Tesi sul tema "Energy Localization"

Among the low-power wireless technologies that have emerged in recent years, ultra-wideband (UWB) has successfully established itself as the reference for accurate ranging and localization, both outdoors and indoors. Due to its unprecedented performance, paired with relatively low energy consumption, UWB is going to play a central role in the next wave of location-based applications. As the trend of integration in smartphones continues, UWB is also expected to reach ordinary users, revolutionizing our lives the same way GPS and similar technologies have done. But the impact of UWB may not be limited to ranging and localization. Because of its considerable data rate, and its robustness to obstacles and interference, UWB communication may hold untapped potential for sensing and control applications. Nevertheless, several research questions still need to be answered to assess whether UWB can be adopted widely in the communication and localization landscapes. On one hand, the rapid evolution of UWB radios and the release of ever more efficient chips is a clear indication of the growing market for this technology. However, for it to become pervasive, full-fledged communication and localization systems must be developed and evaluated, tackling the shortcomings affecting current prototypes. UWB systems are typically single-hop networks designed for small areas, making them impractical for large-scale coverage. This limitation is found in communication and localization systems alike. Specifically for communication systems, energy-efficient multi-hop protocols are hitherto unexplored. As for localization systems, they rely on mains-powered anchors to circumvent the issue of energy consumption, in addition to only supporting small areas. Very few options are available for light, easy to deploy infrastructures using battery-powered anchors. Nonetheless, large-scale systems are required in common settings like industrial facilities and agricultural fields, but also office spaces and museums. The general goal of enabling UWB in spaces like these entails a number of issues. Large multi-hop infrastructures exacerbate the known limitations of small, single-hop, networks; notably, reliability and latency requirements clash with the need to reduce energy consumption. Finally, when device mobility is a factor, continuity of operations across the covered area is a challenge in itself. In this thesis, we design energy-efficient UWB systems for large-scale areas, supporting device mobility across multi-hop infrastructures. As our opening contribution, we study the unique interference rejection properties of the radio to inform our design. This analysis yields a number of findings on the impact of interference in communication and distance estimation, that are directly usable by developers to improve UWB solutions. These findings also suggest that concurrent transmissions in the same frequency channel are a practical option in UWB. While the overlapping of frames is typically avoided to prevent collisions, concurrent transmissions have counter-intuitively been used to provide highly reliable communication primitives for a variety of traffic patterns in narrowband radios. In our first effort to use concurrent transmissions in a full system, we introduce the UWB version of Glossy, a renowned protocol for efficient network-wide synchronization and data dissemination. Inspired by the success of concurrency-based protocols in narrowband, we then apply the same principles to define a novel data collection protocol, Weaver. Instead of relying on independent Glossy floods like state-of-the-art systems, we weave multiple data flows together to make our collection engine faster, more reliable and more energy-efficient. With Glossy and Weaver supporting the communication aspect in large-scale networks, we then propose techniques for large-scale localization systems. We introduce TALLA, a TDoA solution for continuous position estimation based on wireless synchronization. We evaluate TALLA in an UWB testbed and in simulations, for which we replicate accurately the behavior of the clocks in our real-world platforms. We then offer a glimpse of what TALLA can be employed for, deploying an infrastructure in a science museum to track visitors. The collected movement traces allow us to analyze fine-grained stop-move mobility patterns and infer the sequence of visited exhibits, which is only possible because of the high spatio-temporal granularity offered by TALLA. Finally, with SONAR, we tackle the issue of large-scale ranging and localization when the infrastructure cannot be mains-powered. By blending synchronization and scheduling operations into neighbor discovery and ranging, we drastically reduce energy consumption and ensure years-long system lifetime. Overall, this thesis enhances UWB applicability in scenarios that were previously precluded to the technology, by providing the missing communication and localization support for large areas and battery-powered devices. Throughout the thesis, we follow an experiment-driven approach to validate our protocol models and simulations. Based on the evidence collected during this research endeavor, we develop full systems that operate in a large testbed at our premises, showing that our solutions are immediately applicable in real settings.

Wireless devices have invaded the medical industry with a wide range of capability as components of a wireless personal area network (WPAN) and Wireless Body Area Network (WBAN). The recent advances in Internet of Things (IoT) promises even larger contributions to the future of medical applications. This paper investigates the Bluetooth Low Energy (Bluetooth Smart- BTLE) for indoor localization of HealthCare devices used in medical telemetry applications and demonstrates the key role that localization plays in tracking of Bluetooth Low Energy enabled medical devices. Proper tracking of these devices provides better management which would directly reduce the transmission of infectious diseases which can result from improper sharing of these devices. This work will investigate the novel indoor localization technologies of BTLE devices with creative research strategies, and their applications as a basis for ultimately improving health standard using BTLE localization.

This work addresses the problem of localizing an impact in a dispersive medium (waveguide) using a network of vibration sensors (accelerometers), distributed at various locations in the waveguide, measuring (and detecting the arrival of) the impact-generated seismic wave. In particular, the last part of this document focuses on the problem of localizing footsteps using underfloor accelerometers. The author believes the outcomes of this work pave the way for realizing real-time indoor occupant tracking using underfloor accelerometers; a system that is tamper-proof and non-intrusive compared to occupant tracking systems that rely on video image processing. A dispersive waveguide (e.g., a floor) causes the impact-generated wave to distort with the traveled distance and renders conventional time of flight localization methods inaccurate. Therefore, this work focuses on laying the foundation of a new alternative approach to impact localization in dispersive waveguides. In this document, localization algorithms, including wave-signal detection and signal processing, are developed utilizing the fact that the generated wave's energy is attenuated with the traveled distance. The proposed localization algorithms were evaluated using simulations and experiments of hammer impacts, in addition to occupant tracking experiments. The experiments were carried out on an instrumented floor section inside a smart building. As will be explained in this document, energy-based localization will turn out to be computationally cheap and more accurate than conventional time of flight techniques.
PHD

Positioning technologies have been created over the last few decades to provide users with location and navigation services by utilizing technological advancements in digital circuitry. GPS was one of the first positioning systems to be created (Global Positioning System). This system is a location-based navigation system that operates through satellites. Using GPS used to necessitate special (expensive) hardware, but smartphone technology has made it possible to use GPS on our handheld devices without the need for any additional equipment. We're all familiar with this; we use GPS on our smartphones for navigating in our daily lives. For outdoor location, GPS has become the de facto standard. However, due to the lack of Line-of-Sight (LoS) inside buildings, GPS cannot be used in our indoor environments. Positioning systems for indoor environments (market) are being developed since humans spend more time indoors than outdoors. Indoor positioning systems have been developed using a variety of available signal technologies (such as WiFi, ZigBee, Bluetooth, UWB, and others) depending on the context and application scenario. The Bluetooth-Low Energy (or Bluetooth Smart) protocol was first released in 2010. This signal technology was created with the goal of being low-cost and energy efficient. Apple Inc. and Aruba (Hewlett Packard Enterprise) introduced Beacon technology, which uses the Bluetooth Low Energy standard to communicate with smartphones and provide context and location awareness. The fact that all new smartphones (and tablets) include the BLE protocol can be exploited to aid in the development of low-cost, energy-efficient, precise, and accurate indoor positioning systems (by making use of Beacon and smartphone). The BLE protocol has the potential to become the de facto standard for the Internet of Things phenomenon, and so a BLE-based localization system in an indoor environment might become an integrated part of IoT.

In the new scenarios foreseen by the Internet of Things (IoT), billions of smart devices are worldwide spread and connected to each other to provide sensing information or to detect and locate tagged items with high accuracy using cheap, energy autonomous, and disposable tags. In this context, the use of energy harvesting techniques to supply devices, nowadays, plays an important role in order to create energy autonomous systems able to reduce the use of batteries, by containing the infrastructure maintenance costs, for better environmental safeguard. Hence, by considering real scenarios in which tags can be placed, where only few µW are available as input source, low-power design aspects, strategies and policies have to be taken into account during the implementation approach. In order to cover all possible solutions, radio-frequency and light energy harvesting sources are considered to build battery-less nodes. Thus, PV passive tags for indoor and outdoor environments will be presented, which allows the creation of long range Wireless Sensor Networks (WSNs) used for environmental monitoring. In harsh scenarios where the presence of obstacles makes energy scavenging operations more critical, radio-frequency sources can be adopted to build battery-less, individually addressable, UHF tags, featuring high-directive behaviour with single-monopole structures or an orientation-independent usage through double-monopole architectures. UWB circuitry for localization purposes will be introduced in both configurations: transmitting and backscattering tag solutions adopting, in the first case, a customized protocol for the UHF link, while in the second one, a RFID integration compliant with European standard, by making this activity more attractive for the market.

Internet of things will bring connected devices to a new level of pervasiveness, where any tangible thing of our daily life may embed some electronics. From a sophisticated smartwatch that embeds complex sensing and communication technologies, to the use of a basic electronic component to implement a digital signature, such as RFIDs. All these smart things worn or distributed around us enables multiple functionalities, when they can interact with each other. In this thesis, I describe the design, characterization and validation of a monitoring system based on Internet of Things technologies, for managing groups moving together in a city. Communication and energy efficiency aspects are firstly explored, to identify Bluetooth Low Energy as a promising protocol enabling scalable and energy efficient networks of things. In the thesis, the protocol has been stressed to demonstrate trade-offs between throughput, energy efficiency, scalability and the possibility to perform multi-hop communication. The potential of the protocol has been exploited within the framework of the CLIMB project. Here, the application requirements and constraints fostered the use of Bluetooth for localization and proximity detection, leading to the investigation of novel strategies to improve accuracy without affecting power consumption and ease of use.

Thesis (Ph. D.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Accurate needle placement is critical to the success of needle-based interventions. Needle deflection due to tissue non-homogeneity and dynamic forces results in targeting error, potentially requiring repeated insertions. Real-time imaging enables closed-loop control of the needle during insertion, improving insertion accuracy. The needle localization algorithm proposed in this thesis models the needle as a parametric polynomial equation optimized to minimize beam bending energy relative to a set of observed needle coordinates. Simulated insertions using an MRI dataset show that the minimum bending energy model allows planning of subsequent imaging planes to capture the moving needle while estimating the shape of the needle with low error.

