Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nas últimas décadas, o problema de escalonamento da produção em oficina de máquinas, na literatura referido como JSSP (do inglês Job Shop Scheduling Problem), tem recebido grande destaque por parte de pesquisadores do mundo inteiro. Uma das razões que justificam tamanho interesse está em sua alta complexidade. O JSSP é um problema de análise combinatória classificado como NP-Difícil e, apesar de existir uma grande variedade de métodos e heurísticas que são capazes de resolvê-lo, ainda não existe hoje nenhum método ou heurística capaz de encontrar soluções ótimas para todos os problemas testes apresentados na literatura. A outra razão basea-se no fato de que esse problema encontra-se presente no diaa- dia das indústrias de transformação de vários segmento e, uma vez que a otimização do escalonamento pode gerar uma redução significativa no tempo de produção e, consequentemente, um melhor aproveitamento dos recursos de produção, ele pode gerar um forte impacto no lucro dessas indústrias, principalmente nos casos em que o setor de produção é responsável por grande parte dos seus custos totais. Entre as heurísticas que podem ser aplicadas à solução deste problema, o Busca Tabu e o Multidão de Partículas apresentam uma boa performance para a maioria dos problemas testes encontrados na literatura. Geralmente, a heurística Busca Tabu apresenta uma boa e rápida convergência para pontos ótimos ou subótimos, contudo esta convergência é frequentemente interrompida por processos cíclicos e a performance do método depende fortemente da solução inicial e do ajuste de seus parâmetros. A heurística Multidão de Partículas tende a convergir para pontos ótimos, ao custo de um grande esforço computacional, sendo que sua performance também apresenta uma grande sensibilidade ao ajuste de seus parâmetros. Como as diferentes heurísticas aplicadas ao problema apresentam pontos positivos e negativos, atualmente alguns pesquisadores começam a concentrar seus esforços na hibridização das heurísticas existentes no intuito de gerar novas heurísticas híbridas que reúnam as qualidades de suas heurísticas de base, buscando desta forma diminuir ou mesmo eliminar seus aspectos negativos. Neste trabalho, em um primeiro momento, são apresentados três modelos de hibridização baseados no esquema geral das Heurísticas de Busca Local, os quais são testados com as heurísticas Busca Tabu e Multidão de Partículas. Posteriormente é apresentada uma adaptação do método Colisão de Partículas, originalmente desenvolvido para problemas contínuos, onde o método Busca Tabu é utilizado como operador de exploração local e operadores de mutação são utilizados para perturbação da solução. Como resultado, este trabalho mostra que, no caso dos modelos híbridos, a natureza complementar e diferente dos métodos Busca Tabu e Multidão de Partículas, na forma como são aqui apresentados, da origem à algoritmos robustos capazes de gerar solução ótimas ou muito boas e muito menos sensíveis ao ajuste dos parâmetros de cada um dos métodos de origem. No caso do método Colisão de Partículas, o novo algorítimo é capaz de atenuar a sensibilidade ao ajuste dos parâmetros e de evitar os processos cíclicos do método Busca Tabu, produzindo assim melhores resultados. / In recent decades, the Job Shop Scheduling Ploblem (JSSP) has received great attention of researchers worldwide. One of the reasons for such interest is its high complexity. The JSSP is a combinatorial optimization problem classified as NP-Hard and, although there is a variety of methods and heuristics that are able to solve it, even today no method or heuristic is able to find optimal solutions for all benchmarcks presented in the literature. The other reason builds on noted fact that this problem is present in day-to-day of industries of various segments and, since the optimal scheduling may cause a significant reduction in production time and thus a better utilization of manufacturing resources, it can generate a strong impact on the gain of these industries, especially in cases where the production sector is responsible for most of their total costs. Among the heuristics that can be applied to the solution of this problem, the Tabu Search and the Particle Swarm Optimization show good performance for most benchmarcks found in the literature. Usually, the Taboo Search heuristic presents a good and fast convergence to the optimal or sub-optimal points, but this convergence is frequently interrupted by cyclical processes, offset, the Particle Swarm Optimization heuristic tends towards a convergence by means of a lot of computational time, and the performance of both heuristics strongly depends on the adjusting of its parameters. This thesis presents four different hybridization models to solve the classical Job Shop Scheduling Problem, three of which based on the general schema of Local Search Heuristics and the fourth based on the method Particle Collision. These models are analyzed with these two heuristics, Taboo Search and Particle Swarm Optimization, and the elements of this heuristics, showing what aspects must be considered in order to achieve a best solution of the one obtained by the original heuristics in a considerable computational time. As results this thesis demonstrates that the four models are able to improve the robustness of the original heuristics and the results found by Taboo Search.

