• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.455-467
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• 2008

The dynamic vehicle running tests were performed to analyze dynamic behavioral characteristics such as displacement, strain history loop and vibration acceleration in arch bridges. Also, the validity of the modeling was verified by comparing the results of the tests and those of the structural analysis modeling. With the resonance revision of verified modeling, when the ratio of excited frequencies to natural frequencies exceeds ${1{\pm}0.04}$, the stability of the bridge is obtained. Also, in the event of resonance by speed parameter, the second mode shape is dominant to the dynamic behaviors of arch bridges. It is found that manipulating the parameters involving arch ribs can increase the second mode natural frequency. It makes critical velocity greater than operational velocities to guarantee the stability of arch bridges.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.23-29
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• 1993

내부공진 (.omega.$_{3}$ = .omega.$_{1}$ + 2.omega.$_{2}$)을 가진 원판 의 조합공진(.OMEGA. = 2.omega.$_{1}$ + .omega.$_{2}$)응답의 안정성 을 해석한 결과 다음과 같은 결론을 얻었다. 1) 모든 진폭이 0(.alpha.$_{1}$=.alpha.$_{2}$=.alpha.$_{3}$=0)인 공진응답 은 매개변수의 값에 관계없이 안정하다. 2) 모든 진폭이 0이 아닌 (.alpha.$_{1}$.neq.0, .alpha.$_{2}$.neq.0, .alpha.$_{3}$.neq.0) 공진응답은 쌍으로 존재하는데 진폭이 큰 응답(upper branch)은 안정하나 진폭이 작은 응답(lower branch)은 불안정하다. 3) 진폭이 0이 아닌 공진응답이 존재하지 않는 경우에는 선형계와 마찬가지 로 모든 진폭이 0이 공진응답(결과적으로 비공진 응답)이 계의 응답을 지배 하지만 모든 진폭이 0이 아닌 공진응답이 존재하는 경우에는 안정한 공진응 답이 2개이므로 초기조건이 실제의 응답을 결정하게 된다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1588-1595
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• 2006

The stabilities of a pinned-pinned straight pipe conveying fluid are investigated by complexification-averaging method. The flow is assumed to vary harmonically about a constant mean velocity. Instability conditions of a governing equation are analytically obtained about parametric primary, secondary and combination resonances. The resulted stability conditions show that instabilities exist when the frequency of flow fluctuation is close to one and two times the natural frequency or to the sum of any two natural frequencies. In case that the fluctuated flow frequency is close to the difference of two natural frequencies, instabilities does not exist.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.255-258
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• 2000

초음속 유동장 내에 설치된 끝이 막힌 관에 의해 발생하는 공진 현상에는 스크리치 모드 (jet screech mode)와 토출 모드 (jet regurgitant mode)가 있다 이중 토출 모드는 원리상 음향학적 공진과 밀접한 관련이 있다. 본 연구에서는 경계 조건으로, 주어진 강도와 주파수를 갖는 마하 수의 진동을 통하여 압축성 유동장을 가진하는 개념적 모델을 통하여 공진 현상을 모사한다. 비선형 효과의 탐구를 위해 축대칭 오일러 방정식을 수치적으로 풀이하면서, 4 가지의 주요한 파라메터들 (가진 강도, 가진 주파수, 진 동부와 관 사이의 거리, 관의 깊이)을 추출하고 이에 대한 영향을 연구하였다. 또한 비선형 유동 효과에 의해 발생하는, 고전 이론에 의해 예측된 공진 주파수와의 차이를 정량적으로 나타내고 그 원인을 고찰하였다.

• Korean Journal of Optics and Photonics
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• v.8 no.1
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• pp.52-57
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• 1997

We report an investigation of the statistical fluctuations of the two-mode laser output as the asymmetry parameter is varied. The above results relate to computer solutions of the coupled Langevin equations both with and without pumping fluctuations. We find that as the asymmetry parameter is changed positively, the mean intensity of one mode is increased because the normalized intensity auto-correlation is decreased so that the natural dwell time is lengthen. The laser output does respond to a sinusoidally injected asymmetry parameter for small pump parameter.

• Korean Journal of Optics and Photonics
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• v.11 no.3
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• pp.187-192
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• 2000

We analyze the parametric amplification by the nonlinear characteristics in a semiconductor laser using a perturbation theory and discuss its result. The parametric gain increases with increase of the pump modulation current. It is due to shift of the resonance frequency as the pump modulation current increases. However, it decreases with increase of the bias current and damping constant. Also, it needs phase matching between the pump modulation current and signal modulation current to maximize the parametric gain. The gain decreases for a large signal modulation current due to the saturation of the amplified power. power.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.3
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• pp.76-86
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• 1998

The Two-Mass Spring(TMS or Two-Inertia Resonance) system is one of the simplest models which generate a torsional vibration. In this system, it is required to design a controller achieving the control performance while suppressing the torsional vibration. In this paper, we compared and considered with the state feedback effects for the TMS system. By connecting each controller design to the state feedback control, we could predict each controller performances and decide weighting functions and parameters of LQ and $H_\infty$ controller.

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.154-155
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• 2004

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.121-122
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• 2006

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.21-28
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• 2011

Several theoretical soil nonlinear models to predict damping ratio, which is one of the typical dynamic properties of soils, it is impractical to predict damping ratio. The resonant column and torsional shear test(RC-TS) is used to represent the dynamic behavior of soils from intermediate to medium shear strains. A limitation of RC-TS is measure precise shear strain in large strains and the modified equivalent radius($R_{eq}$) was obtained using both modified hyperbolic model and Ramberg-Osgood model. Bonneville clays were tested using RC-TS test to obtain rotation and torque. The measured rotation and torque were then compared with calculated rotation and torque using curve-fitting method. Then, the nonlinear soil model parameters were obtained and the equivalent radius was calculated using the model parameters.