Une méthode innovante pour simuler des interactions fluide-structure complexes tout en gardant un bon compromis temps de calcul/précision est présenté.Pour réduire le temps de simulation des modèles d’ordre réduits sont utilisés au lieu des modèles complets aussi bien pour les modèles structuraux que pour les modèles aérodynamiques. Un des challenges de base était d'utiliser des modèles industrielles hautes fidélités. La technique de condensation dynamique est utilisée pour réduire la taille du modèle éléments finis structures et la décomposition aux valeurs propres est utilisé sur une base de données aérodynamiques construite à partir de simulations CFD.Les non-linéarités structurelles sont réintroduites à posteriori.Une comparaison poussée des méthodes classique d'interpolation comme des méthodes de spline, d’interpolation sur des Manifold de Grassmann avec des méthodes innovantes d'apprentissage statistiques a été amené.Afin de valider complètement la méthodologie développée, une maquette expérimentale visant à imiter le comportement du carénage au sol avant le décollage a été conçue.Ce cas a pu être assimilé à une plaque avec des raideurs de liaisons dans une couche de mélange.La validation de cette méthode est réalisée en comparant les résultats des simulations numériques avec les données enregistrées pendant des essaies en soufflerie. On pourra ainsi comparer aussi bien des champs que des mesures locales. L'ensemble des essais a permis d'améliorer la compréhension de ce phénomène vibratoire qui mène à des problèmes récurrents de fatigue dans cette sous structures.Cette méthode est enfin appliquée à une structure aéronautique: les carénages de volet hypersustentateur / An innovative method for numerical simulating complex problems of fluid structure interaction, such as non-linear transients, characterized by good performances and high precision is presented in this manuscript. To cut down the simulation time, reduced order models are used for both the aerodynamic and structural modules. High fidelity industrial models have been used. A technique of dynamic condensation is employed to reduce the size of the finite element model while the technique of Proper Orthogonal Decomposition is used on a database of aerodynamic pressures built from CFD simulations. Structural non-linearities are reintroduced a posteriori. Different interpolation techniques such as the classic spline interpolation, interpolation on a Grassmann Manifold with more innovative methods of statistical learning have been compared. In order to validate the developed methodology a test campaign has been designed to reproduce a simplified mechanism of interaction inspired by a flap track fairing in take-off configuration. A plate whose stiffness depends on the springs at its attachment to the wind tunnel test section floor is immersed in a mixing layer. In parallel to the test activities a numerical model of the test rig has been developed. The validation of the methodology of fluid structure interaction is done through direct comparison between test data and simulation results. The testing activities have granted a deeper comprehension of the vibratory phenomenon that has led to recurrent fatigue problems on the impacted structures. The methodology is ultimately applied to an industrial problem: the load prediction on flap track fairings excited by engine exhaust.

