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 122 for “"mean free path"”.
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Experimental and numerical investigation of phonon mean free path distribution
Knowledge of phonon mean free path (MFP) distribution is critically important to engineering size effects. Phenomenological models of phonon relaxation times can give us some sense about the mean free path distribution, but they are not accurate. Further improvement of thermoelectric performance …
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Field-driven dynamics of dilute gases, viscous liquids and polymer chains
… microscopic underpinnings, and are treated by means of coarse-graining principles that exploit this scale separation. Specifically, the first part of this thesis investigates the dynamics caused by the existence of a slip velocity at a fluid-solid interface. The macroscopic slip boundary …
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The effect of condenser temperature and location on the molecular distillation characteristics of stearic acid
… molecular still is not as critical, as far as mean free-path design criteria are concerned, as formerly believed. It had been recommended that studies be made on the present apparatus at Virginia Polytechnic Institute to determine exactly how critical this factor is. The purpose of this …
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Experimental studies of the thermoelectric properties of microstructured and nanostructured lead salts
… size is comparable to or less than the phonon mean free path. Samples of PbTe and PbSe were prepared by hot pressing nano-size and micro-sized particles and the thermal diffusivity, the Seebeck coefficient, and the electric conductivity of the samples were measured. The samples made from the …
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Molecular dynamics analysis of spectral characteristics of phonon heat conduction in silicon
… some lingering questions surrounding the phonon mean free path and importance of different polarizations. This research investigates phonon transport in bulk crystalline silicon using molecular dynamics and lattice dynamics. The interactions are modeled with the environment dependent interatomic …
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The superconducting penetration depth in thin films of lead
… determined the film thickness and the electron mean free path. From the field attenuation, the film thickness, and the mean free path, we derived the superconducting conductivity, the London penetration depth ~ and penetration depth A, which would be expected for pure, bulk lead. In order to …
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Studies of ion kinetic effects in shock-driven inertial confinement fusion implosions at OMEGA and the NIF and magnetic reconnection using laser-produced plasmas at OMEGA
… moderate-density plasma with an ion mean free path approximately the size of the fuel region, have, for the first time, been explored in a comprehensive experimental campaign. These experiments at the OMEGA laser facility, in which the ion mean free path was systematically varied in a …
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Radiation of strongly interacting particles by thermal sources: Violation of the Stefan-Boltzmann law
… Particles emitted from a hot thermal source by means of Hawking radiation could self- interact. With such strong interactions, the Stefan-Boltzmann law would not accurately describe the properties of the radiation. This thesis discusses two different regions of a strongly interacting gas around …
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The design, construction, and operation of a centrifugal molecular still
… three basic requirements for unobstructed, short path distillation are: a surface over which a think layer of distilland is distributed, a cooler condensing surface in close proximity to the evaporating surface, and a suitable system for evacuating the space between the two surfaces. When the …
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Electromagnetic penetration depth in superconducting alloys containing magnetic impurities
… resistance between 77 and 140 K. The electron mean free path was determined from the normal-state resistance at low temperatures. The electromagnetic penetration depth lambda, the reduced penetration depth lambda(sigmanTco)1/2, and the London penetration depth lambdaL were determined from the …
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MULTISCALE SIMULATIONS OF THERMAL TRANSPORT IN GRAPHENE-BASED MATERIALS AND ACROSS METAL-SEMICONDUCTOR INTERFACES
… same order of or even below the wavelength or mean-free-path of heat carriers, the transport of heat carriers and the interaction between them will differ from those in the macroscopic regime. This imposes challenges on designing micro/nano-devices with required thermal performance, while, at …
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Thermoelectric properties of silicon-germanium alloys
… nanocomposites can scatter phonons, when their mean free path is longer than the grain size. Mean free path of electrons is usually shorter than the grain size of nanocomposites, so that the electrical conductivities of nanocomposites are not expected to change significantly. However, the …
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Elastic and inelastic scattering of fast neutrons in fusion reactor materials
… and fast. neutrons were detected.by means of a plastic scintillator mounted on a fast focused photomultiplier tube. The samples used were extended flat plates of thicknesses up to 0.9 mean-free-path for Lithium and 1.562 mean-free-path for Lead. The differential elastic scattering …
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A moment-preserving single-event Monte Carlo model of electron and positron energy-loss straggling
… energy-losses and extremely small collision mean free paths. The resulting transport process is dominated by very frequent small energy transfer collisions but a significant contribution to the overall energy-loss distribution comes from the infrequent high energy-losses. Sufficient …
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Electrodeposition of Cobalt for Advanced Interconnect Applications
… of BEOL structures approaches the electron mean free path of Cu or below, the Cu resistivity exponentially increases, posing significant challenges on further scaling. Metals with shorter electron mean free path, for example cobalt (Co), have been explored as the alternative material to …
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Optical transient grating measurements of micro/nanoscale thermal transport and mechanical properties
… First-principles calculations of the phonon mean free paths in Si and GaAs were compared with experimental results and showed good agreement. Preliminary measurements on promising thermoelectric materials such as PbTe and Bi2Te3 are presented showing evidence of non-diffusive transport at …
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Transition Flow in Edge Plasmas: Solution of the Two-Fluid Region With Sources
… region, up to second order in the ratio of the mean free path over the scale height of the system, is discussed. The governing equations for this problem are laid out, and the methods of solving them are presented in detail.
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A hybrid hydrodynamic-Monte Carlo simulation of the transport of neutral radicals in low-pressure remote plasma sources
… (milliTorr to hundreds of milliTorr) the mean free path of excited state neutrals can be commensurate with the vessel dimensions. Deposition species may collide with the wall several times before encountering the substrate. While the movement of these particles is essentially ballistic, …
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The edge flaking of tungsten carbide hardmetal cermets under repetitive impact loading
… The fractography of the crack surfaces and crack paths, occurring in the cermets, have been studied in order to explain the edge flaking performance. Contiguity and mean-free path are found to have important influences on the edge flaking performance. The performances of the various grades of …
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The Phase Space Time Evolution method applied to multigroup neutron transport
… the particles travel on the order of their mean free path, a small time increment must be used. To illustrate the usefulness of the PSTE method, the time evolution of the neutron density of a nuclear device is modeled in slab geometry and the energy dependent scalar and angular flux is …
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