Bio-hybrid approaches have recently provided a possible solution to address the challenge of on-board actuation, control and communication modules for micro/nanoscale cargo-carrying vehicles by integrating live prokaryotic or eukaryotic cells with synthetic objects. More specifically, because micro/nanoparticles are able to transport cargos efficiently and bacteria can play the role of targeted and selective delivery agents, a hybrid of these two can advance the current strategies for environmental monitoring, drug delivery and medical imaging. The main goal of this dissertation was to fabricate, assemble, and characterize different components of a mobile network of bacteria-based bio-hybrid systems for long-term applications in drug delivery and biosensing. First, a new library of bacteria-enabled delivery systems was developed by coupling live engineered bacteria with non-spherical particles and the transport of these bacteria-based systems was investigated in the absence and presence of chemical cues using microfluidic platforms. Next, a quorum-sensing (QS) based bacterial cell-cell communication network was characterized in a high-throughput manner in order to understand the coordinated behavior of the bacterial species ferrying the cargoes. Lastly, the QS behavior of a chemotactic population of the bacterial species in response to the endogenously produced signaling molecules was studied. The work presented in this dissertation lays the foundation for a well-characterized generation of bacteria-assisted cargo delivery devices with enhanced transport properties and capable of executing pre-programmed multi-agent coordinated tasks upon their arrival at the target site. / Ph. D.

Master of Science / Department of Computing and Information Sciences / William H. Hsu / A recommender system is a computational mechanism for information filtering, where users provide recommendations (in the form of ratings or selecting items) as inputs, which the system then aggregates and directs to appropriate recipients. With the advent of web based media and publicity methods, the age where standardized methods of publicity, sales, production and marketing strategies do not. As such, in many markets the users are given a wide range of products and information to choose which product they like, to find a way out of this recommender systems are used in a way similar to the live social scenario, that is a user tries to get reviews from friends before opting for a product in a similar way recommender system tries to be a friend who recommends the options. Most of the recommender systems currently developed solely accuracy driven, i.e., reducing the Mean Absolute Error (MAE) between the predictions of the recommender system and actual ratings of the user. This leads to various problems for recommender systems such as lack of diversity and freshness. Lack of diversity arises when the recommender system is overly focused on accuracy by recommending a set of items, in which all of the items are too similar to each other, because they are predicted to be liked by the user. Lack of freshness also arises with overly focusing on accuracy but as a limitation on the set of items recommended making it overly predictable. This thesis work is directed at addressing the issues of diversity, by developing an approach, where a threshold of accuracy (in terms of Mean Absolute Error in prediction) is maintained while trying to diversify the set of item recommendations. Here for the problem of diversity a combination of Attribute-based diversification and user preference based diversification is done. This approach is then evaluated using non-classical methods along with evaluating the base recommender algorithm to prove that diversification is indeed is possible with a mixture of collaborative and content based approach.