Cette thèse présente l'implémentation d'une stratégie visuelle bio-inspirée sur un aéroglisseur miniature totalement actionné, qui lui permet de naviguer dans le plan horizontal d'un tunnel inconnu. L'élaboration de ce pilote automatique, nommé LORA, fait suite aux études éthologiques menées sur l'abeille depuis ces dernières décennies et nous ont amené à énoncer le principe de la régulation du flux optique pour le contrôle du vol de croisière. Ce pilote automatique est un double régulateur de flux optique latéral constitué de deux boucles visuo-motrices interdépendantes contrôlant conjointement la vitesse d'avance et la position du robot par rapport aux obstacles sans avoir à mesurer ou estimer aucun de ces paramètres. La clé de voûte de ce système de guidage est une troisième boucle destinée à maintenir le cap grâce à un micro-gyromètre et un micro-compas magnétique permettant au robot d'effectuer des mouvements de translation qui génèrent sur son œil composé artificiel du flux optique de translation, seul dépendant du ratio vitesse/distance aux obstacles. Cet œil estime le flux optique grâce à ses deux ou quatre Détecteurs élémentaires de mouvement (total de 4 ou 8 pixels). L'aéroglisseur est alors capable de franchir sans collision, à la manière d'une abeille, divers tunnels : droit, fuselé ou présentant une pente, un virage, une absence de texture sur un mur ou même une zone non-stationnaire. Cette stratégie visuelle bio-inspirée fournit non seulement une solution de navigation élégante à destination de robots totalement actionnés mais elle permet aussi d'expliquer comment une abeille de 100mg peut naviguer sans l'aide de SONAR, RADAR, LIDAR, ou GPS. / In this work, we present for the first time a bio-inspired motion vision-based navigation strategy embedded on a miniature fully-actuated hovercraft allowing it to navigate safely on the horizontal plane of an unknown corridor. The design of this autopilot, called LORA, follows the ethological findings made on honeybees these last decades, which led us to elaborate the principle of the optic flow regulation which might be used by insects to control their flight. The bee-inspired LORA autopilot is a dual optic flow regulator which consists in two intertwined visuomotor feedback loops which control jointly the forward speed of the robot and its clearance to the obstacles. The keystone of this bio-inspired guidance system is a heading-lock system enabling the robot to move in translations and therefore experience a purely translational optic flow which depends only on the ratio speed/clearance to obstacles thanks to a micro-gyrometer and a micro-magnetic compass. The estimation of optic flow is made by a minimalist compound eye, made of two or four Elementary Motion Detectors (only 4 or 8 pixels). The hovercraft is therefore able to cross without crashing a straight or a tapered corridor, presenting a frontal sloping terrain, a bend, a textureless wall, or even a non-stationary section by automatically adapting both its forward speed and its clearance to the walls imitating the honeybee. This bio-inspired visual strategy not only provides an elegant navigation solution in an unknown environment aimed to equip fully-actuated miniature vehicles but also to explain how a 100mg honeybee can navigate with few computational ressources, i.e., without any SONAR, RADAR, LIDAR or GPS.

