A mina de carbonatito de Cajati contém mineralização de apatita, utilizada na fabricação de ácido fosfórico, que é aplicado a matéria-prima carbonática para obtenção de foscálcio, suplemento mineral em rações animais. Dentre as unidades litológicas em lavra destacam-se as Zonas de Xenólitos, formadas pela interação da rocha encaixante com o magma carbonatítico. São constituídas de fragmentos do jacupiranguito de dimensões métricas distribuídos de forma aparentemente errática na massa carbonatítica e zonas de reação centimétricas, compostas por minerais carbonáticos e silicáticos neoformados. Essas regiões apresentam apatita e constituem significativa parcela dos recursos minerais da jazida, porém devido à abundância de minerais silicáticos, essencialmente flogopita, diopsídio, forsterita e tremolita, seus teores de MgO e SiO2 são elevados e lhe conferem características distintas das unidades carbonatíticas, interferindo no processo de beneficiamento. Visando fornecer subsídios para o desenvolvimento de processos que otimizem o aproveitamento das Zonas de Xenólitos como minério de fosfato foram realizados ensaios de separação em escala de caracterização utilizando o Frantz de Barreiras (modelo LB-1). O procedimento objetivou o conhecimento do comportamento magnético dos silicatos em oposição ao da apatita e dos carbonatos; para o que foram coletadas amostras volumétricas em diferentes pontos da mina. Os silicatos, todos portadores de MgO, mostraram variações de cores e de composição química além de distribuição peculiar em cada litotipo componente das Zonas de Xenólitos. Diopsídio ocorreu principalmente no litotipo jacupiranguito, enquanto flogopita, forsterita e tremolita foram mais abundantes na zona de reação. Esses minerais ocorreram em intervalos de campo magnético bem definidos, concentrando-se principalmente entre 0,25 e 0,75 A (equivalentes a 2.800 e 8.800 Gauss, respectivamente), e distintos da fluorapatita e dos carbonatos, minerais predominantemente diamagnéticos. Para campo magnético da ordem de 13.800 Gauss obteve-se um produto com 95,2% do P2O5 total contido no intervalo granulométrico adotado para o ensaio e apenas 1,0% de SiO2 associado. Aplicando-se um campo magnético de menor intensidade (aproximadametne 5.700 Gauss) o conteúdo de P2O5 aumenta (97,4%) assim como o de SiO2 (11,1%). Assim mostrou-se viável a utilização de separação magnética como método complementar no beneficiamento de fluorapatita proveniente das Zonas de Xenólitos, desde que o campo magnético aplicado tenha um gradiente de campo adequado para melhor seletividade entre o mineral de minério e os silicatos. Os trabalhos de caracterização desenvolvidos também mostraram uma outra possibilidade de aproveitamento da unidade litológica, a partir da classificação granulométrica após a britagem secundária. Nessa etapa observou-se tendência à segregação dos litotipos, com geração de um material fino (abaixo de 12,7 mm) enriquecido em P2O5 (2,48 a 4,08%) que contém de 26,4 a 59,8% do P2O5 total da amostra. / The Cajati carbonatite mine produces apatite used for phosphoric acid manufacturing. This material is added to carbonatic raw material in order to obtain phoscalcium (foscálcio), used as mineral supply for animal feeding. Among the exploited lithological units there are the Xenolithic Zones, which are generated by assimilation process between the host rock and the carbonatitic magma. They are constituted by jacupiranguite blocks (metric sizes) of random distribution within the carbonatitic matrix and by the reaction zones (centimetric thickness), composed by neoformed carbonatic and silicate minerals. These regions show apatite mineralization and represent a significant part of the mineral resources of the deposit. However their abundance of silicate minerals, essentialy phlogopite, diopside, forsterite and tremolita, leads to high MgO e SiO2 contents, which implies in distinct characteristics from carbonatites, interfering on the concentration plant process. Intending to support the development of new processes seeking the utilization of the Xenolithic Zones as phosphate ore, a laboratory study of mineral separation was taken at the Barrier Frantz Magnetic Separator (model LB-1). Such procedure aims the characterization of magnetic behavior of silicates versus apatite and carbonates, using bulk samples collected in different parts of the mine. Silicates, all Mg-bearing, showed color and chemical composition variations with non-systematic distribution within each lithotipe comprising the Xenolithic Zones. Diopside occurred mainly in the jacupiranguite, while phlogopite, forsterite and tremolite were most abundant in the reaction zone. These minerals occurred in well defined magnetic field intervals, specially between 0,25 and 0,75 A (equivalent to 2.800 and 8.800 Gauss, respectively), and distinct from fluorapatite and carbonates, which are mainly diamagnetics. For magnetic field around 13.800 Gauss a product with 95,2% of total P2O5 content was obtained in the granulometric