• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.6
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• pp.418-424
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• 2000

Pure $TiO_2$and 10 mol % Pb-doped $TiO_2(Pb_xTi_{1-x}O_2$(x = 0.1)) powder and thin films have been prepared by the sol-gel method. Titanium isopropoxide and ethanol are used for pure $TiO_2$, lead acetate trihydrate and titanium triisopropoxide monoacethylacetonate are used for Pb-doped $TiO_2$, respectively. Films are coated on p-type Si(100) wafer and ITO glass substrates by the sol-gel spin-coating method. The powder and multi-coated films are annealed at different temperature (400~$800^{\circ}C$) for phase formation and crystallization. TGA/DTA, XRD analysis, SEM and UV-visible transmission spectroscopy have been used to study the characteristics of the powder and films. XRD results show that the films are polycrystalline, anatase type and oriented predominantly to the A(101) plane. A slight shift in the d-spacing for the Pb-doped film indicates the incorporation of the Pb into $TiO_2$lattice. A shift of the absorption wavelength in the transmission spectrum towards longer wavelength has been observed about $Pb_xT_{1-x}O_2$(x = 0.1) thin film, which indicates a decrease in the bandgap of $TiO_2$upon Pb-doping.

• Journal of the Korean Chemical Society
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• v.39 no.11
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• pp.856-862
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• 1995

The tungsten oxo-nitrosyl complexes (n-Bu4N)2[W5O12(NO)2{RC(NH2)NHO}2{RC(NH)NO}2] (R=(CH3)2CH, CH3CH2CH2, CH3SCH2) have been synthesized by the reactions of polyoxotungsten complex (n-Bu4N)2[W6O19] and tungsten dinitrosyl monomeric complex [W(NO)2(acac)(CH3CN)2](BF4) with butylamidoxime derivatives. The prepared complexes have been characterized by elemental analysis, infrared, UV-visible, 1H NMR and 13C NMR spectroscopy. The pentanuclear species was formed by the interaction of the electron-withdrawing {W(NO)2}2+ unit between the two dinuclear tungsten {W2O5}2+ cores. We can estimate to exist large proton interactions viewed from the four doublet in 1H NMR spectrum of (n-Bu4N)2[W5O12(NO)2{(CH3)2CHC(NH2)NHO}2{(CH3)2CHC(NH)NO}2]. We also drew informations of the two different coordination mode and symmetry of the complexes because two ligands appear in 13C NMR spectra instead of four. The {W(NO)2}2+ unit has been cis-form and C2v symmetry in geometric structure.

• Journal of the Korean Ceramic Society
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• v.39 no.9
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• pp.896-901
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• 2002

Since many process parameters of FHD(Flame Hydrolysis Deposition) are involved in forming multi-component amorphous silica film ($SiO_2-B_2O_3-P_2O_5-GeO_2$), it has not been easy to predict the optical, mechanical and thermal properties of deposited film from the simple process parameters, such as source flow rate. Furthermore, the prediction of final composition of film becomes even more difficult after sintering at high temperature due to the evaporation of volatile dopants. The motivation of the study was to clarify the quantitative relationship between simple process parameters such as the flow rate of source gases and resulting chemical composition of sintered film. Hence, the compositional analysis of silica soot by FTIR(Fourier Transformation Infrared Spectroscopy) and ICP-AES(Inductively Coupled Plasma-Atomic Emission Spectrometry) under the control of the amount of dopant was carried out to obtain the quantitative composition. By measuring spectrum of absorbance from FTIR, the compositional change of B-O, Si-O, OH($H_2O$) in silica film was measured. The concentrations of these dopants were also measured by ICP-AES, which were compared with the FTIR result. The final quantitative relationship between simple process parameters and composition was deduced from the comparison between two results.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.2
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• pp.195-202
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• 2018

As a rule, geological disposal is considered a safe method for final disposal of high-level radioactive waste. However, some long-lived fission products like $^{99}Tc$ and $^{129}I$ contained in spent nuclear fuel are highly mobile as less sorbing anionic species in the subsurface environment and can mainly cause exposure dose to the ecosystem by emission of beta rays in the hundreds of keV range. Therefore, if these two nuclides can be separated and converted with high efficiency into radioactively unharmful nuclides, this would have a positive effect on disposal safety. One candidate method is to transmute these two nuclides in nuclear reactors into short-lived nuclides or into stable nuclides. For this purpose, it is necessary to evaluate which reactor type is more efficient in burning these two nuclides. In this study, the simulation results of nuclear transmutation of $^{99}Tc$ and $^{129}I$ in light water reactor (PWR), heavy water reactor (CANDU) and fast neutron reactor (SFR, MET-1000) are compared and discussed.