I Sverige är 99.9 % av alla företag SME-företag. I dagens samhälle har förändrade förutsättningar och globala marknader ändrat kundkraven på exempelvis ledtid. Svenska tillverkande SME-företag kräver således ett sätt att anpassa sin produktion till dessa förändrade förutsättningar. VSM är en metod där current- och future-state mappas för att tydliggöra hur produktionen ser ut idag och hur det ska se ut imorgon. Det påvisas dock i tidigare studier att det finns hinder med VSM som motverkar framtagning av FSM. Det ska dock noteras att merparten av de studier som tidigare utförts har gjorts vid utländska företag eller företag större än SME. Dessa studier har dessutom genomförts i syfte att observera VSM i helhet och de fördelar som metoden har, eller undersöka vissa få hinder. Syftet med arbetet är därför att undersöka vilka hinder som kan försvåra för svenska SME-företag att designa future-state värdeflödeskartor som är lämpliga sett till deras verksamhet. Detta för att bättre möjliggöra för VSM implementation hos dessa företag. Detta har utförts genom att jämföra tidigare litteratur med en fallstudie på ett svenskttillverkande SME-företag inom metallindustrin och undersöka de mönster i hindren som observerats. Resultatet av arbetet var en modell av hinder som kan komma att försvåra försvenska SME-företag att designa future-state värdeflödeskartor som är lämpliga sett till deras verksamhet. Från denna modell tydliggörs ett stor överlapp mellan det empiriska resultatet och resultatet från tidigare studier. Ett hinder från tidigare litteratur motbevisas även och exkluderas från modellen. Detta medför att framtida utövare på svenska tillverkande SME-företag aktivt kan göra sig medvetna om de hinder som de kan tänkas stöta på samt vad dessa kan ha för påverkan på deras FSM, och genom detta förbereda sig för att möta dessa hinder. Framtida studier skulle kunna undersöka hinder vid användning av VSM-metoden på flera olika svenska tillverkande SME-företag och således skapa en bredare bild av hinder med VSM för framställning av en FSM / In Sweden, 99.9% of all companies are SMEs. In today's society, changing conditions and global markets have altered customer requirements, such as lead time. Therefore, Swedish manufacturing SMEs require a way to adapt their production to these changing conditions. Value Stream Mapping (VSM) is one such method that maps the current and future states to clarify how production looks today and how it should look tomorrow. However, previous studies have shown that there are obstacles with VSM that hinder the development of Future State Maps (FSMs). It should be noted that the majority of previous studies have been conducted in foreign or larger-than-SME companies. These studies have also been carried out to observe the entirety of VSM and its benefits or to investigate a few specific obstacles. The purpose of this study is to examine the obstacles that may hinder Swedish SMEs from designing future-state value stream maps suitable for their operations, in order to better enable VSM implementation in these companies. This has been accomplished by comparing previous literature with a case study conducted at a Swedish manufacturing SME in the metal industry and examining the patterns observed in the obstacles. The result of this work was a model of obstacles that may hinder Swedish SMEs from designing future-state value stream maps suitable for their operations. This table clearly shows a significant overlap between the empirical findings and the results from previous studies. Additionally, one obstacle from previous literature is contradicted. As a result, future practitioners in Swedish manufacturing SMEs can actively become aware ofthe obstacles they may encounter and understand their impact on their FSMs, thereby preparing to address these obstacles. Future studies could investigate obstacles in the use of the VSM method in several different Swedish manufacturing SMEs to create a broader understanding of obstacles with VSM for the development of an FSM.

Les hélices sont connues pour leur avantage significatif en termes de rendement propulsif. Ces avantages se traduisent directement par une réduction de la consommation de carburant de sorte qu’elles connaissent aujourd’hui un regain d’intérêt. Actuellement, les avancées récentes en simulations numériques rendent possible d’appliquer l’optimisation multidisciplinaire au cas exigeant du design de pales d’hélice transsonique. Pour ces raisons, une méthode d’optimisation est développée, dans laquelle les objectifs de performance aérodynamique, aéroacoustique et aéroélastique sont en concurrence. Cette méthode est appliquée au design de pales d’hélice à haute vitesse et à simple rotation. L’optimisation s’appuie sur l’Evolution Différentielle Multi-Objectifs (Multi-Objective Differential Evolution - MODE). Cette technique est une des formes d’algorithme évolutionnaire qui mimique l’évolution naturelle des populations par le concours de la sélection, de la