The purpose of this research work was to develop a nozzle capable of depositing dense CoNiCrAlY coatings via cold gas dynamic spray (CGDS) as well as compare the oxidation performance of bond coats manufactured by CGDS, high-velocity oxy-fuel (HVOF) and air plasma spray (APS) at temperatures of 1000°C and 1100°C. The work was divided in two sections, the design and manufacturing of a CGDS nozzle with an optimal profile for the deposition of CoNiCrAlY powders and the comparison of the oxidation performance of CoNiCrAlY bond coats. Throughout this work, it was shown that the quality of coatings deposited via CGDS can be increased by the use of a nozzle of optimal profile and that early formation of protective α-Al2O3 due to an oxidation temperature of 1100°C as opposed to 1000°C is beneficial to the overall oxidation performance of CoNiCrAlY coatings.

[EN] In the last years, several studies have been developed in order to guarantee safety operation of Nuclear Power Plants (NPP), for both, the design plant life and for the Long Term Operation (LTO). In those situations, NPP must face the Periodic Safety Review (PSR). An important part of PRS involves the evaluation of risk impact of Structures, Systems and Components (SSC) ageing and how current asset management programs, e.g. maintenance and testing programs, are successful to achieve the objective of allowing a safe operation. In order to perform this evaluation, it is necessary to extend the current Probabilistic Safety Assessment (PSA) models to take into account, not only equipment ageing, but also maintenance and testing policies. This Ph Dissertation aims to help in NPP safety evaluation in the framework of PSR in both, design life and long-term operation. In this context, two main objectives are proposed. The first one is based on the proposal and application of risk-informed decision making methodology to evaluate the impact of changes to licensing bases, particularly in the ETF, using PSA models and considering aleatory uncertainties. The second is based on the adaptation and development of SSC reliability and availability models to consider not only the effect of aging, but also the effect of components management policies, in particular the testing and maintenance. Finally, these models have been joined to APS in order to obtain a new and extended APS (APSE). Some application cases, for both, risk-informed decision making on changes of licensing bases and for the use of the new APSA in the process of decision making, are provided in order to assess the feasibility and applicability of the new methodologies proposed The work of this thesis is part of the research supported by the Ministry of Economy and Competitiveness in the project ENE2013-45540-R, "Development of Advanced Surveillance Requirements with a focus on safety and competitiveness of Nuclear Power Plants operation in the long term", and in the Doctoral Fellow ENE2010-17449. / [ES] En los últimos años se han desarrollado diversos estudios enfocados a garantizar la operación segura de las centrales nucleares (CCNN), tanto en la operación dentro de la vida de diseño como en la operación a largo plazo. En ambos casos, las centrales deben de afrontar una Revisión Periódica de Seguridad (RPS), la cual, involucra, entre otras tareas, la evaluación del impacto en el riesgo del envejecimiento de Estructuras, Sistemas y Componentes (ESC) y del papel de los programas de gestión de activos, tales como los programas de vigilancia y de mantenimiento de la central. Para llevar a cabo esta evaluación, urge la necesidad de extender los modelos actuales del Análisis Probabilista de Seguridad (APS) para que tenga en cuenta de forma explícita no sólo el efecto del envejecimiento sino también el efecto de las políticas de gestión de componentes activos, en particular, las pruebas y mantenimientos. La presente tesis doctoral pretende servir de ayuda en las evaluaciones de la seguridad de las CCNN, y en el contexto de las RPS, tanto en la operación dentro de la vida de diseño como en la operación a largo plazo. En este contexto se plantean dos objetivos principales. El primero, se basa en la propuesta y aplicación de una metodología de toma de decisiones basada en la utilización de los modelos y datos del APS para