No description available.

This research was undertaken to investigate the effects of solid modeling and visualization on technical problem solving. The participants were 47 students enrolled in solid modeling classes at Southeast Missouri State University. The control and experimental groups consisted of 23 and 24 randomly assigned students respectively. This study was a posttest only design that used logistic regression to analyze the results. Both groups were required to take the Purdue Spatial-Visualization Test/Visualization of Rotations (PSVT/TR). Participants in the control group used only sketching to design their solutions while participants in the experimental group used parametric solid modeling software to design their solutions. All participants then constructed prototypes of their designs. The prototype was evaluated to determine if it successfully met the design specifications. The findings revealed that visualization was a significant predictor of technical problem solving as defined by successful prototype construction (p=.021). There was no significant difference between the sketching and solid modeling design methods used for technical problem solving (p=.752). The interaction between the method of design, solid modeling or sketching, was analyzed to determine if using solid modeling would offset low visualization scores It was found that the interaction was not significant (p=.393). / Ph. D.

Subdivision surfaces are capable of modeling and representing complex shapes of arbi-trary topology. However, methods on how to build the control mesh of a complex surfaceare not studied much. Currently, most meshes of complicated objects come from trian-gulation and simplification of raster scanned data points, like the Stanford 3D ScanningRepository. This approach is costly and leads to very dense meshes.Subdivision surface based one-piece representation means to represent the final objectin a design process with only one subdivision surface, no matter how complicated theobject's topology or shape. Hence the number of parts in the final representation isalways one.In this dissertation we present necessary mathematical theories and geometric algo-rithms to support subdivision surface based one-piece representation. First, an explicitparametrization method is presented for exact evaluation of Catmull-Clark subdivisionsurfaces. Based on it, two approaches are proposed for constructing the one-piece rep-resentation of a given object with arbitrary topology. One approach is to construct theone-piece representation by using the interpolation technique. Interpolation is a naturalway to build models, but the fairness of the interpolating surface is a big concern inprevious methods. With similarity based interpolation technique, we can obtain bet-ter modeling results with less undesired artifacts and undulations. Another approachis through performing Boolean operations. Up to this point, accurate Boolean oper-ations over subdivision surfaces are not approached yet in the literature. We presenta robust and error controllable Boolean operation method which results in a one-piecerepresentation. Because one-piece representations resulting from the above two methodsare usually dense, error controllable simplification of one-piece representations is needed.Two methods are presented for this purpose: adaptive tessellation and multiresolutionanalysis. Both methods can significantly reduce the complexity of a one-piece represen-tation and while having accurate error estimation.A system that performs subdivision surface based one-piece representation was im-plemented and a lot of examples have been tested. All the examples show that our ap-proaches can obtain very good subdivision based one-piece representation results. Eventhough our methods are based on Catmull-Clark subdivision scheme, we believe they canbe adapted to other subdivision schemes as well with small modifications.

As the use of simulation increases across many diff erent application domains, the need for high- fidelity three-dimensional virtual representations of real-world environments has never been greater. This need has driven the research and development of both faster and easier methodologies for creating such representations. In this research, we present two diff erent inference-based geometric modeling techniques that support the automatic construction of complex cluttered environments. The fi rst method we present is a surface reconstruction-based approach that is capable of reconstructing solid models from a point cloud capture of a cluttered environment. Our algorithm is capable of identifying objects of interest amongst a cluttered scene, and reconstructing complete representations of these objects even in the presence of occluded surfaces. This approach incorporates a predictive modeling framework that uses a set of user provided models for prior knowledge, and applies this knowledge to the iterative identifi cation and construction process. Our approach uses a local to global construction process guided by rules for fi tting high quality surface patches obtained from these prior models. We demonstrate the application of this algorithm on several synthetic and real-world datasets containing heavy clutter and occlusion. The second method we present is a generative modeling-based approach that can construct a wide variety of diverse models based on user provided templates. This technique leverages an inference-based construction algorithm for developing solid models from these template objects. This algorithm samples and extracts surface patches from the input models, and develops a Petri net structure that is used by our algorithm for properly fitting these patches in a consistent fashion. Our approach uses this generated structure, along with a defi ned parameterization (either user-defi ned through a simple sketch-based interface or algorithmically de fined through various methods), to automatically construct objects of varying sizes and con figurations. These variations can include arbitrary articulation, and repetition and interchanging of parts sampled from the input models. Finally, we affim our motivation by showing an application of these two approaches. We demonstrate how the constructed environments can be easily used within a physically-based simulation, capable of supporting many diff erent application domains.

Our work applies techniques for blending and tightening solid shapes represented by sets. We require that the output contain one set and exclude a second set, and then we optimize the boundary separating the two sets. Working within that framework, we present mason, tightening, tight hulls, tight blends, and the medial cover, with details for implementation. Mason uses opening and closing techniques from mathematical morphology to smooth small features. By contrast, tightening uses mean curvature flow to minimize the measure of the boundary separating the opening of the interior of the closed input set from the opening of its complement, guaranteeing a mean curvature bound. The tight hull offers a significant generalization of the convex hull subject to volumetric constraints, introducing developable boundary patches connecting the constraints. Tight blends then use opening to replicate some of the behaviors from tightenings by applying tight hulls. The medial cover provides a means for adjusting the topology of a tight hull or tight blend, and it provides an implementation technique for two-dimensional polygonal inputs. Collectively, we offer applications for boundary estimation, three-dimensional solid design, blending, normal field simplification, and polygonal repair. We consequently establish the value of blending and tightening as tools for solid modeling.

