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La tomodensitométrie à faisceau conique (CBCT) est répandue à travers les centres de cancérologie pour le positionnement du patient avant chaque traitement de radiothérapie. Ces images pourraient potentiellement être utilisées pour des tâches plus complexes. En radio-oncologie, les techniques de planification adaptative sont en développement et nécessitent l'utilisation des images de tomodensitométrie synthétiques (sCT). Alors, plusieurs groupes de recherche ont proposé différentes techniques pour générer des images sCT à partir des données CBCT. L'objectif principale de ce projet est d'évaluer une nouvelle méthode d'apprentissage profond pour générer des images sCT de pelvis à partir des images CBCT. Onze patients ont été rétrospectivement étudiés. Chaque patient a été imagé en séquence par deux techniques d'imagerie volumétrique dans la même position, soit un scan au CBCT et un autre au CT sur rails (CTr). Afin de pouvoir utiliser les images synthétiques dans un contexte clinique, la qualité de l'image et l'impact dosimétrique entre les sCT et les CTr doivent être évalués. Les nombres CT des images sCT sont comparés à ceux des images CTr. Finalement, pour évaluer l'impact dosimétrique, les plans de traitement optimaux sont recalculés sur les images sCT et CTr. Les différences de dose sont évaluées à l'aide d'une analyse gamma et des histogrammes dose-volume. L'évaluation quantitative montre qu'il y a des différences statistiquement significatives dans les os et les cavités d'air. Tandis que, les différences des tissus adipeux et mous ne sont pas statistiquement significatives. Les doses estimées dans les organes à risque et les PTV à partir des données des sCT sont surestimées comparativement à celles calculées à partir des données des CTr. Cependant, les erreurs de doses sont inférieures à 2% pour la plupart des cas étudiés. Ces erreurs de doses sont probablement causées par le manque de tissus dans la périphérie du patient et les erreurs des nombres CT. Bien que les différences de doses soient cliniquement acceptable, la méthode proposée devrait temporairement être limitée aux validations quotidiennes de plans de traitement pour des cas pelviens. / The cone-beam computed tomography (CBCT) is widely spread in cancer centers for positioning the patient before their radiotherapy treatment. These images could potentially be used for more complex tasks. In radio-oncology, adaptive planning technics are in development and require the use of synthetic CT (sCT) images. So, multiple research groups proposed different methods to generate sCT images from CBCT data. The main purpose of this project is to assess a new deep-learning method to generate sCT images from CBCT images. Eleven patients were retrospectively studied. Each patient was subsequently imaged by two volumetric imaging methods in the same position, one CBCT scan and the other from CT on rails (CTr). In order to clinically use the synthetic images, image quality and dosimetric impact between sCT and CTr must be evaluated. sCT images' CT values are compared to those in CTr images. Finally, to evaluate the dosimetric impact, optimal treatment plans are recalculated with sCT and CTr images. Dose differences are assessed by gamma analysis and dose-volume histograms. The quantitative evaluation shows that differences are statistically different in bones and air cavities. As for adipose and soft tissues, differences were not statistically different. The estimated doses in organs-at-risk and PTVs from sCT data are overestimated compared to those from CTr data. However, dose errors are inferior to 2% in the majority of studied cases. These dose errors are most likely due to missing tissues on the outskirt of the patient and the errors of CT numbers. Although dose differences are clinically acceptable, the proposed method should temporarily be limited to daily validations of pelvic treatment plans.

Tracking an individual specimen can be a difficult task especially when one also has to keep track of the environmental factors that affect the tracked specimen’s behavior. The task of tracking these animals becomes impossible when they become submerged in water and their number increases to more than just one. The aquatic species that are being tracked by this project in Lake Pontchartrain and the Gulf of Mexico are: tarpon, scalloped hammerhead, whale shark, tiger shark, yellowfin tuna, spotted seatrout, redfish, and bull shark. We are tracking these fish using acoustic and satellite transmitters. The insertion of transmitters in the fish was handled by the Louisiana Department of Wildlife and Fisheries biologists. The acoustic transmitters were implanted on smaller fish that only swam in Lake Pontchartrain. Due to this, receivers were only implanted at locations across the lake on various types of attachments such as buoys, PVC pipes, and pilings. These receivers were positioned at more than ninety locations in order to maximize the acquisition of detections. These species were tracked in Lake Pontchartrain and the Gulf of Mexico. After this preliminary setup, a constant batch of data was generated on a regular basis and this data was process by the application developed in this project. A Ruby on Rails application was then setup in order to store this data and manipulate it to display an animated track. The application utilizes: Ruby, Rails, HTML, CSS, SQL, JavaScript and multiple third part libraries. Many optimizations were performed in order to ensure reliability and performance when loading a high volume of fish or if a high volume of users were to use the application.

