8,383 research outputs found
A characterization of the scientific impact of Brazilian institutions
In this paper we studied the research activity of Brazilian Institutions for
all sciences and also their performance in the area of physics between 1945 and
December 2008. All the data come from the Web of Science database for this
period. The analysis of the experimental data shows that, within a nonextensive
thermostatistical formalism, the Tsallis \emph{q}-exponential distribution
can constitute a new characterization of the research impact for
Brazilian Institutions. The data examined in the present survey can be fitted
successfully by applying a universal curve namely, with for {\it all} the available citations
, being an "effective temperature". The present analysis ultimately
suggests that via the "effective temperature" , we can provide a new
performance metric for the impact level of the research activity in Brazil,
taking into account the number of the publications and their citations. This
new performance metric takes into account the "quantity" (number of
publications) and the "quality" (number of citations) for different Brazilian
Institutions. In addition we analyzed the research performance of Brazil to
show how the scientific research activity changes with time, for instance
between 1945 to 1985, then during the period 1986-1990, 1991-1995, and so on
until the present. Finally, this work intends to show a new methodology that
can be used to analyze and compare institutions within a given country.Comment: 7 pages, 5 figure
Are citations of scientific papers a case of nonextensivity ?
The distribution of citations of scientific papers has recently been
illustrated (on ISI and PRE data sets) and analyzed by Redner [Eur. Phys. J. B
{\bf 4}, 131 (1998)]. To fit the data, a stretched exponential () has been used with only partial success. The success
is not complete because the data exhibit, for large citation count , a power
law (roughly for the ISI data), which, clearly, the
stretched exponential does not reproduce. This fact is then attributed to a
possibly different nature of rarely cited and largely cited papers. We show
here that, within a nonextensive thermostatistical formalism, the same data can
be quite satisfactorily fitted with a single curve (namely, for the available values of . This is
consistent with the connection recently established by Denisov [Phys. Lett. A
{\bf 235}, 447 (1997)] between this nonextensive formalism and the
Zipf-Mandelbrot law. What the present analysis ultimately suggests is that, in
contrast to Redner's conclusion, the phenomenon might essentially be one and
the same along the entire range of the citation number .Comment: Revtex,1 Figure postscript;[email protected]
Homotheties and topology of tangent sphere bundles
We prove a Theorem on homotheties between two given tangent sphere bundles
of a Riemannian manifold of , assuming different
variable radius functions and weighted Sasaki metrics induced by the
conformal class of . New examples are shown of manifolds with constant
positive or with constant negative scalar curvature, which are not Einstein.
Recalling results on the associated almost complex structure and
symplectic structure on the manifold , generalizing the
well-known structure of Sasaki by admitting weights and connections with
torsion, we compute the Chern and the Stiefel-Whitney characteristic classes of
the manifolds and .Comment: 15 pages, to appear in Journal of Geometr
O aplicativo computacional "Irrigafácil" implementado via web para o manejo de irrigação dos campos experimentais da Embrapa Milho e Sorgo.
bitstream/item/79197/1/ct-203.pd
Estimativa de coeficientes de cultura (kc) da fase inicial de culturas anuais no Estado do Mato Grosso.
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