In 2011, the Canadian enhanced Polar Outflow Probe (ePOP) satellite will be launched. The ePOP satellite is equipped with several scientific Earth observation instruments, including a Radio Receiver Instrument (RRI) which will be used to detect High Frequency (HF) radio waves transmitted from a ground-based transmitter. The ground-based instrument will be one of the Super Dual Auroral Radar Network (SuperDARN) array of radars. A radio wave transmitted from the SuperDARN radar will propagate through the ionosphere and be detected by the RRI on ePOP. Analysis of the characteristics of the signal received by the RRI will provide information about the plasma density in the ionosphere between the transmitter and receiver. As the ePOP satellite is not yet operational, extensive ray path modelling has been performed to simulate the expected signal at the RRI for various ionospheric conditions.<p> The other major objective of this research was to examine the effect of the variable refractive index in the ionosphere on SuperDARN drift velocity measurements. Past comparisons between velocities measured by SuperDARN and other instruments have found that velocities measured by SuperDARN typically were about 20-30% lower. This research has shown that underestimation of drift velocities by SuperDARN is a consequence of not including the refractive index when these velocities are calculated. As refractive index measurements are not readily available, this research has involved developing and implementing various methods to estimate the refractive index in the ionosphere. These methods have demonstrated that plasma density values within the SuperDARN scattering volume are appreciably higher than background plasma densities in the ionosphere. Application of these methods, which has resulted in a much better understanding of the physics of the coherent scattering process, has resulted in agreement between velocities measured by SuperDARN and other instruments.

In 2011, the Canadian enhanced Polar Outflow Probe (ePOP) satellite will be launched. The ePOP satellite is equipped with several scientific Earth observation instruments, including a Radio Receiver Instrument (RRI) which will be used to detect High Frequency (HF) radio waves transmitted from a ground-based transmitter. The ground-based instrument will be one of the Super Dual Auroral Radar Network (SuperDARN) array of radars. A radio wave transmitted from the SuperDARN radar will propagate through the ionosphere and be detected by the RRI on ePOP. Analysis of the characteristics of the signal received by the RRI will provide information about the plasma density in the ionosphere between the transmitter and receiver. As the ePOP satellite is not yet operational, extensive ray path modelling has been performed to simulate the expected signal at the RRI for various ionospheric conditions.<p> The other major objective of this research was to examine the effect of the variable refractive index in the ionosphere on SuperDARN drift velocity measurements. Past comparisons between velocities measured by SuperDARN and other instruments have found that velocities measured by SuperDARN typically were about 20-30% lower. This research has shown that underestimation of drift velocities by SuperDARN is a consequence of not including the refractive index when these velocities are calculated. As refractive index measurements are not readily available, this research has involved developing and implementing various methods to estimate the refractive index in the ionosphere. These methods have demonstrated that plasma density values within the SuperDARN scattering volume are appreciably higher than background plasma densities in the ionosphere. Application of these methods, which has resulted in a much better understanding of the physics of the coherent scattering process, has resulted in agreement between velocities measured by SuperDARN and other instruments.

Current consumer GPUs can be used as high performance stream processors and are a tempting platform to be used to implement raytracing. In this paper I briefly present raytracing principles and methods used to accelerate it, modern GPUs programmable pipeline and examples of its use. I describe stream processing in general and available interfaces enabling the usage of GPU as stream processor. Then I present my GPU raytracer implementation, used algorithms and experiments I have made.

Memoria para optar al título de Ingeniero Civil en Computación / Encontrar un error en una aplicación gráfica mediante las herramientas de depurado que proveen los lenguajes de programación convencionales suele no ser una tarea fácil. En este trabajo se propone un método y se implementa una solución para llevar a cabo el depurado de aplicaciones que utilizan raytracing como técnica de renderizado. En concreto, se describe el diseño y construcción de una plataforma web que permite la carga, manipulación y visualización de rayos a través de un esquema particular, que consta de propiedades que describen rayos como típicamente se encuentran en los raytracers, como el origen, dirección, y punto de término, en el caso de rayos finitos. Se propone un sistema de etiquetado, que consiste en asignarle etiquetas a los rayos durante el proceso de generación del esquema, y se muesta cómo se pueden realizar consultas del tipo "¿cuáles son los rayos que fueron reflejados desde un espejo?", o "¿cuáles son los rayos que intersectan con el n-ésimo objeto de la escena?". Por último, la herramienta se valida con 4 desarrolladores, a quienes se les presenta un conjunto de 5 problemas. Estos consisten de una descripción de una escena, una imagen con un error generada por un raytracer con algún tipo de problema, y un registro de rayos generado por este raytracer. El objetivo en cada caso es descubrir, mediante el uso de la aplicación web cargada con este registro, cuál es el problema con la imagen. En 2 de los 5 casos, todos los desarrolladores fueron capaces de encontrar el problema, mientras que en los restantes 3, la mitad fue capaz de encontrar el problema.