interval used for the separation procedures with 1,0% of SiO2 associated. Using a lower intensity magnetic field (around 5.700 Gauss) the P2O5 content rises (97,4%) as well as the SiO2 (11,1%). Thus the use of complementary magnetic separation procedures was proved to be a practicable method for beneficiation of fluorapatite from the Xenolithic Zones by applying a magnetic field with adequate field gradient for the selectivity of ore mineral and silicates. Another possibility for utilization of the lithological unit showed by the characterization studies was the grain-size classification after secondary crushing. In this stage a lithotipe segregation was observed and generation of fine material (below 12,7 mm) P2O5 enriched (2,48 to 4,08%), with 26,4 to 59,8% of total P2O5 content in the sample.

The subject of this PhD thesis is the development of an efficient system that can simultaneously pump and separate a gas-liquid mixture, in particular an oil-air mixture. Two-phase flows are encountered in many applications (petroleum extraction, flow in nuclear power plant pumps, pulp and paper processing, etc.) but this study is mainly focused on lubrication systems of aircraft gas turbine engines.<p><p>The pump and separator system (PASS) for two-phase flows developed in this PhD thesis aims to perform three functions simultaneously:<p>• Send back the oil to the tank (oil pumping)<p>• Separate the air from the oil (de-aeration)<p>• Separate the oil from the air (de-oiling) and release the sealing air into the atmosphere (venting). <p>Particular care is given to the liquid flow rate lost at the gas outlet of the system.<p>Consequently, it could replace the scavenge pumps and oil-air separators existing in present lubrication systems. This modification provides several advantages: simplification of the lubrication circuit, reduction of oil consumption and of the size of the lubrication system.<p><p>This research is divided into three axes: the theoretical study of the important physical mechanisms taking place inside the two-phase flow pump and separator system, the experimental development, tests and optimization of different PASS prototypes, and also the numerical simulations of the two-phase flow inside these prototypes. Although the experiments were the central pillar of this research, the three axes were closely imbricated.<p><p>The PASS design includes three main components:<p>• An inlet chamber with one or several tangential inlets giving a natural centrifugation to the flow,<p>• An impeller (forced centrifugation) with an axial and a radial part followed by a volute chamber,<p>• A metallic foam that lets pass micron and sub-micron droplets and which is followed by an axial vent port.<p><p>The centrifugation causes the liquid (oil) to move radially outwards in an annular body (a liquid ring) generating pressure. The thickness of this liquid ring inside the impeller is mainly determined by the pressure coefficient (related to the back-pressure and the rotational speed). When the back-pressure increases, the thickness of the liquid ring increases too. An advantage of the PASS is that it does not impose any relation between the liquid head and the liquid flow rate, contrary to common centrifugal pump. It self-regulates the radial position of the gas-liquid interface to sustain the operating conditions.<p><p>The de-aeration efficiency mainly depends on the pressure coefficient (for a constant liquid viscosity or temperature) or on the thickness of the liquid ring. The pressure gradient which appears in the liquid rotating in an annular body acts like a dam for the gas phase. Indeed, the gas movement is mainly determined by the pressure field (buoyancy) while the liquid distribution is dominated by centrifugal and Coriolis forces. Buoyancy tends to accumulate the gas phase near low pressure areas (PASS hub, suction side of the blades, clearances between closed impeller and casing).<p><p>The first oil-air PASS prototype produces high viscous losses due to the high peripheral velocity and liquid viscosity. Therefore, the pumping efficiency is poor compared to common impeller pumps. However, the pumping is not the key function of the PASS and a power consumption below 5 kW is acceptable for the application considered in this work. For applications that require lower power consumptions, a reduction of the rotational speed must be considered.<p><p>Thus, the rotational speed and the impeller diameter are two major constraints for the PASS design which determine the de-aeration and pumping efficiencies. The impeller diameter also influences the size of passage sections for the air flow. The air velocity must be kept as low as possible because the entrainment of droplets increases when the air velocity rises (drag forces on droplets). Indeed, this large influence of the air flow rate on the oil consumption (de-oiling efficiency) was demonstrated by a theoretical analysis, the experiments and the CFD simulations. The production of droplets in the inlet pipes when the two-phase flow is annular is a key phenomenon regarding the oil consumption.