llevar a cabo la evaluación del impacto en el riesgo de cambios en las bases de licencia, concretamente en las ETF de las CCNN, en presencia de incertidumbres. El segundo, se basa en la adaptación y desarrollo de los modelos de fiabilidad y disponibilidad convencionales de ESC para que consideren de forma explícita no sólo el efecto del envejecimiento, sino también el efecto de las políticas de gestión de componentes activos, en particular de las pruebas y mantenimiento. Finalmente, estos modelos se han incorporado al APS con el objetivo de obtener un nuevo APS Extendido (APSE). Tanto para la toma de decisiones informada en el riesgo para cambios en las bases de licencia, cómo para la toma de decisiones utilizando el nuevo modelo extendido, APSE, se aportan casos de aplicación que demuestran la viabilidad y aplicabilidad de los mismos. El trabajo realizado en la presente tesis doctoral se enmarca dentro de la línea de investigación financiada por el Ministerio de Economía y Competitividad en el proyecto ENE2013-45540-R, "Desarrollo de Requisitos de vigilancia avanzados enfocados a la seguridad y competitividad de la operación a largo plazo de centrales nucleares" y en la beca de Formación de Personal Investigador (FPI) ENE2010-17449. / [CAT] En els últims anys s'han desenvolupat diversos estudis enfocats a garantir l'operació segura de les centrals nuclears (CCNN), tant en l'operació dins de la vida de disseny com en l'operació a llarg termini. En ambdos casos, les centrals han d'afrontar una Revisió Periòdica de Seguretat (RPS), la qual, involucra, entre altres tasques, l'avaluació de l'impacte en el risc de l'envelliment d'Estructures, Sistemes i components (ESC) i del paper dels programes de gestió d'actius, com els programes de vigilància i de manteniment de la central. Per dur a terme aquesta avaluació, urgeix la necessitat d'estendre els models actuals de l'Anàlisi Probabilista de Seguretat (APS) perquè tinga en compte de manera explícita no sols l'efecte de l'envelliment sinó també l'efecte de les polítiques de gestió de components actius, en particular, les proves i manteniments. La present tesi doctoral pretén servir d'ajuda en les avaluacions de la seguretat de les CCNN, i en el context de les RPS, tant en l'operació dins de la vida de disseny com en l'operació a llarg termini. En aquest context es plantegen dos objectius principals. El primer, es basa en la proposta i aplicació d'una metodologia de presa de decisions basada en la utilització dels models i dades de l'APS per a dur a terme l'avaluació de l'impacte en el risc de canvis en les bases de llicència, concretament en les ETF de les CCNN, en presència d'incerteses. El segon, es basa en l'adaptació i desenvolupament dels models de fiabilitat i disponibilitat convencionals d'estructures, sistemes i components perquè considerin de forma explícita no només l'efecte de l'envelliment, sinó també l'efecte de les polítiques de gestió de components actius, en particular de les proves i manteniment. Finalment, aquests models s'han incorporat al APS amb l'objectiu d'obtenir un nou APS Estès (APSE). Tant per a la presa de decisions informada en el risc per canvis en les bases de llicència com per a la presa de decisions utilitzant el nou model estès, APSE, s'aporten casos d'aplicació que demostren la viabilitat i aplicabilitat dels mateixos. El treball realitzat en la present tesi doctoral s'emmarca dins de la línia d'investigació finançada pel Ministeri d'Economia i Competitivitat en el projecte ENE2013-45540-R, "Desarrollo de Requisitos de vigilancia avanzados enfocados a la seguridad y competitividad de la operación a largo plazo de centrales nucleares" i en la beca de Formació de Personal Investigador (FPI) ENE2010-17449. / Martón Lluch, I. (2015). Gestión de la operación, vigilancia y mantenimiento de equipos de seguridad de centrales nucleares a corto y largo plazo [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/58615 / TESIS

The thesis deals with choosing the appropriate conception for a 3D CNC machining module, design, and construction of the given machine. This work is laid out into several parts that deal with automated production assemblies, appropriate construction alternate design, design of the selected machining module, and FEM method.