Wireless Sensor Networks (WSNs) have been widely studied in the last decade because of the large set of applications that can be potentially enabled by this novel network paradigm, as environmental monitoring, home automation, localization and tracking of mobile users, seamless and ubiquitous data exchange. However, the severe constraints in terms of energy, processing, memory and reliability of the low--cost sensor devices left a number of unresolved problems, open to research. This thesis tackles two of the most interesting problems concerning WSNs, namely localization and traffic management. Accurate sensor localization is crucial for a wide variety of WSN applications and protocols, including monitoring, routing, scheduling, data fusion and so on. Typically, localization algorithms are based on an infrastructure of nodes which are aware of their geographical positions, called beacons. These nodes broadcast their coordinates in order to let the other nodes in the network, referred to as stray nodes, infer their own position by means of some estimation technique. The topic has been widely investigated, both in simulation and, more recently, in experimental testbeds. Nonetheless, the performance obtained by most of the proposed algorithms is still unsatisfactory, in particular in indoor environments. Therefore, further research is needed. In this thesis, the problem has been tackled from different perspectives, in order to gain a deep and clear understanding of the several facets that characterize this interesting domain. As a consequence, we collected a rather wide set of results that apparently may not seem to be strongly correlated, though they all fit within the same research project. As a first step, we compare well known localization algorithms in indoor environments for static networks, based on a Received Signal Strength Indicator (RSSI) ranging estimation technique. Results shed light on the actual potentialities and limits of common localization algorithms in indoor environments in a real testbed. In particular, we observed the strong impact of the shadowing random attenuation of the power of the received signal on the performance of the localization algorithms. Therefore, research has been addressed to the reduction of the shadowing term in the RSSI measures. To this end, we investigated the effect of the carrier frequency and of the antenna anisotropy on the randomness of the shadowing component, again using real measurements collected in different testbeds. Successively, our attention turned to the problem of beacon positioning that we observed may strongly affect the localization performance. We analyzed the optimal beacons placement both using an exhaustive but very complex approach and a heuristic scheme that provides close to optimal solutions while maintaining a linear complexity with the number of beacons. Looking at the localization performance separating the different effects of localization algorithms, channel parameters and beacon positioning, has been important to understand the contribution of each one of these aspects to the localization error and how much is it possible to improve the localization accuracy by means of a single technique, that usually is chosen depending on the particular scenario and available resources. Then nodes mobility has been included into the framework. We first considered an Autonomous Mobile Robot (AMR) that can interact with sensors, but is also capable to self--localize using onboard odometry. Leveraging on the complementarities of WSN and AMR, we considered the Simultaneous Localization and Mapping (SLAM) problem that consists in creating the map of an area without any a priori knowledge of the environment, while localizing the nodes in the WSN by combining the information provided by the WSN and by the AMR odometry. Second, we considered a completely mobile wireless networks in which heterogeneous nodes with different self--localization capabilities can interact one another on an opportunistic basis, exchanging localization information with other nodes that occasionally happen to be in geographical proximity. The performance of this scheme has been analyzed through a mathematical framework. We considered a Maximum Likelihood (ML) approach, a Linear Matrix Inequality (LMI) system and a simple heuristic strategy to define opportunistic localization algorithms. The validity of the mathematical model has been confirmed through experimental measures. We considered two main settings, one in which a node can rely on a single opportunistic interaction and one in which multiple contacts can be set while the node remains in the same position. We analyzed the different techniques, finding that in the first scenario, if the channel is not very noisy and the self--localization of the cooperative node quite accurate, the heuristic algorithm performs very well, in some case slightly better than ML, while the ML approach is very robust and improves localization accuracy even in difficult scenarios. If multiple interactions are available, then the heuristic technique is quite poor and it is better to rely on the LMI technique. Moreover LMI is quite flexible, because it does not require an initial guess of the position by the stray node and it can be used both with and without ranging information. The static scenario analysis was very useful to focus on the mobile localization. The design of the proposed algorithms and scenarios, the simulation parameters and limits, are strictly related to the knowledge of the channel behavior and localization performance gained from the previous studies. The opportunistic idea raises from two main considerations: the limited accuracy of the beacon based RSSI localization in a real scenario and the quite good ranging accuracy of RSSI when limiting the distance. Alongside the main research line concerning localization in WSN, during the Ph.D. we also investigated other research topics, namely traffic management and underwater sensor network, which are not directly related to the previous ones but still of great scientific and educational interest. The most significant achievements obtained in these areas have also been collected in the thesis for two reasons. First, these topics still belong to the context of wireless sensor networks, sharing some basic characteristics such as the assumptions of simplicity and energy constraints. Second, the excursion on different but correlated fields may potentially open new perspectives to well known problems, thus contributing to the innovation and the progress of the research. As mentioned, the second problem addressed in this thesis regards the traffic management in WSN. Usually all the nodes in a WSN send packets to a common node, called sink. This traffic pattern, under a certain load, can lead to congestion problems, causing packet losses, high delays and waste of energy. The proposed solutions in literature usually aim at detecting the occurence of congestion by involving in this task many nodes, sometimes the entire network. We propose a different protocol, called Efficient Packet Converge Casting (EPC$^2$), that mitigates the congestion at the sink involving only a fixed number of nodes, namely the sink's neighbors. Another scenario we look into was that of underwater wireless sensor networks (UWSNs), which enable a number of applications as for radio WSNs, fostering interest in this research field. Similarly to radio networks, the energy efficiency remains a main issue. Nodes are powered by battery and it is very important to extend the network lifetime as much as possible. The different characteristics of the environment in which nodes are deployed raise new research challenges that require novel protocol design. We addressed the energy efficiency problem in UWSN with two different approaches. First, we investigated the effect of duty--cycle and node density on the energy consumption of the network, assuming that nodes can use different power levels to transmit. Second, we proposed a channel management scheme to optimize the energy consumption, considering the strong relationship between distance, frequency and channel attenuation. Both solutions are very simple and suitable for the low--complexity underwater sensor devices and do not need any central unit to coordinate, but they work asyncronously and distributely.
Negli ultimi anni, le reti wireless di sensori (WSN) sono state molto studiate a causa delle numerose applicazioni in cui possono essere usate, come il monitoraggio ambientale, la domotica, la localizzazione e il tracking di utenti mobili. Le forti limitazioni dei nodi sensori in termini di energia, processamento, memoria e affidabilita', lasciano ancora aperti molti problemi per la ricerca. Questa tesi affronta due problemi molto importanti relativi alle reti wireless di sensori: la localizzazione e la gestione del traffico. Un'accurata localizzazione dei sensori e' importante per molte applicazioni per WSN, come monitoraggio, routing, scheduling, data fusion e molte altre. Tipicamente, gli algoritmi di localizzazione si basano su una infrastruttra di nodi, detti nodi ancora che conoscono la loro posizione geografica. Questi nodi trasmettono in broadcast le loro coordinate agli altri nodi della rete, che da queste informazioni ricavano la loro posizione tramite tecniche di stima. L'argomento e' stato largamente studiato, sia con simulazioni sia, piu' recentemente, con testbed sperimentali. Ciononostante, l'accuratezza ottenuta dalla maggior parte degli algoritmi proposti e' ancora insufficiente, soprattutto in ambienti interni. E' quindi necessario cercare nuove metodologie e nuovi approcci. In questa tesi, il problema e' stato affrontato da diversi punti di vista, in modo da capire in maniera piu' chiara e accurata i diversi aspetti che lo caratterizzano. Come conseguenza, abbiamo raccolto una vasta quantita' di dati che potrebbero apparire come non molto legati uno all'altro, ma che in realta' rientrano tutti nello stesso progetto di ricerca. Come primo passo, abbiamo confrontato algoritmi di localizzazione proposti in letteratura in uno scenario indoor e con nodi statici, stimando la distanza tra i nodi utilizzando la potenza del segnale ricevuto (RSSI). I risultati ci hanno permesso di capire le potenzialita' e i limiti dei piu' diffusi algoritmi di localizzazione in ambiente indoor e in un testbed reale. In particolare, abbiamo osservato il grande impatto che ha sulle prestazioni di localizzazione l'aleatorieta', data dal termine di shadowing, della misura di potenza ricevuta. Abbiamo quindi cercato delle strategie per ridurre la varianza di questo termine aleatorio. A questo scopo, abbiamo studiato l'effetto della frequenza della portante, utilizzando una stima della potenza ricevuta multi--canale, e l'impatto dell'anisotropia dell'antenna sulle oscillazioni dei valori di potenza ricevuta. Entrambi glil studi sono stati fatti con misure reali raccolte in diversi testbed. Successivamente, abbiamo analizzato il problema del posizionamento dei nodi ancora, dopo aver osservato l'incidenza che questo ha sull'accuratezza della localizzazione. Abbiamo confrontato il posizionamento ottimo dei nodi ancora usando sia una tecnica esaustiva, ma computazionalmente molto complessa, sia uno schema euristico che raggiunge prestazioni molto vicine all'ottimo pur mantenendo una complessita' lineare con il numero di ancore. Guardare alle prestazioni di localizzazione separando i diversi effetti degli algoritmi, dei parametri di canale e del posizionamento dei nodi ancora e' stato importante per capire il contributo dei diversi aspetti all'interno dell'errore di localizzazione e quanto sia possibile migliorare la precisione della localizzazione ottimizzando uno di questi aspetti, che solitamente viene scelto in base allo scenario e alle risorse disponibili. Quindi, abbiamo incluso nel nostro scenario anche nodi mobili. All'inizio abbiamo considerato un robot mobile (AMR) che poteva interagire con i sensori, ma anche capace di localizzarsi grazie all'odometria. Facendo leva sulla complementarieta' della rete di sensori e del robot mobile, abbiamo studiato e implementato un algoritmo di localizzazione e mappatura simultanea (SLAM), problema che consiste nel creare la mappa di un'area senza nessuna conoscenza a priori dell'ambiente e in contemporanea localizzare i nodi sensore confrontando le informazioni provenienti dai sensori e quelle ricavate dall'odometria del robot. Poi abbiamo considerato uno scenario piu' generale composto da nodi mobili ed eterogenei, con diverse capacita' di autolocalizzazione, che possono interagire uno con l'altro in modo opportunistico, scambiandosi informazioni di localizzazione con altri nodi che occasionalmente si trovano in prossimita'. Le prestazioni di questo schema sono state analizzate in un modello matematico. Abbiamo studiato un approccio a Massima Verosimiglianza (ML), uno basato su Linear Matrix Inequalities (LMI) e una semplice strategia euristica per definire gli algoritmi di localizzazione opportunistica. La validita' del modello matematico e' stata confermata attraverso misure sperimentali. Abbiamo considerato due scenari principali, uno in cui un nodo puo' contare su una sola interazione opportunistica e uno dove possono essere fatti contatti multipli mentre il nodo resta nella stessa posizione. Abbiamo analizzato le diverse tecniche, trovando che nel primo caso, se le informazioni di autolocalizzazione del nodo cooperatore e di ranging sono buone, l'algoritmo euristico ha buone prestazioni, a volte addirittura meglio della Massima Verosimiglianza, che invece e' estremamente robusto e riesce a migliorare la stima di localizzazione anche in scenari molto difficili. Se invece sono disponibili numerose interazioni, allora l'algoritmo euristico porta prestazioni scarse ed e' meglio utilizzare la tecnica LMI, specialmente utilizzando l'informazione di ranging. Inoltre l'LMI non richiede una conoscenza della posizione iniziale del nodo incognito. Lo scenario statico e' stato molto utile per studiare in maniera efficace la localizzazione mobile. La scelta degli algoritmi proposti e dello scenario, i parametri di simulazione e i limiti, sono strettamente legati a quello che abbiamo studiato riguardo al canale wireless e alle prestazioni di localizzazione nei lavori precedenti. L'idea dello scenario opportunistico infatti e' venuta a partire da due considerazioni: la limitata precisione della localizzazione con ancore basata su RSSI in uno scenario reale e la buona precisione nella stima di distanza con RSSI quando la distanza e' limitata. Affianco al principale filone di ricerca riguardante la localizzazione nelle WSN, durante il dottorato di ricerca abbiamo approfondito anche altri argomenti, come la gestione del traffico e le reti di sensori sottomarine, che non sono direttamente collegate con il tema principale, ma sono comunque di grande interesse scientifico. I risultati piu' significativi ottenuti in questi temi sono stati inseriti all'interno della tesi per due motivi. Innanzitutto, questi argomenti appartengono al contesto delle reti di sensori wireless, condividendo alcune caratteristiche di base quali l'assunzione di semplicita' e le limitazioni energetiche. Inoltre, il trattare campi diversi ma correlati, puo' aprire nuove prospettive a problemi noti, contribuendo cosi' all'innovazione della ricerca. Il secondo problema affrontato in questa tesi e' stato la gestione del traffico in reti di sensori wireless. Spesso, i nodi di una rete di sensori mandano i pacchetti ad un nodo comune, chiamato sink. Questo modello di traffico, quando il carico cresce, puo' portare a problemi di congestione, causando perdita di pacchetti, ritardi e spreco di energia. Le soluzioni proposte in letteratura solitamente cercando di individuare l'inizio di una congestione, utilizzando in questo compito molti nodi, talvolta l'intera rete. Il protocollo proposto, chiamato Efficient Packet Converge Casting (EPC$^2$), mitiga la congestione al sink, ma coinvolgnedo solo un numero fissato di nodi, i vicini del sink. Un altro scenario che abbiamo analizzato in questa tesi, sono state le reti sottomarine di sensori che, come nel caso delle reti radio, possono essere utilizzato per molteplici applicazioni e quindi hanno ricevuto molta attenzione dal mondo della ricerca. Similmente alle reti radio, l'efficienza energetica e' un problema molto sentito. I nodi sono alimentati a batteria ed e' molto importante incrementare la vita della rete il piu' possibile. La profonda diversita' dell'ambiente in cui i nodi sono disposti crea nuove sfide per la ricerca che richiedono la progettazione di nuovi protocolli. Abbiamo affrontato il problema dell'efficienza energetica in reti sottomarine con due diversi approcci. Abbiamo studiato l'effetto del duty--cycle and della densita' dei nodi sul consumo energetico della rete, assumendo che i nodi potessero usare diversi livelli di potenza in trasmissione. Quindi abbiamo proposto uno schema di utilizzazione della banda disponibile per ottimizzare il consumo energetico, facendo leva sulla forte relazione tra distanza, frequenza e attenuazione del canale. Entrambe le soluzioni sono molto semplici e adatte ai dispositivi sottomarini che hanno forti limitazioni. Inoltre non richiedono una unita' centrale per essere coordinate, ma operano in modo asincrono e distribuito.

