No description available.

The main objective of this research is to use IGA as an efficient and robust alternative for numerical simulation of unsaturated seepage problems. Moreover, this research develops an IGA-based probabilistic framework that can properly account for the variability of soil hydraulic properties in the simulations. In the first part, IGA is used in a deterministic framework to solve a head-based form of Richards’ equation. It is shown that IGA is able to properly simulate changes in pore pressure at the soils interface. In the second part of this research, a new probabilistic framework, named random IGA (RIGA), is developed. A joint lognormal distribution function is used with IGA to perform Monte Carlo simulations. The results depict the statistical outputs relating to seepage quantities and pore water pressure. It is shown that pore water pressure, flow rate, etc. change considerably with respect to standard deviation and correlation of the model parameters.

Geometric models, such as for use in CAD/CAM or animation, are often constructed in a piece-wise fashion. Historically, these models have been made of NURBS surfaces. For various reasons it is problematic and often times mathematically impossible to combine several NURBS models into one continuous surface. The recent invention of a surface type called T-splines has made the combining of NURBS surfaces into a single continuous surface possible, but much of the mathematics has yet to be explored. This thesis explores the mathematics and algorithms necessary to merge multiple NURBS, T-spline, or T-NURCC surfaces into a single continuous surface. This thesis addresses two main problems. The first problem is merging surfaces with different parameterizations. In order to merge surfaces with different parameterizations, it is often necessary to modify the parameter values of the surface, which can change the shape of the surface. This change can be alleviated through shape control methods. The second problem is merging surfaces that meet at extraordinary points, or points with a valence other than four. Results show that the merging algorithm is able to successfully convert models composed of multiple NURBS, T-spline, or T-NURCCS surfaces into models composed of a single T-spline or T-NURCC surface. The resulting models are gap-free and contain little distortion in the parameterization.

T-Splines is a freeform surface type similar to NURBS, that allows partial rows of control points. Up until now, T-Splines have only been formally defined for the degree three case. This paper extends the definition to support all odd, even, and mixed degree T-Spline surfaces, making T-Splines a proper superset of all standard NURBS surfaces.

