In this paper, finite element method is used to compute inductance parameters of asquirrel cage induction machine. To take into account saturation effect, saturatedequivalent parameters are introduced, which depend on the instantaneous value of themagnetising current. For a balanced induction machine, the particular inductance behaviors allow straightforward flux expressions without any cross saturation effect.Moreover, these expressions are explained thanks to an extended analytical approachconsidering a magnetic saliency phenomenon by a second order air-gap permeance. Asimple way of transformation ratio and leakage inductance computation is also deduced.The numerical results show the compatibility between finite element approach and extended analytical Park's method. Besides, two operating points (at no load and for nominal speed) studied by the both methods give very closed results.

This paper deals with the modeling of Printed Circuit Boards (PCB) for numerical resolution of a power circuits electromagnetic Compatibility (EMC). The well-adapted model for numerical resolution is the thin wire model. Thus, the PCB trace is replaced by N thin wires. Each wire radius is calculated as a function of the PCB dimensions. This model is applied to calculate the radiated electric field from a PCB circuit using the moment method which is well-suited for thin wire modeling. By observing the influence of the electromagnetic field radiated from the circuit, the number of equivalent wires required to have coherent results is established. The study of the current distribution in the wires shows that the thin wire model takes into account both the skin and the proximity effects.

L'article présente une méthode itérative de type point fixe, pour calculer le champ magnétiquedans un dispositif présentant de l'hystérésis magnétique. La méthode est appliquée à un calcul de champbidimensionnel, par la méthode des éléments finis, dans lequel l'hystérésis est modélisé par un modèlescalaire analytique simple. La convergence du calcul est vérifiée. Un problème test élémentaire, qui neconverge pas par les méthodes habituelles, est résolu en potentiel magnétique scalaire d'une part, et enpotentiel magnétique vecteur d'autre part. Les résultats prouvent l'efficacité de l'algorithme, appliqué à la modélisation d'un dispositif d'enregistrement magnétique.

We report the local study of an operating double hetero-junction GaAs/GaAlAs laser diode by apertureless Scanning Near-field Optical Microscopy (SNOM). This study allows the characterization of the spatial properties of the light emitted by the laser source. The optical probe used is a tungsten tip vibrating (at frequency f) perpendicularly to theemitting surface. Suitable experimental parameters permitting us to accede tonear-field information have been defined. This has leaded to an experimentalconfiguration in which the probe vibration amplitude is "optimal". A far-fielddetection at grazing angle is used and a second harmonic (at frequency 2f) lock-indetection is performed. This configuration has permitted us to obtain SNOM images instimulated emission as well as in spontaneous emission. Above the threshold current,information concerning the emitted laser mode are obtained, whereas in spontaneousemission the SNOM images are linked to the index contrast of the laser diode frontfacet.

The failure of electrolytic capacitors is the cause of most breakdowns of static converters. The function of these capacitors is to filter and to store electrical energy. Accelerated aging tests showed that the increase of the internal resistance ESR of the capacitors is a good indicator of their faulty state. The filter function is affected by the capacitors wearout on the one hand. At high frequency, the voltage ripple at the terminals of the capacitors increases according to ESR rise. On the other hand, the storage function is not much influenced by the capacitors aging. As static converters work most of the time at variable load, high transient values of the voltage ripple occur when output current changes that can induce false alarms. These transients are verified theoretically and experimentally. In order to avoid these transients effects, we suggest to monitor the fundamental component of the voltage ripple. This latter waveform is the best signature of the capacitors state. The ESR of the capacitors and the time before their failure are deduced from the processing of this waveform with other converter parameters such as input voltage, output current and ambient temperature.

Gratings can be considered as resonant structures in near-field.The enhancement of the intensity recorded by Scanning Near-FieldOptical Microscopes (SNOM) is due to interferences in relation with the ratio ofthe wavelength to the product of the optical index by the period of thegrating. We discuss the effect of this ratio (in the range 0.9, 1.1) on theintensity patterns. The influence of the polarization on near-field data isanalyzed in both theoretical computations and experimental result.

Using the technique of frequency-domain interferometry, we demonstrate a new way of studying laser-induced breakdown at the surface of dielectric materials. A theoretical model based on electron production by multiphoton ionisation, inverse bremsstrahlung heating, and collisional ionisation is in quantitative agreement with both the detailed time variation of the dielectric constant and the pulse width variation of the fluence threshold. From the complex reflection coefficient measured with the two probe pulse polarisations in quadrature, we deduce the time variation of the dielectric constant of silica during breakdown.

In this paper, we propose a model for the LDMOS transistor used for poweramplification in the frequencies band 1.8–2.2 GHz dedicated to the mobiletelephony system Digital Cellular System (DCS). This model takes into account thebehaviour of each internal region of the power structure. A new representation of thenon-linear inter-electrode capacitances, drain-gate Cgd and drain-source Cds , is proposed. The obtained model is implemented in the circuit simulator PSPICE, whichgives an overall evaluation of the transistor performances in the radio frequencypower amplification mode. This model is Maynly intended to the system designer. Astudy of the power amplification in the SHF band at 2 GHz is performed. A goodagreement between experimental and simulation results is found.

