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Search Results: 1 - 10 of 401229 matches for " M. Fallot "
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Aerul ?i Apa : Componente ale Mediului , 2012,
Abstract: Efficiency of gumbel analyses for determining extreme daily precipitation in Switzerland. Gumbel analyses were carried out on rainfall time-series at 151 locations in Switzerland for 4 different periods of 30 years in order to estimate daily extreme precipitation for a return period of 100 years. Those estimations were compared with maximal daily values measured during the last 100 years (1911-2010) to test the efficiency of these analyses. This comparison shows that these analyses provide good results for 50 to 60% locations in this country from rainfall time-series 1961-1990 and 1980-2010. On the other hand, daily precipitation with a return period of 100 years is underestimated at most locations from time-series 1931-1960 and especially 1911-1940. Such underestimation results from the increase of maximal daily precipitation recorded from 1911 to 2010 at 90% locations in Switzerland.
R. Receanu,J.-A. Hertig,J.-M. Fallot
Aerul ?i Apa : Componente ale Mediului , 2012,
Abstract: This paper presents a very fine grid hydrological model based on the spatiotemporal repartition of precipitation and on the topography. The goal is to estimate the flood on a catchment area, using a Probable Maximum Precipitation (PMP) leading to a Probable Maximum Flood (PMF). The spatiotemporal distribution of the precipitation was realized using six clouds modeled by the advection-diffusion equation. The equation shows the movement of the clouds over the terrain and also gives the evolution of the rain intensity in time. This hydrological modeling is followed by a hydraulic modeling of the surface and subterranean flows, done considering the factors that contribute to the hydrological cycle, such as the infiltration, the exfiltration and the snowmelt. This model was applied to several Swiss basins using measured rain, with results showing a good correlation between the simulated and observed flows. This good correlation proves that the model is valid and gives us the confidence that the results can be extrapolated to phenomena of extreme rainfall of PMP type. In this article we present some results obtained using a PMP rainfall and the developed model.
Microscopic calculations of double and triple Giant Resonance excitation in heavy ion collisions
E. G. Lanza,F. Catara,M. V. Andres,Ph. Chomaz,M. Fallot,J. A. Scarpaci
Physics , 2006, DOI: 10.1103/PhysRevC.74.064614
Abstract: We perform microscopic calculations of the inelastic cross sections for the double and triple excitation of giant resonances induced by heavy ion probes within a semicalssical coupled channels formalism. The channels are defined as eigenstates of a bosonic quartic Hamiltonian constructed in terms of collective RPA phonons. Therefore, they are superpositions of several multiphonon states, also with different numbers of phonons and the spectrum is anharmonic. The inclusion of (n+1) phonon configurations affects the states whose main component is a n-phonon one and leads to an appreacible lowering of their energies. We check the effects of such further anharmonicities on the previous published results for the cross section for the double excitation of Giant Resonances. We find that the only effect is a shift of the peaks towards lower energies, the double GR cross section being not modified by the explicity inclusion of the three-phonon channels in the dynamical calculations. The latters give an important contribution to the cross section in the triple GR energy region which however is still smaller than the experimental available data. The inclusion of four phonon configurations in the structure calculations does not modify the results.
Microscopic description of Coulomb and nuclear excitation of multiphonon states in $^{40}$Ca + $^{40}$Ca collisions
M. V. Andres,F. Catara,E. G. Lanza,Ph. Chomaz,M. Fallot,J. A. Scarpaci
Physics , 2001, DOI: 10.1103/PhysRevC.65.014608
Abstract: We calculate the inelastic scattering cross sections to populate one- and two-phonon states in heavy ion collisions with both Coulomb and nuclear excitations. Starting from a microscopic approach based on RPA, we go beyond it in order to treat anharmonicities and non-linear terms in the exciting field. These anharmonicities and non-linearities are shown to have important effects on the cross sections both in the low energy part of the spectrum and in the energy region of the Double Giant Quadrupole Resonance. By properly introducing an optical potential the inelastic cross section is calculated semiclassically by integrating the excitation probability over all impact parameters. A satisfactory agreement with the experimental results is obtained.
Anharmonic vibrations in nuclei
M. Fallot,Ph. Chomaz,M. V. Andres,F. Catara,E. G. Lanza,J. A Scarpaci
Physics , 2001, DOI: 10.1016/j.nuclphysa.2003.10.001
Abstract: In this letter, we show that the non-linearitites of large amplitude motions in atomic nuclei induce giant quadrupole and monopole vibrations. As a consequence, the main source of anharmonicity is the coupling with configurations including one of these two giant resonances on top of any state. Two-phonon energies are often lowered by one or two MeV because of the large matrix elements with such three phonon configurations. These effects are studied in two nuclei, 40Ca and 208Pb.
Coulomb versus nuclear break-up of 11Be halo nucleus in a non perturbative framework
M. Fallot,J. A. Scarpaci,D. Lacroix,Ph. Chomaz,J. Margueron
Physics , 2001, DOI: 10.1016/S0375-9474(01)01303-3
Abstract: The 11Be break-up is calculated using a non perturbative time-dependent quantum calculation. The evolution of the neutron halo wave function shows an emission of neutron at large angles for grazing impact parameters and at forward angles for large impact parameters. The neutron angular distribution is deduced for the different targets and compared to experimental data. We emphasize the diversity of diffraction mechanisms, in particular we discuss the interplay of the nuclear effects such as the towing mode and the Coulomb break-up. A good agreement is found with experimental data.
