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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Use of a Net Rate of Energy Intake Model to Examine Differences in Juvenile Steelhead (Oncorhynchus mykiss) Densities and the Energetic Implications of Restoration

Wall, C. Eric 01 May 2014 (has links)
The Bonneville Power Administration (BPA) Fish and Wildlife Program mitigates for impacts of hydroelectric dams on ESA-listed salmon and steelhead populations in the Columbia River Basin (CRB). Considering the sizable investments in mitigation and the diversity of stream habitats within the CRB, there has been a pointed effort to develop and identify meaningful metrics relating to fish populations and trends in their habitat across the CRB. The Integrated Status and Effectiveness Monitoring Program (ISEMP) was developed in 2003 specifically for this purpose, and is tasked with developing and testing strategies for determining the status and trend of salmonid populations and their habitats in the CRB. This thesis was funded by the BPA, ISEMP, Eco Logical Research Inc., the Snake River Salmon Recovery Board, and the Intensively Monitored Watershed project in the Asotin Creek basin with the purpose of investigating the efficacy of foraging modeling as part of a large fish habitat monitoring program. The primary objectives were i) to assess a foraging model's ability to predict fish density in study sites involved in long-term monitoring and ii) to evaluate energetic implications of restoration design and progress after implementation using a foraging model. To assess the foraging model's ability to predict fish density (objective i), we collected topography, drift, temperature, discharge, and fish population information to support foraging modeling, and we simulated flow patterns, drift, foraging, swimming costs, carrying capacity, and density. We then compared observed and predicted densities in 22 study sites from the John Day and Asotin Creek watersheds: Linear regression between observed and predicted fish densities was significant (R2 = 0.61, p < 0.001). When assuming spatially uniform drift densities and small fish territories, carrying capacity predictions were related to the number of foraging locations simulated, suggesting the model is highly sensitive to territory size assumptions. To evaluate restoration design and monitor restoration progress (objective ii), we simulated foraging before restoration, after a virtual restoration (carried out using the restoration designs in a GIS environment), and again followinfg restoration implementation. We used raster differencing to compare the "before" results to the virtual restoration results and then the "before" results to the "after" results. Hydraulic and foraging models suggested: Mean net energy intake increased following both simulated and actual restoration. Restoration structures generally slowed water's progress through the study site or caused pooling, both resulting in an increase in energetically favorable areas. Generally, more areas shifted from another state to having an acceptable energy balance than to an unacceptable energy balance.
112

Modelovanje mehanizma prenosa toplote pri konvektivnom sušenju i utvrđivanje numeričkih pokazatelja / Analysis of energy characteristics of pneumatics dryers, from the standpoint of the development of convective drying method

Prvulović Slavica 20 May 2004 (has links)
<p style="text-align: justify">Doktorska disertacija &quot;Modelovanje mehanizma prenosa toplote pri konvektivnom su&scaron;enju i utvrđivanje numeričkih pokazatelja&quot; - sadrž i eksperimentalna i teorijska istraživanja vezana za metodu konvektivnog su&scaron;enja. Izvr&scaron;ena su istraživanja parametara sistema konvektivne pneumatske su&scaron;are u eksploatacionim uslovima proizvodnje. Na osnovu rezultata ispitivanja utvrđeni su: modeli kinetike su&scaron;enja, energetski bilansi, koeficijenti prenosa toplote, optimalni režim su&scaron;enja, modeli mehanizma prenosa toplote, numerički pokazatelji i izvr&scaron;ena njihova analiza.</p> / <p>PhD Thesis &quot;Modelling the mechanism for heat<br />transfer at the convective drying and establishing of<br />numerical readers&quot; - contains the experimental and<br />theoretical researches connected with the convective<br />drying method. The parameter researches of the<br />convective pneumatic dryer system in the<br />exploitation conditions in production, are done. On<br />the basis of the testing results are established: the<br />models of drying kinetics, energetic bilances, heat<br />transfer coefficients, optimal regime of drying, heat<br />transfer models mechanism, numerical readers and<br />there was also realized their analysis.</p>
113

Normal impact of liquid droplets on smooth solid surfaces / Impact normal des gouttelettes liquides sur les surfaces solides lisses

