• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.4
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• pp.166-173
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• 2021

The rutile phase of TiO₂ forms a stable phase at high temperatures compared to anatase phase, but the stable temperature range of anatase changes depending on the synthesis conditions. In this study, nano-sized TiO₂ was synthesized by the Sol-gel method using TiOSO₄ and a mixed solvent of ethanol and distilled water, and the phase change of anatase and rutile according to pH and heat treatment temperature was investigated. Changes in the ratio of anatase and rutile were observed by changing the pH (3, 5, 7, 9) and heat treatment temperature (500, 600, 700, 800, 900℃) conditions of the prepared TiO₂. As a result of observing these changes through XRD and FE-SEM analysis, anatase TiO₂ at 500℃ and rutile TiO₂ at 900℃ were observed. According to the pH, at these intermediate temperatures of 600, 700 and 800℃, the ratio of anatase and rutile changes. At 700℃, it was concluded that pH = 3~5 had a larger ratio of anatase TiO₂, and pH = 7~9 had a larger ratio of rutile TiO₂.

• Applied Chemistry for Engineering
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• v.34 no.6
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• pp.590-595
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• 2023

Novel aromatic imine derivatives with yellow were designed and synthesized for their potential application in color filters for image sensors. The synthesized compounds possessed chemical structures using aromatic imine groups. This innovative material was evaluated thoroughly, considering its optical and thermal properties under conditions similar to commercial device manufacturing processes. Following a rigorous performance evaluation, it was found that (E)-3-methyl-4-((3-methyl-5-oxo-1-phenyl-1H-pyrazol-4(5H)-ylidene)methyl)-1-phenyl-1H-pyrazol-5(4H)-one, abbreviated as MOPMPO, exhibited an impressive solubility of 0.5 wt% in propylene glycol monomethyl ether acetate, predominantly utilized as the solvent in the industry. Furthermore, MOPMPO showed exceptional performance as a color filter material for image sensors, having a high decomposition temperature of 290 ℃. These data unequivocally establish MOPMPO as a viable yellow dye additive for coloring materials in image sensor applications.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.13-18
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• 2024

To develop flexible electrode materials for wearable devices, we investigated the electrochemical characteristics of carbon fibers tow according to pretreatment. And an electrochemical non-enzymatic sensor was fabricated using glucose as a target. The carbon fibers tow was pretreated through desizing and activation processes, and activation was performed in two ways: chemical oxidation and electrochemical oxidation. Surface morphology of carbon fibers tow samples was observed by SEM and their electrochemical characteristics and sensing performance were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. Carbon fibers tow samples showed improved electrochemical properties such as reduced R_et, ΔE_p, and increased I_p through pretreatment. And similar electrochemical properties were obtained with both activation methods. We selected electrochemically activated carbon fibers tow as the final electrode material for application of electrochemical sensor. The non-enzymatic glucose sensor based on this electrode has an enhanced sensitivity of 0.744 A/mM (in a linear range of 0.09899~3.75423 mM) and 0.330 mA/mM (3.75423~50 mM), respectively. Through this study, the possibility of using carbon fibers tow was confirmed as an electrode material. It is expected to be used as basic research for development of high-performance flexible electrode materials.

• Korean Chemical Engineering Research
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• v.62 no.2
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• pp.147-152
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• 2024

Most medical sensors are disposable products. In order to reduce inspection and diagnosis costs, it is more important to develop the inexpensive electrode materials. We fabricated the CuO NPs/PANI/E-PGE as an electrode material for disposable electrochemical sensors and applied it to a non-enzymatic glucose sensor. For surface activation of PGE, pretreatment was performed using chemical and electrochemical methods, respectively. Electrochemical properties according to the pretreatment method were analyzed through chronoamperometry (CA), cyclic voltammetry (CV) and electrochemical impedance (EIS). From these analytical results, the electrochemically pretreated PGE (E-PGE) was finally adopted. The non-enzymatic glucose sensor based on CuO NPs/PANI/E-PGE shows sensitivity of 239.18 mA/mM×cm² (in a linear range of 0.282~2.112 mM) and 36.99 mA/mM×cm² (3.75423~50 mM), detection limit of 17.6 μM and good selectivity. Based on the results of this study, it was confirmed that the modified PGE is a high-performance electrode material. Therefore, these electrodes can be applied to a variety of disposable sensors.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.528-537
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• 2008

