This work reports the results of a systematic study of the factors that affect the bridging behaviour of bagasse. It shows that traditional bulk solids theory is inappropriate for predicting bagasse flow mainly because of the impossibility of obtaining a reliable measure of internal friction. It demonstrates the significant influence of fibre length and moisture content on its handling charateristics. Correlations of pertinent bulk properties such as compactibility, tensile strength, surface friction and translation of vertical into horizontal pressure have been developed. These were derived as a result of measurements in equipment that was designed for the purpose. Finally, an empirical model utilising these correlations is proposed by which the likelihood of bridge formation in any piece of bagasse handling equipment can be determined. The validity of the model is assessed by comparison with bridging tests that were performed under controlled conditions. / Thesis (Ph.D.)-University of Natal, 1996

Les dispositifs optoélectroniques organiques possèdent plusieurs avantages pour les applications dans le domaine du biomédical. Le photodétecteur organique (OPD) est un type de dispositif optoélectronique qui n’est pas encore utilisé pour la détection d’activité cérébrale. L’objectif de cette thèse a été d’explorer l’utilisation des OPD, constitués de différent matériaux donneur-accepteur d’électrons, dans le domaine des neurosciences. Nous avons présenté différent types d’OPD possédant une structure minimale, une excellente sensibilité et un grand potentiel d’intégration dans les méthodes de microfabrication existantes. Les détecteurs organiques ont été utilisés pour l’enregistrement de signaux optiques intrinsèques et de signaux fluorescents reflétant l’activité du calcium dans le cerveau. De plus, un autre aspect des OPD est présenté (en combinaison avec les transistors électrochimiques organiques (OECT)) : des systèmes électroniques biomimétiques basé sur une architecture électronique neuro-inspirée. Cette thèse démontre le potentiel des OPD pour enregistrer des activités cérébrales. Elle ouvre une nouvelle perspective, grâce à leur grande sensibilité, comme capteur optique en combinaison avec des dispositifs neuronaux implantables. Ceci élargira les frontières de l’électrophysiologie optique pour explorer les mécanismes complexes du cerveau et des maladies neurodégénératives. / Organic optoelectronic devices have many promising qualities for biomedical applications. Organic photodetectors (OPD), one type of such devices, have yet to be utilized for the detection of signals in the brain, to the best of our knowledge. The goal of this thesis was to explore the use of OPDs, based on different electron-donor and -acceptor materials in neuroscience applications. Different types of minimal-structure OPDs are presented, which have an excellent sensitivity and a high potential for incorporation into existing microfabrication methods. The organic sensors were utilized for monitoring the brain’s intrinsic optical signals and fluorescent calcium dynamics. Additionally, another aspect of these devices is presented (in combination with organic electrochemical transistors (OECT)): neuroinspired electronics, electronics that mimic biology. This thesis establishes the promise of OPDs for monitoring brain activities, which would lead to their integration, as high-sensitive micron-scale optical sensors in organic neural probes. Such device would result in exploring optical biological activities in the deep brain on the cellular level and would push the frontiers of optical-electrophysiology by giving a better understanding of complex mechanisms of the brain function and neurodegenerative diseases.

