The irradiation of high Tc superconducting thin films with a focused electron beam, such as that obtained in a scanning transmission electron microscope (STEM), can result in the formation of a Josephson junction. The conditions required for the formation of these Josephson junctions in YBa2Cu3O7-d and related compounds are discussed as well as the physical properties of the irradiated material. From electrical transport measurements of individual Josephson junctions it was found that these junctions have a Superconductor/Normal/Superconductor (SNS) nature. Low temperature anneal studies indicate that Josephson junctions with optimum properties can be obtained by a combination of a high electron dose and subsequent low temperature anneal. Extremely high electron doses resulted in the formation of a purely resistive region. The electrical transport in such regions with a dimension of 200 nm in the direction of current transport is shown to be compatible with variable range hopping (VRH). Barriers with the same length but a finite superconducting transition temperature showed a low bias resistance that is significantly lowered due to proximity coupling. Using purely resistive regions in combination with Josephson junctions, devices consisting of two closely spaced Josephson junctions with a third terminal connected to the shared electrode were fabricated and characterised (minimum separation 20 nm). The distinct behaviour of the Josephson critical current with applied magnetic field (Ic(B)) of these devices was found to be well described by a newly developed model, which incorporates the effect of the static redistribution current in the shared electrode on the phase distribution of the Josephson junctions. An important finding is that the behaviour of the high critical current with applied magnetic field of two closely spaced junctions was found to be consistent with a model system consisting of a closely spaced Josephson junction and a resistive barrier. A three terminal device with Josephson junctions at small separations was found to have a significantly increased trans resistance when compared with the individual resistance of the Josephson junctions it constituted of. A number of illustrative examples of device structures realised with the focused electron beam irradiation technique are also included.

The resonance frequency of electrostatically actuated micromachined beams can be tuned substantially by applying a DC voltage bias, first by decreasing the frequency until the onset of pull-in and then by increasing it by the virtue of contact. With the objective of modeling and designing the micromechanical structures after pull-in, a semi-analytical method was developed to determine the length of the contact between the beam and the substrate. The semi-analytical method which is validated on the straight beams is extended for the folded beam structures. This method provides a tool to the microsystem designer to quickly evaluate the deformed configuration of the folded beams after pull-in without the time-intensive contact analysis. This tool is used to design the micro‐speaker elements suitable for emitting low frequency sounds. Multiple instabilities after the pull-in were numerically observed and it was shown that the resonant frequency of an L-shaped beam can be varied in different frequency bands. The speaker element can emit any frequency in a given range, as the resonant frequency of the beam structures can be tuned both before and after pull-in. Operating the speaker element at resonance maximizes the efficiency of the speaker design because the amplitude of vibration is maximum at the resonance frequency. Furthermore, the interplay between the torsional and bending loads is used to minimize the out-of-plane deflection under self weight. A selection criterion is employed to choose a beam structure with optimum stiffness and natural frequency. Beam-based micro-speaker element designs with single and multi-layered suspended structures are proposed. Practical considerations such as volume displacement, mode shapes and dynamic coupling are discussed, on the basis of which design guidelines for a speaker element are proposed. Squeeze film effects and nonlinearity due to the midplane stretching is integrated into the transient analysis model to analyze the effect on the stroke of beam operating at resonance. A comparison between various speaker elements is presented.

This thesis deals with the design of cost-effective large-scale RFID networks from both software and hardware aspects. To start with, different computer-aided tools were developed to maximize performance. The first set of algorithms focused on the elimination of redundant readers to minimize the cost and interference in large-scale RFID networks. For validation, uniform reader coverage was assumed, as widely used in most available publications. Then, both omni-directional and directional commercial reader antenna data were included for more reliability. Besides redundancy, an efficient physical placement of readers was also investigated by considering both uniform and random distribution over space. For this purpose, genetic-based algorithms have been proposed to increase reader coverage using commercial reader antenna beams. Energy consumption is also a critical design parameter for dense RFID networks. Therefore, a third set of algorithms was developed to efficiently minimize the energy consumption of large-scale RFID systems. Note that all above optimization techniques were achieved without compromising the whole RFID network performance. To further optimize cost and performance of large-scale RFID networks, a hardware approach through reader antenna design has been considered. In fact, since different RFID frequency bands have been assigned worldwide, large-scale RFID networks implemented in industrial parks, airports, or international trade zones, may deal with imported merchandise using tags operating at different frequencies. Therefore, in-house single and dual-band microstrip and CPW fed monopole antennas were successfully designed and tested to improve system adaptability to various RFID standards. These antennas were designed using both electromagnetic commercial simulators (HFSS) and in-house FDTD-based techniques. Finally, to further extend dense RFID network capabilities, one may implement a substantial number of readers and antennas with small reading ranges to cover a large monitoring area, or use high gain phased array antenna system for an extended reading range of an RFID reader for a smaller number of total reader deployments. Therefore, a phased antenna array system can be an efficient alternative for dense RFID networks. Thus, a switched beam network to control the phase of the radiating elements of the array has been successfully designed and tested.