<p><p>In addition to the air flow rate, other variables also influence the oil consumption:<p>• Air-oil temperature: when the temperature rises, the oil consumption increases because the surface tension and the oil density are reduced. Moreover, as the air density also decreases, the air velocity rises.<p>• Oil flow rate: the oil consumption rises more or less linearly with the oil flow rate. However, the influence of the oil flow rate on the inlet droplet size is uncertain.<p>• Rotational speed: the rotational speed has obviously a strong impact on the oil consumption without metallic foam. However, experiments showed that the metallic foam efficiency is almost independent on the rotational speed. Therefore, the oil consumption with the Retimet foam does not depend on the PASS rotational speed.<p>• Altitude or air density: the oil consumption decreases when the air density is reduced because the drag forces on droplets also decrease.<p>The gas density (altitude) is also supposed to influence the de-aeration efficiency but this could not be tested or simulated in this work (the de-aeration efficiency gets probably better when decreasing the gas density because the buoyancy forces increase).<p><p>Theory, experiments and numerical simulations also allowed the prediction of performance of the first oil-air prototype for real in-flight operating conditions. Two problems have been identified: the de-aeration efficiency at MTO and cruise ratings and the oil leak throughout the vent in cold start and windmilling. To solve them, some modifications of the lubrication system have been suggested. With these modifications, the oil-air PASS should become very efficient and attractive for engine manufacturers. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

The first part of the diploma thesis deals with research in the field of design of process apparatuses. The research continues describing the function, division and main parts of separators. The research part ends with a more detail overview of flange connections. The second part deals with the design and control calculations of the separator using ČSN EN 13445-3 with tightness-strength calculation of the main flange join using ČSN EN 1591-1. At the end of the second part, partial calculations are performed using finite element method in the ANSYS Workbench R2 program, which aim to verify the required tightness of the joint and describe the effect of the bolts tightening procedure on the gasket.

Dissertation thesis falls within the area of indoor climate and deals with a hydraulics of heating systems, mainly with the hydraulic separator. This earlier widely used element of the heating system, which hydraulically separates heat source and heat appliance, is nowadays in the heating systems based on condensation technologies inappropriate, as the results obtained from experimental measurements show. This findings also well correlate with own theoretical solution based on the calorimetric equation. Conclusion of the dissertation thesis shows fact that in case of imbalance flow rate between heat source and heat appliance adverse warming of return pipe water in the heating system with hydraulics separátor is caused. This effect in practice reduces the efficiency of heat production and expected condensation process of flue gas is discontinued.

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Five chapters of this dissertation concentrate on the characterization and cancellation of high frequency parasitic parameters in EMI filters. One chapter addresses the interaction between the power interconnects and the parasitic parameters in EMI filters. The last chapter addresses the characterization, evaluation and design of noise separators. Both theoretical and experimental analyses are applied to each topic. This dissertation tries to explore several important issues related to EMI filters and noise separators. The author wishes to find some helpful approaches to benefit the understanding and design of EMI filters. The contributions of the dissertation can be summarized below: 1) Identification of mutual couplings and their effects on EMI filter performance 2) Extraction of mutual couplings using scattering parameters 3) Cancellation of mutual couplings to improve EMI filter performance 4) Cancellation of equivalent series inductance to improve capacitor performance 5) Analysis of mode transformations due to the imperfectly balanced parameters in EMI filters 6) Analysis of interaction between power interconnects and EMI filters on filter high-frequency performance 7) Modeling and design of high-performance noise separator for EMI diagnosis 8) Identification of the effects of parasitics in boost PFC inductor on DM noise Although all topics are supported by both theory and experiments, there may still be some mistakes in the dissertation. The author welcomes any advice and comments. Please send them via email to shuowang@ieee.org. Thanks / Ph. D.

