Thesis (M.S.)--Brigham Young University. Dept. of Computer Science, 2007. / Includes bibliographical references (p. 59-61).

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xv, 99 p.; also includes graphics (some col.). Includes bibliographical references (p. 95-99). Available online via OhioLINK's ETD Center

A etapa de broad-phase para a detecção de colisão em cenas compostas de n objetos que se movimentam é um problema desafiador, pois enumerar os pares de colisão revela uma complexidade quadrática. Estruturas de dados espaciais são desenvolvidas para acelerar o processo, mas muitas vezes a natureza estática dessas estruturas dificulta o manejo de cenas dinâmicas. Nesse trabalho, é proposta uma nova estrutura chamada de árvore BSP semi-ajustável para representar cenas compostas de milhares de objetos dinâmicos. Um algoritmo de agendamento avalia onde a árvore BSP torna-se desbalanceada, usa várias estratégias para alterar os planos de corte e atualizações preguiçosas para reduzir os custos de reconstrução. É mostrado que a árvore não precisa uma total reconstrução mesmo em cenas altamente dinâmicas, ajustando-se e mantendo propriedades desejáveis de balanceamento e profundidade. / The broad-phase step of collision detection in scenes composed of n moving objects is a challenging problem because enumerating collision pairs has an inherent O(n²) complexity. Spatial data structures are designed to accelerate this process, but often their static nature makes it difficult to handle dynamic scenes. In this work we propose a new structure called Semi-Adjusting BSP-tree for representing scenes composed of thousands of moving objects. A scheduling algorithm evaluates locations where the BSP-tree becomes unbalanced, uses several strategies to alter cutting planes, and defers updates based on their re-structuring cost. We show that the tree does not require a complete re-structuring even in highly dynamic scenes, but adjusts itself while maintaining desirable balancing and height properties.

A etapa de broad-phase para a detecção de colisão em cenas compostas de n objetos que se movimentam é um problema desafiador, pois enumerar os pares de colisão revela uma complexidade quadrática. Estruturas de dados espaciais são desenvolvidas para acelerar o processo, mas muitas vezes a natureza estática dessas estruturas dificulta o manejo de cenas dinâmicas. Nesse trabalho, é proposta uma nova estrutura chamada de árvore BSP semi-ajustável para representar cenas compostas de milhares de objetos dinâmicos. Um algoritmo de agendamento avalia onde a árvore BSP torna-se desbalanceada, usa várias estratégias para alterar os planos de corte e atualizações preguiçosas para reduzir os custos de reconstrução. É mostrado que a árvore não precisa uma total reconstrução mesmo em cenas altamente dinâmicas, ajustando-se e mantendo propriedades desejáveis de balanceamento e profundidade. / The broad-phase step of collision detection in scenes composed of n moving objects is a challenging problem because enumerating collision pairs has an inherent O(n²) complexity. Spatial data structures are designed to accelerate this process, but often their static nature makes it difficult to handle dynamic scenes. In this work we propose a new structure called Semi-Adjusting BSP-tree for representing scenes composed of thousands of moving objects. A scheduling algorithm evaluates locations where the BSP-tree becomes unbalanced, uses several strategies to alter cutting planes, and defers updates based on their re-structuring cost. We show that the tree does not require a complete re-structuring even in highly dynamic scenes, but adjusts itself while maintaining desirable balancing and height properties.

abstract: The collision between the Indian and Eurasian tectonic plates marked the onset of the rise of the Himalayan-Tibetan orogen, but also brought about profound changes to the Earth's oceans and climate. The exact sequence of events that occurred during this collision is poorly understood, leading to a wide range of estimates of its age. The Indus and Yarlung sutures are generally considered to represent the final collision between India and Eurasia, and together form a mostly continuous belt that can be traced over 2000 km along strike. In the western portions of the orogen the Karakoram Fault introduces a key complexity to the study of timing of collision by offsetting the Indus and Yarlung sutures. Recent work has used the complexities introduced by the Karakoram Fault to suggest that the more northerly Shyok suture, not the Indus suture, represents the India-Eurasia collision zone. Estimates for timing of the India-Eurasia collision fall into one of three groups: 40-34 Ma, 55-50 Ma, and 66-60 Ma. Attempts to reconcile these models have thus far been unsuccessful. In order to provide additional data that might further clarify the timing and location of collision, studies have been performed along the Shyok suture in India and along the Yarlung suture in Tibet at Sangsang. A study along the Shyok suture argues that the suture formed between 92-85 Ma. This timing precludes an interpretation that the Shyok suture marks the location of the India-Eurasia collision. A second study demonstrates the utility of two new geochronometers, (U-Th)/Pb joaquinite and 40Ar/39Ar neptunite, that play an important role in unraveling the tectonic history of the Yarlung suture. A third study is an investigation of the structure and geochronology of the Sangsang ophiolite complex. Here, multiple (U-Th)/Pb and 40Ar/39Ar systems record magmatism and metamorphism spanning ca. 125-52 Ma. By tying these chronometers to tectonic process, a history is reconstructed of the southern margin of Tibet that includes Early Cretaceous to Late Cretaceous forearc rifting associated with mid ocean ridge subduction, Paleocene accretionary wedge uplift and erosion, and finally Eocene metasomatism and collision. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2016

