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The microstructure and physical properties of hot pressed (Hf, Ti) C have been investigated with the aim of producing a cutting tool material with similar hardness to that of WC-Co and TiC-based cermets. Sintered samples were hot pressed from HfC0.7 and TiC0.9 powders using powder metallurgical techniques and the processing cycle was optimized for this system. Ni was used as a binder in selected samples and C black was added to compensate for sub-stoichiometry and to aid in the reduction of oxides formed during milling. Microstructural analyses were performed by scanning and transmission electron microscopy (SEM and TEM) and the composition was determined from X-ray diffraction (XRD) and energy dispersive X-ray spectrometry (EDS). The physical properties measured are density and Vickers hardness, and the indentation fracture toughness was determined using the Shetty formula. The fundamental interactions between HfC, TiC and Ni during hot pressing were investigated and the results obtained used to explain the microstructure that develops in samples made from powder mixtures. The interactions studied are the inter-diffusion of HfC and TiC through the solid state, and the dissolution and re-precipitation rate of the carbides in a liquid Ni binder. EDS analysis revealed that the rate at which Ti diffuses into HfC is higher than the rate at which Hf diffuses into TiC. Upper limits to the diffusion coefficients for these processes are determined and show that solid solution carbides will form from HfC + TiC powder mixtures at 2000 ºC in 1 hour if the average powder particle size is less than 5 μm. The diffusion rates decrease with a decrease in hot pressing temperature but mass transport between the phases can be enhanced by addition of a metallic binder. TEM and EDS analysis shows that Ni wets TiC more efficiently than HfC and that the solubility of TiC in Ni is also higher than that of HfC. The grain size of the carbide phases increases with an increase in the rate at which they dissolve into and re-precipitate from the liquid binder. The crystal structure of the binder phase depends on the concentration of Ti and Hf that remain in the binder after cooling and the carbide phase in which the binder is embedded. Analysis of TEM electron diffraction patterns show that the binder phase consists of cubic solid solutions as well as intermetallic and cubic phases in which atomic ordering is observed.

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Cette thèse prend pour objet d’étude l’innovation pédagogique dans les universités palestiniennes. Elle émet l’hypothèse de l’échec de l’intervention de l’Université Islamique de Gaza à construire des usages constructivistes autour du portfolio dans ses programmes pratiques de la formation initiale des maîtres. Cet échec est dû à l’incapacité de provoquer un changement de fond du modèle pédagogique traditionnel en place, faute notamment d’une considération complexe du processus de l’innovation. A la lumière des résultats obtenus, la chercheuse conçoit une modélisation de soutien à la transition entre les deux modèles pédagogiques sous-jacents : béhavioriste et constructiviste. Dans ce cadre, la chercheuse a eu recours aux apports de l’ingénierie pédagogique de la façon la plus proche possible des approches de la gestion universitaire en Palestine. Tout au long de cette recherche, des éléments éclairant le contexte éducatif palestinien ont été révélés dans un diagnostic holistique et critique afin de pouvoir trouver l’équilibre entre deux perspectives : développer une réflexion théorique et épistémologique valable sur la professionnalisation des enseignants palestiniens et optimiser les ingénieries de pilotage de cette professionnalisation à faire émerger dans un contexte particulièrement complexe. / This thesis discusses the qualitative contributions of pedagogical innovation initiatives in Palestinian Universities. The research examines the integration of the portfolio into the pre-service teacher education program conducted by Islamic University of Gaza. The study hypothesizes the failure of this intervention to create constructive learning activities due mainly to the incapacity of producing a deep change on the established traditional model of learning. This failure comes mostly from the lack of the complexity of conducted innovation process. This study uses qualitative research method with a focus on macro policy analysis. In light of the obtained results, the researcher concludes with developing a conceptual model to support the transition between the two underlying pedagogical models: behaviorist and constructivist. In this context, the researcher makes use of the contributions of instructional design science of the closest way possible to university management approaches in Palestine.

Background It is estimated that up to 50% of individuals begin dialysis with a suboptimal start. Objective To explore the transition to home dialysis, with a special emphasis on this transition after a suboptimal start. Methods A two-phased mixed methods study including: 1) a scoping review and meta-synthesis on the facilitators and barriers to home dialysis and 2) a qualitative study using thematic analysis on the transition to home dialysis after a suboptimal start. Findings 12 studies were included in the scoping review. Principle facilitators and barriers included Support, Burden of Care, and Disruption of Life. Six individuals were included into the qualitative phase. Through their interviews, they expressed the importance of the timely delivery of information, support, living with loss, managing fear, living with hope, and learning to live with dialysis. Conclusions The facilitators and barriers to home dialysis were similar in both studies suggesting that the transition to home dialysis is similar regardless of the nature of dialysis start. Several subthemes obtained from the qualitative study however revealed that a suboptimal dialysis start entails unique challenges, requiring the delivery of more support and education.