Several important errors and misinterpretations present in a recent publication by Khan et al. [Eur. Phys. J. Appl. Phys. 45, 11002 (2009)] are pointed out and discussed. In particular, it is shown that the method used to calculate the rate coefficients for the electron impact excitation of 3p54p and 3p55p states of argon is incorrect and leads to unrealistically high rate coefficients.

We investigated the pulsed laser ablation of metallic (Al), semiconductor (Si), and wide bandgap dielectric (LiNbO3) targets in air at normal atmospheric conditions by using 4.5 ns pulses at 532 nm wavelength. We determined the dependence of the ablation rate on the pulse number and laser fluence. The number of consecutive laser pulses hitting the target on the same area was between 5 and 40, and the laser fluence was varied in the range of 10–250 J/cm2 by changing the irradiated area at the target surface. We find that the ablation rate of the three targets is approximately constant when the pulse number is smaller than 15. Further increase of the pulse number leads to a decrease of the ablation rate, the fastest decrease of the ablation rate with pulse number being observed for the dielectric target. The dependence of the ablation rate on the laser fluence indicates two different regimes. In the first regime, which is for values of the fluence smaller than the threshold value (~70 J/cm2 for Al, ~90 J/cm2 for Si, and ~180 J/cm2 for LiNbO3), the ablation rate increases approximately logarithmically with the fluence. In the second regime, characterized by values of the fluence greater than the threshold value, there is a steep increase of the ablation rate. This sudden jump of the ablation rate at the threshold fluence is due to the transition from normal vaporisation to phase explosion, and to the changes in the dimensionality of the plasma-plume hydrodynamics from one-dimensional to three-dimensional.

We present an experimental study of pattern formation in a Dielectric Barrier Discharge in Neon at 100 torr and 1 mm gap. An intensified CCD camera is used to analyze the time evolution of the patterns during one cycle of the voltage waveform. The formation of a hexagonal pattern of filaments in a transient, glow-like regime is observed, followed by a honeycomb structure that corresponds to a Townsend discharge occurring outside the regions delimited by the previous filaments. A 2D fluid model can qualitatively reproduce these features and is used to help interpreting the experimental results.

Three dielectric barrier discharge jets have been analyzed mainly by spectroscopic methods. Power densities, electron concentrations, and heavy particle temperatures are in the same range for the jets. All three jets are excited by sinusoidal voltages with kilohertz frequencies. High speed imaging proves that for quite different excitation schemes the jet plasma consists of isolated, fast moving, light-emitting structures. These so-called plasma bullets are emitted at a certain phase of the excitation voltage and occur in one half-cycle only.

The present paper deals with the investigation of Argon ions – substrate interactions during film growth and their influence on sputtered hydrogenated amorphous silicon (a-Si:H) thin films structural properties. These interactions are characterized by mean of the calculation of the energy distribution of Ar ions striking the substrate and their striking force measurement in the case of Rf diode sputtering. The influence of the Ar ions bombardment on structural and physical properties of amorphous silicon thin properties is discussed. The ion bombardment affects the film growth processes and consequently, it causes films densification and evolution of film microstructure from amorphous state at low power towards a microcrystalline material with increasing the Rf power.

Embedded electric HVDC distribution network are facing difficult issues on quality and stability concerns. In order to help to resolve those problems, this paper proposes to develop an analytical model of an electric drive. This self-contained model includes an inverter, its regulation loops and the PMSM. After comparing the model with its equivalent (abc) full model, the study focuses on frequency analysis. The association with an input filter helps in expressing stability of the whole assembly by means of Routh-Hurtwitz criterion.

An electric network is constituted by generators providing power to various loads. The induction machine is the most common motor in the industrial applications because of its simplicity of construction, its reliability and its low cost. It allows the constant speed applications when it is directly supplied by the network and variable speed ones with the use of power converters. These speed drives induce important harmonic perturbations in the power system and in the motor side. In this context, we are interested by the frequential modelling of the induction machine in order to simulate the line current with its harmonic components. In order to use the induction machine models, it is necessary to identify their parameters and therefore realizing specific and sufficiently informative tests. Several tests of identification are presented in the literature; their differences and their relevance have not been discussed. This study deals with the realization and the comparison of several types of frequential tests (constant voltage, constant V/f, injection of DC current) for induction machine models identification. The comparison of the simulation results with the experimental measurements allows electing the most representative of the induction machine behaviour.

Dielectric barrier discharges (DBD) in air at atmospheric pressure and at low frequency are mainly constituted of thin transient plasma filaments (or microdischarges) with radii of a few hundreds of micrometers. In this work, we consider a point-to-plane geometry with the dielectric covering the plane electrode. Plasma filaments are initiated by streamers, starting from the high-field region close to the point electrode. The plasma filaments deposit charges on the dielectric plate which screen the electric field and lead to an extinction of the discharge filaments. In this work we experimentally demonstrate the synchronous start of several filaments in a time range of less than a few tens of nanoseconds and we show that the charges deposited on the dielectric have a strong impact on the discharge structure. This is validated using a simple electrostatic model. Then, the dynamics of the 2D streamer propagation in the gas gap and its interaction with the dielectric plane is calculated. The influence of space charges and surface charges on the discharge structure are discussed and compared with the experiment.