Notre recherche consiste à concevoir et réaliser une source de flux statique à aimants permanentsgénérant un champ de 4 à 5 Tesla dans un volume de quelques mm3. Un des aspects novateurs decette approche est que nous avons cherché à obtenir un champ magnétique intense (principe du dipôleponctuel) et non pas un champ magnétique homogène (principe du dipôle infini utilisé dans les structuresde Leupold/Halbach). Après optimisation du modèle analytique, nous avons discrétisé la structurede manière à obtenir un modèle réalisable à partir de pavé d'aimants réels. Une originalité du travailest la recherche d'une géométrie performante et une combinaison de divers matériaux magnétiques durs(nuances d'aimants Néodyme-Fer-Bore) et de matériau magnétique doux (Fer-Cobalt). Les configurationsparticulières d'aimants sont optimisées par simulation numérique grâce à des logiciels complémentaires,développés par le LEG : DIPOLE-3D (calcul analytique de champ), FLUX2D et FLUX3D (éléments finis).L'étude de faisabilité du projet a été réalisée en calculant les forces et les champs démagnétisants lors dela séquence de montage. Le modèle de source actuel fournit un champ atteignant 4,3 T dans un volume dediamètre de 6 mm pour une hauteur de 2,8 mm et ayant un diamètre extérieur de 100 mm.

This contribution presents an application of scanningnear-field optical microscopy to the characterization of semi-conductors.It is based on the photocurrent mapping of a patterned Au/GaAs structure(Schottky barrier) under local illumination by the nanosource. The resultsobtained with different wavelengths, metallized or dielectric probes anddifferent bias voltages exhibit photocurrent variations independent of the topography and induced by interface defects. Finally, from this study ofa patterned planar structure, we propose a method to determine the meanfree path of the charge carriers in the volume.

Previous modeling techniques of P–N junctions have been applied for studying the annealing of Gamma-ray damage in power MOSFETs. The degradation of the physical parameters of the body-drain junction for a dose rate of 103.8 rad/min is presented. Large decrease of the reverse recombination current, of the series resistance and of the ideality factor are shown to be related to the thermal anneal. These effects are discussed and explained by the evolution of the radiation-induced defects.

Results of investigation concerning a new application of ferrofluids (magnetic fluids) in the doMayn of non-reciprocal X-band devices are shown. Values of ferrofluid slab position x 0, biasing field and ferrofluid saturation magnetization are determined for the optimum performance of an insulator. The advantages of using ferrofluids in non-reciprocal devices are also highlighted.

We have developed an apertureless Scanning Near field Optical Microscope (SNOM) in transmission, devoted to near field magneto-optics. Our apertureless SNOM combines an inverted optical microscope, which has been adapted to Faraday effect imaging, with a commercial stand-alone Scanning Probe Microscope, used in Atomic Force Microscope (AFM) mode. Two different probes are validated as apertureless SNOM tips: a home-made etched tungsten wire and a commercial AFM silicon probe. We present and analyze preliminary images of the doMayn structure in iron garnets. They indicate a SNOM resolution clearly in the sub-micrometric range. Besides, the near field magneto-optical image presents some unexpected features, not revealed in far field images.

In Near-Field Optical microscopy, the resolution isdirectly related to the experimental conditions of illuminationand separation between tip and sample. In general, there is nowell-defined linear transfer function of the measurement system.The local resolution can be described by the signal-to-noiseratio, by the separation of individual objects or in terms of datashape sharpness. In this paper we use wavelet analysis todetermine local resolution. We deduce the resolution from thecharacteristics of the wavelet and with the help of the localenergy in the decomposition.

The N2 dissociation yield has been measured in a flowing post-dischargecontaining H2 between 0 to 5%. The N atom density has been determinedin the fast post-discharge (Δt = 5 × 10−2 s) electric field has beenmeasured by electrostatic probes as a function of H2 relative concentration.It is demonstrated that the H2 produces a significant increase in the N-atom concentration measured in the post-discharge. For our experimental conditions it was determined an increase up to 3 times in comparison to pure nitrogendischarge. The maximum yield of N-atoms was obtained for a H2 relative concentration of about 2%. This result cannot only be explained by the decrease of N atoms surface losses. It is demonstrated that the N2dissociation increase is also the result of an increase of the discharge reduced electric field.

