Antennas play a crucial role in communication systems since they are the transmitting/receiving elements that transition information from guided transmission to open-space propagation. Antennas are used in many different applications such as aerospace communications, mobile phones, TVs and radios. Since the dimensions of antennas are usually physically proportional to the wavelength at their operating frequencies, it is important to develop large antennas and arrays that can be stowed compactly and easily deployed. Also, it is important to minimize the number of antennas on a platform by developing multifunctional antennas. The first aim of this research is to develop new deployable, collapsible, light-weight and robust reconfigurable antennas based on origami principles. All designs will be validated through simulations and measurements. Paper as well as other substrates, such as, Kapton and fabric, will be used to develop our origami antennas. The second aim of this research is to derive integrated analytical and simulation models for designing optimal origami antennas for various applications, such as, satellite or ground communications. This dissertation presents research on origami antennas for novel reconfigurable communication systems. New designs of reconfigurable monofilar, bifilar and quadrifilar antennas based on origami cylinders are developed and validated. Novel fabrication methods of origami antennas are presented with detailed geometrical analysis. Furthermore, multi-radii origami antennas are proposed, analyzed, fabricated and validated and they exhibit improved circular polarization performance and wide bandwidths. An actuation mechanism is designed for these antennas. For the first time, a low-cost and lightweight reconfigurable origami antenna with a reflector is developed here. In addition, an array is developed using this antenna as its element. Finally, a kresling conical spiral antenna and a spherical helical antenna are designed with mode reconfigurabilities.

Among all thermal energy storage (TES) systems, latent heat thermal energy storage (LHTES) attracts high interest due to its high energy density and high exergetic efficiency. Due to the high enthalpy of fusion and low cost, inorganic salts are becoming popular as phase change materials and are used as the storage media in LHTES systems. The main drawbacks for the inorganic salts are their low thermal conductivity and high reactivity above 500°C. Therefore, designing a cost-effective containment at these conditions with longevity is a challenge. Macro-encapsulation of the PCM is one way to solve both the PCM containment issue as well as the low thermal conductivity problem. However, finding a practically viable encapsulation technique is a challenge especially for temperatures above 500°C. In the present study, encapsulation techniques were investigated for two temperature ranges; 500°C – 600°C and 600°C above. Metallic encapsulation was adopted for the 500°C – 600°C temperature. Commercially available, low-cost carbon-steel tubes were used, and the encapsulation shape was cylindrical. A 200µm coating of Ni was applied to strengthen the corrosion resistance. For temperatures above 600°C, a novel approach involving the use of ceramic materials was investigated for encapsulating chloride based PCMs. Low-cost ceramics with excellent thermal and chemical stability under molten-salt conditions were identified as the encapsulants. The influence of sintering temperature on the reactivity of feldspar, ball clay, kaolin and the mixture thereof with molten sodium chloride was investigated. The results were used to develop an optimum ceramic capsule fabrication procedure, using a green ceramic body followed by sintering at 1190°C. An innovative sealing process of in-situ layered eutectic formation was introduced. Sealing was performed at a temperature above the eutectic melting point of the salt mixture but below the individual melting points of each salt. The fabricated capsule survived more than 500 thermal cycles without showing degradation in its thermo-physical properties. Alumina (99%) based capsule containing NaCl-KCl was tested successfully for 1000 thermal cycles with a PCM weight loss of less than 5%. A lab-scale setup was designed and constructed to test an industry scalable LHTES system suitable for supplementing heat to a steam-powered cycle. Metallic cylindrical capsules were used with a eutectic of sodium sulfate (Na2SO4) and potassium chloride (KCl), which melts at 515°C, as the PCM for energy storage. This system was modeled and validated with experimental measurements. The calculated ratio of exergy to energy efficiency was around 89% (for 380-535°C). Flow irregularities were found due to a bend in the flow channel. Therefore, flow conditioners were investigated. A modified system with the flow conditioners and radiation shields showed 98% exergy to energy efficiency ratio (for 495-535°C). The overall efficiency of the system, however, was found to be low due to the heat losses from the storage tank. Finally, a novel design of a TES system using spherical capsules is proposed with additional enhancement gained from the experimental work on the lab-scale LHTES system. The innovation of this design lies in the manufacturing process to forms multiple spherical capsules using sheet metals. The adoptability of this technique for higher or lower temperature LHTES applications depends on the properties of the selected sheet metal. Any formable sheet metal can be used depending on the compatibility with PCM and HTF.

