Dielectric barrier discharges (DBDs) have been investigated under a wide range of experimental conditions (pulsed and sinusoidal excitation, input energy, frequency, and residence time) to remediate NOx from atmospheric O2 rich gas streams. In a given reactor under identical gas composition and equivalent energy density deposition, results show that the main parameter which controls the efficiency of the plasma process is the energy deposition mode. For example, in a pulsed DBD processing at energy density deposition of 30 J/L, 25% of NOx and 40% of C3H6 were converted at 35 mJ/pulse whereas, at 195 mJ/pulse these values were 0% and 15%, respectively. Furthermore, significantly different end products were observed when changing the nature of electrical excitation.

We present the calculation of the impedance variation using a half-analytical formulation based on coupled electromagnetic variables. Such a formulation concerns an axisymmetrical device constituted with a voltage supplied solenoïdal inductor and a conducting workpiece. In this field of modelling, authors have already developed a method [Maouche and Feliachi, J. Phys. III France 10, 1967 (1997)] that determines the current distribution inside inductor coil loops in the case of weak skin depth and a low number of these coil loops. In the proposed development, the number of loops is relatively large and the skin effect in these loops is negligible. This formulation uses a voltage excitation, which makes the source field depending on induced currents and permits to consider the real geometry of the inductor. The model is applied to study an eddy current non destructive testing (ECNDT) device. The variation of the system impedance is calculated in the case of an axisymmetrical device. The obtained modelling results are validated by comparison to measurements and finite element computations [Rémy, Ph.D. thesis, University of Compiègne, France, 1997; La et al., Rev. Prog. Quant. Non-Destructive Eval. 16A, 295 (1997)]. Once validated, the proposed model is applied to determine geometrical and physical characteristics of an ECNDT device. To assemble this interest, we visualise the evolution of the impedance variation according respectively to the air-gap, to the thickness of the workpiece and its electric conductivity. The model is implemented within a software tool (CECM: Coupling Electromagnetic Circuits Method) developed in Matlab environment.

The conditions for formation of ion acoustic weak double layer in a dusty plasma are investigated. In case of much lower value of ion-electron temperature ratio, the weak double layer is observed when the fraction of the negative charge in the plasma on the dust grain is ${\geq}0.45$, whereas for equal ion-electron temperature it is observed only when the fraction is ${\geq}0.6$. The parameter regimes of transition from compressive to rarefactive double layer are also specified.

The electrical supply of portable electronic devices is a crucial problem, which may be solved by harvesting a part of the mechanical energy dissipated in our environment. For the last ten years, many prototype piezoelectric generators have been proposed in research literature, offering different technological choices, but always working according to the same schematics: three different conversion stages. The first one, named mechanical application device (MAD), transforms the initial mechanical stress into a higher level or higher frequency stress. This stress is applied to the second stage, the piezoelectric device (PD). The last stage, an electronic circuit named harvesting system (HS), is essential to maximise the electrical energy delivered to the targeted electronic device. In this paper, we present an experimental test bench that can replace any association of MAD and PD. Then we describe our HS, and demonstrate its performances for our application, where the applied mechanical stress is exponential and varies with a low frequency. Thanks to this HS, the conversion from mechanical energy to electrical energy is improved, and this phenomenon can be explained by simulation, using an equivalent circuit. At last, some experimental results are commented, leading to the perspectives of this research project.

The heating rate effects in simulated liquid Al2O3 have been investigated by Molecular Dynamics (MD) method. Simulations were done in the basic cube under periodic boundary conditions containing 3000 ions with Born-Mayer type pair potentials. The temperature of the system was increasing linearly in time from the zero temperature as $T(t)=T_0 +\gamma t$, where $\gamma $ is the heating rate. The heating rate dependence of density and enthalpy of the system was found. Calculations show that static properties of the system such as the coordination number distributions and bond-angle distributions slightly depend on $\gamma $. Structure of simulated amorphous Al2O3 model with the real density at the ambient pressure is in good agreement with Lamparter's experimental data. The heating rate dependence of dynamics of the system has been studied through the diffusion constant, mean-squared atomic displacement and comparison of partial radial distribution functions (PRDFs) for 10% most mobile and immobile particles with the corresponding mean ones. Finally, the evolution of diffusion constant of Al and O particles and structure of the system upon heating for the smallest heating rate was studied and presented. And we find that the temperature dependence of self-diffusion constant in the high temperature region shows a crossover to one which can be described well by a power law, $D\propto (T-T_c )^\gamma $. The critical temperature Tc is about 3500 K and the exponent $\gamma $ is close to 0.941 for Al and to 0.925 for O particles. The glass phase transition temperature Tg for the Al2O3 system is at anywhere around 2000 K.

