• KIEE International Transactions on Electrophysics and Applications
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• 제4C권3호
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• pp.106-110
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• 2004

The operating condition of the OLED (organic light-emitting diode) is very sensitive to electrode thickness properties. The electrode thickness is a significant issue in the construction of OLEDs because of its transparency, high conductivity and high efficiency as an injector into organic materials. We carried out a systematic study to optimize the electrode thickness conditions in Indiumtin oxide (ITO), Molybdenum (Mo) and Aluminum (Al). Further, we measured electrode thickness under standard conditions [ITO 1500$\AA$, Mo 2600$\AA$, Al 1500$\AA$]. We also evaluated power consumption. In addition, we analyzed substrate uniformity with IVL measurement results. From these results, it is known that the electrode thickness should be optimized in order to accomplish optimal power efficiency.

• 한국재료학회지
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• 제24권11호
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• pp.573-577
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• 2014

The existing metal getters are invariably covered with thin oxide layers in air and the native oxide layer must be dissolved into the getter materials for activation. However, high temperature is needed for the activation, which leads to unavoidable deleterious effects on the devices. Therefore, to improve the device efficiency and gas-adsorption properties of the device, it is essential to synthesize the getter with a method that does not require a thermal activation temperature. In this study, getter material was synthesized using palladium oxide (PdOx) which can adsorb $H_2$ gas. To enhance the efficiency of the hydrogen and moisture absorption, a porous layer with a large specific area was fabricated by an etching process and used as supporting substrates. It was confirmed that the moisture-absorption performance of the $SiO_2/Si$ was characterized by water vapor volume with relative humidity. The gas-adsorption properties occurred in the absence of the activation process.

• 대한전자공학회논문지
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• 제19권6호
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• pp.17-32
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• 1982

집적광학용 광도파전에 전기팡 효파 혹은 자기광 효과를 나타내는 이방성 매질을 사용할 때 매질정수 및 박막두께등 광학적 변수가 모드 변환에 미치는 영향괼 엄밀한 파동광학의 접근 방법으로 조사하여 어떠한 박막형 광도파관 구조에도 적용될 수 있는 일반적인 해석방법을 제시하였다. 균일한 이방성 매질에서의 고유 모드와 그 구성성분 및 위상속도를 먼저 결정하고 그 결과를 이용하여 박자형 광도파관에서의 고유 모드 성분에 대한 위상특성식을 구하였고 전자파의 진행방향에 대한 모드 성분의 변화를 Jones 행열 령태로 표시하여 박막형 광도파관에서 모드 젼환의 조건과 그 변환율이 Bulk 매질에서와는 다름을 나타내었다. Wave propagation in gyrotropic or anisotropic medium is analyzed in terms of the eigenmodes of the medium, which are admixture of TE and TM waves. The field composition and the phase velocity of the modes are also determined. The results of the analysis are applied to thin film optical waveguide using such medium as substrate and/or film. Based on the characteristic equations for phase constants of the waveguide, the condition for TE-TM mode convection is derived, and wave propagation in the guide is represented in the form of Jones matrix, which allows a new interpretation in the conversion efficiency of the thin-film optical waveguides.

• International Journal of Fluid Machinery and Systems
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• 제5권3호
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• pp.134-142
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• 2012

The competition to deliver ultra-low emitting vehicles at a reasonable cost is driving the automotive industry to invest significant manpower and test laboratory resources in the design optimization of increasingly complex exhaust after-treatment systems. Optimization can no longer be based on traditional approaches, which are intensive in hardware use and laboratory testing. The CFD is in high demand for the analysis and design in order to reduce developing cost and time consuming in experiments. This paper describes the development of a comprehensive practical model based on experiments for simulating the performance of automotive three-way catalytic converters, which are employed to reduce engine exhaust emissions. An experiment is conducted to measure species concentrations before and after catalytic converter for different loads on engine. The model simulates the emission system behavior by using an exhaust system heat conservation and catalyst chemical kinetic sub-model. CFD simulation is used to study the performance of automotive catalytic converter. The substrate is modeled as a porous media in FLUENT and the standard k-e model is used for turbulence. The flow pattern is changed from axial to radial by changing the substrate model inside the catalytic converter and the flow distribution and the conversion efficiency of CO, HC and NOx are achieved first, and the predictions are in good agreement with the experimental measurements. It is found that the conversion from axial to radial flow makes the catalytic converter more efficient. These studies help to understand better the performance of the catalytic converter in order to optimize the converter design.

