Shocks in non-loaded bead chains with impurities

We numerically investigate the problem of the propagation of a shock in an horizontal non-loaded granular chain with a bead interaction force exponent varying from unity to large values. When $\alpha$ is close to unity we observed a cross-over between a nonlinearity-dominated regime and a solitonic one, the latest being the final steady state of the propagating wave. In the case of large values of $\alpha$ the deformation field given by the numerical simulations is completely different from the one obtained by analytical calculation. In the following we studied the interaction of these shock waves with a mass impurity placed in the bead chain. Two different physical pictures emerge whether we consider a light or a heavy impurity mass. The scatter of the shock wave with a light impurity yields damped oscillations of the impurity which then behave as a solitary wave source. Differently an heavy impurity is just shifted by the shock and the transmitted wave loses its solitonic character being fragmented into waves of decreasing amplitudes.Comment: 9 pages, 18 figures, Accepted in European Physical Journal

Approach Tolerance in the Assemblies of Evolutionary Hybrid Prototypes

A new answer is proposed to replace the traditional “one shot” prototype (manufactured in one piece with one process): the hybrid rapid prototype. It is used to highly reduce time, cost and increase reactivity during the development times of new products. The part is decomposed in several components which can quickly be changed and can be manufactured with a process the most adapted. The main objective of the presented method is to propose an available technological assembly between the different components of the part in the respect of technological and topological function, and initial tolerance. Using a graph of representation, fuzzy logic and a tolerance point of view, some entities are associated with a CIA (Assembly Identity Card) in accordance with evolutionary and manufacturing analysis. This work will be illustrated by an industrial tooling for plastic injection.Mechanical Engineerin

The prompt-early afterglow connection in gamma-ray bursts: implications for the early afterglow physics

The early X-ray afterglow of gamma-ray bursts revealed by Swift carried many surprises. We focus in this paper on the plateau phase whose origin remains highly debated. We confront several newly discovered correlations between prompt and afterglow quantities (isotropic emitted energy in gamma-rays, luminosity and duration of the plateau) to several models proposed for the origin of plateaus in order to check if they can account for these observed correlations. We first show that the scenario of plateau formation by energy injection into the forward shock leads to an efficiency crisis for the prompt phase and therefore study two possible alternatives: the first one still takes place within the framework of the standard forward shock model but allows for a variation of the microphysics parameters to reduce the radiative efficiency at early times; in the second scenario the early afterglow results from a long-lived reverse shock. Its shape then depends on the distribution of energy as a function of Lorentz factor in the ejecta. In both cases, we first present simple analytical estimates of the plateau luminosity and duration and then compute detailed light curves. In the two considered scenarios we find that plateaus following the observed correlations can be obtained under the condition that specific additional ingredients are included. In the forward shock scenario, the preferred model supposes a wind external medium and a microphysics parameter epsilon_e that first varies as n^{-\nu} (n being the external density), with \nu~1 to get a flat plateau, before staying constant below a critical density n_0. To produce a plateau in the reverse shock scenario the ejecta must contain a tail of low Lorentz factor with a peak of energy deposition at \Gamma >~ 10.Comment: 8 pages, 5 figures, submitted to MNRA

Transitivity and the Choice of a Preposition in any Language

This thesis examines the question of determination of transitivity for a verb through a comparison of processes involved in English and in French. It takes in several theories belonging to the area of the syntax-semantics interface in order to understand how a predicate is construed as either intransitive or direct transitive or indirect transitive in either language.The study focuses on a corpus of verbs that present different argument structures in French and in English. It analyses the various factors that determine the choice of a transitivity status for a given predicate. It discusses whether that process of determination lies in the lexicon on first acquisition of a new verb, or in an interaction of pertinent semantic categories that develop as part of an individual’s language acquisition process, in order to yield the correct syntactic output. This thesis refers in particular to the study of prepositions in the field of cognitive semantics. It concludes that determination of a verb’s transitivity status takes in the “power struggle” between the various participants involved in the process. Semantic values such as human vs. non-human, active vs. passive, agency and volition, are analysed for all participants involved, in order to establish a predicate’s a-structure