Made available in DSpace on 2014-12-17T14:56:04Z (GMT). No. of bitstreams: 1 GiordanoMF.pdf: 774778 bytes, checksum: b977df28e6c6f90822e09729743a9dc1 (MD5) Previous issue date: 2005-03-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work consists on the theoretical and numerical analysis of some properties of circular microstrip patch antennas on isotropic and uniaxial anisotropic substrates. For this purpose, a full wave analysis is performed, using Hertz Vector Potentials method in the Hankel Transform domain. In the numerical analysis, the moment method is also used in order to determine some characteristics of the antenna, such as: resonant frequency and radiation pattern. The definition of Hertz potentials in the Hankel domain is used in association with Maxwell?s equations and the boundary conditions of the structures to obtain the Green?s functions, relating the components of the current density on the patch and the tangential electric field components. Then, the Galerkin method is used to generate a matrix equation whose nontrivial solution is the complex resonant frequency of the structure. In the analysis, a microstrip antenna with only one isotropic dielectric layer is initially considered. For this structure, the effect of using superconductor patches is also analyzed. An analysis of a circular microstrip antenna on an uniaxial anisotropic dielectric layer is performed, using the Hertz vector potentials oriented along the optical axis of the material, that is perpendicular to the microstrip ground plane. Afterwards, the circular microstrip antenna using two uniaxial anisotropic dielectric layers is investigated, considering the particular case in which the inferior layer is filled by air. In this study, numerical results for resonant frequency and radiation pattern for circular microstrip antennas on isotropic and uniaxial anisotropic substrates are presented and compared with measured and calculated results found in the literature / Este trabalho consiste na an?lise te?rica e num?rica das caracter?sticas de uma antena de microfita com patch circular, cujo substrato ? composto por materiais diel?tricos isotr?picos e anisotr?picos uniaxiais. Para isto, uma an?lise de onda completa ? realizada, utilizando-se o M?todo dos Potenciais Vetoriais de Hertz no dom?nio da transformada de Hankel. Na an?lise num?rica da estrutura, ? utilizado tamb?m o M?todo de Galerkin, como um caso particular do M?todo dos Momentos, visando a determina??o de suas caracter?sticas, tais como a freq??ncia de resson?ncia e o diagrama de radia??o. A defini??o dos potenciais vetoriais de Hertz, em conjunto com as equa??es de Maxwell e as condi??es de contorno da estrutura, permite a obten??o das fun??es di?dicas de Green, relacionando as componentes da densidade de corrente no patch com as componentes tangenciais do campo el?trico. O M?todo de Galerkin ? ent?o usado para gerar a equa??o matricial, cuja solu??o n?o trivial permite a obten??o da freq??ncia de resson?ncia complexa da estrutura. Na an?lise, s?o consideradas, inicialmente, antenas de microfita com uma camada diel?trica isotr?pica separando o patch e o plano de terra, sendo analisado ainda para esta estrutura, o caso no qual o patch ? composto por um material supercondutor. Em seguida, ? considerado tamb?m o caso no qual o substrato diel?trico ? composto por um material anisotr?pico uniaxial, orientando os potenciais vetoriais na dire??o do eixo ?ptico, que ? tomado na dire??o perpendicular ao plano de terra. ? feita ainda a an?lise da antena de microfita com patch circular situado sobre duas camadas diel?tricas anisotr?picas uniaxiais, considerando o caso particular do patch suspenso, no qual a camada inferior ? composta pelo ar. S?o apresentados resultados da freq??ncia de resson?ncia e do diagrama de radia??o para patches circulares isotr?picos e anisotr?picos, fazendo-se compara??es com outros resultados obtidos na literatura

