Made available in DSpace on 2014-12-17T15:41:51Z (GMT). No. of bitstreams: 1 JoseFO_DISSERT.pdf: 3189033 bytes, checksum: 64cad7815c9f8b1ecd534fc0cb92765f (MD5) Previous issue date: 2010-07-09 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work makes use of the Pechini process for synthesis of the solutions and the dip-coating process for the addition of zirconium oxide films pure and doped cerium metal substrates. The metals with ceramic substrates were subjected to severe conditions of salinity. The x-ray fluorescence of the substrate showed a great diversity of chemical elements. The x-ray diffraction of the samples showed the phase of iron substrate because the thickness of nano-thin film. Tests using an LPR probe showed that the film presents with zirconia corrosion independent of film thickness. The substrates of ZrO2-doped ceria showed low chemical attack of the salt in films with less than 15 dives. The results imply that ultrathin films are shown in protecting metallic substrates / O presente trabalho faz uso do processo Pechini para s?ntese das solu??es e do processo de dip-coating para a adi??o de filmes de ?xido de zirc?nio puro e dopado com c?rio a substratos met?licos. Os metais com substratos cer?micos foram submetidos a condi??es severas de meio salino. A fluoresc?ncia de raios x do substrato mostrou uma grande diversidade de elementos qu?micos. A difra??o de raios x das amostras mostrou a fase de ferro do substrato devido a espessura nanom?trica do filme fino. Os ensaios utilizando uma sonda LPR mostraram que o filme com zirc?nia apresenta corros?o independente da espessura dos filmes. Os substratos de ZrO2 dopado com c?rio mostraram baixo ataque qu?mico do sal em filmes com menos de 15 imers?es. Os resultados levam a concluir que filmes ultrafinos s?o indicados na prote??o de substratos met?licos

De nouveaux protocoles ont été standardisés afin d'intégrer les réseaux de capteurs sans fil (WSN) dans l'Internet. Parmi eux, RPL pour la couche routage et IEEE 802.15.4 pour la couche MAC. L'objectif de cette thèse est d'améliorer ces protocoles en prenant compte des contraintes énergétiques des dispositifs du WSN. Tout d'abord, nous avons conçu une nouvelle méthode de diffusion dans la norme IEEE 802.15.4, afin d'assurer une livraison fiable des paquets de contrôle des couches supérieures. Ensuite, nous avons fourni une évaluation exhaustive de RPL, en soulignant un problème d'instabilité qui génère une surcharge d'énergie importante. Compte tenu que la durée de vie des WSN est très limitée, nous avons aussi proposé une nouvelle métrique de routage qui identifie les goulets d'étranglement énergétiques afin de maximiser la durée de vie du réseau. Enfin, en couplant cette mesure avec une version multiparent de RPL, nous avons résolu le problème d'instabilité souligné précédemment. / New protocols have been standardized in order to integrate Wireless Sensor Networks (WSN) in the Internet. Among them, the IEEE 802.15.4 MAC layer protocol, and RPL, the IPv6 Routing Protocol for Low-power and Lossy Networks. The goal of this thesis is to improve these protocols, considering the energy constraints of the devices that compose the WSN. First, we proposed a new MAC layer broadcast mechanism in IEEE 802.15.4, to ensure a reliable delivery of the control packets from the upper layers (especially from RPL). Then, we provided an exhaustive evaluation of RPL and highlighted an instability problem. This instability generates a large overhead, consuming a lot of energy. Since the lifetime of WSN is very limited, we proposed a new routing metric that identifies the energy bottlenecks and maximizes the lifetime of the network. Finally, by coupling this metric with a multipath version of RPL, we are able to solve the instability problem previously highlighted.

