I propose to develop a new method for the synthesis of metal matrix composites (MMC) using aerosol reactants in a radio frequency (RF) plasma torch. An inductivelycoupled RF plasma torch (ICPT) may potentially be designed to maintain laminar flow and a radial temperature distribution. These two properties provide a method by which a succession of metal layers can be applied to the surface of SiC fibers. In particular, the envisaged method provides a means to fully bond any desired metal to the surface of the SiC fibers, opening the possibility for MMCs in which the matrix metal is a highstrength steel. A crucial first step in creating the MMC is to test the feasibility of constructing an ICPT with completely laminar flow in the plasma region. In this work, a magnetohydrodynamic (MHD) model is used along with a computational fluid dynamic (CFD) software package called FLUENT© to simulate an ICPT. To solve the electromagnetic equations and incorporate forces and resistive heating, several userdefined functions (UDF) were written to add to the functionality of FLUENT©. Initially, an azimuthally-symmetric, two-dimensional model was created to set a test baseline for operating in FLUENT© and to verify the UDF. To incorporate coil angle and current leads, a fully three dimensional model UDF was written. Preliminary results confirm the functionality of the code. Additionally, the results reveal a non-mixing, laminar flow outer region for an axis-symmetric ICPT.

In modern automotive engines, the vast majority of light vehicle diesel (LVD) pistons are made from gravity die cast monolithic AlSi based alloy systems. Presently, the market drivers for reduced emissions, more efficient fuel consumption and increased specific power output are providing cyclic thermal and mechanical fatigue loading above the safe life durability threshold for the current AlSi based alloy systems. Peak temperatures in the diesel piston’s fatigue critical combustion bowl region are presently 420 °C for the AlSi based alloys, which represents a homologous TH value in excess of 0.8. In combination with peak temperatures of 420 C, the pistons are subject to cylinder pressures up to 220 bar, inducing mechanical stress amplitudes 15-20% greater than the allowable component fatigue strength for 1x108 cycles, in some applications. This durability deficit naturally leads to a requirement for new material and process solutions aimed at improving thermal and mechanical fatigue resistance at temperatures in excess of 420 C.One solution to this problem is to locally reinforce the pistons combustion bowl edge with a metal matrix composite (MMC) system. In this study, an aluminium based metal matrix composite (AlMMC) has been investigated and has shown some promise with increases in iso-thermal high cycle (1x 107) fatigue strength of 50 % compared to standard monolithic piston alloys. The AlMMC consists of a premium AlSi based LVD piston alloy matrix reinforced with 0.15 Vf of an interconnected network of 2-4 mm long Fe based fibres. The AlMMC is manufactured by pressure assisted infiltration of a sintered metallic fibre preform with as cast materials having a pore density of 0.2 %. In contrast to the use of ceramic fibre reinforcement systems generally requiring high pressure infiltration techniques, preform infiltration is considered possible with a comparably inexpensive manufacturing route. The Fe based fibre preforms can be infiltrated at lower pressure due to the reactivity between the Fe based fibres and the AlSi based matrix alloy. Unfortunately, this increased reactivity, although an advantage for preform infiltration, can result in (FeAlXX)Si(+X) interfacial reaction products forming between the fibre and matrix at operating temperatures of greater than 440 °C. These interfacial reactions result in a 15-20 m interfacial intermetallic layer after prolonged periods of exposure (>500 hrs), resulting in depleted fibre Vf and void formations on the matrix side of the interface.

This thesis proposes a novel consolidated approach for substantial compaction of HVDC lines that includes both new tower geometries as well as novel control concepts. This is based on a thorough discussion on the basic overhead line design parameters and their impact on the right of way width and tower height. Then the electrical aspects of the new approach such as dc overvoltage assessment and lightning performance are investigated. The required horizontal clearances between pole conductors and tower members, as a component of the right of way width, depend on the maximum expected overvoltages. Detailed electromagnetic transient models for the point to point MMC HVDC with different transmission configurations, all including the proposed dc overhead line, are developed for this thesis. The models are used to assess fault contingencies that result in the most significant overvoltage stresses on the HVDC transmission line for finding minimum air clearances and for the design of overvoltage limiting devices, such as surge arresters. New control approaches are proposed that significantly reduce the dc side overvoltage and consequently minimize the required air clearances for maximum compaction of the HVDC overhead lines and also reduce the required surge arrester size for line insulation. Because power transmission lines are the most exposed component within a power system, they are subject to lightning strikes which, in turn, are the main cause of disruption to power flows. This thesis will include an analysis of lightning occurrence on the proposed compact transmission line in order to assess the risk of pole faults. The focus of this analysis is mainly on evaluation of the critical lightning currents that cause fast front overvoltage stresses that may result in insulation failure. / May 2017