This report describes the results of computerized ultrasonic C-scanning of solid steel bridge pins using a raytrace model. The raytrace model was developed to facilitate interpretation of data obtained from an ultrasonic C-scanning system for the Virginia Transportation Research Council (VTRC). The report discusses the reasons behind the development of the raytrace model, as well as specifications of the model, the input conditions, and the data output and visualization. The model uses as input, various "boundary" conditions of the solid steel pin with reduced diameter pin ends, as well as size and location information of a flaw or a wear groove placed within the main pin body. The model considers sound beams to be composed of rays and calculates ray reflections/conversions. This is done until the ray returns to a receiver location or is lost due to exceeding the time-of-flight. Once the model has returned with the received ray data, it uses the receiver conditions provided (transducer used, size of scanning grid, grid resolution, etc.), and calculates a 2-Dimensional C-scan image for each particular depth/time selected. Using PV-Wave visualization software, it is possible to plot the values for each depth to view a color graph. This graphical plot can then be analyzed/compared with the field C-scans to determine the closest match of a flaw or a wear groove inside the bridge pin. This helps in deciding if the condition of the pin is acceptable. / Master of Science

Bifacial photovoltaics (PV) is a promising technology which allows solar cells to absorb light and generate power from both front and rear sides of the cells. Bifacial PV systems generate more power per area compared to their monofacial counterparts because of the additional energy generated from the backside. However, modeling the performance of bifacial PV systems is more challenging than monofacial systems and industry requires novel and accurate modeling tools to understand and estimate the benefit of this technology. In this dissertation, a rigorous model utilizing a backward raytracing software tool called RADIANCE is developed, which allows accurate irradiance modeling of the front and rear sides of the bifacial PV systems. The developed raytracing model is benchmarked relative to other major bifacial irradiance modeling tools based on view-factor model. The accuracy of the irradiance models is tested by comparing with the measured irradiance data from the sensors installed on various bifacial PV systems. Our results show that the raytracing model is more accurate in modeling backside irradiance compared to the other irradiance models. However, this higher accuracy comes at a cost of higher computational time and resources. The raytracing model is also used to understand the impact of different installation parameters such as tilt angle, height above the ground, albedo and size of the south-facing fixed-tilt bifacial PV systems. Results suggest bifacial gain has a linear relationship with albedo, and an increasing saturating relationship with module height. However, the impact of tilt angle is much more complicated and depends on other installation parameters. It is shown that larger bifacial systems may have up to 20º higher optimum tilt angle compared to small-scale systems. We also used the raytracing model to simulate and compare the performance of two common configurations for bifacial PV systems: optimally tilted facing south/north (BiS/N) and vertically installed facing east/west (BiE/W). Our results suggest that in the case of no nearby obstruction, BiS/N performs better than BiE/W for most of the studied locations. However, the results show that for high latitude locations such as Alaska, having a small nearby obstruction may result in having better yield for vertical east-facing system than south-facing tilted system. RADIANCE modeling tool is also used in combination of a custom tandem device model to simulate the performance of tandem bifacial PV systems. Modeling results suggest that while the energy gain from bifacial tandem systems is not high, range of suitable top-cell bandgaps is greatly broadened. Therefore, more options for top-cell absorber of tandem cell are introduced.

