Browsing by Author "Marques, Bruno"
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- Application-Driven design to extend WSN lifetimePublication . Marques, Bruno; Ricardo, Manuelhe lifetime of a WSN depends on the energy of the nodes. As soon as nodes run out of energy, they get disconnected from the WSN. This paper proposes an Application Driven solution that increases the WSN lifetime by limiting the routing and forwarding functions of the network mainly to nodes running the same applications. The solution is evaluated against AODV, and the results obtained show gains of about 30%
- Application-Driven Wireless Sensor NetworksPublication . Marques, Bruno; Ricardo, ManuelThe growth of wireless networks has resulted in part from requirements for connecting people and advances in radio technologies. Recently there has been an increasing trend towards enabling the Internet-of-Things (IoT). Thousands of tiny devices interacting with their environments are being inter-networked and made accessible through the Internet. For that purpose, several communications protocols have been defined making use of the IEEE 802.15.4 Physical and MAC layers. The 6LoWPAN Network Layer adaptation protocol is an example which bridges the gap between low power devices and the IP world. Since its release, the design of routing protocols became increasingly important and the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) emerged as the IETF proposed standard protocol for IPv6-based multi-hop Wireless Sensor Networks (WSN). This thesis considers that the sensor nodes form a large IPv6 network making use of above technologies and protocols, and that the sensor nodes are enabled to run one or more applications. It is also assumed that the applications and the sensor nodes to which they are associated, are not always active, alternating between active and inactive states. The thesis aims to design a new energy efficient communications solution for WSN by exploring the hypothesis that the network is aware of the traffic generated by the applications running in the sensor nodes. Therefore, the thesis provides two major contributions: 1) a cross-layer mechanism using application layer and network layer information to constrainRPL-defined routing trees (RPL-BMARQ); 2) an Application-Driven WSN node synchronization mechanism for RPL-BMARQ. RPL-BMARQ is designed as an extension to the RPLrouting protocol using information shared by the application and routing layers to construct Directed Acyclic Graphs (DAGs), allowing the nodes to select parents with respect to the applications they run. By jointly considering the neighbors of each node, the applications each node runs, and the forwarding capabilities of a node, we provide a communications solution which enables the data of every application and sensor node to be transferred, while keeping the overall energy consumed low by reducing the time the nodes are active and reducing the total number of multicast packets exchanged. Therefore, RPL-BMARQ helps reducing the network energy consumption since it restricts radio communication activities while maintaining throughput fairness and packet reception ratio high. The mechanism was evaluated using four scenarios with different network topologies and compared against "standard RPL". The results obtained show that the mechanism enables lower energy consumption since the nodes are more often put a sleep, reducing the total number of packets exchanged, while maintaining fairness and query success rates high. The Application-Driven WSN node synchronization mechanism for RPL-BMARQ was designed to maintain the sensor nodes synchronized according to the duty cycle of the applications they run. The mechanism jointly uses cross-layer information and the Exponentially Weighted Moving Average (EWMA) technique for calculating in run-time average network delays which are used to control the time the sensor nodes would sleep in the next cycle in order to wake up just before the next activity period starts. This mechanism enables all the sensor nodes to go asleep and to wake up in synchronism. The mechanism was theoretically evaluated and simulated, and the results obtained show that the synchronization mechanism works as previewed. The results also showed that, when designing WSN applications with this mechanism, the nodes not involved in communications are kept sleeping as much as possible, waking up when necessary and in synchronism. In order to confirm the validity of the mechanisms designed, we also tested them in real environments where the results were confirmed.
