Modeling the sequential switching shunt series regulator

This letter characterizes, in terms of the bandwidth and limit cycle frequency of its constituent subsystems, the sequential switching shunt series regulator -S/sup 4/R, a high-efficiency, low-mass and volume power cell devised to power the next generation of regulated power buses in telecommunication spacecrafts. Transconductance power source modeling is used to obtain linear and nonlinear models. These are used to establish a design control strategy which involves the dynamic response in large load requirements or at the end of the satellite life. Simulations and experimental results are also given to demonstrate the validity of the model.     

Synthesis and dispersion of Ni(OH)2 platelet-like nanoparticles in water

Synthesis of nanometric platelet-like Ni(OH)2 particles is described. The role of several experimental parameters on the particle size is investigated. A colloidal dispersion of particles is produced by adsorbing ionizable organic ligands (trisodium citrate) on the particle surface. The stability of this colloidal dispersion and the particle charge density are determined for different citrate ions concentrations.     

A dynamic gradient approach to Pareto optimization with nonsmooth convex objective functions

In a general Hilbert framework, we consider continuous gradient-like dynamical systems for constrained multiobjective optimization involving nonsmooth convex objective functions. Based on the Yosida regularization of the subdifferential operators involved in the system, we obtain the existence of strong global trajectories. We prove a descent property for each objective function, and the convergence of trajectories to weak Pareto minima. This approach provides a dynamical endogenous weighting of the objective functions, a key property for applications in cooperative games, inverse problems, and numerical multiobjective optimization.     

Étude expérimentale et théorique de l'électroréflexion de l'or en incidence oblique

Electroreflectance spectra of gold have been investigated at oblique incidence, the light wave being polarized either perpendicular or parallel to the plane of incidence. The experimental procedure is described and the electrochemical behaviour of the metal-electrolyte junction is examined in great detail. A phenomenological interpretation of the electro-reflectance at the metal-electrolyte interface is given, in which this effect is due to a surface current related to a change in the electron density at the surface of the metal. The agreement between the theoretical and experimental results is quite good.     

Phenomenological interpretation of electroreflectance in gold

Electroreflectance spectra at the gold-electrolyte interface have been investigated at oblique incidence, the light wave being polarized either parallel or perpendicular to the plane of incidence. A new interpretation of the electroreflectance is given, in which this effect is assumed to be due to a surface current related to a change in the electron surface density. The agreement between the theoretical and experimental results is quite good.     

Melting for lead particles of very small sizes; influence of surface phenomena

Melting, solidification and undercooled state of lead particles of very small sizes (mean radius \(\bar r\) lower than 100 Å) have been investigated through high sensitive optical measurements. A phenomenological interpretation of melting is proposed which is based both on thermodynamic size effect and surface phenomena.     

Numerical and experimental investigations of the size ordering of nanocrystals

The nucleation and growth of particles on the 1–100 nm length scale is a phenomenon of increasing interest in the areas of electronics and optoelectronics. Dealing with the preparation of nanoparticle distribution on a substrate by self-organization, we wish to determine whether conditions exist where the distributions approach an array structure which can be compared to so-called quantum dot organized structures. This means that it is fundamental to obtain particles of the same shape with a low dispersion in size and an isotropic distribution on the substrate. This work is devoted to the numerical investigation of growth phenomena on a plane substrate in the case where diffusion and coalescence are mainly taken into account. Experiments on a model system, i.e. Sn/SiO_x, are compared to simulations.     

Optical behaviour of melting for a thin metal film

Reflectance measurements have been performed for gallium films at normal incidence (from 0.3 to 0.9 μm) in terms of temperature (from -20°C to + 40°C). The basic results are: (i) a drastic change in reflectance when melting occurs (about 20% at 0.6 μm), and (ii) a shift in the temperature of the solid-liquid transition with the thickness of the film which only takes place on and after the second melting (about 7°C for a film 250A?thick).     

Methyl carbon chemical shifts of methylbenzoic acids and methylbenzoate anions

Methyl carbon chemical shifts have been assigned for methylbenzoic acids dissolved in CDCl₃, and for methylbenzoate anions obtained by dissolving these acids in aqueous NaOH solution. Chemical shifts have been interpreted by means of additive substituent parameters which reflect conformational features existing between adjacent substituents. Barriers to rotation of a methyl group adjacent to a carboxyl or carboxylate group have been estimated to differ by less than 2 kJ mol^?1 from the barrier of a methyl group in o-xylene.     

Neuro-fuzzy modeling techniquesfor microwave components

Two modeling techniques of microwave devices are proposed to generate neuro-fuzzy-based models. These techniques use the adaptive neuro-fuzzy inference system approach, which compensates the error between an initial coarse model and an electromagnetic simulator (or measurement data). The aim of these techniques is to generate accurate models from a set of fuzzy if-then rules and coarse models. Models so obtained could be integrated in a toolbox of any commercially available computer-aided design tools for radio frequency/microwave circuits. Results with artificial neural network and neuro-fuzzy based models are listed and discussed for a microwave tunable phase shifter.