Some special features of the structural changes of epoxy resins under the action of magnetic fields

Conclusions 1. The action of a magnetic field leads to a change in the structure of an epoxy resin both at the molecular and at the supramolecular levels.2. A homogeneous magnetic field acting on the hardening process of an epoxy resin, due to the presence of the orientating moment, is able to produce ordered formations.3. A nonhomogeneous magnetic field results in a distribution of anisotropic morphological formations along the field gradient, promoting a change in the physicomechanical properties of the material.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 583–587, July–August, 1978.     

Increasing the wear resistance of graphitoplast parts

The effect of compression molding conditions on the physicomechanical properties of graphitoplast is studied. The question of the correlation between the microstructure of the material and its wear resistance is considered. It is shown that in order to obtain optimal properties it is necessary to establish the proper compression molding conditions for each part, in particular, the molding pressure and its conditions of application.Mekhanika Polimerov, Vol. 1, No. 3, pp. 115–119, 1965     

Thermodynamic determination of the shift factor

The determination of the shift factor is examined on the basis of the thermodynamics of irreversible processes assuming a closed homogeneous system. It is shown that for any internal state the shift factor is equal to the product of the temperature and stress shift factors. An equation in which the nonequilibrium character of the processes is taken into account is obtained for the temperature shift factor.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1001–1010, November–December, 1973.     

Limit laws for sums of products of exponentials of<Emphasis Type="Italic">iid</Emphasis> random variables

We study limit laws for sums of products of exponentials of nonnegative,iid random variables {V _ij }, namely . Under a Cramér type condition,E[e ^sV _ij ]<∞ for somes>0, a weak law of large numbers, central limit theorem, and convergence to stable laws is established for appropriate rates of growth ofN(n) and proper normalizations and scalings. Research of authors supported by grants from NSF.     

Martin boundaries for the direct product of Markov processes

Siberian Mathematical Journal -     

Crystal structure of La3Nb0.5Ga5.5O14 at 20 K

The atomic structure of La₃Nb_0.5Ga_5.5O₁₄ single crystals (space group P321, R = 2.21%, R _w = 2.31%) at 20 K was determined using X-ray diffraction. A comparative analysis of the structural characteristics determined at temperatures of 293 and 20 K did not reveal a noticeable redistribution of bond valences that could be considered precursors of a possible phase transition accompanied by the reduction of the symmetry of the crystal. The assumption was made that the anomalous behavior of the permittivity e ₃₃ of the La₃Nb_0.5Ga_5.5O₁₄ single crystals is associated with the decrease in the possible relative displacements of the Ga(1) and Nb atoms occupying the cation position with point symmetry 32 in a 1: 1 ratio.     

On the Spectrum of the Surface Maryland Model

We study spectral properties of the discrete Laplacian H on the half space Z₊ ^d+1 = Z^d× Z₊ with a boundary condition (n,-1) = tan( ... n + )(n,0), where [0,1]^d. We denote by H₀ the Dirichlet Laplacian on Z₊ ^d+1. Whenever is independent over rationals (H) = R. Khoruzenko and Pastur have shown for a set of 's of Lebesgue measure 1, the spectrum of H on R\ (H₀) is pure point and that corresponding eigenfunctions decay exponentially. In this Letter we show that if is independent over rationals, then the spectrum of H on the set (H₀) is purely absolutely continuous.