Export 4142 results:
Sort by: Author Title Type [ Year  (Desc)]
2018
Mendes, Manuel J., Sirazul Haque, Olalla Sanchez-Sobrado, Andreia Araújo, Hugo Águas, Elvira Fortunato, and Rodrigo Martins. "{Optimal-Enhanced Solar Cell Ultra-thinning with Broadband Nanophotonic Light Capture}." iScience. 3 (2018): 238-254. AbstractWebsite

{\textless}h2{\textgreater}Summary{\textless}/h2{\textgreater}{\textless}p{\textgreater}Recent trends in photovoltaics demand ever-thin solar cells to allow deployment in consumer-oriented products requiring low-cost and mechanically flexible devices. For this, nanophotonic elements in the wave-optics regime are highly promising, as they capture and trap light in the cells' absorber, enabling its thickness reduction while improving its efficiency. Here, novel wavelength-sized photonic structures were computationally optimized toward maximum broadband light absorption. Thin-film silicon cells were the test bed to determine the best performing parameters and study their optical effects. Pronounced photocurrent enhancements, up to 37{%}, 27{%}, and 48{%}, respectively, in ultra-thin (100- and 300-nm-thick) amorphous, and thin (1.5-$μ$m) crystalline silicon cells are demonstrated with honeycomb arrays of semi-spheroidal dome or void-like elements patterned on the cells' front. Also importantly, key advantages in the electrical performance are anticipated, since the photonic nano/micro-nanostructures do not increase the cell roughness, therefore not contributing to recombination, which is a crucial drawback in state-of-the-art light-trapping approaches.{\textless}/p{\textgreater}

Marouani, H., A. Sallem, M. Chaoui, P. Pereira, and N. Masmoudi. "A Robustness Study of Metaheuristics to the Optimal Design of RF Integrated Inductors." 2018 15th International Multi-Conference on Systems, Signals Devices (SSD). 2018. 1459-1464. Abstract

In this paper, three metaheuristics are investigated to optimize RF Integrated Inductors; namely Differential Evolution (DE) from the field of evolutionary computation, Gravitational Search Algorithm (GSA) based on the law of gravity and mass interactions and Particle Swarm Optimization (PSO) inspired by swarm behaviors in nature. A particular interest is given to the optimization of RF Integrated Inductors. Performances in terms of optimum quality and computing time of the metaheuristics are checked via three test functions and one application that consist of optimizing performances of characterize integrated inductors based on the double$π$-model.

Cardoso, P., T. C. Mateus, G. Velu, R. P. Singh, J. P. Santos, M. L. Carvalho, V. M. Louren{\c c}o, F. Lidon, F. Reboredo, and M. Guerra. "Localization and distribution of Zn and Fe in grains of biofortified bread wheat lines through micro- and triaxial-X-ray fluorescence spectrometry." Spectrochim. Acta Part B. 141 (2018): 70-79. Abstract

n/a

Machado, J., C. I. Szabo, J. P. Santos, P. Amaro, M. Guerra, A. Gumberidze, Guojie Bian, J. M. Isac, and P. Indelicato. "{High-precision measurements of $n=2\rightarrow n=1$ transition energies and level widths in He- and Be-like argon ions}." Physical Review A. 97 (2018): 032517. AbstractWebsite

Phys. Rev. A 97, 032517 (2018). doi:10.1103/PhysRevA.97.032517

{T. Vicente}, António, Andreia Araújo, Manuel J. Mendes, Daniela Nunes, Maria J. Oliveira, Olalla Sanchez-Sobrado, Marta P. Ferreira, Hugo Águas, Elvira Fortunato, and Rodrigo Martins. "{Multifunctional cellulose-paper for light harvesting and smart sensing applications}." Journal of Materials Chemistry C. 6 (2018): 3143-3181. AbstractWebsite

{\textless}p{\textgreater}Opto-electronics on/with paper is fostering a novel generation of flexible and recyclable devices for sunlight harvesting and intelligent optical sensing.{\textless}/p{\textgreater}

Correia, Ana, Pedro Barquinha, João Marques, and João Goes. "A High-resolution ∆-Modulator ADC with Oversampling and Noise-shaping for IoT." 14th Conference on PhD Research in Microelectronics and Electronics, PRIME 2018. Prague, Czech Republic: IEEE, 2018.
Neves, F., A. Stark, N. Schell, MJ Mendes, H. Aguas, E. Fortunato, R. Martins, J. B. Correia, and A. Joyce. "{Investigation of single phase Cu2ZnSnxSb1-xS4 compounds processed by mechanochemical synthesis}." Physical Review Materials. 2 (2018). Abstract

