Estudo dos sistema de automação da protecção diferencial de linha e comparação direccional

O tema do sistema de automação da protecção diferencial de linha e comparação direccional é merecedor de uma nova abordagem devido às recentes inovações tecnológicas ocorridas desde o aparecimento dos relés digitais e à consequente comunicação entre os sistemas de protecção, em particular na comunicação entre protecções diferenciais de linha. A protecção diferencial de linha apresenta claras vantagens face às protecções actualmente utilizadas para a protecção de linhas de transmissão e distribuição, tais como, Protecção de Máximo Intensidade de Fase, Máximo Intensidade Homopolar Direccionale Protecção de Distância. Contudo, existem alguns problemas associados a este tipo de protecções, nomeadamente na comunicação entre relés. Para automação e comunicação de protecções diferenciais de linhas de transmissão, no caso da ocorrência de defeitos na zona protegida pelo sistema de protecção diferencial foi empregue um método inovador para este tipo de sistema. Uma vez que a eficácia da actuação das protecções diferenciais depende do rigor das variáveis que são necessárias enviar entre protecções que se encontram localizadas em subestações distintas, recorreu-se à utilização de um automatismo para comunicação entre relés suportado pelo desenvolvimento de novos algoritmos para detectar quase instantaneamente um defeito em qualquer zona de protecção de uma linha de transmissão. Estes algoritmos são baseados na Transformada de Park, pelo que, é introduzido um novo conceito neste tipo de protecções. Através destes algoritmos é possível atenuar os problemas associados à protecção diferencial de linha. No sentido de verificar a aplicabilidade destes algoritmos à protecção diferencial de linha são apresentados diversos casos de estudo. Através dos resultados obtidos também foi possível verificar as vantagens associadas à utilização dos algoritmos propostos.

Reliable real-time communication in CAN networks

Controller area network (CAN) is a fieldbus network suitable for small-scale distributed computer controlled systems (DCCS), being appropriate for sending and receiving short real-time messages at speeds up to 1 Mbit/sec. Several studies are available on how to guarantee the real-time requirements of CAN messages, providing preruntime schedulability conditions to guarantee the real-time communication requirements of DCCS traffic. Usually, it is considered that CAN guarantees atomic multicast properties by means of its extensive error detection/signaling mechanisms. However, there are some error situations where messages can be delivered in duplicate or delivered only by a subset of the receivers, leading to inconsistencies in the supported applications. In order to prevent such inconsistencies, a middleware for reliable communication in CAN is proposed, taking advantage of CAN synchronous properties to minimize the runtime overhead. Such middleware comprises a set of atomic multicast and consolidation protocols, upon which the reliable communication properties are guaranteed. The related timing analysis demonstrates that, in spite of the extra stack of protocols, the real-time properties of CAN are preserved since the predictability of message transfer is guaranteed.

As potencialidades da internet no jornalismo digital: Jornal de Notícias vs Diário de Notícias

Dissertação apresentada à Escola Superior de Comunicação Social como parte dos requisitos para obtenção de grau de mestre em Jornalismo.

A communication support for real-time distributed computer controlled systems

In this paper, we analyse the ability of P-NET [1] fieldbus to cope with the timing requirements of a Distributed Computer Control System (DCCS), where messages associated to discrete events should be made available within a maximum bound time. The main objective of this work is to analyse how the network access and queueing delays, imposed by P-NET’s virtual token Medium Access Control (MAC) mechanism, affect the realtime behaviour of the supported DCCS.

Os millennials em Portugal: estudo exploratório a partir de um coorte etário sobre engagement consumidor-marca

Dissertação apresentada à Escola Superior de Comunicação Social como parte dos requisitos para obtenção de grau de mestre em Publicidade e Marketing.

Criação de uma plataforma e-commerce para a página de Facebook Handmade, nós apoiamos

Trabalho de projeto apresentado à Escola Superior de Comunicação Social como parte dos requisitos para obtenção de grau de mestre em Publicidade e Marketing.

A influência do acompanhamento em suporte digital na motivação dos alunos de saxofone: relatório de estágio

I (Prática pedagógica)- Esta secção do Relatório de Estágio pretende apresentar elementos referentes ao Estágio do Ensino Especializado da Música no ensino do saxofone, efectuado na Escola de Música Luís António Maldonado Rodrigues, no ano lectivo 2012/2013. Neste estágio foram envolvidos e analisados três alunos, em níveis distintos de desenvolvimento, mas com orientações semelhantes no que respeita à organização do trabalho. Para cada aluno foram realizados trinta planos de aula, uma planificação anual e três gravações vídeo/áudio em contexto de sala de aula, permitindo uma análise e reflexão mais profunda do trabalho docente. A secção é composta pela caracterização da escola onde se realizou o estágio, através da sua contextualização/funcionamento, dos seus espaços e equipamentos, recursos humanos existentes e organização pedagógica. Posteriormente é efectuada a caracterização dos três alunos envolvidos no estágio, baseada na experiência docente e nos conhecimentos fornecidos pelas Unidades Curriculares do Mestrado em Ensino da Música. Seguidamente descrevem-se as práticas lectivas desenvolvidas ao longo do ano lectivo por parte do docente, incorporando linhas orientadoras da docência aplicadas na prática pedagógica. É feita uma análise crítica da actividade docente no âmbito do estágio do Ensino Especializado da Música, e, por último, uma conclusão desta primeira secção. .

