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RISS 인기검색어
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- 저자 : 윤수환(Soohwan Yoon) (검색결과 3 건)
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다양한 활성제 이온이 도핑된 SrWO<sub>4</sub>:RE<sup>3+</sup> (RE=Dy, Sm, Dy/Sm) 형광체의 특성과 위조 방지 응용
윤수환,조신호,Yoon, Soohwan,Cho, Shinho 한국전기전자재료학회 2020 전기전자재료학회논문지 Vol.33 No.5
A series of phosphors, SrWO<sub>4</sub>:5 mol% Dy<sup>3+</sup>, SrWO<sub>4</sub>:5 mol% Sm<sup>3+</sup>, and SrWO<sub>4</sub>:5 mol% Dy<sup>3+</sup>:x Sm<sup>3+</sup> (x=1~15 mol%), were prepared using a facile co-precipitation. The crystal structure, morphology, photoluminescence properties, and application in anti-counterfeiting fields were investigated. The crystalline structures of the prepared phosphors were found to be tetragonal systems with the dominant peak occurring at the (112) plane. The excitation spectra of the Dy<sup>3+</sup> singly-doped SrWO<sub>4</sub> phosphors were composed of an intense charge-transfer band centered at 246 nm in the range of 210~270 nm and two weak peaks at 351 nm and 387 nm due to the <sup>6</sup>H<sub>15/2</sub>→<sup>6</sup>P<sub>7/2</sub> and <sup>6</sup>H<sub>15/2</sub>→<sup>4</sup>I<sub>13/2</sub> transitions of Dy<sup>3+</sup> ions, respectively. The wavelength of 246 nm was optimum for exciting the luminescence of Dy<sup>3+</sup> and Sm<sup>3+</sup> co-doped SrWO<sub>4</sub> phosphors. The emission spectra consisted of two intense blue and yellow emission bands at 480 nm and 573 nm corresponding to the <sup>4</sup>F<sub>9/2</sub>→<sup>6</sup>H<sub>15/2</sub> and <sup>4</sup>F<sub>9/2</sub>→<sup>6</sup>H<sub>13/2</sub> transitions of Dy<sup>3+</sup>, and two strong emission peaks at 599 nm and 643 nm originating from the <sup>4</sup>G<sub>5/2</sub>→<sup>6</sup>H<sub>7/2</sub> and <sup>4</sup>G<sub>5/2</sub>→<sup>6</sup>H<sub>9/2</sub> transitions of Sm<sup>3+</sup>, respectively. As the concentration of Sm<sup>3+</sup> ions increased, the emission intensities of Dy<sup>3+</sup> rapidly decreased, while the emission intensities of Sm<sup>3+</sup> gradually increased. These results suggest that the color of the emission light can be tuned from yellow to white by changing the concentration of Sm<sup>3+</sup> ions at a fixed 5 mol% Dy<sup>3+</sup>. Furthermore, the fluorescent security inks were synthesized for use in anti-counterfeiting applications.
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디젤 엔진 실린더 헤드의 워터 재킷 표면의 온도가 침식 및 부식에 미치는 영향
황준식(Joonsik Hwang),김동훈(Donghoon Kim),한상욱(Sangwook Han),배충식(Choongsik Bae),홍재웅(Jaewoong Hong),윤수환(Soohwan Yoon) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
In recent years, there have been reports of erosion on cylinder head water jacket from several vehicle manufacturers. The degree of erosion may cause deterioration in the cooling capabilities and serious damage to the engine. The reason for the erosion is widely known as repeating formation and collapse of bubble caused by temperature difference between coolant and surface temperature. Therefore, in this study, the erosion and corrosion behavior of water jacket was investigated with rectangular specimen under 3 different specimen temperature conditions (170℃, 200℃, 230℃). The experiment was conducted in test bench which provide the similar conditions as diesel engine cylinder head. The surface of specimen was visualized with SEM-images after 25hours of operation in the test bench and the weight was measured with precise mass scale. The surface composition of specimen which was exposed to coolant during the experiment was quantified with energy dispersive spectroscopy (EDS) analysis every 25hours in the experiment. From the results, the greatest differential rate of mass reductions were observed with highest surface temperature (230℃) experiment. The composition of aluminum and silicon on the specimen did not have clearly consistent tendency.
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실린더 헤드 워터 재킷 표면 조건이 침식에 미치는 영향
이민석(Minseok Lee),황준식(Joonsik Hwang),김동훈(Donghoon Kim),한상욱(Sangwook Han),배충식(Choongsik Bae),홍재웅(Jaewoong Hong),윤수환(Soohwan Yoon),신상연(Sangyeon Shin) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
The occurrence of erosion on cylinder head water jacket recently has been reported from some vehicle manufacturers and it may cause deterioration of cooling capability and serious damages to the engine. Therefore, in this study, the erosion behavior of A356 aluminum alloy which consists cylinder head water jacket was investigated with rectangular specimen under various surface conditions. The experiment was conducted in the test bench which simulates cylinder head water jacket. The surface of specimen was analyzed with scanning electron microscopy(SEM) after 10 hours of operation in the test bench and weighted by precise mass balance. The surface composition of specimen also was quantified with energy dispersive spectroscopy(EDS) analysis. The results showed that the dominant factor affecting erosion was the temperature of specimen.
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