Interaction of dielectrics with femtosecond laser pulses: application of kinetic approach and multiple rate equation

We calculate the transient free-electron density in laser-irradiated dielectrics with two different approaches, both considering the energy distribution of excited electrons. The kinetic approach solves a system of complete Boltzmann collision integrals describing different excitation and relaxation processes in detail. The multiple rate equation (MRE) is an approximative way to keep track of the energy distribution of excited electrons with reduced numerical effort. Both methods are applied to trace dielectric breakdown, considering the changing optical parameters during irradiation with a high-intensity laser pulse. In the MRE approach we include also fast recombination, leading to a delay of the increase of the electronic density and to a decrease of the maximum number of free electrons.     

Pulse-detonation burner unit operating on natural gas

The possibility of controlled cyclic deflagration-to-detonation transition within a length of 2.5–3.0 m in an open-end tube (94 mm in diameter) with separate continuous supply of natural gas and air was demonstrated for the first time. Based on experimental studies, a workable pulse detonation burner, a prototype of new generation of industrial burners, was developed. It can produce a combined effect on the objects blown on with combustion products—shock-wave (mechanical) and thermal.     

Formation of nitrogen oxides in detonation waves

Based on detailed kinetic calculations and experimental data, it is demonstrated that the emission of nitrogen oxides from detonation burner units (DBUs) is significantly lower than that from powerful conventional burners with similar characteristics. Under certain conditions, realized largely in DBUs with rotating detonation, the main component of the nitrogen oxides may turn out to be N₂O.     

Adsorption Plastification of Aluminum-Oxide Ceramic Filaments

The dependence of tensile load and elongation upon tension to break on a changed concentration of sizing emulsion is investigated. When the concentration of sizing emulsion varies from 2 to 20%, a correlation is observed between the values of the tensile load and elongation upon tension with changed surface activity and specific electric conductivity of the sizing emulsion. This indicates that electrophysical processes play an important role in the mechanism of the adsorption plastification, namely, the appearance of free electric charges on the surface of filaments under their mechanical loading.     

In memory of our authors

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In memory of our authors     

Effect of a random crystalline field on the Curie temperature of an anisotropic crystalline ferromagnet

We examine how substitution of nonmagnetic atoms of one species by another that leads to the emergence of a random crystalline field affects the Curie temperature T _C of an anisotropic crystalline ferromagnet. We study the case of low concentrations, in which individual substitutional impurities create isolated clusters of perturbed magnetic ions with additional easy-or hard-magnetization axes. Finally, we analyze the various sign relations among the parameters D and d of regular and impurity second-order anisotropies with Kramers (J=1) and non-Kramers (J=3/2) angular momenta, and show that usually the effects of a random crystalline field lower the Curie temperature as the concentration of the nonmagnetic impurity atoms increases. Zh. éksp. Teor. Fiz. 111, 127–143 (January 1997)     

Geometrical surface vortex pinning in superconducting films

A model is proposed for vortex pinning in a superconducting film with a rough surface. The model relates the critical current to the steepness of the surface relief and, at a high vortex concentration, to the distance between neighboring steepness maxima on the paths of vortex motion. The dependence of the critical current density on the thickness of a high-T_c superconducting film is measured in a weak magnetic field. Its behavior can be explained by the pinning at the stepped surface relief.     

Orders on Braid Groups

It is shown that the braid group defies lattice ordering.