• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2505-2511
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• 2014

Indium oxide nanocrystals ($In_2O_3$ NCs) with sizes of 5.5 nm-10 nm were synthesized by hot injection of the mixture precursors, indium acetate and oleic acid, into alcohol solution (1-octadecanol and 1-octadecence mixture). Field emission transmission electron microscopy (FE-TEM), High resolution X-Ray diffraction (X-ray), Nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FT-IR) were employed to investigate the size, surface molecular structure, and crystallinity of the synthesized $In_2O_3$ NCs. When covered by oleic acid as a capping group, the $In_2O_3$ NCs had a high crystallinity with a cubic structure, demonstrating a narrow size distribution. A high mobility of $2.51cm^2/V{\cdot}s$ and an on/off current ratio of about $1.0{\times}10^3$ were observed with an $In_2O_3$ NCs thin film transistor (TFT) device, where the channel layer of $In_2O_3$ NCs thin films were formed by a solution process of spin coating, cured at a relatively low temperature, $350^{\circ}C$. A size-dependent, non-monotonic trend on electron mobility was distinctly observed: the electron mobility increased from $0.43cm^2/V{\cdot}s$ for NCs with a 5.5 nm diameter to $2.51cm^2/V{\cdot}s$ for NCs with a diameter of 7.1 nm, and then decreased for NCs larger than 7.1 nm. This phenomenon is clearly explained by the combination of a smaller number of hops, a decrease in charging energy, and a decrease in electronic coupling with the increasing NC size, where the crossover diameter is estimated to be 7.1 nm. The decrease in electronic coupling proved to be the decisive factor giving rise to the decrease in the mobility associated with increasing size in the larger NCs above the crossover diameter.

• Journal of the Korean Wood Science and Technology
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• v.30 no.3
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• pp.48-58
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• 2002

This study was carried out through scanning electron microscopy to elucidate the mechanism of thickness swelling in wood particle-polypropylene composite which is a typical way of using wood and plastic materials. For this purpose, control particleboards and nonwoven web composites from wood particle and polypropylene fiber formulations of 100:0, 70:30, 60:40, and 50:50 were manufactured at target density levels of 0.5, 0.6, 0.7, and 0.8 g/cm³. Their water absorption and thickness swelling were tested according to ASTMD 1037-93 (1995). To elucidate thickness swelling mechanism of composite through the observation of morphological change of internal structures, the specimens before and after thickness swelling test by 24-hour immersion in water were used in scanning electron microscopy. From the scanning electron microscopy, thickness swelling of composite was thought to be caused by the complicated factors of degree of built-up internal stresses by mat compression and/or amount of wood particles encapsulated with molten polypropylene fibers during hot pressing. In the composites with wood particle contents of 50 to 60% at target densities of 0.5 to 0.8 g/cm³ and with wood particle content of 70% at target densities of 0.5 to 0.7 g/cm³, thickness swellings seemed to be largely dependent upon the restricted water uptake by encapsulated wood particles with molten polypropylene fibers. Thickness swelling in the composite with wood particle content of 70% at target density of 0.8 g/cm³, however, was thought to be principally dependent upon the increased springback phenomenon by built-up internal stresses of compressed mat.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.120-120
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• 2006

