Dissertations / Theses on the topic 'Flexible Curves'

The purpose of this project is to find an identification tag that can be used in a future automated pinch analysis tool. It can be used to further analyse composite curves and pinch results by tracking the original streams that was converted. In real life situations, retrofitting a process industries streams, can decrease heat demands and costs. A pinch analysis and a heat exchange network is created with fixed and flexible flows to show a recommendation on how the system model can handle this type of situations. The models have been created by hand with support from pinch literature and the calculations validated with mathematical software such as matlab and other graphing tools. The literature study and pinch modelling resulted in a recommendation of tagging Hstart and Hend for each individual stream. By using a geographical tag in a coordinate system the analyst will be able to find the original streams in the pinch analysis and composite curves. The project also resulted in a heating exchange network created from the fixed and flexible data set. The enthalpy differences between the ideal pinch result and the fixed data set is smaller than one might expect because of enthalpy abundance in the specific intervals.

La première partie du seizième problème de Hilbert traite de la topologie des courbes algébriques réelles régulières dans le plan projectif. Il est bien connu que bon nombre des propriétés topologiques satisfaites par de telles courbes sont également vraies pour la classe plus large des courbes flexibles, introduites par O. Viro en 1984. Le but de cette thèse est d'approfondir les origines topologiques des restrictions sur les courbes réelles, en lien avec le seizième problème de Hilbert. Nous ajoutons une condition naturelle à la définition de courbe flexible, à savoir qu'elles doivent intersecter une conique réelle vide Q comme une courbe algébrique, c'est-à-dire en des points positifs uniquement. Nous voyons CP(2) comme un cylindre sur un espace lenticulaire L(4,1)×R, que l'on compactifie en ajoutant RP(2) et Q aux bords, et nous utilisons la décomposition induite sur S(4)=CP(2)/conj. C'est un fait standard que la surface d'Arnold joue un rôle essentiel dans l'étude des courbes de degré pair. Nous introduisons un analogue de cette surface pour des courbes de degré impair. Nous généralisons également la notion de courbe flexible pour inclure des surfaces non orientables. Nous considérons qu'une courbe flexible est de degré m si son auto-intersection est m² et si elle intersecte la conique Q de manière transverse en exactement 2m points. Notre résultat principal affirme que pour une telle courbe flexible (non nécessairement orientable) de degré impair m=2k+1 ne peut pas posséder plus de -χ(F)/2-k²+k+1, où χ(F) est la caractéristique d'Euler de F. Cette borne supérieure se simplifie en k² dans le cas d'une courbe flexible au sens usuel. Nous généralisons également notre résultat pour des courbes flexibles sur des quadriques, ce qui produit une nouvelle restriction, même pour des courbes algébriques. Dans les chapitres introductifs, un aperçu détaillé de la théorie classique des courbes réelles planes est fait, en s'appuyant aussi bien sur le point de vue réel que complexe. Certains résultats à propos de la théorie des surfaces nouées dans les 4-variétés sont énoncés. Plus précisément, il est question de faits concernant la classe d'Euler du fibré normal d'une surface plongée. Cela nous amène ensuite à considérer la fonction de genre non-orientable d'une 4-variété. Cela constitue un analogue de la conjecture de Thom (résolue par Kronheimer et Mrowka en 1994) pour des surfaces non orientables. Nous calculons presque totalement cette fonction pour CP(2), et nous étudions cette fonction sur d'autres 4-variétés. Enfin, nous digressons autour de la nouvelle notion de courbes flexibles non orientables, où nous dressons une liste de résultats connus qui restent vrai dans ce cadre. Nous nous concentrons aussi sur la classe des courbes algébriques et flexibles qui sont invariantes sous l'action d'une involution holomorphe de CP(2), une notion introduite par T. Fiedler et appelées courbes symétriques. Nous donnons un état de l'art, et nous formulons une succession de petits résultats à propos de la disposition d'une courbe symétrique par rapport aux éléments de symétrie. Nous proposons également une approche pour tenter de généraliser la congruence de Fiedler p-n≡k² [16], valable pour des M-courbes symétriques de degré 2k, à des (M-1)-courbes symétriques de degré 2k
The first part of Hilbert's sixteenth problem deals with the topology of non-singular real plane algebraic curves in the projective plane. As well-known, many topological properties of such curves are shared with the wider class of flexible curves, introduced by O. Viro in 1984. The goal of this thesis is to further investigate the topological origins of the restrictions on real curves in connection with Hilbert's sixteenth problem. We add a natural condition to the definition of flexible curves, namely that they shall intersect an empty real conic Q like algebraic curves do, i.e. all intersections are positive. We see CP(2) as a cylinder over a lens space L(4,1)×R which is compactified by adding RP(2) and Q respectively to the ends, and we use the induced decomposition of S(4)=CP(2)/conj. It is a standard fact that Arnold's surface plays an essential role in the study of curves of even degree. We introduce an analogue of this surface for curves of odd degree. We generalize the notion of flexible curves further to include non-orientable surfaces as well. We say that a flexible curve is of degree m if its self-intersection is m² and it intersects the conic Q transversely in exactly 2m points. Our main result states that for a not necessarily orientable curve of odd degree 2k+1, its number of non-empty ovals is no larger than χ(F)/2-k²+k+1, where χ(F) is the Euler characteristic of F. This upper bound simplifies to k² in the case of a usual flexible curve. We also generalize our result for flexible curves on quadrics, which provides a new restriction, even for algebraic curves. In the introductory chapters, a thorough survey of the classical theory of real plane curves is outlined, both from the real and the complex points of view. Some results regarding the theory of knotted surfaces in 4-manifolds are laid down. More specifically, we review statements involving the Euler class of normal bundles of embedded surfaces. This eventually leads us to consider the non-orientable genus function of a 4-manifold. This forms a non-orientable counterpart of the Thom conjecture, proved by Kronheimer and Mrowka in 1994 in the orientable case. We almost entirely compute this function in the case of CP(2), and we investigate that function on other 4-manifolds. Finally, we digress around the new notion of non-orientable flexible curves, where we survey which known results still hold in that setting. We also focus on algebraic and flexible curves invariant under a holomorphic involution of CP(2), a smaller class of curves introduced by T. Fiedler and called symmetric curves. We give a state of the art, and we formulate a collection of small results results regarding the position of a symmetric plane curve with respect to the elements of symmetry. We also propose a possible approach to generalize Fiedler's congruence p-n≡k² [16], holding for symmetric M-curves of even degree 2k, into one for symmetric (M-1)-curves of even degree

