513 research outputs found
Avaliação de modelos de estimativa de radiação solar global para o Estado de Goiás.
O objetivo deste estudo foi calibrar e avaliar o desempenho, de forma diária, de cinco modelos empÃricos de estimativa de radiação solar. Foram utilizados dados de 10 municÃpios do estado de Goiás. A calibração e validação dos modelos BC, CD, DB e DCBB foram feitas utilizando a minimização do erro do quadrado médio. Já o modelo HG foi utilizado o método de iteração. O desempenho da calibração e validação dos modelos foi avaliado pelo coeficiente de determinação, erro do quadrado médio, erro relativo do quadrado médio, erro médio absoluto, eficiência do modelo pelo método de Nash-Sutcliff e pelos Ãndices de concordância de Willmott e de confiança de Camargo. Os resultados permitiram observar que os modelos que mais subestimam ou superestimam os valores de radiação solar foram o modular DCBB e o HG, nessa ordem, com o erro médio absoluto variando em média de 2,60 a 3,02 M.J.m-2.dia-1 tanto na calibração quanto na validação. Conclui-se que os modelos CD e DB tiveram os melhores desempenhos em estimar os valores de radiação solar para o estado de Goiás
Sistema de suporte a decisões agronômicas via Web para o Estado de Goiás.
O objetivo desse trabalho é ilustrar o desenvolvimento de um SSD, via web, no qual disponibilizará a cada hora, as variáveis meteorológicas precipitação, temperatura máxima e mÃnima do ar, umidade relativa do ar, velocidade média e direção do vento para diferentes localidades de Goiás com a finalidade de dar suporte a decisões relacionadas as práticas de manejo agrÃcolas
Retinal response of low myopes during orthokeratology treatment
The aim of this study was to evaluate the changes in retinal activity during orthokeratology (OK) treatment in 20 myopic eyes. Pattern electroretinography (PERG) and visual evoked potential (VEP) were assessed with the RETI-port/scan21 (Roland Consult, Wiesbaden, Germany). Measurements were taken at baseline (BL) and 1 night (1N), 15 nights (15N), 30 nights (30N), and 60 nights (60N) of OK lens wear. Repeated measures analysis of variance (ANOVA) and the Friedman test were used. Twenty eyes (23.20 ± 3.46 years, 70% female) with visual acuity ≤ 0.00 logMAR in post-treatment showed that despite a slight increase in retinal and cortical response amplitude, observed with both PERG and VEP, respectively, immediately after the initial treatment, these differences found were not statistically significant during the 60 days of OK treatment, despite a statistically significant increase in N95 response with PERG. This shows that retinal and cortical visual-related electrical activity is maintained or slightly increased during OK treatment.This research was supported by the Portuguese Foundation for Science and Technology (FCT) PTDC/FIS-OPT/0677/2014, the Strategic Funding UID/FIS/04650/2013 at Center of Physics, UMinho, and predoctoral grant SFRH/BD/136684/2018 to A.A.
The spatially resolved star formation history of CALIFA galaxies: Cosmic time scales
This paper presents the mass assembly time scales of nearby galaxies observed
by CALIFA at the 3.5m telescope in Calar Alto. We apply the fossil record
method of the stellar populations to the complete sample of the 3rd CALIFA data
release, with a total of 661 galaxies, covering stellar masses from 10
to 10 M and a wide range of Hubble types. We apply spectral
synthesis techniques to the datacubes and process the results to produce the
mass growth time scales and mass weighted ages, from which we obtain temporal
and spatially resolved information in seven bins of galaxy morphology and six
bins of stellar mass (M) and stellar mass surface density
(). We use three different tracers of the spatially resolved
star formation history (mass assembly curves, ratio of half mass to half light
radii, and mass-weighted age gradients) to test if galaxies grow inside-out,
and its dependence with galaxy stellar mass, , and morphology.
Our main results are as follows: (a) The innermost regions of galaxies assemble
their mass at an earlier time than regions located in the outer parts; this
happens at any given M, , or Hubble type, including
the lowest mass systems. (b) Galaxies present a significant diversity in their
characteristic formation epochs for lower-mass systems. This diversity shows a
strong dependence of the mass assembly time scales on and
Hubble type in the lower-mass range (10 to 10), but a very
mild dependence in higher-mass bins. (c) All galaxies show negative
log age gradients in the inner 1 HLR. The profile
flattens with increasing values of . There is no significant
dependence on M within a particular bin, except for
the lowest bin, where the gradients becomes steeper.Comment: 15 pages, 13 figures, 3 tables, accepted for publication in Astronomy
& Astrophysics. *Abridged abstract
Spatially resolved mass-to-light from the CALIFA survey. Mass-to-light ratio vs. color relations
We investigated the mass-to-light versus color relations (MLCRs) derived from
the spatially resolved star formation history of a sample of 452 galaxies
observed with integral field spectroscopy in the CALIFA survey. We derived the
stellar mass () and the stellar mass surface density from the
combination of full spectral fitting (using different sets of stellar
population models) with observed and synthetic colors in optical broad bands.
This method allows obtaining the radial structure of the mass-to-light ratio
() at several wavelengths and studying the spatially resolved MLCRs. Our
sample covers a wide range of Hubble types from Sc to E, with stellar masses
ranging from to M. The scatter in the
MLCRs was studied as a function of morphology, stellar extinction, and emission
line contribution to the colors. The effects of the initial mass function (IMF)
and stellar population models in the MLCRs were also explored. Our main results
are that (a) the ratio has a negative radial gradient that is steeper
within the central 1 half-light-radius (HLR). It is steeper in Sb-Sbc than in
early-type galaxies. (b) The MLCRs between and optical colors were
derived with a scatter of 0.1 dex. Extinction and emission line
contributions do not affect the scatter of these relations. Morphology does not
produce a significant effect, except if the general relation is used for
galaxies redder than or bluer than . (c) The IMF has a
large effect on MLCRs, as expected. The change from a Chabrier to a Salpeter
IMF produces a median shift of \oimf\ dex when mass loss from stellar
evolution is also taken into account. (d) These MLCRs are in agreement with
previous results, in particular for relations with and bands and the
and Johnson systems. FITS tables available at http://pycasso.iaa.es/MLComment: 13 pages, 10 figures, 12 tables, accepted for publication in
Astronomy & Astrophysics. Abridged abstract. All tables are available in
electronic format at http://pycasso.iaa.es/M
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