• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.6
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• pp.256-259
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• 2006

The amorphous $SiO_x$ nanowires were synthesized by the vapor phase epitaxy (VPE) method. $SiO_x$ nanowires were formed on silicon wafer of temperatures ranged from $800{\sim}1100^{\circ}C$ and nickel thin film was used as a catalyst for the growth of nanowires. A vapor-liquid-solid (VLS) mechanism is responsible for the catalyst-assisted amorphous $SiO_x$ nanowires synthesis in this experiment. The SEM images showed cotton-like nanostructure of free standing $SiO_x$ nanowires with the length of more than about $10{\mu}m$. The $SiO_x$ nanowires were confirmed amorphous structure by TEM analysis and EDX spectrum reveals that the nanowires consist of Si and O.

• Journal of Convergence for Information Technology
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• v.7 no.5
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• pp.123-128
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• 2017

Nanostructured materials have received attention due to their unique electronic, optical, optoelectrical, and magnetic properties as a results of their large surface-to-volume ratio and quantum confinement effects. Thermal chemical vapor deposition process has attracted much attention due to the synthesis capability of various structured nanomaterials during the growth of nanostructures. In this study, silicon oxide nanowires were grown on Si\$SiO_2$(300 nm)\Pt(5~40 nm) substrates by two-zone thermal chemical vapor deposition with the source material $TiO_2$ powder via vapor-liquid-solid process. The morphology and crystallographic properties of the grown silicon oxide nanowires were characterized by field-emission scanning electron microscope and transmission electron microscope. As results of analysis, the morphology, diameter and length, of the grown silicon oxide nanowires are depend on the thickness of the catalyst films. The grown silicon oxide nanowires exhibit amorphous phase.

• Membrane and Water Treatment
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• v.7 no.3
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• pp.257-275
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• 2016

The enantiomeric and racemic effects of tartaric acid (TA) on the properties of polysulfone (PSn) ultrafiltration membranes were studied in terms of morphology and hydrophilicity (HPCT) of membrane. Asymmetric membranes were prepared by direct blending of polyvinyl pyrrolidone (PVP) with D-TA and DL-TA in membrane casting solution. FTIR analysis was done for the confirmation of the reaction of PVP and TA in blended membranes and plain PSn membranes. Scanning electron microscope (SEM), field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM) were used for analyzing the morphology and structure of the resulting membranes. The membranes were characterized in terms of pure water flux (PWF), hydraulic permeability and HPCT. PWF increased from $52L/m^2h$ to $79.9L/m^2h$ for plain and D-TA containing PSn membrane, respectively. Water contact angle also found to be decreased from $68^{\circ}$ to $55^{\circ}$. In Additionally, permeation and rejection behavior of prepared membranes was studied by bovine serum albumin (BSA) solution. A considerable increase in BSA flux (from $19.1L/m^2h$ for plain membrane to $32.1L/m^2h$ for D-TA containing membrane) was observed. FESEM images affirm that the pore size of the membranes decreases and the membrane permeability increases from 0.16 to 0.32 by the addition of D-TA in the membrane. D-TA increases the HPCT whereas; DL-TA decreases the HPCT of PSn membrane. PVP (average molecular weight of 40000 Da) with D-TA (1 wt%) gave best performance among all the membranes for each parameter.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.6-10
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• 2021

The shorting resistance (SR) of the PEMFC(Proton Exchange Membrane Fuel Cell) polymer membrane is an important indicator of the durability of the membrane. When SR decreases, shorting current (SC) increases, reducing durability and performance. When SR becomes less than about 0.1 kΩ·㎠, shorting occurs, the temperature rises rapidly, and MEA(Membrane Electrode Assembly) is burned to end stack operation. In order to prevent shorting, we need to control the SR, so the conditions affecting the SR were studied. There were differences in the SR measurement methods, and the SR measurement method, which improved the DOE(Department of Energy) and NEDO(New Energy and Industrial Technology Development Organization) method, was presented. It was confirmed that the SR decreases as the relative humidity, temperature and cell compression pressure increase. In the final stage of the accelerated durability evaluation process of the polymer membrane, SR rapidly decreased to less than 0.1 kΩ·㎠, and the hydrogen permeability became higher than 15 mA/㎠. After dismantling the MEA, SEM(Scanning Electron Microscope) analysis showed that a lot of platinum was distributed inside the membrane.