La ureteroscopia flexible (fURS) con el laser de Holmio:YAG (Ho:YAG) es uno de los tratamientos estándar para la urolitiasis ya que el Ho:YAG ha demostrado destruir eficientemente cualquier tipo de urolitiasis. Aunque se han descrito diversas técnicas de litotricia, en los últimos años se han añadido nuevos parámetros al Ho:YAG y se han evaluado diferentes métodos de manejo de las fibras laser lo cual pretende mejorar la efectividad de la fURS. Por otro lado, los resultados de la fURS están asociados a limitaciones de la técnica como trabajar en ángulos agudos que pueden llevar a rotura de la fibra láser. Las técnicas y los parámetros del laser no han sido suficientemente estudiados para tratar ese tipo de casos y hacer la técnica mas segura y efectiva. El objetivo de esta tesis es evaluar la técnica de fragmentación sin contacto (FSC) con una variedad amplia de parámetros del Ho:YAG y tamaños de fibras laser. Asimismo estudiar in-vitro los factores de riesgo de ruptura de la fibra laser al curvarse. Los experimentos de la FSC se realizaron con 4 piedras artificiales en un tubo de ensayo. Un ureteroscopio, fijo y con flujo constante fue insertado a través de una camisa ureteral al tubo. El laser se fijó a 1 mm de la base del tubo entre las piedras. Una combinación de 0.5-1.5 Julios, 10-20 y 40 Hz y pulso largo y corto fueron evaluados por 2 y 4 minutos, utilizando fibras de 273 and 365 μm. Los experimentos se realizaron 3 veces cada uno. Las piedras analizadas fueron pesadas antes y después del experimento para evaluar la eficiencia de la FSC. Se realizaron un total de 144 experimentos. La media de peso de las piedras por cada tubo fue de 0.23g y tras los experimentos una diferencia media de 0.7 gr (0.01-0.243). Escogiendo una reducción del 50% peso como corte para calificar la técnica de efectiva los valores predictivos que promovían una técnica adecuada fueron: El pulso largo (OR = 2.7, 95% CI 1.05 – 7.15), Tiempo de 4 min (OR = 11.4, 95% CI 3.88 – 33.29), Fibra de 273μm (OR = 0.23, 95% CI 0.08 – 0.70), y alta energía (OR = 1.14, 95% CI 1.09 – 1.20). Con respecto a la evaluación de la curvatura de la fibra, se utilizaron fibras de 272 y 365m, dobladas a 9, 12, 15, 18 y 20mm de diámetro. Se evaluaron parámetros de fragmentación y pulverización laser a 7.5 Vatios. El láser fue activado por 5 minutos repitiendo los experimentos 10 veces. Como resultado se vio que utilizando parámetros de pulverización ambos tamaños de fibra se rompían solo al curvarse 9 mm (p<0.05). Utilizando parámetros de fragmentación las fibras se rompían mas, al estar curvadas 12mm para fibras de 272m y 15mm para fibras de 365m (p=0,007 and 0,033 respectivamente). El pulso corto y la alta energía fueron factores de riesgo significativos para romper fibras de 365m (p=0,02) pero no de 272m (p=0,35). La frecuencia (Hz) no fue un factor de riesgo significativo para la rotura. Hubo una tendencia a una mayor rotura de fibras de 365m comparada con las fibras de 272m no siendo significativa (p>0,05). Concluimos que las fibras de 272m eran mas resistentes ya que requieren una curvatura aguda (<9mm) para su rotura. También se evidenció que la utilización de parámetros de pulverización reduce el riesgo de rotura comparado con parámetros de fragmentación.
Flexible ureteroscopy (fURS) with Holmium: YAG laser (Ho:YAG) is one of the standard procedures for renal urolithiasis as Ho:YAG has shown to efficiently fragment urinary stones of any composition. Several techniques of laser lithotripsy have been described although new laser parameters have been added to the Ho:YAG in recent years and studies on laser fiber handling have provided new recommendations to improve performance. Regarding fURS, treatment outcomes are associated with technical limitations of fURS when working in acute angle calices and Ho:YAG fiber breakages can be associated with costly repairs. The techniques and laser parameters for treating such difficult cases have not been widely described. The purpose of this thesis is to evaluate the non contact “pop-corn” (PC) technique with a wide range of Ho:YAG settings and fiber sizes as to evaluate the risk factors for fiber fracture while curved in systematic in-vitro assessments. The evaluations for the PC were done with 4 artificial stones in a Vacutaner. A fix ureteroscope was inserted trough a ureteral access sheath allowing constant irrigation flow. The laser was placed at 1 mm from the bottom of the Vacutaner within the stones. The combination of 0.5-1.5 Joules, 10-20 and 40Hz and long and short pulse were tested for 2 and 4 minutes. 273 and 365 μm laser fibers were used. All tests were repeated 3 times. The stones were weighed before and after the experiments to evaluate the setting efficiency. Significant predictors for a highly efficient technique were assessed. A total of 144 experiments were conducted. Stone groups had a consistent weight: mean of 0.23g. After the experiment median weight difference was 0.7 gr (0.01-0.243). Choosing a cumulative percentage of 50% of the stones volume reduction as the cut-off level the significant predictors for high efficiency PC technique were the use of long pulse (OR = 2.7, 95% CI 1.05 – 7.15), longer time (4 min) (OR = 11.4, 95% CI 3.88 – 33.29), small (273μm) laser fiber (OR = 0.23, 95% CI 0.08 – 0.70), and higher power (watt) (OR = 1.14, 95% CI 1.09 – 1.20). We concluded that higher energy (>1.5 J), longer pulse, higher frequency of (20Hz),longer time, and small laser fiber are predictors for high efficient PC technique. As for the curved fiber evaluations, 272m and 365m fibers were employed. Five different fiber curve diameters were tested: 9, 12, 15, 18 and 20mm. Fragmentation and dusting settings were used at 7.5W. The laser was activated for 5 minutes. Each experiment was repeated 10 times. We found that with dusting settings, fibers broke more frequently at a curved diameter of 9mm f or both 272m and 365m fibers (p=0,037 and 0,006 respectively). Using fragmentation setting, fibers broke more frequently at 12mm for 272m and 15mm for 365m (p=0,007 and 0,033 respectively). Short-pulse and high energy were significant risk factors of fiber fracture for the 365m fibers (p=0,02), but not for the 272m fibers (p=0,35). Frequency was not a risk factor for fiber rupture. Fiber diameters also seemed to be involved in the failure with a higher number of broken fibers for the 365m fibers but no significant differences were found comparing to the 272m fibers (p>0,05). We concluded that small fibers are more resistant than large ones as lower bending diameters (<9mm) are required to break small fibers. In acute angles the use small-diameter fibers, at a low energy and long-pulse (dusting setting) may reduce the likelihood of fiber rupture.