- Efeito da secagem sobre a textura de peras da variedade Packhams.Publication . Henriques, Francisca; Marques, Bruno; Guiné, RaquelA textura é uma das características mais importantes no que diz respeito à qualidade dos alimentos, que, em conjugação com a aparência e sabor, tem grande influência na aceitação do produto alimentar por parte do consumidor (1). A textura caracteriza-se por um conjunto de propriedades físicas que são consequência da estrutura interna do material que por sua vez é determinada pelas interacções moleculares dos seus constituintes. Os alimentos no geral e as pêras em particular apresentam diferentes propriedades de textura. Estas derivam das diferenças inerentes às diferentes variedades, diferentes estados de maturação e aos métodos de processamento sofridos, neste caso a secagem (2). Neste trabalho, são objecto de estudo as pêras da variedade Packams, em fresco, secadas em estufa com convecção de ar a uma temperatura de 50 ºC, liofilizadas e rehidratadas, de forma a determinar as propriedades físicas de textura nos diferentes estados (frescas e secadas) e consequentemente fazer a respectiva análise e comparação dos resultados obtidos. O objectivo deste estudo prende-se por um lado, com a aquisição de conhecimento científico acerca das modificações ocorridas ao nível das propriedades de textura na pêra Packams, antes e depois do processo de secagem e, por outro lado, compreender o efeito que a desidratação tem nas diferentes propriedades de textura desta variedade de pêra. O método de secagem utilizado neste trabalho foi a secagem em estufa com circulação de ar a uma temperatura constante de 50ºC e pretendeu-se que o ponto final da secagem das pêras ocorresse para teores de humidade de cerca de 20%. A Liofilização foi efectuada num liofilizador, a partir das peras congeladas, a uma pressão de cerca de 0,7 Pa e uma temperatura à volta de – 50 ºC. As propriedades de textura foram avaliadas pelo método de análise do perfil de textura (TPA), utilizando como instrumento de medida um texturómetro. Esta análise foi efectuada para as mesmas pêras antes e depois da secagem. Os parâmetros de textura avaliados foram a dureza, a adesividade, a coesividade, a elasticidade e a mastigabilidade.
- Energy-efficient node selection in application-driven WSNPublication . Marques, Bruno; Ricardo, ManuelThe growth of wireless networks has resulted in part from requirements for connecting people and advances in radio technologies. Wireless sensor networks are an example of these networks in which a large number of tiny devices interacting with their environments may be inter-networked together and accessible through the Internet. As these devices may be scattered in an unplanned way, a routing protocol is needed. The RPL protocol is the IETF proposed standard protocol for IPv6-based multi-hop WSN. RPL requires that communication paths go through a central router which may provide suboptimal paths, not considering the characteristics of the applications the nodes run. In this paper is proposed an Application-Driven extension to RPL which enables to increase the WSN lifetime by limiting the routing and forwarding functions of the network mainly to nodes running the same application. As nodes may join a network at a non predictable time, they must be synchronized with respect to their application duty cycles. Therefore, nodes have to wake up and sleep in a synchronized way. In this paper it is also proposed such synchronization mechanism. The results confirm that the proposed solutions provide lower energy consumption and lower number of packets exchanged than the conventional RPL solution, while maintaining fairness and the packet reception ratio high.
- Evaluation of Texture of Packhams PearsPublication . Guiné, Raquel; Marques, BrunoThe textural parameters, together with appearance and flavor, are sensory attributes of great importance for the product to be accepted by the consumer. The objective of the present study was the evaluation of the textural attributes of Packhams pears in the fresh state, after drying in a chamber with forced convection at 50ºC, lyophilized and re-hydrated. In texture analysis it was used the method of Texture Profile Analysis (TPA). The parameters analyzed were hardness, cohesiveness, adhesiveness, elasticity and chewiness. From the results obtained is possible to see that the drying operation greatly affected some textural properties of the pears, so that the hardness diminished very much with drying, for both drying methods
- Evaluation of Texture of Packhams PearsPublication . Guiné, Raquel; Marques, BrunoThe textural parameters, together with appearance and flavor, are sensory attributes of great importance for the product to be accepted by the consumer. The objective of the present study was the evaluation of the textural attributes of Packhams pears in the fresh state, after drying in a chamber with forced convection at 50 ºC, lyophilized and re-hydrated. In texture analysis it was used the method of Texture Profile Analysis (TPA). The parameters analyzed were hardness, cohesiveness, adhesiveness, elasticity and chewiness. From the results obtained is possible to see that the drying operation greatly affected some textural properties of the pears, so that the hardness diminished very much with drying, for both drying methods.
