Thesis (M.S.) -- Worcester Polytechnic Institute. / Keywords: sensor testing; glottal waveform; speech processing. Includes bibliographical references (p. 97-102).

La télémétrie biomédicale et l’interfaçage neuronal à base de dispositifs miniatures et autonomes sans fil constituent de nouvelles applications en émergence. Elles visent à répondre à de nombreux enjeux y compris dans les domaines de la santé, du sport et bien être, ou encore de la sécurité au travail et de la défense. Parmi les applications typiques de biotélémétrie, nous pouvons citer le monitoring de certains paramètres physiologiques : température corporelle, pression artérielle, rythme cardiaque, taux de glucose et d’anticorps, détection d’agents chimiques, etc. En ce qui concerne l’interfaçage neuronal, il permet de restaurer les informations sensorielles, d’aider à la réadaptation des amputés, des personnes atteintes de paralysie ou des patients atteints de maladies neurodégénératives. L’objectif principal de cette thèse est de contribuer au développement de dispositifs miniaturisés et communicants pour le monitoring, en continu, de variables physiologiques d’humains ainsi que d’animaux. Ces dispositifs innovants nécessitent un système de communication fiable. Plus particulièrement, il s’agit d’analyser le milieu de propagation à l’intérieur des tissus biologiques et de développer des antennes miniatures innovantes ainsi que des méthodes pour leur analyse et leur caractérisation. Le verrou majeur concerne le rendement des antennes miniatures. Les effets de forte hétérogénéité, dispersion, pertes très élevées des milieux biologiques et les contraintes de miniaturisation et d’intégration dans des dispositifs in-body limitent la portée des systèmes existants à quelques dizaines de centimètres. Tout d’abord, des outils spécifiques de modélisation et d’optimisation ont été développés en collaboration avec l’Université de Bohème de l’Ouest. Ces outils sont indispensables pour l’analyse des composants de systèmes antennaires complexes : le code Agros2D (CAO interne) utilise des méthodes entièrement adaptatives. Cette approche permet de réduire la complexité d’optimisation des antennes in-body jusqu’un seul dégrée de liberté. Puis, la limite fondamentale de rendement des antennes pour les applications in-body a été définie ; les liens entre cette limite et la taille de l’antenne, sa fréquence de fonctionnement, la polarisation et les matériaux utilisés (dont hypothétiques) ont été quantifiés pour la première fois. Ce travail fondamental a d’abord pour objectif l’optimisation des performances de l’antenne actuelle de la capsule e-Celsius de l’entreprise BodyCAP pour accroître la portée de la gélule, en prenant en compte les caractéristiques des matériaux et le milieu de propagation que constituent les tissus biologiques. Dans cette étape on inclut également la fabrication des prototypes de gélules télémétriques ainsi que leurs mesures d’impédance. L’antenne optimisée a une portée trois fois plus importante que celle actuelle tout en occupant le même volume. En utilisant ces principes de conception, nous avons développé et caractérisé une antenne à 434 MHz adaptée à une large gamme d'applications in-body. Des dimensions ultra-miniatures, une robustesse et un rendement accrus permettent de l'utiliser à la fois pour des applications des capsules à implanter et à avaler. Enfin, en développant davantage les méthodes de conception et d’optimisation, nous avons conçu une antenne double-bande. Ayant la même robustesse que son équivalent actuel mono-bande, elle présente également un rendement encore plus élevé, permettant ainsi de fonctionner au-delà de 10 m. La caractéristique double-bande permet de concevoir les dispositifs in-body rechargeables sans fil dans le corps. Les antennes proposées contribuent au développement ultérieur d'une nouvelle génération de dispositifs miniatures in-body qui impliquent une intégration complexe et dense