Search

We study a problem concerning the estimation of the Hausdorff deviation of convex polygons in $\mathbb R^2$ from their geometric difference with circles of sufficiently small radius. Problems with such a subject, in which not only convex polygons but also convex compacts in the Euclidean space $\mathbb R^n$ are considered, arise in various fields of mathematics and, in particular, in the theory of differential games, control theory, convex analysis. Estimates of Hausdorff deviations of convex compact sets in $\mathbb R^n$ in their geometric difference with closed balls in $\mathbb R^n$ are presented in the works of L.S. Pontryagin, his staff and colleagues. These estimates are very important in deriving an estimate for the mismatch of the alternating Pontryagin’s integral in linear differential games of pursuit and alternating sums. Similar estimates turn out to be useful in deriving an estimate for the mismatch of the attainability sets of nonlinear control systems in $\mathbb R^n$ and the sets approximating them. The paper considers a specific convex heptagon in $\mathbb R^2$. To study the geometry of this heptagon, we introduce the concept of a wedge in $\mathbb R^2$. On the basis of this notion, we obtain an upper bound for the Hausdorff deviation of a heptagon from its geometric difference with the disc in $\mathbb R^2$ of sufficiently small radius.

This paper is concerned with ultrafilters and maximal linked systems of widely understood measurable spaces (nonempty sets with π-systems of its subsets are meant). The sets of ultrafilters and maximal linked systems are transformed to bitopological spaces by applying constructions that (in idea) meet the Wallman and Stone schemes. The focus is on ultrafilter space with topology of Wallman type. Conditions on the initial π-system for which the given space is supercompact are specified. Concrete classes of (widely understood) measurable spaces are listed for which the above-mentioned conditions are realized. Special attention is also given to one abstract problem of attainability under conditions when the choice of a concrete solution may have the following uncertainty: the set defining constraints can be an arbitrary element of a given nonempty family. The question of the existence of universally realized (in limit) elements in the space of values of the goal operator in our problem is considered. To obtain sufficient solutions, the supercompactness property of the ultrafilter space for special measurable structure is used; this structure is sufficient (under corresponding suppositions) for realization of all variants of constraints on the choice of a usual solution (control). © 2019 А. Г. Ченцов. Russian Foundation for Basic Research, RFBR: 18–01–00410 Funding. The research was funded by the Russian Foundation for Basic Research, project number 18–01–00410.

This paper considers two problems of dynamical reconstruction of unknown characteristics of a system of nonlinear equations describing the process of innovation diffusion through inaccurate measurements of phase states. A dynamical variant for solving these problems is designed. The system is assumed to operate on a given finite time interval. The evolution of the system’s phase state, i.e., the solution of the system, is determined by an unknown input. A precise reconstruction of the real input (acting on the system) is, generally speaking, impossible due to inaccurate measurements. Therefore, some approximation to this input is constructed which provides an arbitrary smallness to the real input if the measurement errors and the step of incoming information are sufficiently small. Based on the dynamical version of the discrepancy method, two algorithms for solving the problems in question are specified. One of them is oriented to the case of measuring all coordinates of the phase vector, and the other, to the case of incomplete measurements. The algorithms suggested are stable with respect to informational noises and computational errors. Actually, they are special regularizing algorithms from the theory of dynamic inverse problems. © 2019 М.С. Близорукова.

We consider a routing problem with constraints and complicated cost functions. The visited objects are assumed to be clusters, or megalopolises (nonempty finite sets), and the visit to each of them entails certain tasks, which we call interior jobs. The order of visits is subject to precedence constraints. The costs of movements depend on the set of pending tasks (not yet complete at the time of the movement), which is also referred to as "sequence dependence", "position dependence", and "state dependence". Such a dependence arises, in particular, in routing problems concerning emergencies at nuclear power plants, similar to the Chernobyl and Fukushima Daiichi incidents. For example, one could consider a disaster recovery problem concerned with sequential dismantlement of radiation sources; in this case, the crew conducting the dismantlement is exposed to radiation from the sources that have not yet been dealt with. This gives rise to dependence on pending tasks in the cost functions that measure the crew's radiation exposure. The latter dependence reflects the "shutdown" operations for the corresponding radiation sources. This paper sets forth an approach to a parallel solution for this problem, which was implemented and run on the URAN supercomputer.

The paper presents the model of anisotropic growth of dendritic crystallization of chemically pure and binary liquid (solution or melt) based on forced convection of the liquid phase. The dependencies of the growth rate and the radius of the top of a dendrite from under-cooling fluid in cases of a chemically pure material and alloys are presented. A comparative analysis of the influence of forced convection on the dendrite growth kinetics is carried out. Evaluation of growth rate and morphology of dendrite by high-speed crystal growth model was done. The contribution of convective flow and the anisotropic properties of the liquid-crystal boundary were taking into account. The model is also used hyperbolic diffusion equation to describe the non-equilibrium impurity capture by crystal surface, which occurs under the rapid crystals growth.