Cette thèse s’inscrit dans le cadre général de l’étude de la tolérance au dommage des pièces tournantes dans les turbomachines d’hélicoptères et porte sur la résistance à la propagation de fissures courtes 2D.Pour mener à bien cette étude, l’effet de la température est d’abord étudié sur les seuils de propagation de fissures longues à R=0,1 sur deux alliages TA6V et Ti6242 de microstructure bimodale (20°C et 400°C pour le TA6V et 20°C, 200°C et 500°C pour le Ti6242). Au voisinage du seuil, le comportement effectif(après correction de la fermeture) est sensiblement identique pour les deux alliages aux températures testées. La fermeture est principalement induite par l’oxyde à haute température et par la rugosité des surfaces de rupture à température ambiante.L’évolution du seuil de propagation en fonction de la longueur de fissure a ensuite été étudiée à R=0,1. Un outil de détermination automatique du niveau de fermeture a été mis en place afin d’améliorer la mesure pour des fissures très courtes (80 μm). La fermeture mesurée pour différentes longueurs de fissure obtenues par usinage progressif du sillage plastique est comparable à celle obtenue au cours de la propagation d’une fissure courte 2D au seuil, sauf pour les hautes températures où la fermeture induite par l’oxyde se développe rapidement. Les différences de comportement entre fissure longue et fissure courte sont expliquées par une contribution réduite de la fermeture lorsque le sillage de la fissure est réduit.Un critère de non-propagation s’inspirant du formalisme initialement proposé par Kitagawa et une loi de propagation adaptée permettent de mieux prédire la résistance à la propagation des fissures physiquement courtes. / Damage tolerance analyses of rotating parts, containing 2D-short crack, in turbomachines of helicopters is the main focus of this thesis.Fatigue crack propagation tests were performed at R=0.1 on two bimodal Titanium alloys at different temperatures (20°C and 400°C for TA6V and 20°C, 200°C and 500°C for Ti6242). Near-threshold effective behaviors (after crack closure correction) were approximately the same for the two alloys attested temperatures. Crack closure was principally due to oxide layer at high temperatures and to fracture surface roughness at ambient temperature.Then the variations of the crack propagation threshold with crack length was studied at R=0.1 and different temperatures. A numerical tool was developed to automatically detect crack closure level more precisely for, as short as, 80μm cracks. Crack closure levels measured at different crack lengths obtained from progressive machining of the plastic wake were quite similar to the ones obtained during propagation of 2D-short cracks near the threshold, except at high temperatures where oxide-induced crack closure developed rapidly. Differences in behavior of long cracks and short cracks were explained by a reduction of crack closure level when crack wake was not fully developed.A non-propagation criterion based on formalism initially proposed by Kitagawa and a modified-Paris propagation law allow to give a better description of physically 2D-short crack propagation resistance.

Les cellules épithéliales forment des tissus cohésifs, sous forme de monocouches que l'on retrouve dans les poumons, les reins ou la peau. Travaillant à partir d'expériences in vitro, nous avons caractérisé le comportement mécanique de monocouches cellulaires. Nous avons étudié la fermeture de blessures circulaires sur un substrat non adhésif. En comparant différents modèles, nous avons montré comment la fermeture est possible grâce à un cable contractile d'acto-myosine et aux fluctuations de la tension du tissu. La Microscopie des Forces de Traction (TFM) permet de mesurer les forces que les cellules exercent sur leur substrat. A partir de cette mesure et en utilisant l'équilibre des forces, nous avons développé une méthode qui résout ce problème sous-déterminé par inversion bayésienne et permet d'obtenir le champ des contraintes internes au tissu. En appliquant cette méthode sur des images (BISM: Microscopie des contraintes par inversion bayésienne) et en l'adaptant à l'aide d'un filtre de Kalman sur des films (KISM: Microscopie des contraintes par inversion de Kalman), nous avons inféré le tenseur des contraintes de monocouches cellulaires sans faire aucune hypothèse sur la rhéologie du tissu. Enfin, nous avons estimé les contraintes directement depuis les déplacements du substrat, sans passer par les forces de tractions et donc en réduisant le nombre d'inversions de matrice (BISMu: Microscopie des contraintes par inversion bayésienne à partir des déplacements du substrat). / Epithelial cells are known to form cohesive monolayers, a form of tissue organization encountered in the lung, the kidney or the skin. From in vitro experiments, we have characterized the mechanical properties of cell monolayers. We have studied the closure of circular wounds over a nonadhesive substrate. Comparing different models, we have shown how closure is possible thanks to a contractile acto-myosin cable and to fluctuations of the tissue tension. Traction Force Microscopy (TFM) allows to measure the forces that cells exert on their substrate. Starting from this measurement and using the force balance equations, we have solved this underdetermined problem by Bayesian inversion and obtained the internal stress field of the tissue. Applying this method on single images (BISM: Bayesian Inversion Stress Microscopy), and adapting it with a Kalman filter for movies (KISM: Kalman Inversion Stress Microscopy) we have inferred the stress tensor of cell monolayers, without making any hypothesis on the tissue rheology. Finally, we have estimated the stresses directly from the substrate displacements, without computing the traction forces and thus reducing the number of matrix inversions (BISMu: Bayesian Inversion Stress Microscopy from substrate displacements).

