O propósito deste estudo foi o de avaliar a influência do sistema adesivo e do envelhecimento na resistência adesiva da interface dentina humana-resina composta. Cento e sessenta terceiros molares extraídos tiveram suas raízes removidas e as coroas seccionadas no sentido mésio-distal. As faces vestibulares foram incluídas em anel de PVC/resina acrílica e divididas em quatro grupos correspondentes aos quatro sistemas adesivos testados: um sistema adesivo de condicionamento total, como controle, Adper Single Bond 2 (ASB 2) (3M ESPE); um sistema adesivo autocondicionante de passo único, Adper Easy One (AEO) (3M ESPE); e dois sistemas adesivos autocondicionantes de dois passos, P90 System Adhesive (P90SA) (3M ESPE), e Clearfill SE Bond (CSEB) (Kuraray). Cada grupo foi dividido em quatro subgrupos correspondentes aos quatro tipos de envelhecimentos artificiais utilizados: termociclagem com 500, 10.000 e 30.000 ciclos e estocagem em água destilada a 37ºC por um ano e, após este período, termociclagem com 500 ciclos. Desta maneira, formou-se 16 subgrupos: ASB2.1, ASB2.2, ASB2.3, ASB2.4; AEO.1, AEO.2, AEO.3, AEO.4; P90SA.1, P90SA.2, P90SA.3, P90SA.4; CSEB.1, CSEB.2, CSEB.3, CSEB.4. Após o envelhecimento artificial padronizado foi realizado o teste de resistência ao cisalhamento ISO TR 11405, usando uma máquina universal de testes EMIC-2000, regulada a 0,5mm/minuto e célula de carga de 200 Kgf. Os resultados foram submetidos à análise estatística de variância (Testes ANOVA, Tukey e Scheffé). Houve diferença estatística significante (p<0,01) para dois fatores de variação (adesivo e envelhecimento) e a interação adesivo x envelhecimento (p<0,01) não apresentou diferença estatística significante. O adesivo Adper Single Bond 2, apresentou maiores valores, enquanto que, o P90 System Adhesive, os menores valores de resistência adesiva ao cisalhamento em relação aos demais sistemas adesivos. A termociclagem de 500 ciclos e a estocagem em água a 37ºC por um ano, seguida de 500 ciclos térmicos apresentaram os mais elevados valores de resistência adesiva, sem diferenças estatísticas significantes, assim com a termociclagem de 10.000 e 30.000 ciclos apresentaram os valores mais baixos. Baseado nestes achados pode-se concluir o sistema adesivo e o envelhecimento influenciaram a resistência ao cisalhamento da interface dentina humanaresina composta. / The purpose of this study was to evaluate the influence of the adhesive system and aging on the bond strength of human dentin-composite resin interface. One hundred and sixty extracted third molars had their crowns removed and the roots sectioned mesiodistally. The buccal faces were included ring PVC/acrylic resin and they were divided into four groups corresponding to the four tested adhesive systems tested. A total etch adhesive system, as controls, Adper Single Bond 2 (ASB 2) (3M ESPE), an all-in-one self-etching adhesive system, Adper Easy One (AEO) (3M ESPE) and two two steps self-etching adhesive systems, P90 System Adhesive (P90SA) (3M ESPE), and Clearfill SE Bond (CSEB) (Kuraray). Each group was divided into four subgroups corresponding to four types of used artificial aging: thermocycling with 500, 10,000 and 30,000 cycles and storage in distilled water at 37°C for one year and after this period, thermocycling with 500 cycles. Thus was formed 16 subgroups: ASB2.1, ASB2.2, ASB2.3, ASB2.4; AEO.1, AEO.2, AEO.3, AEO.4; P90SA.1, P90SA.2, P90SA.3, P90SA.4; CSEB.1, CSEB.2, CSEB.3, CSEB.4. After accelerated aging test was standardized shear bond strength ISO TR 11405, using a universal testing machine (EMIC-2000) set at 0.5 mm/minute and a load cell of 200 kgf. The results were subjected to statistical analysis of variance (ANOVA, Tukey and Scheffe). There was a statistically significant difference (p<0.01) for two factors of variation (adhesive and aging) and not for the interaction adhesive x aging (p<0.01). The adhesive Adper Single Bond 2 showed higher values of shear bond strength, whereas the P90 System Adhesive showed the lowest values of shear bond strength compared to other adhesive systems. The thermocycling regimen of 500 cycles and storage in water at 37°C for one year, followed by 500 thermal cycles showed the highest bond strength values, no statistically significant differences, as well as thermocycling of 10,000 and 30,000 cycles showed the lowest values. Based on these findings it can be concluded the adhesive system and aging affected the shear bond strength of human dentin-composite resin interface.

