A Study on the YBCO-Coated Conductor Current Lead With Asymmetric Structure Tape Considering Temperature Distribution

Seokho Nam,Woo Seung Lee,Jeyull Lee,Haeryoung Jeon,Seunghak Han,Yojong Choi,Jiho Lee,Tae Kuk Ko Institute of Electrical and Electronics Engineers 2017 IEEE transactions on applied superconductivity Vol.27 No.4

<P>A current lead is a connecting device between the superconducting magnet and the power supply. A large amount of heat transfer ocurrs through the current lead because the cold-end in a superconducting system is thermally linked with the warm-end part. Therefore, high-Tc superconductor (HTS) is used in the current lead for a tokamak system. However, it is hard to consider the dependance of HTS's critical current with respect to temperature because the conventional HTS current leads consist of the HTS tapes with the same width and thickness, and their critical currents can differ from their temperature. For this reason, cold-end of the HTS section in current lead is designed excessively than necessary specifications. This generates the additional heat transfer between cold-end and warm-end within the HTS current lead. In this paper, a study on the HTS current leads with asymmetric structure is conducted to reduce the heat transfer by reducing the cross-sectional area of the HTS current lead. Asymmetric current leads are fabricated considering the design parameters about heat transfer within the HTS current lead. Current transporting tests on the conventional, symmetrical, and asymmetrical HTS current leads are performed to confirm the feasibility of the suggested design. And then, heat load of the asymmetric current lead is compared with the symmetric current lead. From this study, it is found that heat load of the current lead is reduced by using the asymmetric HTS current lead.</P>

Conceptual Design of Current Leads for 154 kV SFCLs

Seokho Nam,Jin Bae Na,Hyoungku Kang IEEE 2012 IEEE transactions on applied superconductivity Vol.22 No.3

<P>Study of the dielectric characteristics on gaseous insulation media is important for designing and developing current leads of superconducting machines with a sub-cooled cooling method. In the case of using a sub-cooled N<SUB>2</SUB> cooling method, a gaseous insulation medium, such as He, Ne, SF<SUB>6</SUB>, CF<SUB>4</SUB>, or N<SUB>2</SUB>, should be injected to control the pressure and enhance the dielectric performance of current leads simultaneously. In this study, dielectric experiments on various gaseous insulation media are conducted and experimental results are analysed by considering field utilization factors. In addition, the functional equations are derived from experimental results and computational analyses. It is found that the dielectric characteristics of gaseous insulation media are determined by the maximum electric field intensity at sparkover voltage. This denotes that the electrical breakdown voltage of insulation gas could be estimated using deduced functional equations. Finally, the conceptual electrical insulation designs of current leads for a superconducting apparatus according to various insulation media are presented and the results are compared. The results may be applied to develop and commercialize a high voltage superconducting apparatus using a sub-cooled N<SUB>2</SUB> cooling method.</P>

A numerical study on the feasibility evaluation of a hybrid type superconducting fault current limiter applying thyristors

Seokho Nam,Woo Seung Lee,Jiho Lee,Young Jin Hwang,Tae Kuk Ko 한국초전도저온학회 (구 한국초전도저온공학회) 2013 한국초전도저온공학회논문지 Vol.15 No.4

Operational Characteristics of a Small-Scale Novel Hybrid Resistive-Type SFCL With Controlled Power Electronics

Nam, Seokho,Lee, Jiho,Lee, Woo Seung,Park, Young Gun,Song, Seunghyun,Jin, Hongwoo,Ko, Tae Kuk Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3

<P>As electric power systems become more complicated, the fault current experiences more frequent changes. To solve this problem, we suggest a novel hybrid-type superconducting fault current limiter (SFCL). Some issues accompany application of resistive-type SFCLs to electric power systems, including initial installation price, operation and maintenance costs, and high-current problems. To overcome these problems, <I>hybrid SFCLs </I> have been developed in some institutions. This paper presents experimental tests of a novel hybrid-type SFCL composed of a resistive superconducting coil, two thyristors, and a control circuit. The superconducting coil limits the first peak of the fault current, and the thyristors control the magnitude of the fault current other than the first peak by adjusting the firing angles. The interactions between the superconducting coil and the thyristors reduce the use of superconducting wire.</P>