abstract: In 2013, 1.8 million US drivers were responsible for rear-end collisions with other vehicles (NHTSA 2014), for which driver distraction has been identified as the main factor (Campbell, Smith & Najm, 2003; Knipling, Mironer, Hendricks, Tijerina, Everson, Allen & Wilson 1993; Wang, Knipling & Goodman, 1996). The ubiquity of cell phones and their use behind the wheel has played a major role in distracting these drivers. To mitigate this, some manufacturers are equipping vehicles with forward collision warning (FCW) systems. Generally, warnings that are perceived as being urgent produce lower response times. One technique for increasing perceived urgency of a warning is called looming, where the signal increases in or more dimensions over time. Looming warning signals have been shown to produce low response times, likely because the recipient perceives the signal as a potential approaching threat, prompting defensive reactions (Graziano and Cooke, 2006). The present study evaluates the effect of veridical (intensity increases at the rate of closure with the lead vehicle) and high urgency (intensity increases at a rate of Time to Collision minus 0.5 seconds) looming FCW, as well as a static FCW, on drivers’ brake reaction times in the presence of a secondary texting task. Participants’ brake reaction times were recorded as they followed a lead car in a driving simulator, encountering multiple sudden-braking events across the five conditions (a control condition as well as four counterbalanced conditions using a secondary texting task). In the four conditions with a secondary task, participants received no FCW, static FCW, veridical FCW, and high-urgency FCW, respectively. Performance data was analyzed using a repeated measures ANOVA, and a series of pairwise comparisons were then made using Bonferroni corrected pairwise t-tests. The presence of a visually and manually distracting secondary task (texting) seems to diminish the performance of the looming signals as compared to previous studies that did not use a distraction component. While looming FCW do seem to effectively lower BRTs when the driver is distracted, it is recommended that further research investigate the relationship between secondary task types and their respective levels of distraction, and the effectiveness of auditory looming FCW. / Dissertation/Thesis / Masters Thesis Applied Psychology 2016

A etapa de broad-phase para a detecção de colisão em cenas compostas de n objetos que se movimentam é um problema desafiador, pois enumerar os pares de colisão revela uma complexidade quadrática. Estruturas de dados espaciais são desenvolvidas para acelerar o processo, mas muitas vezes a natureza estática dessas estruturas dificulta o manejo de cenas dinâmicas. Nesse trabalho, é proposta uma nova estrutura chamada de árvore BSP semi-ajustável para representar cenas compostas de milhares de objetos dinâmicos. Um algoritmo de agendamento avalia onde a árvore BSP torna-se desbalanceada, usa várias estratégias para alterar os planos de corte e atualizações preguiçosas para reduzir os custos de reconstrução. É mostrado que a árvore não precisa uma total reconstrução mesmo em cenas altamente dinâmicas, ajustando-se e mantendo propriedades desejáveis de balanceamento e profundidade. / The broad-phase step of collision detection in scenes composed of n moving objects is a challenging problem because enumerating collision pairs has an inherent O(n²) complexity. Spatial data structures are designed to accelerate this process, but often their static nature makes it difficult to handle dynamic scenes. In this work we propose a new structure called Semi-Adjusting BSP-tree for representing scenes composed of thousands of moving objects. A scheduling algorithm evaluates locations where the BSP-tree becomes unbalanced, uses several strategies to alter cutting planes, and defers updates based on their re-structuring cost. We show that the tree does not require a complete re-structuring even in highly dynamic scenes, but adjusts itself while maintaining desirable balancing and height properties.

