• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.5
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• pp.462-467
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• 2009

Reduction of the structure-borne noise of the naval vessel is very important in order to reduce the underwater radiated noise of it. One of the important factors to reduce the structure-borne noise of the installed machine in a ship is the design of the foundation having sufficiently high mechanical impedance. In this paper, the mechanical impedance of the foundation for the fan-coil unit in a naval vessel is evaluated numerically according to variation of the thickness of the foundation. And also, the forced vibration analysis is conducted considering the dynamic property of the anti-vibration mount. Through the analysis results, it can be known that the dynamic property of the anti-vibration mount should be considered when the minimum level of the mechanical impedance of the foundation is set.

• Journal of KSNVE
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• v.9 no.3
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• pp.493-501
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• 1999

The vibration modes of resilient mounting system and foundation structure which support diesel engine/generator set and acoustic enclosure walls play an important role in the vibration transmission process. So, it is necessary to perform vibration mode analysis of resilient mounting system and foundation structure. For some reasons, if the vibration modal analysis of resilient mounting system and foundation structure of acoustic enclosure could be simultaneously done by finite element method, it would be very efficient approach. In this paper, vibration modal analysis method using finite element method for multi stage mounting system having n d.o.f model was proposed. Vibration analysis of single and double stage resilient mounting system was performed to verify the validity of the proposed method. Also frequency response results were compared in case of rigid foundation model and finite element foundation model which was compared with experimental modal analysis results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.423-426
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• 2007

In this paper, vibration reduction of resiliently mounted machinery and effect of the foundation impedance is studied. SBN (Structure-borne noise) reduction through the mount is analyzed by assuming that the system is modeled as a mass-spring system, while the impedance of the floor is included in the prediction. The comparison of the SBN difference through the mount between predictions and measurements show that the slopes are similar in the case of single-mount system, while the measurements differs significantly from the predictions in the case of the double-resilient system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.227-231
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• 2014

Underwater radiated noise is one of the vital factors in underwater weapon systems like submarine. A passive elastic mount is an effective reduction method for the vibration from a ship-board machinery transmitted to the hull which is radiated as noise outside the hull. A passive elastic mount shows the limitation on the vibration reduction and needs multi stage mounting system including double stage one to meet the required underwater radiated noise criteria. It is necessary for the multi stage mounting system to consider the large displacement in the underwater shock explosion. So it is difficult to apply the multi stage mounting system in submarine because of space limitation. Also recent navy sonar system are trying to have the capability to detect the ship-borne acoustic signals in the low frequency range. An alternative to the passive mount is an active mount with moving-coil type electromagnetic actuator based on a conventional rubber mount in the low frequency range. In the previous paper, 4 active mounts with moving-coil type electromagnetic actuator based on the rubber mount were installed on the hard floor of the facility, which means no consideration on the elastic foundation effect for the control of the active mounts was taken into account. In this study, an experimental performance analysis on the active mount was carried out using 4 active mounts installed on the cylindrical structure to investigate the elastic foundation effect.

• The Journal of Engineering Geology
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• v.30 no.3
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• pp.289-302
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• 2020

To determine the shallow subsurface structure and sliding surface of land creeping in 2016 at Hadong-gun, Gyeongsangnam-do, geophysical surveys (electric resistivity, and refraction seismic methods, borehole televiewer) and slope stability analysis were conducted. The subsurface structure delineated with borehole lithologies and seismic velocity structures provided the information that the sediment layer on the top of the slope was rather as thick as 20 m and the underlying weathered rock (anorthosite) was thinner than 1 m. Based on the tension cracks observed during the geological mapping, televiewer scanning was performed at the borehole BH-2 and detected the intensive fracture zones at the ground-water level, associated with the slip weak zones mapped in dipole-dipole electrical resistivity section. Downslope sliding and slightly upward pushing at the apex of high resistive bedrock explains the curved slip plane of the land creeping. Such a convex structure might play a role of natural toe abutment for preventing the downward development of slip weak zones. In slope stability analysis, the safety factors of the slip weak zone are calculated with varying the groundwater levels for dry and rainy seasons and the downslope is founded to be unstable with safety factor of 0.89 due to fully saturated material in rainy season.