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Stability of a Rotating Disk in an Enclosed Compressible Fluid
강남철(Namcheol Kang) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.6
The stability of a thin, flexible annular disk rotating in an enclosed compressible fluid is investigated. The discretization procedure utilizes Green's theorem and exposes two distinct gyroscopic effects explaining the coupled system dynamics: One describes the gyroscopic coupling between the disk and acoustic oscillations, and the other arises from the disk rotation. For the undamped system, coupled structure-acoustic traveling waves can destabilize through mode coalescence leading to flutter instability. A detailed investigation of the effects of dissipation arising from acoustic and disk damping predicts instability mechanisms for this system.
밀폐된 용기 안에서 동시에 회전하는 디스크의 진동과 안정성에 관한 연구
강남철(Kang, Nam-Cheol) 한국소음진동공학회 2009 한국소음진동공학회 논문집 Vol.19 No.1
The vibration and stability of thin, flexible corotating disks in an enclosed compressible fluid is investigated analytically and compared with the results of a single rotating disk. The discretized dynamical system of the corotating disks is derived in the compact form of a classical gyroscopic system similar with a single disk. For the undamped system, coupled structure-acoustic traveling waves destabilize through mode coalescence leading to flutter instability. However, it is found that the flutter regions of the corotating disks are wider than those of a single disk. A detailed investigation of the effects of dissipation arising from acoustic or disk damping is also performed. Finally, in the presence of both acoustic and disk dampings, the instability regions are found and compared with those of a single disk. Although this study does not allow a radial clearance between the disk and the enclosure, the computational frame work of the problem can be expanded to the system having the radial clearance in an enclosure.
강남철 ( Kang Nam Cheol ) 한국대학선교학회 2016 대학과 선교 Vol.31 No.-
본 논문의 목적은 몰트만의 평화사상을 교육적으로 적용하여 평화교육과 평화실천에 기여하는 것이다. 몰트만은 신학적 재해석 작업을 통해서 그의 독창적인 평화사상의 기초를 마련하였다. 칭의는 죄의 용서를 넘어서 평화를 향한 출발이다. 평화를 창조하는 하나님은 적대감으로 형성된 친구-적, 선-악의 원수관계를 십자가의 고난을 통해서 극복한다. 몰트만의 평화사상은 비폭력적 평화, 정의로운 평화, 창조적인 원수사랑이다. 비폭력적 평화란 비폭력적인 방법으로 친구-적 관계를 극복하는 것이다. 악을 악으로 제압하는 대신에 악을 선으로 바꾸는 것이다. 정의로운 평화는 `우리의 죄를 사하소서`가 아니라 `우리를 악에서 구하소서`를 기초로 한다. 하나님은 희생자를 의롭게 하시는 의, 가해자를 의롭게 하시는 의, 그리고 불의한 구조를 변화시키는 의를 통해서 평화를 창조하신다. 창조는 원수관계를 극복하고 평화의 나라를 건설하는 것이다. 창조적 사랑에 근거한 평화를 실천하는 것이 평화적 제자직이며, 오직 평화적 제자직을 통해서만 하나님의 평화를 창조할 수 있다. This study has aimed to present a new perspective of peace ethics. Moltmann`s thought of peace is peace of nonviolence, peace of justice, and peace of creative love to enemy. By overcoming the structure of enemy- friend we could transform violence into power of life. Instead of conquering evil with evil, we should let the evil surrender by goodness. The disciples of Jesus are who practice the love of God in the world, take part in the suffering of God for the world. Moltmann`s Eschatology doesn`t think the End of this world means the revenge of God to the sinner. The End of the world means the End of the relation of enemy-friend, and the Start-Point of the peaceful kingdom of God. The vocation of disciples is the practice of peace on the basis of creative love which overcomes evil with non-violent and good action.
Roll-to-roll 연속 공정을 위한 Multi-span Web 시스템의 횡방향 운동 해석
강남철(Namcheol Kang) 한국소음진동공학회 2013 한국소음진동공학회 논문집 Vol.23 No.12
Based on the string, Euler beam, and Timoshenko beam theories, the transfer functions of axially translating web system to predict the lateral tracking are introduced in this paper. In addition, total transfer function of a multi-span web handling system is developed by the combination of the transfer functions of each single span. Experiments and computations are carried out and the results obtained for the Timoshenko beam model are compared with those of other models. The comparison indicates that the predictions from the Timoshenko and Euler beam models are quite different from that of the classical string model in both the gain and phase response. The results are expected to help in the development of high fidelity models of web tracking systems within a general computational framework.