539 research outputs found
Adaptive Covariance Estimation with model selection
We provide in this paper a fully adaptive penalized procedure to select a
covariance among a collection of models observing i.i.d replications of the
process at fixed observation points. For this we generalize previous results of
Bigot and al. and propose to use a data driven penalty to obtain an oracle
inequality for the estimator. We prove that this method is an extension to the
matricial regression model of the work by Baraud
Two-to-one Auger decay of a double L vacancy in argon
We have observed L223−M3 Auger decay in argon where a double vacancy is filled
by two valence electrons and a single electron is ejected from the atom. A
well-resolved spectrum of these two-to-one electron transitions is compared to
the result of the second-order perturbation theory and its decay branching
ratio is determined
Subfemtosecond Control of Molecular Fragmentation by Hard X-Ray Photons
Tuning hard x-ray excitation energy along Cl 1s→σ∗ resonance in gaseous HCl
allows manipulating molecular fragmentation in the course of the induced
multistep ultrafast dissociation. The observations are supported by
theoretical modeling, which shows a strong interplay between the topology of
the potential energy curves, involved in the Auger cascades, and the so-called
core-hole clock, which determines the time spent by the system in the very
first step. The asymmetric profile of the fragmentation ratios reflects
different dynamics of nuclear wave packets dependent on the photon energy
Auger resonant-Raman decay after Xe L-edge photoexcitation
We have investigated resonant Auger decay of xenon following photoexcitation
of each of the three L edges under resonant-Raman conditions, which allowed us
to characterize several higher Rydberg transitions. Relative intensities for
spectator final states reached after L1−, L2−, and L3-edge excitations are
studied in detail. Thanks to state-of-the-art experimental arrangements, our
results not only reproduce the previously calculated 3d−25d and nd(n>5) state
cross sections after L3 excitation, but also allow extracting the 3d−26d
spectator state energy position and revealing its resonant behavior, blurred
by the insufficient experimental resolution in previous data sets. The 3d−26p
and 3d−27p states reached after L1 excitation as well as the 3d−25d and 3d−26d
states reached after L2 excitation are also investigated and their relative
intensities are reported and compared to ab initio Dirac-Hartree-Fock
configuration-interaction calculations. We found the signature of electronic-
state-lifetime interference effects between several coherently excited
intermediate states, due to large lifetime broadening. Electron recapture
processes are also identified above all three photoionization thresholds
Data fusion of ultrasound and GPR signals for analysis of historic walls
[EN] This paper presents an application of ultrasounds and ground-penetrating radar (GPR) for analysis of historic walls. The objectives are to characterize the deformation of a historic wall under different levels of load weights and to obtain an enhanced image of the wall. A new method that fuses data from ultrasound and GPR traces is proposed which is based on order statistics digital filters. Application results are presented for non destructive testing (NDT) of two replicates of historic ashlars' masonry walls: the first one homogeneous and the second one containing controlled defects such as cracks and nooks. The walls are measured separately using ultrasounds and GPR at different load steps. Time and frequency parameters extracted from the signals and different B-Scans for each of the NDT techniques are obtained. After this, a new fused representation is obtained, which results demonstrate the improvement of characterization and defect detection in historic walls using data fusion.This work has been supported by Generalitat Valenciana under grant PROMETEO/2010/040, and Spanish Administration and European Union FEDER Prog. under grant TEC2011-23403 01/01/2012.Salazar Afanador, A.; Gosálbez Castillo, J.; Safont Armero, G.; Vergara Domínguez, L. (2012). Data fusion of ultrasound and GPR signals for analysis of historic walls. IOP Conference Series: Materials Science and Engineering. 42:1-4. https://doi.org/10.1088/1757-899X/42/1/012008S144
Lithofacies uncertainty modeling in a siliciclastic reservoir setting by incorporating geological contacts and seismic information
Deterministic modeling lonely provides a unique boundary layout, depending on the geological interpretation or interpolation
from the hard available data. Changing the interpreter’s attitude or interpolation parameters leads to displacing the
location of these borders. In contrary, probabilistic modeling of geological domains such as lithofacies is a critical aspect
to providing information to take proper decision in the case of evaluation of oil reservoirs parameters, that is, applicable
for quantification of uncertainty along the boundaries. These stochastic modeling manifests itself dramatically beyond this
occasion. Conventional approaches of probabilistic modeling (object and pixel-based) mostly suffers from consideration
of contact knowledge on the simulated domains. Plurigaussian simulation algorithm, in contrast, allows reproducing the
complex transitions among the lithofacies domains and has found wide acceptance for modeling petroleum reservoirs.
Stationary assumption for this framework has implications on the homogeneous characterization of the lithofacies. In this
case, the proportion is assumed constant and the covariance function as a typical feature of spatial continuity depends only
on the Euclidean distances between two points. But, whenever there exists a heterogeneity phenomenon in the region, this
assumption does not urge model to generate the desired variability of the underlying proportion of facies over the domain.
Geophysical attributes as a secondary variable in this place, plays an important role for generation of the realistic contact
relationship between the simulated categories. In this paper, a hierarchical plurigaussian simulation approach is used to construct
multiple realizations of lithofacies by incorporating the acoustic impedance as soft data through an oil reservoir in Iran.This research was funded by the National Elites Foundation of Iran in collaboration with research Institute Petroleum of Industry in Iran under the project number of 9265005
Geostatistical modeling and spatial distribution analysis of porosity and permeability in the Shurijeh-B reservoir of Khangiran gas field in Iran
The main objectives of this study are analysis of spatial behavior of the porosity and permeability, presenting direction of anisotropy for each variable and describing variation of these parameters in Shurijeh B gas reservoir in Khangiran gas field. Porosity well log data of 32 wells are available for performing this geostatistical analysis. A univariate statistical analysis is done on both porosity and permeability to provide a framework for geostatistical analysis and modeling. For spatial analysis of these parameters, the experimental semivariogram of each variable in different direction as well as their variogram map plotted to find out the direction of anisotropy and their geostatistical parameters such as range, sill, and nugget effect for later geostatistical work and finally for geostatistical modeling, two approaches kriging and Sequential Gaussian Simulation are used to get porosity and permeability maps through the entire reservoir. All of statistical and geostatistical analysis has been done using GSLIB and PETREL software. Maximum and minimum direction of continuity are found to be N75W and N15E, respectively. Geostatistical parameters of calculated semivariogram in this direction like range of 7000 m and nugget of 0.2 are used for modeling. Both kriging and SGS method used for modeling but kriging tends to smooth out estimates but on the other hand SGS method tends to show up details. Cross-validation also used to validate the generated modeling
Detailed assignment of normal and resonant Auger spectra of Xe near the L edges
We present a comprehensive experimental and theoretical investigation on the LMM, LMN, and LNN normal Auger spectra of xenon, which reveal excellent agreement with theory when core-hole lifetimes of the two-hole final states are taken into account. Generally, the spectra turned out to be highly complex due to a strong overlap of the Auger transitions subsequent to 2s−11/2, 2p−11/2, and 2p−13/2 ionization. This overlap is due to the splitting of the three initial L core holes and the different final M and N core holes being on the same order of magnitude of several hundred eV. The Auger transitions are assigned in detail based on the theoretical results. Most of the MM, MN, and NN final states are described well based on jj coupling. In addition, we present a detailed assignment of the resonant LM45M45 Auger transition subsequent to the 2s→6p, 7p and 2p→5d, 6d excitations
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