• Transactions of Materials Processing
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• v.27 no.4
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• pp.250-256
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• 2018

Oxygen-free copper (OFC) was prepared as a 90 mm cube and then processed with Multi-Axial Diagonal Forging - Initialization of Prior manufacturing History (MADF). The MADF process has been newly developed as a severe plastic deformation method. The MADF process consists of upset forging with a thickness reduction of 30% and diagonal forging with a diagonal angle of $135^{\circ}$. 1 cycle process consists of a 12 passes forging process. In order to analyze the characteristic changes according to the number of iterations, 1, 2, and 3 cycles of the MADF process were performed. The OFC specimens were MADF processed without surface cracks up to 3 cycles. The microstructure, hardness and tensile test of processed materials were analyzed to study the change of material properties according to the amount of MADF process. The results showed that the MADF process effectively refined the microstructure and increased the strength of OFC. In the case of specimens processed for more than 2 cycles, the grains of all measurement regions were refined to be less than $7{\mu}m$ of grain size. The 1 cycle MADF processed OFC showed the highest mechanical properties with the hardness of 132 HV and tensile strength of 395 MPa. Hardness and strength seemed to be saturated when processed over 2 cycles.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.4
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• pp.368-374
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• 2016

The perennial edible wild plants such as Aster glehnii, Solidago virgaurea subsp. gigantean, Allium ochotense, Athyrium acutipinnulum, Aruncus dioicus var. kamtschaticus and Codonopsis lanceolata have cultivated as the main income crops introduced into the fields about 30 years ago in Ulleung island. Soil samples were collected from 190 fields and assessed the effects of management practices on soil chemical properties at wild edible plant fields under no-till system. The strong acidic soils of pH 5.4 or less were detected in 45% of the soil samples. The level of soil organic matter was being held at mean $63{\pm}28g\;kg^{-1}$, 2.7 times higher than upland soils in Korea. Available phosphate and exchangeable potassium showed more than recommended levels of upland crops as $680{\pm}489mg\;kg^{-1}$ and $1.94{\pm}1.7cmol_c\;kg^{-1}$, respectively. The fields of Solidago and Aster showing strong soil acidity and high level of available phosphate and water soluble $NO_3{^-}$ were distinguished from other crops in analysis of variance and principal component analysis of soil chemicals. These results suggested that high frequency of acidic soil and high levels of available $P_2O_5$, exchangeable $K_2O$ and water soluble $NO_3{^-}$ were accompanied with the use of urea and NPK-fertilizer based on nitrogen in the field. However, further research is needed to understand the appropriate management of fertilization and the prevention of soil acidification for wild edible plants.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.793-797
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• 2014

To develop a methodology for absolute determination of the surface areal density of functional groups on organic and bio thin films, medium energy ion scattering (MEIS) spectroscopy was utilized to provide references for calibration of X-ray photoelectron spectroscopy (XPS) or Fourier transformation-infrared (FT-IR) intensities. By using the MEIS, XPS, and FT-IR techniques, we were able to analyze the organic thin film of a Ru dye compound ($C_{58}H_{86}O_8N_8S_2Ru$), which consists of one Ru atom and various stoichiometric functional groups. From the MEIS analysis, the absolute surface areal density of Ru atoms (or Ru dye molecules) was determined. The surface areal densities of stoichiometric functional groups in the Ru dye compound were used as references for the calibration of XPS and FT-IR intensities for each functional group. The complementary use of MEIS, XPS, and FT-IR to determine the absolute surface areal density of functional groups on organic and bio thin films will be useful for more reliable development of applications based on organic thin films in areas such as flexible displays, solar cells, organic sensors, biomaterials, and biochips.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.913-918
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• 2014