Seismic survey design methods often rely on qualitative measures to provide an optimal image of their objective target. Fold, ray tracing techniques counting ray hits on binned interfaces, and even advanced 3-D survey design methods that try to optimize o?set and azimuth coverage are prone to fail (especially in complex geological or structural settings) in their imaging predictions. The reason for the potential failure of these commonly used approaches derives from the fact that they do not take into account the ray geometry at the target points. Inverse theory results can provide quantitative and objective constraints on acquisition design. Beylkin??s contribution to this ?eld is an elegant and simple equation describing a reconstructed point scatterer given the source/receiver distribution used in the imaging experiment. Quantitative measures of spatial image resolution were developed to assess the e?cacy of competing acquisition geometries. Apart from the source/receiver con?guration, parameters such as the structure and seismic velocity also in?uence image resolution. Understanding their e?ect on image quality, allows us to better interpret the resolution results for the surveys under examination. A salt model was used to simulate imaging of target points located underneath and near the ?anks of the diapir. Three di?erent survey designs were examined. Results from these simulations show that contrary to simple models, near-o?sets do not always produce better resolved images than far-o?sets. However, consideration of decreasing signal-to-noise ratio revealed that images obtained from the far-o?set experiment are degrading faster than the near-o?set ones. The image analysis was performed on VSP ?eld data as well as synthetics generated by ?nite di?erence forward modeling. The predicted image resolution results were compared to measured resolution from the migrated sections of both the ?eld data and the synthetics. This comparison con?rms that image resolution analysis provides as good a resolution prediction as the prestack Kirchho? depth migrated section of the synthetic gathers. Even in the case of the migrated ?eld data, despite the presence of error introducing factors (di?erent signal-to-noise ratios, shape and frequency content of source wavelets, etc.), image resolution performed well exhibiting the same trends of resolution changes at di?erent test points.

Seismic survey design methods often rely on qualitative measures to provide an optimal image of their objective target. Fold, ray tracing techniques counting ray hits on binned interfaces, and even advanced 3-D survey design methods that try to optimize o?set and azimuth coverage are prone to fail (especially in complex geological or structural settings) in their imaging predictions. The reason for the potential failure of these commonly used approaches derives from the fact that they do not take into account the ray geometry at the target points. Inverse theory results can provide quantitative and objective constraints on acquisition design. Beylkin??s contribution to this ?eld is an elegant and simple equation describing a reconstructed point scatterer given the source/receiver distribution used in the imaging experiment. Quantitative measures of spatial image resolution were developed to assess the e?cacy of competing acquisition geometries. Apart from the source/receiver con?guration, parameters such as the structure and seismic velocity also in?uence image resolution. Understanding their e?ect on image quality, allows us to better interpret the resolution results for the surveys under examination. A salt model was used to simulate imaging of target points located underneath and near the ?anks of the diapir. Three di?erent survey designs were examined. Results from these simulations show that contrary to simple models, near-o?sets do not always produce better resolved images than far-o?sets. However, consideration of decreasing signal-to-noise ratio revealed that images obtained from the far-o?set experiment are degrading faster than the near-o?set ones. The image analysis was performed on VSP ?eld data as well as synthetics generated by ?nite di?erence forward modeling. The predicted image resolution results were compared to measured resolution from the migrated sections of both the ?eld data and the synthetics. This comparison con?rms that image resolution analysis provides as good a resolution prediction as the prestack Kirchho? depth migrated section of the synthetic gathers. Even in the case of the migrated ?eld data, despite the presence of error introducing factors (di?erent signal-to-noise ratios, shape and frequency content of source wavelets, etc.), image resolution performed well exhibiting the same trends of resolution changes at di?erent test points.

The goal of this thesis was to assess the validity of a computer simulated Radiostereometric Analysis (RSA) environment and assess the use of novel migration origin styles for use in the assessment of spinal fusion success in post-surgical adolescent idiopathic scoliosis patients. A parallel precision study was conducted with a physical phantom and identical computed simulated spinal fusion model. This study was used to conduct a precision validation of the simulate RSA environment. The origin style assessment was done in comparison with the translational and rotational Limits of Clinical Significance defined by Pape et al (2002) and Johnsson et al (2002) respectively [1], [2]. This thesis concluded that the use of a simulated environment is an acceptable method for the creation of phantom RSA research studies. It was also shown that both the Apex and Dual Origin Styles equally accurate and precise.

This master thesis focuses on photon mapping rendering technique. A simple photon mapping was implemented as a baseline and then progressive photon mapping was prepared for CPU and GPU. After implementing progressive photon mapping on GPU, further acceleration techniques were proposed. Finally, in the thesis, genetic clustering algorithm for suitable clusters on GPU was proposed.