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김재국,이영석,김성환,Kim, Jae-Kuk,Lee, Young-Seok,Kim, Sung-Hwan 한국음향학회 1997 韓國音響學會誌 Vol.16 No.4
In this paper, a new time delay estimation algorithm, WTD-LMSTDE was proposed. This method has great improvement in convergence rate relative to the time domain approach by decreasing the eigen value spread of input signal autocorrelation matrix. The performance of the algorithm was evaluated for the cases of time invariant time delay and time varying time delay. In the case of time invariant time delay, the estimation accuracy of WTD-LMSTDE was better than that of LMSTDE from 3.3% to 12.5% with respect to SNR. In the case of time varying time delay, the mean error power of WTD-LMSTDE in linear increased delay environment was decreased about 2.4dB compared to that of LMSTDE under noise-free condition. As a result, we showed that the performance of WTD-LMSTDE is better than of LMSTDE. 본 논문에서는 웨이브렛 변환을 이용한 새로운 시지연 추정방법인 WTD-LMSTDE을 제안하였다. 이 방법은 시평면에서 입력 신호 자기상관 행렬의 고유치 분포를 줄임으로서 수렴속도를 향상시켰다. 이 알고리즘의 성능을 시불변과 시변인 경우에 대해서 평가하였다. 결과로서 시불변 시지연의 경우에, WTD-LMSTDE의 추정 정확도가 LMSTDE보다 SNR에 따라서 3.3%에서 12.5%까지 개선되었다. 시변 시지연의 경우에는, 선형적으로 증가하는 자연 환경에서 WTD-LMSTDE의 평균 오차 전력이 잡음이 없는 상태에서 LMSTDE와 비교하여 2.4dB정도 감소하였다. 결론적으로 WTD-LMSTDE의 성능이 LMSTDE보다 우수함을 확인할 수 있었다.
김재국(Jae Kuk Kim),조암(Am Cho) 대한인간공학회 2008 大韓人間工學會誌 Vol.27 No.3
The purpose of this study was to examine the effects of sensibility and compatibility from function sounds of mobile phones. For this purpose, the present study extracted sensibility adjectives and carried out sensibility evaluation to identify the sensibility factors in the function sounds of mobile phones. And 65 sound sources out of six categories were investigated for 27 subjects. The result showed that two dominant sensibility factors were the duration and the melody pattern of the sound sources. The compatibilities of opening and closing sounds were evaluated lowly with short duration and quick tempo. Especially, the most of the subjects preferred more attractive and longer opening sounds than other function sounds. Another finding was that the short sounds with melodies were preferred for cancellations and alerts, unliked the commonly used sound sources in industry and other traditional electronic products.
PC 파워 서플라이용 비대칭 하프브리지 DC/DC 컨버터의 초기 구동시 돌입전류 제거 기법
김재국(Jae-Kuk Kim),이성세(Sung-Sae Lee),오원식(Won-Sik Oh),김정은(Jung-Eun Kim),문건우(Gun-Woo Moon),길창현(Chang-Hyun Gil),조자룡(Ja-Ryong Cho) 전력전자학회 2006 전력전자학술대회 논문집 Vol.- No.-
This paper presents a start-up in-rush current reduction technique of asymmetry half-bridge DC/DC converter for PC power supply. The proposed converter is composed center-tapped half-bridge converter with blocking capacitor. The proposed converter can reduce the severe in-rush current when the proposed converter is power up. The validity of this study is confirmed from the experimental results.
김재현(Jae-Hyun Kim),이일운(Il-Woon Lee),김영도(Young-Do Kim),김재국(Jae-kuk Kim),문건우(Gun-Woo Moon) 전력전자학회 2010 전력전자학술대회 논문집 Vol.2010 No.7
본 논문에서 대전력, 고전압에 적합한 three-level 의사공진형 PWM 컨버터를 제안한다. 의사공진형으로 동작함으로써 넓은 ZVS 영역을 가지며, 고정 주파수를 사용하므로 자기 소자의 설계가 쉬워지는 장점을 가진다. 그리고, 변압기에 인가되는 전압 파형의 주파수가 스위칭 주파수의 2배가 되므로 변압기의 크기를 줄 일 수 있고, 변압기 2차측에 출력 인덕터가 없는 전압배가기를 적용하여 정류기 양단에 전압리깅이 발생하지 않아 정류단의 전압 스트레스가 감소되는 장점 또한 가진다. 본 논문에서는 제안한 컨버터을 분석하고, 프로토타입을 통해 그 동작을 검증한다.
SOC 밸런싱 기능을 갖춘 새로운 배터리 스위칭 시스템
최재성(Jae-Seong Choi),김재국(Jae-Kuk Kim) 전력전자학회 2023 전력전자학회 논문지 Vol.28 No.3
The conventional dual-voltage automotive system has a large size and high cost due to its magnetic components. To eliminate the magnetic components, previous research adopted switched-capacitor converters. However, to provide the proper output voltage with small capacitance, high switching frequency should be employed, which leads to high energy loss and EMI problems. To mitigate the drawbacks, the battery switching system using some switches was considered. This system has charging and discharging modes through series or parallel battery connections. However, the batteries can be under-utilized and unbalanced due to the state of charge (SOC) problem. Therefore, this paper proposes a new battery switching system with SOC balancing capability. The proposed system only adds a few switches, in which switching in the order of battery connection can be applied. Through this structure, all batteries can be utilized and balanced. In addition, battery switching can be controlled simply. To confirm the validity of the proposed system, a 160 W prototype was implemented and experimented.