• 전기화학회지
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• 제12권1호
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• pp.11-25
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• 2009

연료전지는 가까운 미래를 위한 핵심 청정 신에너지원 중의 하나로 기대된다. 그러나 고분자 연료전지에서 공기극은 느린 산소환원반응과 많은 백금 사용 때문에 상업화에 어려움을 겪고 있으며, 이것을 해결하는 것이 최근 당면 과제이다. 또한 연료극은 일산화탄소의 피독 현상과 전극의 안정성이 문제시 되고 있다. 본 총설에서는 고분자 연료전지를 위한 연료극, 공기극 전기화학 촉매의 이론적 접근을 통해 촉매를 설계하는 최근 연구 내용을 소개하려 한다. 촉매 설계는 합금 전기 화학 촉매를 통해 접근 했으며, 이는 electronic, geometric, lateral effects를 손쉽게 조절할 수 있게 한다. 이것은 계산되어진 d-band center의 함수에 의존하며, 촉매의 활성과 큰 관계를 가짐을 발견하였다. 본고에서 지향하는 촉매의 최종 방향은 이론적 접근을 통해서 촉매의 사용량을 줄이면서 효율적으로 사용하는 것이다.

• 반도체디스플레이기술학회지
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• 제8권4호
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• pp.15-19
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• 2009

A high efficient organic red light emitting device with structure of DNTPD/TAPC/$Bebq_2$ :[$(pq)_2Ir(acac)$, SFC-411]/SFC-137 was fabricated on the plastic substrate, which can be applied in the fields of flexible display and illumination. In the device structure, N,N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolylamino)-phenyl]-biphenyl-4,4'-diamine[DNTPD] as a hole injection layer and 1,1-bis-(di-4-tolylaminophenyl) cyclohexane [TAPC] as a hole transport were used. Bis(10-hydroxybenzo[h]quinolinato) beryllium complex [$Bebq_2$] was used as a light emitting host material. The host material, $Bebq_2$ was doubly doped with volume ratio of 7% iridium(III)bis-(2-phenylquinoline)acetylacetonate[$(pq)_2$Ir(acac)] and 3% SFC-411[red phosphor dye coded by the proprietary company]. And then, SFC-137 was used as an electron transport layer. The luminous intensity and current efficiency of the fabricated device were $22,780\;cd/m^2$ at 9V and 17.3 cd/A under $10,000\;cd/m^2$, respectively. The maximum current efficiency of the device was 22.4cd/A under $580\;cd/m^2$.

• Biomolecules & Therapeutics
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• 제21권6호
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• pp.487-492
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• 2013

Cytochrome P450 4A11 (CYP4A11) is a fatty acid hydroxylase enzyme expressed in human liver. It catalyzes not only the hydroxylation of saturated and unsaturated fatty acids, but the conversion of arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE), a regulator of blood pressure. In this study, we performed a directed evolution analysis of CYP4A11 using the luminogenic assay system. A random mutant library of CYP4A11, in which mutations were made throughout the entire coding region, was screened with luciferase activity to detect the demethylation of luciferin-4A (2-[6-methoxyquinolin-2-yl]-4,5-dihydrothiazole-4-carboxylic acid) of CYP4A11 mutants in Escherichia coli. Consecutive rounds of random mutagenesis and screening yielded three improved CYP4A11 mutants, CP2600 (A24T/T263A), CP2601 (T263A), and CP2616 (A24T/T263A/V430E) with ~3-fold increase in whole cells and >10-fold increase in purified proteins on the luminescence assay. However, the steady state kinetic analysis for lauric acid hydroxylation showed the significant reductions in enzymatic activities in all three mutants. A mutant, CP2600, showed a 51% decrease in catalytic efficiency ($k_{cat}/K_m$) for lauric acid hydroxylation mainly due to an increase in $K_m$. CP2601 and CP2616 showed much greater reductions (>75%) in the catalytic efficiency due to both a decrease in $k_{cat}$ and an increase in Km. These decreased catalytic activities of CP2601 and CP2616 can be partially attributed to the changes in substrate affinities. These results suggest that the enzymatic activities of CYP4A11 mutants selected from directed evolution using a luminogenic P450 substrate may not demonstrate a direct correlation with the hydroxylation activities of lauric acid.

