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A Pre-Rake TDD-CDMA System Using Modified ZCD Code
정인철,차재상,경문건,Jeong, Incheol,Cha, Jaesang,Kyeong, Mungeon Korea Society of Satellite Technology 2012 한국위성정보통신학회논문지 Vol.9 No.2
주파수선택성 패이딩 채널 상황에서 Pre-Rake 다이버시티 기술은 이동단말에게 충분한 다이버시티 효과를 제공하며 이동단말의 수신기가 단순한 구조가 되도록 도와준다. 하지만, 기존의 Pre-Rake 시스템은 주파수선택성 페이딩 환경에서 Rake 시스템보다 두 배에 가까운 멀티패스에 의해 영향을 받기 때문에 다중유저 간섭을 Rake 시스템보다 훨씬 더 심각하게 받게 된다. 결국 이와 같은 간섭은 사용자가 증가할수록 성능이 열화하게 되는 원인이 된다. 따라서 이러한 문제점을 해결하기 위해 본 논문에서는 ZCD (Zero Correlation Code) 확산코드를 이용한 Pre-Rake TDD-CDMA 시스템을 제안한다. 또한 GI (Guard interval)를 포함하는 수정된 ZCD 코드들을 제시하고 다양한 채널환경에서 컴퓨터 시뮬레이션을 수행하고 그 성능을 평가한다. In a frequency selective fading channel, Pre-Rake diversity technique provides simple receiver structure and sufficient diversity effect for mobile terminals. However, conventional Pre-Rake systems are more severely affected than Rake systems with regard to multiple access interference since the number of multipaths received at the mobile unit is nearly twice that of the Rake systems. In order to overcome the problem, a Pre-Rake TDD-CDMA system using zero correlation duration (ZCD) spreading code is proposed. Modified ZCD codes including guard interval (GI) is also proposed and the performance is evaluated by computer simulation under the condition of various channel environment.
이멀션유의 일차원 액적 배열에서 점화특성에 관한 실험적 연구
정인철(Incheol Jeong),이경환(Kyung-Hwan Lee),김재수(Jaesoo Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The auto-ignition characteristics and combustion behaviors of one-dimensional array of water-in-fuel droplets suspended in a high temperature air chamber have been investigated experimentally with various droplet spacing, number of droplet. The used fuels were pure n-Decane and emulsified n-Decane with varied water contents. All experiments have been performed under the atmospheric conditions. The imaging technique with high-speed camera has been adopted to measure ignition delay, flame life time. It was also applied to observe micro-explosion behaviors. As the droplet array spacing increases, the ignition delay was increased regardless of water contents. However, the life time of droplet array was decreased as the droplet spacing increases.
단일 유화액적의 분위기 온도와 액적크기에 따른 자발화와 미소폭발에 대한 영향
정인철(Incheol Jeong),이경환(Kyung-Hwan Lee) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1
The characteristics of auto-ignition and combustion process of a single droplet of emulsified fuel suspended in a high-temperature air chamber have been investigated experimentally with various droplet sizes, surrounding temperatures, and water contents. The used fuels was n-Decane and it was emulsified with varied water contents whose maximum is 30%. The high-speed camera has been adopted to measure ignition delay and flame life time. It was also applied to observe micro-explosion behaviors. The increase of droplet size and chamber temperature causes the decrease of the ignition delay time and flame life-time. As the water contents increases, the ignition delay time increases and the micro-explosion behaviors are strengthened. The starting timings of micro-explosion and fuel puffing are compared for different droplet sizes and the amount of water contents.
경유와 바이오 디젤 액적의 혼합비율과 크기에 따른 연소특성
정만석(Manseok Jeong),정인철(Incheol Jeong),강건아(Keon-a Kang),이경환(Kyung-Hwan Lee) 한국에너지학회 2008 한국에너지공학회 학술발표회 Vol.2008 No.-
경유와 바이오 디젤이 혼합된 액적을 고온의 연소실에서 액적의 크기, 주위온도 그리고 각각의 혼합비율에 따라 연소특성에 미치는 영향에 대해 연구하였다. 경유에 0%, 20%, 50%, 80%, 100%의 비율로 바이오 디젤을 혼합하여 다양한 크기의 액적을 만든 후 서스펜더에 매달고 970K에서 1070K까지 50K 간격으로 고온에서 자발화를 시키면서, 전체의 연소 과정을 고속 디지털 카메라로 촬영하여 점화지연, 수명시간, 전연소시간, 그리고 미소폭발 등의 연소 특성을 파악하였다. 액적의 크기가 증가하고 연소실 온도가 낮을수록 점화가 지연되었다. 경유에 대한 바이오 디젤의 혼합비율이 감소할수록 점화지연이 증가하였고 미소폭발 발생률도 증가하였다. 또한, 미소폭발이 발생하는 경우 전연소기간이 조금 짧아짐을 확인하였다. The combustion characteristics of a single droplet of diesel and bio-diesel have been investigated experimentally with varying droplet size, ambient temperature and compound ratio in a high temperature chamber. The fuels used were diesel with bio-diesel contents varied from 0% to 100%. Each experiment has been performed from 970K to 1070K by 50K intervals. Imaging with a high-speed digital camera was adopted to measure the ignition delay and flame life-time, as well as to observe micro-explosion behavior. The increase of droplet size and decrease of furnace temperature cause an increase of the ignition delay time. As the bio-diesel content decreases, the ignition delay increases and the micro-explosion behavior is strengthened. It is also confirmed that the full combustion time decreases as the micro-explosion occurred.