Die 3D-Kartierung von Umgebungen spielt in der Robotik eine zunehmend wichtige Rolle. Mit Hilfe von 3D-Sensoren lassen sich dreidimensionale Umgebungen präzise erfassen. Allerdings vermessen selbst hochaufgelöste Scanner Oberflächen nur stichprobenartig. Zudem verbrauchen die gewonnenen Punktwolken viel Speicher. Eine Möglichkeit, die Diskretisierung aufzulösen und die Darstellung zu optimieren, ist, eine polygonale Umgebungsdarstellung aus den Punktdaten zu erzeugen. In dieser Arbeit wird ein Verfahren vorgestellt, mit dem sich komprimierte Polygonkarten automatisch erstellen lassen. Die Oberflächenrekonstruktion basiert auf einem modifizierten Marching-Cubes-Algorithmus. Die mit diesem Verfahren erzeugten Polygonnetze werden durch Optimierungsschritte in eine kompakte Darstellung überführt, die sich für Anwendungen in der Robotik einsetzen lässt, wie anhand von verschiedenen Einsatzbeispielen demonstriert wird.

Adaptive all-hexahedral meshing algorithms have many desirable features. These algorithms provide a mesh that is efficient for analysis by providing a high element density in specific locations, such as areas of high stress gradient or high curvature and reduced mesh density in other areas of less importance. In addition, inside-out hexahedral grid based schemes, using Cartesian structured grids for the base mesh, have shown great promise in accommodating automatic all-hexahedral algorithms. In these algorithms mesh refinement is generally used to capture geometric features. Unfortunately, most adaptive mesh generation algorithms employ a 3-refinement method. This method, although easy to employ, provides a mesh that is coarse in most areas and highly refined in other areas. Because a single refined hex is subdivided into 27 new hexes, regardless of the desired refinement, there is little control on mesh density. This paper will present an adaptive all-hexahedral grid-based meshing algorithm that employs a 2-refinement insertion method. 2-refinement is based on dividing a hex to be refined into eight new hexes. This allows greater control on mesh density which in turn increases computational efficiency.

Gear transmission systems are considered one of the critical aspects of vibration analysis, and it contains various potential faults such as misalignment, cracks, and noise. Therefore, it requires vibration monitoring to ensure the system is operating properly. Case mounted accelerometers are frequently used to monitor frequencies in a system. However, it is not a simple task to identify and interpret the acceleration data since there are many gear mesh frequencies present. One of the approaches utilized by researchers to perform gear diagnostic is Finite Element Modeling. This study focuses on stiffness cycle and meshing stiffness of non-linear quasi-static finite element modeling. The comparisons of meshing stiffness will concentrate on the type of elements, the integration methods, the meshing quality, plane stress and plane strain analysis, sensitivity of model tolerance, and crack modeling. The results show that the FEA approach is extremely sensitive to tolerance, mesh density, and element choice. Also, the results indicate that a complete sensitivity and convergence studies should be carried out for a satisfactory stiffness match.

In this dissertation, I draw on comparative studies of English to establish a framework for looking at how Portuguese studies and teaching are shaped by political economies, cultural hierarchies, and educational institutions in Brazil and Cape Verde. I examine how English and Portuguese are constructed as world languages and how English and Portuguese rhetorics shape language teaching. People who are locally engaged contest these global constructions. As a result, diverse people construct world languages by adopting, adapting, resist, and transforming it in specific locations (Pennycook). First, I identify compositionists in the U.S. with what I call a rhetoric of multilingualism in which teachers of English should view English in relation to other Englishes and other languages. Secondly, I examine how the transnational organization for Portuguese-speaking countries perpetrates lusotropicalism--Gilberto Freyre's social theory of the Portuguese exceptionality to create a hybrid culture in the tropics. Despite fostering adaptability to local cultures, peoples, and languages, Freyre's lusotropical rhetoric eschews diversity by maintaining that a culture and a language should promote homogeneity. Then, I analyze the linguistic contexts, educational policies, and data gathered from questionnaires and interviews with language teachers in Brazil and Cape Verde. In light of higher education expansion and the maintenance of excellence, I argue that language teachers should promote the writing of Portuguese as a rhetorical construction in which grammar and mechanical correctness is only one aspect of writing instruction. Lastly, I propose the use of code meshing as a pedagogical strategy in academic discourse because it values language in its diversity and its relation to other languages. I argue that students' multilingual strategies deserve a place in academic writing. The rhetorical construction of language in academia could also become multilingual--globally networked and locally engaged. This study contributes to the internationalist discussions about how to teach writing in different languages and educational contexts.