La mobilité devienne un partie intégrante de l’Internet des Object d’aujourd’hui, comme beaucoup d’applications (monitorage des animaux sauvage, suivi des cible dans le champs de bataille) sont impossible de mettre en œuvre juste avec des nœuds statiques. L’objective de cette thèse est de définir une nouvelle architecture de communication articule autour de la mobilité dans les réseaux avec pertes et à bas puissance (Low Power and Lossy Networks - LLNs) (réseaux des capteurs sans fils). Tout d’abord, nous avons analysé théoriquement l’auto configuration des adresses IPv6, fait avec toutes les optimisations disponibles dans Neighbor Discovery Optimization for IPv6 over 6LoWPAN. Cette étape est cruciale pour des protocoles qui donnent de support pour la mobilité dans des réseaux IP, comme MIPv6. Les résultats obtenues – taille des paquets trop grande et consumations énergétique importante pour les routeurs qui tournent Neighbor Discovery – n’ont amener a utiliser le IPv6 Routing Protocol for Low Power and Lossy Networks (RPL). RPL est développe d’el debout pour les LLN. Notre deuxième contribution sont améliorer les opérations du RPL pour mieux supporter les nœuds mobiles. Enfin, nous avons développe une mécanisme inter-couche – Mobility Triggered-RPL – qui profite des actions dans le protocole avec préambule X-Machiavel à la couche accès au medium dans le protocole RPL à la couche routage. / Mobility is becoming an integrating part of todays Internet of Things, as many applications such as wildlife monitoring or target tracking in the battlefield cannot be done only with the help of static nodes. The goal of this thesis is to provide new communication architecture articulated around providing mobility support in Low Power and Lossy Networks (LLNs). First we analyzed from a theoretical point of view the IPv6 address auto-configuration with all optimizations made in Neighbor Discovery Optimization for IPv6 over 6LoWPAN. This step is of crucial importance for protocols that offer mobility support in IP networks, such as MIPv6. Our findings, increased message size that leads to fragmentation and high energy consumption for routers that are involved in Neighbor Discovery message exchange, have lead us to use the IPv6 Routing Protocol for Low Power and Lossy Networks (RPL) in order to provide mobility support. RPL is build from ground up with respect to LLN requirements. Our second contribution enhanced RPL operations to support mobility management. Finally, we proposed a cross-layer protocol – Mobility Triggered-RPL – that leverages actions from the X-Machiavel preamble sampling MAC protocol into RPL.

This study explored the implementation of the recognition of prior learning (RPL) at Unisa by investigating the strengths and weaknesses of the RPL methodology, instruments and processes when taking students through the RPL process. The successes and challenges experienced by the RPL academic advisors and the academic assessors were determined and guidelines provided for the effective implementation of RPL at Unisa. The empirical research design was exploratory within a qualitative framework employing participant observation, focus group interviewing, individual interviewing and the distribution of questionnaires that consisted of open-ended questions. The research sample comprised 26 purposefully selected participants. With regard to the research findings, the challenges include a lack of administrative support, a lack of support from top management and the academic staff, and a lack of communication between management and the RPL department. The strength of the RPL department lay in its well-documented process manual. / Teacher Education / M. Ed. (Education Management)

Owing to past injustices, the South African higher education sector is characterised by inequalities of resource allocation and of learning opportunities. Through the National Qualification Framework (NQF), recognition of prior learning (RPL) was established to address the previous inequalities in higher education and training. RPL can be used as a mechanism to offer non-traditional learners such as workers, adult learners, and community workers access to learning programmes in Library and Information Science (LIS) schools. It can also be used for up-skilling within LIS sector, to enable staff to migrate from paraprofessional to professional roles. LIS schools could possibly use this approach to offer experienced but unqualified library workers opportunities for progressive professional development and career growth. Despite it being a national policy and its obvious benefits, very little is known about RPL implementation in LIS schools in South Africa. This study was conducted to investigate the nature of RPL implementation in LIS schools in South Africa and make recommendations for effective and efficient RPL practice in these schools. The study used the questionnaire as the main data collection tool. In addition, document analysis was used to validate the collected data. The results of the study indicated that there were islands of good RPL practice in LIS schools in South Africa specifically with regard to the aspect of RPL assessment process. However, certain weaknesses were identified in other aspects of RPL implementation in LIS schools including the policy environment, training of personnel conducting RPL assessment and the quality management systems. Among other things, the study recommends that RPL quality management system (QMS) should ideally be driven by the head/chair of the school/department. Furthermore, an integrated student management system should be used to monitor the progression of RPL candidates through the formal academic system post RPL. / Information Science / D. Litt et. Phil. (Information Science)