The copper zinc tin sulfide (CZTS) compound is a promising candidate as an alternative absorber material for thin-film solar cells. In this study, we investigate the direct formation of Cu1.92ZnSnx(Sb1-x)S4 compounds [CZT(A)S], with x=1, 0.85, 0.70, and 0.50, via a mechanochemical synthesis (MCS) approach, starting from powders of the corresponding metals, zinc sulfide, and sulfur. The thermal stability of the CZT(A)S compounds was evaluated in detail by in situ synchrotron high-energy x-ray diffraction measurements up to 700 °C. The CZT(A)S compounds prepared via MCS revealed a sphalerite-type crystal structure with strong structural stability over the studied temperature range. The contribution of the MCS to the formation of such a structure at room temperature is analyzed in detail. Additionally, this study provides insights into the MCS of CZTS-based compounds: the possibility of a large-scale substitution of Sn by Sb and the production of single phase CZT(A)S with a Cu-poor/Zn-poor composition. A slight increase in the band gap from 1.45 to 1.49-1.51 eV was observed with the incorporation of Sb, indicating that these novel compounds can be further explored for thin-film solar cells.

Monteiro, C. M. B., F. D. Amaro, M. S. Sousa, M. Abdou-Ahmed, P. Amaro, F. Biraben, T. Chen, D. S. Covita, A. J. Dax, M. Diepold, L. M. P. Fernandes, B. Franke, S. Galtier, A. L. Gouvea, J. Götzfried, T. Graf, T. W. Hänsch, M. Hildebrandt, P. Indelicato, L. Julien, K. Kirch, A. Knecht, F. Kottmann, J. J. Krauth, Y. Liu, J. Machado, F. Mulhauser, B. Naar, T. Nebel, F. Nez, R. Pohl, J. P. Santos, J. M. F. dos Santos, K. Schuhmann, C. I. Szabo, D. Taqqu, J. F. C. A. Veloso, and A. Antognini. "{On the double peak structure of avalanche photodiode response to monoenergetic x-rays at various temperatures and bias voltages}." Journal of Instrumentation. 13 (2018): C01033. Abstract
n/a
{Ben Wannes}, H., Benabderrahmane R. Zaghouani, R. Ouertani, A. Araújo, MJ Mendes, H. Aguas, E. Fortunato, R. Martins, and W. Dimassi {Study of the stabilizer influence on the structural and optical properties of sol-gel spin coated zinc oxide films}. Vol. 74. Materials Science in Semiconductor Processing, 74. Elsevier Ltd, 2018. Abstract

In this work, we highlight the influence of three different sol stabilizers, namely diethanolamine (DEA), Ammonium Hydroxide (NH4OH), and Nitric Acid (HNO3), on the optical and structural properties of spin-coated zinc oxide (ZnO) thin films. The XRD patterns related to all films exhibit a hexagonal crystal structure with a preferential orientation along the (0 0 2) direction. However an additional {\textless}100{\textgreater} peak arises when the films are prepared with DEA and NH4OH showing a better crystallinity than that displayed by HNO3-prepared films. The elaborated films show a high transparency reaching 80{%} for DEA-prepared films. The analysis of the transmittance and the reflectance measurements confirms a direct band-to-band transition. Depending on the sol stabilizer, the optical band gap energy is varying from 3.16 to 3.22 eV. The relatively wide band-gap of DEA-prepared ZnO films is correlated to their high crystallinity. Room temperature photoluminescence spectra indicate strong UV emission at around 377 nm originated from nearby band-edge transitions. Yet, the use of DEA as a stabilizer leads to a net intensity increase of the blue peak emission.

Mateus, Octávio, Eduardo Puértolas-Pascual, and Pedro M. Callapez. "A new eusuchian crocodylomorph from the Cenomanian (Late Cretaceous) of Portugal reveals novel implications on the origin of Crocodylia." Zoological Journal of the Linnean Society (2018). AbstractWebsite
n/a
Rudkin, Fiona M., Ingrida Raziunaite, Hillary Workman, Sosthene Essono, Rodrigo Belmonte, Donna M. MacCallum, Elizabeth M. Johnson, Lisete M. Silva, Angelina S. Palma, Ten Feizi, Allan Jensen, Lars P. Erwig, and Neil A. R. Gow. "Single human B cell-derived monoclonal anti-Candida antibodies enhance phagocytosis and protect against disseminated candidiasis." Nature communications. 9 (2018): 5288. Abstract

