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Search Results: 1 - 10 of 15686 matches for " Pierre-Olivier Montiglio "
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Building an ecological knowledge of virtual worlds
Pierre-Olivier Montiglio,Julien Céré
PeerJ , 2015, DOI: 10.7287/peerj.preprints.473v1
Abstract: Virtual worlds supporting massively multiplayer games have become so complex that they exhibit temporal and spatial dynamics mostly driven by interactions between players. In this respect, virtual worlds resemble closely natural ecosystems. Studying the ecology of virtual worlds is an outstanding opportunity for ecologists as well as the game industry to collaborate in order to test several aspects of ecological theory difficult to study in nature, and build manageable, resilient virtual worlds.
Naissance de la bestialité. Une anthropologie du rapport homme-animal dans les années 1300
Pierre-Olivier Dittmar
Atelier du Centre de Recherches Historiques , 2011, DOI: 10.4000/acrh.3958
Abstract: Composition du juryMonsieur Jér me Baschet,Monsieur Philippe Descola,Monsieur Michel Pastoureau,Monsieur Jean-Claude Schmitt (dir.),Madame Claudine Vassas,Monsieur Jean-Jacques Vincensini.Thèse soutenue à l’INHA, Salle Walter Benjamin, le 29 juin 2010RésuméLe rapport à l’animal dans le contexte chrétien est paradoxal. Alors qu’il se trouve pour la première fois totalement exclu du sacré légitime (abandon du sacrifice antique, des interdits alimentaires juifs), l’animal est extrêmement présent...
Deux comparatismes pour une anthropologie historique
Pierre-Olivier Dittmar
Atelier du Centre de Recherches Historiques , 2010, DOI: 10.4000/acrh.1956
Abstract: Malgré des appels répétés depuis plus d’un siècle de la part des historiens, le comparatisme, qui est un élément majeur de l’anthropologie, demeure très peu pratiqué. Ce rejet est ici analysé comme un refus d’une quête des invariants de l’homme qui aboutirait à des résultats an-historiques. Un autre comparatisme est cependant possible, qui instrumentalise la confrontation des univers pour mieux relever les différences. C’est les conditions et les avantages d’une telle pratique qui sont ici exposés, à partir de l’exemple des tabous alimentaires. Despite the repeated calls by some historians for more than a century, many seldom practice a major element of anthropology: comparativism. This paper will analyze this rejection as a refusal to investigate the constants of the human experience that lead to a-historical conclusions. However, another kind of comparativism is possible, one that examines the contrast between cultures in order to better understand their differences. Using the case of dietary taboos, this paper will look at the conditions and advantages of such a practice. Nonostante i molteplici appelli da più di un secolo da parte degli storici, il comparatismo, che costituisce un elemento fondamentale dell’antropologia, è ancora oggi troppo poco spesso praticato. Si proporrà di interpretare questo rifiuto come un rifiuto della ricerca di invarianti umane che condurrebbe a risultati a-storici. Un’altra forma di comparatismo è nondimeno possibile, una forma precisamente che ricorre al confronto di universi diversi per meglio comprenderne le difference reciproche. L’articolo espone le condizioni e i vantaggi di questa metodologia di ricerca, a partire dall’esempio degli interdetti alimentari.
Multiple Resonances in Fluid-Loaded Vibrating Structures
Pierre-Olivier Mattei
Physics , 2009,
Abstract: This study deals with spectral analysis of fluid-loaded vibrating structure. It was recently observed in a numerical study on a high order perturbation method under heavy fluid loading that a loaded vibrating plate results, not only in the classical frequency shift of the in vacuo single resonance (in both the real part because of the fluid added mass and the imaginary part because of energy lost by radiation into the fluid), but also in an increase in the number of the resonance frequencies : as a result of the loading, a single in vacuo resonance frequency of the structure is transformed into a multiple resonance frequency. Here we show that this phenomenon is said to be a refinement of the Sanchez's classical result in their book (Vibration and coupling of continuous systems, Springer-Verlag -1989-, paragraph 9.3) where it was established, using asymptotic analysis, that in the case of a light loading conditions "the scattering frequencies of a fluid loaded elastic structure (ie the resonance frequencies) are nearly the real eigenfrequencies of the elastic body alone and the complex scattering frequencies of the fluid with a rigid solid". A theoretical explanation of the observed phenomenon of multiple resonance is given using classical results of the distribution of zeros of entire functions. It is established that every single in vacuo resonance frequency of a rectangular plate is transformed into an infinite number of resonances when the fluid-loading is accounted for.
Multiple Resonances in Fluid-Loaded Vibrating Structures
Pierre-Olivier Mattei
Physics , 2008,
Abstract: This study deals with vibroacoustics under heavy fluid loading conditions. Considerable attention has been and remains focused on this subject not only because industry is very concerned but also because of mathematical difficulties that make the numerical resolution of the problem very difficult. It was recently observed in a numerical study on a high order perturbation method under heavy fluid loading that a loaded vibrating plate results in a frequency shift of the in vacuo single resonance (in both the real part because of the fluid added mass and the imaginary part because of energy lost by radiation into the fluid) as well as increase in the number of the resonance frequencies : as a result of the loading, each single in vacuo resonance frequency of the structure is transformed into a multiple resonance frequency. Here we show that this phenomenon is said to be an extension to the heavy loading condition of the Sanchez's classical result that have established that in the case of a light loading conditions "the scattering frequencies of a fluid loaded elastic structure (ie the resonance frequencies) are nearly the real eigenfrequencies of the elastic body alone and the complex scattering frequencies of the fluid with a rigid solid". Using classical results in the framework of the theory of entire functions, it is established that a single resonance of a simply supported fluid loaded rectangular plate is transformed into an infinite number of resonances.
