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Namwon Kim,Gyeong-Hun Kim,Kwang-Min Kim,Minwon Park,In-Keun Yu,Sangjin Lee,Song, E.,Tae-Won Kim IEEE 2012 IEEE transactions on applied superconductivity Vol.22 No.3
<P>In order to improve the efficiency of wind power generation system (WPGS), many researchers have tried to develop a larger WPGS and a superconducting synchronous generator (SCSG) has been suggested to develop over 5 MW class WPGS. There are two expected types of drive-train, geared and gearless. The structure and electrical parameters of the SCSG depend on the type of drive-train used. This paper deals with a comparative analysis of the 10 MW class geared and gearless types of the SCSG for WPGS. Three drive-trains are designed for the 10 MW class SCSGs using the finite elements method analysis tool. The PSCAD/EMTDC is utilized to simulate electrical and dynamic behaviors of the modeled SCSGs. The simulation results show the operation characteristics of the designed SCSGs and suggest that the single-stage gearbox type drive-train is the most efficient drive-train for the SCSG due to the reduction of the number of rotor poles and the volume of the generator, even though the geared-type drive-train requires periodical maintenance.</P>
Design of a back-to-back converter to simulate transient state of renewable sources
김남원(Namwon Kim),김상용(Sang-Yong Kim),이효근(Hyo-Guen Lee),황철상(Chulsang Hwang),김경훈(Gyeong-Hun Kim),서효룡(Hyo-Ryong Seo),박민원(Minwon Park),유인근(In-Keun Yu) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7
This paper describes a design of grid-simulator for experiment of transient stability of grid-connected renewable energy system. A transient analysis of renewable energy system has been researched by a simulation, because direct connection of renewable energy system and real utility is dangerous and it is hard to produce the transient grid condition. If a grid-simulator is used in the transient stability experiment, the transient grid condition might be generated easily with reference data and there is no impact on the grid. The grid-simulator composed of a back-to-back converter was designed and simulated with PSCAD/EMTDC to verify its operational characteristics.
Real time simulation and analysis techniques for Jeju power system using RTDS
김경훈(Gyeong-Hun Kim),김진근(Jin-Guen Kim),이효근(Hyo-Guen Lee),김남원(Namwon Kim),황철상(ChulSang Hwang),김상용(Sang-Yong Kim),서효룡(Hyo-Rong Seo),배형택(Hyeong-Teak Bae),박정도(Jung-Do Park),이동영(Dong-Young Yi),이상진(Sangjin L 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7
A new high voltage direct current (HVDC) system from Jindo-to-Seojeju and 80 ㎿ wind farms will be installed in Jeju-island in the near future. The real time simulation for Jeju power system is needed for analysing newly installed systems in advance. This paper provides real time simulation techniques for Jeju power system using a real time digital simulator (RTDS). Simulation results show the frequency and power output variations under variable wind speed patterns of each wind farm.
Namwon Kim,Chondon Roy,Robert Cox,Babak Parkhideh 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper presents the development of a plugand-play (P&P) power electronics education board designed to build a hands-on power electronics lab incorporating widebandgap (WBG) semiconductor switches and circuits. The developed education board adopts modular architecture and P&P concept to allow students to construct various power electronics experiment setups and handle different semiconductor devices such as Si-based and WBG devices. By inserting the modular daughter boards and completing system connections on the motherboard, various lab experiments can be conducted; from switching characteristic analysis of different semiconductor devices to control of different power converters such as basic DC-DC and DC-AC converters and isolation-type DC-DC converters. This helps students to get familiar with the system/subsystem-level design of power converters and experience the impact of WBG devices compared to Si-based one. The system design considerations are discussed, and the fabricated hardware and its experiments are presented.
