Yes / In this paper, we present an analytical study for the investigation of the effects of the magnetoelectric elements of a reciprocal and nonreciprocal bianisotropic grounded substrate on the input impedance, resonant length of a dipole antenna as well as on the mutual coupling between two element printed dipole array in three configuration geometries: broadside, collinear and echelon printed on the same material. This study examines also the effect of the considered bianisotropic medium on the electric and magnetic field distributions that has been less addressed in the literature for antenna structures. Computations are based on the numerical resolution, using the spectral method of moments, of the integral equation developed through the mathematical derivation of the appropriate spectral Green’s functions of the studied dipole configuration. Original results, for chiral, achiral, Tellegen and general bi-anisotropic media, are obtained and discussed with the electric and magnetic field distributions for a better understanding and interpretation. These interesting results can serve as a stepping stone for further works to attract more attention to the reciprocal and non-reciprocal Tellgen media in-depth studies.

The main objective of this research is to model and analyse complex electromagnetic problems by means of a new hybridised computational technique combining the frequency domain Method of Moments (MoM), Finite-Difference Time-Domain (FDTD) method and a subgridded Finite-Difference Time-Domain (SGFDTD) method. This facilitates a significant advance in the ability to predict electromagnetic absorption in inhomogeneous, anisotropic and lossy dielectric materials irradiated by geometrically intricate sources. The Method of Moments modelling employed a two-dimensional electric surface patch integral formulation solved by independent linear basis function methods in the circumferential and axial directions of the antenna wires. A similar orthogonal basis function is used on the end surface and appropriate attachments with the wire surface are employed to satisfy the requirements of current continuity. The surface current distributions on structures which may include closely spaced parallel wires, such as dipoles, loops and helical antennas are computed. The results are found to be stable and showed good agreement with less comprehensive earlier work by others. The work also investigated the interaction between overhead high voltage transmission lines and underground utility pipelines using the FDTD technique for the whole structure, combined with a subgridding method at points of interest, particularly the pipeline. The induced fields above the pipeline are investigated and analysed. FDTD is based on the solution of Maxwell's equations in differential form. It is very useful for modelling complex, inhomogeneous structures. Problems arise when open-region geometries are modelled. However, the Perfectly Matched Layer (PML) concept has been employed to circumvent this difficulty. The establishment of edge elements has greatly improved the performance of this method and the computational burden due to huge numbers of time steps, in the order of tens of millions, has been eased to tens of thousands by employing quasi-static methods. This thesis also illustrates the principle of the equivalent surface boundary employed close to the antenna for MoM-FDTD-SGFDTD hybridisation. It depicts the advantage of using hybrid techniques due to their ability to analyse a system of multiple discrete regions by employing the principle of equivalent sources to excite the coupling surfaces. The method has been applied for modelling human body interaction with a short range RFID antenna to investigate and analyse the near field and far field radiation pattern for which the cumulative distribution function of antenna radiation efficiency is presented. The field distributions of the simulated structures show reasonable and stable results at 900 MHz. This method facilitates deeper investigation of the phenomena in the interaction between electromagnetic fields and human tissues.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In this work the Method of Manufactured Solutions (MMS) is introduced for the code veri cation of full-wave frequency dependent electromagnetic computational software. At rst the method is sketched in the context of the veri cation and validation process and the need for proper code veri cation is highlighted. Subsequently, the MMS is investigated in its natural context: the Finite Element Method, speci cally for the E- eld Vector Wave Equation. The usefulness of the method to detect error in a computational code is demonstrated. The selection of Manufactured Solutions is discussed and it is demonstrated how it can be used to nd the probable cause of bugs. Mutation testing is introduced and used to show the ability to detect errors present in code. The MMS is nally applied in a novel manner to a Method of Moments (MoM) code. The challenges of numerical integration associated with the application of the operator is discussed and correct integration is successfully demonstrated. Subsequently the MMS is demonstrated to be successfully applied to the MoM and mutation testing is used to demonstrate the practical e cacy of the method. The application of the MMS to the MoM is the main contribution of this work. / AFRIKAANSE OPSOMMING: Die Metode van Vervaardigde Oplossings (MVO) word hier bekend gestel vir die veri kasie van numeriese volgolf frekwensie-afhanklike elektromagnetise kode. Die metode word eerstens in die bre e konteks van algemene veri kasie en validasie geplaas en gevolglik word die noodsaaklikheid van kode veri kasie beklemtoon. Daarna, word die toets-metode in die konteks van die Eindige Element Metode vir die E-veld vektorgolf vergelyking bestudeer. Die MVO is oorspronklik ontwikkel in die di erentiaalvergelyking omgewing. Die bruikbaarheid van die metode vir elektromagnetiese simulasies word prakties gedemonstreer deur die opsporing van werklike foute. Die metode word ook verder ondersoek vir die oorsprong van foute. Mutasietoetsing word bekendgestel en word gebruik om die metode verder prakties te veri eer. Die MVO word laastens in 'n nuwe manier gebruik om 'n Moment Metode kode te veri eer. Die praktiese probleme betrokke by numeriese integrasie word ondersoek en die korrekte toepassing van die integraal operator word prakties gedemonstreer. Daarna, word die MVO in hierdie konteks gedemonstreer deur verskeie voorbeelde te ondersoek. Mutasietoetsing word weereens gebruik om na die e ektiewiteit van die MVO te kyk om 'n Moment Metode kode te toets. Die toepassing van die MVO op 'n Moment Metode kode is die hoof bydrae van hierdie werk.