Five mol % tungsten-doped tin oxide ($W_{0.05}Sn_{0.95}O_2$, TTO5) was prepared by co-precipitation of $SnCl_4{\cdot}5H_2O$ and $WCl_4$, followed by calcination at $1000^{\circ}C$. The as-prepared TTO5 was in the pure cassiterite phase with a particle size of ~50 nm and optical bandgap of 2.51 eV. Herein it was applied for the formation of TTO5/$TiO_2$ heterojunctions by covering the TTO5 surface with $TiO_2$ by sol-gel method. Under visible-light irradiation (${\lambda}{\geq}420$ nm), TTO5/$TiO_2$ showed a significantly high photocatalytic activity in removing gaseous 2-propanol (IP) and evolving $CO_2$. It is deduced that its high visible-light activity is caused by inter-semiconductor holetransfer between the valence band (VB) of TTO5 and $TiO_2$, since the TTO5 nanoparticle (NP) exhibits the absorption edge at ~450 nm and its VB level is located more positive side than that of $TiO_2$. The evidence for the hole-transport mechanism between TTO5 and $TiO_2$ was also investigated by monitoring the holescavenging reaction with 1,4-terephthalic acid (TA).

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.875-880
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• 2014

Adsorption of 4,4'-bis(mercaptomethyl)biphenyl (44BMBP) on silver nanoparticles has been investigated by surface-enhanced Raman scattering (SERS) spectroscopy. In addition, the Raman spectra of 44BMBP in solid state and in basic condition have been obtained for comparative study to elicit the characteristics of adsorption. The observed Raman and SERS spectra were analyzed comparing with the normal modes and vibrational frequencies from density functional theory (DFT) calculations performed for the feasible structures of 44BMBP molecule. On the basis of excellent agreement between the calculated and the experimental results, the molecule is found to have both the cis- and trans-forms for the mercaptomethyl groups in the solid state as well as in the basic condition. In contrast, the molecule is found to be chemisorbed on the silver surface by forming two Ag-S linkages only in the cis-form but not in the trans-form due to the steric interruption, which indicates the parallel orientation of molecules on the surface. Particularly, the spectral features in the SERS spectra such as the absence of the C-H stretching band and enhancement for the out-of-plane skeletal modes are confirmatory for the parallel geometry through ${\pi}$ interaction between the phenyl rings and the metal surface, based on the electromagnetic surface selection rule.

• Transactions of Materials Processing
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• v.23 no.8
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• pp.489-494
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• 2014

Micro forming is an appropriate process to manufacture very small metal parts which can be employed in the field of electronic devices or electrically controlled mechanical systems. The purpose of the current study was to investigate the influences of both blankholding force and blank diameter for the deep drawing of very small cups. It is essential to control the blankholding force because improper force can result in defects such as wrinkles in the flange or cracks in the corner of the drawn cups. In the current study blankholding force was controlled by springs connected to the blankholder of a press die. Exchangeable bushing dies with various die-corner radii were also used. To obtain the limit drawing ratio for each working condition several sizes of circular specimens were prepared using blanking tools. Beryllium copper(C1720) alloy sheet of $50{\mu}m$ thickness was chosen for the experiments. The maximum limit drawing ratio of 2.1 was achieved experimentally for the conditions of the blankholder force(BHF)=5.3kgf and Rd=0.3mm. Both thickness and hardness along the central section of drawn cups were measured and compared for different drawing conditions. It was found that the deviation of measured data in the thickness and hardness distribution increases with increasing blankholder force and blank diameter.

• The Journal of Advanced Prosthodontics
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• v.10 no.3
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• pp.177-183
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• 2018

PURPOSE. The purpose of the current study was to evaluate the effect of incorporating nanoparticles of silver (NAg) and amorphous calcium phosphate (NACP) into a self-etching primer of a resin cement on the microtensile bond strength of dentin, regarding the proven antibacterial feature of NAg and remineralizing effect of NACP. MATERIALS AND METHODS. Flat, mid-coronal dentin from 20 intact extracted human third molars were prepared for cementation using Panavia F2.0 cement. The teeth were randomly divided into the four test groups (n=5) according to the experimental cement primer composition: cement primer without change (control group), primer with 1% (wt) of NACP, primer with 1% (wt) of physical mixture of NACP+Nag, and primer with 1% (wt) of chemical mixture of NACP+Nag. The resin cement was used according to the manufacturer's instructions. After storage in distilled water at $37^{\circ}C$ for 24 h, the bonded samples were sectioned longitudinally to produce $1.0{\times}1.0mm$ beams for micro-tensile bond strength testing in a universal testing machine. Failure modes at the dentin-resin interface were observed using a stereomicroscope. The data were analyzed by one-way ANOVA and Tukey's post-hoc tests and the level of significance was set at 0.05. RESULTS. The lowest mean microtensile bond strength was obtained for the NACP group. Tukey's test showed that the bond strength of the control group was significantly higher than those of the other experimental groups, except for group 4 (chemical mixture of NACP and NAg; P=.67). CONCLUSION. Novel chemical incorporation of NAg-NACP into the self-etching primer of resin cement does not compromise the dentin bond strength.