recombinaison et de l’éventuelle mutation de formes de pales, chacune d’elles étant représentée par un vecteur de variables (corde, angle de flèche, etc. . .). MODE offre l’avantage de considérer tous les objectifs en concurrence lors de la sélection des designs prometteurs au sein d’une population. Afin de garder le coût computationnel dans des limites acceptables, l’évaluation des performances des designs proposés est faite par une approche à deux niveaux. Un meta-modèle fournit les estimations de performance pour chaque design à un coût computationnel extrêmement faible alors que des codes d’analyse à haute fidélité calculent les performances précises à un coût nettement plus élevé. Pour préserver la précision des estimations, le meta-modèle est initialement entraîné sur une population composée à cet effet. L’entraînement est ensuite répété de temps à autres avec les performances haute fidélité de designs prometteurs. Différents outils à haute fidélité ont été développés et utilisés dans ce cadre. L’outil CFD exécute la simulation RANS stationnaire d’un seul passage d’entrepales pour une hélice isolée sans angle d’attaque dans un écoulement libre. Ces simulations délivrent les valeurs de performance aérodynamique. L’hélice complète est modélisée grâce à des conditions aux limites cycliques. Le modèle de turbulence k - ε est utilisé en combinaison avec un traitement adapté près des murs. Des conditions adiabatiques et sans glissement sont imposées sur le carénage et la surface de la pale tandis que la limite radiale de la section d’essais reproduit les effets d’un champ de pression lointain. Cette approche a prouvé sa robustesse et, par-dessus tout, sa précision puisque une correspondance acceptable avec des résultats expérimentaux est obtenue pour différentes conditions d’utilisation et un large éventail de formes de pales. De plus, l’indépendance par rapport au maillage est satisfaisante. Lors de l’analyse a posteriori des résultats aérodynamiques, le Sound Pressure Level (SPL) est calculé par l’outil aéroacoustique (CHA) pour le bruit tonal en différentes positions. La formulation 1A de Farassat est utilisée à cette fin. Cette formulation découle de l’équation non-homogène d’onde dérivée de l’analogie acoustique de Lighthill par Ffowcs Williams et Hawkings (FW-H). Elle bénéficie du découplage partiel des aspects aérodynamiques et aéroacoustiques en plus d’être particulièrement adaptée pour le calcul du bruit d’hélice. Le bruit d’épaisseur et le bruit de charge sont exprimés par des termes séparés dans le domaine temporel tandis que les quadripôles de l’équation de FW-H sont négligés. La surface de la pale est utilisée comme surface d’intégration et une nouvelle technique de troncation a été développée et appliquée pour circonvenir la singularité mathématique qui apparaît lorsque des parties de la pale ont des conditions soniques en termes de cinématique par rapport à l’observateur. Cette approche délivre des résultats fiables à un coût acceptable. [...] / Open rotors are known to have significant advantages in terms of propulsive efficiency. These advantages translate directly in reduced fuel burn so that they nowadays benefit from a surge of interest. At the same time, recent advances in numerical simulations make the application of multidisciplinary optimization for the demanding design of transonic propeller blades, an affordable option. Therefore, an optimization method in which the performance objectives of aerodynamics, aeroacoustics and aeroelasticity compete against each other, is developed and applied for the design of high-speed single-rotation propellers. The optimization is based on Multi-Objective Differential Evolution (MODE).This technique is a particular kind of evolutionary algorithm that mimics the natural evolution of populations by relying on the selection, recombination and eventually mutation of blade designs, each of them being represented by a vector of design variables (e.g. chord width, tip sweep, etc). MODE has the advantage of dealing concurrently with all the objectives in the selection of potentially promising designs among a population. In order to keep the computational cost within reasonable margins, the assessment of the performance of proposed designs is done in a two-level approach. A metamodel provides performance estimates for each proposed design at extremely low computational effort while high-fidelity analysis codes provide accurate performance values on some promising designs at much higher cost. To safeguard the accuracy of the estimates, the metamodel is initially trained on a population that is specifically assembled for that purpose. The training is repeated from time to time with the high-fidelity performance values of promising designs. Different high-fidelity tools have been developed and used for the assessment of performance.The CFD-tool performs steady RANS simulations of a single blade passage of the isolated propeller in free air under zero angle of attack. These