• Journal of the Korea Institute of Building Construction
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• v.11 no.1
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• pp.51-59
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• 2011

With the increased demand for membrane structures in recent years, there have been many studies of their mechanical properties, to the extent that such structures have become recognized as independent structures with a level of safety and durability comparable to those of other general structures. But in reality, the study for the maintenance of membrane structures has not been as active. In particularly, the study of watertightness from the perspective of maintenance has been very limited. Accordingly, a study on securing watertightness performance and the guidelines for maintenance is necessary. In this study, through a case study of water leakage accidents in membrane structures overseas, causes of leakage were selected from the membrane material itself, joint parts and open door of roof part in membrane structure. The water leakage and deterioration elements were analyzed from those leakage causes. The degree of importance of the water leakage and deterioration index was also designated using the AHP (Analytic Hierarchy Process) method. As a result, the basic technical index was suggested for the maintenance of the roofs of large-span membrane structures to prevent water leakage. This index will be used to make a guideline for the long-term maintenance of the roofs of large-span membrane structures.

• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.558-563
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• 2014

To study the effects of fabrication methods on the performance and durability of polymer electrolyte membrane fuel cells (PEMFCs), membrane-electrode assemblies (MEAs) were fabricated using a Dr blade method, a spray method, screen print method and screen print + spray method. The performance of single cells assembled with the prepared MEAs were initially measured and compared. Electrode accelerated stress testing (AST) involving a potentiostatic step-wave with 10 s at 0.6 V followed by 30 s at 0.9 V was applied to test durability of MEAs. Before and after 6,000cycles of the AST, I-V curves, impedance spectra, cyclic voltammograms, linear sweep voltammetry (LSV) and transmission electron microscope (TEM) were measured. Under the operating conditions, the Dr Blde MEA exhibited the highest initial performance. After electrode accelerated stress testing, screen print + spray MEA showed lowest degradation rate.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.87-91
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• 2004

We have investigated the effects of W-N/Pt bottom electrode on the ferroelectric degradation of $Sr_{0.8}Bi_{2.4}Ta_2O_9(SBT)/Pt$ due to hydrogen annealing at $350^{\circ}C$ in $N_2$ gas atmosphere containing $5{\%}\;H_2$ gas for 1hr. As a result, inserting the W-N thin films between SBT and Pt, this W-N thin film prevents hydrogen molecules to be chemisorbed at the Pt electrode surface of at the electrode/ferroelectric interface during hydrogen annealing. These hydrogen atoms can diffuse into the SBT and react with the oxide causing the oxygen deficiency in the SBT film, which will result in the ferroelectric degradation. Experimental results show that W-N thin film is a good diffusion barrier during the hydrogen annealing.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.3 s.345
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• pp.9-14
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• 2006

The dependence of NBTI lifetime on the BEOL processes such as sintering gas type and passivation layer has been characterized in depth. Then, optimized BEOL process scheme is proposed to improve NBTI lifetime. NBTI showed degradation due to the plasma enhanced nitride (PE-SiN) passivation film and $H_2$ sintering anneal. Then, new process scheme of $N_2$ annealing instead of $H_2$ annealing prior to PE-SiN deposition is proposed. The proposed BEOL process flow showed that NBTI lifetime can be improved a lot without degradation of device performance and NMOS hot carrier reliability.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.5
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• pp.453-460
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• 2018

The impact of sodium hydroxide, which is one of chemicals of clean in place (CIP) for removing membrane fouling, on the PVDF membrane is reviewed with respect to physical/chemical structural change, the permeability affected therefrom. Based on the cleaning concentration applied in membrane water treatment facilities, 10% of accumulated defluorination was confirmed up to 166g.hr/L which reflects the exposure time. However, membrane resistance was confirmed to be reduced by about 10%. Through FT-IR and EDS analysis, reduction of F and change of are confirmed as factors that affect the permeability of membrane. Membrane resistance, which affects permeability, is affected by loss of additives for hydrophilicity, rather than defluorination of PVDF material. Therefore, in order to check membrane degradation degree, an accelerated test by NaOH was carried out, loss of additives was confirmed, and then PVDF inherent characteristic was observed.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.177-182
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• 1999

The electrolyte was brought into contact with air and potassium carbonate concentration was measured with various contact time in order to check the effect of carbon dioxide in the air on zinc-air cell. The relationship between potassium carbonate concentration in electrolyte and battery capacity was also studied. The potassium carbonate concentration increased due to carbon dioxide absorption with increasing contact time with air, but the cell capacity linearly decreased with increasing potassium carbonate concentration in the electrolyte. The rate of carbon dioxide absorption was mainly affected by the pore size of hydrophobic membrane. Our study showed that adapting the pore of hydrophobic membrane decreased the loss of cell discharge performance due to the presence of carbon dioxide or water vapor in the atmosphere.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.3
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• pp.249-258
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• 2002

Thermochemical water-splitting IS(Iodine-Sulfur) process has been investigating for large-scale hydrogen production. For the construction of an efficient process scheme, two kinds of membrane technologies are under investigating to improve the hydrogen producing HI decomposition step. One is a concentration of HI in quasi-azeotropic HIx ($HI-H_2O-I_2$) solution by elecro-electrodialysis. It was confirmed that HI concentrated from the $HI-H_2O-I_2$ solution with a molar ratio of 1:5:1 at $80^{\circ}C$. The other is a membrane reactor to enhance the one-pass conversion of thermal decomposition reaction of gaseous hydrogen iodide (HI). It was found from the simulation study that the conversion of over 0.9 would be attainable using the membrane reactor using the gas permeation properties of the prepared silica hydrogen permselective membrane by chemical vapor deposition (CVD). Design criterion of the membrane reactor was also discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.427-427
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• 2011

