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 “"Anisotropic Diffusion"”.
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Magnetic resonance diffusion imaging and spectral localization: New methods and their quantitative applications
… interest, in recent years, in the measurement of diffusion of water and metabolites in living systems by magnetic resonance (MR) techniques. Knowledge of the diffusion coefficients of the molecules can yield unique information about microstructure and function of tissue. We have developed a method …
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Advanced numerical methods for image denoising and segmentation
… and examined. These include the isotropic diffusion model, the anisotropic diffusion model (the P-M model), the fourth-order PDE model (the Y-K model), and the active contour model in image segmentation. Based on the analysis of behaviours of each model, some improvements are proposed. …
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Mathematical models and numerical methods for the movement and life cycle of invasive pests across multiple scales
… differential equation approximations can exhibit anisotropic diffusion and drift even when agent behavior is symmetric in space. Finally, we look at the macroscopic spread of Spotted Lanternfly, directly modeling the effects of population growth and human-mediated spread, and present a model …
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Structure-Preserving High Performance Computational Methods for Transport in Porous Media
… to meet the non-negative constraint under anisotropic diffusion (i.e., they violate dis- crete maximum principles) and the inability of the standard finite element formulation to ensure local mass balance. Moreover, there is no platform-agnostic performance model that can simultaneously …
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Diffusion of a rodlike virus in complex solutions
… One way to study such motion is to follow the diffusion of a probe particle while increasing the concentration of the polymer. Many such studies have been done using probes ranging from linear and star polymers to various colloidal particles; however, relatively few studies have used rodlike …
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Generalizing smoothed aggregation-based algebraic multigrid
… motivate our development. For example, rotated anisotropic diffusion and linearized elasticity problems using standard discretizations can easily generate non-M-matrices that prove difficult for standard SA and AMG. High- and low-order discontinuous Galerkin discretizations also generate …
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Nuclear magnetic resonance and rheo-NMR investigations of wormlike micelles, rheology modifiers, and ion-conducting polymers
… such as "rheo-NMR," 2H NMR, and NMR self-diffusion experiments to analyze alignment, orientational order, elaborate rheological behavior, and ion transport in polymer films and complex fluids. We employed self-diffusion and quadrupolar deuterium NMR methods to water-swollen channels in …
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Structural Characterisation of Heteroepitaxial Zincblende Gallium Nitride
… layers and epilayers is explained by the anisotropic diffusion of adatoms on the low-symmetry top monolayer of (001)-oriented zincblende GaN lattice. Defects, including stacking faults and dislocations, are found to relax the heteroepitaxial zincblende GaN film in both nucleation layers …
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Characterising Heterogeneity of Glioblastoma using Multi-parametric Magnetic Resonance Imaging
… sub-region with decreased isotropic diffusion and increased anisotropic diffusion was associated with progression-free survival (PFS, hazard ratio [HR] = 1.08, P < 0.001) and overall survival (OS, HR = 1.36, P < 0.001) in multivariate models. II. Using a thresholding method, two low …
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Normal and superconducting many-body systems
… be viewed as effective ""bulk"" disorder, with anisotropic diffusion coefficients. This study can offer quantitative insight to transport properties of multilayers and devices, which contain inadvertently structural disorder at the interfaces."
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Computational fluid dynamics modelling of PEM fuel cells to investigate transport limitations.
… fuel cell. The simulation results show that gas diffusion layer permeability has no effect on cell performance for a value lower than 10-11 m2. GDL porosity is one of the major design parameters which have significant influence on limiting current density, hence on cell performance. Land area …
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Electroanalytical chemistry for biological and environmental applications
… of a biologically important molecule and the diffusional factors that may affect this generation.The first study involves the dynamics of the bond cleavage involved in the electro-generation of nitric oxide from a range of N-nitrosoamines. Adsorption phenomena is found to be of pivotal …
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Anisotrope Hydrogele
… horizontal dazu nahezu konstant bleibt. <br>Diffusionsexperimente mit Tracermolekülen gaben weiteren Aufschluss über die Schichtstruktur der Hydrogele. Diffusion senkrecht zu den Lamellen ist wesentlich langsamer.
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Probing the effect of microstructure on water diffusion in engineered or biological materials with MRI
Water diffusion within skeletal muscles is a complex mass transport process due to the presence of barriers at multiple scales and the anisotropic structure of muscles. Magnetic Resonance Imaging (MRI) is an effective non-invasive technology for studying water transport in biological or engineered …
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Modelización microscópica del daño por irradiación en metales hcp (a-Zirconio) : efecto de la anisotropía en la difusión y evolución de defectos
… of this crystallographic anisotropy, defect anisotropic diffusion is expected (jump distances and jump rates depend on jump directions). This study has focused on hcp α-Zirconium (c/a 1.594, lower than ideal 1.633). The aim of this thesis is the creation of a new and original model for the …
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Anisotropic variational models and PDEs for inverse imaging problems
In this thesis we study new anisotropic variational regularisers and partial differential equations (PDEs) for solving inverse imaging problems that arise in a variety of real-world applications. Firstly, we introduce a new anisotropic higher-order total directional variation regulariser. We …