In recent years, digital media has seen incredible advancements in rendering visually stunning computer graphics scenes. Photo-realistic games, animated films, and more leave viewers blown away by the sheer beauty of their graphics. However, challenges arise when depicting dark scenes, often resulting in visual monotony and difficulty in comprehension due to insufficient detail within the scene. In order to enhance readability and visual interest of a scene, additional, artificial lights can be placed throughout a scene to enhance the aesthetic. These lights, however, must be strategically placed in order to retain an essence of darkness and maintain the delicate balance between light and dark. In this thesis, we explore an algorithm for light placement within low light, ray-traced scenes which leverages a k-means layering scheme to partition a scene and place artificial lights for artistic enhancement. Multiple scenes were generated and user feedback was collected comparing various lighting configurations for each scene, assessing the algorithm's effectiveness in improving readability and maintaining the desired level of darkness as well as how additional lighting affects the user's perception of the scene.

With rising complexity of high performance computing systems and their parallel software, performance analysis and optimization has become essential in the development of efficient applications. The comparison of performance data is a key operation required in performance analysis. An analyst may conduct different types of comparisons in order to understand the performance properties of an application. One use case is comparing performance data from multiple measurements. Typical examples for such comparisons are before/after comparisons when applying optimizations or changing code versions. Besides comparing performance between multiple runs, also comparing performance characteristics across the parallel execution streams of an application is essential to detect performance problems. This is typically useful to detect imbalances, outliers, or changing runtime behavior during the execution of an application. While such comparisons are straightforward for the aggregated data in performance profiles, only limited solutions exist for comparing event traces. Trace-based analysis, i.e., the collection of fine-grained information on individual application events with timestamps and application context, has proven to be a powerful technique. The detailed performance information included in event traces make them very suitable for performance analysis. However, this level of detail also presents a challenge because it implies a large and overwhelming amount of data. Currently, users need to perform manual comparison of event traces, which is extremely challenging and time consuming because of the large volume of detailed data and the need to correctly line up trace events. To fill the gap of missing solutions for automatic comparison of event traces, this work proposes a set of techniques that automatically align traces. The alignment allows their structural comparison and the highlighting of differences between them. A set of novel metrics provide the user with an objective measure of the differences between traces, both in terms of differences in the event stream and timing differences across events. An additional important aspect of trace-based analysis is the visualization of performance data in event timelines. This has proven to be a powerful approach for the detection of various types of performance problems. However, visualization of large numbers of event timelines quickly hits the limits of available display resolution. Likewise, identifying performance problems is challenging in the large amount of visualized performance data. To alleviate these problems this work proposes two new approaches for event timeline visualization. First, novel folding strategies for event timelines facilitate visual scalability and provide powerful overviews of performance data at the same time. Second, this work presents an effective approach that automatically identifies and highlights several types of performance critical sections in an application run. This approach identifies time dominant functions of an application and subsequently uses them to analyze runtime imbalances throughout the application run. Intuitive visualizations present the resulting runtime variations and guide the analyst to performance hot spots. Evaluations with benchmarks and real-world applications assess all introduced techniques. The effectiveness of the comparison approaches is demonstrated by showing automatically detected performance issues and structural differences between different versions of applications and across parallel execution streams. Case studies showcase the capabilities of the event timeline visualization techniques by demonstrating scalable performance data visualizations and detecting performance problems and code inefficiencies in real-world applications.

