• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.977-981
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• 2002

The ordinary differential equations governing free vibrations of elastic horizontally curved beams are derived, in which the effect of shear deformation as well as the effects of vertical, rotatory and torsional inertias are included. Frequencies and mode shapes are computed numerically for parabolic curved beams with the hinged-hinged, hinged-clamped and clamped-clamped ends. Comparisons of natural frequencies between this study and ADINA are made to validate the theories and numerical methods developed herein. The lowest three natural frequency parameters are reported, with and without the effect of shear deformation, as functions of the three non-dimensional system parameters: the horizontal rise to span length ratio, the slenderness ratio and the stiffness parameter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.206-210
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• 1998

A study on dynamic characteristics of rotating disks in magneto optical disk drives is presented. Natural frequencies of rotating disks are investigated experimentally and numerically. The frequency response and critical speeds of the ASMO disk are discussed. The characteristics of airflow around the disk and their effects on disk vibrations are also investigated. It is found that the numerical calculation of the natural frequencies of rotating disks agrees well with the experimental results. The airflow around the disk in the cartridge affects the characteristics of the disk vibrations to reduce the modal frequencies of the disk. The experiment shows that negative vertical offsets of the disk in the cartridge possibly increase the vibration amplitudes. As being influenced by the geometry of the cartridge, the rotation of the disk causes an asymmetric airflow in the presence of window.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.395.1-395
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• 2002

The ordinary differential equations governing free vibrations of elastic horizontally curved beams are derived, in which the effect of shear deformation as well as the effects of vertical deflection, rotatory and torsional inertias are included. Frequencies and mode shapes are computed numerically fer parabolic curved beams with hinged-hinged, hinged-clamped and clamped-clamped ends. Comparisons of natural frequencies between this study and ADINA are made to validate the theories and numerical methods developed herein. (omitted)

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.726-733
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• 2000

In this article, we introduce a practical case study of the structural design improvement for a vertical machining center. During test operations, it have experienced excessive deflections and vibrations due to the fluctuating forces generated by the ball-screw thrust motor. At first we did investigate where and how much deflections and vibrations had been brought about on it. Next we made some possible structural design alternatives. It is a matter of course to compare finite element static and dynamic analysis results of both the original design and alternatives. Fortunately we have been able to find out a good one among those alternatives.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.1
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• pp.63-69
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• 2003

The ordinary differential equations governing free vibrations of elastic horizontally curved beams are derived, in which the effects of rotatory inertia and shear deformation as well as the effects of both vertical and torsional inertias are included. Frequencies and mode shapes are computed numerically for parabolic curved beams with the hinged-hinged, hinged-clamped and clamped-clamped ends. Comparisons of natural frequencies between this study and ADINA are made to validate the theories and numerical methods developed herein. The lowest three natural frequency parameters are reported. with and without the effects of rotatory inertia and shear deformation. as functions of the three non-dimensional system parameters: the horizontal rise to span length ratio. the slenderness ratio and the stiffness parameter.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.476-484
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• 2010

Precise positioning stages are often employed for precise machinery. For the purpose of vibration isolation, these precise positioning stages are mounted on a heavy base structure which is supported by compliant springs. Then the base structure is subjected to residual vibration due to the reactive force and vertical moving load induced by the stage motion. This paper investigates the vibration behavior of a positioning stage base and the associated vibration suppression technique. A dynamic model is developed to investigate the base vibration due to the reactive force and moving load effects by the moving stage. An input shaping technique is also developed to suppress the residual vibrations in base structures. Simulations and experiments show that the developed dynamic model adequately represents the base vibration and that the proposed input shaping technique effectively removes the residual vibrations from the positioning stage base.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.729-737
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• 2014

A study has been carried out that effectively controls the vibration of asymmetric cable-stayed bridges caused by earthquakes with MR dampers. In order to enhance the practical serviceability of MR dampers, an asymmetric cable-stayed bridge structure has been designed and produced, and a MR damper has been produced so as to have this bridge structure controlled appropriately. An experiment that controls vertical and horizontal vibrations has been carried out by exciting the asymmetric cable-stayed bridge in the horizontal direction with the El-centro seismic wave. The control performance of the MR damper has been evaluated under the five control conditions in the experiments of vibration control in each direction. As a result of the experiment, MR dampers were proved to control vibrations more effectively when either Lyapunov control algorithm or Clipped-optimal control algorithm was used to control vibrations of the asymmetric cable-stayed bridge caused by earthquakes. In addition, different controlling effects were found in vibration controls in vertical and horizontal directions due to the asymmetry of the structure and the horizontal excitation. With such controlling effects, semi-active MR dampers are evaluated to effectively control vibrations caused by earthquakes in flexible and asymmetric structures such as asymmetric cable-stayed bridges.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.108-113
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• 2007

This study aims to find equivalent comfort contours, reciprocal of frequency weighting curves, for vertical steering wheel vibration. Psychophysical responses were measured from twelve male subjects by using magnitude estimation of relative discomfort due to vertical steering wheel vibrations of magnitude of 0.1 to 1.58 $m/s^2$ in the frequency range of 4 to 250 Hz. Relative discomfort were estimated with a reference vibration of 0.4 $m/s^2$ at 31.5 Hz. Equivalent comfort contours were produced from the median of sensation magnitudes judged by twelve subjects, which showed variation in the shapes with increase of vibration magnitude. A shape of the contour came close to the perception threshold curve with decrease of vibration magnitude. When the vibration magnitude increases, the shape changed close to those in the references of Hong and et al (2003). It is also recommended frequency weighting curves for vertical steering wheel vibration must be expressed as a function of vibration magnitude as well as frequency.

• Bulletin of the Society of Naval Architects of Korea
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• v.12 no.2
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• pp.3-12
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• 1975

As for two dimensional added mass coefficients for straight framed hull forms in a free surface of an ideal fluid, theoretical calculations by F.M. Lewis, vertical, K. Wendel, J.H. Hwang, and etc. are available; vertical modes of rectangular and triangle sections by Lewis, vertical, horizontal and torsional models of rectangular and triangle section by Wendel, and systematical calculations for vertical modes of single chine forms by Hwang. In this paper, employing the conformal transformation by which a unit circle and its exterior region can conformally mapped to a polygon and its exterior region, the author calculated two dimensional added inertia coefficients systematically for straight framed sections with single chine in horizontal and torsional modes of vibrations. As the results, it was found that sloping side angle is an important factor measuring the magnitude of two dimensional added inertia coefficient for a set of given values of the sectional area coefficient and the beam-draft ratio. To grasp it cleary in physical sense, pressure distributions are investigated for some typical section contours. The numerical results are presented graphically in the form of two dimensional added sectional area coefficients with beam-draft ratios and sloping side angles as parameters, so that the data may conveniently utilized for estimation of the added inertia coefficients based on a three parameter technique.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.730-733
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• 2003

In this study, it have been measured the vertical and lateral vibrations of car bodies which have an equivalent conicity of 1/20 and 1/40. Based on the measured data, it is revealed that the wheel, XP-50, which has the equivalent conicity of 1/20 causes the better riding comfort of KTX.