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Various commodity plastics used today are based on fossil fuels. Most of these plastics are non-biodegradable and will persist in the environment over a long time. The bioplastics from renewable resources have the potential to support a greener economy. The two of such renewably resourced bioplastics are poly (hydroxyl butyrate-co-valerate), PHBV and poly (butylene succinate), PBS. We have used petro-based PBS in our study, but renewable resource based PBS is expected to be available on a commercial scale in a very near future. These two bioplastics are both biodegradable. These two bioplastics are both biodegradable. In our study we have used PBS from petroleum resource but PHBV is a brittle bioplastic with a high modulus value and a low elongation at break while PBS is a low modulus bioplastic with a high elongation at break. Complementary properties can be obtained by blending PHBV and PBS. The direct melt blends showed poor mechanical properties due to limited interaction between PHBV and PBS phases. This research focuses on increasing the interaction between PHBV and PBS blends by using compatibilizers. The compatibilizers used in this thesis were dicumyl peroxide, DCP and trimethylolpropane triacrylate, TMPTA. Use of an in situ compatibilization method was done for the melt mixing of PHBV and PBS yielding blends with improved characteristics. The investigations were performed at three different ratios of PHBV and PBS blends. The increase in the compatibility between the two phases was demonstrated through various thermal, thermo-mechanical, rheological and morphological means. The increase in elongation at break was used as a primary marker for compatibilization. The optimization of DCP and TMPTA was carried out, which showed the enhanced interaction between PHBV and PBS phases, with the successful stress transfer from PHBV phase to the PBS phase resulting in increase in elongation at break. Inward shifts in tan delta peak on addition of DCP and TMPTA to the blends also showed increase in compatibility between the two phases. The interfacial adhesion between a brittle and ductile polymer, PHBV and PBS respectively was increased by using DCP and TMPTA. This opened gateways to various novel applications of PHBV and PBS blends via in situ reactive extrusion process. / The Ontario Ministry of Agriculture, Food, and Rural Affairs (OMAFRA) for their financial support via New directions research program (SR9235). We would also like to thank Canadian Foundation for Innovation (CFI) and Ontario Ministry of Agriculture, Food, and Rural Affairs (OMAFRA) for their equipment supports.

Crew planning is a complex optimization problem that usually is divided into two separate parts, pairing and rostering. In the rostering process crewmembers are assigned a personal roster, a schedule, for the next coming time period. In order for the crew to have an influence on their roster, SAS have implemented a Preferential Bidding System (PBS) where the crew has the ability to express their wishes regarding their roster, formulated as bids. Generally there is an outspoken dissatisfaction among the crew about PBS and how it works and therefore the questions were raised of how the system could be more transparent and how the bid fulfillment could be communicated both internally and externally. The performed analysis was made with regard to bidding pattern and bid fulfillment and was both quantitative and qualitative. The quantitative part consisted of a thorough review of historic data (delimited to only four months) and a questionnaire, targeting the whole crew collective, was set up as a complementary qualitative analysis. In this thesis the work and result is presented. The result of the analysis shows that satisfaction felt by the crew cannot be directly compared to bid fulfillment as it is measured today. The major aspects of improving the PBS should include a simplification regarding mainly bid types, but also actions in order to increase the transparency of the system and awareness. The recommendation to SAS is to present statistics to crew for each bid type regarding number of placed bids, number of possible fulfillments and how much that is fulfilled thus visualizing the possibility to get a bid fulfilled. A revised range of bid types have also been recommended along with a few minor changes.

This PhD project investigated the effects of a co-continuous phase structure on the ductility of poly(lactic acid) (PLA) blends. An empirical model was used to predict the phase inversion point of the blends. The co-continuous phase morphology was first observed in polybutylene succinate(PBS)/PLA blends. With as little as 10 wt% of PBS, PBS/PLA blends achieved a dramatic improvement in ductility, over 250% elongation-to-break. Clay additives were incorporated in PBS/PLA blends. Clay was found out to affect the compatibility and co-continuous phase morphology of PBS/PLA blends. The clay dispersion was found to have an intercalated and exfoliated structure at a PBS/PLA composition ratio of 20/80. The clay particles increased the mixing conditions between the polymers by producing a finer structure, but also destroyed the co-continuous phase morphology, resulting in a substantial decrease in elongation-at-break. PLA was then blended with Poly(butylene adipate-co-terephthalate) (PBAT) to examine whether the co-continuous phase model could also be applied to other PLA-polymer blends. From the melt viscosity ratio of PLA and PBAT in the processing regime used in the study, the predicted phase inversion value was 19 wt% of PBAT. This value was verified by the results of mechanical properties, where results for elongation-to-break show a dramatic rise from around 10% up to 300% in the composition range between 10 and 20wt% of PBAT. Polyhydroxyalkanoate (PHA) was also blended with PLA and this project investigated how co-continuous phase morphology affects the blends of two brittle polymers. It was found that when PHA content ranged from 10 to 20wt%, the brittle-brittle polymer blends showed ductile behaviour due to a plane stress effect.

