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 21 for “"heat-pulse"”.
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Accuracy of Heat-Pulse Sensors for Determining Moisture of Capillary Mat Material Used to Support Plant Growth
… capillary action. The TMAS sensors, single probe heat-pulse moisture sensors, will measure the moisture level of the capillary mat as part of a moisture feedback irrigation control regime. Tests were done to determine temperature calibrations and the best mode of operation of the sensors in this …
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I. Resonant Two-Photon Reabsorption by Exciton-Polaritons in Cuprous Chloride Films. Ii. Heat Pulse Propagation Across Metal/sapphire Interfaces. Iii. Phonon Focusing in Piezoelectric Crystals
The work described in this thesis involves the study of optical and thermal properties of semiconductors and consists of three separate topics.
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I. Resonant two-proton reabsorption by exition-polaritons in cuprous chloride films ; II. Heat pulse progration across metal/sapphire interfaces ; III. Phonon focusing in piezoelectric crystals
… resonant reabsorption process is described. 2.Heat pulse propagation across metal/sapphire interfaces. The angular dependerce of ballistic phonon propagatior ir sapphire is found to exhibit three distinct types of features. The first corresponds to mathematical singularities in the bulk phonon …
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Heat transfer, evaporation and carbon dioxide transfer in soil
<p>Latent heat flux associated with soil water evaporation connects the surface water balance with the surface energy balance. Soil water evaporation and soil carbon dioxide (CO2) fluxes both involve soil gas transport processes and properties, and both impact the soil environment and physical, …
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Acoustic waves in crystals: I. Ultrasonic flux imaging and internal diffraction. II. Imaging phonons in superconducting niobium
… waves in crystals. (II) The low-temperature heat-pulse technique is applied to a study of phonon transport in superconducting niobium, providing the first phonon images of a metal and revealing interesting interactions between phonons and quasiparticles.
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Phonon imaging
… of phonons emitted from a point source of heat in insulators at low temperatures. It is a derivative of the ballistic heat pulse method, but one which uses a pulsed laser to allow continuous two dimensional scanning of the phonon source. In this work we have applied this method to the …
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Laboratory investigation of a method for determining in situ saturated hydraulic conductivity
… involves measuring the advective component of a heat pulse generated within the borehole porous medium. The second technique involves determining the dilution rate of an electrolytic tracer introduced into the borehole porous medium. For each technique, experimental instruments were designed and …
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Tropical bracken, a powerful invader of pastures in South Ecuador: Species composition, ecology, control measures, and pasture restoration
… In a laboratory experiment, the effects of heat pulse by a simulated bushfire on the bracken rhizomes were investigated. Separated long and short shoots were heated for a short time either in a water bath or embedded in soil. Subsequent to this heat pulse, they were cultivated in original …
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Untersuchungen junger Grundwässer mit Hilfe anthropogener Spurenstoffe
… und die Ergebnisse mit Messungen eines heat pulse flowmeters verglichen. Im zweiten Teil wurden drei Fallstudien zur Datierung junger Grundwässer mit Hilfe mehrerer anthropogen erzeugter Spurenstoffe durchgeführt. Dabei wurden 3H, 20Ne, 22Ne, 85Kr, FCKW und erstmalig Schwefelhexafluorid …
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Exploring possible coupling between phonons and internal nuclear states
… attempt to look for excitation transfer effect. Heat pulse can trigger X-ray signal increments. We performed angular anisotropy experiments which appears to support the conjecture that slow resonant excitation transfer occurs for the 136 keV excited state of Co-57. We also performed …
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Study of phonon-dislocation interaction in LiF and KCl crystals
… modes are strongly scattered by dislocations. Heat-pulse measurements on KCl samples support this interpretation. 1-irradiation restores the thermal conductivity of the deformed KCl samples, suggesting that the phonon-dislocation interaction in KCl also is dynamic in nature. The experimental …
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An Unsteady State Tracer Dilution Method for Characterizing Water Contributing Fractures in Crystalline Bedrock Wells
… an order of magnitude of those calculated using heat-pulse flow meter data from a previous study.</p>
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Study of phonon transmission through solid-solid interfaces and superlattices by phonon imaging
… explores the low-temperature propagation of heat pulses (phonons) through crystals and across solid-solid interfaces. The phonon imaging technique has been used to examine the angular and temporal dependence of the phonon-flux intensity in several systems, listed below. 1. Phonon focusing in …
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The scattering of thermal phonons by extended defects in dielectric crystals
… of thermal conductivity and ballistic heat pulse propagation. The thermal conductivities of LiF and NaCt containing 500 low-angle grain boundaries per cm were measured in the range 0.08-5 K. The measurements gave little or no evidence for phonon scattering from the·grain boundaries. In …
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ENGINEERING STRUCTURE AND PHASE VIA TEMPERATURE MANIPULATION IN THIN FILM OXIDES GROWN BY ALD
… with ALD precursors. A method called resistive pulsed-heating ALD (PH-ALD) is introduced as a strategy to circumvent the thermal limitations of ALD precursors by applying a short heat pulse to the film after low-temperature deposition cycles in the ALD process. The PH-ALD technique is used to …
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Pedestal structure and stability in high-performance plasmas on Alcator C-Mod
… transport leading to unacceptable levels of heat loading and erosion damage to plasma-facing materials. As such, the suppression, mitigation, or avoidance of large ELMs is the subject of much current research. In light of this, a firm physical understanding of the pedestal structure and …
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Thermal Pollution in Urban Streams of the North Carolina Piedmont
… and, as will be discussed in this thesis, heat surges (Booth 1990, Tsihrintzis and Hamid 1997, Walsh et al. 2005a, Nelson and Palmer 2007, Bernhardt et al. 2008). At baseflow, urban streams are contaminated by sanitary sewage leakages, are unable to exchange water with their floodplains due …
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The influence of drought, and other abiotic factors on tree water use in a temperate remnant forest
… Principle methods applied were (a) use of heat-pulse technology to measure rates of sap flow through trees; (b) open-top chambers to measure understorey and soil evapotranspiration; (c) application of the Penman-Monteith equation to estimate canopy conductance and transpiration rates; (d) …
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Phonon Spectroscopy and Low-Dimensional Electron Systems
The generation and propagation of pulses of nonequilibrium acoustic phonons and their interaction with semiconductor nanostructures are investigated. Such studies can give unique information about the properties of low-dimensional electron systems, but in order to interpret the experiments and to …
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