The prognosis of cancer patients suffering from solid tumors significantly depends on the developmental stage of the tumor. For cervix carcinoma the prognosis is better for compact shapes than for diffusive shapes since the latter may already indicate invasion, the stage in tumor progression that precedes the formation of metastases. In this paper, we present methods for describing and evaluating tumor objects and their surfaces based on topological and geometric properties. For geometry, statistics of the binary object's distance transform are used to evaluate the tumor's invasion front. In addition, a simple compactness measure is adapted to 3D images and presented to compare different types of tumor samples. As a topological measure, the Betti numbers are calculated of voxelized tumor objects based on a medial axis transform. We further illustrate how these geometric and topological properties can be used for a quantitative comparison of histological material and single-cell-based tumor growth simulations.

This dissertation presents a method for the design of customizable products that interface with the human body. The method presented involves first, a consistent method of capturing and representing the human model so that the model can be used with CAx tools and solid modeling techniques. Second, it provides a design methodology based on feature structure planning and assembly modeling that provides a consistent structure to the design process so that it can be reused and parameterized. Third, a strategy for identifying parametric variables that are referenced to the human body is introduced. The core of this method is the definition of biomechanical products as an assembly model, where human data is defined as the base part. This research expands on traditional mating conditions in assembly model methods by identifying different ways products can interface with the human body. With the identification of these mating conditions, products can be designed to interact with the body in definable ways through the definition of parametric strategies. This dissertation also presents the necessary theoretical and numerical methods for implementation of these mating conditions in a CAD system.

No description available.

Southern North Sea Basin is one of the mature hydrocarbon basins in NW Europe and is shaped by a number of phases of tectonic deformations during the Phanerozoic. In addition, mobilization and halokinesis of thick Permian Zechstein Salt has enhanced and contributed to the deformation of the region since Triassic, which further complicated the geology of the region. The Friesland Platform, which is a stable platform area located in northern Netherlands, experienced the main deformation phases that Europe has been endured together with the deformation of Permian Zechstein salt. In this study a computer based 3D modeling has been carried out within the Friesland Platform with the use of 3D seismic and borehole data in order to delineate structural elements and geological development of the area with special emphasis on the salt tectonic deformation. The model was constructed by picking key horizons and major faults from the seismic sections in time domain and then migrated into depth domain. The stratigraphy of the area is correlated with horizons by well-seismic matching. The model includes major structures and seismostratigraphic units of Permian to recent, revealing salt and salt induced structures formed during the periods of active salt movements. Thick Zechstein salt layers deposited in N-S-oriented grabens and half grabens of South Permian Basin acted as the primary control for the location of salt diapirs and are reflected on the overburden without a direct continuation (unlinked) of the basement faults into the overburden. The mapped N-S oriented salt-cored anticline and a convergent conjugate transfer zone between a pair of segmented normal growth faults at the crest of the anticline are controlled by the ascent of the Zechstein salt.

Este estudo apresenta uma tentativa para investigação do efeito que a sensibilidade à taxa de deformação do material poderia provocar no modo de falha do ponto de solda. É sabido que alguns materiais quando deformados dinamicamente sofrem elevação na sua resistência mecânica, e portanto este aumento poderia afetar o comportamento, ou seja, o modo de falha da junta. Os modos de falha esperados neste estudo são o de cisalhamento do ponto na interface ou o arrancamento do ponto na região da zona termicamente afetada. Uma formulação analítica para as tensões atuantes devido à solicitação dinâmica no ponto foi proposta com base em estudos existente para juntas solicitadas estaticamente. Propôs-se uma forma de quantificar a taxa de deformação, que foi incorporada à formulação da tensão dinâmica atuante na região da junta. Em conjunto à formulação analítica, um modelo de elementos finitos foi desenvolvido e diversas condições de carregamento e geometrias foram analisadas e posteriormente comparadas com os resultados analíticos. Como resultado principal verificou-se que, para a estimativa adotada para a taxa de deformação de material, o modo de falha da junta não se altera quando comparado com o modo de falha presente na junta solicitada a carregamento estático. E que para as formulações estimadas e modelos investigados a falha teria uma tendência a ocorrer na região da zona termicamente afetada para qualquer dos casos de carregamento analisados. / This study presents an attempt to probe the effect that some materials strain rate sensitivity could set in the failure mode of the spot weld joint. It is well known that some materials when dynamically loaded and deformed have its mechanical strength increased and therefore this strength increase could affect the joint failure behavior. The failure modes taken in account in this study are the shear of the spot weld in the interface region and the pull-out of the spot weld in the heat affected zone. An analytical formulation to the acting stress in the spot weld region owing to the dynamic loading has been proposed based on studies performed to the statically loaded spot weld joint. Moreover, an analytical formulation has been proposed to quantify the strain rate, and it has been incorporated in the dynamic stress formulation. A finite element model has been also built. Several geometrical configurations of this model have been analyzed under several velocity loading conditions, and their results have been compared with the analytical considerations. As the main result, it has been verified, to the estimated strain rate formulation, the failure mode in the dynamic loading condition has not effectively changed in comparison with the statically loaded joint failure. And according to the formulation considered and the finite elements models results the failure would tend to happen in the heat affected zone to any of the loading cases taken in account in this study.