Petri net based development of globally-asynchronous locally-synchronous distributed embedded systems

Dissertação para obtenção do Grau de Doutor em Engenharia Electrotécnica e de Computadores

Design, implementation, and performance of a distributed and scalable sensor system for critical distance measurements in the CMS detector at LHC

The “CMS Safety Closing Sensors System” (SCSS, or CSS for brevity) is a remote monitoring system design to control safety clearance and tight mechanical movements of parts of the CMS detector, especially during CMS assembly phases. We present the different systems that makes SCSS: its sensor technologies, the readout system, the data acquisition and control software. We also report on calibration and installation details, which determine the resolution and limits of the system. We present as well our experience from the operation of the system and the analysis of the data collected since 2008. Special emphasis is given to study positioning reproducibility during detector assembly and understanding how the magnetic fields influence the detector structure.

Medium access control design for distributed opportunistic radio networks

Existing wireless networks are characterized by a fixed spectrum assignment policy. However, the scarcity of available spectrum and its inefficient usage demands for a new communication paradigm to exploit the existing spectrum opportunistically. Future Cognitive Radio (CR) devices should be able to sense unoccupied spectrum and will allow the deployment of real opportunistic networks. Still, traditional Physical (PHY) and Medium Access Control (MAC) protocols are not suitable for this new type of networks because they are optimized to operate over fixed assigned frequency bands. Therefore, novel PHY-MAC cross-layer protocols should be developed to cope with the specific features of opportunistic networks. This thesis is mainly focused on the design and evaluation of MAC protocols for Decentralized Cognitive Radio Networks (DCRNs). It starts with a characterization of the spectrum sensing framework based on the Energy-Based Sensing (EBS) technique considering multiple scenarios. Then, guided by the sensing results obtained by the aforementioned technique, we present two novel decentralized CR MAC schemes: the first one designed to operate in single-channel scenarios and the second one to be used in multichannel scenarios. Analytical models for the network goodput, packet service time and individual transmission probability are derived and used to compute the performance of both protocols. Simulation results assess the accuracy of the analytical models as well as the benefits of the proposed CR MAC schemes.

A importância da comunicação estratégica na alteração de comportamentos na sociedade : o caso Sociedade Ponto Verde

A comunicação estratégica poderá ser entendida como a comunicação alinhada com a estratégia global de uma organização para alcançar o seu posicionamento estratégico. Ou seja, para alcançar o sucesso, uma organização precisa de ter uma comunicação consistente com a sua identidade e, ao mesmo tempo, adequada ao seu público-alvo e ao tipo de sector onde se insere. Só desta forma consegue conquistar a confiança e fidelidade dos consumidores, essenciais para o alcance dos objectivos. Em relação à alteração comportamentos, é essencial que as empresas costruam uma estratégia de comunicação coerente e consistente, adaptando as mensagens e os públicos-alvo escolhidos. Neste âmbito da alteração de comportamentos, estudou-se neste trabalho a Sociedade Ponto Verde (SPV), uma associação portuguesa sem fins lucrativos, que actua no âmbito da gestão e reciclagem de resíduos de embalagens. Procurou estudar-se a evolução da sua comunicação ao longo dos anos e a forma como adaptou as suas mensagens, de forma a conseguir incutir na sociedade portuguesa a importância do comportamento de reciclagem de resíduos. Neste estudo, procedeu-se a uma análise individualizada de cada uma das campanhas de comunicação da SPV e, posteriormente, aplicou-se um inquérito por questionário, para verificar a eficácia das mesmas campanhas perante o público-alvo. A metodologia utilizada neste trabalho consistiu na distribuição de um inquérito por questionário online, que permitiu recolher uma amostra probabilística por conveniência. Em seguida, recolhidos e tratados os dados referentes às 482 respostas recebidas, utilizou-se o programa SPSS (Stastitical Package for the Social Sciences) para analisar, tratar e discutir os resultados obtidos. Estes resultados demonstraram que, de facto, não houve uma grande percentagem de inquiridos que se lembram das campanhas da SPV. Os resultados são positivos e não desmentem a qualidade e coerência das mensagens, mas a verdade é que a percentagem de indivíduos que não se lembra de algumas campanhas chega a ser elevada (em especial nas campanhas iniciais da organização, quando existia falta de uma estratégia coerente). Justifica-se este facto, em parte, pelo excesso de informação e estímulos a que as pessoas estão sujeitas, pelo que a informação que retêm não fica para sempre, acabando por dar lugar a outras informações. Os indivíduos são inconscientemente selectivos com a informação que processam e guardam, pois não seria possível guardar toda a informação que lhes é transmitida. No que diz respeito à comunicação estratégica que visa alterar uma atitude e, posteriormente, um comportamento, conclui-se que, no geral, o comportamento das pessoas inquiridas aparenta ter sido influenciado pela comunicação da SPV, caso contrário, as respostas afirmativas quanto à reciclagem e de concordância com algumas das afirmações teriam sido inferiores. Ou seja, mesmo reconhecendo o carácter um pouco enviesado da amostra (não deverá ser considerada representativa da população portuguesa), é possível dizer que a estratégia de comunicação da SPV (em especial a partir de 2005) foi eficiente. Palavras-

