2,738 research outputs found
Spectral analysis for nonstationary audio
A new approach for the analysis of nonstationary signals is proposed, with a
focus on audio applications. Following earlier contributions, nonstationarity
is modeled via stationarity-breaking operators acting on Gaussian stationary
random signals. The focus is on time warping and amplitude modulation, and an
approximate maximum-likelihood approach based on suitable approximations in the
wavelet transform domain is developed. This paper provides theoretical analysis
of the approximations, and introduces JEFAS, a corresponding estimation
algorithm. The latter is tested and validated on synthetic as well as real
audio signal.Comment: IEEE/ACM Transactions on Audio, Speech and Language Processing,
Institute of Electrical and Electronics Engineers, In pres
Estimating hyperparameters and instrument parameters in regularized inversion. Illustration for SPIRE/Herschel map making
We describe regularized methods for image reconstruction and focus on the
question of hyperparameter and instrument parameter estimation, i.e.
unsupervised and myopic problems. We developed a Bayesian framework that is
based on the \post density for all unknown quantities, given the observations.
This density is explored by a Markov Chain Monte-Carlo sampling technique based
on a Gibbs loop and including a Metropolis-Hastings step. The numerical
evaluation relies on the SPIRE instrument of the Herschel observatory. Using
simulated and real observations, we show that the hyperparameters and
instrument parameters are correctly estimated, which opens up many perspectives
for imaging in astrophysics
Statistical Power, the Bispectrum and the Search for Non-Gaussianity in the CMB Anisotropy
We use simulated maps of the cosmic microwave background anisotropy to
quantify the ability of different statistical tests to discriminate between
Gaussian and non-Gaussian models. Despite the central limit theorem on large
angular scales, both the genus and extrema correlation are able to discriminate
between Gaussian models and a semi-analytic texture model selected as a
physically motivated non-Gaussian model. When run on the COBE 4-year CMB maps,
both tests prefer the Gaussian model. Although the bispectrum has comparable
statistical power when computed on the full sky, once a Galactic cut is imposed
on the data the bispectrum loses the ability to discriminate between models.
Off-diagonal elements of the bispectrum are comparable to the diagonal elements
for the non-Gaussian texture model and must be included to obtain maximum
statistical power.Comment: Accepted for publication in ApJ; 20 pages, 6 figures, uses AASTeX
v5.
Multi-scale morphology of the galaxy distribution
Many statistical methods have been proposed in the last years for analyzing
the spatial distribution of galaxies. Very few of them, however, can handle
properly the border effects of complex observational sample volumes. In this
paper, we first show how to calculate the Minkowski Functionals (MF) taking
into account these border effects. Then we present a multiscale extension of
the MF which gives us more information about how the galaxies are spatially
distributed. A range of examples using Gaussian random fields illustrate the
results. Finally we have applied the Multiscale Minkowski Functionals (MMF) to
the 2dF Galaxy Redshift Survey data. The MMF clearly indicates an evolution of
morphology with scale. We also compare the 2dF real catalog with mock catalogs
and found that Lambda-CDM simulations roughly fit the data, except at the
finest scale.Comment: 17 pages, 19 figures, accepted for publication in MNRA
Modelling soil water conent in a tomato field: proximal gamma ray spectroscopy and soil-crop system models
Proximal soil sensors are taking hold in the understanding of soil
hydrogeological processes involved in precision agriculture. In this context,
permanently installed gamma ray spectroscopy stations represent one of the best
space-time trade off methods at field scale. This study proved the feasibility
and reliability of soil water content monitoring through a seven-month
continuous acquisition of terrestrial gamma radiation in a tomato test field.
By employing a 1 L sodium iodide detector placed at a height of 2.25 m, we
investigated the gamma signal coming from an area having a ~25 m radius and
from a depth of approximately 30 cm. Experimental values, inferred after a
calibration measurement and corrected for the presence of biomass, were
corroborated with gravimetric data acquired under different soil moisture
conditions, giving an average absolute discrepancy of about 2%. A quantitative
comparison was carried out with data simulated by AquaCrop, CRITeRIA, and
IRRINET soil-crop system models. The different goodness of fit obtained in bare
soil condition and during the vegetated period highlighted that CRITeRIA showed
the best agreement with the experimental data over the entire data-taking
period while, in presence of the tomato crop, IRRINET provided the best
results.Comment: 18 pages, 9 Figures, 3 Table
Final Report of the DAUFIN project
DAUFIN = Data Assimulation within Unifying Framework for Improved river basiN modeling (EC 5th framework Project
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