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Jinwoo KIM(Jinwoo KIM),Hosung WOO(Hosung WOO) 한국4차산업학회 2023 4차산업연구 Vol.3 No.1
Purpose – By designing a PEF(Personalized Education Feedback) system for real-time prediction of learning achievement and motivation through real-time EEG analysis of learners, this system provides some modules of a personalized adaptive learning system. By applying these modules to e-learning and offline learning, they motivate learners and improve the quality of learning progress and effective learning outcomes can be achieved for immersive self-directed learning Research design, data, and methodology – EEG data were collected simultaneously as the English test was given to the experimenters, and the correlation between the correct answer result and the EEG data was learned with a machine learning algorithm and the predictive model was evaluated.. Result – In model performance evaluation, both artificial neural networks(ANNs) and support vector machines(SVMs) showed high accuracy of more than 91%. Conclusion – This research provides some modules of personalized adaptive learning systems that can more efficiently complete by designing a PEF system for real-time learning achievement prediction and learning motivation through an adaptive learning system based on real-time EEG analysis of learners. The implication of this initial research is to verify hypothetical situations for the development of an adaptive learning system through EEG analysis-based learning achievement prediction.
Magnetic mesoporous materials for removal of environmental wastes
Kim, Byoung Chan,Lee, Jinwoo,Um, Wooyong,Kim, Jaeyun,Joo, Jin,Lee, Jin Hyung,Kwak, Ja Hun,Kim, Jae Hyun,Lee, Changha,Lee, Hongshin,Addleman, R. Shane,Hyeon, Taeghwan,Gu, Man Bock,Kim, Jungbae Elsevier 2011 Journal of hazardous materials Vol.192 No.3
<P><B>Highlights</B></P><P>• Iron oxide particle embedded mesoporous silica and carbon are synthesized. • Both mesoporous materials are separated easily under aqueous condition using magnet. • Mercury or fluorescein is removed by using magnetic mesoporous material. • Tyrosinase is immobilized in magnetic mesoporous silica and reused after reaction. • Magnetic mesoporous materials are applicable to removal of environmental wastes.</P> <P><B>Abstract</B></P><P>We have synthesized two different magnetic mesoporous materials that can be easily separated from aqueous solutions by applying a magnetic field. Synthesized magnetic mesoporous materials, Mag-SBA-15 (magnetic ordered mesoporous silica) and Mag-OMC (magnetic ordered mesoporous carbon), have a high loading capacity of contaminants due to high surface area of the supports and high magnetic activity due to the embedded iron oxide particles. Application of surface-modified Mag-SBA-15 was investigated for the collection of mercury from water. The mercury adsorption using Mag-SBA-15 was rapid during the initial contact time and reached a steady-state condition, with an uptake of approximately 97% after 7h. Application of Mag-OMC for collection of organics from water, using fluorescein as an easily trackable model analyte, was explored. The fluorescein was absorbed into Mag-OMC within minutes and the fluorescent intensity of solution was completely disappeared after an hour. In another application, Mag-SBA-15 was used as a host of tyrosinase, and employed as recyclable catalytic scaffolds for tyrosinase-catalyzed biodegradation of catechol. Crosslinked tyrosinase in Mag-SBA-15, prepared in a two step process of tyrosinase adsorption and crosslinking, was stable enough for catechol degradation with no serious loss of enzyme activity. Considering these results of cleaning up water from toxic inorganic and organic contaminants, magnetic mesoporous materials have a great potential to be employed for the removal of environmental contaminants and potentially for the application in large-scale wastewater treatment plants.</P>
Kim, Jinwoo,Jin, Youngeup,Kim, Jaehong,Jung, Jaeyeon,Kim, Sun Hee,Lee, Kwanghee,Suh, Hongsuk Wiley Subscription Services, Inc., A Wiley Company 2009 Journal of polymer science Part A, Polymer chemist Vol.47 No.5
