Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2019-02-08T11:08:03Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Willian Ricardo.pdf: 8465496 bytes, checksum: a01921f9da37abb9909a79e5b398408c (MD5) / Made available in DSpace on 2019-02-08T11:08:03Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Willian Ricardo.pdf: 8465496 bytes, checksum: a01921f9da37abb9909a79e5b398408c (MD5) Previous issue date: 2018-08-24 / Turbinas hidráulicas usadas em usinas hidrelétricas podem apresentar desgastes por cavitação e trincas em sua operação, as quais em alguns casos reparadas por soldagem a arco elétrico, por ser um processo de menor custo em comparação à troca da turbina. O aço inoxidável martensítico A743 grau CA6NM é empregado em serviços que requerem boa resistência mecânica associada a resistência à corrosão, principalmente em equipamento para extração de petróleo nos rotores e componentes de turbinas hidráulicas. Este trabalho tem por escopo analisar a microestrutura formada após processo de soldagem TIG (Tungsten Inert Gas) de um aço ASTM A743 CA6NM, usando material de adição similar, avaliando a presença da estrutura ferrita delta, austenita retida e carbonetos. Variando as espessuras das amostras e parâmetros de soldagem como passe único de soldagem e multipasse, mantendo temperatura de pré-aquecimento e interpasse de150ºC. Estimando a influência dos parâmetros na microestrutura com a dureza dos cordões e da ZTA. Os experimentos revelaram que um único passe de solda é suficiente para a formação de ferrita delta na forma de rede ao longo do cordão de solda e nas regiões expostas a altas temperaturas na zona termicamente afetada (ZTA), assim como o perfil de durezas da seção transversal do cordão de solda apontam durezas que variam desde 344 ± 6 HV para a região fundida, passando por um pico de dureza de 379 ± 4 HV na ZTA e terminando no metal base com 290 ± 5 HV, na solda multipasse a origem das diferentes morfologias de ferrita é múltipla, havendo uma diferença da taxa de resfriamento nos cordões,sendo que entre a base e o topo da solda pode ser percebido acumulo de ferrita delta na região interpasse e no topo do ultimo cordão de solda e a variação de largura da ZTA pelos passes subsequentes, a morfologia da ferrita delta zona termicamente afetada (ZTA) na condição multipasse, assim como o perfil de durezas da seção transversal dos cordões de solda apontam durezas que variam desde 311 ± 24 HV para a região fundida, passando por um pico de dureza de 326 ± 33 HV na ZTA. / Hydraulic turbines used in hydroelectric plants may present wear by cavitation and cracks in their operation, and in some cases repaired by electric arc welding, being a process of lower cost compared to the turbine exchange. A743 grade martensitic stainless steel CA6NM is used in services that require good mechanical resistance associated with corrosion resistance, especially in oil extraction equipment, rotors and hydraulic turbine components. This work aims to analyze the microstructure formed after TIG (Tungsten Inert Gas) welding of an ASTM A743 CA6NM steel, using similar addition material, evaluating the presence of the delta ferrite, retained austenite and carbides structure. By varying the sample thicknesses and welding conditions as single pass welding and multipass, maintaining preheating temperature and interpass of 150ºC. Estimating the influence of the parameters in the microstructure with the hardness of the strands and the ZTA. The experiments revealed that a single soldering pass is sufficient for the formation of delta ferrite in the form of a net along the weld bead and in the regions exposed to high temperatures in the thermally affected zone (ZTA), as well as the hardness profile of the section cross section of the weld beads indicate hardness ranging from 344 ± 6 HV to the molten region, passing through a hardness peak of 379 ± 4 HV in the ZTA and ending in the base metal with 290 ± 5 HV, in the multipass weld the origin of the different In the present study, the ferrite morphologies are multiple, with a difference in the cooling rate in the cords, between the base and the top of the weld it is possible to detect the accumulation of delta ferrite in the interpass region and at the top of the last weld bead and the ZTA The thermally affected zone delta ferrite (ZTA) morphology in the multipass condition, as well as the cross section hardness profile of the weld beads, point to hardnesses that vary from 311 ± 24 HV for the molten region, passing through a hardness peak of 326 ± 33 HV in the ZTA.

