Dans les plasmas de tokamak peuvent se développer des instabilités MHD (Magneto-Hydro-Dynamiques) se manifestant sous la forme d’îlots magnétiques qui réduisent le confinement. Ces îlots peuvent être contrôlés par la génération localisée de courant dans le plasma. Dans cette thèse, nous nous intéressons à la modélisation des îlots magnétiques et de leur contrôle en utilisant une description fluide (MHD) du plasma, à l’aide du code XTOR. Nous détaillons l'inclusion d'une source de courant au sein du modèle MHD, ce qui nécessite l'ajout d'une équation supplémentaire pour modéliser la propagation de la densité de courant le long des lignes de champ magnétique. Cette implémentation est ensuite vérifiée sur la base de modèles analytiques, nous permettant de retrouver l'influence de paramètres tels que la largeur du dépôt ou son désalignement. Nous avons mis en évidence des effets non-décrits par les modèles asymptotiques, liés à la nature de la localisation spatiale de la source de courant. Nous nous sommes ensuite intéressés aux stratégies de contrôle envisageable pour la suppression des îlots. Nous avons ajouté au sein du code XTOR un système de contrôle qui ajuste le dépôt de courant selon les stratégies choisies. Des simulations MHD non-linéaires des différents schémas de contrôle ont été effectuées, et les différentes stratégies comparées, permettant de préciser pour chacune une gamme d’intérêt. / Magneto-Hydro-Dynamic (MHD) instabilities are susceptible to develop within a tokamak plasma. These instabilities manifest themselves as magnetic islands which reduce the plasma confinement. The islands can however be controlled by driving current inside them. In this thesis, we consider the modeling of the magnetic islands and their control using first principle approaches, which rely on a global MHD description of the plasma. We have detailed the inclusion a RF-driven current like source term in an MHD code, which requires special care to be given to the modeling of the current density evolution. The implementation has been benchmarked against the asymptotic models, allowing us to retrieve the influence of parameters such as deposition width or misalignment with respect to the island width and position. Beyond these aspects, we have evidenced new effects, linked to the 3D nature of the current deposition. We have observed a flip instability in which an island, reduced by the ECCD, brutally inverse its phase so that its X-Point faces the current deposition, allowing the mode the grow further. We then moved on to the topic of the best suitable control strategies for the control of the island. We have implemented in XTOR a control system that mimics the experimental ones and adapt the current deposition in function of a preset strategy. Nonlinear MHD simulations have been carried out using different control schemes, allowing us to quantify the gain to expect from each of these methods depending on the characteristics of the current deposition.

The aim of this study is to create a better understanding of how preschool teachers in ametropolitan region in Sri Lanka view their opportunities to create quality preschools and alsoidentify factors that affect quality enhancement. Three research questions were created focusingon the preschool teachers’ perceptions of the quality of their preschools, what actions theyimplement to enhance the quality of preschools and what they consider affects their preschools’quality. In order to achieve the aim of the study, interviews were conducted with six preschoolteachers, all from different preschools. The results show that preschool teachers have anapparent positive attitude towards the quality of their own preschools. The actions theyimplement in hope of improving quality are staff meetings, where they plan for the future andenvironmental improvements. Further the results also show that four out of six preschools carryout some part of the Systematic Quality Development Work (SQDW). The factors that theteachers believed influence the quality of preschools included the minimum standards in SriLanka, shortcomings in preschool teacher education and expectations.

This study explored the current practices implemented by Early Childhood Care and Development (ECCD) caregivers / preschool teachers in Swaziland. It further investigated how the lack of an appropriate policy on Early Childhood Care and Development impacted on the delivery of services to the sector. The research was conducted using a qualitative methodology, eliciting responses through semistructured interview schedules. In order to conduct a more in-depth analysis, eight interviews were held at various early childhood care and development sites. The criteria for selection depended on whether the participating caregiver had direct, hands-on experience of the day-to-day care and running of ECCD sites. They also had to be involved in a full-time preschool teaching programme and were purposively selected from the geographical location of Manzini, in Swaziland. The sites could be distinguished into three categories, namely: community (non-profit making), private and church or missionrun centres. The results showed that caregivers implemented diverse and uncoordinated practices and that there was no uniformity in terms of professional training, classroom practice and curriculum application. It was evident that the participants did not link the theory of their training to their practice, leaving gaps in the provision of services and educational programmes to the children. The study concluded that unless the government of Swaziland and the ECCD unit at the national level of Education made a concerted effort to formulate a national ECCD policy, Education for All would remain a pipedream. The study recommended that government should formulate national ECCD policy guidelines to encourage uniformity in practice and provision of ECCD sites. Not only should government accelerate the development of the guidelines but they should also support the caregivers by continuous professional development activities.