des capteurs, de la logique et de la source d'alimentation. / Emerging wireless biotelemetry using miniature implantable, ingestible or injectable (in-body) devices allows continuously monitor and yield human or animal physiological parameters while maintaining mobility and quality of life. Recent advances in microelectromechanical systems and microfluidics—along with ongoing miniaturization of electronics—have empowered numerous innovations in biotelemetry devices, creating new applications in medicine, clinical research, wellness, and defense. Among the typical applications, I can mention, for example, the monitoring of physiological variables: body temperature, blood pressure, heart rate, detection of antibodies, chemical, or biological agents. Biotelemetry devices require a reliable communication system: robust, efficient, and versatile. Improving the transmission range of miniature in-body devices remains a major challenge: for the time being, they are able to operate only up to a few meters. Among the main issues to face are low radiation efficiencies (< 0.1%), antenna impedance detuning, and strong coupling to lossy and dispersive biological tissues. Thus, the main goal of the thesis is to conduct a multi-disciplinary study on development, optimization and characterization of antennas for in-body biotelemetry devices. After state-of-the-art and the context, I start with the development on both physical and numerical approaches to account for the effect of human tissues on the antenna. I propose the methodology to achieve given electromagnetic properties at a given frequency based on the full factorial experiment and surface response optimization. In addition, I describe the spherical physical phantom for the far-field characterization along with a combination of feed decoupling techniques. I proceed by reviewing the trough-body propagation mechanisms and deriving the optimal frequency for the in-body devices. I formulate the problem using four phantoms (homogeneous and heterogeneous) and perform full-wave analysis using an in-house hp-FEM code Agros 2D. Next, I study the existing antenna used by the BodyCap Company for its e-Celsius capsule and the ways on how to improve its operating range and robustness under strict integration and material constraints. The mechanisms of antenna–body coupling are analyzed and the found solution improves the antenna IEEE gain by 11 dBi (the operating range is at least tripled). The existing matching circuit and balun are optimized too for the given application reducing its size from eleven to seven discrete elements. In the following chapters, I continue studying the decoupling of antennas from a body using specific microstrip designs and dielectric loading via capsule shell. By applying the developed approaches, a high robustness and radiation efficiency can be achieved. At first, I develop a proof-of-concept antenna that demonstrates that the perfect matching (detuning immunity) is achievable for the operation within all human tissues. Based on these results, I develop a miniature and versatile biotelemetry platform: a 17 mm x 7 mm alumina capsule containing a conformal 434 MHz antenna. The antenna is well matched to 50 Ohm within the majority of human tissues and operates with an arbitrary device circuitry. Like this, one can use it ''as is,'' applying it for a wide range of in-body applications. Then, I develop a low profile conformal dual-band antenna operating in 434 MHz and 2.45 GHz bands. Such antenna can integrate both data transmission and wireless powering functionality increasing the available space inside an in-body device and increasing its scope of applications. Finally, I present the perspective developments including in-body sensing methodology. The obtained results contributes to further development of a new generation of miniature in-body devices that involve complex and dense integration of sensors, logic, and power sources.

