Renewable forsterite production by a solar furnace

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Éxito académico, compromiso y autoeficacia de los estudiantes universitarios de primer año: variables personales y desempeño del primer semestre

Higher education can be hugely transformative for students and has an important role in empowering human capital, innovation, and society’s social, cultural, and environmental development. The expansion of higher education has promoted access for a more heterogeneous mix of students, but ensuring access does not guarantee academic success. This paper aims to analyse predictors of academic achievement in 447 first-year students in their 1stand 2ndsemesters, considering variables including sex, age, parents’ educational level and grades on entering higher education, along with levels of students’ academic engagement and self-efficacy after some weeks at university. Results show statistically significant paths for sex, age, and GPA to 1st-semester achievement, for parent’s educational levels to perceived self-efficacy, for students’ academic engagement to 1st-semester achievement, and 1st-semester achievement to 2nd-semester achievement. Students’ academic engagement also had an indirect effect on the 2nd-semester achievement. The correlation between academic engagement and self-efficacy was positive, strong, and statistically significant. The model explained 35.2% of the variance in 2nd-semester achievement and 15.0% of the variance in 1st-semester achievement. Knowledge about predictors of academic achievement and the importance of engagement and self-efficacy will support timely interventions, promoting success and preventing failure and dropout.La educación superior puede ser extremadamente transformadora para los estudiantes y tiene un papel importante en la formación del capital humano, en la innovación y en el desarrollo social, cultural y ambiental de la sociedad. La expansión de la educación superior promovió el acceso de una mezcla de estudiantes más heterogénea, pero garantizar el acceso no garantiza el éxito académico. Este artículo tiene como objetivo analizar los predictores de desempeño académico en 447 estudiantes de primer año en el 1er y 2do semestre, considerando variables como sexo, edad, nivel educativo de los padres y calificaciones al ingresar a la educación superior, junto con los niveles de compromiso académico e autoeficacia de los estudiantes tras algunas semanas en la universidad. Los resultados muestran trayectorias estadísticamente significativas para sexo, edad y GPA hasta el desempeño del primer semestre, para los niveles educativos de los padres hasta la autoeficacia percibida, para la implicación académica de los estudiantes hasta el desempeño del primer semestre y el desempeño del primer semestre hasta el desempeño del segundo semestre La participación académica de los estudiantes también tuvo un efecto indirecto en el desempeño del segundo semestre. La correlación entre compromiso académica y autoeficacia fue positiva, fuerte y estadísticamente significativa. El modelo explicó el 35.2% de la varianza del rendimiento académico en el segundo semestre y el 15.0% de la varianza del rendimiento académico en el primer semestre. El conocimiento sobre los predictores del rendimiento académico y la importancia del compromiso y la autoeficacia respaldará las intervenciones oportunas, promoviendo el éxito y previniendo el fracaso y el abandono

Enquadramento energético do sector residencial português

Portugal não possui reservas de energias fósseis, pelo que importa grande parte dos recursos energéticos que consome. Nos últimos anos tem sido feita uma aposta na instalação de sistemas de produção de energia a partir de energias renováveis no sentido de reduzir a dependência energética nacional. Contudo, os níveis de dependência, em 2010, ainda eram muito elevados principalmente devido à importação de petróleo. O sector residencial é o que apresenta o terceiro maior consumo energético. Tendo-se verificado nos últimos anos um aumento crescente dos consumos, em especial de eletricidade. Através da avaliação da tendência de evolução do consumo energético das habitações, é possível determinar qual a melhor forma de reduzir esses consumos aquando da reabilitação energética dos edifícios. O estudo apresentado tem por objetivo analisar os consumos energéticos do sector residencial, de forma a saber em que fatores intervir para aumentar a eficiência energética do parque habitacional Português

Energy rehabilitation of Portuguese residential building stock through its transformation into NZEB

