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정성철(Sungchul Jung),김연호(Younho Kim),오화영(Hwayoung Oh),허환일(Hwanil Huh),명노신(Rhoshin Myong) 한국추진공학회 2007 한국추진공학회지 Vol.11 No.6
In this study, we analyzed flow characteristics of micro-nozzles for basic research to develop micro propulsion system. Cold gas propulsion system was used, and micro-nozzles having nozzle throat diameters of 1.0, 0.5, 0.25 mm were fabricated with EDM method. Thrust was measured through the use of plate-spring and strain gage based thrust measurement system, and flow characteristics of micro-nozzles were analyzed under ambient condition and vacuum condition. We used argon and nitrogen gases as propellant, and compared experimental results with CFD analysis. From the result, we verified the flow losses of viscosity and back-pressure caused by minimization of nozzle.
마이크로 추진장치에 적용을 위한 누센수에 따른 열적발산원리의 효율분석
정성철(Sungchul Jung),허환일(Hwanil Huh) 한국항공우주학회 2008 韓國航空宇宙學會誌 Vol.36 No.5
마이크로 추진장치에서 노즐의 소형화는 많은 유동손실을 유발한다. 이러한 유동손실을 극복하기 위해 본 연구에서는 열적발산원리를 이용한 마이크로 추진장치에 대한 기초 연구를 진행하였다. 움직이는 부품 없이 오직 온도구배만으로 추진제를 낮은 온도에서 높은 온도로 자체 펌핑이 가능한 열적발산장치를 설계, 제작 하였으며, 진공환경에서 누센수에 따른 맴브레인 압력구배효율을 분석하였다. 실험결과 천이영역에서는 두꺼운 맴브레인의 효율이 다소 높았으며, 자유분자영역에서는 두께에 관계없이 최대 압력구배 효율이 82%까지 증가하는 것을 확인할 수 있었다. Minimization of nozzle induces many flow losses in micro-propulsion system. In this study, we studied about thermal transpiration based micro propulsion system to overcome these losses. Thermal transpiration device(Knudsen pump) having no moving parts can self-pump the gaseous propellant by temperature gradient only (cold to hot). We designed, fabricated the Knudsen pump and analyzed pressure gradient efficiency of membrane according to Knudsen number under vacuum condition. Experimental results showed that thick membranes are more effective than thin membranes in transition flow regime, and pressure gradient efficiency according to Knudsen number is increased to maximum 82% apart from membrane thickness in free molecular regime.
Lane Detection and Detection-Error Correction by using Hough Transform
Jaegwon Seo(서재권),Sungchul Jung(정성철),Mirza Waqar Baig(미르자 와카르 백),Hyunchul Shin(신현철) 대한전기학회 2010 정보 및 제어 심포지엄 논문집 Vol.2010 No.4
Intelligent vehicles with robust lane detection and warning systems (LDWS) have been gaining popularity for enhanced safety. Robust lane following is important to warn the driver efficiently from lane departure. Accurate lane detection under diverse road and weather conditions is a critical issue for LDWS. In this paper, we have developed a cost effective vision based approach which is capable of detecting the lanes with robustness and capable of overcoming the errors caused due to the illumination changes or clutters. A cost effective technique using a single camera has been used to capture the road. The edges are detected by Sobel edge detector. A filtering process is used to remove noises e.g., shadows and clutters in the edge map. The Hough transform is used to find the lanes in the filtered edge map. The online tracking of lanes is done by using data comparison through Hough transform.