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  1. 1

    Over 100 mV VOC improvement for rear passivated ACIGS ultra‐thin solar cells

    Publicação
    por Oliveira, Antonio
    Outros Autores: Rocha Curado, Marco; Teixeira, J. P.; Tomé, Daniela; Çaha, Ihsan; Oliveira, Kevin et al.
    A decentralized energy system requires photovoltaic solutions to meet new aesthetic paradigms, such as lightness, flexibility, and new form factors. Notwithstanding, the materials shortage in the Green Transition is a concern gaining momentum due to their foreseen continuous demand. A fruitful strategy to shrink the absorber thickness, meeting aesthetic and shortage materials consumption targets, arises from interface passivation. However, a deep understanding of passivated systems is required to close the efficiency gap between ultra-thin and thin film devices, and to mono-Si. Herein, a (Ag,Cu)(In,Ga)Se2 ultra-thin solar cell, with 92% passivated rear interface area, is compared with a conventional nonpassivated counterpart. A thin MoSe2 layer, for a quasi-ohmic contact, is present in the two architectures at the contacts, despite the passivated device narrow line scheme. The devices present striking differences in charge carrier dynamics. Electrical and optoelectronic analysis combined with SCAPS modelling suggest a lower recombination rate for the passivated device, through a reduction on the rear surface recombination velocity and overall defects, comparing with the reference solar cell. The new architecture allows for a 2% efficiency improvement on a 640 nm ultra-thin device, from 11% to 13%, stemming from an open circuit voltage increase of 108 mV.
    2023 artigo Portugal acesso restrito
  2. 2

    Multidefect detection tool for large-scale PV plants: Segmentation and classification

    Publicação
    por Rocha, Daniel
    Outros Autores: Alves, Joao; Lopes, Vitor; Teixeira, Jennifer P.; Fernandes, Paulo A.; Costa, Mauro et al.
    Unmanned aerial vehicles (UAVs) with highresolution optical and infrared (IR) imaging have been introduced in recent years to perform inexpensive and fast inspections in operation and maintenance activities of solar power plants, reducing the labor needed, while lowering the on-site inspection time. Even though UAVs can acquire images extremely quickly, the analysis of those images is still a time-consuming procedure that should be performed by a trained professional. Therefore, a computer vision approach may be used to accelerate image analysis. In this work, a dataset of IR images was created from a 10-MW solar power plant and a comparative analysis between mask R- convolutional neural network (CNN) and U-Net was performed for two experiments. Concerning the defective module segmentation, the mask R-CNN algorithm achieved a mean average precision at intersection over union (IoU) = 0.50 of 0.96, using augmentation data. Regarding the segmentation and classification of failure type, the algorithm reached a value of 0.88 considering the same evaluation metric and data augmentation.When compared to the U-Net in terms of IoU, the mask R-CNN outperformed it with 0.87 and 0.83 for the first and second experiments, respectively.
    2023 artigo Portugal acesso restrito
  3. 3

    Irradiance level and elevation shape the soil microbiome communities of Coffea arabica L.

    Publicação
    por Tapaça, Inocência da Piedade E.
    Outros Autores: Obieze, Chinedu C.; Pereira, Gilberto V.de Melo; Fangueiro, David; Coutinho, João; Fraga, Irene et al.
    Background: The nexus plant-microbe-environment is essential to understand the ecosystem processes shaping plant health and fitness. Within this triangle, soils and associated microflora are among the key ecosystem’s drivers, underpinning plant productivity and evolution. In this study, we conducted a comprehensive analysis (physicochemical properties, enzyme activities, and taxonomic diversity) of soils under the canopy projection of Coffea arabica trees along a gradient of elevation (600, 800, and 900 m) and shade (0, 50, 100%). Results: While shade had no influence on most parameters, altitude shaped the dynamics of microbial communities. Available phosphorus, soil organic carbon, and nitrate were significantly higher at 800 m, likely due to the higher activities of β-glucosidase and phosphatases at this altitude. Microbial biomass (carbon and nitrogen) and moisture were significantly higher at 600 and 900 m, which might be attributed to the abundance and richness of soil microorganisms. Indeed, metabarcoding analysis revealed a complex pattern of microbial consortia (bacteria, archaea, fungi) at the three altitudes, with the lowest index of richness recorded at 800 m. The highest number of Amplicon Sequence Variants was observed in bacteria, whose functional analysis revealed distinct metabolic adaptations across different altitudes. At 900 m, the main functional attributes favored the responses to environmental stimuli and microbial interactions; at 800 m, the predominant metabolic pathways were related to organic matter, fermentation, and bioremediation; and at the lower 600 m, the pathways shifted towards the breakdown of plant-derived compounds (e.g. geraniol, limonene, and pinene degradation). Conclusion: Overall, the results indicate a higher effectiveness of the microbial consortium at 800 m, which might result in better nutrient cycling. The study highlights the importance of canopy shade species and elevation for the composition of microbial consortia in C. arabica, unveiling ecological functions beyond plant health, with implications for bio-based solutions and biotechnology.
    2024 artigo Portugal acesso aberto
  4. 4

