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박상윤,이정섭,최병호,Il Hyuk Ahn,문승기 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
Numerous numerical models of mimicking cellular structures have been proposed, but, in many cases, those models were not able to describe the random cell geometry which is common for most cellular products. The concept of Voronoi tessellation has recently applied to construct the random characteristics of cell structures, but the structure generated by classical Voronoi tessellation method is too ideal by comparing with the actual cell structures. Moreover, the verification of physical and mechanical behaviors of random cell structures is scarcely researched due to the complexity of fabricating the cell structures which are numerically generated. In this study, Central Voronoi Tessellation (CVT) theory which considers the center of mass of each cell for further iteration of cell structure modification is adopted to generate realistic shape of cell structures. Some key parameters such as relative density, anisotropy, and number of iteration are considered. Mechanical behaviors of samples with numerically generated cell structures are investigated using elasto-plastic finite element analysis considering instability conditions. In addition, test samples in some cases considered in FEA are fabricated by aluminum alloy using 3-D printer based on the selective laser melting (SLM) technique, and the test results are compared with the numerical simulation results.
박상윤,최원종 한국항공대학교 항공우주산업기술연구소 2003 航空宇宙産業技術硏究所 硏究誌 Vol.13 No.-
In this study, the design and analysis of various energy storage flywheel types such as single material rotors(7075-T6, T300/epoxy, S2-glass/epoxy, and Kevlar/epoxy), multiple material rotors (S2 glass/epoxy+T300/epoxy), and hoop/helical wounded flywheel rotors were performed. An analytical model has been used to calculate the elastic stress of rotor systems subjected to internal force. The exact solution for rotating circular thick cylindrical shells has been obtained under assumption of axis-symmetric and plane strain conditions. Analysis results show that the behavior of flywheel rotors were strongly influenced by the key design parameters such as material properties and hoop/helical winding pattern. Also, the result of tradeoff study revealed that the multiple material rotor system was the most effective design concept for energy storage flywheel.
학교 스포츠클럽 활동에 대한 스포츠강사의 태도 유형과 개선 방향 모색
박상윤,윤양진,구수용 한국체육정책학회 2018 한국체육정책학회지 Vol.16 No.3
This purpose of the study was to investigate the attitude type and improvement direction of the instructor about the school sports club activities. To determine the subjectivity of individual, Q methodology focused on qualitative subjectivity analysis was applied. At the beginning of research, total 8 of 4 sports instructors and 4 physical education teachers selected in P city were interviewed with questionnaire including open-ended items. Total 40 items collected were reduced to 27 statements through modification and refinement. For the statements acquired, 20 sports instructors employed in sports club activities in P city were selected and asked to classify cards written statements, and then after coding process, Q-sort was carried out with principle component analysis using QUANL program. For extracting factors only factors over eigen value of 1.5 were extracted. This findings showed as follows. First, all four factors yielded, which reported total explained variance of 56.05%. This means that the result of this study accounts for 56.06% of the instructor’s attitude style for school sports club. In addition, given the explained variance by each style, 22.06% of the explained variance was for the first style, 15.04% for the second style, 10.29% for the third style, and 5.66% for the fourth style. Second, characteristics by each style were examined, and each style was labelled based on characteristics. The first style was ‘seeking sports game participation support’, the second style was ‘seeking safe environmental factor’, the third style was ‘seeking alternative curriculum’ and the fourth style was ‘seeking interaction’. Third, directional solution of improvement for the school sports club activities discussed as belows. The first style told that recognizing the overall growth of sports through the sports, which was originally intended for the contest. The second style reported that students should be able to choose from a variety of sports that can be made available at school. The third style told that it is necessary to secure space and allocate a fixed space, and various kinds of direct and indirect learning activities for holistic development should be done. The fourth style reported that through the linkage within the curriculum, the integrated goal of physical education should be achieved.