• Bulletin of the Korean Chemical Society
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• 제35권10호
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• pp.2917-2921
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• 2014

Cerium-activated yttrium aluminate ($Y_3Al_5O_{12}:Ce^{3+}$) exhibiting a garnet structure has been widely utilized in the production of light emitting diodes (LEDs) as a yellow emitting phosphor. The commercialized yttrium aluminum garnet (YAG) phosphor is typically synthesized by a solid-state reaction, which produces irregular shape particles with a size of several tens of micrometers by using the top-down method. To control the shape and size of particles, which had been the primary disadvantage of top-down synthetic methods, we synthesized YAG:Ce nanoparticles with a diameter of 500 nm using a coprecipitation method under the atmospheric pressure without the use of template or special equipment. The precursor particles were formed by refluxing an aqueous solution of the nitrate salts of Y, Al, and Ce, urea, and polyvinylpyrrolidone (55 K) at $100^{\circ}C$ for 12 h. YAG:Ce nanoparticles were formed by the calcination of precursor particles at $1100^{\circ}C$ for 10 h under atmospheric conditions. The phase identification, microstructure, and photoluminescent properties of the products were evaluated by X-ray powder diffraction, scanning electron microscopy, absorption spectrum and photoluminescence analyses.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.99-106
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• 2013

Polyaniline-yttrium trioxide (PAni-$Y_2O_3$) composites were synthesized by the in-situ polymerization of aniline in the presence of $Y_2O_3$ The composite formation and structural changes in these composites were investigated by X-ray diffraction (XRD), Fourier transform infra red spectroscopy (FTIR), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The direct current (DC) electrical conductivity of the order of $0.51{\times}10^{-2}\;S\;cm^{-1}-0.283\;S\;cm^{-1}$ in the temperature range 300 K-473 K indicates semiconducting behavior of the composites. Room temperature AC conductivity and dielectric response of the composites were studied in the frequency range of 10 Hz to 1 MHz. The variation of AC conductivity with frequency obeyed the power law, which decreased with increasing weight percentage (wt %) of $Y_2O_3$. Studies on dielectric properties shows the relaxation contribution coupled by electrode polarization effect. The dielectric constant and dielectric loss in these composites depend on the content of $Y_2O_3$ with a percolation threshold at 20 wt % of $Y_2O_3$ in PAni. Electromagnetic interference shielding effectiveness (EMI SE) of the composites in the frequency range 100 Hz to 2 GHz was in the practically useful range of -12.2 dB to -17.2 dB. The observed electrical and shielding properties were attributed to the interaction of $Y_2O_3$ particles with the PAni molecular chains.

• Applied Science and Convergence Technology
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• 제26권2호
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• pp.26-29
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• 2017

Thin films of europium-doped yttrium oxide ($Y_2O_3$:Eu) were prepared on Si (100) substrates by using a radio frequency (RF) magnetron sputtering. After the deposition, the films were annealed at $1000^{\circ}C$ in an air ambient for 1 hour. X-ray diffraction analysis revealed that the $Y_2O_3$:Eu films had a polycrystalline cubic ${\alpha}-Y_2O_3$ structure. The as-deposited films showed no photoluminescence (PL), which was due to poor crystalline quality of the films. The crystallinity of the $Y_2O_3$:Eu films was significantly improved by annealing. The strong red PL emission was observed from the annealed $Y_2O_3$:Eu films and the highest intensity peak was centered at around 613 nm. This emission peak originated from the $^5D_0{\rightarrow}^7F_2$ transition of the trivalent Eu ions occupying the $C_2$ sites in the cubic ${\alpha}-Y_2O_3$ lattice. The broad PL excitation band was observed at wavelengths below 280 nm, which was attributed to the charge transfer transition of the trivalent Eu ion.

• 한국세라믹학회지
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• 제40권9호
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• pp.855-858
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• 2003

Liquid Phase Epitaxy (LPE)법으로 Yttrium Iron Garnet (YIG:Y$_3$Fe$_{5}$O$_{12}$) 단결정 후막을 성장시킬 때 PbO계 응제에서는 Pb 이온이 성장되는 결정내로 혼입되어 성장된 막의 격자상수를 증가시키고, 일축 자기이방성 상수값(Ku)을 변화시키거나 전기 전도도를 변화시킨다. 또한 광 흡수율을 증가시키는 등의 성장된 막의 물성에 악영향을 미친다. 열처리 후 Pb 이온의 휘발로 인한 결정내의 농도감소로 성장된 단결정 후막의 격자상수가 평균 0.0115$\AA$ 감소하였다.

• Nuclear Engineering and Technology
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• 제51권2호
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• pp.539-545
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• 2019

Yttrium-90 is a useful therapeutic radioisotope for tumor treatment because of its high-energy-emitting beta rays. However, it has been difficult to select appropriate collimators and main energy windows for Y-90 Bremsstrahlung imaging using gamma cameras because of the broad energy spectra of Y-90. We used a Monte Carlo simulation to investigate the effects of collimator selection and energy windows on Y-90 Bremsstrahlung imaging. We considered both MELP and HE collimators. Various phantoms were employed in the simulation to determine the main energy window using primary-to-scatter ratios (PSRs). Imaging performance was evaluated using spatial resolution indices, imaging counts, scatter fractions, and contrast-to-noise ratios. Collimator choice slightly affected energy spectrum shapes and improved PSRs. The HE collimator performed better than the MELP collimator on all imaging performance indices (except for imaging count). We observed minor differences in SR and SF values for the HE collimator among the five simulated energy windows. The combination of an HE collimator and improved-PSR energy window produced the best CNR value. In conclusion, appropriate collimator selection is an important component of Bremsstrahlung Y-90 photon imaging and main energy window determination. We found HE collimators to be more appropriate for improving the imaging performance of Bremsstrahlung Y-90 photons.

