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홍슬기(Seulki Hong),채석봉(Seokbong Chae),김주하(Jooha Kim) 한국가시화정보학회 2017 한국가시화정보학회지 Vol.15 No.2
In the present study, the characteristics of kinematics and dynamics in the fluttering motion of free-falling plates are investigated at Reynolds number of 105. We record quasi-two-dimensional trajectories of free-falling plates with and without superhydrophobic coating using high-speed camera, and compute the drag and lift forces by trajectory analysis. Translational and angular velocities are modeled as harmonic functions with specific phase differences. In particular, periodic mass elevations near turning points are explained using the suggested models. At each turning point, a sudden drop in lift and a rapid increase in drag occur simultaneously due to fast increase in angle of attack. However, the lift is increased over the buoyancy-corrected weight of plate during gliding flight, resulting in periodic mass elevations near turning points. Superhydrophobicity is shown to increase lift but to reduce drag on a fluttering plate, resulting in the decrease of mean descent speed.
한국의 우주발사체 산업 발전을 위한 우주발사서비스 시장진입 전략 평가
홍슬기(Seulki Hong),안재명(Jaemyung Ahn) 한국항공우주학회 2015 韓國航空宇宙學會誌 Vol.43 No.10
국가위상 제고와 국내 발사체산업 발전에 따른 경제 발전을 위하여 우주발사서비스 시장진입은 필수적이다. 발사체 개발의 후발주자로써 시장에 효과적으로 진입하기 위해서는 시장의 트렌드를 정확하게 파악하고, 체계적인 시장진입전략을 수립하여야한다. 본 논문에서는 세계 우주발사서비스 시장의 3가지 핵심트렌드(고성능의 대형 우주발사체 수요 증가, 저가형 우주발사체 증가, Dual/Multi-Launch 증가)를 도출하고, 각 핵심트렌드에 대응하기 위한 전략의 우선순위를 쌍대비교분석법을 통해 평가하였다. 그 결과 모든 트렌드 하에서 발사체 신뢰성 확보 전략이 가장 중요하며, 고성능의 대형 우주발사체 수요 증가 트렌드하에서는 정부 지원 전략이, 저가형 우주발사체 및 Dual/Multi-Launch 증가 트렌드 하에서는 가격 경쟁력 확보전략이 두 번째 우선순위를 보였다. This paper suggests the significant strategies and their priority to deal with space transportation market trends. First, market trends related with technical improvement and change in demand are analyzed by the literature research. The three key trends are obtained: ‘Increasing Demand of High-Performance Launch Vehicles’, ‘Rising of Low-Price Launch Vehicles’, and ‘Rising of Dual/Multi-Launch’. And then, strategies for developing the launch vehicle industry in Korea are selected from several studies about commercialization of Korean launch vehicle. The strategies are evaluated by the experts through pairwise comparison matrix and the criteria for this process is how significantly does the strategy effect on the launch vehicle industry through market assessment. As a result, reliable order of priority among the strategies are obtained. Under the three key trends, strategy to enhance reliability is most important. And, strategy to have price competitiveness has secondary priority to deal with ‘Rising of Low-Price Launch Vehicles’ trend and ‘Rising of Dual/Multi-Launch’ trend. On the contrary, strategy of government’s support is secondary under ‘Increasing Demand of High-Performance Launch Vehicles’ trend.