simulations provide the aerodynamic performance values. The full propeller is modelled thanks to cyclic boundary conditions. The k - ε turbulence model is used in combination with wall treatment. Adiabatic no-slip wall conditions are imposed on the spinner and blade surfaces whereas the test-section radial boundary is reproducing the effects of a pressure far-field. This approach has proven its robustness and, above all, its accuracy as satisfactory agreement with experimental results has been found for different operating conditions over a wide range of blade shapes, as well as sufficient grid independency. In the post-processing of the aerodynamic results, the Sound Pressure Level (SPL)is computed for tonal noise at various observer locations by the aeroacoustic solver(CHA). Formulation 1A from Farassat is used for this purpose. This formulation is related to the inhomogeneous wave equation derived from Lighthill’s acoustic analogy by Ffowcs Williams and Hawkings (FW-H). It benefits from the partial decoupling of the acoustic and aerodynamic aspects and is particularly suited to compute the noise from propellers. The thickness noise and loading noise are expressed by separate equations in the time-domain whereas the quadrupole source term is dropped from the original FW-H equation. The blade surface is chosen as integration surface and a newly developed truncation technique is applied to circumvent the mathematical singularity arising when parts of the blade reach sonic conditions in terms of kinematics with respect to the observer. This approach delivers accurate values at acceptable computational cost. Besides, CSM-computations make use of a finite elements solver to compute the total mass of the blade as well as the stresses resulting from the centrifugal and aerodynamic forces. Considering the numerous possibilities to tailor the blade structure so that it properly takes on the stresses, only a simplified blade model is implemented. [...]

Les cellules souches suscitent de grands espoirs pour la thérapie cellulaire et l'ingénierie tissulaire. Les CSM du tissus foetaux (sang placentaire et gelée de Wharton du cordon ombilical), à l'origine d'épiblaste embryonnaire, sont considérées comme plus primitives que les CSM provenant de sources adultes. Les conditions de culture ayant un impact sur le comportement des cellules, dans notre étude, nous avons exploré l'effet de la concentration de l'oxygène sur l'expansion, l'immunophénotypage et la différenciation de ces cellules. L'objectif de ce travail est d'identifier la méthode optimale d'isolation des CSM issues de tissus foetaux. Compte tenu du faible taux de succès dans l'isolement des CSM extraites du sang placentaire, nous nous sommes dirigés vers les CSM-GW. Nous y avons déterminé in situ, les marqueurs spécifiques exprimés dans la gelée de Wharton et à la périphérie. Des études sur la morphologie, la cinétique de croissance, et sur l'expression phénotypique des marqueurs de surface, des CSM-GW, ont été effectuées sur une longue durée (7 passages) à différentes conditions de culture. Nous avons montré que la GW est composée d'une abondante matrice extracellulaire riche en collagènes et glycosaminoglycannes et que les cellules possèdent un phénotype variable selon leur localisation dans la gelée. Ce tissu est capable de fournir une quantité importante de CSM (6,7x105 Cs/cm de cordon) qui gardent une morphologie constante. Enfin, quel que soit le passage, la concentration de l'oxygène ne semble pas avoir d'effet sur le phénotype des cellules. En revanche, une faible teneur en oxygène durant l'expansion semble diminuer le temps de doublement des cellules, favoriser la chondrogénèse et inhiber la différenciation ostéogénique. Enfin, quelles que soient les conditions de culture, la différenciation adipogénique des CSM-GW semble difficile à obtenir / Stem cells are the hopes for cell therapy and tissue engineering. MSCs from fetal tissue (umbilical cord blood and WJ), which are a source of embryonic epiblast grow relatively faster comparing to other adult sources. The culture condition can affect cell behavior. In our study, we explored the effect of oxygen concentration on the expansion, immunophenotyping, and differentiation of these cells. The aim of this work is to identify the optimal method for isolation of MSCs derived from fetal tissue. Given the low rate of success in the isolation of MSCs from cord blood, we headed to WJ-MSCs. We have determined in siu, the specific markers expressed in the WJ and in the perivascular region. Studies on the morphology growth kinetics, and phenotypic expression of surface makers of MSCs isolated from WJ were made over a long period (7 passages) in different culture conditions. We have shown that WJ is composed of an abundant extracellular matrix rich in collagen and glycasominoglycans and have variable phenotype depending from their localization in the jelly. This tissue is able to provide a large amount of MSCs (6.7x105 Cs/cm of cord) that maintain a constant morphology. Finally, regardless of the passage, the oxygen concentration does not effect on the phenotype of the cells. In contrast, a low oxygen concentration during expansion appears to decrease the doubling time of MSCs, promote chondrogenesis and inhibit osteogenic differentiation. Finally, whatever the culture conditions, adipogenic differentiation of WJ-MSC seems difficult to obtain

