By means of the ultrafast X-ray tomography facility, data were obtained at different superficial gas velocities UG in a bubble column (0.1 m in ID) operated with an air-deionized water system at ambient conditions. Raw reconstructed images were treated by both the information entropy (IE) and the reconstruction entropy (RE) algorithms in order to identify the main transition velocities in a bub...

OTR has been widely investigated in the literature as an electron beam diagnostic tool in the high energy region (E > 50 MeV). At lower energy both the model of OTR emission and the experimental observation of the phenomena require a different and more complex approach. Nevertheless the information which can be drawn from OTR spectra at these low energies play a relevant role in new injectors. ...

Non-Brownian suspensions present a transition from Newtonian behavior in the zero-shear limit to a shear thickening behavior at a large shear rate, none of which is clearly understood so far. Here, we carry out numerical simulations of such an athermal dense suspension under shear, at an imposed confining pressure. This setup is conceptually identical to recent experiments of Boyer, Guazzelli, ...

We propose a new Markov switching model with time varying probabilities for the transitions. The novelty of our model is that the transition probabilities evolve over time by means of an observation driven model. The innovation of the time varying probability is generated by the score of the predictive likelihood function. We show how the model dynamics can be readily interpreted. We investigat...

Introduction Over the last fifty years gas-solids fluidized beds have played a very important role in many areas in the process industry, especially in chemical and petroleum industries. The existence of different flow regimes in fluidized beds at different operating conditions has been known for a long time and numerous studies have been carried out to define the flow regimes [1-6]. It is well...

Non-brownian suspensions present a transition from a newtonian behaviour in the zero-shear limit to a shear thickening behaviour at large shear rate, none of which is clearly understood so far. Here, we carry out numerical simulations of such an athermal dense suspension under shear, at imposed confining pressure. This set-up is conceptually identical to the recent experiments of Boyer and co-w...

Many financial time series processes appear subject to periodic structural changes in their dynamics. Regression relationships are often not robust to outliers nor stable over time, whilst the existence of changes in variance over time is well documented. This paper considers a vector autoregression subject to pseudocyclical structural changes. The parameters of a vector autoregression are mode...

Abstract. We present in this paper an exact study concerning a first order transition induced by an inhomogeneous boundary magnetic field in the 2D Ising model. From a previous analysis of the interfacial free energy in the discrete case (J. Phys. A: Math. Gen. 38, 2849, 2005), we identify, using an asymptotic expansion in the thermodynamic limit, the transition line that separates the regime w...

We investigate a mean field approximation to the statistical mechanics of complex fields with dynamics governed by the nonlinear Schr6dinger equation. Such fields, whose Hamiltonian is unbounded below, may model plasmas, lasers, and other physical systems. Restricting ourselves to one-dimensional systems with periodic boundary conditions, we find in the mean field approximation a phase transiti...

We calculate the normal modes of vibration in jammed sphere packings to obtain the energy diffusivity, a spectral measure of transport. At the boson peak frequency, we find an Ioffe-Regel crossover from a diffusivity that drops rapidly with frequency to one that is nearly frequency independent. This crossover frequency shifts to zero as the system is decompressed towards the jamming transition,...