A solution-hardening of AISI 316L stainless-steel powder was conducted. The expansion of the crystal lattice and a strong increase in the nanoindentation hardness confirm the successful diffusion of carbon and nitrogen in the interstices. A multiphase state of the powder feedstock with phase fractions of the metastable S-phase (expanded austenite) mainly at the particle’s edge, and the initial austenitic phase within the core was found. Thermal spraying using high velocity oxy-fuel (HVOF) and atmospheric plasma spraying (APS) prove the sufficient thermal stability of the Sphase. Microstructural investigations of the HVOF coating reveal the ductility of the S-phase layer, while the higher heat load within the APS cause diffusion processes with the initial austenitic phase. The lattice expansion and the nanoindentation hardness decrease during thermal spraying. However, the absence of precipitates ensures the sufficient heat stability of the metastable S-phase. Even though further efforts are required for the thermochemical treatment of powder feedstock, the results confirm the feasibility of the novel powder treatment approach.

This master thesis project was performed in collaboration with Scania CV AB, Engine Materials group. The purpose with the project was to investigate different ceramic TBC (Thermal Barrier Coating) thermal insulation properties inside the combustion chamber. Experimental testing was performed with a Single-Cylinder engine with TBC deposited on selected components. A dummy-valve was developed and manufactured specifically for this test in order to enable a water cooling system and to ease the testing procedure. The dummy-valve consists of a headlock, socket, valve poppet and valve shaft. Additionally, a copper ring is mounted between the cylinder head and the valve poppet to seal the system from combustion gases. Thermocouples attached to the modified valve poppet and valve shaft measured the temperature during engine test to calculate the heat flux. The TBCs consisted of three different materials: 7-8% yttrium-stabilized zirconia (8YSZ), gadolinium zirconia and lanthanum zirconia. The 8YSZ TBC was tested as standard, but also with microstructural modifications. Modifications such as pre-induced segmented cracks, nanostructured zones and sealed porosity were used. The results indicated that the heat flux of 8YSZ-standard, 8YSZ-nano and 8YSZ-segmented cracks was in level with the steel reference. In the case of 8YSZ-sealed porosity the heat flux was measured higher than the steel reference. Since 8YSZ-standard and 8YSZ-sealed porosity are deposited with the same powder it is believed that the high heat flux is caused by radiative heat transfer. The remaining samples have had some microstructural changes during engine testing. 8YSZ-nano had undergone sintering and its nanostructured zones became fewer and almost gone after engine testing leading to less heat barrier in the top coat of the TBC. However, for 8YSZ-segmented cracks and gadolinium zirconia lower heat flux was measured due to the appearance of horizontal cracks. These cracks are believed to act as internal barriers as they are orientated perpendicular to the heat flow. During long-time (5 hour) engine tests the 8YSZ-standard exhibited the same phenomena: a decrease in heat flux due to propagation of horizontal cracks. One-dimensional heat flux was not achieved and the main reason for that was caused by heating and cooling of the shafts outer surface. However, the dummy-valve system has proven to be a quick, easy and stable to perform tests with a Single-Cylinder engine. Both water-cooling and long-time engine tests were conducted with minor issues. The dummy-valve has been further developed for future tests. Changes to the valve shaft are the most remarkable: smaller diameter to reduce heat transfer and smaller pockets to ensure better thermocouple positioning. Another issue was gas leakage from the combustion chamber through the copper ring and valve poppet joint. The copper ring will be designed with a 1 mm thick track to improve sealing, hence better attachment to the valve poppet.