60 nm and 20 nm thick hydrogenated amorphous silicon(a-Si:H) layers were deposited on 200 nm $SiO_2$/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by an e-beam evaporator. Finally, 30 nm-Ni/(60 nm and 20 nm) a-Si:H/200 nm-$SiO_2$/single-Si structures were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from $200^{\circ}C$ to $500^{\circ}C$ in $50^{\circ}C$ increments for 40 sec. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide from the 60 nm a-Si:H substrate showed low sheet resistance from $400^{\circ}C$ which is compatible for low temperature processing. The nickel silicide from 20 nm a-Si:H substrate showed low resistance from $300^{\circ}C$. Through HRXRD analysis, the phase transformation occurred with silicidation temperature without a-Si:H layer thickness dependence. With the result of FE-SEM and TEM, the nickel silicides from 60 nm a-Si:H substrate showed the microstructure of 60 nm-thick silicide layers with the residual silicon regime, while the ones from 20 nm a-Si:H formed 20 nm-thick uniform silicide layers. In case of SPM, the RMS value of nickel silicide layers increased as the silicidation temperature increased. Especially, the nickel silicide from 20 nm a-Si:H substrate showed the lowest RMS value of 0.75 at $300^{\circ}C$.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.31 no.3
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• pp.243-248
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• 2009

Purpose: Rehabilitation of the edentulous posterior maxilla with dental implants often poses difficulty because of insufficient bone volume caused by pneumatization of the maxillary sinus and by crestal bone resorption. Sinus grafting technique was developed to increase the vertical height to overcome this problem. The present study was designed to evaluate the sinus floor augmentation with anorganic bovine bone (Bio-$cera^{TM}$) using histomorphometric and clinical measures. Patients and methods: Thirteen patients were involved in this study and underwent total 14 sinus lift procedures. Residual bone height was ${\geq}2mm$ and ${\leq}6mm$. Lateral window approach was used, with grafting using Bio-$cera^{TM}$ only(n=1) or mixed with autogenous bone from ramus and/or maxillary tuberosity(n=13). After 6 months of healing, implant sites were created with 3mm diameter trephine and biopsies taken for histomorphometric analysis. The parameters assessed were area fraction of new bone, graft material and connective tissue. Immediate and 6 months after grafting surgery, and 6 months after implantation, computed tomography (CT) was taken and the sinus graft was evaluated morphometric analysis. After implant installation at the grafted area, the clinical outcome was checked. Results: Histomorphometry was done in ten patients.Bio-$cera^{TM}$ particles were surrounded by newly formed bone. The graft particles and newly formed bone were surrounded by connective tissue including small capillaries in some fields. Imaging processing revealed $24.86{\pm}7.59%$ of new bone, $38.20{\pm}13.19%$ connective tissue, and $36.92{\pm}14.51%$ of remaining Bio-$cera^{TM}$ particles. All grafted sites received an implant, and in all cases sufficient bone height was achieved to install implants. The increase in ridge height was about $15.9{\pm}1.8mm$ immediately after operation (from 13mm to 19mm). After 6 months operation, ridge height was reduced about $11.5{\pm}13.5%$. After implant installation, average marginal bone loss after 6 months was $0.3{\pm}0.15mm$. Conclusion: Bio-$cera^{TM}$ showed new bone formation similar with Bio-$Oss^{(R)}$ histomorphometrically and appeared to be an effective bone substitute in maxillary sinus augmentation procedure with the residual bone height from 2 to 6mm.

• Korean Journal of Plant Resources
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• v.24 no.1
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• pp.76-88
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• 2011

The flora of vascular plants in the mountains located in the Uiryeong-gun area, in the South province of the Korean Peninsula, such as Jagul-san(897.1 m), 676 Highland(676 m), Byeokhwa-san(522 m), and the Bangeo-san(530.4 m), was investigated between April 2008 and August 2009. These investigations found 580 taxa consisting of 496 species, 1 subspecies, 77 varieties, and 6 forms, found within 319 genera under 103 families. The count totaled at 744 taxa(16.2% of all vascular plant taxa in Korea), which was made up of 648 species, 3 subspecies, 81 varieties, and 12 forms, found within of 362 genera under 109 families, when voucher specimens from the previous research studies were added. Forests of the investigated areas were generally composed of mixed Pinus densiflora and Quercus sp. The areas with comparatively excellent vegetation were the valley neighboring Baekun-sa(temple) (in the eastern slope of Mt. Jagul-san), the southwest slope of Mt. 676 Highland, the eastern slope of Mt. Byeokhwa-san, and the northern slope of Mt. Bangeo-san. 10 families were collected in abundance: Compositae, Graminae, Leguminosae, Liliaceae, Rosaceae, Cyperaceae, Labiatae, Polygonaceae, Ranunculaceae, and Violaceae these families made up 50% of all collected taxa. 19 taxa were endemic to the area, including Salix hallaisanensis H.Lev, S. koriyanagi Kimura, Aconitum austrokoreense Koidz, A. pseudolaeve Nakai, Clematis trichotoma Nakai, Thalictrum uchiyamai Nakai, Stewartia pseudocamellia Maxim, Philadelphus schrenkii Rupr., Lespedeza ${\times}$ robusta Nakai, Vicia chosenensis Ohwi, Euonymus trapococca Nakai, and Angelica cartilagino-marginata var. distans(Nakai) Kitag. Eight of the taxa were rare and endangered plants, as designated by the Korea Forest Service, including Jeffersonia dubia(Maxim.) Baker & S. Moore and Viola diamantiaca Nakai. 38 taxa of alien plants were found. Vegetation of the surveyed areas falls in the South province of the Korean Peninsula. Of all the taxa collected, 463 taxa(10.06% of all vascular plants in Korea) are considered useful plants, 231 taxa are edible, 193 taxa have medicinal uses, 65 taxa are used ornamentally, 234 taxa are important forage, 3 taxa are used as an industrial raw material, 17 taxa are used for timber, 18 taxa contain useful dyes, and 7 taxa are used for fiber.

