Dissertations / Theses on the topic 'Sensor heterogeneity'

Las redes de sensores inalámbricos están destinadas a revolucionar nuestra manera de vivir, trabajar y relacionarnos con el entorno. Aunque este tipo de redes ha estado en el foco de la investigación científica durante la última década, su rendimiento en implementaciones prácticas está todavía muy por detrás de los resultados teóricos. Esto es en gran parte debido a los problemas prácticos que aparecen en entornos reales. Como resultado, su uso está generalmente limitado a aplicaciones simples de monitorización del entorno. El objetivo de esta tesis es reducir el margen entre el potencial teórico y real de las redes de sensores inalámbricos y de esta manera incrementar su integración dentro de la sociedad. En concreto, la tesis se centra en los siguientes cuatro obstáculos: alta densidad de nodos, movilidad de nodos, tráfico heterogéneo e integración en el internet de las cosas. Primero, el objetivo es el de reducir las interferencias en despliegues de alta densidad de nodos. Para ello se propone un esquema práctico para realizar el enrutado, el control de potencia y la selección de canal, basado en el protocolo RPL (Routing Protocol for Low-Power and Lossy Networks). Esta solución permite reducir las colisiones entre paquetes y además mejorar el consumo energético de este tipo de redes. Segundo, se pretende mejorar la baja fiabilidad y robustez de las redes de sensores inalámbricos con nodos móviles. Con este objetivo se presenta un método que combina RPL con un sistema de enrutado que considera la posición de los nodos basado en el filtro de Kalman. Éste combina la eficiencia y fiabilidad de RPL permitiendo además manejar nodos móviles. Tercero, se estudian maneras de proporcionar la calidad de servicio necesaria a las redes de sensores con tráfico heterogéneo. Para ello se propone una estrategia multi árbol basada en la construcción de múltiples instancias RPL. Ésta construye diferentes topologías virtuales para cada función objetivo, y de esta manera es posible atender los requisitos de cada flujo de tráfico de manera independiente. Finalmente, se estudia la manera de integrar las redes de sensores inalámbricos dentro de la nube y el internet de las cosas. Con este objetivo se propone una formulación para coordinar la utilización de los recursos de la red de manera conjunta usando estrategias de virtualización y computación móvil en la nube. Esto permite reducir el consumo energético de la red, teniendo en cuenta las capacidades y limitaciones de cada nodo, satisfaciendo tanto los requisitos de los diferentes servicios como los de los usuarios.
Wireless sensor networks (WSNs) are expected to revolutionize the way we live, work, and interact with the physical environment. Although WSNs have been in the spotlight of the research community for the last decade, their performance in practical implementations is still far behind the theoretical results. This is mainly due to the practical issues that arise in real-life scenarios. As a result, WSNs are generally limited to simple environmental sensing applications. The aim of this thesis is to reduce the gap between the theoretical and real potential of WSNs, and therefore increase their integration in society. In particular, this thesis focuses on the following four practical obstacles: high node density, node mobility, traffic heterogeneity and integration with the future Internet of Things (IoT). First, we deal with the interference problem in high density sensor deployments. We address this issue proposing a pragmatic joint routing, transmission power control and channel allocation approach, built upon the well-known RPL (Routing Protocol for Low-Power and Lossy Networks). This reduces the average packet collisions and the energy consumption of WSNs. Second, we address the low communication reliability and robustness in WSNs with mobile nodes. In particular, we propose a solution that combines RPL with a position-based routing approach based on Kalman filtering. This provides the efficiency and reliability of RPL, and also includes mobility support for non-static nodes. Third, we study the problem of QoS (Quality of Service) provisioning in WSNs managing heterogeneous traffic. With this in mind, we propose a multi-tree approach based on the construction of multiple RPL Instances. This constructs multiple virtual topologies to address the particular requirements of each traffic flow individually. Finally, we focus on the efficient integration of wireless sensors with Cloud-based IoT platforms. In particular, we propose a formulation to orchestrate the resource utilization of the whole network, taking advantage of the recent advances in virtualization and mobile cloud computing. This optimizes the overall consumption, considering the capabilities and limitations of each node, while satisfying the service requirements and the individual users' demands.