Il coordinamento dell’aiuto pubblico allo sviluppo, evocato negli ultimi anni da più parti come la soluzione alla deludente efficacia degli aiuti è in realtà un argomento che nasce quasi contemporaneamente alle prime organizzazioni internazionali dedicate allo sviluppo . La funzione ambivalente delle Nazioni Unite, agente di mediazione diplomatica da un lato (mediazione tra stati e tra gruppi di potere all’interno dello stesso stato), e agente di sviluppo dall’altro, garantisce all’organizzazione un ruolo preminente nel coordinamento degli aiuti nei contesti di guerra e di post-conflitto. E’ questa stessa ambivalenza che impone all’organizzazione un rapporto ufficiale con i territori sottosviluppati, incardinato nella relazione con i governi centrali degli stati. La critica radicale all’aiuto pubblico allo sviluppo individua tutte le distorsioni politiche ed economiche legate all’afflusso dei fondi, sottolineandone le aggravanti possibili laddove esista una discrasia tra gli obiettivi di sviluppo delle Nazioni Unite e quelli dell’élite che occupa le posizioni apicali dello stato. Questa ricerca attraverso un’analisi storica del contesto, mette in luce l’interazione tra il sistema degli aiuti e il sistema-paese in Tajikistan dall’ingresso delle organizzazioni ai giorni nostri. L’analisi dimostra infine che la struttura politico-economica radicata sul territorio, pur conservando i tratti di uno “stato predatorio” (tratti non alleviati bensì aggravati dalle distorsioni legate all’afflusso dei fondi per lo sviluppo), sfugge in realtà alla definizione stessa di “Stato”. Questo dato rivela una debolezza insita nell’approccio metodologico del sistema degli aiuti che si fonda proprio sull’archetipo dello “Stato”. / The Official Development Assistance (ODA) coordination has been recently launched as a genuine mean to increase aid effectiveness. Actually, the “aid coordination” paradigm was born almost contemporaneously to the first international organizations dedicated to “development”. The ambivalent function of the United Nation that acts both as an agent of diplomatic mediation (among states and among different lobbies within the borders of the same state), and as a development agent, guarantees to United Nations a preeminent role in the field of aid coordination in conflict and post-conflict contexts. It’s this real ambivalence that compels the United Nations to deal with development countries through official relations with the central governments. The radical critique to development aid shows different political and economic distortions related to the incidence of foreign funds. At the same time, it underlines that wherever the goals of the official governments diverge from the development goals of the aid community these distortions might be even more burdensome for the country. This research, through an historical analysis, draws attention on the interaction among the development industry and the country-system in Tajikistan from the arrival of the international organizations to our days. The analysis demonstrates that the political and economic structure of the country, while maintaining the features of a “predatory state” (features which are not alleviated but worsened by the distortions brought about by the aid industry), simply do not comply with the definition of a “State”. This result highlights an innate weakness of the aid industry methodological approach that is in fact, fully based on the political archetype of the “State”.

Les composites de type Cf/C sont utilisés en tant que pièces structurales dans les propulseurs spatiaux du fait de leurs excellentes propriétés mécaniques dans le domaine des très hautes températures. Néanmoins, l’atmosphère oxydante et corrosive créée lors du décollage des lanceurs et les hauts flux gazeux dégradent ces matériaux. Afin d’améliorer les performances de ces matériaux vis-à-vis de l’oxydation/corrosion, une protection composée de céramiques ultra-réfractaires (dites UHTC) peut être appliquée. Pour une efficacité de protection optimale, des phases UHTC ont été introduites en tant que constituants de la matrice. Dans ces travaux de thèse, la matrice a été réalisée par l’intermédiaire d’un procédé d’élaboration en phase liquide combinant : (i) l’introduction de poudres et (ii) la densification par infiltration réactive d’un métal fondu. La composition de la matrice appartient au système (B;C;Si;Zr). La caractérisation des matériaux après élaboration a permis de comprendre les mécanismes d’infiltration et les réactions permettant de mieux contrôler la composition chimique et la répartition des phases. Des essais sous torche oxyacétylénique ont été utilisés pour se placer dans des conditions proches de l’application visée. La caractérisation post-test des matériaux a permis d’évaluer l’efficacité de la protection dans le cas d’une utilisation unique et également d’une possible réutilisation. Les résultats en oxydation/corrosion ont permis de classer les matériaux en fonction de leur efficacité de protection. / Since many decades, Carbon/Carbon composites are used as structural parts in rocket engines due to their excellent thermomechanical properties. However, under highly oxidizing/corrosive atmosphere and high gas flow rates, carbon suffers from severe oxidation. To improve oxidation resistance of these composites, Ultra High Temperature Ceramics (UHTC) can be used as a protection. To protect the whole composite, the introduction of UHTC as a matrix has been done using a liquid phase process combining: (i) slurry infiltration process and (ii) reactive melt infiltration. Matrix constituents belong to the (B;C;Si;Zr) system. Material characterisation allowed a better understanding of the infiltration mechanisms and of the phase distribution and composition in respect to the processing conditions. To select the best composition, oxyacetylene torch testing has been done to recreate spacecraft launch environmental conditions. Post-test characterisation has been done to evaluate protection efficiency of each matrix composition for single use and possible reuse. Finally, advantages and drawbacks assessment of each composition allowed to highlight the most protective composition and phase distribution.

