• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2436-2440
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• 2009

In this work, TCO-less dye-sensitized solar cells (DSCs) using Ti-mesh layer is fabricated for high-efficient low-cost solar cell application. The Ti-mesh metal can replace TCO in the photo-electrode part of DSCs, thus the cell structure is composed of a glass/dye sensitized TiO2 particle/ Ti-mesh layer/electrolyte/Pt sputtered counter electrode/ glass. The Ti-mesh electrode with high conductivity can collect electrons from the $TiO_2$ layer and allows the ionic diffusion of $I^-/I_3^-$ through the mesh hole. Thin Ti-mesh ($\sim40{\mu}m$ in thickness) electrode material is processed using rapid prototype method. The efficiency of prepared TCO-less DSCs sample is about 1.45 % ((ff: 0.5, Voc: 0.52V, Jsc: 5.55 $mA/cm^2$).

• Membrane and Water Treatment
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• v.2 no.4
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• pp.267-279
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• 2011

At steady state, the simultaneous transport of sulphuric acid and nickel sulphate through an anion-exchange membrane Neosepta-AFN (Astom Corporation, Tokyo, Japan) was investigated in a two-compartment counter-current dialyzer with single passes. The transport was quantified by the recovery yield of acid, rejection of salt and four phenomenological coefficients, which were correlated with the acid and salt concentrations in the feed. The phenomenological coefficients were determined by the numerical integration of the basic differential equations describing the concentration profiles of the components in the dialyzer. This integration was combined with an optimizing procedure. The experiments proved that the acid recovery yield is in the limits from 63 to 91 %, while salt rejection is in the limits from 79 to 97 % in the dependence on the volumetric liquid flow rate and composition of the feed.

• East Asian mathematical journal
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• v.37 no.5
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• pp.553-566
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• 2021

In the over-the-counter market, option's buyers could have a problem for default risk caused by option's writers. In addition, many participants try to maximize their benefits obviously in investing the financial derivatives. Taking all these circumstances into consideration, we deal with the vulnerable power options under a constant elasticity variance (CEV) model. We derive an analytic pricing formula for the vulnerable power option by using the asymptotic analysis, and then we verify that the analytic formula can be obtained accurately by comparing our solution with Monte-Carlo price. Finally, we examine the effect of CEV on the option price based on the derived solution.

• Journal of the Korean Society of Safety
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• v.27 no.1
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• pp.20-25
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• 2012

The purpose of the study is to assess the extinguishing concentration of inert gases in engine nacelle fire. The experiment was performed with a two dimensional rectangular bluff body stabilized flames, where the fuel was ejected to counter flow and co-flow against an oxidizer stream. Two inert gases, $CO_2$ and $N_2$, were used for extinguishing agent in the oxidizer and methane was used for fuel. The main experimental parameters were the direction of injecting fuel, the kinds of agent and the velocity ratio between air and fuel streams, which controlled the mixing characteristic near bluff body and the strength of recirculation zone in the downstream. The result shows the flame structure and the mode were strongly dependent with fuel/air ratio and the fuel jet direction. For both flow configurations, the extinguishing concentration of $CO_2$ was smaller than the $N_2$ because of the large heat capacity of $CO_2$. However, the concentration of inert gasesat blowout was much smaller than those in the cup burner and coflow jet diffusion flames, which implies that the extinction mechanism of bluff body stabilized flames was mainly due to the aerodynamic aspect. Compared to co-flow fuel injection, the extinguishing concentration of inert gases under counter flow configuration was lower. The effect of direction might result from the mixing characteristic and strength of recirculation zonearound a bluff body. More details should be investigated for the characteristic of recirculation zone in the wake of bluff body using the LES(Large Eddy Simulation).

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.78-88
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• 2005

The combustion characteristics of End-Burning hybrid combustor using different types of injector system are numerically investigated to visualize the temperature fields in the combustion chamber The basic characteristics of combustion with different O/F ratio is also analyzed in order to capture the main behavior of diffusion flame inside the swirl induced hybrid combustion chamber It was found that the arrangement of oxidizer injectors give strong effect on the temperature field dominating mixing between fuel and oxidizer. The results show that among five different oxidizer injectors arrangement, the counter flow injector has the highest mixing efficiency. However, the observed high wall temperature presence near the oxidizer injectors remains to be solved.