X-ray micro-tomography has become an increasingly important technique for characterizing the 3D microstructure of materials. This became possible mainly because spatial resolution of the imaging detectors has improved, and synchrotron radiation is more accessible for micro-tomography imaging. In the presented project a novel experimental system has been designed and built at Biomedical Imaging and Therapy (BMIT)’s 05B1-1 beamline at Canadian Light Source (CLS). This system allows imaging structural transformation during in-situ loading experiments under tensile stress. The system was tested and several examples illustrating the application of this experimental system are presented. The system has been used to image the structure of porous aluminum and the size and distribution of pores was analyzed. The system was also used to image the structure of Al/Al2O3/TiC hybrid composites manufactured by accumulated roll bonding (ARB) process and this allowed analyzing the size distribution of reinforcing particles and voids. It was further demonstrated that in-situ imaging of deformation can be used to image consecutive stages of structural transformation (change in volume, change of position of reinforcing particles, creation of voids etc.) in aluminum alloy and aluminum composites during application of tensile stress and to illustrate the nucleation of failure. This system of dynamic imaging at BMIT-BM at CLS can help in better description of structural transformation associated with the application of stress and will contribute to better understanding of the failure mechanisms of different types of materials during straining.

The microstructures and performance of Ni-based alloys and Ni-WC (nickel-tungsten carbide) composite overlays deposited by plasma transferred arc welding have been studied. The Ni-alloy overlays had similar microstructures consisting of Ni dendrites, with interdendritic Ni-based eutectics, borides and carbides. Low hardness alloy overlays contained a smaller fraction of interdendritic phases relative to the high hardness alloys. The interdendritic regions make a significant contribution to the hardness since they are more than twice as hard as primary dendrites. The Ni-WC composites contained similar phases, however WC dissolution was observed leading to the formation of other carbides. Ni-alloys with low carbon and Cr content exhibited the lowest WC dissolution. The Ni-WC overlays produced using these dilute alloys generally performed better in ASTM G65 wear tests. This was likely due to the reduced dissolution which avoided formation of brittle secondary phases, maintaining a short mean free path between WC particles and allowing increased impact energy absorption. / Materials Engineering

