: Fourier inversion of EXAFS data is a powerful new technique for structural investigation of non-crystalline materials with the unique capability to determine the near neighbor environment of each type of atom in a complex material. The radial structure function so obtained contains information on the number, distance to, and distribution of atoms surrounding the absorbing atom. The data on Ge and Ge02 generally agree with previous findings but with added detail. The environment of both Ge and Se in amorphous GeSe show a significant change from the crystalline material with evidence for local satisfaction of the directed bonding tendencies of each atomic species. (Author)

The Structure of Non-Crystalline Materials

This paper presents chaos synchronization between two identical Lorenz–Stenflo (LS) and a new four-dimensional chaotic system (Qi systems) by using active control technique. The designed controller ensures that the state variables of the controlled chaotic slave LS and Qi systems globally synchronizes with the state variables of the master systems respectively. It is also shown that Qi system globally synchronizes with LS system under the generalized active control. The results are validated using numerical simulations.

Synchronization of identical and non-identical 4-D chaotic systems using active control

Synchronization of Rikitake chaotic attractor using active control

Reinforcement of elastomers by colloidal nanoparticles is an important application where microstructure needs to be understood—and, if possible, controlled—if one wishes to tune macroscopic mechanical properties. Here, the three-dimensional structure of large aggregates of nanometric silica particles embedded in a soft polymeric matrix is determined by small angle neutron scattering. Experimentally, the crowded environment leading to strong reinforcement induces a strong interaction between aggregates, which generates a prominent interaction peak in the scattering. We propose to analyze the total signal by means of a decomposition in a classical colloidal structure factor describing aggregate interaction and an aggregate form factor determined by a reverse Monte Carlo technique. The result gives new insight to the shape of aggregates and their complex interaction in elastomers. For comparison, fractal models for aggregate scattering are also discussed.

https://hal.archives-ouvertes.fr/hal-00148575/document

Structure of interacting aggregates of silica nanoparticles in a polymer matrix: small-angle scattering and reverse Monte Carlo simulations

Intermetallics such as the transition metal aluminides present theorists with a challenge since bonding is not well described by currently available pair or embedded atom potentials. We show that a new angularly dependent, many-body potential for the bond order has all the necessary ingredients for an adequate description. In particular, by linearizing the moment-recursion coefficient relations, a cluster expansion is derived which is applicable to any lattice and chemical ordering and which allows a derivation of the earlier ring ansatz. It can account for both the negative Cauchy pressure of cubic metals and the oscillatory behaviour across the transition metal aluminide series of the three-body cluster interaction Φ 3 .

Bonding and structure of intermetallics : a new bond order potential. Discussion

We study chaotic phase synchronization of unidirectionally coupled deterministic chaotic ratchets. The coupled ratchets were simulated in their chaotic states and perfect phase locking was observed as the coupling was gradually increased. We identified the region of phase synchronization for the ratchets and show that the transition to chaotic phase synchronization is via an interior crisis transition to strange attractor in the phase space.

Phase synchronization in unidirectionally coupled chaotic ratchets

Thermodynamics of liquid Al–Fe alloys

The bifurcation and chaotic behavior of unidirectionally coupled deterministic ratchets is studied as a function of the driving force amplitude a and frequency . A classification of the various types of bifurcations likely to be encountered in this system was done by examining the stability of the steady state in linear response as well as constructing a two-parameter phase diagram in the a- plane. Numerical explorations revealed varieties of bifurcation sequences including quasiperiodic route to chaos. Besides, the familiar perioddoubling and crises route to chaos exhibited by the one-dimensional ratchet were also found. In addition, the coupled ratchets display symmetry-breaking, saddle-nodes and bubbles of bifurcations. Chaotic behavior is characterized by using the Lyapunov exponent spectrum; while a perusal of the phase space projected in the Poincare cross section confirms some of the striking features.

O. Akinlade

Papers

Phase synchronization in unidirectionally coupled chaotic ratchets

Thermodynamics of liquid Al–Fe alloys

Bifurcation and chaos in coupled ratchets exhibiting synchronized dynamics.

Assessment of size effect on the surface properties of some binary liquid alloys

Bulk and surface properties of liquid In–Cu alloys