• Journal of dental hygiene science
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• v.21 no.4
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• pp.251-259
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• 2021

Background: The purpose of this study was to investigate the effects of commercially available calamansi soju and other alcoholic beverages on the microhardness and erosion of resin restorations. Methods: In this study, we evaluated the effects of Calamansi soju, Chamisul fresh, Cass fresh, and Gancia Moscato D'asti on resin restorations. Jeju Samdasoo and Coca-Cola were used as negative and positive controls, respectively. Specimens to be immersed in the beverages were manufactured using composite resin according to the product instructions. In each group, the surface microhardness was measured using a surface microhardness instrument before and after immersion for 5, 15, 30, and 60 minutes. The pattern of change in the surface of the composite resin was observed under a scanning electron microscope (SEM). Paired t-tests, one-way ANOVA, and repeated measures ANOVA were performed to compare the surface microhardness of the specimens, and the Tukey test was used as a post hoc test. Results: The pH of all beverages except Jeju Samdasoo was <5.5, which is the critical pH that can induce erosion. The difference in surface microhardness of the composite resin before and after immersion for 60 minutes was significant in all groups. In particular, the largest change in surface microhardness was observed in the calamansi soju group. In the SEM analysis, loss of composite resin was observed in all groups except the Jeju Samdasoo group, and rough surfaces with pores of various sizes were observed. Conclusion: In this study, all beverages except Jeju Samdasoo decreased the microhardness of the composite resin surface, and it was confirmed that calamansi soju had the greatest change.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.343-350
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• 2022

In recent years, nanomaterials, such as nano-silica, carbon nanotubes, and graphene oxide (GO), have been suggested to improve the properties of the interfacial transition zone (ITZ) between aggregates and cement pastes, which has most adversely affected the strength of quasi-brittle concrete. Among the nanomaterials, GO with superior dispersibility has been reported to be effective in improving the properties of ITZ of normal-strength concrete by forming interfacial chemical bonds with Ca²⁺ ions abundant in ITZ. In this study, the effect of GO on the properties of ITZ in the high-strength mortar was elucidated by calculating the change in hydration heat release, ITZ thickness, and the porosity around ISO sand, which was obtained with isothermal calorimetry tests and scanning electron microscope image analysis, respectively.

• Korean Journal of Materials Research
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• v.32 no.8
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• pp.345-353
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• 2022

In this study, using deep learning, super-resolution images of transmission electron microscope (TEM) images were generated for nanomaterial analysis. 1169 paired images with 256 × 256 pixels (high resolution: HR) from TEM measurements and 32 × 32 pixels (low resolution: LR) produced using the python module openCV were trained with deep learning models. The TEM images were related to DyVO₄ nanomaterials synthesized by hydrothermal methods. Mean-absolute-error (MAE), peak-signal-to-noise-ratio (PSNR), and structural similarity (SSIM) were used as metrics to evaluate the performance of the models. First, a super-resolution image (SR) was obtained using the traditional interpolation method used in computer vision. In the SR image at low magnification, the shape of the nanomaterial improved. However, the SR images at medium and high magnification failed to show the characteristics of the lattice of the nanomaterials. Second, to obtain a SR image, the deep learning model includes a residual network which reduces the loss of spatial information in the convolutional process of obtaining a feature map. In the process of optimizing the deep learning model, it was confirmed that the performance of the model improved as the number of data increased. In addition, by optimizing the deep learning model using the loss function, including MAE and SSIM at the same time, improved results of the nanomaterial lattice in SR images were achieved at medium and high magnifications. The final proposed deep learning model used four residual blocks to obtain the characteristic map of the low-resolution image, and the super-resolution image was completed using Upsampling2D and the residual block three times.