• Medical Lasers
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• 제10권2호
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• pp.90-95
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• 2021

Background and Objectives Surgery for harvesting costal cartilage is often required for revision septorhinoplasty due to a lack of septal cartilage in patients with a severely contracted nose, and postoperative scarring on the anterolateral rib cage commonly requires additional treatment. This study aimed to evaluate the therapeutic efficacy and safety of combined polydeoxyribonucleotide (PDRN) and microlens array (MLA)-type nanosecond-domain neodymium (Nd):yttrium-aluminum-garnet (YAG) laser treatment for postoperative scars after costal cartilage harvest surgery. Materials and Methods Nine Korean patients with scars after costal cartilage harvest surgery treated with PDRN injections and MLA-type Nd:YAG laser treatments were retrospectively reviewed. Results Most of the scar lesions exhibited clinical improvement at 2 weeks after PDRN and MLA-type nanosecond-domain laser treatments, and the lesions further improved after adding more treatment sessions. The median Vancouver Scar Scale (VSS) score decreased from 6 (interquartile range [IQR]: 6-7) before combined intralesional PDRN injection and MLA-type, nanosecond-domain Nd:YAG laser treatments to 3 (IQR: 2-4) thereafter. Patient satisfaction after the combination treatments was rated as satisfactory. None of our patients reported major adverse events. Conclusion This case series study demonstrated that combined PDRN and MLA-type, nanosecond-domain Nd:YAG laser treatments are effective and safe for treating scars from costal cartilage harvest surgery.

• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2567-2571
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• 2023

Scintillator materials are widely used in the medical and industrial fields for imaging systems using gamma cameras. In this study, image evaluation is performed by modeling a gamma camera system based on a lutetium-yttrium oxyorthosilicate (LYSO) scintillation detector using a pinhole collimator that can improve the spatial resolution. A LYSO detector-based gamma camera system is modeled using a Monte Carlo simulation tool. The geometric concept of the pinhole collimator is designed using various magnification factors, and the spatial resolution is measured using the acquired source image. To evaluate the resolution, the full width at half maximum (FWHM) and natural image quality assessment (NIQE), a no-reference-based parameter, are used. We confirm that the FWHM and NIQE values decrease simultaneously when the diameter of the pinhole collimator increases. Additionally, we confirm that the spatial resolution improves as the magnification factor increases under the same pinhole diameter condition. Particularly, a 0.57 mm FWHM value is obtained using the modeled gamma camera system with a LYSO scintillation detector. In conclusion, our results demonstrate that a pinhole collimator with a LYSO scintillation detector is a promising gamma camera imaging system.

• 한국응용과학기술학회지
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• 제32권1호
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• pp.31-39
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• 2015

용매추출법에서 희토류 금속을 효과적으로 분리하기 위해 추출제만 사용하는 것이 아니라 crown ether와 같은 첨가제를 이용하는 연구를 하였다. Host-guest 화합물인 macrocyclic ligand는 금속과 착화물을 형성하는데, 이 때 crown ether의 cavity 크기와 비슷한 크기의 금속 이온들과 안정한 착화물을 형성한다. 이전 연구에서 europium과 yttrium을 분리하기 위해 여러 사슬 길이의 지방산 추출제를 이용한 추출실험을 행하였었다. 이를 토대로 분리효율이 좋지 않았던 hexanoic acid에 크기가 다른 crown ether (18-crown-6 ether, 15-crown-5 ether, 12-crown-4 ether)를 첨가하여 분리효과가 증가하는 것을 연구하였다. hexanoic acid의 농도별로 분리효율을 본 후 가장 분리 효율이 좋은 농도에서 crown ether를 종류와 농도를 다르게 하여 첨가하였다. 그 결과 0.05 M hexanoic acid에서 분리능이 1.72으로 가장 높게 나타났고, crown ether를 첨가하였을 시 분리능이 0.002 M 15-crown-5 ether에서 가장 높게 나왔으며 기존의 분리능보다 2배 이상 더 높았다. 또한 crown ether를 첨가하였을 때 두 금속이 $MLR_3{\cdot}3RH$의 형태로 추출되는 것도 확인 할 수 있었다.

• 한국결정성장학회지
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• 제29권4호
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• pp.154-159
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• 2019

용융 온도를 낮추고 균질화에 영향을 줄 수 있는 yttrium oxide(산화 이트륨)과 iron oxide(산화철)를 사용하여 $LI_2O-Al_2O_3-SiO_2$ 계 결정화 유리를 제조하였다. 조핵제는 Zirconium sulfate(황산지르코늄)을 사용했고, 유리 점도를 낮추기 위해 calcium phosphate(인산칼슘)을 사용해 유리 유동성을 원활하게 하였다. 결정화 유리는 열충격 $750^{\circ}C$ 이상을 만족했고, $800^{\circ}C$ 이상에서 열팽창계수가 급격하게 상승하는 온도를 약 $30^{\circ}C$ 이상 시프트 하였다. 따라서 yttrium oxide와 iron oxide 포함하는 LAS 계 유리는 고온에서 양호한 용융 상태와 우수한 열팽창 저항성을 확인하였고 특수 주방용 재료 분야에 충분히 활용이 가능하리라 판단되었다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2015년도 임시총회 및 하계학술연구발표회
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• pp.140-140
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• 2015