Solid Oxide Fuel Cells (SOFCs) are considered suitable for alternative energy solutions due to advantages such as high efficiency, fuel flexibility, tolerance to impurities, and potential for combined cycle operations. One of the main operating constraints of SOFCs is fuel starvation, which can occur under fluctuating power demands. It leads to voltage loss and detrimental effects on cell integrity and longevity. In addition, reformer based SOFCs require sufficient steam for fuel reforming to avoid carbon deposition and catalyst degradation. Steam to carbon ratio (STCR) is an index indicating availability of the steam in the reformer. This work takes a holistic approach to address the aforementioned concerns in SOFCs, in an attempt to enhance applicability and adaptability of such systems. To this end, we revisit prior investigation on the invariant properties of SOFC systems, that led to prediction of fuel utilization U and STCR in the absence of intrusive and expensive sensing. This work provides further insight into the reasons behind certain SOFC variables being invariant with respect to operating conditions. The work extends the idea of invariant properties to different fuel and reformer types. In SOFCs, transient control is essential for U, especially if the fuel cell is to be operated in a dynamic load-following mode at high fuel utilization. In this research, we formulate a generalized abstraction of this transient control problem. We show that a multi-variable systems approach can be adopted to address this issue in both time and frequency domains, which leads to input shaping. Simulations show the effectiveness of the approach through good disturbance rejection. The work further integrates the aforementioned transient control research with system level control design for SOFC systems hybridized with storage elements. As opposed to earlier works where centralized robust controllers were of interest, here, separate controllers for the fuel cell and storage have been the primary emphasis. Thus, the proposed approach acts as a bridge between existing centralized controls for single fuel cells to decentralized control for power networks consisting of multiple elements. As a first attempt, decentralized control is demonstrated in a SOFC ultra-capacitor hybrid system. The challenge of this approach lies in the absence of direct and explicit communication between individual controllers. The controllers are designed based on a simple, yet effective principle of conservation of energy. Simulations as well as experimental results are presented to demonstrate the validity of these designs.

Restoration entails the development of a plan consisting of opening or closing of switches, which is called reconfiguration. This dissertation proposes the design of a fast and efficient service restoration with a load shedding method for land-based and ship systems, considering priority of customers and several other system operating constraints. Existing methods, based on centralized restoration schemes that require a powerful central computer, may lead to a single point of failure. This research uses a decentralized scheme based on agents. A group of agents created to realize a specific goal by their interactions is called a Multi-Agent System (MAS). Agents and their behaviors are developed in Java Agent DEvelopment Framework (JADE) and the power system is simulated in the Virtual Test Bed (VTB). The large-scale introduction of Distributed Generators (DGs) in distribution systems has made it increasingly necessary to develop restoration schemes considering DG. The separation of utility causes the system to decompose into electrically isolated islands with generation and load imbalance that can have severe consequences. Automated load shedding schemes are essential for systems with DGs, since the disconnection of the utility can lead to instability much faster than an operator intervention can repair. Load shedding may be the only option to maintain the island when conditions are so severe as to require correction by restoration schemes. Few algorithms have been reported for the problem of maintaining the island, even though load shedding has been reported for power systems using underrequency and under-voltage criteria. This research proposes a new operational strategy for sudden generator-load imbalance due to loss of utility that dynamically calculates the quantity of load to be shed for each island and the quantity of load that can be restored. Results presented in this dissertation are among the first to demonstrate a state-of-the-art MAS for load shedding under islanded conditions and restoration of the shed loads. The load shedding and restoration schemes developed here have behaviors that can incorporate most of the distribution topologies. Achieving service restoration with DG is complicated but new automated switch technologies and communications make MAS a better scheme than existing schemes.

No description available.