탄소나노튜브는 nm급의 크기에 높은 전기전도도, 열전도 효율, 감한 기계적 강도 등의 장점을 가지며, FED(Field Emission Display), 극미세 전자 스위칭 소자, SET(Single Electron Transistor), AFM(Atomic Force Microscope) tip등 여러 분야로의 응용을 연구하고 있다. 본 연구에서는 탄소나노튜브를 Si 웨이퍼 위에 Ni/Ti 금속층을 촉매층으로 사용하고, 암모니아($NH_3$)가스와 아세틸렌 ($C_2H_2$)가스를 각각 희석가스와 성장원으로 사용하여 합성하였다. 탄소나노튜브의 성장은 Hot filament 화학기상증측(HFPECVD) 방식을 사용하였으며, 이 방법은 다량의 합성, 높은 균일성, 좋은 정렬 특성등의 장점을 가진다. 성장 온도는 탄소나노튜브의 성장 특성을 변화시키는 중요한 요소이다. 성장 온도에 따라 수직적 성장, 성장 밀도등의 특성 변화를 관찰하였다. 성장된 탄소나노튜브층 성분 분석은 에너지 분산형 X-선 측정기(EDS)를 통해 관찰하였고, 끝단에 촉매층이 존재하는 30~50 nm 폭을 가진 다중벽 탄소나노튜브를 고배율 투과전자현미경(HRTEM) 분석을 통해 관찰하였다. 전계방사 주사전자현미경(FESEM) 분석을 동해 1~3${\mu}m$의 길이를 가진 탄소나노튜브가 높은 밀도로 성장된 것을 확인하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.1
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• pp.8-14
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• 2012

The device performances of n-channel MuGFET with different fin numbers and fin widths but the total effective channel width is constant have been characterized. Two kinds of Pi-gate devices with fin number=16, fin width=55nm, and fin number=14, fin width=80nm have been used in characterization. The threshold voltage, effective electron mobility, threshold voltage roll-off, inverse subthreshold slope, PBTI, hot carrier degradation, and drain breakdown voltage have been characterized. From the measured results, the short channel effects have been reduced for narrow fin width and large fin numbers. PBTI degradation was more significant in devices with large fin number and narrow fin width but hot carrier degradation was similar for both devices. The drain breakdown voltage was higher for devices with narrow fin width and large fin numbers. With considering the short channel effects and device degradation, the devices with narrow fin width and large fin numbers are desirable in the device layout of MuGFETs.

• Journal of the East Asian Society of Dietary Life
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• v.18 no.6
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• pp.1072-1080
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• 2008

The optimization of the addition ratios of Houttuynia cordata, Saururus chinensis, and Polygonatum odoratum var. pluriflorum hot water extract to Houttuynia cordata beverage was evaluated by applying response surface methodology. The quality characteristics of a selected best product were investigated. Sweet, savory, and fishy taste, and overall acceptability were optimized by response surface methodology using a central composite design. The concentration of effect of Houttuynia cordata, Saururus chinensis, and Polygonatum odoratum var. pluriflorum hot water extract was modeled using an equation. Hot water extracts of Houttuynia cordata ($1.75{\sim}1.89%$), Saururus chinensis ($1.03{\sim}1.04%$), and Polygonatum odoratum var. pluriflorum ($2.17{\sim}2.31%$) represented the optimal concentration conditions to obtain the best taste. The physical and chemical characteristics of the beverage manufactured at optimized conditions were pH 4.18, soluble solids 0.41 $^{\circ}Brix$, total acidity 0.21%, color value ($L^*$ value 40.08, $a^*$ value 4.53, and $b^*$ value 10.69), total polyphenol 54.63 mg/L, and electron donating ability 26.98%.

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.210-216
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• 2012

For the recycling of rapid-cooled steel slag, various specimens were prepared with the various replacement ratios of the rapid-cooled steel slag and the addition ratios of polymer binders. The physical properties of these specimens were then investigated by absorption test, compressive strength test, flexural strength test and hot water resistance test, and the pore and the micro-structure analysis was performed using scanning electron microscope. Results showed that the flexural strength increased with the increase of rapid-cooled steel slag and polymer binder, but the compressive strength showed a maximum strength at a certain proportion. By the hot water resistance test, compressive strength and flexural strength decreased remarkably and the total pore volume increased but the pore diameter decreased. SEM observation of the structure before the hot water resistance test revealed a very compact infusion of structure but the decomposition or thermal degradation appeared in polymer binders when observed after the hot water resistance test.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.43-46
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• 2010

