The work presented in this thesis investigates novel transducer implementations that take advantage of directional sensing and generation of acoustic waves. These transducers are conceived by exploiting a Fourier-based design methodology. The proposed devices find application in the broad field of Structural Health Monitoring (SHM), which is a very active research area devoted to the assessment of the structural integrity of critical components in aerospace, civil and mechanical systems. Among SHM schemes, Guided Waves (GWs) testing has emerged as a prominent option for inspection of plate-like structures using permanently attached piezoelectric transducers. GWs-based methods rely on the generation and sensing of elastic waves to evaluate structural integrity. They offer an effective method to estimate location, severity and type of damage. It is widely acknowledged among the GWs-SHM community that effective monitoring of structural health is facilitated by sensors and actuators designed with ad hoc engineered capabilities. The objective of this research is to design innovative piezoelectric transducers by specifying their electrode patterns in the Fourier domain. Taking advantage of the Fourier framework, transducer design procedures are outlined and tailored to relevant SHM applications, such as (i) directional actuation and sensing of GWs, (ii) simultaneous sensing of multiple strain components with a single device, and (iii) estimation of the location of impact sites on structural components. The proposed devices enable significant reductions in cost, hardware, and power requirements for advanced SHM schemes when compared to current technologies.

Éléments essentiels des systèmes de télécommunication depuis environ trente ans, les dispositifs à ondes élastiques de surface offrent également l'opportunité, de par leur sensibilité aux conditions environnementales et leur caractère passif, de réaliser des capteurs sans-fil autonomes (sans électronique ni source d'énergie embarquées), configuration particulièrement intéressante pour la mesure à haute température. Nos travaux se sont focalisés sur le choix des matériaux pouvant constituer de tels capteurs, au niveau des deux éléments les constituant : le substrat piézoélectrique et les électrodes métalliques. Ces dernières sont généralement constituées de platine, de par l'inertie chimique particulièrement importante de ce métal noble. Nos travaux nous ont permis d'attribuer la dégradation de ces électrodes, généralement observée aux alentours de 700°C, à un phénomène spécifique des films minces, dénommé agglomération, nous conduisant par la suite à envisager et à tester des solutions plus efficaces. En ce qui concerne le substrat, nos efforts ont porté sur la structure bicouche AlN/Saphir, prometteuse pour de telles applications, mais encore peu étudiée. Après l'optimisation des paramètres de dépôt du film mince par pulvérisation réactive magnétron, permettant d'obtenir une couche épitaxiée, nous nous sommes intéressés à la résistance à l'oxydation de l'AlN à haute température dans l'air. L'utilisation croisée de la diffraction des rayons X, de l'ellipsométrie et de la spectroscopie de masse des ions secondaires nous a permis de montrer que l'on peut envisager l'emploi de cette structure bicouche pour les applications visées à des températures allant jusqu'à 700°C / Surface acoustic waves devices are key components of telecommunication systems for more than thirty years or so. Because they are passive and very sensitive to external conditions, they also offer the possibility to make autonomous wireless sensors (electronic-less and battery-less), which could be particularly interesting in high-temperature environments. Our work was focused on the choice of materials allowing the fabrication of such sensors for both parts of the device: piezoelectric substrate and metallic electrodes. The latter are generally made of platinum because of the great chemical inertness of this noble metal. Our work allowed us to attribute their degradation, starting around 700°C on, to a phenomenon called agglomeration which is very specific to thin films. This result led us to consider and test more efficient solutions. Regarding the substrate, we mainly studied AlN/Sapphire bilayer structure, promising for such applications but not really studied yet. After the optimization of the deposition parameters of the thin film, realized by reactive magnetron sputtering, leading to the epitaxial quality, we studied the strength of AlN to oxidation under high temperature in air atmosphere. Results given by X-ray diffraction, ellipsometry and secondary ion mass spectroscopy converged to show that AlN/Sapphire structure is a good candidate for such applications at temperatures up to 700°C

This work presents a new low-temperature fabrication process of metal oxide nanostructures that allows high-aspect ratio zinc oxide (ZnO) and titanium dioxide (TiO2) nanowires and nanotubes to be readily integrated with microelectronic devices for sensor applications. This process relies on a new method of forming a close-packed array of self-assembled high-aspect-ratio nanopores in an anodized aluminum oxide (AAO) template in a thin (2.5 µm) aluminum film deposited on a silicon and lithium niobate substrate (LiNbO3). This technique is in sharp contrast to traditional free-standing thick film methods and the use of an integrated thin aluminum film greatly enhances the utility of such methods. We have demonstrated the method by integrating ZnO nanowires, TiO2 nanowires, and multiwall TiO2 nanotubes onto the metal gate of a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), and the delay line of a surface acoustic wave (SAW) device to form an integrated ChemFET (Chemical Field-Effect Transistor) and a orthogonal frequency coded (OFC) SAW gas sensor. The resulting metal oxide nanostructures of 1-1.7 µm in height and 40-100 nm in diameter offer an increase of up to 220X the surface area over a standard flat metal oxide film for sensing applications. The metal oxide nanostructures were characterized by SEM, EDX, TEM and Hall measurements to verify stoichiometry, crystal structure and electrical properties. Additionally, the electrical response of ChemFETs and OFC SAW gas sensors with ZnO nanowires, TiO2 nanowires, and multiwall TiO2 nanotubes were measured using 5-200 ppm ammonia as a target gas at room temperature (24ºC) showing high sensitivity and reproducible testing results.

