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RUSSIAN FEDERAL NUCLEAR CENTER 
ALLRUSSIAN RESEARCH INSTITUTE OF EXPERIMENTAL PHYSICS 

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Issue N^{o} 1, 2018  "LOGOS" PROGRAM PACKAGE. A MODULE FOR SOLVING THE DYNAMIC STRENGTH PROBLEMS
D. Yu. D'yanov, V. F. Spiridonov, K. V. Tsiberev, E. I. Naumova, V. V. Borlyaev, S. V. Starodubov, E. V. Shuvalova, M. V. Medvedkina, E. O. Artemova, A. A. Chelakov, A. V. Kazantsev, A. A. Ryabov, V. I. Romanov, S. S. Kukanov VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 1. P. 314.
The paper describes a finiteelement module implemented in the LOGOS program package for solving the dynamic strength problems. The methods and algorithms implemented in the module are briefly described. The application of the dynamic strength module is illustrated by the example of simulation results for a number of realworld problems. Key words: LOGOS program package, a dynamic strength module, the finite element method, contact algorithms.
 A METHOD FOR THE SIMULATION OF A PERFECTLY RIGID BODY MOVING IN ELASTIC MEDIUM USING A FIXED COMPUTATIONAL GRID A. A. Krayukhin, Yu. V. Yanilkin, A. L. Stadnik, M. Yu. Eguzhova VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 1. P. 1529.
The paper suggests the BODY3D method to simulate the motion of a perfectly rigid body in an elastoplastic medium with regard to friction using an Eulerian computational grid, its implementation in the EGAK code is described and results of test simulations are presented. Two problems were used to test the method. An exact solution was obtained for the first one, the problem of a freely falling rotating rigid body impacting a barrier. The second was the problem of a moving rigid body penetrating into a soft ground at an angle. Key words: penetration, rigid body, friction, elastoplastic medium, noninertial frame of reference, Eulerian computational grid, the EGAK code.
 AN ALGORITHM OF CORRECTING A GRID FOR A REGION FORMED BY SURFACES OF REVOLUTION WITH PARALLEL AXES OF REVOLUTION O. V. Ushakova VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 1. P. 3041.
The paper offers an algorithm for correcting boundary nodes of a structured grid as applied to the boundary of a region formed by surfaces of revolution with parallel axes of revolution. The use of a correction algorithm is a necessary step of constructing grids for regions of interest and during the grid reconstruction it allows moving boundary nodes not over linear surfaces of cell faces of the original grid constructed for the region discretization, but directly along the region boundary (surfaces of revolution). The algorithm presented in the paper can be used independently for correcting a grid, which nodes fell out of the region boundary. The algorithm in Ñ++ implemented in software systems for constructing 3D computational grids and in an individual code for correcting a grid with respect to a region boundary significantly improves the efficiency of mathematical modeling of multimaterial media. Key words: grids, boundary nodes, surfaces of revolution, projection.
 NUMERICAL SIMULATION OF THE DEFORMATION OF AN OCTOGENEBASED EXPLOSIVE UNDER LOWVELOCITY LOADING CONDITIONS USING GODUNOV'S METHOD O. M. Velichko VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 1. P. 4253.
The paper presents a viscoelastic model of medium with the kinetics of fracturing due to shear stresses, which has been implemented using Godunov’s method. The algorithm is based on the coupled method of solving the differential equations of hydroelasticity and Riemann problem in a hydroelastic environment. The paper also presents results of the computational model application to solve the problem of a steel ball colliding with a cylindrical sample of lazy octogene and the problem of deforming an explosive in experiments with Hopkinson's compound rods. Key words: explosive, deformation and rupture, viscoelastic model with fractures, Godunov's method, numerical simulation.
 PARALLELIZATION AND OPTIMIZATION OF THE CONSTRUCTION OF BLOCK COMPUTATIONAL GRIDS IN PREPROCESSOR OF "LOGOS" PROGRAM PACKAGE V.V. Lazarev VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 1. P. 5463.
The methods optimizing the block computational grid construction using the previously made decomposition of a geometric model into blocks are considered. Data structures representing the decomposition and block grids are described. The parallelized algorithms of constructing a block grid are described on the base of these representations. The plots of the parallelization efficiency and speedup versus the number of threads are presented. An algorithm that allows reconstructing a grid on the varied blocks only with respect to the modified decomposition into blocks has been also developed. For grids of sizes beyond the memory size, the fragmentbyfragment construction method with recording to separate files is proposed. A grid of 1 billion cells has been constructed. The developed algorithms have been implemented in the LOGOS preprocessor beginning from version 5.1. Key words: parallelization, OpenMP, a block computational grid, geometry decomposition into blocks, preprocessor of the LOGOS program package.
 USE OF NEURON NETS TO PREDICT PARAMETERS OF THE VERTICAL DISTRIBUTION OF THE NEUTRON FLOW DENSITY IN REACTOR CORE V. Yu. Samonin VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 1. P. 6470.
The feasibility of the online predictive evaluation of parameters of the vertically distributed neutron flow density in a production reactor core using the artificial neuron network mechanism has been examined. The neuron network has been created, learnt and verified using actual data. The numerical simulation results are presented. Key words: nuclear reactor, core, neutron flow density, irregularity of the neutron field, artificial neuron net, control line, direct charge detector.
 EXAMINATION OF ENGINEERING SOLUTIONS ON THE DESIGN OF COMPLETELY OPTICAL LOGICAL COMPONENTS K. I. Balashov, V. V. Shubin VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 1. P. 7181.
The paper gives criteria for assessing the physical and structural principles of designing completely optical passive logical components. The criteria were used to examine the known engineering solutions. From viewpoint of meeting the criteria, the technology of optical logical components based on microring resonators seems to be promising. Key words: a completely optical logical component, nonlinear optical effects, a microring resonator, dark and bright solitons.
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