All issues

The Arctic region contains large hydrocarbon deposits. The presence of different ice formations, such as icebergs, ice hummocks, ice fields, complicates the process of carrying out seismic works on the territory. The last of them, ice fields, bring multiple reflections, spreading all over the surface of ice, into seismogramms. These multiple reflections are necessary to be taken into account while analyzing the seismograms, and geologists should be able to exclude them in order to obtain the reflected waves from the lower geological layers, including hydrocarbon layers.

In this work, we solve the problem of the seismic waves spread in the heterogeneous medium. The systems of equations for the linear elastic medium and for the acoustic medium describe the geological layers. We present the detailed description of the numerical solution of these systems of equations with the help of the grid-characteristic method. The final 1D transfer equations are solved with the use of the Rusanov scheme of the third order of accuracy. In the work, we examine the way of multiple waves decrease in ice by establishing the source of impulse deep into the ice field on border with water. We present the results of computer modelling of the seismic waves spread in geological layers, where the seismic source of impulse is situated on the contact border between ice and water, and also with the seismic source of impulse on the surface of ice for the 3D case. The results of the numerical modelling are presented by wave fields, graphs of the velocity x-components and seismogramms for the two problem formulations. We carry out the analysis of influence of establishing the source of impulse on the border between ice and water on the decrease of the x-components of seismic wave velocities, on seismogramms and on wave fields. As a result, the model, where the seismic source of impulse is situated on the contact border between ice and water, makes worse the final result. The model with the source of impulse on the surface of ice demonstrates a decrease of the x-components of seismic wave velocities.

In a number of fundamental and practical problems, it is necessary to describe the dynamics of the motion of complexshaped particles in a high-speed gas flow. An example is the movement of coal particles behind the front of a strong shock wave during an explosion in a coal mine. The paper is devoted to numerical simulation of the dynamics of translational and rotational motion of a square-shaped body, as an example of a particle of a more complex shape than a round one, in a supersonic flow behind a passing shock wave. The formulation of the problem approximately corresponds to the experiments of Professor V. M. Boiko and Professor S. V. Poplavski (ITAM SB RAS).

Mathematical model is based on the two-dimensional Euler equations, which are solved in a region with varying boundaries. The defining system of equations is integrated using an explicit scheme and the Cartesian grid method which was developed and verified earlier. The computational algorithm at the time integration step includes: determining the step value, calculating the dynamics of the body movement (determining the force and moment acting on the body; determining the linear and angular velocities of the body; calculating the new coordinates of the body), calculating the gas parameters. To calculate numerical fluxes through the edges of the cell intersected by the boundaries of the body, we use a two-wave approximation for solving the Riemann problem and the Steger – Warming scheme.

The movement of a square with a side of 6 mm was initiated by the passage of a shock wave with a Mach number of 3,0 propagating in a flat channel 800 mm long and 60 mm wide. The channel was filled with air at low pressure. Different initial orientation of the square relative to the channel axis was considered. It is found that the initial position of the square with its side across the flow is less stable during its movement than the initial position with a diagonal across the flow. In this case, the calculated results qualitatively correspond to experimental observations. For the intermediate initial positions of a square, a typical mode of its motion is described, consisting of oscillations close to harmonic, turning into rotation with a constant average angular velocity. During the movement of the square, there is an average monotonous decrease in the distance between the center of mass and the center of pressure to zero.

GIS INTEGRO is the geo-information software system forming the basis for the integrated interpretation of geophysical data in researching a deep structure of Earth. GIS INTEGRO combines a variety of computational and analytical applications for the solution of geological and geophysical problems. It includes various interfaces that allow you to change the form of representation of data (raster, vector, regular and irregular network of observations), the conversion unit of map projections, application blocks, including block integrated data analysis and decision prognostic and diagnostic tasks.

The methodological approach is based on integration and integrated analysis of geophysical data on regional profiles, geophysical potential fields and additional geological information on the study area. Analytical support includes packages transformations, filtering, statistical processing, calculation, finding of lineaments, solving direct and inverse tasks, integration of geographic information.

Technology and software and analytical support was tested in solving problems tectonic zoning in scale 1:200000, 1:1000000 in Yakutia, Kazakhstan, Rostov region, studying the deep structure of regional profiles 1:S, 1-SC, 2-SAT, 3-SAT and 2-DV, oil and gas forecast in the regions of Eastern Siberia, Brazil.

The article describes two possible approaches of parallel calculations for data processing 2D or 3D nets in the field of geophysical research. As an example presented realization in the environment of GRID of the application software ZondGeoStat (statistical sensing), which create 3D net model on the basis of data 2d net. The experience has demonstrated the high efficiency of the use of environment of GRID during realization of calculations in field of geophysical researches.

