• 조명전기설비학회논문지
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• 제30권3호
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• pp.65-72
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• 2016

This paper discussed the LCL-type & Isolated bidirectional dc-dc converter(BDC) with dual full bridge inverter. In order to verify the analysis of the BDC, Experimental prototype has been designed and implemented to supply constant voltage regardless of loads and proposed a method to select switching frequency that depended on two inductors' inductance ratio and transformer parameters. The proposed converter has been composed of LCL resonant network with unit inductance ratio ($L_r/L_f$=1) and then operated with fixed duty, 50% duty ratio and fixed frequency. There are some characteristics that input voltage and output voltage of the BDC is nearly identical and zero voltage turn-on switching is possible in forward and reverse mode. Finally, it has been showed that BDC is possible to commutate operating mode normally and provide constant output voltage in selected switching frequency.

• Journal of Power Electronics
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• 제14권4호
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• pp.649-660
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• 2014

A novel non-isolated bidirectional soft-switching SEPIC/ZETA converter with reduced ripple currents is proposed and characterized in this study. Two auxiliary switches and an inductor are added to the original bidirectional SEPIC/ZETA components to form a new direct power delivery path between input and output. The proposed converter can be operated in the forward SEPIC and reverse ZETA modes with reduced ripple currents and increased voltage gains attributed to the optimized selection of duty ratios. All switches in the proposed converter can be operated at zero-current-switching turn-on and/or turn-off through soft current commutation. Therefore, the switching and conduction losses of the proposed converter are considerably reduced compared with those of conventional bidirectional SEPIC/ZETA converters. The operation principles and characteristics of the proposed converter are analyzed in detail and verified by the simulation and experimental results.

• Journal of Power Electronics
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• 제15권2호
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• pp.319-326
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• 2015

In this paper, a cost-effective single switch multi-channel LED (light emitting diode) driver is proposed. While conventional LED drivers require as many non-isolated DC/DC converters as the number of LED channels, the proposed LED driver needs only one power switch and several balancing capacitors instead of expensive non-isolated DC/DC converters. Therefore, the proposed driver features a simpler structure, with a lower cost and a higher efficiency. Because its power switch can be turned off under the zero current switching condition, it has very desirable advantages such as improved electromagnetic interference characteristics and high efficiency. Moreover, it uses only a small number of DC blocking capacitors with no additional active devices for the current balancing of multi-channel LEDs. As a result, the proposed driver exhibits high reliability and is cost effective. To confirm the validity of the proposed driver, a theoretical analysis is performed, and design considerations and experimental results obtained from a prototype that is applicable to a 46" LED-TV are presented.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.430-432
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• 2005

This paper presents a novel, single stage, isolated, three-phase switching rectifier capable of switching at high frequency. The circuit topology Provides zero-voltage switching for all switches, output voltage regulation, unity input power factor, all in a single power conversion stage. Operating principle and experimental results in the 48V/100A DC power supply of three-phase single stage method are presented.

• Journal of Electrical Engineering and Technology
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• 제11권5호
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• pp.1265-1273
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• 2016

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.528-532
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• 2019

본 연구는 뉴런 세포와 슈반 세포의 공동 배양에 의한 수초화 발생 과정과 herpes simplex virus-1 감염에 의한 탈수초화 발생과정을 전자 현미경과 분자생물학적 분석에 의하여 확인하고자 하였다. 쥐의 배아로부터 후근신경절(dorsal root ganglion, DRG)을 분리하여 슈반(Schwann) 세포와 뉴런 세포(neuronal cell)를 in vitro에서 각각 배양하였다. 유사 분열 억제인자로 처리한 뉴런세포와 정제된 슈반 세포를 함께 공동 배양을 하여 수초화를 발생시켰다. 이렇게 수초화된 공동 배양 세포에 herpes simplex virus-1를 감염시켜 탈수초화를 진행시켰다. 수초 형성의 존재를 의미하는 myelin protein zero(MPZ) 항체를 사용하고 전자 현미경을 이용하여 수초 발생 및 탈수초화 과정을 관찰하였다. 이 연구는 과학 기술부, ICT 및 미래 계획 (NRF-2016R1A2B4016552 및 2017R1A2B3005753)이 자금을 지원하는 국립 연구 재단 (NRF)을 통한 기초 연구 프로그램의 지원을 받았다.

