We have supposed a new approach for the investigations of the effect of roughness on the propagation of the elastic surface waves. The presence of the rough layer is accounted by the modification of the boundary conditions. In the framework of this approach we have investigated the propagation of Rayleigh waves on an isotropic substrate having rough surface. It is shown that the roughness leads to the linear dispersion of the phase velocity of the surface waves, which are non dispersive on the ideal surfaces. Also we have investigated the influence of a rough surface of films, deposited on the substrate. The roughness of the film surface produces contributions to the phase velocities of Love and Rayleigh modes. In all cases the contributions are proportional to the effective thickness of the rough layer. It is shown that the effect of the rough layer is equivalent to the effect of a thin film, having loading characteristic. The approach can be used for investigations of the effect of roughness on the propagation of surface waves on the rough surface of the anisotropic crystals.

The controlled production of a local hot spot in supercompressed deuterium + tritium fuel is examined in details. Relativistic electron beams (REB) in the MeV and proton beams in the few tens MeV energy range produced by PW-lasers are respectively considered. A strong emphasis is given to the propagation issues due to large density gradients in the outer core of compressed fuel. A specific attention is also paid to the final and complete particle stopping resulting in hot spot generation as well as to the interplay of collective vs. particle stopping at the entrance channel on the low density side in plasma target. Moreover, REB production and fast acceleration mechanisms are also given their due attention. Proton fast ignition looks promising as well as the wedged (cone angle) approach circumventing most of transport uncertainties between critical layer and hot spot. Global engineering perspectives for fast ignition scenario (FIS) driven inertial confinement fusion are also detailed. 


The very intense radiation environment of high luminosity future colliding beam experiments (LHC, etc.) makes radiation hardness the most important issue for Si detectors. The crucial question is whether the Si strip detectors can withstand the harsh radiation environment for sufficiently long time (full LHC lifetime) and hence the central issue concerning all LHC experiments is the breakdown performance of these detectors. In this paper the simulations have been performed to analyze electrical parameters for the most deleterious long-term effect of radiation: the change in effective charge carrier concentration and resulting increase in full depletion bias. Detailed calculations using Hamburg Model have allowed the parameterization of these effects, and helped to simulate the operation scenario of Si detectors over 10 years of LHC operation. The systematic studies of the electric field to get an insight into the device behavior provide, for the first time, a possible explanation for the improvement in breakdown performance with radiation. Simulation study is also carried on optimized guard ring structures to study the change in guard voltage distribution after 10 years of neutron radiation damage.

Electron-induced X-ray emission spectroscopy (EXES) combined with a semi-empirical electron scattering model, which describes the ionizations inside a material under electron irradiation, is used to determine the depth profile of shallow and ultra-shallow dopants in silicon. Two approaches are presented, depending on whether the shape of the profile is known or not. To test the method, X-ray intensities of implanted phosphorus atoms at various energies and doses in silicon are measured at a wide range of incident electron energies. From the experimental data combined with the model, the resulting profile parameters are determined. Comparison of secondary ion mass spectrometry and EXES associated with the electron scattering model shows that the proposed method is suitable for determining the shallow implant profiles with a depth resolution of one nanometer.

We have theoretically studied the electronic structure of Si δ-doped GaAs inserted into an infinite quantum well as dependent on the applied electric field. For the uniform distribution we have investigated the influence of the electric field on the donor distribution thickness as different from other authors. The present method is based on a self-consistent solution of the Schrödinger and Poisson equations. From our calculations, we have seen that a high applied electric field is significantly changed the subband structure of the δ-doped GaAs and the change of the electronic properties as dependent on the applied electric field is more pronounced at wide doping thickness. The high electric fields can induce a spatial separation between confined electrons and ionized dopants in the δ-doped GaAs structure resulting in enhanced free carrier mobility in semiconductor devices.