Les diodes électroluminescentes (DEL) à base de GaN ont déjà été commercialisées comme solution économique d’éclairage, étant donné que les multi-puits quantiques (MQW) basés sur InGaN/GaN peuvent être conçus pour produire de la lumière dans toute la gamme spectrale visible. Pour obtenir une émission de lumière blanche, la conversion à base de phosphore conduit à une faible efficacité due à la perte de Stokes et peut également produire un faible indice de rendu des couleurs (IRC). Par conséquent, pour une efficacité élevée et une lumière blanche avec un IRC élevé, la génération de lumière blanche par combinaison rouges-vertes-bleues (RGB) est nécessaire. La DEL bleue basée sur InGaN/GaN présente une bonne performance aujourd'hui. La DEL rouge à base de III-phosphure est également très efficace. Cependant, avec des longueurs d'onde intermédiaires pour l'émission de spectre vert, l'efficacité des dispositifs diminue avec l'augmentation de la composition d’indium (In) dans la région active à cause de l'épitaxie selon la direction de GaN communément utilisée (0001-Ga). Ce «green-gap» est le principal obstacle pour obtenir une DEL blanche sans phosphore. Les structures DEL non ou semi-polaires pourraient être une solution pour réduire ou omettre le problème de polarisation, cependant, une croissance plus facile de bonne qualité cristalline avec moins d'étapes de fabrication font que la croissance de la direction (0001-Ga) est toujours commercialement prometteuse. Par conséquent, une conception de structure optimisée pour atténuer la polarisation et augmenter l'émission optique provenant d'hétéro-structures élaborées dans cette direction de croissance est toujours demandée. Les structures de DEL classiques multi-puits quantiques (MQW) InGaN/GaN sont développées sur une template GaN et utilisent du GaN comme couches barrières. Cependant, notre objectif a été de faire croître des MQW à contenu élevé avec des barrières InGaN sur une nouvelle template InGaN appelé «semi-bulk» (SB). La réalisation de la thèse est de simuler, décroître par épitaxie en phase vapeur organométallique (MOVPE) et de fabriquer la structure de DELs à haute teneur en In dans les barrières MQW avec InGaN, crues sur une template InGaN «semi-bulk» de haute qualité, et qui émettent dans le spectre du bleu au vert / GaN-based light-emitting diodes (LEDs) have already been commercialized for solid-state lighting, since the InGaN/GaN-based multi-quantum-well (MQW) of LEDs can be designed to produce light in the entire visible spectral range. To obtain white LED, phosphor-based down-conversion results in low efficiency due to Stokes loss and also can yield low colour rendering index (CRI). Hence, for highly efficient and with high CRI white light, generation of white light by monolithic red-green-blue (RGB) combination is necessary. InGaN/GaN-based blue LED has good performance now-a-days. III-phosphides based red LED has also achieved good efficiency. However, with intermediary wavelengths for green spectra emission, the efficiency of devices from epitaxy grown along the commonly used (0001-Ga) direction of GaN decreases with increasing indium (In) content in the active region and this “green-gap” is the main obstacle to get phosphor-free white LEDs. Non- or semi-polar LED structures could be a solution to reduce or omit the polarization problem, however, easier growth of good crystal quality and fewer processing steps make (0001-Ga) direction growth still commercially promising. Therefore, optimized structure design to alleviate polarization and enhance optical emission from hetero-structures grown along this direction growth is still in demand. The conventional InGaN multi-quantum-well (MQW) LED structures are grown on GaN buffer and use GaN as barrier layers. However, the objective of this thesis has been to grow high In-content MQWs with InGaN barriers on a novel so called “semi-bulk” (SB) InGaN buffer. The achievement of the thesis was to simulate, grow by metalorganic vapour phase epitaxy (MOVPE) and process LED structure with high In-content in the MQW with InGaN barriers, grown on high quality “semi-bulk” InGaN buffer, that will emit in the blue to green spectra. 70 nm thick high crystal quality InGaN SB buffer was obtained with 5% In-content. On top of this, In0.15Ga0.85N/In0.05Ga0.95N MQW was grown followed by 200 nm optimized p-GaN. The room temperature IQE was 67.5% at 460 nm emission wavelength. The processed LED chips yielded turn-on voltage less than 3 V with leakage current of ~10-3 A. In0.25Ga0.75N/ In0.05Ga0.95N MQW was also realized on InGaN SB with 7% In, with emission peak at ~530 nm

