Fast switching operations in IGBTs generate electromagnetic field disturbances, which might cause EMI and functionality issues. For higher frequency characterization, the parasitic inductances and capacitances have to be considered. The characterization of the electromagnetic field disturbances in- and around the converter module could be predicted early in the design. The study involves a high frequency characterization of electric fields (Efield), magnetic fields (H-fields) and the surface currents distribution in a converter module. The high frequency electromagnetic software (CST) was used for the analysis. A given 3D CAD model of an AC/DC converter module was analyzed in CST. The CAD contained IGBT bus-bars interconnections, converter casing, heat sink and other metallic structures. The ACside has six IGBTs and the DC-side has a chopper which has two switches. The IGBTs ONstate and OFF state was modeled with lumped elements. The DC link capacitor was just modeled as lumped elements, while the metallic capacitor casing was included in the 3D model for analyzing the field distribution inside the converter casing. To check the model accuracy, CST models were compared with PEEC (Partial Element Equivalent Circuit) models for simple antenna cases. Using the converter geometry, CST estimates the parasitics and the eventual current, voltage and electromagnetic field distributions for a given excitation signal. The DC-link was excited with a step pulse and the fields were computed. With consideration of specific design details, the modeling approach developed in this study, could be used to construct high frequency models of converter modules for different projects.

[pt] O comportamento de vigas de concreto armado com barras de polímero reforçado com fibras de vidro (PRFV) submetidas ao esforço cortante tem diferenças quando comparada ao tradicional uso de armaduras de aço. O relativo baixo módulo de elasticidade e menor resistência ao carregamento transversal de barras de PRFV alteram a ação dos mecanismos de resistência e cinemática da fissura crítica ao cortante. Nesse contexto, a aplicação de fibras dispersas na matriz de concreto se coloca como uma possibilidade para buscar a redução da flexibilidade desse tipo de elemento. Sendo assim, este trabalho investiga o comportamento experimental de quatro vigas de concreto armado com barras de PRFV sem e com estribos e fibras de basalto. Utilizando-se da técnica de Correlação de Imagem Digital (CID), os campos de deslocamentos do vão de ruptura foram mapeados e, por meio de modelos constitutivos dos mecanismos resistentes à força cortante disponíveis na literatura, analisou-se o comportamento resistente das vigas. A quantificação de resistência através dos modelos constitutivos apresentou uma satisfatória correlação com os resultados experimentais. Além disso, a análise possibilitou uma melhor compreensão da contribuição dos mecanismos resistentes em diferentes estágios de carregamento. / [en] The shear behavior of reinforced concrete beams with Glass Fiber Reinforced Polymer Bars (GFRP) has differences when compared to traditional steel reinforcement. The relative low modulus of elasticity and the lower resistance to transverse loading of GFRP bars change the resistance mechanisms and kinematics of the critical shear crack. In this context, the application of dispersed fibers in the concrete matrix may be used to try to reduce the flexibility of this type of element. Therefore, this work investigates the experimental behavior of four reinforced concrete beams with GFRP bars with and without stirrups and basalt fibers. By using Digital Image Correlation (DIC) technique, the displacement fields of the failure span were mapped and, by means of constitutive models of the shear resistant mechanisms available in the literature, the resistant behavior of the beams was analyzed. The evaluation of resistance mechanisms through the constitutive models showed a satisfactory correlation with the experimental results. In addition, the analysis provided a better understanding of the contribution of each resistant mechanisms at different stages of loading.

No description available.

Yes / This paper explores the development of the most suitable machine learning models for predicting the bending capacity of steel and FRP (Fiber Reinforced Ploymer) bars hybrid reinforced ECC (Engineered Cementitious Composites)-concrete composite beams. Five different machine learning models, namely Support Vector Regression (SVR), Extreme Gradient Boosting (XGBoost), Multilayer Perceptron (MLP), Random Forest (RF), and Extremely Randomized Trees (ERT), were employed. To train and evaluate these predictive models, the study utilized a database comprising 150 experimental data points from the literature on steel and FRP bars hybrid reinforced ECC-concrete composite beams. Additionally, Shapley Additive Explanations (SHAP) analysis was employed to assess the impact of input features on the prediction outcomes. Furthermore, based on the optimal model identified in the research, a graphical user interface (GUI) was designed to facilitate the analysis of the bending capacity of hybrid reinforced ECC-concrete composite beams in practical applications. The results indicate that the XGBoost algorithm exhibits high accuracy in predicting bending capacity, demonstrating the lowest root mean square error, mean absolute error, and mean absolute percentage error, as well as the highest coefficient of determination on the testing dataset among all models. SHAP analysis indicates that the equivalent reinforcement ratio, design strength of FRP bars, and height of beam cross-section are significant feature parameters, while the influence of the compressive strength of concrete is minimal. The predictive models and graphical user interface (GUI) developed can offer engineers and researchers with a reliable predictive method for the bending capacity of steel and FRP bars hybrid reinforced ECC-concrete composite beams.