In this dissertation, we propose decentralized and scalable algorithms for Gaussian process (GP) training and prediction in multi-agent systems. The first challenge is to compute a spatial field that represents underwater acoustic communication performance from a set of measurements. We compare kriging to cokriging with vehicle range as a secondary variable using a simple approximate linear-log model of the communication performance. Next, we propose a model-based learning methodology for the prediction of underwater acoustic performance using a realistic propagation model. The methodology consists of two steps: i) estimation of the covariance matrix by evaluating candidate functions with estimated parameters; and ii) prediction of communication performance. Covariance estimation is addressed with a multi-stage iterative training method that produces unbiased and robust results with nested models. The efficiency of the framework is validated with simulations and experimental data from field trials. The second challenge is to perform predictions at unvisited locations with a team of agents and limited inter-agent information exchange. To decentralize the implementation of GP training, we employ the alternating direction method of multipliers (ADMM). A closed-form solution of the decentralized proximal ADMM is provided for the case of GP hyper-parameter training with maximum likelihood estimation. Multiple aggregation techniques for GP prediction are decentralized with the use of iterative and consensus methods. In addition, we propose a covariance-based nearest neighbor selection strategy that enables a subset of agents to perform predictions. Empirical evaluations illustrate the efficiency of the proposed methods / Doctor of Philosophy / In this dissertation, we propose decentralized and scalable algorithms for collaborative multiagent learning. Mobile robots, such as autonomous underwater vehicles (AUVs), can use predictions of communication performance to anticipate where they are likely to be connected to the communication network. The first challenge is to predict the acoustic communication performance of AUVs from a set of measurements. We compare two methodologies using a simple model of communication performance. Next, we propose a model-based learning methodology for the prediction of underwater acoustic performance using a realistic model. The methodology first estimates the covariance matrix and then predicts the communication performance. The efficiency of the framework is validated with simulations and experimental data from field trials. The second challenge regards the efficient execution of Gaussian processes using multiple agents and communicating as little as possible. We propose decentralized algorithms that facilitate local computations at the expense of inter-agent communications. Moreover, we propose a nearest neighbor selection strategy that enables a subset of agents to participate in the prediction. Illustrative examples with real world data are provided to validate the efficiency of the algorithms.

Reducing the operating costs of chemical processes is very beneficial in decreasing a company's bottom line numbers. Since chemical processes are usually run in steady-state for long periods of time, saving a few dollars an hour can have significant long term effects. However, the complexity involved in most chemical processes from nonlinear dynamics makes them difficult processes to optimize. A nonlinear, open-loop unstable system, called the Tennessee Eastman Chemical Process Control Problem, is used as a test-bed problem for minimization routines. A decentralized controller is first developed that stabilizes the plant to set point changes and disturbances. Subsequently, a genetic algorithm calculates input parameters of the decentralized controller for minimum operating cost performance. Genetic algorithms use a directed search method based on the evolutionary principle of "survival of the fittest". They are powerful global optimization tools; however, they are typically computationally expensive and have long convergence times. To decrease the convergence time and avoid premature convergence to a local minimum solution, an auxiliary fuzzy logic controller was used to adapt the parameters of the genetic algorithm. The controller manipulates the input and output data through a set of linguistic IF-THEN rules to respond in a manner similar to human reasoning. The combination of a supervisory fuzzy controller and a genetic algorithm leads to near-optimum operating costs for a dynamically modeled chemical process. / Master of Science

Blockchains, smart contracts and cryptocurrencies are reaching further global adoption each day and are becoming more prominent to be the foundation for a new technological era and to be used in transactions globally. The technology has strong coherent properties, including a high level of security, decentralization, and its use of smart contracts to obviate intermediaries. These technologies offer the possibility to do any transaction without a centralized bank controlling, denying, or reversing the transaction. This report aims to shed light on blockchain technologies possible impact on society and if the current centralized-based system can be replaced or if it is deemed as necessary. What the potential outcome would be if these centralized authorities sees a decrease in power and how blockchains, smart contracts and stablecoins can be used as an everyday payment and transaction system, excluding all third parties. To do this, a literature review, a quantitative survey, and qualitative interviews were conducted. The literature review, to lay the ground for the questions in the survey, interviews, and additionally, to determine what blockchain and what kind of stablecoin is most suited for global adoption. The result from the qualitative interview were to acquire knowledge from more experienced individuals working or owning a company that is based on top of blockchains. Lastly, considering blockchain technology and web 3.0 is still under development and yet to become globally accepted, the questionnaire survey was conducted to retrieve the general consensus from individuals inside crypto communities. The report overall, came out to be successful, indicating that blockchain technologies has a bright future and that the decentralization it adds to society can benefit the individual in multiple of different ways, specifically in the financial sector. However, although the conclusion that blockchain technologies can be used as a global payment system were deemed successful, objective, and subjective opinions were discussed and reported relevant, whereas one individual might view the exclusion of intermediaries as necessary and beneficial, while the other – as something negative. Scalability issues in blockchains and smart contracts controversy, such as its complexity and its immutability aspect are also analyzed and discussed as a potential hindrance for further global adoption.

