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Jeon, Hyo Sang,Jee, Michael Shincheon,Kim, Haeri,Ahn, Su Jin,Hwang, Yun Jeong,Min, Byoung Koun American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.44
<P>Oxygen evolution reaction (OER) is the key reaction in electrochemical processes, such as water splitting, metal–air batteries, and solar fuel production. Herein, we developed a facile chemical solution deposition method to prepare a highly active Co<SUB>3</SUB>O<SUB>4</SUB> thin film electrode for OER, showing a low overpotential of 377 mV at 10 mA/cm<SUP>2</SUP> with good stability. An optimal loading of ethyl cellulose additive in a precursor solution was found to be essential for the morphology control and thus its electrocatalytic activity. Our results also show that the distribution of Co<SUB>3</SUB>O<SUB>4</SUB> nanoparticle catalysts on the substrate is crucial in enhancing the inherent OER catalytic performance.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-44/acsami.5b06189/production/images/medium/am-2015-06189z_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b06189'>ACS Electronic Supporting Info</A></P>
내용 통합 텍스트 읽기를 위한 초등 영어 어휘 지도 전략에 대한 연구
김혜리(Kim Haeri),전병규(Jeon ByungKyu),강영옥(Kang YungOk),김은하(Kim, EunHa) 팬코리아영어교육학회(구 영남영어교육학회) 2012 영어교육연구 Vol.24 No.4
This study investigated the effects of vocabulary teaching strategies while reading content-based informational text in primary English classes. Both quantitative and qualitative data were collected, and the data analysis yielded four major findings. First, the quantitative data analysis showed that there was no one particular strategy that fit all learning situations. However, from qualitative analysis, the study found that students Preferred application strategy to list strategy and could transfer inference strategy in learning words from other texts. Second, effective vocabulary teaching strategies were different according to the characteristics of the texts and types of words in the text. Third, there were different learning transfer effects according to word types. For example, there was significant learning transfer effect with compound and loan words, whereas less transfer effect with collocation. Last, there were learning differences according to students’ English level. Based on the conclusions, suggestions were made for follow-up studies.
Lee, Minoh,Jeon, Hyo Sang,Lee, Si Young,Kim, Haeri,Sim, Sang Jun,Hwang, Yun Jeong,Min, Byoung Koun Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.36
<▼1><P>The chemical composition change of Ni and Fe on a cratered stainless steel surface as a result of electrochemical oxidation leads to significantly enhanced water oxidation properties in a neutral electrolyte.</P></▼1><▼2><P>An electron-mediated CO2-to-chemical conversion system is regarded as one of the effective solutions for the depletion of fossil fuels and the accumulation of atmospheric CO2. In this process, the protons and electrons generated from the water-oxidation reaction at an anode are used during the reduction of CO2 at a cathode, in order to produce high-value hydrocarbon chemicals. Therefore, water oxidation is also a key reaction for the overall electron-mediated CO2-to-chemical conversion. In this work, a facile preparation method is developed for a highly efficient water oxidation electrocatalyst which stably operates in a neutral bicarbonate electrolyte optimized for CO2-reduction conditions. Ni-rich cratered structures were spontaneously formed on the stainless steel surface by harsh electro-oxidation, and the chemical composition changes of Fe and Ni on the catalyst surface dramatically enhance water-oxidation activity showing an overpotential value of 504 mV at 10 mA cm<SUP>−2</SUP> in a CO2-saturated bicarbonate electrolyte. In contrast to a severe degradation in the phosphate electrolyte, the cratered stainless-steel (CSS) catalyst is very stable for an 18 h reaction in the bicarbonate electrolyte. Surface spectroscopic analyses of CSS consistently revealed that the active-surface structure of the NiOOH and adsorbed water molecules is remarkably stable throughout water-oxidation in the neutral bicarbonate electrolyte, while the destruction of Ni structures by the phosphate electrolyte is proposed to cause concomitant activity loss for water oxidation.</P></▼2>
Stable surface oxygen on nanostructured silver for efficient CO<sub>2</sub> electroreduction
Jee, Michael Shincheon,Kim, Haeri,Jeon, Hyo Sang,Chae, Keun Hwa,Cho, Jinhan,Min, Byoung Koun,Hwang, Yun Jeong Elsevier 2017 CATALYSIS TODAY - Vol.288 No.-
<P><B>Abstract</B></P> <P>We investigated properties involved in the enhancement in electrocatalytic carbon dioxide (CO<SUB>2</SUB>) reduction to carbon monoxide (CO) in electrochemically treated Ag surfaces with surface sensitive analysis methods such as Auger spectroscopy, atomic force microscopy (AFM) coupled with Kelvin probe force microscopy (KPFM) techniques, and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The absence of Ag M<SUB>4,5</SUB>VV Auger signals for the electrochemically treated Ag indicate the presence of localized surface oxygen (O) which survives on the best performing Ag electrocatalysts even in the reductive environment of the CO<SUB>2</SUB> reduction reaction. Higher work functions were located at the nanostructure boundaries observed by KPFM/AFM implying the higher surface O concentrations in these regions. Furthermore, NEXAFS measured the selective prominence of π * states over σ * in the active Ag surfaces which suggests stronger interaction with intermediates of CO<SUB>2</SUB> reduction while minimizing the –OH interaction contributing to increase CO<SUB>2</SUB> reduction activity and selectivity. These results provide direction in engineering surfaces for efficient electrochemical CO<SUB>2</SUB> conversion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanostructured Ag surface exhibited enhanced electrochemical CO<SUB>2</SUB> reduction activity. </LI> <LI> Surface analysis revealed that enhanced nanostructured Ag possess locally stable surface O. </LI> <LI> Surface O is suggested to contribute to COOH and CO intermediate interaction for CO<SUB>2</SUB> reduction. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
김윤재,Min Hyuk Lim,Byoungjun Jeon,최동현,Haeri Lee,정애진,Min Jung Kim,Ji Won Park,Ja-Lok Ku,Seung-Yong Jeong,Sang-Kyu Ye,Youdan Kim,KIMSUNGWAN 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.1
Gravity is omnipresent for all objects on Earth. However, in an environment of different gravitational stress (e.g., microgravity or partial gravity), cells and organs show different biological responses. So, researchers have attempted to achieve micro- or partial gravity on Earth through various approaches, such as parabolic flight or free fall. However, the duration of such ground experiments is highly limited, making it very difficult to conduct time-consuming tasks, such as cell culture. Thus, a three-dimensional (3D) clinostat is utilized as an alternative for experiments on the International Space Station. It provides time-averaged simulated micro- and partial gravity by using mechanical frames with two rotating actuators. This study proposes novel control algorithms for simulating micro- and partial gravity and validates them by applying it to the control of a manufactured 3D clinostat. First, the novel algorithm for time-averaged simulated microgravity (taSMG) provided a more uniformly distributed gravity field by reducing two poles the gravity-concentrated areas. The taSMG with reduced poles provides isotropic gravitational patterns, from which it is possible to minimize the unnecessary effect due to nonuniformity of the gravity vector direction. Second, the other suggested novel algorithm for time-averaged simulated partial gravity (taSPG) controls the pole sizes asymmetrically to generate the intended size of partial gravity. The suggested algorithms are based on mathematical models rather than totally randomized motions. Therefore, the convergence of gravity values, in the rotating frame over time, can be analytically predicted with improved accuracy compared with previously reported algorithms. The developed 3D clinostat hardware and algorithms will effectively provide well-validated taSMG and taSPG for cell growth experiments in future studies for space medicine.