Yes / This paper investigates the feasibility of using artificial neural networks (NNs) to predict the shear capacity of concrete members reinforced longitudinally with fibre reinforced polymer (FRP) bars, and without any shear reinforcement. An experimental database of 138 test specimens failed in shear is created and used to train and test NNs as well as to assess the accuracy of three existing shear design methods. The created NN predicted to a high level of accuracy the shear capacity of FRP reinforced concrete members. Garson index was employed to identify the relative importance of the influencing parameters on the shear capacity based on the trained NNs weightings. A parametric analysis was also conducted using the trained NN to establish the trend of the main influencing variables on the shear capacity. Many of the assumptions made by the shear design methods are predicted by the NN developed; however, few are inconsistent with the NN predictions.

[pt] As barras pultrudadas de polímeros reforçados com fibras, em especial, as fibras de vidro (GFRP), vem ganhando espaço como reforço de elementos estruturais, principalmente devido a características únicas de compósitos de FRP como, elevada resistência mecânica, baixo peso específico e natureza não corrosiva. Entretanto, diferente das armaduras de aço, em geral, as barras de FRP se comportam com propriedades elásticas anisotrópicas, não homogêneas e lineares, o que pode resultar em um mecanismo de transferência de forças diferente, entre a armadura e o concreto. Estas propriedades aliadas ao seu baixo módulo de elasticidade podem levar a um cenário de elementos estruturais com maiores aberturas de fissuras e maiores deslocamentos quando comparado a elementos armados por barras de aço. Sob esta perspectiva, este trabalho pretende avaliar a partir de um programa experimental, o comportamento estrutural de elementos de concreto reforçado com barras pultrudadas de GFRP e com adição fibras de aço. Seis vigas hiperestáticas foram submetidas a flexão, avaliando-se a influência da adição de fibras de aço em teores de 40 e 80 kg/m3 com taxas de armaduras variando entre 181 por cento e 368 por cento da taxa balanceada. Ensaios estruturais foram realizados para investigar o padrão de formação de fissuras, as deflexões, a transferência de esforços e a variação do modo de falha dos elementos. O concreto reforçado com fibras de aço (CRFA) foi caracterizado por meio de ensaio de flexão de três pontos, segundo a NBR 16940, para obtenção das tensões residuais utilizadas no dimensionamento dos elementos. Os CRFA apresentaram comportamento deflection softening e deflection hardening, além do acréscimo de tensões pós-fissuração com o aumento do teor de fibras. Os ensaios estruturais realizados em vigas hiperestáticas apresentaram ganhos de até 42 por cento na carga resistida pelas vigas com concreto reforçado com fibras de aço, além de menores deflexões e menores aberturas de fissura. Contudo, os estribos de GFRP, mesmo combinados com a adição de fibras de aço, se mostraram insuficientes para combater a influência da força cortante, levando as vigas à falha por cisalhamento. / [en] Pultruded bars made of fiber-reinforced polymers, especially glass fibers (GFRP), have been gaining ground as a reinforcement of structural elements, mainly due to the unique characteristics of FRP composites, such as high mechanical strength, low specific weight, and non-corrosive nature. However, unlike steel reinforcement, in general, FRP bars behave with anisotropic, non-homogeneous and linear elastic properties, which can result in a different force transfer mechanism between the reinforcement and the concrete. These properties allied to its low young modulus can lead to a scenario of structural elements with greater crack openings and greater displacements when compared to steel bars reinforced elements. From this perspective, this work intends to evaluate, from an experimental program, the structural behavior of concrete elements reinforced with pultruded GFRP bars and with addition of steel fibers. Six statically indeterminate beams were subjected to bending and the influence of the addition of steel fibers in ratios of 40 and 80 kg/m3 with reinforcement rate varying between 181 per cent and 368 per cent regarding the balanced rate was evaluated. Structural tests were carried out to investigate the crack formation pattern, deflections, stress transfer and the variation in the failure mode of the elements. The steel fiber reinforced concrete (SFRC) was characterized by means of a three-point bending test, according to NBR16940, to obtain the residual strength used in the design of the elements. The SFRC showed both deflection softening and deflection hardening behavior, in addition to the post-cracking strength improvement with the increase of the fiber content. The structural tests carried out on statically indeterminate beams showed an increase of up to 42 per cent in the load bearing capacity of beams with steel fiber reinforced concrete, in addition to lower deflections and reduced crack width. However, the GFRP stirrups, even combined with the addition of steel fibers to concrete, proved to be insufficient to withstand the influence of the shear force, leading the beams to shear failure.

