O ensino das ciências e a promoção da literacia científica na educação básica : representações e conhecimento profissional dos professores de ciências

Tese de doutoramento, Educação (Didática das Ciências), Universidade de Lisboa, Instituto de Educação, 2015O estudo emerge na intersecção de três contextos: (a) reconhecimento que a literacia científica é vital para o indivíduo e para a sociedade; (b) os dados do desempenho em literacia científica e do interesse dos alunos portugueses pela ciência em estudos internacionais são preocupantes; (c) o professor é um elemento chave para reverter esta situação. A investigação tem como principais objetivos: (a) identificar, descrever e compreender as representações de literacia científica dos professores e a sua coerência com as conceções presentes na literatura e nos documentos curriculares; (b) compreender a sinergia entre as representações de literacia científica e o conhecimento profissional dos professores; (c) averiguar a existência de padrões nas representações de literacia científica dos professores; e (d) compreender os fatores que influenciam a emergência dessas representações e o desenvolvimento do conhecimento pedagógico do conteúdo. A natureza do problema remeteu para uma abordagem empírica de estudo de caso, estruturado em duas fases consecutivas. Uma primeira foi primordialmente extensiva e quantitativa, tendo os dados sido recolhidos por questionário. Numa segunda foi aprofundado numa matriz qualitativa, recorrendo a uma entrevista a professores. As conceções de literacia científica difundidas pelos documentos curriculares oficiais foram também analisadas. Foi conceptualizado um quadro bidimensional (Natureza e Operacionalização do Ensino das Ciências) para analisar as representações de literacia científica dos professores. Constata-se que a distribuição dos professores por estas representações não é homogénea e que existe inconsistência entre as conceções de literacia científica difundidas pelos documentos curriculares e as representações dos professores Os resultados apontam também para que o conhecimento pedagógico do conteúdo dos professores acomoda as suas representações de literacia científica mas moldado sobretudo pelos constrangimentos associados à sua operacionalização. Tecem-se conclusões e ensaiam-se recomendações para o ensino das ciências, a formação de professores e a investigação em ensino das ciências e em formação de professores.The study emerges from the intersection of three contexts: (a) recognition that scientific literacy is vital for both the individual and society; (b) international studies show concern regarding performance data in scientific literacy and the interest of Portuguese students in science ; (c) the teacher is a key element to reverse this situation. The main objectives of the study are: (a) to identify, to describe and to understand the teachers scientific literacy representations and their consistency with the conceptions found in the literature and curriculum documents; (b) to understand the synergy between the representations of scientific literacy and professional knowledge of teachers; (c) to explore the existence of patterns in teachers scientific literacy representations; and (d) to understand the factors that influence the emergence of these representations and the development of pedagogical content knowledge. The nature of the problem has led to a case study as an empirical approach, structured in two consecutive phases. The first was primarily extensive and quantitative and data were collected by questionnaire. During the second phase, a qualitative matrix deepened the study, using a teachers’ interview. The scientific literacy conceptions spread by the official curriculum documents were also analyzed. A two-dimensional framework (Nature and Operationalization of science education) was conceptualized to analyze teachers’ scientific literacy representations. It was found that teachers’ distribution these representations is not homogeneous and that there is inconsistency between the scientific literacy conceptions spread by the curriculum documents and the teachers representations. The results also suggest that the pedagogical content knowledge of teachers accommodates their representations of scientific literacy but are mainly shaped by the constraints associated with its operationalization. Conclusions and recommendations for teacher practices, for science teachers training and for science teaching and teacher training research were drawn.Fundação para a Ciência e a Tecnologia (FCT

Outage probability due to intercore crosstalk from multiple cores in short-reach networks

The outage probability (OP) due to intercore crosstalk (ICXT) arising from multiple interfering cores in short-reach binary intensity modulation-direct detection optical links supported by homogeneous weakly-coupled multicore fibers is assessed through numerical simulation. The maximum acceptable ICXT level for a given OP is extracted from simulation results, for low and high skew-bit rate products (SBRPs). (i) For high SBRP, a 3 dB reduction of the maximum acceptable ICXT level per core for a given OP is observed when the number of interfering cores doubles. In this case, as a very large number ( ≫1 ) of bits of each interfering core is contributing to ICXT, the total detected ICXT tends to a Gaussian distribution that makes the maximum acceptable total ICXT level independent of the interfering core count. (ii) For low SBRP, the number of bits contributing to ICXT is similar to the interfering core count and the total detected ICXT assumes a set of discrete amplitudes, which deviates it from the Gaussian distribution. Hence, the reduction of the maximum acceptable ICXT level per core, when the number of interfering cores is doubled, is about 2 dB, and the maximum acceptable total ICXT level increases with the interfering core count, by around 3 dB, when the interfering core count increases from 1 to 8.info:eu-repo/semantics/acceptedVersio