The intent of this master’s thesis is to look for the best solution of finding lost items of everyday use. Described solution is based on GPS for outdoor and Bluetooth Low Energy for indoor localization. User of this system will be able to find his/her lost items using smartphone application.

This thesis reports magnetotransport measurements in graphene Hall bar devices. Graphene samples fabricated from different techniques (epitaxial growth on silicon carbide, exfoliation, and CVD) are measured and compared. Measurements are taken primarily using a 21T magnet, at liquid Helium 4 temperatures. The first three chapters present the background for the work. Chapter One details the motivation for the thesis, and gives a general background to carbon and the state of carbon research. Chapter Two covers the theoretical background of graphene, including the anomalous quantum Hall effect and weak localization. Chapter Three covers the synthesis of graphene and a typical procedure undertaken for device fabrication. The next three chapters report experimental results. Chapter Four presents measurements of the energy loss rates in exfoliated graphene. The mechanism of carrier energy loss is investigated, and compared to theory. Further, the breakdown of the quantum Hall effect in the device is investigated, demonstrating peak current densities far in excess of those found in the literature for exfoliated graphene. Chapter Five shows measurements comparing the carrier energy loss rates in graphene derived from the epitaxial, exfoliated and CVD fabrication techniques. An unconventional method for measuring the energy loss rate based on measuring the weak localization peak is developed, and trends in the energy loss rates with carrier density are investigated for a wide range of devices. Chapter Six reports a comparison of the decomposed weak localization scattering lengths from graphene devices derived from the epitaxial and CVD methods, and compares these to measurements from the literature. Further, a previously reported saturation of the weak localization in graphene is investigated, and demonstrated to be an experimental artefact. This thesis provides a development of the understanding, and an experimental verification, of several aspects of heat transfer in graphene. An understanding of heat transfer is of critical importance to proposed high-density nano-electronics, and bolometry applications. The high breakdown currents and observed trends in carrier density are also of significant assistance in the design of low-cost resistance metrology devices based on graphene.

[EN] Metamaterials are periodic structures whose unit cells are small compared to the wavelength at the operating frequency. Under these conditions, these artificial materials can be considered as homogeneous media whose constitutive parameters depend on the characteristics of the unit cells. The discovery of metamaterials opened a new research field that has produced many works with microwaves, optical waves and acoustic waves. In this context, the main goal of this thesis is the study of new structures based on metamaterials that allow controlling of electromagnetic energy. In particular, new solutions for localization and absorption of electromagnetic waves are proposed. The thesis has been developed in the Wave Phenomena Group of the Polytechnic University of Valencia and in collaboration with the Group of Acoustic and Electromagnetic Metamaterials at the University of Exeter. The problems studied in the first part of this thesis are energy harvesting for subsequent absorption, wireless power transfer and new systems that can be used as position sensors. To solve these problems a new type of cylindrical, multilayer and anisotropic structures known as Radial Photonic Crystals are used. The radial dependence of the constitutive parameters generates, in these structures, a behavior like a one dimensional photonic crystals. Among the results obtained with these structures, it is included the first experimental demonstration of a Radial Photonic Crystals based resonator. Absorption of electromagnetic waves by thin layers of lossy materials is the second topic of this thesis. The main target is the theoretical and experimental study of the absorption enhancement in thin layers by using two-dimensional periodic structures, also called metasurfaces. Specifically, we studied the effects of a square lattice of coaxial cavities covered by a thin layer of lossy material. As a result, an enhancement of the absorption peaks that can produce total absorption is achieved. The semi-analytical study of this structure has allowed obtaining expressions that control the position of the absorption peak and its amplitude; which have helped to develop a design methodology for total absorption systems.
[ES] Los metamateriales son estructuras periódicas cuyas celdas unidad son muy pequeñas en comparación con la longitud de onda a la frecuencia de trabajo. Bajo estas condiciones, estos materiales artificiales pueden considerarse como medios homogéneos cuyos parámetros constitutivos dependen de las características de las celdas unidad que los componen. La aparición de los metamateriales abrió un nuevo campo de investigación que ha generado multitud de trabajos en las líneas de microondas, óptica y acústica. En este contexto, el objetivo principal de esta tesis es el estudio de nuevas estructuras basadas en metamateriales que permitan el control de la energía electromagnética. En particular, plantea nuevas soluciones para problemas de localización y absorción de ondas electromagnéticas. La tesis ha sido desarrollada en el Grupo de Fenómenos Ondulatorios de la Universidad Politécnica de Valencia y en colaboración con el Grupo de Metamateriales Acústicos y Electromagnéticos de la Universidad de Exeter. Los problemas estudiados en la primera parte de esta tesis son la concentración de energía para su posterior absorción, la transferencia inalámbrica de potencia y nuevos sistemas capaces de ser empleados como sensores de posición. Para la solución de estos problemas se emplean un nuevo tipo de estructuras cilíndricas, multicapa y anisótropas conocidas como Cristales Fotónicos Radiales. La dependencia radial de los parámetros constitutivos de los materiales que componen cada una de sus capas genera, en estas estructuras, un comportamiento similar al de los cristales fotónicos unidimensionales. Entre los resultados obtenidos con estas estructuras, cabe destacar la primera demostración experimental de un resonador basado en Cristales Fotónicos Radiales. La absorción de ondas electromagnéticas por capas delgadas de materiales con pérdidas es el segundo tema tratado en esta tesis. El objetivo principal es el estudio teórico y experimental del aumento de la absorción en capas delgadas mediante el uso de estructuras periódicas bidimensionales, también llamadas metasuperficies. En concreto, se han estudiado los efectos de una red cuadrada de cavidades coaxiales sobre la que se coloca una capa delgada de un material con pérdidas. Como resultado, se consigue un aumento de la absorción que permite obtener picos de absorción total. El estudio semianalítico de esta estructura ha permitido obtener expresiones que controlan la posición del pico de absorción y su amplitud; las cuales han permitido desarrollar una metodología de diseño para sistemas de absorción total.
[CAT] Els metamateriales són estructures periòdiques en els que les cel·les unitat són molt xicotetes en comparació amb la longitud d'ona a la freqüència de treball. Tenint en consideració aquestes condicions, aquestos materials artificials poden considerar-se com a mitjans homogenis en els que els paràmetres constitutius depenen de les característiques de les cel·les unitat que els componen. A més, l'aparició dels metamateriales va obrir un nou camp d'investigació que ha generat multitud de treballs en les línies de microones, òptica i acústica. En aquest context, l'objectiu principal d'aquesta tesi és l'estudi de noves estructures basades en metamateriales que permeten el control de l'energia electromagnètica. En particular, planteja noves solucions per a problemes de localització i absorció d'ones electromagnètiques. La tesi ha sigut realitzada en el Grup de Fenòmens Ondulatoris de la Universitat Politècnica de València i en col·laboració amb el Grup de Metamateriales Acústics i Electromagnètics de la Universitat d'Exeter. Els problemes analitzats en la primera part de la tesi són la concentració d'energia per a la seua posterior absorció, la transferència inalàmbrica de potència i nous sistemes capaços de ser empleats com a sensors de posició. Per a la solució dels problemas identificats s'utilitza un nou tipus d'estructures cilíndriques, multicapa i anisòtropes conegudes com a Cristalls Fotónics Radials. La dependència radial dels paràmetres constitutius dels materials que componen cadascuna de les seues capes genera, en aquestes estructures, un comportament semblant al dels Cristalls Fotónics Unidimensionals. Entre els resultats obtinguts, cal destacar la primera demostració experimental d'un ressonador basat en Cristalls Fotónics Radials. Pel que respecta a la segon part de la tesi, l'absorció d'ones electromagnètiques per capes primes de materials amb pèrdues és tema tractat. L'objectiu principal és l'estudi teòric i experimental de l'augment de l'absorció en capes primes per mitjà de l'ús d'estructures periòdiques bidimensionals, també denominades metasuperficies. En concret, s'han examinat els efectes d'una xarxa quadrada de cavitats coaxials sobre la qual es col·loca una capa prima d'un material amb pèrdues. Com a resultat, s'aconseguix un augment de l'absorció que permet obtindre pics d'absorció total. Així mateix, l'estudi semi-analític d'aquesta estructura ha permés obtindre expressions que controlen la posició del pic d'absorció i la seua amplitud; les quals han permés desenvolupar una metodologia de disseny per a sistemes d'absorció total.
Díaz Rubio, A. (2015). Control of electromagnetic energy by metamaterials [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/54137
TESIS

