A detailed crystal-field analysis, based on the Racah' theory, was carried out for the so-called A, B and G1 isolated charge-compensation centers of Er3+ ion doped in CaF2 crystal. Three sets of crystal-field parameters were obtained by a least-squares fitting of the optical data of Er3+ ion diluted in epitaxial Ca1−xErxF2+x thin film. This theoretical analysis confirms the expected $C_{4\nu}$ site symmetry for the A center and the $C_{3\nu}$ site symmetry for the G1 center. For the B center, however, the site symmetry is not exactly $C_{3\nu}$ in contrast to what is believed.

Marked effect of imposed low frequency oscillations with amplitudes of 6.6 × 10−4−11.6 × 10−4 during creep of pre-aged Al-40 wt.% Zn alloy samples under constant stress at 423 K, was observed. Increasing the frequency or amplitude at a certain temperature, increased both n and ${\dot \varepsilon}_{\rm st}$ but decreased β values. The value of the ratio γ (0.75−0.77) shows the high dependence of the steady creep on the transient creep stage. The results were explained in view of the nature of the thermally induced structures during aging and their mode of interaction with lattice defects generated by the applied stress and the imposed oscillations. Grain boundary sliding and grain boundary diffusion of Zn and Al are suggested as the rate controlling mechanisms for both the transient and steady creep stages, respectively.

Using calculated tables of the second-rank constitutive tensors for linear bianisotropic media, some general electromagnetic properties of the media are discussed. We consider enantiomorphism, crosscoupling tensors and nonreciprocity. The presented tables obtained by group-theoretical methods and comprising 122 discrete point and 21 continuous magnetic groups of symmetry can serve for investigation of some other physical properties of the media. Also considered are the main distinctions of the tables from those published earlier.

Charge diffusion in thin ${\rm Al}_2{\rm O}_3$ layers has been investigated by Atomic Force Microscopy (AFM). The layers were made by anodic oxidation of Al plates, in order to obtain plane and homogeneous amorphous oxides of known thicknesses. Under dry-nitrogen atmosphere, the charges are deposited by contact electrification: a deposit voltage is applied between the Al substrate of the layer and the metallized AFM tip brought to contact with the oxide. This process is perfectly controllable and reproducible, the quantity of charges deposited being proportional to the deposit voltage. Afterwards the tip is lifted up and scans the surface of the oxide in order to observe the diffusion of the deposited charges. Two behaviors were observed for the diffusion process depending on the thickness and on the deposit voltage. These results are interpreted by introducing an inhomogeneous trap distribution in the layer, the diffusion process being considered mainly as diffusion by hopping transport in the bulk.

Ferrobielastic twinning in quartz single crystals has been investigated in relation to crystallographic orientation and crystal origin. By means of uniaxial compressive stress experiments, complete volumetric transformation to the alternate Dauphiné twin state was performed in X- and AT-cut samples of natural and synthetic quartz. Either polarized light or synchrotron radiation X-ray topography was employed to observe the movement of twin boundaries. The dependence of the coercive stress and the preferential orientation of twin boundaries on the crystallographic orientation are explained in terms of the thermodynamic potential of the Gibbs free energy. In relation to natural crystals, the stress levels related to optical visualization and complete transformation to the alternate twin state were 50% and 30% lower for synthetic quartz. These results are qualitatively discussed by the pinning of Dauphiné twin boundaries at randomly distributed impurity-related point defects which were evaluated by infrared spectroscopy and ion coupled plasma spectrometry. The spontaneous irreversibility of ferrobielastic twinning on unloading is confirmed.

When the frequency of infrared light and the plasma frequency of highly doped n-GaAs are in resonance (e.g. for a doping concentration N = 7 × 1018cm−3 and a wavelength $\lambda=10.6 \mu$m), the free-electron induced optical nonlinearity is soundly pronounced. At such high doping concentrations it is necessary to extend the rigid quantum mechanical description of the free-electron induced nonlinearity to a multi-valley model. The central valley of GaAs was treated as a fully nonparabolic degenerated electron gas, whereas the satellite valley was modeled as an anisotropic electron gas of arbitrary degeneracy. The following intra- and intervalley absorption mechanisms were taken into account: impurity assisted, thermal and hot polar optical phonon assisted intravalley absorption on one hand and intervalley phonon assisted absorption in equivalent and nonequivalent intervalley absorption on the other hand. The dependence of the different absorption and energy relaxation mechanisms on the doping concentration, free electron heating, optical power density and the equivalent LL-intervalley deformation potential are discussed. We demonstrated for the first time that the behavior of the optical intervalley nonlinearity, i.e. the nonlinear absorption and nonlinear intervalley transfer, strongly depend on the equivalent LL-intervalley deformation potential. In the linear regime the model calculations are in good agreement with experimental results.

