• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.37-38
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• 2012

무정전전원장치(UPS: Uninterruptible Power Supply)는 정전 등의 사고가 발생할 때 양질의 전원을 부하에 공급하는 장치이다. 무정전전원장치의 구성은 크게 역률개선회로, 인버터, battery charger, battery discharger부로 크게 4개로 나눌 수 있다. 그 중 정전 등의 사고발생 시 battery에 충전되었던 에너지를 인버터 부로 공급하여야하며 이를 담당하는 부분이 battery discharger부이다. battery의 전압은 비교적 낮은 전압이며 인버터의 입력에 필요한 전압은 비교적 큰 전압이기 때문에 승압형 컨버터가 필요하게 된다. 본 논문에서는 UPS battery discharger용 3KW급 LLC 공진형 컨버터를 설계하고 실험 검증하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.826-833
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• 2004

Cascade impactors are widely used to collect size classified aerosol. A major disadvantage of this instrument is the required long sampling time. Electrical low pressure impactor has been developed to overcome this disadvantage and to achieve real-time measurements on the particle size distribution. The instrument consists primarily of a corona charger, low pressure cascade impactor and multi channel electrometer. We designed and evaluated the performance of a potable 3-stage low pressure impactor using an electrical method. For the calibration of the impactor, monodispersed particles were generated using evaporation-condensation method followed by electrostatic classification using a DMA(Differential Mobility Analyzer). The collection efficiency curves of the stages can be determined by analysing the fraction of particles collected by each stage.

• Journal of Korean Society for Quality Management
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• v.47 no.3
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• pp.631-639
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• 2019

Purpose: In this paper we present a case study of applying quick and easy experimental design approach to develop a Halogen free flame retardant material for cellular phone charger cable. Methods: We employ sequential experimentation of mixture design, verification design, and factorial design. A quick and easy approach is adopted based on data investigation and graphical method instead of strict statistical analysis, which helped enhancing smooth communication with the engineers and speeding up the development process. Results: Flame retardant material in pellet type produced from the optimal condition is transported to the customer and tested, to pass the customer retardancy criteria. Conclusion: The quick and easy experimental design approach is considered to be useful in this case study.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.6
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• pp.424-432
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• 2018

This study presents a single-phase single-stage three-level AC/DC converter with a wide controllable output voltage. The proposed AC/DC converter is designed to extend the application of e-mobility, such as electric vehicles. The single-stage converter integrates a PFC converter and a three-level DC/DC converter, operates at a fixed frequency, and provides a wide controllable output voltage (approximately 200-430Vdc) with high efficiencies over a wide load range. In addition, the input boost inductors operate in a discontinuous mode to improve the input power factor. The switching devices operate with ZVS, and the converter's THD is small, especially at full load. The feasibility of the proposed converter is verified by the experimental results of a 1.5 kW prototype.

• Particle and aerosol research
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• v.15 no.1
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• pp.15-25
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• 2019

The influences of corona charging parameters on collection efficiency and surface potential of air filters were investigated. A polypropylene filter medium was electrically charged using a corona charger, and the resulting surface potential and filtration efficiency against neutralized KCl particles were measured. The filter media was charged under different conditions of applied voltage, voltage polarity, charging time, and distance between electrodes. In addition, we considered charging both sides of the filter as well as charging one side of the filter. As a result, electrical force obtained by charged fiber affected filtration efficiency when the apply voltage strength was higher than 7 kV. Negatively charged filter had higher filtration efficiency than positively charged filter while the surface potential of the negatively charged filter was slightly lower than those of positively charged filter. Moreover, the filtration efficiency increased as the charging time of filter fiber increased and the distance between electrodes decreased. The filtration efficiency was more sensitive to changes of charging time than to those of electrode distance, and the efficiency of both sides charged filter was higher than that of single side charged filter.

• Research in Community and Public Health Nursing
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• v.30 no.3
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• pp.257-270
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• 2019

Purpose: This study is designed as a non-equivalent, control group pre/post-test for identifying effectiveness of a workplace walking program using a fitness tracker including individual counseling and tailored text messaging. Methods: Seventy-nine employees from two large companies were allocated into an intervention group (n=39) and a control group (n=40). Participants were asked to wear a fitness tracker (Fitbit Charger HR) during 24-hour, 5-days per week, for 10 weeks. The intervention group was provided with daily walking steps measured by Fitbit, weekly counseling with a specifically designed workbook, and seven weekly text messaging, and the control group with the fitness tracker only. Results: At the week 10 measurement, there were significant differences between the intervention and control groups in physical activity self-efficacy (p<.001), physical activity behavior (p<.001), daily walking steps (p<.001), systolic blood pressure (p=.033), and wellness (p<.001). Conclusion: These results suggest that the workplace walking program using a fitness tracker including individual counseling and tailored text messaging is more effective for persons with 10,000 steps/day. Therefore, it is recommended to actively apply this workplace walking program to inactive employees for encouraging regular physical activities and improving their wellness.