• Journal of the Korean Applied Science and Technology
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• v.29 no.3
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• pp.421-428
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• 2012

We investigated an electrochemical properties for Langmuir-Blodgett (LB) nano-films of polyimide and phospholipid mixture. LB films of polyamic acid and phospholipid monolayer were deposited by the Langmuir-Blodgett method on the indium tin oxide(ITO) glass. The electrochemical properties measured by cyclic voltammetry with three-electrode system(an Ag/AgCl reference electrode, a platinum wire counter electrode and LB film-coated ITO working electrode) in $KClO_4$ solution. The current of reduction and oxidation range was measured from 1650 mV to -1350 mV, continuously. The scan rates were 50, 100, 150, 200 and 250 mV/s, respectively. As a result, monolayer LB films of polyamic acid and phospholipid mixture was appeared on irreversible process caused by the reduction current from the cyclic voltammogram. Diffusion coefficient (D) effect in the polyamic acid and phospholipid mixture was used in the LAPC with LLPC fewer than the diffusion coefficient values.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.5
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• pp.742-749
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• 2002

Numerical Study with detailed chemistry has been conducted to investigate the flame structure and NOx formation characteristics in oxygen -enhanced(CH$_4$/O$_2$-$N_2$) and oxygen-enhanced-EGR(CH$_4$/O$_2$-$CO_2$) counter diffusion flame with various strain rates. A small amount of $N_2$is included in oxygen-enhanced-EGR combustion, in order to consider the inevitable $N_2$contamination by $O_2$production process or air infiltration. The results are as follows : In CH$_4$/O$_2$-$CO_2$flame it is very important to adopt a radiation effect precisely because the effect of radiation changes flame structure significantly. In CH$_4$/O$_2$-$N_2$flame special strategy to minimize NO emission is needed because it is very sensitive to a small amount of $N_2$. Special attention is needed on CO emission by flame quenching, because of increased CO concentration. Spatial NO production rate of oxygen-enhanced combustion is different from that of air and oxygen-enhanced-EGR combustion in that thermal mechanism plays a role of destruction as well as production. In case CH$_4$/O$_2$-$CO_2$flame contains more than 40% $CO_2$it is possible to maintain the same EINO as that of CH$_4$/Air flame with accomplishing higher temperature than that of CH$_4$/Air flame. EINO decreases with increasing strain rate, and those effects are augmented in CH$_4$/O$_2$flame.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.185-190
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• 2001

Numerical Study with detailed chemistry has been conducted to investigate the flame structure and NOx formation characteristics in oxygen-enhanced$(CH_4/O_2-N_2)$ and oxygen-enhanced-EGR$(CH_4/O_2-CO_2)$ counter diffusion flame with various strain rates. A small amount of $N_2$ is included in oxygen-enhanced-EGR combustion, in order to consider the inevitable $N_2$ contamination by $O_2$ production process or air infiltration. The results are as follows : In $CH_4/O_2-CO_2$ flame it is very important to adopt a radiation effect precisely because the effect of radiation changes flame structure significantly. In $CH_4/O_2-N_2$ flame special strategy to minimize NO emission is needed because it is very sensitive to a small amount of $N_2$. Special attention is needed on CO emission by flame quenching, because of increased CO concentration. Spatial NO production rate of oxygen-enhanced combustion is different from that of air and oxygen-enhanced-EGR combustion in that thermal mechanism plays a role of destruction as well as production. In case $CH_4/O_2-CO_2$ flame contains more than 40% $CO_2$ it is possible to maintain the same EINO as that of $CH_4/Air$ flame with accomplishing higher temperature than that of $CH_4/Air$ flame. EINO decreases with increasing strain rate, and those effects are augmented in $CH_4/O_2$ flame. Complementary study is needed with extending the range of strain rate variation.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3440-3445
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• 2007

For proton exchange membrane fuel cell, it is very important to design the flow channel on separation plate optimally to maximize the current density at same electrochemical reaction surface and reduce the concentration polarization occurred at high current density. In this paper, three dimensional computation model including anode and cathode domain together was developed to examine effects of flow patterns and operation conditions such as humidity and operating temperature on performance of fuel cell. Results show that voltage at counter flow condition is higher than that at coflow condition in parallel and interdigitated flow pattern. And fuel cell with interdigitated flow pattern which has better mass transport by convection flow through gas diffusion layer has higher performance than with parallel flow pattern but its pressure drop is increased such that the trade off between performance and pressure drop should be considered for selection of flow pattern of fuel cell.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.171-177
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• 2005

In order to investigate the effect of dimethyl ether (DME) on PAH and soot formation, the fuel has been mixed to the counter-flow diffusion flames of ethylene. Laser-induced incandescence and laser-induced fluorescence techniques were employed to measure relative concentrations of soot volume fraction and polycyclic aromatic hydrocarbon (PAH) concentration, respectively. Results showed that even though pure DME flame produces the minimal amount of PAH and soot, the mixture fuel of DME and ethylene could increase PAH and soot formation, as compared to those of pure ethylene flame. This implies that even though DME has been known to be a clean fuel for soot formation, the mixture fuel of DME and the hydrocarbon fuel could produce enhanced production of soot. Numerical simulation demonstrated that methyl (CH$_{3}$) radical generated by the initial pyrolysis of DME can be contributed to the enhancement of PAH and soot formation, through the formation of propargyl (C$_{3}$H$_{3}$) radical.