The standard model of the thermal and chemical structure of cratons has been scrutinized in recent years as additional data have been collected. Recent seismological and petrological studies indicate that the notion of cratonic lithosphere as a thick thermal boundary layer with a very depleted and dehydrated composition may be too simplistic and does not fully explain all aspects of the seismological and petrological observations. We hypothesized that the cratonic lithosphere may be more complicated and designed an experiment to investigate its thermal, chemical, and mineralogical properties using a global database of fundamental mode Rayleigh surface waves. To test this hypothesis, the phase velocities of Rayleigh wave that travel paths primarily over cratons were selected. A 1-D global craton phase velocity profile was generated from these observations and compared to predicted phase-velocity curves using two different forward modeling techniques. With the first approach, profiles of shear velocity were generated based on educated guesses of upper mantle temperatures using geotherms. With the second approach, profiles of shear velocity were generated using random permutations about 1-D global model STW105. In total 5,625 geotherm and 80,000 random 1-D forward models were generated for comparison. Each shear velocity model was converted to phase velocity and compared to the observed range of cratonic phase velocities, defined as within one standard deviation of the mean. This method was able to constrain shear velocity in cratons relatively well though the 1-D profiles deviate at depths shallower than 100 km. Shear velocity is faster than PREM/STW105 to depths greater than 200 km with constantly increasing velocity with depth in the random model and a low velocity layer at 100-150 km.

A large data set comprising normal-mode eigenfrequencies, quality factors and splitting functions, Earth's mass and moment of inertia, surface-wave phase anomalies and dispersion curves, body-wave arrivals and traveltime curves, as well as long-period waveforms is inverted to obtain the distribution of elastic properties, shear attenuation and density in the Earth's interior. We address three fundamental aspects of global seismology by reconciling and modeling data sets with several methodological improvements, such as accounting for radial and azimuthal anisotropy, development of better methods for crustal corrections, and devising novel regularization and parameterization schemes. In the first contribution, we incorporate normal-mode splitting functions with other seismological data sets to examine the variation of anisotropic shear-wave velocity in the Earth's mantle. Our preferred anisotropic model, S362ANI+M, has strong isotropic velocity anomalies in the transition zone while the anisotropy is restricted to the upper 300~km in the mantle. When radial anisotropy is allowed throughout the mantle, large-scale anisotropic patterns are observed in the lowermost mantle with v_SV > v_SH beneath Africa and South Pacific and v_SH > v_SV beneath several circum-Pacific regions. However, small improvements in fits to the data on adding anisotropy at depth leave the question open on whether large-scale radial anisotropy is required in the transition zone and in the lower mantle. We demonstrate the utility of mode-splitting data in reducing the tradeoffs between even-degree variations of isotropic velocity and anisotropy in the lowermost mantle. We then devise a methodology to detect seismological signatures of chemical heterogeneity using scaling relationships between shear velocity, density and compressional velocity in the Earth's mantle. Several features reported in earlier tomographic studies persist with the inclusion of new and larger data sets; anti-correlation between bulk-sound and shear velocities in the lowermost mantle as well as an increase in velocity scaling (nu=dlnv_S/dlnv_P) with depth in the lower mantle are found to be robust. Many spheroidal and toroidal modes are largely incompatible with perfect correlations between density and shear-velocity variations in the lowermost mantle. A way to fit concurrently the various data sets is by allowing independent density perturbations in the lowermost mantle. Our preferred joint model consists of denser-than-average anomalies (~1% peak-to-peak) at the base of the mantle roughly coincident with the low-velocity superplumes. The relative variation of shear velocity, density and compressional velocity in this study disfavors a purely thermal contribution to heterogeneity in the lowermost mantle. In the third contribution, we introduce an approach to construct a 1-D reference model that is consistent with crustal heterogeneities and various asphericities in the Earth's mantle. We demonstrate that the crust contributes substantially to fundamental-mode dispersion curves when the nonlinear effects of its thickness and velocity variations are taken into consideration. We apply appropriate crustal corrections and perform several iterations to converge to our preferred radial model NREM1D, which is anisotropic in the upper mantle and smooth across the 220-km discontinuity for all physical parameters. Radial anisotropy in the shallowest mantle, with a maximum at ~150~km depth, is required to fit global averages of fundamental-mode Rayleigh and Love wave dispersion (25--250s). NREM1D also predicts arrival times of major mantle and core phases in agreement (+/- 0.5s) with a recent isotropic velocity model that was optimized for earthquake location. The new reference Earth model NREM1D introduced here is easily extendable due to its modular construction as a linear combination of radial basis functions and can be used for earthquake location, spherical-earth normal mode calculations, and as a starting model in studies of lateral heterogeneity.