(001) surfaces of indium phosphide (InP) single crystals have been deformed at room temperature by a Vickers indenter. The indents formed were observed by transmission electron microscopy (TEM) in plan views as well as in cross-sectional views obtained by focused-ion beam (FIB) milling. The in-depth structure of the plastic zone has been investigated as well as the dislocation arrangements. The polarity of the crystal was determined by convergent beam electron diffraction (CBED) and the plastic anisotropy was discussed.

The toroidal technique is used in the determination of the complex, frequency dependent magnetic susceptibility, $\chi (\omega) = \chi'(\omega) - {\rm i} \chi''(\omega)$, of four magnetic fluids consisting of colloidal suspensions of magnetite in water with corresponding saturation magnetisation of 134 G, 107 G, 90 G and 30 G. Plots of the susceptibility components against f (Hz) over the frequency range 10 Hz to 1 MHz, are shown to have approximate Debye-type profiles with the presence of Brownian relaxation being indicated by the frequency, fmax, of the maximum of the loss-peak in the $\chi''(\omega)$ profiles. Corresponding calculations of particle hydrodynamic radius indicate the presence of aggregation. An estimate of the aggregate size distribution in the samples is determined by fitting the measured susceptibility profiles to susceptibility profiles generated by the Debye equations modified by Frohlich, Cole-Cole, Normal and Lognormal distribution functions. The fits obtained from the four fitting functions are found to be similar and thus it is concluded that none of these functions offers any particular advantage over the other functions.

Synthesis of PZT solutions for thin films applications are realised either by sol-gel methods using reactive precursors or by MOD (metallorganic deposition) methods using heavy and/or hydrophobic precursors (applications: piezo or pyroelectric devices, integrated capacitors). Understanding these processes is difficult because of the complex chemistry of alkoxides. A specific MOD solution to produce PZT films is taken as an example to study the most important parameters influencing the behaviour of the final solution during deposition (spin coating) and subsequent thermal treatments. In this context a pilot reactor was developed in order to control and to measure this main parameters with the objective of a process optimization.

This paper deals with adaptive meshing in the case of time dependent problems within a 3D non linear multi-static approximation. In order to evaluate the numerical errors, the notion of ligurian is introduced. This estimator requires a couple of admissible fields. A method for the determination of this last couple is exposed. At least, on a three-phased transformer, we highlight the difficulties of the calculation of a well adapted error distribution for adaptive meshing. Three methods are exposed and compared.

On the basis of one-dimensional paracrystalline model, we have calculated the linear disorder when oligonucleotide single crystals of DNA are irradiated by X-rays. For this purpose, the noticeable broadening of the meridional reflection at 3.2 Å was used as a marker to quantify the disorder, induced in the linear array of base pairs as one travels along the helical axis of DNA molecule.

Composites made of iron and Cr doped magnetite are obtained by precipitation from the metallic chlorides salts into a KOH solution heated under reflux. A KOH concentration of 14 mol l−1 is required. The composition of the samples is determined by X-ray diffraction, TG measurements, chemical analysis and Mössbauer spectrometry. The higher the chromium content, the smaller the lattice parameter and the lower the metal ratio. For Cr/Fe ≤ 0.1, the chemical formula of the composites can be written FeA/(Fe $^{\nu+}_{x}$ Cr $^{3+}_{y}\square_{3-(x+y)}$ O $_{4})_{1-{\rm A}}$ , $0\le y\le0.23$ . We show that only in-field Mössbauer spectrometry at low temperature is suitable to estimate unambiguously both the proportions of octahedral and tetrahedral iron sites in spinel and the valence of delocalised iron state, if any. A peculiar A-site occupation by either vacancies or Cr3+ ions is observed. This is probably due to the low temperature synthesis. The two phases, metal and spinel are found to be intimately mixed within the nanometer sized particles. For Cr/Fe ratios higher than 0.1, hydroxide phase is also present.