This thesis aids at comparing two frameworks based on Python and Ruby used for agile web development. Besides the basic description, history and philosophy of both Django and Ruby on Rails, all criteria used for their evaluation are laid down, described and put into wider context. In addition, the implementation of the MVC architecture in both frameworks is described along with the basic project structure and tools available.

Robôs verdadeiramente autônomos devem conhecer o ambiente para executar tarefas complexas. Em ambientes desconhecidos o robô deve concorrentemente construir o mapa do ambiente e se localizar usando sensores proprioceptivos e exteroceptivos imprecisos. Isto é problemático, uma vez que o mapa parcial e possivelmente incorreto do ambiente será usado para corrigir erros de localização. Este problema importante da robótica móvel é conhecido como Localização e Mapeamento Simultâneos (SLAM). Quando um robô autonomamente executa o algoritmo de SLAM concorrentemente com uma estratégia de exploração, o problema passa a se chamar SLAM Ativo ou Exploração Integrada. Um dos principais desafios por trás destes problemas é o tratamento de fechamento de ciclos. Ao atravessar regiões desconhecidas ou ambientes esparsos, a pose do robô e o mapa podem não ser propriamente corrigidos por falta de informação. Quando isto acontece, as incertezas da posição do robô e do mapa aumentam, podendo levar a erros irrecuperáveis. Por outro lado, quando o ciclo é fechado corretamente, estas incertezas diminuem consideravelmente. Portanto, a escolha do caminho para explorar o ambiente pode drasticamente melhorar ou degradar a qualidade do mapeamento e da localização. Uma técnica bem conhecida de exploração de ambientes é a adaptação do problema de valor de contorno (BVP) para a equação de Laplace e condições de contorno de Dirichlet. Apesar de ser fácil de implementar, resultando em trajetórias de exploração suaves, esta técnica não endereça cuidadosamente erros de SLAM, uma vez que ela segue a descida do gradiente, o que pode não possibilitar revisitas, uma limitação crucial para o SLAM Ativo. Mesmo sendo uma técnica de exploração gulosa e direcionada a fronteiras, consideramos que a flexibilidade do BVP e condições de contorno de Dirichlet ainda são pouco exploradas. Nossa proposta é modificar o algoritmo de Exploração por BVP para executar comportamentos complexos, tais como revisitas e, em particular, fechamentos de ciclo. Apresentamos duas novas abordagens: a primeira faz uso de uma condição de contorno direcionada pelo tempo combinada a distorções de potencial para gerar comportamentos de fechamento de ciclo, além de um potencial que nunca cessa de existir, mesmo após o ambiente ter sido completamente explorado; a segunda, propicia o fechamento de ciclos aproveitando a propagação do potencial em regiões desconhecidas, através de um par dinâmico de condições de contorno que funcionam como obstáculos e objetivos virtuais. Ambas abordagens aproveitam o Esqueleto de Voronoi do ambiente para reduzir o custo computacional do algoritmo. Testes em ambientes reais e simulados usando o robô Pioneer 3DX mostram que as técnicas apresentadas apresetam melhores resultados quando comparadas a técnicas concorrentes. / Truly autonomous robots must know the environment in order to execute complex tasks. In unknown environments, the robot must construct a map and localize itself using noisy proprioceptive and exteroceptive sensors. This is problematic, since the partial and possibly inaccurate map of the environment will be used to correct localization errors. This important problem of mobile robotics is known as Simultaneous Localization and Mapping (SLAM). When a robot autonomously execute a SLAM algorithm concurrently with an exploration strategy, this problem is called Active SLAM or Integrated Exploration. One of the main challenges behind both these problems is the treatment of loop closures. While the robot traverses unknown regions or sparse environments, the robot pose and the map may not be properly corrected due to lack of information. When this happens, the uncertainties about the map and the robot pose increase, which may lead to unrecoverable SLAM errors. On the other hand, when a loop is closed successfully, these uncertainties drastically decrease. Therefore, path chosen to explore the environment can considerably improve or degrade the quality of both localization and mapping. One well known way to explore the environment is the adaptation of the Boundary Value Problem (BVP) for the Laplace Equation and Dirichlet boundary conditions. Even though it is easy to implement, resulting in smooth exploration trajectories, it does not carefully address SLAM errors, since it follows a gradient decent which not always allows revisits, a crucial limitation for Active SLAM. Despite being a greedy frontier driven exploration strategy, we consider the flexibility of the BVP and Dirichlet boundary conditions still under-explored for Active SLAM. Our proposal is to modify the BVP Exploration algorithm to execute complex exploration behaviors, such as revisits and, in particular, loop-closures. We present two new approaches: the first makes use of a time driven boundary value condition together with potential distortions to generate loop closing behaviors and a potential field that never ceases to exist, even after the exploration ends; the second enables loop closure behaviors with BVP by taking advantage of potential propagation in unknown space generated by a pair of dynamic boundary conditions functioning as virtual walls and goals. Both approaches take advantage of a local optimization that uses the Voronoi Skeleton to reduce the computational cost of the algorithm. Tests in real and simulated environments using a Pioneer 3DX show that the proposed approaches present better results when compared with competing approaches.