The work presented herein explores the ability of Ultra High Frequency Radio Frequency (UHF RF) devices, specifically (Radio Frequency Identification) RFID passive tags and Bluetooth Low Energy (BLE) to be used as tools to locate items of interest inside a building. Localization Systems based on these technologies are commercially available, but have failed to be widely adopted due to significant drawbacks in the accuracy and reliability of state of the art systems. It is the goal of this work to address that issue by identifying and potentially improving upon localization algorithms. The work presented here breaks the process of localization into distance estimations and trilateration algorithms to use those estimations to determine a 2D location. Distance estimations are the largest error source in trilateration. Several methods are proposed to improve speed and accuracy of measurements using additional information from frequency variations and phase angle information. Adding information from the characteristic signature of multipath signals allowed for a significant reduction in distance estimation error for both BLE and RFID which was quantified using neural network optimization techniques. The resulting error reduction algorithm was generalizable to completely new environments with very different multipath behavior and was a significant contribution of this work. Another significant contribution of this work is the experimental comparison of trilateration algorithms, which tested new and existing methods of trilateration for accuracy in a controlled environment using the same data sets. Several new or improved methods of triangulation are presented as well as traditional methods from the literature in the analysis. The Antenna Pattern Method represents a new way of compensating for the antenna radiation pattern and its potential impact on signal strength, which is also an important contribution of this effort. The performance of each algorithm for multiple types of inputs are compared and the resulting error matrix allows a potential system designer to select the best option given the particular system constraints.

GPS is widely used for localization and tracking, however traditional GPS receivers consume too much energy for many applications. This thesis implements and evaluates the performance of a low energy GPS solution, including a working hardware prototype, that reduces energy consumption significantly. The prototype operates for 2 years on a coin cell battery, sampling every minute. The corresponding time for a traditional receiver is 2 days. The main difference is that a traditional receiver requires 30 seconds of data to estimate a position; this solution only requires 2 milliseconds of data, a reduction of a factor 15 000. The solution consists of a portable device, sampling the GPS signal, and server software that utilizes Doppler navigation and Coarse Time Navigation to estimate positions. The median positioning error is at most 38 meters in our tests. We expect that this solution will enable positioning for billions of devices in the near future.

The ability to swim and navigate the surrounding environment confers an advantage to motile bacteria, allowing the occupation of niches that are optimum for survival and growth. Bacteria are too small to sense their environment spatially, so they must sense the environment temporally by comparing the past and present environments and altering their motility accordingly. Chemotaxis systems coordinate flagellar motility responses with temporal sensing of the environment. Chemotaxis is proposed to be involved in plant root colonization by directing soil bacteria toward root exudates of various cereals, promoting growth. The nitrogen-fixing alpha-proteobacterium Azospirillum brasilense utilizes chemotaxis to navigate its environment by integrating various environmental signals into a chemotaxis signal transduction pathway. In chemotaxis, transducers receive environmental sensory information and transmit the signal to the histidine kinase CheA, which relays the signal to the response regulator CheY. A novel chemotaxis transducer, Tlp1, has been identified and characterized as an energy sensor by constructing a tlp1 mutant and performing behavioral and root colonization assays. In order to adapt to changing environmental conditions, chemotactic microorganisms must employ a molecular “memory” comparing present environmental conditions to ones previously experienced and resetting the chemotaxis transducer to a prestimulatory status. A recently identified chemotaxis operon revealed a methyltransferase CheR and methylesterase CheB, comprising an adaptation system, suggesting that A. brasilense undergoes methylation-dependent taxis responses, contrary to previous reports. Chemotaxis and methanol release assays suggest that adaptation by methylation in locomotor behavior involves the presence of other unknown methylation systems, and the contribution of CheR and CheB to chemotactic and aerotactic responses is complex. There is growing evidence that chemotaxis-like signal transduction pathways control a myriad of other cellular processes regulated in a temporal fashion. This would convey an advantage to cells by allowing modulation of cellular processes based on slight changes in environmental conditions and provide checkpoints for energetically consuming processes. Mutations in components of the chemotaxis-like signal transduction system revealed differences in cell size and exopolysaccharide production. This work shows that the signal transduction pathway of A. brasilense modulates cell length in response to changes in nutrient conditions, independently of growth rate.

Mutations in BEST1, the gene encoding for Bestrophin-1 (Best1), cause five, clinically distinct inherited retinopathies: Best vitelliform macular dystrophy (BVMD), adult-onset vitelliform macular dystrophy (AVMD), autosomal recessive bestrophinopathy (ARB), autosomal dominant vitreoretinochoroidopathy (ADVIRC), and retinitis pigmentosa (RP). Little is known regarding how BEST1 mutations cause disease and why mutations cause multiple disease phenotypes. Within the eye, Best1 is a homo-oligomeric, integral membrane protein that is exclusively localized to the basolateral plasma membrane of the retinal pigment epithelium (RPE). Here, it regulates intracellular Ca2+ signaling and putatively mediates anion transport. Since defects in localization and oligomerization are known to underlie other channelopathies, we investigated how mutations causal for BVMD, AVMD, ARB, ADVIRC, and RP impact the localization and oligomerization of Best1. We generated replication-defective adenoviral vectors encoding for WT and 31 mutant forms of Best1 associated with these five diseases and expressed them in confluent, polarized Madin-Darby canine kidney and/or RPE cells. Localization was assessed via immunofluorescence and confocal microscopy. Oligomerization was examined using live-cell fluorescence resonance energy transfer (FRET) as well as reciprocal co-immunoprecipitation experiments. We report that all 31 BVMD, AVMD, ARB, ADVIRC, and RP mutants tested can reciprocally co-immunoprecipitate with and exhibit comparable FRET efficiencies to WT Best1, indicative of unimpaired oligomerization. While all RP and ADVIRC mutants were properly localized to the basolateral plasma membrane, many but not all AVMD, ARB, and BVMD mutants were mislocalized to intracellular compartments. When co-expressed with WT Best1, mislocalized mutants predominantly co-localized with WT Best1 in intracellular compartments. Studies involving four ARB truncation mutants reveal that the first 174 amino acids are sufficient to mediate oligomerization with WT Best1 and that amino acids 472-585 are not necessary for proper trafficking. We conclude that, although mislocalization is a common result of BEST1 mutation, it is not an absolute feature of any individual bestrophinopathy. Moreover, we show that some recessive mutants mislocalize WT Best1 when co-expressed, indicating that mislocalization cannot, on its own, generate a disease phenotype, and that the absence of Best1 at the plasma membrane is well tolerated.

