• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.268-275
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• 2000

A hybrid mass damper that combines a tuned mass damper and an actuator has been recognized to be one of the most promising devices for vibration control of a tall building subjected to dynamic loads such as wind and earthquake. In this paper, in order to reduce vibration levels of a 5-story test structure, a hybrid mass damper using AC-servomotor was designed and developed. And control performances using HMD and TMD under random and earthquake excitations are compared through experimental test. It is confirmed that it is more effective to reduce the vibration levels of the test structure using HMD especially for earthquake excitation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.37-43
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• 1991

An efficient method for generating floor response spectra with the structure-equipment interaction effects is proposed. Floor response spectra are computed from a prescribed ground response spectrum by a random vibration approach. Transfer function of equipment response for earthquake excitation is constructed directly from the modal properties of the individual structures. The method also can account for the nonproportional damping characteristics of the combined system.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.37-41
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• 1995

In order to analyze the rolling motion of a ship in random beam waves we use the partial stochastic linearization method. The quadratic damping and the nonlinear restoring moments given by the odd polynomials up to the 11th order are added to a single degree of freedom linear equation of roll motion. The irregular excitation moment is assumed to be the Gaussian white noise. The statistical characteristics of the response by the partial stochastic linearization method is compared with results by the equivalent linearization method and Monte Carlo simulation. It is fecund that the partial stochastic linearization method is not necessarily superior to the equivalent linearization method.

• Journal of Biosystems Engineering
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• v.21 no.3
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• pp.293-305
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• 1996

Effects on the tractor vibrations of tread, wheelbase and axle load distribution were analyzed by using mathematical models of tractor and random road surface. A 4 degrees of freedom tractor model was developed to predict the bounce, pitch and roll motions of tractor. The front axle which is constrained to roll with respect to tractor body was also included in the model. A random road profile was generated and used as an excitation input to the tractor. Output vibrations of the model were predicted and analyzed by a computer simulation method. In general, longer tread tends to reduce rolling and longer wheelbase does bouncing and pitching motions. Tractor vibrations were minimum when the ratio of front to rear axle loads was in the range of 30:70-35:65. Sensitivity analysis showed that rolling and pitching motions most sensitively varied with changes in tread and wheelbase while bouncing motion did with the location of mass center.

• Journal of KSNVE
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• v.8 no.3
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• pp.513-523
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• 1998

Impact response of a vibro-impact system and its contact mechanism was studied. The vibro-impact system is composed of a small secondary system is constrained to move along a slot of fixed length in a large primary system. The contact mechanism is characterized by its coefficient of restitution. Numerical simulation analysis has been used to determine the time-history and the impact statistics of the primary and secondary systems. Input excitation of the primary system was random, and the responses obtained were the velocities of the primary and secondary system, the closing velocity in time axis and the duration time between impacts. The validity of the numerical simulation method was checked by comparing the results with those obtained by other researchers analytically. It is shown that the results obtained by the nemerical simulation analysis showed a good agreement with those for the analytical method.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.785-790
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• 2008

Vibration of a non-linear system under random parametric excitations was evaluated by probablistic methods. The non-linear characteristic terms of a system were quasi-linearized and excitation terms were remained as they were given. An analytical method where the square mean of error was minimized was ysed. An alternative method was an energy method where the damping energy and rstoring energy of the linearized system were equalized to those of the original non-linear system. The numerical results were compared with those obtained by Monte Carlo simulation. The comparison showed the results obtained by Monte Carlo simulation located between those by the analytical method and those by the energy method.

• KSTLE International Journal
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• v.1 no.1
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• pp.29-33
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• 2000

In this study, a methodology is developed and confirmed to find the physical contact between the slider and disc due to the defects of disk during head seeking operation using acoustic emission (AE) signal. The head/disk contact was detected during random and standard seeks, whereas no contact was detected during track fellowing. During standard and random seeks, the torsion mode of slider excitation was observed at 680KHz. Therefore, it is thought that AE technique can be used as an alternative method of the glide test by monitoring existence of the torsional mode of the slider during seek operation or can be used to detect the spacing loss during seeking operation. By appropriately choosing the location of the sensor an order of magnitude increase in the sensitivity for RMS AE signal is observed. Therefore we can find take-off velocity clearly with high signal to noise ratio of AE signal.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.55-59
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• 1997

Investigation is performed on the stability of general form of dynamic system whose damping and stiffness are varying in irregular manner along time, which is a preliminary result in the course of research on the characteristic and the control of the stochastic system. The governing equation of the 'parametric' system is derived via F-P-K approach in stochastic sense. The influence on the stability due to the magnitude of auto power spectral density and cross power spectral density of random variation of system parameters is studied and the region is surveyed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.60-68
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• 1997

The motion of an aircraft landing gear over rough runway at variable speed is nonstationary. In this paper a method for the computation of nonstationary response variance is presented which uses a state space form for the combination of landing gear and runway excitation. The dynamic characteristics of the landing gear under nonstationary random excitations has also been analyzed using the proposed method. The formulation is for linear systems of arbitrary order and allows any deterministic velocity history. It has been found by a series of simulation that correlation parameter, damping coefficients of landing gear and tire, and velocity profiles plays a prominent role on the dynamic characteristics.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.4
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• pp.39-45
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• 1993

In order to analyze the rolling motion of a ship in random beam waves we have used the equivalent linearization method. The quadratic nonlinear damping, the cubic and quintic nonlinear restoring moments were added to a single degree of freedom linear equation of roll motion. The irregular excitation moment was assumed to be the Gaussian white noise. The statistical characteristic of the response by the equivalent linearization method was compared with the simulation result.