Made available in DSpace on 2011-05-04T12:42:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2010 / A coordenação dos cuidados é um tema pendente tanto para os países europeus, quanto para países latinoamericanos. Mudanças no perfil epidemiológico, sobretudo, predomínio das doenças crônicas e a reconhecida fragmentação dos sistemas de saúde e a descontinuidade na prestação do cuidado tornaram premente a busca de soluções. A coordenação dos cuidados pode ser definida como a articulação entre os diversos serviços e ações relacionados à atenção em saúde de forma que, independentemente do local onde sejam prestados, estejam sincronizados e voltados ao alcance de um objetivo comum. O presente estudo teve por objetivo descrever e analisar o desenvolvimento de estratégias e instrumentos de coordenação dos cuidados em municípios brasileiros com experiências exitosas de expansão e consolidação da Estratégia Saúde da Família (ESF) com base em dois eixos: fortalecimento da Atenção Primária à Saúde (APS) e integração entre níveis assistenciais . Partiu-se de duas premissas. Somente uma APS fortalecida em seus atributos essenciais poderia assumir a coordenação doscuidados. Logo, nos interessou saber quais as iniciativas empreendidas pelos municípios brasileiros para fortalecer a ESF. Segundo, sendo a integração da rede um elemento necessário para alcançar melhor coordenação dos cuidados, quais as estratégias e instrumentos desenvolvidos por grandes centros urbanos para integrar a ESF aos demais níveis do sistema? Os municípios analisados foram Aracaju, Belo Horizonte, Florianópolis e Vitória. A consolidação de uma APS forte foi avaliada pela posição ocupada pela ESF no sistema de saúde, capacidade de resolução, reconhecimento profissional e social de seus trabalhadores, descentralização das ações de saúde coletiva para a APS e conseqüentes reflexos no acesso e utilização dos serviços. As estratégias de integração entre níveis assistenciais foram descritas e analisadas com base na identificação das estruturas de regulação da rede de serviços de saúde, instrumentos de integração e de continuidade informacional e organização de fluxos. Neste estudo não tivemos como objetivo medir ou avaliar a coordenação dos cuidados em si, mas descrever e analisar elementos que contribuam para sua consecução. Os resultados apresentados são produtos de três fontes principais, trianguladas para responder às perguntas de investigação: entrevistas com gestores e estudos transversais com aplicação de questionários a amostra de famílias cadastradas e profissionais das equipes de Saúde da Família. Os resultados apontam que em todos os municípios foram identificadas ações para fortalecer as estruturas de APS no contexto do Sistema Único de Saúde, em etapas distintas de implementação. As iniciativas mais exitosas foram aquelas que buscaram ampliar a acessibilidade, consolidar a função de porta de entrada, aumentar sua capacidade resolutiva e articular medidas de saúde pública, vigilância e assistência. Ainda assim, permanecem desafios para melhor equalizar atendimento à demanda espontânea e à programada de formamais resolutiva e para tornar a Unidade de Saúde da Família o serviço de uso regular. A baixa credibilidade e o insuficiente reconhecimento dos profissionais de atenção primária representam obstáculo à coordenação dos cuidados por esse nível de atenção. Em relação à integração da rede, estratégias semelhantes, com resultados diferenciados, foram encontradasnos quatro casos como investimentos em sistemas informatizados e descentralizados de regulação, monitoramento das filas de espera, aumento da oferta de serviços próprios municipais, implantação de protocolos clínicos e prontuários eletrônicos. Ainda assim, a ausência de regulação e de fluxos formais para a atenção hospitalar torna incompleto o processo de integração da rede. A insuficiência na oferta de atenção especializada, agravada pela pouca integração entre prestadores estaduais e municipais foi outra dificuldade identificada. A quase ausência de contra-referência também minimiza as possibilidades de coordenação dos cuidados pela equipe de APS. O retrato oferecido pela pesquisa mostra que Belo Horizonte e Vitória apresentaram sistematicamente melhores resultados na avaliação de profissionais e usuários em relação aos dois eixos de análise. Pode-se afirmar que a APS se fortaleceu e está mais integrada à rede nos casos estudados, embora ainda não seja acoordenadora de todo o ciclo de cuidados. A necessidade de estabelecer objetivos comuns, de forma que o cuidado em saúde tenha o usuário como centro e seja organizado de acordo com suas expectativas pessoais e necessidades em saúde, componentes do atributo da