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 200 for “"Power spectrum"”.
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Estimating the Medical Ultrasound in Vivo Power Spectrum
… thesis considered the estimation of the in vivo power spectrum from the backscattered waveforms by finding the total attenuation along the propagation path. The total attenuation was estimated by assuming model for the scatterers (i.e., spherically symmetric Gaussian impedance distributions of …
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The power spectrum and bispectrum of inflation and cosmic defects
… progress in cosmology has come from studying the power spectrum of the cosmic microwave background (CMB). The latest results from the Planck satellite confirmed that the inflationary paradigm with the $\Lambda$CDM six-parameter model provides a very good description of the observed structures in …
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Measurement of the noise power spectrum of a microwave oscillator
Thesis (M.S.) Massachusetts Institute of Technology. Dept. of Electrical Engineering, 1952.
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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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Detecting the turnover of the power spectrum with SKAO and other surveys
Detecting the turnover of the power spectrum with SKAO and other surveys. This thesis explores the potential of next-generation experiments, specifically the Square Kilometre Array and the Dark Energy Spectroscopic Instrument, to detect and constrain the power spectrum turnover, a key feature of …
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Detecting the turnover of the power spectrum with SKAO and other surveys
… Instrument, to detect and constrain the power spectrum turnover, a key feature of the universe’s large-scale structure holding the key for probing ultra-large scales. Employing intensity mapping and galaxy surveys, we utilize Fisher forecasts and Markov Chain Monte Carlo simulations to …
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Instrumental Effects in 21 cm Cosmology: One-point Statistics and Power Spectrum with the HERA Interferometer
… such as the one-point statistics and power spectrum, using the Hydrogen Epoch of Reionization Array (HERA). First, I investigate one-point statistics measured from image cubes based on HERA Phase I observations after foreground removal for the first time. I highlight the influence of …
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Power spectrum analysis of heart rate fluctuations : the renin-angiotensin system's role as short term cardiovascular control system
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1981.
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Simulations of dark energy cosmologies
… and baryonic acoustic oscillations. We study the power spectrum in redshift space in $\Lambda$CDM and quintessence dark energy models and test predictions for the form of the redshift space distortions. An improved model for the redshift space power spectrum, including the non-linear velocity …
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Quantification of Ultrasound Contrast Agents Using High-Frequency Ultrasound
… to the magnitude of the ultrasonic backscattered power spectrum. To demonstrate the ability to quantify UCAs from ultrasonic backscatter, several experiments were conducted. All experiments were conducted with FDA approved Definity® contrast agents and were performed in vitro, i.e., within a …
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Cosmology with Weak Lensing Peaks
… the traditional cosmological WL observable (the power spectrum). To investigate the first question, we use a suite of ray-tracing N-body simulations, in which we identify individual dark matter halos. We study the halos' contribution to the peaks. We find that high peaks are typically dominated …
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Constraining fundamental physics from cosmology
… of inflation with a small red tilt in the scalar power spectrum generically yield an observable tensor spectrum. I show that criteria for fine-tuning based upon the algebraic simplicity of the potential depend strongly upon the assumptions they incorporate about the potential. Furthermore, several …
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Primordial black hole seeding from hybrid inflation : the direct integration approach
… method in hybrid inflation and obtain a power spectrum, which we try to relate to the literature. Our results do not directly show the plausibility of seeding supermassive black holes, but the shape of the power spectrum suggests that further work might yield positive results.
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Probing Cosmology with the MeerKAT Interferometer
… on the COSMOS field is used to measure the Hi power spectrum signal in the Early Science frequency range of 1310- 1420 MHz, in a sub-band of 60 MHz spanning a redshift range of 0.02 ≤ z ≤ 0.066, corresponding to 1332 MHz ≤ ν ≤ 1392 MHz. After mitigating low-level broadband contamination through …
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Polarization and its Discontents: How Polarized Foregrounds Affect 21cm Epoch of Reionization Measurements
… isolated to particular regions of the 21cm EoR power spectrum, but Faraday-rotated, polarized sources can contaminate all regions, even those typically reserved for the 21cm EoR signal. To estimate the level of contamination we can expect from polarized foregrounds, we create a physically …
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System Design And Optimization Of Optical Coherence Tomography
… common practice of assuming a Gaussian source power spectrum. As part of our work to quantify axial resolution we first brought forth two more metrics unlike FWHM, which accounted for side lobes in the axial PSF caused by irregularities in the shape of the source power spectrum, such as …
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Improvements In Interferometric Data Modeling For The New Era Of Radio Cosmology
… of polarization contamination in 21 cm power spectrum measurements using visibility simulations based on historical ionospheric plasma density data. I showed how we can use closed-form calculations of the cross-frequency angular power spectrum on the sky to generate simple mock …
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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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Totally Asymmetric Simple Exclusion Processes with Finite Resources
… finite resources are also studied through the power spectra associated with the total particle occupancy of each TASEP and the reservoir. Again, we find new phenomena not seen in the power spectrum of the ordinary TASEP. For a single constrained TASEP, we find a suppression at low frequencies …
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