• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.487-488
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.942-943
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• 2012

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.78-79
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.260-261
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• 2011

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.542-543
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• 2012

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.182-183
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• 2013

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.8 s.101
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• pp.988-995
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• 2005

Vibration has been severly increased at the branch pipe of main steam header since the commercial operation of nuclear power plant. Intense broad band disturbance flow at the discontinuous region such as elbow, valve, and header generates the acoustical pulsation which is propagated through the piping system. The pulsation becomes the source of low frequency vibration at piping system. If it coincide with natural frequency of the pipe system, excessive vibration is made. High level vibration due to the pressure pulsation related to high dynamic stress, and ultimately, to failure probability affects fatally the reliability and confidence of plant piping system. This paper discusses vibration effect for the branch pipe system due to acoustical pulsations by broad band disturbance flow at the large main steam header in 700 MW nuclear power plant. The exciting sources and response of the piping system are investigated by using on-site measurements and analytical approaches. It is identified that excessive vibration is caused by acoustical pulsations of 1.3 Hz, 4.4 Hz and 6.6 Hz transmitted from main steam balance header, which are coincided with fundamental natural frequencies of the piping structure. The energy absorbing restraints with additional stiffness and damping factor were installed to reduce excessive vibration.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.444-449
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• 2005

In Seoul, several railway depots are located at the places where a public can easily access. Since a depot occupy a large amount of land itself, it is natural to use those sites for a public building construction such as an apartment complex or a transportation terminal, as an example. Most of the buildings on a depot, however, are exposed to vibration problems, because foundations are excited from the dynamic loading whenever heavy trains pass on the track. Severe vibration may cause a damage to building structures and a troublesome to a community. In this paper, some vibration practices have been examined in order to resolve the vibration problems. First, a critical speed of a train in a railway depot is evaluated. Then, a structural effect on the transmission of a vibration energy has been investigated. Finally, practical approaches to reduce the vibration level have been proposed. In this first half part of the paper, the focus has been on the critical speed and a structural transmission phenomena.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1373-1378
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• 2000

Vibration caused by railroad vehicle including subway train running raises a lot of problems to the neighboring buildings. Therefore lots of methods to isolate the railway vibration have been studied and practically applied to sites. As one of them, specially designed vibration isolation device was installed in the some section of Seoul subway. This device is installed between the rail and track slab. Because the process of installation is relatively simple, this method can be applied to the existing railways in servicing. We measured the vibration and noise to check the effectiveness of this device before and after the installation. The result showed that the vibration level of the slab and platform was reduced to 7 - 10 dB. Expecially high frequency component was reduced to a large amount. From this result, we can conclude that these kind of devices are useful to the reduction of the railroad vibration, expecially the high frequency vibration which can cause structure born noise.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.11a
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• pp.99-107
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• 2000

With the results of calculation for natural frequencies, the forced reponses of coupled vibration of propulsion shafting were analysed by the modal analysis method. For the forced response analysis, axial exciting forces, axial damper/detuner, propeller exciting forces and damping coefficients were extensively investigated. As the conclusion of this study, some items are cleared as next. - The torsional amplitudes are not influenced by the radial excitation forces. - The axial vibrational amplitudes are influenced by the tangential exciting forces. An increase of amplitude is observed for the speed range in the neighbourhood of any torsional critical speed. - The coupling effect becomes larger if torsional and axial critical speed are closer together. - The axial exciting force of propeller is relatively strong, comparing with those of axial forces of cylinder gas pressure and oscillating inertia of reciprocating mechanism. Therefore, as a resume one can say, that- Torsional vibration calculation with the classical one dimension model is still valid. - The influence of torsional excitation at each crank upon the axial vibration is impotent, especially in the neighbourhood of a torsional critical speed. That means that the calculation of axial vibration with the classical one dimension model is insufficient in most of cases. - The torsional exciting torque of propeller can be neglected in most of cases. But, the axial exciting forces of propeller can not be neglected for calculating axial vibration of propulsion shafting.