In this study, a control algorithm was developed to suppress the free vibration amplitude of a cantilever beam with time-varying dynamic characteristics. In other words, since it is assumed that the natural frequency and mode shape of the vibrating structure are not fixed, the system model of the vibrating structure was not used in the control algorithm. A single electromagnet was chosen as the actuator, so the attractive force was applied to only one fixed location in the structure. Through experiments, the proposed control algorithm is proven to effectively suppress the amplitude of vibration even when the dynamic characteristics of the cantilever beam change. Contrary to the usual active vibration control method, the proposed algorithm is just simple and intuitive without complicated mathematics in the modeling and control process. However, the proposed control method is very effective to suppress the vibration even when the dynamic characteristics of the target structure is not exactly known, as is often the case in industries or laboratories.

This paper is focused on an optimal design of two degree of freedom (2-DOF) dynamic vibration absorber (DVA) for the simply supported damped beam subject to a harmonic force excitation. In order to achieve this aim, we first show how to define the objective function of optimal design problem for 2-DOF DVA. Second, we apply the cyclic topology-based particle swarm optimization (PSO) to find the optimal design parameters of 2-DOF　DVA. Finally, some numerical results are compared with those of conventional researches, which demonstrates a reliability of the proposed design method

초고층 건축물은 매우 세장하여 지진하중보다는 오히려 풍하중에 대해 매우 취약하다. 이러한 초고층건축물에 작용하는 풍진동은 buffeting, 와류 및 wake에 의해서 주로 발생한다. 풍진동은 구조적인 안전성뿐만 아니라 거주 성을 결정짓는 중요한 인자이다. 본 논문에서는 풍진동을 줄이기 위해 와류진동에 대한 메커니즘을 변화시켜 저감효과를 연구하였다. 원형기둥과 원형기둥에 대하여 공력학적 형상으로 변화시킨 경우에 각각 rib와 spiral을 설치하였다. 풍동실험결과, rib와 spiral의 효과는 풍직각 방향에서 비슷한 저감정도를 보였고 원형기둥을 공력학적으로 변화시킨 형상에 rib와 spiral을 사용함으로써 공력학적인 이점이 복합적으로 작용하여 원형기둥의 풍직각방향에 대해 50%정도의 저감효과가 있었다.

The component materials threatened by cavitation include ship propellers as well as turbine runners, pump impellers, pipe lines and radiators. Today it is known that cavitation damage takes place on many other components including on the coding water side of the cylinder liners of diesel engines. Cavitation erosion - corrosion implies damage to materials due to the shock pressure or shock wave that results when bubbles form and collapse at a metal surface within a liquid. To suppress cavitation erosion as well as cavitation erosion - corrosion to hydraulic equipment, innovations such as the improvement in the geometric design of the equipment or the selection of suitably resistant construction materials are necessary. In this study, we investigated that the cavitation erosion - corrosion damage under vibratory cavitation can be reduced by adding of side now velocity to the cavitation bubble group in order to eliminate bubbles formed in sea water environment.