<p>U okviru doktorske disertacije, realizovane su podešljive feritne komponente sa jezgrima koja su proizvedena od komercijalno dostupnih ESL 40011 feritnih traka čije se induktivnosti podešavaju primenom jednosmerne struje. Rad realizovanih podešljivih feritnih komponenti je verifikovan u kolu DC-DC konvertora podizača napona. U disertaciji je predložena merna metoda koja omogućava ispitivanje uticaja jednosmerne struje na karakteristike SMD induktora postavljenih u realnom okruženju. Metoda je verifikovana na komercijalno dostupnim SMD induktorima.</p> / <p>As part of this thesis variable ferite components with cores produced from comercialy available ESL 40011 ferite tapes manufactured in Low Temperature Co-fired Ceramic technology are implemented. Inductivity of the components is varied by applying DC current. Functionality of the implemented ferite components is verified in a circuit of DC-DC boost converter. This thesis proposes a measurement method which enables examining the influence of DC current on the characteristics of SMD inductors in real environment. The method is verified on comercialy available SMD inductors</p>

Made available in DSpace on 2014-12-17T15:41:43Z (GMT). No. of bitstreams: 1 AlyssonEGM.pdf: 4274696 bytes, checksum: 0f940193275b15ce59b4b1f45e3dc11c (MD5) Previous issue date: 2008-09-24 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Were synthesized different ferrites NixZn1-xFe2O4 (0,4 &#8804; x &#8804; 0,6) compositions by using citrate precursor method. Initially, the precursors citrates of iron, nickel and zinc were mixed and homogenized. The stoichiometric compositions were calcined at 350?C without atmosphere control and the calcined powders were pressed in pellets and toroids. The pressed material was sintered from 1100? up to 1200?C in argon atmosphere. The calcined powders were characterized by XRD, TGA/DTG, FTIR, SEM and vibrating sample magnetometer (VSM). All sintered samples were characterized using XRD, SEM, VSM and measurements of magnetic permeability and loss factor were obtained. It was formed pure ferromagnetic phase at all used temperatures. The Rietveld analyses allowed to calculate the cations level occupation and the crystallite size. The analyses obtained nanometric crystals (12-20 nm) to the calcined powder. By SEM, the sintered samples shows grains sizes from 1 to 10 &#956;m. Sintered densities (&#961;) were measured by the Archimedes method and with increasing Zn content, the bulk density decrease. The better magnetization results (105-110 emu/g) were obtained for x=0,6 at all sintering temperatures. The hysteresis shows characteristics of soft magnetic material. Two magnetization processes were considered, superparamagnetism at low temperature and the magnetic domains formation at high temperatures. The sintered toroids presents relative magnetic permeability (&#956;r) from 7 to 32 and loss factor (tan&#948;) of about 1. The frequency response of toroids range from 0,3 kHz to 0,2 GHz. The composition x=0,5 presents both greater &#956;r and tan&#948; values and x=0,6 the most broad range of frequency response. Various microstructural factors show influence on the behavior of &#956;r and tan&#948;, such as: grain size, porosity across grain boundary and inside the grain, grain boundary content and domain walls movement during the process of magnetization at high frequency studies (0,3kKz 0,2 GHz) / Foram sintetizadas diferentes composi??es da ferrita Ni1-xZnxFe2O4 com 0,4 &#8804; x &#8804; 0,6 pelo uso do m?todo dos citratos precursores. Para se obter a fase estequiom?trica do sistema Ni1-xZnxFe2O4 foram misturados e homogeneizados os citratos precursores de ferro, n?quel