Объектом исследования являются блокчейн-технологии и децентрализованные сервисы. В данном исследовании предлагается разработать децентрализованное приложение для проведения лотерей. Исследование проводится с целью изучения блокчейн-технологий. Для разработки децентрализованного приложения использовался блокчейн Ethereum. В результате был разработан смарт-контракт для проведения лотерей, а также веб-интерфейс для взаимодействия с ним, образующие децентрализованное приложение. / The object of research is blockchain technologies and decentralized services. In this study, it is proposed to develop a decentralized application for conducting lotteries. The research is conducted in order to study blockchain technologies. The Ethereum blockchain was used to develop a decentralized application. As a result, a smart contract for conducting lotteries was developed, as well as a web interface for interacting with it, forming a decentralized application.

La nécessaire lutte contre la pauvreté découle d'un constat troublant : la richesse combinée des quinze personnes les plus riches de la planète est supérieure à la valeur annuelle cumulée de la production de biens /services de l'ensemble des pays de l'Afrique subsaharienne. 20% de la population mondiale consomme plus de 80% des ressources disponibles sur la surface de la terre. Ce double constat révèle l'ampleur des efforts à accomplir pour répondre au défi des objectifs du millénaire pour le développement (OMD). La responsabilité des Etats est évidemment engagée mais les solutions sont plus à rechercher au niveau des villes et des territoires. Au plus proche des habitants, les autorités locales peuvent et doivent jouer un rôle de catalyseur du développement. Il revient aux citoyens des territoires confrontés aux problèmes de sous-développement d'imaginer et de proposer ces solutions locales. La coopération décentralisée contribue à la recherche et à l'invention de telles politiques territoriales : cadre de dialogue privilégié entre gouvernements locaux. Définie comme un partenariat entre autorités locales de nationalités différentes, cette coopération décentralisée permet un partage d'expériences – micro finance, décentralisation, bonne gouvernance etc. En clair, tous les espoirs peuvent s'inviter dans la symbiose « Coopération décentralisée et Objectifs du Millénaire pour le Développement», en tenant compte de leurs enjeux et perspectives dans l'espace francophone subsaharien. / The necessary struggle against poverty comes from an elementary remark observation: the combined wealth of the 15 richest people in the planet exceeds the total annual value of the production of the properties / services of all the countries of Sub-Saharan Africa. 20 % of the world population consumes more than 80 % of the resources available on the surface of the earth. This observation reminds the magnitude of the efforts which remain to carry out to answer the challenge of the millennium through the OMD. The responsibility of States is obviously engaged but the solutions are more to look for at the level of cities and territories. In the closest to the inhabitants, the local authorities can and have to play a role of catalyst of the development. It is up to the citizens of territories confronted with the problems of underdevelopment to imagine and to propose these local solutions. The decentralized cooperation contributes to the search and the invention of such territorial policies, because it is a frame of privileged dialogue between local governments. Defined as a partnership between local authorities of different nationalities, it allows a sharing of experiences - microfinances, decentralization, good governance etc.- Clearly, all the hopes can invite itself in the symbiosis "Decentralized Cooperation and Objectives of the Millennium for the Development by taking into account their stakes and perspectives in the Sub-Saharan French-Speaking Space".

