1,720,971 research outputs found
C–doped TiO2(B): A density functional theory characterization
No full textCalculations based on the Density Functional Theory (DFT) were applied to study structural, electronic and optical properties of pure and C–doped TiO2(B) taking into account five different types of substitutional impurities. Our calculations indicate that the substitution of a C atom at an O site (C@O) is not only thermodynamically more favorable, but also independent of the growing conditions. The presence of impurity states in the band gap, along with a great reduction of the gap energy (Eg) were obtained after C@O doping, which leads to an enhancement of the absorbance in the visible and IR spectrum caused partially by trapped holes and electrons that the introduction of the impurity induces. Additionally, our results showed that the substitution of a C atom at a Ti site (C@Ti) originated a significant change not only in the structural arrangement of the neighborhood of the impurity, but also on its electronic and optical behavior compared to the pure TiO2(B) model.Fil: Heffner, Herman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Faccio, Ricardo. Universidad de la República; UruguayFil: López Corral, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentin
Electronic structure properties of boron-doped and carbon-boron-codoped TiO2(B) for photocatalytic applications
No full textA path to enhance the efficiency of photocatalytic devices is by doping the active semiconductor in order to maximize the light absorption. However, impurities could increase the recombination of photoinduced charge carriers, in order that a careful analysis on the effects of those impurities it is necessary. On this research, density functional theory calculations were applied to analyze the structure and electronic characteristics of B?doped and C+B?codoped TiO2(B) considering the lowest formation energy of substitutional impurities. Our calculations suggest that the swapping of a boron or carbon atom for an oxygen atom (B@O or C@O) is energetically more favorable than the replacement of titanium atoms. The obtained results seem to indicate that the boron substitution into O2C and O3C1 sites leads to its migration towards interstitial sites in both mono and codoping, thus causing a great geometrical distortion compared to pure TiO2(B). Furthermore, impurity states in the band gap were obtained after B@O doping and C+B?codoping, producing an improvement of the optical properties, so it can be assumed that this nanomaterial might act as a photoelectrode after an adequate design optimization that facilitates the charge carrier separation.Fil: Heffner, Herman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Faccio, Ricardo. Universidad de la República. Facultad de Química; UruguayFil: López Corral, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Novel Green Solvent for Sustainable Fabrication of Quasi‐2D Perovskite Solar Cells
No full textDespite the remarkable advances in the field of perovskite photovoltaics, the use of toxic solvents for their fabrication poses a significant challenge to their scale-up and commercialization. The vast majority of studies rely on using the highly hazardous N, N-Dimethylformamide (DMF), with green alternatives remaining scarce. In this work, the use of glycerol formal (Gly-F) is reported as a green solvent for fabricating quasi-2D (n = 5) perovskite solar cells. Quasi-2D perovskite films processed from Gly-F exhibit a high degree of uniformity and a compact microstructure. When integrated into solar cells, the green solvent-processed films reach a promising power conversion efficiency of 14.53%. This performance is lower than that of DMF-based perovskites, most likely due to the presence of laterally oriented low n perovskite phases. Interestingly, while the performance of DMF-based devices is rather irreproducible, the performance of Gly-F-based devices is robust and consistent. These results demonstrate the potential of Gly-F- as a promising green alternative to DMF.Fil: Guerrero León, L. Andrés. Technische Universität Dresden.; AlemaniaFil: Bautista Quijano, José Roberto. Technische Universität Dresden.; AlemaniaFil: Heffner, Herman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina. Technische Universität Dresden.; AlemaniaFil: Shilovskikh, Vladimir. Technische Universität Dresden.; AlemaniaFil: Campos, Raquel. Technische Universität Dresden.; AlemaniaFil: Rivkin, Boris. Technische Universität Dresden.; AlemaniaFil: Vaynzof, Yana. Technische Universität Dresden.; Alemani
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Optoelectronic performance of indium tin oxide thin films structured by sub-picosecond direct laser interference patterning
Full text linkA route to increase the efficiency of thin film solar cells is improving the light-trapping capacity by texturing the top Transparent Conductive Oxide (TCO) so that the sunlight reaching the solar absorber scatters into multiple directions. In this study, Indium Tin Oxide (ITO) thin films are treated by infrared sub-picosecond Direct Laser Interference Patterning (DLIP) to modify the surface topography. Surface analysis by scanning electron microscopy and confocal microscopy reveals the presence of periodic microchannels with a spatial period of 5 µm and an average height between 15 and 450 nm decorated with Laser-Induced Periodic Surface Structures (LIPSS) in the direction parallel to the microchannels. A relative increase in the average total and diffuse optical transmittances up to 10.7% and 1900%, respectively, was obtained in the 400–1000 nm spectral range as an outcome of the interaction of white light with the generated micro- and nanostructures. The estimation of Haacke’s figure of merit suggests that the surface modification of ITO with fluence levels near the ablation threshold might enhance the performance of solar cells that employ ITO as a front electrode.Fil: Heffner, Herman. Institut Für Fertigungstechnik, Technische Universität Dresden; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Soldera, Marcos Maximiliano. Technische Universität Dresden; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lasagni, Andrés Fabián. Technische Universität Dresden; Alemani
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