With extraction of low-grade and high throughput deposits, elimination of tonnes of uneconomic material is highly desired to reduce energy consumption and water usage in the mine/mill production cycle. Even though technologies such as sensor-based sorting has wide application for pre-concentration purposes, effectiveness of sorter systems and key parameters for sortability of a material are still in the developmental stage. Number of factors such as grade variability, mineralogical alteration and ore blending scenarios during material handling will significantly affect contents of a material resulting in unforeseen changes in downstream processes. For these reasons, the ‘ore heterogeneity’ parameter is studied to evaluate sortability of an ore material under varying mine production scenarios. Production data, drillhole data and representative drawpoint samples were provided from the New Afton copper-gold mine located near Kamloops, BC. The New Afton mine utilizes the block caving method for extraction of ore from the copper-gold alkali-porphyry deposit. The distribution heterogeneity (DH) parameter is estimated for the data sets and the quantity of potentially removable material ahead of delivery to mill is studied. The DH is defined by variation of grade of a group of samples that constitute a lot, i.e. a group being an equal tonnage of material drawn from a drawpoint and the lot being the drawpoint. With this approach, the DH is analyzed across drawpoints, vertically within a drawpoint and along drill holes with changing vertical intervals of 0.5m – 10m. The DH values are compared with copper grades and an inverse relationship is found. This finding indicated that sortability of ore material can be defined by a heterogeneity parameter, especially the information can be obtained earlier from drillcore samples. The drillcore information can indicate a measure of heterogeneity and related copper grade of an in-situ material in advance of assay samples or sensor detection where a certain degree of mixing has occurred. Overall, 27% of the sample data from the New Afton historical production record has grades less than 0.4% Cu, which is the current cut-off grade, and it correlates with relatively high heterogeneity and presents an opportunity for sorting and feed grade upgrade.
Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate

In this study, we considered a heterogeneous, clustered WSN, which consists of two types of nodes (clusterheads and sensor nodes) deployed randomly over a sensing field. We investigated two cases based on how clusterheads can reach the sink: direct and multi-hop communication cases. Network dimensioning problems in randomly deployed WSNs are among the most challenging ones as the attributes of these networks are mostly non-deterministic. We focused on a number of network dimensioning problems based on the connected coverage concept, which is the degree of coverage achieved by only the connected devices. To evaluate connected coverage, we introduced the term cluster size, which is the expected value of the area covered by a clusterhead together with sensor nodes connected to it. We derived formulas for the cluster size and validated them by computer simulations. By using the cluster size formulas, we proposed a method to dimension a WSN for given targeted connected coverage. Furthermore, we formulated cost optimization problems for direct and multi-hop communication cases. These formulations utilize not only cluster size formulas but also the well-connectivity concept. We suggested some search heuristics to solve these optimization problems. Additionally, we justified that, in practical cases, node heterogeneity can provide lower cost solutions. We also investigated the lifetime of WSNs and for mulated a cost optimization problem with connected coverage and lifetime constraints. By solving this optimization problem, one can determine the number of nodes of each type and the initial energies of each type of node that leads to lowest cost solution while satisfying the minimum connected coverage and minimum lifetime requirements.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 22-26).
Genetically encoded ratiometric sensors can provide valuable mechanistic understanding of biological systems. Characterization of cellular response of these sensors is the first step in validating their use. Here, we characterize the response of a genetically encoded H₂O₂ sensor, HyPer, expressed in HeLa cells. Using quantitative fluorescence microscopy, we found significant heterogeneity in HyPer response among the cell population. Further analysis showed that the variation in HyPer response was dependent on expression of HyPer protein as well as on cell cycle phase. Cells with higher levels of expressed HyPer protein showed a stronger HyPer response to H₂O₂. Cells synchronized in S-phase showed a weaker HyPer response than unsynchronized cells. It was determined that this weaker response could be a function of higher antioxidant capacity in S-phase cells. The dependence of HyPer response on these factors needs to be accounted for to avoid experimental artifacts.
by Sohail Feroz Ali.
S.M.