Något som finns i alla projekt är en uppstart och ett slut. Vägen till slutet är väl planerat innan projektet startar upp. Men vad händer om planen felar och det inte går att fullfölja den? Säg att det dyker upp ett antal oförutsägbara händelser på vägen, händelser som kan ske internt och externt. Går det inte att hantera dessa oförutsägbara händelser så kan det leda till att projektet läggs ner. Ett förtida projektavslut är ett ovanligt fenomen som behöver belysas mer, för att kunna ge projektledaren en chans att hantera de problem som kan uppstå. Denna studie har som mål att undersöka vilka interna och externa faktorer som kan bidra till ett förtida projektavslut. Data är insamlat från fyra olika verksamheter som arbetar med projekt, verksamheterna är aktiva inom olika branscher inom den svenska projekt- och organisationskulturen. Personerna som ingår i studien är representativa för verksamheten de representerar. De har befogenhet att yttra sig om området förtida projektavslut. Verksamheterna som ingår i studien är: -  Trafikverket väst. De framställer sig själva som en offentlig verksamhet som ansvarar för att planera transportsystemen i Sverige. De har även ansvar för byggnationen, driften och underhållet av statliga vägar och järnvägar. -  Landstinget i Värmland. Landstinget i Värmland är en offentlig verksamhet som arbetar med hälso- och sjukvård och även tandvård. Det finns cirka 30 vårdcentraler runt om i länet samt sjukhusen i Arvika, Karlstad och Torsby. Landstinget i Värmland är en politiskt styrd organisation. -  Tieto. Beskriver att de är en verksamhet vars mål är att vara kundernas förstahandsval för affärsförnyelse. De strävar efter att vara det ledande mjukvaru- och tjänsteföretaget i Norden. -  Valmet Corporation beskriver sin verksamhet som den ledande globala utvecklaren och leverantör av teknik, automation och service inom massa-, pappers- och energiindustrin. Data samlades in med hjälp av fem semistrukturerade intervjuer med individer med en högre hierarkisk befattning inom verksamheten som arbetar med projekt. Genom denna studie har jag kommit fram till följande slutsatser. Förtida projektavslut är ett ovanligt fenomen i de verksamheter som ingår i studien. Det är vanligare att projekt läggs på is under en kortare eller längre period, för att sedan tas upp vid ett senare tillfälle. De externa faktorerna spelar en avgörande roll för projektets framtid. Det är faktorer som finns i projektets omvärld som i denna studie avgör om projektet skall läggas ner eller inte. De interna faktorerna blir inte avgörande för beslut om att lägga ner ett projekt. / Something that exist in all projects is an start and an end. The road to the end is well planned before the project starts up. But what if the plan fails and it is not possible to fulfill the plan? What if it shows up a number of unpredictable events on the way, events that can occur internally and externally. If these unpredictable events cant be handled they may cause a shutdown for the project. An premature project closure is an unusual phenomenon in projects that need to be explored more. This study aims to investigate the internal and external factors that may contribute to the early shutdown in projects. Data is collected from four diffrent businesses working with projects, the businesses are active in different sectors. The subjects included in this study are representative of the business they represent. They have the authority to express themselves in the field of project premature project closure. The businesses included in this study is. -  Trafikverket väst. They present themselves as a public service responsibility to plan transport in Sweden. They are also responsible for the construction, operation and maintenance of state roads and railways. -  Landstinget in Värmland. As according to the Landstinget in Värmland it is a public agency that works with health care and even detal care. There are about 30 medical centers around the county and hospitals in Arvika, Karlstad and Torsby. The county council is a politically-driven organization. -  Tieto. Describes that they are an organization whose goal is to be the customers first choice for business renewal. They strive to be the leading software and services company in the nordic region. -  Valmet Corporation describes its business as a leading global developer and supplier of technology, automation and service of pulp, paper and energy industries. Data were collected with the help of five semi-structured interviews with individuals with a higher hierarchic position in their organization. Through this study, I have come to the following conclusions. Premature projcet closure is an unusual phenomenon in the activities included in the study. It is common for projects that they are put on ice for a shorter or longer period, then taken up again later. The external factors play a crucial role in the future of the project. There are factors that are in the project environment that this study will determine if the project should be closed or not. The internal factors are not crucial to the decision to close down a project.

