The instability of an accelerated solid slab with elastoplastic properties is analysed by means of numerical simulations. The study is performed in the framework of experiments to be carried out at the future synchrotron facility SIS100 at the Gesellschaft fűr Schwerionenforschung (GSI), Darmstadt, which consider the implosion of a heavy pusher layer driven by the expansion of a material heated by an intense beam of heavy ions. We have found that for the megabar pressures involved in these experiments, the solid pusher may retain elastoplastic properties that are beneficial for the stabilization of the shortest perturbation wavelengths.

The predicted acceleration performance of the ram accelerator at elevated pressures, based on the quasi-steady model, is much greater than that observed in experiments. This discrepancy is attributed to the increase of mass of the propellant accumulating in the control volume, such that it approaches the mass of the projectile itself. A revision of the conservation equations to account for unsteady flow effects was conducted. The corresponding predicted thrust as a function of Mach number is significantly less than that derived from the quasi-steady model. By using a virial-type equation of state for the combustion products, a better agreement with experimental data was obtained using this unsteady modeling approach.

This paper is devoted to atactic polystyrene (aPS) thin films treatment under DC pulsed discharge in nitrogen. The experiments were performed using a symmetrical plane-to-plane of electrodes configuration in order to improve the treatment homogeneity and also to compare the treatment efficiency when the aPS is on the cathode or on the anode. During these experiments, the pressure and the electrical conditions were maintained unchanged. The experimental results were compared for the two positions of samples, when the gap length and the afterglow duration time were varied. It appears that the treatment depends on the sample position and an interpretation is proposed. The physical conditions and the reaction processes in the plasma bulk and on the aPS surface were analysed in order to understand their influence on the surface treatment. The importance of metastables is pointed out and it is deduced that these long-life excited states are firstly produced near the anode and fill the gap following the evolution and distribution of the electron current density.

Optical spectroscopy studies of Nd3+-doped scheelite calcium molybdate (CaMoO4) single crystal grown by a floating zone-like technique was performed using Judd-Ofelt analysis, besides luminescence data and lifetime measurements in the visible and near infrared domains. The excited state absorption in cross section units of this material was measured by two different methods for all expected infrared emission. By using calculated intensity parameters $\Omega _{t}$ (t=2, 4, 6), it were determined branching ratios, emission cross-sections, and lifetimes for all related transitions. The observed single excited state absorption calibrated in absorption cross-section units was found too small to disturb the laser efficiency in the 1030–1100 nm spectral range. A comparison of main spectroscopic parameters of this material with those of other Nd3+-doped crystals is presented.

In this paper, we present a model of a hysteresis motor based on Maxwell's equations coupled with the Jiles-Atherton (J-A) hysteresis model solved by the finite element method. The aim of this work is to validate such a model by comparison with the experimental results (electromagnetic torque, voltage, current). We also present an analysis of this motor when imposing current or voltage in the 2D vector potential formulation.

This paper presents several techniques for determining the complex conductivity of highly electrically conducting polymer films at microwave frequencies. The advantages and disadvantages of these techniques are discussed. Microwave measurements were investigated using resonant cavity, reflection/transmission and impedance surface techniques. The dc conductivity was measured using the four wires technique. Polyaniline (Pani/DEHEPSA) films of 120 $\mu $m thickness, have conductivity of (5000-6000 S/m) and permittivity of $6000 \pm 1000$ over X and S bands. The high values of the measured conductivity and its weak dependence on frequency at least up to 12 GHz, confirm the metallic character of Pani-films and their efficient use in micro-electronic technology such as microwave integrated circuits (MMIC) and microwave devices.

A tight control of acidity is needed for performing oxidation–reduction reactions of organic compounds dissolved in liquid media, since the relevant reactions often involve the occurrence of protons; the matching kinetics are therefore acidity dependent. This feature holds for plasma treatments of aqueous wastes which are intended to abate the concentration in organic pollutants. Exposure of aqueous solutions to a gliding arc plasma in humid air induces acid and oxidising reactions in the condensed phase. Acid effect results from the occurrence of NO species formed in the plasma and leads to the formation in water of nitrous and nitric acids, which are responsible for a steep pH fall. Using selected buffers allows accurate controlling of the acidity, which is necessary for most of the plasma-chemical or plasma-biochemical reactions.