We have developed a third-order shear and normal deformable plate/shell theory (TSNDT) incorporating all geometric nonlinearities and used it to analyze, by the finite element method (FEM), transient finite deformations of a sandwich beam with two face sheets and the core made of St. Venant-Kirchhoff materials.  A triangular cohesive zone model with stress based criterion for delamination initiation and energy based relation for complete separation is used to analyze delamination failure in a beam under mixed-mode loading. We have studied transient post-buckling deformations and delamination progression in an axially compressed and initially delaminated clamped-clamped sandwich beam.  The buckling load for transient deformations exceeds that for static deformations and the increase depends upon the loading rate.  This FE software for analyzing deformations of sandwich beam is coupled with that based on the boundary element method (BEM) for studying time-dependent deformations of water and the coupled software is used to analyze deformations of flexible curved hulls due to water slamming loads.  The water is assumed to be inviscid and incompressible and undergo irrotational deformations.  The Laplace equation for the velocity potential is numerically solved by the BEM with normal velocity and pressure assumed to be continuous across the interface between the hull and the water.  Challenging issues resolved in this work include finding the wetted surface of the hull, nonlinear deformations of the fluid due to convective part of acceleration, effects of geometric nonlinearities on hull\'s deformations, resolution of the jet tip, as well as the initiation and propagation of delamination between the face sheets and the core.  It is found that both delamination and geometric nonlinearities significantly affect the hydrodynamic pressure acting on the hull, and transverse shear deformations contribute more to the strain energy absorbed by the core than its transverse normal deformations.  
We have used the discontinuous basis functions to derive the Galerkin formulation of a nonlinear problem involving simple shearing deformations of a homogeneous and isotropic thermo-elasto-visco-plastic body with uniform deformations perturbed to simulate the effect of a defect.  The resulting coupled nonlinear ordinary differential equations are integrated with respect to time by using the package, LSODE (Livermore Solver for Ordinary Differential Equations).  Computed results showing localization of deformations into narrow regions are found to agree well with those found by the FEM, and spatial variations of the shear stress are smoother than those obtained by the FEM.