Darbe yra apžvelgiamos NURBS paviršių atvaizdavimo realizavimo problemos mobiliesiems įrenginiams. Pagrindinis darbo tikslas yra įsitikinti tokios realizacijos galimumu, bei surasti kiek įmanoma efektyvesnį būdą, išsprendžiantį mobiliųjų platformų realizacijų problemas. Dar vienas tikslas, sukurti prototipinį sprendimą, padengiantį NURBS standartą. Analizei pasirinkta M3G mobiliosios grafikos standartas, kuris šiuo metu yra labiausiai paplitęs. Realizacijų palyginimui buvo pasirinkti du algoritmai: Oslo ir tiesioginis. Atlikus veikimo analizę nustatyta, jog tiesioginis algoritmas yra efektyvesnis, kurio pagrindu buvo išbaigtas NURBS standartas, realizuojant Trimmed NURBS modelius. / In the thesis it is analyzed the problems related with NURBS rendering implementation for mobile devices. The main goal of the thesis is to make find out if such implementation is possible at all and to find most effective way to implement it. One more goal is to create a prototype implementation for NURBS standard including Trimmed NURBS. M3G mobile graphics platform was chosen for analysis, which is mostly adopted across the vendors nowadays. There was chosen two rendering algorithms for analysis purposes: Oslo and directional. During analysis it was discovered, that Directional algorithm is more effective than Oslo, and it was adapted to prototype solution – Trimmed NURBS.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-04-05T14:04:54Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Vinícius César.pdf: 8129153 bytes, checksum: ba5d2566020247282af7bc9c09e0ea51 (MD5) / Made available in DSpace on 2016-04-05T14:04:54Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Vinícius César.pdf: 8129153 bytes, checksum: ba5d2566020247282af7bc9c09e0ea51 (MD5) Previous issue date: 2015-08-07 / CNPq / A instalação de dutos flexíveis em ambiente submarino de alta profundidade é realizada recorrentemente pelas indústrias de óleo e gás. Estes dutos transportam fluidos como água, gases e óleo. Durante o minucioso processo de instalação dos dutos flexíveis, é necessário o monitoramento constante de sua geometria a fim de evitar a propagação de esforços e consequentemente danos aos equipamentos envolvidos. Para que este monitoramento seja eficiente, podem ser utilizadas técnicas de reconstrução 3D que usam como entrada as imagens capturadas por um par de câmeras estéreo instaladas nos robôs que acompanham a operação. Esta dissertação de mestrado propõe o desenvolvimento dos algoritmos de rastreamento e reconstrução para dutos flexíveis com o intuito de permitir o monitoramento em tempo real da operação. O algoritmo de rastreamento proposto tem a função de determinar um conjunto de pontos que representam a projeção do eixo medial do duto em cada imagem do par estéreo. Para alcançar esse objetivo, o algoritmo utiliza características da iluminação em ambientes submarinos e de marcações realizadas no duto. A etapa de reconstrução utiliza os pontos rastreados para estimar uma curva B-spline racional não-uniforme (NURBS) sobre um plano tridimensional. Essa aproximação simplifica o processo de reconstrução e permite obter resultados mais precisos. Experimentos realizados em ambiente aquático e aéreo, utilizando uma escala reduzida, permitiram uma análise da acurácia e robustez dos algoritmos propostos. O erro médio alcançado foi menor que meio centímetro em todos os casos analisados. Além disso, concluiu-se que a disposição dos pontos da curva e a posição do plano influenciam na estimativa da reconstrução. Testes com imagens reais da operação foram também realizados e permitiram validar as técnicas propostas neste ambiente. Os resultados obtidos foram robustos em casos de baixa iluminação, ruidosos e com elevada obliquidade. Os métodos propostos são eficientes computacionalmente e permitem a obtenção do resultado a uma taxa superior a 30 quadros por segundo. / Installing flexible pipes in deep underwater environments is a recurrent task in oil production industry. Such flexible pipes are responsible for transporting fluids such as water, gases and oil. The installation pipe connections is a meticulous process that requires continuous monitoring of the pipe’s geometry in order to prevent excessive tension along the line that may cause costly damages to the end equipment. This master thesis develops a 3D reconstruction method to ensure the success of this critical operation. The model makes use of images captured by a stereo rig mounted on the robots supporting the operation. At the heart of the model is a novel algorithm for tracking and reconstructing flexible pipes in order to allow real time pipe monitoring during the installation operation. Our approach tracks a set of points that represents the pipe’s projected medial axis in each image provided by the stereo rig. This is achieved using the scene’s specifications including the as deep-water environment illumination and marks pre-painted over the used pipes. The reconstruction stage uses the tracked points to estimate a plane non-uniform rational B-spline (NURBS) in 3D space. This approximation simplifies the reconstruction and i8s shown to improve accuracy. Underwater and aerial experiments were performed in a reduced scale scenario to evaluate the proposed method’s accuracy and robustness. In all test cases, the mean of reconstruction error was less than 1 centimeter. Furthermore, we conclude that the points’ distribution along the pipeline and the curve plane position impact the reconstruction’s accuracy. In addition, tests carried out using real operation videos were performed. They allowed us to validate our technical proposal in this harsh environment. The results obtained were robust in almost all the analyzed cases. The proposed methods are computationally efficient and allow obtaining results at a rate of 30 frames per second or higher.