Le polymère poreux (PM) associe les avantages double des matériaux poreux et des polymères, ayant la structure unique de pore, la porosité supérieure et la densité inférieure, ce qui possède une valeur d’application importante dans les domaines de l'adsorption, le soutien de catalyseur, le séparateur de batterie, la filtration, etc. Actuellement, il existe plusieurs façons de préparer le PM, comme la méthode de gabarit, la méthode de séparation de phase, la méthode d'imagerie respiratoire, etc. Chacune des méthodes ci-dessus existe ses propres avantages, mais la préparation à grande échelle de PM à structure de pore contrôlable et aux fonctions spécifiques est toujours un objectif à long terme sur le domaine et l'un des principaux objectifs de ce mémoire. La co-extrusion de microcouche est une méthode pour produire de façon efficace et successive des polymères avec des structures de couches alternées, ayant les avantages de haute efficacité et faible coût. Par conséquent, sur les exigences structurelles de PM de l’application spécifique, ce mémoire a conçu le PM avec une structure spécifique et une co-extrusion de microcouche de manière créative combinée avec la méthode traditionnelle de préparation de PM (méthode de gabarit, méthode de séparation de phase), en combinant les avantages des deux méthodes, les PM avec une structure de pore idéale peuvent être préparés en grande quantité et l’on peut également explorer son application dans les séparateurs de batteries au lithium-ion et l'adsorption d'hydrocarbures aromatiques polycycliques.Le plus important, dans la deuxième partie de cet essai, se trouve que la simulation micro-numérique est utilisée pour étudier le transport et le dépôt de particules dans des milieux poreux pour explorer le mécanisme des matériaux poreux dans les domaines de l'adsorption et du séparateur de batterie. Le code de 3D-PTPO (un modèle tridimensionnel de suivi des particules combinant Python® et OpenFOAM®) est utilisé pour étudier le transport et le dépôt de particules colloïdales dans des milieux poreux, l’on adopte trois modèles (colonne, venturi et tube conique) pour représenter différentes formes de matériaux poreux. Les particules sont considérées comme des points matériaux pendant le transport, le volume des particules sera reconstitué et déposé comme partie de la surface du matériau poreux pendant le dépôt, la caractéristique principale de ce code est de considérer l'influence du volume des particules déposées sur la structure des pores, les lignes d'écoulement et le processus du dépôt des autres particules. Les simulations numériques sont d'abord conduites dans des capillaires simples, le travail de chercheurs de Lopez et d’autres est réexaminé en établissant un modèle géométrique tridimensionnel plus réaliste et il explore les mécanismes cachés derrière les règles de transmission et de dépôt. Par la suite, des simulations numériques sont effectuées dans des capillaires convergents-divergents pour étudier la structure des pores et l'effet de nombre Peclet sur le dépôt de particules. Enfin, l’on étudie l’effet double de l'hétérogénéité de surface et de l'hydrodynamique sur le comportement de dépôt de particules. / Due to the combination of the advantages of porous media and polymer materials, polymeric porous media possess the properties of controllable porous structure, easily modifiable surface properties, good chemical stability, etc., which make them applicable in a wide range of industrial fields, including adsorption, battery separator, catalyst carrier, filter, energy storage, etc. Although there exist various preparation methods, such as template technique, emulsion method, phase separation method, foaming process, electrospinning, top-down lithographic techniques, breath figure method, etc., the large-scale preparation of polymeric porous media with controllable pore structures and specified functions is still a long-term goal in this field, which is one of the core objectives of this thesis. Therefore, in the first part of the thesis, polymeric porous media are firstly designed based on the specific application requirements. Then the designed polymeric porous media are prepared by the combination of multilayer coextrusion and traditional preparation methods (template technique, phase separation method). This combined preparation method has integrated the advantages of the multilayer coextrusion (continuous process, economic pathway for large-scale fabrication, flexibility of the polymer species, and tunable layer structures) and the template/phase separation method (simple preparation process and tunable pore structure). Afterwards, the applications of the polymeric porous media in polycyclic aromatic hydrocarbons