coordenação, aponta alguns caminhos para a construção de um Sistema Único de Saúde mais equânime, de melhor qualidade e voltado às necessidades de saúde da população. / Coordination of care is an issue pending in both European and Latin American countries. Changes in epidemiological profile, particularly the predominance of chronic diseases, plus the acknowledged fragmentation in health systems and discontinuity in care, recommend urgent solutions. Coordination of care can be defined as an interrelationship among healthcare-related services and actions such that, regardless of where they occur, they are synchronised and directed to achieving a common purpose. The intention of this study was to describe and analyse the development of strategies and instruments for coordinating care in Brazilian municipalities with successful experience in expanding and consolidating the Family Health Strategy (Estratégia Saúde da Família, ESF) through two key axis: “strengthening Primary Health Care” (PHC) and “integrating among levels of care”. The study rests on two assumptions. Firstly, only PHC that is strong in its essential attributes will be capable of coordinating care. It was therefore of interest to learn what measures Brazilian municipalities had taken to strengthen the ESF. Secondly, given that system integration is a necessary element for achieving improved coordination of care, what strategies and instruments have been developed for integrating the ESF with the other system levels in major urban centres? The municipalities studied were Aracaju, Belo Horizonte, Florianópolis and Vitória. Whether or not strong” PHC had been established was evaluated in terms of the position the ESF occupied in the health system, its resolution capacity, professional’s and social’s recognition of health workers, the decentralisation of collective health measures to PHC and the consequences as reflected in service access and use. Strategies for integration among levels of care were described and analysed by identifying structures for regulating the health service system, instruments for information integration and continuity, and flow organisation. This study was not intended to measure or evaluate coordination of care as such, but to describe and analyse elements that contribute to that end. The results presented draw on three main sources – interviews of managers and transverse studies using questionnaires applied to samples of families enrolled and Family Health team workers – which were triangulated to answer the research questions. The results show that measures to strengthen PHC structures were identified, at different stages of implementation, in the context of the Unified Health System (Sistema Único de Saúde, SUS) in all the municipalities. The most successful initiatives were those seeking to expand accessibility, consolidate the gateway function, increase resolution capacity and coordinate among public health, surveillance and care measures. Nonetheless, challenges remain for care to meet spontaneous demand better and to be planned to achieve higher rates of resolution and make the Family Health Unit the service of first resort. Primary health care workers' low credibility and lack of professional recognition represent obstacles to coordination of care through this service level. As regards system integration, similar strategies with differing outcomes were encountered in the four cases, such as investment in computerised, decentralised regulation systems, waiting list monitoring, increased supply of the municipalities' own services, and introduction of clinical protocols and electronic patient records. All the same, the lack of regulation and of formal flows for hospital care renders the process of network integration incomplete. Another difficulty identified was insufficient supply of specialised care, aggravated by the low degree of integration among state and municipal providers. The near absence of counter-referral also lessens the likelihood of care being coordinated by the PHC team. The picture offered by the study shows that Belo Horizonte and Vitória score systematically better in health workers' and users' evaluations as regards the two dimensions of analysis. PHC has been strengthened and is better integrated into the health system in the cases studied, although it is not yet coordinating the overall care cycle. The need to set common goals, so that health care centres on users and is organised to meet their personal expectations and health needs, which are components of the coordination function, signals some paths to building a Unified Health System that is more equitable, higher quality and directed to the health needs of the population.

