• Title/Summary/Keyword: Steady-state Noise

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On the Stationary Probability Distributions for the $Schl\ddot{o}gl$ Model with the First Order Transition under the Influence of Singular Multiplicative Noise

  • Kyoung-Ran Kim;Dong J. Lee;Cheol-Ju Kim;Kook Joe Shin
    • Bulletin of the Korean Chemical Society
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    • v.15 no.8
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    • pp.627-631
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    • 1994
  • For the Schlogl model with the first order transition under the influence of the multiplicative noise singular at the unstable steady state, the effects of the parameters on the stationary probability distributions obtained by the Ito and Stratonovich methods are discussed and compared in detail.

The $Schl\ddot{o}gl$ Model with the Second Order Transition Under the Influence of a Singular Multiplicative Random Force

  • Kyoung-Ran Kim;Dong J. Lee;Cheol-Ju Kim;Kook Joe Shin
    • Bulletin of the Korean Chemical Society
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    • v.15 no.8
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    • pp.631-636
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    • 1994
  • For the Schlogl model with the second order transition under the influence of the multiplicative noise singular at the unstable steady state, the detailed discussions are presented for various kinds of stochastic phenomena, suchas the effects of parameters on stationary probability distribution, noise-induced phase transitions and escape rate.

Nonlinear Noise-Induced Transitions in Active Rotator Model

  • Kim, Seung-Hwan;Park, Seon-Hee;Ryu, Chang-Su
    • ETRI Journal
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    • v.20 no.2
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    • pp.214-230
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    • 1998
  • We investigate noise-induced transitions in active rotator model with a fluctuating threshold in the presence of an additive noise. The fluctuation of the threshold depends on the additive noise in a nonlinear fashion. In the white-noise limit of the fluctuation, the Fokker-Planck equation of the system reduces to that of the system with correlated linear fluctuation implying that the nonlinearity may be transformed into the correlation of linear noises. We also investigate the system with a nonlinear colored noise which depends on the additive noise as its square. The system shows a single peak, two peaks, and three peaks in its steady state probability distribution according to the noise intensities and the correlation time whose change leads to peak-creating, peak-splitting, and peak-merging transitions.

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Design of Friction Dampers for Seismic Response Control of a SDOF Building (단자유도 건물의 지진응답제어를 위한 마찰감쇠기 설계)

  • Min, Kyung-Won;Seong, Ji-Young
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.1
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    • pp.22-28
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    • 2010
  • Approximate analysis for a building installed with a friction damper is performed to get insight of its dynamic behavior. Energy balance equation is used to have a closed analytical form solution of dynamic magnification factor(DMF). It is found out that DMF is dependent on friction force ratio and resonance frequency. Approximation of DMF and equivalent damping ratio of a friction damper is proposed with such assumption that the building with a friction damper shows harmonic steady-state response and narrow banded response behavior near resonance frequency. Linear transfer function from input external force to output building displacement is suggested from the simplified DMF equation. Root mean square of a building displacement is derived under earthquake-like random excitation. Finally, design procedure of a friction damper is proposed by finding friction force corresponding to target control ratio. Numerical analysis is carried out to verify the proposed design procedure.

Non-linear Vibration of Rectangular Plates (직사각형 평판의 비선형 진동)

  • Chang, Seo-Il;Lee, Jang-Moo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1994.10a
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    • pp.35-39
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    • 1994
  • One of the important characteristics of the response of nonlinear systems is the existence of subharmonic resonances. When some conditions in parameter space are satisfied. It is possible even in the presence of damping for a periodically excited nonlinear system to possess a response which is the combination of a contribution at the excitation frequency and a component at the system natural frequency. The system natural frequency being a submultiple of the excitation frequency implies that the resulting response is a subharmonic oscillation. In general, there also co-exists, for the system, a response at the excitation frequency, and initial conditions determine which of the steady-state responses is achieved in an experiment or a numerical simulation. In single-degree-of-freedom systems with harmonic excitation, depending on the type of the nonlinearity, e.g., cubic or quadratic the frequency of subharmonic response is respectively, one-third or one-half of that of the excitation frequency. Although subharmonic resonance is one of the principal characteristics of a nonlinear system the subharmonic responses of structures in the presence of internal resonances have been studied very rarely. In this work, we consider subharmonic responses in the two-mode approximation of the plate equations. It is assumed that the two modes are in one-to-one internal resonance. Constant and periodic steady-state solutions of the averaged equations are studied. Finally, the results of direct time integration of the original equations of motion are presented and compared with those obtained from the averaged equations.