U.S. military bases and installations represent trillions of dollars of capital investment towards the nation’s defense infrastructure. The Department of Defense, in its response to the end of the Cold War with the Soviet Union in the 1980s, sought to reorganize and optimize this basing infrastructure to meet the emerging threats of the 21st century. A series of nationwide Base Realignment and Closure (BRAC) efforts were chartered by Congress to facilitate this task, identifying hundreds of obsolete or unneeded military installations. During the last BRAC effort in 2005, the Naval Support Activity New Orleans was targeted for closure, with its U.S. Navy and Marine Corps tenants to be reassigned elsewhere. In response to this threat, a group of retired military and civilian elites formed a non-profit entity known as the New Orleans Federal Alliance (NOFA), chartered to lobby the BRAC Commission to salvage the West Bank portion of the NSA from closure and establish a new mixed use, public-private Federal City complex in its stead. The purpose of this study was to examine the life cycle of NOFA and its partners in the context of the Federal City project over a ten year period. Interviews of key personnel involved with this coalition revealed remarkable insight into the characteristics associated with its formation, mobilization, sustainment, and fragmentation. The data illustrated the delicate relationship between the military history of New Orleans and its unique culture, and how that culture influenced actor behavior through the varied governing subsystems in the region. As one would expect, local politics dominated the adverse dynamic of the coalition’s solvency, heightened significantly in national visibility by the effects of Hurricane Katrina. The result was the dissolution of the NOFA-centered coalition and the failure of the Federal City project to achieve full maturity.

As wind farms continue to take up more land throughout Northern Europe, developers are looking to sparsely populated areas, particularly in northern Fennoscandia, which hosts strong winds but also mixed and patchy forests over complex terrain. The complexity makes wind resource assessments difficult, raising uncertainty and therefore cost. Computational fluid dynamics (CFD) has the potential to increase the accuracy and reliability of wind models, but the most common form of commercial CFD modeling, Reynolds averaged Navier-Stokes (RANS), makes limiting assumptions about the effect of the forest on the wind. The wind resource assessment and energy estimation tool WindSim® , developed by WindSim AS, utilizes a porous medium model of a homogeneous forest with the influence of the forest on the airflow as a drag force term in the momentum equations. This method has provided reliable wind speed results but has been less reliable in estimating turbulence characteristics. The measure we evaluate in this study is turbulence intensity (TI). In this investigation, we make two types of modifications to the model and evaluate their impact on the TI estimates by using a benchmark data set collected by Meroney [1]. The first method is a variable profile of leaf area index (LAI) to represent the physical shape of the forest more accurately, and the second is a series of modifications to the closure coefficients in the turbulence transport equations. These modifications focus on the work of Lopes et al. [2], who used a large eddy simulation (LES) model to show that the turbulence production terms originally proposed by Green [3], expanded upon by Sanz [4], and widely used in the industry are unnecessary. Our investigations found that the implementation of a variable LAI profile has a small but non-negligible effect and that the elimination of the production terms from the turbulence transport equations does lead to a significant reduction in TI immediately above the forest. Both methods have minor effects on wind speed estimates, but the modification of closure coefficients has a much more significant impact on the TI. The coefficients proposed by Lopes et al. [2] drastically reduce TI estimates, but the model is still unable to reflect the Meroney data throughout the forest. Continued modification to new closure coefficients in combination with a variable forest LAI and other modifications such as a limited length scale may lead to significant improvement in TI estimates in future models, but these modifications must be compared against real-world data to ensure their applicability.

