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Made available in DSpace on 2014-10-09T12:25:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:15Z (GMT). No. of bitstreams: 1 02289.pdf: 2031136 bytes, checksum: 2465edcd4250346558369b29fc6c8bf3 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

L'électrolyse haute température de l'eau à l'aide de membranes en céramique conductrice de protons est un processus intéressant pour la production d'hydrogène. Ce processus, qui peut être effectué sans catalyseurs nobles, produit de l'hydrogène pur et nécessite moins d'électricité que l'électrolyse classique à basse température. Le développement futur de ces réacteurs à membrane nécessite des efforts accrus sur la simulation numérique afin d'optimiser la chaleur et les transferts de masse ainsi que la conception de cellules d'électrolyse. Ce travail présente un ensemble d'équations sélectionnées dans la littérature et des démonstrations mathématiques rigoureuses permettant la description des phénomènes de transport dans la cellule et en particulier dans les électrodes qui sont composées de cermets. A partir de ce modèle, une étude paramétrique est conduite de façon à caractériser l'influence des différents paramètres opératoires sur ces phénomènes. Les différentes observations de cette étude permettent de dresser un ensemble d'hypothèses pour le développement de méthodes destinées à la simplification du modèle et à la réduction du temps de résolution. Ces modèles simplifiés permettent la détermination analytique des grandeurs dans l'électrode et ont conduit à la construction de nombres adimensionnels et de longueur caractéristiques du dispositif. / High temperature electrolysis of water by using proton conducting ceramic membranes is an interesting process for producing hydrogen. This process can be carried out without noble catalysts and produces pure hydrogen and requires less electricity than classical low temperature electrolysis. The future development of such membrane reactors requires increasing efforts on numerical simulation in order to optimize the heat and mass transfers as well as the design of electrolysis cells. This work presents a set of equations selected from the literature and rigorously demonstrated for the description of transport phenomena in the cell and particularly in the electrodes which are made of cermets. From this model, a parametric study is conducted in order to characterize the influence of various operating parameters on these phenomena. The different findings of this study provide a set of assumptions for the development of methods for simplifying the model and reducing the time of resolution. These simplified models allow analytical determination of quantities in the electrode and leads to the establishment of dimensionless numbers and characteristics length of the device.

Glattochronology is a branch of linguistics which attempts to provide dates for a historical relationship between languages, as well as to establish degrees of lexical relationship. In much the same way as carbon 14 dating provides dates for archaeological finds, glottochronological analysis is a technique utilized to estimate linguistic prehistory. The hypothesis that a proto Balto-Slavonic language has existed in prehistoric times is tested in this paper. This test is based on the cognate count, which reflects the cognation, in percentages, of corresponding lexical forms in both languages. The validity of the results obtained in the cognate count is dependent on the method of determination of cognation. Therefore, only an extremely rigorous approach, in the comparison of corresponding farms in Latvian and Russian, can be accepted as a reasonably valid method of determining true cognation. The corpus of the cognate count consists of 207 items in either language. Each item is formed by corresponding free morphemes in both Latvian and Russian, and is designated as either a positive, or a negative item, depending on the cognation of the corresponding forms. The results of the cognate count are then processed according to the accepted glottochronological methods. According to the results obtained, it was concluded that the hypothesis, claiming a prate Balto-Slavonic language, had to be rejected due to insufficient evidence for such a language. It also appeared that a substantial increase in sample size could furnish this type of investigation with mare reliable results. The conclusions reached indicate that the determination of a genetic relationship between languages, with the aid of the glattochronological technique, tends to be inconclusive. It appears that glattochronological analysis is a valuable method for use in the determination of degrees, of relationship between languages. The results obtained from this type of analysis should be utilized in correlation to results obtained by other disciplines in an endeavour to reconstruct prehistory, as dates obtained via this technique should be viewed as not absolute but rather as relative measurements. / Arts, Faculty of / Linguistics, Department of / Graduate

<p>Waveguides are used to transmit electromagnetic signals.Their geometry is typically long and slender their particularshape can be used in the design of computational methods. Onlyspecial modes are transmitted and eigenvalue and eigenvectoranalysis becomes important.</p><p>We develop a .nite-element code for solving theelectromagnetic .eld problem in closed waveguides .lled withvarious materials. By discretizing the cross-section of thewaveguide into a number of triangles, an eigenvalue problem isderived. A general program based on Arnoldi’s method andARPACK has been written using node and edge elements toapproximate the .eld. A serious problem in the FEM was theoccurrence of spurious solution, that was due to impropermodeling of the null space of the curl operator. Therefore edgeelements has been chosen to remove non physical spurioussolutions that arises.</p><p>Numerical examples are given for homogeneous andinhomogeneous waveguides, in the homogeneous case the resultsare compared to analytical solutions and the right order ofconvergence is achieved. For the more complicated inhomogeneouswaveguides with and without striplines, comparison has beendone with results found in literature together with gridconvergence studies.</p><p>The code has been implemented to be used in an industrialenvironment, together with full 3-D time and frequency domainsolvers. The2-D simulations has been used as input for full3-D time domain simulations, and the results have been comparedto what an analytical input would give.</p>

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