• 한국자기학회지
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• 제19권4호
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• pp.152-155
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• 2009

Ba-ferrite 단결정을 제조하여 자기적 성질을 $M\"{o}ssbauer$ 분광법으로 연구하였다. 단결정 시료를 c-축 방향으로 얇게 절단하고 그 면에 감마선을 조사한 결과 Fe 이온의 스핀방향이 c-축과 일치하였고 시료 전체에 걸쳐 단일 결정체임을 확인하였다. 특히 감마선이 스핀과 나란한 경우 $M\"{o}ssbauer$ 흡수선 중에서 결정 내에 존재하는 Fe의 5개 자리 중에서 단지 4개 자리에서만 공명흡수선이 존재하였고 2b 자리에서는 전혀 공명흡수가 일어나지 않았다. 2b 자리에서의 공명흡수가 일어나지 않는 이유는 대칭성이 있는 2개의 우물 형 위치에너지의 중심 사이를 Fe 이온이 매우 빠른 속도로 c-축을 따라 진동하는 것으로 설명할 수 있다.

• The Korean Journal of Ceramics
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• 제6권2호
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• pp.177-182
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• 2000

At the porous $La_{0.6}Ca_{0.4}MnO_{3-{\delta}}$(LCM)/YSZ electrodes of solid oxide fuel cells (SOFC), the electrochemical redox reaction of oxygen proceeds via the triple boundary (TPB) of gas/LCM/YSZ. The surface diffusion of adsorbed oxygen on LCM has been proposed as the rate determining process, assuming the gradient of oxygen chemical potential from the outer surface of porous layer to TPB. Along with the formation of this gradient, oxygen nonstoichiometry in the bulk of LCM may varies. In this paper, an electrochemical technique was described precisely to determine the variation of oxygen content in LCM of porous LCM/YSZ under polarization. It was shown that the oxygen potential in LCM layer under large cathodic polarization is much lower than that in the gas phase, being determined from the electrode potential and Nernst equation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.429-429
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• 2012

To investigate the gettering effect of B-doped n-type monocrystalline silicon wafer, we made the p-n junction by diffusing boron into n-type monocrystalline Si substrate and then oxidized the boron doped n-type monocrystalline silicon wafer by in-situ wet and dry oxidation. After oxidation, the minority carrier lifetime was measured by using microwave photoconductance and the sheet resistance by 4-point probe, respectively. The junction depth was analyzed by Secondary Ion Mass Spectrometry (SIMS). Boron diffusion reduced the metal impurities in the bulk of silicon wafer and increased the minority carrier lifetime. In the case of wet oxidation, the sheet resistance value of ${\sim}46{\Omega}/{\Box}$ was obtained at $900^{\circ}C$, depostion time 50 min, and drive-in time 10 min. Uniformity was ~7% at $925^{\circ}C$, deposition time 30 min, and drive-in time 10 min. Finally, the minority carrier lifetime was shown to be increased from $3.3{\mu}s$ for bare wafer to $21.6{\mu}s$ for $900^{\circ}C$, deposition 40 min, and drive-in 10 min condition. In the case of dry oxidation, for the condition of 50 min deposition, 10 min drive-in, and O2 flow of 2000 SCCM, the minority carrier lifetime of 16.3us, the sheet resistance of ${\sim}48{\Omega}/{\Box}$, and uniformity of 2% were measured.

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.941-952
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• 2012

In the present contribution the Encounter Theory (ET) (the prototype of the classical Collision Theory in rarefied gases) concepts for widely occurring diffusion assisted irreversible bulk reactions A + A ${\rightarrow}$ C and A + B ${\rightarrow}$ C in liquid solutions examined by the authors in the literature are analyzed and compared with each other for these different types of reactions. It is shown that for a particular case of equal initial concentrations $[A]_0=[B]_0$ in the reaction A + B ${\rightarrow}$ C, when the kinetics of both reactions A + A ${\rightarrow}$ C and A + B ${\rightarrow}$ C in the framework of formal chemical kinetics and ET are the same, the accumulation of macroscopic correlations breaking the concepts of independent encounters and leading to the Generalized Encounter Theory (GET) are drastically different. The influence of the force interaction and the decay of nonstable reactants on the time behavior the macroscopic correlations is also briefly discussed.

• Bulletin of the Korean Chemical Society
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• 제35권9호
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• pp.2679-2683
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• 2014

Mechanisms underlying the impacts of interactions between carbon nanoparticles (CNPs) and ionic liquids (ILs) on the physicochemical behavior of CNPs need to be more full worked out. This manuscript describes a theoretical investigation at multiple levels on the interactions of fullerene $C_{60}$ with 21 imidazolium-based ILs of varying alkyl side chain lengths and anionic types and their impacts on $C_{60}$ dispersion behavior. Results show that ${\pi}$-cation interaction contributed to mechanism of the $C_{60}$-IL interaction more than ${\pi}$-anion interaction. The calculated interaction energy ($E_{INT}$) indicates that $C_{60}$ can form stable complex with each IL molecule. Moreover, the direction of charge transfer occurred from IL to $C_{60}$ during the $C_{60}$-IL interaction. Quantitative models were developed to evaluate the self-diffusion coefficient of $C_{60}$ ($D_{fullerene}$) in bulk ILs. Three interpretative molecular descriptors (heat of formation, $E_{INT}$, and charge) that describe the $C_{60}$-IL interactions and the alkyl side chain length were found to be determinants affecting $D_{fullerene}$.

