Model Driven Engineering and Dependability Analyses: The Topcased Approach

International audienceModel Driven Engineering approaches are widely promoted to overcome difficulties to design, validate and maintain large complex systems. They present interesting dependability characteristics especially in terms of prevention of design faults and validation of design correctness. However industrial needs, practices and applicable standards impose constraints on the dependability activities to perform and justify. Therefore it is necessary to analyze how a complete dependability and safety process can be integrated with model-driven approaches within a seamless global process: which dependability activities are naturally covered or facilitated by model-driven approaches, and which additional activities are needed with which support. This paper presents the results of a study aiming at the establishment of requirements to model-driven engineering methods and tools, to support dependability analyses

Metallic and nonmetallic double perovskites: A case study of A2_2FeReO6_6 (A= Ca, Sr, Ba)

We have investigated the structure and electronic properties of ferrimagnetic double perovskites, A2FeReO6 (A= Ca, Sr, Ba). The A=Ba phase is cubic (Fm3m) and metallic, while the A=Ca phase is monoclinic (P21/n) and nonmetallic. 57Fe Mossbauer spectroscopy shows that iron is present mainly in the high-spin (S=5/2) Fe3+ state in the Ca compound, while it occurs in an intermediate state between high-spin Fe2+ and Fe3+ in the Ba compound. It is argued that a direct Re t2g - Re t2g interaction is the main cause for the metallic character of the Ba compound; the high covalency of Ca-O bonds and the monoclinic distortion (which lifts the degeneracy of t2g states) seem to disrupt the Re-Re interaction in the case of the Ca compound, making it non-metallic for the same electron count.Comment: 1 eps fil

Observation of 10% Fe Solubility in Ammonia-Coprecipitated Fe Doped SnO<SUB>2</SUB> Nanopowders: A Structural, Optical and Hyperfine Property Study

International audienc

Observation of 10% Fe Solubility in Ammonia-Coprecipitated Fe Doped SnO<SUB>2</SUB> Nanopowders: A Structural, Optical and Hyperfine Property Study

International audienc

Transport properties, magnetic ordering, and hyperfine interactions in Fe-doped La<SUB>0.75</SUB>Ca<SUB>0.25</SUB>MnO<SUB>3</SUB>: localization-delocalization transition

Transport properties of La0.75Ca0.25Mn1-xFexO3+y ceramics are examined for "x" values from 0 to 0.05. Dramatic changes are observed in the resistivity and its temperature dependence as "x" increases above about 0.04. Temperature-dependent Mossbauer spectroscopy and magnetization studies are also performed. These data suggest that transport in this system necessarily involves quasiparticle excitation in association with the double exchange process and it undergoes localization-delocalization-type transition at a critical dopant concentration

Self-assembled single-crystal ferromagnetic iron nanowires formed by decomposition

Arrays of perpendicular ferromagnetic nanowires have recently attracted considerable interest for their potential use in many areas of advanced nanotechnology. We report a simple approach to create self-assembled nanowires of α-Fe through the decomposition of a suitably chosen perovskite. We illustrate the principle behind this approach using the reaction 2La0.5Sr0.5FeO3 → LaSrFeO4 + Fe + O2 that occurs during the deposition of La0.5Sr0.5FeO3 under reducing conditions. This leads to the spontaneous formation of an array of single-crystalline α-Fe nanowires embedded in LaSrFeO4 matrix, which grow perpendicular to the substrate and span the entire film thickness. The diameter and spacing of the nanowires are controlled directly by deposition temperature. The nanowires show uniaxial anisotropy normal to the film plane and magnetization close to that of bulk α-Fe. The high magnetization and sizable coercivity of the nanowires make them desirable for high-density data storage and other magnetic-device applications.Accepted versio