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 18 of 18 for “"critical layer"”.
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Lattice Relaxation by Plastic Flow and Study of Apparent Critical Layer Thickness in II-VI/GaAs(001) Heterostructures
… It is applicable to graded and multilayered structures, allows for changes of temperature or growth rate, and accounts for differential thermal expansion. For the implementation of this model we consider an arbitrary structure divided into a number of sublayers, each of which is …
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Indium Gallium Arsenide-Gallium Arsenide-Aluminum Gallium Arsenide Strained-Layer Lasers and Laser Arrays
… separate confinement heterostructure strained-layer quantum well lasers are investigated in this work. The main implications of strain are examined briefly, including the importance of a critical layer thickness, strain-induced changes of the band structure, and their effects on laser …
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Observations of interaction between the internal wavefield and low frequency flows in the North Atlantic
… large-scale vertical shear flow, and, excepting critical layer effects, a small vertical eddy viscosity is to be expected. Using the Garrett-Munk (1975) model internal wave spectrum, estimates were made of the maximum momentum flux (stress) expected to be lost to critical layer absorption. Stress …
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Atlantic tropical cyclone formation: Pre-genesis evolution of tropical easterly waves and impacts of the middle to upper tropospheric dry air
… begins to organize near the center of the wave critical layer about one day prior to genesis, along with the rapid intensification of vorticity. The composites derived from the ERA-Interim reanalysis reveal higher specific humidity and equivalent potential temperature near the center of the wave …
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Greedy layerwise training of convolutional neural networks
Layerwise training presents an alternative approach to end-to-end back-propagation for training deep convolutional neural networks. Although previous work was unsuccessful in demonstrating the viability of layerwise training, especially on large-scale datasets such as ImageNet, recent work has …
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Additively Manufactured, Multi-Langmuir Probe Plasma Sensing Device for Use on CubeSats
… plasma diagnostics. The ionosphere is a critical layer of Earth's atmosphere consisting entirely of plasma, and reliable in-situ measurements made on satellites orbiting within the ionosphere are necessary for better understanding its properties. LPs are an ideal choice for CubeSats due …
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A statistical climatology of mesospheric gravity wave activity over Urbana
… wave variances. However, it is also shown that critical layer filtering by a height dependent wind field could be important in controlling the seasonal characteristics of the variance of the wave field.
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An Observational Investigation on Gravity Wave Characteristics and Propagation in the Lower Stratosphere and Mesopause
… preference, three mechanisms are investigated: critical-layer filtering, wave ducting, and Doppler-shifting by local mean wind. Critical-layer filtering failed to explain the propagation preference. Observed gravity wave propagation directions are largely related to the background wind in the …
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Quasigeostrophic flows and turbulence in a rotating homogeneous fluid
… allows one to make a controlled study of the critical layer problem. For small amplitude waves, the mean flow is accelerated in the entire region between the forcing and the critical latitude which acts as a wall for mean wave momentum. In nonlinear runs the steady profile of the westward flow …
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Shear instabilities between accretion disks and nova objects
… accretion-driven dynamics affect the boundary layer between the accretion disk and the stellar surface. The main goal is to assess how shear-driven mixing modifies the thermodynamic and structural conditions of this region and how this affects the onset of thermonuclear runaway, with additional …
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Baroclinic instability of a meridionally varying basic state
… a meridionally varying version of Phillips' two-layer model. It is shown in chapter four that interactions between neutral modes and the unstable mode strongly influence the evolution of the latter and are capable of stabilising it before significant changes occur in the zonally averaged flow. …
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Safe and secure autonomous vehicles
… of machine learning make its use for safety-critical tasks perilous. This is evident in the plethora of safety challenges facing autonomous vehicles. Autonomous vehicles have the potential to save and improve lives, however, their widespread usage and adoption have been severely inhibited by …
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Multiscale modeling of fracture and deformation in interface controlled materials
… simulations. Cleavage failure of dual phase layered materials is simulated with a mesoscopic model to clarify the scaling behavior of the materials fracture toughness. The model accounts for the confinement effect that a layer geometry imposes on the collective dislocation behaviour near a …
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Effect of heating on sound radiated from a two-dimensional mixing layer
… by instability waves in a two-dimensional mixing layer is studied. A linear stability theory coupled with linearized Euler calculations are used to compute the amplitude of the instability wave and its associated sound field. The linear stability analysis also identifies the point of neutral …
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Mixing and secondary circulation in Juan de Fuca Strait
… from river runoff flow out to sea in the upper layer, while nutrient-carrying oceanic water returns beneath. While there have been many studies of the processes involved in this exchange flow, the dynamics and vertical structure of transverse flows are much less understood, despite the role …
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Eddy forcing of the mean circulation in the western North Atlantic
… the time variation in the thickness of isopycnal layers. This thickness flux is an order of magnitude larger than the relative vorticity flux. The total flux is statistically significant and directed 217° T to the southwest with a magnitude of 1.57 x 10 -5 cm/2s. The direction of the eddy flux …
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Dynamical Processes of Gravity Waves Propagation and Dissipation, and Statistical Characteristics of Their Momentum Flux in the Mesosphere and Lower Thermosphere
… reflection at two different altitudes and near-critical layer filtering in-between. All the retrieved parameters were then applied to a 2-D numerical model whose outputs help to interpret the observations. In case 2, the lidar system is configured in a 5-direction mode, whose laser beams were …
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CO2 capture and utilization using dual-functional catalysts
… we study the formation of a CaCO3 product layer on the outside surface of CaO grains during the fast reaction stage for carbon capture using two types of CaO adsorbents. The carbonation at 400 ˚C filled the small pores in the commercial CaO grains and no distinct product layer of CaCO3 was …