• 한국진공학회지
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• 제9권2호
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• pp.172-178
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• 2000

반도체 제조공정 중 플라즈마 반응기 내에서 입자오염을 유발하는 입자들의 거동과 성장을 모델식을 사용하여 이론적으로 고찰하였다. 플라즈마 반응기 내에서 입자 거동에 영향을 미치는 힘들로 유체 대류, 입자 확산 및 외부힘 (ion drag force, electrostatic force, 중력) 등을 고려하였다. 플라즈마 벌크 영역에서 전하를 가진 입자들간의 충돌에 의한 입자 성장을 고려하기 위해 모델식에 입자 전하 분포를 고려하였다. 대부분의 입자들은 ion drag force와 electrostatic force가 균형을 이루고 있는 두 sheath 경계 영역에 존재하였으며 두 sheath 영역과 벌크 플라즈마에서의 입자 농도는 0에 접근하였다. 시간이 지남에 따라 입자 충돌로 인한 입자들의 크기는 증가하였으며 입자가 성장함에 따라 입자 표면적의 증가와 더불어 입자가 가지는 평균 전하량도 증가하였다.

• 한국광학회지
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• 제7권4호
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• pp.375-385
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• 1996

본 연구에서는 InGaAsP/InP RWG MQW-LD를 제작하기 앞서 이론해석으로부터 RWG MQW-LD의 도파로규격에 따른 측방향 유효굴절율차와 index-guided LD로 동작하는 임계 유효굴절율차의 값, 그리고 이러한 굴절율차에 따른 측방향에서의 단일모드 발진조건과 임계전류를 최소로 하기 위한 ridge 폭을 구하여 도파로를 설계하였다. 이론해석으로 부터는 순수한 index-guided LD로 동작하기 위한 측방향 임계 유효굴절율차 값은 일반적인 bulk층 보다는 약 2배 정도 큰 값인 약 0.015이었으며 도파로 설계에 있어서는 유효굴절율차가 0.015이며 측방향단일모드로 동작하기 위해서는 ridge 폭은 약 4.mu.m이하가 되어야 함을 알 수 있었다. 그리고 이때 임계전류값이 최소가 됨을 지적하였다.

• Journal of Photoscience
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• 제8권3_4호
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• pp.87-92
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• 2001

Intramolecular excimer formation of 1,3-di(1-pyrenyl)propane (Py-3-Py) and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) were used to investigate the effects of parathyroid hormone (PTH) on the bulk bilayer fluidity of the plasma membrane vesicles isolated from cultured osteoblasts (OB-PMV). In a dose-dependent manner, rat PTH-(1-34) [rPTH-(1-34)] increased the excimer to monomer fluorescence intensity ratio (I'/I) of Py-3-Py and decreased the anisotropy (r) of DPH in OB-PMV. This indicates that PTH increased both the lateral and rotational diffusion of the probes in OB-PMY. Selective quenching of DPH fluorescence by trinitrophenyl groups was utilized to examine the transbilayer fluidity asymmetry of OB-PMV. The anisotropy, limiting anisotropy, and order parameter of DPH in the inner monolayer were 0.024, 0.032, and 0.062 greater than calculated for the outer monolayer of OB-PMY. Selective quenching of DPH fluorescence by trinitrophenyl groups was also utilized to examine the transbilayer effects of PTH on the fluidity of OB-PMV. rPTH-(1-34) had a greater fluidizing effect on the outer monolayer as compared to the inner monolayer of OB-PMV. Thus, it has been proven that PTH exhibits a selective rather than nonselective fluidizing effect within transbilayer domains of OB-PMV.

• Journal of Electrochemical Science and Technology
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• 제11권1호
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• pp.1-13
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• 2020

As research on secondary batteries becomes important, interest in analytical methods to examine the condition of secondary batteries is also increasing. Among these methods, the electrochemical impedance spectroscopy (EIS) method is one of the most attractive diagnostic techniques due to its convenience, quickness, accuracy, and low cost. However, since the obtained spectra are complicated signals representing several impedance elements, it is necessary to understand the whole electrochemical environment for a meaningful analysis. Based on the understanding of the whole system, the circuit elements constituting the cell can be obtained through construction of a physically sound circuit model. Therefore, this mini-review will explain how to construct a physically sound circuit model according to the characteristics of the battery cell system and then introduce the relationship between the obtained resistances of the bulk (R_b), charge transfer reaction (R_ct), interface layer (R_SEI), diffusion process (W) and battery characteristics, such as the state of charge (SOC), temperature, and state of health (SOH).

• 한국수소및신에너지학회논문집
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• 제1권1호
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• pp.1-8
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• 1989

The hydriding kinetic mechanism and the change of the hydriding reaction rate of $MmNi_{4.5}Al_{0.5}$ during the thermally induced hydrogen absorption-desorption cycling are investigated. Comparison of the reaction rate data which are obtained by the pressure sweep method with the theoretical rate equations suggests that the hydriding rate controlling step has changed from the dissociative chemisorption of hydrogen molecules at the surface to the hydrogen diffusion through the hydride phase with the increase of the hydriding fraction. These hydriding kinetic mechanism is not changed during the cycling. However, the intrinsic hydriding reaction rate of $MmNi_{4.5}Al_{0.5}$ after 5500 cycles increases significantly comparing with the activated one. It is suggested that the change of the hydriding kinetic behavior due to intrinsic degradation of $MmNi_{4.5}Al_{0.5}$ can be interpreted as follows ; the formation of nickel cluster at the surface of the sample and the host metal atom exchange in bulk by thermal cycling.