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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.
301

Recubrimientos multicapas de tipo orgánico/metal/cerámica para espejos solares de base polimérica flexible / Revêtements multicouches de type organique/métal/céramique pour des concentrateurs souples en polymères / Organic/metal/ceramic type multilayered coating supported on a flexible polymeric base

Gutiérrez Muñoz, Monserrat 30 March 2016 (has links)
La production actuelle d’énergie qui provient principalement des combustibles fossiles a un impact négatif sur l’environnement. Le développement des énergies renouvelables peut limiter cet impact. Si la conversion thermodynamique de l’énergie solaire obtenue en concentrant le rayonnement photonique permet d’atteindre des rendements élevés, l’enjeu est de réaliser, à faible coût, de grandes surfaces de réflecteurs souples et légers ayant une excellente propriété optique réfléchissante.Dans ce travail de recherche, nous avons étudié deux types de miroirs qui entrent dans la réalisation des concentrateurs solaires. Le premier miroir est constitué d’une plaque souple en polymère très transparent (indice de transmission le plus élevé possible) sur laquelle a été déposé un film réfléchissant. Cette couche est protégée contre la corrosion et les agressions environnementales par un revêtement organique opaque élaboré en face arrière. On obtient ainsi un système polymère/métal/ film organique. Le second miroir est constitué d’un substrat opaque souple sur lequel est déposé un film réfléchissant. Une couche mince protectrice organique ou céramique, ayant un indice optique de transmission le plus élevé possible, est élaborée en face avant sur la couche réfléchissante. On obtient ainsi un système céramique/métal/ organique.Cette couche réfléchissante étant indispensable dans les deux configurations de miroir, nous avons étudié l’élaboration d’une couche réfléchissante à base d’argent du fait que la technique de dépôt chimique dynamique, appelée encore technique JetMetalTM, permet d’obtenir des films d’argent à température ambiante et de façon rapide et peu coûteuse. D’autre part, cette technologie agrée « Green Tech » est bien adaptée pour l’élaboration de dépôt sur des grandes surfaces. Ce rapport décrit les étapes et les paramètres nécessaires pour obtenir des réflecteurs optiques à base d’argent de grandes qualités : qualité optique avec des réflectivités supérieures à 95%, qualité mécanique avec des interfaces polymère/métal pouvant encaisser des déformations, un rapport qualité/prix par l’optimisation des cinétiques de dépôt et d’épaisseur de film d’argent (environ 100nm) avec un temps très court d’élaboration. De nombreuses techniques d’analyses et de caractérisations (XPS, AFM, LRX, SEM…) ont été utilisées pour dégager les paramètres pertinents d’un miroir solaire à base d’argent.La propriété optique du film d’argent est stable à l’air et avec le temps. Néanmoins, une protection de l’argent est nécessaire en particulier en face avant. Cette protection doit adhérer au film d’argent, pouvoir être flexible et présenter un indice de transmission le plus élevé possible dans le domaine visible. Si différents vernis ont été étudiés, notre travail a surtout porté sur l’élaboration de revêtements protecteurs organiques (PMMA, PU), céramiques (SiO2, Al2O3) et surtout hybrides organique-céramique. Ce travail de recherche a permis d’identifier les domaines de pertinence de ces différents types de revêtements protecteurs sous contrainte radiative, leur compatibilité avec une couche réflective d’argent, pour conduire à des concentrateurs souples performants. Une solution originale est présentée en conclusion. Elle porte sur la réalisation d’un miroir souple élaboré sur une feuille de verre de 100 µm d’épaisseur revêtue d’un film de 100 nm d’argent. La réflectivité est supérieure à 95% dans le visible. / The present production of energy that mainly comes from the burning of fossil fuels has a negative impact on our environment. The research and development of clean and renewable sources of energy can decrease this damage. If the thermodynamic conversion from solar energy obtained by photons radiation concentration allows us a higher efficiency, the challenge is to build at low cost, large areas for solar reflectors that are flexible and lightweight, with a powerful optical reflection.During this research a study was made on two types of mirrors for achieving solar concentrators. The first mirror is formed of a flexible polymer plate highly transparent (Transmission index as high as possible) in which was deposited a reflective layer. This layer is protected against corrosion and any other environmental aggression by an opaque organic coating built on the rear face. This produces a polymer/metal/organic film system. The second mirrors consist of a flexible opaque substrate in which, a reflective film is deposited. A thin organic or ceramic protector film with a transmission index as high as possible is prepared in front of the reflective layer. Thereby, a ceramic/metal/organic system was obtained.Being that the reflective layer is essential in both configurations of the mirror, research was