L'objectif de cette thèse est l'accélération des solveurs utilisés pour la résolution de l'équation de Poisson pour la pression, dans le cas de la simulation d'écoulements à faible nombre de Mach sur des maillages non structurés. Cet objectif est complété par un besoin de stabilité, en particulier sur des géométries complexes. Plusieurs modifications de la méthode des Gradients Conjugués avec déflation ont été considérées à cet effet. Une méthode de redémarrage basée sur une estimation de l'effet des erreurs numériques a été mise en oeuvre et validée. Par la suite, une méthode consistant à calculer des solutions linéaires ou quadratiques par morceaux sur le maillage grossier s'est avérée instable dans le solveur non structuré YALES2. La nouvelle méthode alors développée consiste à transformer la méthode standard de déflation à deux niveaux de maillage en une méthode à trois niveaux. Cependant, le nombre élevé d'itérations sur le troisième niveau de maillage nouvellement créé ralentit le solveur, ce que nous avons rectifié grâce à deux méthodes développées particulièrement pour réduire le nombre d'itérations sur les niveaux grossiers. La première méthode est la création de solutions initiales grâce à une méthode de projection adaptée. La seconde consiste en une adaptation du critère de convergence sur les niveaux grossiers. Les résultats numériques sur des simulations massivement parallèles, avec le solveur à deux niveaux classique, montrent une réduction considérable du temps de calcul du solveur et une amélioration importante de sa scalabilité faible. L'application de ces techniques à la déflation à trois niveaux induit des gains supplémentaires en termes de temps de calcul. Outre le perfectionnement de ce solveur, des recherches supplémentaires doivent être conduites sur l'équilibrage dynamique de charges de calcul, qui pourrait devenir un développement-clé du solveur.

Le Disjoncteur Différentiel Résiduel (DDR) doit garantir la continuité de service ce qui signifie qu'aucun défaut autre que ceux pouvant mettre l'utilisateur en danger ne doivent faire déclencher le produit pour éviter soit des désagréments (non alimentation du congélateur) soit une perte financière (non exploitation d'une installation photovoltaïque).La fonction mesure est composée de :- Un tore pour la mesure du courant résiduel, il réalise naturellement la somme des courants entrant et sortant de l'installation- Une plaquette de mise en forme (filtrage)- Un actionneur, le relais polarisé qui fixe le seuil du dispositif (par sa puissance de déclenchement et fournit une énergie mécanique pour mettre l'installation hors tension.Ces déclenchements non désirés proviennent des défauts de la chaine de mesure. Nous pouvons en citer 3 principales causes :- Courant de fuite à la terre trop important (perturbation réseau mode commun)- Champs magnétiques rayonnés (courant passant dans le primaire du tore)- Equilibrage du tore (mode différentiel) (courant passant dans le primaire du tore)Les surtensions atmosphériques étant considérées comme étant les perturbations les plus critiques, les travaux faits durant cette thèse reposent sur ce phénomène. Toute la problématique est basée sur la manière avec laquelle le disjoncteur différentiel répond face à ces perturbations. Une bonne compréhension de sa réaction dans de tels cas s'avère nécessaire. Les objectifs visés par cette étude sont de :- Trouver un modèle temporel du phénomène de foudre- Mettre en évidence les différentes phases de fonctionnement engendré lors de la réponse d'un DDR à un coup de foudre- Etablir un modèle comportemental du DDR adapté à chaque phase- Mettre en évidence la cause des déclenchements intempestifs- Proposer des solutions permettant a nos produits de ne pas déclencher de façon intempestives et fiabiliser ainsi leur fonctionnement- Diminuer par conséquent les retours clients / The Residual Current Device (RCD) must ensure the continuity of service which means that no default other than those that can put the user at risk should make the product trigger, to avoid any inconvenience (freezer not supplied) or a financial loss (non-operation of a photovoltaic). The measurement function is made up of:- A torus for measuring the residual current, it naturally carries the sum of currents entering and exiting the installation- A plate shaping (filtering)- An actuator, the polarized relay which sets the threshold of the device (through its power of initiation) and provides mechanical energy to turn off power supply.These false triggering are caused by defaults initiated among the measurement chain. We can cite three main reasons:- Residual current too high (over-voltages on electrical network by common mode)- Radiated Magnetic Fields (current through the primary circuit of the torus)- Balancing the torus (differential mode) (current through the primary circuit of the torus)As the atmospheric over-voltages are considered to be the most critical disturbances, they will appear as the principal subject of this thesis. The main issue is the behavior of the RCD facing a lightning stroke. So, a well understanding of the manner that it will respond in such situations is necessary. The objectives of this study are to:- Establish a temporal model of lightning stroke- Highlight the different working phases in front of a lightning stroke- Establish a RCD's behavioral model adapted to every phase- Highlight the causes of unwanted triggers- Propose solutions enabling our products to not trigger by default and so improve the reliability of their functioning- Reduce customer returns