Atualmente, a Onion-tree [Carélo et al., 2009] é o método de acesso métrico baseado em memória primária mais eficiente para pesquisa por similaridade disponível na literatura. Ela indexa dados complexos por meio da divisão do espaço métrico em regiões (ou seja, subespaços) disjuntas, usando para isso dois pivôs por nó. Para prover uma boa divisão do espaço métrico, a Onion-tree introduz as seguintes características principais: (i) procedimento de expansão, o qual inclui um método de particionamento que controla o número de subespaços disjuntos gerados em cada nó; (ii) técnica de substituição, a qual pode alterar os pivôs de um nó durante operações de inserção baseado em uma política de substituição que garante uma melhor divisão do espaço métrico, independente da ordem de inserção dos elementos; e (iii) algoritmos para a execução de consultas por abrangência e aos k-vizinhos mais próximos, de forma que esses tipos de consulta possam explorar eficientemente o método de particionamento da Onion-tree. Entretanto, a Onion-tree apenas oferece funcionalidades voltadas à inserção dos dados um-a-um em sua estrutura. Ela não oferece, portanto, uma operação de bulk-loading que construa o índice considerando todos os elementos do conjunto de dados de uma única vez. A principal vantagem dessa operação é analisar os dados antecipadamente para garantir melhor particionamento possível do espaço métrico. Com isto, a carga inicial de grandes volumes de dados pode ser melhor realizada usando a operação de bulk-loading. Este projeto de mestrado visa suprir a falta da operação de bulk-loading para a Onion-tree, por meio da proposta de algoritmos que exploram as características intrínsecas desse método de acesso métrico. No total, são propostos três algoritmos de bulk-loading, denominados GreedyBL, SampleBL e HeightBL, os quais utilizam respectivamente as seguintes abordagens: gulosa, amostragem e de estimativa da altura do índice. Testes experimentais realizados sobre conjuntos de dados com volume variando de 2.536 a 102.240 imagens e com dimensionalidade variando de 32 a 117 dimensões mostraram que os algoritmos propostos introduziram vantagens em relação à estrutura criada pelo algoritmo de inserção um-a-um da Onion-tree. Comparado com a inserção um-a-um, o tamanho do índice foi reduzido de 9% até 88%. Em consultas por abrangência, houve redução de 16% até 99% no número de cálculos de distância e de 9% a 99% no tempo gasto em relação à inserção. Em consultas aos k-vizinhos mais próximos, houve redução de 13% a 86% em número de cálculos de distância e de 9% até 63% no tempo gasto / The main-memory Onion-tree [Carélo et al., 2009] is the most efficient metric access method to date. It indexes complex data by dividing the metric space into several disjoint regions (i.e. subspaces) by using two pivots per node. To provide a good division of the metric space, the Onion-tree introduces the following characteristics: (i) expansion procedure, which provides a partitioning method that controls the number of disjoint subspaces generated at each node; (ii) replacement technique, which can replace the pivots of a leaf node during insert operations based on a replacement policy that ensures a better division of the metric space, regardless of the insertion order of the elements; and (iii) algorithms for processing range and k-NN queries, so that these types of query can efficiently use the partitioning method of the Onion-tree. However, the Onion-tree only performs element-by-element insertions into its structure. Another important issue is the mass loading technique, called bulk-loading, which builds the index considering all elements of the dataset at once. This technique is very useful in the case of reconstructing the index or inserting a large number of elements simultaneously. Despite the