We have studied the microstructure and morphology evolution in PbSe films chemically deposited on GaAs(100) substrates. The films consisted of a single phase of nanocrystalline rocksalt PbSe. The deposition temperature was found to be an important parameter which strongly influences the film morphology. A gradual transition to strong (111) texture was obtained with increasing deposition temperature, accompanied by a significant increase in crystallite size. Transmission electron microscopy (TEM) cross-sections showed two distinct regions. A layer of small, rounded crystals near the GaAs/PbSe interface above which a second region composed of columnar, $\langle$111$\rangle$ oriented crystallites was observed. High resolution TEM and Fourier analysis showed that the first layer of crystallites are in epitaxial registry with the GaAs substrate, in spite of the large (8%) lattice mismatch and the presence of a thin, amorphous interfacial layer.

In this paper, we present arobust control strategy which is well adapted to parallel connected Forward/Buck converters. It is based on a non-linear controller which uses the advantages offered bysliding mode control and peak current techniques. This control offers fixed frequencycontrol without using equivalent control calculation, synchronized ramp or variablehysteresis bandwidth. It also provides good robustness depending on variations of loadparameters. A model of the system is developed which allows us to study the systemindependently of the module number that constitutes the structure. The controllability ofthe system is discussed and an analysis of the current behavior is provided.

The modified expression for Debye-Waller factor is derived for the scattering of X-rays from rough surfaces and interfaces. For the large values of scattering vector, the non-Gaussian behaviour of this factor is predicted. This effect can be essential for interpretation of X-ray reflectivity from very rough surfaces and high-order X-ray diffraction data. The experimental X-ray reflectivity measurements are interpreted using the derived expression.

We have studied the well known spectral shift of polyfluorene blue light emitters, using either electrochemical cells or conventional organic light emitting diodes. From the recording of the electroluminescence spectra as a function of “stress” time, we conclude that the degradation mainly depends on the number of electrons which have passed through the conducting polymer, rather than on the hole current magnitude or the dissipated power.

A grooved plate matrix theory of a new high intensity magnetic separator is proposed. The results of the grooved plate devices yet reported, were only experimental. In the present paper, a theoretical approach is developed, in spite of the difficulties caused by the particular shape of the collectors, complicating the calculation of forces involved in the separation process. The work presented here, proposes the modeling used to study filtration efficiency in grooved matrix, for two models of fluid flow, as well as the results which were obtained. The range of validity of these models of fluid flow, applied to establish the matrix efficiency is discussed. The progressive saturation of the extraction matrix is also investigated. Good correspondence between theoretical results and experimental data is found.

A possible application of nanometer-sized junction arrays is to Coulomb blockade thermometry (CBT), although only highly disordered arrays can be fabricated at present. In this paper, the characteristics of CBT device with disordered arrays will be studied. Similar to what is observed for uniform arrays, there is a dip at zero bias voltage in the differential conductance of disordered arrays. However, the half-width $V_{1/2}$ of the dip for one-dimensional disordered arrays is largely dispersed. This study suggests that better devices can be developed by connecting a number of one-dimensional arrays in parallel to form an array group. The dispersion of half-width is quite small with values of $V_{1/2}$ close to a constant. Further, the effects of electromagnetic environment and low temperature on the half-width are investigated. Results are agreed with those observed experimentally, that for the effect of the environment is negligible for large arrays. The half-width of a disordered array may be bigger or smaller than the ideal value, depending on the extend of disorder.