Les molècules MHC de classe II uneixen pèptids generats en l'interior de la cèl.lula i els presenten a les cèl.lules T CD4+, que inicien i regulen la resposta immunitària. Les cadenes a i b que formen les MHC de classe II de nova síntesi, interaccionen amb una chaperona, la cadena invariant (Ii), que estabilitza el plegament dels dímers ab i impedeix la seva unió als pèptids presents en el reticle endoplasmàtic (RE). La interacció amb Ii també permet l'arribada dels complexes MHC II-Ii a la via endocítica on la chaperona es degrada fins que només el segment anomenat CLIP roman unit al solc d'unió a antigen dels dímers ab. L'alliberació del CLIP i la unió amb pèptids antigènics s' afavoreix pel baix pH dels endosomes i és catalitzada per HLA-DM, que estabilitza les MHC II i selecciona els pèptids units més estables. Quan s'ha format el complex MHC II-pèptid, aquest és conduït cap a la superfície cel.lular. En les cèl.lules B s'ha descrit l'expressió de la co-chaperona HLA-DO que interacciona amb el complex MHC II/DM i modula l'acció d'HLA-DM. En les malalties autoimmunitàries específiques d'òrgan, com la diabetis de tipus 1, la resposta autorreactiva destrueix selectivament les cèl.lules epitelials endocrines. En aquestes situacions s'ha descrit l'expressió de MHC II així com l'expressió variable de la cadena invariant (Ii) i HLA-DM, suggerint que la presentació d'epítops críptics per les cèl.lules endocrines podria permetre el manteniment de la resposta autorreactiva. En aquest treball s'ha estudiat aquesta hipòtesi des de dos aproximacions: (i) l'anàlisi del repertori peptídic associat a les MHC II en cèl.lules endocrines mitjançant tècniques d'espectrometria de masses i (ii) la caracterització de la via endocítica on s'associen els lligands a MHC II, per tècniques de microscopia electrònica de transmissió. L'estudi s'ha realitzat sobre el model experimental aconseguit per transfecció estable de la línia cel.lular derivada d'un insulinoma de rata RINm5F, amb els gens de les molècules humanes: HLA-DRB1*0401, Ii i HLA-DM. La transfecció seqüencial dels diferents gens permeté obtenir les cèl.lules endocrines (i) RIN-DR4, (ii) RIN-DR4Ii, (iii) RIN-DR4DM, i (iv) RIN-DR4IiDM. Els resultats mostren que les cèl.lules endocrines reorganitzen la via endocítica amb l'expressió de DR4, Ii i DM, afavorint-se la formació d'endosomes tardans multivesiculars i multilaminars, on es concentren les tres molècules implicades en la presentació d'antigen. En absència de chaperones, els complexes DR4-pèptid de la superfície cel.lular es troben associats a un repertori peptídic inestable i molt heterogeni, on s'identifiquen lligands derivats majoritàriament d' extrems N- i C-terminals de proteïnes citosòliques i que en molts casos no respecten el motiu d'anclatge a DR4. La coexpressió d'Ii permet la detecció d'un major nombre de dímers DR4 fora del RE que es localitzen preferentment a la superfície cel.lular. En absència d'HLA-DM, aquests complexes són inestables i es troben associats a CLIP, tot i que també s'han identificat lligands derivats de proteïnes exògenes i autòlogues. L'expressió d' HLA-DM en absència d'Ii permet la detecció de complexes DR4-pèptid estables amb lligands que respecten el motiu d'anclatge i deriven de proteïnes de membrana i citoplasmàtiques. La màxima eficiència s'aconsegueix amb la coexpressió d'ambdues chaperones. En les cèl.lules DR4IiDM, els dímers DR4 expressats a la superfície són estables i s'associen a un repertori peptídic homogeni en seqüència, longitud i origen, format per lligands autòlegs derivats de proteïnes de la superfície, de la vía secretora i del citoplasma, en algunes ocasions específiques de llinatge. Aquests lligands sempre respecten el motiu d'anclatge a DR4 i difereixen dels identificats en una línia B limfoblastoid homozigota per DR4. Per tant, l'expressió de DR4, Ii i DM en cèl.lules endocrines permet la presentació de pèptids autòlegs, específics de teixit i amb característiques diferents als presentats per cèl.lules amb l'expressió de MHC II constitutiva. Aquests epítops a més de ser condicionats pel llinatge cel.lular, estan influenciats per l'expressió de chaperones i podrien variar durant la resposta autoimmune en l'òrgan diana, condicionant el seu desenvolupament. / MHC class II molecules present peptides to CD4+T cells to iniciate and regulate the immune response. Newly synthetized MHC class II a and b chains interact with a chaperone named invariant chain (Ii) that stabilizes their folding preventing the binding of peptide ligands in the endoplasmic reticulum (ER). The invariant chain targets MHC II-Ii complexes to the endocytic pathway where it is proteolitically degraded leaving a portion of its sequence named CLIP bound to the ab dimers. The exchange of CLIP for stably bound peptides is favoured by the endosomal acidic pH and catalized by another specific chaperone, HLA-DM. Stable MHC II-peptide complexes reach the plasma membrane by vesicular transport. HLA-DO is a third class II chaperone expressed by some antigen presenting cells, like B cells, that modulate HLA-DM function. In organ-specific autoimmune diseases such as type 1 diabetes, epithelial endocrine cells are the specific targets of the autoreactive response. In these situations endocrine cells express MHC II molecules and both chaperones Ii and DM with heterogeneous expression levels that leads to the suggestion that criptic epitopes may be presented by endocrine epithelial cells, thus maintaining the autoreactive response. This hypotesis has ben approached in this work from two different points: (i) analysis of the peptide repertoire associated to MHC II by mass spectrometry techniques and (ii) characterization of the endocytic pathway, where ligands associate to class II molecules, by cryoelectron microscopy. The study has been performed using an experimental model based on the stable transfection of the rat insulinoma cell line RINm5F with human class II genes HLA-DRB1*0401, Invariant chain and HLA-DM. Sequential transfection allowed the generation of four endocrine cell lines expressing (i) RIN-DR4, (ii) RIN-DR4Ii, (iii) RIN-DR4DM, (iv) RIN-DR4IiDM. The data show that class II expression in endocrine cells induce a reorganization of the endocytic pathway, favouring the formation of multivesicular and multilaminar late endosomes where molecules involved in class II antigen presentation are accumulated. In the absence of chaperones, DR4-peptide complexes contain a highly heterogeneous unstable peptide pool, with ligands mostly derived from the N- and C-termini of cytosolic proteins, that in many cases did not respect the DR4-peptide binding motif. Ii expression increase the presence of DR4 dimers outside the ER, mostly accumulated at the cell surface. In the absence of DM, these complexes are unstable and most of them associate to CLIP, although minor ligands from exogenous and autologous proteins are also identified. DM expresion in the absence of Ii allow the detection of stably bound DR4-peptide complexes at the cell surface, containing sequences derived from either cell surface or cytoplasmic proteins. In DR4IiDM cells, DR4 complexes at the cell surafce are stable and are associated to a peptide repertoire highly homogeneous in sequence, length and origin, formed by ligands derived from surface, secreted and cytoplasmic proteins, some of them tissue-specific. All the identified ligands respect the DR4-peptide binding motif and are different from the repertoire identified in a DR4-homozygous B-lymphoblastoid cell line. Thus, DR4, Ii and DM expression in endocrine epithelial cells allow the presentation of a panel of peptides, different from the ones presented by cells with constitutive class II expression, some of which are tissue specific. This repertoire is cell type dependent and influenced by the expression of both chaperones, suggesting the possibility of variations in the target organs during the autoimmune process that may condition its development.