Dans ce travail, nous présentons des techniques de réduction de données et de sécurité conçues pour économiser de l’énergie dans les réseaux de capteurs sans fil. Premièrement, nous proposons un modèle d’agrégation de données basé sur la fonction de similarité servant à éliminer les données redondantes. En plus, nous avons travaillé sur l’envoi, le moins possible, de caractéristiques de données en se basant sur des fonctions d’ajustement qui expriment ces caractéristiques. Deuxièmement, nous nous sommes intéressés à l’hétérogénéité des données tout en étudiant la corrélation entre ces caractéristiques multi variantes après avoir éliminé les mesures identiques durant la phase d’agrégation. Finalement, nous donnons un cadre de sécurité rigoureux, conçu à partir de la cryptographie, qui satisfait le niveau d’exigence atteint normalement dans les réseaux de capteurs sans fil arborescents. Il empêche les pirates d’obtenir des informations à propos des données détectées en assurant une certaine confidentialité de bout-en-bout entre les nœuds du capteur et le puits. Afin de valider nos techniques proposées, nous avons implémenté les simulations de la première technique sur des données collectées en temps réel à partir du réseau Sensor Scope déployé à Grand-St-Bernard. Les simulations de la deuxième et de la troisième technique sont réalisées sur des données collectées en temps réel à partir de 54 capteurs déployés au laboratoire de recherche Intel Berkeley. L’efficacité de nos techniques est évaluée selon le taux de réduction de données, la consommation de l’énergie, la précision des données et la complexité de temps
In this thesis, we present energy-efficient data reduction and security techniques dedicated for wireless sensor networks. First, we propose a data aggregation model based on the similarity function that helps in removing the redundant data. In addition, based on the fitting functions we worked on sending less data features, accompanied with the fitting function that expresses all features. Second, we focus on heterogeneity of the data while studying the correlation among these multivariate features in order to enhance the data prediction technique that is based on the polynomial function, all after removing the similar measures in the aggregation phase using the Euclidean distance. Finally, we provide a rigorous security framework inherited from cryptography satisfies the level of exigence usually attained in tree-based WSNs. It prevents attackers from gaining any information about sensed data, by ensuring an end-to-end privacy between sensor nodes and the sink. In order to validate our proposed techniques, we implemented the simulations of the first technique on real readings collected from a small Sensor Scope network which is deployed at the Grand-St-Bernard, while the simulations of the second and the third techniques are conducted on real data collected from 54 sensors deployed in the Intel Berkeley Research Lab. The performance of our techniques is evaluated according to data reduction rate, energy consumption, data accuracy and time complexity

Aujourd'hui l'Internet permet de connecter des milliards d'appareils électroniques hétérogènes et assure la communication entre eux. Ces appareils sont dotés de capteurs conçus avec des contraintes en ressources qui affectent considérablement la collecte de données, en particulier une limitation de taille de mémoire et de batterie. Les divergences des caractéristiques de ces objets exigent de nouvelles méthodes intelligentes afin d'assurer la communication entre eux. Les solutions heuristiques deviennent obsolètes ou impuissantes pour satisfaire l'exigence de l'utilisateur, d'où une recherche de nouvelles méthodes devient obligatoirement nécessaire afin de satisfaire les usagers. Parmi ces solutions, il y a celles basées sur les modèles bio-inspirés. Dans ce contexte, ayant comme objectif la minimisation de la perte de données, nous proposons différentes approches bio-inspirées pour la mobilité du collecteur de données et le choix des points rendez-vous pour la collecte de données. Tout d'abord, nous proposons une mobilité inspirée du mouvement des bactéries Eschericia coli. Ensuite, nous proposons une technique inspirée du regroupement des loups gris et des baleines pour le choix des points rendez-vous. Après, nous améliorons la mobilité du collecteur par une mobilité inspirée des salpes. Enfin, nous combinons ces approches en prenant en considération l'urgence des données. Les différentes contributions ont été évaluées en utilisant des simulations et ensuite ont été comparé avec des travaux similaires existants. Les résultats obtenus sont très prometteurs en termes de consommation d'énergie et de quantité de données collectées
Today the Internet makes it possible to connect billions of heterogeneous electronic devices and ensures communication between them. These devices have sensors designed with resource constraints that significantly affect data collection, especially memory and battery size limitations. The divergences in the characteristics of these objects require new intelligent methods to ensure communication between them. Heuristic solutions become obsolete or powerless to satisfy the user's requirement, hence a search for new methods becomes necessarily necessary to satisfy users. Among these solutions, we have those based on bio-inspired models. In this context, intending to minimize data loss, we propose different bio-inspired approaches for the mobility of the data collector and the choice of meeting points for data collection.First of all, we propose mobility inspired by the movement of Escherichia Coli bacteria. Then, we propose a technique inspired by the grouping of grey wolves and whales for the choice of meeting points. Afterward, we improve the mobility of the collector by mobility inspired by salps.Finally, we combine these approaches by taking into account the urgency of the data. The different contributions were evaluated using simulations and then were compared with similar existing work.The results obtained are very promising in terms of energy consumption and the amount of data collected

