• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.293-296
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• 2005

This paper is concerned with the sweeping damping controller for beam. The active damping characteristics can be enhanced by moving the damper along the longitudinal axis. In this paper, the equation of motion for a beam including a sweeping damping controller is derived and its stability is proved by using Lyapunov stability theorem. It is found from the theoretical study that the sweeping damping controller can enhance the active damping characteristics, so that a single damper can suppress all the vibration modes of the beam. To demonstrate the concept of the sweeping damping control, the eddy current damper was applied to a cantilever, where the eddy current damping can move along the axis. The experimental result shows that the sweeping eddy current damper Is an effective device for vibration suppression.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.838-843
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• 2001

Internal damping plays an important role in some rotor dynamic systems with the use of various materials for shafts, for example, composite material. However, although the effects of internal damping have been investigated for a couple of decades, there are several different internal damping models in use, none of which are accepted as the most reliable model. The purpose of this paper is to compare the results of dynamic analysis of rotor systems with several different internal damping models. The exact dynamic element method is used to formulate and analyze the problem. The simulation results provided in this paper may be useful for the dynamic analysis of high rotor systems subject to significant internal damping.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.12
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• pp.964-969
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• 2002

The flexural vibration of laminated composite beams with passive constrained layer damping has been investigated to design structure with maximum possible damping capacity. The equations of motion are derived for flexural vibrations of symmetrical, multi-layer laminated beams. The damping ratio and modal damping of the first bending mode are calculated by means of Iterative complex eigensolution method. This paper addresses a design strategy of laminated composite under flexural vibrations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.465-468
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• 2004

The performance of the piezoelectric patches as vibration control elements depends on the shunting electronics which are designed to dissipate vibration energy through a resistive element. In this study, tuning of the shunting circuits is performed based on the wave propagation characteristics. Optimization of the electronic component is performed depending on the dynamic and geometric properties which include boundary conditions and position of the shunted piezoelectric patch relative to the structure. The developed tuning methods showed superior capabilities in minimizing structural vibration and noise radiation compared to other tuning methods. The tuned circuits are relatively insensitive to changes in modal properties and boundary conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.637-640
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• 2004

Structural damping enhancement of composite flexures and aeroelastic stability of a hingeless rotor system are investigated. Constrained layer damping (CLD) treatments are applied in order to increase structural damping of flexures. Material damping property of viscoelastic layer is modelled as complex modulus. Modal analysis of composite flexures with attached viscoelastic layers and constraining layers are performed using MSC/NASTRAN and the effects of CLD treatments are verified with the modal test results. The composite flexures with CLD are applied to a 4-bladed, 2-meter diameter, Froude-scaled, soft-in-plane hingeless rotor system. The aeroelastic stability is tested at hovering condition and the effects of CLD are investigated. It is shown that the CLD treatment effectively enhance the aeroelastic stability at hover.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.188-192
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• 2004

The purpose of this study is to develop an air spring mount that has high damping characteristic. The new type air spring mount has a polyurethane core in the center. By adding the core, the air spring mount shows excellent damping effect and good resistance to lateral force. This study includes both the analytical study and the experimental study of the new type air spring mount.

• Journal of KSNVE
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• v.10 no.1
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• pp.144-152
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• 2000

The identification of a nonlinear vibration system based on the time domain parametric model has been widely studied in recent years. In most of the studies, the NARMAX model has been used for the identification of a nonlinear system. However, the computational load for the identification with this model is quite heavy. In this paper, a new modeling procedure for nonlinear system identification in discrete time domain is proposed. The proposed model has less initial nonlinear terms than NARMAX model, and the terms in the proposed model are derived from physically meaningful way. The performance of the proposed method is evaluated through the simulation, and the result shows that the proposed model can identify the nonlinear characteristics of the vibration system very will less computational effort.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.465-468
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• 2005

The paper deals with the influences of external damping and tip mass on dynamic stability of a vertical cantilevered pipe conveying fluid. In general, real pipe systems may have some valves and attached parts, which can be regarded as attached lumped masses and support-dampers. The support-dampers can be assumed as viscous dampers. The equations of motion are derived by energy expressions using extended Hamilton's principle, and some numerical results using Galerkin's method are presented. Critical flow velocities and stability maps of the pipe with external dampers and tip mass are obtained for various tip mass ratios, external damping coefficients and positions of the viscous dampers.

• Journal of Korea Multimedia Society
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• v.6 no.7
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• pp.1131-1138
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• 2003

Active noise control(ANC) is an approach to noise reduction in which a secondary noise source destructively interferes with the unwanted noise is introduced. Generally, the performance of ANC is determined how well a secondary noise tracks noises. A secondary noise is generated from the cancelling speaker and a error sensor pick up error signal. The transfer function between the cancelling speaker and the error sensor is not flat and distorts secondary noises. Consequently, the performance of ANC is degraded by the transfer function. In this paper, a single sensor ANC which considers the characteristics of the speaker and the error sensor is proposed. To reduce distortion of secondary noises, the transfer function is estimated by adaptive inverse modelling and the primary noises are estimated by Kalman filter. Experimental results show that the proposed single sensor ANC effectively attenuates noises.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.4
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• pp.369-373
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• 2016

Accurate identification of damping matrix in structures is very important for predicting vibration responses and estimating parameters or other characteristics affected by energy dissipation. In this paper, damping matrix identification method that use normal frequency response functions, which were estimated from complex frequency response functions, is proposed. The complex frequency response functions were obtained from the experimental data of the structure. The nonproportional damping matrix was identified through the proposed method. Two numerical examples (lumped-mass model and cantilever beam model) were considered to verify the performance of the proposed method. As a result, the damping matrix of the nonproportional system was accurately identified.