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 28 for “"Frequency fluctuations"”.
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Vertex-Based Analysis of Cerebral Blood Flow and Fractional Amplitude of Low-Frequency Fluctuations (CBF-fALFF) Coupling in Moderate-to-Severe Traumatic Brain Injury During the First Year Post-Injury
… blood flow (CBF) and fractional amplitude of low-frequency fluctuations (fALFF), a proxy for spontaneous neural activity. Using arterial spin labeling (ASL) and functional MRI sequences, CBF and fALFF were measured in 29 msTBI patients 3-, 6- and 12-months post-injury for within-group longitudinal …
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Differentiating schizophrenic patients from healthy control; application of machine learning to resting state fmri
… data. Most of these studies focus on fMRI low frequency oscillations. This study focuses on the amplitude of low-frequency fluctuations (ALFF) and fractional amplitude of low-frequency fluctuations (fALFF). A Voxel-wise analysis is performed on the whole brain for two groups of subjects. A …
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Effect of scan time on resting state parameters
… the interest in studying the spontaneous low-frequency fluctuations (LFF) in a resting-state brain has steadily grown. By measuring LFF (< 0.08 Hz) in blood-oxygen-level-dependent (BOLD) signals, resting-state functional magnetic resonance imaging (rs-fMRI) has proven to be a powerful tool in …
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Upwelling dynamics off Monterey Bay : heat flux and temperature variability, and their sensitivities
… atmospheric fluxes and the causes of high-frequency fluctuations found in ocean thermal balances. We focus on the first upwelling event from August 1- 5, 2006 in Monterey Bay that occurred during the Monterey Bay 06 (MB06) at-sea experiment, for which MSEAS data-assimilative baseline …
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Characterization of low-frequency density fluctuations in dipole-confined laboratory plasmas
Low-frequency fluctuations of plasma density, floating potential, ion saturation current, visible light intensity, and edge magnetic field are routinely observed in the Levitated Dipole Experiment (LDX). For the purposes of this thesis, we define low-frequency as W << Wbe where Wbe is the electron …
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Hydrogen bonding and solvation dynamics of n-methylacetamide in denatured water (D₂O) or denatured chloroform (CDCl₃) from nonlinear spectroscopy
… infrared spectroscopy to probe the frequency fluctuations of the amide I mode of the solvated NMA. An iterative fitting approach was used to extract a correlation function from the experimental data. The correlation function for NMA/D₂O was found to be biexponential with decay …
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Acoustic tomography in the Straits of Florida
… scale signal in the eastern Florida Straits. Low frequency fluctuations of temperature, current velocity, and vorticity occur at periods ranging from several days to nearly two weeks, and are intimately related to meandering of the Florida Current system.
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Synchronization in Coupled Opto-thermal Silicon MEMS Limit Cycle Oscillators
… cycle oscillations, self-synchronization, and frequency entrainment to an external drive. In this work, we chart the behavior of silicon MEMS oscillators that are nominally 40 µm long and 205 nm thick, mechanically coupled, and opto-thermally driven by a continuous-wave helium-neon laser. …
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Ultravioletinės srities šviesos diodų žemadažnio triukšmo tyrimas /
The aim of this work was to investigate low-frequency noise characteristics of UV LEDs, evaluate simultaneous cross-correlation coefficient between electrical and optical fluctuations and apply correlation method for InGaN-based LEDs. Two AlGaN-based LEDs (275 nm) and two InGaN-based LEDs (370 and …
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Superconducting magnetic energy storage for power system stability and quality enhancement
… are addressed in this thesis. The first is the fluctuations in generated power due to variations in wind velocity in wind power systems. The fluctuation in the wind, which is the main energy source in a wind power system, leads directly to voltage and frequency fluctuations in both generation …
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Fire regime change and the boreal forest carbon cycle from 10,000 years ago to 2100 AD
… is unprecedented in the last 10,000 years. Fire frequency fluctuations were the dominant control on carbon dynamics of the past millennium, and the increase in fire activity over the past several decades has caused large regional carbon losses. Fuel limitation due to fire-vegetation feedback …
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Measuring trapped-ion motional decoherence through direct manipulation of motional coherent states
… state decoherence and laser amplitude or frequency fluctuations. In this thesis, we apply a previously-presented mechanism of direct electric field manipulation of a trapped ion motional coherent state in a novel free precession sequence to measure motional coherence times. This sequence …
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A Three-Year Study of the Magnetic Field Fluctuations in the Magnetospheric Cusp
… field turbulence. There are also magnetic field fluctuations that cannot be called turbulence. Some of the low frequency fluctuations observed in the cusp have been shown to be motion of the cusp structure by the spacecraft (back and forth motion of the boundaries surrounding the cusp); others …
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Remaining Unperturbed by the Vibrational Response: Probing Vibrational Coupling, Relaxation, and Solvent Effects with 2D IR Spectroscopy
… an understanding of their native structuresand fluctuations of their environments. One of the most powerful ways to probe the dynamic behavior of molecular systems in solution is through the use of Two-Dimensional Infrared (2D IR) spectroscopy. 2D IR is an ultrafast laser technique that is …
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Response variability in ADHD: exploring the possible role of spontaneous brain activity
… with ADHD might not effectively attenuate low frequency resting brain activity from rest to task and that these low frequency oscillations may then intrude onto task performance and cause periodic attention lapses. These periodic attention lapses would manifest as increased variability in RT …
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An experimental study of the relationship between velocity and pressure fluctuations in a wing-body junction
Velocity and pressure fluctuations were measured in a wind tunnel in the plane of symmetry in front of a wing-body junction at an approach free-stream velocity U<sub>ref</sub>=28.3 m/s and momentum thickness Reynolds number Re<sub>θ</sub>=6900. The cylindrical wing shape was a 3:2 elliptic nose …
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The effects of nonnutritive sucking on state regulation in preterm infants
… analysis indicated that there were other faster frequency fluctuations in state. Following NNS there were more of these fluctuations and they accounted for more variance in state. This pattern is more similar to the pattern observed in low-risk newborns. These results are discussed in terms of …
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Design, Analysis and Experimental Evaluation of a Virtual Synchronous Machine Based Control Scheme for STATCOM Applications
… under different contingencies, PCC voltage fluctuations in magnitude and frequency may impede the STATCOM from tracking the grid frequency correctly, hence worsening its overall compensation performance, and putting at risk the operation of the power plant. Further, the virtual synchronous …
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Neuroimaging study of prenatal alcohol exposure effects on structural and functional connectivity in children
… with reduced fractional amplitude of low frequency fluctuations (fALFF), indicating changes in functional connectivity in the default mode, salience, and dorsal attention networks. The locations of the WM alterations found with DTI suggest that the compromised RSFC found in 3 of the 5 …
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Smart inverters for seamless voltage and frequency dynamics in microgrids
… and employed in BESS to improve the voltage and frequency profiles during abnormalities. Besides, the controllers of PV units are equipped with an adaptive piecewise droop (APD) to cope with disturbances. Lastly, an approach is presented in this dissertation for seamless interconnection of three …
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