1,720,974 research outputs found
Anelastic properties and solid state reactivity of Fe-Al nanostructured intermetallic compounds
No full textIron and Aluminium elemental powders mixed in the atomic ratio Fe50Al50 and Fe75Al25 have been alloyed using an high energy mill system. The structural transformation of the milled products has been followed using XRD techniques. Samples obtained from cold-consolidation of the milled powders have been used for Elastic Energy Dissipation measurements (IF) and analysed in the temperature range 300-980 K. The XRD spectra corresponding to specimens milled for long times reveal the formation of the FeAl and Fe3Al nanostructured intermetallic compounds. The IF spectra show two relaxational damping peaks P-1,P-2 in the temperature range 600-980 K. The peak evolution for different milling treatments indicates a Zener and a grain-boundary relaxation mechanisms for P-1 and P-2 respectively
Anelasticity and structural stability of nanostructured metals and compounds
No full textInternal friction and dynamic elasticity moduli on thin reeds of nanostructured Al, Fe, FeAl and Fe3Al intermetallics prepared by ball milling have been measured. A relaxational damping peak in pure metals at 350-500 K and a modulus increase at 450-500 K without appreciable grain growth has been detected. Moreover, magnetoelastic coupling dependent on grain size has been observed in iron. In the nanophase intermetallic aluminides a strong relaxational damping peak was observed in the 700-800 K range. These results are briefly discussed with reference to the anelastic behaviour of similar coarse grained materials
Structural and elastic behavior of Fe50Al50 nanocrystalline alloys
No full textPure iron and aluminum powders were mixed in the equiatomic ratio and mechanically alloyed in a high-energy ball mill for different times. Structure refinement of x-ray powder diffraction data was performed to study the structural transformations induced by mechanical and subsequent thermal annealing treatments, The mechanical alloying (MA) process induces a progressive dissolution of aluminum phase into the bcc iron phase. After 32 h of MA a single-phase Fe(Al) bcc extended solid solution, with lattice parameter a(0)=2.891 Angstrom, average coherent domain size (D) approximate to 50 Angstrom, and lattice strain 0.5%, was observed. The annealing of the specimens after MA up to 8 h favored the aluminum dissolution in alpha-iron and the precipitation of the Al5Fe2 phase, whereas a nanostructured B2 FeAl intermetallic compound was observed in the annealed samples which were previously milled for 8, 16, and 32 h. In the same specimens a minority cubic phase Fe3AlCX, anti-isomorphous with perovskite, derived from contamination of ethanol and introduced in the steel vial as a lubricant agent, was also observed. Anelasticity measurements have shown the occurrence of two main transient effects during the first thermal run. The first one occurring at 500 K in all mechanically alloyed specimens was attributed to thermally activated structural transformations, whereas the second at about 700 K was attributed to a magnetic order-disorder transition. During the second run of anelasticity measurements a relaxation peak P-1 in the nanostructured B2 FeAl intermetallic compound, attributed to grain-boundary sliding mechanisms and with an activation energy of 1.8+/-0.2 eV was observed. In specimens milled for 8-32 h a second small peak P-2 at the low-temperature tail of the P-1 peak was observed and tentatively attributed to a Zener-type relaxation. (C) 1996 American Institute of Physics
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
Anelastic properties and solid state reactivity of Fe-Al nanostructured intermetallic compounds
No full text- …
