Modeling of heat transfer in a melt in growing single crystals by the stockbarger method using the accelerated crucible rotation technique (ACRT)

In model experiments, the layer of melt bounded by the crystallization front and the heater for heating the diaphragm in a growing furnace is shown to determine crystal growth by the Stockbarger method under conditions of induced convection and also to control the crystallization process. The free volume of the melt exerts no effect on its hydrodynamic and thermal structures. Optimum values of the exposure time are estimated for constant maximum and minimum velocities of modulated rotation of the growing ampoule. Institute of Mineralogy and Petrography, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 1, pp. 98–104, January–February, 1998.     

Circulatory flow in the inter-jet zone of a system of free turbulent jets

Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 4, pp. 97–99, July–August, 1993.     

Problem of the Sand Production in a Producing Well

The problem of sand production (dilatant-plastic reservoir fragmentation) in the process of pumping-out fluid through an uncased borehole is considered. Taking the dilatant change in reservoir porosity into account makes it possible to find a relation between the fluid and solid mass flow rates. There is no steady-state solution if the elasto-plastic boundary does not coincide with the supply contour. In this case a self-similar problem of well start-up with a constant production rate is considered.     

Simulation of attenuation of millimeter radio waves in dry snowfalls

Attenuation of millimeter waves in dry snowfalls is numerically simulated with allowance for the actual shape of snowflakes. It is shown that for moderate-intensity snowfalls the values of attenuation cross-sections averaged over the snowflake orientations are well approximated by power-law function depending on the equivalent diameter of the snowflakes. This allows us to obtain an analytical expression for the attenuation coefficient of a plane electromagnetic wave by snowfall for size distributions of particles of the gamma-distribution type and its modifications. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 4, pp. 446–455, April, 1998.     

Chaotic synchronization as an information process

The chaotic synchronization phenomenon is studied from the information point of view. Synchronization of a chaos receiver by a chaos source is considered as copy recovery of the chaotic signal transmitted by the source. The main idea of this paper is to show that the necessary condition of chaotic synchronization is not the level of physical action of one system on another but the transmission of a certain volume of information on the chaotic process and, therefore, the capacity of the “communication channel” between the source and the receiver. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Institute of Radioengineering and Electronics of the Russian Academy of Sciences, Moscow, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1497–1509, December, 1998.     

Critical thickness and stress relaxation in YBaCuO (123) strained epitaxial layers and YBaCuO based strained superlattices

An energy model has been used to calculate the critical thickness h _c of YBaCuO thin films and YBaCuO based superlattices within an isotropic or anisotropic approximation. The critical thickness of single layers calculated from the anisotropic model (16 nm) is in good agreement with the previously published experimental values which are spread out from 4 to 20 nm. In the case of superlattices, relaxation appears to be governed by the critical thickness of the elementary sub-layers and is then better evaluated through the calculation performed for YBaCuO single layers. XRD measurements on YBa₂Cu₃O₇/PrBa₂Cu_3?xGa_xO₇ superlattices grown on {100{ SrTiO₃ have evidenced a tetragonal stress in the YBaCuO ab plane which remains expanded when the YBaCuO elementary layer thickness is lower than 4.8 nm (4 YBaCuO cells). However the critical temperature of the shortest period superlattices is only slightly affected by this expanded stress in contrast to the effect of an elastic stress externally applied along the ab plane of YBaCuO thin films.     

Slow crack growth in blends of HDPE and model copolymers

The resistance to slow crack growth (SCG) was measured in binary blends of high density polyethylene (HDPE) and 5–10% concentrations of model ethylene-butene random copolymers by measuring the time to failure (t_f) under a constant stress intensity. An increase of t_f with the addition of the copolymer if the copolymer could crystallize and the increase was greater the higher branch density. The copolymer with 117 branches/1000C could not crystallize and therefore its blend had a t_f that was less than that of the HDPE. The fracture energies of the blends as determined by their resistance to SCG were compared with the energy by rapid fracture, J_c, as previously measured by Rhee and Crist. It is concluded that SCG is more sensitive to variations in the microstructure than is rapid fracture and that the differences in SCG behavior can be qualitatively explained in terms of the differences in microstructure of the blends. ©1995 John Wiley & Sons, Inc.     

On the applicability limits of the method of radio-wave refraction scattering

We compare the computational possibilities of the radio-wave refraction-scattering method (RWRSM) and the parabolic-equation method (PEM) in determining the statistical characteristics of radio waves in a medium with large-scale inhomogeneities. It is shown that on the whole the applicability limits of the RWRSM are similar to the corresponding limits of the PEM. However, unlike the PEM, the RWRSM makes it possible, in a number of cases, to use simple means to solve radio-wave-refraction problems in a thick layer with large-scale inhomogeneities.Radiophysical Research Institute, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 11, pp. 1118–1123, November, 1995.