• 전기학회논문지
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• 제58권12호
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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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• 제2권4호
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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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• 제37권5호
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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.

• 한국안전학회지
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• 제27권1호
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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).

• 한국추진공학회지
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• 제9권2호
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• pp.78-88
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• 2005

산화제 주입기 배열 변화에 따른 End-Burning 하이브리드 연소기의 연소실 내부 유동장의 특성 및 온도장 분포도의 경향을 파악하기 위해 수치해석적 연구를 수행하였다. 스월을 동반하는 하이브리드 연소실내 확산 화염의 주요 거동을 얻기 위해 7가지의 다른 O/F 비를 갖는 연소의 기본 특성을 분석하였다. 산화제 주입기의 위치 변화 및 공급방식이 연료와 산화제의 혼합율을 크게 지배하고 온도분포에도 강한 영향을 미치는 것을 확인할 수 있었다. 본 연구에 사용된 여러 산화제 주입기 배열중에서 counter rotating 유동을 유발시키는 주입기가 가장 좋은 혼합효율을 보였으나 벽면 근처에서 관찰된 고온부의 발생 문제가 대두되었다.

• 한국응용과학기술학회지
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• 제29권3호
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• pp.421-428
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• 2012

우리는 순환전압전류법에 의한 폴리이미드와 인지질혼합 나노LB 필름에 대한 전기화학적 특성을 조사하였다. polyamic acid와 인지질 단분자 LB막은 ITO glass에 Langmuir-Blodgett법을 사용하여 제막하였다. 전기화학적 특성은 $KClO_4$ 용액에서 3 전극 시스템 (Ag/AgCl 기준전극, 백금선 카운터 전극 및 LB 필름이 코팅된 ITO 작업 전극)으로 순환전압전류법을 사용하여 측정하였다. 측정 범위는 연속적으로 1650 mV로 산화시키고, 초기전위인 -1350 mV로 환원시켰다. 주사속도는 각각 50, 100, 150, 200 및 250 mV/s였다. 그 결과 polyamic acid와 인지질 혼합물의 LB 필름은 순환전압전류도표로부터 환원전류로 인한 비가역공정으로 나타났다. Polyamic acid와 인지질혼합 LB막에서 확산계수(D)효과는 LAPC를 사용한 경우가 LLPC를 사용한 것 보다 확산계수 값이 적었다.

• 대한기계학회논문집B
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• 제26권5호
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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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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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.

• 한국자동차공학회논문집
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• 제13권3호
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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.