Narrow Results

Atmospheric diffusion of high energy cosmic rays is studied analytically and the obtained integral electromagnetic fluxes are compared with the data measured by emulsion chamber detectors at mountain altitudes. We find a good consistency between them when the average nucleon inelasticity coefficient is varying between 0.50 and 0.65.

We propose a model for two identical granular fluids separated by a piston that can present clustering (volume tending to zero) for a range of parameters. This model is based on point granular particles. For a convenient range of parameters, a granular fluid-cluster collapse is then possible and permits us to get an insight on the physics of granular clusters based on the behavior of the fluid phase itself.

The paper presents a Rayleigh–Ritz based non-discretization method of analysis for the inelastic local buckling of rectangular steel plates subjected to applied in-plane axial, bending and shear actions with various boundary conditions. Use is made of the pb-2 representation of the displacement function as the product of a domain polynomial and a boundary polynomial. The constitutive model for the plate is an adaptation of the von Mises yield criterion and the associated flow rule presented in an infinitesimal form, and which leads to an incremental and iterative method of solution. The convergence and accuracy of the solutions are demonstrated, and it is shown that the method of analysis is computationally feasible for the solution of inelastic bifurcative plate instability problems. A parametric study is then undertaken for a range of plate boundary conditions under various regimes of applied loading.

Granular surface flows have still to be fully modelled. Here, we present the four types of front that can be observed in avalanches. These strongly inhomogeneous and unsteady flows are very sensitive test cases for the different types of model. We show that, at least qualitatively for the moment, the model we propose, based on the analysis of the motion of a single grain and layers of grains, can reproduce the different characteristics of these four fronts.

Magnesium alloys exhibit significant inelastic behavior during unloading, especially when twinning and detwinning are involved. It is commonly accepted that noteworthy inelastic behavior will be observed during unloading if twinning occurs during previous loading. However, this phenomenon is not always observed for Mg sheets with strong rolled texture. Therefore, the inelasticity of AZ31B rolled sheets with different rolled textures during cyclic loading-unloading are investigated by elastic viscoplastic self-consistent polycrystal plasticity model. The incorporation of the twinning and detwinning model enables the treatment of detwinning, which plays an important role for inelastic behavior during unloading. The effects of texture, deformation history, and especially twinning and detwinning on the inelastic behaviors are carefully investigated and found to be remarkable. The simulated results are in agreement with the available experimental observations, which reveals that the inelastic behavior for strongly rolled sheets is very different than the extruded bars.

Granular surface flows have still to be fully modelled. Here, we present the four types of front that can be observed in avalanches. These strongly inhomogeneous and unsteady flows are very sensitive test cases for the different types of model. We show that, at least qualitatively for the moment, the model we propose, based on the analysis of the motion of a single grain and layers of grains, can reproduce the different characteristics of these four fronts.

We consider the radiation emitted in a collision of shock waves, in D-dimensional General Relativity (GR), and describe a remarkably simple pattern, hinting at a more fundamental structure, unveiled by the introduction of the parameter D.

We present a higher order generalisation of the perturbative method to find the metric after the collision of two Aichelburg-Sexl gravitational shock waves in D-dimensions. A central challenge is to extract a higher order estimate for the inelasticity. We present an adaptation of the Bondi mass loss formula in D-dimensions, which allows us to obtain an expression valid non-perturbatively, for axially symmetric asymptotically flat spaces.