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 113 for “"power spectra"”.
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SEMICLASSICAL VIBRATIONAL SPECTROSCOPY BEYOND POWER SPECTRA
… interactions. However, the increasing spectral complexity of medium- and large-sized systems makes theoretical support essential for reliable spectral assignment. Semiclassical (SC) molecular dynamics offers an effective compromise between accuracy and computational cost, incorporating …
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Image Evolution Using 2D Power Spectra
… Based on existing research which uses power spectral density of spatial frequencies as an effective metric for image classification and retrieval, we believe this measure and others based on Fourier decomposition may be effective for guiding evolutionary texture synthesis. We briefly …
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Time-dependent power spectra and first passage probabilities.
Massachusetts Institute of Technology, Dept. of Civil Engineering. Thesis. 1971. Ph.D.
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Statistical Analysis of the Cosmic Microwave Background: Power Spectra and Foregrounds
… of this new algorithm to produce an exact power spectrum in a computationally feasible time, coupled with the foreground component separation and removal is an exciting development in CMB data analysis. When considered with current algorithmic developments such as the ability to include …
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Clestial harmonics - Applications of Angular Power Spectra to Problems in Astroparticle and Cosmological Physics
… topic of this thesis is the use of angular power spectra formalisms in the spherical harmonic space, aimed at inferring information on observables relevant to astroparticle physics and cosmology applications. Part I describes the work I developed at the University of Turin under the …
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Using power spectra to look for anisotropies in ultra-high energy cosmic ray distributions
… the data. The method of using these angular power spectra is an attempt to provide a common language for model builders and experimentalists. Anisotropies of any size are easily detected using these coefficients, making them an ideal way to look at observed events that might not be coming …
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Initial exploration of 21-cm cosmology with imaging and power spectra from the Murchison Widefield Array
… Australia with a primary goal of measuring the power spectrum of the 21-cm signal from neutral hydrogen during the Epoch of Reionization (EoR). In this thesis, we detail efforts to characterize the MWA system, and present scientific results from a 32-element prototype interferometer deployed at …
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Experimental and analytical study of electrical crosstalk in CMB cold readout systems and implications for power spectra
… to the present epoch. The CMB frequency and power spectra have been measured and characterized by groundbreaking space missions such as COBE, which first detected the CMB anisotropies, WMAP, which provided improved angular resolution, and Planck, which achieved the most precise measurements …
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Barkhausen Noise Studies: Pinning Field Statistics and Time-Asymmetries
… size distributions, temporal Barkhausen power spectra, and spatial pinning field power spectra illustrates that the most recent justification for the statistics of the effective pinning field is incomplete.
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Enhanced plasma wave spectral asymmetries
… backscatter radar is used to obtain detailed power spectra of these enhanced plasma waves. Power and frequency asymmetries are detected between spectra of enhanced plasma waves propagating parallel and antiparallel to the radar line-of-sight at the altitude of observation. The power spectra …
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A Study of Narrowband Noise Characteristics Associated with Vortex Motion in High Temperature Superconductors
… similar to those obtained in experiments. The power spectra generated for point and columnar disorder are then compared for increasing vortex density. Above, but near the depinning threshold, broadband noise associated with plastic vortex flow is observed for columnar defects at low vortex …
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Using two-dimensional impedance maps to study acoustic properties of tissue microstructure
… property of a tissue based on the frequency power spectrum estimated from the RF signals corresponding to ultrasonic backscatter. From the BSC, parametric models can be constructed to relate the frequency-dependent BSC to geometrical properties of the underlying tissue. However, most of these …
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The cosmic microwave background: gaussianity and polarization
… those to simulated Gaussian skies with the same power spectrum and noise. We find some discrepancies in the WMAP data, and we can interpret these as either a detection of non-Gaussianity, or some foreground or other overlooked detail in our model of the experiment. The second tool provides a …
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Quantitative ultrasonic characterization of diffuse scatterers in the presence of structures that produce coherent echoes
… that parameterize the backscattered signal power spectrum have demonstrated significant promise for ultrasonic tissue characterization. Some QUS parameters, including the effective scatterer diameter (ESD) and the effective acoustic concentration (EAC) that can be used for disease detection …
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Measurements and implications of the SDSS DR7 galaxy angular power spectrum
We calculate the angular power spectrum of galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) by using a quadratic estimation method with KL-compression. The primary data sample includes over 18 million galaxies covering more than 5,700 square degrees after masking …
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Deterministic chaos in Alcator C-Mod edge turbulence
… Closed Flux Surface (LCFS) exhibit exponential power spectra. Theoretically, the characteristic slope of the data on a semi-log plot gives the full width of the underlying Lorentzian pulses, which give rise to the exponential power spectra due to the dynamics of deterministic chaos. Using a …
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An interactive computer analysis of the aortic ejection click and first heart sound
… (1) computing averages, aligned averages, power spectra of selected segments, envelograms, and deterministic signals; (2) storing and retrieving intermediate results; and (3) plotting data. The program is listed and its interaction is fully described in this thesis. The following steps were …
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