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Prediction and Reduction of Transient Vibration of Piping System for a Rotary Compressor (공조용 압축기 배관계의 과도진동 예측 및 저감설계)

  • Ryu, Sang-Mo;Jeong, Weui-Bong;Han, Hyung-Suk
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.8
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    • pp.733-740
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    • 2011
  • This paper deals with the process to identify the transient exciting force generated from a rotary compressor. The compressor was assumed to be a rigid body. The equation of motion of a rigid compressor supported by three mounts was derived with 6 degree-of-freedom. The exciting forces at the center of mass of the compressor were estimated from the acceleration data measured at compressor shell. Compressor-pipe system was modeled numerically. The accelerations of compressor and pipe were predicted numerically by using the estimated exciting force. A new shape of pipe model was proposed to reduce the vibration. In the prediction by the method in this paper, the maximum acceleration of the pipe could be reduced by 53.7 % at the steady-state and by 12 % at the transient process. In the real experiments, the maximum acceleration of the pipe was reduced by 54.2 % at steady-state and 14.7 % at the transient process. It was verified that the numerical results showed good agreement with experimental results.

Optimal Design of Optical Flying Head for Near-field Recording (근접장 기록을 위한 부상형 광학 헤드의 최적설계)

  • 윤상준;김석훈;정태건;김수경;최동훈
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.13 no.10
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    • pp.785-790
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    • 2003
  • This paper presents an approach to optimally design the air-hearing surface (ABS) of the optical flying head for near-field recording technology (NFR) NFR is an optical recording technology using very small beam spot size by overcoming the limit of beam diffraction. One of the most important problems in NFR Is a head disk interface (HDI) issue over the recording band during the operation. A multi-criteria optimization problem is formulated to enhance the flying performances over the entire recording band during the steady state. The optimal solution of the slider, whose target flying height is 50 nm, is automatically obtained. The flying height during the steady state operation becomes closer to the target values than those for the Initial one. The pitch and roll angles are also kept within suitable ranges over the recording band. Especially. all of the all-hearing stiffness are drastically increased by the optimized geometry of the air hearing surface.

The Dynamic Characteristics of Rotating Cantilever Pipe Conveying Fluid (회전하는 유체이송 외팔 파이프의 동특성 해석)

  • 윤한익;손인수
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.13 no.1
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    • pp.26-32
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    • 2003
  • The vibrational system of this study is consisted of a rotating cantilever pipe and the flow in the pipe. The equation of motion is derived by using Lagrange equation. The influences of the rotating angular velocity and the velocities of fluid flow in the pipe have been studied on the dynamic characteristics of a rotating cantilever pipe by numerical method. The tip-amplitude of axial vibration and maximum tip-deflection of axial direction of cantilever pipe are directly proportional to the velocity of fluid and rotating angular velocity of pipe In the steady state. respectively The bending tip-amplitude of cantilever pipe is inversely proportional to the velocity of fluid in the steady state. When the rotating angular velocity is 5 rad/s, the velocity of fluid increase with increasing the natural frequency of axial vibration at second mode and third mode, but the natural frequency axial direction of first mode is decreased. The natural frequency of lateral direction is decreased due to increase of the rotating angular velocity. It identifies that the Influence of velocity of fluid give much variation lower mode of vibration in lateral direction. And the Influence of velocity of fluid give much variation higher mode of vibration in axial direction.

Dynamic Behavior of Rotating Cantilever Pipe Conveying Fluid with Moving Mass (이동질량을 가진 유체유동 회전 외팔 파이프의 동특성)

  • Yoon, Han-Ik;Son, In-Soo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.5 s.98
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    • pp.586-594
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    • 2005
  • In this paper, we studied about the effects of the rotating cantilever pipe conveying fluid with a moving mass. The influences of a rotating angular velocity, the velocity of fluid flow and moving mass on the dynamic behavior of a cantilever pipe have been studied by the numerical method. The equation of motion is derived by using the Lagrange's equation. The cantilever pipe is modeled by the Euler-Bernoulli beam theory. When the velocity of a moving mass is constant, the lateral tip-displacement of a cantilever pipe is proportional to the moving mass and the angular velocity. In the steady state, the lateral tip-displacement of a cantilever pipe is more sensitive to the velocity of fluid than the angular velocity, and the axial deflection of a cantilever pipe is more sensitive to the effect of a angular velocity. Totally, as the moving mass is increased, the frequency of a cantilever pipe is decreased in steady state.

Duvall-Structure-Based Adaptive Beamforming Method for Cancellation of Coherent and Incoherent Interferences (코히런트/인코히런트 간섭신호제거를 위한 Duvall 구조에 기초한 적응 빔형성 방법)

  • Cho, Yang-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.10A
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    • pp.1006-1012
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    • 2008
  • This paper presents a Duvall-structure-based adaptive beamforming method which efficiently cancels coherent and incoherent interferences. The proposed method exploits several correlation vectors to increase the dimension of the weight vector, compared to the existing method which uses a single correlation vector only. The increased dimension of the weight vector leads to an improvement in the signal-to-interference plus noise ratio (SINR) performance. Moreover, the proposed method can suppress more interferences than the existing one. Simulation shows that the former is superior to the latter in terms of the steady-state and transient responses.