In this work the predictive capability of a number of Reynolds stress transport(RST) models was first tested in a range of non-equilibrium homogeneous flows, comparisons being drawn with existing direct numerical simulation (DNS) results and physical measurements. The cases considered include both shear and normally strained flows, in some cases with a constant applied strain rate, and in others where this varied with time. Models were generally found to perform well in homogeneous shear at low shear rates, but their performance increasingly deteriorated at higher shear rates. This was attributed mainly to weaknesses in the pressure-strain rate models, leading to over-prediction of the shear stress component of the stress anisotropy tensor at high shear rates. Performance in irrotational homogeneous strains was generally good, and was more consistent over a much wider range of strain rates. In the experimental plane strain and axisymmetric contraction cases, with time-varying strain rates, there was evidence of an accelerated dissipation rate generation. Significant improvement was achieved through the use of an alternative dissipation rate generation term, Pε , in these cases, suggesting a possible route for future modelling investigation. Subsequently, the models were also tested in the inhomogeneous case of pulsating channel flow over a wide range of frequencies, the reference for these cases being the LES of Scotti and Piomelli (2001). A particularly challenging feature in this problem set was the partial laminarisation and re-transition that occurred cyclically at low and, to a lesser extent, intermediate frequencies. None of the models tested were able to reproduce correctly all of the observed flow features, and none returned consistently superior results in all the cases examined. Finally, models were tested in the case of a plane jet interacting with a rectangular dead-end enclosure. Two geometric configurations are examined, corresponding a steady regime, and an intrinsically unsteady regime in which periodic flow oscillations are experimentally observed (Mataoui et al., 2003). In the steady case generally similar flow patterns were returned by the models tested, with some differences arising in the degree of downward deflection of the impinging jet, which in turn affected the level of turbulence energy developing in the lower part of the cavity. In the unsteady case, only two of the models tested, a two-equation k-ε model and an advanced RST model, correctly returned purely periodic solutions. The other two RST models, based on linear pressure-strain rate terms, returned unsteady flow patterns that exhibited complex oscillations with significant cycle-to-cycle variations. Unfortunately, the limited availability of reliable experimental data did not allow a detailed quantitative examination of model performance.

The influences of a superheated steam environment and temperature on the nearthreshold crack growth behaviour of mild steel during rotating bending fatigue were investigated. A fatigue machine in which rotating bending is simulated was designed and built to allow continuous crack growth measurement. Experiments compared the threshold stress intensities (∆Kth ) for air at 24 °C, air at 160 °C and steam at 160 °C.Air at 160 °C yielded the lowest threshold stress intensity in both cases. Oxide thicknesses in the vicinity of the threshold were estimated from temper colours. The difference in threshold stress intensities can be explained by the concept of oxideinduced crack closure. / Dissertation (MEng (Metallurgical Engineering))--University of Pretoria, 2007. / Materials Science and Metallurgical Engineering / MEng / unrestricted

In many situations after a big catastrophe such as the one in Fukushima, the disaster area is highly dangerous for humans to enter. It is in such environments that a semi-autonomous robot could limit the risks to humans by exploring and mapping the area on its own. This thesis intends to design and implement a software based SLAM system which has potential to run in real-time using a Kinect 2 sensor as input. The focus of the thesis has been to create a system which allows for efficient storage and representation of the map, in order to be able to explore large environments. This is done by separating the map in different abstraction levels corresponding to local maps connected by a global map. During the implementation, this structure has been kept in mind in order to allow modularity. This makes it possible for each sub-component in the system to be exchanged if needed. The thesis is broad in the sense that it uses techniques from distinct areas to solve the sub-problems that exist. Some examples being, object detection and classification, point-cloud registration and efficient 3D-based occupancy trees. / I många situationer efter en stor katastrof, såsom den i Fukushima, är området ytterst farligt för människor att vistas. Det är i sådana miljöer som semi-autonomarobotar kan begränsa risken för människor genom att utforska och kartlägga området på egen hand. Det här exjobbet fokuserar på att designa och implementera ett mjukvarubaserat SLAM system med real-tids potential