L’introduction de légères perturbations dans la périodicité d’oscillateurs périodiques faiblement couplés s’avère être une solution prometteuse pour améliorer la puissance récupérée ainsi leur bande passante. Ces légères perturbations dans la périodicité des récupérateurs d’énergie créent des modes de vibration localisés, permettant de réduire considérablement leur nombre de transducteurs et leur encombrement. Cette thèse de doctorat porte sur l’optimisation du design de structures périodiques et bi-périodiques pour la récupération d’énergie vibratoire. Tout d’abord, le design d’oscillateurs périodiques faiblement couplés pour les dispositifs de récupération d’énergie à transduction électromagnétique est optimisé. Un algorithme génétique est utilisé pour identifier les perturbations optimales à introduire ainsi que leur emplacement afin de maximiser la puissance récoltée, tout en minimisant le nombre de perturbations introduites. Ensuite, une structure bi-périodique est conçue et optimisée pour surmonter la limitation usuelle de ces récupérateurs périodiques, à savoir une bande passante étroite. Cette structure bi-périodique est constituée de deux sous-systèmes d’oscillateurs périodiques couplés, permettant d’exploiter le phénomène de localisation d’énergie et également d’élargir la bande passante. En récupérant l’énergie d’un tiers des sous-systèmes perturbés de manière optimale dans des structures périodiques et bipériodiques, il est possible de récupérer environ 70 % de la puissance totale du système. Cependant, la structure bi-périodique permet de cibler deux fréquences, au lieu d’une seule dans le cas de structures périodiques. Par la suite, l’optimisation du design de la structurepériodique est étudiée en incorporant une nonlinéarité de type géométrique. Les résultats montrent que ce type de non-linéarité accentue la localisation de l’énergie, améliorant ainsi la puissance récupérée ainsi que la bande passante. Pour valider les résultats théoriques, un récupérateur d’énergie à transduction électromagnétique composé de huit oscillateurs couplés est conçu et fabriqué. Les performances du récupérateur d’énergie ont ensuite été évaluées en reproduisant les résultats issus de l’optimisation. Les résultats expérimentaux sont en bon accord avec les résultats théoriques. Ensuite, la résonance interne non linéaire est exploitée pour la récupération d’énergie à large bande passante. Un récupérateur d’énergie a transduction électromagnétique est conçu avec des fréquences naturelles commensurables et des forces magnétiques non linéaires quadratiques qui dé- clenchent une résonance interne 2:1. Des études analytiques et numériques montrent des échanges d’énergie intermodaux, ce qui améliore la bande passante. Le concept est ensuite étendu à un récupérateur d’énergie basé sur la résonance interne 2:1:2. Les ré- sultats théoriques montrent qu’il est possible d’améliorer d’autant plus la bande passante. Une optimisation est effectuée pour régler le rapport des fréquences propres afin de maximiser cette augmentation de la bande passante. La structure avec le design élaboré est ensuite construite pour les deux cas de ré- sonnance interne étudiés. Les résultats expérimentaux obtenus confirment les résultats théoriques. Le concept proposé peut finalement être généralisé à une structure composée de chaînes d’oscillateurs couplés ayant une ré- sonance interne 2:1:2
Vibration energy harvesting by weakly-coupled periodic oscillators with mistuning are promising candidates to improve power and bandwidth. Introducing mistuning creates localized vibration modes, allowing the design to reduce the number of required transducers and harvesters size significantly. This PhD thesis focuses on the design optimization of periodic and biperiodic structures for vibration energy harvesting. First, an electromagnetic energy harvesting device based on weakly coupled periodic structures is optimized. A genetic algorithm is used to identify the optimal mistuning parameters to maximize the harvested power while minimizing the number of mistuned subsystems. Subsequently, a biperiodic structure is designed using two coupled periodic substructures, which allows simultaneous utilization of energy localization phenomenon and increasing the frequency bandwidth. By mistuning almost one-third of thesubsystems in periodic and biperiodic structures, around 70% of the total power of the system can be harvested. However, the biperiodic structure allows to target two frequency bandwidthsrather than only one in periodic structures. Moreover, the design optimization of the periodicstructure is studied by incorporating geometric nonlinearity. The results indicate that nonlinearity amplifies energy localization, improving the harvested power and frequency bandwidth.To validate the theoretical findings, an electromagnetic harvester composed of eight coupledoscillators is designed and fabricated. Harvester performance is evaluated by replicating theoptimization results. The experimental results are in good agreement with the theoretical ones.Afterward, nonlinear internal resonance is studied for broadband energy harvesting. An electromagnetic harvester is designed with commensurable natural frequencies and quadratic nonlinear magnetic forces that trigger a 2:1 internal resonance. Analytical and numerical studies show intermodal energy exchanges, demonstrating improved bandwidth. The concept is then expanded into a harvester based on 2:1:2 internal resonance. Theoretical results suggest the potential for further bandwidth enhancement. An optimization process is performed to maximize the harvester power and frequency bandwidth. The proposed designs are fabricated and experimental results confirmed the theoretical findings. The proposed concept can be generalized to a structure with chains of coupled oscillators having 2:1:2 internal resonance

With the introduction of Wireless Multimedia Sensor Networks, large-scale remote outdoor surveillance applications where the majority of the cameras will be battery-operated are envisioned. These are the applications where the frequency of incidents is too low to employ permanent staffing such as monitoring of land and marine border, critical infrastructures, bridges, water supplies, etc. Given the inexpensive costs of wireless resource constrained camera sensors, the size of these networks will be significantly larger than the traditional multi-camera systems. While large number of cameras may increase the coverage of the network, such a large size along with resource constraints poses new challenges, e.g., localization, classification, tracking or reactive behavior. This dissertation proposes a framework that transforms current multi-camera networks into low-cost and reactive systems which can be used in large-scale remote surveillance applications. Specifically, a remote surveillance system framework with three components is proposed: 1) Localization and tracking of objects
2) Classification and identification of objects
and 3) Reactive behavior at the base-station. For each component, novel lightweight, storage-efficient and real-time algorithms both at the computation and communication level are designed, implemented and tested under a variety of conditions. The results have indicated the feasibility of this framework working with limited energy but having high object localization/classification accuracies. The results of this research will facilitate the design and development of very large-scale remote border surveillance systems and improve the systems effectiveness in dealing with the intrusions with reduced human involvement and labor costs.

In Wireless Sensor Actor Networks (WSANs), sensor nodes perform the sensing task and actor nodes take action based on the sensed phenomenon. The presence of actors in this configuration can not be benefited from, unless they are able to execute actions at right place and right time in the event region. The right place can be related to the accurate position of the sensor nodes. While, the right time is related to delivering the packets directly to the appropriate actors within the event specific response times. Hence, the efficient localization of sensor nodes, sensor-actor/actor-actor coordination and real-time routing is indispensable in WSANs. Furthermore, the limited energy levels and bandwidth of the state of art sensor nodes currently impose stringent requirements for low-complexity, low-energy, distributed coordination and cooperation protocols and their implementation. In this study, we propose an integrated framework which addresses the issues of sensors localization, network configuration, data aggregation, real-time data delivery, sensor-actor/actor-actor coordination and energy saving mechanisms. The proposal incorporates novel approaches on three fronts
(1) timing-based sensors localization (TSL) algorithm to localize the sensor nodes relative to actors, (2) real-time coordination and routing protocols and (3) energy conservation. The distributed real-time coordination and routing is implemented in addressing and greedy modes routing. A cluster-based real-time coordination and routing (RCR) protocol operates in addressing mode. The greedy mode routing approach (Routing by Adaptive Targeting, RAT) is a stateless shortest path routing. In dense deployment, it performs well in terms of delay and energy consumption as compared to RCR. To keep the traffic volume under control, the framework incorporates a novel real-time data aggregation (RDA) approach in RCR such that the packets deadlines are not affected. RDA is adaptive to the traffic conditions and provides fairness among the farther and nearer cluster-heads. Finally, framework incorporates a power management scheme that eliminates data redundancy by exploiting the spatial correlation of sensor nodes. Simulation results prove that the framework provides the real-time guarantees up to 95 % of the packets with lesser energy consumption of up to 33 % achieved using MEAC as compared to LEACH and SEP. The packet delivery ratio is also 60 % higher than that of semi-automated architecture. Furthermore the action accuracy is supported by TSL which restricts the localization errors less than 1 meter by tuning it according to the expected velocity of nodes and required accuracy.

Damage assessment (damage detection, localization and quantification) in structures and appropriate retrofitting will enable the safe and efficient function of the structures. In this context, many Vibration Based Damage Identification Techniques (VBDIT) have emerged with potential for accurate damage assessment. VBDITs have achieved significant research interest in recent years, mainly due to their non-destructive nature and ability to assess inaccessible and invisible damage locations. Damage Index (DI) methods are also vibration based, but they are not based on the structural model. DI methods are fast and inexpensive compared to the model-based methods and have the ability to automate the damage detection process. DI method analyses the change in vibration response of the structure between two states so that the damage can be identified. Extensive research has been carried out to apply the DI method to assess damage in steel structures. Comparatively, there has been very little research interest in the use of DI methods to assess damage in Reinforced Concrete (RC) structures due to the complexity of simulating the predominant damage type, the flexural crack. Flexural cracks in RC beams distribute non- linearly and propagate along all directions. Secondary cracks extend more rapidly along the longitudinal and transverse directions of a RC structure than propagation of existing cracks in the depth direction due to stress distribution caused by the tensile reinforcement. Simplified damage simulation techniques (such as reductions in the modulus or section depth or use of rotational spring elements) that have been extensively used with research on steel structures, cannot be applied to simulate flexural cracks in RC elements. This highlights a big gap in knowledge and as a consequence VBDITs have not been successfully applied to damage assessment in RC structures. This research will address the above gap in knowledge and will develop and apply a modal strain energy based DI method to assess damage in RC flexural members. Firstly, this research evaluated different damage simulation techniques and recommended an appropriate technique to simulate the post cracking behaviour of RC structures. The ABAQUS finite element package was used throughout the study with properly validated material models. The damaged plasticity model was recommended as the method which can correctly simulate the post cracking behaviour of RC structures and was used in the rest of this study. Four different forms of Modal Strain Energy based Damage Indices (MSEDIs) were proposed to improve the damage assessment capability by minimising the numbers and intensities of false alarms. The developed MSEDIs were then used to automate the damage detection process by incorporating programmable algorithms. The developed algorithms have the ability to identify common issues associated with the vibration properties such as mode shifting and phase change. To minimise the effect of noise on the DI calculation process, this research proposed a sequential order of curve fitting technique. Finally, a statistical based damage assessment scheme was proposed to enhance the reliability of the damage assessment results. The proposed techniques were applied to locate damage in RC beams and slabs on girder bridge model to demonstrate their accuracy and efficiency. The outcomes of this research will make a significant contribution to the technical knowledge of VBDIT and will enhance the accuracy of damage assessment in RC structures. The application of the research findings to RC flexural members will enable their safe and efficient performance.

Liberalized electricity markets, increased awareness of clean energy resources and theirdecreasing costs have resulted in large numbers of distributed power generators beinginstalled on distribution network. Installation of distributed generation has altered thepassive nature of distribution grid. A concept of Active Distribution Network is proposedwhich will enable present day infrastructure to host renewable energy resources reliably.Fault management that includes fault localization, isolation and service restoration ispart of active management of distribution networks.This thesis aims to introduce a distributed protection methodology for fault localizationand isolation. The objective is to enhance reliability of the network. Faults are identifiedbased on root mean square values of current measurements and by comparing thesevalues with preset thresholds. The method based on multi-agent concept can be usedto locate the faulty section of a distribution network and for selection of faulty phases.The nodal Bus Agent controls breakers that are associated with it. Based on indicationof fault, adjacent bus Agents communicate with each other to identify location of fault.A trip signal is then issued to corresponding Breakers in adjacent Bus Agents, isolatingthe faulty section of line. A case study was carried out to verify suitability of the proposedmethod. A meshed network model and multi-agent based protection scheme wassimulated in Simulink SimPowerSystems. Considering nature of Distribution Network,separate breakers for each phase are considered. The distribution network protectionsystem identified fault introduced in the network correctly along with interrupting thefault current.Keywords

Durant la dernière décennie, les personnes âgées vivant seules sont de plus en plus nombreuses. Ainsi, afin de leur assurer une assistance à domicile continue, la notion de "maison intelligente" est apparue. Notre travail consiste à combiner trois technologies (Bluetooth Low Energy, audio et LiFi) afin de proposer un système hybride de localisation d'une personne âgée dans une maison intelligente, qui soit efficace et précis. Le principe d’hybridation de ces trois sous-systèmes repose sur la fusion de leurs résultats respectifs via la proposition de trois nouvelles métriques « DOP-Like » permettant d’évaluer le taux de « précision » et « d’exactitude » du résultat de chaque sous-système. Cette évaluation sert à constituer une pondération des résultats intermédiaires afin de calculer la position finale de la cible à localiser. Grâce à l’introduction de ces indicateurs, l’erreur de localisation de notre système est passée de 0,5m à 0,2m en moyenne
Over the past decade, more and more elderly people are choosing to live alone. Therefore, in order to provide them with continuous home assistance, the notion of "intelligent home" has emerged. Our aim is to combine three technologies (Bluetooth Low Energy, Audio and LiFi) to provide an efficient and accurate hybrid indoor localization system that locates an elderly person inside a smart home. The principle of hybridization of these three subsystems is based on the combination of their respective results by proposing three new DOP-Like metrics to evaluate "precision" and "accuracy" of the result of each subsystem. This evaluation serves to constitute a weighting of the intermediate results in order to calculate the final position of the target to be localized. Thanks to the introduction of these indicators, the localization error of our system decreased from an average of 0.5m to 0.2m

This masters thesis deals with technics of localization for wireless senzor networks with a focus on anchor free location algorithm by authors G. Jianquan and Z. Wei. It also describes the available simulations frameworks based on OMNeT++ platform and implementation of the anchor free algorithm in the simulation program Castalia. Furthermore, it deals with the energy demands of this algorithm based on results of simulations that were done for the communication unit IRIS.

