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Search Results: 1 - 10 of 198249 matches for " N. Pillet "
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El espacio geográfico y el estudio del espacio humanizado en la sociedad global
Pillet Capdepón, Félix
Estudios Geográficos , 2003,
Abstract: In this paper the various references of the aims of study of geography are put in relation with the paradigms. Also the key topics of the humanized space are analysed: the interface man-nature; then the town-country connection, the industrial service predominance and lastly the global versus local reference. [es] Se pone en relación las distintas acepciones del objeto de estudio de la geografía con los paradigmas, para a continuación analizar los temas-clave del espacio humanizado: la relación hombre-naturaleza; la conexión urbano-rural, el predominio servo-industrial y la referencia global-local. [fr] L′espace géographique et l′étude de l′espace humanisé dans la société globale. Dans cet article nous mettons en relation les différentes acceptions de l'objet d'étude de la géographie avec ses paradigmes. Ensuite, nous faisons une analyse des termes-clés de l'espace humanisé, c'est-à-dire, le rapport entre l'homme et son environnement, la conexión urbano- rurale, la prédominance du secteur servo-industriel et la référence globale-locale.
Generic strong coupling behavior of Cooper pairs in the surface of superfluid nuclei
N. Pillet,N. Sandulescu,P. Schuck
Physics , 2007, DOI: 10.1103/PhysRevC.76.024310
Abstract: With realistic HFB calculations, using the D1S Gogny force, we reveal a generic behavior of concentration of small sized Cooper pairs (2-3 fm) in the surface of superfluid nuclei. This study confirms and extends previous results given in the literature that use more schematic approaches.
Cooper pair sizes in superfluid nuclei in a simplified model
X. Vinas,P. Schuck,N. Pillet
Physics , 2010, DOI: 10.1103/PhysRevC.82.034314
Abstract: Cooper pair sizes are evaluated in a simple harmonic oscillator model reproducing the values of sophisticated HFB calculations. Underlying reasons for the very small sizes of 2.0-2.5 fm of Cooper pairs in the surface of nuclei are analysed. It is shown that the confining properties of the nuclear volume is the dominating effect. It is argued that for Cooper pair sizes LDA is particularly inadapted.
Variational multiparticle-multihole configuration mixing method applied to pairing correlations in nuclei
N. Pillet,J. -F. Berger,E. Caurier
Physics , 2008, DOI: 10.1103/PhysRevC.78.024305
Abstract: Applying a variational multiparticle-multihole configuration mixing method whose purpose is to include correlations beyond the mean field in a unified way without particle number and Pauli principle violations, we investigate pairing-like correlations in the ground states of $ ^{116}$Sn,$ ^{106}$Sn and $ ^{100}$Sn. The same effective nucleon-nucleon interaction namely, the D1S parameterization of the Gogny force is used to derive both the mean field and correlation components of nuclear wave functions. Calculations are performed using an axially symetric representation. The structure of correlated wave functions, their convergence with respect to the number of particle-hole excitations and the influence of correlations on single-particle level spectra and occupation probabilities are analyzed and compared with results obtained with the same two-body effective interaction from BCS, Hartree-Fock-Bogoliubov and particle number projected after variation BCS approaches. Calculations of nuclear radii and the first theoretical excited $0^+$ states are compared with experimental data.
Two-particle spatial correlations in superfluid nuclei
N. Pillet,N. Sandulescu,P. Schuck,J. -F. Berger
Physics , 2010, DOI: 10.1103/PhysRevC.81.034307
Abstract: We discuss the effect of pairing on two-neutron space correlations in deformed nuclei. The spatial correlations are described by the pairing tensor in coordinate space calculated in the HFB approach. The calculations are done using the D1S Gogny force. We show that the pairing tensor has a rather small extension in the relative coordinate, a feature observed earlier in spherical nuclei. It is pointed out that in deformed nuclei the coherence length corresponding to the pairing tensor has a pattern similar to what we have found previously in spherical nuclei, i.e., it is maximal in the interior of the nucleus and then it is decreasing rather fast in the surface region where it reaches a minimal value of about 2 fm. This minimal value of the coherence length in the surface is essentially determined by the finite size properties of single-particle states in the vicinity of the chemical potential and has little to do with enhanced pairing correlations in the nuclear surface. It is shown that in nuclei the coherence length is not a good indicator of the intensity of pairing correlations. This feature is contrasted with the situation in infinite matter.
Stormwater Storage Pond Configuration for Hydropower Solutions: Adaptation and Optimization
Helena M Ramos,Kaloyan N. Kenov,Baptiste Pillet
Journal of Sustainable Development , 2012, DOI: 10.5539/jsd.v5n8p27
Abstract: The purpose of this paper is to analyze different storage pond configurations used to manage the water inflow from storm events and to establish a methodology to optimize the energy production using this water. The case study area is a catchment based on the Alcantara zone, in Lisbon, Portugal. This is an urban area, which faces severe occurrences of storm events. These events are caused by a non-efficient drainage system, and the proximity of the river and the sea, which cannot handle large storm event inflows. Due to climate change effects, the storm rainfall hyetographs are modified and runoff in this urban area has increased for the last decades causing major inundations. The Danish Hydraulic Institute (DHI) MIKE BASIN (MB) and Bentley PondPack software are used to define solutions for this case study by embodying some of the Alcantara’s catchment characteristics. Different relevant components used to create the models are presented. In order to model completely the studied area, several physical elements such as reservoirs or hydropower plants are included. The Nedb r-Afstr mnings-Model (NAM model) is also presented. It is a rainfall-runoff simulator, included in DHI MB, which can create runoff time series from rainfall time series. The methodologies used to optimize energy production in each of case studies developed are detailed. Results are presented showing that some ponds configurations permit to produce more energy than others and the production of energy can be maximized by optimizing the hydropower production target demand.