사이리스터로 조절되는 초전도 한류기의 전류제한특성 연구

남석호(Seokho Nam),이우승(Woo Seung Lee),이지호(Jiho Lee),박영건(Young Gun Park),고태국(Tae Kuk Ko) 대한전기학회 2014 대한전기학회 학술대회 논문집 Vol.2014 No.10

Delay and Throughput Performance of Uncompressed Video Streaming Service in mmWave WPAN

Seokho Kim,Xizhi An,Saurabh N. Mehta,Sangkyoon Nam,Yongsun Kim,KyungSup Kwak 대한전자공학회 2008 ICEIC:International Conference on Electronics, Inf Vol.1 No.1

Existing WPAN solutions (IEEE 802.11 a/b/g, UWB) only have limited bandwidth and cannot support uncompressed video transmission. Instead, 60㎓ millimeter-wave(mmWave) band is an attracting method because it can provide huge bandwidth and achieve very high data rate(over 3Gbps). In this paper, we present the comparison of different superframe sizes in terms of delay and throughput for uncompressed video streaming in mmWave WPANs. We use the Constant Bit Rate (CBR) model to emulate the 1080p (30f 20b) video streaming. For simplification, we assume that an error-free PHY wireless channel is adopted. Simulation results show that the superframe size of 1/60s can result in better performance than that of 2㎳ for the uncompressed video service in mmWave WPAN. It is necessary to increase superframe size and use aggregation method, in order to achieve high throughput.

Crystal Structure of LysB4, an Endolysin from Bacillus cereus-Targeting Bacteriophage B4

Hong, Seokho,Son, Bokyung,Ryu, Sangryeol,Ha, Nam-Chul Korean Society for Molecular and Cellular Biology 2019 Molecules and cells Vol.42 No.1

Endolysins are bacteriophage-derived enzymes that hydrolyze the peptidoglycan of host bacteria. Endolysins are considered to be promising tools for the control of pathogenic bacteria. LysB4 is an endolysin produced by Bacillus cereus-infecting bacteriophage B4, and consists of an N-terminal enzymatic active domain (EAD) and a C-terminal cell wall binding domain (CBD). LysB4 was discovered for the first time as an L-alanoyl-D-glutamate endopeptidase with the ability to breakdown the peptidoglycan among B. cereus-infecting phages. To understand the activity of LysB4 at the molecular level, this study determined the X-ray crystal structure of the LysB4 EAD, using the full-length LysB4 endolysin. The LysB4 EAD has an active site that is typical of LAS-type enzymes, where $Zn^{2+}$ is tetrahedrally coordinated by three amino acid residues and one water molecule. Mutational studies identified essential residues that are involved in lytic activity. Based on the structural and biochemical information about LysB4, we suggest a ligand-docking model and a putative endopeptidase mechanism for the LysB4 EAD. These suggestions add insight into the molecular mechanism of the endolysin LysB4 in B. cereus-infecting phages.

독거노인의 자살에 관한 체계적 문헌고찰

남혜진(Nam, Hyejin),장은하(Jang, Eunha),홍석호(Hong, Seokho) 한국노인복지학회 2021 노인복지연구 Vol.76 No.2

