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An overview of BCC climate system model development and application for climate change studies
No full textInternational audienceThis paper reviews recent progress in the development of the Beijing Climate Center Climate System Model (BCC_CSM) and its four component models (atmosphere, land surface, ocean, and sea ice). Two recent versions are described: BCC_CSM1.1 with coarse resolution (approximately 2.8125°×2.8125°) and BCC_CSM1.1(m) with moderate resolution (approximately 1.125°×1.125°). Both versions are fully coupled climate-carbon cycle models that simulate the global terrestrial and oceanic carbon cycles and include dynamic vegetation. Both models well simulate the concentration and temporal evolution of atmospheric CO2 during the 20th century with anthropogenic CO2 emissions prescribed. Simulations using these two versions of the BCC_CSM model have been contributed to the Coupled Model Intercomparison Project phase five (CMIP5) in support of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5). These simulations are available for use by both national and international communities for investigating global climate change and for future climate projections.Simulations of the 20th century climate using BCC_CSM1.1 and BCC_CSM1.1(m) are presented and validated, with particular focus on the spatial pattern and seasonal evolution of precipitation and surface air temperature on global and continental scales. Simulations of climate during the last millennium and projections of climate change during the next century are also presented and discussed. Both BCC_CSM1.1 and BCC_CSM1.1(m) perform well when compared with other CMIP5 models. Preliminary analyses indicate that the higher resolution in BCC_CSM1.1(m) improves the simulation of mean climate relative to BCC_CSM1.1, particularly on regional scales
2D-photochemical modeling of Saturn’s stratosphere: hydrocarbon and water distributions
No full textInternational audienceSaturn’s axial tilt of 27° produces seasons in a similar way as on Earth. The seasonal forcing over Saturn’s 30 years period influences the production/loss of the major atmospheric absorbers and coolants through photochemistry, and influences therefore Saturn’s stratospheric temperatures. We have developed a 2D time-dependent photochemical model of Saturn’s atmosphere [Hue et al., in prep.], coupled to a radiative-climate model [Greathouse et al., 2008] to study seasonal effects on its atmospheric composition. Cassini spacecraft has revealed that the distribution of hydrocarbons in Saturn’s stratosphere [Guerlet et al., 2009] differs from pure photochemical predictions, i.e. without meridional transport [Moses et al., 2005]. Differences between the observed distribution of hydrocarbons and 2D-photochemical predictions are likely to be an indicator of dynamical forcing.Disentangling the origin of water in the stratosphere of this planet has been a long-term issue. Due to Saturn’s cold tropopause trap, which acts as a transport barrier, the water vapor observed by the Infrared Space Observatory (ISO) [Feuchtgruber et al., 1997] has an external origin. Three external sources have been identified: (i) permanent flux from interplanetary dust particles, (ii) local sources form planetary environments (rings, satellites), (iii) large cometary impacts, similar to Shoemaker-Levy 9 on Jupiter. Previous observations of Saturn with Herschel’s Hsso program [Hartogh et al., 2009] led to the detection of a water torus around Saturn [Hartogh et al., 2011], fed by Enceladus’ geysers. A substantial fraction of this torus is predicted to be a local source of water for Saturn’s and its satellites, as it will spread in this system [Cassidy et al., 2010]. Using the new 2D-photochemical model, we test here the validity of Enceladus’ torus as the source of Saturn’s stratospheric water.References : Hue et al., in prep. Greathouse et al., 2008. AGU Fall Meeting(Abstract P21B06). Guerlet et al., 2009. Icarus, 203, 214-232. Moses et al., 2005. JGR 110. Feuchtgruber et al., 1997. 389, 159-162. Hartogh et al., 2009. PSS 57, 1596-1606 Hartogh et al., 2011. A&A, 532, L2. Cassidy et al., 2010. Icarus, 209, 696-70
Chow rings, decomposition of the diagonal, and the topology of families
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Spin physics and TMD studies at A Fixed-Target ExpeRiment at the LHC (AFTER@LHC)
No full text6 pages, 4 figures, 1 table, LaTeX. Proceedings of the Fourth International Workshop on Transverse Polarisation Phenomena in Hard Processes (Transversity 2014), 9-13 June, 2014, Chia, Italy. To appear in EPJ Web of ConferencesInternational audienceWe report on the opportunities for spin physics and Transverse-Momentum Dependent distribution (TMD) studies at a future multi-purpose fixed-target experiment using the proton or lead ion LHC beams extracted by a bent crystal. The LHC multi-TeV beams allow for the most energetic fixed-target experiments ever performed, opening new domains of particle and nuclear physics and complementing that of collider physics, in particular that of RHIC and the EIC projects. The luminosity achievable with AFTER@LHC using typical targets would surpass that of RHIC by more that 3 orders of magnitude in a similar energy region. In unpolarised proton-proton collisions, AFTER@LHC allows for measurements of TMDs such as the Boer-Mulders quark distributions, the distribution of unpolarised and linearly polarised gluons in unpolarised protons. Using the polarisation of hydrogen and nuclear targets, one can measure transverse single-spin asymmetries of quark and gluon sensitive probes, such as, respectively, Drell-Yan pair and quarkonium production. The fixed-target mode has the advantage to allow for measurements in the target-rapidity region, namely at large x^uparrow in the polarised nucleon. Overall, this allows for an ambitious spin program which we outline here
Essais sur les hyper-preferences, la polarisation et l'aggrégation des informations
No full textIn this thesis, some important problems and properties of collective decision-making are studied. In particular, first, a stability property of preference aggregation rules is introduced and some well-known classes of rules are tested in this regard. Second, measuring preferential polarization is studied, both theoretically and empirically. Finally, strategic behavior in information aggregation situations is investigated in light of a sort of bounded rationality model, both theoretically and experimentally. The stability notion studied in the first part of the thesis is imposed particularly on social welfare functions and requires that the outcome of these functions should be robust to reduction in preference submission that are argued to take place when individuals submit a ranking of alternatives when the outcomes are also restricted to be rankings. Given the preference profile of a society, that is a collection of rankings of alternatives, a compatible collection of rankings of rankings are extracted and the outcome of social welfare functions in these two levels are compared. It turns out that no scoring rule gives consistent results, although there might exist Condorcet-type rules. Polarization measures studied in second part are in form of aggregation of pairwise antagonisms in a society. The public opinion polarization in the United States for the last three decades is analyzed in light of this view, by using a well-acclaimed measure of polarization introduced in the literature of income inequality. The conclusion is that no significant trend in public opinion polarization can be claimed to exist over the last several decades. Also, an adaptation of the same measure is shown to satisfy desirable properties in lieu of ordinal preference profiles when three alternatives are considered. Furthermore, a measure that is the aggregation of pairwise differences among individuals' preferences is characterized by a set of axioms. In the final part of the thesis, information aggregation situations described as in Condorcet jury model is studied in light of cognitive hierarchy approach to bounded rationality. Specifically, a laboratory experiment is run to test the theoretical predictions of the symmetric Bayesian Nash equilibrium concept. It is observed that behavior in lab is not correctly captured by this concept that assumes a strong notion of rationality and homogeneity among individuals' behaviors. To better describe the findings in the experiment, a novel model of cognitive hierarchy is developed and shown to perform better than both strong rationality approach and previous cognitive hierarchy models. This endogenous cognitive hierarchy model is compared theoretically to previous models of cognitive hierarchy and shown to improve in certain classes of games.Dans cette thèse, certains problèmes importants et des propriétés de prise de décision collective sont étudiés. En particulier, d'abord, une propriété de stabilité des règles d'agrégation de préférences est introduite et certaines classes bien connues de règles sont testées à cet égard. Deuxièmement, le mesurage de la polarisation préférentielle est étudié, à la fois théorique et empirique. Enfin, le comportement stratégique dans des situations d'agrégation de l'information est étudié à la lumière d'une sorte de modèle de la rationalité limitée, à la fois théoriquement et expérimentalement. La notion de stabilité étudié dans la première partie de la thèse est imposée en particulier sur les fonctions de bien-être sociale et exige que le résultat de ces fonctions doit être robuste à la réduction de la transmission de préférences qui sont soutenu avoir lieu lorsque les individus présentent un ordre des alternatives lorsque les résultats sont également limités à être ordres. Pour tous profils sociétaux de préférences donné, qui est une collection d'ordres des alternatives, une collection compatible d'ordre des classements est extraite et les résultats des fonctions de bien-être social dans ces deux niveaux sont comparés. Il s'avère qu'aucune règle de notation donne des résultats cohérents, bien qu'il puisse y exister des règles Condorcetien. Mesures de polarisation qui sont étudiées en deuxième partie sont en forme d'agrégation des antagonismes par paires dans une société. La polarisation de l'opinion publique aux États-Unis pour les trois dernières décennies est analysé à la lumière de ce point de vue, en utilisant une mesure de polarisation bien acclamé qui est introduit dans la littérature de l'inégalité des revenus. La conclusion est qu'aucune tendance significative dans l'opinion publique polarisation peut être réclamé à exister au cours des dernières décennies. En outre, une adaptation de la même mesure est montrée à satisfaire des propriétés souhaitables à la place de profils de préférences ordinales lorsque trois alternatives sont considérées. En outre, une mesure qui est en effet l'agrégation des différences par paires entre les préférences des individus est caractérisée axiomatiquement. Dans la dernière partie de la thèse, situations de l'agrégation de l'information telles que décrites comme dans le modèle du jury de Condorcet sont étudiées à la lumière d'une approche de rationalité limitée qui est connue hiérarchie cognitive. Plus précisément, une expérience de laboratoire est exécutée pour tester les prédictions théoriques de la notion d'équilibre symétrique de Nash bayésien. On constate que le comportement en laboratoire n'est pas correctement capturé par ce concept qui suppose une forte notion de la rationalité et de l'homogénéité entre les comportements des individus. Pour mieux décrire les résultats à l'expérience, un nouveau modèle de hiérarchie cognitive est développé et montré à faire mieux que la fois l'approche de la rationalité forte et des modèles précédentes de hiérarchie cognitive. Ce modèle de hiérarchie cognitive endogène est comparé en théorie aux modèles précédents de la hiérarchie cognitive et montré pour améliorer dans certaines catégories de jeux
L'éponge de Menger -itération 2-
No full textThe Menger sponge -iteration 2- (L'éponge de Menger -itération 2-
Les 64 premières lignes du triangle de Pascal
No full textThe 64 first lines of the Pascal's Triangle (Les 64 premières lignes du triangle de Pascal
Vue artistique de Monument Valley au lever du Soleil avec la Grande Ourse
No full textArtistic view of Monument Valley at sunrise with the Great Bear (Vue artistique de Monument Valley au lever du Soleil avec la Grande Ourse
Monument Valley au lever du Soleil
No full textMonument Valley at sunrise (Monument Valley au lever du Soleil