bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of Near-Bottom Suspension-Carrying Flow around a Pipeline
Authors: Vladimirov I.Yu , Korchagin N.N 
Published: December 2019

Abstract
In a model format, the force effect of a stratified ideal fluid flow on streamlined elements of engineering structures is investigated. Integral representations of wave drag and lift force are obtained. Numerical calculations are performed for the real marine medium. The conditions under which significant changes in hydrodynamic reactions to streamlined elements of technical structures occur are revealed.
On hyperbolized nonlinear Schredinger type equations
Authors: Yunakovsky A.D. , Bogomolov Ya.L. , Sapogova N.V. 
Published: December 2019

Abstract
A nonlinear Schredinger type equation in the case of an unbounded in space operator having, a non-divergent form, is considered. A new approach based on the hyperbolization procedure is suggested. The possibilities of the method proposed are tested.
Numerical modelling of wall-bounded turbulent flows based on the CABARET scheme
Authors: Asfandiyarov Danil 
Published: December 2019

Abstract
In this study, the classical problem of turbulent plane channel flow at Rem
= 13750 and Rem
= 21900 is investigated using a numerical algorithm based on the CABARET scheme. Simulations are performed on the fine grids, resolving all the spatial scales of the turbulence according to a direct numerical simulation approach, as well as on coarse grids standard for large eddy simulation of wall-bounded turbulent flows. In the latter case, in order to obtain a more accurate representation of the momentum transfer towards the wall, artificial boundary conditions are introduced. It allows modelling with high accuracy the mean flow characteristics. Numerical results obtained by the CABARET scheme are compared with numerical results obtained by pseudospectral method.
Models of dynamics of contamination propagation in surface waters using simulation of hydrodynamical processes of different level of complexity
Authors: Cherepanov Anatoly , Sorokovikova Olga 
Published: December 2019

Abstract
This paper uses the ideology of solving hyperbolic equations using the Euler balance-characteristic approach, which allows economically and correctly resolving the dynamics of pollution propagation processes with large concentration gradients characteristic of an accident. The purpose of the study is to develop a three-dimensional model of advectiondiffusion in a non-uniform velocity field and non-isotropic field of turbulent diffusion, taking into account some physical processes: gravity sedimentation, sediment accumulation and their dynamics. As well as the implementation of the interaction model with the hydrodynamic module, based on solving the equations of the theory of shallow water in the approximation of Saint-Venant.
Probabilistic models of pollution of the surface waters of large marine areas
Authors: Sorokovikova Olga , Dzama Dmitry , Asfandiyarov Danil 
Published: December 2019

Abstract
Version of Monte-Carlo model for calculation of propagation of contamination in large marine areas with taking into account a coastline is presented. Based on long standing database of sea currents, bathimetry, and mixed layer depth, the probabilistic model of zoning marine areas by concentration of pollutant is offered. In accordance with modern IAEA recommendations general principles of estimation of radiation situation on radiation hazardous object in normal expluataion mode, conclusion of normal expluatation mode, or in accident mode exists. Practical methodology of safety case and tactics of monitoring of state of radiation hazardous object should rely not only on measuring, but also on model calculations and forecasts. Optimal tactics of monitoring includes definition of probabilistic picture of possible pollution different marine areas assuming hypothetical leak of pollutant with violation of defence barriers. One way of building such probabilistic pictures is execution of multi-variant calculations using long standing databases. Different calculations in multi-variant mode executes assuming different accident start time, in advance models multi-variant dynamic of marine area polluton. Not only maximum values of pollution to be interested, but and statistical estimations with different confidence levels (for filtration of rarery big values) for hypothetical leak of pollutant. In the base of the numerical algorithm of proposed technique lies Monte-Carlo method using lagrangian particles with non-zero sizes.
An effective algorithm of the numerical solution to the Stefan problem
Authors: Kurbatova Galina I. , Ermolaeva Nadezhda N. 
Published: December 2019

