1,720,964 research outputs found
Preparation and Characterization of Master Alloys Fe48Cr15Mo14C15B6Y2 Metallic Glasses
Full text linkThe purpose of this work is the characterization of a master alloy of metal glass based on iron Fe48Cr15Mo14C15B6Y2. Two types of alloys studied B1 which has been prepared by the use of pure element and the other B2 which has been prepared by the use of raw materials. The thermal and structural properties of the samples are measured by a combination of high temperature differential scanning calorimeter (HTDSC), X-ray diffraction and scanning electron microscopy (SEM). Chemical compositions are checked by energy dispersive spectroscopy analysis.Fil: Bendjemil, Badis. University of Badji -Mokhtar; Argelia. Faculty of Sciences and Technology; ArgeliaFil: Seghairi, Nassima. Faculty of Sciences and Technology; ArgeliaFil: Lavorato, Gabriel Carlos. Dipa rtimento di Chimica Universita' di Torino; Italia. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; ArgentinaFil: Castellero, Alberto. Dipa rtimento di Chimica Universita' di Torino; ItaliaFil: Bougdira, Jamal. Université de Nancy, Faculté des Sciences et. Techniques; FranciaFil: Vinai, Franco. Instituto Nazionale di Ricerca Metrologica; ItaliaFil: Baricco, Marcello. Dipa rtimento di Chimica Universita' di Torino; Itali
Electronic structure, magnetic and Fermi surface calculations of heavy-fermions superconductors compounds based on Nb3Sn
No full textWe report a theoretical investigation of the electronic structures and Fermi surface of the heavy-fermion superconductors Nb3Sn. The electronic structures are investigated ab-initio on the basis of full-potential local orbital minimum-basis band- structure calculations (FPLO), adopting both the scalar- and fully relativistic formulations within the framework of the local spin-density approximation (LSDA). The possibility of a partial 4d localization occurring for compounds is discussed. The electronic structures of the Nb3Sn compounds are computed to be rather similar to the literature. Our total-energy calculations predict paramagnetic and ferromagnetic order to be favorable for Nb3Sn materials, which is, however, observed experimentally. Also, the calculated magnetic moment is 0.35 ?B. Furthermore, the theoretical Fermi surfaces topology and the possible origins of the superconductivity are discussed. The Bardeen, Cooper and Schreiffer (BCS) energy gap and the Ginzburg-Landau (GL) parameter K for these compounds have been calculated from the Fermi velocity. We found strong indication suggesting the existence of a second superconducting (SC) gap in Nb3Sn. In addition, the average superconductivity-gap at zero temperature is calculated for this compound. The knowledge of energy gap value gives important information on the coupling scenarios. Our results provide an explanation between the electronic structures, the Fermi surface (FS) topology and two-band model of the superconductivity
Electronic and optical properties of the express purified SWCNTs produced by HiPCO process
No full textSingle-walled carbon nanotubes have been synthesized by a gas-phase CO decomposition (HiPCO) process, involving high-pressure disproportionation of CO as carbon feedstock and catalytic iron particles were obtained from pyrolysis of Fe(CO)5. The diameter and diameter distribution of as grown material dependents on various parameters, the strong is the pressure of CO cold transverse the Fe(CO)5, nozzle geometry and position for the injection of the reactant in the reaction chamber to produce smaller diameter (about 0.9 nm) at higher CO pressure. The HiPCO materials containing iron were purified by a two-step process of oxidation in oxygen atmosphere and successive washing the mixture of hydrochloric and nitric acids neutralised and distilled water (1:1:1). The optical and electronic properties were studied using optical absorption and infrared spectroscopyin addition, high-resolution transmission electron energy-loss spectroscopy was used to analyse the loss function, electron diffraction and core level excitations. The degree of purification achieved was estimated using transmission electron microscopy. Furthermore, the present procedure has a no sufficiently change in the diameter and diameter distribution after Gaussian fit of the optical absorbance spectra. The estimation of the degree of purification is possible by the analysis of core level excitationfinally high purity SWCNTs were obtained
Electronic structure, magnetic and Fermi surface calculations of heavy-fermions superconductors compounds based on Nb3Sn
No full textLink to publisher's homepage at http://www.unimap.edu.my/ ; Open access only applicable for vol. 1; issue 1, 2008.We report a theoretical investigation of the electronic structures and Fermi surface of the heavy-fermion superconductors Nb3Sn. The electronic structures are investigated ab-initio on the basis of full-potential local orbital minimum-basis band- structure calculations (FPLO), adopting both the scalar- and fully relativistic formulations within the framework of the local spin-density approximation (LSDA). The possibility of a partial 4d localization occurring for compounds is discussed. The electronic structures of the Nb3Sn compounds are computed to be rather similar to the literature. Our total-energy calculations predict paramagnetic and ferromagnetic order to be favorable for Nb3Sn materials, which is, however, observed experimentally. Also, the calculated magnetic moment is 0.35 μB. Furthermore, the theoretical Fermi surfaces topology and the possible origins of the superconductivity are discussed. The Bardeen, Cooper and Schreiffer (BCS) energy gap and the Ginzburg-Landau (GL) parameter
K for these compounds have been calculated from the Fermi velocity. We found strong
indication suggesting the existence of a second superconducting (SC) gap in Nb3Sn. In
addition, the average superconductivity-gap at zero temperature is calculated for this
compound. The knowledge of energy gap value gives important information on the coupling
scenarios. Our results provide an explanation between the electronic structures, the Fermi surface (FS) topology and two-band model of the superconductivity
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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