The study focussed on the research question namely: “How will the introduction of new ecological taxes impact the South African agricultural sector?” To answer the question, eight international eco-taxes were selected and further investigated. The nature and history of each eco-tax was examined. The effects or expected effects (where implementation have not yet taken place) of the eco-taxes on the agricultural sectors of the foreign countries, were then considered. The study continued by considering the possible impact on South African agriculture, should these taxes be implemented in South Africa. This was accomplished by extrapolating the foreign effects previously investigated. Mindful of findings, recommendations were then made of what eco-taxes could be implemented which will not impede South African agriculture. It was concluded that the British Climate Change Levy and Climate Change Agreement scheme, Australian Carbon Farming Initiative and Swedish meat consumption tax could be considered for implementation. / Financial Accounting / M. Phil (Accounting Science)

Notes: i) the terms "lessee" and "tenant" are used alternatively, the latter only when quoted ii) the terms "lessor" and "landlord" are used alternatively, the latter only when quoted / The research intends to assess the availability of information to determine the contribution of turnover rent to lessor revenue as the publicly available information on building performance, and in specific turnover rent, is not adequate to answer the research problem. Academic, legal and accounting sources are consulted and referenced as background on turnover rent. Limitations applicable to the study is noted. A content analysis of published financial statements analyses the application of the prevailing accounting standards in the real estate sector and assesses to what extent information is available to determine the contribution of turnover rent to lessor revenue. Disclosure was found to be inconsistent and inadequate to calculate the contribution to lessor revenue and to assess individual building performance. With relevant building performance data of a large retail centre sourced from an asset manager, the contribution of turnover rent to lessor revenue was calculated for a period of eight years as part of a retail centre case study. With information available, but not disclosed, it is recommended that the IASB considers additional disclosure for listed real estate entities to enable stakeholders to assess individual building performance. Further recommendations are made in this study. The building performance indicators were further compared to relevant economic indicators. The results of this analysis indicates an indirect correlation between the prime interest rate and three building performance indicators being lessee turnover, total rent collected and centre foot-count. This confirms the strong reliance of the South African retail sector on credit sales. / Financial Accounting / M. Ph. (Accounting Sciences)

The pressing global demand to transform to a low-carbon business community, which is required by the urgency of mitigating climate change, significantly alters the operating procedures for carbon emitters and carbon revenue generators alike. Although agricultural activities are not considered as heavy carbon emission source, the increased public focus on climate change has catapulted the exploitation of sustainable agricultural land management mitigating strategies as intervention by the sector. Additionally, the focus on market-based mechanism to address climate change, which has led to the evolution of cap-and-trade schemes, makes the agricultural sector become a source of low-cost carbon offsets. However, the fact that cap-and-trade schemes in the agricultural sector are voluntary has resulted into not only very diverse farming practices but also diverse accounting practices. The consequences of the diversity practices are that, the impacts on financial performance and position are not comparable. Therefore, the overall objective of this study was to investigate the recognition, measurement and disclosure for cap-and-trade schemes in the agricultural sectors This study was conducted through literature reviews and empirical test. A qualitative research approach utilising constructivist methodology was employed. Primary data was collected in Kenya by administering three sets of semi-structured questionnaires to drafters of financial statements, loan officers and financial consultants. Secondary data involved content analysis of financial statements and reports of listed entities across the globe. It was established that proper accounting for cap-and-trade schemes adaptation activities is critical to the success of an entity’s environmental portfolio. Additionally, a model for valuing an organisation's carbon capture potential as suggested by this study enables entities to better report the impact of the adaptation activities on the financial performance and financial position. The outcome of this study enables entities to integrate the carbon capture potential on an entity sustainability reporting framework. / Colleges of Economic and Management Sciences / D. Phil. (Accounting Science)