carried out about the development of a reflective layer composed of silver with the dynamic chemical plating technique also called “Jet MetalTM technique” which allows the elaboration of silver films at room temperature in a fast and economical manner. Also, this approved technology <<Green Tech>> is well adapted for the deposit development over large surfaces. This report describes the steps and necessary parameters to obtain optical reflectors based on high quality silver: optical quality with a higher reflectivity over 95%, mechanical quality with interfaces of polymer / metal that can absorb deformations, a relation quality/price through the optimization of the deposit kinetic and the silver film thickness (approximately 100 nm) with a very short elaboration time. Many analysis and characterization techniques (XPS, AFM, LRX, SEM…) have been performed to determine the parameters of a solar mirror made of silver.The optical property of the silver film is stable in air ambient and with time. However; the silver protection is necessary mainly on the front face. This protection must adhere to the silver film, be flexible and provide a high visual range. Different varnishes have been researched, and our work has been concentrated in the development of organic (PMMA, PU), ceramics (SiO2, Al2O3), and especially hybrid organic-ceramic covering protection. This research allowed us to identify the relevant areas of these different types of protection coatings under radiation stress, its compatibility with the silver layer to obtain efficient and flexible concentrators. An original solution is presented at the conclusion that corresponds in the elaboration of a flexible mirror, made up of a glass layer of 100 µm thick and covered in a silver film of 100 nm. The reflection is over 95% visible. / La producción actual de energía que proviene principalmente de combustibles fósiles tiene un impacto negativo sobre el medio ambiente. El desarrollo de las energías renovables puede reducir este impacto. Si la conversión termodinámica de la energía solar obtenida por concentración de radiación de fotones permite alcanzar altos rendimientos, el reto es lograr realizar, a bajos costos, grandes áreas de reflectores flexibles y ligeros, con una excelente propiedad óptica reflejante.En esta investigación, se estudiaron dos tipos de espejos que intervienen en la consecución de los concentradores solares. El primer espejo está hecho de una placa flexible de polímero altamente transparente (índice de transmisión lo más alta posible) en el que se depositó una película reflejante. Esta capa está protegida contra la corrosión y el ataque del medio ambiente por un revestimiento orgánico opaco desarrollado en la parte trasera. Esto produce un sistema polímero/metal / película orgánica. El segundo espejo consiste en un sustrato opaco flexible en la que se deposita una película reflejante. Una película delgada y protectora orgánica o cerámica con un índice de transmisión lo más alto posible se prepara en frente de la capa reflejante. Por lo tanto, se obtiene un sistema cerámico / metal / orgánico.Siendo esta capa reflejante esencial en ambas configuraciones de espejo, se investigó el desarrollo de una capa reflejante a base de plata con la técnica de depósito químico dinámico, también llamada “JetMetalTM technique” que permite elaborar películas de plata a temperatura ambiente de manera rápida y económica. Además, esta tecnología, aprobada « Green Tech », está bien adaptada para el desarrollo de depósitos sobre superficies grandes. Este trabajo describe los pasos y los parámetros necesarios para obtener reflectores ópticos basados en plata de grandes cualidades: calidad óptica con reflectividad mayor a 95%, calidad mecánica con interfaces de polímero / metal que pueden absorber deformaciones, una relación calidad / precio mediante la optimización de la cinética de depósito y espesor de la película de plata (aproximadamente 100 nm) con un tiempo corto de elaboración. Numerosas técnicas de análisis y caracterización (XPS, AFM, LRX, SEM ...) han sido utilizadas para determinar los parámetros pertinentes de un espejo solar a base de plata. La propiedad óptica de la película de plata es estable en el aire y en el tiempo. Sin embargo, la protección de la plata es necesaria, en particular en el frente. Esta protección debe adherirse a la película de plata, ser flexible y proporcionar un índice de transmisión lo más alto posible en el rango visible. Se han estudiado diferentes barnices y nuestro trabajo ha sido centrado en el desarrollo de recubrimientos de protección orgánicos (PMMA, PU), cerámicos (SiO2, Al2O3) y especialmente en híbridos orgánico-cerámica. Esta investigación ha permitido identificar las áreas de relevancia de estos diferentes tipos de recubrimientos de protección bajo estrés por radiación y su compatibilidad con una capa reflejante de plata para obtener concentradores flexibles eficientes. Una solución original se presenta en la conclusión y corresponde en la realización de un espejo flexible elaborado en una hoja de vidrio de 100 µm de espesor y recubierto con una película de plata de 100 nm. La reflectividad es superior a 95% en el visible.
302