Ph. D.

Made available in DSpace on 2014-07-29T16:10:31Z (GMT). No. of bitstreams: 1 Dissertacao Frederico Dourado Rodrigues Morais.pdf: 1326761 bytes, checksum: 3917c663223c2bc77e9ad8decc145440 (MD5) Previous issue date: 2011-08-28
This work, resulting from research carried out by the line of research Education, Labor and Social Movements in the Graduate Program in Education at FE / UFG, seeking to understand the relationship between school and work in the phase of flexible accumulation of capital, with the object analysis and study the Colleges of Technology.The objective is to understand this dynamic from literature, picking up changes in the workplace, in the productive structure and expansion of new training courses andqualifications for the job. For this theory is based in Harvey (2009), Frigotto (1989,1998, 1999, 2003), Gentili (1996, 1998), Ramos (2006), Machado (1998, 2006) and Giolo (2006), as well as documents and census data of higher education provided byINEP the period 1999 to 2008. The starting point was the changes in capitalism, showing the crises inherent in the capital and the changing of the work of a social rightfor an individual achievement. In this movement, words such as competence andemployability have become increasingly present in public policy. With this research it was found that the growth of structural unemployment, individuals whose training islimited by the narrowing of time and space, the classification tends to be more aninstrument of domination of capitalism in the face of subjects and a crucial element in the justification unemployment.
Este trabalho, decorrente de pesquisa desenvolvida junto à linha de pesquisa Educação, Trabalho e Movimentos Sociais do Programa de Pós Graduação em Educação da FE/UFG, busca apreender a relação entre escola e trabalho na fase de acumulação flexível do capital, tendo como objeto de análise e estudo os Cursos Superiores de Tecnologia. Objetiva-se compreender esta dinâmica a partir de pesquisa bibliográfica, apanhando as mudanças no mundo do trabalho, na estrutura produtiva e na expansão dos novos cursos de formação e qualificação para o trabalho. Para tanto fundamenta-se teoricamente em Harvey (2009), Frigotto (1989; 1998; 1999; 2003), Gentili (1996; 1998), Ramos (2006), Machado (1998; 2006) e Giolo (2006), bem como em documentos e dados do censo do ensino superior disponibilizado pelo INEP do período de 1999 a 2008. Partiu-se das mudanças ocorridas no capitalismo, evidenciando as crises inerentes ao capital e a mutação do trabalho de um direito social, para uma conquista individual. Nesse deslocamento, palavras como competência e empregabilidade se tornaram cada vez mais presentes nas políticas públicas. Com a realização desta pesquisa constatou-se que o crescimento do desemprego estrutural, cuja formação dos indivíduos é delimitada pelo estreitamento entre o tempo e o espaço, a qualificação tende a ser mais um instrumento de dominação do capitalismo frente aos sujeitos e um elemento crucial na justificação do desemprego.

