Stable poly(methyl methacrylate-co-divinylbenzene) microspheres via precipitation polymerization

Yang, Sunhye,Shim, Sang Eun,Choe, Soonja Wiley Subscription Services, Inc., A Wiley Company 2005 Journal of polymer science Part A, Polymer chemist Vol.43 No.6

<B>Graphic Abstract</B> <P>Stable poly(MMA-co-DVB) microspheres were prepared by precipitation polymerization using acetonitrile as the main medium under various polymerization conditions including monomer and initiator concentrations. <img src='wiley_img/0887624X-2005-43-6-POLA20417-gra001.gif' alt='wiley_img/0887624X-2005-43-6-POLA20417-gra001'> </P>

Enhanced specific capacitance of modified needle cokes by controlling oxidation treatment

Yang, Sunhye,Kim, Ick-Jun,Choi, In-Sik,Soo Kim, Hyun,Tack Kim, Yu Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139

<P>The electric double-layer performance of needle cokes can be affected by the morphology of structures. Hence, we introduce modified needle cokes by using simple oxidation treatment. The degree of graphitization with high specific capacitance is controlled by acid and heat treatment. The active sites of cokes are increased with increasing oxidation time. Dilute nitric acid (HNO<SUB>3</SUB>) and sodium chlorate (NaClO<SUB>3</SUB>) are used for the activation of cokes. In this case, the interlayer distance is dramatically increased from 3.5 to 8.9 Å. The specific capacitances are 33 F g<SUP>−1</SUP> and 30 F ml<SUP>−1</SUP>, respectively, on a two-electrode system with a potential range of 0–2.5 V. The behaviors of double-layer capacitance are demonstrated by the charge–discharge process and the morphologies of modified needle cokes are analyzed by XRD, FE-SEM, BET and elemental analysis.</P>

Influence of electrolytes (TEABF4 and TEMABF4) on electrochemical performance of graphite oxide derived from needle coke.

Yang, Sunhye,Kim, Ick-Jun,Choi, In-Sik,Bae, Mi-Kyeong,Kim, Hyun-Soo American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.5

<P>The structure of needle coke was changed to graphite oxide structure after oxidation treatment with 70 wt.% of nitric acid and sodium chlorate (NaClO3), and the inter-layer distance of the oxidized needle coke was expanded to 6.9 angstroms. The first charge profile of the oxidized needle coke-cell with 1.2 M TEMABF4/acetonitrile solution displayed that the intercalation of electrolyte ions into the inter-layer occurred at 1.0 V, which value is lower than 1.3 V of the oxidized needle coke-cell with 1.2 M TEABF4/acetonitrile solution. After first charge/discharge, the cell using TEMABF4 electrolyte exhibited smaller electrode resistance of 0.05 omega, and larger specific volume capacitance of 25.5 F/ml at the two-electrode system in the potential range 0-2.5 V than those of the cell using TEABF4 electrolyte. Compared to the TEABF4 electrolyte, better electrochemical performance of the TEMABF4 electrolyte in the oxidized needle coke may be caused by the smaller cation (TEMA+) size and better ion mobility in the nanopores between inter-layers.</P>

Aggregation behavior of carborane-poly(ethylene glycol) complexes at the air- water interface

Sunhye Kim,Jingying Yang,Chi Wu,Daewon Sohn 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

근거이론에 기초한 인도주의 리더십 실천 경험에 대한 다면적 영향요인 분석

궁선혜(Sunhye Kung),오인수(Insoo Oh),반지윤(Jiyoon Ban),양수연(Sooyeon Yang) 부산대학교 교육발전연구소 2021 교육혁신연구 Vol.31 No.3