Stavebně technologický projekt montované haly v Olomouci / Construction Technology Project assembled halls in Olomouc

Gajdoš, Nikola January 2018 (has links)
In my diploma thesis I document the construction of administrative, commercial and warehouse building in Olomouc. In particular, I deal with selected parts of the construction and technological preparation of the facility. I deal more closely with the technological regulations for the assembly of reinforced concrete skeleton and sheeting. My diploma thesis includes building site design, set of machinery, control and test plans, budget, schedules, personnel and machine deployment, variation of sheet metal finishing and drawing on the budget.
303

Nanášení kovové vrstvy na keramické substráty pro úpravu povrchových vlastností / Tailoring of physical properties of ceramic surface by the metallic layer deposition

Dvorský, Vojtěch January 2019 (has links)
The master thesis focuses on the preparation of nickel coating on ceramic (Al2O3) substrate. The deposition of nickel was carried out by the electroless plating method in bath at various kinetic conditions. An impact of varied size, shape and roughness on the quality of the coated surface was investigated. The main goal was to find optimized conditions of the plating process of the thin metal coatings. Prepared nickel coatings were analysed by SEM, EDX analysis, mechanical profilometry and the plating bath was analysed by UV-VIS spectrophotometry. The continuous nickel coatings were achieved by modifying the deposition process, and the kinetic mechanism of experimental conditions was described.
304

Pokovování technických plastů pro výrobu odlehčených konstrukčních dílů pro dopravní průmysl / Metallization of technical plastics for lightweight traffic components with reduced fuel consumption

Sanetrníková, Dominika January 2017 (has links)
The beginning of this thesis is dedicated to polymeric materials, which include plastics an composites. Plastics are shortly divided into two groups, thermoplastics and thermosets. The following part is the use of plastics and composites in traffic industry and briefly this work focuses on techniques of recycling of this materials. This work also focuses on the techniques of thin film deposition, electroless plating, electrodeposition as well and plating in the vacuum environment. special techniques of thin film deposition are also mentioned shortly. The coatings of polymer including cleaning and surface activation is introduced using various techniques including plasma treatment. The surface treatment of polyetheretherketone (PEEK) is included too. The final part describes performed experiments and discussion of results.
305

Physics-Based Modelling for SEI and Lithium Plating During Calendar and Cycling Ageing / Fysikbaserad model för SEI och litiumplätering under kalender- och cykelåldring