Xu, Yang 17 October 2018 (has links)
Dans le cadre de la modélisation et de l’expérimentation multi-échelles (projet LabEx MMCD pour les matériaux pour la construction durable) de l’Université Paris-Est Marne-la-Vallée, cette thèse de doctorat vise à modéliser et caractériser les micro-matériaux conçus par impact de gouttelettes de céramique fondue. Les applications de ces matériaux revétus de couches minces sont des traitements de surface pour la construction durable tels que la protection anti-corrosion, les barrières thermiques, le traitement du verre ou les renforts mécaniques. En particulier, nous nous concentrons sur la physique associée à la dynamique des gouttelettes liquides (l'aire de contact et le temps de contact entre la gouttelette et la surface) en effectuant une série de simulations numériques pour les écoulements diphasiques à petite échelle avec le code maison Thetis. Nous avons considéré des variations des conditions d'impact initiales ainsi que l’influence des forces d'inertie, capillaire et visqueuses sur la dynamique des gouttelettes. Nous nous sommes intéressés en particulier au diamètre d'étalement maximal, au temps d’étalement maximal et au temps de contact, sur des surfaces solides de mouillabilité variable. Le code est basé sur l’utilisation d’une méthode Volume-Of-Fluid. Il introduit une fonction auxiliaire régularisée pour estimer la courbure locale et la normale à l'interface. Les principaux liquides de référence adoptés sont l'eau et la céramique fondue, l'eau est choisie pour valider notre code en comparant les simulations aux résultats expérimentaux. La céramique fondue est adoptée car elle est largement utilisée en projection thermique pour créer des barrières thermiques et chimiques (couches anti-oxydantes) ainsi que des renforts mécaniques sur des échantillons spécifiques. Nous nous concentrons sur les cas où les surfaces sont hydrophobes, même si les cas hydrophiles sont également considérés dans les configurations de validation pour des raisons de généralité. Egalement, en introduisant une partie de calcul de l'énergie dans la thèse, une analyse énergétique détaillée de la gouttelette après l'impact est effectuée dans les phases d'étalement et de rétraction pour bien comprendre la dynamique à l'intérieur de la gouttelette. Nous trouvons que le temps de projection est inversement proportionnel à la vitesse d’impact, indépendamment de l’angle de contact lors de l’étalement au temps courts. Une nouvelle mise à l'échelle entre l'étalement maximal et le temps d'étalement est proposée. Celle-ci s'accorde très bien avec les résultats expérimentaux. Par ailleurs, nous introduisons cette mise à l’échelle dans une classe de modèle basée sur la conservation de l’énergie pour prédire l’étalement maximal adimensionné, ce qui permet de mieux prévoir l’étalement maximal adimensionné. Pour finir, une mise à l'échelle du temps de contact est proposée en termes de nombre d'Ohnesorge et de Reynolds / Under the framework of the LabEx Multi-Scale Modelling and Experimentation of Materials for Sustainable Construction, of Université Paris-Est Marne-La-Vallée, the present PhD thesis aims at modelling and characterizing micro-material designed by impact of molten ceramic droplets. The applications of thin coating materials are surface treatments for sustainable construction such as anti-corrosion, heat barrier, glass treatment or mechanical reinforcement of specific structures.In particular, we focus on the physics behind the liquid droplets' dynamics (the contact area and the contact time between the droplet and surface) by conducting a series of small scale multiphase flow numerical simulations with home-made code Thetis. All simulations are axisymmetric. We have considered variations of initial impact conditions, and studied the influence of inertial, capillary and viscous forces on the droplets' dynamics, especially the maximum spreading diameter, spreading time and the contact time, on solid surfaces. The code is based on Volume-Of-Fluid techniques and introduces an auxiliary smooth function to estimate the local curvature and the normal to the interface. The major reference liquid adopted are the water and the molten ceramic, the water is chosen to validate our code against available experiments at the beginning. The molten ceramic is adopted as it is widely used in thermal spray to built thermal and chemical barriers (anti-oxidant layers) as well as mechanical reinforcements on specific samples. We focus on the cases in which the surfaces are hydrophobic, even if hydrophilic cases are also considered in validation configurations for the sake of generality. Meanwhile, by introducing an energy calculation part in the code, a detailed energetic analysis of the droplet after impact is performed in both the spreading and retraction stage to have a deep understanding of the dynamics inside the droplet.We find the jetting time is inversely proportional to the impact velocity, independent of the contact angle in the early spreading. A new scaling between maximum spreading and spreading time is observed, and agrees well with experimental results. Further, we introduce this scaling into the model based on energy conservation to predict the maximum spreading factor, which provides better prediction on maximum spreading factor than existing literature references. Also a scaling of contact time is proposed in terms of Ohnesorge number and Reynolds number
114

