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 61 for “"wave activity"”.
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Planetary Wave Activity Observed in Polar Mesospheric Clouds
… (PMC) dataset was investigated for planetary wave activity following the earlier study by <em>Merkel </em>[2002]. To counter the sparse nature of the data, four separate methods of analysis are used in determining if planetary waves are present and how they effect PMC formation. The four …
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A statistical climatology of mesospheric gravity wave activity over Urbana
… dominated by a spectrum of propagating gravity waves. An alternative approach, time-domain-interferometry (TDI), to estimating the vector winds using the measured radial velocity and angle-of-arrival of the scattered signal is investigated and extended to the estimation of wind variances and …
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Fabry-Perot Observations of Midlatitude Neutral Winds and Atmospheric Gravity Wave Activity
… is modulated by a number of atmospheric waves propagating upward from various sources in the lower atmosphere. Among these are atmospheric gravity waves which have been recognized as a major source of momentum and energy in the mesosphere and lower thermosphere as well as a major factor …
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Small intestine slow wave activity defined through in vivo high-resolution electrical mapping
… these propagating biopotentials are termed slow waves, and they serve a vital role in the regulationand organisation of intestinal motility. Most previous studies of intestinal slow waves utilised low-resolution techniques, where few electrodes were sparsely placed along the intestine. The lack …
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On the Variation of Gravity Wave Activity through the Solar Cycle at the South Pole
… of these phenomena include Atmospheric Gravity Waves which are ubiquitous features around the planet. They are important mechanisms for the transport of momentum and energy from the lower atmosphere to the upper atmosphere. The sun is the ultimate source of energy for the earth and the primary …
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Eurasian Snow Cover and the Role of Linear Interference in Stratosphere-troposphere Interactions
… snow forcing, a vertically propagating Rossby wave train is generated, driving dynamical stratospheric warming and a negative NAM response that couples to the troposphere. It is shown that unexplained aspects of the evolution of this response can be clarified by examining the time evolution of …
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Identifying Signatures of Plasma Waves and Reconnection Associated with Kelvin-Helmholtz Activity
… at the magnetopause can generate kinetic Alfvén wave (KAW) activity. Both magnetic reconnection and plasma wave activity can heat plasma. In this thesis we look for new cases of Kelvin-Helmholtz Instability (KHI) from Cluster spacecraft data and search for signatures of associated magnetic …
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Higher Order Trapped Lee Waves in the Stratosphere
Wave activity with maximum amplitude in the stratosphere downstream of major mountain ranges has previously been explained as a result of wave breaking inducing secondary wave generation in the stratosphere (Vadas et al., 2003) or the vertical propagation of low-amplitude waves from below. However, …
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The vertical structure of stratospheric planetary waves and its variability : theory and observations
… vertical structure of stratospheric planetary waves reveal a large variety of structures, and a variability both on seasonal and on daily time scales. The extent to which linear wave theory explains these structures and their time evolution at a given time or season is not well known. The …
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Optical studies of the mesospheric region
… routine extraction of the parameters of gravity waves observed each night. A cross-spectral analysis was performed on processed data from the photometer to identify short period (less than 3 hours) wave activity on nights where the impact of clouds on the data was minimal. The resulting wave …
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Gravity Wave/large-Scale Flow Interactions: A Comparison of Model Predication and Observation
… predicted by three commonly used gravity-wave parameterizations: critical level filtering, linear saturation filtering, and diffusive filtering. A one-dimensional, time-independent model filters various gravity-wave spectra using the criteria for each of these parameterizations. Background …
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MMS Observations of the Kelvin-Helmholtz Instability and Associated Ion Scale Waves
… of magnetic reconnection, various ion scale wave modes, mode conversion, and turbulence associated with the KHI, all of which can contribute to heating and/or plasma transport across the magnetopause boundary.</p> <p>The launch of the Magnetosphere Multiscale (MMS) mission in 2015 offered a …
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Lidar studies of gravity waves in the mesopause region
Nightly and seasonal variations in gravity wave activity in the mesopause region are examined by analyzing 60 nights of Na lidar observations obtained during a five-year period at Urbana, Illinois. The lidar data were used to calculate atmospheric density perturbations and their spectra. The …
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Relaxed mental state detection using the Emotiv Epoc and Adaptive Threshold Algorithms
… the occipital brain region and monitoring alpha wave activity. Said activity is characterized using an adaptive subject-specific threshold algorithm. Different variations of the threshold algorithm were investigated and their performance was compared using receiver operating characteristic …
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On the maintenance of weak meridional temperature gradients during warm climates
… a weak temperature gradient. I examine planetary wave generation, the energetics of the general circulation, and vertical wave propagation in a general circulation model with a resolved stratosphere forced with a weak surface temperature gradient. Compared to the present climate, transient eddy …
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Impacts of coastal realignment on intertidal sediment dynamics: Freiston Shore, the Wash
… accreted sediment and experienced limited wave activity. However, the channels within the breaches in the embankment were eroded, and a creek system over the adjacent intertidal flats experienced an enhancement in its development. This has allowed the natural and enhanced development of the …
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Injector Characterisation Measurement Technology for a Production Environment
… baseline variance originating from pressure wave activity in the fluid medium, high frequency cavitation activity in the injection event, accuracy of the temperature to speed of sound transfer function, cumulative signal offset driven by fluid dependant properties during the injection event, …
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Middle atmosphere structure and dynamics: Lidar studies at the South Pole, Syowa and Urbana
… the clouds appears to be controlled by gravity waves propagating upward through the clouds. Lidar measurements of the mesospheric Na layer at the South Pole in 1990 and Syowa in 1985 are used to characterize mesopause region gravity wave activity over Antarctica. The structure of the Na layer …
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