Ce travail de thèse porte sur la croissance et sur la caractérisation optique de nanostructures à base d’antimoine sur substrats InP, en vue d’applications dans le domaine des télécommunications optiques. La transition inter-sous-bande est un processus ultrarapide qui permet la modulation de la lumière dans les réseaux de télécommunication optique. Durant cette thèse, une absorption inter-sous-bande dans le proche-infrarouge provenant de puits quantiques Ga0.47In0.53As/AlAs0.56Sb0.44 a été observée pour la première fois au laboratoire. Les analyses par microscopie électronique à effet tunnel sur la face clivée montrent cependant de nombreux déviations à l’idéalité de nos structures : mélange à l’échelle atomique aux interfaces entre GaInAs et AlAsSb, inhomogénéité de l’alliage GaInAs, incorporation non-intentionnel d’antimoine dans le GaInAs. Les puits quantiques InAs/AlAs0.56Sb0.44 sont potentiellement des objets de choix pour la réalisation de composants intersous- bande travaillant à 1,55 μm. Des puits quantiques InAs/AlAs0.56Sb0.44 contraint, exempt de défauts ont été obtenus par croissance assistée par effet surfactant de Sb. En symétrisant la contrainte induite par le dépôt d’InAs par l’insertion de couches nanométriques de AlAs dans les barrières, des multi-puits InAs/AlAs0.56Sb0.44 sans contrainte macroscopique ont été réalisés. L’effet de l’antimoine en surface sur la croissance de structure InAs/GaAs0.51Sb0.49 a également été étudié. En présence d’antimoine sur substrats InP d’orientation (001), le dépôt d’InAs conduit à la formation de puits quantiques. Par contre sur ceux orientés suivant (113)B des boites quantiques sont formées suivant le mode de croissance Volmer-Weber. Ces résultats sont discutés en termes d’effets cinétiques ou énergétiques de l’antimoine en surface. La modification de l’anisotropie de l’énergie de surface induite par l’antimoine permet d’interpréter nos résultats sur substrats (100) et (113) B. / This PhD work presents molecular beam epitaxy growth and optical studies on several Sb-nanostructures on InP substrate, for their potential use in optical telecommunication. Inter-subband transition in Ga0.47In0.53As/AlAs0.56Sb0.44 quantum well is a useful physical process for implementing ultrafast fulloptical modulations. Near-infrared inter-subband transition in this material was achieved and microscopic studies on this structure has revealed that the intermixing at GaInAs/AlAsSb interface, unintentional Sb incorporation in GaInAs layer and the inhomogeneity within GaInAs layer could prevent Ga0.47In0.53As/ AlAs0.56Sb0.44 multiple quantum wells from achieving intersubband transition in 1.55 μm optical telecommunication band. The strained InAs/AlAs0.56Sb0.44 quantum well is another material that has potential use in 1.55 μm full-optical modulation. 2 nm-thick defect-free InAs/AlAs0.56Sb0.44 was obtained under Sb surfactant-mediated growth, and by using strain compensation techniques, InAs/AlAs0.56Sb0.44 multiple quantum wells with zero net-strain were realized. The study of Sb-mediated growth is also carried on to InAs/GaAs0.51Sb0.49 nanostructures. The growths of such structures on InP (001) substrate has led to the formation of flat InAs layer, while high-density InAs/GaAs0.51Sb0.49 quantum dots were obtained on InP (113)B substrates under Volmer-Weber growth mode. We attribute such phenomena to the surfaceorientation dependent surfactant effect of Sb. Emission wavelength close to 2 μm was achieved with only 5 ML of InAs deposition, which makes these quantum dots attractive to InPbased mid-wave applications.

In this article, we present results concerning the existence of solutions for a beam evolution equation with variable coefficients in increasing noncylindrical domains.

