Choosing the technology of combined processing of titanium-rare-metal raw materials

The main rules and principles which govern the choice of new variants for chemical technology of combined processing of titanium-rare-metal raw materials are considered. The existing variants of the technology are characterized from the viewpoint of their technological, economical, and ecological efficiency and social importance for a given region. A realistic choice of a technology from a large number of available variants should take into account the entire combination of their advantages and disadvantages The implementation of a rational technological scheme will result in the creation of economically profitable and efficient domestic production satisfying the demands of Russian industry in rare-metal and titanium materials. Directions are noted in which it is expedient to continue studies on designing a rational technology of loparite concentrate or some other concentrate.     

Analysis of the Functioning of Automatic Synchronous Generator Excitation Regulators with Various Input Signals of Frequency Stabilization Channels in the Certification Scheme1

Power Technology and Engineering - Anecessary requirement for automatic excitation regulation systems is ensuring the stability of the electric energy systems (EES) and the required quality of the...     

Hydrogen effect on the molecular weight distribution of polymers obtained by polymerization of ethylene and α-olefins over supported titanium-magnesium catalysts

Comparative data on the molecular weight distribution of polymers obtained by polymerization of ethylene, propylene and 1-hexene, and copolymerization of ethylene with α-olefins over the titanium-magnesium catalysts (TMC) in the absence and presence of hydrogen are presented. In contrast to the ethylene polymerization, in the cases of propylene and 1-hexene polymerization and copolymerization of ethylene with α-olefins, the hydrogen addition is characterized by noticeable narrowing of the molecular weight distribution (MWD) due to lower contribution of the MWD component with high molecular weight. This result is an evidence of the increased reactivity of TMC active sites producing high molecular weight poly-α-olefins and copolymers of ethylene with α-olefins in the chain transfer reaction with hydrogen. It is suggested that the increased reactivity of these sites in the transfer reaction with hydrogen appears after the 2,1-addition of α-olefin to the growing polymer chain.     

Thermoelastic stresses in ribbons and tubes grown from the melt by the Stepanov method

Ribbons and tubes grown from the melt by the Stepanov technique have a wide range of technical applications. Sapphire ribbons are used as substrates in microelectronics and sapphire tubes are used as gas-discharge balloons in laser engineering, fine chemical technology and high-vacuum equipment. Practice has shown that misorientation angles of small-angle boundaries in sapphire crystals should not exceed several degrees because an increase in the misorientation angles between blocks drastically lowers the strength and worsens the dielectric properties of these crystals. One of the main mechanisms of formation of the block structure of melt-grown crystals, including shaped sapphire crystals, is dislocation polygonization that begins when the dislocation density exceeds a certain critical value. In turn, dislocations are formed under deformations due to thermal stresses. Calculations of thermal fields in crystals and the corresponding thermoelastic stress fields can be used as an input to improve and optimize the growth process. The dependence of thermoelastic stresses in ribbons and tubes on the technological parameters has been calculated.Nomenclature ₁ Thermal diffusivity of the melt - ₂ Thermal diffusivity of the crystal - k ₁ Thermal conductivity of the melt - k ₂ Thermal conductivity of the crystal - V ₁ Velocity vector of the melt - V ₂ Velocity vector of the growing crystal - V ₀ Crystal pulling rate - H _f Latent heat of fusion - ₁ Density of the melt - ₂ Density of the crystal - in Interface normal vector - Crystal-melt interface normal vector - t Interface tangential vector - s Sided crystal-melt tangential vector - T _m Melting temperature - T _e Ambient temperature - T ₁ ⁰ Temperature at the bottom of the meniscus - T ₂ ⁰ Crystal temperature at the top of the meniscus - Normal vector at lateral surfaces of the crystal and meniscus - Stefan-Boltzmann constant - ₁ Emissivity of the meniscus lateral surface - ₂ Emissivity of the crystal lateral surface - g Acceleration due to gravity - _LG Melt-gas surface tension - a Die half dimension - ₀ Angle of growth - _t Thermal expansion coefficient - h ₁ Heat transfer coefficient of the melt - h ₂ Heat transfer coefficient of the crystal - C s Heat capacity - E Young's modulus - Poisson's coefficient - Melt kinematic viscosity - P Pressure in the melt     

Study of the sorption of oil products of power station wastewater modified with a TPP illuminator slurry

We examine the possibility of using a chemical water purification (CWP) slurry from the HS-1 as a sorbent for purifying TPP wastewater of oil products. We propose ways to increase the absorption capacity of the slurry. We present the results of studying the modified sorbent.     

Effect of weak and high magnetic fields in longitudinal and transverse configurations on magneto-thermoelectric properties of quantum Bi wires

We report on the magneto-thermopower of single-crystal Bi nanowires with diameters 75 and 250 nm in a longitudinal and transverse magnetic fields of 0–14 T. The temperature range is 1.5–300 K. Bi nanowires in a glass capillary have been prepared by the high frequency liquid phase casting. The temperature dependence R(T) shows the transition from metallic to semiconducting behavior due to quantum size effect, where the Bi-wire diameter is reduced to less than 80 nm. It is for the first time that the effect of the negative magneto-resistance in a transverse magnetic field, due to the quantum size effect on 75 nm Bi wires, has been observed. The thermopower is very sensitive to the wire diameter, up to a change in the sign from negative to positive at low temperatures, and to a significant extent in a weak longitudinal magnetic field. The field dependences of longitudinal and transverse magneto-resistance have features characteristic of the occurrence of the quantum size effect and galvanomagnetic size effect, and provide information on the parameters of the energy spectrum and charge carrier mobility. The enhancement of the thermoelectric figure of merit for Bi nanowires is discussed. We also discuss the power factor α²σ and its dependence on the diameter, magnetic field and temperature.     

Technique of hybrid microtarget calculation

The problem of simulating neutron-nuclear processes in hybrid microtargets with an external energy source has been considered. A mathematical model of interaction between neutrons and nuclei based on radiation transport multigroup equations is developed. The results of the numerical calculations of the microtarget with a thin layer of ²³⁸U are presented. The influence of the neutron model various simplifications on the neutron-nuclear processes in the microtarget is shown.