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<p> In this thesis, we investigate the possibility that a purely electronic mechanism is the cause of superconductivity in C60 materials. Several computational methods are adopted to calculate the pair-binding energy. They are perturbation theory, exact diagonalization, Gutzwiller projection, and auxiliary field Monte Carlo. Results from these different methods are compared with each other both in a C60 molecule and in other smaller molecules in order to test conclusions about whether or not a purely electronic mechanism can lead to an attractive interactions between electrons in C60 molecules.</p> <p> Besides this test of the superconductivity mechanism, we also explain in detail how to apply these different computational methods to C60 for the specific geometry of C60. Clearly illustrating these computational methods is the second goal of this thesis.</p> <p> Our final conclusion is that for both small and large Hubbard interaction U, there is pair binding in a single C60 molecule. For intermediate Hubbard interaction strength, there is no clear evidence for pair binding for the range of temperatures we explored. We suggest that the truncation of the Coulomb interaction, which is implicit in the Hubbard Hamiltonian, may suppress pair-binding of electrons in C60 and that it may be necessary to consider a model that includes the long range character of Coulomb interaction. This is a subject for further study.</p> / Thesis / Master of Science (MSc)

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The facility layout problem (FLP) is one of the most important and challenging problems in both the operations research and industrial engineering research domains. In FLP research, the continuous-representation-based FLP can consider all possible all-rectangular department solutions. Given this flexibility, this representation has become the representation of-choice in FLP research. Much of this research is based on a methodology of mixed integer programming (MIP) models. However, these MIP-FLP models can only solve problems with a limited number of departments to optimality due to a large number of binary variables used in the models to prevent departments from overlapping. Our research centers around the sequence-pair representation, a concept that originated in the Very Large Scale Integration (VLSI) design literature. We show that an exhaustive search of the sequence-pair solution space will result in finding the optimal layout of the MIP-FLP and that every sequence-pair solution is binary-feasible in the MIP-FLP. Based on this fact, we propose a methodology that combines the sequence-pair and MIP-FLP model to efficiently solve large continuous-representation-based FLPs. Our heuristic approach searches the sequence-pair solution space and then use the sequence-pair representation to simplify and solve the MIPFLP model. Based on this methodology, we systematically study the different aspects of the FLP throughout this dissertation. As the first contribution of this dissertation, we present a genetic algorithm based heuristic, SEQUENCE, that combines the sequence-pair representation and the most recent MIPFLP model to solve the all-rectangular-department continuous-representation-based FLP. Numerical experiments based on different sized test problems from both the literature and industrial applications are provided and the solutions are compared with both the optimal solutions and the solutions from other heuristics to show the effectiveness and efficiency of our heuristic. For eleven data sets from the literature, we provide solutions better than those previously found. For the FLP with fixed departments, many sequence-pairs become infeasible with respect to the fixed department location and dimension restrictions. As our second contribution, to address this difficulty, we present a repair operator to filter the infeasible sequence-pairs with respect to the fixed departments. This repair operator is integrated into SEQUENCE to solve the FLP with fixed departments more efficiently. The effectiveness of combining SEQUENCE and the repair operator for solving the FLP with fixed departments is illustrated through a series of numerical experiments where the SEQUENCE solutions are compared with other heuristics' solutions. The third contribution of this dissertation is to formulate and solve the FLP with an existing aisle structure (FLPAL). In many industrial layout designs, the existing aisle structure must be taken into account. However, there is very little research that has been conducted in this area. We extend our research to further address the FLPAL. We first present an MIP model for the FLPAL (MIP-FLPAL) and run numerical experiments to test the performance of the MIP-FLPAL. These experiments illustrate that the MIP-FLPAL can only solve very limited sized FLPAL problems. Therefore, we present a genetic algorithm based heuristic, SEQUENCE-AL, to combine the sequence-pair representation and MIP-FLPAL to solve larger-sized FLPAL problems. Different sized data sets are solved by SEQUENCE-AL and the solutions are compared with both the optimal solutions and other heuristics' solutions to show the effectiveness of SEQUENCE-AL. The fourth contribution of this dissertation is to formulate and solve the FLP with non-rectangular-shaped departments. Most FLP research focuses on layout design with all rectangular-shaped departments, while in industry there are many FLP applications with non-rectangular-shaped departments. We extend our research to solve the FLP with nonrectangular-shaped departments. We first formulate the FLP with non-rectangular-shaped departments (FLPNR) to a MIP model (MIP-FLPNR), where each non-rectangular department is partitioned into rectangular-shaped sub-departments and the sub-departments from the same department are connected according to the department's orientation. The effect of different factors on the performance of the MIP-FLPNR is explored through a series of numerical tests, which also shows that MIP-FLPNR can only solve limited-sized FLPNR problems. To solve larger-sized FLPNR problems, we present a genetic algorithm based heuristic, SEQUENCE-NR, along with two repair operators based on the mathematical properties of the MIP-FLPNR to solve the larger-sized FLPNR. A series of numerical tests are conducted on SEQUENCE-NR to compare the SEQUENCE-NR solutions with both the optimal solutions and another heuristic's solutions to illustrate the effectiveness of SEQUENCE-NR. As the first systematic research study on a methodology that combines the sequence-pair representation and the MIP-based FLP, this dissertation addresses different types of continuous-representation based facility layout design problems: from block layout design with and without fixed departments to re-layout design with an existing aisle structure, and from layout design with all-rectangular-shaped departments to layout design with arbitrary non-rectangular-shaped departments. For each type of layout design problem, numerical experiments are conducted to illustrate the effectiveness of our specifically designed family of sequence-pair and MIP-based heuristics. As a result, better solutions than those previously found are provided for some widely used data sets from the literature and some new datasets based on both the literature and industrial applications are proposed for the first time. Furthermore, future research that continues to combine the sequence-pair representation and the MIP-FLP model to solve the FLP is also discussed, indicating the richness of this research domain. / Ph. D.

