- / -

No description available.

Resumo: O projeto tem por finalidade integrar técnicas de Computação Gráfica com as de Fotogrametria para obter como resultado final a visualização 3D de uma imagem digital. A partir do DTM regular definido por pontos que se conectam formando uma malha triangular, a tonalização é aplicada triângulo-a-triângulo utilizando um modelo de iluminação, juntamente com o método de tonalização. Para tanto, é necessária a transformação das coordenadas do DTM para as coordenadas fotogramétricas, através da equação de colinearidade, e dessas para as correspondentes coordenadas digitais. Como estas coordenadas não coincidem com as coordenadas de pixel é necessário a aplicação de um método de reamostragem para obter os tons de cinza dos pontos transformados. Esses tons de cinza são usados pelo modelo de iluminação para calcular as intensidades de iluminação nos vértices do MDT, que por sua vez são utilizados pelo modelo de tonalização para tonalizar o MDT. Finalmente, um modelo de projeção é utilizado para obter a sensação 3D no plano 2D. Os resultados obtidos foram satisfatórios, apresentando similaridade entre os métodos de tonalização e a representação da superfície. / Abstract: The main purpose of this research is to integrate techniques of both Computer Graphic and Photogrammetry, in order to obtain as a final result the 3D visualization of a digital image. Starting from regular DTM defined by points connected in such a way that they can form a triangular mesh, the shading is applied triangle-to-triangle using an illumination model, together with the shading method. First it is necessary to transform the DTM coordinates through photogrammetric coordinates or collinearity equation, and then the results to digital coordinates. As these last coordinates do not coincide with pixel coordinates, a resampling technique is needed to get gray levels of computed coordinates. The interpolated gray levels are the basic input of the illumination model, which in turn supplies illumination intensities for the shading method, allowing the DTM to be shaded. Finally, a projection model is used to obtain 3D sensation onto 2D plane. The obtained result was satisfactory, showing similarity between the methods of shading and surface rendering. / Orientador: Aluir Porfírio Dal Poz / Coorientador: Júlio K. Hasegawa / Banca: Jorge Antonio Centeno / Banca: Antonio Maria Garcia Tomaselli / Banca: Aluir Porfírio Dal Poz / Mestre

Masters of Science / Sometimes, dental impressions need to be transported to distant laboratories. It has been reported that the temperature in a vehicle can reach up to 66C when the outdoor temperature is 38C. These temperatures may be reached during South African summers. The objective of this in vitro study was to investigate the effect of temperature and time on the dimensional stability of two elastomeric impression materials. Methodology: Specimens consisted of impressions made of an ISO-specified test-block featuring a pattern of grooves. Materials used were polyether (Impregum Penta) and polyvinylsiloxane (Affinis Precious regular body). Using an SLR camera and standardized technique, the specimens were photographed at 2 different temperatures (21°C and 66°C) and 3 time intervals (30min, 8hrs and 14 days). This resulted in a total of 12 groups (n=10) to be compared. Digital images of the impressions were calibrated and measured using digital analyzing software. These distances were used to evaluate the mean % dimensional change (%DC) for each group. VEPAC module of Statistica 10 was used for the statistical analysis. To analyze exactly where the differences lied, a Fisher LSD correction was applied to correct for multiple pair wise comparisons. Results: Comparing polyether with silicone, there was no difference in the mean %DC for specimens kept at 21°C for 8hrs (polyether=0.364; silicone=0.237). Neither was there a difference between polyether and silicone when heated to 66°C, cooled off, and measured after 8hrs (polyether=0.306; silicone=0.297) or after 14 days (polyether=-0.272; silicone=-0.093). For both polyether and silicone, the mean %DC of the groups exposed to 66°C, cooled off and measured after 8hrs (polyether=0.306; silicone=0.297) differed significantly when compared to the group measured after 14 days (polyether=-0.2723; silicone=-0.092) (P<0.0001 and P=0.0029 resp). For both polyether and silicone, the mean %DC of the groups exposed to 66°C, cooled off and measured after 8hrs (polyether=0.306; silicone=0.297) did not differ when compared to the 21°C (polyether=0.364; silicone=0.237). Conclusions: Within limitations of this study, both materials were heat-sensitive. It is recommended that materials return to 21°C before casting. Despite statistical differences, all results were within ISO specifications of maximum 1.5%DC.