La vérification à l’exécution est une méthode formelle légère qui consiste à vérifier qu’une exécution d’un système est correcte par rapport à une spécification. La spécification exprime de manière rigoureuse le comportement attendu du système, en utilisant généralement des formalismes basés sur la logique ou les machines à états finies. Alors que la verification a l’éxecution traite les systèmes monolithiques de manière exhaustive, plusieurs difficultés se présentent lors de l’application des techniques existantes à des systèmes décentralisés, c-à-d. des systèmes avec plusieurs composants sans point d’observation central. Dans cette thèse, nous nous concentrons particulièrement sur trois problèmes : la gestion de l’information partielle, la séparation du déploiement des moniteurs du processus de vérification lui-même et le raisonnement sur la décentralisation de manière modulaire et hiérarchique. Nous nous concentrons sur la notion de spécification décentralisée dans laquelle plusieurs spécifications sont fournies pour des parties distinctes du système. Utiliser une spécification décentralisée a divers avantages tels que permettre une synthèse de moniteurs à partir des spécifications complexes et la possibilité de modulariser les spécifications. Nous présentons également un algorithme de vérification général pour les spécifications décentralisées et une structure de données pour représenter l’exécution d’un automate avec observations partielles. Nous développons l’outil THEMIS, qui fournit une plateforme pour concevoir des algorithmes de vérification décentralisée, des mesures pour les algorithmes, une simulation et des expérimentations reproductibles pour mieux comprendre les algorithmes.Nous illustrons notre approche avec diverses applications. Premièrement, nous utilisons des spécifications décentralisées pour munir une analyse de pire cas, adapter, comparer et simuler trois algorithmes de vérification décentralisée existants dans deux scénarios: l’interface graphique Chiron, et des traces et spécifications générées aléatoirement. Deuxièmement, nous utilisons des spécifications décentralisées pour vérifier diverses propriétés dans un appartement intelligent: correction du comportement des capteurs de l’appartement, détection d’activité spécifiques de l’utilisateur (Activities of Daily Living, ADL) et composition de spécifications des deux catégories précédentes.En outre, nous élaborons sur l’utilisation de spécifications décentralisées pour la vérification décentralisée pendant l’exécution de programmes parallélisés. Nous commençons par discuter les limitations des approches et des outils existants lorsque les difficultés introduites par le parallélisme sont rencontrées. Nous détaillons la description de zones de parallélisme d’une unique exécution d’un programme et décrivons une approche générale qui permet de réutiliser des techniques de verification à l’éxécution existantes. Dans notre configuration, les moniteurs sont déployés dans des fils d’exécution spécifiques et échangent de l’information uniquement lorsque des points de synchronisation définis par le programme lui-même sont atteints. En utilisant les points de synchronisation existants, notre approche réduit les interférences et surcoûts résultant de la synchronisation, au prix d’un retard pour déterminer le verdict. / Runtime Verification (RV) is a lightweight formal method which consists in verifying that a run of a system is correct with respect to a specification. The specification formalizes the behavior of the system typically using logics or finite-state machines. While RV comprehensively deals with monolithic systems, multiple challenges are presented when scaling existing approaches to decentralized systems, that is, systems with multiple components with no central observation point. We focus particularly on three challenges: managing partial information, separating monitor deployment from the monitoring process itself, and reasoning about decentralization in a modular and hierarchical way. We present the notion of a decentralized specification wherein multiple specifications are provided for separate parts of the system. Decentralized specifications provide various advantages such as modularity, and allowing for realistic monitor synthesis of the specifications. We also present a general monitoring algorithm for decentralized specifications, and a general datastructure to encode automata execution with partial observations. We develop the THEMIS tool, which provides a platform for designing decentralized monitoring algorithms, metrics for algorithms, and simulation to better understand the algorithms, and design reproducible experiments.We illustrate the approach with two applications. First, we use decentralized specifications to perform a worst-case analysis, adapt, compare, and simulate three existing decentralized monitoring algorithms on both a real example of a user interface, and randomly generated traces and specifications. Second, we use decentralized specifications to check various specifications in a smart apartment: behavioral correctness of the apartment sensors, detection of specific user activities (known as activities of daily living), and composition of properties of the previous types.Furthermore, we elaborate on utilizing decentralized specifications for the decentralized online monitoring of multithreadedprograms. We first expand on the limitations of existing tools and approaches when meeting the challenges introduced by concurrency and ensure that concurrency needs to be taken into account by considering partial orders in traces. We detail the description of such concurrency areas in a single program execution, and provide a general approach which allows re-using existing RV techniques. In our setting, monitors are deployed within specific threads, and only exchange information upon reaching synchronization regions defined by the program itself. By using the existing synchronization, we reduce additional overhead and interference to synchronize at the cost of adding a delay to determine the verdict.