A diffuse-interface finite-element method has been applied to simulate the flow of two-component rheologically complex fluids. It treats the interfaces as having a finite thickness with a phase-field parameter varying continuously from one phase to the other. Adaptive meshing is applied to produce fine grid near the interface and coarse mesh in the bulk. It leads to accurate resolution of the interface at modest computational costs. An advantage of this method is that topological changes such as interfacial rupture and coalescence happen naturally under a short-range force resembling the van der Waals force. There is no need for manual intervention as in sharp-interface model to effect such event. Moreover, this energy-based formulation easily incorporates complex rheology as long as the free energy of the microstructures is known. The complex fluids considered in this thesis include viscoelastic fluids and nematic liquid crystals. Viscoelasticity is represented by the Oldroyd-B model, derived for a dilute polymer solution as linear elastic dumbbells suspended in a Newtonian solvent. The Leslie-Ericksen model is used for nematic liquid crystals，which features distortional elasticity and viscous anisotropy. The interfacial dynamics of such complex fluids are of both scientific and practical significance. The thesis describes seven computational studies of physically interesting problems. The numerical simulations of monodisperse drop formation in microfluidic devices have reproduced scenarios of jet breakup and drop formation observed in experiments. Parametric studies have shown dripping and jetting regimes for increasing flow rates, and elucidated the effects of flow and rheological parameters on the drop formation process and the final drop size. A simple liquid drop model is used to study the neutrophil, the most common type of white blood cell, transit in pulmonary capillaries. The cell size, viscosity and rheological properties are found to determine the transit time. A compound drop model is also employed to account for the cell nucleus. The other four cases concern drop and bubble dynamics in nematic liquid crystals, as determined by the coupling among interfacial anchoring, bulk elasticity and anisotropic viscosity. In particular, the simulations reproduce unusual bubble shapes seen in experiments, and predict self-assembly of microdroplets in nematic media.

A diffuse-interface finite-element method has been applied to simulate the flow of two-component rheologically complex fluids. It treats the interfaces as having a finite thickness with a phase-field parameter varying continuously from one phase to the other. Adaptive meshing is applied to produce fine grid near the interface and coarse mesh in the bulk. It leads to accurate resolution of the interface at modest computational costs. An advantage of this method is that topological changes such as interfacial rupture and coalescence happen naturally under a short-range force resembling the van der Waals force. There is no need for manual intervention as in sharp-interface model to effect such event. Moreover, this energy-based formulation easily incorporates complex rheology as long as the free energy of the microstructures is known. The complex fluids considered in this thesis include viscoelastic fluids and nematic liquid crystals. Viscoelasticity is represented by the Oldroyd-B model, derived for a dilute polymer solution as linear elastic dumbbells suspended in a Newtonian solvent. The Leslie-Ericksen model is used for nematic liquid crystals，which features distortional elasticity and viscous anisotropy. The interfacial dynamics of such complex fluids are of both scientific and practical significance. The thesis describes seven computational studies of physically interesting problems. The numerical simulations of monodisperse drop formation in microfluidic devices have reproduced scenarios of jet breakup and drop formation observed in experiments. Parametric studies have shown dripping and jetting regimes for increasing flow rates, and elucidated the effects of flow and rheological parameters on the drop formation process and the final drop size. A simple liquid drop model is used to study the neutrophil, the most common type of white blood cell, transit in pulmonary capillaries. The cell size, viscosity and rheological properties are found to determine the transit time. A compound drop model is also employed to account for the cell nucleus. The other four cases concern drop and bubble dynamics in nematic liquid crystals, as determined by the coupling among interfacial anchoring, bulk elasticity and anisotropic viscosity. In particular, the simulations reproduce unusual bubble shapes seen in experiments, and predict self-assembly of microdroplets in nematic media.

