Les enjeux écologiques de Palo Verde (Costa Rica)

Près de Palo Verde a été créé un parc naturel. Un projet d’irrigation risque de perturber l’écologie de la région. Une carte de son écosystème a été établie par télédétection, pour évaluer l’impact d’un tel projet

Le modele de la ville touristique du midi selon Hermann Hesse (1925). Une lecon de la litterature a la geographie

In 1925, the German-born writer Hermann Hesse, living then in Tessin, the Italian-speaking part of Switzerland, wrote a visionary text entitled The Tourist City in the South.  This text is considered as a primer in the encounter of humanistic geography and literature. In focusing on both structure and lived experience in a tourist city, the writer anticipates the debate in contemporary tourism geography: how to build a model for such a tourist city and what type of criticism may arise from such a social construction?  

Preference Formation, School Dissatisfaction and Risky Behavior of Adolescents

School dissatisfaction is an important component of the subjective well-being of adolescents associated with "risky behavior" like drug use, unprotected sex, norm violations and illegal behavior. We extend the standard human capital model to joint human investment (education) and disinvestment (risky behavior). Based on this model, we develop a general dynamic framework to analyze the preference formation of children and behavioral change at school. Once an educational norm is set by adults, children can rationally deviate from this norm, while staying at school, after experiencing bad surprises like a school failure. The same type of dynamic equation can be used in a sequence to predict education, satisfaction with school, and a host of risky behavior. We test these assumptions with a unique panel data set on American adolescents attending middle or high school. School dissatisfaction is found to have a significant positive effect upon nine different types of risky behavior.Education; Satisfaction; Risky behavior; Preference formation; Economic behavior of children

Hybridization gap and anisotropic far-infrared optical conductivity of URu2Si2

We performed far-infrared optical spectroscopy measurements on the heavy fermion compound URu 2 Si 2 as a function of temperature. The light's electric-field was applied along the a-axis or the c-axis of the tetragonal structure. We show that in addition to a pronounced anisotropy, the optical conductivity exhibits for both axis a partial suppression of spectral weight around 12 meV and below 30 K. We attribute these observations to a change in the bandstructure below 30 K. However, since these changes have no noticeable impact on the entropy nor on the DC transport properties, we suggest that this is a crossover phenomenon rather than a thermodynamic phase transition.Comment: To be published in Physical Review

2-Microlocal Analysis and Application in Signal Processing

International audienceThis paper introduces the use of 2-microlocal analysis in signal processing. 2-microlocal analysis is a powerful tool for studying the regularity of solutions of partial differential equations. It allows to track the evolution of the Hölder exponent under the action of pseudo-differential operators. We first prove theoretical results pertaining to the so-called 2-microlocal frontier, that allow to characterize and prescribe it at a given point. We then show how to combine 2-microlocal analysis with multifractal analysis in order to perform image denoising

Incomplete devil's staircase in the magnetization curve of SrCu2(BO3)2

We report on NMR and torque measurements on the frustrated quasi-two-dimensional spin-dimer system SrCu2(BO3)2 in magnetic fields up to 34 T that reveal a sequence of magnetization plateaus at 1/8, 2/15, 1/6, and 1/4 of the saturation and two incommensurate phases below and above the 1/6 plateau. The magnetic structures determined by NMR involve a stripe order of triplets in all plateaus, suggesting that the incommensurate phases originate from proliferation of domain walls. We propose that the magnetization process of SrCu2(BO3)2 is best described as an incomplete devil's staircase.Comment: 21 pages, 9 figures (main: 12 pages, 4 figures/supplemental material: 9 pages, 5 figures

Texture-based Video Indexing

International audienceWe present a method for indexing and searching video sequences based on textural information. Our method proceeds by first defining and computing texture descriptors relevant to the database at hand. Then a similarity distance is computed between a video sample given by the user and small space-time regions in the sequences. The system returns an ordered set of best matches. We show some results on real sequences, which indicate that this scheme has reasonable complexity and performs well in practice. We believe that these good results stem mainly from a) the introduction of a new texture descriptor based on dynamic local H¨older exponents, and b) the automated adapted choice of the relevant parameters