Proactive services ecosystem framework

Dissertation presented to obtain the degree of Doctor in Electrical and Computer Engineering, specialization on Collaborative Enterprise Networks

Regional change in the Algarve: A Geographic Information System approach

Thesis submitted to the Instituto Superior de Estat��stica e Gest��o de Informa����o da Universidade Nova de Lisboa in partial fulfillment of the requirements for the Degree of Doctor of Philosophy in Information Management ��� Geographic Information Systems

A modular distributed transactional memory framework

Disserta����o para obten����o do Grau de Mestre em Engenharia Inform��tica

UJI's Smart Campus: Place Finder App

Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Geospatial Technologies.

NEGOSEIO: framework for the sustainability of model-oriented enterprise interoperability

Dissertation to obtain the degree of Doctor of Philosophy in Electrical and Computer Engineering(Industrial Information Systems)

A communication strategy for Continente: Proposals to improve the online services

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA ��� School of Business and Economics

Calibration, selection and mosaicing of SMART-1 AMIE images

Disserta����o para obten����o do Grau de Mestre em Engenharia Electrot��cnica e de Computadores

The role of electron transfer in DNA building blocks: evaluation of strand breaks and their implications

Disserta����o para obten����o do Grau de Doutor em Engenharia F��sica

Geospatial technologies for public participation: better decisions for smarter cities?

Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Geospatial Technologies.

Business model: What should be the strategy used by Smart Galp to implement and potentiate its value proposition in the Portuguese market?

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA ��� School of Business and Economics

Service-oriented infrastructure to support the control, monitoring and management of a shop floor system

Disserta����o para obten����o do Grau de Mestre em Engenharia Electrot��cnica e de Computadores

Cell-to cell Communication in Pectobacterium wasabiae

Dissertation presented to obtain the PhD degree in Biology

Enterprise Social Networking

Microblogging in the workplace as a functionality of Enterprise Social Networking (ESN) platforms is a relatively new phenomenon of which the use in knowledge work has not yet received much attention from research. In this cross-sectional study, I attempt to shed light on the role of microblogging in knowledge work. I identify microblogging use practices of knowledge workers on ESN platforms, and I identify its role in supporting knowledge work performance. A questionnaire is carried out among a non-representative sample of knowledge workers. The results shed light on the purposes of the microblogging messages that knowledge workers write. It also helps us find out whether microblogging supports them in performing their work. The survey is based on existing theory that supplied me with possible microblog purposes as well as theory on what the actions of knowledge workers are. The results reveal that ���knowledge & news sharing���, ���crowd sourcing���, ���socializing & networking��� and ���discussion & opinion��� are frequent microblog purposes. The study furthermore shows that microblogging benefits knowledge workers��� work. Microblogging seems to be a worthy addition to the existing means of communication in the workplace, and is especially useful to let knowledge, news and social contact reach a further and broader audience than it would in a situation without this social networking service.

Specification of a partial replication protocol with TLA+

Nowadays, data available and used by companies is growing very fast creating the need to use and manage this data in the most efficient way. To this end, data is replicated overmultiple datacenters and use different replication protocols, according to their needs, like more availability or stronger consistency level. The costs associated with full data replication can be very high, and most of the times, full replication is not needed since information can be logically partitioned. Another problem, is that by using datacenters to store and process information clients become heavily dependent on them. We propose a partial replication protocol called ParTree, which replicates data to clients, and organizes clients in a hierarchy, using communication between them to propagate information. This solution addresses some of these problems, namely by supporting partial data replication and offline execution mode. Given the complexity of the protocol, the use of formal verification is crucial to ensure the protocol two correctness properties: causal consistency and preservation of data. The use of TLA+ language and tools to formally specificity and verify the proposed protocol are also described.

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.