Mechanical properties of two-dimensional materials and their applications
Kim, Jong Hun,Jeong, Jae Hwan,Kim, Namwon,Joshi, Rakesh,Lee, Gwan-Hyoung IOP 2019 Journal of Physics. D, Applied Physics Vol.52 No.8
<P>The mechanical properties of materials are not only indispensable key factors in their application fields, but are also fundamentally important in terms of materials science. Since the successful isolation of graphene with an atomic thickness, two-dimensional (2D) materials have attracted enormous attention over the past decade due to their unique properties. In particular, 2D materials are of interest owing to their outstanding mechanical properties, such as high Young’s modulus and strength, despite their ultrathinness and low weight in comparison to their bulk counterparts. However, studies on the mechanical properties of various 2D materials have been limited, with the exception of graphene, leaving many open questions and challenges. In this article, recent empirical and theoretical advances in studies of the mechanical properties of 2D materials and their applications are reviewed. First, mechanical characterization methods, which are widely used for ultrathin membranes, are summarized. The effects of defects on the mechanical properties of 2D materials are reviewed, including naturally (or intentionally) generated defects and chemically functionalized 2D materials. Finally, we discuss recent advances and the possibility of using 2D materials in diverse mechanical applications. The summary of the unique mechanical properties of 2D materials and their derivatives in this article would be beneficial for the study of 2D materials and their applications in lightweight, flexible, and transparent systems.</P>
소산입자동역학과 분자동역학을 이용한 3D 프린터용 PEEK 분말에 대한 온도에 따른 미시적 구조변화에 대한 연구
김남원(Namwon Kim),이태일(Taeil Yi) 한국기계가공학회 2018 한국기계가공학회지 Vol.17 No.5
3D printing technology and its applications have grown rapidly in academia and industry. We consider a 3D printing system designed for the selective laser sintering (SLS) method, which is one of the powder bed fusion (PBF) techniques to build up the final product by layering sintered powder slices. Thermal distortion of printing products is a critical challenge in 3D printing. This study investigates temperature-dependent conformational behaviors of 3D printed samples of sintered poly-ether-ether-ketone (PEEK) powders using molecular dynamics simulations. The wear and chemical resistance properties of PEEK are understood, as it is a well-known biocompatible material used for implants. However, studies on physical phenomena at nanoscale in PEEK are rarely published in public. We simulate dissipative particle dynamics to elucidate how a cavity regime forms in PEEK at different system temperatures. We demonstrate how PEEK structures deform subject to the system temperature distribution.
비열 유전체장벽방전 플라즈마의 포도상구균 및 대장균 살균효과
김기영 ( Keyyoung Kim ),백남원 ( Namwon Paik ),김용희 ( Yonghee Kim ),유관호 ( Kwanho Yoo ) 한국산업보건학회 (구 한국산업위생학회) 2018 한국산업보건학회지 Vol.28 No.1
Objectives: The objective of this study was to examine the effect of non-thermal dielectric barrier discharge (DBD) plasma on decontamination of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) as common pathogens. Methods: This experiment was carried out in a chamber (0.64m<sup>3</sup>) designed by the authors. The plasma was continuously generated by a non-thermal DBD plasma generator (Model TB-300, Shinyoung Air tech, Korea). Suspensions of S. aureus and E. coli of 0.5 McFarland standard (1.5 x10<sup>8</sup>CFU/mL) were prepared using a Densi-Check photometer (bio Merieux, France). The suspensions were diluted1:1000 in sterile PBS solutions (approximately10<sup>4-5</sup>CFU/mL) and inoculated on tryptic soy agar (TSA) in Petri dishes. The Petri dishes (80mm internal diameter) were exposed to the non -thermal DBD plasma in the chamber. Results: The results showed that 95% of S. aureus colonies were killed after a six-hour exposure to the DBD plasma. In the case of E. coli, it took two hours to kill 100% of the colonies. The gram-negative E. coli had a greater reduction than the gram-positive S. aureus. This difference may be due to the structure of their cell membranes. The thickness of gram-positive bacteria is greater than that of gram-negative bacteria. The S. aureus is more resistant to DBD plasma exposures than is E. coli. It should be noted that average concentrations of ozone, a byproduct of the DBD plasma generator, were monitored throughout the experiment and the results were well below the criteria, 50 ppb, recommended by the Korean Ministry of the Environment. Thus, non-thermal DBD plasma is deemed safe for use in hospital and public facilities. Conclusions: There was evidence that non-thermal DBD plasma can effectively kill S. aureus and E. coli. The results indicate that DBD plasma technology can greatly contribute to the control of infections in hospitals and other public and private facilities.
김상용(Sang-Yong Kim),김남원(Namwon Kim),황철상(Chulsang Hwang),이효근(Hyo-Guen Lee),김경훈(Gyeong-Hun Kim),서효룡(Hyo-Ryong Seo),박민원(Minwon Park),유인근(In-Keun Yu) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7
Converter per photovoltaic module (CPM) system has been researched to increase the efficiency of photovoltaic (PV) power generation system. The stability and efficiency of PV system might be different according to the connection structure of CPMs. Differences between series and parallel connection of CPMs for PV power generation system were analyzed in this paper. Boost type CPM was used to control maximum power of each PV module. CPMs were connected in series, and parallel to compare the PV output power according to the converter connection. More effective connection of CPMs is proposed by the simulation considering abnormal operation of converter of the PV system.