Améliorer la durée de vie est un enjeu important qui s'impose lors du déploiement des réseaux de capteurs sans fil (RCsFs). En effet, ces réseaux sont composés par des capteurs autonomes alimentés par des batteries qu'il est difficile de recharger ou remplacer. Le challenge est donc d'assurer le fonctionnement de ces réseaux pendant plusieurs années sans aucune intervention extérieure majeure.Afin de maximiser la durée de vie des RCsFs, nous avons d'abord exploré la possibilité d'introduire plusieurs puits mobiles. Nous avons proposé deux stratégies. La première détermine les positions optimales sur un réseau de petite échelle et la deuxième, basée sur une heuristique, garantit le passage à l'échelle.Nous nous sommes ensuite intéressés aux RCsFs basés sur IPv6 qui utilisent RPL, le nouveau protocole de routage proposé par l'IETF. Nous avons étudié ce protocole, étendu ses capacités pour gérer des puits mobiles et proposé une stratégie de mobilité des puits adaptée permettant de prolonger la durée de vie du réseau.Puis, nous avons proposé une nouvelle approche qui applique le codage de Slepian-Wolf sur les adresses émises dans les RCsFs. L'idée consiste à exploiter la corrélation des adresses garantie par un schéma approprié d'allocation afin de réduire le nombre de bits d'entête transmis au puits et d'améliorer ainsi la durée de vie du réseau.Finalement, nous avons proposé une infrastructure IPv6 hybride pour bâtiments intelligents qui combine les avantages des technologies sans fil et courants porteurs en ligne afin d'améliorer la durée de vie du réseau, sa connectivité et sa robustesse à faible surcoût
Improving the network lifetime is a very challenging problem that needs to be taken into account during the deployment of wireless sensor networks (WSNs). Indeed, these networks are composed of many autonomous sensors with a limited energy supply provided by batteries which are usually difficult to recharge or replace. The scientific challenge is to ensure the operation of these networks for several years without major external intervention. To maximize the lifetime of WSNs, we first explored the possibility of introducing multiple mobile sinks. We proposed two mobility strategies. The first one provides the optimal placement in a network of small scale. The second one is based on an heuristic algorithm that ensures scalability.We were then interested in IPv6 based WSNs which use the new proposed routing protocol by IETF namely RPL. We studied this protocol, extended its capacity to manage mobile sinks andproposed an appropriate sinks mobility strategy that extends the network lifetime.Next, we proposed a novel approach which consists in applying Slepian-Wolf coding to emitted addresses in WSNs. The basic idea is to exploit the addresses correlation, guaranteed by an appropriate addresses allocation scheme, in order to reduce the header size of packets transmitted to the sink and thus improve the network lifetime.Finally, we proposed an hybrid IPv6 infrastructure for smart buildings which combines the wireless and power line technologies to guarantee energy efficiency and a longer network lifetime

This thesis addresses new security challenges in the Internet of Things (IoT). The current transition from legacy Internet to Internet of Things leads to multiple changes in its communication paradigms. Wireless sensor networks (WSNs) initiated this transition by introducing unattended wireless topologies, mostly made of resource constrained nodes, in which radio spectrum therefore ceased to be the only resource worthy of optimization. Today's Machine to Machine (M2M) and Internet of Things architectures further accentuated this trend, not only by involving wider architectures but also by adding heterogeneity, resource capabilities inconstancy and autonomy to once uniform and deterministic systems. The heterogeneous nature of IoT communications and imbalance in resources capabilities between IoT entities make it challenging to provide the required end-to-end secured connections. Unlike Internet servers, most of IoT components are characterized by low capabilities in terms of both energy and computing resources, and thus, are unable to support complex security schemes. The setup of a secure end-to-end communication channel requires the establishment of a common secret key between both peers, which would be negotiated relying on standard security key exchange protocols such as Transport Layer Security (TLS) Handshake or Internet Key Exchange (IKE). Nevertheless, a direct use of existing key establishment protocols to initiate connections between two IoT entities may be impractical because of the technological gap between them and the resulting inconsistencies in their cryptographic primitives. The issue of adapting existing security protocols to fulfil these new challenges has recently been raised in the international research community but the first proposed solutions failed to satisfy the needs of resource-constrained nodes. In this thesis, we propose novel collaborative approaches for key establishment designed to reduce the requirements of existing security protocols, in order to be supported by resource-constrained devices. We particularly retained TLS handshake, Internet key Exchange and HIP BEX protocols as the best keying candidates fitting the end-to-end security requirements of the IoT. Then we redesigned them so