An advanced power controller in an electric-arc furnace

The increased cost of electrodes in low-power electric-arc furnaces due to frequent breakdowns at the stage of the electric-arc ignition is a problem. Improvement of the mechanical part of the furnace does not eliminate the described problem, while demanding huge investment. The most effective way to do thus is to modernize the automatic control system. The application of new control algorithms, combined with the constantly developing element base, allows the quantitative and qualitative indicators of the power controller and the furnace to be increased. This paper focuses on the development of an advanced power controller that allows the probability of breakage of electrodes to be reduced. A simulation model of the advanced power controller is provided and studied.     

Fluctuating local field approach to the description of lattice models in the strong coupling regime

Journal of Superconductivity and Novel Magnetism - We consider 2D Hubbard clusters magnetism in the strong coupling regime. We show that the mean field approach does not provide sufficient results....     

Subsurface shear instability and nanostructuring of metals in sliding

Dry sliding wear conditions were used to obtain a 500 μm-thick layer of nanosize grains on copper samples. As shown, this layer reveals a flow behavior pattern similar to that of a viscous non-Newtonian fluid. Four structurally different zones were found in the longitudinal cross-sections of samples below the worn surface. Upper two of them are nanocrystalline and consist of many ～1 μm-thick sublayers, which show either laminar or turbulent flow behavior. These sublayers demonstrate different levels of elasticity as compared to each other and may be related to an interplay between work-hardening and thermal softening. Lower two zones undergo usual plastic deformation and severe fragmentation without viscous mass transfer. High level of Young's modulus in the fragmentation zone is evidence of insufficient thermal softening at that depth. We believe that viscous flow zones are the result of shear instability and subsequent shear deformation developed in subsurface layers due to thermal softening. Numerical study has been carried out to simulate friction-induced deformation and shear instability under conditions close to the experiment. As shown, such a situation is possible when deformation-generated heat is taken into account. Another interesting result relates to the sublayers’ strain rate distribution. It was found that 1 μm-thick sublayers may show either high strain rate gradient or zero strain rate as a function of depth below the worn surface. The latter case means that a pack of layers may exist and behave like an elastic body in ductile medium.     

Effect of added reactive agents on the flame propagation velocity in rich hydrogen-air mixtures

An approximate analytical method for evaluating the efficiency of the action of an inhibitor on the velocity and propagation limits of a flame in rich hydrogen-air mixtures with small amounts of added propylene and isobutylene inhibitors is proposed. The method is based on the model of a narrow reaction zone and the distinct features of the branching chain mechanism of hydrogen oxidation reactions. Using this method, it is shown that the occurrence of flame propagation limits at higher concentrations of added reactive agents (inhibitors) is caused by the existence of a positive feedback between the flame front velocity and the number of active combustion sites, which break down in the inhibitor-added reaction. According to this feedback, the action of the inhibitor decreases the flame temperature and flame velocity.     

Effects of drive rotation speed on cold production and startup period in a Gifford-McMahon cryorefrigerator with slide valve gas distribution

Studies have been done on a one-stage microcooler in a Gifford-McMahon cryorefrigerator with a gas distribution mechanism including a rotating slide valve. The following relationships have been determined: heat flow in relation to cryostatic temperature with various motor speeds, temperature on the time to reach the steady state, and slide rotation frequency as a function of temperature. __________ Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 3, pp. 16–18, March, 2006.     

Development of a gas distributing system for a Gifford-MacMahon microrefrigerator having a free expulsor with an automatic control system

A gas distributing system is proposed that curtails the time for attaining the normal operating condition, maintains maximum refrigeration over the whole operation temperature range, and increases reliability and operating life. __________ Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 7, pp. 17–19, July, 2006.     

Regeneration of Cellulose Insulation of Windings of Long-Life Power Transformers

Main aspects of the physicochemical condition of cellulose insulation of windings of power transformers with a long-term service life are analyzed with the aim of determining criteria on the possibility of prolonging the life of the insulation by washing with surface-active substances.     

Heat and mass exchange in an optically thin,turbulent boundary layer in an IR radiation field

The procedure and results of an experimental investigation of the temperature and velocity distribution in a plane, incompressible, turbulent boundary layer of air and of CO₂ in an IR radiation field are presented. Data are given on heat exchange under the conditions of curtain cooling.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 6, pp. 885–894, June, 1985.The authors thank Academician S. S. Kutateladze for support of the work and fruitful discussions.