Orientador: Francisco Haiter Neto / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-26T19:01:13Z (GMT). No. of bitstreams: 1 Brasil_DanieliMoura_M.pdf: 14824425 bytes, checksum: 3057ff676ccce0f70d5ed273ef3ffed8 (MD5) Previous issue date: 2015 / Resumo: O objetivo deste estudo foi avaliar a influência da morfologia craniofacial em volumes e áreas transversais das vias aéreas superiores. Para isso, foram utilizadas 74 imagens por Tomografia Computadorizada de Feixe Cônico (TCFC) e 74 fotografias faciais em perfil lateral, que pertenciam aos mesmos pacientes, sendo 38 do sexo masculino e 36 do sexo feminino, com idades entre 18 e 56 anos (32,8 ± 1,8). As imagens foram selecionadas a partir de um arquivo de exames de pacientes atendidos em uma Clínica de Radiologia. Um radiologista experiente classificou a amostra em tipos esqueléticos ântero-posteriores (classe II e classe III) empregando a análise cefalométrica de Steiner e a medida AO-BO de Jacobson; e em padrões verticais (braquifacial, mesofacial e dolicofacial) utilizando a análise cefalométrica de Ricketts. A análise facial de perfil foi realizada para cada paciente. Medidas de volume total, de nasofaringe e de orofaringe e ainda de cinco áreas transversais ao longo das vias aéreas superiores foram realizadas, utilizando o software Insight ITK-SNAP 2.4.0®. Os resultados foram submetidos à análise estatística, em que o teste Mann-Whitney foi utilizado para analisar a influência do sexo e dos tipos esqueléticos ântero-posteriores nas variáveis do estudo, o teste Kruskal-Wallis foi aplicado para verificar a existência de relação entre os padrões verticais e as variáveis; o teste de Correlação de Spearman foi utilizado para analisar a possível correlação entre as medidas dentro dos padrões esqueléticos ântero-posteriores, dentro dos padrões verticais e dentro das variáveis da análise facial e as demais medidas propostas pelo estudo. Os resultados mostraram que o tipo esquelético ântero-posterior e o padrão vertical da face não influenciaram no volume das vias aéreas superiores; a área transversal na região de palato mole (PM) mostrou-se significativamente maior para classe III; o terço superior da face apresentou correlação negativa com as medidas da faringe e o terço médio da face mostrou correlação positiva com a área transversal PM. Concluiu-se que os padrões faciais não influenciaram no volume da faringe e que a observação fotográfica do perfil facial foi capaz de mostrar tendências de correlações entre terços da face e vias aéreas superiores / Abstract: The aim of this study was to evaluate the influence of craniofacial morphology in volumes and cross-sectional areas of the upper airway. For this 74 Cone Beam Computed Tomography (CBCT) images and 74 facial photographs in side profile were used, which belonged to the same patients, 38 males and 36 females, aged between 18 and 56 years (32.8 ± 1.8). The images were selected from a file examination of patients seen in a Radiology Clinic. An experienced radiologist classified the sample into anteroposterior skeletal types (class II e class III) using Steiner¿s analysis and the AO-BO measure Jacobson; and into vertical groups (brachyfacial, mesofacial and dolichofacial) using Ricketts¿ analysis. The facial profile analysis was performed for each patient. Measurement of volume and of five cross-sectional areas of upper airway were performed using Insight ITK-SNAP 2.4.0®. The data was subjected to statistical analysis, the Kruskal-Wallis test was used to verify the existence of a relationship between the vertical groups and other variables analyzed in the study. The Mann-Whitney test was used to analyze the influence of gender and anteroposterior skeletal types in the variables. Spearman Correlation test was used to analyze the possible correlation between measurements within vertical groups; within the anteroposterior skeletal types; and within variables of facial analysis, and other measures proposed by the study. Results showed that the anteroposterior skeletal type and the vertical pattern did not influence the volume of the upper airway; soft palate (SP) cross-sectional area was significantly greater in type class III; the upper facial third was negatively correlated with measures of the pharynx, and the middle facial third had positive correlation with the SP cross-sectional area. It was concluded that facial patterns do not influence the pharynx volumes. The photographic observation of the facial profiles is able to show trends of correlations between thirds of the face and upper airway / Mestrado / Radiologia Odontologica / Mestra em Radiologia Odontológica