The ageing state of the world's nuclear power infrastructure, and the need to reduce humanity s dependency on fossil fuels, requires that this electrical energy generating capacity is replaced. Economic factors, and its physical and chemical properties, make high purity iron-chromium binary alloys a strong candidate for use in the construction of the pressure vessels of the next generation of nuclear reactors. This relatively inexpensive metal retains the oxidation resistance property of so-called stainless steel alloys, and has demonstrated dimensional stability and low degradation under harsh experimental environments of temperature and radiation. In this work, we consider radiation induced interstitial damage to the atomic lattices of iron-chromium binary alloys using the atomistic modelling methods, Molecular Dynamics and Adaptive Kinetic Monte Carlo, simulating collision cascade sequences, and the migration of defects in the aftermath. Variations in chromium content does not effect the initial damage production in terms of the number of Frenkel pairs produced, but iron and chromium atoms are not evenly distributed in defect atoms with respect to the bulk concentration. In simulations conducted at low temperature, chromium is under-represented, and at high temperature, a greater proportion of interstitial atoms are chromium than in the lattice overall. The latter phenomena is most strongly pronounced in systems of low bulk chromium content. During the simulation of post-cascade defect migration, interstitials atoms are observed to form temporary clusters and vacancies align along adjacent lattice sites, with the two types of defect also migrating to annihilate by recombination. Calculating the energy spectra of cascade events corresponding to an example experimental configuration using the SRIM package, we investigated the evolution of lattice systems in which a sequence of multiple cascade events occurred, both with and without a physically representative time gap between events. These simulations gave us the opportunity to observe the behaviour of cascades in the proximity of damage remaining from previous events, such as the promotion of defect clustering when this occurs.

Le domaine de la réalité virtuelle offre de formidables opportunités tout le long de la conception d’assemblage complexe. L’un des avantages est la possibilité de mettre en situation écologique des utilisateurs dès les premières étapes de conception. Ceci est d’autant plus important dans la conception d’installation industrielle complexe. Il est possible de valider rapidement des tâches d’accessibilité, d’assemblage, de maintenance, voire de démantèlement. L’obtention de la validité écologique des études réalisées en environnement virtuel demande cependant que les interfaces homme-machine soient capables de transmettre des informations réalistes. À l’heure actuelle, les systèmes virtuels ne sont pas capables de fournir une interaction haptique complète, notamment les contacts/collisions entre l’utilisateur et les objets virtuels de l’environnement ne résultent pas en un retour haptique. Ceci peut devenir la cause de comportement inapproprié par rapport à la réalité. L’objectif de cette thèse est de proposer un moyen de renforcer la compréhension spatiale en environnement virtuel. Plus particulièrement, nous souhaitons substituer les informations kinesthésiques par des informations tactiles pour augmenter la conscience spatiale et la cohérence visuo-proprioceptive. Nous avons développé une plateforme vibrotactile capable de fournir des informations spatiales sur l’environnement. Nous avons également commencé à interroger le rôle de la représentation du corps en environnement virtuel. Plusieurs études expérimentales ont été réalisées de manière à valider les développements que nous avons mis en avant. / The virtual reality field offers astounding opportunities throughout the design of complex assembly. One of the advantages is the possibility of immerse users in an ecological situation in the early stages of design. It’s even more important during the design of complex industrial plant. It allows to validate accessibility, assembly, maintenance or even dismantling tasks. The ecological validity of the studies carried out in a virtual environment, requires the human-machine interfaces capable of transmitting and rendering realistic information. At present, virtual systems are not capable of providing a complete haptic interaction, in particular contact/collision between the user and virtual objects in the environment do not result in haptic feedback. This can become the cause of inappropriate behavior compared to reality. The aim of this thesis is to propose a way to reinforce spatial awareness in virtual environment. More specifically, we wish to substitute kinesthetic information with tactile information to increase spatial awareness and visuo-proprioceptive consistency. We developed a vibrotactile platform capable of providing spatial information on the environment. We also studied the role of the representation of the body in a virtual environment. Several experimental studies have been carried out in order to validate the developments we proposed.