Confocal Scanning Laser Microscopy (CSLM) in fluorescence mode was used to characterize microporous membranes. Two microfiltration membranes were investigated: a mixed ester (cellulose nitrate/cellulose acetate) 1.2 μm-rated membrane and a polycarbonate track-etched membrane with cylindrical pores of 2 μm diameter. Optical sections of the membranes stained with rhodamine and mounted in glycerol were performed at 1 μm intervals, from 0 to 10 μm. CSLM was found useful for microporous membrane characterization, as it gives some insight into bulk membrane morphology.

An electrodynamic field is coupled to a magnetic equivalent circuit. The electrodynamic problem is formulated by the electric vector potential and discretised by finite elements. The magnetic lumped parameter model is described in terms of unknown fluxes and magnetomotive forces. The coupled system matrix has a mixed and hybrid nature. In this presentation, the method is applied to simulate eddy current distributions in laminated material and losses in a dielectric heater.

High power pulsed lasers are used to induce shock waves in Hastelloy X targets coated with tungsten carbide of 70 μm and 50 μm thickness. In suitable irradiation conditions, a debonding of the substrate/coating interface due to the generation of tensile stresses is observed. Experimental results are analyzed with the use of numerical simulations yielding the stress history at interface and its dependence on laser pulse intensity up to 600 GW/cm2 with 1 ns and 3 ns durations under direct irradiation, and 23 ns with water confinement. As a consequence of shock decay during the propagation through the substrate, a strong variation of incident intensity results in a small variation of tensile stress. This allows an accurate determination of the debonding threshold which is found in the range of 1.0 to 1.3 GPa for short laser pulses (1 and 3 ns) and 0.5 to 0.6 GPa for long laser pulses (23 ns confined).

Electrostatic interactions of silver colloids with phospholipid monolayers at the air- water interface have been investigated by pressure-area measurements and fluorescence microscopy observations. It has been observed that the presence of silver particles in the subphase induces a change in the compression isotherms of phosphatidylglycerol, in particular in liquid-expanded LE / liquid-condensed LC phase transition. Condensed-phase domains show fractal-like shapes over colloids-containing subphases in contrast with rounded shapes observed over pure water. The effect of colloids on the compressibility was studied for different chain lengths and the change of the critical temperature was also determined. The comparison with the effect of monovalent salt was discussed since the charged colloids could be viewed as "multivalent" ions.

The paper presents the application of Radial-basis-function (RBF) neural networks to speed up deterministic search algorithms used for the design and optimization of superconducting LHC magnets. The optimization of the iron yoke of the main dipoles requires a number of numerical field computations per trial solution as the field quality depends on the excitation of the magnets. This results in computation times of about 30 minutes for each objective function evaluation (on a DEC-Alpha 600/333) and only the most robust (deterministic) optimization algorithms can be applied. Using a RBF function approximator, the achieved speed-up of the search algorithm is in the order of 25% for problems with two parameters and about 18% for problems with three and five design variables.

The microstructure of NdNiO3 thin films deposited on Si (100) has been investigated by high resolution electron microscopy. Deposition at 250 °C and 600 °C and several annealing at high temperature under oxygen pressure were performed. Depending on the deposition temperature and annealing conditions, different texture and microstructure were observed. Relationships between microstructure and transport properties are discussed. The differences of grain boundaries are suggested to be responsible for the difference in transport properties of the films.

Trajectories of superparamagnetic sub-micronic particles submitted to a multi-force field are modeled numerically by a Finite Element Method. The first step is the computation of the magnetic forces and the carrier fluid velocity field, the second step is the computation of the trajectories using a Finite Difference Method with a predictor-corrector scheme.

This article presents a binary classification method which isused in defects detection. It's presented as recursives “boosting”algorithms which allow us to obtain a precise discriminating function bycombination of hypothesis and rules with moderate accuracy. This approachpermits the study of random phenomena governed by nonparametric laws and adirect decision for the observations classification and the determination offrontiers in an observation space. The various analyses which will bedeveloped are illustrated by simulations making it possible to evaluate thepossibilities of the method.