• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.568-574
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• 1998

A systematic procedure for designing a direct-radiator-type loudspeaker has been developed, based on a numerical vibro-acoustic analysis and the Taguchi method. The finite-element model of the speaker cone has been used to calculate the vibration response of the cone excited by the voice coil. The vibration response of the speaker cone has been used as a boundary condition for the acoustic analysis, and the acoustic frequency characteristics of the loudspeaker have been calculated by the boundary element method. The numerical model has been confirmed by comparing the numerical results with experimental ones obtained in an anechoic chamber. Some design parameters contributing dominantly to the acoustic characteristics have been selected by using the Taguchi method, and the variations of the acoustic characteristics due to the changes of the parameter values have been examined using the numerical model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.599-604
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• 2000

Excessive vibration magnitude results in serious damage and economic losses in the turbine and generator system. Therefore, it is of importance to evaluate the accurate dynamic characteristics of the system in advance. In this paper, rotordynamic characteristics of both the shrunk-fit disc and welded drum rotors have been investigated to ensure an excellent running behavior of the system in which low-pressure(LP) turbines of a nuclear power plant were retrofitted to improve thermal efficiency and reliability. Analysis shows that the welded drum rotor has good torsional characteristics rather than the shrunk-fit disc rotor. In addition, verification testing of field test was performed to confirm the retrofit. Test results are good agreement with analysis ones.

• Journal of the Society of Disaster Information
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• v.11 no.1
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• pp.89-96
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• 2015

To reduce noise inside an elevated railroad station, the vibration of the station structure should be lowered, and to establish more effective anti-vibration measures it is required that, reflecting the track-bridge-structure interaction, the transfer characteristics of vibration induced by a train is well identified. In this paper, the current status of domestic railroad stations is classified, and the vibration transfer characteristics is analyzed via measurement data from representative elevated stations. From the analysis results on the measurement data, in transferring vibration from the track to the structure, remarkable vibration reduction in higher frequency range is observed, and, in some stations, amplified response characteristics in lower frequency range is identified. Also, for stations with floating track system or TPS type, relatively greater reduction in transferred vibration is observed.

• Structural Engineering and Mechanics
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• v.77 no.5
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• pp.601-612
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• 2021

To study the vibration characteristics of a high-speed railway continuous girder bridge-track coupling system (HSRCBT), a coupling vibration analysis model of an m-span continuous girder bridge-subgrade-track system with n-span approach bridge was established. The model was based on the energy and its variational method, where both the interlaminar slip and shear deformation effects were considered. In addition, the free vibration equations and natural boundary conditions of the HSRCBT were derived. Further, according to the coordination principle of deformation and mechanics, an analytical method for calculating the natural vibration frequencies of the HSRCBT was obtained. Three typical bridge-subgrade-track coupling systems of high-speed railway were taken and the results of finite element analysis were compared to those of the analytical method. The errors between the simulation results and calculated values of the analytical method were less than 3%, thus verifying the analytical method proposed in this paper. Finally, the analytical method was used to investigate the influence of the number of the approach bridge spans and the interlaminar stiffness on the natural vibration characteristics of the HSRCBT based on the degree of sensitivity. The results suggest the approach bridges have a critical number of spans and in general, the precision requirements of the analysis could be met by using 6-span approach bridges. The interlaminar vertical compressive stiffness has very little influence on the low-order natural vibration frequency of HSRCBT, but does have a significant influence on higher-order natural vibration frequency. As the interlaminar vertical compressive stiffness increases, the degree of sensitivity to interlaminar stiffness of each of the HSRCBT natural vibration characteristics decrease and gradually approach zero.