Star clusters dynamics in a laboratory: electrons in an ultracold plasma
D. Comparat,T. Vogt,N. Zahzam,M. Mudrich,P. Pillet
Physics , 2005, DOI: 10.1111/j.1365-2966.2005.09245.x
Abstract: Electrons in a spherical ultracold quasineutral plasma at temperature in the Kelvin range can be created by laser excitation of an ultra-cold laser cooled atomic cloud. The dynamical behavior of the electrons is similar to the one described by conventional models of stars clusters dynamics. The single mass component, the spherical symmetry and no stars evolution are here accurate assumptions. The analog of binary stars formations in the cluster case is three-body recombination in Rydberg atoms in the plasma case with the same Heggie's law: soft binaries get softer and hard binaries get harder. We demonstrate that the evolution of such an ultracold plasma is dominated by Fokker-Planck kinetics equations formally identical to the ones controlling the evolution of a stars cluster. The Virial theorem leads to a link between the plasma temperature and the ions and electrons numbers. The Fokker-Planck equation is approximate using gaseous and fluid models. We found that the electrons are in a Kramers-Michie-King's type quasi-equilibrium distribution as stars in clusters. Knowing the electron distribution and using forced fast electron extraction we are able to determine the plasma temperature knowing the trapping potential depth.
Convergence of Particle-Hole Expansions for the Description of Nuclear Correlations
N. Pillet,N. Sandulescu,Nguyen Van Giai,J-F Berger
Physics , 2004, DOI: 10.1103/PhysRevC.71.044306
Abstract: The convergence properties of a multiparticle-multihole (mp-mh) configuration mixing approach whose purpose is to describe ground state correlations in nuclei without particle number and Pauli violations is investigated in the case of an exactly solvable pairing hamiltonian. Two different truncation schemes are tested by looking at quantities as correlation energies and single-particle occupation probabilities. Results show that pairing correlations present in usual superfluid nuclei can be accurately described using up to 6 particle-6 hole excitations, a convergence fast enought for envisaging extensions to fully microscopic calculations.
Low-lying spectroscopy of a few even-even silicon isotopes investigated by means of the multiparticle-multihole Gogny energy density functional
N. Pillet,V. G. Zelevinsky,M. Dupuis,J. -F. Berger,J. -M. Daugas
Physics , 2011, DOI: 10.1103/PhysRevC.85.044315
Abstract: A multiconfiguration microscopic method has been applied with the Gogny effective interaction to the calculation of low-lying positive-parity states in even-even $^{26-28}$Si isotopes. The aim of the study is to compare the results of this approach with those of a standard method of GCM type and to get insight into the predictive power of multiconfiguration methods employed with effective nucleon-nucleon force taylored to mean-field calculations. It is found that the multiconfiguration approach leads to an excellent description of the low-lying spectroscopy of $^{26}$Si, $^{28}$Si and $^{32}$Si, but gives a systematic energy shift in $^{30}$Si. A careful analysis of this phenomenon shows that this discrepancy originates from too large matrix elements in the proton-neutron residual interaction supplied by the Gogny interaction. Finally, a statistical analysis of highly excited configurations in $^{28}$Si is performed, revealing exponential convergence in agreement with previous work in the context of the shell model approach. This latter result provides strong arguments towards an implicit treatment of highly excited configurations.
Description of nuclear systems with a self-consistent configuration mixing approach. I: Theory and Algorithm - Application to the $^{12}$C test nucleus
C. Robin,N. Pillet,D. Pe?a Arteaga,J. -F. Berger
Physics , 2015,
Abstract: Although self-consistent multi-configuration methods have been used for decades to address the description of atomic and molecular many-body systems, only a few trials have been made in the context of nuclear structure. This work aims at the development of such an approach to describe in a unified way various types of correlations in nuclei, in a self-consistent manner where the mean-field is improved as correlations are introduced. The goal is to reconcile the usually set apart Shell-Model and Self-Consistent Mean-Field methods. This approach is referred as "variational multiparticle-multihole configuration mixing method". It is based on a double variational principle which yields a set of two coupled equations that determine at the same time the expansion coefficients of the many-body wave function and the single particle states. The formalism is derived and discussed in a general context, starting from a three-body Hamiltonian. Links to existing many-body techniques such as the formalism of Green's functions are established. First applications are done using the two-body D1S Gogny effective force. The numerical procedure is tested on the $^{12}$C nucleus in order to study the convergence features of the algorithm in different contexts. Ground state properties as well as single-particle quantities are analyzed, and the description of the first $2^+$ state is examined. This study allows to validate our numerical algorithm and leads to encouraging results. In order to test the method further, we will realize in the second article of this serie, a systematic description of more nuclei and observables obtained by applying the newly-developed numerical procedure with the same Gogny force. As raised in the present work, applications of the variational multiparticle-multihole configuration mixing method will however ultimately require the use of an extended and more constrained Gogny force.
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