El objetivo del presente trabajo es realizar una adaptación de un sistema de generación de mallas geométricas a una arquitectura orientada a objetos. Se espera entonces evaluar, en cuanto a la ingeniería de software, el sistema resultante. En base al objetivo descrito se realiza una investigación teórica de la ingeniería de software, los estudios de buenas prácticas realizados por el departamento, y una evaluación del sistema a actualizar. Por último se entrega la metodología de desarrollo para el buen cumplimiento de la adaptación.

A diffuse-interface finite-element method has been applied to simulate the flow of two-component rheologically complex fluids. It treats the interfaces as having a finite thickness with a phase-field parameter varying continuously from one phase to the other. Adaptive meshing is applied to produce fine grid near the interface and coarse mesh in the bulk. It leads to accurate resolution of the interface at modest computational costs. An advantage of this method is that topological changes such as interfacial rupture and coalescence happen naturally under a short-range force resembling the van der Waals force. There is no need for manual intervention as in sharp-interface model to effect such event. Moreover, this energy-based formulation easily incorporates complex rheology as long as the free energy of the microstructures is known. The complex fluids considered in this thesis include viscoelastic fluids and nematic liquid crystals. Viscoelasticity is represented by the Oldroyd-B model, derived for a dilute polymer solution as linear elastic dumbbells suspended in a Newtonian solvent. The Leslie-Ericksen model is used for nematic liquid crystals，which features distortional elasticity and viscous anisotropy. The interfacial dynamics of such complex fluids are of both scientific and practical significance. The thesis describes seven computational studies of physically interesting problems. The numerical simulations of monodisperse drop formation in microfluidic devices have reproduced scenarios of jet breakup and drop formation observed in experiments. Parametric studies have shown dripping and jetting regimes for increasing flow rates, and elucidated the effects of flow and rheological parameters on the drop formation process and the final drop size. A simple liquid drop model is used to study the neutrophil, the most common type of white blood cell, transit in pulmonary capillaries. The cell size, viscosity and rheological properties are found to determine the transit time. A compound drop model is also employed to account for the cell nucleus. The other four cases concern drop and bubble dynamics in nematic liquid crystals, as determined by the coupling among interfacial anchoring, bulk elasticity and anisotropic viscosity. In particular, the simulations reproduce unusual bubble shapes seen in experiments, and predict self-assembly of microdroplets in nematic media. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Doctor en Ciencias, Mención Computación / Una malla es una discretización de la geometría de un cierto dominio. Las mallas pueden estar compuestas de diversos elementos: triángulos, cuadriláteros, tetraedros, etc. Una herramienta para la generación de mallas es un aplicación que permite crear, refinar, desrefinar, mejorar, suavizar, visualizar y posprocesar mallas y/o una región particular de ella, como también asignar valores físicos a los elementos de la malla (temperatura, concentración, etc.). Las herramientas para la generación de mallas son complejas y sofisticadas, y construir una herramienta nueva desde cero o mantener una existente, demanda un esfuerzo enorme. Existe una necesidad y oportunidad para usar enfoques nuevos en el desarrollo de estas herramientas, de manera de reducir tanto el tiempo como los costos de desarrollo, sin comprometer la calidad. La experiencia en el desarrollo de estas herramientas provee la motivación para la construcción de otras nuevas mediante la reutilización del trabajo realizado durante los desarrollos previos. Estas herramientas comparten varias características y sus variaciones pueden ser manejadas sistemáticamente. Esto hace que el desarrollo de estas herramientas sea una buena oportunidad