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Yeonhee Kim,Moses Kang,Muljadi, Eduard,Jung-Wook Park,Yong Cheol Kang IEEE 2017 IEEE transactions on sustainable energy Vol.8 No.3
<P>This paper proposes a power-smoothing scheme for a variable-speed wind turbine generator (WTG) that can smooth out the WTG's fluctuating power caused by varying wind speeds, and thereby keep the system frequency within a narrow range. The proposed scheme employs an additional loop based on the system frequency deviation that operates in conjunction with the maximum power point tracking (MPPT) control loop. Unlike the conventional, fixed-gain scheme, its control gain is modified with the rotor speed. In the proposed scheme, the control gain is determined by considering the ratio of the output of the additional loop to that of the MPPT loop. To improve the contribution of the scheme toward maintaining the frequency while ensuring the stable operation of WTGs, in the low rotor speed region, the ratio is set to be proportional to the rotor speed; in the high rotor speed region, the ratio remains constant. The performance of the proposed scheme is investigated under varying wind conditions for the IEEE 14-bus system. The simulation results demonstrate that the scheme successfully operates regardless of the output power fluctuation of a WTG by adjusting the gain with the rotor speed, and thereby improves the frequency-regulating capability of a WTG.</P>
Production of 3-Hydroxypropionic acid from Acetate by Metabolically Engineered Escherichia coli
( Yeonhee Kim ),( Sivachandiran S ),( Sunghoon Park ) 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
Acetate, a major unwanted byproduct of industrial biological production and of lignocellulosic biomass hydrolysate, could have a great potential to be very cost-effective and alternative carbon source in the production of platform chemicals. Here we engineered Escherichia coli strain for 3-hydroxypropionic acid (3-HP) production from acetate. Several strategies of metabolic engineering including the disruption Acetyl-CoA competing pathways, blockage of glyoxylate shunt, improvement of cofactor (i.e., NADPH) supply, and redirection of the gluconeogenesis pathway were employed. Resting cell was adopted in acetate for the conversion of acetate to 3-HP, and the highest yield 0.16 mol/mol, about 32% of maximum theoretical yield was observed with the engineered producing strain.
Kim, Minjung,Lee, Jihye,Kim, Haidong,Lee, Kang-Bong,Lee, Yeonhee American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.10
<P>Chalcopyrite Cu(In,Ga)Se-2 (CIGS) semiconductor films are important as next generation solar cell materials and have great potential for use in device applications, especially for fabricating high-efficiency solar cells with practically no degradation of the absorber layer. In order to understand the physical properties of the CIGS films, the CIGS absorber layers have been characterized by many research groups so that the solar cell efficiencies could be further improved and theoretical efficiencies could be approached as far as practicable. To improve the efficiency of CIGS solar cells, a quantitative and depth-resolved elemental analysis of photovoltaic thin films is strongly required. In this work, using a three-stage evaporation process, different CIGS thin films were prepared on molybdenum back contacts deposited on soda-lime glass substrates. Surface analyses via XPS and SIMS were performed to characterize the CIGS thin films and compare their compositional distribution according to the depth. The average concentrations of the matrix elements, Cu, In, Ga, and Se were compared with the quantitative results of ICP-AES and EPMA. To identify the impurities in the CIGS layer, distributions of trace elements were also observed, according to the depth, by SIMS. Using SEM and TEM, we carried out detailed microstructural studies in cross-sections of CIGS thin film solar cells that had different cell efficiencies. The elemental composition, impurity distribution, and microstructure of the CIGS thin film solar cells were investigated to understand their effects on the solar cell conversion efficiency.</P>
Resistant Mechanism of Escherichia coli to HK 3140 - a New Fluoroquinolone
Yeonhee Lee,Sonduk Lee,Myung Hwan Park,Taeseuk Lee,Jaedu Ha,Jae Yang Kong Wan Joo Kim 생화학분자생물학회 1993 BMB Reports Vol.26 No.4
In our study, the resistant mechanism of Escherichia coli to a new fluoroquinolone-HK3140 (Kim et al., 1991) was characterized. In the presence of carbonylcyanide m-chlorophenyl hydrozone (CCCP), HK3140 uptake was increased and in vivo DNA synthesis was inhibited. This result suggested that both susceptible and resistant strains have efflux systems which are proton gradient dependent. The resistant strain had another efflux system which was ATPase dependent. DNA synthesis of the permeabilized resistant cells was less inhibited by HK3140 than that of the permeabilized susceptible cells. Results suggested that the resistant mechanism against HK3140 came from an ATPase dependent efflux system and changes in DNA gyrase and porin proteins (Lee et al., 1992).
Beyond 70 Years of Armed Peace - Korea Peace Now!
Yeonhee Sophie Kim 통일연구원 2020 International journal of korean unification studie Vol.29 No.1
Korea Peace Now! Women Mobilizing to End the Korean War is a transnational campaign led by four women’s peace organizations calling for the formal end to the Korean War with a peace agreement. These four organizations – Women Cross DMZ, Nobel Women’s Initiative, Women’s International League for Peace and Freedom (WILPF) and Korean Women’s Movement for Peace – are focused on changing policy in the United States, at the United Nations, and key countries, including Canada and South Korea. Women Cross DMZ is leading efforts in the United States and the key organization leading the U.S.-based Korea Peace Now Grassroots Network (KPNGN). As a regional coordinator for one of the eleven regional chapters of the KPNGN, I will examine the way the campaign actualizes, in theory and in practice, a feminist approach to its peace work in the United States. This paper seeks to present the KPNGN as a critical part of the growing peace agenda mobilizing to shape U.S. foreign policy towards North Korea. The paper will identify the practices and tactics of Korea Peace Now! which, I argue, places the movement in the tradition of feminist peace movements. My analysis draws on the intellectual framework developed in Feminist Security Studies (FSS) and Feminist Transitional Justice (FTJ). I argue that feminist peacebuilding is meaningful and important in the context of imagining a recuperative future on the Korean Peninsula.