Abstract
The method of the frontal interval of the numerical solution to Stefan problems is proposed. The method allows the calculation of the position of the phase transition boundary with high accuracy at any of time. Using the example of a plane two-phase Stefan problem, which has an exact analytical solution, the advantages of the proposed method in comparison with a variable time stepping method are demonstrated with respect to the calculation of the position of the phase transition boundary. An example of the solution to the one-phase Stefan problem using the frontal interval method is also given.
Lagrange-Eulerian method for numerical integration of the gas dynamics equations: parallel implementation on GPUs
Authors: Khrapov Sergey , Khoperskov Alexander , Khoperskov Sergey 
Published: December 2019

Abstract
We describe a new CSPH-TVD method for numerical integration of hydrodynamical equations. The method is based on combined Lagrange-Euler approaches, and it has been devoted to simulations of hydrodynamical flows in various astrophysical systems with non-homogeneous gravitational fields and the non-steady boundary between gas and vacuum. A numerical algorithm was tested on analytical solutions for various problems, and a detailed comparison of our method with the MUSCL scheme is also presented in the paper. It is shown that the CSPH-TVD scheme has a second order of accuracy for smooth solutions (well-balanced approach) and it provides reliable solutions in the vicinity of strong shock waves and at the open gas-vacuum interfaces. We also study the effectiveness of parallel implementations of CSPH-TVD method for various NVIDIA Tesla K20/40/80, P100 graphics processors.
Thermal action of pulse radiation on the carbon conic shells loaded with internal pressure
Authors: Matveenko A M , Ostrik A V , Bakulin V N 
Published: December 2019

Abstract
The new mechanism of constructions destruction as a result of thermal action of radiations and particles fluxes was considered. It is supposed that interruption of construction operability comes owing to non-stationary processes of deformation and destruction. Non-stationary deformation and destruction take place as a result of action of quasi-stationary working loadings at saltatory change of construction rigidity. Jump of rigidity arises at volume and impact heating of material by means of action of radiations and particles fluxes.
A numerical method for predicting of the thermal and tension-strain states of thin-walled orthotropic constructions having variable thickness under the action of energy fluxes of different physical nature are considered. Physical and chemical processes in result of heating of composite construction materials were taken into account. These processes are the binder pyrolysis, chemical reactions of carbon and air flow components, and the ablation of carbon residue. Non-stationary processes occurring in the shell has been numerically simulated. Model of layer-by-layer destruction is used in this simulation.
Numerical solution of the inverse coefficient problem of filtration in a multilayer reservoir
Authors: Khairullin M. Kh. , Badertdinova E. R. , Khairullin R. M. 
Published: December 2019

Abstract
This work proposes a computational algorithm based on the regularization method for determining the hydraulic conductivity coefficient of a layered oil reservoir. The results of hydrodynamic investigations of vertical wells, opening a layered reservoir, are used as initial information.
Mathematical modeling of the dynamics of layered and block media with nonlinear contact conditions on supercomputers
Authors: Nikitin I. S. , Burago N. G. , Golubev V. I. , Nikitin A. D. 
Published: December 2019

Abstract
Continual models of solid media with a discrete set of slip planes (layered, block media) and with nonlinear slip conditions at the contact boundaries of structural elements are constructed. The constitutive equations of the resulting system of equations contain a small viscosity parameter in the denominator of nonlinear free terms. For a stable numerical solution of a system of differential equations, an explicit-implicit method is proposed with an explicit approximation of the equations of motion and an implicit approximation of the constitutive relations containing a small parameter. From implicit nonlinear difference approximations analytically, using the perturbation method, various effective formulas for the correction of stress components after an elastic time step are obtained. To calculate the elastic step, we used a grid-characteristic method on hexahedral grids, which allowed us to significantly increase the speed of calculations and simulate a non-stationary three-dimensional problem of generating a response from an oriented layered or block cracked cluster located in a homogeneous medium.
Mathematical model of decomposition of hydrates in a reservoir
Authors: Popov V.V 
Published: December 2019

