Analysis of transient, linear wave propagation in shells by the finite difference method

The applicability of the finite difference method to propagation problems in shells, and the response of a cylindrical shell with cutouts to both longitudinal and radial transient excitations are investigated. It is found that the only inherent limitation of the finite difference method is its inability to reproduce accurately response discontinuities. The short wave length limitations of thin shell theory create significant convergence difficulties may often be overcome through proper selection of finite difference mesh dimensions and temporal or spatial smoothing of the excitation. Cutouts produce moderate changes in early and intermediate time response of a cylindrical shell to axisymmetric pulse loads applied at one end. The cutouts may facilitate the undesirable late-time transfer of load-injected extensional energy into nonaxisymmetric flexural response

Substellar Objects in Nearby Young Clusters (SONYC) IX: The planetary-mass domain of Chamaeleon-I and updated mass function in Lupus-3

Substellar Objects in Nearby Young Clusters -- SONYC -- is a survey program to investigate the frequency and properties of substellar objects in nearby star-forming regions. We present new spectroscopic follow-up of candidate members in Chamaeleon-I (~2 Myr, 160 pc) and Lupus 3 (~1 Myr, 200 pc), identified in our earlier works. We obtained 34 new spectra (1.5 - 2.4 mum, R~600), and identified two probable members in each of the two regions. These include a new probable brown dwarf in Lupus 3 (NIR spectral type M7.5 and Teff=2800 K), and an L3 (Teff=2200 K) brown dwarf in Cha-I, with the mass below the deuterium-burning limit. Spectroscopic follow-up of our photometric and proper motion candidates in Lupus 3 is almost complete (>90%), and we conclude that there are very few new substellar objects left to be found in this region, down to 0.01 - 0.02 MSun and Av \leq 5. The low-mass portion of the mass function in the two clusters can be expressed in the power-law form dN/dM \propto M^{-\alpha}, with \alpha~0.7, in agreement with surveys in other regions. In Lupus 3 we observe a possible flattening of the power-law IMF in the substellar regime: this region seems to produce fewer brown dwarfs relative to other clusters. The IMF in Cha-I shows a monotonic behavior across the deuterium-burning limit, consistent with the same power law extending down to 4 - 9 Jupiter masses. We estimate that objects below the deuterium-burning limit contribute of the order 5 - 15% to the total number of Cha-I members.Comment: Accepted for publication by Astrophysical Journa

Optimization results for a generalized coupon collector problem

We study in this paper a generalized coupon collector problem, which consists in analyzing the time needed to collect a given number of distinct coupons that are drawn from a set of coupons with an arbitrary probability distribution. We suppose that a special coupon called the null coupon can be drawn but never belongs to any collection. In this context, we prove that the almost uniform distribution, for which all the non-null coupons have the same drawing probability, is the distribution which stochastically minimizes the time needed to collect a fixed number of distinct coupons. Moreover, we show that in a given closed subset of probability distributions, the distribution with all its entries, but one, equal to the smallest possible value is the one, which stochastically maximizes the time needed to collect a fixed number of distinct coupons. An computer science application shows the utility of these results.Comment: arXiv admin note: text overlap with arXiv:1402.524

D'un corps de classe à un corps de genre. Les stars, modèles de féminité dans Marie-Claire.

International audienceIn March 1937, when the first issue of Marie-Claire was published, the images of the female body it presented to its female readers from working-class backgrounds contrasted sharply with those featured in previous magazines. The female bodies are dressed and groomed to seduce and replace the hieratic bodies that presented fashions synonymous with membership in the upper classes. The present essay examines this shift and shows that the visual repertoire employed is borrowed from that of the female star constructed by movie magazines. By depicting women as stars, this iconography alters not only the image of the female body but the paradigm of femininity itself. The codes of this new appearance symbolize the social conquests of those who succeed by dint of their beauty, but they also represent women’s reappropriation of their sexuality in a context where the heterosexual couple was being reconfigured on the basis of love.En mars 1937, lorsque le premier numéro de Marie-Claire paraît, l’imagerie du corps féminin proposée aux lectrices issues des milieux populaires tranche avec celle des revues antérieures. Les corps féminins sont apprêtés et soignés pour séduire et remplacent les corps hiératiques utilisés pour présenter une mode synonyme d’apparence de classe. Cette étude revient sur cette mutation et montre que le répertoire visuel mobilisé est emprunté à celui de la star féminine construit par les revues de cinéma. En représentant les femmes comme des stars, ce n’est pas seulement l’imagerie du corps féminin qui évolue mais bien le paradigme de la féminité. Les codes de cette nouvelle apparence symbolisent la conquête sociale de celles qui réussissent grâce à leur beauté, mais aussi une réappropriation, par les femmes, de leur sexualité dans un contexte de reconfiguration du couple hétérosexuel basée sur l’amour