The analysis by means of X-ray $\mu $CT offers a versatile tool for the non destructive characterisation of metallic foams. The most important methods for the quantitative feature determination will be presented and applied to an Al-foam produced by a powder-metallurgical processing route. The special properties of monochromatic synchrotron radiation have been used to study not only the pore- and cell-wall space quantitatively at a high resolution, but also the distribution and geometric parameters of the blowing agent TiH2. The analysis steps can be used as a standard procedure to characterise the structure of metallic foams.

The evaluation of the power brought by an electric arc to the surface of the electrodes still remains an important problem. In this paper we propose a method allowing a macroscopic approach of the power balance at the surface of a copper cathode submitted to a non stationary electric arc in argon. This method is based on a spectroscopic measurement of the instant of apparition of copper vapour in the arc and on the use of a numerical modelling of thermal phenomena occurring in the electrode. Under some simplifying assumptions, we reach an interval of possible values for the power and the surface density brought to the electrode by the arc.

Internal oxidized copper was tested by isothermal mechanical spectroscopy in a medium temperature range (300–600 K). Experimental results show the existence of a non-thermally activated effect at low temperature and of a relaxation peak at higher temperatures. The material microstructure was studied by combination of Transmission Electron Microscopy (TEM) and Electron Energy Loss Spectrometry (EELS). The TEM study allowed us to investigate the distribution of fine spherical particles and the presence of particular network dislocations inside the grains. The EELS method was used to identify the nature of these fine particles as Cu2O. The internal friction has revealed a non thermally activated maximum occurring at 0.1 Hz for temperatures ranging from 290 K to 394 K, and a relaxation peak obtained after annealing at 573 K. This peak is stable after successive annealings at 723 K and 873 K. Comparison of the microstructure observations, their evolution with annealing and the evolution of the relaxation effect with annealing temperature enables us to interpret the phenomena described in this work: on the one hand, the microstructural characterisation using TEM and EELS allows us to assign the first effect to the result of a transformation of metastable Cu2O particles to CuO under the cyclic stress; on the other hand, the relaxation peak that does not change after high temperature annealing is linked with a particular stable dislocation network observed in many grains. 


X-ray emission from a compact diode consisting of a sharp edged cathode and flat anode of copper and lead, energized by simple capacitor discharge is reported. With a sewing machine needle cathode, and lead target, the generation efficiency upto 0.4% is obtained. The efficiency is expected to enhance further with the increase in discharge energy, charging voltage and reducing the parasitic inductance.

Gas mixtures containing humid air, various proportions of CO2 and traces of NO2 are submitted to a short gap point-to-plane DC corona discharge in a reactor at atmospheric pressure. These mixtures can be considered as the basic component of most industrial effluents. Coming after an electrical study previously published, this work is centered on the physico-chemical effects of the discharge. Concentric circular alterations appearing on a copper cathode have been analyzed by XPS, showing an oxidation and acidification spread over a great part of the surface by the electric wind. The NO2 removal and corresponding by-products have been studied by UV absorption spectroscopy on gas samples after treatment, in the 200–400 nm wavelength range where NO2 abatement and O3 concentrations can be evaluated. Being partly produced in liquid phase, HNO3 which is responsible of the acidification of cathode surface, can be studied only qualitatively. A few chemical mechanisms are propounded for both bulk and surface actions of the discharge.

YO molecules in the vapor phase above Y2O3 melted in a solar furnace exhibit a fluorescence phenomenon induced by absorption of the incident radiation. The simulation of these spectra by a two temperature model and comparison with measured spectra allowed to estimate the temperature field in the gas phase above the melted sample. The results are compared to the results of a simulation by a commercial fluid dynamics software.

The dynamics of shock waves and cavitation bubbles generated by short laser pulses in water and elastic-plastic media were investigated theoretically in order to get a better understanding of their role in short-pulsed laser surgery. Numerical simulations were performed using a spherical model of bubble dynamics which include the elastic-plastic behaviour of the medium surrounding the bubble, compressibility, viscosity, density and surface tension. Breakdown in water produces a monopolar acoustic signal characterized by a compressive wave. Breakdown in an elastic-plastic medium produces a bipolar acoustic signal, with a leading positive compression wave and a trailing negative tensile wave. The calculations revealed that consideration of the tissue elasticity is essential to describe the bipolar shape of the shock wave emitted during optical breakdown. The elastic-plastic response of the medium surrounding the bubble leads to a significant decrease of the maximum size of the cavitation bubble and pressure amplitude of the shock wave emitted during bubble collapse, and shortening of the oscillation period of the bubble. The results are discussed with respect to collateral damage in short-pulsed laser surgery.