The aim of this study is to analysis, investigate and find out the solutions for the problems associated with the implementations of antennas RFID Reader and Tag for various applications. In particular, the efficiency of the RFID reader antenna and the detection range of the RFID tag antenna, subject to a small and compact antenna's design configuration have been studied. The present work has been addressed directly to reduce the cost, size and increase the detection range and communication reliability of the RFID framework antennas. Furthermore, the modelling concept of RFID passive tags mounted on various materials including the novel design of RFID reader antenna using Genetic Algorithm (GA) are considered and discussed to maintain reliable and efficient antenna radiation performances. The main benefit of applying GA is to provide fast, accurate and reliable solutions of antenna's structure. Therefore, the GA has been successfully employed to design examples: meander-line, two linear cross elements and compact Helical- Spiral antennas. In addition, a hybrid method to model the human body interaction with RFID tag antenna operating at 900MHz has been studied. The near field distribution and the radiation pattern together with the statistical distribution of the radiation efficiency and the absorbed power in terms of cumulative distribution functions for different orientation and location of RFID's tag antenna on the human body have been demonstrated. Several tag antennas wi th symmetrical and unsymmetrical structure configurations operating in the European UHF band 850-950 MHz have been fabricated and tested. . The measured and simulated results have been found to be in a good agreement with reasonable impedance matching to the typical input impedance of an RFID integrated circuit chip and nominal power gain and radiation patterns.

L’objectif de ce travail de thèse est d’étudier l’interaction des ondes électromagnétiques en bande L avec les vagues côtières déferlantes, en particulier pour un observateur situé à proximité de la surface. Le travail s’attache à effectuer une modélisation électromagnétique précise en lien étroit avec le modèle hydrodynamique. Pour modéliser et calculer les champs électromagnétiques diffusés par les vagues déferlantes, nous utilisons une approche numérique par intégrale de frontière, notamment la Méthode des Moments (MdM). Dans ce cadre, nous focalisons le travail sur la problématique de la fiabilité et la convergence du calcul numérique pour des géométries de forte courbure comme peuvent l’être des surfaces de vagues déferlantes. Après une analyse approfondie de la problématique, nous montrons qu’une solution fondée sur la Méthode des Moments d’Ordre Supérieur (MdM-OS) combinée avec la technique de maillage Non Uniform Rational Basis Splines (NURBS) permet d’améliorer les performances de la méthode MdM-Classique. En parallèle du travail de modélisation électromagnétique, nous nous attachons à introduire un modèle hydrodynamique capable de simuler le plus fidèlement possible le mouvement et la déformation des vagues à proximité de la côte. Nous retenons une modélisation hydrodynamique basée sur la Méthode Désingularisée. Cette approche méthodologique nous permet d’étudier l’évolution des vagues en fonction de la pente du fond, de la hauteur relative et de la cambrure des vagues. La combinaison des résultats issus de la modélisation numérique électromagnétique et de la description hydrodynamique permettent ainsi d’évaluer l’évolution des champs électromagnétiques diffusés par les vagues côtières déferlantes en fonction du temps pour trois types de déferlement standard : glissant, plongeant et gonflant. / The purpose of this thesis work is to study the interaction of electromagnetic waves in L bandwith breaking coastal sea waves, in particular for an observer situated close to the surface. The work attempts to realize a precise electromagnetic modeling in narrow link with hydrodynamic model. To model and calculate electromagnetic fields scattered by breaking sea waves, we use a numerical approach by boundary integral technique, in particular Method of Moments (MoM). In this frame, we focus on the reliability and the convergence problem of numerical computation for strong curvature geometries as the surfaces of breaking sea waves are. After a thorough analysis of the problem, we show that a solution based on Higher-Order Method of Moments (HO-MoM) combined with Non Uniform Rational Basis Splines (NURBS) meshing technique allows the improvement of the performances of Classical-MoM. In parallel of the work on electromagnetic modeling, we attempt to introduce a hydrodynamic model able to precisely simulate the movement and the deformation of waves near the coast. We choose a hydrodynamic modeling based on Desingularized Method. This methodological approach allows the study of the evolution of waves according to the bottom slope, the relative height and the wave steepness. The combination of the results obtained from the numerical electromagnetic modeling and from the hydrodynamic description allows us to estimate the evolution of the electromagnetic fields scattered by breaking coastal sea waves according to time for three types of standard breaking : spilling, plunging and surging.