e zinco. As composi??es estequiom?tricas foram calcinadas em atmosfera ambiente na temperatura de 350?C e depois prensadas em pastilhas e tor?ides. As amostras prensadas foram sinterizadas nas temperaturas de 1100?, 1150? e 1200?C em atmosfera de arg?nio. Os p?s calcinados foram caracterizados por DRX, TGA/DTG, FTIR, MEV e magnetometria de amostra vibrante (MAV) e as amostras sinterizadas por DRX, MEV, MAV, massa espec?fica e medidas de permeabilidade e perdas magn?ticas. Observou-se a forma??o de fase pura ferrimagn?tica em todas as temperaturas aplicadas. A an?lise pelo m?todo de Rietveld calculou o n?vel de ocupa??o dos c?tions e o tamanho de cristalito. Foram obtidos tamanhos de cristais nanom?tricos, de 12 a 20 nm para os p?s calcinados. Por MEV, as amostras sinterizadas apresentam tamanhos de gr?os na faixa de 1 a 10 &#956;m. A massa espec?fica (&#961;) do material sinterizado apresenta uma tend?ncia de diminui??o com a adi??o de Zn. Os melhores resultados de magnetiza??o foram obtidos para x=0,6 nas tr?s temperaturas de sinteriza??o, variando de 105 a 110 emu/g. As histereses mostram um perfil de materiais magn?ticos moles. Dois processos de magnetiza??o foram considerados, o superparamagnetismo a baixa temperatura (350?C) e a forma??o de dom?nios magn?ticos em altas temperaturas. Os materiais sinterizados apresentam permeabilidade (&#956;) de algumas unidades, de 7 a 30, e perdas magn?ticas (tan&#948;) por volta de 1. A resposta em freq??ncia dos n?cleos toroidais est? na faixa de 0,3 kHz a 0,2 GHz. Os maiores valores de &#956; e tan&#948; s?o para x=0,5 e a maior faixa de resposta em freq??ncia ? para x=0,6. V?rios fatores da microestrutura contribuem para o comportamento das grandezas &#956; e tan&#948;, tais como: os tamanhos dos gr?os, porosidade inter e intragranular, quantidade de contornos de gr?os e os aspectos da din?mica das paredes de dom?nios quando excitadas magneticamente sob alta freq??ncia

Made available in DSpace on 2014-12-17T15:42:20Z (GMT). No. of bitstreams: 1 AdilaPGR_DISSERT.pdf: 1981953 bytes, checksum: be68a9256a00a195734cb22cb0bdc5b2 (MD5) Previous issue date: 2014-12-11 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The ferrite composition Ni1 - xCoxFe2O4 (0 &#8804; x &#8804; 0.75) were obtained by the method of microwave assisted synthesis and had their structural and magnetic properties evaluated due to the effect of the substitution of Ni by Co. The compounds were prepared: according to the concept of chemical propellants and heated in the microwave oven with power 7000kw. The synthesized material was characterized by absorption spectroscopy in the infrared (FTIR), Xray diffraction (XRD) using the Rietveld refinement, specific surface area (BET) , scanning electron microscopy (SEM) with aid of energy dispersive analysis (EDS) and magnetic measurements (MAV). The results obtained from these techniques confirmed the feasibility of the method of synthesis employed to obtain the desired spinel structure, the ferrite, nickel ferrite as for nickel doped with cobalt. The results from XRD refinement ally showed the formation of secondary phases concerning stages &#945; - Fe2O3, FeO, (FeCo)O e Ni0. On the other hand, there is an increase in crystallite size with the increase of cobalt in systems, resulting in an increased crystallinity. The results showed that the BET systems showed a reduction in specific surface area with the increase of cobalt and from the SEM, the formation of irregular porous blocks and that the concentration of cobalt decreased the agglomerative state of the system. The magnetic ferrites studied showed different characteristics according to the amount of dopant used, ranging