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Search Results: 1 - 10 of 25767 matches for " Paul-Antoine Santoni "
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Wildland Fire Behaviour Case Studies and Fuel Models for Landscape-Scale Fire Modeling
Paul-Antoine Santoni,Jean-Baptiste Filippi,Jacques-Henri Balbi,Frédéric Bosseur
Journal of Combustion , 2011, DOI: 10.1155/2011/613424
Abstract: This work presents the extension of a physical model for the spreading of surface fire at landscape scale. In previous work, the model was validated at laboratory scale for fire spreading across litters. The model was then modified to consider the structure of actual vegetation and was included in the wildland fire calculation system Forefire that allows converting the two-dimensional model of fire spread to three dimensions, taking into account spatial information. Two wildland fire behavior case studies were elaborated and used as a basis to test the simulator. Both fires were reconstructed, paying attention to the vegetation mapping, fire history, and meteorological data. The local calibration of the simulator required the development of appropriate fuel models for shrubland vegetation (maquis) for use with the model of fire spread. This study showed the capabilities of the simulator during the typical drought season characterizing the Mediterranean climate when most wildfires occur. 1. Introduction The ability of the forest fire community in modelling and simulating forest fire spread [1–4], as well as developing management approaches and techniques [5], has increased significantly in recent years. Modelling has become an essential tool in forest fire research and becomes a crucial instrument in the studies of wildland-urban interface fires [1], fire mitigation, and risk mapping [5]. Wildfires are driven by complex physical and chemical processes, operating on vastly different scales ranging from micrometers to kilometers. Their interactions depend on coupling between nonlinear phenomena such as turbulence in the lower part of the atmospheric boundary layer, topography, vegetation, and fire itself (chemical reactions, radiation heat transfer, and degradation of the vegetation). Different reviews of fire spread models have been conducted these last ten years [6, 7]. Depending on the authors, wildland fire mathematical models may be classified according to the nature of the equations (physical, quasiphysical, quasiempirical, and empirical) or according to the physical system modeled (surface fire models, crown fire models, spotting models, and ground fire models). With regard to the first classification, the simplest models are the statistical ones, which make no attempt to involve physical mechanisms [8]. Empirical models [9] are based upon the conservation of energy, but they do not distinguish the mode of heat transfer. Finally, physical models differentiate the various kinds of heat transfer in order to predict fire behaviour [10]. Among them,
Forest Fire Research: The Latest Advances Tools for Understanding and Managing Wildland Fire
Paul-Antoine Santoni,Andrew Sullivan,Dominique Morvan,William E. Mell
Journal of Combustion , 2011, DOI: 10.1155/2011/418756
Simulation of Coupled Fire/Atmosphere Interaction with the MesoNH-ForeFire Models
Jean-Baptiste Filippi,Frédéric Bosseur,Xavier Pialat,Paul-Antoine Santoni,Susanna Strada,Céline Mari
Journal of Combustion , 2011, DOI: 10.1155/2011/540390
Abstract: Simulating interaction between forest fire and atmospheric processes requires a highly detailed and computationally intensive model. Processing this type of simulations in wildland fires forbids combustion-based models due to the large amount of fuels to be simulated in terms of quantity and diversity. In this paper, we propose an approach that couples a fire area simulator to a mesoscale weather numerical model in order to simulate local fire/atmosphere interaction. Five idealized simulation cases are analysed showing strong interaction between topography and the fire front induced wind, interactions that could not be simulated in noncoupled simulations. The same approach applied to a real-case scenario also shows results that are qualitatively comparable to the observed case. All these results were obtained in less than a day of calculation on a dual processor computer, leaving room for improvement in grid resolution that is currently limited to fifty meter. 1. Introduction Wildland fires are influenced by many physical processes, from which several of them directly stem from the atmosphere behaviour such as wind or humidity, showing a direct influence of the atmosphere on the fire. Feedback from the fire to the atmosphere has been studied and observed since the fifties [1], and several attempts to model and simulate fire-atmosphere interaction have been successful since then. Among the most recent numerical studies of fire/atmosphere interaction, Mell et al. [2] have obtained with the wildland-urban interface fire dynamics simulator (WFDS) model a good correspondence between numerical results and real prescribed burning experiment of Australian grassland Cheney and Gould [3]. Similar numerical results were obtained by Linn et al. [4] using the HIGRAD/FIRETEC model performing several numerical investigations with different topography and wind conditions, but, unlike Mell et al. [2], no comparison to actual burns were made in these academic cases. These models focus on the processes of solid fuel pyrolysis, heat transfer, gas phase combustion, and local fire-atmosphere interaction that are essential to the physical mechanisms involves in fire spread. Nevertheless simulating these interactions at the scale of their appearance (i.e., the combustion scale) requires a highly detailed and computationally intensive model that is nowadays not reachable for actual wildland fires. Moreover, it is rarely possible to gather sufficient data to initiate a simulation at the level of detail required for such simulations. On other hand, less physically detailed models
La rationalité aux limites et les limites de la rationalité : la question de l’intégrité et de l’existence de l’espèce humaine
Paul-Antoine Miquel
Meta : Research in Hermeneutics, Phenomenology and Practical Philosophy , 2011,
Abstract: The purpose of this article is to address the question of our responsibility as human beings, by taking into consideration the intersection between ethics and science. I intend to prove that the issues raised by the existence and the integrity of the human species is a new and curious form of power founded on what I call “the principle of non-reciprocity” that unites the humanity of today with the future generations. The question that I address is the following: how to act on the future of humanity so that this action can not be regarded as unfair?
Adiabatic cooling of trapped nonneutral plasmas
Giovanni Manfredi,Paul-Antoine Hervieux
Physics , 2012, DOI: 10.1103/PhysRevLett.109.255005
Abstract: Nonneutral plasmas can be trapped for long times by means of combined electric and magnetic fields. Adiabatic cooling is achieved by slowly decreasing the trapping frequency and letting the plasma occupy a larger volume. We develop a fully kinetic time-dependent theory of adiabatic cooling for plasmas trapped in a one-dimensional well. This approach is further extended to three dimensions and applied to the cooling of antiproton plasmas, showing excellent agreement with recent experiments [G. Gabrielse et al., Phys. Rev. Lett. 106, 073002 (2011)].
Nonlinear absorption of ultrashort laser pulses in thin metal films
Giovanni Manfredi,Paul-Antoine Hervieux
Physics , 2005, DOI: 10.1364/OL.30.003090
Abstract: Self-consistent simulations of the ultrafast electron dynamics in thin metal films are performed. A regime of nonlinear oscillations is observed, which corresponds to ballistic electrons bouncing back and forth against the film surfaces. When an oscillatory laser field is applied to the film, the field energy is partially absorbed by the electron gas. Maximum absorption occurs when the period of the external field matches the period of the nonlinear oscillations, which, for sodium films, lies in the infrared range. Possible experimental implementations are discussed.
Transcriptional Mutagenesis Induced by 8-Oxoguanine in Mammalian Cells
Damien Brégeon ,Paul-Antoine Peignon,Alain Sarasin
PLOS Genetics , 2009, DOI: 10.1371/journal.pgen.1000577
Abstract: Most of the somatic cells of adult metazoans, including mammals, do not undergo continuous cycles of replication. Instead, they are quiescent and devote most of their metabolic activity to gene expression. The mutagenic consequences of exposure to DNA–damaging agents are well documented, but less is known about the impact of DNA lesions on transcription. To investigate this impact, we developed a luciferase-based expression system. This system consists of two types of construct composed of a DNA template containing an 8-oxoguanine, paired either with a thymine or a cytosine, placed at defined positions along the transcribed strand of the reporter gene. Analyses of luciferase gene expression from the two types of construct showed that efficient but error-prone transcriptional bypass of 8-oxoguanine occurred in vivo, and that this lesion was not repaired by the transcription-coupled repair machinery in mammalian cells. The analysis of luciferase activity expressed from 8OG:T-containing constructs indicated that the magnitude of erroneous transcription events involving 8-oxoguanine depended on the sequence contexts surrounding the lesion. Additionally, sequencing of the transcript population expressed from these constructs showed that RNA polymerase II mostly inserted an adenine opposite to 8-oxoguanine. Analysis of luciferase expression from 8OG:C-containing constructs showed that the generated aberrant mRNAs led to the production of mutant proteins with the potential to induce a long-term phenotypical change. These findings reveal that erroneous transcription over DNA lesions may induce phenotypical changes with the potential to alter the fate of non-replicating cells.
Autoresonant control of the magnetization switching in single-domain nanoparticles
Guillaume Klughertz,Paul-Antoine Hervieux,Giovanni Manfredi
Physics , 2014, DOI: 10.1088/0022-3727/47/34/345004
Abstract: The ability to control the magnetization switching in nanoscale devices is a crucial step for the development of fast and reliable techniques to store and process information. Here we show that the switching dynamics can be controlled efficiently using a microwave field with slowly varying frequency (autoresonance). This technique allowed us to reduce the applied field by more than $30%$ compared to competing approaches, with no need to fine-tune the field parameters. For a linear chain of nanoparticles the effect is even more dramatic, as the dipolar interactions tend to cancel out the effect of the temperature. Simultaneous switching of all the magnetic moments can thus be efficiently triggered on a nanosecond timescale.
Semiclassical Vlasov and fluid models for an electron gas with spin effects
Jerome Hurst,Omar Morandi,Giovanni Manfredi,Paul-Antoine Hervieux
Physics , 2014, DOI: 10.1140/epjd/e2014-50205-5
Abstract: We derive a four-component Vlasov equation for a system composed of spin-1/2 fermions (typically electrons). The orbital part of the motion is classical, whereas the spin degrees of freedom are treated in a completely quantum-mechanical way. The corresponding hydrodynamic equations are derived by taking velocity moments of the phase-space distribution function. This hydrodynamic model is closed using a maximum entropy principle in the case of three or four constraints on the fluid moments, both for Maxwell-Boltzmann and Fermi-Dirac statistics.
Nonlinear dynamics of electron-positron clusters
Giovanni Manfredi,Paul-Antoine Hervieux,Fernando Haas
Physics , 2012, DOI: 10.1088/1367-2630/14/7/075012
Abstract: Electron-positron clusters are studied using a quantum hydrodynamic model that includes Coulomb and exchange interactions. A variational Lagrangian method is used to determine their stationary and dynamical properties. The cluster static features are validated against existing Hartree-Fock calculations. In the linear response regime, we investigate both dipole and monopole (breathing) modes. The dipole mode is reminiscent of the surface plasmon mode usually observed in metal clusters. The nonlinear regime is explored by means of numerical simulations. We show that, by exciting the cluster with a chirped laser pulse with slowly varying frequency (autoresonance), it is possible to efficiently separate the electron and positron populations on a timescale of a few tens of femtoseconds.
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