Esse trabalho tem como objetivo estabelecer um método simples de ensaio que permita determinar a resistência à tração e módulo elástico de partículas individuais de agregados graúdos naturais submetidas à carga de compressão. O método de ensaio foi desenvolvido baseado no ensaio de carga pontual (Point Load Test) que permite obter a resistência à tração de partículas. Para a determinação do módulo de elasticidade foi acoplado ao método um LVDT e foi satisfeita a condição para aplicação da teoria de contato de Hertz (contato curvo-plano entre as partículas e as fixações de aplicação da carga). Inicialmente a metodologia foi avaliada utilizando como material de referência partículas de vidro (com geometrias similares aos agregados). Após a validação no vidro, o método de ensaio foi aplicado em agregados graúdos de granito. Propôs-se um método de seleção de partículas com base na sua distribuição de frequência de absorção, com o intuito de reduzir a quantidade de partículas testadas mecanicamente necessárias para obter a distribuição de Weibull da resistência à tração (e módulo de elasticidade). Para tanto, foi feita a determinação da absorção de água individual de centenas de partículas selecionadas por amostragem a esmo da população de agregados. Com base nos resultados, foi possível determinar a distribuição de Weibull da resistência à tração e módulo de elasticidade das partículas. Observou-se que as resistências à tração variaram de 3 a 15 MPa. Os agregados possuíam aproximadamente 10% da população de partículas com resistência à tração inferior a 5 MPa, o que pode influenciar as classes de resistência à compressão de concretos >50MPa. Os módulos elásticos dos agregados também foram variáveis (18-67 GPa) e aproximadamente 10% da população de partículas com módulo elástico <30 GPa. Isso pode limitar o módulo de elasticidade do concreto (que geralmente é em torno de 27 GPa), dependendo do processo de escolha dos agregados. As funções exponenciais inversas fundamentais entre essas propriedades mecânicas e a porosidade foram confirmadas (para valores médios). / The aim of this work is to establish a simple test method to determine the tensile strength and elastic modulus of individual natural aggregate particles subjected to a compression load. The test method was developed based on the Point Load Test, that allows to obtain the tensile strength of particles. For the determination of the elastic modulus, an LVDT was coupled to the method and the condition for application of Hertz contact theory (curved-plane contact between the particles and the load application fixations) was satisfied. Initially, the method was evaluated using glass particles as reference (with geometries similar to aggregates). After validation on the glass, the test method was applied to coarse granite aggregates. A method of particle selection was proposed based on its absorption frequency distribution, in order to reduce the amount of mechanically tested particles required to obtain the Weibull distribution of tensile strength (and elastic modulus). For this purpose, the determination of the individual water absorption of hundreds of particles selected by random sampling of the population of aggregates was made. Based on the results, it was possible to determine the Weibull distribution of the tensile strength and elastic modulus of the particles. The tensile strengths ranged from 3 to 15 MPa. The aggregates had approximately 10% of the particles population with tensile strength less than 5 MPa, which may influence the classes of concrete with compressive strength > 50MPa. The elastic modulus of the aggregates was also variable (18-67 GPa), with approximately 10% of the particle population with elastic modulus <30 GPa. This may limit the elastic modulus of the concrete (usually around 27 GPa) depending on how the aggregates are selected. The fundamental inverse exponential functions between these mechanical properties and the porosity were confirmed (for mean values).

Sur le restreint territoire de la Vallée d’Aoste, en Italie, deux modalités distinctes de pèlerinage trouvent place. Une modalité est représentée par les pèlerinages locaux, fréquentés par une communauté de dévots qui se connaissent depuis toujours, l’autre par les pèlerinages internationaux, composés de fidèles qui souvent se rencontrent pour la première fois alors qu’ils montent sur le bus qui les conduira vers le lieu saint. Parmi ces pèlerinages internationaux, un des plus fréquentés dans ces dernières années est celui qui amène les pèlerins à la rencontre de la Vierge de Medjugorje, en Bosnie-Herzégovine. Quelles sont les différences qu’on peut retrouver à l’intérieur de ces deux modalités distinctes de voyage saint ? Les participants aux pèlerinages locaux sont les mêmes qui décident d’aller à la rencontre d’une Vierge “étrangère” et non pas encore reconnue par l’Église ? Et qu’est -e que cette dévotion peut offrir de plus par rapport aux nombreux lieux de culte présents sur la région ? A travers l’instrument de l’analyse ethnographique, Nora Demarchi cherche à répondre à ces questions, en illustrant comment l’analyse du phénomène du pèlerinage religieux peut nous dire de plus sur la société plus en général. / In the narrow area of Valle d'Aosta, in Italy, two different approaches to pilgrimage can be found: one is represented by local pilgrimages, attended by a community of devout constantly in touch with each other, the other one being international pilgrimages, composed by followers who meet for the first time when they board the bus that will take them towards the holy place. Among the latter, one of the most frequented lately is the one that brings the pilgrims towards the Virgin of Medjugorje, in Bosnia-Herzegovina. What are the differences we can find between these two different peregrinations ? Are the members of local pilgrimages the same who decide to meet a “foreign” Virgin Mary, which has not even been yet acknowledged by the Church ? Can this second devotion offer something more than the numerous places of worship located in the region ? Through the instruments of ethnographical analysis, Nora Demarchi tries to answer those questions, illustrating how the study of the religious pilgrimage phenomena can say something more about society in a broader sense.