• Korean Journal of Food Science and Technology
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• v.46 no.3
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• pp.347-351
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• 2014

We studied the green synthesis and antibacterial activity of chitosan-silver (Ag) nanocomposite films for application in food packaging. Green synthesis of Ag nanoparticles (AgNPs) was achieved by a chemical reaction involving a mixture of chitosan-silver nitrate ($AgNO_3$) in an autoclave at 0.1 MPa, $121^{\circ}C$, for 15-120 s. The formation of AgNPs in chitosan was confirmed by both UV-Visible spectrophotometry and transmission electron microscopy (TEM) and the effects of chitosan-$AgNO_3$ concentration and reaction time on the synthesis of AgNPs in chitosan were examined. The resulting chitosan-Ag composite films were characterized by various analytical techniques and their antibacterial activity was evaluated based on the formation of halo zones around films, indicating inhibition of the growth of Escherichia coli. A fourier-transform infrared (FTIR) spectroscopy analysis showed that free amino groups in chitosan acted as effective reductants and AgNP stabilizers. The composite films exhibited enhanced antibacterial activity with increasing Ag content on the surface of as-prepared composite films.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.253-260
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• 2019

Radiation dose enhancement is a method of increasing the cross section of interaction, thus increasing the deposited dose. This can contribute to linear energy transfer, LET and relative biological effectiveness, RBE. Previous studies on dose enhancement have been mainly focused on X, ${\gamma}-rays$, but in this study, the dose enhancement was analyzed for proton using Monte Carlo simulation using MCNP6. Based on the mathematical modeling method, energy spectrum and relative intensity of spread out Bragg-peak were calculated, and evaluated dose enhancement factor and dose distribution of dose enhancement material, such as aurum and gadolinium. Dose enhancement factor of 1.085-1.120 folds in aurum, 1.047-1.091 folds in gadolinium was shown. In addition, it showed a decrease of 95% modulation range and practical range. This may lead to an uncertain dose in the tumor tissue as well as dose enhancement. Therefore, it is necessary to make appropriate corrections for spread out Bragg-peak and practical range from mass stopping power. It is expected that Monte Carlo simulation for dose enhancement will be used as basic data for in-vivo and in-vitro experiments.

• Journal of the Korean Society of Radiology
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• v.13 no.4
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• pp.523-530
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• 2019

The purpose of this study was to obtain the K-edge images using a spectral CT system based on a photon-counting detector and implement the 3D fusion imaging using the conventional and spectral CT images. Also, we evaluated the clinical feasibility of the 3D fusion images though the quantitative analysis of image quality. A spectral CT system based on a CdTe photon-counting detector was used to obtain K-edge images. A pork phantom was manufactured with the six tubes including diluted iodine and gadolinium solutions. The K-edge images were obtained by the low-energy thresholds of 35 and 52 keV for iodine and gadolinium imaging with the X-ray spectrum, which was generated at a tube voltage of 100 kVp with a tube current of $500{\mu}A$. We implemented 3D fusion imaging by combining the iodine and gadolinium K-edge images with the conventional CT images. The results showed that the CNRs of the 3D fusion images were 6.76-14.9 times higher than those of the conventional CT images. Also, the 3D fusion images was able to provide the maps of target materials. Therefore, the technique proposed in this study can improve the quality of CT images and the diagnostic efficiency through the additional information of target materials.