Abstract
A mathematical model of the process of decomposition of hydrates in a reservoir by reducing pressure is implemented numerically. The dependence of results obtained on main parameters of the problem such as initial hydrate saturation, initial water saturation, depression on the formation, permeability coefficient, porosity has been studied. We compare results of the numerical implementation of the original model with results obtained after linearization of the heat equation, equations of gas flow continuity both separately and simultaneously. It is shown that with relatively low permeability, initial water saturation and depression one can use the model with linearized equations. The relative difference of the calculated hydrate saturation is a few percent. For the distribution of temperature and pressure, this difference is even smaller. The developed algorithm can easily be expanded for a multidimensional problem.
Mathematical technology for solving the Kardar-Parisi-Zhang equation with a source
Authors: Rassadin A E , Stepanov A V 
Published: December 2019

Abstract
The description of an algorithm for numerical solution of the two-dimensional Kardar-Parisi-Zhang equation with fractal initial condition and spatially inhomogeneous stochastic source of particles has been presented. Using the Cole-Hopf substitution, the KardarParisi-Zhang equation is reduced to an auxiliary linear parabolic equation with a variable coefficient. This reduction provides both compatibility of the algorithm with the concept of mathematical technology and possibility of its practical realization on supercomputer using the MPI parallel programming technology and the ROOT framework. The required profile of the evolving surface is restored by the inverse substitution by solving the auxiliary equation, Opportunity of estimation of its autocorrelation function and its spectral power density, as well as the time dynamics of Shannon surface information, have been discussed.
Multiscale Finite Element Method for scattering problem in heterogeneous domain
Authors: Gavrilieva Uygulaana , Vasilyeva Maria , Harris Isaac , Chung Eric T. , Efendiev Yalchin 
Published: December 2019

Abstract
In this paper, we consider the wave scattering problem in heterogeneous domain. The mathematical model is described by the Helmholtz equation for time-harmonic wave propagation with absorbing boundary condition. We construct a coarse grid approximation for the efficient numerical solution on coarse grids using the Multiscale Finite Element Method (MsFEM), where we construct a multiscale space using solution of some local problems in each local domain. Numerical results are presented to illustrate the performance of the method.
Neural networks for multicontinuum models
Authors: Grigorev A. , Stepanov S. , Nikiforov Dj. 
Published: December 2019

Abstract
Neural networks are developed for multicontinuum models. Multicontinuum models [1] assume that processes divided into several continuums and they are connected by some exchange member. In problems connected with PDE not only solution, but also coefficients can depends on time. First we construct LSTM neural network for exchange coefficient that depend on time. We compare the results obtained on the basis of the reference coefficient and on the basis of the neural network. Next we apply same neural network on the solutions. The proposed approach involves the use of a neural network for the approximate generation of a solutions and the further adaptation of the solution of a neural network for generate coarse grid solution based on DG finite elements.
GMsFEM on unstructured grids for single-phase flow in fractured porous media
Authors: Nikiforov Djulustan , Vasilyeva Maria , Efendiev Yalchin , Vasil’ev Vasily 
Published: December 2019

Abstract
In this work, we consider an unstructured Generalized Multiscale Finite Element Method (GMsFEM) for solution of the filtration problem in a fractured media. The basic idea is that coarse grid blocks are formed as sets of fine grid triangular cells and, thus, can be of an almost arbitrary polygonal shape. In this approach, when constructing the fine grid, the faces of coarse blocks are not considered. Discrete fractured model is used to describe a flows in a fractured media.
Embedded fracture model in numerical simulation of the fluid flow and geo-mechanics using Generalized Multiscale Finite Element Method
Authors: Tyrylgin Aleksei , Vasilyeva Maria , Chung Eric T. 
Published: December 2019