• Proceedings of the Korean Society of Computer Information Conference
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• 2019.07a
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• pp.443-444
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• 2019

본 논문에서는 라즈베리파이(Raspberry Pi)와 실시간 객체 감지 기술인 YOLO를 이용한 전기차충전기앞불법주차 경고 영상인식 시스템을 제안한다. 최근 전기 자동차의 사용과 더불어 충전 인프라는 점점 늘어나는 중이지만, 여전히 전기차 충전기는 많지 않은 것이 현실이다. 전국 1,000여 곳이 넘는 전기차 충전소에 대해 법령으로 인한 규제를 시행 중임에도 불구하고 불법주차를 하는 일반차 오너들은 여전히 많다. 이로 인해 전기차 오너들은 충전에 많은 불편함이 있다. 이 시스템은 전기 자동차의 번호판을 인식하여 실시간 객체 감지 딥러닝 기법인 YOLO를 이용해 전기 자동차의 번호판에 특정 부분을 인식하고 특정 부분이 없는 일반 자동차가 전기차 충전기 앞 불법 주차를 하게 되면 부저와 LED경고를 통해 주차된 일반 차량에게 경고를 하여, 불법 주차자와 더불어 주변을 지나가는 행인들에게도 전기차 앞 불법 주차에 대해 각인을 시켜줄 수 있는 시스템이다.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.127-129
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• 2019

본 논문은 Solid-state Marx modulator (SSMM)용 10 kV, 1 kW급 고전압 커패시터 충전기의 설계에 대해 기술한다. 개발된 Marx modulator용 충전기는 소프트 스위칭방식을 통해 높은 스위칭 주파수로 동작하는 컨버터를 제안함으로써 고밀도 설계를 구현한다. 특히 고전압 변압기 설계에 있어 피할 수 없는 누설 인덕턴스와 기생 커패시턴스를 회로의 파라미터로 사용 할 수 있는 공진형 컨버터를 기반으로 설계한다. 본 논문에서는 순수 전류원 특성을 가지며 스위치 온, 오프 시 모두 소프트 스위칭이 가능한 Discontinuous Conduction Mode (DCM) 직렬 공진형 컨버터와 공진 전류의 RMS값을 줄이고 변압기의 기생 커패시턴스를 공진 탱크로 사용하는 LCC 공진형 컨버터 Continuous Conduction Mode (CCM)를 설계한다. 각 컨버터의 동작에 따른 해석 및 공진 파라메터 상세 설계에 대해 기술하고 정격 운전 (10 kV, 1 kW) 실험결과를 통해 각 컨버터 토폴로지의 장단점을 비교하고 최종 실험결과에 대해 기술한다.

• Journal of IKEEE
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• v.24 no.4
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• pp.1129-1135
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• 2020

The effects of battery aging limit the rechargeable capacity, State of Health(SoH). It is very important to estimate the SoH in the battery monitoring system(BMS) and many algorithms of measuring the internal resistance of the battery were proposed. A method is used by applying a current source of a specific frequency to the battery and measuring the voltage response. When charging harmonic noise is generated in the voltage response, it results in poor resistance measurement accuracy. In this paper, a robust battery internal resistance measurement algorithm is proposed to eliminate the effect of charging noise by integrating the current source and voltage response signals for a certain period. It showed excellent accuracy and stable measurement results. Applying to the BMS for uninterruptible power supply, the usefulness of the proposed method is verified.

• Journal of IKEEE
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• v.25 no.1
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• pp.101-108
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• 2021

This paper proposes a parallel control method of a modular DC/DC converter for electric vehicle (EV) chargers. The EV chargers have been increasing the power capacity using modular converters. There are output current imbalances between the modules, which are caused by the difference of the impedance, delay of the gate driver, and error of the sensors. The conventional strategies for the equal distribution of the output current cause the voltage drop or the high volume and cost of the converters. Therefore, the proposed parallel control strategy effectively balances the output current of modules using a current compensation method. The proposed strategy is verified by simulations. Additional experimental results will be added under various conditions.