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 17 of 17 for “"Asymptotic methods"”.
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Asymptotic methods in applied waveguide problems
… exist only for the simple geometries. The asymptotic methods developed in this dissertation give the approximate solutions for the scattered fields in two practically important geometries: an object placed inside a stratified waveguide, and a waveguide with multiple abrupt width …
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Essays on asymptotic methods in econometrics
… of three essays that contribute to statistical methods in econometrics. Chapter 1 develops new theory of integrable empirical processes and applies it to outlier robustness analysis. A frequent concern in empirical research is to ensure that a handful of outlying observations have not driven the …
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Asymptotic methods applied to the geoenvironmental problems of ground subsidence and soil vapor extraction
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1998.
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Pattern formation in squares and rectangles
… wavelength of the pattern is investigated using asymptotic methods. For the rectangle, the dependence of the solution on the size of the rectangle relative to the characteristic wavelength of the pattern is investigated for non-periodic (rigid) boundary conditions. Most results are obtained for …
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A regularization framework for active learning from imbalanced data
… of the Leave One Out error. Next, we present two methods that estimate multiclass confidence from an asymptotic analysis of RLS and another method that stems from a Bayesian interpretation of the classifier. We show that while the third method incorporates more information in its estimate, the …
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Computation of multiscale time-harmonic electromagnetic radiation
… to other approximate or high-frequency asymptotic methods through a Schur complement analysis of the continuous and discretized equations. The proposed Schur complement EPA-PO hybrid introduces clear physics with applicability to other formulations for the individual domains. The …
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Shear flow instabilities in viscoelastic fluids
… results are confirmed both numerically and with asymptotic methods. We then consider Poiseuille flow and show that a new class of instability exists if the interface is close to the center-line. We analyse the scalings and show that it results from a change in the boundary layer structure of the …
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Swimming at low Reynolds number slip boundaries and interacting filaments
… simple geometries or through the use of asymptotic methods, I capture in the model the main physical features and compare these to previous experimental and numerical results, thereby making important progress toward our understanding of the physics of flagellar bundling.
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The Reasonable Effectiveness of Mathematics in the Natural Sciences
… utilized to understand systems. The qualitative methods rely on asymptotic methods and on sensitivity analysis, whereas the quantitative methods are best understood using backward error analysis. The basic underpinning of this perspective is readily understandable across scientific fields, and it …
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Four Essays on Dynamic Panel Models
… regressors.This paper uses a simulation-based methods that require explicit model and set of assumptions to obtain consistent point estimates and exact confidence sets. A parametric discontinuous starting value is assumed for simulated series that jointly allows for stationary and unit root …
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Acoustic Scattering in Sheared Flow
… passive or active devices, appears to offer methods of reducing far-field noise. The precise mechanisms are not completely understood, and this work focuses on the effect of varying boundary-layer parameters near the trailing-edge on the resulting far-field noise. Alternative methods of noise …
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Mathematical modelling of unsteady tube stretching with internal channel pressurisation for fabricating electrospray ionisation emitters
… of an axisymmetric cylindrical glass tube, using asymptotic methods to exploit the slenderness of the tube and over-pressure applied within the inner channel, to form tapers with a near uniform bore and small wall thickness at the tip. This is an unsteady extensional ow problem. As the glass …
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Nonlinear Methods in the Study of Singular Partial Differential Equations
… purpose of this thesis is to develop analytical methods to investigate a large class of nonlinear elliptic PDEs underlying models from physical and biological sciences. These methods advance the knowledge of qualitative properties of the solutions to equations of the form &Delta u= &fnof(x,u) …
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Rough Surface Scattering and Propagation over Rough Terrain in Ducting Environments
… refractivity profile is derived using the asymptotic methods of stationary phase and steepest descents. This Green's function is then modified to more closely model the one associated with a physical ducting medium, in which the refractivity profile decreases up to a certain height, beyond …
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Planet formation, resonant drag instabilities, and vortices
… each other. I use linear perturbation theory and asymptotic methods in the limit of dilute dust to show that the dust’s drift allows the dust to resonate with one of the gas waves. I then show that RDIs are due to a positive feedback loop between two mechanisms. In the first leg of the loop, the …
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Numerical methods for systems of highly oscillatory ordinary differential equations
… achievements are: to the contrary of classical methods, our numerical methods share the feature that asymptotically the approximation to the exact solution improves as the frequency of oscillation grows; also our methods are computationally feasible and as such do not require fine partition of …
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Shear flow instabilities in stratified magnetohydrodynamics
Shear flows are ubiquitous in nature and man-made settings and they play a fundamental role in the mixing and transition to turbulence of fluid flow. Shear flow instabilities of electrically-conducting fluids play a critical role in the dynamics of astrophysical objects, such as planets, stars, …