Owing to past injustices, the South African higher education sector is characterised by inequalities of resource allocation and of learning opportunities. Through the National Qualification Framework (NQF), recognition of prior learning (RPL) was established to address the previous inequalities in higher education and training. RPL can be used as a mechanism to offer non-traditional learners such as workers, adult learners, and community workers access to learning programmes in Library and Information Science (LIS) schools. It can also be used for up-skilling within LIS sector, to enable staff to migrate from paraprofessional to professional roles. LIS schools could possibly use this approach to offer experienced but unqualified library workers opportunities for progressive professional development and career growth. Despite it being a national policy and its obvious benefits, very little is known about RPL implementation in LIS schools in South Africa. This study was conducted to investigate the nature of RPL implementation in LIS schools in South Africa and make recommendations for effective and efficient RPL practice in these schools. The study used the questionnaire as the main data collection tool. In addition, document analysis was used to validate the collected data. The results of the study indicated that there were islands of good RPL practice in LIS schools in South Africa specifically with regard to the aspect of RPL assessment process. However, certain weaknesses were identified in other aspects of RPL implementation in LIS schools including the policy environment, training of personnel conducting RPL assessment and the quality management systems. Among other things, the study recommends that RPL quality management system (QMS) should ideally be driven by the head/chair of the school/department. Furthermore, an integrated student management system should be used to monitor the progression of RPL candidates through the formal academic system post RPL. / Information Science / D. Litt. et Phil. (Information Science)

This study explored the implementation of the recognition of prior learning (RPL) at Unisa by investigating the strengths and weaknesses of the RPL methodology, instruments and processes when taking students through the RPL process. The successes and challenges experienced by the RPL academic advisors and the academic assessors were determined and guidelines provided for the effective implementation of RPL at Unisa. The empirical research design was exploratory within a qualitative framework employing participant observation, focus group interviewing, individual interviewing and the distribution of questionnaires that consisted of open-ended questions. The research sample comprised 26 purposefully selected participants. With regard to the research findings, the challenges include a lack of administrative support, a lack of support from top management and the academic staff, and a lack of communication between management and the RPL department. The strength of the RPL department lay in its well-documented process manual. / Teacher Education / M. Ed. (Education Management)

L’intérêt croissant de la communauté scientifique et industrielle ces dernières années pour les réseaux de capteurs sans fil (RCSF), a conduit à la définition de nouveaux protocoles normalisés prenant en compte les spécificités matérielles des nœuds utilisés. Dans la couche réseau, le protocole RPL (de l’acronyme anglais IPv6 Routing Protocol for Low-power and Lossy Network) a été proposé en 2012 par l’IETF, comme standard de routage pour les réseaux dont les nœuds sont de type "LLN" (Low-power and Lossy Network), i.e. caractérisés par une faible autonomie énergique et transmettant sur des liens radios dotés d’un taux de perte de données élevé. Dans cette thèse, nous nous intéressons à l’optimisation du routage dans ces réseaux (notamment ceux utilisant la pile protocolaire TCP/IP), ainsi qu’à leur interconnexion efficace à Internet à des coûts soutenables. Tout d’abord, nous proposons deux fonctions d’objectif organisant le routage avec RPL. La première se sert de l’unique critère énergétique, avec comme objectif principal la maximisation de la durée de vie du réseau. Pour ce faire, nous avons implémenté un modèle d’estimation d’énergie, intégré par la suite aux nœuds pour leur permettre d’estimer en temps réel leur énergie résiduelle. La deuxième fonction d’objectif proposée, vise à combiner plusieurs critères pour la prise en compte de la qualité de service durant le routage. Nous développons un modèle à base de la logique floue pour mettre en œuvre la combinaison. En effet, elle nous permet d’obtenir un bon compromis entre les différentes entrées et requiert une empreinte mémoire faible. Dans la dernière partie de cette thèse, nous concevons et implémentons une architecture d’activation de passerelles permettant d’assurer une connexion Internet efficace de divers RCSFs utilisant RPL, pour la réalisation de la vision de l’Internet des Objets / In recent years, the growing interest of scientific and industrial community has led to the standardization of new protocols that consider the unique requirements of Wireless Sensor Networks (WSN) nodes. At network layer, RPL (IPv6 Routing Protocol for Low-power and Lossy Network) has been proposed by IETF as the routing standard for network that uses LLN nodes, namely, those where both nodes and their interconnects are constrained. They operate on low-power embedded batteries and use lossy links, making communications unreliable and lead to a significant data loss rates. This thesis aims to optimize the routing in WSNs (especially those using TCP/IP protocol stack), as well as their efficient and cost-effective connection to the Internet. First, we have proposed two new RPL objective functions. The first uses as unique routing criterion, the node remaining energy with the goal of maximizing the network lifetime. An energy model that allows the nodes to dynamically estimate their remaining energy at runtime has been implemented and integrate to the protocol. The second objective function uses fuzzy logic reasoning to combine several criteria to take Quality of Service into account. Indeed, this scheme provides a good trade-off on several inputs and requires a low memory footprint. In the last part of this thesis, we designed and implemented an architecture that enable an efficient integration of several RPL based WSNs to the Internet to achieve the Internet of Things vision

