1,721,216 research outputs found
Self-diffusion in liquid interfaces
No full textHerth S, Ye F, Eggersmann M, Gutfleisch O, Wurschum R. Self-diffusion in liquid interfaces. Physical Review Letters. 2004;92(9): 95901.For studying self-diffusion in liquid interfaces, Fe-59 tracer diffusion was measured on ultrafine-grained Nd2Fe14B which undergoes an intergranular melting transition for low Nd excess. The diffusion coefficient in the intergranular liquid layers is found to be lower than in bulk melts indicating a hampered atomic mobility due to confinement. Well above the intergranular melting transition, the diffusivity in the liquid interfaces approaches a value characteristic for bulk melts
Sorption properties and reversibility of Ti(IV) and Nb(V)-fluoride doped-Ca(BH4)(2)-MgH2 system
No full textIn the last decade, alkaline and alkaline earth metal tetrahydroborates have been the focuses of the research due to their high gravimetric and volumetric hydrogen densities. Among them, Ca(BH4)(2) and the Ca(BH4)(2) + MgH2 reactive hydride composites (RHC), were calculated to have the ideal thermodynamic properties which fall within the optimal range for mobile applications. In this study, the addition of NbF5 or TiF4 to the Ca(BH4)(2) + MgH2 reactive hydride composite system was attempted aiming to obtain a full reversible system with the simultaneous suppression of CaB12H12. Structural characterization of the specimens was performed by means of in-situ Synchrotron Radiation Powder X-ray diffraction (SR-PXD) and B-11{H-1} Solid State Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR). The evolution of the chemical state of the Nb- and Ti-based additives was monitored by X-ray Absorption Near Edge Structure (XANES). The addition of NbF5 or TiF4 to the Ca(BH4)(2) + MgH2 system have not suppressed completely the formation of CaB12H12 and only a slight improvement concerning the reversible reaction was displayed just in the case of Nb-doped composite material. (C) 2014 Elsevier B.V. All rights reserved
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
Intergranular melting of ultrafine grained Nd2Fe14B studied by means of radiotracer diffusion
No full textEggersmann M, Ye F, Herth S, Gutfleisch O, Wurschum R. Intergranular melting of ultrafine grained Nd2Fe14B studied by means of radiotracer diffusion. Interface Science. 2001;9(3/4):337-341.Grain-boundary (Gb) diffusion was studied in ultrafine grained Nd2Fe14B-based permanent magnets below and above the melting transition of the Nd-enriched intergranular phase using the radiotracer technique with the isotope Fe-59. The product deltaD(Gb) of interface diffusion coefficient and interface thickness shows a substantial increase above the intergranular melting transition. Assuming a volume self-diffusivity as in alpha-Fe, an analysis in the framework of grain-boundary diffusion kinetic of type B yields an Arrhenius-type behaviour deltaD(Gb) = 1.53 x 10(-11) exp(-1.74 eV/kT) m(3) s(-1) below the intergranular melting transition. Similar values deltaD(Gb) are observed for ultrafine grained Nd-Fe-B with reduced Nd excess in the grain boundaries. The diffusion characteristics are compared with the kinetics of the hot-deformation which is of technical relevance for the processing of high-performance permanent magnets
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
Er2Fe14B single crystal as magnetic refrigerant at the spin reorientation transition
No full textIn this paper we study the specific heat under magnetic field c(p)(H(a), T) and the magnetic field induced isothermal entropy change Delta s(H(a), T) of Er(2)Fe(14)B by direct calorimetry and magnetic measurements. We find that the spin reorientation temperature is T(SR) = 322.8 +/- 0.1 K and the entropy change is Delta s = 0.735 +/- 0.005 J kg(-1) K(-1). The measured data are interpreted by a model of the magnetization process taking into account a temperature-dependent uniaxial anisotropy constant K(1)(T), the magnetic field energy, and the effect of the demagnetizing field. The model is able to describe the essential features of the measured Delta s(H(a), T) in terms of reversible rotation of the magnetization induced by the magnetic field. From the model we find that the entropy change has a magnetic field independent saturation value.Delta s(K)(T) = 735 - 5.5 x 10(-3) (T - T(SR)) and that the magnetic field amplitude increases the temperature range over which the effect is observed as Delta T = beta mu(0)H with beta = 54 K T(-1). (C) 2011 American Institute of Physics
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
- …
