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DEVELOPMENT OF A MICRO LOOP HEAT PIPE, A NOVEL MEMS SYSTEM BASED ON THE CPS TECHNOLOGYSHUJA, AHMED 07 July 2003 (has links)
No description available.
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Fabrication techniques to produce micro and macro porous MAX-phase Ti2AlC ceramicThomas, Tony January 2015 (has links)
MAX-phase ceramics are a class of ductile ceramic material group with the general molecular formula Mn+1AXn (n = 1, 2, 3….), where M is an early transition element, A is an element from the ‘A’ group of the periodic table and X is either nitride or carbide. One advantage of these materials is that they maintain their strength at high temperatures. In addition these ceramic materials possess the best properties of both ceramics and metals. Some of their important characteristics are low density, high stiffness, machinability, excellent thermal and electrical conductivity and they even exhibit some plasticity at elevated temperature. These amazing combinations of properties have made researchers foresee the technological importance of these materials as a structural ceramic for high temperature application. Since this ceramic is relatively new to the market, only a handful of work has been undertaken on this material and its applications are limited to heating elements. In addition, analysis of the thermodynamic data on this material is incomplete. This PhD work addresses this issue and conducts a complete thermodynamic analysis involved in the formation mechanism of the ternary titanium carbide MAX-phase Ti2AlC ceramic, using Self-propagating High temperature Synthesis (SHS) form of combustion synthesis process, based on the following exothermic reaction: (2+x) Ti + (y) Al + C → Ti2AlC + (x) Ti + (y) Al (i) Where x and y = 0.1. 0.2, 0.3… A thermodynamic model has been formulated to predict the temperature evolution during the reaction (i), for the formation of Ti2AlC using SHS process. In addition the effect of particle size in the elemental reaction has been studied on the formation mechanism of Ti2AlC and methods to control the porosity by fine tuning the particle size has been recognized. Manufacturing processes such as Self-propagating High temperature Synthesis (SHS), foam replication and freeze casting have been developed in this thesis to produce micro and macro porous Ti2AlC ceramic mainly for electrode applications. A systematic material development technique to produce macro porous Ti2AlC ceramic, using a foam replication technique has been established in this research work. The material fabricated by this technique has a uniform pore size (up to 5mm), with open interconnected pores and is ideal for a flow battery application which requires a multifunctional electrode material which is highly porous to allow the flow of electrolyte through it, is corrosion resistant and at the same time being electrically conductive. The mechanical properties of the ceramic produced by this method has been characterised and steps to mitigate the cracks and defects formed during the fabrication process to obtain structurally stable macro porous Ti2AlC ceramic has been reported in this work. This research demonstrates that one of the applications of macro porous Ti2AlC ceramic formed using foam replication technique is as an electrode material in a photo-Microbial Fuel Cell (p-MFC). Graded porosity micro porous Ti2AlC ceramics have also been fabricated using a freeze casting technique, with camphene as the freezing vehicle. A systematic material development process has been tailored for this particular material. A ceramic material with gradient pore size ranging from 27-305µm has been fabricated using this technique. This type of ceramic is a good candidate as an electrode material in micro-redox battery and for sensing applications. A variety of processing parameters such as solid loading (amount of ceramic content in the material), freezing temperature and mould material which affect the pore formation and pore size have been studied in this PhD and the range of porosities achieved by controlling these parameters have been reported.
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PARAMETRIC EXPLORATION OF AUTOMATED FABRICATION AND ANODIC BONDING OF CPS FOR LHP APPLICATIONSPARIMI, SRINIVAS 17 April 2003 (has links)
No description available.
