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 26 for “"thermal relaxation"”.
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A theoretical investigation of thermal waves
… of one-dimensional heat conduction based on thermal relaxation is presented. Thermal relaxation is introduced through the constitutive equation (modified Fourier's law) which relates this heat flux and temperature. The resulting temperature and flux field equations become hyperbolic rather …
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A miniature, broadband acoustic spectrometer : design of a unified attenuation model, device development, and experimental performance
… Nonclassical attenuation arises from the thermal relaxation between internal and external degrees of freedom for each constituent molecule. Currently, we are not aware of any commercial gas sensors that leverage classical attenuation. Existing methods to detect gas composition using …
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Oscillatory Behavior of Fine AP/HTPB Composite Propellants
… combustion response peak (∼10 Hz) due to the thermal relaxation in the solid and a secondary peak at a higher frequency (50--300 Hz). The frequency of this second peak has a strong correlation with particle size; it only appears for small AP (≤ 50 mum) and its frequency increases with …
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Artificial heating of the lower ionosphere
… of the electron collision frequency and thermal relaxation times between 70 and 120 km, and may increase the understanding of the interaction of plasmas and radio waves. The heating is measured with the 430 Mhz incoherent backscatter radar system. The temperature dependence of the …
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Effects of a Slow Gas-Phase Reaction on the L(*) Instability in Solid-Propellant Rockets
… stemming from the interaction between the thermal relaxation in the solid propellant and the bulk-mode gas motion inside the combustion chamber is examined theoretically and numerically. The explosion reaction, following the quasisteady fizz reaction occurring near the burning surface, is …
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A Study of the Effects of Laser Shock Peening on Residual Stress, Microstructure and Local Properties of IN718 Ni-Base Superalloy
… of LSP process parameters and; (4) Study Thermal relaxation of residual stresses and understand the underlying kinetics.</p><p>Firstly, different LSP process parameters including: Power density, impact overlaps, ablative overlays and coverage were studied to impart deep compressive …
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Geological and thermochronological evolution of the lower crust of southern Africa
… have been used to elucidate the architecture and thermal evolution of the continental lithosphere of southern Africa. U-Pb accessory mineral geochronology of lower crustal xenolith assemblages illustrate the youth of granulite-facies metamorphism relative to the ancient stabilization of the …
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Finite element model of thermoelastic damping in MEMS
… anelastic damping. Specifically, the decreased thermal conductivity in the devices with germanium causes those devices to experience thermoelastic damping of a greater magnitude than the germanium-free devices. The amount of damping exhibited is found to be well explained by existing analytical …
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Predicting Kinetics of Spin-Dependent Reactions in an External Magnetic Field with Nonadiabatic Statistical Theory
… and environmental factors influence the thermal relaxation mechanisms of spirooxazine-based photochromes, aiming to design more efficient photochromic materials. Furthermore, we demonstrate that the coordination of a spirooxazine ligand to a copper(II) complex with potential long …
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The physical response of soft musculoskeletal tissues to short pulsed laser irradiation
… the material remains in an expanded state until thermal relaxation occurs. We use numerical methods to solve the 3-D thermoelastic wave equation for a hydrated sample. In addition to thermoelastic expansion, expansion due to the formation of cavitation bubbles within the tissue was modeled. …
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Preparation and characterization of photo-, thermo-, and solvatochromic materials containing benzospiropyran
… selectively exhibits photochromism only (i.e. no thermal relaxation), thus producing a potentially permanent effect or certainly a sufficiently long term effect for many applications. The control of this solute-solvent interaction by photons was coupled with an increase in viscosity and decreases …
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Diffusion and the thermal stability of amorphous copper-zirconium
Measurements have been made of diffusion and thermal relaxation in amorphous CU50Zr50. Samples were prepared by melt-spinning under vacuum. Diffusion measurements were made over the temperature range from 317 to 385 C, using Ag and Au as substitutional impurities, by means of Auger electron …
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Two-phase flows accompanying fires in enclosures
… particulate with an instantaneous velocity and thermal relaxation time. In this thesis, computational fluid dynamics is used as a tool in order to characterise the applicability of the passive models and the active model. The ability of the passive models to accurately predict the growth of …
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Determining Energy Relaxation Length Scales in Two-Dimensional Electron Gases
… where the carrier mobility is high and the thermal broad- ening of quantised energy levels is minimised. 4.2 K, the temperature of liquid helium, is thought of as relatively warm. Temperatures of 300 mK and below are readily accessible with sorption-pumped helium-3 and 3He/4He dilution …
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Exciton behaviour at organic solar cell interfaces
… linking exciton formation, charge transfer and thermal relaxation are explored, particularly in the context of dependence in the morphology of the donor molecules as well as the non-adiabatic coupling between excited states.
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Structural and thermodynamic properties of sodium actinide ternary oxides
… Knudsen effusion mass spectrometry (KEMS) and thermal-relaxation calorimetry. In addition, the oxygen content required at 900 K within liquid sodium to form pentavalent $Na_3UO_4$ and hexavalent $Na_4UO_5$ were calculated to be 0.7 and 1.5 wppm, respectively, which are levels typically …
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Physicochemical Study of Nano-structuring Within Ionic Liquids Using Photoswitchable Spirocyclic Compounds
… the environment present based upon the rates of thermal relaxation of the compounds from their open merocyanine (MC) form to their closed (SP) form and the equilibrium effects upon the MC-SP inter-conversion and the dependence of cation and anion choice while optimising the choice of probe …
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Expressions of Mantle Dynamics in Landscapes and Sedimentary Basins
… phase of rifiting followed by a long phase of thermal relaxation, a consequence of the basin's location on thick cratonic lithosphere. This post-rift phase is punctuated by periods of uplift and denudation that can be explained by emplacement and cooling of warm asthenospheric material at the …
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Thermomechanics of helical strands and helical-fiber-reinforced rods
… strands is further extended by considering thermal expansion. The finite element analysis demonstrates a coupling between thermal expansion and torsion, due to the structural chirality, which is also incorporated into the final form of the thermomechanical constitutive relation of helical …
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Links between climate feedbacks and the large-scale circulation across idealized and complex climate models
… and determined by a single parameter: The thermal relaxation timescale. The dynamical core model may thus help to fill gaps in the model hierarchies commonly used to study climate forcings and climate feedbacks. I then perform two experiments: One that explores the influence of prescribed …
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