연구목적: 본 연구의 목적은 인도주의 리더십 실천 경험의 핵심요소를 파악하고, 이에 영향을 미치는 인과적, 맥락적 요인들을 다면적으로 탐색하는 것이다. 연구방법: 국내 대표적 인도주의 기관에서 최소 10년 이상 재직한 11명의 관리자를 대상으로 초점질문 인터뷰를 실시, 이를 근거이론(Strauss & Corbin, 1998)으로 분석하였다. 연구결과: 자료분석 결과, 129개의 개념, 46개의 하위범주, 22개의 범주가 나타났고, 이를 기초로 인도주의 리더십 실천 경험에 대한 패러다임 모형을 개발하였다. 중심 현상은 3개의 범주(리스크 관리와 안정성 추구, 인도주의 실천의 노력, 인도주의 참여 및 실천 호소), 저해요인은 2개의 인과적 조건(기부금 중심의 재원, 낮은 사회적 후원)과 4개의 맥락적 조건(관료적 조직문화, 인도주의 리더십의 부족, 스트레스 및 정서적 소진, 취약한 평가체계). 촉진요인은 4개의 중재적 조건(인도주의 실천 참여 및 교육, 공감하고 지지하는 문화, 개방적 소통, 편견 없는 태도)과 4개의 작용/상호작용 전략(수평적 의사결정, 인도주의 비전에 대한 공감, 사회공익 사업 추진, 인도주의에 대한 소신과 헌신), 3개의 결과(벤치마킹 대상, 인도주의 가치 공유, 안정적 재원 및 자율적 의사결정체제)로 정리되었다. 논의 및 결론: 연구결과에 기초하여 인도주의 리더십 실천 경험과 영향요인들 간 관계를 분석하고, 한계점을 바탕으로 후속연구와 시사점을 논의하였다. Purpose: The purpose of this study is to explore key factors of humanitarian leadership experiences and their multifaceted influencing factors of causal and contextual conditions. Method: A grounded theory(Strauss & Corbin, 1998) was applied to analyze focus-group interviews with 11 participants having the least over 10-year of working experience in a representative humanitarian organization in Korea. Results: The in-depth analysis yielded 129 concepts, 46 subcategories, and 22 categories and a paradigm model explaining humanitarian leadership experiences was developed. Phenomena were three categories (risk management and the pursuit of stability, efforts of performing humanitarian leadership, and appeals to engage in and implement humanitarian activities); factors hindering humanitarian leadership consisted of two causal conditions (donation-based finances, weak social sponsorship) and four contextual conditions (bureaucratic organizational culture, lack of humanitarian leadership, job stress and emotional burnout, weak performance-oriented evaluation system); factors facilitating humanitarian leadership consisted of four intervening conditions (engagement in humanitarian leadership and humanitarian education, the culture based on empathy and support, open communication, and attitude without prejudice) and four action/reaction strategies (decentralized decision structure, empathy in humanitarian visions, the pursuit of public works, and the belief in and commitment to humanitarianism); and three results (becoming a benchmarking target, shared humanitarian values, secure finances and autonomous decision-making system) were analyzed. Conclusion: Based on results, humanitarian leadership experiences and influencing factors were analyzed and implications for humanitarian leadership experiences and suggestions for future research were discussed.

Iron Homeostasis and Energy Metabolism in Obesity

( Se Lin Kim ),( Sunhye Shin ),( Soo Jin Yang ) 한국임상영양학회 2022 Clinical Nutrition Research Vol.11 No.4