A multifunctional strain sensor based on Surface Acoustic Wave (SAW) Orthogonal Frequency Coding (OFC) technology on a Langasite substrate has been investigated. Second order transmission matrix models have been developed and verified. A new parameterizable library of SAW components was created to automate the layout process. Using these new tools, a SAW strain sensor with OFC reflectors was designed, fabricated and tested. The Langasite coefficients of velocity for strain (γS = 1.699) and Temperature (γT = 2.562) were experimentally determined. The strain and temperature characterization of this strain sensor, along with the coefficients of velocity, have been used to demonstrate both the ability to sense strain and the capability for temperature compensation. The temperature-compensated SAW OFC strain sensor has been used to detect anomalous strain conditions that are indicators of fastener failures during structural health monitoring of aircraft panels with and without noise on a NASA fastener failure test stand. The changes in strain that are associated with single fastener failures were measured up to a distance of 80 cm between the sensor and the removed fastener. The SAW OFC strain sensor was demonstrated to act as an impact sensor with and without noise on the fastener failure test stand. The average measured signal to noise ratio (SNR) of 50, is comparable to the 29.1 SNR of an acoustic emission sensor. The simultaneous use of a high pass filter for impact detection, while a low pass filter is used for strain or fastener failure, demonstrates the multifunctional capabilities of the SAW OFC sensor to act as both as a fastener failure detector and as an impact detector.

Based on experimentation with the steam bending of wood to curved shapes, this thesis describes my involvement with three basic aspects of the process. First is the procurement, assimilation, and construction of the equipment and apparatus necessary for the steam bending of wood. Secondly, the determination of certain qualities of particular woods in reference to steam bending is made. This includes: woods easily bent; woods not easily bent; the time required to plasticize stock; and the time required to set curves. Also noted are some of the physical limitations involved in bending stock with steam in the craftsman's studio. Thirdly, steam bent wood is related to furniture design in terms of the craftsman's approach to the design and to the problems inherent in this process.

A recent International Technology Roadmap for Semiconductors (ITRS) report (2.0, 2015 edition) has shown that Moore’s law is unlikely to hold beyond 2028. There is a need for alternate devices to replace CMOS based devices, if further miniaturization and high energy efficiency is desired. The goal of this dissertation is to experimentally demonstrate the feasibility of nanomagnetic memory and logic devices that can be clocked with acoustic waves in an extremely energy efficient manner. While clocking nanomagnetic logic by stressing the magnetostrictive layer of a multiferroic logic element with with an electric field applied across the piezoelectric layer is known to be an extremely energy-efficient clocking scheme, stressing every nanomagnet separately requires individual contacts to each one of them that would necessitate cumbersome lithography. On the other hand, if all nanomagnets are stressed simultaneously with a global voltage, it will eliminate the need for individual contacts, but such a global clock makes the architecture non-pipelined (the next input bit cannot be written till the previous bit has completely propagated through the chain) and therefore, unacceptably slow and error prone. Use of global acoustic wave, that has in-built granularity, would offer the best of both worlds. As the crest and the trough propagate in space with a velocity, nanomagnets that find themselves at a crest are stressed in tension while those in the trough are compressed. All other magnets are relaxed (no stress). Thus, all magnets are not stressed simultaneously but are clocked in a sequentially manner, even though the clocking agent is global. Finally, the acoustic wave energy is distributed over billions of nanomagnets it clocks, which results in an extremely small energy cost per bit per nanomagnet. In summary, acoustic clocking of nanomagnets can lead to extremely energy efficient nanomagnetic computing devices while also eliminating the need for complex lithography. The dissertation work focuses on the following two topics: Acoustic Waves, generated by IDTs fabricated on a piezoelectric lithium niobate substrate, can be utilized to manipulate the magnetization states in elliptical Co nanomagnets. The magnetization switches from its initial single-domain state to a vortex state after SAW stress cycles propagate through the nanomagnets. The vortex states are stable and the magnetization remains in this state until it is ‘reset’ by an external magnetic field. 2. Acoustic Waves can also be utilized to induce 1800 magnetization switching in dipole coupled elliptical Co nanomagnets. The magnetization switches from its initial single-domain ‘up’ state to a single-domain ‘down’ state after SAW tensile/compressive stress cycles propagate through the nanomagnets. The switched state is stable and non-volatile. These results show the effective implementation of a Boolean NOT gate. Ultimately, the advantage of this technology is that it could also perform higher order information processing (not discussed here) while consuming extremely low power. Finally, while we have demonstrated acoustically clocked nanomagnetic memory and logic schemes with Co nanomagnets, materials with higher magnetostriction (such as FeGa) may ultimately improve the switching reliability of such devices. With this in mind we prepared and studied FeGa films using a ferromagnetic resonance (FMR) technique to extract properties of importance to magnetization dynamics in such materials that could have higher magneto elastic coupling than either Co or Ni.