Light-harvesting devices made from lead sulfide quantum dot (QD) absorbers are one of the many promising technologies of third-generation photovoltaics. Their simple, solution-based fabrication, together with a highly tunable and broad light absorption makes their application in newly developed solar cells, particularly promising. In order to yield devices with reduced voltage and current losses, PbS QDs need to have strategically passivated surfaces, most commonly achieved through lead iodide and bromide passivation. The interdot spacing is then predominantly filled with residual amorphous lead halide species that remain from the ligand exchange, thus hindering efficient charge transport and reducing device stability. Herein, it is demonstrated that a post-treatment by iodide-based 2-phenylethlyammonium salts and intermediate 2D perovskite formation can be used to manage the lead halide excess in the PbS QD active layer. This treatment results in improved device performance and increased shelf-life stability, demonstrating the importance of interdot spacing management in PbS QD photovoltaics.

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No / The use of queue thresholds is a well known technique for network traffic congestion control. This motivates the study of a single server queue with R(R ¿ 2) distinct priority classes under Head of Line (HoL) service priority discipline, Partial Buffer Sharing (PBS) scheme and a finite capacity vector N, representing a sequence of thresholds (N1, N2, ¿ , NR) for each class jobs. The external traffic is modelled using the compound Poisson process or generalised exponential (GE) distribution which can capture the bursty property of the network traffic. The transmission times have also been modelled using the GE distribution to depict the bulk departures from the system. Using a GE/GE/1/N approximation, a closed form cost-effective analytical solution is obtained using the principle of maximum entropy (ME). The forms of the joint, aggregate and marginal state probabilities, as well as basic performance measures such as utilisation and blocking probabilities are analytically established at equilibrium via appropriate mean value constraints and the generating function approach. Consequently, efficient recursive expressions of low computational cost are determined. Typical numerical experiments are included to illustrate the credibility of the proposed mechanism in the context of different QoS grades for various network traffic classes. This model, therefore, can be used as a powerful tool to provide a required grade of service to a particular class of traffic in any heterogeneous networks.

Ce travail concerne le développement de polymères alvéolaires biosourcés adaptés à l’injection microcellulaire physique (Mucell®) ainsi que l’identification des leviers (procédé et/ou matériau) permettant de contrôler la structure cellulaire.Les paramètres directeurs du procédé ont été optimisés à l’aide d’un plan d’expérience de type Taguchi permettant d’atteindre un allégement de 15% tout en conservant un niveau de performance mécanique acceptable. Par ailleurs, des modifications structurales du PBS ont été menées dans le but de contrôler le processus de formation de la structure cellulaire (dissolution du gaz, nucléation, croissance cellulaire et stabilisation de la structure). La morphologie cellulaire a été améliorée en modifiant la conformation moléculaire des chaînes, en favorisant la nucléation hétérogène ou en modifiant les propriétés élongationnelles et la tension de surface du matériau. La formulation résultante a permis une diminution de plus de 80% de la taille des cellules et une densité cellulaire multipliée par 450.Enfin, une technique de mesure du comportement rhéologique du système monophasé polymère/gaz a été développée à l’aide d’une buse instrumentée en ligne permettant d’évaluer l’effet de la dissolution du gaz sur la viscosité du matériau en fonction des conditions expérimentales de l’étude. / This work focused on the development of biobased polymer foams adapted to the microcellular injection molding (Mucell®) and the identification of the key parameters (process and/or material) controlling the cell structure.The process parameters were optimized using a Taguchi design of experiment which achieves 15% lightweighting while maintaining acceptable mechanical performances. In addition, structural modifications of PBS were carried out in order to control the foaming mechanism (gas dissolution, cell nucleation, cell growth and cell stabilization). Cell morphology has been improved by modifying the molecular conformation, promoting heterogeneous nucleation, or by adjusting the extensional viscosity and surface tension of the material. The resulting formulation exhibit a decrease of more than 80% in cell size and a cell density multiplied by 450.Finally, a measurement technique for the rheological behavior of the single phase polymer/gas mixture was developed using an instrumented on-line nozzle to evaluate the effect of gas dissolution on the viscosity under experimental conditions.

The purpose of the study was to further examine the potential efficacy of the Bully Prevention in Positive Behavior Support (BP-PBS) program in addressing bullying in an urban public elementary school with a large and diverse student population, implementing school-wide positive behavior support with relatively low fidelity. Specifically, the study examined the extent to which BP-PBS could decrease target students’ bullying behavior across settings and increase appropriate active response to bullying of students being bullied. Changes in the students’ perceptions and attitudes on school safety were also examined. This study involved a multiple probe design across participants targeting multiple settings for six students (three bullies and three victims) to assess the impact of the BP-PBS intervention and to examine its generalization effects to a non-targeted setting. The results indicated that the BP-PBS intervention was effective in reducing the target students’ bullying maintained by peer and adult attention and increasing active response to bullying. The intervention also increased positive perceptions and attitudes on school safety in students being bullied and the bullies. Changes in student bullying and appropriate and inappropriate responses to bullying were generalized to non-training settings and remained at intervention levels for all participants. Social validity surveys indicated high acceptability of the BP-PBS intervention by teachers.