Iron plays a role in energy metabolism as a component of vital enzymes and electron transport chains (ETCs) for adenosine triphosphate (ATP) synthesis. The tricarboxylic acid (TCA) cycle and oxidative phosphorylation are crucial in generating ATP in mitochondria. At the mitochondria matrix, heme and iron-sulfur clusters are synthesized. Iron-sulfur cluster is a part of the aconitase in the TCA cycle and a functional or structural component of electron transfer proteins. Heme is the prosthetic group for cytochrome c, a principal component of the respiratory ETC. Regarding fat metabolism, iron regulates mitochondrial fat oxidation and affects the thermogenesis of brown adipose tissue (BAT). Thermogenesis is a process that increases energy expenditure, and BAT is a tissue that generates heat via mitochondrial fuel oxidation. Iron deficiency may impair mitochondrial fuel oxidation by inhibiting iron-containing molecules, leading to decreased energy expenditure. Although it is expected that impaired mitochondrial fuel oxidation may be restored by iron supplementation, its underlying mechanisms have not been clearly identified. Therefore, this review summarizes the current evidence on how iron regulates energy metabolism considering the TCA cycle, oxidative phosphorylation, and thermogenesis. Additionally, we relate iron-mediated metabolic regulation to obesity and obesity-related complications.

개념도 방법을 활용한 인도주의 리더십 개념 분석

오인수(Insoo Oh),궁선혜(Sunhye Kung),반지윤(Jiyoon Ban),양수연(Sooyeon Yang) 연세대학교 교육연구소 2021 미래교육학연구 Vol.34 No.3

본 연구는 인도주의 리더십을 실천하고 있는 현장의 인도주의 리더를 대상으로 이들이 생각하는 인 도주의 리더십의 개념을 개념도 분석 방법으로 탐색하고자 하였다. 이를 위해 인도주의를 실천하는 기관의 실무경력이 10년 이상이면서 중간관리자급 이상의 직급인 연구참여자 11명을 대상으로 개 별·집단 인터뷰를 실시하였다. 개념도 분석 절차에 따라 인도주의에 대한 150개의 개념 진술문을 도 출한 후 46개의 핵심 진술문을 최종 확정하였다. 확정된 진술문에 대해 인터뷰참여자 11명을 포함 한 총 30명을 대상으로 진술문 유사성 분류작업을 수행하고 다차원 척도법과 위계적 군집분석을 사 용하여 2차원(조직적-심리적 차원, 개인외적-개인내적 요인 차원)의 개념도가 도출되었다. 최종 8개 의 개념 군집이 확인되었으며, 46개의 진술문에 대한 중요도와 수행도를 평정하여 비교하였다. 본 연구는 인도주의의 중요성이 재조명되는 시점에서 그 개념을 최초로 실증적 방법으로 탐색한 점에서 의의를 지닌다. The purpose of this research was to explore the concept of humanitarian leadership recognized by humanitarian leaders who conduct humanitarian leadership in practices by using concept mapping analyzing method. In this research, 11 participants having over 10 years work experiences and ranked over mid-levels in a humanitarian organization were interviewed individually or as a group. 46 focal statements were confirmed from 150 extracted outcome statements. 30 participants including 11 interview participants sorted 46 focal statements by similarity and rated their importance and performance. Using multidimensional scaling and hierarchical cluster analysis, a concept map of humanitarian leadership constructed two dimensions(organizational-psychological dimensions, intra-personal and inter-personal factors) and eight clusters. It is significant to explore the concept of humanitarian leadership for the first time using empirical methods.

A visible-light-sensitive siloxene-based composite material with enhanced photocatalytic activity

Kang, Hyeo Ji,Lee, Sunhye,Jung, Hyuk Joon,Yang, Hee Jung,Lee, Kyu Hyung,Hur, Nam Hwi Elsevier 2018 Journal of photochemistry and photobiology Chemist Vol.365 No.-