Afin d'étendre la diversité des composants intégrables dans un System in Package (SiP), il apparaît nécessaire de développer l'intégration de composants hétérogènes. Cette étude présente une solution par report avec un scellement en polymère. L'utilisation de ces matériaux entraîne des problèmes de fiabilité thermomécanique. Grâce à un prototype virtuel, il est possible d'évaluer les sollicitations et de comprendre ce comportement de la structure. Cela permet de mieux appréhender les mécanismes de défaillance et d'optimiser la structure avant sa fabrication. Pour démontrer la faisabilité, nous avons utilisé des filtres à ondes acoustiques de surfaces (SAW filters). Nous avons étudié trois types de polymères (BCB, SU8 et TMMF) pour réaliser le scellement et protéger le filtre. Différents tests mécaniques, électriques et de fiabilité ont permis de valider cette solution. Nous avons réalisé un SiP comprenant un tuner et un filtre SAW dans un même boîtier pour de la télévision sur mobile / In the objective to extend the variety of the integrated components inside a System in Packahe (SiP), it is necessary to develop the integration of heterogeneous component. This study presents a flip-chip solution with an adhesive bonding. The use of such materials involves some problems of thermo-mechanical reliability. With virtual prototyping, it is possible to evaluate the strains and to understand the behaviour of the structure. These allow us to know the origin of the failure and to optimize its design before the fabrication. The feasability of the technique is demonstrated with a surface acoustic waves filter (SAW). We study three different types of polymer (BCB, SU-8 and TMMF) for the sealing and for the protection of the active area of the filter. Different tests : mechanical, electrical and reliability validate our solution. We have made a complete SiP composed by a silicon tuner and a SAW filter inside a single package for a television on mobile application

L'excitation et la propagation des ondes de cisaillement dans les dispositifs à ondes acoustiques de surface SAW à base de nitrure d'aluminium, en milieux liquides, nécessitent l'inclinaison de l'axe c dans la structure hexagonale. Le but de cette étude était de déposer des couches minces d'AlN à axe c incliné par la technique de pulvérisation magnétron sans aucune modification du dispositif de pulvérisation, le substrat et la cible n'ayant subi ni inclinaison ni décalage. Il a été possible, par une approche basée seulement sur la variation des paramètres de croissance, de déposer des couches minces piézoélectriques avec un angle d'inclinaison de 13°±2° dans des conditions de haute pression (0.8 Pa) et basse température (300°C). Une couche de SiO2 a été également déposée afin de favoriser la croissance inclinée des grains et par conséquent de celle des colonnes. Les couches déposées présentent une grande homogénéité de l'épaisseur sur 75% d'un substrat de silicium de 3 pouces. Après la détermination des paramètres optimaux de « croissance inclinée », nous avons réalisé un dispositif à onde acoustique de surface fonctionnant en mode de cisaillement avec lequel nous avons démontré la possibilité d'exciter les ondes de cisaillement dans un dispositif de type AlN/Si02/Si à 486.2 MHz avec une vitesse de propagation d'environ 5835m/s et un facteur de couplage électromécanique de 0.014%. La réponse électrique est fort intéressante si on tient compte du faible couplage électromécanique dû au substrat utilisé. / The excitation and propagation, in liquid media, of shear waves in surface acoustic wave (SAW) devices based aluminum nitride (AlN) require the inclination of the c axis in the hexagonal structure. The purpose of this study was to deposit tilted c-axis AlN thin films by magnetron sputtering technique without any modification of the deposition system. The search approach was based only on the optimisation of deposition parameters. Substrate and the target were not inclined or shifted. It has been possible through an approach based solely on changes in growth parameters, to deposit thin piezoelectric layers with an inclination angle of 13 ° ± 2 ° under conditions of high pressure (0.8 Pa) and low temperature ( 300 ° C). A thin layer of SiO2 was also introduced to enhance the growth of tilted grains and therefore the columns. The deposited layers have a homogeneous thickness of 75% of a silicon substrate of 3 inches. After determining the optimal parameters leading to growth AlN film with tilted c-axis, we achieved a SAW device and hence demonstrate the ability to excite shear waves in AlN/Si02 /Si SAW structure. The performed device operate at 486.2 MHz corresponding to an acoustic velocity of about 5835m/s and an electromechanical coupling coefficient of 0.014%. The obtained electrical response is very interesting if we take into account the low electromechanical coupling of the structure due to the used substrate.