The first global oil crisis, led the European Union to start the necessary procedures in order to control and reduce the energy consumption of buildings. In Europe the energy consumption of residential buildings increased since 1990 until 2003 1.3% per year and it is expected that, by 2050, the energy consumption of buildings will have increased by 40%. According to the EPBD-recast all member states should adopt the necessary measures so that buildings become highly efficient - nearly Zero Energy Buildings (nZEB’s). Nevertheless, quantitative standards are not appointed, so each member state should establish the minimum requirements for energy performance in buildings attending to the local conditions. However before establishing these requirements it is necessary to evaluate the building stock and its energy efficiency. As most of the Portuguese residential buildings are old and degraded an opportunity arises for the energy rehabilitation of the building stock, implementing EPBD-recast principles, making it more energy efficient and comfortable. The aim of this study was to describe the current conditions of the building stock in order to identify whether there are suitable conditions for energy rehabilitation of buildings. The analysis performed showed that although there are a significant potential for building energy rehabilitation, there are also some constraints, namely the lack of credit and loans financing of banks

Durability of etics incorporating high reflectance pigments in finishing coatings

The increase of the durability of building materials and components presents great importance since it contributes to a more sustainable environment by increasing its service life. The development of new building materials and technologies with improved thermal characteristics, such as ETICS with high reflectance coatings, contributes to meet the thermal requirements defined by the European regulation. However, the importance of the durability assessment of new solutions cannot be understated as it plays a key role in the prevention of future early degradation. This paper has the objective of assessing the durability of ETICS incorporating high reflectance pigments in organic coatings. The solar reflectance can be increased through optimized material formulations with the inclusion of nanoparticles in coatings. If the near-infrared (NIR) solar absorption is reduced, the referred benefits can be achieved even in darker colours. One of the main concerns is the durability of the entire system, but the stability of the darker colours must also be taken into account. As such, relevant parameters solar absorptance, surface temperature and colour were measured in a long-term in-situ experimental campaign, in ETICS specimens with distinct coatings. The effect of the thermal insulation layer, in the referred parameters, was also evaluated, by measuring the effect of the same coatings in samples with traditional substrates. The solar absorptance was measured with a pyranometer with an adapted methodology based on the ASTM E1918 standard. The surface temperature of the samples was continuously monitored for an extended period enabling a comparison of the benefits under different climatic conditions. The colour was determined by the CIELAB colour space, by measuring the L*A*B parameters. The results showed that the incorporation of high reflectance pigments leads to a decrease in the solar absorptance and surface temperature even in darker colours. The pigments also influenced the lightness of the coating, by increasing the L parameter. The potential benefits of these thermal enhanced systems combine an enhanced thermal performance, durability and a higher diversity of aesthetic features

Side-pumped continuous-wave Nd:YAG solar laser with 5.4% slope efficiency

The fellowship grants PD/BD/128267/2016, PD/BD/142827/2018, SFRH/BPD/125116/2016 of B.D.The authors report here a significant progress in side-pumped solar laser slope efficiency by pumping a 3.0 mm diameter, 30 mm length Nd:YAG single-crystal laser rod through a heliostat-parabolic mirror solar energy collection and concentration system with 0.9 m2 effective collection area. A large fused silica aspheric lens allowed an efficient focusing of the concentrated solar power from the focal zone of the parabolic mirror into the laser rod mounted within a novel two-dimensional semi-cylindrical pump cavity. 15.3 W continuous-wave 1064 nm solar laser power was measured, resulting in 5.40% slope efficiency and 2.43% solar-to-laser conversion efficency, being 2.08 and 2.30 times, respectively, more than the previous records by side-pumping configuration. The 5.40% slope efficiency is also 1.08 times more than the previous record with Nd:YAG single-crystal rod by end-side-pumping approach. By adopting an asymmetric laser resonator, this novel side-pumping scheme also enabled an efficient production of high-quality solar laser beams in either TEM11 (4.0 W), TEM01 * (doughnut-shaped, 2.9 W), TEM10 (3.2 W) or TEM00 (2.8 W) mode profiles.authorsversionpublishe

Simultaneous solar laser emissions from three Nd:YAG rods within a single pump cavity

FCT-MCTES grants SFRH/BPD/125116/2016, PD/BD/142827/2018, PD/BD/128267/2016 of C. R.Vistas, D. Garcia, B. D. Tiburcio, respectively, and FCT-MCTES Junior Researcher Contract CEECIND/03081/2017 of J. Almeida are acknowledged.We report here, to the best of our knowledge, the first simultaneous emission of three continuous-wave solar laser beams by end-side-pumping three 3.0 mm diameter, 25 mm length Nd:YAG single-crystal rods within a single conical pump cavity. An aspheric fused silica lens was used to couple the concentrated solar radiation from the focal zone of a parabolic mirror with 1.0 m2 effective collection area into the laser rods within the pump cavity. 18.3 W multimode solar laser power was measured, resulting in 5.1% laser slope efficiency. 0.036 W laser beam brightness figure of merit was also achieved for each beam, being 9 times more than that of the most efficient solar laser with 32.5 W/m2 collection efficiency. Since the three laser rods were associated with their own 1064 nm output mirrors, it was possible to adjust individually both solar laser output power levels and beam qualities of the three laser beams by adopting different resonant cavity lengths, enabling potential solar laser applications.authorsversionpublishe