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Etude des interactions hydrodynamiques et colmatage dans des milieux très perméables / Hydrodynamic interactions and clogging study in highly permeable porous mediaJouini, Manel 09 April 2018 (has links)
La Société le Nickel ’SLN’ est l’un des plus grands exploitants de nickel en Nouvelle Calédonie. Le Stockage des déchets de l’exploitation minière sur le site d’exploitation se fait sous forme de tas manufacturés appelés versants. Pour assurer la stabilité de ces versants, il est nécessaire d’assurer un stockage hors d’eau de ces stériles miniers. Pour se faire, une mise en place des ouvrages en enrochement enterrés se fait au fur et à mesure de l’avancement des travaux d’installation des versants. Le rôle de ces ouvrages enterrés est de maintenir l’écoulement d’eau à travers le milieu poreux. Le premier objectif de la thèse est donc de mieux comprendre les interactions hydrodynamiques dans les milieux très perméables dans le cas d’écoulements pleinement turbulents. La première partie de ce travail concerne une étude expérimentale menée à l’Institut National Agronomique de Tunisie (INAT) mais aussi à l’Institut de mécanique de fluide de Toulouse (IMFT) dont le but est d’étudier à la fois l’évolution de la ligne d’eau dans les milieux macroporeux et la variation de la perméabilité de ces derniers en fonction du nombre de Reynolds. Des simulations avec des modèles de perte de charge les plus utilisés dans la littérature ont été effectuées, pour tester leur capacité à reproduire la ligne d’eau dans les conditions de nos expériences. Les deux relations de Forchheimer (1901) et d’Ergun (1952) donnent des résultats proches de nos expériences avec des valeurs de coefficients adaptés pour notre cas, alors que la relation de Barree et Conway (2004) ne semble pas reproduire les résultats attendus. L’eau qui circule dans les ouvrages enterrés est une eau chargée d’où l’intérêt d’étudier le transport sédimentaire dans ces milieux macroporeux. Pour se faire, une étude expérimentale a été réalisée sur le transport et le dépôt des particules dans des milieux synthétiques constitués de particules de diamètre moyen de 15 cm / The 'SLN' Company is one of the largest nickel operators in New Caledonia. The mining wastestorage at the operation site is as a slope. To ensure the stability of these slopes, it is necessary toensure an out of water storage of the waste rock. To do that, an underground rockfillimplementation is installed. The purpose of these buried structures is to maintain the flow of waterthrough its pores. The first objective of the thesis is to better understand the hydrodynamicinteractions in highly permeable porous media and in case of fully turbulent flows. The first part ofthis work relates to an experimental study carried out at the National Agronomic Institute of Tunisia(INAT) and the Institute of Fluid Mechanics of Toulouse (IMFT) whose aim is to study the waterprofile evolution in macro porous media and the permeability variation as a function of theReynolds number. Simulations with the most widely used pressure drop relationships in theliterature were performed to check their ability to reproduce our experimental water profile. Thetwo relations of Forchheimer (1901) and Ergun (1952) give the most satisfactory results withadapted coefficients values for our case, whereas the Barree and Conway (2004) formula doesn’tseems to give expected results. Given that the circulating water in these buried structures is acharged water, we studied the sedimentary transport in macro porous media. To do this, anexperimental study was carried out on the transport and deposition of particles in the studiedporous media which mean diameter is d=15 cm.
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Etude expérimentale et numérique des oscillations hydrodynamiques en milieux poreux partiellement saturés / Experimental and numerical study of hydrodynamic oscillations in partially saturated porous mediaWang, Yunli 16 September 2010 (has links)
Cette thèse vise à étudier expérimentalement, analytiquement et numériquement, les conséquences de variations et d'oscillations hydrodynamiques à forte variabilité temporelle en milieux poreux partiellement saturés. Les problèmes que nous étudions comportent des surfaces libres tant à l'extérieur qu'à l'intérieur des milieux poreux, celles-ci étant définies comme des isosurfaces de pression d'eau égale à la pression atmosphérique (Pwater = Patm). Les différentes études expérimentales réalisées en laboratoire sont, respectivement : une expérience d'imbibition dans une boite à sable avec effets capillaires importants; la transmission d'oscillations de la surface libre à travers un massif sableux intercalaire dans un petit canal à houle (IMFT, Toulouse); l'étude de la dynamique et de la propagation des oscillations des niveaux d'eau dans un grand canal à houle (HYDRALAB, Barcelone), partiellement recouvert d'un fond sableux incliné, avec mesures de niveaux d'eau en pleine eau et sous le sable, et mesures du fond sableux (érosion/dépôts). Pour les études théoriques, nous avons développés des solutions analytiques linéarisées. Un exemple de problème traité