Considering the chemical free energy as a the nonlinear function of temperature, a relationship between temperature and the martensitic volume fraction associated with austenite-martensite phase transformation has been obtained theoretically and compared with experimental results in some iron-based alloys.

Detectability of close reflection peaks in ultrasonic NDT system has been significantly enhanced by using a diverse field algorithm. The CLEAN algorithm, which is popular in image processing of radio astronomy data, has been proposed in the case of ultrasonic testing. The feasibility study of the algorithm has been performed successfully in the application of ultrasonic signal processing and it is conceived that the algorithm might have good potential in ultrasonic NDT for distinguishing between close peaks and removing sidelobes.

Highly (111)- and (001)-oriented rhomboedral PZT thin films have been grown at 500 °C onplatinized silicon substrates by in situ RF magnetron sputtering. Crystallization of the perovskitephase was possible provided that a thin TiOx buffer layer was deposited prior to the PZT. Control ofPZT films orientation is demonstrated by changing the $\rm O_2/(Ar+O_2)$ ratio in the plasma gasduring the TiOx sputtering and its consequences on electrical properties of the ferroelectric samplesare presented. The structural properties of the TiOx buffer layer were studied by means oftransmission electronic microscopy in order to understand the relation between the TiOx seeding andthe orientation control of the PZT film.

A quantitative comparison of the errors introduced by several methods for the reproduction of the crystallographic orientation distribution function from poles figures is presented. The harmonic, ADC, WIMV and component methods have been employed in the characterization of the deformation and recrystallization textures of a Fe-50% Ni alloy in order to investigate the accuracy associated with each one of these methods. To carry out this study, experimental and synthetic pole figures have been used as input data. The strong and weak points of each method are examined showing that the iterative discrete methods (ADC and WIMV) are better suited for the reproduction of the texture function in the present case. In comparing these two discrete methods, it is evidenced that the ADC method reproduces more accurately both the experimental and synthetic texture functions over the entire range of texture sharpness considered.

Silver-copper alloys are condensed in a liquid-solid domain of the phase diagram on a tilted molybdenum substrate regulated in temperature. After a droplets regime, a film which contains a monolayer of nodular solid crystals forms. The size distribution and density of the particles in the film are measured after different condensation times. Results show that in our experimental conditions a ripening process occurs which is evidenced by a decrease of the number of particles with time, and a broad particle size distribution. However, the decrease rate is smaller than expected without a condensation flux. A model is then developed to interpret and generalize these results. This model results from the modification of the Lifshitz-Slyosov model [1] to take into account the supply from the vapour phase. It is shown that the higher the flux of material to solidify from the vapour phase is, the more the growth from the vapour phase overcomes the ripening process. Once the particle density reaches a characteristic value which is simply proportional to the incoming flux, no more particles are dissolved. The system then tends towards a monomodal distribution with a radius which grows in t1/3.

Following the total yield approach (used to predict the sign of charging of electron irradiated insulators) a positive charging is expected when the primary beam energy Ep is situated in the energy range where the number of outgoing electrons, $(\delta + \eta) I_0$, is larger than the number of incoming electrons, I0. But a negative charging is often experimentally observed when a positive charging is predicted. The present paper is an attempt to elucidate this experimental fact. The arguments being developed are based on the use of a dynamic double layer model (+ for the secondary electron mission, SEE; − for the incident electron implantation) which explains a negative charging via the influence of an evolving S-shape potential function, V(z), which induces a partial freezing of the nominal (uncharged) SEE, δ°, combined to a progressive compression of the negative space charge below the surface. The observed large difference in the measurements of the yield by using pulse excitation methods, or by permanent irradiation methods, δ° or δ is then explained. Furthermore, the influence of an oblique incidence is also deduced.

Dielectric response of PLZT(x/65/35) ceramics (with x = 0, 2, 4, 5) was studied using radio frequency and microwave techniques in the temperature range 300−900 K and with a frequency range of 102 Hz-3 × 109 Hz. Dielectric relaxation appears around 1 × 109 Hz at room temperature. The relaxation frequency softens at Tc and the dielectric relaxation exists in both paraelectric and ferroelectric phases and depends on x the lanthanum concentration. A model of correlation chains gives some keys for understanding the frequency behaviour of such materials.