importance of this technique, to the best of our knowledge, there are not in the literature bulk-loading algorithms for the Onion-tree. In this masters thesis, we fill this gap. We propose three algorithms for bulk-loading Onion-trees: the GreedyBL algorithm, the SampleBL algorithm and the HeightBL algorithm. These algorithms are based on the following approaches, respectively: greedy, sampling and estime height of the index. Performance tests with real-world data with different volumes (ranging from 2,536 to 102,240 images) and different dimensionalities (ranging from 32 to 117 dimensions) showed that the indices produced by the proposed algorithms are very compact. Compared with the element-by-element insertion, the size of the index reduced from 9% up to 88%. The proposed algorithms also provided a great improvement in query processing. They required from 16% up to 99% less distance calculations and were from 9% up to 99% faster than the element-by-element insertion to process range queries. Also, they required from 13% up to 86% less distance calculations and were from 9% up to 63% faster than the element-by-element insertion to process k-NN queries

Typ Ia Supernovae (SNe) können verwendet werden, um Bulk-Flows zu messen, die durchschnittliche Bewegung von Materie relativ zur kosmischen Mikrowellenhintergrundstrahlung (CMB). Bulk-Flow-Studien ermöglichen Tests der Behauptung des Kosmologischen Prinzips von Homogenität und Isotropie für ausreichend große Distanzen. Im letzten Jahrzehnt wurden mehrere hohe Bulk-Geschwindigkeiten in großen Skalen gemeldet, die schwer mit den Vorhersagen des ΛCDM-Kosmologiemodells zu vereinbaren sind. In dieser Arbeit schätze ich Bulk-Flows auf der Grundlage einer neuen Probe von SNe aus einer Next-Generation-Sky-Survey namens Zwicky Transient Facility (ZTF). Die Auswahl und Analyse der großen Anzahl von astrophysikalischen Transienten, die jede Nacht von dieser Survey erfasst werden, ist komplex. Ich habe eine flexible Analysis Software namens AMPEL entwickelt, um diese Aufgaben zu erfüllen. Ein neuer ZTF-Datensatz, der aus etwa 850 Typ Ia SNe besteht, wurde für diese Forschung zusammengestellt. Simulationen zeigen, dass die nicht-sphärische Surveygeometrie von ZTF, die aktuellen Stichprobengrößenbeschränkungen und der Malmquist-Bias zusammen systematische Effekte ergeben, die kleiner sind als die aktuellen statistischen Unsicherheiten. Ich habe die ZTF-Probe zusammen mit zwei anderen kosmologischen SNe-Proben im heliozentrischen Inertialsystem verwendet, um das kosmische Ruhesystem unabhängig vom CMB zu etablieren. Der gemessene Beobachter-Dipol innerhalb der Rotverschiebungsschale 0,06 < z < 0,1 zeigt eine Konvergenz mit dem CMB-Temperaturdipol. Im CMB-Inertialsystem im gleichen Skala wird kein signifikanter Bulk-Flow gemessen. / Type Ia supernovae (SNe) can be used to measure bulk flows, the average motion of matter relative to the Cosmic Microwave Background (CMB). Bulk-flow studies enable tests of the Cosmological Principle’s assertion of large-scale homogeneity and isotropy. Over the past decade, several high bulk-velocities at large scales have been reported, which are difficult to unify with constraints from the ΛCDM cosmological model. In this work, I estimate bulk-flows based on a new sample of SNe from a next-generation sky survey called the Zwicky Transient Facility (ZTF). Selecting and analyzing the large number of astrophysical transients detected each night by this survey is complex. I developed a flexible analysis framework called AMPEL to address these challenges. A new ZTF dataset comprising roughly 850 type Ia SNe was assembled for this research. Simulations show that the non-spherical survey geometry of ZTF, the current sample size limitations, and the Malmquist bias together yield systematic effects smaller than current statistical uncertainties. I used the ZTF sample along with two cosmological-grade SNe samples in heliocentric inertial frame to establish the cosmic rest frame independently from the CMB. The measured observer-dipole within the redshift shell 0.06 < z < 0.1 shows convergence with the CMB temperature dipole. In the CMB inertial frame at the same scale, no significant bulk-flow is detected.