from a very soft magnetic material (easy magnetization and demagnetization ) - for the system without cobalt - a magnetic material with a little stiffer behavior - for systems containing cobalt. The values of the coercive field increased with the increasing growth of cobalt, and the values of saturation magnetization and remanence increased up to x = 0,25 and then reduced. The different magnetic characteristics presented by the systems according to the amount of dopant used, allows the use of these materials as intermediates magnetic / As ferritas de composi??o Ni1&#8722;xCoxFe2O4 (0&#8804;x&#8804;0,75) foram obtidas atrav?s do m?todo de s?ntese assistida por microondas e tiveram suas propriedades estruturais e magn?ticas avaliadas em fun??o do efeito da substitui??o do Ni pelo Co. Os compostos foram preparados de acordo com o conceito da qu?mica dos propelentes e aquecidos em forno micro-ondas com pot?ncia 7000kw. O material sintetizado foi caracterizado por espectroscopia de absor??o na regi?o do infravermelho (FTIR), difra??o de raios X (DRX), com o uso do refinamento pelo m?todo de Rietveld, ?rea superficial espec?fica (BET), microscopia eletr?nica de varredura (MEV) com aux?lio de an?lise por dispers?o de energia (EDS) e medidas magn?ticas (MAV). Os resultados obtidos, a partir destas t?cnicas confirmaram a viabilidade do m?todo de s?ntese empregado para a obten??o da estrutura espin?lio desejada, tanto para a ferrita de n?quel quanto para as ferritas de n?quel dopadas com cobalto. Os resultados do DRX, aliado ao refinamento, mostraram a forma??o de fases secund?rias tais como as fases &#945; - Fe2O3, FeO, (FeCo)O e Ni0. Por outro lado, observou-se um aumento no tamanho do cristalito com o incremento do cobalto nos sistemas, implicando em um aumento da cristalinidade. Os resultados do BET mostraram que os sistemas apresentaram uma redu??o da ?rea superficial espec?fica com o incremento do cobalto e a partir do MEV observou-se a forma??o de blocos porosos irregulares e que o aumento da concentra??o de cobalto dimunuiu o estado de aglomera??o dos sistemas. As ferritas estudadas apresentaram caracter?sticas magn?ticas diferenciadas de acordo com a quantidade do dopante utilizado, variando de um material magn?tico bastante mole (f?cil magnetiza??o e desmagnetiza??o) - para o sistema sem cobalto - a um material magn?tico com comportamento um pouco mais duro - para os sistemas contendo cobalto. Os valores do campo coercitivo aumentaram com o crescente incremento do cobalto, e os valores de magnetiza??o de satura??o e reman?ncia aumentaram at? x=0,25 e depois reduziram. As caracter?sticas magn?ticas diferenciadas apresentadas pelos sistemas, de acordo com a quantidade de dopante utilizado, permite o uso desses materiais como magn?ticos intermedi?rios

Made available in DSpace on 2014-12-17T15:42:21Z (GMT). No. of bitstreams: 1 JoseEMS_TESE.pdf: 5374821 bytes, checksum: 56fe60cd3bbf0a42f7512c62fe5b976e (MD5) Previous issue date: 2013-03-08 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Were synthesized spinel-type ferrites with general formula Ni0,8Mg0.2-xMxFe2O4, where M represents the doping Mn, Co or Mn + Co simultaneously, x ranges for the values 0.02, 0.05 and 0.1. The value of x was divided by 2 in cases where M equals Mn and Co conjugates. We used the citrate precursor method and heat treatment to obtain the phases at 1100?C. The materials were characterized by XRD, TGA/ DTGA, SEM, MAV and reflectivity measurements by the method of waveguide. Powders to 350?C/3.5 h were crystalline and nanosized. According to the results this temperature all powders have a percentage of ferrite phase over 90%. The composition had the