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1.
R. Lacaze A. Morel B. Petersson J. Schröper 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):509-523
We present an investigation of the 2D attractive Hubbard model, considered as an effective model relevant to superconductivity
in strongly interacting electron systems. We use both hybrid Monte-Carlo simulations and existing hopping parameter expansions
to explore the low temperature domain. The increase of the static S-wave pair correlation with decreasing temperature, which depends weakly on the band filling in the explored temperature range,
is analyzed in terms of an expected Kosterlitz-Thouless superconducting transition. Using both our data and previously published
results, we show that the evidence for this transition is weak: If it exists, its temperature is very low. The number of unpaired
electrons remains nearly constant with temperature at fixed attractive potential strength. In contrast, the static magnetic
susceptibility decreases fast with temperature, and cannot be related only to pair formation. We introduce a method by which
the Padé approximants of the existing series for the susceptibility give sensible results down to rather low temperature region,
as shown by comparison with our numerical data.
Received: 30 October 1996 / Revised: 23 October 1997 / Accepted: 29 January 1998 相似文献
2.
For comprehension purpose, numerical computations are more and more used to simulate the propagation phenomena observed during experimental inspections. However, the good agreement between experimental and simulated data necessitates the use of accurate input data and thus a good characterization of the inspected material. Generally the input data are provided by experimental measurements and are consequently tainted with uncertainties. Thus, it becomes necessary to evaluate the impact of these uncertainties on the outputs of the numerical model. The aim of this study is to perform a probabilistic analysis of an ultrasonic inspection of an austenitic weld containing a manufactured defect based on advanced techniques such as polynomial chaos expansions and computation of sensitivity factors (Sobol, DGSM). The simulation of this configuration with the finite element code ATHENA2D was performed 6000 times with variations of the input parameters (the columnar grain orientation and the elastic constants of the material). The 6000 sets of input parameters were obtained from adapted statistical laws. The output parameters (the amplitude and the position of the defect echo) distributions were then analyzed and the 95% confidence intervals were determined. 相似文献
3.
We present a parton model interpretation of the predictions of quantum chromodynamics in the process e+e?→hadron + anything. We give thecomplete list of parameters needed for the study of the scaling violations of fragmentation functions up to the next-to-leading logarithmic approximation. This includes flavour non-singlet and flavour singlet anomalous dimensions up to order α2 and coefficient functions up to order α. We also present results for the deep inelastic scattering e?h→e? + anything. We find that in e+e? annihilation the ratio of scaling violations of second order to first order is in general bigger than the corresponding ratio for deep inelastic scattering. The Gribov-Lipatov relation is thus violated in second order. We also find that a modified Drell-Yan analytic continuation relation holds between the deep inelastic and annihilation structure functions for quarks and gluons. In x space we give detailed numerical evaluation of the QCD effects for non-singlet and singlet densities, in the space-like and time-like regions. 相似文献
4.
Lacaze E. Alba M. Goldmann M. Michel J. P. Rieutord F. 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,39(2):261-272
By combining X-ray diffraction under grazing incidence (GIXD) and scanning tunneling microscopy (STM) measurements, we have determined the structure of 4-n-octyl-4-cyanobiphenyl (8CB) molecules adsorbed on MoS2, under the thick organic film. The commensurability of the adsorbed network and the unit cell structure have been determined, revealing a complex 2D structure. This structure is characterized by straight ribbons with two types of ribbons, alternatively stacked. In one type, molecules are equally spaced, as they are paired in the other type. Considering the energetics of adsorption with a model of single ribbon, we recover the two observed ribbon structures. The alternate stacking of the ribbons appears as a consequence of the connection between the commensurabilities in the two main crystallographic directions. Moreover, we have found a particularly high value for the molecule-substrate potential corrugations, indicating that the dipole moment of 8CB molecules could play a fundamental role in the molecule-substrate interactions.Received: 1 April 2004, Published online: 29 June 2004PACS:
61.10.-i X-ray diffraction and scattering - 68.35.Bs Structure of clean surfaces (reconstruction) - 61.30.-v Liquid crystals - 68.35.Md Surface thermodynamics, surface energies 相似文献
5.
6.
Luís Santos Pascal Martin Jalal Ghilane Pierre-Camille Lacaze Hyacinthe Randriamahazaka Luisa Maria Abrantes Jean-Christophe Lacroix 《Electrochemistry communications》2010,12(7):872-875
The electrodeposition of poly(3,4-ethylenedioxythiophene) (PEDOT) films from aqueous surfactant solution through a two-dimensional poly(styrene) (PS) template onto indium tin oxide (ITO) substrate has been investigated. The polymer grows in the interstitial spaces of the self-assembled PS spheres which were subsequently removed by dissolution in tetrahydrofuran (THF). Surface characterization by scanning electron microscopy (SEM) and atomic force microscopy (AFM) reveals that two-dimensional nanoporous honeycomb PEDOT structures can easily be obtained by using PS spheres of different sizes. Gold electrodeposition onto the nanostructured PEDOT electrode was investigated and SEM images show preferential formation of nanoparticles (NP) on the wall and the rim of the PEDOT film but metal clusters inside the pores are also observed. 相似文献
7.
J. Lacaze 《Il Nuovo Cimento C》1978,1(5):389-394
Summary The establishment of the fundamental Sutton's formula is criticized; this formula is recovered by a more correct mathematical
reasoning, and generalized. Applications are only evoked.
Riassunto Si critica l'impostazione della formula fondamentale di Sutton; si ricupera questa formula con un ragionamento matematico più corretto e la si generalizza. Alle applicazioni si accenna solo.
Резюме Критикуется вывод фундаменталъной формулы Суттона. Эта формула выводится заново с помощъю более корректных математических аргументов. Обсуждаются применеия.相似文献
8.
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10.
J. Lacaze 《Il Nuovo Cimento C》1978,1(6):516-522
Résumé Les données expérimentales récentes montrent le r?le de la vitesse acquise dans la convection ascendante et la possibilité,
à échelle suffisante, de préférer des termes d'entra?nement ou de viscosité turbulente aux termes de diffusion. Dans un nuage
convectif en voie de croissance, l'entretien de la vitesse acquise provient en partie des condensations sommitales, sans effets
de convergence localisée. Les hypothèses de l'équilibre hydrostatique et de l'incompressibilité n'ont ici aucune valeur.
Pour accélérer la publication, l'auteur de cet article a agrée à ne pas recevoir les épreuves pour la correction. 相似文献
Summary Recent experimental data show the part of the acquired speed in the ascending convection and the possibility, at a sufficient scale, of preferring entrainment terms, or turbulent-viscosity terms, to diffusion terms. In a growing convective cloud, the supply of acquired speed proceeds partially from summit condensations, without localized convergence effects. The hypotheses of hydrostatic equilibrium and of incompressibility have no value here.
Riassunto Recenti dati sperimentali mostrano la parte della velocità acquistata nella convezione ascendente e la possibilità, a scala sufficiente, di preferire termini di trascinamento o termini di velocità turbolenta ai termini di diffusione. In una nuvola convettiva crescente, l'acquisizione di velocità acquisita procede in parte per condensazione in sommità senza effetti di convergenza localizzati. Le ipotesi di equilibrio idrostatico e di incompressibilità qui non valgono.
Pour accélérer la publication, l'auteur de cet article a agrée à ne pas recevoir les épreuves pour la correction. 相似文献