• 상하수도학회지
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• 제7권1호
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• pp.46-53
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• 1993

This study was carried out to examine substrate removal characteristics with the variation of the hydraulic retention time in an anaerobic filter. The feed concentration of synthetic wastewater used in the experiment was $10,000mg/l$ glucose. As media, the porosity of volcanic stones in Jeju island were 76%. The conditions of the experiment were as follows; HRT ranging from 1 day to 3 day, loading rates ranging from 3.33kg $COD_{er}/void\;m^3.day$ to 10kg $COD_{er}/void\;m^3.day$ and a temperature $35^{\circ}C$. Based on the results of the experiments, the COD removal efficiency was 98~99% in $COD_{er}$ method with loading rates ranging from 3.33kgCOD/void $m^3.day$ to 10kg COD/void $m^3.day$ and HRT ranging from 1day to 3 day. The produced quantity of gas equivalant to a porosity volume was $1.332~3.756Nm^3/void\;m^3.day$. The relationship between $COD_{er}$ loading rates and gas produced quantity equivalant to a porosity volume was well fitted with the equation of $Nm^3/void\;m^3.day{\cdot}=0.359L_0+0.179$($L_0=COD$ loading rate). Judging from the removal efficiency in this experiment, We concluded that anaerobic filter using Volcanic stones is one of improved and effective. As media, practical value of volcanic stones is sufficient.

• 한국식품조리과학회지
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• 제14권5호
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• pp.560-565
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• 1998

The purpose of this study was to investigate any differences in the efficiency of various antioxidants for the three types of substrates such as corn oil in water (O/W) emulsion, water in com oil (W/O) emulsion, and bulky corn oil. ${\alpha}$-Tocopherol (${\alpha}$-Toc) at 0.01 or 0.02%, ascorbic acid (AsA), ascorbyl palmitate (AP), and BHT at 0.02% were added separately to the prepared O/W emulsion, W/O emulsion, and bulk oil, and their antioxidative effects were compared. The mixture of ${\alpha}$-Toc ind AsA or AP at the level of 0.02% also was tested to observe any synergistic effect. Oxidation was made by storing at 42${\pm}$1$^{\circ}C$ for 25 days and the oxidative stability was determined by peroxide value and conjugated dienoic acid with time fluctuation of storage. The results were as follows: 1. In case of O/W emulsion, the order of antioxidative effect was AP> ${\alpha}$-Toc+AP>${\alpha}$-Toc+AsA>AsA>BHT. 2. In case of W/O emulsion, the order of antioxidative effect was AsA>AP>${\alpha}$-Toc+AsA>BHT. ${\alpha}$-Toc+AP mixture showed the prooxidant effect rather than synergistic effect. 3. In case of bulk oil, the order of antioxidative effect was AsA>AP>${\alpha}$-Toc+AsA>${\alpha}$-Toc+AP\ulcornerBHT. Therefore, AsA, a hydrophilic antioxidant, was more effective in W/O emulsion system than in O/W emulsion system, while the opposite trend was found in AP, a lipophilic antioxidant. AsA, a hydrophilic antioxidant, was more efficient in bulk oil of anhydrous substrate. ${\alpha}$-Toc showed prooxidant effects in all substrates.

• 한국물환경학회지
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• 제23권6호
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• pp.961-965
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• 2007

In this study, degradation of carbohydrates and composition of fermentative products were investigated in semi-continuous acid fermenter varying hydraulic retention time (HRT). Rice soup was used as a sole substrate for the acid fermentation. Solubilization efficiency of the substrate was higher than 70% for all HRT, however the gas conversion was ignorable implying that most of organic contents in the influent remained in the form of volatile fatty acids (VFAs) and ethanol after acid fermentation. The VFAs were the predominant product and the VFAs conversion increased as the HRT decreased. The VFAs conversion reached the maximum value at 12 hr HRT accounting for 70% of the influent COD. Similar to VFAs, ethanol conversion was increased with the decrease of HRT and the maximum ethanol conversion efficiency was 8% at the HRT of 12 hr. Composition of VFAs was markedly dependent on HRT. As HRT increased, the composition of acetic acid was increased as a product of acetogenesis from butyrate, valerate and ethanol. This study demonstrated that HRT affected acid fermentation of a carbohydrate containing organic wastes producing VFAs and ethanol which could be effectively used to compensate the lack of carbon in wastewater for biological nutrient removal.