that the constrained peer may delegate its heavy cryptographic load to less constrained nodes in neighbourhood exploiting the spatial heterogeneity of IoT nodes. Formal security verifications and performance analyses were also conducted to ensure the security effectiveness and energy efficiency of our collaborative protocols. However, allowing collaboration between nodes may open the way to a new class of threats, known as internal attacks that conventional cryptographic mechanisms fail to deal with. This introduces the concept of trustworthiness within a collaborative group. The trustworthiness level of a node has to be assessed by a dedicated security mechanism known as a trust management system. This system aims to track nodes behaviours to detect untrustworthy elements and select reliable ones for collaborative services assistance. In turn, a trust management system is instantiated on a collaborative basis, wherein multiple nodes share their evidences about one another's trustworthiness. Based on an extensive analysis of prior trust management systems, we have identified a set of best practices that provided us guidance to design an effective trust management system for our collaborative keying protocols. This effectiveness was assessed by considering how the trust management system could fulfil specific requirements of our proposed approaches for key establishment in the context of the IoT. Performance analysis results show the proper functioning and effectiveness of the proposed system as compared with its counterparts that exist in the literature

Le système nerveux sensoriel somatique détecte et transmet les informations sensorielles périphériques par les neurones sensoriels dont le corps cellulaire est englobé dans les ganglions de la racine dorsale et les ganglions trijumeaux. Bien que cette hétérogénéité fonctionnelle a été mise en évidence, les mécanismes moléculaires qui la caractérisent sont moins connus. Dans l’optique de contribuer à la caractérisation moléculaire de la population neuronale du DRG, nous avons identifié un nouveau gène, stac2. Nous avons pu montrer que stac2 spécifie une sous population neuronale distincte dans le DRG. L’invalidation génétique de stac2 chez la souris n’a révélé aucun effet sur la survie ni sur la maturation neuronale. L’analyse comportementale des souris dépourvues de stac2 a montré un rôle important de stac2 dans la perception et la discrimination des températures fraîches ainsi que dans la sensibilisation périphérique au froid nocif
The somatic sensory nervous system detects and transmits sensory information from peripheral by sensory neurons that have their cell body encompassed in the dorsal root and trigeminal ganglia. Although this functional heterogeneity has been demonstrated, the molecular mechanisms characterizing it are less known. In order to contribute to the molecular characterization of the neuronal population of DRG, we have identified a new gene, stac2. We have shown that stac2 specifies a distinct neuronal subpopulation in the DRG. The genetic invalidation of stac2 in mice showed no effect of stac2 on neuronal survival and maturation. The behavioral analysis of mice lacking stac2 showed an important role of this gene in the perception and discrimination of cold temperatures and in the peripheral sensitization to noxious cold

Le vieillissement de la population dans les pays développés remet en question la soutenabilité des systèmes de retraite par répartition. Plusieurs réformes ont donc été engagées pour faire face à ce défi démographique. Cependant, les effets des réformes mises en place ont été questionnés. Leur efficacité dépend en effet de la manière dont les seniors répondent aux réformes. Or, les seniors présentent des profils très différents notamment autour de deux dimensions qui sont l’environnement de travail et la situation familiale. Cette hétérogénéité entre les seniors peut affecter leurs comportements de départ à la retraite. Ne pas prendre en compte cette diversité en termes d’environnements dans lesquels évoluent les seniors peut donc conduire à des biais lors des évaluations de politiques publiques. De ce fait, ce travail de thèse analyse, en utilisant des méthodes économétriques, les déterminants, et particulièrement le rôle de l’hétérogénéité professionnelle et familiale, du processus de décision de départ à la retraite. Dans un premier temps, l’hétérogénéité des individus en termes d’environnement professionnel est prise en compte lors de l’analyse du rôle de la qualité de vie au travail dans le processus de décision de départ à la retraite. Dans un second temps, l’hétérogénéité en termes d’environnement familial est prise en compte lors de l’analyse du processus de décision au sein des couples et des déterminants à ce processus pour chacun des conjoints. Finalement, une évaluation de politique publique sous le prisme de décisions jointes au sein des couples est réalisée pour tester la présence d’effet de débordement, via le conjoint, de la réforme sur la stratégie de départ à la retraite propre à l’individu. Les résultats de ce travail de thèse soulignent le rôle important de l’hétérogénéité des seniors lors de la décision de départ à la retraite. Ces résultats encouragent donc la prise en compte, par les décideurs publiques, de cette hétérogénéité des seniors. La coordination des politiques sociales liées à la retraite, la famille et la qualité de vie au travail est une piste pour considérer cette hétérogénéité entre les seniors