[pt] Uma das aplicações mais interessantes e desafiadoras da engenharia é a solução dos problemas inversos. Neste tipo de problema enquadra-se o tratamento científico da reconstituição de acidentes de veículos terrestres. Um outro tema diretamente relacionado é a análise de colisões, tanto no contexto da reconstituição de um acidente, quanto no que diz respeito ao grau de adequação do veículo ao impacto, associado à sua integridade estrutural e à segurança passiva dos seus ocupantes. Neste trabalho é aplicada uma técnica de otimização moderna, conhecida como algoritmo genético, para o tratamento do problema inverso em colisão de veículos terrestres, empregando modelos de veículos rígidos. Definiu-se como, a partir de restrições impostas e das posições finais dos veículos após uma colisão, o algoritmo de otimização pode fornecer o conjunto de variáveis e parâmetros que mais provavelmente levam os veículos àquela condição. Como resultado, o método foi considerado perfeitamente aplicável ao problema proposto e passível de ser utilizado como base para implementação como ferramenta de suporte à perícias judiciais em casos reais. / [en] One of the most interesting and challenging applications in engineering is the solution of inverse problems. In this kind of problem we have as an example the scientific approach of the ground vehicle accident reconstruction. Another directly related theme is collisions analysis, either in the context of an accident reconstruction, or in the context of the vehicle crashworthiness, associated to its structural integrity and their occupants passive safety. In this dissertation a modern optimization technique, known as genetic algorithm, is applied to the treatment of ground vehicles collision inverse problem using models of rigid vehicles. We have defined how, starting from imposed constraints and the vehicles final positions after a collision, the optimization algorithm may furnish the set of variables and parameters that most probably lead the vehicles to those positions. As a result, we have been able to evaluate the method as perfectly applicable to the proposed problem and may be used as a base aiming its implementation as a tool for support to the expertise regarding real cases.

The use of robotics has recently seen significant growth in various domains such as unmanned ground/underwater/aerial vehicles, smart manufacturing, and humanoid robots. However, one of the most important and essential capabilities required for long term autonomy, which is the ability to operate robustly and safely in real-world environments, in contrast to industrial and laboratory setup is largely missing. Designing robots that can operate reliably and efficiently in cluttered and changing environments is non-trivial, especially for high degree-of-freedom (DoF) systems, i.e. robots with multiple actuators. On one hand, the dexterity offered by the kinematic redundancy allows the robot to perform dexterous manipulation tasks in complex environments, whereas on the other hand, such complex system also makes controlling and planning very challenging. To address such two interrelated problems, we exploit robot motion synthesis from three perspectives that feed into each other: end-pose planning, motion planning and motion adaptation. We propose several novel ideas in each of the three phases, using which we can efficiently synthesise dexterous manipulation motion for fixed-base robotic arms, mobile manipulators, as well as humanoid robots in cluttered and potentially changing environments. Collision-free inverse kinematics (IK), or so-called end-pose planning, a key prerequisite for other modules such as motion planning, is an important and yet unsolved problem in robotics. Such information is often assumed given, or manually provided in practice, which significantly limiting high-level autonomy. In our research, by using novel data pre-processing and encoding techniques, we are able to efficiently search for collision-free end-poses in challenging scenarios in the presence of uneven terrains. After having found the end-poses, the motion planning module can proceed. Although motion planning has been claimed as well studied, we find that existing algorithms are still unreliable for robust and safe operations in real-world applications, especially when the environment is cluttered and changing. We propose a novel resolution complete motion planning algorithm, namely the Hierarchical Dynamic Roadmap, that is able to generate collision-free motion trajectories for redundant robotic arms in extremely complicated environments where other methods would fail. While planning for fixed-base robotic arms is relatively less challenging, we also investigate into efficient motion planning algorithms for high DoF (30 - 40) humanoid robots, where an extra balance constraint needs to be taken into account. The result shows that our method is able to efficiently generate collision-free whole-body trajectories for different humanoid robots in complex environments, where other methods would require a much longer planning time. Both end-pose and motion planning algorithms compute solutions in static environments, and assume the environments stay static during execution. While human and most animals are incredibly good at handling environmental changes, the state-of-the-art robotics technology is far from being able to achieve such an ability. To address this issue, we propose a novel state space representation, the Distance Mesh space, in which the robot is able to remap the pre-planned motion in real-time and adapt to environmental changes during execution. By utilizing the proposed end-pose planning, motion planning and motion adaptation techniques, we obtain a robotic framework that significantly improves the level of autonomy. The proposed methods have been validated on various state-of-the-art robot platforms, such as UR5 (6-DoF fixed-base robotic arm), KUKA LWR (7-DoF fixed-base robotic arm), Baxter (14-DoF fixed-base bi-manual manipulator), Husky with Dual UR5 (15-DoF mobile bi-manual manipulator), PR2 (20-DoF mobile bi-manual manipulator), NASA Valkyrie (38-DoF humanoid) and many others, showing that our methods are truly applicable to solve high dimensional motion planning for practical problems.