• 대한기계학회논문집A
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• 제20권1호
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• pp.127-134
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• 1996

In general, seismic isolators which are made of laminated rubber and shim plate have characteristics of complex hysteretic behavior. When shear deformation of the seismic isolator is small, the isolator hassimple hysteretic almost bi-linear behabior. But on large shear deformation hardening effects may occur. This paper proposes a moldeling method of the seimic isolator with modified hysteretic bi-linear model which can consider the hardening effects. From the results of the seismic analyses of the isolated system it is shown that the responses are singificantly reduced compared with those of the non-isolated system. The modified hysteretic bi-linear model of the isolator gives larger ZPA(zero period acceleration) than those of the simple hysteretic bi-linear model and the equivalunt spring-damper model.

• 전력전자학회논문지
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• 제20권1호
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• pp.31-37
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• 2015

This paper proposes a 3.3-kW bi-directional EV charger with V2G and V2H functions. The bi-directional EV charger consists of a DC-DC converter and a DC-AC inverter. The proposed EV charger is suitable for wide battery voltage control due to the two-stage configuration of the DC-DC converter. By employing a fixed-frequency series loaded resonant converter as the isolated DC-DC converter, zero-current-switching can be achieved regardless of battery voltage variation, load variation, and power flow. A 3.3-kW prototype of the proposed EV charger has been built and verified with experiments, and indicates a maximum efficiency of 94.39% and rated efficiency of 94.23%.

• 전력전자학회논문지
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• 제23권3호
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• pp.190-198
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• 2018

This paper proposes a nonisolated, bidirectional, soft-switching DC - DC converter with PWM plus phase shift (PPS) control. The proposed converter has an input-parallel/output-series configuration and can achieve the interleaving effect and high voltage gains, resulting in decreased voltage ratings in all related devices. The proposed converter can operate under zero-voltage switching (ZVS) conditions for all switches in continuous conduction mode. The power flow of the proposed converter can be controlled by changing the phase shift angle, and the duty is controlled to balance the voltage of four high voltage side capacitors. The PPS control device of the proposed converter is simple in structure and presents symmetrical switching patterns under a bidirectional power flow. The PPS control also ensures ZVS during charging and discharging at all loads and equalizes the voltage ratings of the output capacitors and switches. To verify the validity of the proposed converter, an experimental investigation of a 2 kW prototype is performed in both charging and discharging modes under different load conditions and a bidirectional power flow.

• 한국균학회지
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• 제20권4호
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• pp.302-308
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• 1992

Seven genera and 15 species of fungi were isolated from 50 samples of then different steps of dried onion (5 samples of each step) collected from an onion factory in Sohag Governorate, Egypt, and grown on glucose-Czapek's agar (7 genera and 15 species) and 10% NaCl glucose-Czapek's (2 genera and 6 species). The average total counts of fungi were gradually decreased throughout the different steps of drying from 2090 to zero and 152 to zero colonies/g on glucose-Czapek's agar and 10% NaCl glucose-Czapek's agar media, respectively. Aspergillus was the most common genus on the two types of media used. The dominant species were Aspergillus niger, A. flavus, A. terreus, Penicillium chrysogenum and Fusarium of oxysporum on glucose-Czapek's agar and A. terreus and A. niger on 10% NaCl glucose-Czapek's agar. The chloroform extracts of different samples were tested for the presence of mycotoxins using thin layer chromatographic analysis. The results indicated that aflatoxin was present at concentrations decreased throughout the different steps of the drying from step No. 1, onion bulbs, $120\;{\mu}g/kg$; to step No. 8, standard A, $20\;{\mu}g/kg$ while step Nos. 9 & 10 (completely dry powdered onion) were free from aflatoxin. Citrinin was also present in the first three steps at concentrations gradually decreased from 30 to 10 mg/kg.