• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.2
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• pp.119-126
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• 2009

LCVA has an advantage that its natural frequency can be easily controlled by changing the area ratio of the vertical column and horizontal part. The previous studies investigated the dynamic characteristics of the LCVA under harmonic load. This study experimentally obtained the first and second mode natural frequencies of the LCVA from shaking table tests using white noise and compared the values with the ones by previous study. Test results show that the measured first mode natural frequency of the LCVA has a different value compared with calculated one. The effective length($L_e$) was revised using by power equation. In the case01 to 19, the standard deviation($S_r$) is 4.7292 and the coefficient of correlation(r) is 0.9856. In the case21 to 61, the standard deviation($S_r$) is 14.2143 and the coefficient of correlation(r) is 0.9935. The second mode frequency increases with the increasing area ratio, which is due to the sloshing motion effect resulting from the large area of the vertical column.

• Journal of Digital Convergence
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• v.14 no.6
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• pp.513-518
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• 2016

The Mechanisms of whole body vibration on the human body is not clearly presented despite of the research result and there is not enough research that shows the effects of vibration on the kinetic changes of the lower joint. Therefore, this study focuses on finding out which lower joint is related with kinetic vertical jump ability. Five male and five female who didn't have orthopedic history were selected as the subjects. The subjects carried out three squat jumps before and after 5minutes of 30Hz whole body vibration. We have utilized a 3D motion analysis system to analyze the kinetic changes of the lower joint in the vertical jump. The height of subjects squat jump was improved after whole body vibration treatment. Also, the lower joint moment and power increased. However, there were no statistically significant changes in GRF, hip joint moment and power after the whole body vibration proved to have positive effect on the ankle and knee joints but showed negative effect on the hip joint.

• Computational Structural Engineering
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• v.26 no.2
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• pp.48-54
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• 2013

• Structural Engineering and Mechanics
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• v.55 no.5
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• pp.1015-1035
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• 2015

A three-dimensional (3D) numerical analysis for the train-bridge interaction (TBI) system is actively developed in this study in order to investigate the vibration characteristics of rigid-frame reinforced concrete (RC) viaducts in both vertical and lateral directions respectively induced by running high-speed trains. An analytical model of the TBI system is established, in which the high-speed train is described by multi-DOFs vibration system and the rigid-frame RC viaduct is modeled with 3D beam elements. The simulated track irregularities are taken as system excitations. The numerical analytical algorithm is established based on the coupled vibration equations of the TBI system and verified through the detailed comparative study between the computation and testing. The vibration responses of the viaducts such as accelerations, displacements, reaction forces of pier bottoms as well as their amplitudes with train speeds are calculated in detail for both vertical and lateral directions, respectively. The frequency characteristics are further clarified through Fourier spectral analysis and 1/3 octave band spectral analysis. This study is intended to provide not only a simulation approach and evaluation tool for the train-induced vibrations upon the rigid-frame RC viaducts, but also instructive information on the vibration mitigation of the high-speed railway.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.11
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• pp.1089-1098
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• 2012

A faulting could be occurred at the end of deck by unexpected loads to bridge bearing after a bridge completion. Serviceability of bridges could be impaired by the faulting which is caused structural damage. Therefore, smart bridge bearing which can continuously observe the supporting points is needed. Some of bridge bearings have been developed for measuring vertical load and vertical displacement by installing sensors in the bearing. In those systems, however it is not easy to be replaced with new sensors when repairs are needed. In this study, the smart bridge bearing of which sensors can be replaced has been developed to overcome such a problem. In this study, strain signals were used for measuring both of vertical displacements and loads. FBG sensors(fiber optic Bragg-grating sensors) have been used for measurement of the strain signals since it is prevented from electronic noise by mediating light, enables the simplification of the measuring cable by multiple measurement, and is easy to place by lightweight and small size. The possibility of use was reviewed for smart bridge bearing based on FBG sensors through tests.

• Journal of KSNVE
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• v.8 no.6
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• pp.1015-1022
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• 1998

This paper addresses the results of an experimental and analytical research of a helical coil spring subjected to dynamic behavior using space curve vector after considering elongation rate. Vibrations in helical coil spring can be divided into 3 modes such as vibrations of coil spring center axis' vertical direction. axis' horizontal direction, direction about center axis. However. these 3 modes are dependent one another and are characterized as coupled. The dependency was proved through both theoretically and experimentally analyzing the results of dynamic characteristics of coil spring center axis' vertical direction vibration by transfer matrix method using the governing equation of static equilibrium. Also this paper shows that pitch angle and active coils in coil spring affect the dynamic spring characteristics of the above 3 modes and are especially sensitive to the mode for vibration of axis' horizontal direction which most affects especially on dynamo stability of helical coil spring.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.613-616
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• 2012

A multi body simulation (MBS) model is developed for predicting the impact harshness of the vehicle. Impact harshness is the vehicle performance to evaluate the impulsive vibration behavior during driving over an obstacle of the road. Thus, the approach is simulated on the time domain for considering the transient behavior of the vehicle. The validity of vehicle component modeling of bushes, dampers and structure flexibilities is verified. The simulations are compared with the test results in both of vertical and longitudinal directions. In particular, the vertical vibration of the vehicle is significantly affected by the body flexibility. Through the sensitivity analysis, main factors for the impact harshness performance are investigated.

• Plant Journal
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• v.9 no.1
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• pp.43-49
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• 2013

In this study, the natural frequency of the actual operating vertical pump in the P combined cycle power plant is measured and the cause of high vibration is determined by using fluid-structure coupled vibration theory. Choosing the vibration reduction plan suited for field conditions and using the numerical analysis verify effectiveness of the plan. The plan is applied to the actual pump and the empirical experiments are conducted.

• Journal of Navigation and Port Research
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• v.41 no.5
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• pp.337-344
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• 2017

In the offshore crane system, the requirements on the operating safety are extremely high due to many external factors. Rope extension is one of the factors producing vertical vibration of load. In this study, the load is carried by the motor-winch actuator control and the rope is modeled as a mass-damper-spring system. To control the load position and suppress the vertical vibration of the load, a control system based on input-output linearization method is proposed. By the simulation and experiment results with pilot crane model, the effectiveness of proposed control method is evaluated and verified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1293-1299
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• 2001

The purpose of this study is to analyze the effects of the parameters of the mass ratio of the car body and the bogie frame in railway rolling-stock for KT-23 type passenger vehicle. According to the results of simulation and the small scale car test. optimal condition was obtained for the mass ratio of the car body and the bogie frame. Also. it is usefull to improve the technology of the ride quality of passenger vehicle.