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[Purpose] The purpose of this study was to investigate the effects of Tai Chi (TC) based exercise on dynamic postural control when people with mild or moderate Parkinson's disease (PD) initiate gait. [Subjects] Ten people with PD, who ranged in age from 70 to 84 years, volunteered to participate in a 12-week intervention of TC exercise. [Methods] Participants with PD were tested pre- and post-intervention in a task in which they were instructed to initiate gait from the position of quiet stance. Participants with PD were trained with TC exercise that emphasizes a shift in weight bearing from bilateral to unilateral support, challenging postural stability, three times per week over a period of 12 weeks. Differences between pre- and post-test in COP displacement in the anteroposterior (A-P) and mediolateral (M-L) directions were assessed using two force plates. [Results] After practicing the TC exercise, participants with PD significantly increased A-P and M-L displacement of the COP. [Conclusion] TC exercise increased COP displacement in the A-P and M-L directions, thereby improving participants' ability to generate momentum to initiate gait and maintain lateral stability. The findings of this study support the use of TC exercise as an effective and safe rehabilitation strategy for some individuals with PD.

In this study, axial vibration analysis has been conducted on a propulsion and lift shafting system for an air cushion vehicle using ANSYS code. The shafting system is totally flexible multi-elements system including wood composite material of air propeller. aluminum alloy of lift fan and thin walled shaft with flexible coupling. The analysis calculated the axial natural frequencies and mode shapes of the shafting system taking into account an equivalent mass-elastic model for shafting system as well as the three-dimensional models for propeller blade and fan impeller. Such a flexible shafting system has very intricate vibrating characteristics and especially, axial natural frequencies of flexible components such as propeller blade and impeller of lift fan can be lower to the extent that causes a resonance in the range of operating revolution. The results for axial vibration analysis are presented and compared with the results of axial vibration test for lift fan conducted during Sea Trial.

A propulsion and lift shafting system in an air cushion vehicle is flexible multi-elements system which consists of two aeroderivative gas turbines with own bevel gears, four stage lift fan reduction gear, two stage propulsion reduction gear air propellers and high capacity of lifting fans. In addition, the system includes the multi-branched shafting with multi-gas turbine engines and thin walled shaft with flexible coupling. Such a branched shafting system has very intricate vibrating characteristics and especially, the thin walled shaft with flexible couplings can lower the torsional natural frequencies of shafting system to the extent that causes a resonance in the range of operating revolution. In this study, to evaluate vibrational characteristics some analytical methods for the propulsion and lift shafting system are studied. The analysis, including natural frequencies and mode shapes, for five operation cases of the system is conducted using ANSYS code with a equivalent mass-elastic model.