A supernova (SN) is the explosive destruction of a star. Via a luminous outpouring of radiation, the SN can rival the brightness of its SN host galaxy for months or years. In the past decade, astronomical surveys regularly observing the sky to deep limiting magnitudes have revealed that core collapse SNe (the demises of massive stars) are sometimes preceded by eruptive episodes by the progenitor stars during the years before the eventual SN explosion. Such SNe tend to show strong signatures of interaction between the SN ejecta and the circumstellar medium (CSM) deposited by the star before the SN explosion, likely by mass-loss episodes like the ones we have started to observe regularly. The complex CSM resolved around certain giant stars in our own galaxy and the eruptions of giant stars like η Car in the 19th century can be seen in this context. As the SN ejecta of an interacting SN sweep up the CSM of the progenitor, radiation from this process offers observers opportunity to scan the late mass loss history of the progenitor. In this thesis, interacting SNe and eruptive mass loss of their progenitors is discussed. The SN iPTF13z (discovered by the intermediate Palomar Transient Factory, iPTF) is presented. This transient was followed with optical photometry and spectroscopy during 1000 days and displayed a light curve with several conspicuous re-brigthenings ("bumps"), likely arising from SN ejecta interacting with denser regions in the CSM. Around 200 days before discovery, in archival data we found a clear precursor outburst lasting >~ 50 days. A well-observed (but not necessarily well understood) event like SN 2009ip, which showed both precursor outbursts and a light curve bump, makes an interesting comparison object. The embedding of the (possible) SN in a CSM makes it hard to tell if a destructive SN explosion actually happened. In this respect, iPTF13z is compared to e.g. SN 2009ip but also to long-lived interacting SNe like SN 1988Z. Some suggestions for future investigations are offered, to tie light curve bumps to precursor events and to clarify the question of core collapse in the ambiguous cases of some interacting SNe.

Infrastructure in the form of payment systems is a necessity to allow for payments to reach from payer to payee, but it is also subject to product differentiation between banks. In the euro countries, a domestic-integration zone termed SEPA that consolidates payment systems into a singular system has been regulated, providing market efficiencies for customers and companies. However, in Sweden, banks use unstandardized file communication that is costly for stakeholders to interface against, and is becoming increasingly difficult to oversee. With the introduction of novel payment solutions (e.g. mobile payments), there is also an increase in competitors that access the infrastructure. A rising customer demand for faster, global and integrated payments has been identified. This increased fragmentation of the market requires large investments for banks and reduces customer mobility, which motivates the need for consolidation of payment flows. The purpose of this thesis is to identify the roles of stakeholders in the clearing and settlement mechanism, and to identify the drivers and inhibitors that affect business decisions to change the systems in place. These results are categorized according to co-opetition theory. Furthermore, the thesis brings forward the global industry standard for financial messaging ISO 20022 to the business context, and discusses its implications in the Swedish market from an interoperability point of view. The study has been conducted using mixed methods with a qualitative approach. It includes: Analysis of documents and materials, non-participative observation, interviews with 9 industry experts and an in-depth case study of real-time payments in Sweden (Betalningar i Realtid). Results show that actors’ perceptions of one another are ambiguous, but cooperation is well-established and reaps many positive effects for firms. Co-opetition activities in banks are inclined to drive change, while competitive moves are likely to leave the system unchanged. Co-opetition is only possible under certain pre-agreed rules such as differentiation by implementing flexible payment solutions. The main implication for migration to an improved, standardized payment flow is connected to the governance of infrastructure. It is suggested that if agreements between stakeholders are not reached in due time then SEPA-like regulation put forward by higher instances is a likely outcome.