The currently mainstream mobile application development became part of several programming classes, and courses are being developed focused on mobile app development. There are fundamental differences in programming topics for mobile, including the small screen and finger-based interactions, connectivity using different communication channels, and a large number of sensors. Because of these differences, there is a need to explore different approaches to teach the concepts of mobile development. Integrated approaches and collaborative learning are key to handle the multi-platform environment of mobile development and the diversity of its devices. One practice that has been used in educational contexts for collaborative learning is Pair Programming (PP); an approach that features two developers working on the same development task. Since it became popular in the 1990s, Pair Programming (PP) has been used by developers who worked on desktop and web applications. During the past two decades, PP has been studied in both industrial and classroom settings. Several studies have shown that PP is a pedagogical tool that can help students enhance their productivity and performance. However, PP has not been studied for mobile development courses before. With the challenging nature of mobile development topics, we saw potential benefits for pair-based learning. To cover the challenges of mobile development, we developed an approach that integrates Lectures, hands-on Tutorials, and in-class Pair Programming (PP) sessions (the LTP approach). Although PP has been studied previously in classroom settings, LTP provides an adapted version that better fits the requirements of mobile application development. Integrating PP as a core element of mobile development classes aims at giving opportunities to students to collaborate, share experiences, and solve problems together. Moreover, providing multiple teaching approaches ensures that students would benefit from the variety of education methods. The LTP approach aims at helping Computer Science (CS) educators to develop curricula and manage classes for teaching mobile app development. / Ph. D. / Developing software applications (apps) for mobile devices is different than for traditional desktop and web applications. Mobile devices have small screens, short battery life, limited memory and processing power, and users interact directly with the touchscreens using their fingers with no mouse nor keyboard attached. Therefore, software developers need to be aware of such considerations, as well as communication and connectivity issues that are unique to mobile devices. Since mobile app development is becoming mainstream, many Computer Science (CS) programs are developing courses that are dedicated to teaching mobile software development. Since these courses are pretty new, educators are still exploring ways to help navigate the challenges of developing apps for mobile devices. By investigating several teaching methods, we found out that collaborative learning might be suitable and beneficial in this sort of classes. One specific practice that we wanted to explore was Pair Programming. Pair Programming (PP) is a development practice where two developers work collaboratively on the same machine to build software apps. It has been used in industry as well as in classrooms, and it has several benefits in enhancing students’ productivity and performance. Therefore, our work studies how PP can help students in emerging mobile software development classes. This research provides a teaching approach that integrates Lectures, hands-on Tutorials, and in-class PP sessions (the LTP approach), which aims at helping CS educators to develop curricula and manage classes for teaching mobile app development. Integrating PP as a core element of mobile development classes aims at giving opportunities to students to collaborate, share experiences, and solve problems together. However, the LTP approach provides an adapted version of PP that better fits the requirements of mobile application development. Moreover, providing multiple teaching approaches ensures that students would benefit from the variety of education methods.