From initial contact with water until hardening, and deterioration, cement and concrete materials are subjected to various chemical and physical transformations and environmental impacts. This thesis focuses on the properties during the fresh state, shortly after mixing until the induction period. During this period flow history, including shearing and resting, and hydration both play big roles in determining the rheological properties. The rheological properties of cement and concrete not only affect the casting and pumping process, but also very critical for harden properties and durability properties. Compared with conventional concrete, self-consolidating concrete (SCC) can introduce many advantages in construction application. These include readiness to apply, decreasing labor necessary for casting, and enhancing hardened properties. However, challenges still remain, such as issues relating to formwork pressure [1-7] and multi-layer casting [8]. Each of these issues is closely related to the property of thixotropy. From the microstructural point of view, thixotropy is described as structural buildup (flocculation) under rest and breakdown (deflocculation) under flow. For SCC, as well as other concrete systems, it is about balancing sufficient flowability during casting and rate of structural buildup after placement for the application at hand. For instance, relating to the issue of SCC formwork, it is ideal for the material to be highly flowable to achieve rapid casting, but then exhibit high rate of structural buildup to reduce formwork pressure. This can reduce the cost of formwork and reduce the risk of formwork failure. It is apparent that accurately quantifying the two aspects of thixotropy, i.e. structuration and destructuration, is key to tackling these challenges in field application. Thus, the overall objective of my doctoral study is to improve quantification of key parameters tied to thixotropy that we have identified to be important: static yield stress, cohesion and degree of shear-induced particle migration. The two main contributions are as follows: Firstly, I quantified structuration of fresh paste and mortar systems by measuring static yield stress. After an extensive review of various rheological methods to probe viscoelastic properties of yield stress fluids, I selected, developed, and implemented a creep recovery protocol. Creep results were supplemented by low-amplitude oscillatory shear results, and supported that the measured static yield stress corresponds to the solid-liquid transition. This improved quantification of static yield stress can help better understand the effect of mix composition on SCC formwork pressure development, as well as static segregation and stability [9]. Since the static yield stress is measured before the structure is broken down, the effects of sand migration are eliminated. This study also analyzed effects of other supplementary cementitous materials such as nanoclay and fly ash. Results showed that nanoclay effectively increases static yield stress and structuration rate, while fly ash decreases static yield stress. To complement this investigation, I studied cohesion using the probe tack test, as cohesion is widely cited to be closely related to formwork pressure. I verified that probe tack test is a quick and useful method to measure static cohesion. Results showed that nanoclay increased cohesion dramatically while fly ash did not have an apparent effect on cohesion. Secondly, I developed an empirical model to fit the stress decay process under constant shear rate, For mortar systems, the stress decay can be attributed to two mechanisms: colloidal destructuration and sand migration. Such a model could be used to characterize particle migration and dynamic segregation [10], a critical issue for casting applications. In addition, shear induced particle migration is a widely recognized challenge in characterizing mortars and concretes through shear rheological methods [11-13]. Therefore this model can help determine the range of shear rates within which migration can be minimized to guide the design of protocols for dynamic rheological characterization and to ultimately develop design strategies to minimize mitigation. Compared with currently existing methods, this model provides a faster approach to quantify the sand migration process, including kinetics.

