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Lee, Kyung Ah,Yoon, Ki Ro,Kwon, Sung Hyun,Lee, Kyung Jin,Jo, Sunhee,Lee, Ju Sung,Lee, Kwan-Young,Lee, Seung Woo,Lee, Seung Geol,Kim, Jin Young The Royal Society of Chemistry 2019 Journal of materials chemistry. A, Materials for e Vol.7 No.13
<P>Self-assembly of inter- and intraphases between the ionomer membrane and mechanical reinforcements in reinforced polymeric composite membranes is of great interest in both physics and chemistry, particularly for proton exchange membrane fuel cell (PEMFC) application. One of the greatest challenges is to obtain an optimally structured polytetrafluoroethylene (PTFE)-reinforced perfluorosulfonic acid (PFSA) composite membrane <I>via</I> solution processing. For high- performance and durable PEMFC applications, the self-assembly of interphases of the ionomers/reinforcements and intraphases of the ionomers in the composite PEM needs to be carefully tailored. Here, we show that post-assembly modification of a PTFE/PFSA composite membrane using a spin-drying method can significantly improve fuel cell performance and reliability. The forced assembly of PFSA ionomers during spinning results in greater infiltration yields into the porous PTFE media. In this way, spin-drying post-treatment results in lower gas crossover and improved mechanical durability. This process also yields larger regions of ionic clusters, which facilitate proton conduction at low relative humidity, affording higher fuel cell currents and greater efficiency.</P>
Lee, Jong-Geol,Park, Sunhoo,Bae, Chang-Hwan,Jang, Won-Suk,Lee, Sun-Joo,Lee, Dal Nim,Myung, Jae Kyung,Kim, Cheol Hyeon,Jin, Young-Woo,Lee, Seung-Sook,Shim, Sehwan Oxford University Press 2016 JOURNAL OF RADIATION RESEARCH Vol.57 No.3
<P>Radiation-induced lung injury (RILI) due to nuclear or radiological exposure remains difficult to treat because of insufficient clinical data. The goal of this study was to establish an appropriate and efficient minipig model and introduce a thoracic computed tomography (CT)-based method to measure the progression of RILI. Göttingen minipigs were allocated to control and irradiation groups. The most obvious changes in the CT images after irradiation were peribronchial opacification, interlobular septal thickening, and lung volume loss. Hounsfield units (HU) in the irradiation group reached a maximum level at 6 weeks and decreased thereafter, but remained higher than those of the control group. Both lung area and cardiac right lateral shift showed significant changes at 22 weeks post irradiation. The white blood cell (WBC) count, a marker of pneumonitis, increased and reached a maximum at 6 weeks in both peripheral blood and bronchial alveolar lavage fluid. Microscopic findings at 22 weeks post irradiation were characterized by widening of the interlobular septum, with dense fibrosis and an increase in the radiation dose–dependent fibrotic score. Our results also showed that WBC counts and microscopic findings were positively correlated with the three CT parameters. In conclusion, the minipig model can provide useful clinical data regarding RILI caused by the adverse effects of high-dose radiotherapy. Peribronchial opacification, interlobular septal thickening, and lung volume loss are three quantifiable CT parameters that can be used as a simple method for monitoring the progression of RILI.</P>
Lee, Jong-Geol,Shim, Sehwan,Kim, Min-Jung,Myung, Jae Kyung,Jang, Won-Suk,Bae, Chang-Hwan,Lee, Sun-Joo,Kim, Kyeong Min,Jin, Young-Woo,Lee, Seung-Sook,Park, Sunhoo Hindawi Publishing Corporation 2017 BioMed research international Vol.2017 No.-
<P><I>Purpose</I>. Radiation-induced lung fibrosis (RILF) is a serious late complication of radiotherapy. In vitro studies have demonstrated that pentoxifylline (PTX) has suppressing effects in extracellular matrix production in fibroblasts, while the antifibrotic action of PTX alone using clinical dose is yet unexplored.<I> Materials and Methods</I>. We used micro-computed tomography (micro-CT) and histopathological analysis to evaluate the antifibrotic effects of PTX in a rat model of RILF.<I> Results</I>. Micro-CT findings showed that lung density, volume loss, and mediastinal shift are significantly increased at 16 weeks after irradiation. Simultaneously, histological analysis demonstrated thickening of alveolar walls, destruction of alveolar structures, and excessive collagen deposition in the irradiated lung. PTX treatment effectively attenuated the fibrotic changes based on both micro-CT and histopathological analyses. Western analysis also revealed increased levels of plasminogen activator inhibitor- (PAI-) 1 and fibronectin (FN) and PTX treatment reduced expression of PAI-1 and FN by restoring protein kinase A (PKA) phosphorylation but not TGF-<I>β</I>/Smad in both irradiated lung tissues and epithelial cells.<I> Conclusions</I>. Our results demonstrate the antifibrotic effect of PTX on radiation-induced lung fibrosis and its effect on modulation of PKA and PAI-1 expression as possible antifibrotic mechanisms.</P>
Lee, Jae Hyeong,Lee, Gil-Ho,Park, Joonbum,Lee, Janghee,Nam, Seung-Geol,Shin, Yun-Sok,Kim, Jun Sung,Lee, Hu-Jong American Chemical Society 2014 NANO LETTERS Vol.14 No.9