addition of Mn and Co simultaneously showed a higher percentage of secondary phase NiO, 5.8%. The TGA/DTGA curves indicate that this sample reached phase (s) crystalline (s) at lowest temperatures. The X-ray diffractograms of the samples calcined at 350?C and 1100?C were treated with the Rietveld refinament technique. The powders calcined at 1100 ?C/3h in air show to be 100% except spinel phase composition with 0.02 doping. The micrographs show clusters of particles with sizes smaller than 1 &#956;m in calcination temperature of 1100?C which agreed with the result of Rietveld refinement. In the compositions doped with Mn were higher values of magnetization (45.90 and 53.20 Am2/kg), which did not cause high microwave absorption. The theoretical calculation of magnetization (MT) was consistent with the results, considering that there was agreement between the increase of magnetization experimental and theoretical. It was observed that there was the interrelation of the final effect of absorption with the thickness of MARE, the composition of ferrimagnetic materials and in particular the specific values of frequency. The analysis shows that the reflectivity increases in the concentration of cobalt increased the frequency range and also for absorption 10.17 GHz and 84%, respectively. The best result of chemical homogeneity and the value of 2.96 x 10-2 tesla coercive field were crucial for high performance ferrite absorber with 0.1 cobalt. The Cobalt has high magnetocrystalline anisotropy, it is associated with an increased coercive field, Hc. Therefore, this property improves the results of reflectivity of spinel ferrites / Foram sintetizadas ferritas do tipo espin?lio com f?rmula geral Ni0,8Mg0,2-xMxFe2O4, onde M representa os dopantes Mn, Co ou Mn + Co simultaneamente, x varia para os valores 0,02; 0,05 e 0,1. O valor de x foi dividido por 2 nos casos em que M equivale a Mn com Co conjugados. Foi utilizado o m?todo dos citratos precursores e tratamento t?rmico na obten??o das fases a 1100?C. Os materiais foram caracterizados por DRX, TGA/DTGA, MEV, MAV e medidas de refletividade pelo m?todo de guia de ondas. Os p?s a 350?C/3,5h foram cristalinos e nanom?tricos. De acordo com os resultados nesta temperatura todos os p?s apresentam um percentual de fase ferrita superior a 90%. A composi??o que teve a adi??o de Mn e Co simultaneamente apresentou maior percentual de fase secund?ria NiO, 5,8%. As curvas TGA/DTGA indicam que essa amostra alcan?ou fase(s) cristalina(s) em temperaturas mais baixas. Os difratogramas de raios X das amostras calcinadas a 350?C e 1100?C foram tratados pela t?cnica de refinamento Rietveld. Os p?s calcinados a 1100?C/3h em atmosfera ambiente mostram ser 100% de fase espin?lio exceto a composi??o com 0,02 de dopantes. As micrografias apresentam aglomerados de part?culas com tamanhos menores que 1 &#956;m na temperatura de calcina??o de 1100?C, o que concordou com o resultado de refinamento Rietveld. Nas composi??es dopadas com Mn ocorreram os maiores valores de magnetiza??o (45,90 e 53,20 Am2/kg), o que n?o acarretou alta absor??o de microondas. O c?lculo te?rico da magnetiza??o (MT) foi coerente com os resultados, considerando-se que houve concord?ncia entre o aumento das magnetiza??es experimental e te?rica. Observa-se que houve interrela??o do efeito final de absor??o com a espessura do MARE, a composi??o do material ferrimagn?tico em particular e os valores espec?ficos de freq??ncia. A an?lise de refletividade indica que o aumento na concentra??o de cobalto aumentou a faixa de freq??ncia e a absor??o para 10,17 GHz e 84%, respectivamente. O resultado indica que a melhor homogeneidade qu?mica e o valor 2,96 x 10-2 tesla de campo coercitivo foram determinantes para o alto desempenho absorvedor da ferrita com 0,1 de cobalto. O Cobalto tem alta anisotropia magnetocristalina, isto est? associado ao aumento do campo coercitivo, Hc. Portanto, essa propriedade melhora os resultados de refletividade das ferritas espin?lio