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nas últimas décadas, o problema de escalonamento da produção em oficina de máquinas, na literatura referido como JSSP (do inglês Job Shop Scheduling Problem), tem recebido grande destaque por parte de pesquisadores do mundo inteiro. Uma das razões que justificam tamanho interesse está em sua alta complexidade. O JSSP é um problema de análise combinatória classificado como NP-Difícil e, apesar de existir uma grande variedade de métodos e heurísticas que são capazes de resolvê-lo, ainda não existe hoje nenhum método ou heurística capaz de encontrar soluções ótimas para todos os problemas testes apresentados na literatura. A outra razão basea-se no fato de que esse problema encontra-se presente no diaa- dia das indústrias de transformação de vários segmento e, uma vez que a otimização do escalonamento pode gerar uma redução significativa no tempo de produção e, consequentemente, um melhor aproveitamento dos recursos de produção, ele pode gerar um forte impacto no lucro dessas indústrias, principalmente nos casos em que o setor de produção é responsável por grande parte dos seus custos totais. Entre as heurísticas que podem ser aplicadas à solução deste problema, o Busca Tabu e o Multidão de Partículas apresentam uma boa performance para a maioria dos problemas testes encontrados na literatura. Geralmente, a heurística Busca Tabu apresenta uma boa e rápida convergência para pontos ótimos ou subótimos, contudo esta convergência é frequentemente interrompida por processos cíclicos e a performance do método depende fortemente da solução inicial e do ajuste de seus parâmetros. A heurística Multidão de Partículas tende a convergir para pontos ótimos, ao custo de um grande esforço computacional, sendo que sua performance também apresenta uma grande sensibilidade ao ajuste de seus parâmetros. Como as diferentes heurísticas aplicadas ao problema apresentam pontos positivos e negativos, atualmente alguns pesquisadores começam a concentrar seus esforços na hibridização das heurísticas existentes no intuito de gerar novas heurísticas híbridas que reúnam as qualidades de suas heurísticas de base, buscando desta forma diminuir ou mesmo eliminar seus aspectos negativos. Neste trabalho, em um primeiro momento, são apresentados três modelos de hibridização baseados no esquema geral das Heurísticas de Busca Local, os quais são testados com as heurísticas Busca Tabu e Multidão de Partículas. Posteriormente é apresentada uma adaptação do método Colisão de Partículas, originalmente desenvolvido para problemas contínuos, onde o método Busca Tabu é utilizado como operador de exploração local e operadores de mutação são utilizados para perturbação da solução. Como resultado, este trabalho mostra que, no caso dos modelos híbridos, a natureza complementar e diferente dos métodos Busca Tabu e Multidão de Partículas, na forma como são aqui apresentados, da origem à algoritmos robustos capazes de gerar solução ótimas ou muito boas e muito menos sensíveis ao ajuste dos parâmetros de cada um dos métodos de origem. No caso do método Colisão de Partículas, o novo algorítimo é capaz de atenuar a sensibilidade ao ajuste dos parâmetros e de evitar os processos cíclicos do método Busca Tabu, produzindo assim melhores resultados. / In recent decades, the Job Shop Scheduling Ploblem (JSSP) has received great attention of researchers worldwide. One of the reasons for such interest is its high complexity. The JSSP is a combinatorial optimization problem classified as NP-Hard and, although there is a variety of methods and heuristics that are able to solve it, even today no method or heuristic is able to find optimal solutions for all benchmarcks presented in the literature. The other reason builds on noted fact that this problem is present in day-to-day of industries of various segments and, since the optimal scheduling may cause a significant reduction in production time and thus a better utilization of manufacturing resources, it can generate a strong impact on the gain of these industries, especially in cases where the production sector is responsible for most of their total costs. Among the heuristics that can be applied to the solution of this problem, the Tabu Search and the Particle Swarm Optimization show good performance for most benchmarcks found in the literature. Usually, the Taboo Search heuristic presents a good and fast convergence to the optimal or sub-optimal points, but this convergence is frequently interrupted by cyclical processes, offset, the Particle Swarm Optimization heuristic tends towards a convergence by means of a lot of computational time, and the performance of both heuristics strongly depends on the adjusting of its parameters. This thesis presents four different hybridization models to solve the classical Job Shop Scheduling Problem, three of which based on the general schema of Local Search Heuristics and the fourth based on the method Particle Collision. These models are analyzed with these two heuristics, Taboo Search and Particle Swarm Optimization, and the elements of this heuristics, showing what aspects must be considered in order to achieve a best solution of the one obtained by the original heuristics in a considerable computational time. As results this thesis demonstrates that the four models are able to improve the robustness of the original heuristics and the results found by Taboo Search.