<P><B>Abstract</B></P> <P>A novel layer-stacking approach that produces a layered composite of siloxene and reduced graphene oxide (RGO) sheets is presented. This method is based on the assembly of siloxene and graphene oxide sheets, followed by reduction at low temperature using solid hydrazine. High-resolution transmission electron microscopy reveals that the resulting siloxene-RGO composite has a layered structure with sheets that appear to be alternately stacked in a face-to-face fashion. This composite exhibits excellent photocatalytic activity under visible-light irradiation, with a photocurrent density that is about 40 times higher than that of the siloxene sheets alone. It is evident that the RGO sheets stacked on the siloxene surfaces are the key elements that increase the photocatalytic activity of the layered composite. This layer-stacking approach enhances siloxene properties in many ways, rendering ample opportunities for the development of new siloxene-based composite materials with novel functionalities.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new siloxene-reduced graphene oxide (RGO) composite was synthesized by a layer-by-layer approach. </LI> <LI> The assembly of siloxene and graphene oxide sheets was reduced at low temperature by solid hydrazine. </LI> <LI> The siloxene-RGO composite has a layered structure that is alternately stacked in a face-to-face fashion. </LI> <LI> The photocurrent density produced by the composite is about 40 times higher than that of siloxene sheets alone. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>A visible-light-sensitive layered siloxene-RGO composite was synthesized by the low-temperature reduction of a siloxene-GO composite with solid hydrazine.</P> <P>[DISPLAY OMISSION]</P>

Influence of graphite size on the synthesis and reduction of graphite oxides

Tran, Minh-Hai,Yang, Cheol-Soo,Yang, Sunhye,Kim, Ick-Jun,Jeong, Hae Kyung Elsevier 2014 Current Applied Physics Vol.14 No.1

We investigated the influence of the precursor, graphite, size on the synthesis and reduction of graphite oxide. Three precursors of graphite with different size were used to synthesize the graphite oxide which was consecutively reduced by hydrazine of different concentration ratios. Size dependent effect on the reduction of the graphite oxide was found, and the graphite oxide of the smallest size provided the best reduction result. Electrochemical properties of the reduced graphene oxide were investigated in both of the base and acid electrolytes, finding the reduced graphene oxide of the smallest size gives the best electrochemical performance due to the high reduction. Therefore, the precursor size is a very important factor in the synthesis and reduction of graphite oxide, affecting the electrochemical performance considerably for the energy storage applications. (C) 2013 Elsevier B.V. All rights reserved.

Changes in mental health of Korean adolescents before and during the COVID-19 pandemic: a special report using the Korea Youth Risk Behavior Survey

Bomi Park,Jihee Kim,Jieun Yang,Sunhye Choi,Kyungwon Oh 한국역학회 2022 Epidemiology and Health Vol.45 No.-

OBJECTIVES: We aimed to study the effects of the coronavirus disease 2019 (COVID-19) pandemic on adolescents’ mental health in Korea. METHODS: We used data from the Korea Youth Risk Behavior Survey 2018-2021 with 227,139 students aged 12-18 years. We estimated the differences in depressive symptoms, suicidal ideation, and stress perception before (2018-2019) and during (2020-2021) the pandemic, as well as before (2019), the first year (2020) of, and the second year (2021) of the pandemic. We also examined whether COVID-19 is statistically associated with mental health. RESULTS: In both male and female adolescents, the prevalence of depressive symptoms, suicidal ideation, and stress perception was higher in the “not living with family,” “low household economic status,” and “self-rated unhealthy status” subgroups. The prevalence of depressive symptoms and stress perception was higher in middle school students. Adolescents were less likely to experience depressive symptoms (adjusted odds ratio [aOR], 0.86; 95% confidence interval [CI], 0.83 to 0.89), suicidal ideation (aOR, 0.80; 95% CI, 0.76 to 0.83), and stress perception (aOR, 0.76; 95% CI, 0.74 to 0.79) in 2020 than in 2019. However, there were more depressive symptoms (aOR, 1.06; 95% CI, 1.02 to 1.09), suicidal ideation (aOR, 1.15; 95% CI, 1.10 to 1.21), and stress perception (aOR, 1.19; 95% CI, 1.16 to 1.23) in 2021 than in 2020. CONCLUSIONS: The COVID-19 pandemic had positive impacts on mental health of adolescents in its early stages but has had negative impacts as the pandemic continues. Attention should be paid to adolescents who are particularly vulnerable to the mental health effects of the pandemic.