Characterization and detection of traces of energetic materials by Nanocalorimetry

Piazzon, Nelly 19 November 2010 (has links) (PDF)
Calorimetry is one of the main techniques of thermal analysis. Most of physical or chemical modifications of material are associated with thermal effects whereby heat is absorbed (i.e., melting) or released (i.e., thermal decomposition). Typically, calorimetric experiments are performed with Differential Scanning Calorimetry (DSC), which measures the heat flux absorbed or released by the sample following the same temperature program as a reference material. In these experiments, measurements are typically carried out on a few milligrams of sample. However, for many applications one has to handle nanograms or even picograms of sample. One of such applications is relevant to studies of materials which can release a significant amount of energy during their decomposition (energetic materials). Calorimetry able to handle nanograms of sample could find potential applications in the field of explosives detection. Nanocalorimetry allows to heat small amounts of sample (a few nanograms to a few hundred picograms) at extreme heating rates, i.e. up to one million °C/s. The temperature increase can initiate several phenomena in energetic materials, therefore the calorimetry could be an appropriate technique to characterize and to detect energetic materials. The energetic materials used in this study are nitrocellulose (NC), hexogen (RDX), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-ltexaazaisowurtzitane (CL-20) and penthrite (PETN). The manuscript presents our results on the nanocalorimeter calibration, on the thermal behaviour of the explosives studied with nanocalorimetry and also includes an evaluation of nanocalorimetry as a tool for explosives detection.
115

Magneto-Hydrodynamic Activity and Energetic Particles - Application to Beta Alfvén Eigenmodes.

Nguyen, Christine 03 December 2009 (has links) (PDF)
La faisabilite de la fusion magnetique est dependante de notre capacite a confiner l'energie des particules supra-thermiques liberees a haute energie par les reactions de fusion, dans les meilleures conditions de securite et d'efficacite. Dans ce but, il est necessaire de comprendre l'interaction entre les particules energetiques et le plasma thermo-nucleaire qui constitue l'environnement des reactions de fusion, afin de la controler. La these que nous presentons ici s'inscrit dans cet effort. Le coeur du travail mene est l'etude d'un type d'instabilite, le Beta Alfven Eigenmode (BAE), que peuvent exciter les particules energetiques, et dont on peut craindre qu'il degrade fortement non seulement le confinement des particules energetiques mais aussi le confinement du plasma dans sa globalite. Dans un premier temps, nous nous attacherons a decrire les caracteristiques de ce mode et nous deriverons sa relation de dispersion ainsi que sa structure. Dans une seconde partie, nous effectuerons l'etude de la stabilite lineaire de ce mode en presence de particules energetiques. Cette etude nous a permis de definir un critere analytique rendant compte de la capacite des particules energetiques a exciter le BAE. Ce critere sera discute et confronte aux resultats d'experiences menees durant la these. Cette etude lineaire presentant cependant quelques limites, il nous est apparu important de nous poser la question de la possibilite d'une modication de la stabilite du BAE liee a l'utilisation d'une description non-lineaire. Nous suggererons dans cette presentation un processus, verifie analytiquement et numeriquement, dont peut resulter l'existence d'etats meta-stables pour le BAE.
116

Bending of an orthotropic cusped plate

Jaiani, George V. January 1998 (has links)
The bending of an orthotropic cusped plate in energetic and weighted Sobolev spaces has been considered. The existence and uniqueness of generalized and weak solutions of admissible boundary value problems (BVPs) have been investigated.
117