Abstract
In this work, we consider a pororelasticity problem in fractured porous media. Mathematical model contains a coupled system of equations for pressure and displacements, for which we use an embedded fracture model. The fine grid approximation is constructed based on the finite volume approximation for the pressure in fractured media and finite element method for the displacements. Multiscale approximation is developed using a structured coarse grid and is based on the Generalized Multiscale Finite Element Method for pressures and displacements. The performance of the method is tested using a two-dimensional model problem with different number of the multiscale basis functions.
Numerical calculation of spectral problems in SP3 approximation by FEM
Authors: Vasilev A. O. , Avvakumov A. V. , Strizhov V. F. , Vabishchevich P. N. 
Published: December 2019

Abstract
The SP3 approximation of the neutron transport equation allows improving the accuracy for both static and transient simulations for reactor core analysis compared with the neutron diffusion theory. Besides, the SP3 calculation costs are much less than higher order transport methods (SN or PN). Another advantage of the SP3 approximation is a similar structure of equations that is used in the diffusion method. Therefore, there is no difficulty to implement the SP3 solution option to the multi-group neutron diffusion codes. In this work, the application of the SP3 methodology based on solution of the - and -spectral problems has been tested for reactor benchmarks. The FEM is chosen to achieve the geometrical generality. The results calculated with the diffusion and SP3 methods are compared with the reference calculation results.
Development of algorithms for the formation of steady-state modes based on the topology of electric power systems
Authors: Akhmetbaev D S , Dzhandigulov A R 
Published: December 2019

Abstract
Implementation of the new algorithm for the formation of the steady state mode based on the distribution coefficients of the driving currents in complex electrical networks. is proposed.
The advantage of the proposed approach, in contrast to previously known ones, is that it is not necessary to calculate all 2-trees, as is done in previously known topological methods, which reduces the number of operations by n
2 times.
The results of calculations by the proposed method on various test examples 99% coincided with the results of calculations obtained using the industrial software RastrWin3.
A computational algorithm for constructing a two-dimensional heat wave generated by a non-stationary boundary condition
Authors: Kazakov A L , Spevak L F , Lempert A A , Nefedova O A 
Published: December 2019

Abstract
The paper discusses solutions of the nonlinear heat equation, which have the form of a heat wave propagating on a zero background with a finite velocity. Such solutions are not typical for parabolic equations, and their existence is associated with the degeneration of the problem at the wave (zero) front. We propose a numerical algorithm for constructing a two-dimensional heat wave, symmetrical with respect to the origin, with a non-zero boundary condition defined on the moving boundary. The main difficulty of the new task is that at each time point a heat wave front (a domain boundary) is unknown. The solution is carried out in two stages. At first, we change the roles of unknown function and radial polar coordinate. For a new unknown function at each time point, we obtain a boundary value problem for the Poisson equation in a known region. The step-by-step solving of this problem by the method of boundary elements at a given time interval allows us to determine the law of the zero front moving. At second, we approximate the found zero front by an analytical function and construct a generalized self-similar solution. The developed algorithm is implemented and tested on a task set.
Management of thermal process for polyethylene gas pipes welding with built-in heater
Authors: Starostin N P , Vasileva M A , Ammosova O A 
Published: December 2019

Abstract
Based on the thermal process control, rapid welding technology for polyethylene pipes with built-in heater in the open air at temperatures below standard is proposed. Technological parameters of welding are determined by calculation from the condition of temperature field dynamics in heat-affected zone according to regularities, that are peculiar to welding at permissible temperatures. The results of determining the welding parameters during electrofusion welding and welding of the saddle branch to the polyethylene pipe of the gas pipeline, as well as the results of tests of the joints obtained by the proposed welding technology are presented.
IDENTIFICATION OF HEAT EXCHANGE BOUNDARY CONDITIONS AT VARIOUS NATURAL AND TECHNOGENIC FACTORS
Authors: Vinokurova T.A , Permyakov P.P 
Published: December 2019