V předložené práci se zabýváme problematikou stochastického modelování úro- kových sazeb. Jedním z nejobvyklejších postup· je modelovat dynamiku úroko- vých sazeb pomocí stochastické diferenciální rovnice difúze, jejímiž základními kameny jsou funkce driftu a funkce difúze. Od 70. let 20. století byla navržena celá řada model· tohoto typu, a ačkoli se tyto modely neustále zdokonalují, vyvstává přirozená otázka, zda se historicky pozorované úrokové sazby skutečně takovými difúzními rovnicemi řídily. V této práci budeme právě uvedenou hypo- tézu testovat pro několik nejběžnějších jednofaktorových model· úrokové sazby první generace. Z historických dat odhadneme obecnou momentovou metodou a metodou maximální věrohodnosti parametry jednotlivých difúzních rovnic a následně provedeme statistické testy dobré shody proložení těchto rovnic pozo- rovanými daty. 1

Le contrôle non destructif (CND) par Courants de Foucault (CF) de défauts de fissuration est l’une des techniques les plus répandues dans de nombreux secteurs industriels. L’utilisation d’outils de modélisation adaptés permet d’améliorer les procédés de contrôle et la compréhension des données expérimentales observées. Ce travail de thèse, réalisé au CEA LIST et sous la direction de D. Lesselier (Laboratoire des Signaux et Systèmes), a pour objectif de proposer une approche de modélisation semi-analytique dédiée à la simulation du CND CF de défauts fins ou très fins dans une pièce plane conductrice composée de plusieurs couches. Il a fait l’objet d’une collaboration, dans le cadre du projet CIVAMONT, avec l’équipe Meander de l’University of Western Macedonia (Grèce), dirigée par le professeur T. Theodoulidis.Du point de vue de la simulation, la complexité du problème à traiter est liée aux particularités des défauts de fissuration : une ouverture très fine, un profil complexe et la possibilité d’avoir des ponts de conductivité entre les deux faces latérales du défaut. Ces caractéristiques expliquent la difficulté qu’ont les méthodes de simulation classiques, semi-analytiques ou purement numériques, à traiter efficacement ce type de configuration. Pour ces raisons, une approche dédiée aux défauts fins, fondée sur la méthode des éléments de frontière, a été développée. Elle présente l’avantage majeur de ne requérir qu’une discrétisation surfacique du défaut, en traitant analytiquement le calcul dans la direction de son ouverture. Après la résolution, avec la Méthode des Moments, de l’équation intégrale décrivant les interactions entre le champ d’excitation et le défaut, la réponse de la sonde est calculée en appliquant le théorème de réciprocité. Les développements théoriques réalisés dans cette thèse ont abouti à la mise en place d’une formulation générale permettant la prise en compte d’un nombre quelconque de défauts fins, d’orientations et des géométries différentes, pouvant être situés dans des couches différentes de la pièce. Par la suite, cette méthode innovante a été implémentée au sein de la plateforme de simulation CIVA, développée au CEA LIST, et a été validée expérimentalement à plusieurs reprises. Une extension de cette méthode a également permis la mise en place d’une approche la couplant à une modélisation volumique standard pour la simulation de configurations complexes comme le contrôle de fissures au voisinage d’un alésage. Ce travail, qui a fait l’objet d’une diffusion internationale affirmée, a permis de lever avec succès un certain nombre de difficultés théoriques et pratiques liées à la modélisation du CND CF de défauts fins. / Non Destructive Testing (NDT) with Eddy Current (EC) techniques are is widely employed in several industrial sectors for cracks detection. Numerical simulation tools are largely used in order to design sensors, understand the signals collected during the measurements process and to provide a support in expertise. This work has been accomplished inside CEA LIST in collaboration with L2S-Supélec. It is also a part of the CIVAMONT 2012 project, with the active participation of MEANDER laboratory members from University of Western Macedonia (Greece) and Technological Educational Institute of Western Macedonia (Greece). The main goal of our work has consisted in to developing a semi-analytical modeling approach, devoted to Eddy Current Testing (ECT) of multiple narrow cracks in planar multilayered structures. From the numerical point of view, simulation of multiple narrow cracks problems is a difficult task for classical methods, like for example the Volume Integral Method (VIM) or the Finite Element Method (FEM). The main issues reside in geometrical characteristics of narrow crack themselves. Indeed, a narrow crack presents a small opening as well as complex profile and a complex shape, with possible electrical contacts inside it. All these features increase enormously, with classical methods, the difficulty to simulate in rapid