Two-phase Ti6246 alloy is a light weight material exhibiting very high strength at higher temperatures compared to the commonly used Ti64 alloy. This particular alloy is used at the later stages of compressor discs within the aero engines. However, compressor discs undergo a number of cyclic stresses, which could eventually lead to fatigue failure. In order to optimize the microstructure for design and lifing models, an improved understanding of the localised deformation mechanisms is crucial, particularly at the surface, as cracks can be initiated leading to failure and in turn affect the life expectancy of the component. Two-phase alloys in use have very complex lamellar microstructures comprising of a mixture of coarse and fine phases and their role in deformation can be very complex and difficult to understand. The focus of this study was particularly based on the importance of the beta phase in strengthening two-phase microstructures. Therefore, this study has been simplified to compare model lamellar microstructures, which have particular sizes of beta phase in between alpha lamellae. Digital Image Correlation along with high resolution imaging was used to develop a detailed understanding of the localised deformation in these microstructures. Widening the beta phase in-between alpha lamellae caused a more homogenous deformation, while ageing the beta phase with fine secondary alpha strengthened the microstructure. However, all microstructures showed that the single continuous alpha layer at beta grain boundaries depicted the highest amount of deformation, which can be detrimental for the life of the component. The behaviour of slip at the α/β interface not only depended on the size of the phases but also depended on the neighbouring crystallographic orientations and the relationship of the two phases, specifically the alignment of the close packed slip directions. Strain maps of these microstructures were subsequently related to corresponding Schmid factor maps and crystal plasticity models to improve this understanding.

Tendinopathy is a common pathology of tendons characterized by pain and a decrease in function resulting from changes in the tissue's structure and/or composition due to injury. Diagnosis of tendinopathy is determined by the qualitative analysis of a trained physician usually with assistance from an imaging modality. Although physicians can often identify tendinopathy, there are no quantitative metrics to evaluate tendon fatigue, damage, or healing. Physical therapy (PT) is a common treatment for patients with tendinopathy, and recent studies have investigated Focused Ultrasound (FUS) for its treatment of tendons. Developments in the use of FUS as a therapeutic have led to studies of the underlying mechanisms by which it operates. Digital Image Correlation (DIC) is a non-contact method of quantifying tissue displacements and strains of a deforming material using high resolution imaging DIC programs can evaluate and interpolate strain data by applying statistical image processing algorithms and solid continuum mechanics principles using a set of sequential image frames capturing the mechanical deformation of the specimen during testing. The studies presented in this thesis investigate methodologies for using DIC with ultrasound imaging of mouse Achilles tendons to characterize strains resulting from FUS therapies. The first method is based upon an orthogonal configuration of therapy and imaging transducers while the second investigates a coaxial experimental configuration. This work explores DIC as a viable means of quantifying the mechanical stimulation caused by FUS therapies on tendon tissue through ultrasound imaging to better understand the underlying mechanisms of FUS therapy. / Master of Science / Tendinopathy is a common injury that many people will experience in their lifetime. Pain and swelling are common symptoms and can make daily actions uncomfortable to perform. Physical therapy (PT) is one of the most common ways to help relieve the symptoms of this condition. A therapy being investigated to help treat tendinopathy utilizes Focused Ultrasound (FUS) technology to help the healing process. PT can be difficult and painful for those experiencing tendinopathy, but if a therapeutic like FUS could mimic the effects of PT, then some patients would not need to perform these physically demanding tasks. To understand if this treatment is viable, we need to better understand the underlying mechanisms by which it operates. Therefore, we are investigating the mechanical stimulation that FUS imparts on tendons because it is believed that the mechanical stimulations from exercise are a primary contributor to healing. Specifically, we want to evaluate the kind of strains applied by FUS therapies to inform decisions about dosage. One method uses Digital Image Correlation (DIC). DIC is a method of evaluating displacements and strains using non-contact high resolution imaging. DIC works using statistically motivated algorithms to calculate the deformation between subsequent video frames in a given material undergoing a state of stress. Using this technology along with ultrasound imaging, this work gives a preliminary exploration of using DIC as a means of quantifying strain to better understand the underlying mechanisms of the mechanical stimulations caused by FUS therapy.