Collaborative Learning is the pedagogical approach that considers social interactions as key means to trigger rich learning processes. Collaborative Learning Flow Patterns define best practices to orchestrate collaborative learning activity flow mechanisms (i.e., group formation, roles or resources allocation, phase change). Flow patterns have been experimented and evaluated as effective in small scale settings for decades. Directly applying these pedagogical methods to large learning scenarios is challenging due to the burden that scale represents in the orchestration load or the difficulty of keeping a dynamic meaningful progression when flexible changes are required in a large classroom or in a MOOC. Some attempts have shown positive results, but research around scalable collaborative learning approaches, models and technologies for large classes is scattered. This dissertation conducts a systematic literature review of collaborative learning applications on large classes and analyses the social learning potential of diverse technology-supported spaces in massive courses. Then the dissertation focuses the study on how collaborative learning could address key challenges (i.e., scalability and dynamism) identified in large collaborative learning contexts. Consequently, the thesis proposes a Pyramid flow pattern instantiation, composed of a model with a set of algorithmic rules for flow creation, flow control and flow awareness as well as a PyramidApp authoring and enactment system implementing the model. Experimentation across diverse learning contexts shows that, on one hand, the contributions support meaningful scalable and dynamic collaborative learning and on the other hand, learners and educators perceive the experiences as engaging, with learning values and effective from the perspective of orchestration.
El aprendizaje colaborativo es el enfoque pedagógico que considera las interacciones sociales como un medio clave para desencadenar procesos de aprendizaje ricos. Los patrones de flujo de aprendizaje colaborativo definen buenas prácticas para orquestar mecanismos de flujo en actividades de aprendizaje colaborativo (es decir, la formación de grupos, la asignación de roles o recursos, los cambios de fase). Los patrones de flujo han sido probados y evaluados como efectivos en entornos de pequeña escala durante décadas. La aplicación de estos métodos pedagógicos en grandes escenarios de aprendizaje supone un reto debido a la carga que representa la escala en la orquestación, así como a la dificultad de mantener una progresión dinámica con sentido pedagógico cuando se requieren cambios flexibles en un aula grande o en un MOOC. Existen algunos intentos interesantes, pero la investigación en torno a enfoques de aprendizaje colaborativo escalables, y modelos y tecnologías para entornos educativos con muchos estudiantes está dispersa. Esta tesis lleva a cabo una revisión sistemática de la literatura sobre aplicaciones de aprendizaje colaborativo con muchos estudiantes y analiza el potencial de aprendizaje social de diversos espacios apoyados por la tecnología en este tipo de contextos. A continuación, la tesis se centra en el estudio de cómo el aprendizaje colaborativo podría abordar desafíos clave identificados en contextos de aprendizaje colaborativo con un gran número de estudiantes (es decir, la escalabilidad y el dinamismo). En consecuencia, la tesis propone una instanciación del patrón de flujo Pirámide, compuesto de un modelo con un conjunto de reglas algorítmicas para la creación, el control y la conciencia del flujo de aprendizaje, así como un sistema de creación e implementación del modelo. La experimentación realizada en distintos contextos de aprendizaje demuestra que, por un lado, las contribuciones apoyan un aprendizaje colaborativo escalable y dinámico, y que, por otro lado, los estudiantes y los educadores perciben las experiencias como amenas, con valor para el aprendizaje y efectivas desde la perspectiva de la orquestación.

Cada vez mais, a competividade fortalece a filosofia de administração empresarial baseada na orientação para o cliente e para o lucro. A busca de novas formas de relacionamento com os clientes requer instrumentos que possam personalizar inclusive os preços que compõem a equação de valor de cada um. O que temos visto, na prática, são ações que não consideram a dinâmica das forças do mercado, representada pelas curvas de oferta e demanda, e por isso expõem a organização ao risco de propor um processo de troca que não atenda ao preceito de que deve beneficiar tanto o vendedor quanto o comprador, como fator mais importante para a manutenção de um relacinamento de longo prazo. Os instrumentos apresentados como equações matemamáticas, pretendem viabilizar a adoção de forma monitorada com os objetos da gestão econômica. Como benefício complementar, os intrumentos por requererem regras claras, objetivas e bem delimitadas para os processos de negociação, permitem compartilhar de maneira justa, a responsabilidade sobre o atingimento dos resultados através de transações comerciais.
Competitiveness fortifies the entrepreneurial management philosophy that prioritizes more and more, customers and profit. The search for new relationship between companies and customers requires appropriate tools to even, embody the prices that composes the equation of value. We have noticed according to the procedures, actions disrespecting the dynamic of market forces, represented by supply and demand curves and, as a consequence, the companies can be involved in a trading process that can not serve neither the seller nor the buyer, damaging the relationship in the long run. The algorithms presented as mathematical equation aim at enabling the approval of the dynamic prices in trading processes to support their own flexibility in a controlled way that is connected to the goals of the economic management. As a complementary benefit, the algorithms require clear, delimitative and objective rules for the dealing processes and make possible sharing in a fair way, the responsability for the achievement of the results through the trading negotiations.

The thesis is devoted to analysing of flexible buried arch structures. Modelling of the flexible concrete arch is carried out via a nonlinear finite element model that accounts for soil constitutive relations, soil-structure interactions, sequential construction stages and soil compaction. Advanced FE-model was verified by measurement obtained by full-scale field testing of two buried arches. Mathematical optimization methods of genetic algorithms and Levenberg-Marquardt method are applied to already calibrated complex computational models in order to reduce bending and associated flexural stresses in the concrete section of buried arch. Centre line of the arch is parameterized by cubic Bezier curve to reach interpolation of thrust line. Optimization technique is applied with extensive parametrical study which shows the optimal shapes for buried arches of various span/rise ratios, backfill depths and foundation soil types. For practical application are given coordinates of Bézier curve control polygons of particular resulting shape. Subsequently is applied optimization method for a theoretical reduction of tensile stresses obtained by shape optimization of previously verified numerical model of buried arch. Comparisons of earth pressure, bending moment axial force and deflection of flexible structure during sequential construction of different span/raise ratios of buried arches are presented. The behaviour of flexible buried arch with effect of local traffic load model LM1 has been analysed via 3D finite elements model with respect to different depth of backfill above crown.