A Gestão Energética Descentralizada é uma forma de gestão dos recursos energéticos cujas primeiras publicações referentes ao tema datam dos anos 1980, no entanto, foi verificado um crescimento do desenvolvimento de estudos e aplicações do conceito na prática de forma substancial somente em tempos recentes (anos 2000). A Gestão Energética Descentralizada é tratada sob uma infinidade de termos e conceitos, e também pode ser aplicada com graus diferentes de descentralização como em vilas, quarteirões, bairros, distritos e estados. Tal conceito está fortemente atrelado ao combate das emissões de Gases de Efeito Estufa, busca pela inserção das fontes de energia renováveis nas matrizes, conservação de energia e eficiência energética, e pela associação entre planejamento urbano, ou das cidades, ao dos sistemas energéticos. Ainda, cabe destacar que nesse modelo de gestão descentralizado- a participação popular e o engajamento dos cidadãos nos processos decisórios e na busca por cidades sustentáveis veem sendo colocado, por muitos pesquisadores do tema, como requisitos indispensáveis ao seu adequado funcionamento. Esta dissertação tem como foco de pesquisa a Gestão Energética Descentralizada em âmbito municipal e seu desenvolvimento nas cidades do Brasil. Dessa forma, foi realizada uma revisão bibliográfica sobre o estado da arte do desenvolvimento da Gestão Energética Descentralizada Municipal no Brasil e no mundo, abarcando principalmente questões do planejamento e de políticas públicas como transparência e participação popular no desenvolvimento dos Planejamentos Energéticos Locais. O resultado da pesquisa mostra que existe Gestão de Energia Descentralizada Municipal no Brasil com desenvolvimento de Planejamentos Energéticos Municipais, os quais têm como principal instrumento incentivador o subprograma PROCEL-GEM, foco de estudo de caso também desenvolvido nessa pesquisa, que demonstrou que os planejamentos realizados dentro do subprograma estão restritos as unidades consumidoras de energia elétrica dos órgãos e serviços públicos, além disso, foram observados indícios de falta de transparência e participação popular nos processos de planejamento, assim como falta de recursos para a implementação dos projetos formulados em tais documentos. / Early publications on Decentralized Energy Management, which is a form of energy resources management, date back to the 1980s, however, a substantial increase in the development of such studies and applications of the concept was verified only in recent times (2000s). The Decentralized Energy Management is treated under a multitude of terms and concepts, and can also be applied with varying degrees of decentralization such as in villages, blocks, neighborhoods, districts and states. This concept is close linked to themes like Greenhouse Gases mitigation, integration of renewable energy sources in the energy matrix, energy conservation, energy efficiency and the relationship between urban planning and the energy system. It is noteworthy that in this management model decentralized the communitys participation and engagement in the decision making in the development of sustainable cities is being pointed out, by many researchers, as an indispensable requirement for the proper functioning of this kind of model. This dissertation focuses on Decentralized Energy Management at the municipal level and its development in the cities of Brazil. Thus, this work performs a state of art review on Decentralized Municipal Energy Management in Brazil as well as in the world, covering mainly planning and public policy issues such as transparency and community participation in the development of local Energy Planning. The results shows that there are Decentralized Municipal Energy Management projects in Brazil which develop Municipal Energy Planning, mostly supported by the PROCEL GEM-subprogram, that is also the case study of this research. Additionally, the results demonstrated that the planning made within this subprogram is restricted to the electricity consumption of public agencies or services. Moreover, were observed indications of a lack of transparency and community participation in the planning process as well as the lack of resources for the implementation of such projects.