A method is described that allows the trapping charge kinetics in insulating materials during their electron irradiation in a scanning electron microscope (SEM) to be studied and the total trapped charge to be evaluated. The method consists in analyzing the leakage and the displacement currents measured simultaneously, during and after irradiation, using an arrangement adapted to the SEM. The dynamic trapping properties of glass-ceramic are investigated and the time constants for charging and discharging processes are evaluated. By correlating the leakage and displacement currents, the total electron yield σ during irradiation is also determined.

This paper is devoted to polystyrene thin films treatment under DC pulsed discharges in oxygen-argon mixtures. AFM analysis is used to study the surface modifications in terms of morphology and corrugation. The use of a glow post-discharge enables to disregard the degradation process in relation to the functionalization process. Thus the increase of the polystyrene wettability is mainly due to the formation of polar functions which are of great interest to a better understanding of the treatment aging. Indeed, the reorganization of the macromolecular chains after a plasma treatment enables to obtain an equilibrium state of the surface in relation to the outer environment. Polar functions orient themselves toward the polymer bulk and may interact with another one to form hydrogen bonds, which establish physical linkages within the surface and its stabilization.

Measurements were carried out in the temperature range 293–453 K over the frequency range 100 Hz–100 kHz on the ac electrical properties of vacuum deposited Sbx S1−x thin films of different thicknesses prepared with different deposition rates. The obtained experimental data have been analyzed with reference to various theoretical models. The ac conductivity increases with frequency according to the relationσ ac(ω) αω s . The analysis shows that the correlated barrier-hopping (CBH) model is the most appropriate mechanism for the ac conduction in these films. The value of the dielectric constant slightly changed for higher frequencies irrespective of temperature change, whereas its value increases at higher temperature with the decrease in frequency. The dielectric loss has been found to increase with increase in temperature and decrease in frequency. The deposition rate and film thickness have a remarkable effect on ac conductivity and dielectric properties. The maximum barrier height w m is calculated from dielectric measurements according to Guintini et al. equation based on Elliott (CBH) model; which suggested the hopping of charge carriers over a potential barrier between charged defect states. The density of states was also calculated using Elliott model.

The physico-chemical environment around the aluminum impurity atomsin commercial Herasil silica is studied by electron-induced X-ray emissionspectroscopy. Despite the low concentration of aluminum and the charging effect occurring upon electron irradiation, we have been able to characterizethe environment of the Al atoms. We show that the Al atoms are in anoctahedral environment, i.e. surrounded by 6 oxygen atoms. The presenceof Al clusters, whose metallic character would make them candidates to beultraviolet absorption centers, is ruled out.

This paper deals with the causal modeling of aTraveling Wave Ultrasonic Motor; the aim of the study is to buildan approach which may take into account the physical contactresponsible for the pull-out phenomenon, but straightforwardenough to be useful for control. As the parameters available forthe modeling can not be obtained following the well knownelectromechanical equivalent scheme identification, a newidentification method is proposed. In this purpose, the model ofthe motor is expressed in the traveling wave rotating frame.

A new indirect method of determining the viscosity of a Newtonian fluid flowing in a tube with a geometrical singularity is proposed. Due to this singularity, the shape of the dimensionless velocity profiles is closely correlated with the Reynolds number of the flow. Newtonian fluid flows were simulated numerically with various Reynolds numbers. Based on the results of these calculations, an abacus was plotted showing the relationship between the dimensionless velocity and the dimensionless viscosity. On the other hand, dimensionless velocities were also obtained by measuring velocity profiles on a hydrodynamic bench with an ultrasonic Doppler velocimeter. These experimental values were plotted on the abacus and the viscosity of the actual fluid was thus determined. Comparisons were made with viscometer measurements in order to assess the accuracy of the method and its range of validity. This method is of great potential interest for application to industrial plans when it is necessary to know the viscosity of a fluid undergoing a transformation without interrupting the process by taking fluid samples.

Thrust calculations of the thermally choked ram accelerator propulsive mode basedon quasi-steady, one-dimensional modeling of the flow process have been quite successful inpredicting the experimental velocity-distance profile when real gas corrections are appliedto the combustion products of propellants at initial fill pressures up to 8 MPa. A furtherrefinement of the modeling takes into account real gas corrections for the initial state athigher fill pressures. It turns out that the Redlich-Kwong equation of state accuratelydetermines the thermodynamic properties of the unreacted propellant for fill pressures up toat least 20 MPa. Using this equation of state for the calculation of the sound speed for atypical ${\rm CH}_4/{\rm O}_2/{\rm N}_2$ propellant provides a 15% higher value at 20 MPathan that predicted for an ideal gas; this increase significantly affects the operatingcharacteristics of the ram accelerator at a given velocity. The corresponding thrust maximumincreases by 30%. This corrected theory is most appropriate under conditions of highpressure operation at relatively low acceleration levels; i.e., less than 10 000 g. The corrections to theaerothermodynamic equations that are discussed in this paper are fully generalized and can beapplied using any equation of state.

YO molecule in the vapor phase above Y2O3 melted at the focus of a solar furnace exhibit a fluorescence phenomenon induced by absorption of the incident solar photons. The diverse spectral profiles measured at various locations from the melted surface reflect the different temperatures in the gas phase. The comparison of the measured spectra with band simulation allows to give an estimation of the upper limit temperature of the gas phase in the vicinity of the hot front.

To achieve optimum imaging performance, any camera system has to be thoroughly checked before being used, particular care being given in evaluating the different contributions due to noise. Our work presents a method for characterising the different sources of noise affecting CCD or CMOS cameras, emphasising the too often overlooked pattern noise. This method is an extended and theoretical approach of the well-known photon transfer technique [1]. Experimentation on our high speed CCD imager illustrates this approach.

A new model of incoherent-to-coherent IR image converter based on a GaAs photoconductor (PC) joined to an electro-optic (EO) Bi12SiO20 crystal has been analyzed theoretically and experimentally. The possibility of field transfer from the PC to the EO crystal under the infrared (IR) radiation sufficient for realization of the EO (Pockels) effect in the EO crystal was assessed. Based on the electric field parameters and the parameters of the PC and EO crystal, the threshold sensitivity of the converter was estimated. The experimental PC-EO crystal structure by which IR-radiation (0.9–1.5 μm) was converted into the coherent visible radiation was obtained on the basis of theoretical calculations. The limiting resolution of readout image was about 10 lp/mm. The measured threshold sensitivity of the converter, 5 × 10−4 W/cm2, was found to be in the limits of theoretical estimation. The results indicate that this device has the potential for use in a high-speed, high-contrast optically addressed spatial light modulators.

This paper describes a 3D finite element formulation used for radiofrequency hyperthermia problems. Edge finite elements have been coupled with an absorbing boundary condition. Results are presented in term of specific absorption rate. They are compared to experimental measurements performed on a phantom having equivalent electromagnetic properties to human tissues. This comparison shows a good agreement between both numerical and experimental results. Simulations are also achieved on a heterogeneous phantom. The model is then used on a real geometry coming from computerized tomography scans.