• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.716-720
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• 2006

In order to examine the effect of constant excitation on nonlinear interactions in vibrating modes of circular plates, we added a constant term to a harmonic excitation. A two-degree-of freedom system is derived by using the Galerkin's procedure. The system is shown to have quadratic and cubic nonlinearities subjected to a harmonic excitation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.703-708
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• 2006

The cantilever beam with nonlinearity has many dynamic characteristics of nonlinear vibration. Nonlinear terms of a flexible cantilever beam include inertia, spring, damping, and warping. When the beam is given basic harmonic excitation, it shows planar and nonplanar vibrations due to one-to-one resonance. And when the one-to-one resonance occurs, the flexible beam shows different behaviors in those vibrations. For the one-to-one resonance occurring in each mode, the phase value of the planar vibration is different from that of the nonlinear vibration. This paper investigates the phase change and the phase difference between such planar and nonplanar vibrations which are caused by one-to-one resonance.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.139-142
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• 2006

This paper describes a new method using random modulated strategies for switched reluctance machines. The proposed method is combined random turn-on, turn-off angle technique and random pulse width modulation technique. The purpose of this proposed method is to decrease harmonic spectrum, and thus reduce the emitted acoustical noise. A random generator is generated by linear congruential generator (LCG) using random pulse position (RPP) scheme. Simulation results show that the harmonic intensity of proposed method is better than that of conventional method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.6
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• pp.583-592
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• 2010

Equations of motion of thin-walled composite H-type cross-section beams exposed to concentrated harmonic and non-harmonic time-dependent external excitations, incorporating a number of nonclassical effects of transverse shear, primary and secondary warping, and anisotropy of constituent materials are derived. The forced vibration response characteristics of a composite H-type cross-section beam exhibiting the circumferentially asymmetric stiffness(CAS) configuration are exploited in connection with the structural bending-torsion coupling resulting from directional properties of fiber reinforced composite materials.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1997.04a
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• pp.116-116
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• 1997

배경 및 목적: 전신마취를 위하여 시행한 기관내 삽관은 삽관튜브와 성대내면의 접촉에 의한 압력과 마찰로 후두 미세한 손상을 주게된다. 저자들은 단기간 기관내 삽관 전,후의 음성분석을 통하여 손상의 유무와 회복을 측정할 수 있는 객관적인 음성지표를 찾아보고자 하였다. 대상 및 방법: 만성 중이염 수술시 전신마취를 목적으로 경구기관 튜브를 거치한 성인 남자 10명과 여자 15명 환자를 대상으로 수술 1일전과 술후 24시간 후 각각 "a"음을 연장 발성시켜 CSL 4300B (KAY elemetrics Corp)의 MDVP(multidimensional voice program)을 이용하여 harmonic to noise ratio(NHR), Jitter, Shimmer, Fundamental frequency를 측정 비교하였다. 결 과: 남녀 모두에서 Jitter, Shimmer는 각각 평균 0.70%에서 1.06%, 1.92%에서2.28%로 증가되는 경향을 보였으나 통계학적 유의성은 없었다. Fundamental frequency는 여자에서 평균 220Hz에서 221Hz로 남자는 125Hz에서 128Hz로 변화를 보이지 않았고 harmonic to noise ratio(NHR)또한 평균 0.11로 수술 전, 후 변화를 관찰할 수 없었다. 결 론: 이상의 결과로 2내지 6시간의 단기간 삽관으로 인한 성대의 손상은 경미하여 24시간 이내에 회복되는 것으로 판단된다. 향후 6시간 이상의 기관내삽관이나 수일이상의 장기간 삽관후의 음성지표의 측정등의 연구가 필요할 것으로 사료된다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.924-929
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• 2001

The flying height of contact slider is determined by vertical and pitching motions of slider. This paper performed the computer simulation for flying height change of contact slider. It is changed by many parameters, contact stiffness, contact damping, air bearing stiffness ratio, a location of mass center, and so on. Computer simulation is performed for knowing for what change of these parameters influences in flying height of contact slider. Disk surface is modeled in harmonic wave with from 10㎑ to 600㎑. Tri-pad slider is modeled in that contact slider has 2-DOF motion (vertical motion, pitching motion). Tri-pad contact slider is analyzed by numerical analysis method in computer simulation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.4 s.97
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• pp.445-451
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• 2005

This paper is the result of a experimental study about non-linear one to one modal coupling of a flexible circular cantilever beam which was transversely excited with harmonic excitation. It was proved that 2 order jumping in out of plane was caused by jump phenomenon in in-plane of flexible circular cantilever beam, because of non-linear coupling. In addition, cantilever beam showed hardening spring characteristics in in-plane and softening spring characteristics in out-of-plane.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.7 s.100
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• pp.851-858
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• 2005

The response characteristics of one to one resonance on the quadrangle cantilever beam in which basic harmonic excitations are applied by nonlinear coupled differential-integral equations are studied. This equations have 3-dimensional non-linearity of nonlinear inertia and nonlinear curvature. Galerkin and multi scale methods are used for theoretical approach to one-to-one internal resonance. Nonlinear response characteristics of 1st, 2nd, 3rd modes are measured from the experiment for basic harmonic excitation. From the experimental result, geometrical terms of non-linearity display light spring effect and these terms play an important role in the response characteristics of low frequency modes. Nonlinear nitration in the out of plane are also studied.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.449-454
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• 2000

A three-parameter model of viscoelastic damper, which has a non-linear spring as an element is incorporated into an oscillator. The behavior of the damper model shows non-linear hysteresis curves which is qualitatively similar to those of real viscoelastic materials. The motion is governed by three-dimensional non-linear dynamical system of equations. The harmonic balance method is applied to get analytic solutions of the system. The frequency-response curves show that multiple solutions co-exist and that the jump phenomena can occur. In addition, it is shown that separate solution branch exists and that it can merge with the primary response curve. Saddle-node bifurcation sets explain the occurences of such non-linear phenomena. A direct time integration of the original equation of motion validifies the use of the harmonic balance method to this sort of problem.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.492-497
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• 2003

The dynamic instability for snapping phenomena has been studied by many researches. There is few paper which deal with the dynamic buckling under the load with periodic characteristics, and the behavior under periodic excitation is expected the different behavior against STEP excitation. We investigate the fundamental mechanisms of the dynamic instability when the sinusoidal shaped arch structures subjected to sinusoidal distributed excitation with pin-ends. In this study, the dynamic direct snapping of shallow arches is investigated under not only STEP load excitation but also sinusoidal harmonic excitations, applied in the up-and-down direction. The dynamic nonlinear responses are obtained by the numerical integration of the geometrically nonlinear equations of motion, and examined by the Fourier spectral analysis in order to get the frequency-dependent characteristics of the dynamic instability for various load levels.