• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.83-90
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• 2015

본 연구에서는 Poisson-Nernst-Plank (PNP) 식의 해를 구할 수 있는 Edison web-based Poisson-Nernst-Plank (EPNP) Solver를 이용하여 나노포어의 이온선택성 및 박막의 유전율, 그리고 이온 농도가 이온 전류와 이온전도도에 미치는 영향에 대해 알아보았다. 계산 결과로부터 나노포어의 이온선택성에 의해 양이온이 이온전류에 미치는 영향이 매우 크며, top buffer와 bottom buffer의 농도가 증가할수록 이온 전도도 (ion conductance)가 비선형적으로 증가함을 알 수 있었다. top buffer와 bottom buffer 간에 농도 차가 있을 때는 농도 차와 나노포어의 이온선택성에 의해 형성되는 Nernst 전위의 영향으로 I-V 곡선이 비대칭적 형태임을 알 수 있었다. 또한, 나노포어의 상대 유전율을 증가시킬 때 I-V 곡선에서의 양이온 전류는 감소했지만 음이온의 전류는 증가하는 경향을 보였다. 이는 나노포어 내에 배열된 쌍극자에 의한 영향과 전하를 가진 입자가 유전경계 (dielectric boundary)에 접근하면서 형성되는 상전하에 의한 영향이 동시에 존재하기 때문임을 알 수 있었다.

• Journal of the Korean Electrochemical Society
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• v.17 no.2
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• pp.94-102
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• 2014

Cation exchange membrane (Nafion) was modified to reduce the vanadium ion permeation through the membrane and to increase the vanadium redox flow battery (VRB) system performance by coating the graphene oxide (GO) which has nano-plate like morphology. Modified membrane properties were studied by measuring the ion exchange capacity (I.E.C), water uptake and proton conductivity. The thickness of the coated layer on the surface of the Nafion membrane was observed as $0.93{\mu}m$ by SEM. Proton conductivity and vanadium ion permeability of the modified membrane were decreased to 27% and 25% compared to that of the commercial Nafion membrane respectively. VRB single cell performance test was performed to compare the system performance of the VRB applied with commercial Nafion membrane and modified membrane. VRB system applied with modified membrane showed higher coulombic efficiency and energy efficiency than the VRB system applied with the commercial Nafion membrane due to the reduction of the vanadium ion permeation. From these result, we could suggest that the membrane modification by coating the GO on the surface of the Nafion membrane could be one of the promising strategies to reduce the vanadium ion permeation and to increase the VRB system performance effectively.

• Journal of Astronomy and Space Sciences
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• v.19 no.4
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• pp.243-254
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• 2002

Various uncertainties involved in ionospheric conductivity estimation utilizing the electron density profile obtained from the Sondrestrom incoherent scatter radar are examined. First, we compare the conductivity which is based on raw electron density and the one based on corrected electron density that takes into account the effects of the difference between the electron and ion temperatures and the Debye length. The corrected electron density yields higher Pedersen and Hall conductivities than the raw electron density does. Second, the dependence of collision frequency model on the conductivity estimation is examined. Below 110 km conductivity does not depend significantly on collision frequency models. Above 110 km, however, the collision models affect the conductivity estimation. Third, the influence of the electron and ion temperatures on the conductivity estimation is examined. Electron and ion temperatures carrying an error of about 10% do not seem to affect significantly the conductivity estimation. Fourth, also examined is the effect of the choice of the altitude range of integration in calculating the height-integrated conductivity, conductance. It has been demonstrated that the lower and upper boundaries of the integration are quite sensitive to the estimation of the Hall and Pedersen conductances, respectively.

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.144-149
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• 2005

Sulfonated poly(ether ether ketone) (SPEEK) was blended with poly(ether sulfone) (PES) at various compositions. To investigate the possibility of using the blend membranes as polymer electrolyte membranes for direct methanol fuel cell, the blend membranes were characterized in terms of methanol permeability, proton conductivity, ion exchange capacity, and water content. Both proton conductivity and methanol permeability of SPEEK were relatively high. As the amount of PES increased, methanol permeability decreased more rapidly compared to proton conductivity. The experimental results indicated that the blend membrane with 40 wt% PES was the best choice in terms of the ratio of proton conductivity to methanol permeability.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.102-107
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• 2016