<p> Mechanical gears can be as small as those in traditional mechanical watches or as large as those in mechanical marine turbines. They can be seen in almost all transportation tools, for example, bicycles, cars, trains and airplanes. Though they have been studied and refined for centuries, there are still some disadvantages. For instance, mechanical gears often create a large amount of noise and vibration. They require regular maintenance as the gears need to be lubricated. In addition, if a gear is overloaded it can catastrophically fail. </p><p> Unlike conventional mechanical gears, magnetic gears can create speed change without physical contact. The force between magnetic gears is not created by geared teeth but instead, it is created by the magnetic poles. There will be a small air gap between different rotors which means no lubricant or maintenance is required. When one rotor rotates, the other one will also rotate driven by magnetic forces. Since the permanent magnets are used, the forces will not recede or disappear as long as the magnets are not overheated. If overloaded, a magnetic gearbox will simply slip poles. Therefore, in many applications, magnetic gears can be more reliable, efficient and safer. </p><p> The goal of this research has been to investigate the torque capabilities of high gear ratio magnetic geared devices. The performance has been investigated based on the gear ratio and torque density. </p><p> A new type of flux focusing cycloidal magnetic gear (MG) was investigated that could operate at a gear ratio of -25:1. The flux focusing topology was used because it increased the air gap flux density and therefore enabled a higher torque density. Using 2-D finite element analysis (FEA), the volume torque density was calculated to be 291 Nm/L with an outer diameter of 0.228 m. A -20:1 prototype cycloidal magnetic gear was designed. It had a calculated volumetric torque density of 260 Nm/L. The cycloidal magnetic gear was mechanically difficult to construct and therefore only the inner rotor of the cycloidal magnetic gear was constructed. In addition, the eccentric air gap will cause bearing failure. </p><p> To achieve an even higher gear ratio, a nested multistage magnetic gear (MSMG) was designed with a 2-D FEA calculated torque density of 424 Nm/L. The desired gear ratio was 59:1 so that the performance could be compared with a Sumitomo mechanical gearbox which had the same gear ratio. In order to minimize the rotor torque ripple, the harmonic field interaction between the inner stage and the outer stage of the magnetic gear had to be mitigated. A unique flux concentration Halbach rotor structure was proposed. The rotor structure was shown to shield the outer rotor from the inner rotor harmonics. The nested multistage magnetic gear contains 4 rotors and complex mechanical structure. In order to provide sufficient mechanical support, the mechanical axial length had to be very large and this negated many of the benefits of using the nested coaxial rotor structure. </p><p> A two-stage series connected 59:1 gear ratio multistage magnetic gear was also designed for wind turbines. The 6.45:1 first stage magnetic gearbox had a diameter of 0.633 m and the 3-D FEA calculated peak torque and torque density were 4.79 kNm and 159 Nm/L. The measured torque and torque density were 4.25 kNm and 141 Nm/L. While the 9.14:1 second stage magnetic gearbox had a diameter of 0.507 m and the 3-D FEA calculated peak torque and torque density were 1.04 kNm and 136 Nm/L, respectively. The series connected multistage magnetic gear had the advantage of being more modular as different gear ratios can be obtained by changing the pole pair combinations for one of the series connected magnetic gears. </p><p> A two-stage series connected 59:1 gear ratio multistage magnetic gear was also designed for a hydropower application. Non-magnetic rods were used to reduce the losses and the mechanical deflection. The 2-D calculated torque density for the stage 1 magnetic gear was 371 Nm/L. And the 2-D calculated torque density was 344 Nm/L for the stage 2 magnetic gear. A stator was also designed that was inserted inside the stage 2 magnetic gear. In order to try to reduce the torque ripple, the stator had a fractional winding distribution with 1.25 slots/pole/phase. (Abstract shortened by ProQuest.) </p><p>