Capital investment reduction, exergetic efficiency improvement and material compatibility issues have been identified as the primary techno-economic challenges associated, with the near-term development and deployment of thermal energy storage (TES) in commercial-scale concentrating solar power plants. Three TES techniques have gained attention in the solar energy research community as possible candidates to reduce the cost of solar-generated electricity, namely (1) sensible heat storage, (2) latent heat (tank filled with phase change materials (PCMs) or encapsulated PCMs packed in a vessel) and (3) thermochemical storage. Among these the PCM macro-encapsulation approach seems to be one of the most-promising methods because of its potential to develop more effective energy exchange, reduce the cost associated with the tank and increase the exergetic efficiency. However, the technological barriers to this approach arise from the encapsulation techniques used to create a durable capsule, as well as an assessment of the fundamental thermal energy transport mechanisms during the phase change. A comprehensive study of the energy exchange interactions and induced fluid flow during melting and solidification of a confined storage medium is reported in this investigation from a theoretical perspective. Emphasis has been placed on the thermal characterization of a single constituent storage module rather than an entire storage system, in order to, precisely capture the energy exchange contributions of all the fundamental heat transfer mechanisms during the phase change processes. Two-dimensional, axisymmetric, transient equations for mass, momentum and energy conservation have been solved numerically by the finite volume scheme. Initially, the interaction between conduction and natural convection energy transport modes, in the absence of thermal radiation, is investigated for solar power applications at temperatures (300 - 400°). Later, participating thermal radiation within the storage medium has been included in order to extend the conventional natural convection-dominated model and to analyze its influence on the melting and freezing dynamics at elevated temperatures (800 - 850°). A parametric analysis has been performed in order to ascertain the effects of the controlling parameters on the melting/freezing rates and the total and radiative heat transfer rates at the inner surface of the shell. The results show that the presence of thermal radiation enhances the melting and solidification processes. Finally, a simplified model of the packed bed heat exchanger with multiple spherical capsules filled with the storage medium and positioned in a vertical array inside a cylindrical container is analyzed and numerically solved. The influence of the inlet mass flow rate, inner shell surface emissivity and PCM attenuation coefficient on the melting dynamics of the PCM has been analyzed and quantified.

The determination of the figure of the Earth and its gravity field has long relied on methodologies that approximate the Earth by a sphere, but this level of accuracy is no longer adequate for many applications, due to the advent of new and advanced measurement techniques. New, practical and highly accurate methodologies for gravity field modelling that describe the Earth as an oblate ellipsoid of revolution are therefore required. The foundation for these methodologies is formed by solutions to ellipsoidal geodetic boundary-value problems. In this thesis, new solutions to the ellipsoidal Dirichlet, Neumann and second-order boundary-value problems, as well as the fixed- and free-geodetic boundary-value problems, are derived. These solutions do not rely on any spherical approximation, but are nevertheless completely based on a simple spherical harmonic expansion of the function that is to be determined. They rely on new relations among spherical harmonic base functions. In the new solutions, solid spherical harmonic coefficients of the desired function are expressed as a weighted summation over surface spherical harmonic coefficients of the data on the ellipsoidal boundary, or alternatively as a weighted summation over coefficients that are computed under the approximation that the boundary is a sphere. / Specific applications of the new solutions are the computation of geopotential coefficients from terrestrial gravimetric data and local or regional gravimetric geoid determination. Numerical closed-loop simulations have shown that the accuracy of geopotential coefficients obtained with the new methods is significantly higher than the accuracy of existing methods that use the spherical harmonic framework. The ellipsoidal corrections to a Stokesian geoid determination computed from the new solutions show strong agreement with existing solutions. In addition, the importance of the choice of the reference sphere radius in Stokes's formula and its effect on the magnitude and spectral sensitivity of the ellipsoidal corrections are pointed out.