Spectrum of a fluid-loaded vibrating plate: the multiple resonance phenomenon
Pierre-Olivier Mattei
Physics , 2009,
Abstract: It was recently observed in a numerical study on a high order perturbation method under heavy fluid loading that a loaded vibrating plate results, not only in the classical frequency shift of the in vacuo single resonance (in both the real part because of the fluid added mass and the imaginary part because of energy lost by radiation), but also in an increase in the number of the resonance. As a result of the loading, a single in vacuo resonance of the structure is transformed into a multiple resonance. Here we show that this phenomenon is a refinement of the Sanchez's classical result where it was established, using asymptotic analysis, that in the case of a light loading conditions " the scattering frequencies of a fluid loaded elastic structure (ie the resonance frequencies) are nearly the real eigenfrequencies of the elastic body alone and the complex scattering frequencies of the fluid with a rigid solid ". A theoretical explanation of the multiple resonances is given using classical results on theory of entire functions. It is established that every single in vacuo resonance of a simply supported rectangular plate is transformed into an infinite number of resonances under fluid-loading condition.
A non-parametric efficient evaluation of Partial Directed Coherence
Pierre-Olivier Amblard
Quantitative Biology , 2013,
Abstract: Studying the flow of information between different areas of the brain can be performed by using the so-called Partial Directed Coherence. This measure is usually evaluated by first identifying a multivariate autoregressive model, and then by using Fourier transforms of the impulse responses identified and applying appropriate normalizations. Here, we present another route to evaluate the partial directed coherences in multivariate time series. The method proposed is non parametric, and utilises the strong spectral factorization of the inverse of the spectral density matrix of the multivariate process. To perform the factorization, we have recourse to an algorithm developed by Davis and his collaborators. We present simulations as well as an application on a real data set (Local Field Potentials in the sleeping mouse) to illustrate the methodology. A comparison to the usual approach in term of complexity is detailed. For long AR models, the proposed approach is of interest.
A closer look at the role of urotensin II in the metabolic syndrome
Pierre-Olivier Barrette,Adel Giaid Schwertani
Frontiers in Endocrinology , 2012, DOI: 10.3389/fendo.2012.00165
Abstract: Urotensin II (UII) is a vasoactive peptide that was first discovered in the teleost fish, and later in mammals and humans. UII binds to the G protein coupled receptor GPR14 (now known as UT). UII mediates important physiological and pathological actions by interacting with its receptor. The metabolic syndrome (MetS) is described as cluster of factors such as obesity, dyslipidemia, hypertension, and insulin resistance (IR), further leading to development of type 2 diabetes mellitus and cardiovascular diseases. UII levels are upregulated in patients with the MetS. Evidence directly implicating UII in every risk factor of the MetS has been accumulated. The mechanism that links the different aspects of the MetS relies primarily on IR and inflammation. By directly modulating both of these factors, UII is thought to play a central role in the pathogenesis of the MetS. Moreover, UII also plays an important role in hypertension and hyperlipidemia thereby contributing to cardiovascular complications associated with the MetS.
Reflection at large distance from the central engine in Seyfert 1s
Julien Malzac,Pierre-Olivier Petrucci
Physics , 2002,
Abstract: We consider the possibility that most of the reflection component, observed in the hard X-ray spectra of Seyfert galaxies, could be formed on an extended medium, at large distance from the central source of primary radiation (e.g. on a torus). Then, the reflector cannot respond to the rapid fluctuations of the primary source. The observed reflected flux is controlled by the time-averaged primary spectrum rather than the instantaneous (observed) one. We show that this effect strongly influences the spectral fit parameters derived under the assumption of a reflection component consistent with the primary radiation. We find that a pivoting primary power-law spectrum with a nearly constant Comptonised luminosity may account for the reported correlation between the reflection amplitude R and the spectral index Gamma, and simultaneously produces an iron line EW that is nearly independent of Gamma. We emphasize the effects of the modelling of the primary component on the determination of the reflection amplitude, and show that in NGC 5548, when these effects are taken into account, the RXTE data are consistent with the reflection features being produced mainly at large distance from the central source.
A note on bounded entropies
Pierre-Olivier Amblard,Christophe Vignat
Physics , 2005, DOI: 10.1016/j.physa.2006.01.002
Abstract: The aim of the paper is to study the link between non additivity of some entropies and their boundedness. We propose an axiomatic construction of the entropy relying on the fact that entropy belongs to a group isomorphic to the usual additive group. This allows to show that the entropies that are additive with respect to the addition of the group for independent random variables are nonlinear transforms of the R\'enyi entropies, including the particular case of the Shannon entropy. As a particular example, we study as a group a bounded interval in which the addition is a generalization of the addition of velocities in special relativity. We show that Tsallis-Havrda-Charvat entropy is included in the family of entropies we define. Finally, a link is made between the approach developed in the paper and the theory of deformed logarithms.
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