This thesis is an ethnographic study of two local institutions within the community of Fallin which explores how twenty-four men understand, maintain and reproduce community and belonging. Throughout, the thesis suggests that the past acts as a stable reference point for the men to deal with social change. The Bowling Club and the Pub are suggested as being sanctuaries for this type of collective remembering to take place as they still reflect a mode of life associated with the past. It is argued that imagined histories were recollected, recreated and maintained through the power of storytelling and sharing experiences to the younger generations or outsiders (Blenkinsopp, 2012; Homans, 1974). This thesis suggests that perceived threats from outsiders only serve to further galvanise the central values of their community (Cohen, 1985; Homans, 1974). Chapter Two provides a review of the literature and theoretical concepts which sets out the academic foundations of this thesis. The work of Bourdieu shapes the theoretical, methodological and reflexive nature of this project. Chapter Three introduces the ethnographic method which gives this study an in-depth account of the narratives and identities of the men in this project. Chapter Four outlines the reflexive nature of the author’s relationship with the community, the Bowling Club and The Goth and how this affects the interpretations presented in this thesis. Chapter Five provides the reader with descriptive and demographic data of the community of Fallin and the research sites. Chapters Six and Seven analyse the data and directly answer the research question through interpreting interview data and using field notes. Concluding in Chapter Eight, this thesis suggests that the version of community that the men helped to reproduce and maintain is strongly associated with a historical working-class mode of life. This thesis suggests that these local institutions reproduce historical notions of community and belonging through outside forces and incomers challenging this traditional mode of life. Of particular interest is how the younger men in the study often adopt this shared habitus and learn how to be a man through regular interactions in The Goth and the Bowling Club.

Cette thèse est composée de deux parties. La première partie est liée à l’augmentation sous impact des résistances des nids d'abeilles en compression uniaxiale. D’abord, nous avons étudié ce phénomène particulier numériquement à l’aide des modèles éléments finis et cela nous a permis de démontrer le rôle de l’inertie latéral dans cette augmentation. Ensuite, le comportement dynamique d'une série de nids d'abeilles (tailles de cellule et épaisseurs des parois et matériau de base différents) a été étudiée expérimentalement pour confirmer les résultats de la simulation. La deuxième partie concerne le comportement biaxial de nids d'abeilles sous cisaillement-compression combinés. Nous y présenterons d'abord un dispositif pour appliquer le cisaillement-compression combiné, en utilisant un système des barres de Hopkinson viscoélastiques de grand diamètre. Une série d'essais sur des nids d'abeille en aluminium sont réalisées en statique et en dynamique, avec les angles de chargement allant de 0° à 60o (part de cisaillement de plus en plus important). Ces essais montrent un important effet du cisaillement supplémentaire sur la résistance globale du nid d'abeille. Une augmentation de la résistance sous chargement d'impact est observée pour tous les angles. Les images capturées lors des essais permettent de la détermination des deux modes de déformations coexistant sous cisaillement-compression combiné. Enfin, les essais de cisaillement-compression sur des nids d'abeilles sont reproduites numériquement afin de séparer le comportement normale et celui du cisaillement. La courbe limite dans le plan de la contrainte normale vs la contrainte du cisaillement a été obtenue, qui montre une augmentation homogène (isotropie) sous chargement dynamique. / The study consists mainly of two parts. The first part is related to the dynamic strength enhancement of honeycombs under uniaxial compression. We firstly study numerically this particular phenomenon of thin-walled structure by using three micro-size FE models and this allows us to reveal the role played by lateral inertia in the dynamic enhancement. Further more, the dynamic enhancement of a series of honeycombs with different cell-size, cell-wall thickness and base material is studied experimentally and the influence of these geometric parameters and the base material on honeycomb strength as well as the dynamic enhancement rate is investigated. The second part of this study concerns the biaxial behavior of honeycombs under combined shear-compression. We firstly present a combined dynamic shear-compression loading device basing on a large-diameter Nylon Split Hopkinson Pressure Bar system. Then, a series of quasi-static and dynamic experiments on an aluminium honeycomb is performed with loading angles ranging from 0o to 60o (part of shear more and more important). It shows a strong effect of the additional shear loading to honeycomb overall strength. A notable strength enhancement under impact loading is observed for all the honeycomby b specimens. Images captured during tests permit for the determination of the two co-existing deforming patterns under combined shear-compression. Finally, the combined shear-compression tests on honeycombs are reproduced by a numerical virtual model and the separated normal and shear behaviors of honeycombs under combined shear-compression are obtained. A crushing envelope in normal strength vs. shear strength plane was obtained on the basis of these simulations, which shows an isotropic expansion behavior from the quasi-static loading to the dynamic loading.