A series of experiments and finite-element simulations were performed in order to assess existing void coalescence criteria and propose a new model for the coalescence of cylindrical holes in a pure metal matrix during uniaxial stretching. The finite-element simulations were performed so that various plastic limit-load models could be evaluated at each strain increment during deformation, rendering predictions concerning the farfield strains required for coalescence. The experiments were performed in order to identify the actual far-field strain at the moment of incipient coalescence for the specimen geometries considered. The cylindrical-void models of Thomason (1990) and McClintock (1966) outperformed all of the other considered models in their original states. A modified form of the Ragab (2004) plastic limit-load model is proposed in the present work and is shown to have good agreement with the experimental results. The present model accounts for ligament work-hardening and ligament orientation.

Digital Image-based Elasto-Tomography (DIET) is an emerging technology for non-invasive breast cancer screening. This technology relies on obtaining high resolution images of a breasts surface under high frequency actuation; typically 50-100Hz. Off-the-shelf digital cameras are unable to capture images directly at these speeds and current digital camera set-ups that are potentially capable of high speed image capture are either low in resolution, expensive, or occupy a volume too large to have them placed about the breast in a dense array. A method is presented for obtaining the required high speed image capture at a resolution of 1280x1024 (1.3 mega-pixels) and actuation frequency of 100Hz. The apparatus uses two Kodak CMOS KAC-9648 imaging sensors in combination with frame grabbers and the dSpace control system, to produce an automated image capture system. The final working system produced images that enabled effective 3D motion tracking of the surface of a silicon phantom actuated at 100Hz. The surface of the phantom was strobed at pre-selected phases from 0 to 360 degrees, and an image was captured for each phase. The times at which image capture occurred were calculated for a phase lag increment of 10 degrees resulting in an image effectively every 0.00028s for the actuator cycle of 0.01s. The comparison of the actual trigger times and pre-selected ideal trigger times gave a mean absolute error of 1.4%, thus demonstrating the accuracy of the final system.

ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / In this paper, we propose a highly precise and fast digital image stabilization technique based on the control grid interpolation. To obtain more stable video sequence than the one from other existing DIS techniques, the small instability should be removed in as small accuracy with sub-pixel. Experimental results show that the proposed digital image stabilizer gives considerable improvement in the sense of computational complexity and the performance of stabilizing compared to conventional DIS techniques.

Disc brake calipers are subjected to complex mechanical loading and interaction of individual components in a typical brake assembly makes design improvement very challenging. To analyse caliper behaviour, complex Finite Element models were created and successfully validated using a variety of experimental techniques, including exceptionally suitable Digital Image Correlation. A novel methodology to optimise caliper design was developed, using non-linear contact Finite Element Analysis and topology optimisation, to generate lightweight, high performance brake calipers. The method was used on a Formula 1 brake assembly and significant improvement in structural design was achieved, with the new caliper being lighter and stiffer than the original. The same approach was used on more conventional 4 pistons calipers using various boundary conditions with particular focus on mass reduction and considerably lighter designs were achieved. The influence of specific features of the optimised calipers on the structural performance was also successfully investigated.