Constraint solving over multi-valued logics - application to digital circuits

Due to usage conditions, hazardous environments or intentional causes, physical and virtual systems are subject to faults in their components, which may affect their overall behaviour. In a ‘black-box’ agent modelled by a set of propositional logic rules, in which just a subset of components is externally visible, such faults may only be recognised by examining some output function of the agent. A (fault-free) model of the agent’s system provides the expected output given some input. If the real output differs from that predicted output, then the system is faulty. However, some faults may only become apparent in the system output when appropriate inputs are given. A number of problems regarding both testing and diagnosis thus arise, such as testing a fault, testing the whole system, finding possible faults and differentiating them to locate the correct one. The corresponding optimisation problems of finding solutions that require minimum resources are also very relevant in industry, as is minimal diagnosis. In this dissertation we use a well established set of benchmark circuits to address such diagnostic related problems and propose and develop models with different logics that we formalise and generalise as much as possible. We also prove that all techniques generalise to agents and to multiple faults. The developed multi-valued logics extend the usual Boolean logic (suitable for faultfree models) by encoding values with some dependency (usually on faults). Such logics thus allow modelling an arbitrary number of diagnostic theories. Each problem is subsequently solved with CLP solvers that we implement and discuss, together with a new efficient search technique that we present. We compare our results with other approaches such as SAT (that require substantial duplication of circuits), showing the effectiveness of constraints over multi-valued logics, and also the adequacy of a general set constraint solver (with special inferences over set functions such as cardinality) on other problems. In addition, for an optimisation problem, we integrate local search with a constructive approach (branch-and-bound) using a variety of logics to improve an existing efficient tool based on SAT and ILP.

LNT: a logical neighbor tree secure group communication scheme for wireless sensor networks

Secure group communication is a paradigm that primarily designates one-to-many communication security. The proposed works relevant to secure group communication have predominantly considered the whole network as being a single group managed by a central powerful node capable of supporting heavy communication, computation and storage cost. However, a typical Wireless Sensor Network (WSN) may contain several groups, and each one is maintained by a sensor node (the group controller) with constrained resources. Moreover, the previously proposed schemes require a multicast routing support to deliver the rekeying messages. Nevertheless, multicast routing can incur heavy storage and communication overheads in the case of a wireless sensor network. Due to these two major limitations, we have reckoned it necessary to propose a new secure group communication with a lightweight rekeying process. Our proposal overcomes the two limitations mentioned above, and can be applied to a homogeneous WSN with resource-constrained nodes with no need for a multicast routing support. Actually, the analysis and simulation results have clearly demonstrated that our scheme outperforms the previous well-known solutions.

RiSeG: a ring based secure group communication protocol for resource-constrained wireless sensor networks

Securing group communication in wireless sensor networks has recently been extensively investigated. Many works have addressed this issue, and they have considered the grouping concept differently. In this paper, we consider a group as being a set of nodes sensing the same data type, and we alternatively propose an efficient secure group communication scheme guaranteeing secure group management and secure group key distribution. The proposed scheme (RiSeG) is based on a logical ring architecture, which permits to alleviate the group controller’s task in updating the group key. The proposed scheme also provides backward and forward secrecy, addresses the node compromise attack, and gives a solution to detect and eliminate the compromised nodes. The security analysis and performance evaluation show that the proposed scheme is secure, highly efficient, and lightweight. A comparison with the logical key hierarchy is preformed to prove the rekeying process efficiency of RiSeG. Finally, we present the implementation details of RiSeG on top of TelosB sensor nodes to demonstrate its feasibility.

A tighter analysis of the worst-case endto- end communication delay in massive multicores

"Many-core” systems based on the Network-on- Chip (NoC) architecture have brought into the fore-front various opportunities and challenges for the deployment of real-time systems. Such real-time systems need timing guarantees to be fulfilled. Therefore, calculating upper-bounds on the end-to-end communication delay between system components is of primary interest. In this work, we identify the limitations of an existing approach proposed by [1] and propose different techniques to overcome these limitations.

A vision of cyber-physical internet

When the Internet was born, the purpose was to interconnect computers to share digital data at large-scale. On the other hand, when embedded systems were born, the objective was to control system components under real-time constraints through sensing devices, typically at small to medium scales. With the great evolution of the Information and Communication Technology (ICT), the tendency is to enable ubiquitous and pervasive computing to control everything (physical processes and physical objects) anytime and at a large-scale. This new vision gave recently rise to the paradigm of Cyber-Physical Systems (CPS). In this position paper, we provide a realistic vision to the concept of the Cyber-Physical Internet (CPI), discuss its design requirements and present the limitations of the current networking abstractions to fulfill these requirements. We also debate whether it is more productive to adopt a system integration approach or a radical design approach for building large-scale CPS. Finally, we present a sample of realtime challenges that must be considered in the design of the Cyber-Physical Internet.

A compositional scheduling framework for digital avionics systems

ARINC specification 653-2 describes the interface between application software and underlying middleware in a distributed real-time avionics system. The real-time workload in this system comprises of partitions, where each partition consists of one or more processes. Processes incur blocking and preemption overheads and can communicate with other processes in the system. In this work we develop compositional techniques for automated scheduling of such partitions and processes. At present, system designers manually schedule partitions based on interactions they have with the partition vendors. This approach is not only time consuming, but can also result in under utilization of resources. In contrast, the technique proposed in this paper is a principled approach for scheduling ARINC-653 partitions and therefore should facilitate system integration.

Para lá dos jornalistas: influencer relations, uma nova era de Media Relations

Dissertação apresentada à Escola Superior de Comunicação Social como parte dos requisitos para obtenção de grau de mestre em Gestão Estratégica das Relações Públicas.