Abstract
The development of permafrost areas requires reliable and long-term projected estimates in a changing climate and man-made impacts. Dangerous natural and man-made factors, such as snowfall, infiltration of precipitation, ice, thermokarst, etc., interact with the ground and determine the stability of the territories of the cryolithozone. In this regard, the work is devoted to the development of new algorithms and software for identifying the boundary conditions on the surface of frozen soil, taking into account the actual process of freezing and thawing of the pore solution of the soil.
A physical-biogeochemical mechanism for negative feedback between marsh crabs and carbon storage
Authors: Guimond Julia A , Seyfferth Angelia L , Moffett Kevan B , Michael Holly A 
Published: December 2019

Abstract
Tidal marshes are valuable global carbon sinks, yet large uncertainties in coastal marsh carbon budgets and mediating mechanisms limit our ability to estimate fluxes and predict feedbacks with global change. To improve mechanistic understanding, we assess how net carbon storage is influenced by interactions between crab activity, water movement, and biogeochemistry. We show that crab burrows enhance carbon loss from tidal marsh sediments by physical and chemical feedback processes. Burrows increase near-creek sediment permeability in the summer by an order of magnitude compared to the winter crab dormancy period, promoting carbon-rich fluid exchange between the marsh and creek. Burrows also enhance vertical exchange by increasing the depth of the strongly carbon-oxidizing zone and reducing the capacity for carbon sequestration. Results reveal the mechanism through which crab burrows mediate the movement of carbon through tidal wetlands and highlight the importance of considering burrowing activity when making budget projections across temporal and spatial scales.
Effect of inhaled acetone concentrations on exhaled breath acetone concentrations at rest and during exercise
Authors: Ager Clemens , Mochalski Pawel , King Julian , Mayhew Chris A , Unterkofler Karl 
Published: December 2019

Abstract
Real-time measurements of the differences in inhaled and exhaled, unlabeled and fully deuterated acetone concentration levels, at rest and during exercise, have been conducted using proton transfer reaction mass spectrometry. A novel approach to continuously differentiate between the inhaled and exhaled breath acetone concentration signals is used. This leads to unprecedented fine grained data of inhaled and exhaled concentrations. The experimental results obtained are compared with those predicted using a simple three compartment model that theoretically describes the influence of inhaled concentrations on exhaled breath concentrations for volatile organic compounds with high blood:air partition coefficients, and hence is appropriate for acetone. An agreement between the predicted and observed concentrations is obtained. Our results highlight that the influence of the upper airways cannot be neglected for volatiles with high blood:air partition coefficients, i.e. highly water soluble volatiles.
The Latent-Variable Structure of the Addenbrooke’s Cognitive Examination-Revised
Authors: Connolly Madeleine L , Bowden Stephen C , Simpson Leonie C , Horne Malcolm , McGregor Sarah 
Published: December 2019

Abstract

Objectives
To establish a theoretically justified factor structure for the Addenbrooke’s Cognitive Examination-Revised (ACE-R).

Methods
Our sample comprised 288 patients with Parkinson’s disease (179 men and 109 women). The mean age of participants was 66.66 (SD = 8.93). Confirmatory factor analysis (CFA) was used to evaluate the test developers’ five-factor model of the ACE-R, and alternative models as guided by the Cattell–Horn–Carroll (CHC) theory. Exploratory structural equation modeling (ESEM) was also employed to examine alternative factor structures to ensure that a good candidate model was not overlooked.

Results
A three-factor CHC-guided CFA and a similar three-factor ESEM model both showed acceptable overall fit, and interpretable factor structures. The three-factor CFA model showed two factors of pure CHC constructs: acquired knowledge (Gc), and visuospatial ability (Gv), and one combined factor, namely, long-term memory retrieval, fluency, and working memory (Glr-Gsm). The three-factor ESEM model showed three factors essentially in line with the CFA results.

Conclusion
The three-factor CHC-guided CFA model was selected as the best model to guide clinical interpretation of cognitive variables underlying ACE-R scores.