As the nuclear power plant has been constructed continuously for several decades in Korea, the welding technology for components manufacturing and installation has been improved largely. Standardization for weld test and qualification was also established systematically according to the concerned code. The welding for the main components requires the high reliability to keep the constant quality level, which means the repeatability of weld quality. Therefore the weld process qualified by thorough test and evaluation is able to be applied for manufacturing. Narrow gap SAW and GTAW process are usually applied for girth seam welding of pressure vessel like Reactor vessel, steam generator, and etc. For the surface cladding with stainless steel and Inconel material, strip welding process is mainly used. Inside cladding of nozzles is additionally applied with Hot wire GTAW and semi-auto welding process. Especially the weld joint having elliptical weld line on curved surface needs a specialized weld system which is automatically rotating with adjusting position of the head torch. The small sized pipe, tube, and internal parts of reactor vessel requests precise weld processes like an automatic GTAW and electron beam welding. Welding of dissimilar materials including Inconel690 material has high possibility of weld defects like a lack of fusion, various types of crack. To avoid these kinds of problem, optimum weld parameters and sequence should be set up through the many tests. As the life extension of nuclear power plant is general trend, weld technologies having higher reliability is required gradually. More development of specialized welding systems, weld part analysis and evaluation, and life prediction for main components should be taken into a consideration extensively.

• The Plant Pathology Journal
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• v.18 no.3
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• pp.115-120
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• 2002

Xanthomonas axonopodis pv. glycines, the causal agent of bacterial pustule of soybean, induces hypersensitive response (HR) in a non-host plant, hot pepper (Capsicum annuum). A wild-type strain (8ra) and its non-patho-genic mutant (8-13) of X. axonopodis pv. glycines were inoculated into the pepper leaf tissues and their subcellular responses to the bacterial infections were examined by electron microscopy. Intrastructural changes related to HR were found in the leaf tissues infected with 8ra from 8 h after inoculation, characterized by separation of plasmalemma from the cell wall, formation of small vacuoles and vesicles, formation of cell wall apposition, and cellular necrosis. No such responses were observed in the tissues infected with the mutant. In 8ra, the bacterial cells were attached to the cell walls, with the cell wall material dissolved into and appearing to encapsulate the bacterial cells. The bacterial cells later became entirely embedded in the cell wall material. On the other hand, in 8-13, the bacterial cells were usually not attached tightly to the plant cell wall, and no or poor encapsulation of the bacteria by the wall material occurred, although these were encircled by rather loose wall materials at the later stages.

• Korean Journal of Food Science and Technology
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• v.31 no.3
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• pp.575-580
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• 1999

In this study, the quality changes of Hoelen was investigated, which were color differences, browning degrees, total phenolic compounds and electron donating abilities to optimize drying condition using hot air and far infrared drying by changing conditions such as temperatures, air velocities and radiation distances. In color values, ${\Delta}b\;value$ decreased with increasing temperatures, while ${\Delta}L$, ${\Delta}a$ and ${\Delta}E\;value$ increased. The browning degrees showed the similar tendency with the color values. Total phenolic components of Hoelen decreased with increasing drying temperature and air velocity, and decreasing radiation distance. On the other hand, there was no significant difference in the changes of electron donating abilities (EDA) of Hoelen among drying methods and conditions. As a result, the hot air drying was more effective method than the far infrared was.

• Food Science and Preservation
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• v.17 no.6
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• pp.835-846
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• 2010

The manufacture of beverages prepared using hot-water extracts of Polygonatum odoratum var. pluriflorum, Houttuynia cordata, and Lycium chinensis was statistically optimized using response surface methodology. The total polyphenol content, electron donation activity, and reducing power of optimized beverages were measured to evaluate antioxidant properties. The coefficients of determination, the $R_2$ values, were 0.9887~0.9957 for color, taste and overall acceptability. Analysis of variance showed that the model fit was a statistically significant (p<0.05). The optimized compositions of processed beverages were: Polygonatum odoratum var. pluriflorum extract, 2.15%; Houttuynia cordata extract, 1.74%; and Lycium chinensis extract, 0.19% (all w/w). Total polyphenol content, electron donation activity, and reducing power of beverages of optimized composition were 3.61 mg/L, 23.78%, and 0.26, respectively.