Security of communications is a major requirement for Mobile Adhoc NETworks(MANETs) since they use wireless channel for communications which can be easily tapped, and physical capture of MANET nodes is also quite easy. From the point of view of providing security in MANETs, there are basically two types of MANETs, viz., authoritarian MANETs, in which there exist one or more authorities who decide the members of the network, and self-organized MANETs, in which there is no such authority. Ensuring security of communications in the MANETs is a challenging task due to the resource constraints and infrastructure-less nature of these networks, and the limited physical security of MANET nodes. Attacks on security in a MANET can be launched by either the external attackers which are not legitimate members of the MANET or the internal attackers which are compromised members of the MANET and which can hold some valid security credentials or both. Key management and authentication protocols(KM-APs)play an important role in preventing the external attackers in a MANET. However, in order to prevent the internal attackers, an intrusion detection system(IDS) is essential. The routing protocols running in the network layer of a MANET are most vulnerable to the internal attackers, especially to the attackers which launch packet dropping attack during data packet forwarding in the MANET. For an authoritarian MANET, an arbitrated KM-AP protocol is perfectly suitable, where trusts among network members are coordinated by a trusted authority. Moreover, due to the resource constraints of a MANET, symmetric key management protocols are more efficient than the public key management protocols in authoritarian MANETs. The existing arbitrated symmetric key management protocols in MANETs, that do not use any authentication server inside the network are susceptible to identity impersonation attack during shared key establishments. On the other hand, the existing server coordinated arbitrated symmetric key management protocols in MANETs do not differentiate the role of a membership granting server(MGS) from the role of an authentication server, and so both are kept inside the network. However, keeping the MGS outside the network is more secure than keeping it inside the network for a MANET. Also, the use of a single authentication server inside the network cannot ensure robustness against authentication server compromise. In self-organized MANETs, public key management is more preferable over symmetric key management, since the distribution of public keys does not require a pre-established secure channel. The main problem for the existing self-organized public key management protocols in MANETs is associated with the use of large size certificate chains. Besides, the proactive certificate chaining based approaches require each member of a MANET to maintain an updated view of the trust graph of the entire network, which is highly resource consuming. Maintaining a hierarchy of trust relationships among members of a MANET is also problematic for the same reason. Evaluating the strength of different alternative trust chains and restricting the length of a trust chain used for public key verification is also important for enhancing the security of self-organized public key management protocols. The existing network layer IDS protocols in MANETs that try to defend against packet dropping attack use either a reputation based or an incentive based approach. The reputation based approaches are more effective against malicious principals than the incentive based approaches. The major problem associated with the existing reputation based IDS protocols is that they do not consider the protocol soundness issue in their design objectives. Besides, most of the existing protocols incorporate no mechanism to fight against colluding principals. Also, an IDS protocol in MANETs should incorporate some secure and efficient mechanism to authenticate the control packets used by it. In order to mitigate the above mentioned problems in MANETs, we have proposed new models and designed novel security protocols in this thesis that can enhance the security of communications in MANETs at lesser or comparable cost. First, in order to perform security analysis of KM-AP protocols, we have extended the well known strand space verification model to overcome some