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Numerical simulation of a gas pipeline network using computational fluid dynamics simulators

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第5期8卷 755-765页

作者： SELEZNEV vadim Physical and Technical Center Joint Stock CompanySarov607180Russia

This article describes numerical simulation of gas pipeline network operation using high-accuracy computational fluid dynamics (CFD) simulators of the modes of gas mixture transmission through long, multi-line pipeline systems (CFD-simulator). The approach used in CFD-simulators for modeling gas mixture transmission through long, branched, multi-section pipelines is based on tailoring the full system of fluid dynamics equations to conditions of unsteady, non-isothermal processes of the gas mixture flow. Identification, in a CFD-simulator, of safe parameters for gas transmission through compressor stations amounts to finding the interior points of admissible sets described by systems of nonlinear algebraic equalities and inequalities. Such systems of equalities and inequalities comprise a formal statement of technological, design, operational and other constraints to which operation of the network equipment is subject. To illustrate the practicability of the method of numerical simulation of a gas transmission network, we compare computation results and gas flow parameters measured on-site at the gas transmission enter-prise.

关键词： Long branched gas pipeline network Unsteady Non-isothermal gas flow CFD-simulator Numerical simulation Finite Volume Method Interior Point Method

Lattice-based digital signatures

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National Science Review 2021年第9期8卷 9-10页

作者： vadim Lyubashevsky Zurich Research Laboratory IBM Research

Digital signatures and key exchange protocols are the two most important public key cryptographic primitives used in the electronic transmission of data. The goal of key exchange is to preserve the secrecy of the communication, while the goal of digital signatures is to guarantee the authenticity of the exchanged messages. Constructions of digital signature schemes based on classical mathematical assumptions appeared shortly following the invention of public key cryptography in the late 1970s. And just like with key exchange,

关键词： lattice cryptography digital signatures standardization

Theoretical and experimental studies of gas preparation system for pressurization and reactive control system of launch vehicle

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Chinese Journal of Aeronautics 2024年第7期37卷 168-177页

作者： Valeriy TRUSHLYAKOV Vladislav URBANSKY vadim YUDINTSEV Department of Aviation and Rocket Building Omsk State Technical UniversityOmsk 644050Russia

A new gas preparation system(GasPS-RCS)is proposed to solve two tasks:(A)to heat helium gas for tank pressurization;(B)to prepare gas for the Launch Vehicle(LV)Reactive Control System(RCS)at the LV orientation and stabilization sections of the LV on passive parts of the flight trajectory,to provide conditions for launching the Liquid Rocket Engine(LRE).The system includes a gas generator based on hydrogen peroxide,a separator for water separation,heat exchangers independent of the LRE,and gas-jet *** proposed new system allowed to reduce the length of pressurizing gas lines and reduce the increased helium gas consumption during the heat exchanger warm-up interval of the LRE during its launch.A special advantage of the proposed system is the possibility of ground testing of heat exchangers without an operating LRE.A mathematical model based on the first law of thermodynamics was used to perform a comparative analysis of GasPS-RCS with traditional pressurization and RCS *** validate the mathematical model,the experimental studies of helium pressurizing of a liquid nitrogen tank were *** results show that the deviation of experimental and calculated values for pressure is 1.1%and for temperature up to 2%.According to the results of comparative analysis,the GasPS-RCS is 259 kg lighter for the first stage and 80 kg lighter for the second stage of the LV.

关键词： Engine restart Reactive control system Tank pressurization Cryogenics Hydrogen peroxide Heat exchanger

Theoretical search for solutions to minimize negative influence of segregation in mixing of particulate solids

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Particuology 2016年第2期14卷 36-41页

作者： vadim Mizonova Henri Berthiaux Cendrine Gatumel Department of Applied Mathematics lvonovo State Power Engineering University Rabfakovskaya 34 153003 Ivanovo Russia Centre RAPSODEE UMR CNR5 5302 Ecole des Mines d'Albi-Carmaux CampusJarlard route de Teillet 81000 Albi France

The objective of this study is to examine several optimization problems in the batch mixing of segregating particulate solids that can be set up and solved using Markov chain models. To improve the adequacy of such models and exclude some physical contradictions that arise in the linear form, a non-linear Markov chain model for the mixing of segregating components is proposed. Optimal solutions are obtained by controlling the particle flow outside the mixing operating volume while the components are being loaded, modifying particle circulation inside the mixing zone during the process, and by structuring the load in the mixing zone. Solutions are found that not only reduce the negative influence of segregation, but also exclude it altogether. The gain resulting from optimization grows with the rate of segregation. The optimal solutions presented here can be used to improve the design of mixers.

关键词： Mixing Segregation Mixture quality Markov chain Optimization

Orbits of 152 globular clusters of the Milky Way galaxy constructed from Gaia DR2

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Research in Astronomy and Astrophysics 2021年第7期21卷 177-191页

作者： Anisa Talgatovna Bajkova vadim vadimovich Bobylev Pulkovo Astronomical Observatory St.Petersburg 196140Russia

We present orbits and their properties for 152 globular clusters of the Milky Way galaxy obtained using average Gaia DR2 proper motions and other astrometric data from the list of Vasiliev. For orbital integration we have applied the axisymmetric model of the Galactic potential based on the Navarro-Frenk-White dark halo, and modified by Bajkova & Bobylev utilizing circular velocities of Galactic objects in a wide region of Galactocentric distances(up to 200 kpc) from the Bhattacharjee et al. catalog. Based on the analysis of the obtained orbits, we have modified the composition of the subsystems of globular clusters presented in Massari et al..

