ICI - Instituto Coordenador da Investigação
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O ICI integra Unidades de Investigação que exerçam as suas atividades na UBI e que tenham sido classificados com notação igual ou superior a Bom pelos painéis internacionais de avaliação periódica designados pela Fundação para a Ciência e Tecnologia.
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- Numerical study of single impinging jets through a crossflowPublication . Barata, Jorge M M; Durão, Diamantino; McGuirk, J. J.
- Em Torno do AgnosticismoPublication . Rosa, José Maria SilvaEste artigo procura determinar em que consiste propriamente a atitude agnóstica face à questão da existência ou não existência de Deus, demarcando-a de outras (gnóstica, fideísta, ateia, etc.) na medida que o agnóstico, por definição, recusa responder à questão alegando a impossibilidade de o espírito humano lhe poder responder. Nesse sentido, o Agnosticismo incorpora elementos do antigo Epicurismo e Cepticismo. Ao longo do artigo rastreia-se o percurso histórico dessa atitude, com o momento especial em Kant e a sua «Crítica da Razão Pura», onde a Filosofia Moderna conclui a impossibilidade de demonstrar tanto a existência como a inexistência de Deus, já que o intelecto humano é um «intelecto éctipo», incapaz de intuição intelectual.
- Judaísmo tardio e Helenismo. AproximaçõesPublication . Rosa, José Maria SilvaEste artigo procura analisar alguns temas da obra de Fílon de Alexandria «De Migratione Abrahami» de modo a encontrar nela relações entre a exegese alegórica que o autor faz de passagens bíblicas (no caso a Migração de Abraão), relacionando essas passagens com temas próprios da Filosofia Platónica (saída da caverna, contemplação das ideias, etc.) e suas reapropriações helenísticas.
- Traffic from Mobility in Mobile Broadband SystemsPublication . Velez, Fernando J.; Correia, Luis M.Models allowing the study of the influence of coveragedistance and velocity on the supported traffic and on thenew calls traffic linear density are examined, and resultsare obtained for typical scenarios in a Mobile BroadbandSystem (MBS) with a linear coverage geometry. For systemswithout guard channels for handover, for a fixed boundingvalue for the blocking probability, the new calls traffic lin-ear density was analyzed, increasing with the decrease of themaximum coverage distance, R, being upper limited by avalue which depends on the characteristics of the mobilityscenario. However, call-dropping probability requirementsalso need to be fulfilled, leading to a new calls traffic densitythat only increases with the decrease of R down to an opti-mum value of R, and being lower for scenarios with highermobility. These optimum values of R are higher for scenar-ios with higher and higher mobility, leading to limitations insystem capacity, mainly for high mobility scenarios. Inorder to resolve these limitations, the use of guard channelsfor handover is studied, particularly for high mobilityscenarios. For these scenarios one concludes that there is adegradation in system capacity because, for the typicalcoverage distances foreseen for MBS, the new calls trafficlinear density is one order of magnitude below the valuesobtained for the pedestrian scenario (where it is approxi-mately 15 Erlang/km), decreasing from 2.47 Erlang/km, inthe urban scenario, down to 0.84 Erlang/km, in the highwayscenario, when two guard channels are used.
- Jornalismo e espaço públicoPublication . Correia, João CarlosO objectivo deste trabalho é, com recurso a uma perspectiva interdisciplinar, indagar sobre a natureza da relação entre a indústria jornalística e os seus públicos no contexto de uma sociedade de massa. Procura-se, assim, definir o lugar que, no âmbito dessa indústria, cabe à interacção, conceito que recentemente tem sido objecto de equívocos graças à crescente mediatização tecnológica da experiência simbólica. Pretende-se ainda interpelar uma forma específica de comunicação - a imprensa regional - a fim de indagar se as suas especificidades concretas são de molde a favorecerem uma maior interacção no seio da esfera pública.