Renewable energy integration into diesel generation systems for remote island communities is a rapidly growing energy engineering field. Fuel supply issues are becoming more common and the disruption, instability and panic caused by fuel shortages results in inefficient and unreliable power supplies for remote island communities. This thesis develops an energy engineering approach for meeting renewable energy development, supply security, cost and sustainability objectives. The approach involves adapting proven energy engineering techniques including energy auditing, energy system modelling with basic cost analysis and demand side management. The novel aspect of this research is the development of critical load engineering in the system design, and informing this with an assessment of essentiality of energy services during the audit phase. This approach was prompted by experiences with previous fuel shortages and long term sustainability policy drivers. The methodology uses the most essential electric loads as the requirement for sizing the renewable energy capacity in the hybrid system. This approach is revolutionary because communication with the customers about availability and the need to shed non-essential loads helps to both meet cost and security requirements and to reduce levels of panic and uncertainty when fuel supply issues arise. A sustainable power generation system is a system that provides continuity of supply for electrical appliances that are considered by the residents to be essential and for which adaptability and resilience of behaviour were key design priorities over growth. The sustainable electrical energy supply should match the critical (essential) load and should have the ability to continue without major disruptions to the daily lives of the people in these communities. Essential energy end uses were identified through energy audits and surveys. The electric power system is designed so that renewable energy sources alone can meet that “essential” demand with a plant that is both economically and technically feasible. Diesel generators were supplemented to meet the short fall in meeting the unconstrained electric demand. This is to design a system that is generally competitive with the present conventional power generation. This method should be particularly suitable for handling the complexities of a modern-day energy system in terms of planning a sizable sustainable energy and electricity system, either based on wholly sustainable sources or integrating sustainable sources of energy into a conventional generation system. The final hybrid system chosen after numerous simulations for the case study (Fenfushi island in the Maldives) community has the minimum renewable energy sources to meet the essential load but uses diesel to supplement the present load. A variety of design parameters such as PV size, wind turbine sizes and numbers and battery capacity have been considered. The minimum renewable energy sources to supply the essential loads of the community were simulated with diesel generators to find the optimal supply mix for the present load (typical unconstrained demand). The final outcome has the following characteristics: NPC and COE were $1,532,340 and $0.37/kWh respectively, lower than any diesel-only systems that could supply the demand. The total annual electricity production is 386,444 units (kWh), of which 9.61% is excess electricity and the annual operating cost is $68,688. Compared to the diesel-only systems there is a fuel savings of 77,021 litres of diesel per year, which is a 66.5 % reduction. An annual carbon dioxide emission reduction of 202,824 kg was achieved, which is a reduction of 66.5%. An annual renewable energy contribution of 70% would be achieved, 34% of which would be from PV arrays and 36% from wind turbines. The selected system shows that even with 30 percent power supply from diesel generators, still the highest NPC is on diesel generation for a life of over 25 years.

No description available.

Multi-agent systems represent a group of agents that cooperate to solve common tasks in a dynamic environment. Multi-agent control systems have been widely studied in the past few years. The control of multi-agent systems relates to synthesizing control schemes for systems which are inherently distributed and composed of multiple interacting entities. Because of the wide applications of multi-agent theories in large and complex control systems, it is necessary to develop a framework to simplify the process of developing control schemes for multi-agent systems. <br /><br /> In this study, a framework is proposed for the distributed control and coordination of multi-agent systems. In the proposed framework, the control of multi-agent systems is regarded as achieving decentralized control and coordination of agents. Each agent is modeled as a Coordinated Hybrid Agent (CHA) which is composed of an intelligent coordination layer and a hybrid control layer. The intelligent coordination layer takes the coordination input, plant input and workspace input. After processing the coordination primitives, the intelligent coordination layer outputs the desired action to the hybrid layer. In the proposed framework, we describe the coordination mechanism in a domain-independent way, as simple abstract primitives in a coordination rule base for certain dependency relationships between the activities of different agents. The intelligent coordination layer deals with the planning, coordination, decision-making and computation of the agent. The hybrid control layer of the proposed framework takes the output of the intelligent coordination layer and generates discrete and continuous control signals to control the overall process. In order to verify the feasibility of the proposed framework, experiments for both heterogeneous and homogeneous Multi-Agent Systems (MASs) are implemented. In addition, the stability of systems modeled using the proposed framework is also analyzed. The conditions for asymptotic stability and exponential stability of a CHA system are given. <br /><br /> In order to optimize a Multi-Agent System (MAS), a hybrid approach is proposed to address the optimization problem for a MAS modeled using the CHA framework. Both the event-driven dynamics and time-driven dynamics are included for the formulation of the optimization problem. A generic formula is given for the optimization of the framework. A direct identification algorithm is also discussed to solve the optimization problem.