Reactor Simulation for Antineutrino Experiments using DRAGON and MURE
C. L. Jones,A. Bernstein,J. M. Conrad,Z. Djurcic,M. Fallot,L. Giot,G. Keefer,A. Onillon,L. Winslow
Physics , 2011, DOI: 10.1103/PhysRevD.86.012001
Abstract: Rising interest in nuclear reactors as a source of antineutrinos for experiments motivates validated, fast, and accessible simulations to predict reactor fission rates. Here we present results from the DRAGON and MURE simulation codes and compare them to other industry standards for reactor core modeling. We use published data from the Takahama-3 reactor to evaluate the quality of these simulations against the independently measured fuel isotopic composition. The propagation of the uncertainty in the reactor operating parameters to the resulting antineutrino flux predictions is also discussed.
Improved Predictions of Reactor Antineutrino Spectra
Th. A. Mueller,D. Lhuillier,M. Fallot,A. Letourneau,S. Cormon,M. Fechner,L. Giot,T. Lasserre,J. Martino,G. Mention,A. Porta,F. Yermia
Physics , 2011, DOI: 10.1103/PhysRevC.83.054615
Abstract: We report new calculations of reactor antineutrino spectra including the latest information from nuclear databases and a detailed error budget. The first part of this work is the so-called ab initio approach where the total antineutrino spectrum is built from the sum of all beta-branches of all fission products predicted by an evolution code. Systematic effects and missing information in nuclear databases lead to final relative uncertainties in the 10 to 20% range. A prediction of the antineutrino spectrum associated with the fission of 238U is given based on this ab initio method. For the dominant isotopes 235U and 239Pu, we developed a more accurate approach combining information from nuclear databases and reference electron spectra associated with the fission of 235U, 239Pu and 241Pu, measured at ILL in the 80's. We show how the anchor point of the measured total beta-spectra can be used to suppress the uncertainty in nuclear databases while taking advantage of all the information they contain. We provide new reference antineutrino spectra for 235U, 239Pu and 241Pu isotopes in the 2-8 MeV range. While the shapes of the spectra and their uncertainties are comparable to that of the previous analysis of the ILL data, the normalization is shifted by about +3% on average. In the perspective of the re-analysis of past experiments and direct use of these results by upcoming oscillation experiments, we discuss the various sources of errors and their correlations as well as the corrections induced by off equilibrium effects.
New antineutrino energy spectra predictions from the summation of beta decay branches of the fission products
M. Fallot,S. Cormon,M. Estienne,A. Algora,V. M. Bui,A. Cucoanes,M. Elnimr,L. Giot,D. Jordan,J. Martino,A. Onillon,A. Porta,G. Pronost,A. Remoto,J. L. Taín,F. Yermia,A. -A. Zakari-Issoufou
Physics , 2012, DOI: 10.1103/PhysRevLett.109.202504
Abstract: In this paper, we study the impact of the inclusion of the recently measured beta decay properties of the $^{102;104;105;106;107}$Tc, $^{105}$Mo, and $^{101}$Nb nuclei in an updated calculation of the antineutrino energy spectra of the four fissible isotopes $^{235, 238}$U, and $^{239,241}$Pu. These actinides are the main contributors to the fission processes in Pressurized Water Reactors. The beta feeding probabilities of the above-mentioned Tc, Mo and Nb isotopes have been found to play a major role in the $\gamma$ component of the decay heat of $^{239}$Pu, solving a large part of the $\gamma$ discrepancy in the 4 to 3000\,s range. They have been measured using the Total Absorption Technique (TAS), avoiding the Pandemonium effect. The calculations are performed using the information available nowadays in the nuclear databases, summing all the contributions of the beta decay branches of the fission products. Our results provide a new prediction of the antineutrino energy spectra of $^{235}$U, $^{239,241}$Pu and in particular of $^{238}$U for which no measurement has been published yet. We conclude that new TAS measurements are mandatory to improve the reliability of the predicted spectra.
Nuclear break-up of 11Be
V. Lima,J. A. Scarpaci,D. Lacroix,Y. Blumenfeld,C. Bourgeois,M. Chabot,Ph. Chomaz,P. Desesquelles,V. Duflot,J. Duprat,M. Fallot,N. Frascaria,S. Grevy,D. Guillemaud-Mueller,P. Roussel-Chomaz,H. Savajols,O. Sorlin
Physics , 2007, DOI: 10.1016/j.nuclphysa.2007.07.005
Abstract: The break-up of 11Be was studied at 41AMeV using a secondary beam of 11Be from the GANIL facility on a 48Ti target by measuring correlations between the 10Be core, the emitted neutrons and gamma rays. The nuclear break-up leading to the emission of a neutron at large angle in the laboratory frame is identified with the towing mode through its characteristic n-fragment correlation. The experimental spectra are compared with a model where the time dependent Schrodinger equation (TDSE) is solved for the neutron initially in the 11 Be. A good agreement is found between experiment and theory for the shapes of neutron experimental energies and angular distributions. The spectroscopic factor of the 2s orbital is tentatively extracted to be 0.46+-0.15. The neutron emission from the 1p and 1d orbitals is also studied.
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