analytiquement est: l'équation linéarisée de Dupuit-Boussinesq (D-B) transitoire à surface libre, en hypothèse d'écoulements plans et vidange/remplissage instantané : oscillations forcées, transmission et dissipation d'ondes à travers une boite à sable rectangulaire. Nous avons aussi développé une solution de l'équation faiblement non linéaire de Dupuit- Boussinesq (D-B) pour étudier le problème d'imbibition avec variation abrupte du niveau d'eau amont (suivi temporel du front de saturation). Nous avons pu étudier les différents types de problèmes transitoires liés aux expériences citées plus haut par simulation numérique. En particulier, nous avons simulé des écoulements partiellement saturés et insaturés, en coupe verticale, à l'aide d'un code de calcul (BIGFLOW 3D) qui résoud l'équation de Richards généralisée en régime transitoire. Nous avons ainsi étudié numériquement en régime non saturé, l'expérience d'imbibition dans un sable initialement sec à frontières verticales (IMFT sandbox), puis l'expérience de propagation d'ondes dans le grand canal à houle de Barcelone (laboratoire HYDRALAB) comportant une plage de sable inclinée, avec un couplage complètement intégré entre les zones micro-poreuse (sable) et “macro-poreuse” (pleine eau). Pour analyser les résultats de cette dernière expérience et les comparer aux simulations, nous avons utilisé plusieurs méthodes de traitement et d'analyse des signaux : analyse de Fourier (spectres de fréquences) ; ondelettes discrètes multi-résolution (Daubechies) ; analyses corrélatoires simple et croisée. Ces méthodes sont combinées avec des méthodes de préfiltrage pour estimer dérives et résidus (moyennes mobiles ; ondelettes multi-résolution). Cette analyse des signaux a permis de comprendre et quantifier la propagation à travers une plage de sable. Au total, les différentes approches de modélisation mis en oeuvre, associé à des procédures de calage en situation de couplage transitoire non linéaire ont permis de reproduire globalement les phénomènes de propagation de teneur en eau et de niveau d'eau dans les différentes configurations étudiées. / This thesis aims at investigating experimentally, analytically and numerically, the consequences of hydrodynamic variations and oscillations with high temporal variability in partially saturated porous media. The problems investigated in this work involve “free surfaces” both outside and inside the porous media, the free surface being defined as the “atmospheric” water pressure isosurface (Pwater = Patm). The laboratory experiments studied in this work are, respectively: Lateral imbibition in a dry sand box with significant capillary effects; Transmission of oscillations of the free surface through a vertical sand box placed in a small wave canal (IMFT, Toulouse); Dynamics of free surface oscillations and wave propagation in a large wave canal (HYDRALAB, Barcelona), partially covered with sand, with measurements of both open water and groundwater levels, and of sand topography (erosion / deposition). For theoretical studies, we have developed linearized analytical solutions. Here is a sample problem that was treated analytically in this work: The linearized equation of Dupuit-Boussinesq (DB) for transient free surface flow, assuming horizontal flow and instantaneous wetting/drainage of the unsaturated zone: forced oscillations, wave transmission and dissipation through a rectangular sandbox. We also developed a weakly nonlinear solution of the Dupuit-Boussinesq equation to study the sudden imbibition (temporal monitoring of the wetting front). We have studied the different types of transient flow problems related to the experiments cited above by numerical simulation. In particular, we have simulated unsaturated or partially saturated transient flows in vertical cross-section, using a computer code (BIGFLOW 3D) which solves a generalized version of Richards’ equation. Thus, using the Richards / BIGFLOW 3D model, we have studied numerically the experiment of unsaturated imbibition in a dry sand (IMFT sandbox), and then, with the same model, we have also studied the partially saturated wave propagation experiment in the large Barcelona wave canal (HYDRALAB laboratory), focusing on the sloping sandy beach, with coupling between the micro-porous zone (sand) and the “macro-porous” zone (open water). To interpret the results of the latter experiment and compare them to simulations, we use several methods of signal analyzis and signal processing, such as: Fourier analysis, discrete multi-resolution wavelets (Daubechies), auto and cross-correlation functions. These methods are combined with pre-filtering methods to estimate trends and residuals (moving averages; discrete wavelet analyses). This signal analyzis has allowed us to interpret and quantify water propagation phenomena through a sandy beach. To sum up, different modeling approaches, combined with model calibration procedures, were applied to transient nonlinear coupled flow problems. These approaches have allowed us to reproduce globally the water content distributions and water level propagation in the different configurations studied in this work.
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