In this article, we report on the simulation and realization of a magnetic circuit allowing to apply an axial magnetic field higher than 1 T. The proposed electromagnet is used to investigate the influence of a magnetic field on the polarization behavior of a vertical-cavity-surface-emitting laser (VCSEL). A non-linear polarization behavior can be experimentally observed for currents as low as the threshold current, provided that the magnetic field is strong enough.

We obtain the approximate solutions for the steady temperature profiles of materials with a temperature-dependent thermal absorptivity inside a microannulus with wavy-rough surfaces considering a quasilinear partial differential equation by the boundary perturbation approach. Our numerical results show that the wave number as well as the small amplitude of the wavy roughness will influence the net temperature significantly especially near the inner wall of a microannulus. Meanwhile we observed that the critical Frank-Kamanestkii parameter depends on the small-amplitude wavy-roughness for specific power-law of thermal absorptivity. Our results could be applied to the relevant fields in MicroElectroMechanical System (MEMS).

Properties of pulsed corona streamers are measured and simulated in full three spatial dimensions (3D). Stereo photography is used to measure branching angles and to investigate whether apparent streamers reconnections are real. 3D simulations of two parallel streamers show that they can repel each other electrostatically, but that they also can merge due to photoionization. The electrostatic interaction of several streamers becomes evident through theoretical investigations of a periodic array of streamers.

This paper presents an analytical approach to estimate the magnitude of a flux density component at a point located outside an AC machine. The study uses the concept of attenuation coefficients which are determined using several hypotheses. The developments consider the different media according to they are flowed by eddy currents or not. Then, the calculations are performed in each medium.

The reaction kinetics of photochemical ozone (O3) generation in humid air and oxygen (O2) using efficient, narrow band vacuum ultra violet (VUV) 172 nm xenon excimer lamps is discussed. Trace amounts of water (H2O) vapor in the process gas leads to hydroxyl (OH) and hydroperoxy (HO2) radical formation. These radicals drive a catalytic O3 destruction cycle limiting O3 saturation concentration. This catalytic O3 destruction cycle was included into a quantitative kinetic model describing photochemical O3 production. Experimental O3 saturation concentrations obtained with coaxial VUV driven photochemical O3 generators compare satisfactorily with the models predictions.

This paper deals with an original approach of the Switched Reluctance Machine (SRM) control for the purpose of reducing stator vibrations. Two combined approaches are studied in the aim of reducing the vibratory acceleration generated and thus the acoustic noise. The first one is based on a sinusoidal control of the magnetic phase current and the second one, on an optimal control of piezoelectric actuators (PZT) stuck on the SRM stator. The sinusoidal control of the magnetic phase current introduces properties on the vibratory acceleration distribution that are used to design an original actuator controller. Principles and viability of these combined vibration damping methods are deduced from theories and experiments.

We explore numerically the feasibility of enhancing the mixing capability of microchannels by employing the Weierstrass fractal function to generate a pattern of V-shaped ridges on the channel floor. Motivated by experimental limitations such as the finite resolution (~10 μm) associated with rapid prototyping through soft lithography techniques, we study the influence on the quality of mixing of having finite width ridges. The mixing capability of the designs studied is evaluated using an entropic measure and the designs are optimized with respect to: the distances between the ridges and the position range of their tip along the width of the channels. The results are evaluated with respect to the benchmarks established by the very successful staggered herring bone (SHB) design. We find that the use of a non periodic protocol to generate the geometry of the bottom surface of the microchannels can lead to consistently larger entropic mixing indices than in cyclic structures. Furthermore, since the optimization curves (mixing index vs. geometric parameters) are broader at the maximum for fractal microchannels than for their SHB counterparts, the microchannel designs using the Weierstrass fractal function are less sensitive to experimental uncertainties.

Everyone knows the importance of sensors in our society and the huge attempt to improve their properties in order to obtain better sensitivity and selectivity. In this paper, we are more particularly focused on gas sensors based on surface acoustic waves (SAW) device. In a previous work, we have developed and studied a structure composed of a 90° rotated ST quartz crystal covered with a ZnO layer. By developing inter-digital transducers (IDT) on this structure, we can generate different types of acoustic waves. Love waves which are confined near the surface are known to be very sensitives to fluids (liquids or gases). The aim of this work is to present the way we have developed this optimal structure and to test it with a specific polymer. This polymer is polyaniline (PANI). Its main advantage is that it should be deposited by cold pulsed plasma process.

Microplasmas inside confined cavities, pores and capillaries of dielectric materials present a great potential for various environmental applications. The paper briefly introduces the physical properties of the AC microplasmas generated by the discharges inside porous ceramics foams and focuses on their chemical effects in various mixtures of nitrogen and oxygen. Ozone formation as an example tool to evaluate the chemical potential of the microplasmas was investigated as a function of discharge power, gas mixture composition and total gas flow rate.

An experimental study is carried out to clarify the mechanism of the ozone zero phenomenon. Temporal variations of both the discharge characteristics and the metallic electrode surface in the ozone generator are investigated by the Lissajous figure method and Auger electron spectroscopy (AES), respectively. The AES results suggest that a number of oxygen atoms penetrate into the stainless-steel electrode owing to the exposure to ozone. Such a surface change would result in the temporal variation of the discharge characteristics of the generator.