The aging of the population calls into question the sustainability of Pay-As-You-Go pension system, especially in Europe. Therefore, several reforms have been implemented to face this demographic challenge. However, the effects of those reforms have been questioned. Indeed, the success of such policies depends on how people respond to changes in their pension eligibility. In reality though, several factors may limit the reforms impact. People are indeed heterogeneous in terms of work environment and family. These heterogeneity may affect their retirement behaviors. To not take into account this individuals’ heterogeneity may lead to bias within public policy evaluations. Hence, this thesis analyses, with econometrics methods, determinants of retirement decisions making process by considering this individuals’ heterogeneity. First, the heterogeneity within work environment is taken into account by analyzing the role of job quality in the process of retirement decisions. Second, the family heterogeneity is studied by questioning joint retirement process into couples and determinants of this process for each spouse. Third, consequences to public policies are then studied as it is estimated to what extent a change in pension eligibility rules has direct and also spillover effects, through the partner, on spouses’ retirement probabilities. Results of this thesis work highlight the significant role of older workers’ heterogeneity during retirement decision. Those findings thus encourage policy makers to take into account this individuals’ heterogeneity. The coordination of social policies relate to retirement, family and job quality is a key issue for reflection

La moelle spinale est un relais majeur permettant aux informations sensorielles perçues à la périphérie d’être transférées et intégrées au niveau des centres supra-spinaux. Les afférences primaires somatosensorielles vont arriver au niveau de la corne dorsale. Celle-ci est constituée d’un réseau hétérogène de neurones formant des circuits excitateurs et inhibiteurs complexes. De précédentes études indiquent que ces circuits neuronaux sont modulés par la dopamine, notamment via les D2R. Un dysfonctionnement des voies dopaminergiques descendantes peut engendrer des physiopathologies comme le syndrome des jambes sans repos. Cependant, les mécanismes d’action de la dopamine spinale sont encore très peu connus. Tous les récepteurs à la dopamine sont exprimés au niveau spinal. Le plus abondant est le D2R mais le rôle et l’identité précise des cellules D2R-positives ne sont pas connus. Dans cette étude, nous nous sommes focalisés sur la caractérisation anatomo-fonctionnelle des cellules exprimant les D2R. Grâce au modèle murin Drd2-Cre :RiboTag crée par l’équipe, nous avons mis en avant que les cellules D2R-positives étaient distribuées tout au long de la moelle spinale avec une expression préférentielle au niveau de la corne dorsale. Les D2R sont exprimés dans des populations très hétérogènes, aussi bien excitatrices qu’inhibitrices. Nous avons montré que le KO conditionnel du gène drd2 au niveau lombaire n’entraîne pas d’ataxie, de paralysie ou d’altération de la locomotion. L’état des lieux concernant la caractérisation neurochimique des cellules D2R-positives ouvrent la possibilité d’avoir une approche fonctionnelle plus spécifique et d’avoir des perspectives d’études sur les sous circuits dopaminergiques spinaux
The spinal cord is the major relay station for sensory information generated at the periphery and transferred for processing to the brain. Sensitive primary afferent fibers arrive to the dorsal horn that is populated by a vast diversity of neurons that forms a complex network of excitatory and inhibitory circuits. Previous studies indicated that these neuronal ensembles could be modulated by the spinal dopaminergic system notably through the dopamine D2 receptors (D2R). A dysfunction of descending dopaminergic pathways could lead to pathology like Rest Less Syndrom. Nevertheless, mechanisms by which dopamine acts are poorly understand. All dopamine receptors are expressed in the spinal cord and the most abundant is the D2R and the precise identity and role of spinal D2R-cells remains largely unknown. In this study, we focused on the anatomo-functional characterization of the neurons containing D2R in the mouse spinal cord. Thanks to the mouse model Drd2:Cre-Ribotag previously developed in our lab, we could show that D2R-positive cells are expressed all along the spinal cord with a preferential expression in the dorsal horn. D2R are expressed in a very heterogeneous population, in excitatory and inhibitory neurons. We have shown that conditional KO of drd2 in lumbar cord didn’t lead to ataxia, paralysis or locomotor alteration. This study allow to unravel the precise neurochemical identity of D2R-neurons. Future studies could use this descriptive study to choose a more specific functional approach to better understand spinal dopaminergic pathways using D2R.Key words: dopamine, D2R, spinal cord, molecular heterogeneity, sensorimotor

Cette thèse aborde des nouveaux défis de sécurité dans l'Internet des Objets (IdO). La transition actuelle de l'Internet classique vers l'Internet des Objets conduit à de nombreux changements dans les modèles de communications sous-jacents. La nature hétérogène des communications de l’IdO et le déséquilibre entre les capacités des entités communicantes qui le constituent rendent difficile l'établissement de connexions sécurisées de bout en bout. Contrairement aux nœuds de l’Internet traditionnel, la plupart des composants de l'Internet des Objets sont en effet caractérisés par de faibles capacités en termes d'énergie et de puissance calcul. Par conséquent, ils ne sont pas en mesure de supporter des systèmes de sécurité complexes. En particulier, la mise en place d'un canal de communication sécurisé de bout en bout nécessite l’établissement d'une clé secrète commune entre les deux nœuds souhaitant communiquer, qui sera négociée en s'appuyant sur un protocole d'échange de clés tels que