The purpose of this work is the modeling and the analysis of fluid-wallinteractions in a deformable cylindrical cavity which has one single orifice for inflow andoutflow. The model is used to study the dynamical behavior of anon linear oscillatory coupled system. Indeed, the deformation of the cavity can be large, therefore the fluid contained inside the cavity changes greatly. Our analysisdescribes the behavior of the system according to its characteristic parameters. Adimensional analysis of the set of coupled equations describing the dynamical behavior ofboth the incompressible fluid and the cavity wall is performed. We show that such a behaviorcan be characterized by five dimensionless parameters. The equations are then solved by using the so-called time-staggered scheme which allows to integrate separately the equations describing the structure and the fluid dynamics during each time step. The fluid part is discretized by the finite difference method associated with an Arbitrary Lagrangian Eulerian formulation of the governing fluid dynamics equations and the structure part including the motion of the piston by a Runge-Kutta method. For an harmonic excitation, we show that after a transient phase, the response of the system is both anharmonic and periodic, with a fundamental period equal to that of the excitation. Moreover, we study the respective influence of the wall rigidity, the fluid viscosity and the inertia effects, for different magnitudes of the excitation. Using an approximation of the damping force associated with the viscous effects of the dynamical flow, we complete this study by showing how the system of equations can be decoupled.

Calorimetric studies have been performed on the Se$_{80-x}$ Te20 Pbx ($0 \leq x\leq 1.4$) samples at different heating rates (5−20 °C/min). The glass transition temperature Tg, the peak crystallization temperature Tp, and the melting temperature Tm are found to increase with increase in heating rate. The apparent activation energies for glass transition Et and for crystallization Ec have been calculated from the heating rate dependence of Tg and Tp respectively. The effect of Pb addition to the Se-Te matrix on the mechanism of crystal growth has been investigated. The glass transition temperature Tg and the peak crystallization temperature Tp initially decrease with small addition of Pb (x = 0.6) but increases with further addition of Pb (x > 0.6). The thermal stability and glass-forming tendency have also been studied.

To contribute to the existing knowledge of thehydrodynamic force exerted on a spherical particle placed in theaxis of a cylinder, at small Reynolds numbers, the influence ofthe uniform and Poiseuille flows on the wall correction factor arenumerically and asymptotically investigated. The Stokes andcontinuity equations are expressed in the stream function andvorticity formulation and are rewritten in an orthogonal system ofcurvilinear coordinates. These equations are solved using afinite differences method. The generation of the grid was carriedout by the singularities method. The accuracy of the numericalcode is tested through comparison with theoretical andexperimental results. In both cases we numerically calculated theseparate contributions of the pressure and viscosity forces. Inconcentrated regime these numerical calculations are in very goodagreement with those obtained by asymptotic expansions. Thisanalysis allowed us to show the prevalence of the pressure termover the viscosity one in the lubrication regime contrary to whathappened for the dilute regime. All our numerical and asymptoticalresults compared with those of Bungay et al. (Int. J. Multiphase Flow 1, 25–56 (1973)) seem to give a response to this problem argued for a long time.

The absorption and excitation spectra of the tetrahedrally coordinated Cr4+ ions doped in LiGaO2 oxide crystal are measured by Kück and Hartung at room temperature. Using the experimentally determined data from these spectra, a theoretical calculation for the crystal-field levels of Cr4+:LiGaO2 was performed by Kück and Hartung, based on the angular overlap model theory (AOM). The calculation reveals an important discrepancy between the theoretical and the experimental energies. A detailed crystal-field analysis of electronic energy levels of Cr4+ doped in LiGaO2 oxide crystal based on the Racah theory is proposed in this work. The observed crystalline-field splitting of the Cr4+ terms was accounted for using a C1 symmetric Hamiltonian. In turn, reliable crystal-field and Racah parameters have been obtained. This theoretical analysis confirms the observed crystalline-field splittings of the 3F and 3P terms of the Cr4+ ion doped in the oxide crystal LiGaO2.

We use High Resolution Electron Microscopy (HRTEM)together with Electron Energy Loss Spectroscopy (EELS) to analyzethe crystallography and the chemical configuration of interfacesin a state-of-the-artLa2/3Sr1/3MnO3/SrTiO3/La2/3Sr1/3MnO3tunnel junction. EELS indicates that manganese ions keep theirbulk valency up to the last atomic plane in contact with theinsulator. Tunnel magnetoresistance however decreases withtemperature faster than magnetisation in these samples.Quantitative HRTEM reveals some local departures from chemicalabruptness at the interfaces, which could play a role in thisdecrease.

