1,721,235 research outputs found
Yb9+xCuMg4x (x = 0.034): A Phase Formed by Lanthanoids
No full textAtom order in the crystal structures of Yb2Cu2-xMg (x = 0.17; Mo2FeB2-type; P4/mbm; a = 0.75592(2) nm; c = 0.40282(1) nm) and Yb9 + xCuMg4 - x (x = 0.034; Hf9Mo4B-type; P63/mmc; a = 1.0169(5) nm; c = 1.0290(5) nm) was determined from powder and X-ray single-crystal counter data analyses supported by electron probe microanalyses. Among the group of the so-called κ -phases, Yb9 + xCuMg4 - x is the first representative formed by a lanthanoid element. The structure of this κ -phase can be viewed as a typical network of corner-connected empty Yb6-octahedra, which encompass Yb6Mg6-icosahedra (filled by a mix of Mg/Yb atoms) and Yb6-trigonal prisms centered by Cu atoms to complete the three-dimensional metal framework. From another point of view, the same structure is considered as built from in finite polyicosahedral columns of Yb9Mg4 composition with Cu atoms located in trigonal prismatic interstices, highlighting similarities with other Yb-rich Yb−Cu−Mg phases. Density functional theory (DFT) calculations classify Yb9CuMg4 as a polar intermetallic. Metallic-like behavior is inferred from the Sommerfeld constant, γ = 49.2 mJ/molK2, derived from the electronic density of states, calculated at the Fermi level. DFT integration of the f-density of states indicates almost completely filled f-states, revealing 13.6 and 13.7 electrons in the valence band for Yb1 and Yb2 atoms, respectively, close to the Yb2+ ground state (1S0) for both Yb atoms. Magnetic susceptibility data recorded on the same compound are consistent with a nonmagnetic divalent Yb2+ state. Temperature-dependent heat capacity data display a metallic behavior characterized by a small Sommerfeld constant γ = 64.8 mJ/molK2 and a rather low Debye temperature ΘD = 140 K as typical for soft materials
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
Influence of Pre-annealing on the Microstructure and Thermoelectric Properties of Mn + Al Doped Iron Disilicide Prepared by Rapid Solidification and Hotpressing
No full textIron disilicide based thermoelectric materials with the
designed composition Fe1-xMnxAlySi2-y (x=0.06, 0.08; y=0,
0.02, 0.04) were prepared by rapid solidification and hot
pressing (1193K, 100 MPa, 30 minutes). The effects of
Mn+Al double doping were investigated. The influence of
pre-annealing on the microstructure and the transport
properties were also studied. X-ray diffraction and scanning
electron microscopy show that after pre-annealing at 800°C
for only 10 hours, the high temperature phases (α-Fe2Si5 and
ε-FeSi) in the rapidly solidified powders Fe1-xMnxAlySi2-y have
been completely transformed to β-FeSi2 phase for y=0 and
y=0.02. It is found that the grain growth during hot pressing
was suppressed for the pre-annealed samples. For the pressed
compacts, the Seebeck coefficient was markedly enhanced by
the pre-annealing treatment, while both the electrical
conductivity and the thermal conductivity were decreased.
Mn+Al double doping improves the electrical conductivity,
but deteriorates the Seebeck coefficient and the thermal
conductivity. The maximum of the figure of merit (ZT = 0.20)
is obtained at 890 K for the sample double doped with y=0.04
(Fe0.94Mn0.06Al0.02Si1.98) that is hot pressed from pre-annealed
powders
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
Influence of Phase Composition on the Thermoelectric Properties of Nanostructured Skutterudite-Ceramic Composites
No full textNanostructuring of unfilled CoSb3 Skutterudites
has been successful in reducing the thermal
conductivity of these materials. First
measurements on a mixture of the Skutterudite and
an inert ceramic with particle sizes in the nanometer
range have shown promising results for a further
reduced thermal conductivity by decorating the
grain boundaries of the thermoelectric material.
A strong influence of additional phases like
CoSb2 and pure Sb in the samples has been
encountered, too. Therefore in the present work a
more detailed investigation of the effect of phase
purity and grain size by an intential variation of the
phase composition is presented.
The impact of a variation in the amount of the
ceramics addition and of the phase composition on
the thermoelectric properties (κ, σ, S) of pure and
doped CoSb3, respectively, are studied and the
results are discussed with respect to an
enhancement of the thermoelectric figure of merit
Processing and Characterization af Nano-Ceramic-Dispersed Thermoelectric Materials
No full textThe addition of ceramic to thermoelectric matrix is
expected to reduce materials thermal conductivity, which is
attributed to a phonon scattering mechanism by ceramic
particles. The effect of ceramic on the overall thermoelectric
performance is worth investigating. In the present work, nano
ZrO2 powders were introduced into well-known
thermoelectric materials (FeSi2, CoSb3, and Zn4Sb3) via ball
milling. The as-milled powders were consolidated by hot
pressing. For comparison, the stated thermoelectric materials
without nano ZrO2 dispersion were also prepared on same
processing conditions. For the achieved compacts, the
temperature-dependent transport properties were
characterized. The correlation of ceramic dispersion and
processing conditions with thermoelectric parameters
(Seebeck coefficient, electrical conductivity, thermal
conductivity, and dimensionless figure of merit) is presented.
The results show how the performance of the investigated
thermoelectric materials is affected by the dispersion of nano
ceramic phase
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