Les cellules sanguines proviennent d’une cellule souche hématopoïétique (CSE), présente dans la moelle osseuse chez l’homme adulte, qui nécessite d’être en contact étroit avec une zone particulière du microenvironnement médullaire (appelée niche hématopoïétique) pour sa différenciation et son autorenouvellement. La nature exacte des cellules qui composent cette niche (appelée cellules stromales) n’est pas encore bien connue, en particulier concernant sa relation avec les cellules souches mésenchymateuses (CSM). Le but de cette thèse a été d’étudier le rôle des CSM dans la régulation de l’hématopoïèse en fonction de leur type et leur stade de différenciation mésenchymateuse et d’évaluer leur rôle dans la migration des progéniteurs hématopoïétique (PH). Nous montrons que les CSM non différenciées possèdent la capacité de soutien de l’hématopoïèse primitive la plus importante (par culture à long terme pendant 5 semaines) et que cette capacité est rapidement perdue dès 3 jours de différenciation adipogénique, otéogénique et vasculaire musculaire lisse. Par ailleurs, nous montrons que le G-CSP agit directement sur les CSM pour augmenter la migration des CSH/PH hors de la niche (par un test de migration trans-stromale) via un mécanisme MMP-2 dépendant. / Blood cells arise from a hematopoietic stem cell (HSC), present into bone marrow (3M) in adult humans, which needs close contacts with a special zone of 3M micro environment (named hematopoietic niche) for its differentiation and self’-renewal. The precise nature of the niche-forming cells (named stromale cells) are not yet well known, particularly in their relationship with mesenchymal stem cells (MSCs). The aim of the study was to investigate further the role of the MSCs in the hematopoiesis control according to their differentiation pathway and state and to evaluate their role in the migration process of hematopoietic progenitor cells (HPÇ,[ We show that non-differentiated MSCs display the best hematopoietic supporting activity (using 5-week long term cultures) that is completely lost after in vitro differentiation into adipocytes, osteoblasts and vascular smooth muscle cells. In addition, we show that G-CSP stimulation of 3M MSCs promotes HSC/HPC migration (using trans-stromal migration assay) via a MMP-2-dependent mechanism.

Le traitement du cancer à l’aide d’une exposition aux radiations ionisantes peut mener au développement de plusieurs effets secondaires importants, dont un retard de réparation et de régénération du tissu hématopoïétique. Les mécanismes responsables de ces effets demeurent encore inconnus, ce qui limite le développement de nouvelles approches thérapeutiques. À l’aide d’un modèle murin de prise de greffe, nos résultats démontrent que l’endommagement du microenvironnement par l’irradiation a un impact limitant sur le nichage hématopoïétique. Parce que le microenvironnement est composé principalement de cellules dérivées des cellules souches mésenchymateuses (CSM), nous avons évalué le potentiel des CSM à régénérer le tissu hématopoïétique par la reconstitution de la niche osseuse. Cette thérapie a mené à une augmentation remarquable du nichage hématopoïétique chez les souris irradiées. Les causes moléculaires impliquées dans le nichage hématopoïétiques sont encore inconnues, mais nous avons remarqué l’augmentation de la sécrétion de la cytokine « granulocyte-colony stimulating factor » (G-CSF) dans l’espace médullaire suite à l’irradiation. Le G-CSF est impliqué dans la mobilisation cellulaire et est fort possiblement nuisible à une prise de greffe. Nous avons évalué le potentiel d’une thérapie à base de CSM sécrétant le récepteur soluble du G-CSF afin de séquestrer le G-CSF transitoirement et les résultats obtenus démontrent que le blocage du G-CSF favorise le nichage hématopoïétique. Globalement, les données présentées dans ce mémoire démontrent que le microenvironnement osseux et le niveau de G-CSF dans la moelle sont importants dans le processus de nichage hématopoïétique et que la baisse du potentiel de régénération du tissu hématopoïétique suite à l’irradiation peut être renversée à l’aide d’une thérapie cellulaire de CSM génétiquement modifiées ou non. / Cancer treatment using ionizing radiation may lead to significant side effects, including delayed hematopoietic tissue repair and regeneration. The mechanisms mediating these defects remain unknown, thus limiting the development of new therapeutic approaches. Using a mouse engraftment model, our results show that microenvironment damage by irradiation limits hematopoietic homing. Since the microenvironment is mainly composed of mesenchymal stem cells (MSCs)-derived cells, we evaluated the potential of MSCs to improve hematopoietic tissue regeneration by bone marrow niche reconstitution. This therapy led to remarkable enhancement of hematopoietic homing in irradiated mice. The molecular causes involved in hematopoietic homing remain unknown, but we noticed an increased in “granulocyte-colony stimulating factor” (G-CSF) secretion within the medullary space after irradiation. G-CSF is involved in cellular mobilization and may possibly be harmful to engraftment. We evaluated the therapeutical potential of MSC genetically-engineered to secrete a soluble G-CSF decoy receptor that would transiently sequester G-CSF. Results obtained show that G-CSF blocking improved hematopoietic homing. Overall, the findings presented in this thesis indicate that bone marrow microenvironment and G-CSF levels are important in hematopoietic homing process, and that the decline in hematopoietic tissue regeneration potential following irradiation can be reversed by cellular therapy using MSC genetically modified or not.