• Clean Technology
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• v.27 no.2
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• pp.146-151
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• 2021

Pure and Sm ion doped BiVO₄ catalysts were synthesized using a conventional hydrothermal method and characterized by XRD, DRS, SEM, and PL. We also examined the activity of these materials on the photocatalytic decomposition of rhodamine B under visible light irradiation. The doping of Sm ion into BiVO₄ catalyst changed the ms-BiVO₄ crystal structure into the tz-BiVO₄ crystal structure in the low synthesis temperature. Light absorption analysis using DRS showed that all the catalysts displayed strong absorption in the visible range of the electromagnetic spectrum regardless of Sm ion doping. In addition, an amorphous morphology was shown in the pure BiVO₄ catalyst, but the morphology of the BiVO₄ catalyst doped with Sm ion was changed into an ellipse shape and also the particle size decreased. In the photocatalytic decomposition of rhodamine B, Sm ion doped BiVO₄ catalyst showed higher photocatalytic activity than the pure BiVO₄ catalyst. In addition, the Sm3-BVO catalyst doped with 3% Sm ion showed the highest photocatalytic activity, as well as the highest formation rate of OH radicals (•OH) and the highest PL peak. This result suggests that the formation rate of OH radicals produced in the interface between the photocatalyst and water is well correlated with the photocatalytic activity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.2
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• pp.45-53
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• 2023

The growth of Si on 4H-SiC substrate has a wide range of applications as a very useful material in power semiconductors, bipolar junction transistors and optoelectronics. However, it is considerably difficult to grow very fine crystalline Si on 4H-SiC owing to the lattice mismatch of approximately 20 % between Si and 4H-SiC. In this paper, we report the growth of a Si epilayer by an Al-related nanostructure cluster grown on a 4H-SiC substrate using a mixed-source hydride vapor phase epitaxy (HVPE) method. In order to grow hexagonal Si on the 4H-SIC substrate, we observed the process in which an Al-related nanostructure cluster was first formed and an epitaxial layer was formed by absorbing Si atoms. From the FE-SEM and Raman spectrum results of the Al-related nanostructure cluster and the hexagonal Si epitaxial layer, it was considered that the hexagonal Si epitaxial layer had different characteristics from the general cubic Si structure.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.59 no.4
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• pp.435-444
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• 2014

This study was carried out to isolate and characterize the flavonoids present in corn silks. Maysin content in the unpollinated corn silks (Kwangpyeongok) showed its highest level at 3 days after silking, and decreased thereafter, while the content of open pollinated silks were consistently decreased after silking. This result indicates that the maysin content is considerably affected by the pollination of corn silk. Unpollinated corn silks were collected with excising, and ethanol employed to extract flavonoids at common temperature for 9 days. After extraction, chlorophyll, lipids etc. were removed with methylene chloride, then submitted to flash column cartridge ($150{\times}40mm$ i.d.) packed with a preparative $RP-C_{18}$ bulk packing material ($125{\AA}$, $55-105{\mu}m$), and monitored at 352 nm. Four fractions, fraction-I, -II, -III, and -IV, were isolated from ethanolic extract of corn silks. Absorption spectrum of fraction I showed its maximum intensity (${\lambda}_{max}$) at 327 nm and 239 nm, fraction-II showed its maximum intensity at 339 nm and 274 nm, fraction-III showed its maximum intensity at 345 nm and 277 nm, and fraction-IV showed its maximum intensity at 352 nm, 270 nm, 257 nm, respectively. On the baisis of ESI micro-TOF analysis, fraction-I was identified as chlorogenic acid (m/z 355, 3-(3,4-dihydroxycinnamoyl) quinic acid, $C_{16}H_{18}O_9$), fraction-II identified as a mixture of chlorogenic acid and luteolin 3'-methyl ether 7-glucuronosyl-($1{\rightarrow}2$)-glucuronide (m/z 653, $C_{28}H_{28}O_{18}$), fraction-III identified as a mixture of chlorogenic acid luteolin 7-O-neohesperidoside (m/z 595, $C_{27}H_{30}O_{15}$), and luteolin 3'-methyl ether 7-glucuronosyl-($1{\rightarrow}2$)-glucuronide, and fraction-IV identified as maysin (m/z 577, 2"-O-${\alpha}$-L-rhamnosyl-6-C-(6-deoxy-xylohexose-4-ulosyl)luteolin, $C_{27}H_{28}O_{14}$), respectively. From the ethanolic extract of corn silks, fraction-I was obtained about 35 mg/100 g F.W., fraction-II was about 48 mg/100 g F.W., fraction-III was about 46 mg/100 g F.W., and fraction-IV was about 138 mg/100 g F.W., respectively.