Ultrawideband (UWB) is one of the promising technologies for future short-range high data rate communications (e.g. for wireless personal area networks) and longer range low data rate communications (e.g. wireless sensor networks).Despite its various advantages and potentials (e.g. low-cost circuitry, unlicensed reuse of licensed spectrum, precision ranging capability etc.), UWB also has its own challenges. The goal of this dissertation is to identify and address some of those challenges, and provide a framework for practical UWB transceiver design.In this dissertation, various modulation options for UWB systems are reviewed in terms of their bit error rate (BER) performances, spectral characteristics, modem and hardware complexities, and data rates. Time hopping (TH) code designs for both synchronous (introduced an adaptive code assignment technique) and asynchronous UWB impulse radio (IR) systems are studied. An adaptive assignment of two different multiple access parame ters (number of pulses per symbol and number of pulse positions per frame)is investigated again considering both synchronous and asynchronous scenarios, and a mathematical framework is developed using Gaussian approximations of interference statistics for different scenarios. Channel estimation algorithms for multiuser UWB communication systems using symbol-spaced (proposed a technique that decreases the training size), frame-spaced (proposed a pulse-discarding algorithm for enhanced estimationperformance), and chip-spaced (using least squares (LS) estimation) sampling are analyzed.A comprehensive review on multiple accessing andinterference avoidance/cancellation for IR-UWB systems is presented.BER performances of different UWB modulation schemes in the presence of timing jitter are evaluated and compared in static and multipath fading channels, and finger estimation error, effects of jitter distribution, and effects of pulse shape are investigated. A unified performance analysis app roach for different IR-UWB transceiver types (stored-reference, transmitted-reference, and energy detector) employing various modulation options and operating at sub-Nyquist sampling rates is presented. The time-of-arrival (TOA) estimation performance of different searchback schemesunder optimal and suboptimal threshold settings are analyzed both for additive white Gaussian noise (AWGN) and multipath channels.

The aim of the thesis is to investigate the design of efficient wireless networks through practical as well as theoretical considerations. We constructed a wireless sensor network (WSN) testbed with battery operated nodes capable of RF communication. The system is a centralized tree-based WSN to study challenges of target modeling, detection, and localization. The testbed employed magnetic sensors, on which relatively few results have been reported in the literature. A ferrous test target is modeled as magnetic dipole by validating experimentally. The problem of sensor sensitivity variation is addressed by including sensitivity estimates in model validation. After reliably detecting the target, maximum-likelihood and least-squares techniques are applied for localization. Practical considerations of constructing a WSN utilizing magnetic sensors addressed. Maximum-lifetime operation of these networks requires joint consideration of sensing and communication. Energy harvesting is promising to overcome this major challenge for energy-constrained systems. In the second part of the thesis, we considered the minimization of transmission completion time for a given number of bits per user in an energy harvesting multiuser communication system, where the energy harvesting instants are known beforehand. The two-user case with achievable rate region having structural properties satisfied by the AWGN Broadcast Channel is studied. It is shown that the optimal scheduler ends transmission to both users at the same time while deferring a nonnegative amount of energy from each energy harvest for later use. The problem is formulated as an optimization problem and solved by exploiting its special structure.

This thesis presents an improvement of the long range battery-less UHF RFID platform for sensor applications which is based on the open source Wireless Identification and Sensing Platform (WISP) project. The purpose of this work is to design a digital logic that performs the RFID EPC gen2 protocol communication, is able to acquire information by sensors and provide an accurate estimation of tag location ensuring low energy consumption. This thesis will describe the hardware architecture on which the digital logic was inserted, the Verilog code developed, the methods by which the digital logic was tested and an explorative study of chip synthesis on Cadence.

O interesse na pesquisa de Lasers randômicos, meios dispersivos com alto ganho, tem crescido nos últimos anos em virtude das novas possibilidades advindas ao se trabalhar com estes sistemas, como emissões em bandas com baixo ganho, bicromaticidade, localização da luz em meios difusos e sistemas ópticos mais compactos. Nesse trabalho serão discutidos temas como espalhamento da luz por partículas, intensidade de retroespalhamento, ganho em meios desordenados e as transições energéticas do neodímio, correlacionando as emissões características obtidas nos experimentos com a teoria. Quanto aos resultados será apresentado a primeira observação de laser randômico com nanopó de Nd:YVO4 através de análise do comportamento da emissão espectral e temporal oriunda da transição 4F3/24I11/2 (1064 nm). Os resultados apresentam outra forma de analisar a cinética temporal da emissão de laser randômico, permitindo uma separação da fração de emissão estimulada e espontânea e comparação desse resultado com o estreitamento sutil da largura de linha, típico de lasers randômicos. As conversões ascendentes e saturação de ETU (conversão ascendente por transferência de energia) serão analisadas na mesma amostra, sendo todos os ajustes provenientes da literatura e de fundamental interesse, principalmente por se tratarem de um mecanismo de perda em lasers operando na região do infravermelho. Por fim, a emissão característica será avaliada pela técnica CBS (retroespalhamento coerente) para determinação da coerência do laser emitido e localização da luz neste meio difuso, com os resultados comparados aos da simulação.
In the past few years, the interest in random lasers, which refer to lasing in disordered media where strong multiple scattering plays a constructive role instead of being only a loss factor, have received considerable attention due to its unique properties and its potential applications, such as emission at new, extremely low gain lines, simultaneous emission of several very different wavelengths at the same time, strong light localization and miniaturization. Single and multiple particle light scattering, backscattering intensity, light diffusion with gain and the energy level diagram of Neodymium will be presented in this current work, alongside with a parallel from the typical emission lines obtained experimentally with theory. The demonstration of random laser action in Nd:YVO4 nanopowder, by analyzing the spectral and temporal behavior from the 4F3/24I11/2 (1064 nm) transition is presented. A method that analyzes the decay kinetics after long-pulse excitation is used to determine the laser characteristics, allowing measuring the fractional contribution of spontaneous and stimulated emission in the samples backscattering cone, with is in agreement to the smoothing linewidth narrowing as a function of pump power typical from random lasers. Also the visible emission along a method to determine quantitatively the ETU (energy-transfer upconversion) rate is presented, which is particularly interesting, as is a mechanism that introduces a loss channel for devices emitting in the infrared region. At last, the coherent laser emission and light localization will be evaluated by using the CBS (coherent backscattering) technique in this diffusive media, in which the results are compared with simulation.

La production endogène ou la prise exogène d’hormones sexuelles chez la femme génère un climat hormonal qui lui est propre. Ces particularités endocriniennes influent sur la composition corporelle et modifient les sécrétions et/ou la sensibilité de certaines hormones clés du métabolisme énergétique pouvant conduire à une utilisation spécifique des substrats énergétiques à l’exercice. L’objectif de ce travail était d’étudier l’influence d’une contraception orale (CO : mini dosée monophasique), de la prise alimentaire pré-exercice et de la localisation des graisses sur les réponses métaboliques et hormonales de la femme préménopausée et normo-pondérée à l’exercice (45 min à 65% de O2max). Nos résultats ont montré que la prise d’une CO ne modifiait pas les réponses métaboliques et hormonales et l’utilisation des substrats énergétiques à l’exercice quel que soit le statut nutritionnel des sujets (exercice à jeun ou en situation postprandiale). Cependant, à l’exercice, une situation de jeûne a favorisé une augmentation de l’oxydation lipidique et cela quel que soit le statut hormonal des sujets (CO+ ou CO-). En situation postprandiale, l’exercice physique a stimulé l’activité lipolytique chez des femmes CO+ et CO- sans distinction entre les deux groupes. Enfin, quand l’utilisation des substrats énergétiques à l’exercice est appréhendée en fonction du rapport de la masse grasse abdominale/masse grasse des membres inférieurs (A/MI), nos travaux ont montré une augmentation de la mobilisation et de l’oxydation des lipides chez les femmes présentant un plus faible rapport A/MI (malgré des masses corporelles et des tours de taille normaux). Ainsi, au sein d’une population féminine normo-pondérée, les CO minidosées monophasiques ne semblent pas influer sur l’utilisation des substrats énergétiques à l’exercice, alors que la prise alimentaire pré-exercice et la localisation des graisses semblent avoir un impact plus important sur le métabolisme énergétique à l’exercice
In the female population, sexual hormones (endogen production or exogenous consumption) induce particular hormonal status leading to specific body composition and metabolic and hormonal responses at rest and during exercise. The aim of this work was to determine the influence of oral contraception (low dose monophasic combined OC), pre-exercise food intake and body fat mass localization on metabolic and hormonal responses during exercise (45 min at 65% of O2max) in normal weight premenopausal women. Our results showed that OC did not alter substrate mobilization and oxidation during exercise (in fast and postprandial conditions). However, during exercise performed in fast condition, women exhibited greater lipid oxidation rates whatever their hormonal status (OC+ vs OC-). In postprandial condition, exercise increased lipolytic activity in OC+ and OC- women without differences between both groups. Finally, it has been observed that abdominal to lower body (A/LB) fat mass ratio influenced substrate mobilization and oxidation in premenopausal women with normal weights and waist circumferences. Subjects with a lower ratio exhibited greater lipid mobilization and oxidation than those with a higher ratio. Therefore, in normal weight women, low dose monophasic combined OC do not appear to influence substrate oxidation whereas pre-exercise food intake and body fat mass localization may have an important impact on substrate metabolism during exercise

