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축 방향 추진력을 받는 자유 비행 구조물의 동적 안정성 해석
은성진(Sung Jin Eun),유홍희(Hong Hee Yoo) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Dynamic stability of a free flying structure undergoing axially driving force is investigated in this paper. The equations of motion of a free-free beam are derived using the hybrid deformation variable method and the assumed mode method. Unstable regions due to periodical driving force are obtained by using the Floquet’s theory. Stability diagrams are presented to illustrate the influence of the dimensionless driving force, amplitude, and frequency. Also, buckling occurs when the driving force exceeds a certain value. It is found that relatively large unstable regions exist around the first bending natural frequency, twice the first bending natural frequency, and twice the second bending natural frequency. The validity of the stability diagram is confirmed by direct numerical integration of the equations of motion.
은성진(Eun, Sung-Jin),유홍희(Yoo, Hong-Hee) 한국소음진동공학회 2005 한국소음진동공학회 논문집 Vol.15 No.9
Dynamic stability of an axially accelerating beam structure is investigated in this paper. The equations of motion of a fixed-free beam are derived using the hybrid deformation variable method and the assumed mode method. Unstable regions due to periodical acceleration are obtained by using the Floquet's theory. Stability diagrams are presented to illustrate the influence of the dimensionless acceleration, amplitude, and frequency. Also, buckling occurs when the acceleration exceeds a certain value. It is found that relatively large unstable regions exist around the first bending natural frequency, twice the first bending natural frequency, and twice the second bending natural frequency. The validity of the stability diagram is confirmed by direct numerical integration of the equations of motion.
은성진 관광경영학회 2000 관광경영연구 Vol.10 No.-
The purpose of this study is to present improve methods for enlarging profitability on hotel business by comparison and analysis of profitability by business environments and understand effective factors upon profitability of hotel. To accomplish the purpose of this study, I have run paralleled with both documentary study and empirical study. For empirical study, I sampled Seoul-based hotels and investigated their financial data and business showings from 1995 to 1999. The collected data were analyzed by SPSS WIN 7.5 program(mostly the correlation analysis and multiple regression analysis). The findings of this study research are summarized below. First, regarding analysis of variation and t-test, grade(second special grade), hotel history(under 15 years) and the number of rooms(200-400 rooms) are willing on factors of profitability. Grade(first special grade), hotel history(under 15 years) and the number of rooms(under 200 rooms) are willing on internal effective factors. Grade(first special grade), management forrn(chain hotel) and the number of rooms(over 400 rooms) are willing on external effective factors. Second, regarding correlation analysis and multiple regression analysis, 'fixed asset turnover', 'room occupancy', 'personnel expenses rate', 'inflation', 'foreign revenue rate', 'inadental facilities rate', 'inventory turnover' and 'receivables turnover' have a effect upon profitability of hotel.