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Choi, Youngjun,Kim, Dongmin,Cho, Jeonwook,Sim, Kideok,Kim, Sungkyu,Kim, Seokho The Korea Institute of Applied Superconductivity a 2019 한국초전도저온공학회논문지 Vol.21 No.4
To reduce the fault current below the current capacity of a circuit breaker, researches on HTS (High Temperature Superconductor) power cables with fault current limiting (FCL) function are increasing. An FCL HTS power cable transports current with low a impedance during normal operation. Yet, it limits the fault current by an increased inductive or resistive impedance of conducting layer when quench occurs at the FCL HTS power cable by the large fault current. An inductive type FCL HTS power cable uses increased inductive impendence caused by leakage magnetic flux outside the cable core when the quench occurs at a shield layer losing the magnetic shielding effect. Therefore, it has an advantage of less resistive heating than resistive type FCL HTS power cable and temperature increase is suppressed. This paper describes an ideal circuit model for the FCL HTS power cable to investigate the effectiveness of increased inductive impedance when quench occurs at the shield layer. Then, FEM analysis is presented with a simplified model cable composed of various iron yokes to investigate the effect of the shape of yoke on the generation of the inductive impedance.
Choi, Jaepil,Kim, Youngwoo,Kang, Junekyung,Choi, Youngjun Architectural Institute of Japan 2014 JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEE Vol.13 No.3
<P> Though apartments are often criticized for their homogeneous nature, they are being actively adopted as an efficient method of providing houses for developing countries. In this paper, the authors argue whether such phenomenon can be seen simply as cultural identity giving in to internationalism. That is, apartments can indeed reflect locality within their spatial structure. To support this argument, apartment units from Korea, Vietnam, and Kazakhstan, three countries from dramatically different climate zones and cultural backgrounds, are analyzed. In doing so, Space Syntax, a quantitative analysis method widely used to interpret the cultural aspects embedded into a spatial structure is utilized. Each country's apartment units had different functions at the topological center, which should not be seen as a mere coincidence since they were consistent with the spatial characteristic found in their respective traditional houses. Therefore, it can be said that apartments, in their unit plans, do reflect locality, a direct contradiction to the general belief. </P>
Youngjun Choi,Seokho Kim 한국초전도저온학회 2023 한국초전도저온공학회논문지 Vol.25 No.2
Recently, interest in renewable energy such as solar and wind power has increased as an alternative to fossil fuels. Renewableenergy sources such as large wind farms require long-distance power transmission because they are located inland or offshore, farfrom the city where power is required. High-Temperature Superconducting (HTS) power cables have more than 5 times thetransmission capacity and less than one-tenth the transmission loss compared to the existing cables of the same size, enabling large-capacity transmission at low voltage. For commercialization of HTS power cables, unmanned operation and long-distance coolingtechnology of several kilometers is essential, and pressure drop characteristic is important. The cryostat's spiral corrugation tube iseasier to bend, but unlike the round tube, the pressure drop cannot be calculated using the Moody chart. In addition, it is moredifficult to predict the pressure drop characteristics due to the irregular surface roughness of the binder wound around the cablecore. In this paper, a CFD model of a spiral corrugation tube with a core was designed by referring to the water experiments fromprevious studies. In the four cases geometry, when the surface roughness of the core was 10mm, most errors were 15% and themaximum errors were 23%. These results will be used as a reference for the design of long-distance HTS power cables.
Subsidiary’s External Networkability as a Source of Competitive Advantage
Youngjun Choi,Dong-Sung Cho,Ki-Hwan Kwon 한국무역학회 2007 Journal of Korea trade Vol.11 No.1
This article focuses on the influence of a subsidiary’s capability to create and cultivate social capital in a host country or the external networkability of MNC’s subsidiary. We first identify the external networkability which is critical to build up social capital with other parties in the relational network, shifting the point of view about social capital from network level to firm level. Then, based on the identification, we examine why and how an MNC’s local subsidiary can successfully play their strategic roles by taking advantage of its external networkability. It is proposed that the differences between subsidiaries in the degree of gaining host country experience and technological learning can be explained by their different ability to create and manage the relationships with their external networks in that host country. This paper also explores how the types of MNCs moderate the relationships between the external networkability of its subsidiaries and organizational performances.
Youngjun Choi,Dongmin Kim,Jeonwook Cho,Kideok Sim,Sungkyu Kim,김석호 한국초전도.저온공학회 2019 한국초전도저온공학회논문지 Vol.21 No.4
To reduce the fault current below the current capacity of a circuit breaker, researches on HTS (High Temperature Superconductor) power cables with fault current limiting (FCL) function are increasing. An FCL HTS power cable transports current with low a impedance during normal operation. Yet, it limits the fault current by an increased inductive or resistive impedance of conducting layer when quench occurs at the FCL HTS power cable by the large fault current. An inductive type FCL HTS power cable uses increased inductive impendence caused by leakage magnetic flux outside the cable core when the quench occurs at a shield layer losing the magnetic shielding effect. Therefore, it has an advantage of less resistive heating than resistive type FCL HTS power cable and temperature increase is suppressed. This paper describes an ideal circuit model for the FCL HTS power cable to investigate the effectiveness of increased inductive impedance when quench occurs at the shield layer. Then, FEM analysis is presented with a simplified model cable composed of various iron yokes to investigate the effect of the shape of yoke on the generation of the inductive impedance.