Open Access Open Access  Restricted Access Access granted  Restricted Access Subscription Access

Vol 64, No 11 (2024)

Cover Page

Full Issue

Open Access Open Access
Restricted Access Access granted
Restricted Access Subscription Access

General numerical methods

THE MULTIPOLE METHOD FOR SOME MIXED BOUNDARY VALUE PROBLEMS AND ITS APPLICATION TO THE CONSTRUCTION OF A CONFORMAL MAPPING

Bagapsh A.O., Vlasov V.I.

Abstract

An analytical and numerical multipole method for solving some mixed boundary value problems for the Laplace equation in planar simply connected domains g of complex shape with application to the construction of conformal mapping of such domains is presented. The method allows obtaining both the solution itself and its gradient with high accuracy up to complex boundary sections near singularities, and also provides a posteriori estimate of the relative error δ in the norm
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2007-2018
pages 2007-2018 views

NUMERICAL AND ANALYTICAL METHOD FOR NONLINEAR KOLMOGOROV–PETROVSKY–PISKUNOV TYPE EQUATIONS

Bezrodnykh S.I., Pikulsh S.V.

Abstract

The question of the effective solution of the basic initial boundary value problems for spatially onedimensional nonlinear equations of the parabolic type describing reaction-diffusion processes is considered. Such equations include the Kolmogorov–Petrovsky–Piskunov and Burgers equations. For these problems, a numerical analytical method based on implicit discretization of the differential operator in combination with explicit Adams–Bashforth extrapolation for the nonlinear term of the equation is proposed. At the same time, a new efficient algorithm based on analytical representations using an explicit form of a fundamental solution system has been developed to solve a sequence of emerging linear problems. The effectiveness of the developed method and its advantages over some traditional algorithms have been demonstrated for a number of complex model examples.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2019-2045
pages 2019-2045 views

Optimal control

AN OPTIMIZATION APPROACH TO THE PROBLEM OF DETERMINING THE VELOCITY FIELD IN IMAGE PROCESSING PROBLEMS

Kotina E.D., Ovsyannikov D.A., Kharchenko D.S.

Abstract

The article considers a new approach to the construction of the velocity field, which is based on the methods of control theory and optimization of dynamics of ensembles of trajectories. This approach does not exclude the possibility that the brightness along the trajectories may vary. This makes it possible to build directional optimization methods for determining optical and non-optical flows. The velocity field is defined as some function depending on the vector of arbitrary parameters, which are determined as a result of minimizing the functional set on the ensemble of trajectories defined by this velocity field. An algorithm has been developed to solve the problems of restoring the velocity field using an analytical representation of the variation of the functional under study according to the parameters determining the velocity field, and taking into account the variation in time. The paper presents the results of testing the proposed algorithm, including splitting the image into subdomains.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2046-2057
pages 2046-2057 views

Ordinary differential equations

ON THE STUDY OF VARIOUS REPRESENTATIONS OF SOLUTIONS OF QUASI-DIFFERENTIAL EQUATIONS IN THE FORM OF SUMS OF SERIES AND THEIR SOME APPLICATIONS

Vatolkin M.Y.

Abstract

In the theory of the matrix equation _
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2058-2076
pages 2058-2076 views

Partial Differential Equations

AN ANALOGUE OF THE POISSON FORMULA FOR SOLVING THE HELMHOLTZ EQUATION

Savchenko A.O.

Abstract

Analogs of the Poisson formula for solving internal and external boundary value problems with Dirichlet or Neumann boundary conditions on a sphere for the Helmholtz equation are obtained, in which the kernels of integrals are represented as series.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2155-2159
pages 2155-2159 views

ON THE QUESTION OF STATIONARY WAVES ON THE SURFACE OF AN IDEAL LIQUID OF FINITE DEPTH. THE SECOND STOKES METHOD

Rudenko A.I.

