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Hyeonmin Jeon,Jaejung Hur,Kyoungkuk Yoon 해양환경안전학회 2019 해양환경안전학회지 Vol.25 No.6
직류전동기는 속도제어가 간단하고, 출력 토크특성이 우수한 장점으로 윈치나 카고 펌프 모터 등으로 선박에서 많이 사용되었으며, 전기추진선박이 도입된 초기에는 선박용 추진전동기로도 적용되었다. 하지만 브러시와 정류기와 같은 기계적 정류장치의 단점으로 인해 최근에는 직류전동기와 전기적인 특성은 매우 유사하지만 기계적인 정류장치를 설치하지 않고 반도체 소자를 이용한 전자적인 정류장치를 사용하는 브러시리스 직류전동기의 사용이 증가하고 있다. 기존의 브러시리스 직류전동기를 구동하기 위한 인버터 시스템은 2 상여자방식을 사용하므로 역기전력파형이 사다리꼴모양으로 되며, 이로인해 전류가 흐르는 권선이 바뀌는 상전류 전환 구간에서 고조파와 토크리플이 발생하게 된다. 이러한 고조파와 토크리플을 저감하기 위한 다양한 방안이 연구되어 발표되었으며, 본 연구에서는 전력분 석프로그램을 이용하여 브러시리스 직류전동기의 구동회로에 비례적분 속도전류제어기 알고리즘을 구현한 Cascaded H-Bridge 멀티레벨 인버터를 적용하였다. 모델링한 브러시리스 직류전동기의 시뮬레이션을 통해 제안하는 전동기의 구동방식을 적용하는 경우에 기존의 구동방식에 비해 전동기 입력측 전압파형 개선과 고조파 및 토크리플이 현저히 저감되는 결과를 확인할 수 있었다. DC motors are used extensively on shipboard, including as the ship’s winch operating motor, owing to their simple speed control and excellent output torque characteristics. Moreover, they were used as propulsion motors in the early days of electric propulsion ships. However, mechanical rectifiers, such as brushes, used in DC motors have certain disadvantages. Hence, brushless DC (BLDC) motors are increasingly being used instead. While the electrical characteristics of both types of motors are similar, BLDC motors employ electronic rectifying devices, which use semiconductor elements, instead of mechanical rectifying devices. The inverter system for driving conventional BLDC motors uses a two-phase excitation method so that the waveform of the back electromotive force becomes trapezoidal. This causes harmonics and torque ripple in the phase current switching period in which the winding wire through which the current flows is changed. Researchers have studied and presented various methods to reduce the harmonics and torque ripple. This study applies a cascaded H-bridge multilevel inverter, which implements a proportional–integral speed current controller algorithm in the driving circuit of the BLDC motor for electric propulsion ships using a power analysis program. The simulation results of the modeled BLDC motor show that the driving method of the proposed BLDC motor improves the voltage waveform of the input side of the motor and remarkably reduces the harmonics and torque ripple compared with the conventional driving method.
A Study on Application of Electric Propulsion System using AFE Rectifier for Small Coastal Vessels
Hyeonmin Jeon,Jongsu Kim,Seongwan Kim 해양환경안전학회 2018 해양환경안전학회지 Vol.24 No.3
The small coastal vessel registered in Korea, small coastal vessels with a gross tonnage of 10 tons or less account for 94.6 % and among them, aged vessels over 16 years age indicate 40.6 %. In order to reduce GHG emissions from small coast vessels, discussions are underway to replace aging ships' propulsion units with eco - friendly propulsion facilities, and the electric propulsion ship is emerging as one of the measures. The electric propulsion system using the DFE rectifier, which was applied in the conventional large commercial vessel, was effective in reducing the harmonics and improving the DC output voltage of the DC link stage, but it occupied a large volume and caused an increase in the overall system price. Therefore, in this paper, we propose an electric propulsion system using AFE rectifier with a small volume of system that can be applied to a small coastal vessel. In order to analyze the effectiveness of the overall system, the load profile was applied to obtain accurate and rapid speed tracking performance of the propulsion motor affected by the speed load. In addition, the power factor and total harmonic distortion factor of the voltage and current on the improved power output side are derived through simulation.
Hyeonmin Park,Hyunji Ahn,Han Na Jang,Hyun-Jin Kim,Mi-Sun Yum,Tae-Sung Ko 대한소아신경학회 2019 대한소아신경학회지 Vol.27 No.3
Purpose: The aim of this study was to evaluate the efficacy and tolerability of perampanel as adjunctive therapy in childhood-onset refractory epilepsy. Methods: We retrospectively reviewed the medical records of 110 patients who were treated with perampanel in Asan Medical Center children’s hospital. Two patients with poor compliance were excluded and 108 patients were enrolled. The clinical characteristics were reviewed, and the total seizure frequency before and after the add-on of perampanel was analyzed. Results: The mean age of the patients (64 males) was 20.2 years (range, 10.5 to 35.6). The mean maintenance dose was 4.8 mg/day (2 to 10 mg). Eight patients (7.4%) achieved seizure freedom and 35 (32.4%) achieved a seizure reduction of ≥50%. Among them, three patients achieved seizure freedom with only 2 mg/day of perampanel. There was no significant difference in sex, age at seizure onset, duration of epilepsy, use of concomitant enzyme-inducing antiepileptic drugs, number of concomitant antiepileptic drugs, and adverse events between responders and non-responders. The retention rate was up to 68.0% in the first year and 59.5% in the second year of the study. Thirty-four patients (31.5%) reported adverse events: violence, somnolence, dizziness, drooling, weight gain, insomnia, and vomiting. There was no contributing factor for the adverse events, including sex, age, and the number of concomitant antiepileptic drugs and enzyme-inducing antiepileptic drugs when comparing the adverse event present group with the adverse event absent group. Conclusion: Low-dose perampanel showed reasonable efficacy and tolerability in patients with refractory childhood-onset epilepsy. Further validation with pharmacokinetic studies is needed.
노현민(Hyeonmin Ro),김동주(Dongju Kim) 한국정보기술학회 2021 Proceedings of KIIT Conference Vol.2021 No.11
옛 한글 특유의 국한문 혼용과 서체의 다양성 등 옛 한글의 판독 난이도가 높아 옛 한글 기록물에 대한 연구와 발굴이 어려움을 겪고 있다, 이에 한문, 현대 손글씨 OCR과는 차별 된 옛 한글 전용 글자 인식 기술의 필요성이 나타났으며, 이 논문에서는 기술 확보를 위한 데이터셋 구성과 글자체 인식 기술 개발방법을 제안하였다. Researches and exploration on Old Korean is having difficulty since its own features such as mixed use of Korean and Chinese characters and the variety of handwriting styles makes more challenging to decipher the old manuscripts. Therefore the necessity need of character recognition technology exclusive for Old Korean has been appered and this paper proposes efficient way of Old Korean dataset compositions and its own character recognition method.