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-07-10T17:54:50Z No. of bitstreams: 1 JAMILSON RAMOS CAMPOS - DISSERTAÇÃO PPGMAT 2006..pdf: 6748825 bytes, checksum: 592fc0c2a05c38766aae5d672c3c4708 (MD5) / Made available in DSpace on 2018-07-10T17:54:50Z (GMT). No. of bitstreams: 1 JAMILSON RAMOS CAMPOS - DISSERTAÇÃO PPGMAT 2006..pdf: 6748825 bytes, checksum: 592fc0c2a05c38766aae5d672c3c4708 (MD5) Previous issue date: 2006-12 / Este trabalho apresenta um estudo de dois modelos computacionais deformáveis aplicados à simulação de tecidos, ambos modelos de mecânica de partículas fisicamente embasados, contemplando algoritmos, um para cada modelo, para o tratamento de colisões. Estudamos um modelos de malha retangular (clássico e pouco robusto) e um baseado em malha triangular (moderno e robusto) através da implementação, simulações e uma análise qualitativa simples entre os resultados visuais obtidos com ambos. Nenhum destes modelos apresenta relações entre deformações tangenciais e normais e portanto, não geram rugas e/ou dobras espontaneamente. Para torná-los mais realísticos, em nossa implementação, propomos o uso de uma força de acoplamento entre as deformações tangenciais normais. / This work presents a study of two deformable computational models applied to the simulation of cloths, both physically based models of particle mechanics, contemplating one per model, collision treatment algorithms. We study a rectangular grid model (classic and not very robust one) and a triangular mesh based model (modern and robust one) throught implementation, simulations and a simple qualitative analysis between visual results reached with them. Neither of these models presents a relationship with tangent and normal deformations therefore don't build folds and/or wrinkles spontaneously. to turn then more realistic, in our implementation, we propose to make use of a coupling force between tangent and normal deformations.

Dans cette thèse, nous présentons un modèle granulaire décrivant la dynamique d'un assemblage de floes rigides de tailles et de formes diverses, soumis aux forces de traînée dues aux courants atmosphérique et océanique. Ce modèle est basé sur les équations des moments linéaire et angulaire pour décrire la dynamique régulière des floes et sur la résolution de problèmes linéaires de complémentarité pour traiter les collisions entre les floes. Entre les collisions, le mouvement d'un floe isolé satisfait la conservation des équations des moments linéaire et angulaire écrites à partir des formulations classiques des traînées dues au vent et à l'océan. Nous décrivons les collisions entre les floes comme des événements instantanés et les traitons avant qu'elles n'entraînent une interpénétration. Cela implique la notion d'impulsion de contact et la mise sous la forme de problèmes linéaires de complémentarité basés sur la condition de Signorini pour la non interpénétration et la loi de Coulomb. La nature du contact est représentée à travers un coefficient de friction et un coefficient de restitution décrivant la perte d'énergie cinétique durant la collision. Dans cette présente version du modèle, le coefficient de restitution est fixé. Le modèle a été validé en utilisant des données obtenues du mouvement de disques de bois évoluant en bassin de test aussi bien qu'en comparant le comportement des floes simulés avec un comportement attendu dans des scénarios classiques de dérive de glace et de collisions entre des solides rigides. Les résultats de simulations comprenant différents assemblages contenant des floes de tailles et de formes variées, soumis à différents scénarios de forçage, sont aussi discutés. Ils montrent tout le potentiel de notre approche sans qu'une analyse détaillée et complète n'ait encore été proposée. / In this thesis, we present a model describing the dynamics of a population of ice floes with arbitrary shapes and sizes, which are exposed to atmospheric and oceanic skin drag. The granular model presented is based on simplified momentum equations for ice floe motion between collisions and on the resolution of linear complementarity problems to deal with ice floe collisions. Between collisions, the motion of an individual ice floe satisfies the linear and angular momentum conservation equations, with classical formula applied to account for atmospheric and oceanic skin drag. To deal with collisions, before they lead to interpenetration, we included a linear complementarity problem based on the Signorini condition and Coulombs law. The nature of the contact is described through a constant coefficient of friction, as well as a coefficient of restitution describing the loss of kinetic energy during the collision. In the present version of our model, this coefficient is fixed. The model was validated using data obtained from the motion of interacting artificial wood floes in a test basin. The results of simulations comprising few hundreds of ice floes of various shapes and sizes, exposed to different forcing scenarios, and under different configurations, are also discussed. They show that the progressive clustering of ice floes as the result of kinetic energy dissipation during collisions is well captured, and suggest a collisional regimes of floe dispersion at small scales, different from a large-scale regime essentially driven by wind forcing.