• The Journal of the Convergence on Culture Technology
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• v.9 no.6
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• pp.855-859
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• 2023

Copper oxide (CuO) nanoparticles were successfully synthesized using a precursor in which industrial starch was impregnated with an aqueous solution of copper (II) nitrate trihydrate. The microstructure of the precursor impregnated with an aqueous solution of copper nitrate trihydrate was confirmed with a scanning electron microscope (SEM), and the particle size and the crystal structure of the copper oxide particles produced as the temperature of the heat treatment of the precursor increased was analyzed by X-ray diffraction (XRD) and the scanning electron microscope (SEM). As a result of the analysis, it was confirmed that the temperature at which the organic matter of the precursor is completely thermally decomposed is 450-490℃, and that the size and crystallinity of the copper oxide particles increased as the heat treatment temperature increased. The size of the copper oxide particles obtained through heat treatment at 500-800℃ during 1 hour was 100nm~2㎛. It was confirmed that the copper oxide crystalline phase is formed at a heat treatment temperature of 400℃, and only the copper oxide single phase existed up to 800℃. And it was also confirmed that the size of particles produced increased as the calcination temperature increased.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.31 no.1
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• pp.13-23
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• 2005

This study was performed to investigate mistletoe extract-induced apoptosis in oral squamous cell carcinoma. In vivo study, HN22 cells were xenografted in nude mice. After tumor was experimentally induced, mistletoe extract was directly injected on the tumor mass. The specimens were evaluated using light and transmission electron microscopes. In vitro study, HN22 cells were cultured and exposed to mistletoe extract. The cells were evaluated using transmissin electron microscope. To evaluate apoptotic cells, flow cytometric analysis was done. The results were obtained as follows: 1. Light microscopic view of tumor mass showed necrosis at 2-4 weeks. 2. Transmission electron micrographs of tumor mass showed apoptosis and necrosis. 3. In TEM view of cell lines, necrosis and apoptosis were shown with mistletoe extract at $300{\mu}g/ml$, apoptosis was shown with mistletoe extract at $100{\mu}g/ml$. 4. In flow cytometric analysis, early and late apoptosis was shown when using caspase-3Ab and annexin-V, but no significant change was noted when using mebstain and Apo2.7 Ab. In this study, mistletoe extract induced necrosis and apoptosis in the tumor mass was induced by HN22 cells, early and late apoptosis in vitro study. Mistletoe extract was likely to induce cell death in oral squamous cell carcinoma through apoptosis.

• Journal of the Korean Vacuum Society
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• v.21 no.6
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• pp.333-341
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• 2012

Indium Tin Oxide (ITO) thin films were prepared by RF magnetron sputtering with different flow rates of $O_2$ gas from 0 to 12 sccm. Electrical and optical properties of these films were characterized and analyzed. ITO deposited on soda lime glass and RF power was 2 kW, frequency was 13.56 MHz, and working pressure was $1.0{\times}10^{-3}$ Torr, Ar gas was fixed at 1,000 sccm. The transmittance was measured at 300~1,100 nm ranges by using Photovoltaic analysis system. Electrical properties were measured by Hall measurement system. ITO thin films surface were measured by Scanning electron microscope. Atomic force microscope surface roughness scan for ITO thin films. ITO thin films secondary electron emission coefficient(${\gamma}$) was measured by ${\gamma}$-Focused ion beam. The resistivity is about $2.4{\times}10^{-4}{\Omega}{\cdot}cm$ and the weighted average transmittance is about 84.93% at 3 sccm oxygen flow rate. Also, we investigated Work-function of ITO thin films by using Auger neutralization mechanism according to secondary electron emission coefficient(${\gamma}$) values. We confirmed secondary electron emission peak at 3 sccm oxygen flow rate.