The high global burden of over one million annual lethal fungal infections reflects a lack of protective vaccines, late diagnosis and inadequate chemotherapy. Here, we have generated a unique set of fully human anti-Candida monoclonal antibodies (mAbs) with diagnostic and therapeutic potential by expressing recombinant antibodies from genes cloned from the B cells of patients suffering from candidiasis. Single class switched memory B cells isolated from donors serum-positive for anti-Candida IgG were differentiated in vitro and screened against recombinant Candida albicans Hyr1 cell wall protein and whole fungal cell wall preparations. Antibody genes from Candida-reactive B cell cultures were cloned and expressed in Expi293F human embryonic kidney cells to generate a panel of human recombinant anti-Candida mAbs that demonstrate morphology-specific, high avidity binding to the cell wall. The species-specific and pan-Candida mAbs generated through this technology display favourable properties for diagnostics, strong opsono-phagocytic activity of macrophages in vitro, and protection in a murine model of disseminated candidiasis.

Cerdeira, Jorge Orestes, Tiago Monteiro-Henriques, Maria João Martins, Pedro C. Silva, Diogo Alagador, Aldina M. A. Franco, Manuel L. Campagnolo, Pedro Arsénio, Francisca C. Aguiar, and Mar Cabeza. "Revisiting niche fundamentals with Tukey depth." Methods in Ecology and Evolution (2018). AbstractWebsite
n/a
Rovisco, Ana, Rita Branquinho, Jorge Martins, Maria João Oliveira, Daniela Nunes, Elvira Fortunato, Rodrigo Martins, and Pedro Barquinha. "{Seed-Layer Free Zinc Tin Oxide Tailored Nanostructures for Nanoelectronic Applications: Effect of Chemical Parameters}." ACS Applied Nano Materials. 1 (2018): 3986-3997. AbstractWebsite

Semiconductor nanowires are mostly processed by complex, expensive and high temperature methods. In this work, with the intent of developing zinc tin oxide nanowires (ZTO NWs) by low-cost and low-complexity processes, we show a detailed study on the influence of chemical parameters in the hydrothermal synthesis of ZTO nanostructures at temperatures of only 200 °C. Two different zinc precursors, the ratio between zinc and tin precursors, the concentration of the surfactant agent and of the mineralizer were studied. The type and the crystallinity of the nanostructures was found to be highly dependent on the used precursors and on the concentration of each reagent. Conditions for obtaining different ZTO nanostructures were achieved, namely Zn2SnO4 nanoparticles and ZnSnO3 nanowires with length ≈ 600 nm, with the latter being reported for the first time ever by hydrothermal methods without the use of seed layers. Optical and electrical properties were analyzed, being obtained band gaps of 3.60 and 3.46 eV, fo...

Agnolin, Federico L., Octávio Mateus, Jesper Milàn, Marco Marzola, Oliver Wings, Jan Schulz Adolfssen, and Lars B. Clemmensen. "Ceratodus tunuensis, sp. nov., a new lungfish (Sarcopterygii, Dipnoi) from the Upper Triassic of central East Greenland." Journal of Vertebrate Paleontology (2018): e1439834. AbstractWebsite
n/a
Revel, A., et al. "Strong Neutron Pairing in $\textrm{core}+4n$ Nuclei." Phys. Rev. Lett.. 120 (2018): 152504. AbstractWebsite
n/a
Guerra, M., J. M. Sampaio, F. Parente, P. Indelicato, P. Hönicke, M. Muller, B. Beckhoff, J. P. Marques, and J. P. Santos. "{Theoretical and experimental determination of $K$- and $L$-shell x-ray relaxation parameters in Ni}." Phys. Rev. A. 97 (2018): 042501. Abstract
n/a
Mateus, Octávio, Bruno Pereira, Rogério Rocha, and José Carlos Kullberg. "Aspiring Geopark Oeste in Portugal: scientific highlights and importance." 8th International Conference on UNESCO Global Geoparks. Adamello Brenta Geopark, Trentino 2018. mateus_et_al_2018_geopark_oeste.pdf
Faria, Ricardo, Rui Marreiros, António Ramos, and Gonçalo Antunes. "Efeito do confinamento e da redistribuição de momentos no comportamento de lajes fungiformes." Encontro Nacional Betão Estrutural 2018. LNEC, Lisboa: GPBE, 2018.
Faria, Ricardo, Catarina Jesus, Rui Marreiros, and António Ramos. "Influência da distribuição transversal de armaduras longitudinais junto ao pilar na resistência ao punçoamento." Encontro Nacional Betão Estrutural 2018. LNEC, Lisboa: GPBE, 2018.
Almeida, André, António Ramos, Rui Marreiros, Válter Lúcio, and Ricardo Faria. "Resposta da ligação pilar-laje fungiforme sujeitas a ações horizontais cíclicas reforçadas com estribos." Encontro Nacional Betão Estrutural 2018. LNEC, Lisboa: GPBE, 2018.
Martins, David, Sueli T. M. Souza, Válter J. G. LUCIO, Carlos Chastre, and Luiz A. S. Souza. "Análise experimental de ligações pilar-pilar em torres treliçadas em concreto pré-moldado para suporte de geradores eólicos." Encontro Nacional Betão Estrutural - BE2018. LNEC, Lisboa, Portugal 2018. 10. Abstract