Abstract

The classical problem of stationary waves on the surface of an ideal incompressible homogeneous liquid of finite depth is considered. The approach to solving the problem is related to the second Stokes method, but has the following differences: due to the obtained one-dimensional integrodifferential equation with cubic nonlinearity for the profile of a stationary wave on the surface of a liquid of finite depth, the original problem is reduced to a one-dimensional one. The solution is obtained up to the seventh approximation.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2143-2154
pages 2143-2154 views

INTEGRAL REPRESENTATION OF SOLUTIONS AND RIEMANN–HILBERT TYPE PROBLEM FOR THE CAUCHY–RIEMANN EQUATION WITH STRONG SINGULARITY IN THE LOWER ORDER COEFFICIENT IN A DOMAIN WITH PIECEWISE SMOOTH BOUNDARY

Rasulov A.B., Yakivchik N.V.

Abstract

The goal of this work is to construct the general solution of the Cauchy–Riemann equation with strong singularities in the lower order coefficient and to study the Riemann–Hilbert boundary value problem in a domain with a piecewise smooth boundary.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2132-2142
pages 2132-2142 views

A MATHEMATICAL THEORY OF THE EXPANSION OF THE UNIVERSE BASED ON THE PRINCIPLE OF LEAST ACTION

Vedenyapin V.V.

Abstract

In classical works, equations for the fields of gravity and electromagnetism are proposed without subtracting the right-hand sides. Here we give the subtraction of the right–hand sides and the analysis of the momentum energy tensor in the framework of the Vlasov–Maxwell–Einstein equations and consider cosmological models of the Milne-McCree and Friedman types.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2114-2131
pages 2114-2131 views

THE SINGULAR PART OF THE ELECTROMAGNETIC FIELD IN DIFFRACTION PROBLEMS ON BODIES WITH EDGES FOR VARIOUS TYPES OF BOUNDARY CONDITIONS

Bogolyubov A.N., Mogilevskiy I.E., Shusharin M.M.

Abstract

The article considers the problem of diffraction of a plane electromagnetic wave on a cylinder of arbitrary cross-section shape with an edge at the boundary. Using the method first proposed in the works of V. A. Kondratiev, for the cases of impedance, ideally conductive and dielectric cylinders, a singular part of the solution is isolated in the vicinity of the edge.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2101-2113
pages 2101-2113 views

DUALISM IN THE THEORY OF SOLITON SOLUTIONS. II

Beklaryan L.A.

Abstract

The paper is a continuation of the work of the same name by Belkarian, Belkarian (2024). The proof of the theorem of the existence and uniqueness of soliton solutions and their corresponding solutions of the functionally differential equation from the dual pair “function-operator”, which was formulated in the noted work in the form of a hypothesis, is presented. This made it possible, in particular, to study soliton solutions with more complex characteristics in the model of traffic flow on the Manhattan lattice than the characteristics given by the additive cyclic subgroup of the group R.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2077-2100
pages 2077-2100 views

Mathematical physics

MAXWELL’S REPRESENTATION OF THE SATELLITE APPROXIMATION POTENTIAL. ON ONE METHOD FOR DETERMINING THE MAIN AXES OF INERTIA OF A SOLID BODY USING THE PARAMETERS OF ITS SECOND-ORDER MULTIPOLE

Nikonova E.A.

Abstract

Maxwell’s approach to the representation of homogeneous harmonic functions in the form of a superposition of derivatives in directions, developed by him within the framework of the study of problems of electrostatics, is applied to the representation of the potential of satellite approximation. The specified representation is determined by two unitary vectors located in a plane orthogonal to the intermediate axis of inertia of the body. In this case, the axis of inertia of the body corresponding to its smallest moment of inertia is the bisector of the angle formed by these vectors. The geometric meaning of the vectors is established: they are orthogonal to the circular sections of the body inertia ellipsoid constructed for the center of mass of the body. The above makes it possible to propose an approach to finding the main axes of inertia of a body based on Maxwell’s representation of its satellite approximation potential.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2205-2211
pages 2205-2211 views

OPTIMIZATION OF A NUMERICAL AND STATISTICAL ALGORITHM FOR ESTIMATING THE AVERAGE PARTICLE FLUX IN A RANDOMMULTIPLYING BOUNDED MEDIUM

Lotova G.Z., Mikhailov G.A., Rozhenko S.A.