para aplicar el enfoque de Línea de Productos de Software (LPS). Los procesos existentes de LPS son generales y requieren usualmente una serie de pasos y documentación innecesaria en el dominio de las herramientas para la generación de mallas. Así, esta tesis propone un modelo de proceso de LPS específico para este tipo de herramientas. Un proceso de desarrollo de LPS está centrado en la reutilización de software, e involucra principalmente dos fases: la ingeniería del dominio (ID) y la ingeniería de la aplicación (IA). El proceso presentado en este trabajo está centrado en dos etapas de la ID: el análisis del dominio (AD) y el diseño del dominio (DD). En el AD se define el modelo del dominio y el alcance de la LPS. En el DD la arquitectura de la línea de productos (ALP) es creada; esta arquitectura es válida y compartida por todos los productos en la LPS. Un modelo de características es comúnmente usado para modelar el dominio. En este trabajo, el AD también ocupa un diccionario, escenarios, acciones y metas para proveer el razonamiento utilizado para la construcción del modelo de características. Esta tesis presenta un proceso riguroso para obtener el modelo del dominio. Este modelo es formalizado mediante condiciones de consistencia y completitud. El proceso de definición del alcance es presentado a través de un diagrama de actividad. Además, el enfoque presentado en esta tesis presenta explícitamente los diferentes productos de la LPS, estableciendo relaciones entre productos y las características de la LPS, lo que permite administrar el desarrollo del producto. La etapa de DD se centra en la creación de la ALP, artefacto esencial para la construcción de productos de la LPS. Para ello, este trabajo provee un proceso deductivo y otro transformacional. En el primero, una ALP explícita es desarrollada, usando los artefactos producidos en el AD. Además, tanto la vista arquitectónica estructural como la de comportamiento son establecidas. Ambas vistas son generales y permiten la representación de cualquier producto dentro del alcance de la LPS. En el proceso transformacional, una ALP implícita es desarrollada usando reglas de transformación, las que han sido creadas usando artefactos producidos en el AD. En este proceso se produce la arquitectura para productos específicos, y la ALP es definida como la suma de todas las arquitecturas de los productos. Tanto el AD como el DD son descritos en detalle, y la aplicación del modelo de la LPS es ilustrado a través de un ejemplo bien documentado en el dominio de las herramientas para la generación de mallas, el que tiene un grado relativamente alto de complejidad. En este ejemplo, un modelo del dominio formalizado es introducido, y la arquitectura es definida tanto para el proceso deductivo como para el transformacional.

The Reproducing Kernel Element Method (RKEM) is a hybrid between finite elements and meshfree methods that provides shape functions of arbitrary order and continuity yet retains the Kronecker-delta property. To achieve these properties, the underlying mesh must meet certain regularity constraints, unique to RKEM. The aim of this dissertation is to develop a precise definition of these constraints, and a general algorithm for assessing a mesh is developed. This check is a critical step in the use of RKEM in any application. The general checking algorithm is made more specific to apply to two-dimensional triangular meshes with circular supports and to three-dimensional tetrahedral meshes with spherical supports. The checking algorithm features the output of the uncovered regions that are used to develop a mesh-mending technique for fixing offending meshes. The specific check is used in conjunction with standard quality meshing techniques to produce meshes suitable for use with RKEM. The RKEM quasi-uniformity definitions enable the use of RKEM in solving Galerkin weak forms as well as in general interpolation applications, such as the representation of geometries. A procedure for determining a RKEM representation of discrete point sets is presented with results for surfaces in three-dimensions. This capability is important to the analysis of geometries such as patient-specific organs or other biological objects.