Diante da evolução da composição das resinas compostas e do lançamento de compósitos do tipo bulk fill, faz-se necessário o estudo do desempenho dessa nova classe de materiais. Para isso, o presente estudo teve como objetivo avaliar propriedades como grau de conversão (GC) , dureza Knoop (KHN), resistência à flexão (RF) e tenacidade à fratura (KIC) de sete compósitos bulk fill (EverX Posterior, EXP; Filtek Bulk Fill Flow, FBFF; Fill-Up!, FU; SonicFill, SF; Surefil SDR, SDR; Tetric EvoCeram Bulk Fill, TECBF; Venus Bulk Fill, VBF) e um compósito nanohíbrido convencional (Charisma Diamond, CD). De forma complementar, foi realizado tratamento térmico a 170 °C por 10 minutos para melhor compreensão do comportamento desses materiais quanto ao potencial de conversão e à indução de tensões na interface carga/matriz. A avaliação do GC (n=3) foi realizada através de espectroscopia FTIR, a leitura da dureza Knoop foi realizada nas superfícies do topo e da base (n=3), e os ensaios de RF de três pontos (n=10) e KIC (n=10) em máquina de ensaios universais. Os resultados obtidos foram submetidos à analise de variância (complementados pelo teste de Tukey) ou teste Kruskal-Wallis, com nível de significância de 5%. A análise do GC (%) revelou diferença entre os materiais testados, sendo que todas as resinas bulk fill apresentaram valores maiores que a resina convencional: SF (75,7) > VBF (66,7) = EXP (66,4) = SDR (62,8), sendo esta também semelhante a FU (60,0); FU, TECBF (56,6), FBFF (56,6) e CD (54,5) apresentaram conversão semelhante. Os valores de KHN variaram de acordo com o material e com a superfície: apenas SF apresentou KHN semelhante (na superfície do topo) a CD, entretanto não foi possível realizar a leitura da superfície da base deste último material; SF, TECBF e FBFF apresentaram valores de KHN diferentes nas superfícies topo e base; EXP, FU, SDR e VBF mantiveram os valores de dureza do topo semelhantes à superfície da base. Para a RF (MPa), os resultados variaram de acordo com o material: EXP (122,54) = SF (101,09) = CD (99,15), sendo estes dois últimos semelhantes a FU (83,86) e TECBF (82,71), os quais não diferiram da resina SDR (65,18); esta última também mostrou comportamento semelhante a FBFF (60,85) e VBF (59,90). Quanto ao KIC (MPa.mm0,5), EXP (3,35) apresentou o maior valor, semelhante a SF (2,42), que por sua vez também foi igual ao compósito convencional CD (2,01); CD apresentou KIC semelhante a SDR (1,74); SDR = VBF (1,59) = TECBF (1,57); TECBF, FU (1,54) e FBFF (1,37) apresentaram valores semelhantes. Na dependência do material, o tratamento térmico aumentou os valores dos parâmetros estudados, apontando limitações da reação de polimerização dos compósitos estudados. Com base nos resultados obtidos, podese concluir que: resinas bulk fill apresentam elevado GC, superior à resina convencional estudada; a nova classe de materiais restauradores é capaz de polimerizar em profundidade e alguns materiais apresentam KHN semelhantes no topo e na base de espécimes de 4 mm de profundidade; RF e KIC variaram de acordo com o material, e o compósito EXP apresentou os maiores valores para ambos os testes. / Facing the evolution of the resin composites and the release of the bulk-fill composite type, it is necessary to study the performance of this new class of materials. For this, the present study aimed to evaluate properties such as degree of conversion (DC), Knoop hardness (KHN), flexural strength (FS) and fracture toughness (KIC) of seven bulk-fill composites (EverX Posterior, EXP; Filtek Bulk Fill Flowable, FBFF; Fill-Up!, FU; SonicFill, SF; Surefil SDR, SDR; Tetric EvoCeram Bulk Fill, TECBF; Venus Bulk Fill, VBF) and a conventional nanohybrid composite (Charisma Diamond, CD). Complementarily, heat treatment was performed at 170 °C for 10 minutes for better understanding the behavior of these materials. Evaluation of DC (n=3) was performed by FTIR spectroscopy, the evaluation of Knoop hardness was made on the top and bottom surfaces (n=3), and three point bending test (n=10) and KIC (n=10) were evaluated on a universal testing machine. The results were submitted to analysis of variance (complemented by Tukey test) or Kruskal-Wallis test with 5% significance level. Analysis of DC (%) revealed differences between tested materials, and all bulk-fill resins had higher values than the conventional resin: SF (75.7) > VBF (66.7) = EXP (66.4) = SDR (62.8), which was also similar to FU (60.0); FU, TECBF (56.6), FBFF (56.6) and CD (54.4) showed similar conversion. KHN values showed variations according to the material and the surface: only SF showed a similar KHN (on the top surface) to CD, however it was not possible to read the bottom surface of this latter material; SF, TECBF and FBFF presented different KHN values on the top and bottom surfaces; EXP, FU, SDR and VBF maintained top and bottom similar hardness values. For FS (MPa), the results varied according to the material: EXP (122.54) = SF (101.09) = CD (99.15), the latter two being similar to FU (83.86) and TECBF (82.71), which did not differ from SDR resin (65.18); the latter showed similar behavior to FBFF (60.85) and VBF (59.90). As for KIC (MPa.mm0.5), EXP (3.35) had the highest value, similar to SF (2.42), which in turn was also equal to the conventional composite CD (2.01); CD presented KIC similar to SDR (1.74); SDR = VBF (1.59) = TECBF (1.57); TECBF, FU (1.54) and FBFF (1.37) were similar. Depending on the material, heat treatment increased the values of the parameters, pointing limitations of polymerization reaction of the studied composites. Based on these results, it can be concluded that: bulk fill resins have high DC, higher than the conventional resin studied; the new class of restorative materials is capable of polymerizing in depth and some materials exhibited similar KHN at the top and bottom surfaces of 4 mm depth specimens; FS and KIC varied according to the material, and the EXP composite showed the highest values for both tests.

