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In this paper, we investigate different alternative ideas for the design of digital predistortion models for radiofrequency power amplifiers. When compared to the greedy search algorithm, these algorithms allow a faster identification of the model parameters combination while still performing reasonably well. For the subsequent implementation, different metrics of model costs and score results in the process of optimization enable us to achieve sparse selections of the model, which balance the model accuracy and model resources (according to the complexity of implementation). The results achieved in the process of simulations show that combinations obtained with explored algorithms show the best performance after a lower number of simulations.

Nowadays, active development of 4th generation nuclear reactors with liquid metal coolants takes place. Therefore, simulation of their elements and units in 3D modelling software are relevant. The thermal-hydraulic analysis of reactor units with liquid metal coolant is recognized as one of the most important directions of the complex of interconnected tasks on reactor unit parameters justification. The complexity of getting necessary information about operating conditions of reactor equipment with liquid-metal coolant on the base of experimental investigations requires the involvement of numerical simulation. The domestic CFD code FlowVision has been used as a research tool. FlowVision software has a certificate of the Scientific and Engineering Centre for Nuclear and Radiation Safety for the nuclear reactor safety simulations. Previously it has been proved that this simulation code had been successfully used for modelling processes in nuclear reactors with sodium coolant. Since at the moment the nuclear industry considers plants with lead-bismuth coolant as promising reactors, it is necessary to justify the FlowVision code suitability also for modeling the flow of such coolant, which is the goal of this work. The paper presents the results of lead-bismuth eutectic flow numerical simulation in the heat exchange tube bundle of NPP steam generator. The convergence studies on a grid and step have been carried out, turbulence model has been selected, hydraulic resistance coefficients of lattices have been determined and simulations with and without $k_\theta^{}$-$e_\theta^{}$ model are compared within the framework of fluid dynamics and heat exchange modeling in the heat-exchange tube bundle. According to the results of the study, it was found that the results of the calculation using the $k_\theta^{}$-$e_\theta^{}$ turbulence model are more precisely consistent with the correlations. A cross-verification with STAR-CCM+ software has been performed as an additional verification on the accuracy of the results, the results obtained are within the error limits of the correlations used for comparison.

The aim of research is to develop software system for solving gas dynamic problem in multiply connected integration domains of regular shape by high-performance computing system. Comparison of the various technologies of parallel computing has been done. The program complex is implemented using multithreaded parallel systems to organize both multi-core and massively parallel calculation. The comparison of numerical results with known model problems solutions has been done. Research of performance of different computing platforms has been done.

Complex geometric organization of subcellular structures such as photosynthetic or mitochondrial membranes determines mechanism of electron and proton transfer processes. We propose new approach in modeling processes, where geometric shape of membranes is accurately taken into account. Different stages of charge transfer process are simulated using different approaches, which are integrated into a combined model. We implemented this model as software which utilizes parallel computations on high-performance clusters and GPUs for better performance.

Mathematical simulation on unsteady natural convection in a closed porous cylindrical cavity having finite thickness heat-conducting solid walls in conditions of convective heat exchange with an environment has been carried out. A boundary-value problem of mathematical physics formulated in dimensionless variables such as stream function and temperature on the basis of Darcy–Boussinesq model has been solved by finite difference method. Effect of a porous medium permeability 10^–5≤Da<∞, ratio between a solid wall thickness and the inner radius of a cylinder 0.1≤h/L≤0.3, a thermal conductivity ratio 1≤λ_1,2≤20 and a dimensionless time on both local distributions of isolines and isotherms and integral complexes reflecting an intensity of convective flow and heat transfer has been analyzed in detail.

A method and a complex of computer programs are developed for the numerical simulation of the polaron states excitation process in condensed media. A numerical study of the polaron states formation in water under the action of the ultraviolet range laser irradiation is carried out. Our approach allows to reproduce the experimental data of the hydrated electrons formation. A numerical scheme is presented for the solution of the respective system of nonlinear partial differential equations. Parallel implementation is based on the MPI technique. The numerical results are given in comparison with the experimental data and theoretical estimations.

Excitation waves are a prototype of self-organized dynamic patterns in non-equilibrium systems. They develop their own intrinsic dynamics resulting in travelling waves of various forms and shapes. Prominent examples are rotating spirals and scroll waves. It is an interesting and challenging task to find ways to control their behavior by applying external signals, upon which these propagating waves react. We apply external electric fields to such waves in the excitable Belousov–Zhabotinsky (BZ) reaction. Remarkable effects include the change of wave speed, reversal of propagation direction, annihilation of counter-rotating spiral waves and reorientation of scroll wave filaments. These effects can be explained in numerical simulations, where the negatively charged inhibitor bromide plays an essential role. Electric field effects have also been investigated in biological excitable media such as the social amoebae Dictyostelium discoideum. Quite recently we have started to investigate electric field effect in the BZ reaction dissolved in an Aerosol OT water-in-oil microemulsion. A drift of complex patterns can be observed, and also the viscosity and electric conductivity change. We discuss the assumption that this system can act as a model for long range communication between neurons.

This work focuses on the application of a method of construction and conversion of three-dimensional computer models for optimization of geometric parameters of simulated devices. The method is used in design of complex technical devices for control system components of an exhaust gas recirculation vehicle – electric EGR valve with magnetic and electric motor. Three-dimensional geometric computer models were created in KOMPAS-3D environment and converted to Maxwell-2D. In Maxwell-2D environment transient electromagnetic processes for further optimization of parameters of therecirculation system devicewere calculated using a criterion of reducing power loss of the automobile engine.

Present work is dedicated to systematic study of equilibrium configurations of gold and silver clusters in size from 2 to 9 atoms. To the lowest energy configurations is performed calculation of electronic excitation spectra. All calculations are carried out within the framework of density functional theory (DFT) using the hybrid B3LYP functional and ECP LANL2DZ. Based on the analysis of the received electronic excitation spectra we try to confirm the assumption that small gold and silver clusters, capable of luminescence can be produced only in the presence of a stabilizing template. The authors show that without stabilization in the solution formed “flat” and “spherical” configuration whose spectra do not correspond to the experimental luminescence excitation spectra for DNA cluster complexes.

Based on CFD computations we provide the analysis of the possibilities for using modern hybrid distributed computational environments for large complex system simulation. We argue that only multilevel approach supported by new mathematical models of transport properties, dynamical representation of the problem with transport and internal processes separated, and modern paradigm of programming, taking into account specific properties of heterogeneous system, will make it possible to scale the problem effectively.