Síntese de Lentes para Aplicação em Antenas

O ritmo a que a capacidade de processamento dos computadores tem evoluido em gerações consecutivas de processadores está a potenciar uma rápida expansão de aplicações multimedia sofisticadas, e de outros serviços via Internet. Existe uma apetência crescente para que estes conteúdos multimedia possam ficar acessíveis a utilizadores móveis através de terminais portáteis. No entanto, os ficheiros associados a estes contéudos serão cada vez mais pesados, com dezenas ou mesmo centenas de megabytes (Mb). O UMTS - Universal Mobile Telecommunications System, sistema de comunicações móveis da chamada terceira geração (3G) que está em fase de pré-lançamento, vem aumentar significativamente a largura de banda em relação ao GSM, mas fica muito aquém da capacidade que vai ficando disponível na rede fixa de banda larga. Para poder estender totalmente essa capacidade a utilizadores móveis com necessidades mais exigentes, será necessário complementar o UMTS com sistemas de comunicações móveis de banda larga

In or out?:The paradox of exclusionary mechanisms in keeping cooperation going

The question of who's in and who's out is not as straightforward as it seems when understanding the dynamics of exclusion in everyday life. This dissertation explores the intricate dynamics of cooperation and exclusionary mechanisms in social networks and groups by combining insights from formal theoretical modeling and empirical analysis, incorporating perspectives from multiple disciplines. From the stability of social value orientations over time to the contextual influence on cooperation dynamics, this dissertation provides novel and nuanced views on the ways in which exclusion encourages cooperative behavior among individuals and – more importantly- when exclusion fails to promote cooperation. The research findings pave the way for future research in the field of exclusion, both theoretically and empirically, and highlight a downside for excluded defectors: If there is no “in” after exclusion, they may fall into a spiral of defection with a difficult road ahead for (if ever) reaching cooperation “at the end of the tunnel.

Enterprise Content Management Systems Potential to Support Human Capital Management Initiatives

Neto, M. D. C., & Fernandes, C. A. (2010). Enterprise Content Management Systems Potential to Support Human Capital Management Initiatives. International Journal of Engineering and Industrial Management, 2, 75-92Enterprise Content Management Systems (ECMS) and the Enterprise Information Portals (EIP) they support are being increasingly referred in the literature as one interesting technological solution to help organizations in their knowledge management initiatives. This paper seeks to explore the hidden potential of enterprise information portals delivered by ECMS to support knowledge management initiatives, namely human capital management, through the usage of social network analysis on research results and co-authorship/co-work relationships that may suggest ways to more effectively utilize knowledge capital and other organizational resources. For that purpose in this paper we will present field research results on human capital assets management based on EIP data repositories using social network analysis. This evaluation will be made through the use of social network analysis techniques applied to authorship data from papers published in international journals with refereeing covering the last twenty years of research activities from a Portuguese leading research institution in the field of telecommunications - Instituto de Telecomunicações (IT).publishersversionpublishe

Assessing the impact of sulfur concentrations on growth and biochemical composition of three marine microalgae

The elemental stoichiometry, growth and biochemical composition of Nannochloropsis gaditana, Rhodomonas marina and Isochrysis sp. were studied in batch cultures against different nitrogen and sulfur molar ratios (N:S) imposed in their surroundings. In N. gaditana, treatments with low N:S lead to an increase in carbon:sulfur (C:S) and N:S molar ratios up to 95 and 81%, respectively. This was reflected in lipid and protein contents which increased up to 67 and 55%, respectively. Moreover, polyunsaturated fatty acids, as well as its precursors, increased in low N/S treatments. In R. marina, the treatments applied promptly the decrease of both C:S and N:S ratios to 70 and 68%, respectively. Nevertheless, eicosapentaenoic:arachidonic acid ratio increased with N:S treatments by three and a half fold. In Isochrysis sp., the elemental stoichiometry was constrained against treatments until the highest sulfur input. Overall, sulfur supply highlighted microalgae taxonomic differences and suggested that biochemical control is required, even in nutrient replete conditions, to fully exploit their potential as added value biomachineries.info:eu-repo/semantics/publishedVersio

Experimental Demonstration of a Structured Material with Extreme Effective Parameters at Microwaves

Following our recent theoretical studies [M. G. Silveirinha, C. A. Fernandes, Phys. Rev. B, 78, 033108, 2008], it is experimentally verified that an array of crossed metallic wires may behave as a nonresonant material with extremely large index of refraction at microwaves, and may enable the realization of ultra-subwavelength waveguides.Comment: accepted for publication in Applied Physics Letters (in press). Applied Physics Letters (in press) (2008

Marine microalgae growth and carbon partitioning as a function of nutrient availability

To understand in which way the structural differences of three marine microalgae (Nannochloropsis gaditana, Rhodomonas marina and Isochrysis sp.) affect their carbon partitioning, growth and applicability; a stoichiometric imbalance was imposed by steady carbon and other nutrients variation. Towards high nutrients concentrations/low carbon availability a decrease of 12-51% in C/N microalgae ratio was observed and maximum cell densities were achieved. Moreover, linear correlation between the nutrient input and microalgae protein content were observed. The macromolecular ratios pointed that carbohydrate was the main contributor for the C/N decrement. Although lipid content in R. marina remained constant throughout the experiment, a rise of 37-107% in N. gaditana and Isochrysis sp. was verified. Lipid fractions revealed high percentages of glycolipids in all microalgae (57-73% of total lipids). The present study shows an easy way to understand and modulate microalgae carbon partitioning relying on the field of application.info:eu-repo/semantics/publishedVersio

Using Stochastic Actor-Oriented Models to Explain Collaboration Intentionality as a Prerequisite for Peer Feedback and Learning in Networks

Peer feedback and collaboration intentionality (CI) are key prerequisites to advance in higher education. For learning, it is crucial that peers do not merely interact, but that students are willing to function as scaffolds by sharing their knowledge from different perspectives and asking each other for academic support. Peer feedback can only take place within a collaborative learning approach and when students are willing to initiate feedback relationships with their peers. Therefore, we analyze peer feedback networks (in terms of academic help and advice-seeking) and CI as an individual characteristic using an advanced statistical tool, namely stochastic actor-oriented models (SAOMs). In SAOMs, we control for selection and influence mechanisms. Selection comprises instances when feedback relations can be initiated based on CI, while influence builds upon existing feedback relations in affecting CI. One important selection mechanism is homophily, which means that individuals prefer to initiate a connection with someone else based on similarity in characteristics, attitudes, or behavior. In this chapter, we introduce this statistical technique within the higher education context and the added value for feedback research in education. We illustrate the SAOM methodology using two-wave peer feedback networks and CI data while controlling for gender and the Five-Factor Model personality traits. In this empirical example, we address the research question: To what extent does homophily of CI plays a role in selecting peers when seeking feedback and to what extent do feedback relationships influence CI? The SAOM shows an homophily effect, which implies that students preferentially seek feedback from others who are similar in CI. We also find an influence effect in which students who seek feedback from one another become more similar in terms of CI over time. Similarity in CI is driven by selection and influence mechanisms in peer feedback networks