In two-phase flow, the void fraction and its distribution are two major factors describing the characteristic of flow patterns. Better understanding of void fraction distribution in two-phase flow would help improve safety and efficiency in the nuclear industry as the heat transfer process is significantly affected by the void distribution in nuclear reactor fuel bundles. Lift force is proposed to explain the lateral migration of bubbles in the shear flow (Feng & Bolotnov, 2017, Lucas & Tomiyama, 2011, Akio Tomiyama, Tamai, Zun, & Hosokawa, 2002). However, the mechanism of lift force is unclear and the research on lift force is limited.<div><br></div><div>An experimental investigation is performed on the lift force of single bubble in weak linear shear flow field in water. In addition, characteristics of bubble motion including bubble terminal velocity, aspect ratio and oscillation amplitude are studied and comparisons are made with existing models.<br></div><div><br></div><div>It was found that the model proposed by Tomiyama et al. (A. Tomiyama, Celata, Hosokawa, & Yoshida, 2002) has the best prediction of bubble terminal velocity with introduction of a tuning factor in consideration of the asymmetric deformation of bubble. Bubble aspect ratio is found to significantly affect its terminal velocity, and a new model is proposed to best fit the experiment data. It is also observed that the shear rate magnitude has no influence on bubble aspect ratio in this study. Oscillation was observed for all the bubbles in this experiment. Oscillation amplitude scattered widely and it was difficult to correlate it only with the bubble equivalent diameter. In terms of lift force, positive lift coefficient was observed for small size bubbles and transits to negative value with growing size. Due to the high Reynolds number of flow and low viscosity of water, widely scattered data is found in the results. Although the accurate prediction of lift coefficient is difficult to obtain in the experiment, the lift coefficient transition trend is given and agrees with many other research. In addition, this research provides a database for further lift coefficient investigation.<br></div>

A presente dissertação enfoca as características de resistência ao cisalhamento e os mecanismos básicos que governam o fenômeno de atrito em rochas fraturadas. Especial atenção é dedicada à identificação de fatores geométricos e geotécnicos importantes e a sua relação com o comportamento e esforços resistentes de rochas fraturadas. A caracterização de fraturas por meio de parâmetros geomecânicos adequados permitirá incluí-los nos modelos de cálculo e simular mais realisticamente o comportamento geomecânico do maciço rochoso fraturado. / This thesis focuses on the shear strenght and mechanisms that change the shear characteristics of jointed rocks. Special attention was devoted to the identification of geometric and geotechnical factors and its relationship with the behavior and strenght of jointed rocks. The characterization of the fractures by apropriated geomechanical parameters Will permite to include them in the models and to simulate more realistically the behavior of fractured rock mass.

O setor eólico está em processo de consolidação no Brasil desde o início dos anos 2000, e oportunidades de pesquisas e desenvolvimento estão presentes em todas as etapas do processo. Este trabalho apresenta uma relação entre os parâmetros de velocidade do vento, energia, efeito de esteira e intensidade de turbulência com diferentes alturas de turbinas existentes no mercado brasileiro, em três regiões distintas, Triunfo/PE, São João do Cariri/PB e São Martinho da Serra/RS. A finalidade do trabalho é auxiliar os desenvolvedores e os investidores de parques eólicos na tomada de decisão sobre as alturas de aerogeradores a serem consideradas em seus projetos eólicos, antecipando a avaliação criteriosa do recurso eólico local. Para tal, primeiramente são citadas referências de trabalhos similares disponíveis na literatura bem como é realizada a fundamentação teórica do estudo com as principais equações e modelos utilizados na área. A metodologia do cálculo é teórica e aplicada às ferramentas computacionais do WAsP para a modelagem do vento e do WindFarmer para avaliar a produção de energia elétrica, com adaptações específicas para cada projeto. Procedimentos estatísticos são efetuados a fim de se garantir que as análises contenham o menor nível possível de incerteza na identificação do recurso eólico de cada região. Os resultados do trabalho são apresentados comparativamente entre os sete modelos de aerogerador testados e também entre as três áreas estudadas. O comportamento das turbinas é consideravelmente diferente em todas as opções estudadas. Os modelos de aerogerador A e D são os que apresentam o maior ganho energético percentual com o incremento da altura da turbina com valores médios de 0,42% e 0,44% a cada metro. Já os modelos C e D apresentam as melhorias mais consideráveis em termos de redução de intensidade de turbulência e diminuição de perdas por efeito de esteira, conforme se aumenta a altura das turbinas. As áreas apresentam, também, recursos eólicos distintos entre elas. O projeto eólico de Triunfo é o que apresenta a maior geração de energia dentre os estudados, sendo 24,2% maior que em São Martinho da Serra e 45,0% maior que em São João do Cariri. Verifica-se, também, que caso a velocidade média do vento de longo prazo fosse dobrada em Triunfo, a energia líquida teria um acréscimo de 88%. Já em São Martinho da Serra este valor chegaria em 170% e em São João do Cariri em 220%. / The wind energy sector has been under consolidation in Brazil since the early 2000s. Opportunities for researches and developments are present at all stages of the process. This paper presents a link among wind speed, energy, wake effect and turbulence intensity parameters and the height of existing wind turbine models in Brazil, considering three distinct regions as Triunfo/PE, São João do Cariri/PB and São Martinho da Serra/RS. This paper also aims to support developers and investors in the decision making process in the wind turbines height that should be considered in its wind farms. To this end, the references of similar studies as well as the theoretical basis for the study, including the main equations and models, are presented. The calculation methodology is theoretical and it has been applied to the computational tools WAsP (wind modeling) and WindFarmer (evaluate the energy production), considering specific adaptations for each project. Statistical procedures are performed in order to ensure that the analyses contain the lowest possible level of uncertainty in the characterization of the wind resources in each region. The results are presented comparatively among the seven tested turbine models and also among the three studied areas. The turbine models behavior is considerably different for all options. The wind turbine models A and D are those with the highest percentage energy increase with increasing the turbine height. Their average values are 0.42% and 0.44% per meter height. The models C and D present the most considerable improvements in terms of turbulence intensity and wake effect reductions with increasing the turbine height. The different locations also present distinguished wind resources among them. Triunfo wind farm is the one with the highest energy generation, 24.2% higher than in São Martinho da Serra and 45.0% higher than in São João do Cariri. It is also noted that if the long term mean wind speed was doubled in the project locations, the energy would have an increase of 88% in Triunfo, 170% in São Martinho da Serra and 220% in São João do Cariri.