Two shape memory Cu-Al-Ni alloys, a polycrystal and a single crystal, exhibiting a martensitic transformation close to 130 °C (in the as-quenched state) have been studied. Specimens have been quenched after heat treatment at 850 °C. The structural evolutions of the high temperature phase (austenite) have been studied for thermal treatments performed below 200 °C. Investigations have been carried out using electrical resistivity measurements, TEM (Transmission Electron Microscopy) observations and X-ray diffraction analysis. The main structural modifications are observed in the polycrystalline alloy and concern first, the reordering process of the austenite structure (B2$\to$L21), and second, the precipitation of the (Cu9Al4) γ2 phase. In the single crystal alloy, the evolutions are very slight and localized on the structural defects. Particular attention is paid to the role of the quenched-in vacancy elimination on the observed mechanisms. In addition, the incidence of the structural evolution on the transformation temperatures is also discussed.

Magnetic properties of nanocrystalline FeZrB-(Cu)-(Nb) compared to FeSiBCuNb are reported. Observations of domain patterns by magneto-optical Kerr effect (MOKE) method presented herein highlight qualitatively the incidence of stress-annealing on the induced anisotropy in soft magnetic materials. Transverse fine domains found in FeSiBCuNb alloys are consistent to a magneto-elastic interpretation of the stress-induced anisotropy. Nevertheless, it is not the case for FeZrB-(Cu)-(Nb) family where we observe a pronounced longitudinal induced anisotropy. According to the so-called “back stress effect” advanced by Herzer, the negative $\lambda_{\rm s}$ of bcc α-Fe grains, as well of bcc α-FeSi grains, should yield transverse anisotropy. Nowadays, this surprising feature is not still clear. For a technical standpoint, stress-induced anisotropy is interesting for new magnetic components in power electronics.

Light emission excited by scanning tunnelling microscopy (STM) has been observed on multiwall carbon nanotubes. The photon yield depends on the scanned tube but it is constant all along the tube. Simultaneous photon spectroscopy evidences emitted wavelengths in the 600−1000 nm range in good agreement with previous field emission data. Emission characteristics are independent of substrate and of STM tip. We discuss how these new results are consistent with radiative transitions involving localized states in carbon nanotubes.

Sublimation and deposition of the metal-organic complex palladium (II) acetylacetonate [ Pd(acac)2] was investigated through thermogravimetry and XRD. The temperature range for sublimation, avoiding thermal decomposition, was determined to be 100−160 °C and required to take place in the presence of an inert gas such as helium. The complex was found to be highly unstable in the presence of hydrogen. The Clausius-Clapeyron equation determined is $\ln P = - 96 \times 10^3/RT + 29.26$. Deposition of the complex on monolithic substrates required the presence of adsorption sites. For the system investigated, change of the apparent deposition activation energy was found to take place within the range 100−150 °C. To obtain Pd metal particles, the precursor was reduced in hydrogen at a subsequent stage and temperatures close to room temperature were found to be sufficient.

In this paper, we study a new kind of continuous-alternating converters: a seven-level neutral point clamping (NPC) voltage source inverter (VSI). We propose this inverter for applications in high voltage and high power fields. In the first part, we develop the knowledge and the control models of this inverter using the connections functions of the semi-conductors. After that, we present two pulse width modulation (PWM) algorithms to control this converter using its control model. We propose these algorithms for digital implementation. This multilevel inverter is associated to the induction machine. The performances obtained are full of promise to use it in the high voltage and high power fields of electrical traction.

This paper presents a flexible numerical technique which is especially suited to analyze lateral modulation of quantum effects in short channel MOS transistors. We discuss boundary conditions for the Schrödinger equation and the impact of the finite element meshing. We show how channel length shortening alters the sub-band structure, thus giving an evaluation of the limits of a 1D quantum approach.

This paper deals with the study of a new generation of ceramic matrix composites, SiCf-SiBC, which consists of a 2.5D perform of SiC fibers and of a self sealing multilayered matrix. Three different batches of these CMCs have been investigated in a morphological point of view thanks to the observations performed at the mesoscopic scale by scanning electron microscopy and automatic image analysis, and also at a microscopic scale by transmission electron microscopy. Through this study, a lot of care was taken about the description of the pyrocarbon interphase and of the different matrix interfaces, which play a key role in the damage features, and more specially in the deflection of the matrix microcracks developed through tested mechanical composites.