<p>Over the past 20 years, the development in ComputationalElectromagnetics has produced a vast choice of methods based onthe large number of existing mathematical formulations of theMaxwell equations. None of them dominate over the others,instead they complement each other and the choice of methoddepends on the frequency range of the electromagnetic waves.This work is focused on the most popular method in the highfrequency scenario, namely the Geometrical Theory ofDiffraction (GTD). The main advantage of GTD is the ability topredict the electromagnetic field asymptotically in the limitof vanishing wavelength, when other methods, such as the Methodof Moments, become computationally too expensive.</p><p>The low cost of GTD is due to both the fact that there is noruntime penalty in increasing the frequency and that the raytracing, which GTD is based on, is a geometrical technique. Thecomplexity is then no longer dependent on electrical size ofthe problem but instead on geometrical sub problems which aremanageable. For industrial applications the geometricalstructures, with which the rays interact, are modelled bytrimmed Non-Uniform Rational B-Spline (NURBS) surfaces, themost recent standard used to represent complex free-formgeometries.</p><p>Due to the introduction of NURBS, the geometrical subproblems tend to be mathematically and numerically cumbersome,but they can be highly simplified by proper Object Orientedprogramming techniques. This allowed us to create a flexiblesoftware package, MIRA: Modular Implementation of Ray Tracingfor Antenna Applications, with an architecture that separatesmathematical algorithms from their implementation details andmodelling. In addition, its design supports hybridisationtechniques in combination with other methods such as Method ofMoment (MoM) and Physical Optics (PO).</p><p>In a first hybrid application, a triangle-based PO solveruses the shadowing information calculated with the ray tracerpart of MIRA. The occlusion is performed between triangles andtheir facing NURBS surfaces rather than between their facingtriangles, thus reducing the complexity. Then the shadowinginformation is used in an iterative MoM-PO process in order tocover higher frequencies, where the contribution of theshadowing effects, in the hybrid formulation, is believed to bemore significant.</p><p>Thesis presented at the Royal Institute of Technology ofStockholm in 2003, for the degree of Licentiate in ScientificComputing.</p>

Cardiovascular disease is the number one reason for emergency room visits in the United States. Understanding the different pathologies of the cardiovascular system is crucial when trying to prescribe proper treatment or intervention. In order best understand these issues proper computer simulations would be necessary. Due to the fact that every patient is different. Being able to analysis and properly simulate each patients data individually to better understanding their specific case is necessary for patient specific interventions. In order to achieve such requirement we propose a new method of mesh generation to better map patient specific geometries. This new framework takes a set of points in a 3D space and generates a 2D NURBS mesh. Insuring a smooth and accurate representation of the patient specific geometry will allow for more specific incite to possible medical issues that may arise. This NURBS based mesh can be then used to run either finite element analysis, computational fluid dynamics, or even fluid solid interactions. Running these patient-specific valve simulations using isogementric modeling is what will allow us to have patient specific treatments and intervention.

Nowadays almost all products used in our daily life are made in pursuit of streamline and good look, including mobiles, motorcycles, aerospace and 3C industry; therefore, how to shorten process time and enhance the smoothness of the product¡¦s surface has become one of the important issues. However, the process method of traditional CNC machines only can support line and circular interpolations but cannot accept motion along curve and circular paths. Therefore, the traditional CNC machines have to rely on CAM, a method to generate the NC code called G-code and M-code by approximating many tiny linear or circular segments, to plan the cutter paths. But this approximating method requires higher transmission speed; it also occupies huge memory capacity and makes the velocity of machine tool discontinuous, in order to difficultly meet the requirement of high speed and better precision. In order to solve the above problems, this thesis adopts the NC code created by CAD/CAM¡¦s NURBS curve which called NURBS-code, making CNC machines have the function of processing NURBS curve interpolations to improve the defect of the traditional processing and thus reach the goal of high speed and better precision. Furthermore, due to NURBS interpolators are always implemented by the controller. This always makes CNC machine become very expensive; meanwhile, adjusting parameters is very troublesome. Therefore this thesis also provides the intergrated method of NURBS and DDA real-time interpolator to make the application in the easy way without the consideration of controller design for AC driver.

Zugl.: Koblenz, Landau (Pfalz), Univ., Diss., 2008