• 한국재료학회지
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• 제30권10호
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• pp.515-521
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• 2020

Organic-inorganic hybrid perovskite nanocrystals have attracted a lot of attention owing to their excellent optical properties such as high absorption coefficient, high diffusion length, and photoluminescence quantum yield in optoelectronic applications. Despite the many advantages of optoelectronic materials, understanding on how these materials interact with their environments is still lacking. In this study, the fluorescence properties of methylammonium lead bromide (CH₃NH₃PbBr₃, MAPbBr₃) nanoparticles are investigated for the detection of volatile organic compounds (VOCs) and aliphatic amines (monoethylamine, diethylamine, and trimethylamine). In particular, colloidal MAPbBr₃ nanoparticles demonstrate a high selectivity in response to diethylamine, in which a significant photoluminescence (PL) quenching (~ 100 %) is observed at a concentration of 100 ppm. This selectivity to the aliphatic amines may originate from the relative size of the amine molecules that must be accommodated in the perovskite crystals structure with a narrow range of tolerance factor. Sensitive PL response of MAPbBr₃ nanocrystals suggests a simple and effective strategy for colorimetric and fluorescence sensing of aliphatic amines in organic solution phase.

• 한국자동차공학회논문집
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• 제12권4호
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• pp.1-11
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• 2004

Combustion and fuel distribution characteristics of heavy duty engine with the liquid phase LPG injection(LPLI) were studied in a single cylinder engine, Swirl ratio were varied between 1.2, 2.3, and 3.4 following Ricardo swirl number(Rs) definition, Rs=2.3 showed the best results with lower cycle-by-cycle variation and shorter burning duration in the lean region while strong swirl(Rs=3.4) made these worse for combustion enhancement. Excessive swirl resulted in reverse effects due to high heat transfer and initial flame kernel quenching. Fuel injection timings were categorized with open valve injection(OVI) and closed valve injection(CVI). Open valve injection showed shorter combustion duration and extended lean limit. The formation of rich mixture in the spark plug vicinity was achieved by open valve injection. With higher swirl strength(Rs=3.4) and open valve injection, the cloud of fuel followed the flow direction and the radial air/fuel mixing was limited by strong swirl flow. It was expected that axial stratification was maintained with open-valve injection if the radial component of the swirling motion was stronger than the axial components. The axial fuel stratification and concentration were sensitive to fuel injection timing in case of Rs=3.4 while those were relatively independent of the injection timing in case of Rs=2.3.

• 열처리공학회지
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• 제6권4호
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• pp.194-203
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• 1993

Rapid solidified splats Al-(1, 3, 5Cr) Alloys were produced by atomization-splat quenching method. Effects of mechanical alloying on the structure and mechanical properties of rapidly solidified Al-(1, 3, 5)Cr alloys were studied. Degree of mechanical alloying of Al-(1, 3, 5)Cr alloys can be determined by observing the microstructural refinement, microhardness and microstructure of Al-(l, 3, 5)Cr splats during processing. In the initial stage of mechanical alloying of the Al-(1, 3, 5)Cr splats fracturing of the grain boundaries occured first, followed after fracturing of zone A regions. Saturation hardness of Al-(1, 3, 5)Cr alloys increased proportionally with increasing concentration of the solute (Cr). Age hardening was not observed in these alloys. Decomposition temperature of Al-1Cr splats after mechanical alloying was higher than that of Al-5Cr splats. The density of $Al_7$ Cr precipitates increased proportionally with increasing chromium content, as a result, there was a transition to finely and spherically dispersed phase after mechanical alloying.

• 청정기술
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• 제24권3호
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• pp.233-238
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• 2018

급속열분해를 통한 바이오-오일 생산 공정은 무산소 조건에서 바이오매스를 급속열분해하여 얻어진 열분해가스를 급속 냉각 시켜 열분해오일을 생산한다. 이에 공정 내부의 산소 농도를 0 ~ 3% 이하로 유지하기 위해 캐리어 가스로 질소를 사용한다. 그러나 공정의 규모가 커질수록 질소의 사용량이 증가하고, 이는 공정 운전비용 증감 및 지속적인 질소 가스 충전을 위한 설비비 증감 할 수밖에 없다. 이에 본 연구에서는 팜 부산물 열분해에서 질소 사용량 감소를 위해 미응축가스 재순환 공정을 적용하여, 가스재순환율에 따른 질소 사용량과 미응축가스의 가연성 성분의 농도 변화를 측정하고 이에 따른 바이오-오일의 품질 수율 변화를 측정하여 가스재순환 공정의 활용 가능성을 연구하였다.

• 대한화학회지
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• 제36권1호
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• pp.100-106
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• 1992

스티렌-말레산(PSMA), 스티렌말레산 무수물(PSMAn), 및 스티렌-말레산의 $Eu^{3+}$ 염(PSMA-Eu)의 형광특성을 tetrahydrofuran 용액에서 연구하였다. 스티렌의 몰%가 75%인 PSMA와 PSMA-Eu은 들뜬 이합체의 결합에너지가 50%나 67%에 비해 크게 나타났다. 들뜬이합체-단위체 형광세기의 비로부터 스티렌 단위체의 농도가 $8.0{\times}10^{-3}M$까지도 분자내 들뜬이합체의 특성을 보였다. 들뜬이합체의 형성메카니즘을 설명하는 기존의 세 가지 모형은 이들 중합체에 대해서는 잘 맞지 않는 듯하다. benzylacetate, mesitylene 및 염소가 치환된 용매들이 들뜬이합체의 형광에 주는 영향을 을 조사하여 그 결과를 몰부피로 해석해 보았다.