Des puits quantiques à base d'hétérostructures In0.53 Ga0.47 As/In0.52 Al0.48 As, fabriqués par épitaxie par jets moléculaires sur substrats InP(111)A, sont étudiés par microscopie et spectroscopie à effet tunnel à basse température et sous ultra-vide. La première partie est consacrée à une étude de la surface épitaxiée (111)A de In0.53 Ga0.47 As de type n. Il est découvert que le niveau de Fermi de surface est positionné dans la bande de conduction, à proximité du niveau de Fermi de volume, et peut être partiellement contrôlé en variant la concentration d'impuretés de type n dans le volume. Ce résultat est confirmé en déterminant la relation de dispersion de la bande de conduction en surface. Un tel dépiégeage partiel du niveau de Fermi de surface indique que la densité d'états de surface accepteurs est faible. Il est proposé que ces états proviennent de défauts ponctuels natifs localisés à la surface. La deuxième partie, basée sur les résultats obtenus dans la première partie, est consacrée à une étude de puits quantiques In0.53 Ga0.47 As de surface, déposés sur des barrières In0.52 Al0.48 As selon la direction (111)A. Les mesures sont conduites sur la surface épitaxiée (111)A du puits quantique In0.53 Ga0.47 As, de manière à pouvoir sonder à l'échelle du nanomètre la distribution de densité locale d'états électroniques dans le plan du puits quantique. Il est confirmé que des sous-bandes électroniques sont formées dans le puits quantique, et que la concentration d'électrons dans le puits peut être contrôlée du fait du dépiégeage partiel du niveau de Fermi de surface. Il est découvert qu'un phénomène de percolation d'états localisés survient dans la queue de chaque sous-bande, ce qui indique la présence d'un potentiel désordonné dans le puits quantique. Les seuils de percolation sont déterminés en utilisant un modèle semi-classique. L'origine du potentiel désordonné est attribuée à une distribution aléatoire des défauts ponctuels natifs à la surface du puits quantique. Il est également découvert qu'un état lié apparaît au bas de chaque sous-bande à proximité d'un défaut ponctuel natif de type donneur. L'énergie de liaison et le rayon de Bohr des états liés peuvent être directement déterminés. De plus, il est démontré que l'énergie de liaison et le rayon de Bohr sont fonctions de l'épaisseur du puits quantique, en accord quantitatif avec des calculs variationnels d'impuretés dans le modèle de l'atome d'hydrogène.

Dizertační práce se zabývá návrhem nového bezkotevního lokalizačního algoritmu sloužícího pro výpočet pozice uzlů v bezdrátových senzorových sítích. Provedené studie ukázaly, že dosavadní bezkotevní lokalizační algoritmy, pracující v paralelním režimu, dosahují malých lokalizačních chyb. Jejich nevýhodou ovšem je, že při sestavení množiny referenčních uzlu spotřebovávají daleko větší množství energie než algoritmy pracující v inkrementálním režimu. Paralelní lokalizační algoritmy využívají pro určení pozice referenční uzly nacházející se na protilehlých hranách bezdrátové sítě. Nový lokalizační algoritmus označený jako BRL (Boundary Recognition aided Localization) je založen na myšlence decentralizovaně detekovat uzly ležící na hranici síti a pouze z této množiny vybrat potřebný počet referenčních uzlu. Pomocí navrženého přístupu lze znažně snížit množství energie spotřebované v průběhu procesu výběru referenčních uzlů v senzorovém poli. Dalším přínosem ke snížení energetických nároku a zároveň zachování nízké lokalizační chyby je využití procesu multilaterace se třemi, eventuálně čtyřmi referenčními body. V rámci práce byly provedeny simulace několika dílčích algoritmu a jejich funkčnost byla ověřena experimentálně v reálné senzorové síti. Navržený algoritmus BRL byl porovnán z hlediska lokalizační chyby a počtu zpracovaných paketů s několika známými lokalizačními algoritmy. Výsledky simulací dokázaly, že navržený algoritmus představuje efektivní řešení pro přesnou a zároveň nízkoenergetickou lokalizaci uzlů v bezdrátových senzorových sítích.

This thesis deals with the development of self-sustained sensors based on non-conventional measurement techniques. The motivation behind this topic is to help utility companies reduce their fault handling time and improve the way faults are handled. As of today, the distribution system does not have widespread surveillance and automation systems in place. The thesis therefore investigates a sensor design based on Rogowski coils (RC), with both measurement and power supply capabilities.The concept of printed-circuit-board Rogowski coils (PCB RC) and conventional RCs for current measurement is presented. A theoretical, dimensional study with respect to feasibility and output signal magnitude is then performed. On basis of this analysis, a PCB RC prototype is manufactured. For the sensor to be implemented in the resonance grounded distribution system, it must be able to measure currents of low magnitude, as the fault current is compensated by Petersen coils. The prototype is therefore tested for common distribution system current values. Due to limitations during construction and design flaws, the PCB RC performance was poor. The induced voltage error, with respect to the theoretical response was 64.3 - 69.1 %.As the prototype's ability to supply enough power to the sensor circuitry (demand found to be > 10 mW) proved so limited, a more thorough analysis concerning the RC is presented. Obtaining this amount of power is, theoretically possible and easier with a conventional RC. Its maximum average power supply capability was found to be 10.4 mW during ideal conditions. Even better results can probably be obtained as well. Based on this RC, the complete sensor system is discussed. This include rectification, digitizing, integration and boosting of the RC voltage to 3 V for battery application. A survey of possible fault localization methods for resonance grounded distribution systems is presented and an implementation is suggested.Finally, the prototype is tested with short circuit currents of 30 kA amplitude. The performance was better than for the load current test, but the magnitude error was still substantial. It varied from 20 % to 40 %. However, the lab's signal integration showed that the prototype reproduced the applied current waveform accurately.The simulations, testing and analysis performed indicate that a RC can be used for both supply of power and measurements. However, a prototype should be manufactured in order to assess this thesis' theoretical results. Combined with the proposed auxiliary circuitry and implementation strategy, it can improve the utility's fault handling.

Les quasicristaux sont des solides ordonnes presentant une coherence orientationnelle a longue distance sans periodicite de translation. Leurs proprietes electroniques sont spectaculaires. Par exemple, la phase alpdre presente une resistivite de semi-conducteur (> 10 ohm. Cm a 4 k), bien que sa densite d'etats au niveau de fermi soit environ 1/10 de celle de l'aluminium pur. Une etude numerique de plusieurs alliages intermetalliques a base d'aluminium et d'approximants realistes de quasicristaux a permis de degager deux caracteristiques essentielles de leur structure electronique: un creusement important de la densite d'etats au niveau de fermi par rapport aux electrons libres, ce qui est attendu pour les alliages de hume-rothery, et une structure tres piquee dans la densite d'etats. Cette derniere propriete, specifique des quasicristaux, a ete correlee avec les proprietes de transport electroniques. Le role des metaux de transition a ete etudie par une generalisation du modele de l'etat lie virtuel en tenant compte de la specificite de ces alliages. Nous presentons, entre autre, une explication de la valence negative apparente des metaux de transition qui est evoquee depuis longtemps dans les intermetalliques. En outre, cette etude montre que les metaux de transition jouent un role important dans le creusement de la densite d'etats au niveau de fermi. Dans le cadre de la theorie de la diffusion, nous analysons la localisation des electrons par un agregat atomique dans une matrice metallique. Cette etude montre l'existence d'etats lies virtuels d'agregats qui peuvent expliquer la structure piquee de la densite d'etats et sont coherents avec la notion d'etats critiques generalement consideres pour decrire le spectre electronique des pavages quasiperiodiques. Cependant, la stabilite des agregats n'est pas due a cette localisation car leur energie de cohesion est la somme d'interactions de paires. Cela renforce l'image des quasicristaux comme des alliages de hume-rothery

Ce travail est consacré à l’ étude théorique et numérique de la propagation des ondes élastiques dans les structures mécaniques désordonnées. L’ objectif principal est d’ étudier comment la localisation induite par le désordre est affectée par la non-linéarité et par la présence de mouvements de rotations. Nous étudions d’abord une chaîne granulaire finie et montrons que non seulement la localisation d’ Anderson est rompue mais aussi que l’ équipartition de l’ énergie est réalisée grâce à la non-linéarité discontinue propre aux chaînes granulaires. De plus, nous étendons nos études à un reseau micropolaire qui supporte les ondes de rotation. Nous montrons que, dans la limite linéaire, la repartition de l’ énergie est facilitée à la fois par des ondes étendues à basse fréquence et par un ensemble de modes quasi-étendus à haute fréquence. Nous identifions aussi un cas où l’ énergie est complètement localisée en réglant la rigidité. Enfin, pour une chaîne LEGO architecturée non linéaire présentant un movement à la fois transversal et rotatif, nous étudions comment la non-linéarité rompt, dans ce système polarisé, la localisation d’ Anderson. Il s’avère que la dynamique de ce système a un caractère unique qui ressemble à une combinaison des modèles Fermi-Pasta-Ulam-Tsingou et Klein Gordon pour le comportement asymptotique et chaotique
This work is devoted to the theoretical and numerical study of elastic wave propagation in disordered mechanical structures. The main goal is to investigate how the localization induced by disorder is affected by nonlinearity and by the presence of rotational motion. Firstly, we study a finite granular chain and show that not only Anderson localization is broken but also energy equipartition is achieved due to the discontinuous nonlinearity which is particular to granular chains. Furthermore, we extend our studies to a micropolar lattice that supports rotational waves. We show that in the linear limit the energy spreading is facilitated both by low frequency extended waves and a set of high frequency quasiextended modes. Also, we identify a case where energy is completely localized by tuning the stiffness. Finally, for a nonlinear architected LEGO chain featuring both transverse and rotational motion we study how nonlinearity breaks Anderson localization in this polarized system. The dynamics is found to have a unique character resembling a combination of the Fermi-Pasta-Ulam Tsingou and Klein-Gordon models regarding the asymptotic dynamical behavior and chaoticity