Orientador: Luciana Asprino / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-27T07:59:26Z (GMT). No. of bitstreams: 1 Santaella_GustavoMachado_M.pdf: 1130922 bytes, checksum: 73dd73d086d83d2c9e2fa04c5f9cd294 (MD5) Previous issue date: 2015 / Resumo: Os fótons de raios X são atenuados quando atravessam materiais, e isso afeta diretamente os valores dos tons de cinza da imagem. No presente estudo teve-se como objetivos avaliar a utilização de diferentes materiais como simuladores de tecidos moles e avaliar a influência dos tecidos moles nos tons de cinza em imagens de tomografia computadorizada de feixe cônico (TCFC). Para isso, foram utilizadas três cabeças humanas com os tecidos moles formolizados presentes e submetidas à aquisição de imagens de TCFC para determinação do grupo padrão-ouro. Posteriormente, as cabeças foram descarnadas e novamente tomografadas, com e sem a utilização de diferentes materiais simuladores de tecidos moles, seguindo o mesmo protocolo de aquisição. Quatro diferentes materiais foram testados, acrílico, água, cera utilidade e poliestireno expandido (EPS), utilizados isoladamente ou em combinação, totalizando 6 grupos de teste (sem simulador, com caixa de EPS de 2 cm de espessura, com acrílico com 0,5 cm de espessura, com caixa de EPS com cera de 1 cm de espessura, com caixa de EPS com cera de 1 cm de espessura e água no interior, e com caixa de EPS com água no interior). Um único avaliador selecionou oito regiões de interesse quadrangulares, sendo em maxila e mandíbula e incluindo dentes e ossos alveolares, e realizou as mensurações de todos os valores dos tons de cinza dos pixels das regiões. As medianas desses valores foram utilizadas para comparação pelos testes de Friedman e Dunn. Os resultados mostraram que os grupos testados não apresentaram diferenças estatisticamente significantes em comparação com o grupo padrão-ouro, com exceção dos grupos que envolveram água no interior das caixas. O EPS com 2 cm de espessura, associado ou não a uma camada de cera utilidade de 1 cm, e o acrílico com 0,5 cm de espessura foram os simuladores que forneceram imagens mais semelhantes às imagens do padrão-ouro. A água não se mostrou eficaz como simulador de tecidos moles. Os tecidos moles não influenciaram nos valores de tons de cinza mensurados na imagem de TCFC / Abstract: X-ray photons suffer attenuation as they pass through materials of different compositions, and this directly affects the values of the image grayscale. This study aimed to test the usefulness of different materials as soft tissue simulators and evaluate the influence of soft tissues on grayscale values in cone beam computed tomography (CBCT). Three human heads with formalin fixed soft tissues were obtained and CBCT images were acquired to determine the gold standard group. The heads were stripped and tomographic images reacquired with and without the use of different materials for soft tissue simulation, following the same acquisition protocol. Four different materials were tested, acrylic, water, utility wax and expanded polystyrene (EPS), and these were used singly or in combination, with a total of 6 test groups (no simulator, with EPS box 2 cm thick, with 0.5 cm thick acrylic, EPS box with 1 cm thick wax, EPS box with 1 cm thick wax and water inside, and EPS box with water inside). A single evaluator selected the eight quadrangular regions of interest, being in the maxilla and mandible and including teeth and alveolar bone, and performed the measurements of all the pixel grayscale values of the regions. The median of these values were used for comparison by Friedman's and Dunn's tests. The results showed that the tested groups showed no statistically significant differences compared to the gold standard group, with the exception of groups involving water inside the boxes. The EPS 2 cm thick, associated or not with a 1 cm layer of utility wax, and the 0.5 cm thick acrylic were the simulators that provided images more similar to the gold standard images. The water was not effective as a soft tissue simulator. The soft tissues did not influence the values of the CBCT image grayscale measured / Mestrado / Radiologia Odontologica / Mestre em Radiologia Odontológica