Muitas alternativas têm sido propostas para melhorar as características nutricionais dos alimentos, algumas delas utilizando fontes de fibra alimentar ainda pouco conhecidas. Entre estas fontes de fibra alimentar (FA), a farinha de banana verde (FBV) tem se mostrado uma boa alternativa por sua alta concentração de amido resistente (AR) que pode melhorar o valor nutricional de diferentes preparações. Neste trabalho foram estudadas barras de cereal elaboradas com FBV, com o objetivo de avaliar in vivo e in vitro as propriedades nutricionais desses produtos. As amostras consistiam em dois tipos de barras de cereais, uma delas elaborada com FBV (barras FBV) e outra sem este ingrediente (barras controle). A composição centesimal e perfil de carboidratos das barras foram avaliados. A fermentabilidade da fração não-disponível das barras foi avaliada através de testes in vitro utilizando inóculo de ratos. A resposta glicêmica das barras foi avaliada após sua ingestão por voluntários saudáveis (n=16), sendo determinados o índice glicêmico (IG) e carga glicêmica (CG). A principal característica que pôde ser observada é que as barras FBV possuem maior conteúdo de AR que as barras controle (7,22 g/100g e 2,11 g/100g na base integral), resultado da adição de FBV. Esta adição reflete na concentração de carboidratos não-disponíveis (soma de FA e AR) das barras FBV, que é de 18,19 g/100g na base integral. As barras FBV apresentam maior fermentabilidade in vitro em relação às barras controle (p<0,05) de acordo com a produção de ácidos graxos de cadeia curta (AGCC), produzindo 4,04 mmol/g de substrato, enquanto as barras controle produzem apenas 3,51 mmol/g de substrato. As barras FBV apresentam baixo IG (em relação à glicose) (41%) e CG (4), enquanto as barras controle apresentam IG médio (60%) e CG baixa (5). A partir dos resultados apresentados, é possível concluir que a adição de FBV às barras de cereal aumenta seu conteúdo de carboidratos não-disponíveis, representados pelo AR e FA, resultando num produto de alta fermentabilidade e de baixa resposta glicêmica pós-prandial. / Several alternatives have been proposed to improve the nutritional characteristics of foods, some of them using sources of dietary fiber that are still underused. Among these sources of dietary fiber (DF), unripe banana flour (UBF) has been considered a good alternative for its high concentration of resistant starch (RS), which can improve the nutritional value of different preparations. The aim of this study was to evaluate, in vivo and in vitro, the nutritional properties of cereal bars made with UBF. The samples consisted of two types of cereal bars, one made with UBF (UBF bars) and the other one without this ingredient (control bars). The chemical composition and carbohydrate profile of the bars were evaluated. The fermentability of the non-available fraction of bars was assessed in vitro using cecal contents of mice. The glycemic response of the bars was assessed after its ingestion by healthy volunteers (n = 16), being determined the glycemic index (GI) and glycemic load (GL). The main feature that could be observed is that the UBF bars have higher RS content than the control bars (7.22 g/100g and 2.11 g/100g wet weight), a result of the addition of UBF. This addition reflects on the concentration of non-available carbohydrates (sum of DF and RS) in UBF bars, which is 18.19 g/100g wet weight. The UBF bars presented better in vitro fermentability in relation to control bars (p <0.05) according to the production of short chain fatty acids (SCFA), yielding 4.04 mmol / g substrate, while the control bars produce only 3.51 mmol / g substrate. The UBF bars have a low GI (based on glucose) (41%) and CG (4), while the control bars show medium GI (60%) and low CG (5). According to these results, it is possible to conclude that the addition of UBF to cereal bars increases their non-available carbohydrate content, represented by RS and DF, resulting in a product of high fermentability and low postprandial glycemic response.

Bartending makes for an interesting case study in that it brings together research on emotional labor and tipped front-line service jobs, as well as the contemporary increase in precarity in work and precarity in life. This project explores the material and identity processes of bartending, examining how a precarious job with high expectations of emotional labor in-turn affects the occupational and personal identities of those employed in the industry. Overall three overarching themes were identified: (1) When wages are outsourced to customers via tipping systems workers are exposed to particularly high emotional demands, rendering bartending a unique form of quid pro quo emotional labor. (2) Bartenders exist in a “default career” mode of employment that is stigmatized for being low-status low-skilled labor. (3) Performing emotional labor and managing stigma creates a divergence between bartender’s personal and occupational identities resulting in constant identity work on and off the job. / Includes bibliography. / Thesis (M.A.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection