Jurnal Edukasi
Not a member yet
4879 research outputs found
Sort by
Building Complete Training Maps for Indoor Location Estimation
No full textInternational audienceIndoor location estimation is a significant task for many ubiquitous and pervasive computing applications, with numerous solutions based on IEEE802.11, bluetooth, ultrasound and infrared technologies. Most of these techniques use the fingerprint-based approach, which needs exhaustive collection of the received signal strengths in various positions of the physical space. In the present work, we exploit the spatial correlation structure of the fingerprints and use the framework of Matrix Completion to build complete training maps from a small number of random sample fingerprints. The experimental evaluation with real data presents the localization accuracy based on complete reconstructed training maps, without making an exhaustive collection of fingerprints
Stochastic partial differential equations with singular terminal condition
No full textIn this paper, we first prove existence and uniqueness of the solution of a backward doubly stochastic differential equation (BDSDE) and of the related stochastic partial differential equation (SPDE) under monotonicity assumption on the generator. Then we study the case where the terminal data is singular, in the sense that it can be equal to +∞ on a set of positive measure. In this setting we show that there exists a minimal solution, both for the BDSDE and for the SPDE. Note that solution of the SPDE means weak solution in the Sobolev sense
Systematic Study of Azimuthal Anisotropy in CuCu and AuAu Collisions at and 200~GeV
No full text424 authors, 22 pages, 22 figures, 6 tables. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htmlInternational audienceWe have studied the dependence of azimuthal anisotropy for inclusive and identified charged hadrons in AuAu and CuCu collisions on collision energy, species, and centrality. The values of as a function of transverse momentum and centrality in AuAu collisions at =200~GeV and 62.4~GeV are the same within uncertainties. However, in CuCu collisions we observe a decrease in values as the collision energy is reduced from 200 to 62.4~GeV. The decrease is larger in the more peripheral collisions. By examining both AuAu and CuCu collisions we find that depends both on eccentricity and the number of participants, . We observe that divided by eccentricity () monotonically increases with and scales as . The CuCu data at 62.4 GeV falls below the other scaled data. For identified hadrons, divided by the number of constituent quarks is independent of hadron species as a function of transverse kinetic energy between $0.
Détection des tendances et la propagation des informations dans les réseaux sociaux dynamiques
No full textDuring the last decade, the information within Dynamic Social Networks has increased dramatically. The ability to study the interaction and communication between users in these networks can provide real time valuable prediction of the evolution of the information. The study of social networks has several research challenges, e.g. (a) real time search has to balance between quality, authority, relevance and timeliness of the content, (b) studying the information of the correlation between groups of users can reveal the influential ones, and predict media consumption, network and traffic resources, (c) detect spam and advertisements, since with the growth of social networks we also have a continuously growing amount of irrelevant information over the network. By extracting the relevant information from online social networks in real time, we can address these challenges. In this thesis a novel method to perform topic detection, classification and trend sensing in short texts is introduced. Instead of relying on words as most other existing methods which use bag-of-words or n-gram techniques, we introduce Joint Complexity, which is defined as the cardinality of a set of all distinct common factors, subsequences of characters, of two given strings. Each short sequence of text is decomposed in linear time into a memory efficient structure called Suffix Tree and by overlapping two trees, in linear or sublinear average time, we obtain the cardinality of factors that are common in both trees. The method has been extensively tested for Markov sources of any order for a finite alphabet and gave good approximation for text generation and language discrimination. The proposed method is language-agnostic since we can detect similarities between two texts in any loosely character-based language. It does not use semantics or based on a specific grammar, therefore there is no need to build any specific dictionary or stemming technique. The proposed method can be used to capture a change of topic within a conversation, as well as the style of a specific writer in a text. In the second part of the thesis, we take advantage of the nature of the data, which motivated us in a natural fashion to use of the theory of Compressive Sensing driven from the problem of target localization. Compressive Sensing states that signals which are sparse or compressible in a suitable transform basis can be recovered from a highly reduced number of incoherent random projections, in contrast to the traditional methods dominated by the well- established Nyquist-Shannon sampling theory. Based on the spatial nature of the data, we apply the theory of Compressive Sensing to perform topic classification by recovering an indicator vector, while reducing significantly the amount of information from tweets. The method works in conjunction with a Kalman filter to update the states of a dynamical system as a refinement step. In this thesis we exploit datasets collected by using the Twitter streaming API, gathering tweets in various languages and we obtain very promising results when comparing to state-of-the-art methods.Au cours de la dernière décennie, la dissémination de l'information au travers des réseaux sociaux a augmenté de façon spectaculaire. L'analyse des interactions entre les utilisateurs de ces réseaux donne la possibilité de la prédiction en temps réel de l'évolution de l'information. L'étude des réseaux sociaux présentent de nombreux défis scientifiques, comme par exemple : (a) peut on trouver un compromis entre la qualité, l'autorité, la pertinence et l'actualité du contenu ? (b) Peut on utiliser les interactions entre les groupes d'utilisateurs pour révéler les utilisateurs influents, pour prédire les pics de trafic ? (c) la publicité, les spams, et autres trafics non pertinent peuvent ils être détectés et