Les Réseaux de Capteurs Sans Fil (RCSF ou Wireless Sensor Network - WSN) sont l'une des technologies les plus importantes du 21ème siècle. La plupart des chercheurs et les analystes estiment que, dans un proche avenir, ces micro-capteurs seront intégrés partout dans l’environnement de notre vie quotidienne. Ces dernières années, l'Internet des Objets (Internet of Things - IoT) est également une des technologies émergentes qui se développe rapidement. Deux nouveaux standards permettent de déployer des réseaux sans fil de faible consommation énergétique connectés à internet : le protocole 6LowPAN (Low power Wireless Personal Area Networks) qui permet notamment d’apporter l’adressage IPv6 aux capteurs grâce à l’encapsulation et la compression des données et le protocole de routage RPL (IPv6 routing protocol for low-power and lossy network) qui permet à l’information de circuler dans les WSN de proche en proche à un faible coût énergétique. Bien que le développement de ces techniques soit extrêmement rapide, plusieurs problèmes causés principalement par le manque de ressources des micro-capteurs (puissance limitée de traitement, problèmes de bande passante et de connexion des liens avec perte de données, problème de ressource énergétique limitée) demeurent et doivent être résolus, notamment pour les applications agro-environnementales. / The wireless sensor network (WSN) is one of the most important technologies of the 21st century. Most researchers and technical analysts believe that in the near future, these micro-sensors will be integrated into the environment of our daily lives. In recent years, the IoT (Internet of Things) and WoT (Web of Things) technologies also have great forwarding. Especially, the IPv6 over Low power Wireless Personal Area Networks (6LoWPAN) protocol has allowed the use of IPv6 protocol stack in the field of WSN, thanks to its encapsulation and compression mechanisms in IPv6 packet header. Moreover, the RPL (IPv6 Routing Protocol for Low-power and Lossy Network) provides such a powerful routing function that can be applied for a variety of application scenarios. These two key standards of IoT and WoT technologies for WSN can be used in an IPv6 stack, and they will successfully achieve the connection between Internet and micro-sensors. Thus, due to the availability of IPv6 address (128-bit), all the communicating objects, such as smart device, sensor, and actuator, can be connected to the Internet. That is the greatest advantage brought by the IoT. Although the progress of these techniques is extremely fast, several issues caused by resource constraints of micro-sensor (limited processing power, bandwidth and lossy connection link, and energy), such as QoS, energy efficient, robustness and lifetime of WSN, and the most important, the special requirement of agricultural applications. Notice that Precision Agriculture is are still very challenging and waiting to be solved. Essentially, these open questions would dabble in the aspects like telemedicine, remote home automation, industrial control etc. Thus, the results obtained in this work will have a significant impact on both economic and scientific. Economically, it can offer a solution for WSN to support sustainable development in the field of agriculture automation. While scientifically, we will contribute to the routing protocol standardization of wireless micro-sensors in the domain of environmental monitoring.

Network security has always been an area of priority and extensive research. Recent years have seen a considerable growth in experimentation with biologically inspired techniques. This is a consequence of our increased understanding of living systems and the application of that understanding to machines and software. The mounting complexity of telecommunications networks and the need for increasing levels of security have been the driving factor. The human body can act as a great role model for its unique abilities in protecting itself from external, foreign entities. Many abnormalities in the human body are similar to that of the attacks in wireless sensor networks (WSN). This paper presents basic ideas drawn from human immune system analogies that can help modelling a system to counter the attacks on a WSN by monitoring parameters such as energy, frequency of data transfer, data sent and received. This is implemented by exploiting two immune concepts, namely danger theory and negative selection. Danger theory aggregates the anomalies based on the weights of the anomalous parameters. The objective is to design a cooperative intrusion detection system (IDS) based on danger theory. Negative selection differentiates between normal and anomalous strings and counters the impact of malicious nodes faster than danger theory. We also explore other human immune system concepts and their adaptability to Wireless Sensor Network Security.