A small flexural wall rigidity brings unique features to cross-sectional shapes and bloodflow within veins, which are characterised by a non-uniform hemodynamical environment actingupon endothelial cells. Velocity fields and related wall shear stress were numerically determinedfor a large number of conditions, assuming a fully developed, steady, incompressible laminar flowthrough an uniform smooth pipe with a constant cross-section. It was shown that the flatness greatlyinfluences the resulting distribution of the wall shear stresses along the lumen perimeter. For instance, under a steady longitudinal pressure gradient at about 500 Pascal per meter inside aconstant oval-shaped tube, with a lumen perimeter of the order of 5 × 10−2 meter, themaximum wall shear stress is found at about 2 Pascal where the local curvature is minimal. Onthe other hand, the minimal wall shear stress of the order of 1 Pascal is found where the localcurvature is maximal. Clear indications have been reported showing that the hemodynamical wall shear stress does alterendothelial cell morphology and orientation. These results are being used for developing anexperimental set-up in order to locally map out the characteristic shear stresses looking for endothelial shape modifications whenever a viscous fluid flow is applied.

Results obtained using a new technique for studying cell metabolism arepresented. The technique, consisting in CO2 production monitoring, has been appliedto Saccharomyces cerevisiae yeast cells. Also the cells were irradiated using thesoft X-ray laser-plasma source at Rutherford Appleton Laboratory with the aim of producing a damage of metabolic processes at the wall level, responsible forfermentation, without great interference with respiration, taking place inmitochondria, and DNA activity. The source was calibrated with PIN diodes and X-rayspectrometers and used Teflon stripes as target, emitting X-rays at about 0.9 keV, witha very low penetration in biological material. X-ray doses delivered to the differentcell compartments were calculated following a Lambert-Bouguet-Beer law. Immediatelyafter irradiation, the damage to metabolic activity was measured again by monitoringCO2 production. Results showed a general reduction in gas production by irradiatedsamples, together with non-linear and non-monotone response to dose. There was alsoevidence of oscillations in cell metabolic activity and of X-ray induced changes inoscillation frequency.

Structural rheological modelling of complex fluids developed in Part I of this series and applied to shear thickening systems (Parts II & III), is now used to improve such a modelling in the case of unsteady behaviour, that is, in the presence of thixotropy. The model is based on an explicit viscosity-structure relationship, η(S), between the viscosity and a structural variable S. Under unsteady conditions, characterized by a reduced shear, Γ(t), shear-induced structural change obeys a kinetic equation (through shear-dependent relaxation times). The general solution of this equation is a time-dependent function, S(t) ≡ S[t, Γ(t)]. Thixotropy is automatically modelled by introducing S[t, Γ(t)] into η(S) which leads directly to η(t) ≡ η[t, Γ(t)], without the need for any additional assumptions in the model. Moreover, whilst observation of linear elasticity requires small enough deformation i.e. no change in the structure, larger deformations cause structural buildup/breakdown, i.e. the presence of thixotropy, and hence leads to a special case of non-linear viscoelasticity that can be called “thixoelasticity”.Predictions of a modified Maxwell equation, obtained by using the above-defined η(S) and assuming G = G 0 S (where G 0 is the shear modulus in the resting state defined by S = 1) are discussed in the case of start-up and relaxation tests. Similarly modified Maxwell-Jeffreys and Burger equations are used to predict creep tests and hysteresis loops. Discussion of model predictions Maynly concerns (i) effects of varying model variables or/and applied shear rate conditions and (ii) comparison with some experimental data.

The plasma plume created during photoablation of various targets by an excimer KrF laser beam is studied in typical conditions of pulsed laser film deposition. For the examination of transport phenomena of ejected species, the space and time resolved evolution of the luminous plume is investigated by fast imaging as a function of laser fluence (from 7 to $200~\mathrm{J/cm}^{2}$ ) and nitrogen background pressure (from 5 × 10−3 to 500 Pa) for five different target materials (boron nitride, graphite, alumina, molybdenum, a superconducting oxide YBCO). Under "vacuum" (5 × 10−3 Pa and for nitrogen background pressures up to 10−1−1 Pa, the plume expands freely. For higher background pressures $(\geq 10~\mathrm{Pa})$ , three successive regions above the target can be distinguished: at first the expansion is free, then the plume expands according to a shock wave-like behaviour, and lastly a drag force model correctly describes the plume shape evolution. Velocities of the luminous plasma front and of the "mass center" of the plume are determined versus laser fluence and background nitrogen gas pressure.

Detailed derivations and further analysis are presented of a recent conceptfor a plasma-based accelerator scheme incorporating a strong circularly polarisedmagnetic wiggler field producing relativistic-strength diamagnetic transverse plasmacurrents. The increase in the plasma Lorentz factor leads to a substantial increase inthe longitudinal component of the wave electric field and therefore of theacceleration rate. It is also found that ultra-high acceleration gradients are possible with relatively low plasma densities and long wave lengths. It also appearspossible that the transverse wiggling motion of the electrons of the beam is able todelay the dephasing with the accelerating wave leading to much higher values of theenergy gained by the beam at saturation and even electron bunches that have beeninjected with the "wrong" phase seem to be able to reverse their motion and accelerateto very high energies in short distances.