Abstract

Approximations of random functions are studied, numerically modeled to study the stochastic process of particle transport, including problems of fluctuations in the criticality of the process in random breeding media. The simplest grid model of an isotropic random field is formulated, reproducing the effective average correlation length, which ensures high accuracy in solving stochastic transfer problems at a small correlation scale. The proposed algorithms have been tested in solving the test problem of estimating the overexponential average particle flux in a random multiplying medium.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2194-2204
pages 2194-2204 views

ITERATIVE NUMERICAL METHODS FOR SOLVING THE PROBLEM OF DETERMINING THE COEFFICIENT IN THE MODEL OF SORPTION DYNAMICS

Denisov A.M., Dongqin Z.

Abstract

The inverse coefficient problem for a mathematical model of sorption dynamics is considered. The inverse problem is reduced to nonlinear operator equations with respect to an unknown function. These equations are used to construct and justify the convergence of iterative methods for solving the inverse problem. Examples of the application of the proposed iterative methods for the numerical solution of the inverse problem are given.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2184-2193
pages 2184-2193 views

APPLICATION OF THE CONJUGATE GRADIENT METHOD FOR SOLVING UNILATERAL DISCRETE CONTACT PROBLEMS FOR AN ELASTIC HALF-SPACE

Bobylev A.A.

Abstract

The problems of unilateral discrete contact of an elastic half-space and a rigid punch of finite dimensions with a surface microrelief are considered. A variational formulation of the problems is obtained in the form of a boundary variational inequality using the Poincare-Steklov operator, which maps normal stresses into normal displacements on a part of the boundary of an elastic half-space. The minimization problem equivalent to the variational inequality is presented, as a result of approximation of which a quadratic programming problem with constraints in the form of equalities and inequalities is obtained. To solve this problem, a new computational algorithm based on the conjugate gradient method is proposed, which includes three equations of punch equilibrium in the calculation. The algorithm belongs to the class of active set methods and takes into account the specifics of the set of constraints. Some patterns of contact interaction of surfaces with regular microrelief have been established.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2168-2183
pages 2168-2183 views

INVESTIGATION OF STABILITY OF SUPERSONIC SOLITARY WAVES IN AN ELASTIC ELECTRICALLY CONDUCTIVE MICROPOLAR MATERIAL

Bakholdin I.B.

Abstract

Stability of solitary waves that are solutions to one of the variants of the Boussinesq equation is investigated. This equation describes elastic waves in the presence of an electromagnetic field. The Evans function method and direct numerical solution of the equation are used to identify the instability of solitary waves. The results obtained by both methods coincided. A method for identifying instability and a method for calculating an eigenfunction that grows with time by analyzing numerical solutions of a partial differential equation are developed.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2160-2167
pages 2160-2167 views

Computer science

ACCELERATED ALGORITHMS FOR GROWING SEGMENTS FROMIMAGE REGIONS

Murashov D.M.

Abstract

The paper proposes new algorithms for combining superpixel regions into segments. The main idea is that when combining super pixels, firstly, a strategy is used in which the segment is grown from neighboring areas as long as the conditions for combining are met, and secondly, when combining areas, the applied information quality measure should not increase. Three algorithms based on this strategy are proposed, which differ in the conditions for making a decision on combining superpixels. A computational experiment was carried out on test images. The experiment showed that the proposed algorithms make it possible to speed up the segmentation process compared to the procedure used, with acceptable losses of information quality measures of the obtained partitions.
Žurnal vyčislitelʹnoj matematiki i matematičeskoj fiziki. 2024;64(11):2212-2226
pages 2212-2226 views