SiClx radicals, the silicon etching by-products, are playing a major role in silicon gate etching processes because their redeposition on the wafer leads to the formation of a SiOClx passivation layer on the feature sidewalls, which controls the final shape of the etching profile. These radicals are also the precursors to the formation of a similar layer on the reactor walls, leading to process drifts. As a result, the understanding and modelling of these processes rely on the knowledge of their densities in the plasma. Actinometry technique, based on optical emission, is often used to measure relative variations of the density of the above mentioned radicals, even if it is well known that the results obtained with this technique might not always be reliable. To determine the validity domain of actinometry in industrial silicon-etching high density plasmas, we measure the RF source power and pressure dependences of the absolute densities of SiClx (x = 0−2), SiF and SiBr radicals, deduced from UV broad band absorption spectroscopy. These results are compared to the evolution of the corresponding actinometry signals from these radicals. It is shown that actinometry predicts the global trends of the species density variations when the RF power is changed at constant pressure (that is to say when only the electron density changes) but it completely fails if the gas pressure, hence the electron temperature, changes.

A computerized model of steady–state photon diffusion within turbid media such as biological tissues, solved by means of the Finite Element Method (FEM) is presented in this paper. Assuming that the different media are illuminated by a flat collimated laser beam source, we develop the basic theory including the suitable boundary conditions along the meshed domain. Model simulations depict firstly photon-flux density patterns in the $r-z$ plane associated with axis fluence rate profiles, plotted as functions of media properties and beam sizes. A second objective was to display both the rate of re-emitted optical power integrated by an optical fibre radially displaced away from the source and the power integrated by an optical fibre axially moved inside the tissue. Simulation studies are further extended to multilayered media such as skin and aorta, in order to describe the light propagation through these tissue structures more realistically.

In this work we have considered the R. Nayak et al. [Immunology 102, 387 (2001)] biological model – Relay Hypothesis – to study the time evolution of the clonal repertoire, including the populations of antibodies. Our results suggest that the decrease of the production of antibodies favors the global maintenance of immune memory.

A spectroscopic investigation of corona discharges in SF6/N2 gas mixtures has been undertaken using an optical multichannel analyser (OMA). A point-to-plane geometry has been used with point radii varying from 3 to 10 μm. Spectra are measured for high pressures ranging from 0.2 MPa up to 1.4 MPa and for different concentrations of SF6 in the gas mixture. The spectra in the 200–850 nm spectral range are mainly made of molecular bands, which is indicative of a low temperature discharge. It has been noted that SF6 emits in the region of 420 nm to 510 nm in positive and negative polarities, although in negative polarity the emission is weaker. For SF6/N2 mixtures, the main source of light emission is from N2. The resultant spectra are used to evaluate the rotational Tr and vibrational Tv temperatures of excited N2, Tr being considered, due to the high pressure, to be equal to the kinetic temperature Tkin in the corona discharge. Tr and Tv are determined by comparing the experimental spectrum of the second positive system ($C^{3}\Pi_{u}\to B^{3}\Pi_{g})$ of N2 and the simulated one, which is obtained using a convolution method. As expected, the results show that the measured rotational temperature Tr increases steadily with the mean discharge current, while its increase with gas pressure is less pronounced. The values of Tr are higher for the positive corona discharge than the negative and also for mixtures having higher amounts of SF6. In all conditions, we found $T_{v}>T_{r}$ and Tv is less sensitive to the variation of the current.

For physical processes which express themselves as a frequency, for example magnetic field measurements using optically-pumped alkali-vapor magnetometers, the precise extraction of the frequency from the noisy signal is a classical problem. We describe herein a frequency measurement system based on an inexpensive commercially available computer sound card coupled with a software single-tone estimator which reaches Cramér–Rao limited performance, a feature which commercial frequency counters often lack. Characterization of the system and examples of its successful application to magnetometry are presented.

A simple and straightforward method to assess the relative temporal fluctuation of the individual pixels in a CCD array with respect to the fluctuation of the spatial average is proposed. This procedure is based on the comparison of the low-frequency temporal noise of the individual pixels and the value of this magnitude averaged over the entire CCD. Moreover, this method is able to detect the presence of bad pixels within the array (drifting and flicking). The importance of this study resides in the need to know whether or not the behavior of the individual pixels can be approximated by that of the spatial average and to assess the stability of Nonuniformity Correction algorithms (NUC). Once the mathematical formulation was developed, it was applied to the analysis of a specific CCD array, the Sony ICX414AL. The results show three different trends in the behavior of its pixels.