Impact of physical layer impairments on C+L-band metro networks

To ensure future data traffic capacities, multi-band transmission in optical networks is being proposed, by adding wavelength division multiplexing channels in the L-band to the existing C-band channels. In this work, we study the filterless drop and waste amplified and unamplified solutions used in metro networks with L-band tributary nodes. The cost and power consumption of these nodes is evaluated, as well as the impact of several physical layer impairments on the network performance. In amplified solutions, we show that L-band networks with 9 tributary nodes are feasible, being the optical signal-to-noise ratio achieved when considering amplifiers noise and fiber non-linear interference above 14 dB. In unamplified solutions, to fullfil the power budget, frequency reuse should be used between spans. We show that the in-band crosstalk caused by this frequency reuse leads to 1.5 dB power budget degradation, for a crosstalk level of -20 dB.info:eu-repo/semantics/acceptedVersio

DD-OOK multicore fiber systems impaired by intercore crosstalk and laser phase noise

Direct-detection on-off keying (DD-OOK) weakly-coupled multicore fiber (WC-MCF) systems impaired by intercore crosstalk (ICXT) and laser phase noise are investigated numerically and experimentally. This is performed for systems with a product between the bit rate and the absolute value of the skew between cores much larger than one. It is shown that the phase noise increases the instantaneous ICXT power fluctuations. The standard deviation of the short-term average ICXT (STAXT) power induced by the phase noise depends on the product between the laser linewidth and the absolute value of the skew between cores (linewidth ×| skew|). When linewidth ×| skew|\gg1, typical of distributed feedback (DFB) lasers (linewidth in the few MHz range) and MCFs with skew in the \mus range, the decrease of the standard deviation of the STAXT power induced by the phase noise is 5 dB per decade of linewidth ×| skew| increase. For linewidth ×| skew|\ll1, typical of external cavity lasers (ECLs) and DFB lasers, and MCFs with skew of a few ns, the standard deviation of the STAXT power remains almost unaffected by the phase noise. Experimental results show that, compared with low linewidth ECLs, 10 Gb/s DD-OOK WC-MCF systems using DFB lasers as optical sources in the interfering cores and skew in the range between 2.4 ns and 5.4 ns, may require an additional ICXT margin up to 8 dB for a given outage probability. The additional ICXT margin and the lower amplitude of the STAXT power fluctuations observed experimentally for DFB lasers suggest that the level of the fluctuations of the STAXT power may be an inadequate system performance indicator. The dependence of the outage probability on the interfering core count is also investigated experimentally. It is shown that, for systems with bit rate ×| skew|\gg1, the outage probability only depends on the total ICXT power and not on the interfering core count.info:eu-repo/semantics/acceptedVersio

Inland or Coastal: That s the Question! Different Impacts of COVID-19 on the Tourism Sector in Portugal

The COVID-19 pandemic had severe implications in different economic sectors, among them tourism, with countries where tourism has a relevant economic role, such as Portugal, being greatly affected. However, the impact was different in the various regions of the country, which could be related to some tourism units, being more isolated or with fewer rooms, being seen as more attractive and safer. Based on data from Portuguese firms, and distinguishing their location between coastal and inland, it is possible to conclude that inland tourism units were less affected than coastal ones, which could be related to tourists seeking less densely populated areas, a relevant conclusion for the different agents.N/

Weakly-coupled MCF direct-detection OOK systems impaired by laser phase noise

On-off-keying multicore fiber systems employing different lasers are experimentally investigated. Laser phase noise increases the instantaneous fluctuations of the crosstalk. DFB-based systems may require an additional crosstalk margin of 4 dB relative to ECL-based systems.info:eu-repo/semantics/acceptedVersio

Assessment of the combined effect of laser phase noise and intercore crosstalk on the outage probability of DD OOK Systems

We study the influence of the combined effect of laser phase noise and intercore crosstalk on the outage probability of direct-detection 10 Gbit/s on-off keying optical communication systems. We show that the laser phase noise can affect significantly the outage probability, for lasers with linewidths in the MHz range, for low and high skew-bit rate products. We also show that the laser phase noise effect on the received eye-pattern is qualitatively similar to the one found for high skew-bit rate product in the absence of laser phase noise.info:eu-repo/semantics/acceptedVersio