Dans notre thèse, nous nous intéressons à la construction d'une infrastructure Pair-à-Pair (P2P) pour la réconciliation des données des applications d'édition de texte collaborative. Cependant, cette tâche est difficile à réaliser étant donné le comportement dynamique des pairs. Au regard de l'état de l'art, le modèle des transformées opérationnelles (OT) est une approche typiquement utilisée pour la gestion de la réplication optimiste dans le contexte d'édition de texte distribuée. Toutefois, la plupart des solutions d'OT ne passent pas à l'échelle et ne sont pas adaptées aux réseaux P2P. Pour répondre à ce problème, nous proposons une nouvelle approche appelée P2P-LTR (Estampillage et Journalisation P2P pour la Réconciliation) pour la réconciliation des données à base d'OT, qui assure la cohérence à terme malgré la dynamicité et les cas de pannes. P2P-LTR offre un service de journalisation P2P et un service d'estampillage fiable et réparti fonctionnant sur un modèle de réseau à base de DHT. Dans notre approche, les mises à jour sont estampillées et stockées en P2P dans des journaux à forte disponibilité. Lors de la réconciliation, ces mises à jour sont récupérées selon un ordre total continu afin d'assurer la cohérence à terme. En outre, P2P-LTR traite les cas où les pairs peuvent rejoindre ou quitter le système pendant les opérations de mise à jour. Nous avons évalué les performances de P2P-LTR par simulation. Les résultats montrent l'efficacité et le passage à l'échelle de notre solution.

Les Systèmes multi-agents ou SMA proposent une approche originale de conception de systèmes intelligents et coopératifs. Ils se caractérisent par la distribution du contrôle global du système et par la présence d'agents autonomes évoluant dans un environnement partagé et dynamique. De plus, il existe plusieurs interdépendances entre les buts des agents, leurs capacités et les ressources qu'ils utilisent, donc afin d'éviter d'éventuels conflits, de favoriser la synergie des activités des agents et de partager les ressources de l’environnement commun, il est important que les agents coordonnent leurs actions. Nous nous sommes intéressés, dans le cadre de cette thèse, au déploiement des systèmes multi-agents sur une architecture pair à pair (Peer-to-Peer ou P2P) et ceci dans le but d’établir la communication entre ces agents et les relier entre eux. Cependant, du fait de la nature dynamique des systèmes P2P où chaque pair peut apparaître et disparaître à tout moment, des nouveaux problèmes se posent pour la coordination d’agents nécessitant des mécanismes de coordination adaptés au contexte spécifique des P2P. Pour cela, nous avons proposé une méthode de formation de groupe comme solution à ces problèmes. Nous nous sommes intéressés ensuite à l’application des systèmes multi-agents à architecture P2P au domaine d’apprentissage collaboratif en ligne où des apprenants contribuent aux apprentissages du groupe, et en retour, le groupe contribue à ceux des apprenants et c’est la cohérence du collectif qui permet d’atteindre l’objectif. Cependant, l’apprentissage collaboratif à distance implique des nouveaux rôles pour l’enseignant ainsi que pour les apprenants. Il est donc essentiel de définir ces rôles pour identifier les besoins qui en découlent pour pouvoir intégrer à l’outil informatique des fonctionnalités afin de satisfaire ces besoins. En effet, il est essentiel de fournir aux enseignants et apprenants la possibilité d’avoir des informations sur la progression de leur apprentissage ainsi que sur les niveaux de collaboration et de sociabilité de chaque apprenant et du groupe. Enfin, nous avons proposé, comme application de nos travaux, un système appelé COLYPAN (COllaborative Learning sYstem for Project mANagment) conçu pour l’apprentissage à distance et de façon collaborative de la gestion des projets. / Multi-Agents systems (MAS) propose an original approach to design intelligent and cooperative systems. They are characterized by the distribution of the overall system control and the presence of autonomous agents operating in a shared and dynamic environment. In addition, there are many interdependencies between: agents' goals, their abilities and used resources. So, in order to avoid possible conflicts, promote synergy of agents activities and share resources of the common environment, it is important that the agents coordinate their actions. We are interested, in the context of this thesis, in the deployment of multi-agents systems on Peer-to-Peer (P2P) networks in order to establish communication between these agents. However, because of the dynamic nature of P2P systems where each peer may appear and disappear at any time, new problems arise concerning the coordination of agents. Thus, coordination mechanisms adapted to the specific context of P2P are required. For that, we have proposed a group formation method to solve these problems. Then, we were interested in the usage of multi-agents systems with P2P architecture in the field of collaborative e-learning. In such applications, each learner contributes in the learning process of the group, and in return, the group contributes in the learning process of its members. The consistency of the whole group allows to achieve the goal. However, collaborative e-learning implies new roles for teachers as well as for learners. It is therefore essential to define these roles in order to identify the users needs and integrate, in the platform, the functionalities that allows us to satisfy such needs. Indeed, it is essential to provide teachers and learners with the opportunity to obtain information about the progress of their learning processes as well as the level of collaboration and sociability of each learner in the group. Finally, we have proposed, as an application of our work, a system called COLYPAN (COllaborative Learning sYstem for Project management) designed for the collaborative e-Learning project management.