Introduction: Root resorption is an undesired but frequent side effect of orthodontic treatment. Several studies have already aimed to evaluate the performance of CBCT on this topic. However, none have addressed the peculiarities of the most common daily orthodontic scenario. The aim of the study was to evaluate the influence of CBCT scans on the diagnosis of artificial external root resorption in the apical third of anterior teeth. Materials and methods: One hundred extracted human anterior teeth were randomly assigned to 2 uneven groups (51 as the control and 49 as the experimental group). A limited area of the apical third of the root of the teeth of the experimental group was selected and a buffer solution was used to induce tooth subsurface demineralization. Before CBCT image acquisition, each tooth was coated with an approximately 0.3 mm thick layer of utility wax to simulate the radiographic appearance of the periodontal space and placed into an empty mandibular anterior socket of a partially edentulous dry human mandible. The mandible was placed into a polystyrene box filled with water prior to the CBCT examination to simulate soft-tissue attenuation and scattering. The CBCT images were obtained on an i-CAT unit (i-CAT Next Generation, Imaging Sciences International, Hatfield, PA) according to three protocols: (I) half scan (180°), 0.40 mm voxel size; (II) full scan (360°), 0.40 mm voxel size; and (III) full scan (360°), 0.125 mm voxel size. The 300 resultant CBCT DICOM volumes were imported into InVivo software (InVivo5, Anatomage, San Jose, CA) for evaluation by three blinded, previously calibrated observers using a five-point confidence rating scale. Cohen’s kappa was used to calculate observers’ agreement. The diagnostic values of sensitivity (Sn), specificity (Sp) and accuracy (Ac) were performed by pooling observer responses for every image modality. Receiver operating characteristic (ROC) were built and the areas under the curve (AUC) were calculated. The Sn, Sp and Ac values were compared by Cochran’s Q test. The AUC values were compared by Mann-Whitney U test. Results: The observers’ agreement ranged from 0.63 to 0.71, which was interpreted as a substantial agreement. Protocol III (0.125 mm voxel size) displayed the highest Sn (81.63 %), Ac (80.67%) and AUC (0.807). There were statistically significant differences between protocol III and the other two protocols (p < 0.001). The specificity of protocol I (84.97 %) was greater than that of protocols II (69.93 %) and III (79.74 %); however statistically significant difference was only found between protocols I and II (p = 0.005). Conclusion: Although there was no difference in accuracy between the degrees of rotation (half and full scan) within the same voxel size (0.4 mm), there was a considerable difference between those and the smallest voxel size (0.125 mm). In fact, it may be suggested that a more dedicated, high resolution scan should be acquired when one intends to investigate the early stage of external root resorption during orthodontic treatment.

Deep ultraviolet light emitting diodes (UV LEDs) are an important emerging technology for a number of applications such as water/air/surface disinfection, communications, and epoxy curing. However, as of yet, deep UV LEDs grown on sapphire substrates are neither efficient enough nor powerful enough to fully serve these and other potential applications. The majority of UV LEDs reported so far in the literature are grown on sapphire substrates and their design consists of AlGaN quantum wells (QWs) embedded in an AlGaN p-i-n junction with the n-type layer on the sapphire. These devices suffer from a high concentration of threading defects originating from the large lattice mismatch between the sapphire substrate and AlGaN alloys. Other issues include the poor doping efficiency of the n- and particularly the p-AlGaN alloys, the extraction of light through the sapphire substrate, and the heat dissipation through the thermally insulating sapphire substrate. These problems have historically limited the internal quantum efficiency (IQE), injection efficiency (IE), and light extraction efficiency (EE) of devices. As a means of addressing these efficiency and power challenges, I have contributed to the development of a novel inverted vertical deep UV LED design based on AlGaN grown on p-SiC substrates. Starting with a p-SiC substrate that serves as the p-type side of the p-i-n junction largely eliminates the necessity for the notoriously difficult p-type doping of AlGaN alloys, and allows for efficient heat dissipation through the highly thermally conductive SiC substrate. UV light absorption in the SiC substrate can be addressed by first growing p-type doped distributed Bragg reflectors (DBRs) on top of the substrate prior to the deposition of the active region of the device. A number of n-AlGaN films, AlGaN/AlGaN multiple quantum wells, and p-type doped AlGaN DBRs were grown by molecular beam epitaxy (MBE). These were characterized in situ by reflected high energy electron diffraction (RHEED) and ex situ by x-ray diffraction, scanning electron microscopy, atomic force microscopy, photoluminescence, and reflectivity. Using the primary elements of the proposed design, this research culminated in the MBE growth, fabrication, and characterization of prototype deep UV LED devices emitting below 300 nm.

This dissertation reports a sensitive single beam experimental technique for measuring nonlinear refraction and nonlinear absorption in a wide variety of materials. The experimental setup is described and a comprehensive theoretical analysis including cases where nonlinear refraction and nonlinear absorption are also presented.