Effective time-independent description of optical lattices with periodic driving

For a periodically driven quantum system an effective time-independent Hamiltonian is derived with an eigen-energy spectrum, which in the regime of large driving frequencies approximates the quasi-energies of the corresponding Floquet Hamiltonian. The effective Hamiltonian is evaluated for the case of optical lattice models in the tight-binding regime subjected to strong periodic driving. Three scenarios are considered: a periodically shifted one-dimensional (1D) lattice, a two-dimensional (2D) square lattice with inversely phased temporal modulation of the well depths of adjacent lattice sites, and a 2D lattice subjected to an array of microscopic rotors commensurate with its plaquette structure. In case of the 1D scenario the rescaling of the tunneling energy, previously considered by Eckardt et al. in Phys. Rev. Lett. 95, 260404 (2005), is reproduced. The 2D lattice with well depth modulation turns out as a generalization of the 1D case. In the 2D case with staggered rotation, the expression previously found in the case of weak driving by Lim et al. in Phys. Rev. Lett. 100, 130402 (2008) is generalized, such that its interpretation in terms of an artificial staggered magnetic field can be extended into the regime of strong driving.Comment: 10 pages, 5 figure

Hierarchical Beamforming: Resource Allocation, Fairness and Flow Level Performance

We consider hierarchical beamforming in wireless networks. For a given population of flows, we propose computationally efficient algorithms for fair rate allocation including proportional fairness and max-min fairness. We next propose closed-form formulas for flow level performance, for both elastic (with either proportional fairness and max-min fairness) and streaming traffic. We further assess the performance of hierarchical beamforming using numerical experiments. Since the proposed solutions have low complexity compared to conventional beamforming, our work suggests that hierarchical beamforming is a promising candidate for the implementation of beamforming in future cellular networks.Comment: 34 page

Analyse qualitative des réponses épilinguistiques et métalinguistiques au test d’acceptabilité du THAM-3 par des étudiants italophones

ABSTRACT. Qualitative analysis of epilinguistic and metalinguistic answers to the THAM‐3 acceptability test by Italian‐speaking students. This article as two aims, methodological and descriptive. It analyses the grammatical and metalinguistic judgements of a group of italians learning French (19 adults) elicitated from the acceptability task of the THAM 3, a linguistic and metalinguistic tests conceived for native speakers. The goal is to show that some difficulties are due to the structure of these acceptabili ty tasks that influences langu

Relation Structure moléculaire - Odeur Utilisation des Réseaux de Neurones pour l’estimation de l’Odeur Balsamique

Les molécules odorantes (parfums ou flaveurs) sont utilisées dans une grande variété de produits de consommation, pour inciter les consommateurs à associer les impressions favorables à un produit donné. La Relation Structure moléculaire-Odeur (SOR) est cruciale pour la synthèse de ces molécules mais est très difficile à établir due à la subjectivité de l’odeur. Ce travail présente une approche de prédiction de l'odeur des molécules basée sur les descripteurs moléculaires. Les techniques d’analyse en composantes principales (PCA) et de d’analyse de colinéarité permettent d’identifier les descripteurs les plus pertinents. un réseau de neurones supervisé5 à deux couches (cachée et sortie) est employé pour corréler la structure moléculaire à l’odeur. La base de données décrite précédemment est utilisée pour l’apprentissage. Un ensemble de paramètres est modifié jusqu’à la satisfaction de la meilleure régression. Les résultats obtenus sont encouragent, ainsi les descripteurs moléculaires convenables corrèlent efficacement l'odeur des molécules. C’est la première étape d’un modèle générique en développement pour corréler l'odeur avec les structures moléculaire

An application of a cocitation-analysis method to find further research possibilities on the area of scheduling problems

In this article we will give firstly a classification scheme of scheduling problems and their solving methods. The main aspects under examination are the following: machine and secondary resources, constraints, objective functions, uncertainty, mathematical models and adapted solution methods. In a second part, based on this scheme, we will examine a corpus of 60 main articles (1015 citation links were recorded in total) in scheduling literature from 1977 to 2009. The main purpose is to discover the underlying themes within the literature and to examine how they have evolved. To identify documents likely to be closely related, we are going to use the cocitation-based method of Greene et al. (2008). Our aim is to build a base of articles in order to extract the much developed research themes and find the less examined ones as well, and then try to discuss the reasons of the poorly investigation of some areas

L'Expert-Comptable du comité d'entreprise, un acteur de gouvernance : Une étude exploratoire

L'expert-comptable auprès du comité d'entreprise est un terrain de recherche peu étudié par la littérature universitaire et qui présente pourtant un intérêt certain. Par son ordonnance de 1945 donnant naissance aux comités d'entreprise, le gouvernement provisoire d'après guerre démontre sa volonté d'instaurer un organe de dialogue social avec comme dessein « d'associer les travailleurs à la direction et à la gestion de l'entreprise. » Afin de répondre aux exigences imposées par cette fonction, et notamment, sa mission d'ordre économique, le comité d'entreprise dispose du droit de se faire assister par un expert-comptable. Ce processus hybride et complexe agrégeant liens formels et informels, met en interaction un certain nombre d'acteurs tant directement qu'indirectement (législateur et syndicat). Par ailleurs, le rôle et la mission de l'expert comptable auprès du comité d'entreprise se sont progressivement étoffés dépassant le simple audit comptable et financier. De ce fait et spécialement dans une vision partenariale, l'expert comptable peut-être considéré comme un outil de la gouvernance d'entreprise. Après avoir mobilisé les techniques de l'analyse textuelle sur un corpus de rapports rédigés par des experts-comptables du comité d'entreprise, nous noterons l'importance accordée aux données de gestion des ressources humaines qui semble aller dans le sens d'une gouvernance partenariale.Analyse textuelle; Comité d'entreprise; Expert-comptable; Gouvernance d'entreprise; Vision partenariale

Observation of Floquet-Bloch states on the surface of a topological insulator

The unique electronic properties of the surface electrons in a topological insulator are protected by time-reversal symmetry. Circularly polarized light naturally breaks time-reversal symmetry, which may lead to an exotic surface quantum Hall state. Using time- and angle-resolved photoemission spectroscopy, we show that an intense ultrashort mid-infrared pulse with energy below the bulk band gap hybridizes with the surface Dirac fermions of a topological insulator to form Floquet-Bloch bands. These photon dressed surface bands exhibit polarization-dependent band gaps at avoided crossings. Circularly polarized photons induce an additional gap at the Dirac point, which is a signature of broken time-reversal symmetry on the surface. These observations establish the Floquet-Bloch bands in solids and pave the way for optical manipulation of topological quantum states of matter.Comment: 23 pages including supplementary material

Resampling technique applied to the characterization of microsegregation

Characterization of short-range chemical heterogeneities in metallic materials, such as the so-called microsegregation resulting from solidification, is most often performed using EDS or WDS spot measurements. The most usual way is to perform countings on points located along a regular grid. Due to experimental limitation, the grid step is generally of the same order of magnitude than the characteristic distance(s) of the chemical heterogeneities under investigation. In such a case, the measurements can not be assumed to be independent one from each other, and the resulting interferences (correlations) preclude application of simple statistics to the solute distribution obtained. In the present work, this is clearly shown by using a resampling technique applied to "chemical" images obtained by phase field modelling