Nordlander, Oskar January 2022 (has links)
Målet med projektet var att undersöka samt implementera en fysikbaserad DFN modell för att simulera kalender samt cyklingåldrande av litiumbatterier som används i elbilar. Den fysikbaserade modellen var konstruerad baserad på ett Python biblioteket vid namn PyBaMM, vilket till skillnad från datadrivna modeller ger essentiell information om de kemiska processerna inuti batteriet. Den första delen av projektet täcker konceptet av kalenderåldring, vilket inkluderar en jämförelse mellan tre olika tre olika hastighetsbegränsande SEI modeller. Parametrar som påverkar det erhållna resultatet från modellen är identifierade, estimerade, och till slut validerade för att säkerhetsställa att modellen och parametrarna är identifierbara gentemot experimentella data. Resultatet av jämförelsen gav att SEI tillväxt begränsad av litium interstitiell diffusion är den mest optimala modellen att applicera när kalenderåldring för litiumbatterier ska modelleras. Resultaten visade också att endast en parameter, inre SEI litium interstitiell diffusivitet ska justeras för att erhålla optimal anpassning mot experimentella data. Andra delen av projektet använde resultatet från den första delen och litium plätering implementerades som en andraåldringsmekanism som undersöktes under tre olika laddningsprotokoll. Modellen var optimerad och anpassad gentemot experimentella data, där parametervärdet för kinetisk hasighetskonstanten för plätering var estimerad. Den optimerade modellen användes därefter för att erhålla mer information om elektrokemiska variabler för att kunna analysera samt beskrivaåldringsprocessen utan att behöva genomföra praktiska laborationer. Resultaten visade att mängden pläterat litium på den negativa elektroden ökade för celler som var exponerade till högre ström under laddningsprocessen, samt när cellerna var laddade vid höga SoC nivåer. Sammanfattningsvis, visade modellen hög potential att representera och evaluera experimentella data, samt tillhandahålla en inblick i elektrokemiska processer och kapacitetsförluster länkade till SEI tillväxt och litium plätering. Däremot, för att erhålla en högre grad noggrannhet av elektrokemiskaåldringsmekanismer i litiumbatterier, fler ytterligare mekanismer måste implementeras såsom mekanisk stress av både negativ och positiv elektrod. / The aim of this study was to investigate and apply a physics-based DFN model to simulate the calendar and cycling ageing of lithium-ion batteries manufactured for EV applications. The physics-based cell ageing model was constructed based on the open-source software Python library PyBaMM, which in comparison to data-driven models provides more essential information about the chemical process within the battery cell. The first part of the project covers the concept of calendar ageing which includes comparisons between three different rate-limiting SEI growth models. Parameters that affect the output from the physics-based model are isolated, estimated with numerical methods, and lastly validated to ensure that the model and the parameters rep- resent the physics behind the experimental data. It was found that the SEI growth limited by lithium interstitial diffusion is the most optimal model to apply for a physics-based model when modeling calendar ageing. It was also found that the only parameter that should be tuned against experimental data is the inner SEI lithium interstitial diffusivity. The second part of the project utilizes the results from the first part and introduces lithium plating as a second cell ageing mechanism under three different charging protocols. The model was optimized and fitted against experimental data by sweeping the lithium plating kinetic rate constant parameter. The optimized model was thereafter used to generate outputs that more thoroughly can explain the degradation effects of the cell without constructing real-world experiments. Where increased rate of plated lithium could be observed for the cell subjected to higher charging C-rate, and when the cells were charged at high SoC levels. To summarize, the model showed great potential in representing and evaluating the experimental data and providing the project with insight into the electrochemical processes and cell capacity losses of SEI growth and lithium plating. However, in order to achieve a higher accuracy of cell ageing model in relation to the lithium-ion cells used in customer vehicles, several additional cell degradation mechanisms have to be introduced, such as mechanical degradation of the two electrodes.
306

Electrochemical and Photocatalytic Oxidation of Hydrocarbons

Rismanchian, Azadeh January 2014 (has links)
No description available.
307

Physics-Based Modelling for SEI and Lithium Plating During Calendar and Cycling Ageing / Fysikbaserad model för SEI och litiumplätering under kalender- och cykelåldring

