Electronic properties of ITGO (Sn+Ge doped In2O3) thin films have been investigated for various compositions with decreasing doping levels (molar ratios [Sn]/[In] ≤ 0.05 with [Ge] = 0.2 [Sn]). Conductivity and Hall measurements versus temperatures ranging from 77 to 500 K have shown that two electron scattering mechanisms are to be considered. Even though ionised impurities dominate the electron scattering in the whole temperature range, the influence of optical phonons cannot be neglected. It appears gradually from 200 to 250 K and involves a marked decrease of the electron mobility with temperature. The influence of the doping level on the electron mobility has also been studied. It can be correlated with the effective mass variations deduced from the evolution of the thermoelectric power versus temperature [1, 2] and with the observation by optical absorption of localised states for the lowest doping levels [1, 8].

Dielectric measurements of a new antiferroelectric liquid crystal series exhibiting different phase sequences have been carried out as a function of frequency from 10 Hz to 10 MHz. Structural properties of SCα* and ferrielectric SCFI* phases were discussed on the basis of the experimental results of temperature and dc bias field dependencies of the dielectric modes. Besides the soft mode observed around the SA−SCα* phase transition, a Goldstone mode was detected in the SCα* phase indicating a helicoidal structure with small pitch values. In agreement with a bilayer ordering model, the dielectric absorption in the SCFI* phase was splitted up into two contributions: one related to a Goldstone mode and the other to an azimuthal antiphase mode.

Based on the deformation theory of plasticity the problem of pressure distribution in a compressed layer at phase transition experiencing a plane plastic deformation is considered. It is found that in the pressure distribution near the phase boundaries anomalies emerge in the form of a “step” or a local maximum caused by volume jumps at phase transition. It is shown that these anomalies and differences in yield limits of the phases can lead to essential change of pressure in the center of the layer in comparison with its value in absence of phase transition, but under equal external load. The maximal value of external load admitting the considered solution is found. The kinetics of possible isothermal regimes of phase transition leading to change in the time-pressure distribution in the plastic layer is investigated.

A new control method of cascaded power supply converters using the sliding approach is presented here. Variable Structure Control enables the problems of stability brought about by cascaded converters to be solved and its robust behaviour acts against variations in the load parameters and supply voltage.

The authors propose study methods of three phase short circuits of an induction traction motor. Methods are based on finite element model or equivalent circuits of the machine and take into account, more or less accurately, saturation and deep bar effects. Depending on the modeling level, they can be used to study short circuit torque or current maxima, waveforms or local constraints. The proposed methods are applied to a 1.5 MW - 4 pole traction motor short circuit study.

The operation of Pichugin pulse generators (named after their Russian inventor) is studied. A set of equations for a one-stage generator enables us to point up the important frequency properties of the magnetic core transformer. An analytical and numerical study of a three-stage generator is performed. Improvements, concerning the voltage gain, are suggested; the consequences on the rise time value are analysed. A new conception method, based on compensated and asymmetrical stages, is proposed. It is a compromise solution to decrease the rise time value and to increase the voltage gain. By using this structure, the realization of a 120 kV, 145 ns rise time three-stage pulser is proposed; its operating at a frequency greater than 1 kHz is studied.

Low-frequency noise measurements were performed on intrinsic low pressure chemical vapor deposited polycrystalline silicon resistors. The current noise exhibits a transition from 1/f to 1/f0.6 behavior with the resistors biased in the linear region. The origin of the noise is related to carrier density fluctuation between conduction band and gap states consisting of deep states lying close to midgap with uniform energy distribution and exponential band tails. From analysis of the experimental data, the quality of the material is characterized with respect to the deposition pressure. When the resistors are biased in the non-linear regime, an additional noise is observed which is attributed to the temperature rise due to Joule-induced heating within the samples.

This paper concerns momentum and heat transfer to a nonevaporating oxidized steel spherical particle (diameter 6.5 mm − 8 mm) levitated at high Reynolds number in argon turbulent plasma jet flowing into cold air. The rapid rotation of the particle in the plasma flow ensures the stability of the levitation phenomenon over a wide range of plasma torch parameters. We use a dimensional analysis to describe the momentum transfer and the equilibrium levitation height data. The convective heat transfer coefficient was further estimated from gas and particle equilibrium temperature at the front stagnation point or from the analysis of the transient temperature signal for a particle abruptly immersed and levitated in the plasma jet. Particle rotation is shown to determine the heat transfer rate in a nonuniform plasma flow.

