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조경석(Kyungseok Cho) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The Wave Fan was developed for the past 10 years. In the developing procedures, many leading edge technologies were adapted such as Aeroacoustic analogy prediction, surface pressure measurements, Computational Fluid Dynamics and Laser Doppler Velocitimeter. The Wave Fan is well known because of its unique design. Now the Wave Fan becomes a best in class automotive part in the world and becomes a name of the lower noise fan. But for the specific vehicle application, it needs some modification and optimizations for the best of the system performance. In this paper we can discuss the surface response method to meet customer requirement and to optimize system performance. The uneven blade spacing technique is also applied to minimize the unpleasant discrete tonal noise.
하이브리드 자동차의 고전압 전동압축기용 IPMSM의 최적화 설계 및 평가
조성국(Seongkook Cho),정경훈(Kyunghun Jung),조경석(Kyungseok Cho),박창호(Changho Park) 한국자동차공학회 2012 한국자동차공학회 지부 학술대회 논문집 Vol.2012 No.10
Automobile industry is a technology-intensive industry which has to develop new product rapidly to comply with the demands of consumers. Recently the importance of motor driven electrical compressor is increased dramatically as hybrid car became more popular for the fuel economy. In this paper, high efficiency IPM type BLDC motor development of the high voltage electric compressor for hybrid car is presented. Firstly optimal design of the motor has been conducted. Taguchi method was used to find optimal solution for motor efficiency and cogging torque. Output power, torque-ripple, cogging-torque were considered in optimization process. Secondly, Response surface method(RSM) was used to find optimal level of design factor among motor efficiency, speed range and cogging torque. Finally designed motor has been made and the validity of design process is verified through the comparison between simulation results and experimental ones.
적응적 블록탐색기법을 적용한 향상된 H.264 부호화 방법
박경석(Kyungseok Park),김민준(Minjun Kim),전재현(Jaehyun Jun),조정현(Jeonghyun Cho),김승호(Sungho Kim) 한국정보과학회 2011 정보과학회논문지 : 소프트웨어 및 응용 Vol.38 No.12
H.264/AVC는 프로파일에 정의되어 있는 것과 같이 다른 표준안들보다 우수한 압축효율과 다양한 특성들을 가지고 있지만, 가변블록 크기로 최적 부호화 모드를 결정하여 움직임 추정을 실행함으로써 부호화 시간이 증가하고 복잡도 또한 훨씬 증가하게 되었다. 따라서 본 논문에서는 H.264 부호화 과정 중화질 손실을 최소한으로 줄이면서 소모되는 시간을 단축시키는 적응적으로 블록모드와 탐색영역을 설정하는 방법을 제안하고자 한다. 실험결과 화질의 열화와 계산량을 측정하기 위해서 PSNR과 움직임추정 시간을 알아보았다. 그 결과, 제안하는 방법이 기존의 H.264 전역 탐색 기법과 비교하여 화질은 거의 비슷하게 유지하면서 실험한 모든 영상의 경우 모든 프레임에서 평균 400∼500ms 정도의 부호화 시간이 단축됨을 보였다. H.264/AVC defined in profile has various characteristics and better coding efficiency than other standards. Its encoding time, However, has increased and complexity has also increased much more by deciding optimal coding mode as variable block size and carrying out motion estimation. This paper propose the method of adaptive block mode to reduce the loss time and setting up search range with reducing the video quality in the process of coding. We examined PSNR and motion estimation time in order to measure both degradation of video-qualityand computation. As a result, this method showed that average coding time is shortened as 400∼500ms in every frame in the case of all experimented videos, keeping video quality nearly similar, compared to existing full search algorithm.
이정한(Jeonghan Lee),조경석(Kyungseok Cho),선효성(Hyosung Sun),신형기(Hyungki Shin),이수갑(Soogab Lee) 한국유체기계학회 1998 유체기계 연구개발 발표회 논문집 Vol.- No.-
Aerodynamic noise generated by automobile cooling fan is investigated. Automobile cooling fans radiate both discrete frequency noise as well as broadband noise. In the present work, the former is considered through free-wake panel method coupled with acoustic analogy fully considering the retarded time variation on the blade surface, while the latter is taken into account by three well-established broadband noise components. Experiments were performed to supplement necessary inputs as well as to provide the final comparison with the predicted noise spectrum. The predicted noise levels at blade passing frequencies agree well with the experimental data for the first few harmonics. Although the predicted broadband noise levels at higher frequencies fall below the experimental data due to the fundamental shortcomings of the utilized formulations, the analysis offers a detailed physical understanding of the fan noise generation processes.