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Seok-Beum Ko,Soo-Chang Yu,J. B. Hopkins Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.9
Picosecond time-resolved resonance Raman spectroscopy has been used to study the photochemistry of Cr(CO$)_6$ in cyclohexane following photoexcitation at 266 nm. Photodissociative loss of CO is found to occur within our pulse width of ${\leq}$5 ps by probing the 533 c$m^{-1}$ vibrational mode of ground state Cr(CO$)_6$. The subsequent dynamics after photodissociation are interpreted in terms of solvation, vibrational and electronic relaxations. The vibrational relaxation time of 100 ps and 83 ps are observed by monitoring v=O and v=l of the 381 c$m^{-1}$ transient mode, respectively. No evidence was found for solvation and electronic relaxation occurring on a time scale of ${\leq}$5 ps.
Seok-Min Kim,June-Seok Lee,Kyo-Beum Lee 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Most proposed methods for a fault-tolerant operation in many of studies are based on a phase-shifted PWM (PS-PWM) method. However these methods are not applied directly to multilevel inverter systems using a levelshifted PWM (LS-PWM). This paper focuses on faulttolerant operation for a cascaded multilevel inverter based on LS-PWM. During the occurrence of a single-inverter-cell fault, reconfiguration of the carrier bands scheme is implemented and modulation assignment of inverter cells is modified in this proposed fault-tolerant operation. It is possible to generate balanced three-phase line-to-line voltages and line currents with the proposed strategy when a device failure occurs in cascaded multilevel inverters using LS-PWM. The feasibility of the proposed method is proved by simulation results.
Seok-Kyoon Kim,June-Seok Lee,Kyo-Beum Lee Institute of Electrical and Electronics Engineers 2016 IEEE transactions on power electronics Vol. No.
<P>This paper proposes a speed-control law for a parametrically uncertain surface-mounted permanent magnet synchronous motor (SPMSM) using a multivariable approach, which robustly and optimally stabilizes the tracking error dynamics using only the lower and upper bounds of the SPMSM parameters. The contributions of this article are twofold. First, both the innerand outer-loop controllers are designed using a multivariable approach; the back-stepping controller design method ensures stability and the offset-free property. Second, it is shown that it is possible to systematically assign the robust global stabilizing control gains by solving an optimization problem. The efficacy of the proposed method is experimentally verified using a 3-kW SPMSM.</P>
SEPIC을 이용한 고역율 정류회로의 과도응답특성 개선
정석언(Seok-Eon Joung),이교범(Kyo-Beum Lee),현동석(Dong-Seok Hyun),송중호(Joong-Ho Song) 전력전자학회 2001 전력전자학술대회 논문집 Vol.2001 No.7
A pulse frequency control(PFM) method for single-phase SEPIC-type rectifier is described in this paper. In the SEPIC rectifier, a relationship between the output power and the respective switching frequency is investigated to establish the control scheme of PFM. The propsed control method is provided with a feed-forward control loop of the output load as well as a feed-back control loop of the output voltage. The simulation results show good dynamic responses and unity power-factor operation.
Kim, Seok-Min,Lee, June-Seok,Lee, Kyo-Beum Institute of Electrical and Electronics Engineers 2016 IEEE transactions on industrial electronics Vol.63 No.11
<P>To increase the fault tolerance for cascaded H-bridge multilevel inverters (CHMIs) based on level-shifted pulse width modulation (LS-PWM), a modified LS-PWM method is proposed for the inverters operating under faulty conditions. To cover both open-and short-device fault cases, two types of switching scheme are included in this PWM method. With this PWM method, the neutral shift can be applied as fault-tolerant control for CHMIs based on LS-PWM. Finally, three-phase-balanced line-to-line voltages and currents with minimum harmonic distortion are produced for the inverter with disabled power cells. In addition, this LS-PWM method has the capability to improve power distribution among the H-bridge power cells under the faulty conditions. Simulation and experimental results show that the proposed PWM method performs satisfactorily to achieve fault tolerance.</P>
Immunohistochemical detection of LOM strain viral antigens in suckling piglets in Jeju
Jae-Beum Kim(Jae-Beum Kim),Won-Gyu Cho(Won-Gyu Cho),Yun-Ho Kim(Yun-Ho Kim),Hyoung-Nam Jo(Hyoung-Nam Jo),Jae-Sung Heo(Jae-Sung Heo),Myeong-Won Suh(Myeong-Won Suh),Hyoung-Seok Yang(Hyoung-Seok Yang),Wan 한국예방수의학회 2019 한국예방수의학회 학술대회자료집 Vol.2018 No.-
Cascaded 멀티레벨 인버터의 고장 허용 제어를 위한 Level-Shifted PWM 기반의 새로운 변조 기법
김석민(Seok-Min Kim),이준석(June-Seok Lee),이교범(Kyo-Beum Lee) 대한전기학회 2015 전기학회논문지 Vol.64 No.5
This paper proposes a novel level-shifted PWM (LS-PWM) strategy for fault tolerant cascaded multilevel inverter. Most proposed fault-tolerant operation methods in many of studies are based on a phase-shifted PWM (PS-PWM) method. To apply these methods to multilevel inverter systems using LS-PWM, two additional steps will be implemented. During the occurrence of a single-inverter-cell fault, the carrier bands scheme is reconfigured and modulation levels of inverter cells are reassigned in this proposed fault-tolerant operation. The proposed strategy performs balanced three-phase line-to-line voltages and line currents when a switching device fault occurs in a cascaded multilevel inverter using LS-PWM. Simulation and experimental results are included in the paper to verify the proposed method.
Self-Tuning Adaptive Speed Controller for Permanent Magnet Synchronous Motor
Kim, Seok-Kyoon,Lee, June-Seok,Lee, Kyo-Beum Institute of Electrical and Electronics Engineers 2017 IEEE transactions on power electronics Vol. No.
<P>This paper presents a self-tuning speed control scheme for the surface-mounted permanent magnet synchronous motor (SPMSM) against parameter variations with the traditional vector control strategy. The proposed control strategy has three novelties; the first one is to design the inner-and outer-loop controllers to stabilize the current and speed dynamics with the self-tuning algorithm for a better transient performance, the second one is to give a systematic way to constitute a robust optimal control gain by solving an optimization problem, and the third one is to show that the proposed inner-loop controller also stabilizes the closed-loop system, including the first-order internal dynamics caused by the SPMSM speed. The efficacy of the proposed method was verified through experiments using a 3-kW SPMSM.</P>
Single‑loop order reduction output voltage control with model‑free filtering for DC/DC converters
Won Seok Jung,Seok-Kyoon Kim,Kyo-Beum Lee 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.11
This study devises an advanced single-loop output voltage control method for DC/DC converters incorporating a model-free filter, active damping, and nonlinearly designed feedback terms. The resultant output-feedback controller ensures the order reduction property and reduces both the dependence level of the system model and the number of feedback loops. There are two main features that differentiate this from extant results. First, a model-free first-order pole-zero cancellation (PZC) filter extracts the time derivative component from the output voltage measurement according to the first-order dynamics by the order reduction property without any converter model information. Second, an active damping controller forming a modified proportional-integral-derivative structure tracks the output voltage to its desired trajectory along the first-order low-pass filter dynamics by the order reduction property from the PZC, which is independent of the current feedback. Experimental evidence obtained from an actual feedback system adopting a 3-kW prototype DC/DC converter validates the effectiveness of the proposed technique, which demonstrates the capability of the current sensor fault tolerance.