No description available.

abstract: Li-ion batteries are being used on a large scale varying from consumer electronics to electric vehicles. The key to efficient use of batteries is implementing a well-developed battery management system. Also, there is an opportunity for research for improving the battery performance in terms of size and capacity. For all this it is imperative to develop Li-ion cell model that replicate the performance of a physical cell unit. This report discusses a dual polarization cell model and a battery management system implemented to control the operation of the battery. The Li-ion cell is modelled, and the performance is observed in PLECS environment. The main aspect of this report studies the viability of Li-ion battery application in Battery Energy Storage System (BESS) in Modular multilevel converter (MMC). MMC-based BESS is a promising solution for grid-level battery energy storage to accelerate utilization and integration of intermittent renewable energy resources, i.e., solar and wind energy. When the battery units are directly integrated in submodules (SMs) without dc-dc interfaced converters, this configuration provides highest system efficiency and lowest cost. However, the lifetime of battery will be affected by the low-frequency components contained in arm currents, which has not been thoroughly investigated. This paper investigates impact of various low-frequency arm-current ripples on lifetime of Li-ion battery cells and evaluate performance of battery charging and discharging in an MMC-BESS without dc-dc interfaced converters. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2018

Atualmente, em virtude do aumento da demanda energética surgem diversas preocupações devido à escassez dos recursos energéticos tradicionais e os impactos ambientais proporcionados pelos mesmos. Neste contexto, para atender a demanda, diversos investimentos têm sido feitos no desenvolvimento de gerações alternativas e renováveis de energia, bem como na interconexão entre países para exportação de energia. Assim, os estudos exigem soluções mais eficazes para transmissão de energia elétrica, como os sistemas de transmissão High Voltage Direct Current (HVDC), uma alternativa aos sistemas de transmissão atuais, que são predominantemente em Corrente Alternada (CA). Dentre as principais vantagens dos sistemas HVDC, destaca-se a possibilidade de transmissão de grandes montantes de energia a longas distâncias com baixas perdas. Desta forma, eles estão susceptíveis às mais diversas condições meteorológicas e geográficas, em regiões isoladas, o que os tornam vulneráveis a descargas atmosféricas, afetando a segurança do sistema. Assim, neste trabalho, foi simulado um sistema HVDC, utilizando conversores Voltage Source Converter (VSC) do tipo modular multinível, do inglês Modular Multilevel Converter (MMC), frente descargas atmosféricas. Foram analisados diversos casos, visando verificar o comportamento dos conversores e validar a eficácia da utilização de para-raios de óxido metálico, comumente chamado de para-raios de óxido de zinco (ZnO), visto que este é um componente geralmente empregado em sistemas CA. O trabalho apresenta uma revisão acerca dos sistemas VSC-based HVDC (VSC-HVDC), tratando principalmente dos conversores MMC. Também foram descritos todos os modelos utilizados nas simulações, as quais foram realizadas através do software PSCAD/EMTDC. Concluiu-se que o correto dimensionamento e locação dos para-raios operam adequadamente em sistemas Corrente Contínua (CC). Um outro fato interresante é que a sobretensão gerada pelo surto atmosférico se propaga para o lado CA ao incidir no lado CC, mas o contrário não ocorre. / Nowadays, due to the increase in energy demand, several concerns arise due to the scarcity of traditional energy resources and the environmental impacts. In this context, to meet the demand, several investments have been made in the development of alternative and renewable generations of energy, as well as in the interconnection among countries for energy exports. Thus, studies require more effective solutions for electric power transmission, such as VSC-HVDC systems, an alternative to current transmission systems, which are predominantly in CA. Among the main advantages of VSC-HVDC systems, we can highlight the possibility of transmitting large amounts of energy over long distances with low losses. In this way, they are susceptible to the most diverse meteorological and geographic conditions, in isolated regions, which make them vulnerable to lightning, affecting the safety of the system. Thus, in this work, an HVDC system was simulated using VSC converters of the multilevel modular type (MMC) in front of lightnings. Several cases were analyzed in order to verify the behavior of the converters and validate the effectiveness of the use of metal oxide arresters, also known as ZnO arresters, since this is a commonly used component in CA systems. The work presents a review about the VSC-HVDC systems, mainly dealing with the MMC converters. We also described all the models used in the simulations, which were performed through the PSCAD/EMTDC software. It was concluded that the correct dimensioning and location of the arresters operate properly in CC systems. Another interresting fact is that the overvoltage generated by the lightning propagates to the AC side when it hits the CC side, but the reverse does not occur.