Nordlander, Oskar January 2022 (has links)
Målet med projektet var att undersöka samt implementera en fysikbaserad DFN modell för att simulera kalender samt cyklingåldrande av litiumbatterier som används i elbilar. Den fysikbaserade modellen var konstruerad baserad på ett Python biblioteket vid namn PyBaMM, vilket till skillnad från datadrivna modeller ger essentiell information om de kemiska processerna inuti batteriet. Den första delen av projektet täcker konceptet av kalenderåldring, vilket inkluderar en jämförelse mellan tre olika tre olika hastighetsbegränsande SEI modeller. Parametrar som påverkar det erhållna resultatet från modellen är identifierade, estimerade, och till slut validerade för att säkerhetsställa att modellen och parametrarna är identifierbara gentemot experimentella data. Resultatet av jämförelsen gav att SEI tillväxt begränsad av litium interstitiell diffusion är den mest optimala modellen att applicera när kalenderåldring för litiumbatterier ska modelleras. Resultaten visade också att endast en parameter, inre SEI litium interstitiell diffusivitet ska justeras för att erhålla optimal anpassning mot experimentella data. Andra delen av projektet använde resultatet från den första delen och litium plätering implementerades som en andraåldringsmekanism som undersöktes under tre olika laddningsprotokoll. Modellen var optimerad och anpassad gentemot experimentella data, där parametervärdet för kinetisk hasighetskonstanten för plätering var estimerad. Den optimerade modellen användes därefter för att erhålla mer information om elektrokemiska variabler för att kunna analysera samt beskriva åldringsprocessen utan att behöva genomföra praktiska laborationer. Resultaten visade att mängden pläterat litium på den negativa elektroden ökade för celler som var exponerade till högre ström under laddningsprocessen, samt när cellerna var laddade vid höga SoC nivåer. Sammanfattningsvis, visade modellen hög potential att representera och evaluera experimentella data, samt tillhandahålla en inblick i elektrokemiska processer och kapacitetsförluster länkade till SEI tillväxt och litium plätering. Däremot, för att erhålla en högre grad noggrannhet av elektrokemiska åldringsmekanismer i litiumbatterier, fler ytterligare mekanismer måste implementeras såsom mekanisk stress av både negativ och positiv elektrod. / The aim of this study was to investigate and apply a physics-based DFN model to simulate the calendar and cycling ageing of lithium-ion batteries manufactured for EV applications. The physics-based cell ageing model was constructed based on the open-source software Python library PyBaMM, which in comparison to data-driven models provides more essential information about the chemical process within the battery cell. The first part of the project covers the concept of calendar ageing which includes comparisons between three different rate-limiting SEI growth models. Parameters that affect the output from the physics-based model are isolated, estimated with numerical methods, and lastly validated to ensure that the model and the parameters rep- resent the physics behind the experimental data. It was found that the SEI growth limited by lithium interstitial diffusion is the most optimal model to apply for a physics-based model when modeling calendar ageing. It was also found that the only parameter that should be tuned against experimental data is the inner SEI lithium interstitial diffusivity. The second part of the project utilizes the results from the first part and introduces lithium plating as a second cell ageing mechanism under three different charging protocols. The model was optimized and fitted against experimental data by sweeping the lithium plating kinetic rate constant parameter. The optimized model was thereafter used to generate outputs that more thoroughly can explain the degradation effects of the cell without constructing real-world experiments. Where increased rate of plated lithium could be observed for the cell subjected to higher charging C-rate, and when the cells were charged at high SoC levels. To summarize, the model showed great potential in representing and evaluating the experimental data and providing the project with insight into the electrochemical processes and cell capacity losses of SEI growth and lithium plating. However, in order to achieve a higher accuracy of cell ageing model in relation to the lithium-ion cells used in customer vehicles, several additional cell degradation mechanisms have to be introduced, such as mechanical degradation of the two electrodes.
308