- Influence of drying on the texture of solar dried pears.Publication . Marques, Bruno; Guiné, Raquel; Cunha, Pedro; Silva, Lizete; Lima, Maria João; Ferreira, DulcineiaTexture is the result of complex interactions among food components, and the changes in texture occurring during the processing of plant materials or certain physiological events have been related to tissue and cell microstructural changes [1]. The texture parameter, together with appearance and flavour, are the organoleptic quality attributes which determine the acceptability of a food by the consumer. Hence, there has been a great interest in the development of methods to predict and control the texture of plant-based foods, particularly in relation to processing treatments. Instrumental texture profile analysis (TPA) is one of the methods to determine the texture by simulating or imitating the repeated biting or chewing of a food. The pears used in the present study are of the Portuguese variety S. Bartolomeu, which is traditionally dried, and they were dried peeled but uncut. However, unlike in the traditional method the pears were not dried under open-air sun exposure, and, alternatively, were dried in two different systems: solar stove with forced convection (STFC) and solar stove with natural convection (STNC). The drying was carried out until the pears reached a desirable moisture content of about 20 % (wet basis). Before drying, along the process and at the end, samples were used from both drying systems to evaluate their textural properties. The texture profile analysis to all the samples was performed using a Texture Analyser, and the textural properties: hardness, springiness, cohesiveness, and chewiness were then calculated after standard equations. The objective of the present work is, on one hand, to evaluate how the textural attributes change along time during the drying operation and, on the other hand, to compare the two drying methods used. From the results obtained is possible to see that the drying operation greatly affects the textural properties of the pears, so that the hardness diminishes very much along drying, for both the drying systems tested.
- Linguagem de Comunicação entre Aplicações de Gestão AutónomasPublication . Marques, Bruno; Oliveira, RaúlO paradigma dos agentes de software desenvolveu-se a partir da área da inteligência artificial. No entanto, apesar do primeiro trabalho sobre os agentes ter sido efectuado há já bastantes anos (falo da década de 70), o paradigma dos agentes inteligentes levou bastante tempo a tornar-se realidade no mundo das telecomunicações. Presentemente, tem-se assistido a um grande crescimento no interesse da utilização de aplicações autónomas de software (agentes) nos sistemas de telecomunicações devido, principalmente, à consciência de que este paradigma pode oferecer melhores meios para a interligação e gestão de grandes redes com características acentuadamente heterogéneas como é o caso das redes de telecomunicações. Assim sendo, as estruturas das comunicações são agora vistas como um domínio natural da aplicabilidade dos agentes inteligentes. A aproximação seguida neste trabalho de mestrado conduziu ao desenvolvimento de uma nova arquitectura multi-agente, apropriada a todo um contexto de fornecimento de serviços ATM de ligação entre redes privadas através de uma ou mais redes operadoras de área alargada. Neste, os agentes são responsáveis por pedir informações sobre serviços e respectivos custos, negociar e estabelecer um serviço qualificado e a pedido de um agente em nome de um utilizador final (rede privada). Com os agentes, pretende-se reduzir o factor humano actualmente encontrado, estabelecendo-se dinâmicamente circuitos de comunicação e fazendo um melhor aproveitamento dos recursos existentes no equipamento das redes. Para além do desenvolvimento desta arquitectura e definição dos possíveis cenários de comunicação, foi necessária a especificação de uma linguagem de conteúdo que, utilizada pelos agentes, conseguisse de uma forma transparente integrar a resolução distribuída de um problema (o do estabelecimento dinâmico de um circuito de comunicação especificado pelo utilizador final) num ambiente de redes heterogéneas. Assim, conseguiu-se definir uma arquitectura de agentes híbridos e reactivos, já que eles agem no seu meio ambiente, actuando nos equipamentos de rede de acordo com o conhecimento que dele possuem. Todos os conceitos ligados a esta nova tecnologia (terminologias, conceitos de linguagens de comunicação e de linguagens de conteúdo), no que se refere a um contexto de redes de telecomunicações, são explicados em detalhe na presente tese
- Synchronization of application-driven WSNPublication . Marques, Bruno; Ricardo, ManuelThe growth of wireless sensor networks (WSN) has resulted in part from requirements for connecting sensors and advances in radio technologies. WSN nodes may be required to save energy and therefore wake up and sleep in a synchronized way. In this paper, we propose an application-driven WSN node synchronization mechanism which, by making use of cross-layer information such as application ID and duty cycle, and by using the exponentially weighted moving average (EWMA) technique, enables nodes to wake up and sleep without losing synchronization. The results obtained confirm that this mechanism maintains the nodes in a mesh network synchronized according to the applications they run, while maintaining a high packet reception ratio.