Atualmente, em virtude do aumento da demanda energética surgem diversas preocupações devido à escassez dos recursos energéticos tradicionais e os impactos ambientais proporcionados pelos mesmos. Neste contexto, para atender a demanda, diversos investimentos têm sido feitos no desenvolvimento de gerações alternativas e renováveis de energia, bem como na interconexão entre países para exportação de energia. Assim, os estudos exigem soluções mais eficazes para transmissão de energia elétrica, como os sistemas de transmissão High Voltage Direct Current (HVDC), uma alternativa aos sistemas de transmissão atuais, que são predominantemente em Corrente Alternada (CA). Dentre as principais vantagens dos sistemas HVDC, destaca-se a possibilidade de transmissão de grandes montantes de energia a longas distâncias com baixas perdas. Desta forma, eles estão susceptíveis às mais diversas condições meteorológicas e geográficas, em regiões isoladas, o que os tornam vulneráveis a descargas atmosféricas, afetando a segurança do sistema. Assim, neste trabalho, foi simulado um sistema HVDC, utilizando conversores Voltage Source Converter (VSC) do tipo modular multinível, do inglês Modular Multilevel Converter (MMC), frente descargas atmosféricas. Foram analisados diversos casos, visando verificar o comportamento dos conversores e validar a eficácia da utilização de para-raios de óxido metálico, comumente chamado de para-raios de óxido de zinco (ZnO), visto que este é um componente geralmente empregado em sistemas CA. O trabalho apresenta uma revisão acerca dos sistemas VSC-based HVDC (VSC-HVDC), tratando principalmente dos conversores MMC. Também foram descritos todos os modelos utilizados nas simulações, as quais foram realizadas através do software PSCAD/EMTDC. Concluiu-se que o correto dimensionamento e locação dos para-raios operam adequadamente em sistemas Corrente Contínua (CC). Um outro fato interresante é que a sobretensão gerada pelo surto atmosférico se propaga para o lado CA ao incidir no lado CC, mas o contrário não ocorre. / Nowadays, due to the increase in energy demand, several concerns arise due to the scarcity of traditional energy resources and the environmental impacts. In this context, to meet the demand, several investments have been made in the development of alternative and renewable generations of energy, as well as in the interconnection among countries for energy exports. Thus, studies require more effective solutions for electric power transmission, such as VSC-HVDC systems, an alternative to current transmission systems, which are predominantly in CA. Among the main advantages of VSC-HVDC systems, we can highlight the possibility of transmitting large amounts of energy over long distances with low losses. In this way, they are susceptible to the most diverse meteorological and geographic conditions, in isolated regions, which make them vulnerable to lightning, affecting the safety of the system. Thus, in this work, an HVDC system was simulated using VSC converters of the multilevel modular type (MMC) in front of lightnings. Several cases were analyzed in order to verify the behavior of the converters and validate the effectiveness of the use of metal oxide arresters, also known as ZnO arresters, since this is a commonly used component in CA systems. The work presents a review about the VSC-HVDC systems, mainly dealing with the MMC converters. We also described all the models used in the simulations, which were performed through the PSCAD/EMTDC software. It was concluded that the correct dimensioning and location of the arresters operate properly in CC systems. Another interresting fact is that the overvoltage generated by the lightning propagates to the AC side when it hits the CC side, but the reverse does not occur.