le Transport Layer Security (TLS) Handshake ou l’Internet Key Exchange (IKE). Or, une utilisation directe de ces protocoles pour établir des connexions sécurisées entre deux entités de l’IdO peut être difficile en raison de l'écart technologique entre celles-ci et des incohérences qui en résultent sur le plan des primitives cryptographiques supportées. Le sujet de l'adaptation des protocoles de sécurité existants pour répondre à ces nouveaux défis a récemment été soulevé dans la communauté scientifique. Cependant, les premières solutions proposées n'ont pas réussi à répondre aux besoins des nœuds à ressources limitées. Dans cette thèse, nous proposons de nouvelles approches collaboratives pour l'établissement de clés, dans le but de réduire les exigences des protocoles de sécurité existants, afin que ceux-ci puissent être mis en œuvre par des nœuds à ressources limitées. Nous avons particulièrement retenu les protocoles TLS Handshake, IKE et HIP BEX comme les meilleurs candidats correspondant aux exigences de sécurité de bout en bout pour l'IdO. Puis nous les avons modifiés de sorte que le nœud contraint en énergie puisse déléguer les opérations cryptographiques couteuses à un ensemble de nœuds au voisinage, tirant ainsi avantage de l'hétérogénéité spatiale qui caractérise l’IdO. Nous avons entrepris des vérifications formelles de sécurité et des analyses de performance qui prouvent la sureté et l'efficacité énergétique des protocoles collaboratifs proposés. Dans une deuxième partie, nous avons porté notre attention sur une classe d’attaques internes que la collaboration entre les nœuds peut induire et que les mécanismes cryptographiques classiques, tels que la signature et le chiffrement, s'avèrent impuissants à contrer. Cela nous a amené à introduire la notion de confiance au sein d'un groupe collaboratif. Le niveau de fiabilité d'un nœud est évalué par un mécanisme de sécurité dédié, connu sous le nom de système de gestion de confiance. Ce système est lui aussi instancié sur une base collaborative, dans laquelle plusieurs nœuds partagent leurs témoignages respectifs au sujet de la fiabilité des autres nœuds. En nous appuyant sur une analyse approfondie des systèmes de gestion de confiance existants et des contraintes de l’IoD, nous avons conçu un système de gestion de confiance efficace pour nos protocoles collaboratifs. Cette efficacité a été évaluée en tenant compte de la façon dont le système de gestion de la confiance répond aux exigences spécifiques à nos approches proposées pour l'établissement de clés dans le contexte de l'IdO. Les résultats des analyses de performance que nous avons menées démontrent le bon fonctionnement du système proposé et une efficacité accrue par rapport à la littérature
This thesis addresses new security challenges in the Internet of Things (IoT). The current transition from legacy Internet to Internet of Things leads to multiple changes in its communication paradigms. Wireless sensor networks (WSNs) initiated this transition by introducing unattended wireless topologies, mostly made of resource constrained nodes, in which radio spectrum therefore ceased to be the only resource worthy of optimization. Today's Machine to Machine (M2M) and Internet of Things architectures further accentuated this trend, not only by involving wider architectures but also by adding heterogeneity, resource capabilities inconstancy and autonomy to once uniform and deterministic systems. The heterogeneous nature of IoT communications and imbalance in resources capabilities between IoT entities make it challenging to provide the required end-to-end secured connections. Unlike Internet servers, most of IoT components are characterized by low capabilities in terms of both energy and computing resources, and thus, are unable to support complex security schemes. The setup of a secure end-to-end communication channel requires the establishment of a common secret key between both peers, which would be negotiated relying on standard security key exchange protocols such as Transport Layer Security (TLS) Handshake or Internet Key Exchange (IKE). Nevertheless, a direct use of existing key establishment protocols to initiate connections between two IoT entities may be impractical because of the technological gap between them and the resulting inconsistencies in their cryptographic primitives. The issue of adapting existing security protocols to fulfil these new challenges has recently been raised in the international research community but the first proposed solutions failed to satisfy the needs of resource-constrained nodes. In this thesis, we propose novel collaborative approaches for key establishment designed to reduce the requirements of existing security protocols, in order to be supported by resource-constrained devices. We particularly retained TLS handshake, Internet key Exchange and HIP BEX protocols as the best keying candidates fitting the end-to-end security requirements of the IoT. Then we redesigned them so that the constrained peer may delegate its heavy cryptographic load to less constrained nodes in neighbourhood exploiting the spatial heterogeneity of IoT nodes. Formal security verifications and performance analyses were also conducted to ensure the security effectiveness and energy efficiency of our collaborative protocols. However, allowing collaboration between nodes may open the way to a new class of threats, known as internal attacks that conventional cryptographic mechanisms fail to deal with. This introduces the concept of trustworthiness within a collaborative group. The trustworthiness level of a node has to be assessed by a dedicated security mechanism known as a trust management system. This system aims to track nodes behaviours to detect untrustworthy elements and select reliable ones for collaborative services assistance. In turn, a trust management system is instantiated on a collaborative basis, wherein multiple nodes share their evidences about one another's trustworthiness. Based on an extensive analysis of prior trust management systems, we have identified a set of best practices that provided us guidance to design an effective trust management system for our collaborative keying protocols. This effectiveness was assessed by considering how the trust management system could fulfil specific requirements of our proposed approaches for key establishment in the context of the IoT. Performance analysis results show the proper functioning and effectiveness of the proposed system as compared with its counterparts that exist in the literature

