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 24 for “"fourier space"”.
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Form as meter: metric forms through Fourier space
The Discrete Fourier Transform, which was initially mentioned in the music theory domain by David Lewin, is an analytical tool developed by Ian Quinn, and later expanded by theorists such as Jason Yust, William Sethares, and Andrew Milne. Though it was originally designed for pitch-class spaces, …
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Kinematics of Vortices in Turbulent Flows
… of a hierarchy of vortices in the physical space of turbulent flows is commonly extended to Fourier space. Through an analysis of Gaussian vortices, we explore the concept a vortex in Fourier space in terms of local flow kinematics. We find that interpreting a hierarchy of vortices in …
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Performance of Algebraic Multigrid for Parallelized Finite Element DNS/LES Solvers
… 2D geometries. This also results in multiple Fourier mode linear systems which must be solved at every timestep, which naturally leads to two parallelization approaches: Fourier space partitioning, where each processor individually and simultaneously solves a linear system, and physical space …
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Elasticity in Microstructure Sensitive Design Through the use of Hill Bounds
… that translate through a multi-dimensional Fourier space depending on the property value of the hyper-surface. Property closures are generated by condensing the information contained within the multi-dimensional Fourier space into a 2-D representation. This compaction of information is …
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Fast simulation methods for soft matter hydrodynamics
… decaying sums evaluated indepently in real space and Fourier space, is used to accelerate the calculation and serves as the basis for a new technique to sample the Brownian displacements that is orders of magnitude faster than prior approaches. The simulation method is first developed using …
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Spectral Analysis of Local Atomic Environments
… accuracy than approaches operating in Fourier space. Dimensionality reduction via latent space embeddings is also explored, showing that essential geometric features can be preserved in significantly compressed representations. Through methodical analysis of descriptor limitations, …
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Tools, techniques, and early results in studies of 21 cm, Lyman-alpha, and H-alpha emission from the cosmic dawn
… limit foreground subtraction in the region of Fourier space where the EOR signal is brightest. We show that this contamination can be mitigated by modeling the observed foreground leakage as covariance in the frequency dimension, then downweighting it using the optimal quadratic estimator of …
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On the path integral formulation and the evaluation of quantum statistical averages
… procedure, and did the necessary sums in Fourier space* We performed the work in temperature space• Finally, slightly modifying the method of Papadopolous, we found the finite temperature expressions for the Debyecaller factor in Bravais lattices, to 0(AZ) and u(/K/ j,where K is the …
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From theoretical promise to observational reality : calibration, foreground subtraction, and signal extraction in hydrogen cosmology
… polynomials to spectra (either in image space or Fourier space) and inverse variance weighting. The latter method is described in a unified mathematical framework that includes power spectrum estimation. Foreground subtraction is also explored in the context of global signal experiments, …
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Physics-Inspired Deep Learning for Inverse Problems in MRI
… propose neural network layers that combine image space representations with representations in Fourier space, where MRI data is acquired. These layers can be used as drop-in replacements for standard image space convolutions in a variety of network architectures and yield higher quality …
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The Fourier Spectrum Element Method For Vibration And Power Flow Analysis Of Complex Dynamic Systems
<p>A general numerical method, the so-called Fourier-Space Element Method (FSEM), is proposed for the vibration and power flow analyses of complex built-up structures. In a FSEM model, a complex structure is considered as a number of interconnected basic structural elements such as beams and …
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Numerical simulations in nuclear magnetic resonance : theory and applications
… our technique for the global optimization on the space of smooth functions, the Grid Search in the Reduce-Dimension Fourier Space (GREDFOS). A series of low-power amplitude-modulated selective excitation pulses have been developed using this strategy. The pulses of this E-Family provide selective …
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Structuring Representations in Deep Learning: Symmetries and Linear Models
… implicitly minimizes the net’s Schatten norm in Fourier space [Lawrence et al., 2022]. While the explicit bias of equivariant nets is the main reason for their usage, this result indicates that a structured implicit bias may impact the types of functions they learn as well. Next, we expand on …
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Precision magnetometry and imaging via quantum manipulation of spins in diamond
… of populations of living bacteria. Second, the Fourier magnetic imaging experiment demonstrates for the first time multiple-NV control using phase encoding. Pulsed magnetic field gradients encode in the NV spin phase the information about the position of the NV centers as well as the external …
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Instrumental Effects in 21 cm Cosmology: One-point Statistics and Power Spectrum with the HERA Interferometer
… foreground emission to contaminate the region of Fourier space expected to be dominated by cosmological signals. I then present the work focused on developing a method to mitigate the calibration errors and foreground leakage, thereby recovering the clean EoR window.
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Hardware accelerated computer graphics algorithms
… is presented. This novel technique utilises Fourier space image filtering to reduce aliasing. Investigation shows that the technique provides reduced levels of aliasing along with comparable levels of detail to currently popular techniques. This adds to the community's knowledge by expanding …
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The application of parallel processing to radiotherapy dose computation
… a large computational effort. Convolution in Fourier space is adequately fast using even standard microprocessor technology, but this approach lacks the flexibility offered by a density-scalable superposition kernel, available only in real space. However, in order for the real-space …
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Single-sided magnetic nanoparticles imaging scanner for early detection of breast cancer
… with an appropriate gradiometer pickup coil. In Fourier space, the received voltage signal consists of the fundamental excitation frequency and harmonics. This research utilises the second harmonic response of the MNPs to determine their position and concentration. Analogue Bandpass and Bandstop …
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Advancing the Matter Bispectrum Estimation in Large-Scale Structure
… correlation function or bispectrum in Fourier space, will be indispensable for furthering our understanding of the Universe. While these methodologies have been developed over the years and applied to CMB analyses, similar work on large-scale structure is still in its infancy. …
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Flows in Grooved Channels
… modelling. Projection of groove shape onto a Fourier space creates a basis for a reduced-order geometry model which has been used to capture the modulation effects. A spectral algorithm based on Fourier and Chebyshev expansions has been developed for numerical simulation which provides …
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