and/or precise way problems involving narrow cracks. We have tackled the narrow crack issue by developing a Boundary Element Method (BEM) dedicated to ECT signal modeling, starting from an approach presented in literature. Then, we have extended its capability to more realistic and challenging cases, such as the ECT of multilayered structures affected by complex narrow cracks. The principle of this method is to introduce additional assumptions, leading to the description of the crack perturbation as the effect of a dipole distribution, oriented toward the crack opening. Numerically speaking, such a description makes it possible to largely reduce, compared to the VIM, the number of unknowns that one needs to properly solve the problem. A particular attention has been devoted to the analytical formulation, in order to achieve generality, accuracy and efficiency. A precise derivation of the spectral-domain Dyadic Green Function (DGF) associated to our problem has first been developed. In this work, analytical expressions of the spectral-domain DGF have been obtained via the Discrete Complex Image Method (DCIM). Then, an accurate approximation of the spectral-domain DGF has been achieved via the Generalized Pencil of Function (GPOF) method. Therefore, the closed-form of the spectral-domain DGF, expressed under the form of Sommerfeld Integrals (SIs), has been calculated analytically. Finally, the integral equation(s) associate to the electromagnetic problem is solved by applying the Method of Moments (MoM).Validations with respect to experiments and commercial simulation software have been performed to test the model. A large set of configurations have been chosen in order to address realistic configurations involving multiple narrow cracks embedded in different layers of a given multilayered structure. The model proposed has shown its promising performance in terms of computational time compared with the VIM and the FEM. Moreover, a very good agreement with respect to the experimental data has always been observed. In the last and very recent part of our work, a coupled approach between BEM and VIM has been studied and developed in order to address, in a efficient way, problems where narrow cracks appear in the vicinity of with volumetric flaws (for example the simulation of fastener sites inspections). Comparisons with experimental measures have shown that the coupled approach is capable to achieve, overall, better results than the VIM and saves a lot of computational time.

A pesquisa realizada tratou do estudo de modelos de estimação da relação ar-combustível e de identificação do tipo de combustível usando o sinal da pressão no cilindro em um motor quatro tempos automotivo, alimentado com gasolina brasileira tipo C, etanol e misturas destes combustíveis. Foi montada uma bancada dinamométrica para realização de testes em um motor originalmente projetado para operar com etanol e que possui relação de compressão de 13,44:1. Durante os testes do motor foram coletados dados referentes às variáveis de desempenho e emissões de gases de exaustão. Os dados coletados em plena carga foram analisados utilizando parâmetros estatísticos e confrontados com os resultados esperados segundo a literatura. As variáveis independentes disponibilizadas nos testes do motor foram utilizadas em conjunto com a aplicação do método dos momentos e da razão de pressões no sinal da pressão no cilindro para o desenvolvimento de novos modelos de estimação da relação ar-combustível e de identificação do tipo de combustível. Os modelos obtidos na presente pesquisa mostraram-se capazes de estimar a relação ar-combustível, sendo sensíveis à variação da composição do combustível nesta estimativa, e de identificar o tipo de combustível utilizado no motor. / This research addressed the study of models for estimating the air-fuel ratio and identifying the type of fuel by in-cylinder pressure signal in a four stroke automotive engine fueled with Brazilian gasoline C type, ethanol, and blends of these fuels. A dynamometer was assembled for tests in an engine originally designed to operate with ethanol and with a 13.44:1 compression ratio. During the engine tests, data were collected related to the performance and exhaustion gas emission variables. Data collected at full load were analyzed using statistical parameters and compared with the expected results according to the literature. The independent variables provided by the engine tests were used together with application of the method of moments and the pressure ratio for in-cylinder pressure in order to develop new models for estimating the air-fuel ratio and to identify the fuel type. The models obtained in this research proved to be capable of estimating the air-fuel ratio, being sensitive to the variation in the type of fuel used in such estimations, and of identifying the type of fuel used in the engine.