The overall objective of this work has been to adopt new developments and techniques in the area of measurement, modelling and control of fermentation processes. Flow cytometry and software sensors are techniques which were considered ready for application and the focus was set on developing tools for research aiming at understanding the relationship between measured variables and process quality parameters. In this study fed-batch cultivations have been performed with two different strains of Escherichia coli (E.coli) K12 W3110 with and without a gene for the recombinant protein promegapoietin. Inclusion body formation was followed during the process with flow cytometric detection by labelling the inclusion bodies with first an antibody against the protein promegapoietin and then a second fluorescent anti-antibody. The approach to label inclusion bodies directly in disintegrated and diluted cell slurry could be adopted as a method to follow protein production during the process, although the labelling procedure with incubation times and washings was somewhat time-consuming (1.5 h). The labelling of inclusion bodies inside the cells to follow protein production was feasible to perform, although an unexplained decrease in the relative fluorescence intensity occurred late in process. However, it is difficult to translate this qualitative measurement into a quantitative one, since a quantitative protein analysis should give data proportional to the volume, while the labelling of the spheric inclusion bodies gives a signal corresponding to the area of the body, and calibration is not possible. The methods were shown to be useful for monitoring inclusion body formation, but it seems difficult to get quantitative information from the analysis. Population heterogeneity analysis was performed, by using flow cytometry, on a cell population, which lost 80-90% viability according to viable count analysis. It was possible to show that the apparent cell death was due to cells incapable of dividing on agar plates after induction. These cells continued to produce the induced recombinant protein. It was shown that almost all cells in the population (≈97%) contained PMP, and furthermore total protein analysis of the medium indicated that only about 1% of the population had lysed. This confirms that the "non-viable" cells according to viable count by cfu analysis produced product. The software sensors XNH3 and µNH3, which utilises base titration data to estimate biomass and specific growth rate was shown to correlate well with the off-line analyses during cultivation of E. coli W3110 using minimal medium. In rich medium the µNH3 sensor was shown to give a signal that may be used as a fingerprint of the process, at least from the time of induction. The software sensor KLaC* was shown to respond to foaming in culture that probably was caused by increased air bubble dispersion. The RO/S coefficient, which describes the oxygen to substrate consumption, was shown to give a distinct response to stress caused by lowered pH and addition of the inducing agent IPTG. The software sensor for biomass was applied to a highly automated 6-unit multi-bioreactor system intended for fast process development. In this way also specific rates of substrate and oxygen consumption became available without manual sampling.
QC 20100819

碩士
國立臺灣大學
電信工程學研究所
94
Technological advances in integrated circuitry, micro-electromechanical systems, wireless communication, and storage battery in combination have driven the development of low-cost, low-power sensor nodes. Sensors can be scattered all over the region to build a wireless sensor network (WSN) for many applications such as environmental observations, habitat monitoring, intruder detection, military surveillance, and so on. Since the major role of these applications is to gather information over a long period of time, the network lifetime of WSNs has become a major concern for network designers. The increasing heterogeneity of sensor nodes, namely nodes with enhanced computation capacity, energy budget, or communication capability, is one direction along which network designers can leverage to increase the network lifetime. In this work, we explore different types of heterogeneity in terms of link heterogeneity, energy heterogeneity, and computation heterogeneity in WSNs and then consider the communication strategy to leverage those resources for maximizing the network lifetime. We formulate our problem as a linear programming (LP) problem for finding the communication strategy and investigate the performance benefits of link heterogeneity, energy heterogeneity, and computation heterogeneity. Based on the insights obtained from the theoretical formulation, we then propose a distributed algorithm to achieve the maximum network lifetime by leveraging heterogeneous nodes in a distributed manner. Simulation results shows that leveraging heterogeneity can improve the network lifetime in the wireless sensor networks.