• Journal of Gastric Cancer
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• v.16 no.3
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• pp.152-160
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• 2016

Purpose: Endoscopic diagnosis of gastric cancer (GC) that emerges after eradication of Helicobacter pylori may be affected by unique morphological changes. Using comprehensive endoscopic imaging, which can reveal biological alterations in gastric mucosa after eradication, previous studies demonstrated that Congo red chromoendoscopy (CRE) might clearly show an acid non-secretory area (ANA) with malignant potential, while autofluorescence imaging (AFI) without drug injection or dyeing may achieve early detection or prediction of GC. We aimed to determine whether AFI might be an alternative to CRE for identification of high-risk areas of gastric carcinogenesis after eradication. Materials and Methods: We included 27 sequential patients with metachronous GC detected during endoscopic surveillance for a mean of 82.8 months after curative endoscopic resection for primary GC and eradication. After their H. pylori infection status was evaluated by clinical interviews and $^{13}C$-urea breath tests, the consistency in the extension of corpus atrophy (e.g., open-type or closed-type atrophy) between AFI and CRE was investigated as a primary endpoint. Results: Inconsistencies in atrophic extension between AFI and CRE were observed in 6 of 27 patients, although CRE revealed all GC cases in the ANA. Interobserver and intraobserver agreements in the evaluation of atrophic extension by AFI were significantly less than those for CRE. Conclusions: We demonstrated that AFI findings might be less reliable for the evaluation of gastric mucosa with malignant potential after eradication than CRE findings. Therefore, special attention should be paid when we clinically evaluate AFI findings of background gastric mucosa after eradication (University Hospital Medical Information Network Center registration number: UMIN000020849).

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.4
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• pp.395-399
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• 2007

The purpose of this study was to investigate the antioxidant and fibrinolytic activities of saltwort fermented juice. Saltwort extract was fermented using lactic acid bacteria at $30^{\circ}C$ for 3 days and the fermented juice was analyzed for its functionality as a potential functional food source. The addition of sugar improved the cell viability during fermentation of saltwort. At the concentration of 50%, lyophilized fermented juice showed DPPH-radical scavenging activities of 23.7% and SOD-likely activity of 34.5%. Fibrinolytic activity of fermented juice was also observed at a concentration of 25%. In conclusion, saltwort fermented juice appears to have not only anti-oxidant effect but also cardiovascular protection.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.2
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• pp.228-235
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• 2009

We synthesized glycidyl azide monomer(GAM) as a monomer for polymerization of glycidy azide polymer(GAP) which is a promising energetic prepolymer for a plastic-bonded explosive. Using quantitative real-tim in-situ infrared(in-situ IR) spectroscopy, kinetic study on the cationic ring opening polymerization of GAM was carried out. The reaction rate was obtained from monitoring the change of ether C-O stretching band($1050cm^{-1}$) in series IR spectra. The reaction was in accordance with the first-order reaction law for each of reaction temperature at 100/1 mole ratio of [GAM]/[$BF_3*etherate$]. In the ring opening polymerization of GAM, with ratio of [GAM]/[$BF_3*etherate$] to equal 100/1 at various temperature, the activation parameters obtained from the evaluation of kinetic data were ${\Delta}H^*$=14.34kcal/mol, ${\Delta}S^*=-12.31cal/mol{\cdot}K$ and $E_a$=14.89kcal/mol.