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지중저장 이산화탄소의 누출이 천부환경에서 방연석의 용해 과정에 미치는 영향
남지은,왕수균,Nam, Jieun,Wang, Sookyun 한국지하수토양환경학회 2015 지하수토양환경 Vol.20 No.1
If $CO_2$ stored for geological sequestration escapes from deep formations and is introduced to shallow aquifers, it dissolves into groundwater, creates acidic environments, and enhance mineral dissolution from rocks and soils. Among these minerals, dissolution and spread of hazardous trace metals can cause environmental problems with detrimental impacts on groundwater quality. This study aims to investigate geochemical effects of $CO_2$ in groundwater on dissolution of galena, the main mineral controlling the mobility of lead. A series of batch experiments are performed with granulated galena in $CO_2$ solutions under various experimental conditions for $CO_2$ concentration and reaction temperature. Results show that dissolution of galena is significantly enhanced under acidic environments so that both of equilibrium concentrations and dissolution rates of lead increase. For thermodynamic analysis on galena dissolution, the apparent rate constants and the activation energy for galena dissolution are calculated by applying rate law to experimental results. The apparent rate constants are $6.71{\times}10^{-8}mol/l{\cdot}sec$ at $15^{\circ}C$, $1.77{\times}10^{-7}mol/l{\cdot}sec$ at $25^{\circ}C$, $3.97{\times}10^{-7}mol/l{\cdot}sec$ at $35^{\circ}C$ and the activation energy is 63.68 kJ/mol. The galena dissolution is suggested to be a chemically controlled surface reaction, and the rate determining step is the dissociation of Pb-S bond of surface complex.
우레아 열분해에 의한 SCR 시스템 내 잔류 고형물 분석
남지은(JiEun Nam),장혜진(Hyejin Jang),이승진(SeungJin Lee) 한국자동차공학회 2020 한국자동차공학회 학술대회 및 전시회 Vol.2020 No.11
In this study, the chemical compositions of deposits in Urea-SCR was analyzed by TGA(Thermal gravimetric analysis), FT-IR(Fourier – transform infrared spectroscopy), Py–GC/MS(Pyrolysis–GC/MS). In order to identify composition of urea deposits, we synthesized the urea deposits at different temperatures(180℃, 200℃, 300℃, 400℃, 500℃, 600℃). As a result of analysis, we demonstrated thermal decomposition process of urea. The deposits (Urea, Biuret, Cyanuric acid, melamine) synthesized at low temperatures could be decomposed at relatively low temperatures, but the deposits (melem, melon) synthesized at high temperatures had low-polar, high-molecule weight and thermal decomposition difficult even at high temperatures.
금속 Powder Bed Fusion 적층제조 기술의 분말 입도 최적화를 위한 시뮬레이션
이화선,김대겸,김영일,남지은,손용,김택수,이빈,Lee, Hwaseon,Kim, Dae-Kyeom,Kim, Young Il,Nam, Jieun,Son, Yong,Kim, Taek-Soo,Lee, Bin 한국분말야금학회 2020 한국분말재료학회지 (KPMI) Vol.27 No.1
Powder characteristics, such as density, size, shape, thermal properties, and surface area, are of significant importance in the powder bed fusion (PBF) process. The powder required is exclusive for an efficient PBF process. In this study, the particle size distribution suitable for the powder bed fusion process was derived by modeling the PBF product using simulation software (GeoDict). The modeling was carried out by layering sintered powder with a large particle size distribution, with 50 ㎛ being the largest particle size. The results of the simulation showed that the porosity decreased when the mean particle size of the powder was reduced or the standard deviation increased. The particle size distribution of prepared titanium powder by the atomization process was also studied. This study is expected to offer direction for studies related to powder production for additive manufacturing.
균질화기법을 이용한 탄소나노튜브 기반 고분자 나노복합재의 유효 물성 예측에 관한 연구
진지원(Ji-Won Jin),최찬웅(Chan-Woong Choi),이학성(Hak-Sung Lee),남지은(Jieun Nam),강기원(Ki-Weon Kang) 대한기계학회 2018 대한기계학회 논문집. Transactions of the KSME. C, 산업기술과 혁신 Vol.6 No.2
본 논문에서는 균질화기법을 이용하여 고분자 나노복합재의 미시 구조 및 거동에 따른 유효물성치를 추정하였다. 이를 위하여 먼저 고분자 나노복합재의 대표 구조를 갖는 단일벽나노튜브 및 폴리비닐리덴 플루오라이드를 선정하였으며, 다양한 분산성을 고려하기 위하여 배향 및 중량 비율에 따른 대표체적요소를 선정하여 모델링을 수행하였다. 이를 통하여 규칙 및 불규칙 대표체적요소의 균질화기법을 이용하여 유효물성을 산출하였다. 이의 결과를 토대로 탄소나노튜브의 분산으로 인한 나노복합재에 미치는 물성의 변동성을 평가하였다. In this paper, the equivalent properties for microstructures and behavior of polymeric nanocomposite were estimated by homogenization method. For this purpose, singlewalled nanotube and polyvinylidene fluoride with representative structure of polymeric nanocomposite were selected. In order to consider various dispersibility, modeling was performed by representative volumetric element on the orientation and weight ratio. Through this, equivalent properties were calculated using homogenization method of regular and irregular representative volumetric elements. Based on the results, variability of nanocomposite properties by variance of carbon nanotube was evaluated.