A spherical wave AVO response is investigated by measuring ultrasonic reflection amplitudes from a water/Plexiglas interface. The experimental results show substantial deviation from the plane-wave reflection coefficients at large angles. However there is an excellent agreement between experimental data and full-wave numerical simulations performed with the reflectivity algorithm. By comparing the spherical-wave AVO response, modeled with different frequencies, to the plane-wave response, I show that the differences between the two are of such magnitude that three-term AVO inversion based on AVA curvature can be erroneous. I then propose an alternative approach to use critical angle information extracted from AVA curves, and show that this leads to a significant improvement of the estimation of elastic parameters. Azimuthal variation of the AVO response of a vertically fractured model also shows good agreement with anisotropic reflectivity simulations, especially in terms of extracted critical angles which indicated that (1) reflection measurements are consistent with the transmission measurements; (2) the anisotropic numerical simulation algorithm is capable of simulating subtle azimuthal variations with excellent accuracy; (3) the methodology of picking critical angles on seismograms using the inflection point is robust, even in the presence of random and/or systematic noise.

We establish a strong connection between buildings and Hecke algebras through the study of two algebras of averaging operators on buildings. To each locally finite regular building we associate a natural algebra B of chamber set averaging operators, and when the building is affine we also define an algebra A of vertex set averaging operators. In the affine case, it is shown how the building gives rise to a combinatorial and geometric description of the Macdonald spherical functions, and of the centers of affine Hecke algebras. The algebra homomorphisms from A into the complex numbers are studied, and some associated spherical harmonic analysis is conducted. This generalises known results concerning spherical functions on groups of p-adic type. As an application of this spherical harmonic analysis we prove a local limit theorem for radial random walks on affine buildings.

Depuis ses débuts, la conception des convertisseurs électromécaniques se limitait à l'optimisation, par l'électrotechnicien, de la conversion d'énergie électrique en énergie mécanique. Cette énergie, alors fournie sous la forme quasi exclusive d'un mouvement à un seul degré de liberté, le plus souvent rotatif, devait ensuite être adaptée, par les mécaniciens, aux besoins du système à actionner. Aujourd'hui, grâce aux évolutions récentes dans des domaines aussi variés que l'électronique de puissance, l'informatique ou encore la conception et la fabrication assistées par ordinateur, il est devenu possible de concevoir de nouveaux actionneurs directement en fonction des besoins des applications auxquelles ils sont destinés. Ainsi, des actionneurs pouvant posséder plusieurs degrés de liberté, tant en rotation qu'en translation, ont été développés. Dans ce contexte, cette thèse poursuit deux objectifs. Le premier est de proposer une démarche de conception intégrant au mieux les aspects électriques et mécaniques de systèmes électromécaniques tels que ces nouveaux actionneurs. Plus largement, elle a pour vocation de s'appliquer à tous types de problèmes multidisciplinaires où la prise en compte des différentes disciplines et de leurs interactions est indispensable pour assurer les performances globales du produit final. Plus particulièrement, elle est adaptée aux cas de recherches qui, contrairement aux cas de développements, font parfois intervenir des concepts mal maîtrisés. Le second objectif est d'appliquer cette démarche à la conception d'un actionneur électrique dont le rotor, de forme sphérique, est actionné avec un débattement illimité selon deux des trois degrés de liberté qu'il possède en rotation. Suivant les différentes étapes constituant cette démarche, divers concepts de solution sont d'abord générés, tant pour les aspects électriques d'actionnement que pour les aspects mécaniques de guidage. Ces concepts sont ensuite caractérisés, via une série de modélisations et d'expérimentations, avant d'être combinés en vue de produire une solution globale, dimensionnée, fabriquée et validée sur un banc d'essai. / From the outset, the design of electromechanical converters was limited to the optimization, by electrical engineers, of the conversion of electrical energy to mechanical energy. The latter was at that time nearly exclusively provided under the form of single degree of freedom motion, more often rotary, and had to be adapted, by mechanical engineers, to the needs of the system to be actuated. Today, thanks to recent evolutions in fields as various as power electronics, computer capabilities or computer-aided design and manufacturing (CAD-CAM), it has become possible to design new actuators by taking directly into account the needs of the applications they are intended for. As a result, actuators with several degrees of freedom, both in rotation and in translation, have been developed. Within this context, this thesis pursues two objectives. The first consists in proposing a new design method integrating as best as possible the electrical and mechanical aspects of electromechanical systems such as these new actuators. More broadly, its vocation is to be applicable to all multidisciplinary problems where taking into account each discipline and their interactions are necessary to ensure the global performances of the final product. More particularly, this method is adapted to the case of researches that, contrary to the case of other developments, sometimes includes badly mastered concepts. The second aim is to apply this approach to the design of an electrical motor with a spherical rotor actuated, with an unlimited angular range, along two of the three degrees of freedom it possesses in rotation. Following the basic steps involved in this approach, various solution concepts were first generated both for the electrical actuation aspects and the mechanical guiding aspects. These concepts were then characterized, via a number of modeling and experimentation phases, before being combined in order to obtain a global solution, which was then sized, manufactured and validated on a test bench.