    Study of the Materials and Techniques of a Rare Papier-Mâché Mushroom Model Crafted in H. Arnoldi Factory

    Publicação
    por Melo, Maria J.
    Outros Autores: Freitas, Ana; Vieira, Cristiana; Vilarigues, Márcia; Vieira, Márcia; Nabais, Paula et al.
    The Natural History and Science Museum of the University of Porto houses a collection of 45 models of fungi in papier-mâché from the 19th-century, which were used at the university until 2015 as didactic models. For the first time, the materials and techniques used in the production of a Boletus edulis model were studied (vernacular name: cep, porcini). These sculptures, made to life-size scale, are painted in colors similar to those of the represented species (white, brown, and light brown). They are fixed to a rectangular base, which is painted black, and to which moss has been pasted. To fully characterize each color, at the molecular level, a multi-analytical approach was used, combining energy-dispersive x-ray fluorescence spectroscopy (micro-XRF) with fingerprinting techniques of Raman microscopy (microRaman and handheld Raman) spectroscopy and microFourier transform infrared spectroscopy (microFTIR). The papier-mâché was prepared with a groundwood paper to which kaolin and a quartz-based material have been added to reinforce the structure. Raman microscopy also identified carbon black in it, which is possibly responsible for its grey color. The white color was unequivocally identified as lithopone by microRaman. This white paint was prepared in a proteinaceous tempera, with calcium carbonate having been identified as filler (by microFTIR). In the brown color, iron was identified by microXRF, pointing to the use of ocher, which was not possible to identify by microRaman and microFTIR. Regarding the black rectangular base, the moss was fixed using a collagen-based glue. The binding medium in this black is possibly a mixture of drying oil and protein. Again, XRF detected iron as the main element, but it was not possible to acquire a Raman spectrum due to the high fluorescence of the binder/varnish. Others, such as the writing inks, will also be discussed. The colors identified are in line with the best materials available for use by artists of that time. This new knowledge is fundamental to informing the choice of the best conservation strategies for the preservation of these extraordinary models.
    2023 artigo Portugal acesso aberto
  5. 5

    Minho, Douro e Trás-os-Montes

    Publicação
    por Carvalho, Ana Cristina
    Outros Autores: Alves, Isabel Maria Fernandes; Luz, Ana Luísa
    A ocidente, o oceano, que dá ao Minho o horizonte “fechado pelas montanhas mais chuvosas da Europa” e bastos rios animando “veigas altamente produtivas”. De leste, a influência continental que endurece o clima, aliado à rocha e à avareza dos solos na criação da fácies transmontana. Território Norte, geográfico e poético, unido a sul pelo fio do Douro, entre as escarpas da fronteira e a calmaria da foz. Dos Cancioneiros Populares aos títulos do século XXI, poucas formas primitivas da natureza e da construção antrópica da paisagem ficaram à margem da sensibilidade dos escritores e das páginas da Literatura Portuguesa. Que valor tem a nossa literatura de ficção enquanto celeiro imaterial da memória de Minho, Douro e Trás-os-Montes? Que imagens desse património nos legaram os escritores nos seus romances, contos e novelas? Podem as suas páginas acender a consciência ecológica, geográfica e climática nos leitores de hoje? As investigadoras Ana Cristina Carvalho (Universidade Nova de Lisboa), Isabel Fernandes Alves (Universidade de Trás-os-Montes e Alto Douro) e Ana Luísa Luz (Universidade Nova de Lisboa) reuniram em torno destas questões 15 investigadores, numa cooperação consagrada à região norte de Portugal, firmada na análise de 35 obras de ficção de 17 escritores da Literatura Portuguesa .
    2024 livro Portugal acesso aberto
  6. 6

    Vamos falar sobre ética na investigação com crianças e jovens?