During the past decades there has been an increase in the use of geosynthetics in construction due to their versatility in providing a wide array of functions such as reinforcement, containment, separation, filtration and drainage. Often, geosynthetics are used in conjunction with other geosynthetics to accomplish these functions. However, geosynthetics create possible planes of weakness which can lead to failures. Textured geomembranes are widely used within landfill and mining industries due to their containment and shear strength properties, however, there are subjected to a wide array of loads and environments which are potentially hazardous, as such is of utmost importance to retain their integrity in order to avoid ecological disasters. The challenge is to understand how geomembranes resist damage, wear and which of these factors control the development of wear on textured geomembranes. Digital imaging techniques have been used in order to develop a protocol that describes the quantification of wear on textured structured geomembranes. Direct shear tests were performed to induce wear on the geomembrane textures (asperities) to analyse the wear mechanisms and study the factors that induce wear on the asperities. The research showed that normal stress and shear displacement have a major role in the development of wear on interfaces. However, the geometrical characteristics of the geomembrane asperities control the amount of wear the geomembrane can sustain without significant shear strength loss. These outcomes help to better understand the behaviour of interfaces which have as component geomembranes, leading to more robust designs. This study also proposed new asperity texture shapes by using Rapid Prototyping (RP) techniques, such as Selective Laser Sintering and Fused Filament Fabrication. Using RP techniques to create new textures for the geomembrane, could allow the creation of textures which have increased shear strength thresholds and better withstand wear, allowing for more advanced and economical designs.

Plantar foot stress causing foot ulceration is a diabetic complication causing major economic burden throughout the world. It has long been thought that shear stresses on the plantar surface of the foot are a major contributing factor to the formation of these ulcers. Although there are many instruments available that measure the vertical foot pressure (vertical forces), there are currently no commercially available instruments to measure the horizontal or shear forces. It is the aim of this project to develop a platform instrument capable of measuring the three dimensional forces (i.e. vertical pressure and shear forces) across the plantar surface of the foot.

Construction practices are constantly evolving in order to adapt to physical locations and economic conditions. These adaptations may result in more cost-effective designs, but may also come at a cost of strength. In masonry shear walls, it is becoming more common to reduce the amount of grouting from every cell to only those with reinforcement, a practice known as partial-grouting. Partially-grouted masonry responds differently and in a more complex matter to lateral loads as compared to fully-grouted masonry. The response is made even more complex by wall discontinuities in the form of openings. The main objective of this study is to validate the strut-and-tie procedure for the in-plane lateral strength prediction of partially-grouted, multistory, reinforced concrete masonry walls with openings. The research included testing six three story, half-scale masonry shear walls. Half of the walls had door openings while the other half had window openings. The configurations were selected to represent typical walls in multi-story buildings. The measured lateral strength was compared to estimations from the equations in the US masonry code and to those from an equivalent truss model and a strut-and-tie model. The results show that the U.S. masonry code equations over predicts while the equivalent truss model under predicts the lateral strength of the walls. The results further show that the strut-and-tie model is the most accurate method for lateral strength prediction and is able to account for wall openings and partial-grouting.