• 한국음향학회지
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• 제8권1호
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• pp.31-37
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• 1989

구속 점탄성 층을 갖는 복합보를 동흡진기로 이용하는 문제를 다루었다. 이 동흡진기의 효과를 조사하기 위해 양단고정 주진동 보에 설치했을 때의 변위전달율을 구하여 기존 균일 재질보 동흡진기 효과와 비교했다. 해석결과 최적 동흡진기를 구성하는 패러매터 값이 현재 활용되는 재질 측면에서 의미있는 범위내에 존재하고 있고 둘이상의 공진 진동수에서 전달율을 동시에 줄일 수 있었다. 이점으로 기존 제시된 비해 점탄성을 복합보가 유리하게 이용될 수 있음을 확인했다.

• 한국산업융합학회 논문집
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• 제3권2호
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• pp.141-147
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• 2000

The nonlinear response statistics of an autoparameteric system under broad-band random excitation is investigated. The specific system examined is a vibration absorber system with internal resonance, which is known to be a good model for a variety of engineering systems, including ship motions with nonlinear coupling between pitching and rolling motions. The Fokker-Planck equations is used to generate a general first-order differential equation in the dynamic moment of response coordinates. By means of the Gaussian closure method the dynamic moment equations for the random responses of the system are reduced to a system of autonomous ordinary differential equations. The jump phenomenon was found by Gaussian closure method under random excitation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.734-735
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• 2008

Shock absorber for rotorcraft landing gear should absorb landing impact during landing and isolate vibration to fuselage during taxiing. Double stage oleo-pneumatic shock absorber is known to have better performances than single stage oleo-pneumatic shock absorber. This paper deals with the z-direction translational acceleration at mass center, roil and pitch angular acceleration of fuselage for single and double stage oleo-pneumatic shock absorber at nose landing gear when a 6DOF rigid model is taxiing on the pound.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 추계학술대회 논문집
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• pp.83-88
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• 2010

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 춘계학술대회 논문집
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• pp.716-717
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• 2010

• 대한기계학회논문집A
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• 제34권5호
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• pp.605-609
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• 2010

적외선 센서를 사용하는 최신 관측용 장비들을 저온으로 유지하기 위해서는 극저온 컴프레서를 센서에 연결한다. 그러나 컴프레서 진동원으로부터 발생한 외란 힘에 의해 취득 영상 품질이 저하된다. 따라서 고품질의 영상을 얻기 위해 극저온 쿨러에 대한 진동 절연 설계가 필요하다. 본 논문은 수동 진동 절연 방법의 장점을 사용하면서 컴프레서 외란 진동에 대한 높은 절연 성능이 있는 시스템을 연구 및 설계하는 것이다. 수동 진동 흡수기는 컴프레서의 구동 주파수를 고려하여 설계했다. 또한, 특정 외란 진동과 고주파수의 진동도 절연되는 쿨러 절연 브래킷을 설계하였고, 성능 분석을 위한 실험을 수행하였다.

• 대한조선학회논문집
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• 제59권3호
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• pp.134-140
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• 2022

Ship local structure sometimes experiences severe vibration due to the resonance with an excitation force generated by the propulsion system. In that case, the installation of dynamic vibration absorber such as Tuned Mass Damper (TMD) on the structure can be considered as an effective alternative countermeasure to reduce the troublesome vibration if structural modification or change of excitation frequencies is difficult. Meanwhile, the conventional optimal design method of TMD premises the target structure exposed on an excitation force without the constraint of its magnitude and frequency range. However, the frequencies of major ship excitation forces due to propulsion system are normally bounded and its magnitude is varied according to its operation speed. Hence, the optimal design of TMD to reduce the resonant vibration of ship local structure should be differently approached compared with the conventional ones. For the purpose, this paper proposes an optimal design method of TMD considering maximum frequency and magnitude variation of a target harmonic excitation component. It is done by both lowering the resonant response at the 1st natural frequency and locating the 2nd natural frequency over maximum excitation frequency for the idealized 2 degree of freedom system consisted of the structure and the TMD. For the validation of the proposed method, a numerical design case of TMD for a ship local structure exposed on resonant vibration due to a propeller excitation force is introduced and its performance is compared with the conventionally designed one.

• Structural Engineering and Mechanics
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• 제87권2호
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• pp.117-127
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• 2023

To efficiently attenuate seismic responses of a structure, a novel pneumatic-driven active dynamic vibration absorber (PD-ADVA) is proposed in this study. PD-ADVA aims to realize closed-loop control using a simple and intuitive control algorithm, which takes the structure velocity response as the input signal and then outputs an inverse control force to primary structure. The corresponding active control theory and phase control mechanism of the system are studied by numerical and theoretical methods, the system's control performance and amplitude-frequency characteristics under seismic excitations are explored. The capability of the proposed active control system to cope with frequency-varying random excitation is evaluated by comparing with the optimum tuning TMD. The analysis results show that the control algorithm of PD-ADVA ensures the control force always output to the structure in the opposite direction of the velocity response, indicating that the presented system does not produce a negative effect. The phase difference between the response of uncontrolled and controlled structures is zero, while the phase difference between the control force and the harmonic excitation is π, the theoretical and numerical results demonstrate that PD-ADVA always generates beneficial control effects. The PD-ADVA can effectively mitigate the structural seismic responses, and its control performance is insensitive to amplitude. Compared with the optimum tuning TMD, PD-ADVA has better control performance and higher system stability, and will not have negative effects under seismic wave excitations.

• Journal of Magnetics
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• 제22권1호
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• pp.109-121
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• 2017

Ferrofluids are a special category of smart nanomaterials which shows normal liquid behavior coupled with superparamagnetic properties. One of the earliest and most prospective applications of ferrofluids is in damping, which has prominent advantages compared with conventional damping devices: simplicity, flexibility and reliability. This paper presents the basic principles that play a major role in the design of ferrofluid damping devices. The characteristics of typical ferrofluid damping devices including dampers, vibration isolators, and dynamic vibration absorbers are compared and summarized, and then recent progress of vibration energy harvesters based on ferrofluid is briefly described. Additionally, we proposed a novel ferrofluid dynamic vibration absorber in this paper, and its damping efficiency was verified with experiments. In the end, the critical problems and research directions of the ferrofluid damping technology in the future are raised.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.518-523
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• 1995

To improve the set comfort of commercial vehicles in various road conditions, it is necessary to design a seat shock absorber which can avoid the vibration zone imposing the discomfort feeling and fatigue on drivers. Through the vibration and dynamic analysis, a shock absorber that has 4 steps of damping ability is developed. Dynamic characteristics analysis of the seat damper is performed considering each valve and oil path for the design purpose.