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 54 for “"Perturbation Methods"”.
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Perturbation methods for slightly damped gyroscopic systems
This dissertation concerns the development of a perturbation theory applicable to the algebraic eigenvalue problem. The objective is to express the perturbed eigenvalues and eigenvectors in terms of the unperturbed eigenvalues and eigenvectors and the perturbing matrices, without solving a new …
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Parameter Identification of Nonlinear Systems Using Perturbation Methods and Higher-Order Statistics
A parametric identification procedure is proposed that combines the method of multiple scales and higher-order statistics to efficiently and accurately model nonlinear systems. A theoretical background for the method of multiple scales and higher-order statistics is given. Validation of the …
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Model simplification and robust control in deterministic and stochastic systems using singular perturbation methods
… and stochastic systems) is the use of ""singular perturbations,"" either as a modeling tool or as a computational tool. The reason for adopting the singular perturbations framework is threefold. First, we must study robustness with respect to fast unmodeled dynamics of different control or …
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Analysis for Taylor vortex flow
… wave selection. In this work, several high-order perturbation methods and a numerical method are established. Both evolution and steady state of the How caused by single or several disturbances are studied. The existence of multiple steady states for disturbances with small wavenumber is …
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Acute Manipulation of Erna Level For Dissecting Its Roles In Transcriptional Regulation
… One important problem is that currently used perturbation methods of enhancer/eRNAs are not acute and cannot distinguish direct from indirect effects.</p> <p>To reveal the dynamics of eRNA-regulated target gene transcription and epigenetic features, I attempted to establish acute and …
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On the flow induced in a thermally stratified fluid by a source of heat
… effects of small nonlineari ties are computed by perturbation methods and the profile alterations thus produced are discussed. A laboratory experiment set up to demonstrate the major features of this circulation is described. Qualitative agreement between theory and experiment is obtained, and …
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A comparison and study of the Born and Rytov expansions
… regions of validity and relative merits of the methods. Although the methods fail for strong fluctuations and distant path lengths, these two perturbation methods are the only approaches available for weak fluctuations in a random in homogeneous media. The approximations have also been applied …
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Amplitude fluctuation effects in shallow water acoustic scattering by internal waves
… it uses the adiabatic approximation and perturbation methods to statistically evaluate acoustic transmission fluctuations caused by internal waves in the ocean; it also investigates acoustic mode coupling effect due to internal waves. Numerically, this thesis simulates the shallow water …
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Homotopy Analysis Method For Nonlinear Ordinary Eigenvalue Problems
… as a more generalized method that encloses many perturbation and non-perturbation methods. It is different from perturbation or other analytical methods in that it allows considerable freedomformanyvariables. Using the modified HAM, especially zero-order and higher-order deformation equations, we …
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Integrated aerodynamic-structural design optimization
… design process numerical optimization methods are required. The present research is focused on a major difficulty associated with the multidisciplinary design optimization process - its enormous computational cost. We consider two approaches for reducing this computational burden: (i) …
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SMALL SIGNAL STABILITY ANALYSIS OF THREE-PHASE MICROGRID SYSTEM IN THE PRESENCE OF CONSTANT POWER LOADS
… stability analysis of such systems in real-time. Perturbation methods can be used to determine system impedance. The perturbation approach involves injecting various perturbation signals into the system and determining impedance from the measured voltage and current responses. In this thesis, two …
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Asymptotic analysis of the parametrically driven damped nonlinear evolution equation
Singular perturbation methods 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 …
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Near-Optimal Control of Atomic Force Microscope For Non-contact Mode Applications
… relatively large cantilever stiffness, singular perturbation methods reduce complexity in the model and allows for faster responses to Van der Waals interaction forces experienced by the cantilever's tip and measurement sample. In this study, we outline a nonlinear near-optimal feedback control …
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Geoacoustic inversion by mode amplitude perturbation
… receiver positions. The algorithm makes use of perturbation results, and computes the small correction to an estimated background profile that is necessary to reproduce the measured mode amplitudes. Range-dependent waveguide properties can be inverted for so long as they vary slowly enough in …
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Brain segmentation using endogenous contrast mechanism using breath holding fMRI signal for tissue characterization
… on the BOLD signal. A number of different perturbation methods including breath holding, hypercapnia, inhalation of various gas mixtures, and injection of acetozolamyde has been used to study spatio-temporal changes in the fMRI signal intensity. Spatiotemporal changes corresponding to …
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Synchronization in Coupled Opto-thermal Silicon MEMS Limit Cycle Oscillators
… laser power. Using numerical and analytical perturbation methods, we extend the analysis to an array of eight coupled oscillators and study self-synchronization and frequency entrainment to an external inertial drive. Key contributions include the mapping of the dynamical behavior of …
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Geoacoustic inversion by mode amplitude perturbation
… receiver positions. The algorithm makes use of perturbation results, and computes the small correction to an estimated background profile that is necessary to reproduce the measured mode amplitudes. Range-dependent waveguide properties can be inverted for so long as they vary slowly enough in …
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Second-Order Relative Motion Equations
… in state variables are kept in the expansion. A perturbation method is employed to obtain an approximate solution of the resulting nonlinear differential equations. This new solution is compared with the previously known solution of the linear case to show improvement, and with numerical …
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The effects of learning schedules and external visual information on implicit sensorimotor adaptation of upper limb movements.
… motor errors before experiencing further perturbations to their movements. This method of error introduction led to significantly larger adaptation compared to both abruptly introducing large errors or introducing small errors in a ramped manner. Next, we determined that when adapting to …
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Biological and Biomechanical Effects of Direct Perturbation of Tissue Structure in the Cirrhotic Liver
… mechanism. First, we investigate microinjury perturbation using a fractional laser. This work revealed an exacerbated injury response in the cirrhotic liver. Through investigating the mechanism of this response, we revealed a novel ischemic susceptibility related to the microvascular …
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