The achievement of predictable and long lasting adhesive restorations in posterior teeth have always been a major objective of studies in the context of materials and techniques development. The use of bulk fill composites could provide better outcomes, but it is important to assess their physico-mechanical properties, responsible for their clinical behavior. The purpose of the present study was to assess the mechanical and physical properties of bulk fill composites. The composites were divided into 2 groups according to their viscosity. For low viscosity composites, the present study assessed: Surefill SDR flow (SDR), X-tra Base (XB), Filtek Bulk Fill Flowable (FBF), and Filtek Z350XT Flow (Z3F- control); and for high viscosity composites: Tetric Evo Ceram Bulk Fill (TBF), X-tra Fil (XF), Filtek Bulk Fill (FBP), Admira Fusion x-tra (ADM) and Filtek Z350 XT (Z3XT- control). Composites were assessed through shrinkage stress test (using 12 and 24mm3 of composite in a custom device adapted in an Universal Testing Machine); volumetric shrinkage (using 64mm3 of composite placed on a Teflon mold and scanned in a micro computed tomography/CT); Youngs modulus (through a 3-point bending test device adapted in an Universal Testing Machine); microhardness and depth of cure tests (using longitudinal Knoop microhardness). All data was evaluated regarding their homogeneity using Shapiro-Wilk test. For polymerization stress, 3-way Variance Analysis (ANOVA) was used. Considering Volumetric Shrinkage, Youngs Modulus, Microhardness and Depth of Cure, one-way ANOVA was used. All ANOVA tests were followed by Tukeys test and 5% was adopted as significance level. Shrinkage stress test with 12mm3 showed SDR, TBF and XF generating the lowest stress after 300s, followed by other high viscosity composites (ADM, FBF, XB and FBP/Z3XT). The regular low viscosity composite (Z3F) generated the highest stress for all assessed times. Considering the same test, with 24mm3, after 300s, SDR, FBP and ADM generated similar stress, followed by TBF and XF. Low viscosity bulk fill composites generated lower stress than Z3F. Considering Youngs modulus, low viscosity composites (SDR, FBF, XB and Z3F) showed the lowest values, followed by ADM and TBF. The other high viscosity composites (Z3XT, FBP and XF) showed the highest values. For microhardness test, all low viscosity composites showed lower values (FBF being the lowest). For high viscosity composites, Z3XT showed the highest values, followed by XF, FBP/TBF and ADM. Assessing depth of cure, regular composites showed lower values when compared with bulk fill composites. All bulk fill composites showed adequate depth of cure over 4.5mm (microhardness 80% of initial reading). SDR and XB showed the highest depth of cure. All high viscosity bulk fill composites generated lower volumetric shrinkage than regular composites. All low viscosity bulk fill composites showed similar volumetric shrinkage when compared to the regular composites (Z3F and Z3XT). Bulk fill composites show characteristics that allow their use in larger increments (i.e. volumetric shrinkage and polymerization stress similar or lower when compared with regular composites). Nonetheless, the mechanical properties of bulk fill composites were widely variable, being important to individually assess each material previously to its clinical application. / A obtenção de restaurações adesivas previsíveis e duradouras em dentes posteriores sempre foi objetivo de estudos na área de desenvolvimento de materiais e técnicas. O uso de resinas compostas do tipo bulk fill pode possibilitar melhores resultados, porém é importante o estudo de suas