Este estudo tem como objetivo principal comparar estruturas de pavimentos flexíveis projetadas através dos métodos empírico do DNER e mecanístico, considerando-se alguns materiais de pavimentação utilizados na região de Campo Grande, estado do Mato Grosso do Sul. Como objetivos decorrentes, pode-se destacar a obtenção das características resilientes e de fadiga destes materiais e a proposta de um catálogo simplificado de estruturas de pavimentos para a referida região. Para a efetivação da pesquisa, foram coletados materiais típicos do subleito da região e daqueles mais utilizados na composição de bases e capas dos pavimentos locais. Após as suas caracterizações, realizaram-se ensaios de compactação, CBR, triaxiais cíclicos e compressão diametral estática e dinâmica. As análises mecanísticas foram realizadas utilizando-se o programa computacional FEPAVE, que leva em conta o comportamento elástico não-linear dos materiais, considerando-se o critério de confiabilidade. A partir da análise comparativa dos métodos de dimensionamento, observou-se que, ora as estruturas estabelecidas pelo método mecanístico são idênticas às determinadas pelo método do DNER, ora são mais esbeltas, ora são menos esbeltas, dependendo do tipo de material que constitui as camadas e do nível de confiabilidade adotado. Verificou-se ainda que a caracterização dos materiais através dos ensaios de módulo de resiliência, vida de fadiga e deformação permanente é imprescindível quando se deseja projetar um pavimento empregando-se o método mecanístico. Por fim, elaborou-se um catálogo simplificado de pavimentos flexíveis para a região de Campo Grande – MS, com as intenções de contemplar o uso de materiais locais e auxiliar os engenheiros na concepção de seus projetos
This study has as main objective to compare structures of flexible pavements designed by two different methods, the DNER empirical method and the mechanistic method, being considered some paving materials used in the area of Campo Grande, state of Mato Grosso do Sul. As secondary objectives, it can stand out the obtaining of the mechanical properties of these materials and the proposal of a simplified catalog of flexible pavements for the referred area. For the accomplishment of the research, typical materials of subgrade, base course and surface layer were collected. After their characterizations, tests of compaction, CBR and repeated load were executed. The mechanistic analyses were accomplished being used the software FEPAVE, that takes into account the non-linear resilient modulus of the materials, being considered the reliability criterion. Starting from the comparative analysis of the design methods, it was observed that the structures established by the mechanistic method can be identical, more slender or less slender to the ones obtained by the empirical method, depending on the type of the material that constitutes the layers and the reliability level adopted. It was also verified that the characterization of the materials by repeated load tests (resilient modulus, fatigue’s life and permanent deformation) is indispensable when one want to project a pavement being used the mechanistic method. Finally, a simplified catalog of flexible pavements was elaborated for the area of Campo Grande – MS, with the intentions of to contemplate the use of local materials and to aid the engineers in the conception of their projects

Diagnostic ultrasound has become invaluable to healthcare professions for the purpose of imaging soft tissue without the risk of exposure to damaging, ionizing radiation. However, the majority of commercially available transducers have rigid, fixed interfaces that cannot conform to the surface of the human body. Such limitations both introduce a potential air gap (requiring the application of ultrasound gel) and make long-term monitoring impractical. In this work, I propose a novel flexible 2D ultrasound phased array with adaptive phasing that is capable of compensating for the radius of curvature. I describe the phasing algorithm and illustrate the detrimental effect of a lack of phase correction through simulation. I conduct phase detection by using time of arrival (TOA) without additional external hardware. In addition to simulations, I provide details of the fabrication process of a flexible 16 by 16 element array. The manufactured array, with an operating frequency of 1.4MHz and bandwidth of 41.3%, was capable of generating pressures up to 600 kPa. Finally, I conduct an in-vivo human study to demonstrate the functionality of the array on a human humerus. Although visible without phase correction, the location of the bone can easily be tracked in real-time after applying the correction algorithm.

Exchange of private information over a public medium must incorporate a method for data protection against unauthorized access. Elliptic curve cryptography (ECC) has become widely accepted as an efficient mechanism to secure private data using public-key protocols. Scalar multiplication (which translates into a sequence of point operations each involving several modular arithmetic operations) is the main ECC computation, where the scalar value is secret and must be secured. In this dissertation, we consider ECC over five standard prime finite fields recommended by the National Institute of Standard and Technology (NIST), with the corresponding prime sizes of 192, 224, 256, 384, and 521 bits. This dissertation presents our general hardware-software approach and technical details of our novel hardware processor design, aimed at accelerating scalar multiplications with flexible security-performance tradeoffs. To enhance performance, our processor exploits parallelism by pipelining modular arithmetic computations and associated input/output data transfers. To enhance security, modular arithmetic computations and associated data transfers are grouped into atomically executed computational blocks, in order to make curve point operations indistinguishable and thus mask the scalar value. The flexibility of our processor is achieved through the software-controlled hardware programmability, which allows for different scenarios of computing atomic block sequences. Each scenario is characterized by a certain trade-off between the processor’s security and performance. As the best trade-off scenario is specific to the user and/or application requirements, our approach allows for such a scenario to be chosen dynamically by the system software, thus facilitating system adaptation to dynamically changing requirements. Since modular multiplications are the most critical low-level operation in ECC computations, we also propose a novel modular multiplier specifically optimized to take full advantage of the fast reduction algorithms associated with the five NIST primes. The proposed architecture has been prototyped on a Xilinx Virtex-6 FPGA and takes between 0.30 ms and 3.91 ms to perform a typical scalar multiplication. Such performance figures demonstrate both flexibility and efficiency of our proposed design and compares favourably against other systems reported in the literature.
Graduate