Diagnosing Fuel Ions in Fusion Plasmas using Neutron Emission Spectroscopy

Hellesen, Carl January 2010 (has links)
Neutron emission spectra, measured with the time of flight spectrometer TOFOR, at the joint European torus (JET) are presented in this thesis. TOFOR has been in use since 2005, routinely measuring the neutron emission from JET plasmas. The work in the thesis mainly concerns the modeling of the signatures in the neutron spectrum that reveal different parts of the fuel ion distribution, such as the thermal bulk plasma as well as energetic ions from neutral beam and ion cyclotron heating. Parametric models of the signatures, using plasma parameters as input, are employed to generate trial neutron spectra. The parameters, such as the fuel ion temperature or the fast ion distribution function, are deduced by iteratively fitting the trial spectra to the measured data. Measurements with TOFOR have been made and the models were applied. The studies are mainly on neutrons from d(d, n)3 He reactions(DD), although the emission from reactions with the plasma impurity 9 Be and triton burn up is covered as well. This has allowed for detailed studies of e.g. the physics ICRF heating as well as the interactions between energetic ions and plasma instabilities, such as toroidal Alfvé Eigenmodes.
118

Energetic Costs of AhR Activation in Rainbow Trout (Oncorhynchus mykiss) Hepatocytes

Nault, Rance 22 September 2011 (has links)
Aquatic organisms in response to toxic insults from environmental pollutants activate defence systems including the aryl hydrocarbon receptor (AhR) in an attempt to metabolize and excrete these toxicants and their metabolites. These detoxification mechanisms however may come with certain energetic costs. I hypothesize that the activation of the AhR by β-Naphthoflavone (β-NF), a model AhR agonist, results in increased energetic costs requiring metabolic reorganization in rainbow trout hepatocytes. While the results obtained suggest that there are no significant energetic costs of AhR activation, analysis of enzyme activities suggests possible metabolic reorganization. This study also showed significant changes in cellular processes in hepatocytes over the incubation periods which previously were not reported. Furthermore, for the first time in fish hepatocytes, metabolic flux analysis (MFA) was used to examine intra-cellular metabolism, the applicability of which is discussed.
119

Energetic Costs of AhR Activation in Rainbow Trout (Oncorhynchus mykiss) Hepatocytes

Nault, Rance 22 September 2011 (has links)
Aquatic organisms in response to toxic insults from environmental pollutants activate defence systems including the aryl hydrocarbon receptor (AhR) in an attempt to metabolize and excrete these toxicants and their metabolites. These detoxification mechanisms however may come with certain energetic costs. I hypothesize that the activation of the AhR by β-Naphthoflavone (β-NF), a model AhR agonist, results in increased energetic costs requiring metabolic reorganization in rainbow trout hepatocytes. While the results obtained suggest that there are no significant energetic costs of AhR activation, analysis of enzyme activities suggests possible metabolic reorganization. This study also showed significant changes in cellular processes in hepatocytes over the incubation periods which previously were not reported. Furthermore, for the first time in fish hepatocytes, metabolic flux analysis (MFA) was used to examine intra-cellular metabolism, the applicability of which is discussed.
120

Dynamic and Quasi-Static Mechanical Properties of Fe-Ni Alloy Honeycomb

Clark, Justin Lewis 12 April 2004 (has links)
Several metal honeycombs, termed Linear Cellular Alloys (LCAs), were fabricated via a paste extrusion process and thermal treatment. Two Fe-Ni based alloy compositions were evaluated. Maraging steel and Super Invar were chosen for their compatibility with the process and the wide range of properties they afforded. Cell wall material was characterized and compared to wrought alloy specifications. The bulk alloy was found to compare well with the more conventionally produced wrought product when porosity was taken into account. The presence of extrusion defects and raw material impurities were shown to degrade properties with respect to wrought alloys. The performance of LCAs was investigated for several alloys and cell morphologies. The results showed that out-of-plane properties exceeded model predictions and in-plane properties fell short due to missing cell walls and similar defects. Strength was shown to outperform several existing cellular metals by as much as an order of magnitude in some instances. Energy absorption of these materials was shown to exceed 150 J/cc at strains of 50% for high strength alloys. Finally, the suitability of LCAs as an energetic capsule was investigated. The investigation found that the LCAs added significant static strength and as much as three to five times improvement in the dynamic strength of the system. More importantly, it was shown that the pressures achieved with the LCA capsule were significantly higher than the energetic material could achieve alone. High pressures, approaching 3 GPa, coupled with the fragmentation of the capsule during impact increased the likelihood of initiation and propagation of the energetic reaction. This multi-functional aspect of the LCA makes it a suitable capsule material.

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