of its limitations. Second, we have proposed a model for the study of membership of principals in MANETs with a view to utilize the concept for analyzing the applicability and the performance of KM-AP protocols in different types of MANETs. Third and fourth, we have proposed two novel KM-AP protocols, SEAP and CLPKM, applicable in two different types of MANET scenarios. The SEAP protocol is an arbitrated symmetric key management protocol designed to work in an authoritarian MANET, whereas the CLPKM protocol is a self-organized public key management protocol designed for self-organized MANETs. Fifth, we have designed a novel reputation based network layer IDS protocol, named EVAACK protocol, for the detection of packet dropping misbehavior in MANETs. All of the three proposed protocols try to overcome the limitations of the existing approaches in their respective categories. We have provided rigorous mathematical proofs for the security properties of the proposed protocols. Performance of the proposed protocols have been compared with those of the other existing similar approaches using simulations in the QualNet simulator. In addition, we have also implemented the proposed SEAP and CLPKM protocols on a real MANET test bed to test their performances in real environments. The analytical, simulation and experimentation results confirm the effectiveness of the proposed schemes.

Cette recherche se penche sur l’impact des facteurs contextuels, familiaux et individuels dans l’accessibilité au postsecondaire des Premières Nations et des Métis âgés entre 18 et 34 ans qui vivent hors collectivités des Premières Nations au Canada. En plus de l’impact de ces facteurs au niveau national, cette recherche s’intéresse aussi à leur impact selon les trois types de systèmes scolaires canadiens « à choix exclusif », « à choix progressif » et « à choix multiples ». Des régressions logistiques multinomiales ont été réalisées sur les données de l’enquête auprès des peuples Autochtones de 2012. Trois groupes de facteurs qui totalisent 24 indicateurs ont été examinés afin de répondre aux questions de recherche. Les résultats de cette recherche montrent que même si les facteurs contextuels, tels que l’environnement social et scolaire au secondaire et les facteurs familiaux, tels que la scolarité des membres de la famille sont déterminants dans l’accès au postsecondaire des Autochtones, les facteurs individuels sont les principaux facteurs prédictifs de cet accès. Parmi les facteurs les plus importants, il y a la performance académique et le décrochage scolaire, suivi de l’âge qui affecte considérablement cet accès, particulièrement à l’université. De plus, l’analyse de l’effet de modération selon les trois systèmes scolaires canadiens a également permis de distinguer une différence significative entre ces derniers qui est perceptible, d’une part, par les variances expliquées et, d’autre part, par l’impact différé des trois groupes de facteurs étudiés. / This research assesses the impact of contextual, family and individual factors in access to postsecondary education of First Nations and Métis people aged between 18 and 34 years old, living outside First Nations communities in Canada. This research examines also the impact of these factors across the three postsecondary types of school systems of Canada, i.e., “exclusive choice”, “progressive choice” and “multiple choice”. Multinomial logistic regression analyses were performed on the data of the Aboriginal Peoples Survey of 2012. Three groups of factors totaling 24 indicators were examined in order to answer the research questions. The results of this research show that, while contextual factors, such as the social and academic environment and family factors, such as the high academic level of family’s members are determinant in access to postsecondary education among Aboriginals living outside First Nations communities, the individual factors are the main predictors of this access. Among these main predictors, there are academic performance, dropping out of school and age. In addition, the analysis of moderation effects according to the three postsecondary types of systems present in Canada showed significant differences that can be seen, first, in the explained variance and second, in the difference between the importance of the different groups of factors in each system.