Ab initio Probing of Magnetic and Electronic Properties of Monoclinic ε-WO3 Doped with 3d Transition Metals Within GGA and GGA+U

Based on ab initio band structure calculations, we have systematically examined the monoclinic tungsten trioxide doped with all 3d metals (M=Sc,Ti,…,Ni,Cu) focusing on the effects of these impurities on the electronic and magnetic properties of ε-WO₃. We found that all of the 3d impurity atoms can be divided into two main groups. The first group includes the atoms of the beginning of the 3d row, and for these systems (for example, ε-WO₃:Ti) the highest magnetic moments and the peculiarities of the near-Fermi states are due to the atoms of the oxygen lattice of trioxides. On the contrary, the impurity atoms of the end of the 3d row play a dominant role in the formation of magnetic and electronic properties. These results are fair for calculations within both GGA and GGA+U approximations. Finally, there are so-called “border” systems (for example, ε-WO₃:Cr), where the Coulomb interactions have a critical influence on the electronic and magnetic parameters.     

Composition of beryllium oxide ceramics

The physicochemical and electrophysical properties of ceramics based on BeO without impregnation and after impregnation with an aqueous solution of sodium carbonate Na₂CO₃ are studied. It is established that impregnation leads to preparation of ceramic specimens with a white color, which develop increased porosity, lower amount of impurities and smaller average microcrystal size, although it has little effect on their electrophysical properties. In order to improve these properties considerably it is necessary to increase ceramic density by increasing its sintering temperature by 20 – 40 K. Values of electrical permittivity δ and dielectric loss tangent tg δ are determined for a series of BeO ceramic specimens (732 pieces), having identical geometric dimensions, but prepared from original BeO powder of different batches. Studies show considerable scatter in the distribution of these parameters, which points to a requirement for further improvement of BeO-ceramic preparation technology.     

Ab Initio Probing of the Magnetic and Electronic Properties of ThCr2Si2-Like Charge-Balanced KFeAgTe2

Based on density functional theory band structure calculations, we address the magnetic and electronic properties of KFeAgTe₂ system. This phase belongs to the newest family of ThCr₂Si₂-type ternary iron-chalcogenide materials A _x Fe_2−y Ch ₂ (A= alkali metals or Tl, Ch= Se or S, discovered in 2010) which have aroused recently a tremendous interest and triggered intense studies owing to intriguing coexistence of metal vacancy ordering, antiferromagnetism, and superconductivity. But, unlike A _x Fe_2−y Ch ₂, KFeAgTe₂ is a Te-containing ThCr₂Si₂-type phase, includes a large amount of the noble metal and is free of vacancies. Here, by means of first-principles FLAPW-GGA calculations, the spin ordering of the magnetic ground state, total and partial densities of states for KFeAgTe₂ were obtained for the first time and analyzed in comparison with the related A _x Fe_2−y Ch ₂ systems.     

A T-113/145-12.8 cogeneration steam turbine for the PGU-410 combined-cycle plant at the Krasnodar cogeneration station

Turbine design, essential features of its control, economic indicators, and main solutions taken for the thermal circuit and layout of the T-113/145-12.8 turbine unit are considered.     

Electronic structure and bonding configuration of theH-Phases Ti2MC and Ti2MN (M = Al, Ga, In)

The electronic structure of theH-phases Ti₂MC and Ti₂MN (M = Al, Ga, In) is calculated by the self-consistent linearized muffin-tin-orbital method in the atomic-sphere approximation and the MO LCAO method using RMH parametrization. The band structure and bonding configuration of theH-phases are compared with those of other Ti-M-C and Ti-M-N phases     

Titanium, vanadium, and nickel impurities in 3C-SiC: Electronic structure and lattice relaxation effects

Variations of chemical bonding and lattice relaxation in cubic silicon carbide in the presence of 3d-series impurity atoms (M=Ti, V, and Ni) were studied within the total-potential version of the method of linear muffin-tin orbitals. Substitution of the silicon atom with M causes a displacement of the closest carbon atoms outward from the impurity atom; the greatest effect is observed for the Ti atom. The conducting properties in doped compounds vary from semiconductor for the titanium atom (electron conduction) and nickel (hole conduction) to metallic in the case of vanadium. Features of chemical bonding were analyzed on the basis of the cohesion energy and charge densities.     

Theoretical and experimental study of capillary constraints on heat transfer in high-temperature heat pipes

The results are presented of experimental and theoretical studies concerning capillary constraints on heat transfer in high-temperature heat pipes, also of the effect of the compressibility of vapor on the calculated power transfer and, accordingly, the limits of validity are established for theoretical methods not taking into account the compressibility of the vapor stream.Deceased.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 5, pp. 773–778, May, 1980.     

Experimental investigation of heat transfer with evaporation of the agent from a corrugated capillary structure

The authors present experimental data on the intensity of heat transfer in a corrugated capillary structure. They propose a physical model of the heattransfer process that explains the results obtained.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 46, No. 4, pp. 533–538, April, 1984.