The thesis deals with finite element method simulations of the two-degree of freedom spherical induction actuator performed using the 2D and 3D models. In some cases non-linear magnetization curves, rotor movement and existence of higher harmonics are taken into account. The evolution of the model leading to its simplification is presented. Several rotor structures are tested, namely the one-layer, two-layers and two-layers-with-teeth rotor. The study of some rotor parameters, i.e. teeth number and size, external and internal layer thickness, in order to improve the actuator electromechanical conversion and reduce the torque ripple is performed. The influence of the rotor teeth geometrical form on the electromechanical conversion is shown. General actuator parameters such as the airgap, source current and parameters of the magnetic material are verified as well. Finally the superiority of the two-layers-with-teeth rotor structure over the one-layer and two-layers structures is confirmed.

The purpose of this study is to present the biographical data and major accomplishments of craftsman François Louis (b. 1954, Belgium) and offer insight into Louis' creative process as evidenced by his technical theories and musical experiences, in hopes of providing exposure to academics, professionals, and laypersons alike. François Louis is a significant figure in the emerging history of woodwind musical instruments. Despite his late entry into a musical career, Louis quickly caught the attention of world-renown saxophonists with his immaculate and individualistic handmade saxophone mouthpieces. After nearly a decade of mouthpiece production, instrument repair, and saxophone performance, Louis developed a unique ligature and reed to compliment his mouthpieces' features. Louis' invention of the Aulochrome, a polyphonic chromatic double-bodied woodwind instrument, is an instrument of the new millennium. More recently, Louis further improved his ligature and designed a composite material for his hand-finished production mouthpiece, the Spectruoso. Extensive oral history was gathered in interviews with Louis and saxophonists Lovano, Ries, Cisi, and Théberge. Interview details are organized to highlight Louis' biography, inventions, and influence on other artists. Further, the unique capabilities of the Aulochrome are presented through an exploration of Lovano's approach for learning the Aulochrome, as well as a fingering diagram developed by the author.

Fast algorithms for potential evaluation in N-body problems often tend to be extremely abstract and complex. This thesis presents a simple, hierarchical approach to solving the potential evaluation problem in O(n) time. The approach is developed in the field of electrostatics and can be extended to N-body problems in general. Herein, the potential vector is expressed as a product of the potential matrix and the charge vector. The potential matrix itself is a product of component matrices. The potential function satisfies the Laplace equation and is hence expressed as a linear combination of spherical harmonics, which form the general solutions of the Laplace equation. The orthogonality of the spherical harmonics is exploited to reduce execution time. The duality of the various lists in the algorithm is used to reduce storage and computational complexity. A smart tree-construction strategy leads to efficient parallelism at computation intensive stages of the algorithm. The computational complexity of the algorithm is better than that of the Fast Multipole Algorithm, which is one of the fastest contemporary algorithms to solve the potential evaluation problem. Experimental results show that accuracy of the algorithm is comparable to that of the Fast Multipole Algorithm. However, this approach uses some implementation principles from the Fast Multipole Algorithm. Parallel efficiency and scalability of the algorithms are studied by the experiments on IBM p690 multiprocessors.