Os tocos, remanescentes da colheita florestal, causam um impedimento físico às operações com máquinas para o preparo do solo para um próximo plantio, ou mesmo quando a área onde estava sendo cultivado o eucalipto vai ser usada para o plantio de uma nova cultura ou estabelecer pastagem para pecuária. O objetivo deste trabalho foi estudar e avaliar o desempenho de uma serra tubular para a extração de tocos de eucalipto remanescentes da colheita. Este implemento, montado em uma grua hidráulica acoplada a um trator agrícola, é constituído de um tubo metálico com borda serrilhada, com diâmetro de 65 cm e altura interna de 70 cm, realizando o corte do sistema radicular e a extração apenas do toco e raízes próximas. O processo de extração com serra tubular foi comparado à extração de tocos com uma escavadora hidráulica equipada com destocador. Para a comparação entre o desempenho da serra tubular com a escavadora, foram realizadas extrações em quatro parcelas, com 108 tocos cada, sendo duas parcelas para cada sistema. Foram mensurados o tempo de extração para cada toco e o tempo de deslocamento das máquinas em cada parcela. O processo de extração pela serra tubular causou menos alterações na estrutura do solo, nas linhas e nas entrelinhas de plantio, se comparado ao uso da escavadora, porém o tempo de extração da serra foi superior em mais de 8 vezes ao tempo da escavadora. Foram realizadas extrações de tocos com DAB (diâmetros a altura da base) variando entre 12 e 31 cm, sendo que o tempo de extração não apresentou diferenças significativas entre os diferentes diâmetros para ambos os tratamentos. A serra tubular apresentou pouca mobilidade e pouca área de atuação em cada parada, contrariando as expectativas do projeto inicial. As análises econômicas mostraram custo operacional superior para a escavadora hidráulica, porém com maior produtividade comparado à serra tubular, resultando em menor custo de extração por unidade de toco. / The stumps, remained from forest harvesting, cause a physical impediment to operations with machinery for soil preparation to the next plantation, or even when the area that had eucalyptus plantation will be used to plant a new crop or establish pasture for livestock. This paper aim to study and evaluate the performance of a tubular saw for the extraction of Eucalyptus stumps remaining after the harvesting. This accessory mounted on a hydraulic crane, attached to a farm tractor, consists of a metal tube with a serrated edge, with a diameter of 65 cm. and internal height of 70 cm., making the cut root and extract only the stump and close roots. The extraction process with tubular saw was compared with an excavator equipped with a stump remover. The extractions were performed in two plots and two parcels with 108 stumps on each for both systems. It was measured the extraction time for each stump and moving time during the extractions. The extraction process by tubular saw caused less soil disturbance on its structure on planting lines and between the planting lines, compared with the excavator use, but the extraction time with the tubular saw was more than five times compared to the excavators extraction. The extractions were performed on stumps with different DAB (diameter at base height), ranging between 12 to 31 cm, and the extraction time showed no significant differences between the different diameters for both treatments. The tubular saw had little mobility and low operating area at each stop, contrary to the expectations of the initial Project. Economic analyzes showed higher operational cost for the hydraulic excavator, but higher productivity compared to tubular saw on a farm tractor, resulting in lower extraction cost per stump.

O presente trabalho apresenta uma revisão bibliográfica sobre o processo de serramento por serra de fita, abordando fatores relativos ao desempenho de corte nas diversas operações deste processo. Na seqüência, apresentam-se os seguintes estudos específicos: características da madeira que exercem influência nas operações de serramento por serra de fita: o processo de serramento e; ferramentas de corte. A fim de se verificar os aspectos teóricos especificados na literatura para adequação do processo de serramento, efetuou-se um estudo de caso em uma serraria, usinando-se a espécie de madeira Pinus oocarpa em operação de desdobro com serra de fita vertical. Neste estudo, realizou-se a medição da potência consumida durante o corte com aquisição de dados em tempo real, a qual possibilitou calcular a potência de corte média. / The present work shows a bibliographical review on band sawing, in respect to the factors related to cutting performance during the several operations of such process. Moreover, the following studies are presented: wood characteristics influencing the band sawing; sawing process itself; and cutting tools. In order to check the theorical aspects encountered in the literature to adequate the sawing process, a case study in a sawmill plant has been carried out. Pinus oocarpa wood species has been machied by unfolding using a vertical bandsaw. The consumed power during the cutting process was measured by a data acquisition system in real time, what allowed the calculation of the average cutting power.