écartés ? Dans cette thèse, nous proposons une nouvelle méthode pour effectuer la détections dans les textes courts des sujets et des tendances, et leur classification. Au lieu de découper les textes en mots ou en n-grames comme le font la plupart des autres méthodes qui utilisent des sac-de- mots, nous introduisons la Complexité Jointe, qui est définie comme le cardinal de l'ensemble des facteurs communs distincts entre les deux textes, un facteur étant une chaîne de caractères consécutifs. L'ensemble des facteurs d'un texte est décomposé en temps linéaire en une structure efficace de mémoire appelée arbre suffixe et on obtient par le superposition des deux arbres, en temps moyen sous-linéaire, la complexité jointe des deux textes. La méthode a été largement testée à grande échelle pour des sources de texte de Markov d'ordre fini et permet en effet une bonne discrimination des sources (langue, etc). La simulation de la production des textes par processus de Markov est une approximation satisfaisante de la génération de textes en langage naturel. La méthode de la complexité jointe est indépendante de la langue agnostique puisque nous pouvons détecter les similitudes entre deux textes sans avoir recours à l'analyse sémantique. Elle ne nécessite pas une analyse sémantique sur la base d'une grammaire spécifique, par conséquent, il ne est pas nécessaire de construire un dictionnaire spécifique. La méthode proposée peut aussi être utilisé pour détecter un changement de thème dans une conversation, ainsi qu'un changement de style d'un écrivain dans un texte. Dans la deuxième partie de la thèse, nous profitons de la faible densité de l'espace des données, ce qui nous a motivé de façon naturelle à appliquer la théorie de Compressive Sensing extrapolée du problème de la localisation des objets physiques. Le Compressive Sensing stipule que les signaux qui sont rares ou compressibles peuvent être récupérés à partir d'un nombre très réduit de projections aléatoires incohérentes dans une base appropriée, contrairement aux méthodes traditionnelles dominées par la théorie classique de Nyquist-Shannon de l'échantillonnage. Grâce à la faible densité spatiale des sujets, nous appliquons la théorie pour récupérer un vecteur d'indicateur, à partir de l'ensemble des tweets. Le procédé fonctionne en conjonction avec un filtre de Kalman pour mettre à jour des états d'un système dynamique comme étape de raffinement. Dans cette thèse, nous exploitons des ensembles de données recueillies en utilisant le flux de l'API de Twitter, sur des tweets collectés en plusieurs langues et nous obtenons des résultats très prometteurs lorsque l'on compare ces méthodes au meilleur de l'existant
Stratified turbulence forced with columnar dipoles: numerical study
No full textInternational audienceThis paper builds upon the investigation of Augier et al. (Phys. Fluids, vol. 26 (4), 2014) in which a strongly stratified turbulent-like flow was forced by 12 generators of vertical columnar dipoles. In experiments, measurements start to provide evidence of the existence of a strongly stratified inertial range that has been predicted for large turbulent buoyancy Reynolds numbers R t = ε K /(νN 2), where ε K is the mean dissipation rate of kinetic energy, ν the viscosity and N the Brunt–Väisälä frequency. However, because of experimental constraints, the buoyancy Reynolds number could not be increased to sufficiently large values so that the inertial strongly stratified turbulent range is only incipient. In order to extend the experimental results toward higher buoyancy Reynolds number, we have performed numerical simulations of forced stratified flows. To reproduce the experimental vortex generators, columnar dipoles are periodically produced in spatial space using impulsive horizontal body force at the peripheries of the computational domain. For moderate buoyancy Reynolds number, these numerical simulations are able to reproduce the results obtained in the experiments, validating this particular forcing. For higher buoyancy Reynolds number, the simulations show that the flow becomes turbulent as observed in Brethouwer et al. (J. Fluid Mech., vol. 585, 2007, pp. 343–368). However, the statistically stationary flow is horizontally inhomogeneous because the dipoles are destabilized quite rapidly after their generation. In order to produce horizontally homogeneous turbulence, high-resolution simulations at high buoyancy Reynolds number have been carried out with a slightly modified forcing in which dipoles are forced at random locations in the computational domain. The unidimensional horizontal spectra of kinetic and potential energies scale like C 1
Phoretic self-propulsion at large Péclet numbers
No full text7 pages, 2 figuresInternational audienceWe analyse the self-diffusiophoresis of a spherical particle animated by a nonuniform chemical reaction at its boundary. We consider two models of solute absorption, one with a specified distribution of interfacial solute flux, and one where this flux is governed by first-order kinetics with a specified distribution of rate constant. We employ a macroscale model where the short-range interaction of the solute with the particle boundary is represented by an effective slip condition. The solute transport is governed by an advection-diffusion equation. We focus upon the singular limit of large P\'eclet numbers, . In the fixed-flux model, the excess-solute concentration is confined to a narrow boundary layer. The scaling pertinent to that limit allows to decouple the problem governing the solute concentration from the flow field. The resulting nonlinear boundary-layer problem is handled using a transformation to stream-function coordinates and a subsequent application of Fourier transforms, and is thereby reduced to a nonlinear integral equation governing the interfacial concentration. Its solution provides the requisite approximation for the particle velocity, which scales as . In the fixed-rate model, large P\'eclet numbers may be realized in different limit processes. We consider the case of large swimmers or strong reaction, where the Damk\"ohler number is large as well, scaling as . In that double limit, where no boundary layer is formed, we obtain a closed-form approximation for the particle velocity, expressed as a nonlinear functional of the rate-constant distribution; this velocity scales as . Both the fixed-flux and fixed-rate asymptotic predictions agree with the numerical values provided by computational solutions of the nonlinear transport problem
Rainfall Patterns in the Southern Amazon: a chronological perspective (1970-2010).