This paper presents a study of the damage production in yttria-stabilized cubic zirconia single crystals irradiated with medium-energy (from 30 to 450 keV) heavy ions (from He to Cs). The disorder created in the two sublattices (Zr4+ and O2−) of the crystals and the lattice sites of heavy ions were determined as a function of the irradiation fluence by in situ Rutherford backscattering and channeling experiments using a 3 MeV 4He ion beam. Damage is created at a depth close to the ion projected range at low fluences and growths towards greater depths with increasing fluences once the saturation has been reached. The kinetics of the damage accumulation process reveals three stages, which (excepted for He) essentially depend on the number of displacements per atom (dpa) induced by irradiating ions (ballistic contribution). Channeling results show that the lattice location of the heaviest atoms (Xe, Cs and I) varies with the nature of implanted species (chemical contribution). The experimental data can be represented in a diagram involving both the number of dpa and the implanted ion concentration, which could be used to predict the damage evolution in other ion-irradiated nuclear ceramics.

In previous work, we have presented a computation method based on the determination of the Green functions of the electromagnetic field with the help of the spectral moments method (SMM). In this method, the Green functions are calculated in the form of continued fractions, and one determines the coefficients of their development. Two approaches have been presented: one, we call global approach, where all space is discretized in a box, the other, we call the local approach, where only the diffracting item is considered. In this work we present the results obtained for the one, two and three-dimensional cases by the local approach. We first develop the necessary tools for the computing. We establish the analytical form of the Green functions of the continuous vacuum and of the discretized vacuum, the dispersion curves and the selection rules which appear. We show that the real part of the diagonal Green functions is directly linked to the vibrational density of states and therefore perfectly determined whatever dimension the space is. Longitudinal, non physical modes are found to play a subsequent role. As regards scattering, we principally report a series of tests on some canonical systems, such as cylinders or spheres, showing that the backscattering cross- section and the impulsional response obtained with SMM are in very good agreement with the analytical results. Bi-static scattering cross section is also studied.

Among the existing non-destructive testing techniques, the flying spot photothermal technique [CITE] appears to be a good alternative to penetrant testing for open-cracks detection in metallic structures. The technique basically consists in the local heating of a structure under test and the measurement of the temperature elevation which depends on the inspected medium properties. During the scanning of the structure, thermal and optical effects contribute to the elaboration of the photothermal signals. The thermal effect is relative to the presence of a thermal barrier in the inspected medium (e.g. crack) and the optical effects are due to the variations of the absorptivity and diffusivity factors of the inspected surface (surface conditions). Both effects are competitive and can lead to hardly interpretable signals.In this paper, the authors present a method allowing to separately identify thermal and optical effects, in order to enhance the characterization of the structure under test. The method was applied on a mockup featuring open-cracks and rough surface conditions, and allows to construct separate optical and thermal images. The resulting so-called thermal image allows to significantly highlight the presence of the cracks. Besides, the optical image enriches the characterization of the structure, since it supplements the diagnosis of the cracks and also enables to characterize other defects such as surface topology and features.

As most part of the industrial effluents contain carbon dioxide and water vapour, it is interesting to study from an electric point of view ‘basic’ gas mixtures including air and various amounts of these gases, in order to precise how the corona discharge inception takes place in such mixtures. In a DC point-to-plane reactor, distinct parameters are varied, such as discharge current, partial pressure of CO2, and relative humidity. Gap voltage and streamer frequency are experimentally measured as functions of the discharge current. Current waveforms are recorded in various gas mixtures and electrical conditions. DC and impulsional current components, as well as streamer frequency are also plotted as functions of the CO2 partial pressure for dry and water saturated mixtures. For dry or wet mixtures, 5% CO2 in volume appears to be the proportion allowing the establishment of a stable corona discharge with the lowest energy cost.