The paper is devoted to constructing approximate heat wave solutions propagating along the cold front at a finite speed for a nonlinear (quasi-linear) heat conduction equation with a power...

The paper deals with two-dimensional boundary-value problems for the degenerate nonlinear parabolic equation with a source term, which describes the process of heat conduction in the case of the power-law temperature dependence of the heat conductivity coefficient. We consider a heat wave propagation problem with a specified zero front in the case of two spatial variables. The solution existence and uniqueness theorem is proved in the class of analytic functions. The solution is constructed as a power series with coefficients to be calculated by a proposed constructive recurrent procedure. An algorithm based on the boundary element method using the dual reciprocity method is developed to solve the problem numerically. The efficiency of the application of the dual reciprocity method for various systems of radial basis functions is analyzed. An approach to constructing invariant solutions of the problem in the case of central symmetry is proposed. The constructed solutions are used to verify the developed numerical algorithm. The test calculations have shown the high efficiency of the algorithm.

The paper discusses the development of an algorithm for solving two-dimensional boundary value problems for a nonlinear partial parabolic differential equation with degeneration. The nonlinearity of the equation is dictated by a power law between the heat conductivity coefficient and temperature. The solution algorithm is based on the boundary element method with the application of the dual reciprocity method. The solution accuracy is analyzed for the discussed type of problems, with the application of different systems of radial basis functions. The most suitable system of functions and their parameters are determined.

Diffusion of deuterium in potassium is studied herein. Mass transfer is controlled predominantly by the mechanism of overbarrier atomic jumps at temperatures 120–260 K and by the tunneling mechanism at 90–120 K. These results together with literature data allowed us to determine conditions under which the quantum diffusion of hydrogen in metals can be observed, which is a fundamental problem. It is established that in metals with a body-centered cubic lattice tunneling can be observed only at temperatures below the Debye temperature θ_D solely for metals with θ_D < 350 K. Predictions are made for metals in which quantum diffusion of hydrogen can be experimentally registered. Metals for which such results cannot be obtained are specified as well. Among them are important engineering materials such as α-Fe, W, Mo, V, and Cr.

The paper deals with an algorithm for solving two-dimensional boundary value problems for a nonlinear partial parabolic differential equation with degeneration. It discusses a problem of heat wave initiation under a boundary condition specified on a closed curve. The solution algorithm based on the boundary element method is proposed. Since the problem solution domain is unknown at each time moment, an interchange between the required function and the radial coordinate of polar coordinate system is used. The constructed algorithm is verified with the use of a known exact solution.