Open Repository of Keldysh Institute of Applied Mathematics of RAS
Not a member yet
5498 research outputs found
Sort by
Flipping the Walking Robot to the Working Position from the Emergency 'Upside Down'
No full textAbstract:
It is shown that the Autonomous rescue of a six-legged machine from an emergency position “upside down” is possible with the help of cyclic movement of the legs, if the body has an upper shell in the form of a truncated cylinder. A method is proposed of rocking the body, which provides a flipping of the body and the return of the robot to the operating position. An analytical study and computer simulation of the full dynamics of the robot were fulfilled which confirmed the effectiveness of the developed technique for restore the functional capability of the robot. The results of numerical experiments and corresponding video materials are presented.Note:
Research direction:Theoretical and applied problems of mechanic
Research paper in Russia: intellectual rights
No full textAbstract:
Who owns the exclusive rights to a research paper created as a duty assignment? What is a work-for-hire? What opportunities does the copyright holder reserve when transferring the article to the publisher under an exclusive license? What is an open license? What is the meaning of the term “self-plagiarism”? Is it acceptable to publish an article in several journals? These issues are considered in this work in the light of the requirements of the Civil code RF.Note:
Research direction:Programming, parallel computing, multimedi
On a two-layer completely conservative difference scheme of gas dynamics in Eulerian variables with adaptive regularization of solution
No full textAbstract:
For the equations of gas dynamics in Eulerian variables, a family of two-layer completely conservative difference schemes with temporal weights profiled on space has been constructed. The effective conservation of an internal energy in this type of divergent difference schemes is ensured by the absence of constantly operating sources of difference origin in the internal energy equation that produce “computational” entropy (including on singular features of the solution). Great attention is paid to the methods of constructing regularizing mass, momentum and internal energy fluxes that do not violate the properties of complete conservatism of difference schemes of this class, to the analysis of their amplitude and to the admissibility of adaptive use on variable structure grids, including on implicit layers in time. The developed type of difference schemes can be used to calculate multitemperature processes (electron and ion temperatures), where for the available number of unknowns, a single balance equation for the total energy of the medium is not enough.Note:
Research direction:Mathematical modelling in actual problems of science and technic
To the construction of the thermodynamics of quantum nonextensive systems in the framework of the statistics of Tsallis
No full textAbstract:
Within the framework of quantum statistics of Tsallis, based on parametric non-additive entropy associated with the density matrix, thermodynamic equations for a large canonical quantum-mechanical ensemble are obtained. A generalization of the zero law of thermodynamics for independent quantum systems at their thermal contact is obtained, which introduces the so-called physical temperature different from the inversion of Lagrange multiplier β. Taking into account the generalized first law of thermodynamics and Legendre transformation, the modified thermodynamic relations in Tsallis statistics are considered. The second law of thermodynamics is discussed on the basis of the convexity property of Ratier−Kannappan discrimination information generalized to the quantum case. Spontaneous transitions between stationary states of a complex quantum-mechanical system are studied and Boltzmann's H-theorem is proved.
The developed approach involves the use of nonextensive quantum thermodynamics in various contexts, in particular, concerning the simulation of quantum thermal effects in nanoelectronic devices, in materials science, biomedicine and other quantum technologies.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Implementation of the bicompact scheme for HOLO algorithms for solving the transport equation
No full textAbstract:
The construction of bicompact schemes of high order of approximation for unsteady transport equation numerical solving in 1D geometry by application of HOLO (High Order – Low Order) algorithm is considered. The fourth order of approximation in space and the third in time are achieved. Two variants for the boundary conditions for the LO part are considered: the classical one using fractional-linear functionals for the flux and radiation density ratio, and also by the radiation density value from the HO part of the system. The efficiency of the algorithm is demonstrated in comparison with the source iterations method. It is shown the second variant of the boundary conditions leads to the third order of convergence on smooth solutions, in contrast to the first method, which allows to obtain only the second order; however the efficiency of the HOLO algorithm can decrease.Note:
Research direction:Mathematical problems and theory of numerical method
Simple mathematical model of tornado
No full textAbstract:
The paper proposes a mathematical model of tornado, based on the apparatus of continuum mechanics, according to which swirling flows of ascending air in a tornado take place without taking into account Coriolis force and vertical convection of warm air. According to the results obtained, the necessary conditions for the occurrence of a tornado are the presence of a powerful vortex motion in the upper atmosphere and an increase in air pressure with distance from the center of the tornado. Finding the parameters of air currents in a tornado reduces to solving a boundary value problem for a nonlinear parabolic integro-differential equation obtained in the work with respect to a complex “temperature”. An algorithm for solving the specified boundary value problem is proposed and its stationary solutions are investigated numerically by the method of establishment.Note:
Research direction:Mathematical modelling in actual problems of science and technic
To the question of astrophysical studies of protoplanetary disks of stars
No full textAbstract:
A brief analytical review of selected works on astrophysical observations of protoplanetary disks of stars is presented. It is shown that the data of astrophysical studies generally confirm the validity of the model of protoplanetary rings - the model of formation of planetary systems of stars, which is based on the origin and development of large-scale gravitational instability (protoplanetary rings) in the protoplanetary disks of stars.Note:
Research direction:Theoretical and applied problems of mechanic
On approximate construction of near equatorial orbits of the satellites of spheroidal celestial bodies
No full textAbstract:
The problem about a motion of material point (satellite) with negligible small mass nearby the equatorial plane of spheroidal body, in particular asteroid, is considered. For the small inclinations of satellite orbit in the first approximation dividing of motions is possible into equatorial and latitudinal components. Equatorial central motion, when a power function depends only on distance of satellite to origin of coordinates (centre of mass of asteroid), is constructed by offered early a semi-analytical method. The construction of latitudinal motion foresees the solution of linearized system of second order differential equations with periodic coefficients by numeral determination of monodromy matrix on the period of equatorial motion and its analytical continuation at time. Model problems are considered about perturbed motion of hypothetical almost equatorial satellites of Ceres and Vesta. The estimation of methodical accuracy is obtained by comparing to the numerical solution.Note:
Research direction:Theoretical and applied problems of mechanic
A conservative limiting method for bicompact schemes
No full textAbstract:
In this work, a new limiting method for bicompact schemes is proposed that preserves them conservative. The method is based upon a finite-element treatment of the bicompact approximation. An analogy between Galerkin schemes and bicompact schemes is established. The proposed method is tested on one-dimensional gasdynamics problems that include the Sedov problem, the Riemann 'peak' problem, and the Shu-Osher problem. It is shown on these examples that bicompact schemes with conservative limiting are significantly more accurate than hybrid bicompact schemes.Note:
Research direction:Mathematical problems and theory of numerical methodsRussia
Convergence estimates of the iterative algorithm for numerical solution of two-dimensional nonstationary problems of Magnetohydrodynamics
No full textAbstract:
In this paper, we investigate the convergence of the applied to the completely conservative difference schemes (CCDS) of Magnetohydrodynamics (MHD) Method of the combined decisions of groups of difference equations broken down by physical processes (the Method of splitting into processes). The area of applicability of this method is shown. The validity of the estimates obtained is confirmed by numerical calculations.Note:
Research direction:Mathematical modelling in actual problems of science and technic