A sensitivity factor for electron mobility with respect to the tunnel oxide thicknessin a floating gate electron-tunneling MOSFET of n-channel is defined. To this end, afield-dependent mobility is assumed.

RHEED controlled ultra-thin buffer layers of SrTiO3 have been deposited on (100) MgO by pulsed laser deposition to growth YBaCuO films for microwave applications. A buffer layer with a thickness between 2 and 15 nm, i.e. 5 to 40 unit cells of SrTiO3, is sufficient to expand to more than 60 °C the range of deposition temperatures leading to low microwave surface resistance. The Rs values are as good as those obtained on LaAlO3 substrates with a slighly lower magnetic field dependency. The SrTiO3 seed layer induces an oriented epitaxial growth with YBCO [100] // MgO [100] over this range of deposition temperatures.

The chemical bonding of different {111} Cu–MgO interfaces obtainedby internal oxidation of (Cu, Mg) alloys at T = 900 °C and for an highoxygen activity of a o2 = 10−8, is studied by transmission electronenergy loss spectroscopy (EELS) at high spatial resolution. For polar {111}interfaces (Cu and MgO in topotactical or pseudotwin orientation), it isshown that the terminating lattice plane in magnesia is occupied by oxygenatoms. An important charge transfer is identified at the interface,yielding Cu–L ELNES features corresponding to those of Cu1+ (Cu(I))in its oxide. O–K edge fine structures at the interface are also modified: an edge enlargement and the presence of a low energy shoulder confirm thebonding of oxygen to Cu1+. Consistent with these results, the Mg–Ledge is never modified compared to the MgO bulk phase. Specifically adaptedto the heterophase interfaces, a spatial difference method, based onnormalised spectra (NSD), is applied to estimatethe relative contribution of the ELNES signal in the interface area. In thepresent case of high oxygen activity, the number of copper atoms in theCu(I) oxidized state corresponds to a total occupancy of the outermostmetal plane at the interface.

Although the risk of embrittlement of materials exposed to liquid metals has been recognized for many years, its prediction reMayns problematical insofar as the knowledge of the mechanisms involved in the phenomenon is limited. However, Liquid Metal Embrittlement (LME) is of prime interest because the risk of damage exists wherever the handling of liquid metals is required in various industrial or scientifical fields (chemical plants, power-producing systems, soldering process, ...). The interest for this phenomenon needs thus to be pursued. The present paper reviews experimental results about the occurrence of LME and the influence of different parameters, and presents a number of mechanisms which have been proposed to explain LME.

Structural antiferrodistortive phase transitions have been studied in mixed disordered perovskites Rb1−x Kx CaF3 crystals over a wide concentration range (0 < x < 1) by Raman spectroscopy and a full group theory analysis has been carried out. Raman spectra have been indexed in all phases and a “one mode” behavior is evidenced. The influence of the cationic substitution on the mechanism driving the transitions is characterized by: i) the disappearance of the strong first-ordercharacter of the low temperature transition in RbCaF3; ii) the continuous evolution of the Raman spectra as a function of temperature, with no sharp indication of a transition except for the classical soft mode behavior; iii) the persistence of hard Raman modes even in the ideal cubic phase; iiii) the appearance of a broad central component associated with relaxation processes. Finally, the results of lattice dynamics calculations, when compared to inelastic neutron scattering measurements, show that the classical virtual crystal model fails. These results are examined in terms of a simple displacive transition for these fluoro-perovskites in which the interactions between F6 octahedra are anisotropic and the importance of the substitutional disorder is highlighted.

The viability of sculptured thin film (STF)implementations of Šolc fan and foldedfilters for optical detection and determinationof gas concentration is established.A nanoscopic–to–continuum model is devisedfor predicting the electromagnetic (optical) response of aSTF Šolc filter whose void regions arefilled with a chemicallynon–reacting gas. Ultra–narrowband–pass featuresin the transmission spectrum are shown to shift withthe gas concentration.

This paper is aimed at the characterization of Electric Power Drive Systems based on the Induction Machine fed by Multi-level Voltage-source inverters, to be used within instantaneous torque and flux control methodologies. The input/output transfer function for a N-level inverter is discussed and the correspondent available output voltage vectors, as well as the input sequences that give them rise, represented in the stationary Park reference plane. Concerning the induction machine characterization, an analytical study on the torque and stator flux instantaneous behavior is made, demonstrating that the first one highly depends on the delivered torque and speed. In consequence, a sampling scale predictive model of the induction machine is deduced in order to make possible the optimal choice of the inverter configuration for a sampling period. Finally, a DEADBEAT based control law is discussed and simulated as an illustration example of both the voltage-inverter and induction machine models presented within this paper.

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.

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.

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.

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.

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.