卷 297, 编号 Suppl 1 (2017)

We consider a class of infinite-horizon optimal control problems with not necessarily bounded set of control constraints. Sufficient conditions for the existence of an optimal control are derived in the general nonlinear case by means of finite-horizon approximations and the tools of the Pontryagin maximum principle. Conditions guaranteeing the uniform local boundedness of optimal controls are also obtained.

We find possible orders and fixed point subgraphs of a hypothetical distance-regular graph with intersection array {99, 84, 1; 1, 12, 99}. We show that, for a vertex-symmetric graph Γ with intersection array {99, 84, 1; 1, 12, 99}, its automorphism group is a {2, 3, 5}-group.

The problem of guaranteed guidance to a convex target set at a fixed time is considered for a linear system with delay in the control. A solvability criterion is given and an illustrating example is presented.

A time-optimal control problem for a singularly perturbed linear autonomous system is considered. The main difference between this case and the case of systems with fast and slow variables studied earlier is that the eigenvalues of the matrix at the fast variables do not satisfy the standard requirement of negativity of the real part. We obtain and justify a complete power asymptotic expansion in the sense of Erdélyi of the optimal time and optimal control in a small parameter at the derivatives in the equations of the system.

We show the unimprovability of a theorem on sufficient convergence conditions for the trigonometric Fourier series of a function in classes ϕ(L) in the case when the class ϕ(L) is “close” to L.

A graph Γ is called a Deza graph if it is regular and the number of common neighbors of any two distinct vertices is one of two fixed values. A Deza graph is called a strictly Deza graph if it has diameter 2 and is not strongly regular. In 1992, Gardiner et al. proved that a strongly regular graph that contains a vertex with disconnected second neighborhood is a complete multipartite graph with parts of the same size greater than 2. In this paper, we study strictly Deza graphs with disconnected second neighborhoods of vertices. In Section 2, we prove that, if each vertex of a strictly Deza graph has disconnected second neighborhood, then the graph is either edge-regular or coedge-regular. In Sections 3 and 4, we consider strictly Deza graphs that contain at least one vertex with disconnected second neighborhood. In Section 3, we show that, if such a graph is edge-regular, then it is the s-coclique extension of a strongly regular graph with parameters (n, k, λ, μ), where s is an integer, s ≥ 2, and λ = μ. In Section 4, we show that, if such a graph is coedge-regular, then it is the 2-clique extension of a complete multipartite graph with parts of the same size greater than or equal to 3.

The Capacitated Vehicle Routing Problem (CVRP) is a classic combinatorial optimization problem with a wide range of applications in operations research. Since the CVRP is NP-hard even in a finite-dimensional Euclidean space, special attention is traditionally paid to the issues of its approximability. A major part of the known results concerning approximation algorithms and polynomial-time approximation schemes (PTAS) for this problem are obtained for its particular statement in the Euclidean plane. In this paper, we show that the approach to the development of a PTAS for the planar problem with a single depot proposed by Haimovich and Rinnooy Kan in 1985 can be successfully extended to the more general case, for instance, in spaces of arbitrary fixed dimension and for an arbitrary number of depots.

We discuss the problem of guaranteed guidance of a linear control system by a fixed time under the assumption that the system is subject to an unknown disturbance. We consider the case when a part of state coordinates are measured and the set of unknown initial states is finite. We specify a solution algorithm based on the combination of the package approach, the theory of dynamic inversion, and the extremal shift method.

We discuss the initial and boundary value problems for the system of dimensionless Navier–Stokes equations describing the dynamics of a viscous incompressible fluid using the method of characteristics and the geometric method developed by the authors. Some properties of the formulation of these problems are considered. We study the effect of the Reynolds number on the flow of a viscous fluid near the surface of a body.

We consider problems of approximating the curvature of plane curves from smooth classes by the curvature of elements of smooth finite-dimensional function spaces (trigonometric polynomials, splines with equidistant knots) in the uniform norm.

The problem of singularities appearing in generalized solutions of the Dirichlet boundary value problem for eikonal-type first-order partial differential equations is considered. The object of study is the pseudovertices of the edge set. Finding the pseudovertices is an element of the procedure for constructing branches of the singular set. Necessary conditions of pseudovertex existence are obtained under weakened assumptions on the smoothness of the boundary of a nonconvex edge set. The situation of the first-order smoothness of the boundary and breaks of the second-order derivatives is studied. The necessary conditions are written in terms of the stationarity of coordinate functions and with the use of one-sided curvatures.

The deconvolution problem, which arises in the description of well testing processes, is formulated in the form of a Volterra equation of the first kind with discontinuous input data (the kernel is the flow rate and the right-hand side is the pressure change) characterized by large measurement errors. In addition, the solution of this equation has multiscale behavior in its domain. In this situation, the traditional solution algorithms for Volterra equations, as a rule, do not provide satisfactory results. To solve the problem, we use the variational regularization methods and construct a function basis (a system of exponents), which allows us to take into account in the algorithm all a priori constraints known for the desired solution. As a result, we form a family of approximate solutions that satisfies the conditions of smoothness and exactness required for the interpretation of well tests. For the constructed regularizing algorithms, we formulate convergence theorems and describe the details of numerical implementation.

We study the largest and the smallest values of coefficients of odd trigonometric polynomials upper bounded by the function ϕ(x) = x on the interval [0, 2π]. A similar problem for the first and second coefficients was studied by the author earlier.