A model of phase transitions in multicomponent elastic media

A mathematical model of phase transitions in multicomponent solids, taking into account the influence of elastic strains and stresses, was constructed. The conservation laws of the mechanics of continua were used to obtain a system of equations at the interphase boundary. An additional condition necessary for determining the position of a moving interphase boundary was derived

Mathematical models and finite element approaches for nanosized piezoelectric bodies with uncoulped and coupled surface effects

In this chapter the dynamic problems for piezoelectric nanosized bodies with account for coupled damping and surface effects are considered. For these problems we propose new mathematical model which generalizes the models of the elastic medium with damping in sense of the Rayleigh approach and with surface effects for the cases of piezoelectric materials. Our model of attenuation and surface effects has coupling properties between mechanical and electric fields, both for the damping terms and constitutive equations for piezoelectric materials on the surface. For solving the problems stated the finite element approximations are discussed. A set of effective finite element schemes is examined for finding numerical solutions of week statements for nonstationary problems, steady-state oscillation problems, modal problems and static problems within the framework of modelling of piezoelectric nanosized materials with damping and surface effects. For transient and harmonic problems, we demonstrate that the proposed models allow the use of the mode superposition method. In addition, we note that for transient and static problems we can use efficient finite element algorithms for solving the systems of linear algebraic equations with symmetric quasi-definite matrices both in the case of uncoupled surface effects and in the case of coupled surface effects

Harmonic vibrations of nanosized magnetoelectric bodies with coupled surface and interphase effects: Mathematical models and finite element approaches

The harmonic problems for piezomagnetoelectric nanosized bodies with taking into account the coupled damping and surface effects are considered on the base of the generalized Gurtin-Murdoch model. In the development of previous investigations, the coupled mechanical, electric and magnetic surface effects with surface inertial terms are introduced into the model. For a homogeneous model, the composite material is considered as homogeneous with the suitable effective material properties. The weak or generalized formulation of the steady-state oscillation problem is given together with the suitable formulation of the modal problem. For numerical solution of these problems, the finite element approximations, leading to a symmetric structure of finite element matrices, are present. The procedures of homogenization of piezomagnetoelectric nanostructured composite materials with piezoelectric and piezomagnetic phases are described on the base of the methods of effective moduli and finite elements

Transport features in layered nickelates: correlation between structure, oxygen diffusion, electrical and electrochemical properties

Oxygen migration is increasingly acknowledged as playing an important role in the ionic transport in mixed conductors and influencing the electrode electrochemical performance. The aim of this work was to establish correlations between the structural and electrical properties of undoped (Ln2NiO4 + δ, Ln = La, Pr) and doped (La1.7M0.3NiO4 + δ, M = Ca, Sr, Ba, La0.85Pr0.85Ca0.3NiO4 + δ, Pr1.7Ca0.3NiO4 + δ) layered nickelates and the oxygen diffusion in these materials to determine what influences their electrochemical response. A new technique for temperature programmed isotope exchange of oxides with C18O2 in a flow reactor was applied to investigate oxygen mobility and surface reactivity in the polycrystalline powder samples which provided the means to experimentally demonstrate the appearance of two channels of oxygen migration in the doped materials via cooperative mechanism and via near-dopant position. The electrochemical performance of the electrodes based on the developed materials was found to exhibit a strong dependence on their oxygen transport characteristics

NESTOR - A NEUTRINO PARTICLE ASTROPHYSICS UNDERWATER LABORATORY FOR THE MEDITERRANEAN

An underwater neutrino astrophysics laboratory, to be located in the international waters off the Southwest of Greece, near the town of Pylos is now under construction. In the last two years a group of physicists from Greece and Russia have carried out two demonstration experiments in 4km deep water, counting muons and verifying the adequacy of the deep sea site. Plans are presented for a 100,000 m2 high energy neutrino detector composed of a hexagon of hexagonal towers, with 1176 optical detector units. A progress report is given and the physics potential of a single tower with 168 phototubes (currently under construction) is described

NESTOR: a status report

NESTOR is an underwater neutrino astrophysics laboratory to be located in the international waters of the southwest of Greece. The first phase of this experiment is the construction and deployment of one hexagonal tower consisting of 168 optical modules, with effective area of 20000m(2) for E greater than or equal to TeV neutrinos. Over the past few years detailed studies of the site have been carried out while many tests have been performed. The current status of the preparation of the experiment and the future plans will be presented