The studied problem for the essentially loaded heat equation is connected with mathematical modeling of thermophysical processes in the electric arc of high-current disconnecting devices. Experimental studies of such phenomena are difficult due to their transience, and in some cases only a mathematical model is able to provide adequate information about their dynamics. The study of the mathematical model is carried out when the order of the derivative in the loaded summand is less than, equal to and greater than the order of the differential part of the heat equation, at a fixed point of the load and in the case when the load point moves at a variable speed. The article is focused mainly on scientific researchers engaged in practical applications of loaded differential equations.

We consider a second-order differential equation with rapidly growing intermediate coefficients. We obtain a solvability result in the cases that the diffusion coefficient of equation is unbounded or it tends to zero at the infinity. Under additional conditions, we prove the Lp− maximal regularity estimate for the solution of this equation.

Mathematical modeling of thermophysical processes in an electric arc of high-current disconnecting apparatuses leads to a boundary value problem for an essentially loaded heat conduction equation. Taking into account the transience of such phenomena, in some cases only a mathematical model is able to give adequate information about their dynamics. The mathematical model in the form of the boundary value problem is reduced to the Volterra integral equation of the second kind, as a result, we have that the solvability of the boundary value problem is equivalent to the solvability of the reduced integral equation. Thus, there is a need to study the reduced integral equation. The results of this study (various representations and properties of the kernel-forming function in general case and the types of the kernel of the integral equation in special cases) are presented in this article. The article is focused at physicists and engineers, as well as scientific researchers engaged in the practical applications of loaded differential equations.

The article deals with the existence of a generalized solution for the second order nonlinear differential equation in an unbounded domain. Intermediate and lower coefficients of the equation depends on the required function and considered smooth. The novelty of the work is that we prove the solvability of a nonlinear singular equation with the leading coefficient not separated from zero. In contrast to the works considered earlier, the leading coefficient of the equation can tend to zero, while the intermediate coefficient tends to infinity and does not depend on the growth of the lower coefficient. The result obtained formulated in terms of the coefficients of the equation themselves; there are no conditions on any derivatives of these coefficients.

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