Les enjeux majeurs des dispositifs hyperfréquences utilisés dans les systèmes de télécommunication modernes sont la montée en fréquence de fonctionnement, la miniaturisation des circuits et l’intégrabilité des composants.Grâce à l’émergence des métamatériaux et à la maîtrise des propriétés des ferrites, il est possible de développer nouveaux dispositifs répondant à ces nouvelles exigences de l’électronique embarquée.Cette thèse développe, à partir d’une ligne métamatériau HIW coplanaire basée sur un substrat de ferrite, un nouveau dispositif hyperfréquence non réciproque de faible encombrement, opérant à des fréquences situées entre 13 et 15 GHz.Les prototypes fabriqués et caractérisés sous de faibles valeurs de champ magnétique, présentent les performances caractéristiques d’un isolateur bande étroite: isolation supérieure à 30 dB, pertes d’insertion inférieures à 1 dB. / The main challenges of microwave devices used in modern telecommunication systems are the increase of the operating frequency, the circuit’s miniaturization and the integration of components.Thanks to the emergence of metamaterials and the control of the properties of ferrites, it is possible to develop new circuits that meet these new requirements for embedded electronics.This thesis investigates, from a coplanar HIW metamaterial line based on a ferrite substrate, a new non-reciprocal microwave device, operating in frequency range between 13 and 15 GHz.Prototypes were fabricated and characterized under low magnetic field. They achieved the characteristic performances of a narrow band isolator: isolation over 30 dB and insertion losses of less than 1 dB.

Dans le domaine des hyperfréquences, les composants passifs actuellement commercialisés, de type circulateurs ou isolateurs, sont fabriqués de façon unitaire à partir des substrats de ferrite et avec des structures microruban ou triplaque. La miniaturisation et l'intégration des ces circulateurs nécessitent de disposer d'une couche mince magnétique qui possède des propriétés magnétiques proche des matériaux massifs. Ce travail s'intéresse donc à deux points particuliers pour la réalisation du circulateur : miniaturisation et fabrication collective. Les travaux relatés dans ce manuscrit ont pour objectif la conception et la réalisation d'un circulateur coplanaire à couche magnétique de YIG en bande X pour des applications en télécommunications. L'étude présentée débute la mise en place d'un processus de dimensionnement. A partir des travaux de Bosma, les règles de design sont mises en place de façon analytique pour un circulateur triplaque. Après avoir affiné les dimensions de façon numérique, les résultats sont transposés à la structure coplanaire et optimisés à l'aide d'un simulateur électromagnétique. Plusieurs structures de circulateur en couche mince et couche massive sont utilisées. Les épaisseurs vont de 16 à 1000 µm. Plusieurs séries de prototypes sont fabriquées puis caractérisées à partir d'un banc de mesure hyperfréquence composé d'un testeur sous pointes à trois accès et d'un analyseur vectoriel de réseaux. Les résultats expérimentaux de différents prototypes de différentes épaisseurs sont présentés tout en dressant une comparaison avec les rétro-simulations en 3D. Une réflexion sur les résultats généraux est réalisée et nous proposons des pistes pour l'amélioration des performances de nos prototypes.

