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Choi Minseon,Lee Suyeon,Jang Dawoon,Park Sungjin 한국탄소학회 2022 Carbon Letters Vol.32 No.3
Electrochemical water splitting is an important process for next generation of eco-friendly energy systems. The oxygen evolution reaction (OER), which occurs at an anode during the process, requires efficient electrocatalysts to reduce activation energies. Although Ru- or Ir-containing materials show excellent electrocatalytic activities, their high cost is a critical drawback. Consequently, the development of efficient electrocatalysts composed of low-cost metal components is a great challenge. In this study, we develop a new route to produce a hybrid material (Fe–NC) containing Fe3C particles dispersed on the surface of N-doped carbon (NC) materials by heat treatment of a mixture of urea and Fe(II)Cl2(H2O)4. Microscopic analyses prove that the Fe3C particles are placed on the surfaces of thin NC materials. Additionally, various characterizations reveal that the particles contain Fe3C structure. Fe–NC shows good electrocatalytic properties with onset and overpotentials of 1.57 V and 545 mV, respectively, for OER in KOH electrolyte. This study suggests the possibility of the use of Fe3C-based composites as OER electrocatalysts.
Analysis of fatty acid methyl ester in bio-liquid by hollow fiber-liquid phase microextraction
Choi, Minseon,Lee, Soyoung,Bae, Sunyoung The Korean Society of Analytical Science 2017 분석과학 Vol.30 No.4
Bio-liquid is a liquid by-product of the hydrothermal carbonization (HTC) reaction, converting wet biomass into solid hydrochar, bio-liquid, and bio-gas. Since bio-liquid contains various compounds, it requires efficient sampling method to extract the target compounds from bio-liquid. In this research, fatty acid methyl ester (FAME) in bio-liquid was extracted based on hollow fiber supported liquid phase microextraction (HF-LPME) and determined by Gas Chromatography-Flame Ionization Detector (GC-FID) and Gas Chromatography/Mass Spectrometry (GC/MS). The well-known major components of biodiesel, including methyl myristate, palmitate, methyl palmitoleate, methyl stearate, methyl oleate, and methyl linoleate had been selected as standard materials for FAME analysis using HF-LPME. Physicochemical properties of bio-liquid was measured that the acidity was 3.30 (${\pm}0.01$) and the moisture content was 100.84 (${\pm}3.02$)%. The optimization of HF-LPME method had been investigated by varying the experimental parameters such as extraction solvent, extraction time, stirring speed, and the length of HF at the fixed concentration of NaCl salt. As a result, optimal conditions of HF-LPME for FAMEs were; n-octanol for extraction solvent, 30 min for extraction time, 1200 rpm for stirring speed, 20 mm for the HF length, and 0.5 w/v% for the concentration of NaCl. Validation of HF-LPME was performed with limit of detection (LOD), limit of quantitation (LOQ), dynamic range, reproducibility, and recovery. The results obtained from this study indicated that HF-LPME was suitable for the preconcentration method and the quantitative analysis to characterize FAMEs in bio-liquid generated from food waste via HTC reaction.
최민선(Minseon Choi),김장헌(Jangheon Kim),조성환(Sunghwan Cho) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In view of growing concerns over global warming, diesel engine is more effect tool. This paper starts with a description of the experiments on combustion and reduced friction, followed by analysis the objectives of achieving the lowest fuel consumption for diesel passenger car. It's considered surface engineering treatment and reduction of piston ring tangential forces and bearing widths reduction to reduce the friction between engine moving parts like a piston ring and cylinder liner. With this analysis, it is possible to decide the direction of the reduce the diesel engine fuel reduction development.
적응형 온라인 학습환경에서 학습자 특성 및AI튜터 추천문항 학습활동의 학업성취도 예측력 탐색
최민선(Minseon Choi),정재삼(Jaesam Chung) 한국IT서비스학회 2021 한국IT서비스학회지 Vol.20 No.4
Recently, interest in AI tutors is rising as a way to bridge the educational gap in school settings. However, research confirming the effectiveness of AI tutors is lacking. The purpose of this study is to explore how effective learner characteristics and recommended item learning activities are in predicting learner’s academic performance in an adaptive online learning environment. This study proposed the hypothesis that learner characteristics (prior knowledge, midterm evaluation) and recommended item learning activities (learning time, correct answer check, incorrect answer correction, satisfaction, correct answer rate) predict academic achievement. In order to verify the hypothesis, the data of 362 learners were analyzed by collecting data from the learning management system (LMS) from the perspective of learning analytics. For data analysis, regression analysis was performed using the regsubset function provided by the leaps package of the R program. The results of analyses showed that prior knowledge, midterm evaluation, correct answer confirmation, incorrect answer correction, and satisfaction had a positive effect on academic performance, but learning time had a negative effect on academic performance. On the other hand, the percentage of correct answers did not have a significant effect on academic performance. The results of this study suggest that recommended item learning activities, which mean behavioral indicators of interaction with AI tutors, are important in the learning process stage to increase academic performance in an adaptive online learning environment.