Submitted by Livia Mello (liviacmello@yahoo.com.br) on 2016-10-06T19:29:46Z No. of bitstreams: 1 DissBFCL.pdf: 3054153 bytes, checksum: 1caf30db8cc357680434154f64e1cc86 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T18:33:37Z (GMT) No. of bitstreams: 1 DissBFCL.pdf: 3054153 bytes, checksum: 1caf30db8cc357680434154f64e1cc86 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T18:33:42Z (GMT) No. of bitstreams: 1 DissBFCL.pdf: 3054153 bytes, checksum: 1caf30db8cc357680434154f64e1cc86 (MD5) / Made available in DSpace on 2016-10-20T18:33:49Z (GMT). No. of bitstreams: 1 DissBFCL.pdf: 3054153 bytes, checksum: 1caf30db8cc357680434154f64e1cc86 (MD5) Previous issue date: 2016-05-04 / Outra / Coragyps atratus is a New World vulture species from the Order Cathartiformes. This species benefits from human activities, especially the improper disposal of organic waste, which increases food supply. The proximity of C. atratus with urban areas can lead to various problems, such as the risk of collision between these birds and aircrafts because of their mass and flight pattern, causing millionaire losses as well as serious consequences to society. This study aims to understand and analyze ecological and biological aspects of the population of C. atratus on Fontes do Ipiranga State Park (PEFI) in order to generate data that supports decision making regarding the management of this species within the park. Searches for identification and mapping of rest areas, feeding grounds and nesting were held on PEFI. To monitor the concentration of animals in the park and understand which climate variables influence it, these animals counts were performed on three different times of the day (morning, noon and evening) over five months. Statistical analysis of these data led to the conclusion that the period of data collection and humidity are variables that significantly influence the amount of animals sighted in the study area. The concentration of C. atratus on PEFI is highest during the afternoon, when the temperature is higher and the percentage of moisture in the air is lower. / Coragyps atratus é uma espécie de abutre do Novo Mundo pertencente à Ordem Cathartiformes. Essa espécie é beneficiada pelas atividades humanas, principalmente quanto à oferta de alimento devido à disposição incorreta de resíduos orgânicos. Tal proximidade de C. atratus com áreas urbanas pode acarretar em diversas problemáticas, como o risco de colisão entre essas aves e aeronaves, por conta de sua massa e seu padrão de voo, causando prejuízos milionários, além de sérias consequências à sociedade. O presente estudo tem como objetivo compreender aspectos ecológicos e biológicos da população de C. atratus do Parque Estadual das Fontes do Ipiranga (PEFI), a fim de gerar subsídios para tomada de decisão quanto ao manejo desta espécie dentro do Parque. Foram realizadas no PEFI buscas para identificação e mapeamento de locais de descanso, sítios de alimentação e de nidificação. Para monitorar a concentração de animais dentro do Parque e entender quais as variáveis climáticas influenciam essa concentração, foram realizadas contagens desses animais em três diferentes períodos do dia (manhã, meio-dia e tarde) ao longo de cinco meses. A análise estatística desses dados permitiu concluir que o período de coleta e a umidade do ar são variáveis que influenciam significativamente a quantidade de animais avistados na área de estudo. A concentração de C. atratus no PEFI é maior durante o período da tarde, quando o grau de temperatura é maior e a porcentagem de umidade do ar é menor.