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달 탐사를 위한 우주통신에서 텔레메트리 링크에 대한 최대 전송속도 성능분석
이우주(Wooju Lee),윤동원(Dongweon Yoon),이재윤(Jaeyoon Lee) 한국항공우주학회 2011 韓國航空宇宙學會誌 Vol.39 No.1
달 탐사를 위한 우주 통신 하향링크는 대용량 데이터의 전송을 위해 높은 전송속도를 요구한다. 따라서 본 논문에셔는 달 탐사를 위한 하향링크 S, X, Ku, Ka 대역별로 CCSDS에서 권고하는 변조 및 채널 부호화 기법에 대하여 전송속도를 분석한다. 이를 통해 달 탐사를 위한 텔리매트리 링크에 대하여 최대 전송속도를 가지며 링크마진을 만족하는 변조 및 채널 부호화 기법을 제시한다. Telemetry link requires high data rate to transmit the multimedia data for lunar explorations in space communications. In this paper, we analyze a data rate with the modulation and channel coding schemes based on Consultative Committee for Space Data Systems (CCSDS) in S, X, Ku and Ka bands, respectively. Then, we suggests modulation and channel coding schemes to meet the link margins and have a maximum data rate for lunar explorations in telemetry links.
포트 마스킹과 흡기 밸브 타이밍이 실린더 내부의 싸이클별 HC와 NOx 생성에 미치는 영향
전우주(Wooju Jeon),최관희(Kwanhee Choi),명차리(Cha-Lee Myung),박심수(Simsoo Park),이경환(Kyung-Hwan Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
This paper investigated the behaviors of combustion characteristics at part load condition with various intake charge motions induced by the port masking schemes in the CVVT (Continuously Variable valve Timing) engine. Time resolved in-cylinder and exhaust emissions were measured by the fast response HC and NOx analyzers to examine their formation mechanisms and behavior characteristics. As a result, in-cylinder HC decreased with the advanced intake valve timings but HC at the exhaust port increased due to the worse combustion stabilities. However HC reduction could be achieved by the application of the port maskings with a enhancement of the engine stability. NOx also decreased with early intake timings by internal EGR but increased with the charge motion controls which enhance the combustion behavior.
다중물리 기반 triply periodic bicontinuous 구조체의 기계적 특성 연구
이우주(Wooju Lee),김동철(Dongchoul Kim) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Metamaterials are engineered materials with material properties which do not exist in nature. The major reason for the properties is result from structure rather than composition. Particularly, mechanical metamaterials have their distinct characteristics, such as negative bulk modulus or Poisson’s ratio, from mechanical properties. Here, we apply the concept of the mechanical metamaterial to triply periodic bicontinuous structures which have been researched as a promising candidate for 3D photonic crystals. Elastic properties should be measured to evaluate the prospect of mechanical metamaterials. We conduct simulations to evaluate Young’s modulus and shear modulus of triply periodic bicontinuous structures, such as simple cubic(P), diamond(D), and gyroid(G). Volume fraction and aspect ratio of unit cell are considered as shape determining parameters. Each ratio of the Young’s modulus to the shear modulus is compared to common materials in nature. Finally, we suggest that the simple cubic structure with low volume fraction and large aspect ratio has extremely high moduli ratio. Therefore it is suitable for the 3D mechanical metamaterial.