• Structural Engineering and Mechanics
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• 제51권4호
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• pp.643-650
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• 2014

A chaotic vibration isolation system is designed according to the chaotic vibration theory in this paper. The strong nonlinearity is generated by the system. Line spectra in the radiated noise maybe easily detected caused by marine vessels. It is Important to reduce the line spectra by improving the acoustic stealth of marine vessels. A multi-degree-freedom (MDF) nonlinear vibration isolation system (NVIS) system is setup by the experiment and finite element method. The model is established with finite element method. The results show that the behavior of the device gradually varies from period bifurcation into chaotic state and the line spectrum is changed from single spectral structure into broadband spectral structure. It is concluded that chaotic vibration isolation is preferable contrasted on line spectra isolation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1437-1441
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• 2007

This paper formulates the finite element model is formulated taking into consideration of the effects of the fluid flow in a pipe. The characteristic of vibration is presented using mass, damping and stiffness matrix in the finite element equation of this pipe system. The displacement distribution of pipe system caused by fluid force is discussed. The variation of vibration of a pipe system according the change of mount stiffness is discussed.

• 소음진동
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• 제5권4호
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• pp.555-563
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• 1995

This paper proposes the method of antiresonance frequency analysis of multi-input multi-output system. The structural dynamic modification techniques by antiresonance frequency analysis are also applied to reduce the undertest at specimen attachment points on the fixture in environmental vibration test, which is resulted from the inconsistency of antiresonance frequencies at any specified points. Several computer simulations show that the proposed method can remove the undertest problem which is not removed in conventional vibration test control. And the effectiveness of the method is verified with the impact hammer excitation of aluminium fixture model.

• 융복합기술연구소 논문집
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• 제9권1호
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• pp.21-24
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• 2019

This research presents an development of impact damper for reduction of vehicle vibration from road excitation. The structural vibrations are transferred through the vehicle body. The impact damper for reducing structural vibration from road excitation were designed and derived by using simplified numerical model. To analyze the characteristics of the impact damper, the vibration of simplified beam attached to impact damper was simulated. The damping ratios for different mass ratios of the impact dampers were calculated. The numerical results can be utilized to reduce the radiated noise from the electric vehicle.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제2B권3호
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• pp.95-99
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• 2002

This paper deals with the influence of the various stator structures in a Switched Reluctance Motor (SRM) on the vibration behaviors. The stator part in SRMs produces most vibrations. Therefore, the geometric design of the stator is necessary to reduce the vibration. The free and forced vibrations for four different stator yoke structures are analyzed by the electromagnetic and structural Finite Element Method (FEM). Then vibration stator structure that offers less is proposed. The modal analysis results of a tested motor are compared with measurements.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권4호
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• pp.151-155
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• 2001

The simple motor construction and low cost, fault tolerant power electronic drive has made the switched reluctance drive a strong contender for many applications. But the switched reluctance drive does exhibit higher levels of vibration and acoustic noise than that of most competing drives. The main source of vibration in the switched reluctance drive is generated by rapid change of radial magnetic force when phase current is extinguished during commutation action. In this paper, a hybrid excitation method is proposed to reduce vibration and acoustic noise of the switched reluctance drive. The hybrid excitation has 2-phase excitation by long dwell angle as well as conventional 1-phase excitation. The vibration and acoustic noise are reduced because the scheme reduces abrupt change of excitation level by distributed and balanced excitation.

• 소음진동
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• 제10권3호
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• pp.457-464
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• 2000

Vibrations of a fan are often generated by mechanical unbalance magnetic force and air flow. These vibrations depend on the design of a fan the machining accuracy of each element and assembled conditions. An experimental study is carried out to reduce the vibration and noise of an industrial fan in this paper. In order to identify the vibration sources of a fan the signal analysis and system analysis are performed, It is shown that the industrial fan studied in this paper has a natural frequency at 144 Hz and resonance occurs when the running speed of the fan is 1750 rpm. The results may be helpful to design a fan with low vibration and noise.

• 대한기계학회논문집A
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• 제20권2호
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• pp.564-574
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• 1996

This paper describes as Electronic Speckle Pattern Interferometry system which has been designed for measuring vibration patterns and quantitative measurement of vibration amplitude fields by using the time average method on a object. Visbility of fringe patterns is more improved by using the phase stepping and frame average method to reduce speckle and electric noise. And a bias vibration is introduced into the reference beam to shift the $\frac{2}{0}$ fringes so that fringe shift algorithms can be used to determine vibration amplitude. The experimental results are compared to those of the FFT analyzer and the FEM model analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.518-523
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• 2009

Main source of URN(Underwater Radiated Noise) which is related to the ship's survivability is divided into two groups. Cavitation is main source of URN when the speed of ship is upper than CIS(Cavitation Inception Speed). But when the speed of ship is lower than CIS, main source of URN is structure-borne noise on the hull which is originated from propulsion system, pump system or transmitted vibration of pipe system. In this paper, to reduce the vibration of discharge pipe and valve system, back flow prevent globe valve and new rubber mount are applied to the ship. As the result of applying new valve and mount, the vibration is reduced drastically.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계 학술대회논문집(수송기계편)
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• pp.41-44
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• 2005

This paper described improvement and operation of a 'Tail-Fan' anti-torque performance test system KARI (Korea Aerospace Research Institute) developed a 'Tail-Fan' anti-torque system of a helicopter and a performance test-rig to test the performance of the Tail-Fan. The test-rig was improved for full rotating test in 4300rpm(100%). Machinery and hydraulic parts ware changed to reduce vibration and to increase safety. To find the operation rotating speed for the performance test, vibration test were carried out rising accelerometers on tail gear box. The performance test conditions of the Tail-Fan to avoid a resonance were found from vibration test results. The Tail-Fan operation tests were performed safely frier to carry out performance test.