Thesis (Master of Engineering in Mechanical Engineering)--Cape Peninsula University of Technology, 2018. / South Africa’s railway system is the most highly developed in Africa. There are different kinds of transport systems in South Africa but rail transport is considered as one of an important element of the country’s transport infrastructure. In South Africa, over 2.4 million passengers make use of rail transport to get them to their destinations. However, evidence shows that train accidents have become a common occurrence across the country. Train-related accidents such as collision, derailments, platform change incidents and commuter accidents, cost South Africa over R400 million per year. The analysis of derailments indicates that the most significant single contributor to derailments is rail breaks. This contrasts considerably with prescribed relevant local and international benchmarks, which show a much lower percentage of derailments due to rail break. The frequency of derailments due to rail breaks in South Africa seems to be higher in the northern than the southern region. Furthermore, the proportion of rail breaks that result in derailment is considerably higher than the set benchmarks and therefore, if there is a rail break, then the probability of this translating into a derailment is astonishingly high. Equally, the high incidence of derailments due to rail breaks is affected by the train length and axle load and further exacerbated by the absence of track circuitry. Since derailments are a direct function of the incidence of rail breaks, focus is required to characterize the factors causing defects on rail lines. This study investigated steel rail material by characterising the piece of the damaged rail with the aim to gain a better understanding of the wear mechanism. Chemical composition analysis of steel rail sample was conducted with the use of a Scanning Electron microscopy. Hardness of steel rail was measured with a Vickers hardness tester. An Optical Microscopy was used to examine the microstructure features of the worn rail samples. This study discovered that the worn out rail, which was produced from high carbon steel with pearlite and ferrite microstructure, undergoes decarburization and a plastic deformation process. The decarburization process happens when the rail track is heated to 700 oC and above when the carbon atoms at the surface interact with the atmospheric gases and are removed from the steel as a gaseous phase. Plastic deformation is created when the iron atoms are heated above the elastic point resulting in the permanent movement of iron atoms.