Designing Cyber-Physical Systems is hard. Physical testing can be slow, expensive and dangerous. Furthermore computational components make testing all possible behavior unfeasible. Model-based design mitigates these issues by making it possible to iterate over a design much faster. Traditional simulation tools can produce useful results, but their results are traditionally approximations that make it impossible to distinguish a useful simulation from one dominated by numerical error. Verification tools require skills in formal specification and a priori understanding of the particular dynamical system being studied. This thesis presents rigorous simulation, an approach to simulation that uses validated numerics to produce results that quantify and bound all approximation errors accumulated during simulation. This makes it possible for the user to objectively and reliably distinguish accurate simulations from ones that do not provide enough information to be useful. Explicitly quantifying the error in the output has the side-effect of leading to a tool for dealing with inputs that come with quantified uncertainty. We formalize the approach as an operational semantics for a core subset of the domain-specific language Acumen. The operational semantics is extended to a larger subset through a translation. Preliminary results toward proving the soundness of the operational semantics with respect to a denotational semantics are presented. A modeling environment with a rigorous simulator based on the operational semantics is described. The implementation is portable, and its source code is freely available. The accuracy of the simulator on different kinds of systems is explored through a set of benchmark models that exercise different aspects of a rigorous simulator. A case study from the automotive domain is used to evaluate the applicability of the simulator and its modeling language. In the case study, the simulator is used to compute rigorous bounds on the output of a model.

Identificar e localizar faltas em alimentadores de distribuição representa um passo importante para a melhoria da qualidade de energia, pois proporciona impactos diretos sobre o tempo de inspeção. Na verdade, a duração da inspeção implica consideravelmente no intervalo em que os consumidores estão sem energia elétrica, quando ocorre uma interrupção não programada. O objetivo deste trabalho é fornecer um sistema de detecção automática de curtos-circuitos, permitindo aos profissionais das companhias de distribuição acompanhar e monitorar de maneira on-line a ocorrência de possíveis faltas e transitórios eletromagnéticos observados na rede primária de distribuição. A abordagem de detecção utiliza um sistema híbrido que combina ferramentas inteligentes e convencionais para identificar e localizar faltas em redes primárias. Os resultados que foram compilados demonstram grande potencialidade de aplicação da proposta em sistemas de distribuição. / Efficient faults identification and location in power distribution lines constitute an important step for power quality improvement, since they provide direct impacts on the inspection time. In fact, the duration of inspection implies directly in the time interval where consumers are without power, considering here the occurrence of a non-programmed interruption. The objective of this work is to provide an automated fault detection system, allowing to the power companies engineers to online track and monitor the possible occurrence of faults and electromagnetic transients observed in the primary network for the distribution circuits. The detection approach uses a hybrid system, which combines a set of intelligent and conventional tools to identify and locate faults in the primary networks. Validation results show great application potential in distribution systems.