No full textInternational audienceThe aim of this study is to characterize rainfall patterns in a vast transition zonebetween the Amazon and the Cerrado Biomes. The analysis is focused on annual and seasonaltendencies, mainly about the onset and offset of the rainy season, its length and shifts. Morethan 200 Rain Gauges (RGs) were analyzed in the study area using Pettitt’s and Mann-Kendall’s non-parametric tests allied to a Linear Regression Analysis over the period 1971–2010. The onset and offset dates of the rainy season and its duration are also identified for 89RGs. Pettitt’s test indicates ruptures in 16 % of the rainfall time series while Mann-Kendall’smonthly test indicates that 45%of the RGs had negative trends, mainly in the transition seasons(spring and austral autumn). Linear Regression Analysis indicates negative trends in 63 % ofthe time series concomitant to the rainy season onset and offset analysis, which confirmes adelay for the onset of the rainy season in 76 % of the RGs and a premature demise for 84 % oftheRGs. Identification of the tendencies for rainy season duration indicates that the rainy seasonhas become shorter at 88 % of the RGs. There were recurring patterns in the results displayingdrier conditions in RGs localized in deforested areas opposed to forested locations
Fiscal Devaluations in a Monetary Union and the Extensive Margin of Trade
No full textInternational audienc
Search for a pseudoscalar boson decaying into a Z boson and the 125 GeV Higgs boson in llbb final states
No full textSubmitted to Phys. Lett. B ; see paper for full list of authorsInternational audienceResults are reported on a search for decays of a pseudoscalar A boson into a Z boson and a light scalar h boson, where the Z boson decays into a pair of oppositely-charged electrons or muons, and the h boson decays into b anti-b. The search is based on data from proton-proton collisions at a center-of-mass energy sqrt(s)=8 TeV collected with the CMS detector, corresponding to an integrated luminosity of 19.7 inverse femtobarns. The h boson is assumed to be the recently discovered standard model-like Higgs boson with a mass of 125 GeV. With no evidence for signal, upper limits are obtained on the product of the production cross section and the branching fraction of the A boson in the Zh channel. Results are also interpreted in the context of two Higgs doublet models
Evidence for collective multi-particle correlations in pPb collisions
No full textsee paper for full list of authorsInternational audienceThe second-order azimuthal anisotropy Fourier harmonics, v2, are obtained in pPb and PbPb collisions over a wide pseudorapidity (eta) range based on correlations among six or more charged particles. The pPb data, corresponding to an integrated luminosity of 35 inverse nanobarns, were collected during the 2013 LHC pPb run at a nucleon-nucleon center-of-mass energy of 5.02 TeV by the CMS experiment. A sample of semi-peripheral PbPb collision data at sqrt(s[NN])= 2.76 TeV, corresponding to an integrated luminosity of 2.5 inverse microbarns and covering a similar range of particle multiplicities as the pPb data, is also analyzed for comparison. The six- and eight-particle cumulant and the Lee-Yang zeros methods are used to extract the v2 coefficients, extending previous studies of two- and four-particle correlations. For both the pPb and PbPb systems, the v2 values obtained with correlations among more than four particles are consistent with previously published four-particle results. These data support the interpretation of a collective origin for the previously observed long-range (large Delta[eta]) correlations in both systems. The ratios of v2 values corresponding to correlations including different numbers of particles are compared to theoretical predictions that assume a hydrodynamic behavior of a pPb system dominated by fluctuations in the positions of participant nucleons. These results provide new insights into the multi-particle dynamics of collision systems with a very small overlapping region