본 연구에서는 동역학적 격자기반 대정준 Monte Carlo (Kinetic Lattice Grand Canonical Monte Carlo, KLGCMC) 모의실험 방법을 이용하여 비정상 몰분율 효과 (Anomalous mole fraction effect)에 대해서 알아보고자 하였다. 이를 위해 양이온 선택성을 가진 이온채널 모델에서 $NH_4{^+}$와 $Rb^+$의 혼합물에 대하여 몰분율의 변화에 따른 이온전도도를 KLGCMC 모의실험을 이용하여 계산하고, 이를 평균장 이론인 Poisson-Nernst-Planck (PNP)의 결과와 비교해 봄으로써 비정상 몰분율 효과에 대하여 심도 있게 이해하고자 하였다. 본 연구 결과로부터 비정상 몰분율 효과는 이온채널의 이온 선택성에 의해서 발생함을 확인할 수 있었다. 즉, 두 종류 이상의 이온들이 채널 내부로 이동할 때, 이온채널의 이온 선택성에 의해서 각 이온들과 채널 간에 서로 상이한 상호작용을 하게 되고, 이로 인해서 이온 혼합물 조성의 변화, 즉 몰분율의 변화에 대해서 이온 전류가 선형적이 아닌 비선형적으로 변하게 됨을 알 수 있었다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.44-48
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• 2004

A silent type ozone generator using water surface electrode was proposed. And it was investigated experimentally that a variation of water conductivity affected to water surface discharge. Important factors affecting to water surface discharge are ions in discharge space and ions and polarized molecules in water and so on. In this study, It was intended to change the characteristics of discharge by controlling the number of ions in water. The number of ions in water could be controlled by changing the water conductivity. Water conductivity was controlled by quantity of inserted NaCl to distilled water. At this time, current-voltage characteristics and characteristics of ozone generation quantity were investigated in each case. As a result, when NaCl was inserted in distilled water, more stable discharge was generated. As the quantity of NaCl was increased, discharge starting voltage could be lowered.

• Korean Journal of Materials Research
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• v.2 no.3
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• pp.207-212
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• 1992

The defect structure of calcium titanates with CaO excess or $TiO_2$ excess was studied by measuring electrical conductivities as a funcition of oxygen partial pressure at $85O^{\circ}C$ to $1050^{\circ}C$. Execess CaO may divide itself equally between A and B sites, resulting in $Ca_{Ti}$" and Vo", while excess $TiO_2$ form $V_{Ca}$" and Vo". The equilibrium electrical conductivity data indicate that the solubilities of CaO and $TiO_2$ in $CaTiO_3$ are 5000ppm and 2000ppm, respectively. Oxygen vacancies contributed to the ionic conduction which flatten the conductivity minima and did not make any defect association with oppositely charged defects.ely charged defects.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.192.1-192.1
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• 2013

본 연구는 기존의 Sputtering 방식에 Modulation 방식을 적용한 Modulated Sputtering System (MSS)에 관한 특성 관찰과 이를 이용한 박막 증착 및 분석에 관한 내용이다. MSS에 인가하는 전압은 pulse on 시간동안 타겟에 음의 전압이 인가되어 sputtering에 의한 박막이 증착되고, pulse off 시간동안에는 양의 전압을 인가하여 증착된 박막에 양이온을 입사시켜 에너지 전달에 의한 박막의 특성을 향상시키고 자한다. MSS에 인가되는 전압과 주파수, 그리고 펄스폭을 변화시키며 전압과 전류, 그리고 기판에 입사하는 이온에너지 특성을 관찰하였다. 또한 MSS를 이용하여 티타늄(Ti), 탄소(C), 알루미늄이 도핑된 산화아연(AZO) 박막을 증착하였다. 증착된 박막은 a-step, SEM, XRD, AFM, 4 point probe를 이용하여 박막의 두께, 결정성장면, 표면 거칠기, 비저항 등을 분석하였다. Ti 박막에서는 기판에 입사되는 양이온의 에너지가 증가함에 따라 결정 방위면이 (002)에서 (001)로 변화함을 확인하였고 탄소 박막과 AZO 박막의 경우에는 기판에 입사되는 양이온의 에너지 변화에 따라 박막의 전도도를 조절할 수 있음을 확인하였다.

• Membrane Journal
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• v.13 no.1
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• pp.47-53
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• 2003

Poly(ether ether ketone)(PEEK) was sulfonated using sulfuric acid and blended with polysulfone with various ratios. The blended polymer electrolyte membranes were characterized in terms of methanol permeability, proton conductivity and ion exchange capacity. As the amount of sulfonated PEEK increased, both methanol permeability and proton conductivity increased. This was due to the increase of ion exchange capacity. The experimental results indicated that the blend membrane with 20% polysulfone was the best choice In terms of the ratio of proton conductivity to methanol permeability.

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.243-250
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• 1988

The cross effect between an ion flux and an electronic current in a nonstoichiometric binary oxide, $A_{1-\delta}O_\mu$, has been analyzed in the light of irreversible thermodynamics. It has been shown that a net flux of the mobile cation vacancy is induced through the system in an electrical potential gradient applied across a pair of the reversible electrodes, which makes the Fick frame shift relative to the laboratory frame. As a consequence, the relative shift is a measure of the effective charge responsible for the cross effect. Two experiments are proposed to measure the shift.