La thèse traite de l’utilisation des systèmes hybrides dans le contexte particulier des communications sécurisées et de la cryptographie. Ce travail est motivé par les faits suivants. L’essor considérable des communications qui a marqué ces dernières décennies nécessite des besoins croissants en terme de sécurité des échanges et de protection de l’information. Dans ce contexte, la cryptographie joue un rôle central puisque les informations transitent la plupart du temps au travers de canaux publics. Parmi les nombreuses techniques de chiffrement existants, le chiffrement par flot se distingue tout particulièrement lorsqu’on le débit d’une communication sécurisée est privilégié. Les chiffreurs par flot sont construits à partir de générateurs de séquences complexes décrits par des systèmes dynamiques et devant être synchronisés de part et d’autre du canal d’échanges. Les objectifs et les résultats de ce travail se déclinent en trois points. Tout d’abord, l’intérêt d’utiliser des systèmes hybrides en tant que primitives cryptographiques est motivé. Par la suite, une étude comparative est menée afin d’établir une connexion entre les algorithmes de masquage de l’information basés sur le chaos et les algorithmes de chiffrement usuels. L’étude porte exclusivement sur des considérations structurelles et repose sur des concepts de la théorie du contrôle, en particulier l’inversibilité à gauche et la platitude. On montre que la technique de masquage dite par inclusion, qui consiste à injecter l’information à protéger dans une dynamique complexe, est la plus efficace. De plus, on montre que sous la condition de platitude, un système de masquage par inclusion est structurellement équivalent à un chiffreur par flot particulier appelé auto-synchronisant. Enfin, des méthodes de cryptanalyse pour évaluer la sécurité du masquage par inclusion sont proposées pour une classe particulières de systèmes hybrides à savoir les systèmes linéaires à commutations. A nouveau, des concepts de la théorie du contrôle sont utilisés, il s’agit de l’identifiabilité paramétrique et des algorithmes d’identification. Des spécificités relatives au contexte particulier de la cryptographie sont prises en compte. En effet, contrairement à la plupart des cas rencontrés dans le domaine du contrôle où les variables des modèles dynamiques sont continues car relatives à des systèmes physiques, les variables prennent ici des valeurs discrètes. Les modèles dynamiques sont en effet décrits non plus dans le corps des réels mais dans des corps finis en vue d’une implémentation sur des machines à états finis tels ordinateur ou tout autre dispositif numérique / This manuscript deals with a specific engineering application involving hybrid dynamical systems : secure communications and cryptography. The work is motivated by the following facts. The considerable progress in communication technology during the last decades has led to an increasing need for security in information exchanges. In this context, cryptography plays a major role as information is mostly conveyed through public networks. Among a wide variety of cryptographic techniques, stream ciphers are of special interest for high speed encryption. They are mainly based on generators of complex sequences in the form of dynamical systems, which must be synchronized at the transmitter and receiver sides. The aim of this work is threefold. First, the interest of resorting to hybrid dynamical systems for the design of cryptographic primitives is motivated. Secondly, a connection between chaotic and conventional cryptography is brought out by comparing the respective algorithms proposed in the open literature. The investigation focuses on structural consideration. Control theoretical concepts, in particular left invertibility and flatness, are the central tools to this end. It is shown that the so-called message-embedding technique, consisting in injecting the information to be concealed into a dynamical system, is the most relevant technique. Furthermore, it is shown that, under the flatness condition, the resulting cipher acts as a self-synchronizing stream cipher. Finally, cryptanalytic methodologies for assessing the security of the message-embedded cryptosystem involving a special class of hybrid systems, namely the switched linear systems, are proposed. Again concepts borrowed from control theory, namely identifiability and identification, are considered. Specificities related to the context are taken into account. The variables describing the dynamical systems do not take values in a continuum unlike what usually happens in automatic control when physical models are considered. They rather take values in finite cardinality sets, especially finite fields, since an implementation in finite state machines, say computers or digital electronic devices, is expected