Novel fabrication and testing of light confinement devices

Ring, Josh January 2016 (has links)
The goal of this project is to study novel nanoscale excitation volumes, sensitive enoughto study individual chromophores and go on to study new and exciting self assemblyapproaches to this problem. Small excitation volumes may be engineered using light con-finement inside apertures in metal films. These apertures enhance fluorescence emissionrates, quantum yields, decrease fluorescence quenching, enable higher signal-to-noiseratios and allow higher concentration single chromophore fluorescence, to be studied byrestricting this excitation volume. Excitation volumes are reported on using the chro-mophore's fluorescence by utilising fluorescence correlation spectroscopy, which monitorsfluctuations in fluorescence intensity. From the correlation in time, we can find the res-idence time, the number of chromophores, the volume in which they are diffusing andtherefore the fluorescence emission efficiency. Fluorescence properties are a probe ofthe local environment, a particularly powerful tool due to the high brightness (quantumyield) fluorescent dyes and sensitive photo-detection equipment both of which are readilyavailable, (such as avalanche photodiodes and photomultiplier tubes). Novel materialscombining the properties of conducting and non-conducting materials at scales muchsmaller than the incident wavelength are known as meta-materials. These allow combi-nations of properties not usually possible in natural materials at optical frequencies. Theproperties reported so far include; negative refraction, negative phase velocity, fluorescenceemission enhancement, lensing and therefore light confinement has also been proposed tobe possible. Instead of expensive and slow lithography methods many of these materialsmay be fabricated with self assembly techniques, which are truly nanoscopic and otherwiseinaccessible with even the most sophisticated equipment. It was found that nanoscaled volumes from ZMW and HMMs based on NW arrays wereall inefficient at enhancing fluorescence. The primary cause was the reduced fluorescencelifetime reducing the fluorescence efficiency, which runs contrary to some commentatorsin the literature. NW based lensing was found to possible in the blue region of the opticalspectrum in a HMM, without the background fluorescence normally associated with a PAAtemplate. This was achieved using a pseudo-ordered array of relatively large nanowireswith a period just smaller than lambda / 2 which minimised losses. Nanowires in the traditionalregime lambda / 10 produced significant scattering and lead to diffraction, such that they werewholly unsuitable for an optical lensing application.
309

Microstructure of radiation damage in the uranium film and its backing materials irradiated with 136 MeV �������Xe�������� / Microstructure of radiation damage in the uranium film and its backing materials irradiated with 136 MeV 136Xe+26

Sadi, Supriyadi 14 March 2012 (has links)
Microstructure changes in uranium and uranium/metal alloys due to radiation damage are of great interest in nuclear science and engineering. Titanium has attracted attention because of its similarity to Zr. It has been proposed for use in the second generation of fusion reactors due to its resistance to radiation-induced swelling. Aluminum can be regarded as a standard absorbing material or backing material for irradiation targets. Initial study of thin aluminum films irradiation by �������Cf fission fragments and alpha particles from source has been conducted in the Radiation Center, Oregon State University. Initial study of thin aluminum films irradiation by �������Cf fission fragments and alpha particles from source has been conducted in the Radiation Center, Oregon State University. Aluminum can be regarded as a standard absorbing material or backing material for irradiation targets. The AFM investigation of microstructure damages of thin aluminum surfaces revealed that the voids, dislocation loops and dislocation lines, formed in the thin aluminum films after bombardment by �������Cf fission fragments and alpha particles, depends on the irradiation dose. The void swelling and diameter and depth of voids increase linearly with the fluence of particles and dose; however, the areal density of voids decreased when formation of dislocation loops began. Study of deposition of uranium on titanium backing material by molecular plating and characterization of produced U/Ti film has been performed. The U/Ti film has smooth and uniform surfaces but the composition of the deposits is complex and does not include water molecules which probably involve the presence of U (VI). A possible structure for the deposits has been suggested. X-ray diffraction pattern of U/Ti films showed that The U/Ti film has an amorphous structure. Uranium films (0.500 mg/cm��) and stack of titanium foils (thickness 0.904 mg/cm��) were used to study the microstructural damage of the uranium film and its backing material. Irradiation of U/Ti film and Ti foils with 1 MeV/u (136 MeV) �������Xe�������� ions in was performed in the Positive Ion Injector (PII) unit at the Argonne Tandem Linear Accelerator System (ATLAS) Facility at Argonne National Laboratory, IL. Pre- and post- irradiation of samples was analyzed by X-ray diffraction, Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and Atomic Force Microscopy (AFM). The irradiation of U/Ti films results in the formation of a crystalline U���O��� phase and polycrystalline Ti phase. Annealing of the thin uranium deposit on a titanium backing at 800��C in the air atmosphere condition for an hour produced a mixture of UO���, U���O���, Ti, TiO and TiO��� (rutile) phases; meanwhile, annealing at 800oC for an hour in the argon environment produced a mixture of ��-U���O���, Ti and TiO��� (rutile) phases. These phenomena indicate that the damage during irradiation was not due to foil heating. Microstructural damage of irradiated uranium film was dominated by void and bubble formation. The microstructure of irradiated titanium foils is characterized by hillocks, voids, polygonal ridge networks, dislocation lines and dislocation networks. Theory predicts that titanium undergoes an allotropic phase transformation at 882.5 ��C, changing from a closed-packed hexagonal crystal structure (��-phase) into a body-centered cubic crystal structure (��- phase). When the titanium foils were irradiated with 136MeV �������Xe�������� at beam intensity of 3 pnA corresponding to 966��C, it was expected that its structure can change from hexagonal-close packed (hcp) to body-centered cubic (bcc). However, in contrast to the theory, transformation from ��-Ti (hcp) phase to fcc-Ti phase was observed. This phenomenon indicates that during irradiation with high energy and elevated temperature, the fcc-Ti phase more stable than the hcp-Ti Phase. / Graduation date: 2012
310

