Generalized percolation theory for the analysis of the structure and properties of porous and composite materials

Expressions are obtained for calculating percolation characteristics of heterogeneous systems with the use of refined auxiliary relations in the entire range of their porosity (concentration of a disperse phase).Institute of Engineering Thermophysics, Academy of Sciences of the Ukraine, Kiev. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 3, pp. 348–352, March, 1994.     

Calculation method for percolation thresholds in modeling porous and composite materials

A method is suggested for calculating percolation thresholds in two- and three-dimensional materials allowing for remote interaction and elongation of particles forming these materials. Calculated results are compared with known data. It is shown that it is possible to use the method when simulating elastic and plastic properties of porous materials.     

Conductivity estimation for highly porous permeable cellular materials

A simple but geometrically fairly rigorous model is proposed for the structure in order to estimate the conductivities of highly porous permeable cellular materials. The model is based on elementary cells that take the form of semiregular polyhedra (truncated octahedra with conducting edge bridges). A method is given for determining the increase in conductivity because of increase in the cross section of these edge bridges on intersection. The calculations agree well with experiment.     

Comparison of computational results obtained with different programs for radiation transfer

Main Science Center of the Russian Federation — Institute of High-Energy Physics. Translated from Atomnaya énergiya, Vol. 79, No. 4, pp. 269–279, October, 1995.     

Production and properties of zirconia ceramics

Conclusions A study was made of the effect of preliminary milling and the process temperature of a mixture of zirconium and yttrium hydroxides on the technical aspects of preparing large articles from partially stabilized zirconia.A procedure was developed for making such items from tetragonal zirconia, both by monoaxial pressing and by slip casting in gypsum molds. The main physicochemical and frictional properties of the materials were investigated.The material has been tested for pushers, piston units, inserts and gaskets, friction pairs of the gas distribution tract in internal combustion engines, and the axles of shafts for pumps handling corrosive media. The tests confirmed the workability of the material in friction pairs.Translated from Ogneupory, No. 2, pp. 6–9, February, 1991.     

Generation of transverse direct current in a superlattice under a bichromatic high-frequency electric and constant magnetic fields

Direct-current generation in a semiconductor superlattice exposed to a high-frequency bichromatic electric field applied along its axis and to a constant magnetic field perpendicular to the surface, i.e., superlattice axis, is studied. In the first non-vanishing approximation in terms of the magnetic-field strength, an explicit expression for the current density in the case of the ratio of electric-field frequencies equal to two is derived.