Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 21 for “"Parametric resonance"”.
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The Convergence of Parametric Resonance and Vibration Energy Harvesting
… The convention has relied on directly excited resonance to maximise the mechanical-to-electrical energy conversion efficiency. This thesis takes a fundamentally different approach by employing parametric resonance, which, unlike the former, its resonant amplitude growth does not saturate due to …
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Nonlinear transverse vibrations of centrally clamped rotating circular disks
… rotational speeds. We have studied the primary resonance of a pair of orthogonal modes under a space-fixed constant loading, the principal parametric resonance of a pair of orthogonal modes when the disk is subject to a massive loading system, and the combination parametric resonance of two …
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Verificação experimental de vibrações paramétricas em vigas
Experimental investigation of parametric resonance of a bar subjected to an axial compressive force P, smaller than the buckling load and to an oscillating torque of the type T = T₀ + T₁1 cos Ω t, , where T₀, T₁ e Ω are independent pameters. The regions of elastodynamic instability are determined …
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Instabilidade elastodinâmica de uma viga sob ação de um momento axial periódico
… of these systems determine the regions of parametric resonance of flexural vibrations of beam as functions of their natural frequencies and excitation parameters. Some numerical resul ts related to the problem are presented.
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Vibrações e estabilidade paramétrica de cascas axissimétricas
… is studied and the first approximation of parametric resonance regions is explicity derived.
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Problems in nonlinear dynamics
… with one-to-one and three-to-one internal resonances. Cubic geometric nonlinearities are considered. The system under investigation possesses similar nonlinear normal modes for the case of One-to-one internal resonance and nonsimilar nonlinear normal modes for the case of three-to-one …
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Terahertz oscillations of hot electrons in graphene
… hot carriers in graphene undergo an anomalous parametric resonance. Such resonance occurs at about half the frequency ωF = 2πeF/~ωOP , where 2π/ωF is the time taken for carriers to accelerate ballistically to the optic phonon energy ~ωOP in a dc field F. For weak elastic scattering, the phase …
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The effects of pulsed static and oscillating magnetic fields on rat pineal serotonin N-acetyltransferase activity
… exposure of rats to magnetic fields tuned to ion parametric resonance conditions for Ca²⁺. The ion parametric resonance model of Blanchard and Blackman was used to determine the exposure parameters. Rats were thus exposed for an hour to a vertical AC field, of strength 14.3μT (rms), frequency was …
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Estudo das características estocásticas do roll paramétrico
… required in order to reproduce numerically the parametric roll resonance phenomenon. Numerical realizations of the motions of a containership type vessel have been generated for the purpose of studying the stationarity and ergodicity of the roll motion under parametric resonance conditions. The …
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Asymptotic analysis of the parametrically driven damped nonlinear evolution equation
… are used to obtain amplitude equations for the parametrically driven damped linear and nonlinear oscillator, the linear and nonlinear Klein-Gordon equations in the small-amplitude limit in various frequency regimes. In the case of the parametrically driven linear oscillator, we apply the …
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Resposta dinâmica e estabilidade de tubos com escoamento interno
… It is shown that, for a periodic flow velocity, parametric resonance occurs and the boundaries of these instability regions are determined. A computer program was developed and used to get some numerical results namely: stability maps for pipes with different support conditions;existence of a …
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Preheating in new Higgs inflation
… called reheating. If reheating begins with parametric resonance, the process is called preheating. New Higgs Inflation presumes that the Higgs field is the scalar field in question, involving a characteristic non-minimal "derivative" coupling. The equation of motion for the field evolves …
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Mechanism and the Effect of Microwave-Carbon Nanotube Interaction
… irradiation can be attributed to transverse parametric resonance, as occurs in the analysis of Melde's experiment on forced longitudinal vibrations of a stretched elastic string. For many kinds of carbon nanotubes (SWNT, DWNT, MWNT, ropes and strands) the resonant parameters are found to be …
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Modelling and analysis of vibrations in flexible cylinders subjected to internal multiphase and external single-phase flows.
… and dominant modes excited by SIV and VIV. Parametric studies capture the effects of key SIV and VIV flow characteristics on the vibration responses of vertical and horizontal fluid-conveying cylinders. Results from SIV in submerged vertical straight cylinders revealed amplitude-modulation …
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Probabalistic quantification of intermittently unstable dynamical systems
… Mathieu equation, featuring intermittent parametric resonance.
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Noise and delays in adaptive interacting oscillatory systems
… in the network opens the possibility for parametric resonance and destabilization of a consensual oscillatory state, found for purely static networks. Finally, we introduce external noise environments which corrupt the orbits of the local systems. For ''All-to-All'' network topology, we …
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Hydromagnetic Oscillations and Instabilities in Astrophysical Discs
… from the excitation of inertial waves by a local parametric instability provides one mechanism for curbing this growth. However, eccentric discs also provide an environment for the excitation of additional, inherently global oscillations, and I present a framework facilitating a semi-analytical …
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A theoretical and experimental investigation of parametrically excited nonlinear mechanical systems
… fundamental, principal, and combination harmonic parametric excitations is investigated theoretically and experimentally. The method of multiple scales (MMS) is used to determine the equations that describe to first and second order the amplitude- and phase-modulations with time. These equations …
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A theoretical and experimental investigation into the nonlinear dynamics of floating bodies
… mode is externally excited through a primary resonance. Force-response and frequency-response curves are generated. Coexistence of multiple solutions is found. The jump phenomenon continues to exist, whereas the saturation phenomenon ceases in the presence of quadratic damping. Hopf …
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