Open Repository of Keldysh Institute of Applied Mathematics of RAS
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Optimal scheduling of homogeneous products transportation
No full textAbstract:
The paper regards the problem of optimal planning of homogeneous products transportation. Three solution methods are presented: model events approach, technique, comprising simulation modeling and branch and bound algorithm, and the method, based on technological charts and genetic algorithms. Peculiarities of each approach are discussed. The paper also considers the advantages of the combined application of the developed methodologies.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Numerical algorithms and architecture of HPC systems
No full textAbstract:
The influence of mathematics techniques to the progress in architecture and performance of computing systems is discussed. The properties of computational algorithms aimed for solving the problem of fault tolerance, which is topical for prospective exaflops and super-exaflops systems, are considered.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Simulation of supersonic flow in the wake behind a wing at M = 2–4
No full textAbstract:
The structure of a supersonic vortex and its features depending on the Mach number M are described in this paper. The investigations are performed both in the near and far regions. Numerical and experimental data are compared. Numerical simulations were carried out in Keldysh Institute of Applied Mathematics RAS using parallel algorithms for turbulent flows simulating. The experimental part was carried out in Khristianovich Institute of Theoretical and Applied Mechanics SB RAS.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Two-phase flow modelling within fractured vuggy reservoir
No full textAbstract:
The paper presents a mathematical model for two-phase flow within a discrete fracture network with vugs at the intersections of fractures. An investigation of influence of liquid flow within vugs on the displacement dynamic within fractured media accounting for different types of the rock wettability, has submitted.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Multimodel approach for helicopter rotor aeroacoustic and aerodynamic characteristics modeling using numerical simulation
No full textAbstract:
The multimodel approach for evaluation of helicopter rotor aerodynamical and acoustical properties is developed. The matrix of models which provides the optimal model choice for the prediction of aerodynamic and acoustic rotor characteristics
depending on helicopter flight regimes is built.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Analysis of the results of ocean dynamics modeling using various methods of assimilation of observational data
No full textAbstract:
The paper presents the results of comparing the application of two different data assimilation methods. the method of generalized Kalman filtration (GKF) developed by the authors and standard objective ensemble interpolation method (EnOI) that is a partial case of extended Kalman filter scheme (EnKF). Those methods are applied in conjunction with the ocean dynamical model Hybrid Circulation Ocean Model (HYCOM). The methods are compared with respect to various criteria, in particular, with respect to minimum of the forecast error and with respect of a posterior error over a given time-interval. As observed data we used the Archiving Validating and Interpolating Satellite Observation (AVISO) i.e. altimetry data. It is shown that the method GKF has a number of advantages comparing with the method EnOI.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Numerical simulation of two-dimensional two-phase fluid flows accounting for wettability with quasi-hydrodynamic equations
No full textAbstract:
The present paper is devoted to further development of numerical algorithm for simulation of two-dimensional two-phase isothermal viscous flows with surface effects accounting for wettability on solid boundaries in voxel domains. Quasi-hydrodynamic regularization of Navier–Stokes–Cahn–Hilliard equations is used. Voxel boundary is interpreted as approximation of some (unknown) piecewise-smooth surface. Simulation results of stationary droplet touching two plane walls with different wetting angles are presented. Also two-phase flow simulations in pore doublet geometry model are performed.Note:
Research direction:Mathematical modelling in actual problems of science and technic
Localization of the spectral features of the encephalograms in psychic disorders
No full textAbstract:
In this work a spatial localization inside the human brain of spectral features of various psychic disorders is considered. Systematic bibliographic review is presented on the estimation of pathological activity sources location in the brain. The method is proposed for precise quantitative analysis of this activity based on the encephalography data.Note:
Research direction:Mathematical modelling in actual problems of science and technic
How to optimize preconditioners for the conjugate gradient method: a stochastic approach
No full textAbstract:
The conjugate gradient method (CG) is usually used with a preconditioner which improves efficiency and robustness of the method. Many preconditioners include parameters and a proper choice of a preconditioner and its parameters is often not a trivial task. Although many convergence estimates exist which can be used for optimizing preconditioners, they typically hold for all initial guess vectors, reflecting the worst convergence rate. To account for the mean convergence rate instead, in this paper, we follow a simple stochastic approach. It is based on trial runs with random initial guess vectors and leads to a functional which can be used to monitor convergence and to optimize preconditioner parameters in CG. Presented numerical experiments show that optimization of this new functional usually yields a better parameter value than optimization of the functional based on the spectral condition number.Note:
Research direction:Programming, parallel computing, multimedi
Mathematical modeling of the macroeconomic indicators dynamics on the basis of the dynamic stochastic general equilibrium model
No full textAbstract:
The paper presents a small dynamical stochastic model of general equilibrium in Kazakhstan. A special feature of the approach is the Keynesian microeconomic foundation, which takes into account market failures such as imperfect competition, inflexible prices and wages. The second specific feature is the hypothesis of rational expectations.
The model is a system of equations describing the dynamics of the national income, inflation and interest rates relative to its equilibrium trajectories. Equilibrium is treated dynamically - stationary states are determined on the basis of the Hodrick-Prescott filter (for comparison, the results of determining the potential output based on the Cobb-Douglas production function with exogenous technological progress are given).
The system consists of three equations: the dynamic equation of the IS curve, the New keynesian Philipps curve, the Taylor equation. The first one relates the output gap and the real expected interest rate. The second one relates inflation with inflationary expectations and output (an analog of the aggregate supply equation). Finally, Taylor equation is used by central banks in inflation targeting to establish interest rates that smooth economic cycles.
To estimate the parameters of the model, a Bayesian approach was used that allows to take into account a priori information about the properties of the economy and statistical information. The latter is important in the context of short time series in the post-Soviet countries, as well as in the conditions of a change in monetary policy in connection with the transition to the policy of inflation targeting.
Using the constructed model, the effects on key macroeconomic indicators from demand shocks, prices shocks, and changes in the interest rate policy of the monetary regulator are estimated.
The results of modeling and calculations can be used by monetary authorities in the development of monetary policy.Note:
Research direction:Mathematical modelling in actual problems of science and technic