Chiral sculptured thin films (STFs) have unidirectionally periodic electromagnetic constitutive properties and therefore exhibit the circular Bragg phenomenon. The time-domain Maxwell equations are solved using finite difference calculus in order to establish the spatiotemporal anatomy of the action of axially excited, chiral STF slabs on optical narrow-extent pulses (NEPs) modulating circularly polarized carrier waves. A Lorentzian model was adopted for the permittivity dyadics of the chiral STFs. The time-domain manifestation of the circular Bragg phenomenon is focussed on. First, on examining the refraction of NEPs by a chiral STF half-space, a light pipe and the pulse bleeding phenomenon are shown to occur -when the handednesses of the carrier wave and the chiral STF coincide and the carrier wavelength is in the vicinity of the center-wavelength of the Bragg regime. Next, pulse bleeding inside a chiral STF slab is shown to be responsible for the long wakes of reflected pulses and low energy contents of transmitted pulses, when the incident wave spectrums significantly overlap with the Bragg regime and the carrier waves have the same handedness as the chiral STF slab. Thus, a chiral STF slab can drastically affect the shapes, amplitudes, and spectral components of femtosecond pulses.

The transmissivity of heterogeneous films is computed with the help of Green functions, solutions of discretized Maxwell's equations. These functions, developed in continued fractions, are determined using the spectral moments method (SMM). This spectral method, which allows us to obtain the response for all frequency with two series of iterations. We report computation of the transmissivity of a 2d photonic lattice and a 3d granular layer.

Performing both ex situ transmission electron microscopy (TEM) and in situ scanning tunnelling microscopy (STM) experiments on the same samples, we have characterized in detail a model catalyst (Pd/graphite). The Pd clusters were epitaxially grown at high temperature on clean natural graphite substrates under ultra high vacuum (UHV) conditions. For the chosen growth conditions the density of clusters is rather low (109 cm−2), and their size is typically few tens of nanometers. TEM diffraction studies reveal that most of the clusters (92% ) are in a same epitaxial orientation which is defined by: (1 1 1)Pd$\parallel$ (0 0 . 1)Gr and $[1 1\bar{2}]_{\rm Pd}$$\parallel$$[1 \bar{1} . 0]_{\rm Gr}$. Moreover, both STM imaging and TEM observations show that the clusters have truncated tetrahedron shapes. The combination of TEM and STM characterizations of the same samples appears to be a very efficient way to get a detailed knowledge of the global properties of a collection of supported clusters (spatial and size distributions) as well as of their individual properties (structure, morphology).

The fabrication of refractive microlenses with self-developing photopolymers is reported. A spatially controlled illumination of the photosensitive layer induced an inhomogeneous photopolymerization involving formation of 3-D polymer network, mass-transport process of reactive species and bending of the surface. The process exhibited a completely self-processing character without any chemical post-treatment to reveal the relief. The lens arrays displayed diameters ranging from less than 100 μm to 1 mm and focal lengths from 100 μm to a few millimeters, depending on photonic, optical and physico-chemical parameters. The paper focuses on the importance of photonic parameters in the generation of microlens arrays and discusses the flexibility of this technique in the visible range.

This article presents the numerical simulation with finite element method of the transient regime of an asynchronous generator with iron-free cylindrical solid rotor. During this operation kinetic energy of the rotor is transferred through the ideal rectifier bridge to a load-inductance in order to create a high magnetic field pulse. The interest of this device is the less value of capacitors battery for self-oscillations of the asynchronous generator compared to this one necessary for direct transfer of its energy to the load-inductance.

The presence of materials with a relative large difference in permeability has a harmful influence on the convergence of Krylov subspace iterative solvers. Some slow converging components are not cured by preconditioning and correspond to eigenvectors reflecting the domains with relatively low permeable material. Approximations for those eigenvectors are determined using physical knowledge of the problem. The iterative solution process is split up in a small problem counting for the separated eigenmodes and a full-size problem out of which the slow converging modes are removed. This deflated preconditioned solver is faster converging compared to more common approaches, such as the incomplete Cholesky conjugate gradient method.

One of the main research issues in the thermonuclear fusion area is the identification of plasma contour starting from external magnetic measurements. Possible approaches to this inverse problem make use of equivalent currents to represent the plasma internal current density, regularizing in this way the magnetic field reconstruction. Of course, the choice of the representation basis for such equivalent currents is critical. The paper aims at analyzing the effect of the number and position of base currents on the performance of the identification algorithm.

The study of forces exerted by an arc on silver-based electrical contacts is important in order to understand the dynamic phenomena concerning the opening or closing phases of contacts in a variety of switching applications. For that, an experimental device was built. It allows us to measure accurately the force on the static electrode and the displacement of the mobile electrode (and hence the force on it) when the two contacts, crossed by a current pulse (from 0 to 4 kA) separate. The measured forces are the sum of Lorentz magnetic forces (constriction force and loop effect force) and blow open forces due to the arc plasma (evaporation and (or) decomposition of contact materials). A simple method allowed us to asses the value of the blow open forces. We have also studied the influence on the measured forces of the contact material, the amplitude of the current pulse, the polarity of the electrodes. For the electrode materials tested in this study (Ag-SnO2, Ag-CdO and Ag-CW), it appeared that forces exerted on cathode and anode are of the same order and that AgSnO2 use allows to have higher forces (and longer opening phase) than for the two other materials and then may decrease the contact welding.

A systematic parameters study is performed in a DC pulsed glow discharge in nitrogen in order to improve the wettability of thin polystyrene layers. The experimental parameters considered are the pressure P, the interelectrode voltage V, the frequency ν of the pulsed power supply and the treatment time tt. The wettability is characterized by the contact angle technic. The $(\Theta_{\rm i} - \Theta_{\rm f})/\Theta_{\rm i} = \Delta \Theta / \Theta_{\rm i}$ ratio is measured, where $\Theta_{\rm i}$ and $\Theta_{\rm f}$ are respectively the initial and final contact angles. In the first part of the paper, the variations of $\Delta \Theta / \Theta_{\rm i}$ as a function of the electrical energy E are investigated, the variations of E being obtained by modifying the parameters V, ν and/or tt. In the second part, the specific energy ε and the economical criterion γ are introduced to deduce the best running conditions through a chemical engineering approach. Taking into account the weak duty factor of the power supply (1% ), it is shown that the polymer surface is treated with a minimum of energy.