Impact of Incorporating NIR Reflective Pigments in Finishing Coatings of ETICS

Near-infrared (NIR) reflective materials are being developed for mitigating building cooling needs. Their use contributes to broadening the range of colours, responding to the urban aesthetic demand without compromising the building performance. Despite the increase in NIR reflective pigments investigation, there is still a knowledge gap in their applicability, impact, and durability in multilayer finishing coatings of External Thermal Insulation Composite Systems (ETICS). Hence, the main goal of this work consists of evaluating the impact of incorporating NIR reflective pigments (NRP) in the solar reflectance of the surface layer of ETICS, without affecting the colour perception, as well as their influence on the colour durability and surface temperature. As such, colour, solar reflectance, and surface temperature were monitored for 2 years in dark-coloured specimens of ETICS, with and without NRP and a primer layer. It was confirmed that the main contribution of NRP is the increase of solar reflectance and, consequently, the decrease in surface temperature, especially for high exterior temperatures (around 30 degrees C). Moreover, these pigments highly increase the NIR reflectance without affecting the visible colour. In addition, they contribute to maintaining the colour characteristics. The application of primer increased the surface temperature, especially for higher exterior temperatures. However, it contributes to a lower colour difference and solar reflectance variation, which is an important achievement for durability purposes

Dynamics of Microbial Communities in Phototrophic Polyhydroxyalkanoate Accumulating Cultures

DFA/BD/8201/2020 UIDP/04378/2020 UIDB/04378/2020 LA/P/0140/2020Phototrophic mixed cultures (PMC) are versatile systems which can be applied for waste streams, valorisation and production of added-value compounds, such as polyhydroxyalkanoates (PHA). This work evaluates the influence of different operational conditions on the bacterial communities reported in PMC systems with PHA production capabilities. Eleven PMCs, fed either with acetate or fermented wastewater, and selected under either feast and famine (FF) or permanent feast (PF) regimes, were evaluated. Overall, results identified Chromatiaceae members as the main phototrophic PHA producers, along with Rhodopseudomonas, Rhodobacter and Rhizobium. The findings show that Chromatiaceae were favoured under operating conditions with high carbon concentrations, and particularly under the PF regime. In FF systems fed with fermented wastewater, the results indicate that increasing the organic loading rate enriches for Rhodopseudomonas, Rhizobium and Hyphomicrobiaceae, which together with Rhodobacter and Chromatiaceae, were likely responsible for PHA storage. In addition, high-sugar feedstock impairs PHA production under PF conditions (fermentative bacteria dominance), which does not occur under FF. This characterization of the communities responsible for PHA accumulation helps to define improved operational strategies for PHA production with PMC.publishersversionpublishe

Colour degradation of facade coatings - the effect of nanopigments incorporation

The increasing interest in the use of a wide range of colours in buildings, especially dark colours, may lead to the early degradation of the facades, compromising their aesthetic and thermal performance. On the other hand, the incorporation of nanopigments with high reflectance properties can contribute to reducing the absorption of solar radiation. The nanoparticles contribute to increasing the solar reflectance of coatings, decreasing the surface temperature and improving the coating performance. This work evaluates the natural degradation of the colour of finishing coat with nanopigments in ETICS. The colour parameters were evaluated in different ETICS specimens, considering the colour black and red with and without incorporated nanopigments, under natural ageing. The colour measurement was performed according to ISO 1164-4, using a portable spectrophotometer. The results confirmed that the use of nanopigments improved the colour durability, promoting the maintenance of the colours parameters. The total colour difference was lower than the perceptible by the human eyes, even as the lower variation on chroma and hue parameters of the colours with nanopigments. In summary, the incorporation of nanoparticles in finishing coat of ETICS can contribute to increasing their durability and improve their thermal performance without compromising the aesthetic characteristics