Distributed solar micro generation

Taking into account the fact that the sun’s radiation is estimated to be enough to cover 10.000 times the world’s total energy needs (BRAKMANN & ARINGHOFF, 2003), it is difficult to understand how solar photovoltaic systems (PV) are still such a small part of the energy source matrix across the globe. Though there is an ongoing debate as to whether energy consumption leads to economic growth or whether it is the other way around, the two variables appear correlated and it is clear that ensuring the availability of energy to match a country’s growth targets is one of the prime concerns for any government. The topic of centralized vs distributed electricity generation is also approached, especially in what regards the latter fit to developing countries needs, namely the lack of investment capabilities and infrastructure, scattered population, and other factors. Finally, Brazil’s case is reviewed, showing that the current cost of electricity from the grid versus the cost from PV solutions still places an investment of this nature with 9 to 16 years to reach breakeven (from a 25 year panel lifespan), which is too high compared to the required 4 years for most Brazilians. Still, recently passed legislation opened the door, even if unknowingly, to the development of co-owned solar farms, which could reduce the implementation costs by as much as 20% and hence reduce the number of years to breakeven by 3 years.

Evaluation of foamed bitumen efficiency in warm asphalt mixtures recycling

The recycling of pavements is nowadays a very important question to the road paving industry. With the objective of incorporating higher percentages of reclaimed asphalt (RA) materials in recycled asphalt mixtures, new techniques have been developed in the last years. The use of foamed bitumen is normally associated with the production of cold asphalt mixtures, which usually show lower quality standards. However, the objective of the work presented in this paper is to assess the use of foamed bitumen as the binder of warm asphalt mixtures incorporating 30% RA, which have quality standards similar to those of conventional mixtures. Thus, five mixtures have been produced with 30% RA, one of them with a conventional bitumen (control mix) and the others with foamed bitumen at different production temperatures. The mixtures were tested for compactability and water sensitivity and the results show a possible reduction of 25 ºC in the production temperatures, while the water sensitivity test results were kept close to 90 %.

A mechanical analysis of asphalt recycled mixtures produced with high recycling rates

In this work four asphalt mixtures were compared in terms of mechanical characteristics. One of the mixtures (control mixture) was used as a reference to the study of three mixtures produced with reclaimed asphalt pavement (RAP). One of the recycled mixtures incorporated 30% of RAP and the other two were produced with 50% of RAP. The effect of using a rejuvenator additive (3% rejuvenator) was also evaluated in one of the mixtures with 50% of RAP.

Monitoring and analysis of queries in distributed databases

Dissertação de Mestrado em Engenharia Informática

A survey of distributed data aggregation algorithms

Distributed data aggregation is an important task, allowing the de- centralized determination of meaningful global properties, that can then be used to direct the execution of other applications. The resulting val- ues result from the distributed computation of functions like count, sum and average. Some application examples can found to determine the network size, total storage capacity, average load, majorities and many others. In the last decade, many di erent approaches have been pro- posed, with di erent trade-o s in terms of accuracy, reliability, message and time complexity. Due to the considerable amount and variety of ag- gregation algorithms, it can be di cult and time consuming to determine which techniques will be more appropriate to use in speci c settings, jus- tifying the existence of a survey to aid in this task. This work reviews the state of the art on distributed data aggregation algorithms, providing three main contributions. First, it formally de nes the concept of aggrega- tion, characterizing the di erent types of aggregation functions. Second, it succinctly describes the main aggregation techniques, organizing them in a taxonomy. Finally, it provides some guidelines toward the selection and use of the most relevant techniques, summarizing their principal characteristics.

maintenance model for systems with phase-type distributed times to failure

Magdeburg, Univ., Fak. für Mathematik, Diss., 2010

Keyword search across distributed heterogenous structured data sources

Magdeburg, Univ., Fak. für Informatik, Diss., 2012

Collaboration process design for ideation in distributed environments : approaches to support collaborative ideation in global virtual groups using technological support

Magdeburg, Univ., Fak. für Informatik, Diss., 2012

Assessing the role of Piccolo and Bassoon zinc finger domains on synapse vesicle recycling and maintenance

Magdeburg, Univ., Fak. für Naturwiss., Diss., 2013