Synchrotron X-ray diffraction study of nanostructured Er2O3-TiO2 (50–60 mol % Er2O3) solid solutions

Monochromatic synchrotron X-ray diffraction data demonstrate that single-crystal and polycrystalline xEr₂O₃ · (1 ? x)TiO₂ (x = 0.5–0.6) solid solutions consist of a fluorite-like disordered (Fm3m) phase and a nanoscale (40–1000 nm) pyrochlore-like ordered phase (Fd3m) of the same composition in the range 0.5 ≤ x ≤ 0.57, coherent with the disordered phase. Reducing the density of structural defects in the unit cell of Er₃TiO_6.5 (x = 0.6) leads to a structural transformation of the pyrochlore-like phase into a Ta₂O₃-type ordered phase (Ia3), derived from the fluorite phase. In the composition range of the solid solutions (0.5 < x < 0.6), the lattice parameter of the fluorite-like phase follows Vegard’s law. The formation of nanodomains with different degrees of order is shown to be caused by the internal strain due to the high density of structural defects in their unit cells.     

Optimization of the procedure of plasma spraying of erosion-resistant coatings according to strength criteria

It is shown that mechanical characteristics of the coatings depend on their technological conditions of their deposition. We propose a procedure of optimization of the technological process and control over this process according to the criteria of strength and specific consumption of materials by analyzing an example of plasma spraying of erosion-resistant coatings. The erosion resistance exhibits the most stable correlation with the cohesive strength of the coatings. The regression equations are used to determine the maximum levels of cohesive strength of the coatings and erosion resistance for the optimal combinations of technological parameters of. Translated from Problemy Prochnosti, No. 6, pp. 136–151, November–December, 2008.     

Field electron emission from nanodiamond

Nanodiamond (ND) films on silicon substrates have been synthesized by plasmachemical deposition (PCD). Films with minimum differences in the structure and morphology, which were obtained by varying the PCD process parameters, exhibited significantly (several orders in magnitude) different field-emission currents. It was found that the surface of ND films showing by the maximum field-emission currents contains needle-like carbon structures. Based on the obtained experimental data, it is concluded that the field-emission properties of ND films are determined by the presence of non-diamond carbon inclusions.     

Model predictive control of systems with random dependent parameters under constraints and its application to the investment portfolio optimization

The problem of model predictive control for discrete systems with random dependent parameters is considered. The dynamics of parameters’ vector is described by the difference stochastic equation. The control strategy is determined with regard to explicit constraints on control variables. The results are applied to the investment portfolio control under constraints on the volumes of assets.