• 한국대기환경학회지
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• 제32권6호
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• pp.559-574
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• 2016

Based on air quality monitoring data ('10~'14) of Suwon City provided by the Korean Department of Environment, a fundamental statistic for 5 criteria pollutants such as $SO_2$, CO, $NO_2$, $O_3$, and $PM_{10}$ was initially investigated. The purpose of this paper was to review the ambient air quality standards(AAQS) of Korea, the U.S.A. and the EU and further to assess the degree of standard strength by the achievability of the AAQS comparing each national standard. Since the level and the way of standards for each air pollutant are various among countries, it is difficult to determine the degree of relative attainment using the same set of data above. Further when all the areas having bad air quality for a specific pollutant are classified as non-attainment case, it is more difficult to assess the degree of standard strength. Thus we introduced a new concept called the average concentration distance (ACD) to quantitatively estimate the strength. As results, the Korean 1-hr $NO_2$ AAQS is slightly stronger than the US standard and weaker than the EU standard. The Korean $O_3$ standard is strongest; however, the Korean $PM_{10}$ standard is weakest. Furthermore the equivalent levels of 8-hr $O_3$ standards in the U.S.A. and the EU were respectively estimated as 97.5 and 95.7 percentiles of the Korean standard with maintaining the existing standard of 60 ppb.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.566-569
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• 1999

The blue emitting BAM Phosphor Particles with various compositions were Prepared by the spray Pyrolysis. The effect of composition on the morphology of BAM particles was Investigated. In the case of BaMgAl$_{10}$ /O$_{22}$ : Eu$^{2+}$, the morphology of particles with sphericity and non-aggregation characteristics disappeared after post-treatment at 1400 $^{\circ}C$ for 3 hrs. On the other hand, the ocher composition particles except BaMgAl$_{10}$ /O$_{22}$ : Eu$^{2+}$ maintained their original morphology after post-treatment, even if the particles were prepared at low temperatures in the spray pryrolysis. The BAM particles with MgAl$_{2}$/O$_4$as intermediate material at low post-treatment temperature had high thermal stability and maintained sphericity of particles after post-treatment. All the samples had main omission peak at 450 nm, which corresponds to blue emission. The optimum post-treatment temperature of BAM:Eu$^{2+}$ particles for the maximum PL(photoluminescence) intensity in the spray pylolysis was 1200 $^{\circ}C$ because of high crystallinity, Phase-Purity, and good morphology.ology.

• 한국세라믹학회지
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• 제50권1호
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• pp.50-56
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• 2013

Phosphorescent materials coated with titanium dioxide were fabricated and photocatalytic reactions between these materials and VOCs gases were examined. A thin film (approx. 100 nm) of nanosized $TiO_2$ was deposited on the $Sr_4Al_{14}O_{25}$ : $Eu^{2+}$, $Dy^{3+}$, $Ag^+$ phosphor using low-pressure chemical vapor deposition (LPCVD). The characteristics of the photocatalytic reaction were examined in terms of the decomposition of benzene gas using a gas chromatography (GC) system under ultraviolet (${\lambda}$ = 365 nm) and visible light (${\lambda}$ > 420 nm) irradiation. $TiO_2$-coated $Sr_4Al_{14}O_{25}$ : $Eu^{2+}$, $Dy^{3+}$, $Ag^+$ phosphor showed different photocatalytic behavior compared with pure $TiO_2$. $TiO_2$-coated phosphorescent materials showed a much faster photocatalytic decomposition of benzene gas under visible irradiation compared to the pure $TiO_2$ for which the result was practically negligible. This suggests that the extension of the absorption wavelength to visible light occurred through energy band bending by a heterojunction at the interface of the $Sr_4Al_{14}O_{25}-TiO_2$ composite. Also, the $Sr_4Al_{14}O_{25}-TiO_2$ composite showed the photocatalytic decomposition of benzene in darkness due to the photon light emitted from the $Sr_4Al_{14}O_{25}$ phosphors.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.1087-1090
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• 2004

Samples of yttrium oxide doped with trivalent europium have been prepared by ceramic techniques, under different synthesis conditions; barium chloride ($BaCl_2$) and sodium tetraborate ($Na_2B_4O_7$) were tested as flux. The improvement of luminescence properties in dependence on substitution of $Eu^{3+}$ for $Y^{3+}$ in the host lattice, under electron and UV excitations is demonstrated The obtained results are discussed with respect to the employed processing method.

• Bulletin of the Korean Chemical Society
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• 제13권5호
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• pp.511-516
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• 1992

The catalytic oxidation of CO on perovskite $Eu_{1-x}Sr_xCoO_{3-y}$, has been investigated at reaction temperatures from 100 to $250^{\circ}C$ under stoichiometric CO and $O_2$ partial pressures. The microstructure and Sr-substitution site of the catalyst were studied by means of infrared spectroscopy. The reaction rates were found to be correlated with 1.5-and 1.0-order kinetics with and without a $CO_2$ trap, respectively; first-and 0.5-order with respect to CO and 0.5-order to $O_2$ with the activation energy of 0.37 eV $mol^{-1}$. It was found from IR, ${\sigma}$ and kinetic data that $O_2$ adsorbs as an ionic species on the oxygen vacancies, while CO adsorbs on the lattice oxygens. The oxidation reaction mechanism is suggested from the agreement between IR, ${\sigma}$ and kinetic data.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2006년도 춘계학술대회
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• pp.194-197
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• 2006

Lead-free bismuth-layered perovskite ferroelectric europium-substituted $Bi_{4}Ti_{3}O_{12}(BTO)$ thin films have been successfully deposited on Pt/Ti/$SiO_2$/Si substrate by a sol-gel spin-coating process. $Bi(TMHD)_3,\;Eu(THMD)_3,\;Ti(OiPr)_4$ were used as the precursors, which were dissolved in 2-methoxyethanol. The thin films were annealed at various temperatures from $600^{\circ}\;to\;720^{\circ}C$ in oxygen ambient for 1 hr, which was followed by post-annealed for 1 hr after depositing a Pt electrode to enhance the electrical properties. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the crystallinity and surface morphology of layered perovskite phase, respectively. The remanent polarization value of the BET thin films annealed at $720^{\circ}C\;was\;25.95{\mu}C/cm^2$ at an applied voltage of 5 V.

