Surface processes in hydrogen permeation through metal membranes

The phenomenon of hydrogen permeation through metals is considered as a complex of interphase and diffusion processes. Basic principles of application of the hydrogen permeation technique to studies of various stages of hydrogen interaction with metals are formulated. An analysis is made of possible errors of the permeation technique when used to measure the characteristics of hydrogen diffusion through metals originating from the finite rate of the interphase processes. The permeation of nonequilibrium and corrosion-produced hydrogen through metal membranes, and the hydrogen permeability of multilayer systems are considered.     

Kinetics of methane conversion over microspherically grained nickel-alumina catalysts

Kinetics of methane conversion in a fluidized bed of microspherically grained nickel-alumina catalyst has been studied at pressures from 0.3 to 3.1 MPa. The rate equation shows that the reaction is inhibited by H₂O.

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0,3 3,1 . , .

     

Fundamental and parasitic wave modes of a shielded microstrip line

Conclusions It was demonstrated that for the usually employed widths of the shield in MSL a parasitic quasi-LM₁₀ wave may propagate besides the working quasi-TEM wave; the quasi-LM₁₀ wave interacts with the working wave in the inhomogeneities of the line and may disrupt the normal operation of devices having MSL. The propagation constants of these two lower wave modes may be determined comparatively simply with an accuracy of the order of 1% by means of the first-approximation dispersion equation derived in the present paper. The system of linear algebraic equations derived in the present paper may serve for the analysis and calculation of the characteristics of the higher wave modes.Patrice Lumumba University of Friendship among Peoples. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 16, No. 1, pp. 118–128, January, 1973.     

Riesz Bases of Eigenfunctions of an Integral Operator with a Variable Limit of Integration

We prove a theorem on the Riesz basis property in the space L ₂[0,1] of the eigenfunctions and associated functions of an integral operator whose kernel possesses a derivative discontinuous on the line $t = 1 - x$ .     

Mechanisms of martensitic transformations in boron nitride and conditions of their development

Abstract

The dependence of the pressure threshold of martensitic transformations on the disordering degree of starting structures is considered for graphite-like BN into diamond-like BN modifications transitions. The effect of loading conditions on transformation mechanisms of rhombohedral BN into zinc blende or wurtzite modifications is analyzed also. Analytical relations obtained allow to explain the experimental data and to predict a behavior of various graphite-like structures under different p, T conditions.     

Formation of dynamic spatial flame structures for gas burning in microchannels with temperature gradients on walls

The thermal-diffusive model was applied to the problem of flame propagation in a microchannel with controlled temperature distribution in the walls; this demonstrated the possibility of formation of oscillating or rotating spatial flame structures, which were described previously in experimental works on microcombustion. Two cases were considered: combustion in a rectangular channel and in the clearance between two disks with radial feeding of premixture. In both cases, the typical across size of the channel was lower than the critical diameter determined with respect to the ambient temperature. The gas flow was assigned and described by the Poiseuille-flow velocity profile. Formation of oscillating flame in a rectangular channel and rotating patterns in a radial channel was observed for a certain range of gas flow rate. At low flow rates beyond this range, repetitive ignition/extinction of flame took place; at high flow rate we observed a steady flame mode. Formation of these special flame structures is related to heat transfer between gas and hot walls of the channel, as well as to velocity maldistribution in the microchannel.