användandes en Kinect 2 sensor. Exjobbet har fokuserat på att skapa ett system som tillåter effektiv lagring och representering av kartan för att tillåta utforskning utav stora områden. Det görs genom att separera kartan i olika abstraktionsnivåer, vilka korresponderar mot lokala kartor sammankopplade med en global karta. Strukturen av system har tagit hänsyn till under utvecklingen för att tillåta modularitet. Vilket gör det möjligt att byta ut komponenter i systemet. Det här exjobbet är brett i det avseende att det använder tekniker från flera olika områden för att lösa de sub-problem som finns. Några exempel är objektdetektion och klassificering, punkt-molnsregistrering och effektiva 3D-baserade okupationsträd. / Después de grandes catástrofes, cómo la reciente en Fukushima, está demasiado peligroso para permitir humanes a entrar. En estás situaciones estaría más preferible entrar con un robot semi-automático que puede explorar, crear un mapa de la ambiente y encontrar los riesgos que hay. Está obra intente de diseñar e implementar un sistema SLAM, con la potencial de crear está mapa en tiempo real, utilizando una camera Kinect 2. En el centro de la tesis está el diseño de una mapa que será eficiente alojar y manejar, para ser utilizado explorando áreas grandes. Se logra esto por la manera de la separación del mapa en distintas niveles de abstracción qué corresponde a mapas métricos locales y una mapa topológica que conecta estas. La estructura del sistema ha sido considerado para permitir utilizar varios tipos de sensores, además que permitir cambiar ciertas partes de la sistema. Esté tesis cobra distintas áreas cómo lo de detección de objetos, estimación de la posición del sistema, registrar nubes de puntos y alojamiento de 3D-mapas.

Objetivos: O objetivo deste estudo foi avaliar em adultos com perdas dos primeiros molares inferiores permanentes, as inclinações e angulações dentárias dos dentes adjacentes, bem como a espessura do rebordo após movimentação mesial de segundos molares para suprir a perda e verticalização dos segundos molares para reabilitação protética. Métodos: Foram selecionados 2 grupos de estudo. O Grupo Fechamento (GF) foi composto por 12 hemiarcos com ausência de primeiros molares permanentes e espaços variando entre 2 a 7mm, que foram tratadas ortodonticamente com fechamento do espaço. O Grupo Abertura (GA) foi composto por 14 hemiarcos com ausência de primeiros molares permanentes e espaços variando entre 7,1 a 12mm, que foram tratadas ortodonticamente com verticalização do segundo e terceiro molar e reabertura de espaço para reabilitação protética. Avaliou-se em modelos dentários digitais a angulação, a inclinação, a dimensão cérvico-oclusal e a espessura do rebordo. As comparações interfases e intergrupos foram realizadas com os testes t-pareado e t-independente respectivamente (p<0,05). Resultados: Houve melhora na angulação dos segundos molares inferiores tanto no GF quanto no GA, mostrando eficácia da mecânica em ambas as terapias; não houve alterações significantes nas inclinações vestibulolinguais dos dentes posteriores em ambos os grupos; a espessura do rebordo aumentou no GF e manteve-se constante no GA. Conclusões: As duas modalidades de tratamento demonstraram resultados adequados. A escolha do plano de tratamento deve ponderar a relação custo-benefício de cada caso, considerando-se a dimensão inicial do espaço, a presença dos terceiros molares, as condições periodontais iniciais, o tempo de tratamento e o custo financeiro. / Objectives: The aim of this study was to evaluate, in adults with loss of the first permanent molars, the inclinations and angles of adjacent teeth as well as the alveolar ridge thickness after mesial movement of second molars to close the space of the tooth loss and second molar uprighting to rehabilitation prosthetic. Methods: Two study groups were selected. The Group Closure (GC) was composed of 12 quadrants with no permanent first molars and edentulous spaces varying from 2 to 7mm, which were treated with orthodontic space closure. The Group Opening (GO) was composed of 14 quadrants with no permanent first molars and edentulous spaces varying from 7.1 to 12mm, which were treated with orthodontic uprighting of the second and third molars and reopening space for prosthetic rehabilitation. In digital dental models were evaluated the angulation, inclination, the cervical-occlusal dimension and alveolar ridge thickness. Interphase and intergroup comparisons were performed with with paired t-test and independent t-test, respectively (p <0.05). Results: There was improvement in the angulation of the mandibular second molars both in GC and GO, showing the mechanical efficiency in both therapies; there were no significant changes in buccolingual inclinations of the posterior teeth in both groups; the alveolar ridge thickness increased in GC and remained constant in GO. Conclusions: Both treatment modalities have demonstrated appropriate results. The choice of treatment plan should consider the cost-benefit of each case, taking into account the initial dimension of the space, the presence of third molars, initial periodontal conditions, treatment time and the financial cost.