Heat and mass transfers occuring in a counterflow direct contact liquid-gas exchanger determine the performance of a new greenhouse air dehumidifier designed at INRA. This prototype uses triethylene glycol (TEG) as the desiccant fluid which extracts water vapor from the air. The regeneration of the TEG desiccant fluid is then performed by direct contact with combustion gas from a high efficiency boiler equipped with a condensor. The heat and mass transfers between the thin film of diluted TEG and the hot gas were simulated by a model which uses correlation formula from the literature specifically relevant to the present cross-corrugated plates geometry. A simple set of analytical solutions is first derived, which explains why some possible processes can clearly be far from optimal. Then, more exact numerical calculations confirm that some undesirable water recondensations on the upper part of the exchanger were limiting the performance of this prototype. More suitable conditions were defined for the process, which lead to a new design of the apparatus. In this second prototype, a gas-gas exchanger provides dryer and cooler gas to the basis of the regenerators, while a warmer TEG is fed on the top. A whole range of operating conditions was experimented and measured parameters were compared with numerical simulations of this new configuration: recondensation did not occur any more. As a consequence, this second prototype was able to concentrate the desiccant fluid at the desired rate of 20 kg H2O/hour, under temperature and humidity conditions which correspond to the dehumidification of a 1000 m2 greenhouse heated at night during the winter season.

A new structural model of shear-thickening “dilatancy” is proposed for (strongly) stabilized disperse systems. This model is based on the effective volume fraction (EVF) concept, developed in Part I of this series and previously used for the rheological modeling of complex fluids. In such a description, the latter are considered as concentrated dispersions of basic structural units (SUs) — either small, compact clusters or primary particles —, forming large structures at low shear. As shear rate increases, rupturing of these large structures leads to the shear thinning observed prior to dilatancy. The novelty of this model lies in assuming that, beyond the onset of dilatancy, hydrodynamic forces promote, at the expense of basic-SUs, the formation of hydrodynamic clusters as both rheo-optical experiments and numerical simulations recently demonstrated, in contradiction with the (classical) theory based on a shear induced disruption of particle layering. Dilatancy directly results from the increase of the EVF of the dispersion, closely related to the increasing volume of continuous phase imprisoned inside hydroclusters whose size grows as the shear rate increases. Predictions of the model are discussed in comparison with the Mayn features observed in a large number of dilatant dispersions, especially the volume fraction dependences of viscosity and critical shear rates (onset of dilatancy, maximum and discontinuity in viscosity) also the effects of particle size, polydispersity and suspending fluid viscosity.

The use of rheometers for the evaluation of rheological properties and the establishment of behaviour laws for fluids requires the knowledge of the shear rate at any moment and everywhere in the region between the cone and the plate, referred to as “the gap” throughout this paper. However, the accurate determination of the shear rate supposes that the constitutive equation of the fluid is known beforehand. In order to avoid this paradox, rheometers are generally built such that the shear rate is supposed to be approximately constant throughout the gap. This approximation is realistic for steady flow but may be crude for other types of fluid motion. The aim of the present work is to determine the limits of validity of such an approximation when testing complex fluids in a cone and plate geometry. In this paper, only purely viscous properties are taken into account. The numerical solution is based on the control-volume method. When non-linear and time-dependent effects occur, it is shown that the flow cannot be represented by simple shearing conical surfaces. This result is especially important for the characterisation of time-dependent fluids (as thixotropic fluids), typical of unsteady flow. Finally the abilities of the proposed model which is named “RHEOUTIL” are highlighted by comparison between numerical simulations and experimental results. The analysis of non Newtonian fluids emphasises the limits of the code “RHEOUTIL”. Indeed, the model has to evolve in order to take into account the whole complexity of the fluid, which may also exhibit viscoelastic properties, yield stress and so on.

The design of the main current systems of an actively shielded and of an iron shielded MRI device for nuclear resonance imaging, is considered. The model for the analysis of the magnetic induction produced by the current system, is based on the combination of a Boundary Element technique and of the integration of two Fredholm integral equations of the first and the second kind. The equivalent current magnetization model is used for the calculation of the magnetization produced by the iron shield. High field uniformity in a spherical region inside the device, and a low stray field in the neighborhood of the device are required. In order to meet the design requirements a multi-objective global minimization problem is solved. The minimization method is based on the combination of the filled function technique and the (1+1) evolution strategy algorithm. The multi-objective problem is treated by means of a penalty method. The actively shielded MRI system results to utilize larger amount of conductor and produce higher magnetic energy than the iron shield device.

The possibility of characterizing immersed targets in laboratory conditions, whatever the water surface roughness is discussed in this paper. The first idea was to reduce the interface effects or better to suppress them within the analysis.We used the Mueller formalism to characterize targets in the laboratory. In optics, each element can be described by a Mueller matrix. Then, in the present work we tried to decompose the global measured matrix and to separate the interface matrix from the target matrix which is the one of interest. This paper shows it impossible to perform such a decomposition. We succeeded in reducing the interface effects without eliminating them entirely. So this paper focuses on finding a decomposition algorithm of a Mueller matrix to deduce the polarimetric type of a target whatever the interface state.