Vol 299, No Suppl 1 (2017)

We consider a periodic impulse harvesting of a renewable resource distributed in a domain of the arithmetic space and obeying the logistic growth low. We prove that, for a given harvesting effort, there exists an appropriate stationary distribution of the effort in the resource domain providing the maximum efficiency of the harvesting at infinite horizon, where the efficiency is the ratio of the harvesting profit to the total effort applied.

The connection is established between theorems of the alternative for linear systems of equations and/or inequalities and duality theorems in linear programming. We give new versions of theorems of the alternative in which the alternative systems have different matrices of various sizes.

A motion control problem for a dynamic system under disturbances is considered on a finite time interval. There are compact geometric constraints on the values of the control and disturbance. The equilibrium condition in the small game is not assumed. The aim of the control is to minimize a given terminal performance index. The guaranteed result optimization problem is posed in the context of the game-theoretical approach. In the case when realizations of the disturbance belong to some a priori unknown compact subset of L₁ (the space of functions that are Lebesgue summable with the norm), we propose a new discrete-time control procedure with a guide. The proximity between the motions of the system and the guide is provided by the dynamic reconstruction of the disturbance. The quality of the control process is achieved by using an optimal counter-strategy in the guide. Conditions on the equations of motion under which this procedure ensures an optimal guaranteed result in the class of quasi-strategies are given. The scheme of the proof makes it possible to estimate the deviation of the realized value of the performance index from the value of the optimal result depending on the discretization parameter. Illustrative examples are given.

J. Koolen posed the problem of studying distance-regular graphs in which neighborhoods of vertices are strongly regular graphs with nonprincipal eigenvalue at most t for a given positive integer t. This problem was solved earlier for t = 3. In the case t = 4, the problem was reduced to studying graphs in which neighborhoods of vertices have parameters (352,26,0,2), (352,36,0,4), (243,22,1,2), (729,112,1,20), (204,28,2,4), (232,33,2,5), (676,108,2,20), (85,14,3,2), or (325,54,3,10). In the present paper, we prove that a distance-regular graph in which neighborhoods of vertices are strongly regular with parameters (85, 14, 3, 2) or (325, 54, 3, 10) has intersection array {85, 70, 1; 1, 14, 85} or {325, 270, 1; 1, 54, 325}. In addition, we find possible automorphisms of a graph with intersection array {85, 70, 1; 1, 14, 85}.

We consider the problem of partitioning a finite sequence of points in Euclidean space into a given number of clusters (subsequences) minimizing the sum over all clusters of intracluster sums of squared distances of elements of the clusters to their centers. It is assumed that the center of one of the desired clusters is the origin, while the centers of the other clusters are unknown and are defined as the mean values of cluster elements. Additionally, there are a few structural constraints on the elements of the sequence that enter the clusters with unknown centers: (1) the concatenation of indices of elements of these clusters is an increasing sequence, (2) the difference between two consequent indices is lower and upper bounded by prescribed constants, and (3) the total number of elements in these clusters is given as an input. It is shown that the problem is strongly NP-hard. A 2-approximation algorithm that is polynomial for a fixed number of clusters is proposed for this problem.

We study the computational complexity of the vertex cover problem in the class of planar graphs (planar triangulations) admitting a plane representation whose faces are triangles. It is shown that the problem is strongly NP-hard in the class of 4-connected planar triangulations in which the degrees of vertices are of order O(log n), where n is the number of vertices, and in the class of plane 4-connected Delaunay triangulations based on the Minkowski triangular distance. A pair of vertices in such a triangulation is adjacent if and only if there is an equilateral triangle ∇(p, λ) with p ∈ R² and λ > 0 whose interior does not contain triangulation vertices and whose boundary contains this pair of vertices and only it, where ∇(p, λ) = p + λ∇ = {x ∈ R²: x = p + λa, a ∈ ∇}; here ∇ is the equilateral triangle with unit sides such that its barycenter is the origin and one of the vertices belongs to the negative y-axis. Keywords: computational complexity, Delaunay triangulation, Delaunay TD-triangulation.

In modeling the dynamics of capital, the Ramsey equation coupled with the Cobb–Douglas production function is reduced to a linear differential equation by means of the Bernoulli substitution. This equation is used in the optimal growth problem with logarithmic preferences. The study deals with solving the corresponding infinite horizon optimal control problem. We consider a vector field of the Hamiltonian system in the Pontryagin maximum principle, taking into account control constraints. We prove the existence of two alternative steady states, depending on the constraints. This result enriches our understanding of the model analysis in the optimal control framework.

We obtain a description of nonabelian composition factors of a finite nonsolvable group in which any maximal subgroup of odd index is a Hall subgroup.

We continue the study of approximation properties of alternative duality schemes for improper problems of linear programming. The schemes are based on the use of the classical Lagrange function regularized simultaneously in primal and dual variables. The earlier results on the connection of its saddle points with the lexicographic correction of the right-hand sides of constraints in improper problems of the first and second kind are transferred to a more general type of improperness. Convergence theorems are presented and an informal interpretation of the obtained generalized solution is given.

For the correction of improper problems of convex programming, the residual method is used, which is the standard regularization procedure for ill-defined optimization models. We propose new iterative implementations of the residual method, in which the constraints of the problem are included by means of penalty functions. New convergence conditions are established for algorithmic schemes, and estimates are found for the approximation error.

We study a regularization algorithm for the approximate solution of integral equations of the first kind. This algorithm includes a finite-dimensional approximation of the problem. More exactly, the integral equation is discretized in two variables. An error estimate of the algorithm is obtained with the use of the equivalence of the generalized discrepancy method and the generalized discrepancy principle.

We study α-sets in Euclidean space ℝⁿ. The notion of α-set is introduced as a generalization of a convex closed set in ℝⁿ. This notion appeared in the study of reachable sets and integral funnels of nonlinear control systems in Euclidean spaces. Reachable sets of nonlinear dynamic systems are usually nonconvex, and the degree of their nonconvexity is different in different systems. This circumstance prompted the introduction of a classification of sets in ℝⁿ according to the degree of their nonconvexity. Such a classification stems from control theory and is presented here in terms of α-sets in ℝⁿ.