1,720,989 research outputs found
Interfacial reactivity of the filled skutterudite smy(Fexni1−x)4sb12 in contact with liquid in-based alloys and sn
No full textThe study of the wettability of thermoelectric materials, as well as the search for the most proper brazing alloys, is of the maximum importance to get one step closer to the realization of a thermoelectric device. In this work, a wettability study of the filled skutterudite Smy(FexNi1−x)4Sb12 by Sn and In-based alloys is presented. Samples, having both p- and n- characters were prepared by the conventional melting-quenching-annealing technique and subsequently densified by spark plasma sintering (SPS). Afterward, wettability tests were performed by the sessile drop method at 773 K for 20 min. Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analyses performed on the cross-section of the solidified drops suggest quite a complicated scenario due to the coexistence and the interaction of a large number of different elements in each analyzed system. Indeed, the indication of a strong reaction of In-based alloys with skutterudite, accompanied by the formation of the InSb intermetallic compound, is clear; on the contrary, Sn exhibits a milder reactivity, and thus, a more promising behavior, being its appreciable wettability, whilst coupled to a limited reactivity
Formation and Decomposition Process of the Filled Skutterudite Smy(FexNi1−x)4Sb12(0.40 ≤ x ≤ 1) as Revealed by Differential Thermal Analysis
No full textFilled skutterudites are among the most promising thermoelectric materials, and the obtainment of monophasic samples is crucial for the study of their transport properties. In this work, a differential thermal analysis study was performed on samples belonging to the Smy(FexNi1-x)4Sb12system with the aim to determine the most proper annealing temperature to possibly obtain skutterudite monophasic samples, and to study the effect of Sm addition on the thermodynamics of the Fe-Ni-Sb system. Samples were prepared through the traditional procedure consisting in melting–quenching–annealing the starting elements. DTA analyses were carried out on annealed samples, and results were interpreted using the Fe25Sb75-Ni25Sb75pseudobinary phase diagram taken from the literature as a starting point. They reveal that 870 K is the best annealing temperature, being the formation of a liquid phase just above this point; moreover, the Sm introduction results in widening the one-phase skutterudite stability region toward both higher temperatures and higher Fe concentrations compared with the Sm-free system
Effect of the (Nd,Dy)-double doping on the structural properties of ceria
No full textThe crystallographic properties of the Ce1-x(Nd0.63Dy0.37)xO2-x/2 system (0 ≤ x ≤ 0.6) were studied by means of synchrotron powder X-ray diffraction and compared to the ones of Sm-doped ceria. The aim of this work was to investigate the effect of substituting Sm3+ by a mixture of a smaller and a larger ion that ensures a more pronounced Ce4+/dopant size mismatch while having the same average ionic size as Sm3+. Two main findings came to light: (a) the compositional region of the CeO2-based solid solution widens up to x ranging between 0.4 and 0.5, and (b) the cell parameter is larger than the one of Sm-doped ceria at each composition. Both effects are expected to play a significant role on the ionic conductivity of the material. The results are discussed in terms of disorder and cation-vacancy association
Impact of the Oxygen Vacancies of the LSCF (La0.6Sr0.4Co0.2Fe0.8O3–δ) Perovskite on the Activation Energy of the Oxygen Reduction/Evolution Reaction
No full textLa0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF) perovskites, in the form of in–house electrospun nanofibers and commercial powders, have been tested through synchrotron x–ray diffraction and electrochemical impedance spectroscopy in the 800–1200 K range. The former analyses make it possible to evaluate the oxygen vacancies (OV) concentration, and the latter allows to assess the electrokinetics of the oxygen reduction/evolution reaction. Equivalent circuit modeling is carried out to identify the basic electrochemical processes and evaluate the associated polarization resistance Rp. One high-frequency process and two intermediate-frequency processes are recognized. For all electrochemical processes, OV concentration and Rp behave similarly with temperature in both nanofiber and granular electrodes. This led to the proposal of a new equation. For each electrochemical process, it was shown that the activation energy is the sum of an intrinsic electrochemical activation energy, plus the formation energy of OVs. For the LSCF perovskites tested in this work, the intrinsic electrochemical activation energy was found to be independent of the preparation procedure and crystal structure. In contrast, the OV formation energy was found to be strongly dependent on the preparation procedure and crystal structure, with values ranging between 0.5 and 24.1 kJ mol−1. A complete set of data is provided, which can be useful for future simulation studies
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
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
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