1,196 research outputs found
Adaptive density estimation for stationary processes
We propose an algorithm to estimate the common density of a stationary
process . We suppose that the process is either or
-mixing. We provide a model selection procedure based on a generalization
of Mallows' and we prove oracle inequalities for the selected estimator
under a few prior assumptions on the collection of models and on the mixing
coefficients. We prove that our estimator is adaptive over a class of Besov
spaces, namely, we prove that it achieves the same rates of convergence as in
the i.i.d framework
Polynomial growth of volume of balls for zero-entropy geodesic systems
The aim of this paper is to state and prove polynomial analogues of the
classical Manning inequality relating the topological entropy of a geodesic
flow with the growth rate of the volume of balls in the universal covering. To
this aim we use two numerical conjugacy invariants, the {\em strong polynomial
entropy } and the {\em weak polynomial entropy }. Both are
infinite when the topological entropy is positive and they satisfy
. We first prove that the growth rate of the volume of
balls is bounded above by means of the strong polynomial entropy and we show
that for the flat torus this inequality becomes an equality. We then study the
explicit example of the torus of revolution for which we can give an exact
asymptotic equivalent of the growth rate of volume of balls, which we relate to
the weak polynomial entropy.Comment: 22 page
Assimilation of atmospheric methane products into the MACC-II system: From SCIAMACHY to TANSO and IASI
The Monitoring Atmospheric Composition and Climate Interim Implementation
(MACC-II) delayed-mode (DM) system has been producing an atmospheric methane
(CH4) analysis 6 months behind real time since June 2009. This analysis
used to rely on the assimilation of the CH4 product from the SCanning
Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY)
instrument onboard Envisat. Recently the Laboratoire de
Météorologie Dynamique (LMD) CH4 products from the Infrared
Atmospheric Sounding Interferometer (IASI) and the SRON Netherlands Institute
for Space Research CH4 products from the Thermal And Near-infrared Sensor
for carbon Observation (TANSO) were added to the DM system. With the loss of
Envisat in April 2012, the DM system now has to rely on the assimilation of
methane data from TANSO and IASI. This paper documents the impact of this
change in the observing system on the methane tropospheric analysis. It is
based on four experiments: one free run and three analyses from respectively
the assimilation of SCIAMACHY, TANSO and a combination of TANSO and IASI
CH4 products in the MACC-II system. The period between December 2010 and
April 2012 is studied. The SCIAMACHY experiment globally underestimates the
tropospheric methane by 35 part per billion (ppb) compared to the HIAPER
Pole-to-Pole Observations (HIPPO) data and by 28 ppb compared the Total
Carbon Column Observing Network (TCCON) data, while the free run presents an
underestimation of 5 ppb and 1 ppb against the same HIPPO and
TCCON data, respectively. The assimilated TANSO product changed in October
2011 from version v.1 to version v.2.0. The analysis of version v.1 globally
underestimates the tropospheric methane by 18 ppb compared to the
HIPPO data and by 15 ppb compared to the TCCON data. In contrast, the
analysis of version v.2.0 globally overestimates the column by 3 ppb.
When the high density IASI data are added in the tropical region between
30° N and 30° S, their impact is mainly positive but more
pronounced and effective when combined with version v.2.0 of the TANSO
products. The resulting analysis globally underestimates the column-averaged
dry-air mole fractions of methane (xCH4) just under 1 ppb on
average compared to the TCCON data, whereas in the tropics it overestimates
xCH4 by about 3 ppb. The random error is estimated to be less
than 7 ppb when compared to TCCON data
Adaptive estimation in circular functional linear models
We consider the problem of estimating the slope parameter in circular
functional linear regression, where scalar responses Y1,...,Yn are modeled in
dependence of 1-periodic, second order stationary random functions X1,...,Xn.
We consider an orthogonal series estimator of the slope function, by replacing
the first m theoretical coefficients of its development in the trigonometric
basis by adequate estimators. Wepropose a model selection procedure for m in a
set of admissible values, by defining a contrast function minimized by our
estimator and a theoretical penalty function; this first step assumes the
degree of ill posedness to be known. Then we generalize the procedure to a
random set of admissible m's and a random penalty function. The resulting
estimator is completely data driven and reaches automatically what is known to
be the optimal minimax rate of convergence, in term of a general weighted
L2-risk. This means that we provide adaptive estimators of both the slope
function and its derivatives
Chronological age, somatic maturation and anthropometric measures: Association with physical performance of young male judo athletes
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.Sport for children and adolescents must consider growth and maturation to ensure suitable training and competition, and anthropometric variables could be used as bio-banding strategies in youth sport. This investigation aimed to analyze the association between chronological age, biologic maturation, and anthropometric characteristics to explain physical performance of young judo athletes. Sixty-seven judokas (11.0–14.7 years) were assessed for anthropometric and physical performance. Predicted adult stature was used as a somatic maturation indicator. A Pearson’s bivariate correlation was performed to define which anthropometric variables were associated with each physical test. A multiple linear hierarchical regression was conducted to verify the effects of age, maturity, and anthropometry on physical performance. The regression models were built with age, predicted adult stature, and the three most significantly correlated anthropometric variables for each physical test. Older judokas performed better in most of the physical tests. However, maturation attenuated the age effect in most variables and significantly affected upper body and handgrip strength. Anthropometric variables attenuated age and maturity and those associated with body composition significantly affected the performance in most tests, suggesting a potential as bio-banding strategies. Future studies should investigate the role of anthropometric variables on the maturity effect in young judokas
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