In the recent years, there has been a trend to run metallic pipelines carrying petroleum products and high voltage AC power lines parallel to each other in a relatively narrow strip of land. The case of electromagnetic interference between high voltage transmission lines and metallic pipelines has been a topic of major concern since the early 60’s. The main reasons for that are: • The ever increasing cost of right-of-ways, suitable for power lines and pipelines, along with recent environmental regulations, aiming to protect nature and wildlife, has forced various utilities to share common corridors for both high voltage power lines and pipelines. Therefore, situations where a pipeline is laid at close distance from a transmission line for several kilometers have become very frequent. • The rapid increase in energy consumption, which has led to the adoption of higher load and short circuit current levels, thus making the problem more acute. Due to this sharing of the right-of-way, overhead AC power line field may induce voltages on the metallic pipelines running in close vicinity leading to serious adverse effects. This electromagnetic interference is present both during normal operating conditions as well as during faults. The coupling of the field with the pipeline takes place either through the capacitive path or through the inductive or conductive paths. In the present work, the induced voltages due to capacitive and inductive coupling on metallic pipelines running in close vicinity of high voltage power transmission lines have been computed.The conductor surface field gradients calculated for the various phaseconfigurations have been presented in the thesis. Also the electric fields under transmission lines, for both single circuit and double circuit (various phase arrangements) have been analysed. Based on the above results, an optimum configuration giving the lowest field under the power line as well as the lowest conductor surface gradient has been arrived at and for this configuration induced voltage on the pipeline has been computed using the Charge Simulation Method (CSM). For comparison, induced voltages on the pipeline have been computed for the various other phase configurations also. A very interesting result is that the induced voltage on the pipeline becomes almost negligible at a critical lateral distance from the center of the powerline and beyond which the induced voltage again increases.This critical distance depends on the conductor configuration. Hence it is suggested that the pipeline be located close to the critical distance so that the induced voltage would be close to zero. For calculating the induced voltage due to the inductive coupling, electromotive force (EMF),induced along the pipeline due to the magnetic field created by the transmission line has been calculated. The potential difference between the pipeline and the earth, due to the above induced EMFs, is then calculated. As the zones of influence are generally formed by parallelism, approaches, crossings as well as removals, the computation involves subdividing the zone into several sections corresponding to these zones. The calculation of voltages is carried out at both the ends of the sections. Each section is represented by an equivalent π electrical network, which is influenced by the induced EMF. The induced EMF is calculated during faulted conditions as well as during steady state conditions. Inductive coupling calculations have been carried out for the following cases: •Perfect parallelism between powerline and pipeline. •zone of influences formed by parallelism, approaches, crossings and removals. It has been observed that when the pipeline is approaching the HV transmission line at an angle, then running parallel for certain distance and finally deviating away, the induced voltage is maximum at the point of approach or removal of the pipeline from the transmission line corridor.The induced voltage is almost negligible near to the midpoint of the zone of influence. The profile of the induced voltage also depend on whether the pipeline is grounded or left open circuited at the extremities of the zone of influence. Effect of earth resistivity and anti-corrosive coatings on induced voltage has also been studied. For mitigating the induced voltage on the pipeline,numerous low resistive earthings have been suggested. Results show that significant reduction in induced voltage can be achieved as the number of earth points is increased.