Les composites alumine-chrome sont obtenus par pressage à chaud de poudres provenant du broyage réactif entre des poudres d'aluminium, d'alumine et d'oxydes de chrome. Différents types de composites ont été caractérisés : ils correspondent à des fractions volumiques de chrome comprises entre 5 et 36% et différentes voies d'élaboration. Une étude microstructurale a été menée pour mieux connaître les différents constituants et les différentes phases des poudres mais aussi des échantillons massifs (notamment ceux qui sont minoritaires). Une approche micromécanique est utilisée pour déterminer le champ de contraintes internes, générées lors du refroidissement après le pressage des poudres, du fait des différences existant entre les coefficients de dilatation thermique et les propriétés thermo-mécaniques des phases. Ces différences et ces contraintes pouvant conduire à la détérioration et à la fissuration du composite pourraient peut-être aussi être utilisées avec avantage et renforcer le composite, du moins localement selon les tailles et dispositions relatives de la phase métallique. Les résultats des calculs par éléments finis ont été confrontés aux résultats expérimentaux de détermination des contraintes moyennes dans les phases, obtenus en utilisant le rayonnement synchrotron. Pour évaluer le comportement de la microstructure et des contraintes internes vis à vis de la fissuration, une procédure d'indentation de type hertzien (indentation d'un échantillon plan par une sphère) a été mise en place pour analyser le mode de fissuration des échantillons massifs. Les résultats issus de l'étude de la microstructure, des calculs et de la fissuration sont comparées pour analyser l'influence de la microstructure et des champs locaux de contraintes sur le comportement et les trajectoires des fissures dans des composites biphasés alumine-chrome. Des voies concrètes d'amélioration voire d'optimisation des microstructures au regard de la résistance à la fissuration en sont ainsi dégagées.

L'étude acoustique des milieux granulaires secs a jusqu'alors fait l'objet de peu d'études. Celles-ci se repartissent en deux familles théoriques et expérimentales. La première, basse fréquence (à la limite quasi-statique), accorde une importance majeure au contact de hertz qui relie la déformation de la zone commune et le rapprochement des centres de deux sphères homogènes en fonction de la contrainte imposée sur celles-ci. Des théories de milieux effectifs peuvent alors être utilisées pour la propagation de la déformation de la zone de contact au milieu global. L'approche expérimentale explore un domaine haute fréquence (HF) de longueurs d'onde comparable à la taille des grains du milieu. Seule l'approche de la diffusion multiple apporte alors un cadre théorique pour ces milieux granulaires secs confinés sous contrainte. Dans cette thèse, nous présentons une expérience qui permet de généraliser la propagation acoustique pour différentes dimensions topologiques (1D et 3D), en utilisant à la fois des techniques classiques (transducteurs ultrasonores) ainsi que des techniques acousto-optiques. Dans un premier temps, nous nous intéressons à des ensembles de billes de verre et de billes d'acier calibrées en contrôlant les arrangements du milieu global. Nous sommes partis du problème simplifié à l'extrême de la bille seule. Nous avons ensuite étudié des colonnes de billes, des macro-cristaux ordonnés ainsi que des milieux désordonnés et nous avons pu obtenir les résultats suivants. Premièrement, nous avons pu montrer qu'en contradiction partielle avec un travail récent et en accord avec un second travail que la propagation d'ondes de surface sur les billes du milieu est effective quelle que soit la dimension topologique du milieu même si elle devient difficile dans le cas où le désordre est élevé. Deuxièmement, la transmission de l'énergie acoustique (BF), ne s'effectue pas préférentiellement le long des chaînes de force du milieu.