关键词： (Galaxy) globular clusters general

A Numerical Analysis of Turbulent Compressible Radial Channel Flow with Particular Reference to Pneumatic Controllers

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Journal of Thermal Science 2004年第1期13卷 24-29页

作者： Gilles Roy Dinh Vo-Ngoc vadim Bravine Faculty of Engineering Université de MonctonMonctonNBCanadaE1A 3E9Faculty of EngineeringUniversité de MonctonMonctonNBCanadaE1A 3E9Faculty of EngineeringUniversité de MonctonMonctonNBCanadaE1A 3E9

A numerical analysis of turbulent axisymmetric radial compressible channel flow between a nozzle and a flat plate is presented in this paper. In particular, the application of this type of flow situation in pneumatic dimensional control systems is considered. The Spalart-Allmaras one-equation turbulence model is used. The resulting highly coupled PDE system has been solved using the control volume based numerical approach where the power-law scheme was used extensively to compute the diffusive and convective fluxes of momentum. Results show that local Mach numbers can easily achieve and surpass unity for typical industrial configurations. Also, in the case of a standard industrial nozzle geometry, the presence of a toroidal recirculation zone that moves radially outward is clearly identified in most cases. Separated flow areas are of particular concern as it has been shown previously that they can cause nozzle fouling in industrial applications. It has been shown that the size of this region is dependant on feed pressure. Considerable differences between results obtained using the Spalart-Allmaras and standard k- εturbulence models have also been noticed.

关键词： compressible radial flow numerical simulation pneumatic controllers impinging jet with confinement.

Analysis of the Quantity and Causes of Outages in LV/MV Electric Grids

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CSEE Journal of Power and Energy Systems 2020年第3期6卷 537-542页

作者： Alexander Vinogradov Alina Vinogradova vadim Bolshev Laboratory of power supply and electrical safety Federal Scientific Agroengineering Center VIMMoscow109428 Russia

The paper considers the quantity and causes of outages in electric grids of low and medium voltages using the example of an electric grid of a regional power supply *** main types of damage to the equipment of power lines and transformer substations were *** on other areas of rural and urban electric grids are also *** main directions for reducing the quantity of outages in electric grids are proposed based on this *** them,there are the use of isolated wires in power transmission lines,the improvement of design of switching devices,switches and terminals of transformers,the application of technical condition diagnostics,the disaggregating of power lines and the increase of protection sensitivity of power *** of the causes of equipment damage can be prevented by increasing the maintenance level of this equipment.

关键词： Electrical network grid power line power outages power supply reliability PTL transformer

Heterogeneous LBM Simulation Code with LRnLA Algorithms

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Communications in Computational Physics 2023年第1期33卷 214-244页

作者： vadim Levchenko Anastasia Perepelkina Keldysh Institute of Applied Mathematics RAS

A design of a new heterogeneous code for LBM simulations is *** heterogeneous computing wemean a collaborative computation on CPU and GPU,which is characterized by the following features:the data is distributed between CPU and GPU memory spaces taking advantage of both parallel hierarchies;the capabilities of both SIMT GPU and SIMD GPU parallelization are used for calculations;the algorithms in use efficiently conceal the CPU-GPU data exchange;the subdivision of the computing task is performed with an account for the strong points of both processing units:high performance of GPU,low latency,and advanced memory hierarchy of *** code is a continuation of our work in the development of LRnLA codes for *** LRnLA codes had good efficiency both for CPU and GPU computing,and allowed GPU simulation performed on data stored in CPU RAM without performance loss on CPU-GPU data *** the new code,we use methods and instruments that can be flexibly adapted to GPU and CPU instruction *** present the theoretical study of the performance of the proposed code and suggest implementation *** bottlenecks are *** a result,we conclude that larger problems can be simulated with higher efficiency in the heterogeneous system.

关键词： LBM Roofline memory-bound GPU LRnLA

A Markov chain model of mixing kinetics for ternary mixture of dissimilar particulate solids

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Particuology 2017年第2期15卷 80-86页

作者： vadim Mizonov Ivan Balagurov Henri Berthiaux Cendrine Gatumel Department of Applied Mathematics Ivanovo State Power Engineering University Russia Centre RAPSODEE UMR CNRS 5302 Ecole des Mines d'Albi-Carmaux Campus Jarlard Route de Teillet 81000 Alhi France

This paper presents a simple but informative mathematical model to describe the mixing of three dissimilar components of particulate solids that have the tendency to segregate within one another. A nonlinear Markov chain model is proposed to describe the process. At each time step, the exchange of particulate solids between the cells of the chain is divided into two virtual stages. The first is pure stochastic mixing accompanied by downward segregation. Upon the completion of this stage, some of the cells appear to be overfilled with the mixture, while others appear to have a void space. The second stage is related to upward segregation. Components from the overfilled cells fill the upper cells （those with the void space） according to the proposed algorithm. The degree of non-homogeneity in the mixture （the standard deviation） is calculated at each time step, which allows the mixing kinetics to be described. The optimum mixing time is found to provide the maximum homogeneity in the ternary mixture. However, this “common” time differs from the optimum mixing times for individual components. The model is verified using a lab-scale vibration vessel, and a reasonable correlation between the calculated and experimental data is obtained

关键词： Ternary mixture Segregation Mixing kinetics Markov chain Matrix of transition probabilities Optimum mixing time