH^*$ and ${C_2}^*$ chemiluminescence intensity were measured. The sequence of the chemiluminescence intensity peak position was affected by chemical characteristics of fuels rather than changing combustor pressure. The emission zone thickness of $C_2H_4$ and $C_3H_8$, defined by the full width at half maximum (FWHM) of $CH^*$ intensity profile, were increased with decreasing combustor pressure. however, the thickness of $C_2H_4$ exhibited the opposite tendency due to the characteristics of the fuel as the bond structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.1
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• pp.45-49
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• 2014

We have fabricated white organic light-emitting diodes (OLEDs) using several thicknesses of electron-transport layer. The multi-emission layer structure doped with red and blue phosphorescent guest emitters was used for achieving white emission. 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) was used as an electron-transport layer. The thickness of BCP layer was varied to be 20, 55, and 120 nm. The current efficiency, emission and recombination characteristics of multi-layer white OLEDs were investigated. The BCP layer thickness variation results in the shift of emission spectrum due to the recombination zone shift. As the BCP layer thickness increases, the recombination zone shifts toward the electron-transport layer/emission-layer interface. The white OLED with a 55 nm thick BCP layer exhibited a maximum current efficiency of 40.9 cd/A.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.3
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• pp.87-95
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• 2005

The object of this study is to investigate the effect of joinability by using acoustic emission(AE) signals and doing a pattern recognition for weld heat affected zone(HAZ) in tensile testing. This study was carried out an SWS 490A high tension steel for electric shielded metal arc welding(SMAW), $CO_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. The results of the tensile test of weld HAZ come out electric shield arc welding $>\;CO_2$ gas arc welding > TIG welding in case of single welding. It is believed that this is a phenomenon where difference of its root opening or base metal thickness. Also, the technique of AE is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.40-48
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• 2004

The object of this study is to investigate the effect of joinability by using acoustic emission (AE) signals and doing a pattern recognition for weld heat affected zone (HAZ) in tensile testing. This study was carried out an SWS 490A high tension steel for electric shielded metal arc welding (SMAW), $CO_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. The results of the tensile test of weld HAZ come out electric shield arc welding > $CO_2$ gas arc welding > TIG welding in case of single welding. It is believed that this is a phenomenon where difference of its root opening or base metal thickness. Also, the technique of AE is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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• pp.781-785
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• 2009

We have fabricated simple triple-layer blue-emitting phosphorescent organic light emitting diodes (OLEDs) using different thicknesses (25 and 55 nm) of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) electron transport layers. 1,1-bis[4-bis (4-methylphenyl)- aminophenyllcyclohexane (TAPC), bis[(4,6-di-fluorophenyl)-pyridinate-$N,C^{2'}$]picolinate (FIrpic) and N,N' -dicarbazolyl-3,5-benzene (mCP) were used as hole transport, blue guest and host materials, respectively. The driving voltage, electroluminescence (EL) efficiency and emission characteristics of devices were investigated. The maximum EL efficiency was 20 cd/A in the device with 55 nm BCP layer, which efficiency was about 33% higher than the device with 25 nm BCP layer. The higher efficiency in the 55 nm BCP device resulted from the enhanced electron-hole balance. In the EL spectrum of blue phosphorescent OLED with BCP layer, the relative intensity between 470 and 500 nm peaks was related to the location of emission zone.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.432-432
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• 2007

We studied optical simulation method for ultra slim backlight system. We designed 0.7mm thickness light guide plate and combined 48 white color LEDs for 12 inch wide size TFT-LCD. We designed flat shape PMMA light guide plate with both side patterned. It have vertical prism shape on upper side and ellipse dot pattern on the other side. We targeted 4500 nit brightness and uniform emission characteristic without hot spot or dark area. At first, we designed uniform emission area with more high brightness in center area and then, debugged light entering hot spot zone and direction of outgoing light flux. Although it was designing step, we obtained good result with reverse prism optical sheet and it had good repeatability because it was based on the stamper method in injection process without laser engraving or micro groove engraving method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.2
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• pp.265-270
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• 1989

The present study considers the thermal structure variation in a porous medium caused by changing the most important radiative property of porous medium, absorption coefficient, as well as altering the physical dimension of porous medium and the equivalence ratio of premixed gas mixture. The radiation model was introduced as an unsteady differential form using the two-flux gray radiation model. The role of the conductive heat transfer through both gas phase and porous medium was found to be almost insignificant compared with that of the radiative heat transfer. The reaction zone shifted upstream and the flame thickness decreased as either the geometrical length of porous medium increased or the absorption coefficient decreased.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.251-253
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• 2017

Numerical study of air-blast type injector for low emission aircraft engines was conducted. Volume-of-fluids approach was used to track interface of fuel and air. Primary atomization of fuel stream was visualized, and thickness and mean velocity at the injector exit was calculated. Liquid fuel injected from fuel slots joined together as a thin film on preflimer surface, and interacted with swirling air. As instability on the fuel surface increased, separation of fuel as ligaments and droplets occured. The film thickness and velocity were used to as fuel injection boundary condition for reactive flow simulation. Primary reaction zone was formed in vicinity of the fuel nozzle, creating a stable flame inside the combustor.

• Journal of Convergence for Information Technology
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• v.7 no.5
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• pp.123-128
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• 2017

Nanostructured materials have received attention due to their unique electronic, optical, optoelectrical, and magnetic properties as a results of their large surface-to-volume ratio and quantum confinement effects. Thermal chemical vapor deposition process has attracted much attention due to the synthesis capability of various structured nanomaterials during the growth of nanostructures. In this study, silicon oxide nanowires were grown on Si\$SiO_2$(300 nm)\Pt(5~40 nm) substrates by two-zone thermal chemical vapor deposition with the source material $TiO_2$ powder via vapor-liquid-solid process. The morphology and crystallographic properties of the grown silicon oxide nanowires were characterized by field-emission scanning electron microscope and transmission electron microscope. As results of analysis, the morphology, diameter and length, of the grown silicon oxide nanowires are depend on the thickness of the catalyst films. The grown silicon oxide nanowires exhibit amorphous phase.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.353-358
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• 2013

The hot corrosion behavior of plasma sprayed 4 mol% $Y_2O_3-ZrO_2$ (YSZ) thermal barrier coatings (TBCs) with volcanic ash is investigated. Volcanic ash that deposited on the TBCs in gas-turbine engines can attack the surface of TBCs itself as a form of corrosive melt. YSZ coating specimens with a thickness of 430-440 ${\mu}m$ are prepared using a plasma spray method. These specimens are subjected to hot corrosion environment at $1200^{\circ}C$ with five different duration time, from 10 mins to 100 h in the presence of corrosive melt from volcanic ash. The microstructure, composition, and phase analysis are performed using Field emission scanning electron microscopy, including Energy dispersive spectroscopy and X-ray diffraction. After the heat treatment, hematite ($Fe_2O_3-TiO_2$) and monoclinic YSZ phases are found in TBCs. Furthermore the interface area between the molten volcanic ash layers and YSZ coatings becomes porous with increases in the heat treatment time as the YSZ coatings dissolved into molten volcanic ash. The maximum thickness of this a porous reaction zone is 25 ${\mu}m$ after 100 h of heat treatment.