La formation de la périphérie urbaine d’Orléans des années 1870 à l’après-guerre, étudiée à partir d’une échelle d’analyse particulière, le lotissement, constitue le sujet central de cette thèse. L’analyse des processus d’extension resitue plus largement les lotissements dans la ville. Elle montre d’abord les relations étroites qu’ils entretiennent avec le quartier Dunois, aménagé en 1879-1880. Si les Plans d’aménagement, d’embellissement et d’extension (loi Cornudet, 1919), ont peu d’impact sur la construction des lotissements, ces derniers témoignent, à des degrés divers, de la mise en oeuvre du Projet de reconstruction et d’aménagement de la commune (1949). La compréhension du cadre réglementaire et juridique permet d’éclairer la politique d’aménagement de voirie municipale et les projets de lotissement sur une longue durée. Elle nous renseigne également sur la constitution du paysage urbain. Cette étude offre ainsi de nouvelles clés de lecture du territoire orléanais, en nous informant non seulement sur les acteurs et leurs pratiques, mais également sur les formes urbaines et architecturales que ces hommes ont générées / This dissertation focuses on the urbanization of Orléans’ (France) outskirts, from the 1870s to the post-war period, studied from a special analysis of scale, i.e. subdivisions. Analysis of mechanisms and forms of urban extension situates subdivisions in the city on a wider scale. It first enhances the close relationship that subdivisions have with the quartier Dunois that was planned in 1879-1880. In 1919, a French town-planning law named “Cornudet Act” was established. It appears that it had little impact on the construction of subdivisions. In fact, it is the implementation of town-planning for reconstruction and rehabilitation in 1949 that showed more its influence on the construction of subdivisions. Understanding the regulatory and legal framework can illuminate road system rehabilitation policy of the city and subdivision projects on a long-term perspective. It highlights the creation of urban landscape as well. This study provides new keys to understand Orléans’ territory: not only does it accounts for the actors’ roles and their practices, but it also provides new insights into urban and architectural forms that these people generated.

Ce travail étudie le rôle de la densité de trous à l’équilibre sur la dynamique des charges et de la norme de l’aimantation de (Ga,Mn)As pour des densités de manganèse et d’impuretés fixées indépendamment. Des expériences « pompe-sonde » mettent en relation les dynamiques de réflectivité et d’angle de rotation Kerr. Deux relaxations sont mises en évidence. La première traduit un échauffement variable du gaz de trous entre 1ps et 100ps. La seconde traduit une diffusion-recombinaison des charges entre 100ps et 1500ps et évolue en fonction du rapport entre extension spatiale d’états d’impuretés, piégeant les électrons photo générés, et vitesse de Fermi. Pour compléter l’approche, une étude numérique de l’état fondamental des échantillons par la théorie de la fonctionnelle de la densité relie aimantation, température et densité de trous. Elle interprète la dynamique de la norme de l’aimantation à partir d’un diagramme de phase statique correspondant aux données publiées pour (Ga,Mn)As, qui est fonction de la température et de la densité de trous. Cette dynamique se ramène à celle de la réflectivité. Ceci permet de préciser les contributions de la norme et de l’orientation de l’aimantation dans le signal dynamique de rotation Kerr. / The effects of the background hole density on the charge and magnitude of the magnetization dynamics in (Ga,Mn)As grown with independently fixed manganese and impurity densities. A pump and probe experiment monitored simultaneously the reflectivity and Kerr angle dynamics. Two relaxation steps are highlighted. First the cooling down of the charge clouds between 1ps and 100ps and second the carrier’s diffusion-recombination between 100ps and 1.500 ns. The latter depends on the ratio between the spatial extent of impurity states, which trap the photo electrons, and the Fermi velocity. To complete these experimental results, a numerical study of the ground state of the samples, using a density functional theory, relates the magnitude of the magnetization, the temperature of the carriers and the density of holes. Phase diagram are computed, and compared to already published results. We show that the magnitude of the magnetization dynamics can be fully determined from the reflectivity measurements. We conclude that it is possible to distinguish the dynamics of the magnetization magnitude and direction using the Kerr angle dynamical signal.