adsorption and lithium-ion battery separator have been investigated.More importantly, in the second part of the thesis, numerical simulations of particle transport and deposition in porous media are carried out to explore the mechanisms that form the theoretical basis for the above applications (adsorption, separation, etc.). Transport and deposition of colloidal particles in porous media are of vital important in other applications such as aquifer remediation, fouling of surfaces, and therapeutic drug delivery. Therefore, it is quite worthy to have a thorough understanding of these processes as well as the dominant mechanisms involved. In this part, the microscale simulations of colloidal particle transport and deposition in porous media are achieved by a novel colloidal particle tracking model, called 3D-PTPO (Three-Dimensional Particle Tracking model by Python® and OpenFOAM®) code. The particles are considered as a mass point during transport in the flow and their volume is reconstructed when they are deposited. The main feature of the code is to take into account the modification of the pore structure and thus the flow streamlines due to deposit. Numerical simulations were firstly carried out in a capillary tube considered as an element of an idealized porous medium composed of capillaries of circular cross sections to revisit the work of Lopez and co-authors by considering a more realistic 3D geometry and also to get the most relevant quantities by capturing the physics underlying the process. Then microscale simulation is approached by representing the elementary pore structure as a capillary tube with converging/diverging geometries (tapered pipe and venturi tube) to explore the influence of the pore geometry and the particle Péclet number (Pe) on particle deposition. Finally, the coupled effects of surface chemical heterogeneity and hydrodynamics on particle deposition in porous media were investigated in a three-dimensional capillary with periodically repeating chemically heterogeneous surfaces.

Let G be a connected graph and k be a positive integer. A vertex subset D of G is a k-hop connected dominating set if the subgraph of G induced by D is connected, and for every vertex v in G, there is a vertex u in D such that the distance between v and u in G is at most k. We study the problem of finding a minimum k-hop connected dominating set of a graph (Mink-CDS). We prove that Mink-CDS is NP-hard on planar bipartite graphs of maximum degree 4. We also prove that Mink-CDS is APX-complete on bipartite graphs of maximum degree 4. We present inapproximability thresholds for Mink-CDS on bipar- tite and on (1, 2)-split graphs. Interestingly, one of these thresholds is a parameter of the input graph which is not a function of its number of vertices. We also discuss the complex- ity of computing this graph parameter. On the positive side, we show an approximation algorithm for Mink-CDS. When k = 1, we present two new approximation algorithms for the weighted version of the problem, one of them restricted to graphs with a poly- nomially bounded number of minimal separators. Finally, also for the weighted variant of the problem where k = 1, we discuss an integer linear programming formulation and conduct a polyhedral study of its associated polytope. / Seja G um grafo conexo e k um inteiro positivo. Um subconjunto D de vértices de G é um conjunto dominante conexo de k-saltos se o subgrafo de G induzido por D é conexo e se, para todo vértice v em G, existe um vértice u em D a uma distância não maior do que k de v. Estudamos neste trabalho o problema de se encontrar um conjunto dominante conexo de k-saltos com cardinalidade mínima (Mink-CDS). Provamos que Mink-CDS é NP-difícil em grafos planares bipartidos com grau máximo 4. Mostramos que Mink-CDS é APX-completo em grafos bipartidos com grau máximo 4. Apresentamos limiares de inaproximabilidade para Mink-CDS para grafos bipartidos e (1, 2)-split, sendo que um desses é expresso em função de um parâmetro independente da ordem do grafo. Também discutimos a complexidade computacional do problema de se computar tal parâmetro. No lado positivo, propomos um algoritmo de aproximação para Mink-CDS cuja razão de aproximação é melhor do que a que se conhecia para esse problema. Finalmente, quando k = 1, apresentamos dois novos algoritmos de aproximação para a versão do problema com pesos nos vértices, sendo que um deles restrito a classes de grafos com um número polinomial de separadores minimais. Além disso, discutimos uma formulação de programação linear inteira para essa versão do problema e provamos resultados poliédricos a respeito de algumas das desigualdades que constituem o politopo associado à formulação.