La présente thèse contribue à la littérature sur trois principaux axes de recherche relatifs à la structure du capital: les déterminants de la structure du capital, la profitabilité et la demande de travail. (i) Le fondement théorique des déterminants de la structure du capital montre qu’il existe trois modèles qui peuvent expliquer la structure du capital: la théorie de ratio optimal d’endettement, la théorie hiérarchique de financement et récemment la théorie de market timing. De plus, l’évaluation empirique montre un effet positif des coûts d’ajustement et de la garantie. Par contre, l’opportunité de croissance, l’impôt non lié à la dette et la rentabilité sont corrélés de façon négative avec l’endettement. (ii) L’impact de la structure du capital sur la profitabilité peut être expliqué par trois théories essentielles: la théorie du signal, l’influence de la fiscalité et la théorie de l’agence. L’analyse empirique a permis de distinguer trois groupes différents de secteurs: pour le premier groupe, la structure du capital n’a aucune incidence sur la profitabilité. Le deuxième, c’est le groupe où l’endettement affecte négativement la profitabilité de manière linéaire. Le dernier groupe se caractérise par la présence d’un effet négatif de façon linéaire et non linéaire (iii) Théoriquement, un impact négatif de la structure du capital sur la demande de travail est prévu. L’application empirique montre une hétérogénéité des comportements entre les secteurs en ce qui concerne l’effet de l’endettement sur la demande de travail, donc, il existe aussi trois groupes différents de secteurs (pas d’effet, effet négatif linéaire et effet négatif linéaire et non linéaire). De plus, la magnitude de l’effet de l’endettement sur la demande de travail et sur la profitabilité dépend, non seulement du secteur, mais aussi de la taille d’entreprise. / This thesis contributes to the literature in three main areas of research about capital structure: the determinants of capital structure, the profitability and the labour demand. (i) The theoretical basis of the determinants of capital structure shows that there are three models that explains the capital structure: Trade-Off theory, Pecking Order theory and Market Timing theory. Further, the empirical evaluation shows a positive effect of the adjustment costs and the tangibility. On the other hand, growth opportunity, non-debt tax shield and profitability are negatively correlated with debt. (ii) The impact of capital structure on profitability can be explained by three essential theories: signal theory, tax theory and the agency costs theory. The empirical analysis allowed to distinguish three different groups of sectors: for the first group, the capital structure has no impact on profitability. The second, it is the group where the debt affects negatively the profitability in a linear way. The last group is characterized by the presence of a negative effect in a linear and nonlinear way. (iii) Theoretically, a negative impact of the capital structure on labour demand is expected. The empirical application shows heterogeneity of behavior between sectors regarding the impact of debt on the demand for labor; therefore, there are three different groups of sectors (i.e. no effect, negative linear effect, and linear and non linear negative effect). Furthermore, the magnitude of the effect of debt on the labour demand and on the profitability depends not only of the sector, but also of the size of company.

In this dissertation, a Method of Moments (MoM) Volume Integral Equation (VIE)-based modeling approach suitable for a patch or slot antenna on a thin finite dielectric substrate is developed and validated. Two new key features of this method are the use of proper dielectric basis functions and proper VIE conditioning, close to the metal surface, where the surface boundary condition of the zero tangential-component must be extended into adjacent tetrahedra. The extended boundary condition is the exact result for the piecewise-constant dielectric basis functions. The latter operation allows one to achieve a good accuracy with one layer of tetrahedra for a thin dielectric substrate and thereby greatly reduces computational cost. The use of low-order basis functions also implies the use of low-order integration schemes and faster filling of the impedance matrix. For some common patch/slot antennas, the VIE-based modeling approach is found to give an error of about 1% or less in the resonant frequency for one-layer tetrahedral meshes with a relatively small number of unknowns. This error is obtained by comparison with fine finite- element method (FEM) simulations, or with measurements, or with the analytical mode matching approach. Hence it is competitive with both the method of moments surface integral equation approach and with the FEM approach for the printed antennas on thin dielectric substrates. Along with the MoM development, the dissertation also presents the models and design procedures for a number of practical antenna configurations. They in particular include: i. a compact linearly polarized broadband planar inverted-F antenna (PIFA); ii. a circularly polarized turnstile bowtie antenna. Both the antennas are designed to operate in the low UHF band and used for indoor positioning/indoor geolocation.