Cette thèse a apporté une contribution au défi de la caractérisation des canaux radios en bandes millimétriques ainsi que la validation d'un outil de simulation déterministe à travers un grand nombre de campagnes de mesures réalisées dans divers scénarios représentatives. Des questions de recherche liées à la caractérisation des canaux radio en bandes millimétriques et sa prédiction à travers un outil de simulation déterministe ont été abordées. Fournir des résultats précis et reproductibles est nécessaire dans le développement d'un système de communication. Ce défi peut être relevé en réalisant des campagnes de mesures qui capturent la réalité du canal de propagation constituant le point de départ. Dans cette thèse, les principales motivations scientifiques derrière ces campagnes de mesures étaient d'étudier la variabilité dans le temps et l'effet de l'environnement sur le canal de propagation dans les bandes millimétriques. Les bandes de fréquences adressées dans cette thèse sont identifiées comme étant importantes par l'UIT en vue d'un futur déploiement de la 5G à savoir 15, 28, 32 et 83 GHz. Les environnements considérés sont une conférence room, bureau, bibliothèque et micro-cellulaire. Les campagnes de mesures ont été menées en utilisant un sondage de canal fréquentiel avec l'utilisation d'un analyseur de réseau. L'exploitation des résultats de mesures ont permis d'apporter des éléments de réponses concernant le canal de propagation dans ces bandes de fréquences. D'autre part, les données de mesures ont été utilisés pour évaluer les performances et contribuer à la calibration d’un simulateur de canal radio à tracé de rayons (RT) reposant sur une approche déterministe. Le simulateur de canal déterministe utilisé dans cette thèse incorpore les mécanismes de propagation tels que le LOS, la réflexion et la diffraction. Le RT a permis de prédire le canal de propagation dans les bandes millimétriques avec une concordance acceptable avec les données de mesures. Ces résultats démontrent que le canal de propagation en bandes millimétriques a pour avantage d'être prédit avec de simple outil déterministe. / This thesis has contributed to the challenge of the radio channel characterizations in millimeter wave bands as well as the validation of a deterministic simulation tool through a large number of measurement campaigns carried out in various representative scenarios. Research questions related to the characterization of radio channels in millimetric bands and its prediction through a deterministic simulation tool were discussed. Providing accurate and repeatable results is necessary for the development of a communication system. This challenge can be meet by conducting measurement campaigns that capture the reality of the propagation channel and therefore constituting the starting point. In this thesis, the main scientific motivations behind these measurement campaigns were to study the time variability and the effect of the scattering environment of the propagation channel in the millimetric bands. The frequency bands addressed in this thesis are identified as important by the ITU for a future deployment of 5G, namely 15, 28, 32 and 83 GHz. The environments considered are a conference room, office, library and microcellular. The measurement campaigns were conducted using a frequency channel sounding technique with the use of a vector network analyzer. The exploitation of the measurement data provided some answers about the radio chennel propagation in these frequency bands. On the other hand, the measurements data were used to evaluate the performance and to contribute to the calibration of the ray-tracing tool (RT) based on a deterministic approach. The RT used in this thesis incorporates propagation mechanisms such as LOS, reflection and diffraction. The RT predicted the propagation channel in the millimeter bands with an acceptable level of agreement with respect to the measurement data. These results demonstrate that the propagation channel in millimetric bands has the advantage of being predicted with a simple deterministic tool.

High nitrogen discharge from mining sites has been an environmental issue that has been closely studied in the recent years. The environmental effects of high nitrogen discharge are mainly eutrophication, but can also lead to changed species composition and algae blooms. Nitrogen is a highly abundant element and is the most abundant element in the atmosphere, where 78% by volume is present as dinitrogen (N2 ). Nitrogen is present in reduced form in all organic life as ammonium (NH4 + ). Nitrogen is also present in reduced form as nitrate (NO3 - ) or nitrite (NO2 - ) in most aquatic systems.  Both nitrate and ammonium is contributing to eutrophication problems worldwide and ammonia (NH3 ) is direct toxic in high concentration to certain sensitive aquatic species. Nitrate in high concentration is also direct toxic, both to humans but also to aquatic biota.  To trace and quantify different nitrogen transforming processes, their sources and their sinks is called tracing nitrogen cycling and is important due to the environmental effect of nitrogen. Nitrogen is available in many different species and oxidation states which all have their respective geochemistry. This thesis focuses on tracing the complex nitrogen cycle in two different cold climate mining systems in northern Sweden using two different methods. The two studied systems are: The LKAB underground iron ore mine in Kiruna Boliden Minerals AB open pit copper ore mine Aitik outside Gällivare  Two different approaches were used to trace the nitrogen cycling. The LKAB Kiruna mine was investigated using stable nitrogen isotopes. The isotope analysis showed high capability to trace nitrogen cycling, both quantative and qualitative. We also showed the origin of the isotope signals which gives indication to the different sources of nitrogen in the mine. The presented study shows presence of nitrification, ammonium volatilization and ammonium adsorption to waste rock to occur in the water transport system.  The nitrogen cycling in the Boliden Aitik mine was investigated using a nitrogen model which we developed as part of this thesis. The model is based on Yakushevs Redox Layer model (ROLM). The model contains the state variables ammonium, nitrate, nitrite, plankton, phosphate, dead organic material (both particulate and dissolved) as well as oxygen. The nitrogen concentrations in the Boliden Aitik mine was modeled for the clarification pond and showed, in general, low biological activity. The biological mediated reactions such as nitrification, denitrification, phytoplankton growth and grazing were low in relation to natural lake systems

The propagation paths of sound in water can be somewhat complicated due to the fact that the sound speed in water varies with properties such as water temperature and pressure, which has the effect of curving the propagation paths. This thesis shows how sound propagation in water can be simulated using a ray-tracing based approach on a GPU using Nvidia’s OptiX ray-tracing engine. In particular, it investigates how much speed-up can be achieved compared to CPU based implementations and whether the RT cores introduced in Nvidia’s Turing architecture, which provide hardware accelerated ray-tracing, can be used to speed up the computations. The presented GPU implementation is shown to be up to 310 times faster then the CPU based Fortran implementation Bellhop. Although the speed-up is significant, it is hard to say how much speed-up is gained by utilizing the RT cores due to not having anything equivalent to compare the performance to.