Modélisation ultra-rapide des transferts de chaleur par rayonnement et par conduction et exemple d'application / Fast Modeling of Radiation and Conduction Heat Transfer and application example

Ghannam, Boutros 19 October 2012 (has links)
L'apparition de CUDA en 2007 a rendu les GPU hautement programmables permettant ainsi aux applications scientifiques et techniques de profiter de leur capacité de calcul élevée. Des solutions ultra-rapides pour la résolution des transferts de chaleur par rayonnement et par conduction sur GPU sont présentées dans ce travail. Tout d'abord, la méthode MACZM pour le calcul des facteurs de transferts radiatifs directs en 3D et en milieu semi-transparent est représentée et validée. Ensuite, une implémentation efficace de la méthode à la base d'algorithmes de géométrie discrète et d'une parallélisation optimisée sur GPU dans CUDA atteignant 300 à 600 fois d'accélération, est présentée. Ceci est suivi par la formulation du NRPA, une version non-récursive de l'algorithme des revêtements pour le calcul des facteurs d'échange radiatifs totaux. La complexité du NRPA est inférieure à celle du PA et sont exécution sur GPU est jusqu'à 750 fois plus rapide que l'exécution du PA sur CPU. D'autre part, une implémentation efficace de la LOD sur GPU est présentée, consistant d'une alternance optimisée des solveurs et schémas de parallélisation et achevant une accélération GPU de 75 à 250 fois. Finalement, toutes les méthodes sont appliquées ensemble pour la résolution des transferts de chaleur en 3D dans un four de réchauffage sidérurgique de brames d'acier. Dans ce but, MACZM est appliquée avec un maillage multi-grille et le NRPA est appliqué au four en le découpant en zones, permettant d'avoir un temps de calcul très rapide une précision élevée. Ceci rend les méthodes utilisées de très grande importance pour la conception de stratégies de contrôle efficaces et précises. / The release of CUDA by NVIDIA in 2007 has tremendously increased GPU programmability, thus allowing scientific and engineering applications to take advantage of the high GPU compute capability. In this work, we present ultra-fast solutions for radiation and diffusion heat transfer on the GPU. First, the Multiple Absorption Coefficient Zonal Method (MACZM) for computing direct radiative exchange factors in 3D semi-transparent media is reviewed and validated. Then, an efficient implementation for MACZM is presented, based on discrete geometry algorithms, and an optimized GPU CUDA parallelization. The CUDA implementation achieves 300 to 600 times speed-up. The Non-recursive Plating Algorithm (NRPA), a non-recursive version of the plating algorithm for computing total exchange factors is then formulated. Due to low-complexity matrix multiplication algorithms, the NRPA has lower complexity than the PA does and it runs up to 750 times faster on the GPU by comparison to the CPU PA. On the other hand, an efficient GPU implementation for the Locally One Dimensional (LOD) finite difference split method for solving heat diffusion is presented, based on an optimiwed alternation between parallelization schemes and equation solvers, achieving accelerations from 75 to 250 times. Finally, all the methods are applied together for solving 3D heat transfer in a steel reheating furnace. A multi-grid approach is applied for MACZM and a zone-by zone computation for the NRPA. As a result, high precision and very fast computation time are achieved, making the methods of high interest for building precise and efficient control units.

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