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 39 for “"Nonlinear Regime"”.
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Ultra-Wideband Fibre-Optic Systems in the Nonlinear Regime
… are mainly limited by the power-dependent fibre nonlinearity which limits the capacity that can be achieved in such systems. This PhD thesis addresses the problem of maximising the information throughput from single- to multi-channel point-to-point transmission to optical networks. The first part …
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Acoustic metamaterials comprised of dead-end pores and black hole effect for low frequency sound absorption in linear and nonlinear regimes
… in a conventional impedance tube (linear regime), in a specially modified impedance tube that allows pressures (RMS) up to 250 Pa using sine wave excitation (weakly nonlinear regime for continuous sound) and in a shock tube (nonlinear regime for pulsed sound of amplitude of up to 100 kPa). …
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Dynamics and stability of gravity-capillary solitary waves
… a new class of solitary waves can propagate in nonlinear dispersive wave systems if the phase speed of linear waves attains a local extremum at some finite wavenumber. Near such a point, solitary waves in the form of small-amplitude wavepackets can be obtained for which the phase speed of the …
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Particle-In-cell simulations of nonlocal and nonlinear effects in inductively coupled plasmas
… simulation. In the low pressure, low frequency regime, electron mean free paths are large relative to device size and the trajectories are strongly curved by the induced radio frequency (RF) magnetic field. This causes problems for linear theories, which ignore the influence of the magnetic …
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An Exploration of Nonlinear Locally Resonant Metamaterials with Electromechanical and Topological elements
… greater versatility in controlling vibrations. Nonlinear elements introduce features such as discrete breathers and frequency shift. Electromechanical metamaterials have been established to have great potential for use in simultaneous energy harvesting in addition to vibration control. …
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Inertial tearing modes in magnetically-confined plasmas
… known as the tearing mode in parameter regimes relevant to magnetically-confined fusion plasmas. This included a derivation of the relevant equations and a method of solving them using Fourier analysis. This method allowed the derivation of several analytic results and efficient …
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Hamiltonian bifurcations in Schrodinger trimers
… space of the three-mode discrete NLS in the nonlinear regime with periodic boundary conditions is investigated by reducing the degree of freedom from three down to two. The families of standing waves are enumerated and normal forms are used to describe several families of relative periodic …
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Bifurcations in nonlinear Schrödinger equations with double well potentials
In this thesis, we consider nonlinear Schrödinger equations with double well potentials with attractive and repelling nonlinearities. We discuss bifurcations along bound states, especially ground states and the first excited states, and also deal with orbital stability of the ground states. In …
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Dynamics of Small Elastic Systems in Fluid: Tension and Nonlinearity
… the case of large perturbations, resulting in nonlinear dynamics, is explored. This regime is motivated by exploring the theoretical dynamics of a uniformly shrinking doubly clamped beam. The challenges of modeling such a beam using finite element simulations are discussed. As a simpler and …
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The design of low-frequency, low-g piezoelectric micro energy harvesters
… stiffens the beam and transforms the dynamics to nonlinear regime, and increases the bandwidth. However, the high resonance frequency (1.3kHz) and the high-g acceleration requirement (4-5g) shown in the testing experiments limited the applications of this technology. To improve the performance of …
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Resonant readout of a superconducting persistent current qubit
… a shift in the resonant frequency at 300 mK. The nonlinearity due to the Josephson inductance has characteristic effects on the resonant behavior of the readout circuit. We observed novel manifestation of this nonlinearity given the high quality factor of the resonance. The readout circuit was …
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Neural network estimation of disturbance growth and flow field structure of spatially excited jets
… by a spatially excited jet spans a linear and nonlinear regime in the downstream flow field. For the linear portion, the neural network was trained to identify critical flow field parameters using numerical data generated from linear stability analysis code. It was shown that the neural network …
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MIMO-OFDM Symbol Detection via Echo State Networks
… network structure composed of high dimensional nonlinear dynamics and learned readout weights. This thesis considers applying ESN for symbol detection in multiple-input, multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems. A new ESN structure, namely, windowed echo …
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The taiji and infinity-loop microresonators: examples of non-hermitian photonic systems
… also be used to break Lorentz reciprocity in the nonlinear regime (high incident laser powers), discussing the effect of the Fabry-Perot of the bus waveguide facets. The effect of backscattering, mainly due to the waveguide surface-wall roughness, on the microresonators is also studied. This …
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Optical Propagation of Self-sustaining Wavefronts and Nonlinear Dynamics in Parabolic Multimode Fibers
… these special beams are found both in linear and nonlinear situations. For example, in the linear regime, localized spatio-temporal waves which resemble the spherical harmonic symmetries of the hydrogen quantum orbitals can simultaneously negotiate both diffractive and dispersive effects. In the …
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Causal and stable stochastic relativistic hydrodynamics
… formulate stochastic hydrodynamics in the linear regime. This approach is applied to several conventional theories of relativistic hydrodynamics, finding that new subtleties appear when fluctuations are included. To extend these results to the nonlinear regime, we consider effective action …
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The mode-dependent dynamics of nonlinear nanomechanical resonators
… the extreme miniaturization of NEMS, the role of nonlinear dynamics has become increasingly important -- even when the dynamics are driven by the Brownian force. This nonlinearity has imposed a mechanical noise floor on the linear frequency measurements made in sensing applications. Given that …
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Spectroscopic perspectives on ultrafast coupling phenomena in perovskite oxides
… the technique to investigate the linear and nonlinear acoustic response in bulk SrTiO_3, which displays a ferroelastic phase transition from a cubic to a tetragonal structural phase at T_a=105 K. In the linear regime, I observe a coupling of the observed acoustic phonon mode to the softening …
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The Madden-Julian oscillation and nonlinear moisture modes
… this thesis hypothesizes that the MJO is a nonlinear moisture mode whose existence depends on moisture-convection feedback (the feedback between deep convection and environmental free-tropospheric humidity), and that weak moisture convection feedback in general circulation models accounts …
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On Applications of Resonances, from One to Infinity
… enhancement bounds in the radiative transfer regime and apply the results to ocean buoy energy extraction. Our results, which match full-wave simulations, enable us to propose and quantify approaches to increase performance through careful particle design and/or using external reflectors. …
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