La collision d'un camion sur un pont est un événement courant et peut engendrer des efforts considérables dans la structure. Selon la norme canadienne CSA-S6-14, la pile d'un pont doit être conçue pour résister à une charge statique de 1400 kN à 1,2 m au-dessus du niveau du sol. Peu d'études récentes abordent ce sujet et aucune des études trouvées dans la littérature ne présente des résultats expérimentaux. Le but de ce mémoire est d'approfondir davantage nos connaissances sur le phénomène des collisions d'un véhicule avec un pont et de recueillir des résultats tant expérimentaux que numériques. La méthode expérimentale comprend les essais en laboratoire de deux piles en béton armé à échelles réduites 1:6 ainsi que la modélisation de ces essais à l'aide d'un modèle par éléments finis avec le logiciel LS-DYNA. Le premier essai consiste à imposer un chargement cyclique quasi-statique au niveau du chevêtre de la pile. Ceci permet de caractériser la pile et de calibrer un modèle numérique statique. Par la suite, un deuxième modèle numérique incluant la super-structure est utilisé pour simuler la collision d'un camion semi-remorque sur la pile étudiée. Les résultats du déplacement du chevêtre en fonction du temps du modèle numérique sont par la suite utilisés comme cas de chargement du deuxième essai. Finalement, un troisième modèle numérique est calibré à l'aide des résultats expérimentaux du deuxième essai. Les résultats démontrent que le montage expérimental ainsi que le modèle numérique reproduisent avec succès une charge d'impact. De plus, la nature dynamique de l'essai atteint des taux de déformations dans l'armature au-dessus de la limite quasi-statique. L'essai dynamique présente donc une charge pseudo-statique supérieure à la charge quasi-statique équivalente. Finalement, la force pseudo-statique maximale à l'échelle 1:1 atteint plus de 1832 kN alors que la force prescrite par la norme CSA-S6-14 est de 1400 kN.

Intersections tests between meshes in physics engines are time consuming and computationalheavy tasks. In order to speed up these intersection tests, each mesh can be decomposedinto several smaller convex hulls where the intersection test between each pair of these smallerhulls becomes more computationally efficient. The decomposition of meshes within the game industry is today performed by digital artistsand is considered a boring and time consuming task. Hence, the focus of this master thesislies in automatically decompose a mesh into several smaller convex hulls and to approximatethese decomposed pieces with bounding volumes of different complexity. These boundingvolumes together represents a collision mesh that is fully usable in modern games.

Detailed sensitivity numerical studies have shown that the mesh cell-size may have a drastic effect on the modelling of circulating fluidized bed with small particles. Typically, the cell-size must be of the order of few particle diameters to predict accurately the dynamical behaviour of a fluidized bed. Hence, the Euler-Euler numerical simulations of industrial processes are generally performed with grids too coarse to allow the prediction of the local segregation effects. Appropriate modelling, which takes into account the influence of unresolved structures, have been already proposed for monodisperse simulations. In this work, the influence of unresolved structures on a binary mixture of particles is investigated and models are proposed to account for those effect on bidisperse simulations of bidisperse gas-solid fluidized bed. To achieve this goal, Euler-Euler reference simulations are performed with grid refinement up to reach a mesh independent solution. Such kind of numerical simulation is very expensive and is restricted to very simple configurations. In this work, the configuration consists of a 3D periodical circulating fluidized bed, that could represent the established zone of an industrial circulating fluidized bed. In parallel, a filtered approach is developed where the unknown terms, called sub-grid contributions, appear. They correspond to the difference between filtered terms, which are calculated with the reference results then filtered, and resolved contributions, calculated with the filtered fields. Then spatial filters can be applied to reference simulation results to measure each sub-grid contribution appearing in the theoretical filtered approach. A budget analysis is carried out to understand and model the sub-grid term. The analysis of the filtered momentum equation shows that the resolved fluid-particle drag and inter-particle collision are overestimating the momentum transfer effects. The analysis of the budget of the filtered random kinetic energy shows that the resolved production by the mean shear and by the mean particle relative motion are underestimating the filtered ones. Functional models are proposed for the subgrid contributions of the drag and the inter-particle collision.