Documentos apresentados no âmbito do reconhecimento de graus e diplomas estrangeiros
Flexible roll forming is an advanced sheet metal forming process for cost-effective innovative manufacturing of 3D profiles for automotive lightweight structures. In contrast to roll forming, the flexible roll forming process employs rolls that are not fixed in their position and can be moved along a path in order to describe the desired bend line of the profile. One of the most important defect in flexible roll forming is wrinkling that leads to an undesirable produc. This research work presents a new understanding on the deformation mechanics of the flexible roll forming and is focused on the occurrence of flange wrinkling. A new analytical-numerical model combining the energy method and the finite element simulation is developed to predict wrinkling. In this model, unlike previous models, the purpose is not the calculation of a critical stress assumed to be uniform over the compressive region, but that is the calculation of a factor to indicate the possibility of wrinkling considering the real distribution of stress in the compressive region. Thus, a wave function is assumed in accordance with the boundary conditions of the region under compression in the finite element simulation and the wrinkling factor is obtained as the ratio of the external work done by the in-plane membrane forces and the internal energy of the buckled sheet at each increment. The wrinkling factor depends on mechanical properties, geometry parameters, and current strain and stress field In this thesis, a new theoretical and experimental methodology based on the utilization of rectangular test specimens loaded in axial compression is developed to determine the wrinkling limit curve in the principal strain space. The wrinkling limit curve is then transformed into the space of effective strain versus stress triaxiality and checked against the finite element–predicted evolutions of effective strain with stress triaxiality of the deformed strip in the flexible roll forming process. Another wrinkling factor is proposed based on the wrinkling limit curve. This factor is defined in ABAQUS software by means of a subroutine and applied to determine the possibility of wrinkling during the simulation. A flexible roll forming setup is designed and built to perform the experiments. This setup has three major parts: Forming stand, Feeding mechanism and Control unit. Forming stand consists of two pairs of rolls that are integrated in a parallel kinematic system that allows following the varying contours of the profiles. The experiments were performed on the flexible roll forming setup and the history of longitudinal strain, the warping defect and the geometry of the variable cross-sectional profiles are measured by strain gauge, dial indicator and 3D scanner, respectively. The experimental observations and measurements give support to the numerical results and show that the proposed wrinkling criteria can correctly predict wrinkling in the flexible roll forming. Two proposed wrinkling criteria are applied to determine effects of the geometric parameters (Flange length, radius of bending line, width of transition zone and thickness) of the variable cross-sectional channel profiles and material properties (yield stress and hardening exponent) on the critical forming angle in the flexible roll forming. The results show that flange length, sheet thickness and yield stress have the greatest influence on the critical forming angle.

This thesis deals with motion planning of flexible one-dimensional objects and hyper-redundant serial robots moving in a plane or in three dimensional space. The flexible one-dimensional object is modeled as a continuous curve and a point on the curve is given a prescribed dis-placement. The key problem studied in the thesis is to obtain the motion of all points on the curve for the prescribed displacement subject to the condition of the length of the curve being preserved. Such motions are motivated by the need to model, analyze and realistically render of motion of hair, ropes and, more recently, flexible endoscopes where the assumption of constant axial length is realistic and reasonable. In this thesis, the discretized form of the flexible one-dimensional object is related to hyper-redundant robots and motion planning for such robots are obtained when the robot moves in free space and in a cluttered environment, avoiding obstacles. The motion planning of flexible one-dimensional objects is posed as an optimization problem with constraints and calculus of variation is employed to derive general analytical results. The first analytical result is that, for a given motion of a point on the curve and subject to the preservation of the length of the curve, the infinitesimal motion of any other point on the curve is minimized when the velocity vector at that point of the curve is along the tangent to the curve at that point. This leads to the second key result that when one end of a straight line segment is moved along a straight line, the velocity of the distal (far) end is minimized when it is along the straight line segment and the curve traced by the distal end is the well-known tractrix curve whose closed-form analytic expressions can be obtained using hyperbolic functions. If the flexible one-dimensional object is discretized by several piece-wise straight line segments, the magnitude of the velocity vector of the distal end of the segments attenuates as one goes away from the end where the input displacement is provided and if the direction of the input displacement is not changed, all the line segments eventually line up along the direction of the input displacement. It is shown that the attenuating and eventual aligning features lead to realistic and a more natural motion of the discretized segments and results in the establishment of a O(n) algorithm for motion planning. It is shown that the developed algorithm can be used for real-time simulation of the motion of discretized flexible one-dimensional objects and hyper-redundant serial robots. For realistic simulation and rendering of the motion, the flexible object must be discretized into a large number of straight segments. In the second part of the thesis, the flexible one-dimensional object is represented by a spline and motion planning algorithm is applied to the segments of the underlying control polygon of the spline. Since the number of segments in a control polygon can be significantly less, a significant increase in efficiency in simulation and rendering of the motion is obtained. However, it is known that as the control polygon is moved, the length of the spline curve changes. To overcome this problem, an innovative adaptive algorithm, involving sub-division and merging of the segments of the control polygon, is presented and this restricts the variation in the length of the curve to within a user prescribed tolerance. New analytical results related to the length of the curve and the angle between the adjacent segments of the control polygon are derived for quadratic and cubic splines and, depending on the prescribed tolerance, threshold values of the angle are obtained and used in the algorithm for approximate length preservation. The last part of the thesis deals with development of a planar hyper-redundant robot and implementation of motion planning algorithm on this robot. The hyper-redundant robot contains 12 links connected by actuated rotary joints which can change the angle between the links in a controlled manner. The links are on the wheels which provide support and allow it to move forward. The leading link also has a DC motor which can rotate the wheels so that it can move forward and pull the trailing links. Using the motion planning algorithm, for a prescribed motion of the leading link, the angle between two successive links are computed. These are given as input to the robot and the path traced by the 12 link robot is observed. It is seen that the motion of the hyper-redundant robot has the expected natural and realistic motion characteristics. It is furthermore demonstrated that the calculus of variation based approach for motion planning can be extended to include obstacle avoidance by adding additional constraints related to the location and size of the obstacles. It is shown that the entire robot optimally avoids the obstacles and moves in a more natural and realistic way.