In this work we have developed a new efficient program for the numerical simulation of 3D global chemical transport on an adaptive finite-difference grid which allows us to concentrate grid points in the regions where flow variables sharply change and coarsen the grid in the regions of their smooth behavior, which significantly minimizes the grid size. We represent the adaptive grid with a combination of several dynamic (tree, linked list) and static (array) data structures. The dynamic data structures are used for a grid reconstruction, and the calculations of the flow variables are based on the static data structures. The introduction of the static data structures allows us to speed up the program by a factor of 2 in comparison with the conventional approach to the grid representation with only dynamic data structures.

We wrote and tested our program on a computer with 6 CPU cores. Using the computer microarchitecture simulator gem5, we estimated the scalability property of the program on a significantly greater number of cores (up to 32), using several models of a computer system with the design “computational cores – cache – main memory”. It has been shown that the microarchitecture of a computer system has a significant impact on the scalability property, i.e. the same program demonstrates different efficiency on different computer microarchitectures. For example, we have a speedup of 14.2 on a processor with 32 cores and 2 cache levels, but we have a speedup of 22.2 on a processor with 32 cores and 3 cache levels. The execution time of a program on a computer model in gem5 is 104–105 times greater than the execution time of the same program on a real computer and equals 1.5 hours for the most complex model.

Also in this work we describe how to configure gem5 and how to perform simulations with gem5 in the most optimal way.

We present a novel model for the dynamical trap of the stimulus – response type that mimics human control over dynamic systems when the bounded capacity of human cognition is a crucial factor. Our focus lies on scenarios where the subject modulates a control variable in response to a certain stimulus. In this context, the bounded capacity of human cognition manifests in the uncertainty of stimulus perception and the subsequent actions of the subject. The model suggests that when the stimulus intensity falls below the (blurred) threshold of stimulus perception, the subject suspends the control and maintains the control variable near zero with accuracy determined by the control uncertainty. As the stimulus intensity grows above the perception uncertainty and becomes accessible to human cognition, the subject activates control. Consequently, the system dynamics can be conceptualized as an alternating sequence of passive and active modes of control with probabilistic transitions between them. Moreover, these transitions are expected to display hysteresis due to decision-making inertia.

Generally, the passive and active modes of human control are governed by different mechanisms, posing challenges in developing efficient algorithms for their description and numerical simulation. The proposed model overcomes this problem by introducing the dynamical trap of the stimulus-response type, which has a complex structure. The dynamical trap region includes two subregions: the stagnation region and the hysteresis region. The model is based on the formalism of stochastic differential equations, capturing both probabilistic transitions between control suspension and activation as well as the internal dynamics of these modes within a unified framework. It reproduces the expected properties in control suspension and activation, probabilistic transitions between them, and hysteresis near the perception threshold. Additionally, in a limiting case, the model demonstrates the capability of mimicking a similar subject’s behavior when (1) the active mode represents an open-loop implementation of locally planned actions and (2) the control activation occurs only when the stimulus intensity grows substantially and the risk of the subject losing the control over the system dynamics becomes essential.

Automated urban traffic monitoring systems are widely used to solve various tasks in intelligent transport systems of different regions. They include video enforcement, video surveillance, traffic management system, etc. Effective traffic management and rapid response to traffic incidents require continuous monitoring and analysis of information from these complexes, as well as time series forecasting for further anomaly detection in traffic flow. To increase the forecasting quality, data fusion from different sources is needed. It will reduce the forecasting error, related to possible incorrect values and data gaps. We implemented the approach for short-term and middle-term forecasting of traffic flow (5, 10, 15 min) based on data fusion from video enforcement and video surveillance systems. We made forecasting using different recurrent neural network architectures: LSTM, GRU, and bidirectional LSTM with one and two layers. We investigated the forecasting quality of bidirectional LSTM with 64 and 128 neurons in hidden layers. The input window size (1, 4, 12, 24, 48) was investigated. The RMSE value was used as a forecasting error. We got minimum RMSE = 0.032405 for basic LSTM with 64 neurons in the hidden layer and window size = 24.

The paper considers the process of flow formation in an outflow of a binary gas mixture through a thin slit into vacuum. An approach to modeling the flows of rarefied gas mixtures in the transient regime is proposed based on the direct solution of the Boltzmann kinetic equation, in which the conservative projection method is used to calculate the collision integrals. Calculation formulas are provided; the calculation procedure is described in detail in relation to the flow of a binary gas mixture. The Lennard–Jones potential is used as an interaction potential of molecules. A software modeling environment has been developed that makes it possible to study the flows of gas mixtures in a transitional regime on systems of cluster architecture. Due to the use of code parallelization technologies, an acceleration of calculations by 50–100 times was obtained. Numerical simulation of a two-dimensional outflow of a binary argon-neon gas mixture from a vessel into vacuum through a thin slit is carried out for various values of the Knudsen number. The graphs of the dependence of gas mixture components output flow on time in the process of establishing the flow are obtained. Non-stationary regions of strong separation of gas mixture components, in which the molecular densities ratio reaches 10 or more, were discovered. The discovered effect can have applications in the problem of gas mixtures separation.