The time required for inspection and maintenance of piping systems and vessels needs to be reduced to both minimize down time and decrease operational costs of petrochemical plants. Current ultrasonic inspection systems are not suited for on-line monitoring, with the main issues being the resistance of transducers and their coupling to high temperatures and the removal of insulation to access structures. The use of welded cylindrical rods is thus proposed, but measurements are threatened by "trailing echo" generation in waveguides. The introduction of a taper angle is investigated to attenuate these undesired echoes. While clean signals can always be obtained by increasing the taper angle in long rods, that is not always the case for short rods, which are considered here. In addition, temperature variations have a non-negligible impact on the arrival time of the backwall echo when performing measurements with a waveguide, and on-line compensation is essential. Since the interface echo between the rod and the pipe wall may be suppressed after the welding operation, a notch is machined at the end of the rod to create a reflected echo, which can be used for on-line compensation. Finally, the implementation of waveguides is considered for both pulse-echo and pitch-catch modes. In the pitch-catch mode, the backwall echo and the notch echo are received by different transducers and signals of interst are both first arrivals. As a result, trailing echoes do not impede measurements and their attenuation becomes unnecessary. In contrast, pulse-echo measurements are sensitive to trailing echoes and the waveguide's design plays an essential role in the feasibility of measurements. However, the environment also imposes a set of constraints on waveguide dimensions that complicates the implementation of pulse-echo measurements. Being more flexible, the pitch-catch configuration is chosen for final implementation. Experiments are performed to verify the concept feasibility, and the accuracy of measurements with thickness and temperature changes is also confirmed.

Obtaining an accurate whole program path (WPP) that captures a program’s runtime behaviour in terms of a control-flow trace has a number of well-known benefits, including opportunities for code optimization, bug detection, program analysis refinement, etc. Existing techniques to compute WPPs perform sub-optimal instrumentation resulting in significant space and time overheads. Our goal in this thesis is to minimize these overheads without losing precision. To do so, we design a novel and scalable whole program analysis to determine instrumentation points used to obtain WPPs. Our approach is divided into three components: (a) an efficient summarization technique for inter-procedural path reconstruction, (b) specialized data structures called conflict sets that serve to effectively distinguish between pairs of paths, and (c) an instrumentation algorithm that computes the minimum number of edges to describe a path based on these conflict sets. We show that the overall problem is a variant of the minimum hitting set problem, which is NP-hard, and employ various sound approximation strategies to yield a practical solution. We have implemented our approach and performed elaborate experimentation on Java programs from the DaCapo benchmark suite to demonstrate the efficacy of our approach across multiple dimensions. On average, our approach necessitates instrumenting only 9% of the total number of CFG edges in the program. The average runtime overhead incurred by our approach to collect WPPs is 1.97x, which is only 26% greater than the overhead induced by only instrumenting edges guaranteed to exist in an optimal solution. Furthermore, compared to the state-of-the-art, we observe a reduction in runtime overhead by an average and maximum factor of 2.8 and 5.4, respectively.