Sistemas Supervisórios Híbridos podem ser definidos como sistemas de controle cujos estados são representados por variáveis discretas e contínuas, e cuja dinâmica é determinada em função do tempo e da ocorrência de eventos discretos. O desenvolvimento desta classe de Sistemas Supervisórios pode ser dividido em duas fases. A 1ª Fase consiste na elaboração de um modelo protótipo para o Sistema Supervisório, que é descrito usando um formalismo, e que é validado com base nas especificações do problema. Na 2ª Fase, este modelo, já validado, é convertido na linguagem de programação do Sistema Supervisório propriamente dito. Esta tese concentra-se na 1ª Fase, para qual abordam-se três questões principais: (1) a escolha do formalismo de modelagem; (2) como construir o modelo do Sistema Supervisório Híbrido usando este formalismo; e (3) como validar o Sistema Supervisório Híbrido usando o modelo construído. Para questão (1), introduz-se um novo formalismo de modelagem baseado na aplicação dos conceitos de Orientação a Objetos (OO) às redes Predicado Transição Diferenciais (redes PTD). Este novo formalismo é chamado de redes PTD-OO. No que se refere a questão (2), é proposto um procedimento para obtenção do modelo do Sistema Supervisório em redes PTD-OO usando os diagramas da UML (‘Unified Modeling Language’). Finalmente, para a questão (3), o problema de validação é abordado através da definição de um conjunto de propriedades que o modelo em redes PTD-OO deve respeitar afim de que sejam garantidos os requisitos do Sistema Supervisório. Estas propriedades são, então, verificadas através de um procedimento proposto para análise de redes PTD-OO. / Hybrid Supervisory Systems can be described as control systems with states that are represented by both discrete and continuous variables. Their dynamics are function of time and depend also on the occurrence of discrete events. The development of Hybrid Supervisory Systems can be divided in two phases. In the 1st Phase, a prototype-model for the Supervisory System is described using a specific formalism and is validated based on the system requirements. In the 2nd Phase, this validated model is converted to the programming language of the Supervisory System. This thesis is focused on the 1st Phase of Hybrid Supervisory System development. It approaches three main issues: (1) the choice of the modelling formalism; (2) how to build the Hybrid Supervisory System model using this formalism; and (3) how to validate the Hybrid Supervisory System using this model. For issue (1), a new modelling formalism is introduced based on Differential Predicate Transition nets (DPT nets) and object-oriented (OO) paradigm. This new formalism is called DPT-OO net. Then, for the issue (2), a modelling procedure that assists the building of the DPT-OO net model using Unified Modelling Language (UML) diagrams is proposed. Finally, for the issue (3), the validation problem is approached by defining a set of properties of the DPT-OO net model that assures the Supervisory System requirements. These properties are then formally verified using a proposed analysis procedure.

A constituição de sistemas híbridos como alternativa ao fornecimento de energia da concessionária, gerando energia própria e operando de forma isolada ou interconectada ao sistema de distribuição, tem originado estudos e implementações em nível industrial, comercial e mais recentemente residencial. A principal discussão que surge são as análises das vantagens técnicas e econômicas pela opção desse tipo de instalação. Neste trabalho, é apresentado um estudo complementar às pesquisas realizadas, onde é projetado um sistema híbrido contendo aerogeradores, painéis fotovoltaicos, processo de eletrólise, célula a combustível, microturbina a gás e geradores diesel. Esse sistema é simulado e comparado técnica e economicamente a um sistema que contém apenas geradores diesel. O sistema híbrido proposto possui uma microrrede conectada a um típico sistema de distribuição mas com um limite de demanda contratada que impede a satisfação de todas as necessidades energéticas da instalação apenas com a energia da concessionária. Procura-se avaliar os impactos técnicos e econômicos do atendimento da demanda por eletricidade através deste sistema híbrido além de executar-se a otimização, via PSO, do dimensionamento deste sistema, que utiliza uma ordem de despacho para gerenciar as mini unidades geradoras de energia. Foi utilizado o software TRNSYS devido a sua característica de permitir estimar a potência e energia produzidas no intervalo de um ano com detalhamento horário de cada recurso, considerando estimativas reais e localizadas para a disponibilidade dos recursos eólicos e fotovoltaicos. / The designing of hybrid systems as an alternative to power supply from power utility, generating their own energy in operating islanded or grid-tie to the power utility, has resulted in studies and implementations in industrial, commercial and residential level recently. The main discussion that arises is the analysis of the technical and economical advantages for this type of solution. This work presents a complementary study to the researches conducted nowadays, which is designed a hybrid system containing wind turbines, photovoltaic panels, electrolysis process, fuel cell, gas micro turbine and diesel generators. This system was simulated and was compared technically and economically to a system with only diesel gensets. The proposed hybrid system has a microrrede connected to a typical distribution system with a limited power demand value that prevents the satisfaction of all energy needs of the installation only with the utility power. This study evaluates the technical and economical impacts to meeting electric power consumption through this hybrid system and optimize using PSO, the design of this system that uses a dispatch order to manage the mini power generation units. The TRNSYS software was used due to its feature of allowing estimate the electric power and electric energy produced in one year apart with hourly details of each feature, considering actual estimates and localized availability of wind and photovoltaic resources.