• 한국재료학회지
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• 제22권2호
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• pp.103-109
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• 2012

Red-emitting $Eu^{3+}$-activated $(Y_{0.95-x}Al_x)VO_4$ (0 < x $\leq$ 0.12) nanophosphors with the particle size of ~30 nm and the high crystallinity have been successfully synthesized by a hydrothermal reaction. In the synthetic process, deionized water as a solvent and ethylene glycol as a capping agent were used. The crystalline phase, particle morphology, and the photoluminescence properties of the excitation spectrum, emission intensity, color coordinates and decay time, of the prepared $(Y_{0.95-x}Al_x)VO_4:Eu^{3+}$ nanophosphors were compared with those of the $YVO_4:Eu^{3+}$. Under 147 nm excitation, $(Y_{0.95-x}Al_x)VO_4$ nanophosphors showed strong red luminescence due to the $^5D_0-^7F_2$ transition of $Eu^{3+}$ at 619 nm. The luminescence intensity of $YVO_4:Eu^{3+}$ enhanced with partial substitution of $Al^{3+}$ for $Y^{3+}$ and the maximum emission intensity was accomplished at the $Al^{3+}$ content of 10 mol%. By the addition of $Al^{3+}$, decay time of the $(Y,Al)VO_4:Eu^{3+}$ nanophosphor was decreased in comparison with that of the $YVO_4:Eu^{3+}$ nanophosphor. Also, the substitution of $Al^{3+}$ for $Y^{3+}$ invited the improvement of color coordinates due to the increase of R/O ratio in emission intensity. For the formation of transparent layer, the red nanophosphors were fabricated to the paste with ethyl celluloses, anhydrous terpineol, ethanol and deionized water. By screen printing method, a transparent red phosphor layer was formed onto a glass substrate from the paste. The transparent red phosphor layer exhibited the red emission at 619 nm under 147 nm excitation and the transmittance of ~80% at 600 nm.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.200-203
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• 2003

Ferroelectric europium-substitution $Bi_4Ti_3O_{12}$ thin films were fabricated by spin-coating onto a Pt/Ti/$SiO_2$/Si substrate. The $Bi_{3.25}Eu_{0.75}Ti_3O_{12}$ (BET) films have polycrystalline structure annealed at 700 C. We investigated that the influence of $Bi_4Ti_3O_{12}$ thin films by substituting for Bi ions with Bi ions using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). From the XPS measurement, it was suggested that the stability of the metal-oxygen octahedral should be related to substitute for Bi ions with Eu ions at annealed $800^{\circ}C$. The BET thin films showed a large remanent polarization (2Pr) of $60.99C/cm^2$ at an applied voltage of 10 V. The BET thin films exhibited no significant degradation of switching charge at least up to $5{\times}10^9$ switching cycles at a frequency of 50 kHz.

• 한국방사선학회논문지
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• 제4권4호
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• pp.25-28
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• 2010

본 연구에서는 고해상도 영상획득을 위해 저온액상법을 이용하여 Europium doped gadollium oxide($Gd_2O_3$:Eu) 미세 형광체를 제조하여 입자의 형상 및 구조를 분석하였으며, 발광체 필름에 대한 방사선에 대한 광학적 반응특성 실험을 통해 고해상도 영상검출기 적용 가능성을 확인하였다. 제조된 형광체 필름 두께에 따른 광량 및 선량에 따른 발광의 선형성을 조사하였다. 측정결과, $270{\mu}m$ 두께의 $Gd_2O_3$:Eu에서 $2945pC/cm^2/mR$의 발광 강도로 이 값은 벌크 형광체 필름의 발광 강도보다 약 1.2배 높은 영상 획득을 위한 충분한 신호임을 확인할 수 있었다. 또한, 임상 진단 영역의 X선 조사선량 범위에서 대체로 좋은 선형적 특성을 보였다.

• Bulletin of the Korean Chemical Society
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• 제8권1호
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• pp.6-9
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• 1987

The study of the $Na_3YSi_3O_9$ structure, by x-ray diffraction and infrared spectrum, showed that $Na_3YSi_3O_9$ is similar to $Na_4CaSi_3O_9$ except for its being pseudo-cubic instead of cubic. The peaks in the x-ray diffraction pattern of $Na_3YSi_3O_9$ could therefore be indexed on the basis of the $Na_4CaSi_3O_9$ cell. Also, modified $Na_3MSi_3O_9$ (M = Lu, Yb, Tm, Er, Y, Ho, Dy, Gd, Eu, and Sm) type compounds were synthesized by introducing excess sodium, decreasing M(III) concentration, and substituting small amount of phosphorus for silicon. The unit cell parameters of the composition $Na_{3.2}M_{0.7}Si_{2.9}P_{0.1}O_{8.7}$ were estimated from x-ray powder diffraction patterns using the Cohen method.