BARRETO, Isaac Moreira. Cálculo do Fator-de-Forma exato entre Áreas Diferencial e Finita Usando CSG. 2008. 55 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências, Departamento de Computação, Fortaleza-CE, 2008. / Submitted by guaracy araujo (guaraa3355@gmail.com) on 2016-07-01T17:52:27Z No. of bitstreams: 1 2008_dis_imbarreto.pdf: 752627 bytes, checksum: 2c1a97d41785e527e97633cc6c7e9756 (MD5) / Approved for entry into archive by guaracy araujo (guaraa3355@gmail.com) on 2016-07-01T17:56:22Z (GMT) No. of bitstreams: 1 2008_dis_imbarreto.pdf: 752627 bytes, checksum: 2c1a97d41785e527e97633cc6c7e9756 (MD5) / Made available in DSpace on 2016-07-01T17:56:22Z (GMT). No. of bitstreams: 1 2008_dis_imbarreto.pdf: 752627 bytes, checksum: 2c1a97d41785e527e97633cc6c7e9756 (MD5) Previous issue date: 2008 / The Ray-Tracing and Radiosity methods are the main representatives of the method that solve the global illumination problem. In both mthods it is necessary to know the energy tranfer ratio between two areas. This ratio, called form factor, is one of the key concepts in Radiosity methods and is being more frequently used in Ray-Tracing methods with finite area light sources. There are many methods for the computation of the form factor, most of them are approximative due to a matter of performance, but, in some specific cases, the extra computational effort needed to compute the exact value of the form factor can improve the overall performance of the illumination method. In general, in these cases, the computational effort needed to obtain an acceptable approximation of the form factor outweighs the effort necessary to compute the exact value. Furthermore there are situation, for example, shadow boundary shading, in which a high precision is far more important than a performance gain. In this work we present a method to compute the exact form factor between a finite area and a differential area which uses CSG techniques to identify the ooccluded areas of the source. / Os métodos de Ray-Tracing e Radiosidade são os principais representantes dos métodos existentes para resolver o problema de iluminação global. Em ambos os métodos se faz necessário saber a taxa de transferência de energia luminosa entre duas áreas. Essa taxa de transferência, chamada de fator-de-forma, é um dos pontos principais no método de Radiosidade e vem sendo usado cada vez com mais frequência em métodos de Ray-Tracing com fontes luminosas de área finita. Existem vários métodos para o cálculo do fator-de-forma, a maioria deles são aproximativos por uma questão de desempenho. Porém, em casos específicos, o trabalho extra para calcular o valor exato do fator-de-forma pode melhorar o desempenho global do método. Em geral, nesses casos, o esforço necessário para se obter uma aproximação aceitável do valor do fator-de-forma supera o esforço necessário para calcular o valor exato em si. Além disso, existem situações, tais como a renderização nas áreas de fronteiras de sombras, em que uma alta precisão é mais importante do que um ganho no desempenho. Nessas situações, é desejável que o método tenha ao seu dispor uma maneira de calcular o valor exato do fator-de-forma. Neste trabalho é apresentado um método para calcular o fator-de-forma exato entre uma área finita e uma área diferencial que utiliza de técnicas CSG para identificar as áreas ocluídas do polígono emissor.

Universidade Federal do Cearà / Os mÃtodos de Ray-Tracing e Radiosidade sÃo os principais representantes dos mÃtodos existentes para resolver o problema de iluminaÃÃo global. Em ambos os mÃtodos se faz necessÃrio saber a taxa de transferÃncia de energia luminosa entre duas Ãreas. Essa taxa de transferÃncia, chamada de fator-de-forma, à um dos pontos principais no mÃtodo de Radiosidade e vem sendo usado cada vez com mais frequÃncia em mÃtodos de Ray-Tracing com fontes luminosas de Ãrea finita. Existem vÃrios mÃtodos para o cÃlculo do fator-de-forma, a maioria deles sÃo aproximativos por uma questÃo de desempenho. PorÃm, em casos especÃficos, o trabalho extra para calcular o valor exato do fator-de-forma pode melhorar o desempenho global do mÃtodo. Em geral, nesses casos, o esforÃo necessÃrio para se obter uma aproximaÃÃo aceitÃvel do valor do fator-de-forma supera o esforÃo necessÃrio para calcular o valor exato em si. AlÃm disso, existem situaÃÃes, tais como a renderizaÃÃo nas Ãreas de fronteiras de sombras, em que uma alta precisÃo à mais importante do que um ganho no desempenho. Nessas situaÃÃes, à desejÃvel que o mÃtodo tenha ao seu dispor uma maneira de calcular o valor exato do fator-de-forma. Neste trabalho à apresentado um mÃtodo para calcular o fator-de-forma exato entre uma Ãrea finita e uma Ãrea diferencial que utiliza de tÃcnicas CSG para identificar as Ãreas ocluÃdas do polÃgono emissor. / The Ray-Tracing and Radiosity methods are the main representatives of the method that solve the global illumination problem. In both mthods it is necessary to know the energy tranfer ratio between two areas. This ratio, called form factor, is one of the key concepts in Radiosity methods and is being more frequently used in Ray-Tracing methods with finite area light sources. There are many methods for the computation of the form factor, most of them are approximative due to a matter of performance, but, in some specific cases, the extra computational effort needed to compute the exact value of the form factor can improve the overall performance of the illumination method. In general, in these cases, the computational effort needed to obtain an acceptable approximation of the form factor outweighs the effort necessary to compute the exact value. Furthermore there are situation, for example, shadow boundary shading, in which a high precision is far more important than a performance gain. In this work we present a method to compute the exact form factor between a finite area and a differential area which uses CSG techniques to identify the ooccluded areas of the source.

The main goal of this thesis is ray tracing optimization, especially with the use of acceleration data structure. It'll be focused on discretion about various structure build strategies and their traversal. Different algorithms on the CPU and on the GPU will be implemented and compared in the thesis, specifically will be compared the speed of build and final structure quality, which have a direct influence on ray tracing performance. A ray tracing application will be implemented for the purpose of the acceleration structure quality test. A part with acceleration structure building will be added to GPUEngine library.