• Journal of KSNVE
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• v.10 no.3
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• pp.500-507
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• 2000

Dynamic forces due to mechanical and hydraulic related causes are always exerted on operating turbomachinery such as centrifugal pumps. To ensure the safety and the reliability of the pump. the magnitudes of the vibration must be kept within an acceptable limit. The focus of this paper is on the identification of the vibration behavior and the quantitative analysis of the hydraulic excitation forces. As the structure becomes more complex finite element analysis is essential to accurately predict the vibration characteristics and the excitation forces, This paper presents an experimental and analytical technique to find and solve to vibration problems in double volute double suction centrifugal pump. Measured vibration data due to the dynamic forces are presented and individual causes are identified, finally excitation forces of the pump are inversely estimated at each frequency on operating conditions.

• Journal of KSNVE
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• v.7 no.1
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• pp.143-152
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• 1997

This paper introduces experimental results of the ride qulaity characteristics of automotive seats fixed on the vibration table that is noving simultaneously to the three-axis in a similar way to the real running condition. Vibration experiment was carried out for five different automotive seats and four Korean individuals. The assessment of the ride quality characteristics for each seat and indiviual was made not only from the analysis of vibration measurements but also from the evaluation of weighied vibration signals, which were obtained using the frequency weighting function and the multiplication factor dependent on the position and axis of vibration exposure to wehole-body. The usefulness of those assessment results in analysis of the ride quality of seats is discussed and their limitation is also pointed out in this paper.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.36-42
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• 2017

Helical gear excitation is transmitted to a gearbox through the shafts and bearings and the vibration of the gearbox radiates the noise in the air. Therefore gearbox modeling is essential to evaluate the gear noise. This work deals with vibration and acoustic analysis of a cylindrical shell-type gearbox with/without holes excited by helical gears and focuses on the development of the simple gearbox model. To do so, helical gears and bearing forces are calculated. Gearbox with/without holes is modeled by the aluminum end plates and PMMA cylindrical shell body. The vibration mode and the forced harmonic response were calculated by the commercial FE software and the end plate of the gearbox is more contributed to vibration than the body. Acoustic analysis was also conducted by the commercial acoustic software and a cylindrical shell type gearbox with/without holes has the similar vibro-acoustic characteristics.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.299-304
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• 2008

Dynamic characteristics of smart hull structure are investigated and active vibration control performance is evaluated. Dynamic model of smart hull structure with surface bonded Macro-fiber Composite (MFC) actuators is established by analytical method. Equations of motion of the host hull structure are derived based on Donnell-Mushtari equilibrium equations for a thin cylindrical shell. A general model for the interaction between hull structure and MFC actuator is included in the dynamic model. Modal analysis is then conducted and mode shapes and corresponding natural frequencies are investigated. After constructing of the optimal control algorithm, active vibration control performance of the proposed system is evaluated. It has been shown that structural vibration can be reduced effectively with proper control input.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.8
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• pp.832-840
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• 2008

Dynamic characteristics of smart hull structure are investigated and active vibration control performance is evaluated. Dynamic model of smart hull structure with surface bonded macro-fiber composite(MFC) actuators is established by analytical method. Equations of motion of the host hull structure are derived based on Donnell-Mushtari equilibrium equations for a thin cylindrical shell. A general model for the interaction between hull structure and MFC actuator is included in the dynamic model. Modal analysis is then conducted and mode shapes and corresponding natural frequencies are investigated. After constructing of the optimal control algorithm, active vibration control performance of the proposed system is evaluated. It has been shown that structural vibration can be reduced effectively with proper control input.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2048-2053
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• 2003

The present study investigated the effect of the transversal vibration on the flow characteristics for non-Newtonian fluids. The effect was tested by experiment and numerical analysis. For Newtonian fluids, both of experiment and numerical analysis results showed that mechanical vibration did not affect the flow rate. For non-Newtonian fluids, however, there was significant disagreement between experiment and numerical results. The numerical results showed a negligibly small effect of vibration on the flow rate whereas experimental results showed a significant flow rate increase associated with transversal vibration. The results implied that the increased flow rate was caused not only by imposed shear rates at the wall but also by the changes of rheological characteristics due to the transversal vibration.