• Bulletin of the Korean Chemical Society
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• 제30권6호
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• pp.1252-1256
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• 2009

A simple, selective and sensitive fluorescence quenching method was developed to the determination Cr(VI). The method is based on the oxidation of $I^-\;to\;{{I_3}^-}$ by Cr(VI) in sulfuric acid solution followed by immediate formation of ion association compound between I3 − and rhodamine 6G in Tween-80 micellar media at room temperature. The influence of several surfactants on rhodamine 6G fluorescence signal was studied; particular attention was paid in the aggregation behavior of rhodamine 6G–Tween-80 system. The experimental parameters (e.g., type of surfactant, reagent concentration) were studied and the optimal conditions were established. The linear calibration graph was obtained in the range 2.0 - 100.0 ng m$L^{-1}$ Cr(VI). The detection limit of the method was 0.37 ng m$L^{-1}$. The relative standard deviation (R.S.D.) is less than 5% (n = 5). The efficiency of the method for the determination of Cr(VI) in the presence of Cr(III) in the sample was investigated. The method was applied successfully to the determination of Cr(VI) and total Cr in water, and liver tissue samples.

• 한국세라믹학회지
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• 제38권12호
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• pp.1144-1149
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• 2001

본 연구에서는 화염가수분해증착법(Flame Hydrolysis Deposition : FHD)을 이용하여 실리콘(Si)/실리카(SiO$_2$) 광도파막을 제조하고, 이 박막에 Solution Doping 법을 이용해 Er/Al을 복합 첨가하여 광증폭 매질을 제작하는 연구를 수행하였다. 형광 측정을 통해 Al의 복합첨가에 의한 형광효율의 감소 방지 및 형광 스펙트럼의 반치폭 증가를 확인할 수 있었다. 즉, Al가 0.48wt%가 첨가된 경우, Er가 0.14wt% 첨가되는 경우에도 형광세기가 감소하지 않음을 확인하였으며, $1.5mu extrm{m}$ 대역의 형광스펙트럼의 대역폭이 약 5nm 정도 증가됨을 관찰하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.91-91
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• 2008

$SnO_2-B_2O_3-P_2O_5$ system were prepared by melt-quenching technique in the compositional series containing 50, 55 aod 60mol.% of $SnO_2$. A large glass-forming region was found at the phosphate side of the ternary system with homogeneous glasses containing up to 5-25mol.% of $B_2O_3$. For these glasses, thermal expansion coeffient($\alpha$), glass transition temperature(Tg), and glass softening temperature(Ts), were determined. The values a decrease with increasing $B_2O_3$ content, while Tg and Ts increased. The reason for the observed changes is local structure of the glasses. Local structure of the glasses was investigated by Raman and FT-IR measurements, suggesting that the number of bridging oxygens decreased whereas the non-bridging oxygen concentration increased with increasing $SnO_2$ content in the glasses.

• Bulletin of the Korean Chemical Society
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• 제35권4호
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• pp.1105-1109
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• 2014

While single strand DNAs have been widely used for the scaffold of brightly fluorescent silver nanoclusters (Ag NCs), double strand DNAs have not been as successful. Herein, we report a novel synthetic approach for bright Ag NCs using branched double strand DNAs as the scaffolds for synthesis. X-shaped DNA (X-DNA) and Y-shaped DNA (Y-DNA) effectively stabilized Ag NCs, and both X-DNA and Y-DNA resulted in brightly fluorescent Ag NCs. The concentration and molar ratio of silver and DNA were found important for the fluorescence efficiency. The brightest Ag NC with the photoluminescence quantum efficiency of 19.8% was obtained for the reaction condition of 10 ${\mu}M$ X-DNA, 70 ${\mu}M$ silver, and the reaction time of 48 h. The fluorescence lifetime was about 2 ns for the Ag NCs and was also slightly dependent on the synthetic condition. Addition of Cu ions at the Ag NC preparations resulted in the quenching of Ag NC fluorescence, which was different to the brightening cases of single strand DNA stabilized Ag NCs.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3058-3067
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• 2021

Sodium zinc borate glasses doped with dysprosium and modified with different concentrations of barium oxide (0-50 mol %) were fabricated using the melting quenching technique. The structural properties of the prepared glass systems were characterized using XRD and FTIR methods. The absorption spectra of the prepared glasses were measured to determine their energy gap and their related optical properties. The density of the glasses and other physical parameters were also reported. Additionally, with the help of Photon Shielding and Dosimetry (PSD) software, we investigated the radiation shielding parameters of the prepared glass systems at different energy values. It was found that an increase in the density of the glasses by increasing the concentration of BaO significantly improved the gamma ray shielding ability of the samples. For practical results, a compatible irradiation set up was designed to check the shielding capability of the obtained glasses using a gamma ray source at 662 keV. The experimentally obtained results strongly agreed with the data obtained by PDS software at the same energy. These results demonstrated that the investigated glass system is a good candidate for several radiation shielding applications when comparing it with other commercial shielding glasses and concretes.