Search results for "rection"
showing 10 items of 965 documents
A method for the surface reflectance retrieval from PROBA/CHRIS data over land: application to ESA SPARC campaigns
2005
The Compact High Resolution Imaging Spectrometer (CHRIS) onboard the Project for On-Board Autonomy (PROBA) platform system provides the first high spatial resolution hyper-spectral/multiangular remote sensing data from a satellite system, what represents a new source of information for Earth Observation purposes. A fully consistent radiative transfer approach is always preferred when dealing with the retrieval of surface reflectance from hyperspectral/multiangular data. However, due to the reported calibration anomalies for CHRIS data, a direct atmospheric correction based on physical radiative transfer modeling is not possible, and the method must somehow compensate for such calibration pr…
Hölder stability for Serrin’s overdetermined problem
2015
In a bounded domain \(\varOmega \), we consider a positive solution of the problem \(\Delta u+f(u)=0\) in \(\varOmega \), \(u=0\) on \(\partial \varOmega \), where \(f:\mathbb {R}\rightarrow \mathbb {R}\) is a locally Lipschitz continuous function. Under sufficient conditions on \(\varOmega \) (for instance, if \(\varOmega \) is convex), we show that \(\partial \varOmega \) is contained in a spherical annulus of radii \(r_i 0\) and \(\tau \in (0,1]\). Here, \([u_\nu ]_{\partial \varOmega }\) is the Lipschitz seminorm on \(\partial \varOmega \) of the normal derivative of u. This result improves to Holder stability the logarithmic estimate obtained in Aftalion et al. (Adv Differ Equ 4:907–93…
A new force field including charge directionality for TMAO in aqueous solution
2016
We propose a new force field for trimethylamine N-oxide (TMAO), which is designed to reproduce the long-lived and highly directional hydrogen bond between the TMAO oxygen (OTMAO) atom and surrounding water molecules. Based on the data obtained by ab initio molecular dynamics simulations, we introduce three dummy sites around OTMAO to mimic the OTMAO lone pairs and we migrate the negative charge on the OTMAO to the dummy sites. The force field model developed here improves both structural and dynamical properties of aqueous TMAO solutions. Moreover, it reproduces the experimentally observed dependence of viscosity upon increasing TMAO concentration quantitatively. The simple procedure of the…
New Proposal on the Symbology of the Protohistoric Tray of El Gandul (Alcalá de Guadaira, Seville)
2018
En el presente artículo se realiza una nueva propuesta acerca del universo simbólico reflejado en la bandeja de bronce de El Gandul (Alcalá de Guadaíra, Sevilla). En primer lugar se presenta la pieza prestando atención a sus características formales y cronológicas. En un segundo apartado se realiza un resumen historiográfico de las anteriores hipótesis publicadas sobre parte o la totalidad de la simbología de la fuente. Tras dicho repaso se procede a describir la nueva propuesta, basada en el reflejo del mitema que tiene por objeto el empleo de una planta con propiedades en ocasiones rejuvenecedoras, en otras inmortales, como medio para alcanzar una vida eterna y/o revigorizada. Dicho mitem…
Refitting Solutions Promoted by $$\ell _{12}$$ Sparse Analysis Regularizations with Block Penalties
2019
International audience; In inverse problems, the use of an l(12) analysis regularizer induces a bias in the estimated solution. We propose a general refitting framework for removing this artifact while keeping information of interest contained in the biased solution. This is done through the use of refitting block penalties that only act on the co-support of the estimation. Based on an analysis of related works in the literature, we propose a new penalty that is well suited for refitting purposes. We also present an efficient algorithmic method to obtain the refitted solution along with the original (biased) solution for any convex refitting block penalty. Experiments illustrate the good be…
Volumetric Bias Correction
2007
This paper presents a method to suppress the bias artifact, also known as RF-inhomogeneity, in Magnetic Resonance Imaging (MRI). This artifact produces illumination variations due to magnetic field fluctuations of the device. In the latest years many works have been devoted to face this problem. In this work we present the 3D version of a new approach to bias correction, which is called Exponential Entropy Driven Homomorphic Unsharp Masking (E2D-HUM). This technique has been already presented by some of the authors for the 2D case only. The description of the whole method is detailed, and some experimental results are reported.
Search for patterns by combining cosmic-ray energy and arrival directions at the Pierre Auger Observatory
2015
Energy-dependent patterns in the arrival directions of cosmic rays are searched for using data of the Pierre Auger Observatory. We investigate local regions around the highest-energy cosmic rays with E ≥ 6×1019 eV by analyzing cosmic rays with energies above E ≥ 5×1018 eV arriving within an angular separation of approximately 15∘. We characterize the energy distributions inside these regions by two independent methods, one searching for angular dependence of energy-energy correlations and one searching for collimation of energy along the local system of principal axes of the energy distribution. No significant patterns are found with this analysis. The comparison of these measurements with …
Techniques for measuring aerosol attenuation using the Central Laser Facility at the Pierre Auger Observatory
2013
The Pierre Auger Observatory in Malargue, Argentina, is designed to study the properties of ultra-high energy cosmic rays with energies above 10(18) eV. It is a hybrid facility that employs a Fluorescence Detector to perform nearly calorimetric measurements of Extensive Air Shower energies. To obtain reliable calorimetric information from the FD, the atmospheric conditions at the observatory need to be continuously monitored during data acquisition. In particular, light attenuation due to aerosols is an important atmospheric correction. The aerosol concentration is highly variable, so that the aerosol attenuation needs to be evaluated hourly. We use light from the Central Laser Facility, lo…
Canopy directional emissivity: Comparison between models
2005
Land surface temperature plays an important role in many environmental studies, as for example the estimation of heat fluxes and evapotranspiration. In order to obtain accurate values of land surface temperature, atmospheric, emissivity and angular effects should be corrected. This paper focuses on the analysis of the angular variation of canopy emissivity, which is an important variable that has to be known to correct surface radiances and obtain surface temperatures. Emissivity is also involved in the atmospheric corrections since it appears in the reflected downwelling atmospheric term. For this purpose, five different methods for simulating directional canopy emissivity have been analyz…
Estimation of atmospheric water vapour content from direct measurements of radiance in the thermal infrared region
2012
Atmospheric water vapour content is a required parameter in thermal infrared (TIR) to carry out processes such as atmospheric correction or retrieving atmospheric factors (downwelling or upwelling irradiance, transmittance of the atmosphere and so on). This study proposes an alternative method to the ones already in use to measure water vapour content from direct measurements of downwelling atmospheric radiance in the TIR range. It was possible to estimate a linear relationship between atmospheric water vapour and downwelling atmospheric radiance using a simulated study, based on data from a radiosounding database. A subsequent validation concludes that it is possible to obtain water vapour…