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 40 for “"Variational Method"”.
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The Gutzwiller variational method for strongly correlated systems
… research on new developments in the Gutzwiller variational method as well as the applications of the method to two specific correlated electron systems of current interest: (i) the spinless fermion model with non-local Coulomb interaction in one dimension and (ii) the pressure-induced …
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A variational method for approximate solutions to laminar flow problems
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1961.
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Application of cubic B-splines to boundary value and optimal control problems
… boundary value problem will be approximated by a variational method using cubic B-splines. This method will then be extended to solving N-dimensional two-point boundary value problems. In the final part of the thesis, certain control problems will be converted into boundary value problems, which …
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Variational Calculation of Optimum Dispersion Compensation for Nonlinear Dispersive Fibers
… in closed form. Although, the split-step Fourier method can be used to numerically determine pulse properties from this nonlinear equation, numerical results are time consuming to obtain and provide limited insight into functional relationships and how to design input pulses. One technique, called …
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Monte Carlo Studies of Momentum Distributions and Longitudinal Response Functions of a = 3 and 4 Nuclei
… describing their theoretical basis. The Faddeev method for the three-body nuclei, and variational approaches for the three- and four-body nuclei wave functions are used to represent the ground state of these nuclei. The variational method is discussed in some detail, and results for the binding …
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Variational Modeling of Ionic Polymer-Based Structures
… of the measured system. Here we present a variational approach to the dynamic modeling of structures which incorporate ionic polymer materials. The modeling approach requires a priori knowledge of three empirically determined material properties: elastic modulus, dielectric permittivity, …
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Monte Carlo studies of ground state and optical properties of multiexcitonic complexes in semiconductors
… correlations and excitonic effects, using the variational method along with Monte Carlo methods to calculate binding energies and ground-state expectation values. Transition matrix elements are studied with various extensions of the Monte Carlo method to obtain information on optical properties.
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The weakly coupled polaron
… is lower than the upper bound obtained from the variational method. Also, the spectral weight function for several momentum values has been calculated. It shows that the quasi-particle description is good for polarons with small momentum while for polarons with momentum values near the phonon …
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System-level design, simulation and measurement for high-speed data links
… arrive at the results. Modeling and simulation methodologies for high-speed interconnect are discussed and studied, using both conformal mapping and the variational method in closed-form solutions, with examples provided to study the frequency-dependent channel effects in high-speed digital …
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Active geometric model : multi-compartment model-based segmentation & registration
We present a novel, variational and statistical approach for model-based segmentation. Our model generalizes the Chan-Vese model, proposed for concurrent segmentation of multiple objects embedded in the same image domain. We also propose a novel shape descriptor, namely the Multi-Compartment …
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Finite element-boundary elements modelling of acoustic scattering from viscoelastic anechoic structures
… such as lead oxide and mica. Successively, a new method for identifying the viscoelastic frequency-dependent properties of such materials from experimental data is presented. The method is based on a variational method analogous to the Hamilton Principle. It allows calculating hard-to-find …
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Multiphase immiscible flow through porous media
… namely air, water, and an organic fluid. A variational method is employed for the finite element formulation corresponding to the coupled differential equations governing the flow of the three fluid phase porous medium system with constant air phase pressure. Constitutive relationships for …
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Near-optimal feedback guidance for an accurate lunar landing
This research presents a novel guidance method for a lunar landing problem. The method facilitates efficiency and autonomy in a landing. The lunar landing problem is posed as a finite-time, fixed-terminal, optimal control problem. As a key finding of this work, the method of solution that is …
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Fluid-structural interaction effects on vibrations of pipework.
… and various results were procured by the variational method. The effects of fluid upon the vibratory characteristics of the pipe system are assessed, mainly under three sections; the natural frequency, the damping ratio and the vibration patterns. To appraise the effect of the fluid on the …
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Analysis of solitary waves in inhomogeneous systems
… second problem, we use coupled mode reduction method to yield conditions for symmetry breaking bifurcations. We notably obtain that the bifurcation is degenerate. There are two distinct asymmetric bifurcating solutions with the same norm. We provide an estimate of the bifurcation point. We also …
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Disorder-driven phase transitions in weak, boundary-obstructed, and non-Hermitian topological insulators
… of the thesis, we will develop real-space methods to compute weak, boundary-obstructed, and non-Hermitian topological invariants, establish their stability at weak and strong disorder, and connect these disordered topological invariants to physical signatures. The remainder of the thesis …
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A fully numerical lifting line method for the design of heavily loaded marine propellers with rake and skew
… of heavily loaded marine propellers by numerical methods. In this work, a wake-adapted, fully numerical, lifting line model is used to obtain the optimum circulation distribution along the propeller's blade via variational method, presented by Coney [9]. In this context, two approaches to the …
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Finite element analysis of geodesically stiffened cylindrical composite shells using a layerwise theory
… adapted to circular cylindrical shells. The Ritz variational method is used to develop an analytical approach for studying the buckling of simply supported geodesically stiffened shells with discrete stiffeners. This method utilizes a Lagrange multiplier technique to attach the stiffeners to the …
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Computational methods for the shape from shading problem
… aim of this thesis is to explore computational methods for the shape from shading problem as formulated through the image irradiance equation. We seek to develop robust, efficient methods and test our algorithms on synthetic images ranging from simple smooth surfaces to complex digital terrain …
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