Characterization of crosstalk-impaired OOK signals in WC-MCF systems with high and low skew×bit rate

The received amplitudes of crosstalk-impaired on-off keying signals in weakly-coupled multicore fibre (WC-MCF) systems are experimentally assessed for high and low skew×bit-rate. Gaussian-distributed crosstalk-induced amplitudes are shown for high skew×bit-rate. The mean of these amplitudes can also be modelled by Gaussian distributions.info:eu-repo/semantics/acceptedVersio

5G fronthauls with multicore fibers: CPRI signals performance degradation induced by intercore crosstalk

Weakly-coupled multicore fibers (MCFs) have been proposed to support the huge data capacity demanded by future 5G fronthauls. However, in MCFs, intercore crosstalk (ICXT), i.e., power coupling between different MCF cores, can degrade significantly the performance of the 5G fronthaul, particularly, when using Common Public Radio Interface (CPRI) signals and direct-detection at the optical receiver. In this work, the performance degradation induced by ICXT in 5G fronthauls with MCFs and direct-detection is assessed by numerical simulation. We show that the study of the outage probability is essential to ensure the reliability and the good quality of service in 5G fronthauls supported by MCFs impaired by ICXT with CPRI signals transmission. The ICXT level that leads to an outage probability of 10-4 is more than 5.6 dB lower than the ICXT level necessary to reach the power penalty of 1 dB. Our results also indicate that fronthaul systems with lower extinction ratio exhibit an higher tolerance to ICXTinfo:eu-repo/semantics/acceptedVersio

Avaliação da influência da poda no desempenho da máquina de colheita em pomares superintensivos de amendoeira

O sucesso da tecnologia de colheita dos olivais superintensivos terá contribuído para a implantação de pomares superintensivos de amendoeira.Nestes pomares é necessário garantir que a dimensão da copa se adeque às dimensões da máquina de colheita para minimizar as perdas de amêndoa e os danos nas árvores.Para aumentar o conhecimento sobre esta tecnologia, estabeleceu-se num pomar comercial, um ensaio para avaliar o efeito da poda na produção de amêndoa e no desempenho da máquina de colheita.O pomar foi plantado em setembro de 2014, na Herdade da Torre das Figueiras – Monforte - Portalegre - Portugal (39º 04’ N; 07º 29’ W), com a orientação Este-Oeste, entrelinha de 5 m e 1,5 m de afastamento entre as árvores na linha.Definiram-se os seguintes tratamentos: T0 – poda de verão: corte horizontal da copa e corte lateral em cada uma das faces, em 2015 e 2017. Em 2015, os cortes laterais foram executados em julho e os cortes horizontais em julho e em setembro. Em setembro de 2017, após a colheita, realizou-se corte lateral em cada uma das faces da copa e corte horizontal da copa. Poda de inverno: em 2016, poda manual para eliminar ramos vigorosos; em 2017, corte horizontal da copa seguido de poda manual para melhorar a exposição solar no interior da sebe; T1 – sem intervenções de poda em 2015, 2016 e 2017; T2 – poda de verão: corte lateral em cada uma das faces da copa, realizado em julho de 2015; corte lateral em cada uma das faces da copa e corte horizontal em setembro de 2017, após a colheita; T3 – poda de verão: corte horizontal da copa e corte lateral em cada uma das faces, em 2015 e 2017. Em 2015, os cortes laterais foram executados em julho e os cortes horizontais em julho e em setembro. Em setembro de 2017, após a colheita, efectuou-se corte lateral em cada uma das faces da copa e corte horizontal da copa.Em 2018, em todos os tratamentos, procedeu-se a uma poda manual de inverno para eliminar ramos vigorosos excessivamente desenvolvidos para a entrelinha.Em 2017, selecionaram-se aleatoriamente 3 blocos de 10 árvores em cada linha para monitorizar a altura da árvore e a largura da copa na perpendicular à linha. Em 2017 e 2018 procedeu-se à colheita de cada linha, registando a massa de amêndoa colhida e o tempo de trabalho, tendo-se avaliado por amostragem as perdas de amêndoa para o solo.Verificaram-se diferenças na produção de amêndoa entre os anos, bem como diferenças significativas entre os tratamentos em 2018. Houve uma diminuição de perdas de amêndoa para o solo de 2017 para 2018. Em 2018 o tratamento 1 registou uma percentagem de perdas significativamente superior aos outros tratamentos