No description available.

The point of the book is to provide characteristics of present customs warehouses in Czech Republic, their types, the conditions and the proceedings during establishments and during their operation times. Point out mutual relations of involved people and by using practical examples show the financial outcome of using a customs warehouses under an effective legislature.

O objetivo deste trabalho é apresentar um novo tipo de sistema de levitação baseado na força de interação magnética entre uma bobina de núcleo não-magnético e um imã permanente, em casos de simetria axial entre os dispositivos, nos moldes do problema 23 proposto no TEAM Workshop. Este tema é bastante atual e vários métodos têm sido estudados e propostos em razão da complexidade na determinação precisa das forças sobre os imãs permanentes imersos em um campo magnético em um circuito magnético aberto. O primeiro grande desafio deste trabalho é obter uma expressão analítica para esta força de interação magnética em casos de simetria axial usando o método de cargas magnéticas ligadas. Para tal, algumas hipóteses simplificadoras foram adotadas como considerar o campo magnético gerado pela bobina aproximadamente uniforme em toda a face do imã permanente e assumir que a magnetização do imã é constante e independente da variação de sua distância para a bobina. Pretende-se aproveitar o sistema implementado neste trabalho como bancada experimental no Laboratório de Controle da Universidade de São Paulo. Foi projetado um controlador PID através de ferramentas gráficas obedecendo a alguns critérios de desempenho, tanto no domínio do tempo como no domínio da freqüência. Uma vez sintonizado, foi utilizado o toolbox Real-Time Windows Target do Simulink e a placa de aquisição PCI 6221 (da National Instruments) para controlar em tempo real a planta de levitação em malha fechada. Os resultados experimentais foram muito satisfatórios de modo que o modelo analítico foi considerado válido. O sistema apresentou boas características como, por exemplo, um bom acompanhamento do sinal de referência, mesmo em grandes excursões, erro de regime nulo, levitação estável em distâncias relativamente grandes e uma boa estabilidade radial. O uso de dois sensores Hall mostrou-se eficiente na determinação da posição do imã permanente. / The objective of this work is to present a new kind of levitation system based on the interaction force between a non-magnetic core coil and a permanent magnet, in the case of axial symmetry between devices, as proposed by TEAM Workshop problem 23. This theme is very current and various methods have been studied and proposed in face of the complexity in determining precisely the force over permanent magnets immersed in a magnetic field in an open magnetic circuit. The first big challenge of this work is to obtain an analytical expression for this interaction magnetic force in the case of axial symmetry using the equivalent magnetic charge method. For this, some simplifying hypothesis have been adopted like considering the magnetic field created by the coil approximately uniform over all the permanent magnets face and assuming that magnets magnetization is constant and independent of the variation of its distance to the coil. The system implemented in this work is intended to be used as an experimental bench for the Laboratory of Control of Sao Paulo University. A PID controller was projected by means of graphical tools according to some criteria for performance, both in the field of time as in the frequency domain. Once tuned, the toolbox Real-Time Windows Target of Simulink and the PCI-6221 acquisition board (of National Instruments) were used to control in real time the levitation plant in closed loop. The experimental results were very satisfactory so that the analytical model was considered valid. The system showed good characteristics as, for instance, a good tracking of reference signal, even in large excursions of it, null stationary error, stable levitation at relatively big gaps and a good radial stability. The use of two Hall-effect sensors proved to be efficient in the determination of permanent magnets position.