propriedades físico-mecânicas, responsáveis por seus comportamentos clínicos. O objetivo do presente estudo foi o de avaliar as propriedades físicas e mecânicas das resinas bulk fill. As resinas foram divididas em 2 grupos de acordo com sua viscosidade. Para resinas de baixa viscosidade, o presente estudo avaliou: Surefill SDR flow (SDR), X-tra Base (XB), Filtek Bulk Fill Flowable (FBF) e Filtek Z350XT Flow (Z3F-controle); e, para alta viscosidade: Tetric Evo Ceram Bulk Fill (TBF), X-tra Fil (XF), Filtek Bulk Fill (FBP), Admira Fusion x-tra (ADM) e Filtek Z350 XT (Z3XT-controle). As resinas foram avaliadas em relação à tensão de polimerização (utilizando 12 e 24mm3 de resina adaptadas em um dispositivo adaptado a uma máquina de testes universal); contração volumétrica (utilizando 64mm3 de resina composta inserida em um molde de Teflon e escaneada em um micro-tomógrafo/CT), modulo de Young (através de um dispositivo de flexão em 3 pontos adaptado a uma máquina de testes universal), microdureza e profundidade de polimerização (utilizando microdureza Knoop). Todos os resultados foram avaliados em relação à homogeneidade utilizando o teste de Shapiro-Wilk. Para avaliação da tensão de polimerização, foi empregada a Análise de Variância (ANOVA) a 3 critérios. Para as analyses de contração volumétrica, Módulo de Young, microdureza e profundidade de polimerizaçao, ANOVA a um critério foi empregada. Todas as Análises de Variância foram seguidas pelo teste de Tukey e 5% foi adotado como nível de significância. A tensão de polimerização com 12mm3 demonstrou que SDR, TBF e XF geraram valores significantemente mais baixos após 300s, seguidas por outras resinas de alta viscosidade (ADM, FBF, XB e FBP/Z3XT). A resina convencional de baixa viscosidade (Z3F) gerou valores de tensão significantemente mais elevados para todos os tempos avaliados. Considerando o mesmo teste, com 24mm3, após 300s, SDR, FBP e ADM geraram valores estatisticamente inferiores, seguidas por TBF e XF. As resinas bulk fill de baixa visocidade geraram menor tensão de polimerização que a Z3F. Considerando o modulo de Young, resinas de baixa viscosidade (SDR, FBF, XB e Z3F) apresentaram valores significantemente inferiores, seguidas por ADM e TBF. As outras resinas de alta viscosidade (Z3XT, FBP e XF) apresentaram valores significantemente mais elevados. Para o teste de microdureza, todas as resinas de baixa viscosidade apresentaram valores inferiores (FBF apresentou o menor). Para as resinas de alta viscosidade, Z3XT apresentou os valores mais elevados, seguida por XF, FBP/TBF e ADM. Para profundidade de polimerização, resinas compostas convencionais apresentaram valores signifixantemente mais baixos quando comparadas com resinas bulk fill. Todas as resinas bulk fill apresentaram profundidade de polimerização adequada até pelo menos 4,5mm (microdureza 80% da leitura inicial/superfície). SDR e XB apresentaram os valores mais altos de profundidade de polimerização. Todas as resinas bulk fill de alta viscosidade geraram menor contração volumétrica que resinas compostas convencionais. Todas as resinas bulk fill de baixa viscosidade apresentaram contração volumétrica similar às resinas convencionais (Z3F e Z3XT). Resinas compostas bulk fill apresentaram características que possibilitam sua indicação para serem empregadas em grandes incrementos (contração volumétrica e tensão de polimerização similar ou inferiores às resinas convencionais, além de maior profundidade de polimerização). No entanto, as propriedades mecânicas variaram grandemente entre as resinas estudadas sendo importante uma avaliação individual de cada material previamente ao seu uso clínico.