Dans cette thèse, nous présentons une nouvelle méthode de cartographie visuelle hybride qui exploite des informations métriques, topologiques et sémantiques. Notre but est de réduire le coût calculatoire par rapport à des techniques de cartographie purement métriques. Comparé à de la cartographie topologique, nous voulons plus de précision ainsi que la possibilité d’utiliser la carte pour le guidage de robots. Cette méthode hybride de construction de carte comprend deux étapes. La première étape peut être vue comme une carte topo-métrique avec des nœuds correspondants à certaines régions de l’environnement. Ces cartes sont ensuite complétées avec des données métriques aux nœuds correspondant à des sous-séquences d’images acquises quand le robot revenait dans des zones préalablement visitées. La deuxième étape augmente ce modèle en ajoutant des informations sémantiques. Une classification est effectuée sur la base des informations métriques en utilisant des champs de Markov conditionnels (CRF) pour donner un label sémantique à la trajectoire locale du robot (la route dans notre cas) qui peut être "doit", "virage" ou "intersection". L’information métrique des secteurs de route en virage ou en intersection est conservée alors que la métrique des lignes droites est effacée de la carte finale. La fermeture de boucle n’est réalisée que dans les intersections ce qui accroît l’efficacité du calcul et la précision de la carte. En intégrant tous ces nouveaux algorithmes, cette méthode hybride est robuste et peut être étendue à des environnements de grande taille. Elle peut être utilisée pour la navigation d’un robot mobile ou d’un véhicule autonome en environnement urbain. Nous présentons des résultats expérimentaux obtenus sur des jeux de données publics acquis en milieu urbain pour démontrer l’efficacité de l’approche proposée. / In this thesis, a novel vision based hybrid mapping framework which exploits metric, topological and semantic information is presented. We aim to obtain better computational efficiency than pure metrical mapping techniques, better accuracy as well as usability for robot guidance compared to the topological mapping. A crucial step of any mapping system is the loop closure detection which is the ability of knowing if the robot is revisiting a previously mapped area. Therefore, we first propose a hierarchical loop closure detection framework which also constructs the global topological structure of our hybrid map. Using this loop closure detection module, a hybrid mapping framework is proposed in two step. The first step can be understood as a topo-metric map with nodes corresponding to certain regions in the environment. Each node in turn is made up of a set of images acquired in that region. These maps are further augmented with metric information at those nodes which correspond to image sub-sequences acquired while the robot is revisiting the previously mapped area. The second step augments this model by using road semantics. A Conditional Random Field based classification on the metric reconstruction is used to semantically label the local robot path (road in our case) as straight, curved or junctions. Metric information of regions with curved roads and junctions is retained while that of other regions is discarded in the final map. Loop closure is performed only on junctions thereby increasing the efficiency and also accuracy of the map. By incorporating all of these new algorithms, the hybrid framework presented can perform as a robust, scalable SLAM approach, or act as a main part of a navigation tool which could be used on a mobile robot or an autonomous car in outdoor urban environments. Experimental results obtained on public datasets acquired in challenging urban environments are provided to demonstrate our approach.