• Journal of the Korean Chemical Society
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• v.47 no.6
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• pp.614-618
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• 2003

$Sr_2Ru_{1-x}Cu_xO_{4-y}(0.0{\le}x{\le}0.5)$ compounds were prepared using a conventional solid state reaction. Based on the Rietveld refinements of X-ray diffraction results, it is revealed that $Sr_2Ru_{1-x}Cu_xO_{4-y}$ compounds are the single phases with K2NiF4 type tetragonal system in the range of 0=x=0.3, while the mixed phases of$Sr_2RuO_4$ and $Sr_2CuO_3$ in the range of $0.4{\le}x{\le}0.5$. By means of X-ray photoelectron spectroscopy, the valence states of Ru and Cu in $Sr_2Ru_{1-x}Cu_xO_{4-y}$, have been confirmed to 4+ and 2+, respectively. The bond length difference between $Ru-O_1 ({\times}4)\;and\;Ru-O_2 ({\times}2)\;in\;RuO_6$ octahedron is gradually decreased with increasing Cu content in $Sr_2Ru_{1-x}Cu_xO_{4-y}$, which results in the lower c/a ratio. So, it might be assured that the variation of local symmetry of $RuO_6$ octahedron is very closely related to the transporting property of $Sr_2Ru_{1-x}Cu_xO_{4-y}$ compounds. The behavior of resistivity discloses that the metallic property in $Sr_2RuO_4$ changes into the semiconducting one in proportion to the Cu content in $Sr_2Ru_{1-x}Cu_xO_{4-y}$.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.271-281
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• 2019

This study investigated the shielding efficiency of various types of shielding materials and measured the dose by organ using the phantom. Results of Shielding Efficiency Measurement Using Personal Radiation Meter. Among the various shielding materials, 1.1 mm RNS-TX composed of nano tungsten showed the highest shielding efficiency and 0.2 mm lead shielding showed the lowest shielding efficiency. 99mTc 30 mCi was exposed to the phantom for 120 minutes and the result of the measurement of the organs. 20.53 mSv without radiation protective clothing, 8.75 mSv when wearing 0.25 mm Pb protective clothing, 6.03 mSv when wearing 0.5 mm Pb protective clothing. 131I 2 mCi mCi was exposed to the phantom for 120 minutes and the result of the measurement of the organs. 7.71 mSv without radiation protective clothing, 4.88 mSv when wearing 0.25 mm Pb protective clothing, 2.79 mSv when wearing 0.5 mm Pb protective clothing. 18F 5 mCi was exposed to the phantom for 120 minutes and the result of the measurement of the organs. 16.39 mSv without radiation protective clothing, 15.84 mSv when wearing 0.25 mm Pb protective clothing, 12.52 mSv when wearing 0.5 mm Pb protective clothing. None of the radiation workers working in the nuclear medicine department exceeded the dose limit. However, when compared with other workers in the hospital, they showed a relatively high dose. Therefore, it is necessary to prepare measures to reduce and manage the dose of radiation workers in the nuclear medicine department through the wearing of radiation protective clothing made of lightweight, shielding material with good shielding efficiency, circulation task, task sharing, and substitution equipment such as auto dispenser.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.611-616
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• 2011

In the study, annealing temperature was optimized by comparing with avrami crystallization rate and constant (k) using non-oriented PLA film as a base film. Crystallization rate constant of PLA film was 1.64, 1.68, and 1.26 at $120^{\circ}C$, $130^{\circ}C$, and $140^{\circ}C$, respectively. Annealing temperature was mainly affected on the surface properties such as rougnness (Ra) and kinetic friction coefficient (${\mu}_k$). Roughness of PLA film was 0.006 ${\mu}m$ at $80^{\circ}C$ and increased to 0.009 ${\mu}m$ 0.015 ${\mu}m$, 0.027 ${\mu}m$, and 0.029 ${\mu}m$ at $110^{\circ}C$, $120^{\circ}C$, $130^{\circ}C$ and $140^{\circ}C$, respectively. Kinetic friction coefficient decreased 0.45 to 0.43, 0.33, 0.31, 0.27 as annealing temperature was at $80^{\circ}C$, $110^{\circ}C$, $120^{\circ}C$, $130^{\circ}C$, and $140^{\circ}C$, respectivly. In addition, rate constant (k) was 0.58, 0.46, and 0.39 with adding 1 wt%, 3 wt%, and 5 wt% talc, respectively.