    Publicação
    por Castro, Teresa Sofia Pereira Dias de
    Outros Autores: Carvalho, Maria João Leote; Brites, Maria José
    2024 livro Portugal acesso aberto
  7. 7

    Exceptional Illuminated Manuscripts at the Gulbenkian Museum

    Publicação
    por Grigoryan, Hermine
    Outros Autores: Vieira, Márcia; Nabais, Paula; Araújo, Rita; Melo, Maria J.; Manso, Marta et al.
    The illuminated manuscripts at the Gulbenkian Museum were produced in the 17th century, in scriptoria of the Armenian diaspora. In this work, we selected analytical methods that can be used in situ to study the colors of the illuminations. Scientific analysis based on fiber-optics reflectance spectroscopy in the visible and Raman spectroscopy has shown the use of a medieval palette based on inorganic pigments such as lapis lazuli, minium, vermilion, orpiment, indigo, two different greens (vergaut and malachite), lead white and carbon black. More importantly, in this context, it showed that the very important reds and pinks are possibly based on carminic acid. The painting technique is, however, different, as are the ways of painting the faces, hands, and vestments. The range of colors in the Bible and the three Gospel Books, enhanced by lapis lazuli blue and organic reds and pinks, demonstrates a desire to create exceptional illuminated manuscripts.
    2023 artigo Portugal acesso aberto
  8. 8

    A Royal Mystery

    Publicação
    por Malcolm-Davies, Jane
    Outros Autores: Behlen, Beatrice; Teixeira, Natércia; Nabais, Paula
    Early modern materials are not well represented in dye and mordant analyses despite extensive documentary evidence suggesting the enormous demand for coloured fabrics, even among those below the elite. Non-wovens likewise receive less attention than woven textiles despite their ubiquity in the early modern historical record. Knitted garments, in particular, have rarely been subjected to dye analysis. One garment is noteworthy for its colourfulness, despite not being visible in formal wear. Men throughout society wore knitted undergarments known as waistcoats from the late sixteenth century. The waistcoats under investigation here are from the collections at the London Museum and the Grimsthorpe and Drummond Castle Trust, Scotland. They are made of silk and are now a pale blue-green colour. Small samples were taken from each and subjected to a series of analytical techniques: micro-Raman spectroscopy, UV-Vis microspectrofluorimetry, and high-performance liquid chromatography (HPLC) coupled with a mass spectrometer. Using this protocol, it was possible to characterise the dyes in the waistcoats by ensuring that maximum information was gleaned from a sample before it was exhausted.
    2024 artigo Portugal acesso aberto
  9. 9

    Tuning basic poly(ionic liquid) solutions towards atmospheric pressure CO2 capture

    Publicação
    por Silva, Ana
    Outros Autores: Barrulas, Raquel V.; Corvo, Marta C.; Zanatta, Marcileia
    Ionic liquids and poly(ionic liquid)s are interesting materials for CO2 capture, however, the deployment of their industrial application has been delayed on account of economic and technical issues that demand further optimization. The control over viscosity has serious consequences over the process, therefore, this work is focused on the study of imidazolium and pyrrolidinium-derived ILs and PILs with basic anions, such as acetate, hydroxide, and imidazolate that were synthesized and characterized by NMR, ATR-FTIR, TGA, and DSC. Different solvents and concentrations were tested in the preparation of PIL and IL solutions, which were used to capture CO2 by bubbling this gas at room temperature and atmospheric pressure (1 atm). The evaluation of the CO2 sorption capacity of each sample was carried out through the analysis of quantitative 13C NMR. The poly(1-vinyl-3-ethylimidazolium) acetate showed and sorption capacity of 5.68 mmol CO2/g PIL, and also the capacity to capture CO2 from exhaust gas mixture and the possibility to be recycled at least 5 times.
    2023 artigo Portugal acesso aberto
  10. 10

    Natural Colorants for a Bio-Based Economy

    Publicação
    por Cleveland, Imogen
    Outros Autores: Beeby, Andrew; Vieira, Márcia; Pina, Fernando; Branco, Paula S.; Nabais, Paula et al.
    Natural colorants, with their sustainable origins, offer a promising alternative for various applications. Advanced studies have unveiled the remarkable properties, resilience, and durability of these ancient dyes, which our ancestors developed through sustainable material processing. This serves as a testament to the potential of sustainable solutions in our field. As part of our research, we prepared three medieval temperas using gum arabic, parchment glue, and casein glue. These tempera were explicitly designed to protect the purples obtained from Chrozophora tinctoria extracts. A comprehensive multi-analytical approach guides our research on natural colorants. Central to this approach is the use of molecular fluorescence by microspectrofluorimetry, a key tool in our study. By analyzing the emission and excitation spectra in the visible range, we can identify specific formulations. This method is further supported by fingerprinting techniques, including Fourier Transform Infrared Spectroscopy (FTIR) and High-Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD). These are further complemented by Fiber Optics Reflectance Spectroscopy (FORS) and colorimetry. Building on our understanding of orcein purples, we have extended our research to purples derived from Chrozophora tinctoria extracts. Our findings reveal the unique properties of Chrozophora tinctoria, which can be accurately distinguished from orcein purples, highlighting the distinctiveness of each.
    2025 artigo Portugal acesso aberto