• Journal of KSNVE
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• v.9 no.4
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• pp.754-760
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• 1999

The valve motions of a reciprocating compressor generate the pressure fluctuation at the plenum which is a main source of noise and vibration of a compressor unit. But a cycle of a compressor process consists of complicated phenomena interacting in a short period of time. A mathematical model is developed by simplifying and idealizing the complicated phenomena to simulate the compressor process. The governing equations about the pressure and working fluid flow are developed from the unsteady Bernoulli equation. The pressure fluctuations at the plenums are derived from the Helmholz's resonator model. The valves are modeled as one degree of freedom spring-mass-damper system. This model is verified by the experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.558-563
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• 2014

To reduce the transmission of large gun-generated noise from the firing test range to the community, we have tested a silencer to be used with howitzer(155mm KM114A2) after simulation. Numerical analysis was conducted by using a commercial CFD code, FLUENT. To analyze complex blast flow fields, the Spalart-Allmaras model was applied under 2 dimensional and axisymmetric conditions. Firing tests were also performed with the KM114A2 howitzer while the silencer was installed. This paper describes a result of comparison between results of computer analysis and test outcomes which were gotten by firing 155mm projectiles at the testing range. This paper will also be informative to the muffler design which will be adapted to 155mm large gun in the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1007-1010
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• 2006

In order to optimize the rotating angle of the auto louver, the air-cleaner with turbo fan was numerical and experimentally analyzed . The noise generated from the auto louver was changed by modifying the installation angle of the louver. Flow field and flow noise were analyzed numerically by commercial tool SC/Tetra and FlowNoise S/W. Experiment was also done at anechoic chamber. From the numerical and experimental data, we can find the optimal rotating angle for auto louver of the air-cleaner.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.920-923
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• 2004

천공 요소는 자동차나 공조기 등의 유체기계의 흡/배기계에 널리 사용된다. 천공요소는 일반적으로 유동과 소음원이 동시에 존재하는 환경에서 사용되며, 유동 및 음압 레벨의 변화에 의해서 큰 영향을 받게 된다. 천공요소의 임피던스의 변화는 소음기의 음향학적 특성에 영향을 미치게 되므로, 유동이나 음압 조건이 임피던스에 미치는 영향에 대한 연구가 중요하다. 본 연구에서는 통과하는 유동이 존재하는 천공요소의 임피던스를 실험을 통하여 측정하고 경계요소법을 사용하여 예측하였다. 측정 및 예측된 임피던스를 무차원화 해석을 수행하여 영향을 미치는 인자들을 분석하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.239-245
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• 2006

In this paper, the performance of a toggle brace-MR damper system is evaluated for the control of the structure excited by earthquake load and the non-linearity of the toggle system is investigated. Considering that the control force of MR damper described by Bingham model is a function of velocity, velocity amplification factor by the toggle brace system is calculated and the effect of toggle configuration on the amplification factor is also evaluated. Numerical results show that the control performance can be largely enhanced using toggle brace system especially for the case that the MR damper installed with conventional brace system such as Chevron and diagonal cannot provide enough control force under severe earthquake load.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1199-1205
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• 2011

In the present work, a seat suspension system adopting semi-active damper is evaluated for driver's ride quality. A cylindrical type of ER(electrorheological) damper is designed and manufactured for the seat suspension of heavy vehicles. The governing equation is derived under consideration of human vibration. A sliding mode controller is then synthesized and experimentally realized on the manufactured ER seat suspension while a driver is sitting on the controlled seat. Ride quality is evaluated by fatigue decreased proficiency boundary, vibration dose value and crest factor utilizing weighted-acceleration according to ISO2631.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1000-1007
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• 2007

In this study, structural vibration analyses of a smart unmanned aerial vehicle (UAV) have been conducted considering dynamic hub-loads of tilt rotor. Practical computational structural dynamics technique based on the finite element method is applied using MSC/NASTRAN. The present UAV(TR-S5-04) finite element model is constructed as a full three-dimensional configuration with different fuel conditions and tilting angles for helicopter, transient and airplane flight modes. In addition, the 3-dimensional supporting equipment structures of electronic devices are considered for vibration analysis. As the results of this study, transient structural displacements and accelerations are presented in detail. Moreover, vibration characteristics of structural parts and installed equipments are investigated for different fuel conditions and tilting angles.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.313-317
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• 2001

Magneto-Rheological fluid (MR fluid) is known as a class of functional fluid with controllable apparent viscosity of the fluid by the applied magnetic field strength. Extensive researches with the functional fluids have been done on applications of the fluid to mechanical components such as suspension, absorber, engine mount, clutch, break, valve, etc. In this study, a new torsional damper using MR fluid is proposed, and the response property of the damper was theoretically investigated. The present damper is quit effective for reducing the driveline vibration in a wide range of the engine speed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.61-66
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• 2002

The nonlinear differential equations of motion of a fluid conveying curved pipe are derived by use of Hamiltonian approach. The extensible dynamics of curled pipe is based on the Euler-Bernoulli beam theory. Some significant differences between linear and nonlinear equations and the dynamic characteristics are discussed. Generally, it can be shown that the natural frequencies in curved pipes are changed with flow velocity. Linearized natural frequencies of nonlinear equations are slightly different from those of linear equations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1049-1054
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• 2002

Fluid Pulsation in pipe usually cause several forces and these forces make mechanical vibration and noise. Protecting pipe from mechanical vibration is very important problem because vibration make pipe damage and break. To analyze pipe, we must formulate both the fluid pulsation force and vibration of pipe. In this paper fluid force from pulsation is modeled by Fluid Dynamics and solved by FEM(finite element method). The discharge pipe is also modeled by the FEM with use of 6 dof beam model. The acceleration of discharge pipe is estimated by the suggested method in this paper. The comparision of estimated results with experimental results show good agreement, which verified the validation of this method