본 연구는 독거노인의 자살에 관한 체계적 문헌고찰 연구 방법을 사용하여 국내 연구 동향을 살피고 후속연구 및 실천적 함의를 도출하고자 하였다. 이를 위하여 KISS, e-article, KCI, RISS 4개의 웹 데이터베이스에 독거노인 자살을 키워드로 조합하여 2021년 2월 24일까지 게재된 국내 학술지 792건의 논문을 검색하였다. 중복된 문헌 및 회색 문헌을 제외하고, 관련 키워드 중심으로 초록과 전문검토를 거쳐 최종적으로 55건의 문헌을 분석하였다. 연구결과 첫째, 독거노인의 자살과 관련된 연구는 여러 학술지에서 활발히 게재되고 있다. 연구대상자의 경우 여성 독거노인의 비율이 높았으며, 70대가 가장 많은 비중을 차지했다. 둘째, 분석문헌에서 자살 유형 중 자살 생각, 자살시도, 자살 경향성을 주로 다루고 있으며, 그중 자살 생각을 다룬 문헌의 비중이 가장 높았다. 셋째, 독거노인의 자살 관련 변인으로 인구학적 변인, 건강상태 및 건강 행동 변인, 심리·정서적 변인, 사회·환경적 변인으로 구분하여 살펴보았다. 인구학적 변인을 제외하고 심리·정서적 변인의 우울과 사회·환경적 변인의 사회적 지지에 대한 분석 빈도가 높았으며, 대부분의 연구에서 독거노인의 우울감이 높을수록 또는 사회적 지지가 낮을수록 자살위험이 높게 나타나는 결과를 확인하였다. 이러한 결과를 바탕으로 후속연구 및 실천적 개입에 대한 함의를 제시하였다. The purpose of this study was to examine domestic research trends and to derive follow-up research and practical implications by using a systematic literature review on suicide of the elderly people living alone. Based on four web databases, KISS, e-article, KCI, and RISS, 792 articles published by February 24, 2021 were searched by combining key words, suicide, and the elderly living alone. A number of 55 articles were finally analyzed through abstract and full-text review focusing on related keywords after excluding overlapping papers and gray literature. As results, it was found that studies related to suicide of the elderly living alone are actively published in various academic journals. Regarding the study subjects, the proportion of female elderly living alone was higher than the male, and the elderly in seventies were studied the most. Second, the literature mainly deals with suicidal thoughts, suicidal attempts, and suicidal tendencies in suicide concepts. Third, the suicide-related variables of the elderly living alone were classified into demographic variables, health status and health behavior variables, psychological and emotional variables, and social and environmental variables. The frequency of depression in the psychological and emotional variables and social support in the social and environmental variables was high. Also, in most studies, the higher the depression or the lower social support of the elderly living alone, the higher the suicide risk was confirmed. Based on these results, implications for follow-up research and practical intervention were suggested.

Structure-based protein engineering of bacterial β-xylosidase to increase the production yield of xylobiose from xylose

Hong, Seokho,Kyung, Myungok,Jo, Inseong,Kim, Yong-Ro,Ha, Nam-Chul Elsevier 2018 Biochemical and biophysical research communication Vol.501 No.3

<P><B>Abstract</B></P> <P>Xylobiose consists of two molecules of xylose and has been highly recognized as a food supplement because it possesses high prebiotic functions. β-xylosidase exhibits enzymatic activity to hydrolyze xylobiose, and the enzyme can also catalyze the reverse reaction in the presence of high concentrations of xylose. Previously, β-xylosidase from <I>Bacillus pumilus</I> IPO (BpXynB), belonging to GH family 43, was employed to produce xylobiose from xylose. To improve the enzymatic efficiency, this study determined the high-resolution structure of BpXynB in a complex with xylobiose and engineered BpXynB based on the structures. The structure of BpXynB deciphered the residues involved in the recognition of the xylobiose. A site-directed mutation at the residue for xylobiose recognition increased the yield of xylobiose by 20% compared to a similar activity of the wild type enzyme. The complex structure of the mutant enzyme and xylobiose provided the structural basis for a higher yield of the engineered protein. This engineered enzyme would enable a higher economic production of xylobiose, and a similar engineering strategy could be applied within the same family of enzymes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The crystal structures of β-xylosidase from <I>Bacillus pumilus</I> in complex with xylobiose were determined. </LI> <LI> β-xylosidase was engineered to increase the yield of xylobiose based on the determined structures. </LI> <LI> The protein engineering strategy used in this study could be applied within the same family of enzymes. </LI> </UL> </P>

표준형 선형계획과 공정계획을 위한 흡필드형 신경회로

張錫浩(Seokho Chang),南副熙(Boo-Hee Nam) 대한전기학회 1994 전기학회논문지 Vol.43 No.8