On considère un système constitué de plusieurs atomes où les noyaux sont supposés fixes et ponctuels. Les particules interagissent via le potentiel de Coulomb et les électrons ont une énergie cinétique pseudo-relativiste donnée par (p2+m2)1/2-m. On démontre la loi de van der Waals-London qui dit que l'énergie d'interaction entre atomes neutres décroit comme |D|-6 où |D| est la distance entre atomes. Nous calculons rigoureusement tous les termes de l'énergie de liaison jusqu'à l'ordre |D|-9 avec un terme d'erreur en O(|D|-10). Comme étape intermédiaire, nous établissons la décroissance exponentielle des fonctions propres de l'opérateur de Schrödinger à plusieurs particules avec les symétries imposées par le principe de Pauli, et des estimations sur le terme d'erreur de localisation. Nous montrons de plus la loi de van der Waals-London pour l'opérateur de Dirac projeté connu sous le nom d'opérateur de Brown et Ravenhall. Dans ce dernier cas on obtient un terme d'erreur en O(|D|-7)
We consider a multiatomic system where the nuclei are assumed to be point charges at fixed positions.Particles interact via Coulomb potential and electrons have relativistic kinetic energy given by (p2+m2)1/2-m.We prove the van der Waals-London law, which states that the interaction energy between neutral atoms decays as the sixth power of the distance |D| between the atoms. We rigorously compute all terms in the binding energy up to order |D|-9 with error term of order O(|D|-10). As intermediate steps we prove exponential decay of eigenfunctions of multiparticle Schrödinger operators with permutation symmetry imposed by the Pauli principle and new estimates of the localization error. In addition we prove the van der Waals-London law for the projected Dirac operator, known as the Brown-Ravenhall operator. In this case we do not calculate the coefficients explicitly and we obtain an error term of order O(|D|-7)

A hybrid quantum-classical approach to the interaction of atomic clusters with intense laser fields in the vacuum ultra-violet (VUV) has been developed. Much emphasis is put on localized electrons, those quasi-free electrons which localize about the ions and screen them. These electrons set a time scale, which is used to interpolate between the quantum, rate based description of photon absorption by bound electrons and the classical, deterministic description of the cluster nano-plasma. Typical observables such as total energy absorption, electron and ion spectra are in very good agreement with the experimental findings. A scheme to probe the multi-electron motion in clusters with attosecond laser pulses is introduced. Conventional final state measurements in the energy domain cannot provide information about earlier states of the system due to the incoherent nature of the dynamics. Time-delayed attosecond pulses in the extreme ultra-violet (XUV) are used to probe the transient charging of the cluster ions during the interaction with the laser by measuring the kinetic energy of the electrons detached by the probe pulse. This information is otherwise lost at later times due to recombination. Knowledge about the transient charging would also shed more light on the still controversial subject of the energy absorption mechanisms in the VUV regime. Moving to shorter duration of the excitation, the characteristic time-scales for ionization and plasma equilibration are inversed. An attosecond laser pulse in the VUV regime creates a dense, warm nano-plasma far from equilibrium. Time-delayed attosecond pulses in the XUV probe then both the creation and the relaxation. The latter shows the breakup of the Bogoliubov hierarchy of characteristic times, indicating strongly-coupled plasma dynamics and drawing parallels to the relaxation of extended ultra-cold neutral plasmas with millions of particles.

A hybrid quantum-classical approach to the interaction of atomic clusters with intense laser fields in the vacuum ultra-violet (VUV) has been developed. Much emphasis is put on localized electrons, those quasi-free electrons which localize about the ions and screen them. These electrons set a time scale, which is used to interpolate between the quantum, rate based description of photon absorption by bound electrons and the classical, deterministic description of the cluster nano-plasma. Typical observables such as total energy absorption, electron and ion spectra are in very good agreement with the experimental findings. A scheme to probe the multi-electron motion in clusters with attosecond laser pulses is introduced. Conventional final state measurements in the energy domain cannot provide information about earlier states of the system due to the incoherent nature of the dynamics. Time-delayed attosecond pulses in the extreme ultra-violet (XUV) are used to probe the transient charging of the cluster ions during the interaction with the laser by measuring the kinetic energy of the electrons detached by the probe pulse. This information is otherwise lost at later times due to recombination. Knowledge about the transient charging would also shed more light on the still controversial subject of the energy absorption mechanisms in the VUV regime. Moving to shorter duration of the excitation, the characteristic time-scales for ionization and plasma equilibration are inversed. An attosecond laser pulse in the VUV regime creates a dense, warm nano-plasma far from equilibrium. Time-delayed attosecond pulses in the XUV probe then both the creation and the relaxation. The latter shows the breakup of the Bogoliubov hierarchy of characteristic times, indicating strongly-coupled plasma dynamics and drawing parallels to the relaxation of extended ultra-cold neutral plasmas with millions of particles.

Este trabalho apresenta o desenvolvimento e a implementação computacional de um algoritmo para a localização de faltas em linhas de transmissão. O algoritmo proposto é baseado em métodos heurísticos, isto é, Algoritmos Genéticos (AG) e Pattern Search (PS), sendo capaz de identificar o ponto de ocorrência da falta utilizando fasores de tensão e corrente de pré e pós-falta, estimados a partir de medições disponíveis apenas no terminal local da linha de tranmsissão. Nesta abordagem, ambas as ferramentas de otimização possuem natureza heurísticas sendo menos propensas a cair em valores mínimos locais, o que implica uma maior eficiência e precisão na determinação da localização da falta. Além disso, o método utiliza potências de curto-circuito monofásicas e trifásicas de ambos os terminais da linha (local e remoto), a fim de obter seus equivalentes de Thévenin, e os parâmetros elétricos da linha de transmissão. Com o objetivo de avaliar o desempenho do algoritmo proposto, consideram-se nas simulações quatro sistemas de transmissão diferentes, que representam sistemas reais de transmissão brasileiros. O primeiro está constituído por uma típica linha de transmissão de 138 [kV] com circuito duplo, e os outros três sistemas são constituídos por linhas de transmissão típicas de 230, 500 e 765 [kV] com circuito simples. A partir dos quatro sistemas de transmissão simulados no software Alterative Transients Program (ATP/EMTP), foram gerados um total de 928 situações de falta. A versão do algoritmo desenvolvido para localização de faltas foram descritas e implementadas, através do software científico MATrix LABoratory (MATLAB), apresentando resultados com altos níveis de precisão.
This paper presents the development and implementation of a computational algorithm for location faults in transmission line. The proposed algorithm is based on heuristic methods, namely AG and PS, being able to identify the occurrence of the fault point using phasor voltage and current pre and post-fault, estimated from measurements available only on the local terminal of the transmission line. In this approach, both optimization tools have heuristic nature being less prone to falling into local minimum values, which implies grater efficiency and accuracy in the determination of fault location. Moreover, the method use singles-phase and three-phase short-circuit powers of both the line terminals (Local and remote), to obtain the Thévenin equivalent and the electrical parameters of the transmission line. In order to evaluate the performance of the proposed algorithm were considered four different transmission systems; these systems represent real systems of Brazilian transmission. The first this made up of a transmission line typical of 138 [kV] with double circuit, the other three systems are made up of transmission line typical of 230, 500 and 765 [kV] of single circuit. Whereas the four simulated transmission systems in the softwareATP/ EMTP, generated a total of 928 situations fault. The version of the algorithm designed to locate faults, have been described and implemented through scientific software MATLAB, presenting results high levels of accuracy.

This thesis consists of the evaluation of sensor-based risk management against oil spills using an underwater distributed sensor network. The work starts by highlighting the importance of having a performing leak detection system both from an environmental, safety and economic point of view. The case study is the Goliat FPSO in the Barents Sea which has to meet requirements dictated by Norwegian authorities to prevent oil spills. The modeled network is made of passive acoustic sensors monitoring the subsea manifolds. These sensors send their local 1-bit decision to a Fusion Center which takes a global decision on whether the leakage is occurring. This work evaluates how the choice of adapted Fusion Rules (Counting Rule and Weighted Fusion Rule) can affect the performances of the leak detection system in its current geometry. It will also be discussed how different thresholds, selected for a specific FR or sensor test, can change the system performance. The detection methods are based on statistical signal processing adapted to fit this application within the Oil&Gas field. The work also proposes some new leak localization methods developed so they can be coupled with the proposed leak detection methods, giving a coherent set of operations that the sensors and the FC must perform. Performances of detection techniques are assessed balancing the need for high values of True Positive Rate and Precision and low values of False Positive Rate using indexes based both on the ROC curve (like the Youden's Index) and on the PR curve (the F-scores). Whereas, performances of localization techniques will be assessed on their ability to localize the spill in the shortest time; if this is not possible, parameters like the difference between the estimated and the real leak position will be considered. Finally, some tests are carried out applying the different sets of proposed methods.

Dans ce travail de thèse, on s'intéresse é l'emploi de techniques de traitement de signal de systèmes de communication MIMO (Multiple Input Multiple Output) pour des applications aux réseaux de capteurs sans fil. Les contraintes énergétiques de cette classe de réseau font appel à des topologies particulières et le réseau peut être perçu comme étant un ensemble de grappes de nœuds capteurs. Ceci ouvre la porte à des techniques avancées de communication de type MIMO. Dans un premier temps, les différents aspects caractérisant les réseaux de capteurs sans fil sont introduits. Puis, les efforts engagés pour optimiser la conservation de l'énergie dans ces réseaux sont résumés. Les concepts de base de systèmes MIMOs sont abordés dans le deuxième chapitre et l'exploration par voie numérique de différentes pistes de la technologie MIMO sont exposées. Nous nous intéressons à des techniques de diversité de polarisation dans le cadre de milieux de communication riches en diffuseurs. Par la suite, des méthodes de type beamforming sont proposées pour la localisation dans les réseaux de capteurs sans fil. Le nouvel algorithme de localisation est présenté et les performances sont évaluées. Nous identifions la configuration pour la communication inter-grappes qui permet pour les meilleurs compromis entre énergie et efficacité spectrale dans les réseaux de capteurs sans fil. Finalement, nous envisageons la technique de sélection de nœuds capteurs afin de réduire la consommation de l'énergie dans le réseau de capteur sans fil
The aim of this work is to study from a signal processing point of view the use of MIMO (Multiple Input Multiple Output) communication systems for algorithms dedicated to wireless sensor networks. We investigate energy-constrained wireless sensor networks and we focus on cluster topology of the network. This topology permits for the use of MIMO communication system model. First, we review different aspects that characterize the wireless sensor network. Then, we introduce the existing strategies for energy conservation in the network. The basic concepts of MIMO systems are presented in the second chapter and numerical results are provided for evaluating the performances of MIMO techniques. Of particular interest, polarization diversity over rich scattering environment is studied. Thereafter, beamforming approach is proposed for the development of an original localization algorithm in wireless sensor network. The novel algorithm is described and performances are evaluated by simulation. We determine the optimal system configuration between a pair of clusters that permits for the highest capacity to energy ratio in the fourth chapter. The final chapter is devoted to sensor nodes selection in wireless sensor network. The aim of using such technique is to make energy conservation in the network