This paper formulates and solves a practical problem of data recovery regarding the distribution of languages on regional level in context of China. The necessity of this recovery is related to the problem of the determination of the linguistic diversity indices, which, in turn, are used to analyze empirically and to predict sources of social and economic development as well as to indicate potential conflicts at regional level. We use Ethnologue database and China census as the initial data sources. For every language spoken in China, the data contains (a) an estimate of China residents who claim this language to be their mother tongue, and (b) indicators of the presence of such residents in China provinces. For each pair language/province, we aim to estimate the number of the province inhabitants that claim the language to be their mother tongue. This base problem is reduced to solving an undetermined system of algebraic equations. Given additional restriction that Ethnologue database introduces data collected at different time moments because of gaps in Ethnologue language surveys and accompanying data collection expenses, we relate those data to a single time moment, that turns the initial task to an ’ill-posed’ system of algebraic equations with imprecisely determined right hand side. Therefore, we are looking for an approximate solution characterized by a minimal discrepancy of the system. Since some languages are much less distributed than the others, we minimize the weighted discrepancy, introducing weights that are inverse to the right hand side elements of the equations. This definition of discrepancy allows to recover the required variables. More than 92% of the recovered variables are robust to probabilistic modelling procedure for potential errors in initial data.

An approach to numerical analysis of thermo-hydraulic processes proceeding in a fast-neutron reactor is described in the given article. The description covers physical models, numerical schemes and geometry simplifications accepted in the computational model. Steady-state and dynamic regimes of reactor operation are considered. The steady-state regimes simulate the reactor operation at nominal power. The dynamic regimes simulate the shutdown reactor cooling by means of the heat-removal system.

Simulation of thermo-hydraulic processes is carried out in the FlowVision CFD software. A mathematical model describing the coolant flow in the first loop of the fast-neutron reactor was developed on the basis of the available geometrical model. The flow of the working fluid in the reactor simulator is calculated under the assumption that the fluid density does not depend on pressure, with use a $k–\varepsilon$ turbulence model, with use of a model of dispersed medium, and with account of conjugate heat exchange. The model of dispersed medium implemented in the FlowVision software allowed taking into account heat exchange between the heat-exchanger lops. Due to geometric complexity of the core region, the zones occupied by the two heat exchangers were modeled by hydraulic resistances and heat sources.

Numerical simulation of the coolant flow in the FlowVision software enabled obtaining the distributions of temperature, velocity and pressure in the entire computational domain. Using the model of dispersed medium allowed calculation of the temperature distributions in the second loops of the heat exchangers. Besides that, the variation of the coolant temperature along the two thermal probes is determined. The probes were located in the cool and hot chambers of the fast-neutron reactor simulator. Comparative analysis of the numerical and experimental data has shown that the developed mathematical model is correct and, therefore, it can be used for simulation of thermo-hydraulic processes proceeding in fast-neutron reactors with sodium coolant.

The biological structure is considered as an open nonequilibrium system which properties can be described on the basis of kinetic equations. New problems with nonequilibrium boundary conditions are introduced. The nonequilibrium distribution tends gradually to an equilibrium state. The region of spatial inhomogeneity has a scale depending on the rate of mass transfer in the open system and the characteristic time of metabolism. In the proposed approximation, the internal energy of the motion of molecules is much less than the energy of translational motion. Or in other terms we can state that the kinetic energy of the average blood velocity is substantially higher than the energy of chaotic motion of the same particles. We state that the relaxation problem models a living system. The flow of entropy to the system decreases in downstream, this corresponds to Shrödinger’s general ideas that the living system “feeds on” negentropy. We introduce a quantity that determines the complexity of the biosystem, more precisely, this is the difference between the nonequilibrium kinetic entropy and the equilibrium entropy at each spatial point integrated over the entire spatial region. Solutions to the problems of spatial relaxation allow us to estimate the size of biosystems as regions of nonequilibrium. The results are compared with empirical data, in particular, for mammals we conclude that the larger the size of animals, the smaller the specific energy of metabolism. This feature is reproduced in our model since the span of the nonequilibrium region is larger in the system where the reaction rate is shorter, or in terms of the kinetic approach, the longer the relaxation time of the interaction between the molecules. The approach is also used for estimation of a part of a living system, namely a green leaf. The problems of aging as degradation of an open nonequilibrium system are considered. The analogy is related to the structure, namely, for a closed system, the equilibrium of the structure is attained for the same molecules while in the open system, a transition occurs to the equilibrium of different particles, which change due to metabolism. Two essentially different time scales are distinguished, the ratio of which is approximately constant for various animal species. Under the assumption of the existence of these two time scales the kinetic equation splits in two equations, describing the metabolic (stationary) and “degradative” (nonstationary) parts of the process.