<P>We report a surface-dominant Josephson effect in superconductor–topological insulator–superconductor (S–TI–S) devices, where a Bi<SUB>1.5</SUB>Sb<SUB>0.5</SUB>Te<SUB>1.7</SUB>Se<SUB>1.3</SUB> (BSTS) crystal flake was adopted as an intervening TI between Al superconducting electrodes. We observed a Fraunhofer-type critical current modulation in a perpendicular magnetic field in an Al–TI–Al junction for both local and nonlocal current biasing. Fraunhofer-type modulation of the differential resistance was also observed in a neighboring Au–TI–Au normal junction when it was nonlocally biased by the Al–TI–Al junction. In all cases, the Fraunhofer-like signal was highly robust to the magnetic field up to the critical field of the Al electrodes, corresponding to the edge-stepped nonuniform supercurrent density arising from the top and rough side surfaces of the BSTS flake, which strongly suggests that the Josephson coupling in a TI is established through the surface conducting channels that are topologically protected.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-9/nl501481b/production/images/medium/nl-2014-01481b_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl501481b'>ACS Electronic Supporting Info</A></P>
Efficient simultaneous production of biodiesel and glycerol carbonate via statistical optimization
Lee, Youngrak,Lee, Ja Hyun,Yang, Ho Jin,Jang, Min,Kim, Jung Rae,Byun, Eui-Hong,Lee, Jinwon,Na, Jeong-Geol,Kim, Seung Wook,Park, Chulhwan THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2017 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.51 No.-
<P><B>Abstract</B></P> <P>The purpose of this study was to simultaneously produce biodiesel and glycerol carbonate. Glycerol carbonate is a high-value material that could be obtained from glycerol. Response surface methodology was used to perform optimization of simultaneous enzymatic production of biodiesel and glycerol carbonate. Independent factors for optimization of simultaneous enzymatic production included enzyme concentration, a molar ratio of dimethyl carbonate to soybean oil, and reaction temperature. The levels of satisfaction with the production reaction model for biodiesel and glycerol carbonate were high, 0.994 and 1, respectively. The optimum condition for simultaneous production was 116.76g/L enzyme concentration, 9.27:1 molar ratio, and 52.56°C reaction temperature. Under the optimum condition, biodiesel 96.3% and glycerol carbonate 99.7% were produced at the same time.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biodiesel and glycerol carbonate were simultaneously produced by the enzymatic process. </LI> <LI> RSM was used to optimize the production of biodiesel and glycerol carbonate. </LI> <LI> The optimum condition was 116.76g/L enzyme concentration, 9.27:1 molar ratio, and 52.56°C reaction temperature. </LI> <LI> Optimum production of biodiesel (96.3%) and glycerol carbonate (99.7%) yield was achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Seung Geol Lee,Ji Il Choi,Wonsang Koh,Seung Soon Jang,Jongman Kim,Gene Kim IEEE 2011 IEEE transactions on components, packaging, and ma Vol.1 No.10
<P>The effect of temperature on the distribution and transport of water molecules in a model epoxy molding compound (EMC) system is investigated using atomistic molecular dynamics simulation with 4 and 7 wt% water content at various temperatures, such as 298, 323, 353, and 373 K. The thermal expansion of the hydrated model EMC was evaluated as 1-5% of its dried volume with increasing temperature. The spatial distributions of the amine groups and hydroxyl groups are not significantly affected by temperature due to the crosslinked topological constraint. The correlation of these functional groups with water molecules was not affected by temperature due to their hydrophilicity. In contrast, it is observed that the water phase is expanded with increasing temperature, which is more distinct as a function of water content. The temperature effect on the water diffusion was clearly observed: the diffusion coefficient became larger with increasing temperature. The activation energy for the water diffusion via a hopping mechanism was 21.9 kJ/mol (0.23 eV) and 21.2 kJ/mol (0.22 eV) for the 4 wt% and the 7 wt% water contents, respectively, which infers that the water transport is more facilitated with increasing water content because the water structure of the water phase in the model EMC is more developed.</P>
이승표(Seung Pyo Lee),김봉철(Bong Chul Kim),이인하(In Ha Lee),조영걸(Young Geol Cho),김용찬(Yong Chan Kim) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.12
자동차용 휠 베어링은 동력을 전달하고 차량의 무게를 지지해주는 중요한 부품으로써 너클에 체결된다. 이때 체결 토크에 의하여 시일 압입부와 궤도부를 포함하는 휠 베어링 외륜의 변형이 발생한다. 본 연구에서는 휠 베어링 외륜의 변형을 유한요소법을 이용하여 해석하였다. 상용 소프트웨어 MSC.MARC 를 이용하였고, 외륜, 볼트, 너클의 체결거동을 보다 정확하게 예측하기 위하여 탄소성 해석과 접촉 해석을 수행하였다. 외륜 플랜지는 가공에 따라서 다소 오목하게 형성될 수 있으며, 이는 너클과의 체결 시 틈새 발생을 유발하여 변형에 영향을 줄 수 있다. 따라서, 본 연구에서는 외륜의 오목한 정도를 변화시키면서 변형 해석을 수행하였다. 해석 결과를 검증 하기 위하여 시험을 수행하였고, 해석과 시험 결과를 비교한 결과 비교적 유사함을 알 수 있었다. The wheel bearing is one of the important parts in a vehicle for translating power and bearing weight. When it is mounted on the knuckle by using bolts, the distortion of the outer ring including the seal mounting point and raceway occurs. In this study, a numerical analysis was performed to analyze the distortion of the outer ring by using a finite element method. The commercial software MSC.MARC was used for this purpose. Elastoplastic and contact analysis were carried out to compute the clamping behavior of the outer ring, bolts, and knuckle. Because the concavity on the flange of the outer ring affects the deformation, its effect was considered. To verify the reliability of this study, the roundness of the outer ring was measured. The experimental results were comparatively in agreement with the computational results.