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RUSSIAN FEDERAL NUCLEAR CENTER 
ALLRUSSIAN RESEARCH INSTITUTE OF EXPERIMENTAL PHYSICS 

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Issue N^{o} 4, 2014  ON THE NATURE OF THE ENTROPY TRACE IN FLUIDS AND SOLIDS
A. E. Mayer, K. V. Khishchenko VANT. Ser.: Mat. Mod. Fiz. Proc. 2014. No 4. P. 313.
Physical reasons for the occurrence of the entropy trace at the interface between colliding bodies are analyzed. We show that application of the viscous fluid or elastoplastic solid model provides a physically consistent structure of the entropy trace, which is driven by the processes of dissipation of mechanical energy (viscosity, plasticity). To adequately account for this effect, one should use numerical methods with negligibly small scheme viscosity. Incorporating physical viscosity into the original set of equations of motion makes it possible to obtain a stable solution by a numerical method without artificial or scheme viscosity; by choosing a detailed mesh one can ensure that the numerical solution is stable with an arbitrarily small physical viscosity coefficient. The presence of the physically consistent entropy trace leads us, in particular, to the conclusion that melting of a solid body near the plane of impact begins at smaller impact velocities than melting behind a steadystate shock wave. Key words: entropy trace, viscous fluid, elastoplastic deformations, melting, numerical method.
 APPROACHES TO THE MODELING OF THE URANIUM HEXAFLUORIDE DESUBLIMATION PROCESS A. A. Orlov, R. V. Malyugin VANT. Ser.: Mat. Mod. Fiz. Proc. 2014. No 4. P. 1421.
The paper provides an overview and an analysis of the known approaches to the mathematical modeling of the process of uranium hexafluoride desublimation. Drawbacks of existing mathematical models are demonstrated. A concept is formulated for the development of theoretical research and optimization of the desublimation process. Key words: uranium hexafluoride, heat and mass transfer, desublimation, mathematical model, transient process.
 GAS DYNAMICS AND HEAT TRANSFER SIMULATIONS ON GRAPHIC PROCESSING UNITS K. N. Volkov, Yu. N. Deryugin, V. N. Emelyanov, A. G. Karpenko, A. S. Kozelkov, I. V. Teterina, A. V. Yalozo VANT. Ser.: Mat. Mod. Fiz. Proc. 2014. No 4. P. 2234.
The paper considers implementation of the finitevolume method for nonsteadystate viscous compressible gas flow and heat transfer simulations on unstructured grids on GPUaccelerated computers. The code LOGOS is provided with an additional GPU paralleling capability. Code optimization approaches related to the use of different types of memory and methods to calculate fluxes through control volume faces are presented. A number of model gas dynamics problems are used as illustrations to discuss the code optimization potential, and the speedup of calculations for different grid sizes is presented in comparison with CPU calculations. Key words: GPU, parallel algorithm, gas dynamics, finite volume method, unstructured grid, CUDA, LOGOS package.
 A MATHEMATICAL MODEL OF HEAT AND MASS TRANSFER DURING ZONE MELTING OF TiAl INTERMETALLIC COMPOUNDS WITHOUT CRUCIBLE S. M. Ganina, V. P. Ginkin, K. G. Chernov VANT. Ser.: Mat. Mod. Fiz. Proc. 2014. No 4. P. 3543.
The paper presents the results of mathematical modeling of the process of heat and mass transfer during recrystallization of an intermetallic TiAl (Nb,Cr,Zr) specimen by vertical zone melting without crucible. The calculations were done using a nonequilibrium mathematical model of multicomponent melt hardening extended from the binary melt hardening model proposed earlier. The aim of the work was to establish correlations between process conditions of crystallization and microstructure of the resulting ingots. Key words: crystallization, multicomponent melt, twophase zone, convection, heat and mass transfer, zone melting without crucible.
 THE CONCEPT OF GeRa CODE DEVELOPMENT AND APPLICATION FOR SAFETY STUDIES OF RADIOACTIVE WASTE DISPOSAL SITES I. V. Kapyrin, S. S. Utkin, Yu. V. Vasilevsky VANT. Ser.: Mat. Mod. Fiz. Proc. 2014. No 4. P. 4454.
In the paper we present the development principles of the GeRa code intended for direct and inverse problem simulations for safe disposal of radioactive waste, i.e. for safety studies of disposal sites and specification of requirements to the waste subject to disposal. The functionality of the code should enable threedimensional simulations of subsurface flow and migration starting from the development of the subsurface model through the uncertainty quantification and validation. The code will address the tasks of the Russian nuclear industry. In particular, the code is expected to incorporate the features of closed nuclear fuel cycle solutions. In addition to the traditional models of saturated flow and advection, diffusion and dispersiondriven transport, the code offers modeling capabilities for thermal and density convection, saturatedunsaturated and multiphase flow, chemical interactions in the waterrock system (including nonequilibrium conditions). The code is intended for use on threedimensional unstructured grids and for parallel simulations on supercomputers. The corresponding mathematical models provide for the use of secondorder schemes, and advection modeling will be done using lowdissipation schemes. GeRa has a modular structure focused on individual model construction phases. The functionality of each individual module of the code is discussed in detail, including numerical models of physical and chemical processes. Key words: radioactive waste, disposal safety, threedimensional modeling, flow, transport, subsurface, parallel simulations, supercomputers.
 HARDWARE METRICS MONITORING SYSTEM. ARCHITECTURE, IMPLEMENTATION A. A. Bogdanov, N. N. Zalyalov, A. A. Yarulina VANT. Ser.: Mat. Mod. Fiz. Proc. 2014. No 4. P. 5564.
SKAM is a software system for hardware metrics monitoring, which detects hardware failures or malfunctions in large computing systems (monitoring system), collects sensor readings, records events reported by computing system components, and delivers them to users upon request. All the functions of SKAM are implemented by its modules. The current version includes two data collection modules, a data delivery module and a database storage module. The modules are integrated into a service. Several services operating on different servers form a decentralized system. This approach provides flexibility in linking the monitoring system's modules together as necessary. In the paper, we describe the architectural features of SKAM and details of its implementation. Key words: hardware metrics monitoring system, IPMI protocol, monitoring system, computing system, modular decentralized architecture.
 ALGORITHM AND PROGRAM FOR THE DETECTION OF DATA TRANSFER INTERRUPTIONS IN FIBER OPTICS O. N. Naryshkina, S. I. Ovechkin, V. V. Shubin VANT. Ser.: Mat. Mod. Fiz. Proc. 2014. No 4. P. 6572.
The paper presents the results of developing an algorithm for damage detection in fiber optics used for data signal transfer. The algorithm is implemented in the Assembler language within the PIC16C717 microcontroller software and in the C++ language for the PIC18F1320 microcontroller, which are used in the monitoring system of direct data and pilot signal losses in fiber optics. Key words: digital signal recognition, signal/noise ratio, telecommunication signal analyzer.
 PRE AND POSTPROCESSOR LOGOS PREPOST. SPECIAL FEATURES OF THE ELEMENT PICKING MECHANISM D. V. Antoshin, A. V. Gordeev VANT. Ser.: Mat. Mod. Fiz. Proc. 2014. No 4. P. 7378.
The paper describes the grid element picking mechanism implemented in the LOGOSPrepost pre and postprocessor. Two element picking models are presented: the old one using the VTK filters, and the new one based on the mechanism of operations. The drawbacks of the old model are listed. The features of the new model are described, which provide high gain in speed and enhanced functionality. The model is compared with foreign counterparts with respect to the grid element picking rate. Key words: pre and postprocessor, picking, VTK, mechanism of operations, visualization.
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