1,721,065 research outputs found
Determination of the enthalpy of hydration of oxygen vacancies in Y-doped BaZrO(3) and BaCeo(3) by TG-DSC
No full textFacet-engineered TiO2 nanomaterials reveal the role of water–oxide interactions in surface protonic conduction
No full textWater adsorption and surface protonic conduction have been investigated at 25–400 °C in wet (H2O and D2O) atmospheres on nanocrystalline TiO2 hydrothermally grown to a predominance of different crystal facets. In situ Fourier transform infrared spectrometry shows that a portion of the water molecules in the first chemisorbed layer adsorbs dissociatively on the {001} and {100} surfaces, but molecularly on the {101} surface. The next layer of physisorbed molecular water is solid (ice)-like on the {001} and {100} surfaces, a fact that is attributed to relatively strong bonds to the surface terminating hydroxyls. On the other hand, it is looser, liquid-like on the {101} surface due to the lack of rigid hydroxyl groups to bond to. As relative humidity (RH) increases with decreasing temperature, additional water layers physisorb and eventually become liquid-like also on the {001} and {100} surfaces. The differences can be attributed to the different atomic arrangements and surface energies of the different crystal facets. Surface protonic conduction on {001} and {100} dominated samples exhibits high pre-exponentials, indicating a high concentration of sites for dissociative chemisorption, and high activation energies reflecting difficult proton migration in the rigid water layers on those surfaces. The surface protonic conduction on the {101} dominated sample reflects a lower coverage of dissociable water and lower activation enthalpies for protonic migration in the more loosely bonded water. This suggests that, more generally, surfaces with dissociative chemisorption may exhibit high surface protonic conductivity at the highest and lowest temperatures (corresponding to lowest and highest RH, respectively), while surfaces with molecular chemisorption may exhibit a relatively high conductivity (less deep minimum) at intermediate temperatures. H/D isotope effects show that the protonic conduction mechanism changes from Grotthuss to vehicle as the physisorbed water layers gain thickness and become liquid-like. The protonic conductivity decreased when the surface was terminated by more strongly bonded fluoride ions, believed to reflect that they block the sites for water adsorption
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
On the development of proton ceramic fuel cells based on Ca-doped LaNbO4 as electrolyte
No full textWe review the key properties of Ca-doped LaNbO4 (LCNO) and related materials for use as proton conducting electrolyte, from the discovery of its proton conductivity, through developments of synthesis and production, anodes and cathodes, to demonstrations of it in laboratory fuel cells, exemplified through published and new results from a range of collaborative projects in Norway and Europe the last years. Important new knowledge has been obtained concerning the reliable synthesis of line compounds like LaNbO4, B-site doping and co-doping, grain boundary resistance, phase transformations, thin film fabrication, and electrodes for proton conducting ceramics. However, as LCNO still requires films too thin for reliable fabrication of large areas and operation over prolonged times, and since cathodes with acceptable electrocatalytic performance have not been identified, one must conclude that high-power fuel cells (and steam electrolysers) based on LCNO are not viable.Funding from the European Union (FP7 ENERGY Project EFFIPRO – Grant Agreement 227560) and The Research Council of Norway (notably projects NANOMAT/NANIONET 182065/S10, NANOMAT/NANOPCFC 182090/S10, and RENERGI/STACKPRO 185322/S30) is kindly acknowledged, as are the collaboration and inputs from all contributing partners.Peer Reviewe
Ionic conductivity in LixTaOy thin films grown by atomic layer deposition
Get PDFThe material system Li-Ta-O is a promising candidate for thin-film solid-state electrolytes in Li-ion batteries. In the present study, we have varied the Li content x in LixTaOy thin films grown by atomic layer deposition (ALD) with the aim of improving the Li-ion conductivity. The amorphous films were grown at 225 degrees C on insulating sapphire and on conductive Ti substrates using tantalum ethoxide (Ta(OEt)(5)), lithium tert-butoxide ((LiOBu)-Bu-t) and water as reactants. The film composition was determined by time-of-flight elastic recoil detection analysis (TOF-ERDA), displaying an almost linear relationship between the pulsed and deposited Li content. The ionic conductivities were determined by in-plane and cross-plane AC measurements, exhibiting an Arrhenius-type behaviour and comparatively weak thickness-dependence. Increasing Li content x from 0.32 to 0.98 increases the film conductivity by two orders of magnitude while higher Li content x = 1.73 results in decreased conductivity. A room-temperature conductivity ciRT of similar to 10(-8) S cm(-1) is obtained for a 169 nm thick Li0.98TaOy film. The evolution of conductivity and activation energy suggests a competing effect between the concentration and the mobility of mobile Li ions when more Li are incorporated. The compositional dependence of Li transport mechanism is discussed. (C) 2020 The Author(s). Published by Elsevier Ltd.Peer reviewe
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