Vol 10, No 2 (2016)

We consider an identification problem for a stationary nonlinear convection–diffusion–reaction equation in which the reaction coefficient depends nonlinearly on the concentration of the substance. This problem is reduced to an inverse extremal problem by an optimization method. The solvability of the boundary value problem and the extremal problem is proved. In the case that the reaction coefficient is quadratic, when the equation acquires cubic nonlinearity, we deduce an optimality system. Analyzing it, we establish some estimates of the local stability of solutions to the extremal problem under small perturbations both of the quality functional and the given velocity vector which occurs multiplicatively in the convection–diffusion–reaction equation.

We consider the Cauchy problem for a class of systems of ordinary differential equations of large dimension.We prove that, for sufficiently large number of equations, the last component of a solution to the Cauchy problem is an approximate solution to the initial value problem for a delay differential equation. Estimates of the approximation are obtained.

We consider some mathematical model of isothermal acoustics in a composite medium consisting of two different porous soils (poroelastic domains) separated by a common boundary. Each of the domains has its own characteristics of the solid skeleton; the liquid filling the pores is the same for both domains. The differential equations of the exactmodel contain some rapidly oscillating coefficients. The averaged equations (i.e., without rapidly oscillating coefficients) are derived.

Under study is the complexity of optimal recombination for various flowshop scheduling problems with the makespan criterion and the criterion of maximum lateness. The problems are proved to be NP-hard, and a solution algorithm is proposed. In the case of a flowshop problem on permutations, the algorithm is shown to have polynomial complexity for “almost all” pairs of parent solutions as the number of jobs tends to infinity.

This paper deals with the user equilibrium problem (flow assignment with equal journey time by alternative routes) and system optimum (flow assignment with minimal average journey time) in a network consisting of parallel routes with a single origin-destination pair. The travel time is simulated by arbitrary smooth nondecreasing functions. We prove that the equilibrium and optimal assignment problems for such a network can be reduced to the fixed point problem expressed explicitly. A simple iterative method of finding equilibriumand optimal flow assignment is developed. The method is proved to converge geometrically; under some fairly natural conditions the method is proved to converge quadratically.

Under consideration is a 2D-problem of elasticity theory for a body with a thin rigid inclusion. It is assumed that there is a delamination crack between the rigid inclusion and the elastic matrix. At the crack faces, the boundary conditions are set in the form of inequalities providing mutual nonpenetration of the crack faces. Some numerical method is proposed for solving the problem, based on domain decomposition and the Uzawa algorithm for solving variational inequalities.We give an example of numerical calculation by the finite element method.

We consider two algorithms for orthogonal projection of a point to the standard simplex. These algorithms are fundamentally different; however, they are related to each other by the following fact: When one of them has the maximum run time, the run time of the other is minimal. Some particular domains are presented whose points are projected by the considered algorithms in the minimum and maximum number of iterations. The correctness of the conclusions is confirmed by the numerical experiments independently implemented in the MatLab environment and the Java programming language.