Open Repository of Keldysh Institute of Applied Mathematics of RAS
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5498 research outputs found
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Modification of Guidance at the End of the First Entry for Skip Trajectory after Return from the Moon
No full textAbstract:
The task of reentry vehicle (RV) guidance at the skip trajectory after return from the Moon is considered. Some modification of reentry terminal guidance algorithm (modified) – RTGA-M is suggested. It provides two-parametric guidance during the first reentry phase entire for majority of disturbed trajectories. By statistical test of 1000 disturbed trajectories was shown efficiency of the modification.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Radiation transport in quasi-one-dimensional model of the ionizing gas flows in the plasma accelerator channel
No full textAbstract:
Algorithms for solving the problem of radiation transport are developed based on the methods of long and short characteristics taking into account their optimization in the framework of the quasi-one-dimensional approximation used to study the axisymmetric flows of the ionizing gas in coaxial channels of plasma acceleratorsNote:
Research direction:Mathematical modelling in actual problems of science and technic
Formal methods for detection of large-scale electoral fraud on the material of the federal elections 1999-2018
No full textAbstract:
I offer 4 different tests for the detection of large-scale electoral fraud at the level of subjects of the federation. These tests bases only on official data on election results and do not use any assumptions about voter behavior or reference results.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Scraping on the fly of external web resources, driven by HTML page markup
No full textAbstract:
The paper presents an approach to displaying data from cross origin resources on web pages using the REST API and describes a tool based on this approach that allows one to extract and display on the web page metadata of html documents, pdf files and documents Word posted on the Internet, as well as microdata and data in JSON LD format. The tool includes the REST API on the IIS web server and JavaScript scripts. Examples of using this tool are given. The created REST API enables cross origin resource sharing (CORS) and can be requested from web pages of any origins.Note:
Research direction:Programming, parallel computing, multimedi
Schrödinger equation as a consequence of new Vlasov type equations
No full textAbstract:
It is well known that the Schrödinger equation can be reduced to the Hamilton–Jacobi equation in Bohmian mechanics. Corresponding new equations of the Vlasov and Lamb types are derived, and their stationary solutions are investigated.Note:
Research direction:Mathematical problems and theory of numerical method
The parametric method of moments for solving the Smolukhovsky coagulation equation in the theory of accumulation of dust bodies in a preplanetary disk
No full textAbstract:
In the paper, as applied to the problem of combining dust particles, which are the main structure-forming element of planetesimals in the preplanetary cloud, a parametric method of moments for solving the Smoluchowski integro-differential equation describing dispersed coagulation of disk matter is proposed. A parametric approach to finding the distributions is considered, based on the Pearson diagram, which is used to satisfactorily find the adequate distributions from the knowledge of their first four moments. This approach is especially effective when it is necessary to know only the general properties of the distribution function of coagulating bodies by volume and their temporal evolution. Since the kinetics of the enlargement of pre-planetary bodies substantially depends on the specific type of coagulation nuclei, a sufficiently general approximation method was proposed in the work, which allows us to obtain simplified expressions for them for both laminar and turbulent motion modes. As a practical application, the parametric method of moments is demonstrated on a number of examples of the growth of pre-planetary bodies. The obtained results provide a new approach to solving the key problem of stellar-planetary cosmogony, associated with the explanation of the process of growth of interstellar dust particles to large planetesimals.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Translation-invariant bipolaron theory of superconductivity and spectroscopic experiments
No full textAbstract:
The explanation of the nature of superconducting gap in high temperature superconductors (HTSC) is a fundamental task which solution can lead to the understanding of superconducting mechanism. However it has not been fully solved as yet. From the mid of the twentieth centure when Bardeen, Cooper and Schrieffer constracted their theory it has been believed that a superconducting gap is a collective phenomenon of electron excitations. In this work it is demonstrated that according to translation-invariant bipolaron theory of HTSC the different types of experiments measure for the gap different values. Thus tunneling experiments determine the bipolaron energy for a superconducting gap. On the other hand the angle – resolved photoemission spectroscopy method measures the phonon frequency for which the electron-phonon interaction is maximum. Such effects as kinks in spectral measurements of gap, its angular dependence, existence of pseudogap and others have got natural explanations.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Numerical simulation of methane flame propagation in a gap between parallel plates
No full textAbstract:
Numerical simulations are performed for premixed methane-air combustion in a narrow gap between parallel horizontal plates. Simulations are based on the solution of Navier--Stokes equations for multicomponent gas in the small Mach number approximation, chemical reactions are described by a detailed kinetic scheme. Numerical integration
is performed by an explicit scheme on hierarchical adaptively refined meshes (AMR). Instability development resulting in the formation of cells on the flame front diverging from the ignition point is demonstrated. Dependence of the visible flame speed and cell size on the gap width between the plates is shown.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Bicompact schemes for multidimensional hyperbolic equations on Cartesian meshes with solution-based AMR
No full textAbstract:
High-order bicompact schemes for hyperbolic equations on Cartesian meshes with solution-based adaptive mesh refinement are constructed. The algorithm for implementation of these schemes on such meshes is described in detail. A new solution-based criteria of mesh refinement is proposed. Bicompact schemes with this refinement criteria are tested on the two-dimensional problem of compactly supported pulse advection and the two-dimensional Sedov blast wave problem. It is shown, that the design of bicompact schemes allows them to be implemented on meshes of such class with good accuracy of the computed solution ensured.Note:
Research direction:Mathematical problems and theory of numerical methodsRussia
To the derivation of symmetry of matrix of kinetic coefficients Onsager in framework of the nonextensive statistical mechanics of Tsallis
No full textAbstract:
In the framework of the nonextensive statistical mechanics of Tsallis, Onsager symmetry relations for the kinetic coefficients in linear regression equations for even and odd (when the velocities of elementary particles change direction) small fluctuations of macroscopic state parameters are derived. At a macroscopic level, these relations reflect the invariance of microscopic equations of motion with respect to time reversal. As in the case of classical Gibbs statistics, this conclusion is based on the theory of equilibrium fluctuations of dynamic variables characterizing the system, and on the properties of their invariance with respect to time reversal. In addition, the Onsager postulate was used, according to which the attenuation of the equilibrium fluctuations of the thermodynamic parameters of the state is described by linear differential equations of the first order. Traditional reciprocity relations for extensive systems are obtained from the derived relations in the case when the deformation parameter q, included in the parametric entropy functional of Tsallis, is equal to one.Note:
Research direction:Mathematical modelling in actual problems of science and technic