Le traitement du cancer à l’aide d’une exposition aux radiations ionisantes peut mener au développement de plusieurs effets secondaires importants, dont un retard de réparation et de régénération du tissu hématopoïétique. Les mécanismes responsables de ces effets demeurent encore inconnus, ce qui limite le développement de nouvelles approches thérapeutiques. À l’aide d’un modèle murin de prise de greffe, nos résultats démontrent que l’endommagement du microenvironnement par l’irradiation a un impact limitant sur le nichage hématopoïétique. Parce que le microenvironnement est composé principalement de cellules dérivées des cellules souches mésenchymateuses (CSM), nous avons évalué le potentiel des CSM à régénérer le tissu hématopoïétique par la reconstitution de la niche osseuse. Cette thérapie a mené à une augmentation remarquable du nichage hématopoïétique chez les souris irradiées. Les causes moléculaires impliquées dans le nichage hématopoïétiques sont encore inconnues, mais nous avons remarqué l’augmentation de la sécrétion de la cytokine « granulocyte-colony stimulating factor » (G-CSF) dans l’espace médullaire suite à l’irradiation. Le G-CSF est impliqué dans la mobilisation cellulaire et est fort possiblement nuisible à une prise de greffe. Nous avons évalué le potentiel d’une thérapie à base de CSM sécrétant le récepteur soluble du G-CSF afin de séquestrer le G-CSF transitoirement et les résultats obtenus démontrent que le blocage du G-CSF favorise le nichage hématopoïétique. Globalement, les données présentées dans ce mémoire démontrent que le microenvironnement osseux et le niveau de G-CSF dans la moelle sont importants dans le processus de nichage hématopoïétique et que la baisse du potentiel de régénération du tissu hématopoïétique suite à l’irradiation peut être renversée à l’aide d’une thérapie cellulaire de CSM génétiquement modifiées ou non. / Cancer treatment using ionizing radiation may lead to significant side effects, including delayed hematopoietic tissue repair and regeneration. The mechanisms mediating these defects remain unknown, thus limiting the development of new therapeutic approaches. Using a mouse engraftment model, our results show that microenvironment damage by irradiation limits hematopoietic homing. Since the microenvironment is mainly composed of mesenchymal stem cells (MSCs)-derived cells, we evaluated the potential of MSCs to improve hematopoietic tissue regeneration by bone marrow niche reconstitution. This therapy led to remarkable enhancement of hematopoietic homing in irradiated mice. The molecular causes involved in hematopoietic homing remain unknown, but we noticed an increased in “granulocyte-colony stimulating factor” (G-CSF) secretion within the medullary space after irradiation. G-CSF is involved in cellular mobilization and may possibly be harmful to engraftment. We evaluated the therapeutical potential of MSC genetically-engineered to secrete a soluble G-CSF decoy receptor that would transiently sequester G-CSF. Results obtained show that G-CSF blocking improved hematopoietic homing. Overall, the findings presented in this thesis indicate that bone marrow microenvironment and G-CSF levels are important in hematopoietic homing process, and that the decline in hematopoietic tissue regeneration potential following irradiation can be reversed by cellular therapy using MSC genetically modified or not.