Com o crescente consumo de energia elétrica são cada vez mais os países que procuram fontes de energia renovável e limpa, entre elas a eólica. A quantidade de energia produzida é influenciada pela altura das torres, dimensões das pás e potência dos aerogeradores. Quanto maior for a elevação da turbina maiores são a velocidade e estabilidade dos ventos alcançados. A solução de torre treliçada em concreto armado pré-moldado idealizada por Lúcio e Chastre [2] permite a construção de torres altas e é competitiva em relação aos outros sistemas estruturais.As ligações têm uma importância fundamental no comportamento global das estruturas pré-moldadas. A viabilidade da ligação (fácil execução, baixo custo, comportamento/capacidade resistente) é preponderante na viabilização da construção destas torres.Até à data foram estudadas quatro ligações (S1, S2, S3 e S4), sendo neste artigo abordadas apenas as ligações do modelo S3 com junta de 3mm (barras salientes/bainhas corrugadas/selagem com grout) e do modelo S4 com junta de 50 mm (ligações aparafusadas produzidas comercialmente).Através dos resultados experimentais pode-se concluir que o mecanismo de rutura foi o mesmo nos dois modelos e que as soluções estudadas preenchem os requisitos para a sua utilização em estruturas pré-moldadas de concreto armado para suporte de aerogeradores.

Mudrov, Mikhail, Anatoliy Ziuzev, Konstantin Nesterov, and Stanimir Valtchev. "Asynchronous electric drive power-hardware-in-the-loop system." Proceedings - 2018 17th International Ural Conference on AC Electric Drives, ACED 2018. Vol. 2018-April. United States: Institute of Electrical and Electronics Engineers Inc., 2018. 1-5. Abstract

Power Hardware-in-the-Loop (PHiL) system for asynchronous electric drives application based on power inverter with Field Programmable Gate Array (FPGA)-based control system is discussed. Proposed PHiL structure and scheme for asynchronous electric drives are under discussion as well. Described PHiL can be used for power inverters multi-stage testing.

Mihaylov, Kaloyan, Rumen Arnaudov, and Stanimir Valtchev. "Design and analysis of wireless sensor network powered through neutral to earth voltage." Proceedings - 2018 17th International Ural Conference on AC Electric Drives, ACED 2018. Vol. 2018-April. United States: Institute of Electrical and Electronics Engineers Inc., 2018. 1-6. Abstract

A low power wireless sensor network utilizing the neutral to earth voltage as a power source is developed and analyzed. It consists of a batteryless energy harvesting powered wireless sensor nodes, a gateway (if needed) and a local or remote server (if used). An invasive energy harvesting method to use the voltage between the neutral conductor and the ground conductor is used for the sensor module. A test network is built in a household. Statistics of the household's electric current and the corresponding neutral conductor's voltage is obtained during a two months period. The statistics is further processed to verify the working principle of the proposed network and to enlighten its strengths and weaknesses. The sensor nodes are developed using widely existing electronic components and don't require specialized devices.

Braslavsky, {Isaak Ya}, {Vladimir P. } Metelkov, {Alex V. } Kostylev, and Stanimir Valtchev. "On reliability and energy efficiency increasing of the vehicles electric drives." Proceedings - 2018 17th International Ural Conference on AC Electric Drives, ACED 2018. Vol. 2018-April. United States: Institute of Electrical and Electronics Engineers Inc., 2018. 1-6. Abstract

Problem of the reliability increasing of the vehicles electric drives is discussed in context of the reduction of the electric motor heating during variable character of movement. Opportunities of the induction motor stator winding heating reduction by means of the control of the vehicles electric drives in transient and steady state modes of movement are shown. Analytical expressions for dynamic torque, optimal on minimal of the winding temperature rise during acceleration, as well as expressions for dynamic torque and value of the motor torque limitation, optimal on energy consumption during acceleration are presented. It is shown that desire to reduce the stator winding temperature rise by means of dynamic torque optimal value selection or motor torque limitation can lead to the rise of energy consumption. Results of the modeling are presented.