Este estudo analisou, em um primeiro momento, soldas de trilhos perlíticos para carga pesada soldados pelo processo aluminotérmico e solda topo com centelhamento (Flash butt-weld) focando nas alterações macro e microestruturais, bem como alterações de dureza decorrentes do processo. Uma junta em situação de uso real também foi estudada comparando-se o comportamento de deformação e desgaste à condição sem uso. Todos os casos apresentaram comportamento semelhante na zona afetada pelo calor possuindo perda de dureza em região de microestrutura esferoidizada. A origem desta estrutura foi, então, discutida. A formação de esferoidização pelo fenômeno de redução de energia de interface por movimentação de interfaces sólidas é considerado incompatível com os tempos dos processos utilizados. A hipótese de formação da zona esferoidizada por transformação do eutetóide divorciado (Divorced Eutectoid Transformation, DET) foi testada por meio de simulações de ciclos térmicos em dilatômetro de têmpera, para três diferentes aços. Com base nos resultados é seguro afirmar que o processo envolvido na esferoidização ao final da zona afetada pelo calor de trilhos perlíticos soldados é, de fato, a transformação do eutetóide divorciado. Confirmando esta hipótese, observa-se que o aumento do teor de carbono nos trilhos aumenta a faixa de esferoidização. / This work analyzed, initially, pearlitic heavy haul rail thermite welds and flash buttwelds, focusing in macro and microstructural changes as well as hardness changes occurring due to the processes. A weld in real use was also studied comparing the deformation behavior and wear to the unused condition. All cases presented similar behavior at the heat-affected zone with hardness loss associated to a spheroidized microstructure. The mechanisms for the formation of this structure, was discussed. The spheroidization by solid interface movement, driven by interface energy reduction, is not compatible with the processing times for welding. The hypothesifs of spheroidized region formation by a divorced eutectoid transformation (DET) was tested by simulated heat-treatments using a dilatometer and three different steels. Based on that it is safe to conclude that the process for the formation of an spheroidized zone at the end of the heat-affected zone on welded pearlitic rails is, indeed, the divorced eutectoid transformation. Furthermore, the carbon content was shown to increase spheroidization range.

Thèse doctorat : Génie Civil : Villeurbanne, INSA : 2004. / Titre provenant de l'écran-titre. Bibliogr. p. 175-180.

This study examines the status and distribution of rail populations in northern Indiana. Because rails are secretive and difficult to study, there have been few attempts in Indiana to determine the impact of wetland loss on the populations of rails and other marsh-nesting birds. There can be little doubt, however, that the loss of Indiana wetlands during historic times has caused a dramatic decline in rail populations.Using tape-recorded calls to elicit vocalizations, the status and distribution of five species of rails were studied in a 25,900 km2 area in northern Indiana in 1993 and 1994. A total of 107 surveys were conducted at 46 natural wetlands and 42 restored wetlands. The species surveyed were Sora (Porzana carolina), Virginia Rail (Rallus limicola), King Rail (Rallus elegans), Yellow Rail (Coturnicops noveboracensis), and Black Rail (Laterallus jamaicensis). Playbacks were also used to detect American Bittern (Botaurus lentiginosus), Least Bittern (Ixobrychus exilis), Marsh Wren (Cistothorus palustris) and Sedge Wren (Cistothorus platensis). Data were also collected on all other species of marsh-nesting birds detected during this study.Rails exhibited a patchy distribution. A total of 25 Soras, 33 Virginia Rails, and 1 King Rail was detected in natural wetlands in 1993. In 1994, 75 Soras, 46 Virginia Rails, and 1 King Rail was detected in the natural wetlands. A total of 30 Soras and 9 Virginia Rails was found in the restored wetlands studied in 1993 and 1994. No Yellow or Black Rails were found. Ten Least Bitterns, 31 Marsh Wrens, and 6 Sedge Wrens were detected in natural wetlands, but these species were not observed in restored wetlands.The occurrence of rails in natural wetlands was positively correlated with wetland size, presence of shrub vegetation in the watershed, amount of emergent vegetation, proximity of other wetlands, and extent of cattail cover. Negative correlations were found for human disturbance, amount of open water, and watershed characteristics. The strongest negative correlationswere found for human disturbances in or around the wetland.In restored wetlands, a significant difference was found between the occurrence of Sora and Virginia Rails with Soras occurring more frequently than Virginia Rails. A near significant difference in rail occurrence between natural and restored wetlands was also found, with rails occurring more frequently in natural wetlands, suggesting that natural wetlands surveyed may be a more suitable habitat for rails than the restored wetlands surveyed.Restored wetlands surveyed in this study failed to attract American Bitterns, Least Bitterns, Marsh Wrens or Sedge Wrens. American Bitterns were reported in natural wetlands during this study, but they were not observed. / Department of Biology