최민선(Minseon Choi),박민규(Minkyu Park),조성환(Sunghwan Cho),한석재(Seogjae Han) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
In view of growing concerns over global warming, diesel engine is more effect tool. Current development activities on diesel engines are aimed primarily on reducing emissions and improving fuel consumption. This paper describes how the water pump, traditionally driven from the crankshaft through a mechanical link, can be enhanced to satisfy increased demands for coolant flow and also save power by eliminating unnecessary operation. It's considered variable water pump to reduce the engine motoring friction by using non operating water pump controls and reduced engine operating friction with the reduction of warm up period with water and oil temperature relatively increased. With this analysis, it is possible to decide the direction of the reduction of the diesel engine fuel reduction development.
Choi, Ki-Choon,Hwang, Jung-Min,Bang, Sung-Jun,Son, Young-Ok,Kim, Beom-Tae,Kim, Dong-Hern,Lee, Seung-Ah,Chae, Minseon,Kim, Da Hye,Lee, Jeong-Chae Informa Healthcare USA, Inc. 2013 PHARMACEUTICAL BIOLOGY Vol.51 No.8
<P><I>Context</I>: Recently, there has been renewed interest in barley (<I>Hordeum vulgare</I> L. Poaceae) as a functional food and for its medicinal properties.</P><P><I>Objective</I>: This study examines the anti-inflammatory potential of the active fractions of barley and the mechanisms involved.</P><P><I>Materials and methods</I>: The macrophages were exposed to 100 μg/mL of each of the barley extracts in the presence of 1 μg/mL lipopolysaccharide (LPS) and after 24 or 48 h of incubation, cells or culture supernatants were analyzed by various assays. The anti-inflammatory potential of barley fractions was also investigated using the LPS-injected septic mouse model. The active constituents in the fractions were identified using gas chromatography-mass spectrometry (GC-MS).</P><P><I>Results</I>: The active fractions, named F<SUB>4</SUB>, F<SUB>7</SUB>, F<SUB>9</SUB> and F<SUB>12</SUB>, inhibited almost completely the LPS-induced production of nitric oxide (NO) and inducible NO synthase. Pre-treatment with these fractions at 100 μg/mL diminished the tumor necrosis factor-α (TNF-α) levels to 19.8, 3.5, 1.2 and 1.7 ng/mL, respectively, compared to LPS treatment alone (41.5 ng/mL). These fractions at 100 μg/mL also suppressed apparently the secretion of interleukin (IL)-6 and IL-1β and the DNA-binding activity of nuclear factor-κB in LPS-stimulated cells. Mice injected intraperitoneally with LPS (30 mg/kg BW) showed 20% survival at 48 h after injection, whereas oral administration of the fractions improved the survival rates to 80%. GC-MS analysis revealed the presence of the derivatives of benzoic and cinnamic acids and fatty acids in the fractions.</P><P><I>Discussion and conclusion</I>: The aerial parts of barley are useful as functional food to prevent acute inflammatory responses.</P>
Choi, Ki-Choon,Son, Young-Ok,Hwang, Jung-Min,Kim, Beom-Tae,Chae, Minseon,Lee, Jeong-Chae TaylorFrancis 2017 PHARMACEUTICAL BIOLOGY Vol.55 No.1
<P><B>Abstract</B></P><P><B>Context:</B> Interest has recently renewed in using <I>Lolium multiflorum</I> Lam. (Poaceae) (called Italian ryegrass; IRG) silage as an antioxidant and anti-inflammatory diet.</P><P><B>Objective:</B> This study investigated the antioxidant, anti-inflammatory and anti-septic potential of IRG silage and identified the primary components in IRG active fractions.</P><P><B>Materials and methods:</B> Total 16 fractions were separated from the chloroform-soluble extract of IRG aerial part using Sephadex LH-20 column before HPLC analysis. Antioxidant and anti-inflammatory activities of the fractions at doses of 0–100 μg/mL were investigated using various cell-free and cell-mediated assay systems. To explore anti-septic effect of IRG fractions, female ICR and BALB/c mice orally received 40 mg/kg of phenolic acid and flavonoid-rich active fractions F<SUB>7</SUB> and F<SUB>8</SUB> every other day for 10 days, respectively, followed by LPS challenge.</P><P><B>Results:</B> The active fractions showed greater antioxidant and anti-inflammatory potential compared with other fractions. IC<SUB>50</SUB> values of F<SUB>7</SUB> and F<SUB>8</SUB> to reduce LPS-stimulated NO and TNF-α production were around 15 and 30 μg/mL, respectively. Comparison of retention times with authentic compounds through HPLC analysis revealed the presence of caffeic acid, ferulic acid, myricetin and kaempferol in the fractions as primary components. These fractions inhibited LPS-stimulated MAPK and NF-κB activation. Supplementation with F<SUB>7</SUB> or F<SUB>8</SUB> improved the survival rates of mice to 70 and 60%, respectively, in LPS-injected mice and reduced near completely serum TNF-α and IL-6 levels.</P><P><B>Discussion and conclusion:</B> This study highlights antioxidant, anti-inflammatory and anti-septic activities of IRG active fractions, eventually suggesting their usefulness in preventing oxidative damage and inflammatory disorders.</P>