General Aspects of the Combustion Synthesis of a Cobalt Alloy with Dispersion and Precipitation Modification

Inorganic Materials - We have studied the potentialities of dispersion and precipitation modification of a cobalt alloy in combustion mode under the effect of centrifugal forces. The starting...     

Polymerization of propylene in liquid monomer using state-of-the-art high-performance titanium-magnesium catalysts

A comparative study of propylene polymerization in liquid monomer is performed under laboratory conditions using the IK-8-21 Ti-Mg catalyst designed at the Boreskov Institute of Catalysis and imported industrial catalysts (conditionally labeled TMC-1, -2, and -3). The activity and stereospecificity of the catalysts are estimated along with properties of the resulting polypropylene (granular composition and physicomechanical characteristics). It is shown that the IK-8-21 catalyst is not inferior to imported counterparts in terms of catalytic properties in the synthesis of polypropylene. The polypropylene powder formed on IK-8-21 is homogeneous and has good morphology. The physicomechanical characteristics of polypropylene synthesized on the domestic IK-8-21 catalyst are similar to those for polypropylene prepared with the imported TMK-1 catalyst.     

Adjustment of circular grinders in machining conical surfaces

The adjustment and calculation of the geometric, kinematic, and mechanical parameters are considered when shaping conical surfaces on centerless circular grinders.     

Microstrip Spurious-Coupling Band-Pass Filters with Quarter-Wavelength and Π-Shaped Resonators

Journal of Communications Technology and Electronics - Microstrip band-pass filters (BPFs) containing quarter-wavelength resonators and a Π-shaped half-wavelength resonator placed next to each...     

Coupling coefficients of step-impedance resonators in stripeline band-pass filters of array type

There are researched specificities of electromagnetic coupling coefficients at main and higher resonance frequencies between step-impedance resonators, fabricated from symmetric stripe transmission lines with open ends. It is shown, modification of step resonators parameters can result in modification of the coupling coefficient at main resonance frequency in wide range, that allows to realize band-pass filters of array type. It is stated in case of several values of parameters of stripe resonators their coupling coefficients values at frequencies higher than main one are zero. It is proposed a new method of expansion of suppressed frequency band of pass-band filters of array type, which is based on suppression of the first parasitic pass band due to zero coupling coefficient.     

Effect of gas content and actual stresses on coalbed permeability

The analytical review covers the key factors that influence permeability of a coalbed under mining-induced alteration of stress state. The authors put forward an analytical relation between coal permeability, stresses and adsorbed gas to define parameters of gas leakage zone parameters and laws of mass transfer. The analytically derived relation is compared with the known model of coal structure and with the experimental results. The proposed model of coalbed permeability allows mechanism of leakage and localization of seepage zones in coal provided that the model parameters are properly selected or found experimentally.     

Modeling of prebreakdown stage of gaseous discharge

A mathematical model of electron cascade transfer is presented. It is developed for studying the prebreakdown stage of gaseous discharge based on the kinetic equation for electrons in a self-consistent electromagnetic field. An elastic scattering of electrons, excitation of molecules by electron impact, and impact ionization are taken into account. A natural ionization background is used as the initial distribution of free electrons. The results of the computational experiment are compared to the data of measurements of drift velocity and the average energy of electrons of discharge, as well as the Townsend coefficient in a flat charged condensor filled with diluted xenon. The comparison showed that the model is not in contrast with the experiment. In order to contract the volume of the discharge’s full current calculation, a transport approximation is built. It is based on the averaging of angular scattering. The applicability of the transport approximation for modeling the full current of the capillary discharge is studied.