There's been a lot of debate behind frames per seconds in gaming recently and many people come with all kinds of strange claims. For example, that the eye can only see 30 frames per second, its more “cinematic” and that it is the optimal framerate for games.This thesis studies about the importance of frames per second within games and the history behind frames per seconds, in games and all the way back when movie industry began. What is best for higher player performance and what should developers strive for? There was a personal preliminary test with an extended playthroughs of each game, to see if the playstesters would experience similar issues. Afterwards two quantitative tests with two different methods, a blind test and a performance test, are conducted to measure if any player notices the differences, how the framerate can affect the player’s performance and what they preferred. / Det har varit en hel del debatt om bilder per sekund inom spel under de senaste åren och det har kommit fram alla möjliga konstiga påståenden. Till exempel, att ögat kan bara se 30 bilder per sekund, det är mer ”filmiskt” och att det är den optimala bildhastigheten för spel. Denna studier handlar om hur viktigt bilder per sekund inom spel är och historien bakom bilder per sekund, allt ifrån spel till filmindustrins början. Vad är bäst för högre prestationer för spelarna och vad bör spelutvecklare sträva efter? Ett personligt förberedande test med utsträckt igenomspelning av båda spelen, för att se om speltestarna skulle få ett liknande problem. Därefter två kvantitativa tester med två olika metoder, ett blindtest och ett prestandatest, genomförs för att mäta om någon spelare märker skillnaderna, hur de olika nivåerna av bilder per sekund kan påverka spelarna prestanda och vad de föredrog.

Thesis (Ph. D.)--University of Chicago, Committee on the History of Culture, March 2000. / Includes bibliographical references. Also available on the Internet.

During the project a test rig was constructed in which experiments were performed on radial bearings to evaluate the acoustic emission amplitude and RMS value of the signal. The acoustic emission amplitude depends on the Hertz contact time, i.e. the time it takes for the Hertz contact to roll over its own contact length. When the load remains constant on the bearing the Hertz contact time is directly reliant on the rotational speed of the inner ring of the bearing. Two experiments were performed, one on a spherical roller bearing and another identical experiment on a spherical ball bearing. Throughout both experiments the load on the bearing remained constant and the rotational speed of the inner ring was changed, the response of the speed change was measured using an acoustic emission sensor. The experiments found a quadratic dependency between the amplitude of the acoustic emission signal and the rotational speed of the inner ring. During the experiments the bearings were lubricated using grease and a total of 195 measurements were performed on each type of bearing at 13 different rotational speeds ranging between 1 and 3000 RPM.

Motivation of this master‘s thesis is solution of practical problem of the newly developed slewing ring for tram Škoda, type: 15T. Next impulse for thesis creation was the possibility to extend product range of roller bearing ZKL. There is processed strain – stress analysis of bearing inner design making use the finite element method (FEM). Obtained results are compared with classic approach based on the Hertz theory. Important aim of this work is three main parameters optimal establishment: rolling element diameter, arrangement radius and number of rolling elements. Optimization job is realized by solutions of direct tasks with different parameters. With regard to necessity of detailed stress analysis and conservation of reasonable computational time it was chosen approach of combination global and local FEM model. It was used pre/postprocessor PATRAN and solver MARC for solution of strain and stress analysis. Analytic solution was accomplished in software EXCEL.

Indiana University-Purdue University Indianapolis (IUPUI) / This thesis deals with three phase inverters and the different control strategies that can be associated with an inverter being used together. The first part of this thesis discusses the present research in the fields of PV panels, motor drive systems and three phase inverters along with their control. This control includes various strategies like MPPT, Volts-Hertz and modulation index compensation. Incorporating these techniques together is the goal of this thesis. A new topology for operating an open end motor drive system has also been discusses, where a boost converter and a flyback converter have been used in cascade to run a three phase motor. The main advantage of this is increasing the number of levels and improving the quality of the output voltage, not to mention a few other benefits of having the proposed circuit. A new algorithm has also been designed for starting and stopping the motor, which controls the current drawn from the power source during starting.