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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.
Namcheol LEE,Jina BAIK,Minyoung LEE,Moonsun CHO,Taek Jin KANG,Sung-Kyu HONG 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
In general, enzymes with a whitening effect are water-soluble and lose their activity or their activity is lowered when they contact with oxygen in the air. In addition, the pH and temperature of cosmetics also affect the activity of the whitening enzyme. Therefore, in this study, a W/O/W multi-capsule was prepared using fat-soluble semi-solid oil, which is widely used in cosmetics, as a wall material for a water-soluble whitening enzyme to maintain the activity of the whitening enzyme. As a result, the size of the capsule manufactured by the cosmetic manufacturing apparatus is 300-900㎛, and at room temperature, it maintains its shape in a solid or semi-solid state. In addition, there is little irritation to the skin, and when applied to the skin, the capsule quickly turns into a liquid and is easily absorbed into the skin. At room temperature, it was confirmed that the water-soluble whitening enzyme was not released to the external water phase and that contact with oxygen was blocked, so that the enzyme activity could be maintained for a long period of time.