In this paper, we give nonlinearobservers for the estimation of the rotor flux and the loadtorque in an induction motor. The observers are designed onthe basis of the standard α − β Park's model. Theperformance of these observers are shown via experimentalmeasurements.

The electron temperature Te as the often most essential parameter for applications of low pressures plasma has been derived from comparative in situ measurements with a single and a double electrostatic probe, and with optical emission spectroscopy OES and energy dispersive mass spectrometry EDMS as remote techniques. Electrodeless rf discharges maintained by electron cyclotron wave resonance ECWR in pure Ar and N2 in the pressure regime from 10−2 to 1 Pa have been used as sample plasmas. The evaluation of the OES- and EDMS-signals is described in detail. The pressure dependence of the Te-results derived therefrom is found to compare well with the data from the probe measurements, and with calculations from a charge carrier balance equation. By matching the OES data to the absolute Te-values from the probe measurements, numerical expressions have been obtained by which Te can be quantitatively calculated from the intensity ratios between selected emission lines from the Ar- and the N2-plasma. Furthermore, the EDMS-results are also shown to deliver quantitative information about Te.

This paper is aimed at the modelling of an electrical discharge controlled by mean of a dielectric barrier, at atmospheric pressure; we focus our study on the homogeneous “regime”. This model is based on the use of equivalent electrical circuits and is taking into account the main phenomena of the discharge. We also offer a method for the determination of the parameters of the model; the comparison of the experimental waveforms with the simulated ones is validating the accuracy of the proposed model in the case of discharges in nitrogen or helium. Our model is exploited to point out the drastic importance of the electrical characteristics of the power supply with respect to the main waveforms of the discharge. (including computer-aided circuit design and analysis)

The aim of this paper is to explain the intrinsic fail-safe capability of a high-voltage IGBT inverter source. The inverter is an imbricated cells structure which provides redundancy. The major failures can be either a wrong gate voltage (malfunctioning of the driver board, auxiliary power supply failure, dv/dt disturbance) or an intrinsic IGBT failure (over-voltage/avalanche stress, temperature overshoot). The IGBT failures are studied and show that no opening of the bondings can appear and consequently no risk of explosion. Owing to the imbricated cells structure, an IGBT failure can be withstand a few switching periods, with nevertheless non-optimized output waveforms. The design and the lab-test of a sensor able to perform monitoring and failure diagnosis are also presented. This real-time diagnosis allows either a safety stop or a remedial control strategy based on the reconfiguration of the control signals. The real-time reconfiguration allows to decrease internal stresses and to optimize the shape of the output voltage. In this case, a fail-safe operating may be gained for high power applications.

In this paper, electrical and acoustical characteristics of negative point-to-plane corona discharge loudspeakers are investigated. In the first part, the electrical behaviour of point-to-plane corona discharges is modelled by a three-parameters $(r_i, r_u, C_u)$ equivalent circuit. An experimental set-up for estimating these electrical parameters has been developed and improved. Based on the experimental results, evolution of the parameters with discharge conditions has been traced. In the second part, the electrode gap in negative point-to-plane corona discharges is divided into an ionisation region near the point, and a drift region. In each region, interactions between charged and neutral particles in the ionised gas lead to a perturbation of surrounding air, and so generate an acoustic field. For each region, seen as a separate acoustic source, an acoustical model is developed. An experimental set-up for measuring acoustic pressure has been developed, and allows us to confirm expectations based on directivity pattern, monopolar and dipolar directivities being associated to the ionisation and drift region respectively.

The confinement properties of a low beta argon discharge plasma in a spindle cusp magnetic field was investigated. Plasma was produced by ionisation collisions by the electrons which were produced by thermionic emission of electrons. The central problem involved with plasma confinement by a cusped magnetic field is the loss of particles along the flux lines. Electron and ion leak widths were studied in the ring and point cusps and measured over a range of magnetic field strengths (B), neutral pressures (P) and discharge currents (Id). It was found that the leak width was reduced with increase in Id and B. The ion leak widths were found to be larger than the electron leak widths. The normalised effect of magnetic field and pressure on ion and electron leak widths in cusps are reported, compared and discussed. The dependence of electron and ion leak widths on plasma densities were also studied. At very low pressures, high plasma densities and high magnetic field strengths, a quasineutrality condition was attained.