<P>The syntheses and characterization of poly((2,6-(4,4-bis(4-((2-ethylhexyl)oxy)phenyl)-4H-cyclopenta[def]phenanthrene))-co-(2,6-(4,4-bis(4-(((9-carbazolyl)hexyl)oxy)phenyl))-4H-cyclopenta[def]phenanthrene)) (BCzPh-PCPPs) and poly((2,6-(4,4-bis(4-((2-ethylhexyl)oxy)phenyl)-4H-cyclopenta[def]phenanthrene))-co-(2,6-(4-(4-(((9-carbazolyl)hexyl)oxy)phenyl)-4-(4-((2-ethylhexyl)oxy)phenyl)-4H-cyclopenta[def]phenanthrene))) (CzPh-PCPPs), with carbazole unit as pendants, are presented. The carbazole moiety, which can improve the hole injection ability, was introduced as a pendant on the PCPP backbone. The devices of the polymers with the configurations of ITO/PEDOT:PSS/polymers/Ca/Al generate EL emission with maximum peaks at 400–450 nm, CIE coordinates of (x = 0.11–0.29, y = 0.11–0.33), low turn-on voltages of 4–6 V, maximum brightness of 60–810 cd/m<SUP>2</SUP>, and luminescence efficiencies of 0.04–0.22 cd/A. The PL spectra of CzPh-PCPPs films did not show any peak at around 550 nm, which corresponds to keto defect or aggregate/excimer formation, even after annealing for 30 h at 150 °C in air. Out of the series, CzPh-PCPP1 (PCPP derivative with 10% of carbazole moiety as pendant) shows blue emission with the maximum brightness of 810 cd/m<SUP>2</SUP> at 9 V, and the highest luminescence efficiency of 0.22 cd/A at 395 mA/cm<SUP>2</SUP>. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1327–1342, 2009</P> <B>Graphic Abstract</B> <P>The conjugated copolymers of BCzPh-PCPPs and CzPh-PCPPs with carbazole pendant were synthesized by Suzuki reaction. The carbazole moiety, which can improve the hole injection ability, was introduced as a pendant on the PCPP backbone. Their thermal, electrochemical, photoluminescent, and electroluminescent properties were investigated. <img src='wiley_img/0887624X-2009-47-5-POLA23241-gra001.gif' alt='wiley_img/0887624X-2009-47-5-POLA23241-gra001'> </P>
Standard Auctions with Security Bids
Jinwoo Kim 한국계량경제학회 2013 JOURNAL OF ECONOMIC THEORY AND ECONOMETRICS Vol.24 No.1
Peter DeMarzo, Ilan Kremer and Andrzej Skrzypacz (2005) study auctions where bidders compete in securities. As the main results, they show that: a steeper security generates a higher revenue for the seller; the revenue ranking between the first-price and second-price auction depends on the steepness of security; and the first-price auction combined with call option achieves the highest revenue among a general set of auction mechanisms. As pointed out by Che and Kim (2010), using steeper securities can cause the adverse selection problem and reduce the seller's revenue, in case a bidder who expects a higher return must incur a higher investment cost. While the analysis of Che and Kim (2010) focuses on the second-price auction, this paper analyzes the first-price auction to show that it is plagued by the same problem and in fact more vulnerable than the second-price auction to the adverse selection problem, which may lead to a reversal of the DKS's revenue ranking between the two auctions.
Kim, Dong Kyu,Lee, Ji Sung,Kim, Jinwoo,Kim, Mo Se,Kim, Min Soo Elsevier 2017 APPLIED ENERGY Vol.189 No.-
<P>A parametric study and performance evaluation of an organic Rankine cycle (ORC) system that uses low-grade heat at a temperature below 80 degrees C and with a cycle power of less than 10 kW was undertaken to analyze the effects of the operating conditions on the performance and efficiency. R245fa was used as the working fluid, and a scroll expander as the power generation device. A model of the system was developed and its predictions were verified by the results of experiments, which were also used to determine the appropriate charge of the working fluid for maximizing the system power output. Owing to the difference between the variations of the power generated by the expander and the power consumed by the pump, the performance of the system was found to initially increase and then decrease with increasing refrigerant charge. The parametric investigation of the ORC system was conducted by varying the pressure ratio and mass flow rate of the working fluid. Increases in both parameters were found to increase the system performance by improving the torque generation and expander speed. The variation of the system performance with the heat sink temperature, which was varied between 20 and 35 degrees C, was also examined. The system power and efficiency were observed to decrease with increasing heat sink temperature owing to the decrease in the pressure ratio resulting from the increased condensation temperature. Based on the study findings, we propose a performance map for a low-temperature low-cycle-power ORC. The power and efficiency are shown to be proportional to the heat source temperature and capacity, which varies in a manner similar to the expander performance. The findings of this study highlight the feasibility of an ORC system that uses low-grade heat at a temperature below the boiling point. (C) 2016 Elsevier Ltd. All rights reserved.</P>