그래핀은 탄소원자가 육각형의 벌집형태로 배열되어 있는 원자단위 두께의 가장 얇은 재료중의 하나이다. 이는 우수한 기계적, 전기적, 광학적 특성을 지니고 있어 다양한 분야로의 응용이 가능할 것으로 예측되고 있다. 그래핀의 산업적 응용을 위해서는 대면적으로 두께 균일도가 높은 그래핀을 저렴한 방법으로 합성하는 것이 무엇보다도 우선적으로 요구된다. 그래핀을 얻는 방법으로는 물리 화학적 박리, 탄화규소의 흑연화, 열화학기상증착법(thermal chemical vapor deposition; TCVD) 등의 다양한 방법이 있으며, 현재로선 그 중 TCVD법이 대면적으로 두께균일도가 높은 그래핀을 합성할 수 있는 가장 적합한 방법으로 인식되고 있다. 그러나 이 방법은 탄소가 포함된 원료가스를 분해하기 위하여 고온의 공정이 요구되는 단점이 있다. 이러한 이유로 최근 그래핀은 저온에서 합성하기 위한 많은 연구들이 진행 중에 있으며 그 결과가 속속 보고 되고 있다. 본 연구에서는 고주파 플라즈마가 결합된 TCVD장치를 이용하여 원료가스를 효율적으로 분해함으로서 그래핀의 저온합성을 도모하였다. 기판은 300 nm 두께의 니켈박막이 증착된 산화막 실리콘 기판을 사용하였으며, 원료가스로는 메탄을 사용하였다. 실험결과, 350 W의 파워로 플라즈마를 방전하여 30분간 합성을 수행하였을 때 약 $450^{\circ}C$ 근처의 저온에서 수 겹의 그래핀이 합성 가능한 것을 확인하였다. 합성된 그래핀은 분석의 용이함 및 향후 다양한 응용을 위하여 산화막 실리콘 기판 및 투명 고분자 기판 등으로 전사하였다. 그래핀의 특성분석을 위해서는 광학현미경, 라만 분광기, 투과전자현미경, 자외 및 가시선 분광광도계, 4탐침측정기 등을 이용하였다.

• The Korean Journal of Vision Science
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• v.20 no.4
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• pp.497-504
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• 2018

Purpose : The purpose of this study was to investigate the temperature changes of the ocular surface before and after cataract surgery using thermography of a thermal imaging camera. Methods : The study included 75 patients (75 eyes) aged from 50 to 79 years who underwent cataract surgery. In the past, those who underwent corneal-related surgery, wearing contact lens, disorder of tear secretion and taking medication for systemic disease were excluded from this study. The temperature changes of the eyeball surface were measured using a thermal imager (Cox CX series, Answer, Korea) following Tear Break Up Time (TBUT) test, Mcmonnies questionnaire and Schirmer's Test in real time, Results : While the temperature of preoperative ocular surface was $35.20{\pm}0.54^{\circ}C$ and that of postoperative temperature was $35.30{\pm}0.53^{\circ}C$, the difference was not significant. The temperature changes in the ocular surface were statistically significant at $-0.12{\pm}0.08{\Delta}$ ($^{\circ}C/sec$) before the surgery and $-0.18{\pm}0.07{\Delta}$ ($^{\circ}C/sec$) after the surgery. In comparison of the age groups, it was shown that the changes in the surface temperature before the surgery were from $-0.19{\pm}0.05{\Delta}$ ($^{\circ}C/sec$) to $-0.14{\pm}0.09{\Delta}$ ($^{\circ}C/sec$) in the 50s group, and from $-0.12{\pm}0.08{\Delta}$ ($^{\circ}C/sec$) to $-0.15{\pm}0.07{\Delta}$ ($^{\circ}C/sec$) in 60s group, and $-0.18{\pm}0.07{\Delta}$ ($^{\circ}C$) to $-0.12{\pm}0.08{\Delta}/sec$) in the 70s group, showing significant changes in the ocular surface temperature at all ages. Conclusion : Following the cataract surgery, all the indicators of dry eye syndrome were decreased, and eye surface temperature changes were significant. The thermography technique of the ocular surface would be expected to be useful for the evaluation of various dry eye syndromes because it is easy to evaluate dry eye syndrome noninvasively and can be quantified.

• Journal of Sensor Science and Technology
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• v.12 no.5
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• pp.218-224
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• 2003

The devices of n-channel poly silicon thin film transistors(TFTs) hydrogenated by plasma, $H_2$ and $H_2$/plasma processes are fabricated. The carriers sensitivity characteristics are analyzed with voltage bias stress at the gate oxide. The parametric sensitivity characteristics caused by electrical stress conditions in hydrogenated devices are investigated by measuring the drain current, threshold voltage($V_{th}$), subthreshold slope(S) and maximum transconductance($G_m$) values. As a analyzed results, the degradation characteristics in hydrogenated n-channel polysilicon thin film transistors are mainly caused by the enhancement of dangling bonds at the poly-Si/$SiO_2$ interface and the poly-Si grain boundary due to dissolution of Si-H bonds. The generation of traps in gate oxide are mainly dued to hot electrons injection into the gate oxide from the channel region.