8,415 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
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
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]
A Neural Network Gravitational Arc Finder based on the Mediatrix filamentation Method
Automated arc detection methods are needed to scan the ongoing and
next-generation wide-field imaging surveys, which are expected to contain
thousands of strong lensing systems. Arc finders are also required for a
quantitative comparison between predictions and observations of arc abundance.
Several algorithms have been proposed to this end, but machine learning methods
have remained as a relatively unexplored step in the arc finding process. In
this work we introduce a new arc finder based on pattern recognition, which
uses a set of morphological measurements derived from the Mediatrix
Filamentation Method as entries to an Artificial Neural Network (ANN). We show
a full example of the application of the arc finder, first training and
validating the ANN on simulated arcs and then applying the code on four Hubble
Space Telescope (HST) images of strong lensing systems. The simulated arcs use
simple prescriptions for the lens and the source, while mimicking HST
observational conditions. We also consider a sample of objects from HST images
with no arcs in the training of the ANN classification. We use the training and
validation process to determine a suitable set of ANN configurations, including
the combination of inputs from the Mediatrix method, so as to maximize the
completeness while keeping the false positives low. In the simulations the
method was able to achieve a completeness of about 90% with respect to the arcs
that are input to the ANN after a preselection. However, this completeness
drops to 70% on the HST images. The false detections are of the order of
3% of the objects detected in these images. The combination of Mediatrix
measurements with an ANN is a promising tool for the pattern recognition phase
of arc finding. More realistic simulations and a larger set of real systems are
needed for a better training and assessment of the efficiency of the method.Comment: Updated to match published versio
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
COVID-19 and Portuguese Adults with Intellectual Disabilities
The COVID-19 pandemic has changed the lives of people all over the world, including in Portugal. This study explores the impact of the pandemic on several life domains of Portuguese adults with Intellectual Disabilities (ID) and their families; identifies the difficulty level in the implementation of the most common preventive measures by adults with ID; addresses the consequences of health authorities’ guidelines in the activities carried out in daycare centers for people with disabilities. A total of thirty-three daycare centers participated; they were attended by a total of 1192 adults at the time the study took place (between the 15th of September 2020 and the 15th of October 2020), and a professional belonging to the daycare center answered an online survey. The results showed that: 1) participants agreed that the pandemic had a negative impact on adults with ID and their families, although only in a percentage of them; 2) in the cases of the adults and families where that negative impact occurred, it was generalized, expressing itself in various life domains; 3) almost all of the preventive measures where considered difficult to apply by adults with ID; 4) the participants agreed that the health authorities' guidelines influenced the activities that were performed in the daycare centers, i.e., there were less activities, and the existing ones were less diversified, more sedentary and occurring indoors more often. The implications of the negative impact of the pandemic on adults with ID, their families, and the services provided have to be addressed
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