博士
國立臺灣大學
機械工程學研究所
106
The polymer process faces the problems of slow temperature rise and uneven temperature. Increasing the heating rate and improving the temperature uniformity become an urgent challenge. In this study, a flexible large-area graphene-composite heating film was developed .The heating films were then applied to the processes of curved micro-hot embossing and micro-hot rolling embossing. First, the effects of different colloids on dispersibility, resistance, sheet resistance and flexible testing were investigated to determine the feasibility of flexible flexible heaters. Then, a flexible graphene composite flat panel heater was developed. The results show that as the voltage increases, the heating rate and steady-state temperature increases. The flexible heater was used to the hot embossing on the curved substrate. With the power of 25V, the temperature was raised from 40 ° C to 160 ° C in 130s. Stable temperature can be maintained. The V-shaped microstructures are replicated with replication rate higher than 97%. A roller heater was developed for roller hot embossing. The heater was fabricated by wire bar coating of graphene polymer composite onto the inner wall of the hollow roller. The electrothermal property, the four-quadrant dynamic temperature uniformity, the lateral dynamic temperature uniformity and the steady-state temperature and voltage are tested by adjusting the voltage. The four-quadrant dynamic temperature control temperature is controlled within 2.8 °C, and the lateral dynamic temperature result is controlled within 1.2 °C. The roller heater was used in micro-hot roller embossing to fabricate microlens array and V-type structures. The relationship between pressure, working temperature and feed rate on forming were investagated. Under the fixed feed rate parameter, the height and diameter of the microlens array were all larger than original sizes of the mold. The V-shaped structure is formed at the fixed rolling speed rate parameter. With the embossing temperature fixed at 120 ° C, the replication rate were higher than 97%. Finally, the application of V-type structure to light intensity enhancement was verified. This study proved the feasibility and potential of the graphene polymer composite heater successfully.

Moisture can significantly affect flexible pavement performance. As such, it is crucial to remove moisture as quickly as possible from the pavements, mainly to avoid allowing moisture into the pavement subgrade. In the 1990s the Indiana Department of Transportation (INDOT) adopted an asphalt pavement drainage system consisting of an open-graded asphalt drainage layer connected to edge drains and collector pipes to remove moisture from the pavement system.

Over the intervening two decades, asphalt pavement materials and designs have dramatically changed in Indiana, and the effectiveness of the pavements drainage system may have changed. Additionally, there are challenges involved in producing and placing open-graded asphalt drainage layers. They can potentially increase costs, and they tend to have lower strength than traditional dense-graded asphalt pavement layers.

Given the potential difficulties, the overall objective of this research was to evaluate the effectiveness of the INDOT’s current flexible pavement drainage systems given the changes to pavement cross-sections and materials that have occurred since the open-graded drainage layer was adopted. Additionally, the effectiveness of the filter layer and edge drains were examined.

Laboratory experiments were performed to obtain the hydraulic properties of field-produced asphalt mixture specimens meeting INDOT’s current specifications. The results were used in finite element modeling of moisture flow through pavement sections. Modeling was also performed to investigate the rutting performance of the drainage layers under various traffic loads and subgrade moisture conditions in combination with typical Indiana subgrade soils. The modeling results were used to develop a design tool that can assist the pavement designer in more accurately assessing the need for pavement drainage systems in flexible pavements.