Dans le domaine de l'électronique de spin, le filtrage de spin est un phénomène physique qui permet de générer des courants d'électrons polarisés en spin grâce au transport dépendant du spin à travers une barrière tunnel ferromagnétique. Alors que le filtrage de spin à température ambiante est très attractif pour les applications, il existe peu de matériaux ayant les proprieties électriques et magnétiques requises. Les ferrites isolants XFe2O4 (X= Co, Ni, Mn), qui présentent des températures de Curie nettement supérieures à 300 K, sont de bons candidats pour jouer le rôle de filtre à spin à température ambiante. Dans cette thèse, je présente une étude approfondie des ferrites MnFe2O4, NiFe2O4 et CoFe2O4 en films ultraminces épitaxiés pour le filtrage de spin à température ambiante, en me penchant sur leur croissance par épitaxie par jets moléculaires. Les proprieties structurales, chimiques, magnétiques et électriques ont été étudiées par plusieurs méthodes de caractérisation in situ et ex situ, qui ont permis de démontrer le fort potentiel de ces oxydes pour jouer le rôle de barrière tunnel magnétique à temperature ambiante. Les filtres à spin ont ensuite été intégrés dans des jonctions tunnel afin de faire des mesures de transport tunnel polarisé en spin, soit par la méthode de Meservey-Tedrow, soit par des mesures de magnétorésistance tunnel (TMR). Ces mesures ont révélé pour la première fois un effet de filtrage de spin à travers MnFe2O4(111) et des effets de TMR ont été obtenus dans des nano-jonctions tunnel à base de CoFe2O4(111), permettant d'obtenir la plus forte polarisation en spin actuelle à température ambiante par effet de filtrage de spin.

<p>This thesis presents solutions and studies related to the design of wideband antennas for wireless handheld terminal applications. A method of electrically shortening the terminal chassis length to obtain resonance at high frequencies has been proposed and evaluated, thereby increasing the antennas impedance bandwidth. No significant effect on the lower frequency band in a dual-band antenna prototype has been observed, making the method suitable for multi-band applications. The chassis has further been utilized as a zero-thickness 0.9 - 2.7 GHz high efficiency antenna by inserting a notch in the chassis center, and a feasibility study for typical phones has been performed. Additionally, the effect of talk position on the chassis wave-mode has been investigated, where the standard equivalent circuit model for terminal antennas has been modified to include the presence of the users head. The model has been used to explain measured and simulated effects concerning frequency detuning, efficiency reduction and bandwidth enhancements when the terminal is placed in talk position.</p><p>The use of a hands-free earpiece cord is currently mandatory for FM radio reception as the cord is utilized as antenna. However, there is currently a market driven demand for removing the cord requirement since many modern phones are equipped with speakers and Bluetooth headsets. In this thesis, an active ferrite loop antenna is proposed as an internal replacement/complement with a performance of -23 dB (G/T degradation) compared to a full-size lossless dipole in urban environments. Also, a modification to the cord is suggested for DVB H reception.</p><p>Complex matching networks have been investigated to increase the bandwidth of dual band PIFA antennas, and a printed dual band dipole has been integrated with a modified Marchand balun for dual resonance at two separate frequency bands, thus covering the commercial cellular bands 824-960 and 1710-2170 MHz with a single antenna.</p>

L'objectif du travail présenté est d'acquérir expérimentalement de nouvelles données thermodynamiques sur les espèces qui constituent les produits de corrosion présents dans le circuit primaire des REP. Le volet expérimental de cette étude se focalise sur deux phases solides du nickel : l'oxyde de nickel NiO (ou bunsenite) et le ferrite de nickel NiFe2O4. La vitesse de dissolution de l'oxyde de nickel a été mesurée jusqu'à 130°C en milieu acide (pH 3 à 5). Un modèle cinétique a été utilisé afin de décrire les vitesses de dissolution mesurées expérimentalement. Ce modèle a permis de déterminer l'énergie d'activation réelle de la réaction de dissolution de l'oxyde de nickel. La solubilité d'un ferrite de nickel stœchiométrique synthétisé expérimentalement a été mesurée entre 100 et 200°C dans une cellule potentiométrique à électrodes à hydrogène. La spéciation du fer et du nickel dans la solution expérimentale a été discutée au regard des données thermodynamiques disponibles à haute température et des constantes d'équilibre calculées par le code MULTEQ. L'un des aspects de cette étude a consisté en la conception et la mise en route d'une cellule de mesure de solubilité à haute température : la boucle SOLO. Les spécifications techniques et le fonctionnement de cette installation seront présentés en détail.