The objective of this thesis is to study the fracture behavior of bulk metallic glasses. For this purpose, detailed finite element investigation of the mode I and mixed mode (I and II) stationary crack tip fields under plane strain, small scale yielding conditions is carried out. An implicit backward Euler finite element implementation of the Anand and Su constitutive model [Anand, L. and Su, C., 2005, J. Mech. Phys. Solids 53, 1362] is used in the simulations. The effects of internal friction (μ), strain softening, Poisson's ratio (ν) and elastic mode mixity (Me) on the near-tip stress and deformation fields are examined. The results show that under mode I loading, a higher μ leads to a larger normalized plastic zone size and higher plastic strain level near the notch tip, but causes a substantial decrease in the opening stress. The brittle crack trajectories and shear band patterns around the notch are also simulated. An increase in ν reduces the extent of plastic zone and plastic strain levels in front of the notch tip. The results from mixed mode simulations show that increase in the mode II component of loading dramatically increases the maximum plastic zone extent, lowers the stresses and significantly enhances the plastic strain levels near the notch tip. Higher μ causes the peak magnitudes of tensile tangential stress to decrease. The implications of the above results on the fracture response of bulk metallic glasses are discussed. The possible variations of fracture toughness with mode mixity predicted by employing two simple fracture criteria are examined. Finally, mixed mode (I and II) fracture experiments on a Zr-based bulk metallic glass are performed. It is found that the fracture toughness increases with Me and Jc under mode I is higher than that under mode II loading by a factor of 4. The operative failure mechanism and fracture process zone size are discerned based on observations of incipient crack growth and fractographs. Lastly, a fracture criterion is proposed which predicts the experimentally observed variation of fracture toughness with mode mixity.

One of the most important properties of an explosive is its velocity of detonation (VOD). It is essential that the explosive should detonate at its optimum rate and release sufficient detonation pressure to get good fragmentation under the existing field conditions. The main objectives of this research study are to investigate the effects of explosive type, blast hole diameter, and degree of confinement on the VOD of bulk ANFO and bulk emulsion in Kumtor Open Pit Gold Mine. In this study, the continuous resistance wire method is employed to measure in-situ VOD of both bulk ANFO and bulk emulsion. The VOD values are measured for different hole diameters and under different confinements for both explosives. The ideality of bulk ANFO and bulk emulsion is calculated by comparing the in-situ measured VOD&rsquo / s and their ideal detonation values. It is found that the VOD of both explosives increases as the blast hole diameter and the degree of confinement increases. In addition to this, VOD of bulk ANFO decreases when it gets wet in the blast hole. Another finding is that, proportion of bulk emulsion ingredients has influence on its VOD. This research study provides a good understanding to use suitable explosive in existing rock conditions in Kumtor Open Pit Gold Mine.

The analysis and development of robust sensing platforms based on solidly-mounted ZnO bulk acoustic wave devices was proposed. The exploitation of acoustic energy trapping was investigated and demonstrated as a method to define active sensing areas on a substrate. In addition, a new "hybrid" acoustic mode experiencing acoustic energy trapping was studied theoretically and experimentally. This mode was used as an explanation of historical inconsistencies in observed thickness-shear mode velocities. Initial theoretical and experimental results suggest that this mode is a coupling of thickness-shear and longitudinal particle displacements and, as such, may offer more mechanical and/or structural information about a sample under test. Device development was taken another step further and multi-mode ZnO resonators operating in the thickness-shear, hybrid, and longitudinal modes were introduced. These devices were characterized with respect to sample viscosity and conductivity and preliminary results show that, with further development, the multi-mode resonators provide significantly more information about a sample than their single-mode counterparts. An alternative to resonator-based platforms was also presented in the form of bulk acoustic delay lines. Initial conceptual and simulation results show that these devices provide a different perspective of typical sensing modalities by using properly designed input pulses, device tuning, and examining overall input and output signal spectra.