Network performance maps can be used as a tool to predict network conditions at a given location, based on previous measurements at that location. By using measurement data from other users in similar locations, these predictions can be significantly improved. This thesis looks into the accuracy of predictions when using different approaches to distribute this data between users, we compare the accuracy of predictions achieved by using a central server containing all known measurements to the accuracy achieved when using a crowd-based approach with opportunistic exchanges between users. Using data-driven simulations, this thesis also compares and evaluates the impact of using different exchange policies. Based on these simulations we conclude which of the exchange policies provides the most accurate predictions.

The present study thesis aims to contribute to increased knowledge about how a shared leadership in the school can be constructed and understood. The study's knowledge object is shared leadership in the school. The study objects are school leaders who work together as well as their ideas about how they jointly construct a shared leadership in the school. In the present study, school leaders refer to the persons at the school who are the head of the teachers and other staff, with the task of leading the school's activities. This can thus be a principal or an assistant principal. The thesis is based on a qualitative study with interviews of school leaders who work together in what can be described as shared leadership. The interviews were conducted in pairs using a technique that in Swedish school development research has come to be called an interview with a performance chart. In the interviews, the school leaders who participated in the study were given the opportunity to jointly design the leadership as they perceived it to be designed whitin their activities. The study describes, analyzes and discusses these social constructions. The starting point for the analysis and the subsequent discussion is linked to previous research on shared leadership and organizational theory's way of managing leadership in relation to the business's need for structures that enable both stability and change. Based on an organizational argument, I discuss how school leaders working in shared leadership distribute tasks among themselves and how this distribution affects work organization and development organization. On the basis of the social constructivist theory as a theory of science in the study, I have found hermeneutics useful to describe how I have interpreted my results. The result shows that the different pairs of leaders lead with different kinds of shared leadership: co-leadership, functional leadership and in some cases even a mixture of these. The time spent on building a shared base for shared leadership influences the form of shared leadership that was constructed. The more time that was devoted to talking to each other and creating a common foundation to stand on, the more the school leaders came to lead together in a so-called co-leadership. Unless joint time was allocated, there was a tendency to divide work tasks between themselves and lead through functional leadership.

Cette thèse évalue d'abord le potentiel thermodynamique du cycle au CO2 supercritique (sc-CO2) pour une large gamme de température de source chaude et étudie son couplage aux applications nucléaires, 45.7% d’efficacité thermique étant obtenu pour un réacteur à neutrons rapides refroidi au sodium. Des simulations CFD sont réalisées sur un compresseur à échelle réduite et confrontées à une expérience, apportant des éléments de qualification. Des simulations sur un compresseur à échelle 1:1 révèlent des particularités liées à la compression du sc-CO2 au comportement gaz réel, offrant un retour d’expérience pour la conception. Dans ce cadre, une approche de cartes de performance est proposée et validée à l'aide de simulations. Enfin, une étude de la collapse d’une bulle dans le CO2 liquide au voisinage du point critique est réalisée et indique l'absence d’effet destructif de cavitation, ouvrant la voie au fonctionnement du compresseur en phase liquide, lieu optimum de l'efficacité du cycle. / This study first evaluates the thermodynamic performance of the supercritical CO2 (sc-CO2) cycle in a large range of heat source temperature, with a focus on the nuclear applications; a thermal efficiency of 45.7% is reported for a Sodium-cooled Fast Reactor. Second, CFD simulations have been performed on a small scale sc-CO2 compressor and results have been confronted positively with the experimental data. Simulation results on a real scale compressor have then revealed some particularities during the compression of a real fluid, providing feedbacks for the component design. In addition, a reliable performance maps approach has been proposed for the sc-CO2 compressor and validated using the CFD results. Finally, an investigation of bubble collapse in the liquid CO2 near the critical point has disclosed the likely absence of detrimental effects. As such, risks of cavitation damage should be low, favoring the compressor operation in the liquid region for cycle efficiency improvement.