abstract: A new loop configuration capable of reducing power radiation magnitudes lower than conventional loops has been developed. This configuration is demonstrated for the case of two coaxial loops of 0.1 meter radius coupled via the magnetic reactive field. Utilizing electromagnetism theory, techniques from antenna design and a new near field design initiative, the ability to design a magnetic field has been investigated by using a full wave simulation tool. The method for realization is initiated from first order physics model, ADS and onto a full wave situation tool for the case of a non-radiating helical loop. The exploration into the design of a magnetic near field while mitigating radiation power is demonstrated using an real number of twists to form a helical wire loop while biasing the integer twisted loop in a non-conventional moebius termination. The helix loop setup as a moebius loop convention can also be expressed as a shorted antenna scheme. The 0.1 meter radius helix antenna is biased with a 1MHz frequency that categorized the antenna loop as electrically small. It is then demonstrated that helical configuration reduces the electric field and mitigates power radiation into the far field. In order to compare the radiated power reduction performance of the helical loop a shielded loop is used as a baseline for comparison. The shielded loop system of the same geometric size and frequency is shown to have power radiation expressed as -46.1 dBm. The power radiated mitigation method of the helix loop reduces the power radiated from the two loop system down to -98.72 dBm. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015

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Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第17511号 / 工博第3670号 / 新制||工||1558(附属図書館) / 30277 / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 西脇 眞二, 教授 田畑 修, 教授 蓮尾 昌裕 / 学位規則第4条第1項該当

This thesis presents optical characterizations of interfaces in ferromagnetic heterostructures and thin films used for spin polarized electronic devices. In these experiments, femtosecond laser spectroscopies are exploited to investigate the interface magnetization reversal, spin precession, and band offset, which are crucial in determining the performances of spintronic devices.;First, magnetization-induced second-harmonic-generation (MSHG) is applied to study interface magnetism in a hybrid structure containing a noncentrosymmetric semiconductor---Fe/AlGaAs. The reversal process of Fe interface layer magnetization is compared with the bulk magnetization reversal. In Fe/AlGaAs (001), the interface magnetization is found to be decoupled from the bulk magnetization based on the different switching characteristics---single step switching occurs at the interface layer, whereas two-jump switching occurs in the bulk. In contrast, the interface layer in Fe/AlGaAs (110) is rigidly coupled with the bulk Fe, indicating a strong impact of electronic structure on the magnetic interaction despite the same chemical composition. Furthermore, a time-resolved MSHG study demonstrates a coherent interface magnetization precession in Fe/AlGaAs (001), implying the feasibility of fast precessional control of interfacial spin. The interface magnetization precession exhibits a higher frequency and opposite phase for a given applied field compared to the bulk magnetization precession.;Second, uniform magnetization precession in the Lac0.67Ca 0.33MnO3 (LCMO) and La0.67Sr0.33MnO 3 (LSMO) films grown on different substrates are investigated by time-resolved magneto-optic Kerr effect. The parameters of magnetic anisotropy are determined from the field dependence of the precession frequency. The strain-free LCMO films grown on NdGaO3 exhibit a uniaxial in-plane anisotropy induced by the tilting of the oxygen octahedra in NdGaO3 An easy-plane magnetic anisotropy is found in the tensile-strained films grown on SrTiO 3, whereas the compressive-strained film grown on LaAlO3 exhibits an easy normal-to-plane axis.;Third, a table-top internal photoemission system is developed to measure the band offsets across semiconductor heterointerfaces by utilizing an optical parametric amplifier as the bright light source. The conduction band offsets DeltaE c = 660 meV and 530 meV at the CdCr2Se4-GaAs and CdCrZSe4-ZnSe interfaces are determined from the threshold energies of the photocurrent spectrum. The band offset is shown to be reduced by engineering the interface bonding and stoichiometry.

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This thesis presents ultrafast laser pump-probe differential transmission experiments on epitaxial CrO2 (110). The experiments were conducted at the wavelengths of 600 nm, 800 nm and 1200 nm, corresponding to the transition energies of 2 eV, 1.5 eV and 1 eV respectively. The wavelength dependent results, comparing with linear optical absorption, revealed the electronic structure of the material. The experimental results also showed polarization dependence of the probe beams. This is attributed to the electronic orbital anisotropy.;Temperature dependence was observed in the pump-probe experiments. The ultrafast transmission data show similar temperature dependence as ultrafast MOKE (Magneto-Optical Kerr Effect) data. A critical change of transient transmission was observed at the Curie temperature of 386 K. Spin decay processes are discussed based on these temperature dependent time resolved data.;Ultrafast MOKE experiments are also presented. Oscillations of the time resolved MOKE signal corresponding to the ferromagnetic resonance were observed. The magnetic anisotropies of the CrO2 thin film were studied by analyzing these oscillations. A computer program was developed for data analysis.;A general discussion of the relation between magnetic properties and the electronic properties of the material is delivered.