- Influence of Traffic from Mobility on the Microcellular Coverage Distance in Mobile Broadband SystemsPublication . Velez, Fernando J.; Correia, Luis M.Models allowing the study of the influence of coverage distance and velocity on the supported traffic and on the new calls traffic linear density are examined, and results are obtained for typical scenarios in a Mobile Broadband System (MBS) with a linear coverage geometry. For situations without using guard channels for handover, for a fixed bounding value for the blocking probability, the new calls traffic linear density has been analyzed, increasing with the decrease of the coverage distance R, and being upper limited by a value which depends on the characteristics of the mobility scenario. However, call-dropping probability requirements also need to be fulfilled, leading to a new calls traffic linear density that only increases with the decrease of R down to an optimum value of R, and being lower for scenarios with higher mobility. This situation leads to limitations in system capacity for lower values of the coverage distance, mainly for high mobility scenarios.
- Microcellular Design and System capacity determination for Outdoors Urban Mobile Broadband Communication Systems in the Millimetrewave BandsPublication . Velez, Fernando José; Brazio, José M.This paper addresses lhe cellular design of mobile microcellular communications systems operating in lhe millimetrewave bands in outdoor urban environments. ln such systems and environments lhe shape of cells and lhe interference among them are highly dependent on lhe geomctry of lhe surrounding obstacles (c.g., buildings) and lhe classical regular geametry based approaches to frequency reuse and capacity evaluation eannat be used. In lhe paper is described an approach to frequency reuse and system capacity evaluation where canclusions are drawn frem cellular layouts obtained, via an interactive computer graphical tool, for specific urban environments. Numerical examples are presented for coverage in lhe 40 and 60 GHz bands showing that, depending on lhe celI size, reuse factors in lhe range 5-11 are achievable. It is also concluded that, in interference límited scenarios, if cells with similar coverage length are used, equal values are obtained for lhe reuse factor and system eapacity in both bands.
- Capacity trade-offs in mobile broadband systems using guard channels for high mobility handoverPublication . Velez, Fernando J.; Correia, Luis M.Models allowing the study of the influence of coverage distance and mobile velocity on the supported traffic and on the new calls traffic linear density are examined, and results are obtained for typical scenarios in a mobile broadband system (MBS) with a linear coverage geometry. In order to cope with handover failure probability requirements, the use of guard channels for handover is assumed, mainly for high mobility scenarios. For these scenarios one concludes that there is a degradation in system capacity because, for the typical coverage distances foreseen for MBS, the new calls traffic linear density is one order of magnitude bellow the values obtained for the pedestrian scenario (where it is approximately 15 Erlang/km), decreasing from 2.47 Erlang/km, in the urban scenario, down to 0.84 Erlang/km, in the highway scenario, when two guard channels are used.
- Modelos de Tráfego de Mobilidade em Sistemas de Comunicações Móveis MicrocelularesPublication . Velez, Fernando J.; Correia, Luis M.Approximate models for traffic resulting from mobility are presented and their validity is examined for a system without guard channels for handover. The system can be modelled by a Markov chain whose exact solution for the steady-state probabilities is obtained by solving a system of equations with a dimension that considerably increases with the number of cells and the number of channels, which strongly limits its use. However, the blocking probability for both new and handover calls is assessed via this Markov chain, which can be approximated by a model that allows the use of the theory from Jackson networks. Some examples are given where the blocking and handover failure probabilities are computed; their approximation error being negligible in a wide range of coverage distances foreseen for MBS (Mobile Broadband System), environments, mainly for the blocking probability. Although it is usual to consider the handover traffic as Poisson distributed, one can show that for homogeneous traffic in the whole coverage area this is not strictly necessary. The independence among the number of calls being served in each cell is also presented as a conclusion in the range of validity of the approximation.
- Cultura clássica e cristianismo nascente. Continuidade ou ruptura?Publication . Rosa, José Maria SilvaO clássico esta na moda. Todos nós ouvimos dizer, a propósito e a despropósito, que isto ou aquilo é clássico, que tal ou tal filme se tornou um clássico; em certos meios, inclusive, fica bem dizer-se que se «está a reler os clássicos» ... Numa palavra: o cIássico é actual, sem ser claro o sentido que cada um atribui a tal afirmação. Todavia, este casamento entre o clássico - algo perene - e a moda - império do efémero - só aparentemente é paradoxal. Com efeito, tal como a moda é uma forma de classificar mercadorias, produtos, ideias, pessoas, etc., também os períodos clássicos trazem consigo movimentos niveladores, modais, massivos. Talvez possamos, então, inverter a ordem: ao invés de dizermos que o clássico é actual, digamos que a época actual se tornou equivocamente clássica.