Decomposition of tasks in a group of robots using cloud computing technologies

In this paper, various variants of decomposition of tasks in a group of robots using cloud computing technologies are considered. The specifics of the field of application (teams of robots) and solved problems are taken into account. In the process of decomposition, the solution of one large problem is divided into a solution of a series of smaller, simpler problems. Three ways of decomposition based on linear distribution, swarm interaction and synthesis of solutions are proposed. The results of experimental verification of the developed decomposition algorithms are presented, the working capacity of methods for planning trajectories in the cloud is shown. The resulting solution is a component of the complex task of building effective teams of robots.

A new approach to the hydraulic fracture geometric dimensions determination

Based on the generalized Perkins-Kern-Nordgren model (PKN) for the development of a hyperbolic type vertical hydraulic fracture, an exact solution is obtained for the hydraulic fracture self-oscillations after terminating the fracturing fluid injection. These oscillations are excited by a rarefaction wave that occurs after the injection is stopped. The obtained solution was used to estimate the height, width and half-length of the hydraulic fracture at the time of stopping the hydraulic fracturing fluid injection based on the bottomhole pressure gauge data.

Liquid temperature dependence of the shock formation in a cavitation bubble

The dependence of the radially convergent shock wave formation in a cavitation bubble on the surrounding liquid temperature TL in the range from 273.15 to 400 K is investigated at the liquid pressure equal to 50 bar. Realistic mathematical model is applied, in which the effects of the liquid compressibility, the heat conductivity of the vapor and liquid, the evaporation and condensation on the bubble surface are taken into account, wide-range equations of state are utilized. The governing equations of the vapor and liquid dynamics are solved numerically using a modification of the Godunov method of the second order of accuracy. It has been found that a radially convergent shock wave arises in the bubble in 273.15≤T_L≤375 К. In this interval, the distance between the shock wave formation position and the bubble surface decreases with decreasing the liquid temperature. The possibility of using a known simplified criterion of the formation of a shock wave inside a bubble to estimate its formation position under the studied conditions is considered. It is shown that with applying that criterion the shock wave formation position turns out to be correctly predicted at T_L≈325 К, while at T_L>325 К and T_L<325 К it is predicted closer to and more distant from the bubble surface, respectively.

Hydrodynamic interaction of weakly nonspherical gas bubbles in a liquid in the three-dimensional problem statement

The influence of the relative location of weakly nonspherical gas (air) bubbles in liquid (water) on their hydrodynamic interaction at the pressure antinode of an ultrasonic standing wave is studied. Three essentially different configurations of the mutual arrangement of the bubbles are considered: the linear, planar, and spatial ones. In the linear configuration, three bubbles are located on one straight line. In the planar configuration, five bubbles are situated on two mutually orthogonal straight lines. In the spatial configuration, seven bubbles are located on three mutually orthogonal straight lines. In all the cases, one of the bubbles is central, the others are equally-spaced from it on those lines. All the bubbles are initially spherical with a radius of 3 ?m. Room conditions are considered, the frequency of the wave is 20 kHz, its amplitude is 1.2 times the static liquid pressure. A mathematical model is used, in which the liquid is assumed weakly compressible, the bubbles being homobaric. It is shown that in each configuration of the bubbles the influence of their interaction on their radial dynamics is insignificant. In each configuration, the central bubble remains stationary, while the others move to it at a speed equal for a fixed configuration. At transition from a linear configuration to a planar one and from a planar configuration to a spatial one, the bubble motion speed increases. In all the cases, the deformations of the central stationary bubbles are smaller than those of the rest. Among the central bubbles, the bubble in a planar configuration is deformed most.

About of the injection of hydrate-forming gas into a layer of snow saturated with the same gas

The problem of injecting a hydrate-forming gas into a snow massif in the initial state saturated with the same gas are solved. Self-similar solutions describing the temperature and pressure fields, the distribution of snow, water, hydrate and gas saturation in the massif are constructed. It is shown that when forming a hydrate, depending on the initial thermobaric state of the ice-gas system, as well as the intensity of gas injection, it is possible to distinguish various characteristic zones in the filtration region that differ in their structure and length. It has been established that with an increase in the gas injection pressure and a decrease in the initial snow-saturation of the massif, the volume formation zone of the hydrate increases.

Layered anisotropic liquids: deformation of structures in electric and magnetic fields

On the basis of the analysis of the free energy of a viscoelastic anisotropic layer liquid, a chiral ferroelectric liquid crystal C^∗ , located in a thin cell in a ”bookshelf“ geometry the possibility of the smectic layers periodic distortions in the external magnetic H and electric E fields applied perpendicularly and along the plates, respectively, are investigated. The polar angle θ formed by the unit vector n and the normal a to the smectic planes is fixed, and the appearing Helfrich–Yuro distortions u of the smectic layers are assumed to be small in the proposed continuum model of the liquid ferroelectrics.

Restoration of the linear potential in the Sturm-Liouville problem

The problem of identifying the variable coefficient of elasticity of a medium with respect to natural frequencies of a string oscillating in this medium is considered. A method for solving the problem is found, based on the representation of linearly independent solutions of the differential equation in the form of Taylor series with respect to two variables, substituting them into the frequency equation, and determining the unknown coefficients of the linear function from this frequency equation. An analytical method has also been developed that allows one to prove the uniqueness or nonuniqueness of the restored polynomial coefficient of elasticity of a medium by a finite number of natural frequencies of oscillations of a string, and also to find a class of isospectral problems, that is, boundary value problems for which the eigenvalue spectra coincide. The latter is based on the method of variation of an arbitrary constant. We consider examples of finding isospectral classes, and also unique boundary value problems having a given spectrum.

Propagation of weak disturbances in warm water with air bubbles

The features of reflection and refraction of harmonic waves at the interface between a ”pure“ liquid and a liquid with bubbles with a vapor-gas mixture under direct and oblique incidence are studied. A numerical analysis is made of the effect of the initial volumetric gas content αg0 for two initial bubble sizes a0=10–6 m and 10–3 m. The influence of the disturbance frequencies on the reflection and refraction coefficients of sound in direct incidence and on the dependence of the angle of refraction on the angle of incidence is studied.

The replacement of methane hydrate in the reservoir by injection into the liquid carbon dioxide

The paper deals with the process of injecting liquid carbon dioxide into a hydrate reservoir. It is shown that the process of methane replacement in a hydrate reservoir by injecting liquid carbon dioxide into it can consist of the following steps: piston displacement of free gas from the pores; replacement of methane with liquid carbon dioxide, its dissolution and leaching from the formation; completion of hydrate formation and leaching of the remaining methane gas from the hydrate reservoir. We have presented the distributions of pressure, density, hydrate saturation and temperature at different times.

Synthesis of distributed control system for a group of mobile robots

The technique of synthesis of specialized architecture of the control system, taking into account the peculiarities of the organization of the team of robots, the specifics of information flows and hardware is considered. To implement the proposed architecture contains three levels, and supports cloud-based and multithreaded technology of information processing, focuses on modern types of controllers and processors. The technology of forming an intranet in a team of robots based on a ”domain“ wireless network created using Wi-Fi Protocol and software of its own development.