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Comets and asteroids are recognized by the scientists and the governments of all countries in the world to be one of the most significant threats to the development and even the existence of our civilization. Preventing this threat includes studying the motion of large meteors through the atmosphere that is accompanied by various physical and chemical phenomena. Of particular interest to such studies are the meteors whose trajectories have been recorded and whose fragments have been found on Earth. Here, we study one of such cases. We develop a model for the motion and destruction of natural bodies in the Earth’s atmosphere, focusing on the Benešov bolid (EN070591), a bright meteor registered in 1991 in the Czech Republic by the European Observation System. Unique data, that includes the radiation spectra, is available for this bolid. We simulate the aeroballistics of the Benešov meteoroid and of its fragments, taking into account destruction due to thermal and mechanical processes. We compute the velocity of the meteoroid and its mass ablation using the equations of the classical theory of meteor motion, taking into account the variability of the mass ablation along the trajectory. The fragmentation of the meteoroid is considered using the model of sequential splitting and the statistical stress theory, that takes into account the dependency of the mechanical strength on the length scale. We compute air flows around a system of bodies (shards of the meteoroid) in the regime where mutual interplay between them is essential. To that end, we develop a method of simulating air flows based on a set of grids that allows us to consider fragments of various shapes, sizes, and masses, as well as arbitrary positions of the fragments relative to each other. Due to inaccuracies in the early simulations of the motion of this bolid, its fragments could not be located for about 23 years. Later and more accurate simulations have allowed researchers to locate four of its fragments rather far from the location expected earlier. Our simulations of the motion and destruction of the Benešov bolid show that its interaction with the atmosphere is affected by multiple factors, such as the mass and the mechanical strength of the bolid, the parameters of its motion, the mechanisms of destruction, and the interplay between its fragments.

This paper is devoted to the application of the method of numerical solution of the Boltzmann equation for the solution of the problem of modeling the behavior of radionuclides in the cavity of the interelectric gap of a multielement electrogenerating channel. The analysis of gas-kinetic processes of thermionic converters is important for proving the design of the power-generating channel. The paper reviews two constructive schemes of the channel: with one- and two-way withdrawal of gaseous fission products into a vacuum-cesium system. The analysis uses a two-dimensional transport equation of the second-order accuracy for the solution of the left-hand side and the projection method for solving the right-hand side — the collision integral. In the course of the work, a software package was implemented that makes it possible to calculate on the cluster architecture by using the algorithm of parallelizing the left-hand side of the equation; the paper contains the results of the analysis of the dependence of the calculation efficiency on the number of parallel nodes. The paper contains calculations of data on the distribution of pressures of gaseous fission products in the gap cavity, calculations use various sets of initial pressures and flows; the dependency of the radionuclide pressure in the collector region was determined as a function of cesium pressures at the ends of the gap. The tests in the loop channel of a nuclear reactor confirm the obtained results.

The study of complex processes in various spheres of human activity is traditionally based on the use of mathematical models. In modern conditions, the development and application of such models is greatly simplified by the presence of high-speed computer equipment and specialized tools that allow, in fact, designing models from pre-prepared modules. Despite this, the known problems associated with ensuring the adequacy of the model, the reliability of the original data, the implementation in practice of the simulation results, the excessively large dimension of the original data, the joint application of sufficiency heterogeneous mathematical models in terms of complexity and integration of the simulated processes are becoming increasingly important. The more critical may be the external constraints imposed on the value of the optimized functional, and often unattainable within the framework of the constructed model. It is logical to assume that in order to fulfill these restrictions, a purposeful transformation of the original model is necessary, that is, the transition to a mathematical model with a deliberately improved solution. The new model will obviously have a different internal structure (a set of parameters and their interrelations), as well as other formats (areas of definition) of the source data. The possibilities of purposeful change of the initial model investigated by the authors are based on the realization of the idea of strategic reflection. The most difficult in mathematical terms practical implementation of the author's idea is the use of simulation models, for which the algorithms for finding optimal solutions have known limitations, and the study of sensitivity in most cases is very difficult. On the example of consideration of rather standard discrete- event simulation model the article presents typical methodological techniques that allow ranking variable parameters by sensitivity and, in the future, to expand the scope of definition of variable parameter to which the simulation model is most sensitive. In the transition to the “improved” model, it is also possible to simultaneously exclude parameters from it, the influence of which on the optimized functional is insignificant, and vice versa — the introduction of new parameters corresponding to real processes into the model.

The simplest and most desirable method of traffic signal control is precalculated regulation, when the parameters of the traffic light object operation are calculated in advance and activated in accordance to a schedule. This work proposes a method of forming a signal plan that allows one to calculate the control programs and set the period of their activity. Preparation of initial data for the calculation includes the formation of a time series of daily traffic intensity with an interval of 15 minutes. When carrying out field studies, it is possible that part of the traffic intensity measurements is missing. To fill up the missing traffic intensity measurements, the spline interpolation method is used. The next step of the method is to calculate the daily set of signal plans. The work presents the interdependencies, which allow one to calculate the optimal durations of the control cycle and the permitting phase movement and to set the period of their activity. The present movement control systems have a limit on the number of control programs. To reduce the signal plans' number and to determine their activity period, the clusterization using the $k$-means method in the transport phase space is introduced In the new daily signal plan, the duration of the phases is determined by the coordinates of the received cluster centers, and the activity periods are set by the elements included in the cluster. Testing on a numerical illustration showed that, when the number of clusters is 10, the deviation of the optimal phase duration from the cluster centers does not exceed 2 seconds. To evaluate the effectiveness of the developed methodology, a real intersection with traffic light regulation was considered as an example. Based on field studies of traffic patterns and traffic demand, a microscopic model for the SUMO (Simulation of Urban Mobility) program was developed. The efficiency assessment is based on the transport losses estimated by the time spent on movement. Simulation modeling of the multiprogram control of traffic lights showed a 20% reduction in the delay time at the traffic light object in comparison with the single-program control. The proposed method allows automation of the process of calculating daily signal plans and setting the time of their activity.

The article describes an improved paired comparison method, which systematizes in tables the rules of logical conclusions and formulas of checking indices for comparison of technical systems. To achieve this goal, the authors formulate rational rules of logical conclusions in making a paired comparison of the systems. In addition, for the purpose of consistency check of the results of the assessment, the authors introduce parameters such as «the number of scores gained by one system» and «systems’ quality index»; moreover, they design corresponding calculation formulas. For the purposes of practical application of this method to design computer programs, the authors propose to use formalized variants of interconnected tables: a table for processing and systematization of expert information, a table of possible logical conclusions based on the results of comparison of a set number of technical systems and a table of check values in the paired comparison method used in quality assessment of a definite number of technical systems. These tables allow one to organize procedures of the information processing in a more rational way and to predominantly exclude the influence of mistakes on the results of quality assessment of technical systems at the stage of data input. The main positive effect from the implementation of the paired comparison method is observed in a considerable reduction of time and resources needed to organize experts work, process expert information, and to prepare and conduct distant interviews with experts (on the Internet or a local computer network of an organization). This effect is achieved by a rational use of input data of the quality of the systems to be assessed. The proposed method is applied to computer programs used in assessing the effectiveness and stability of large technical systems.

The paper presents the results of numerical simulation of different-temperature water flows turbulent mixing in a T-junctions in the FlowVision software package. The article describes in detail an experimental stand specially designed to obtain boundary conditions that are simple for most computational fluid dynamics software systems. Values of timeaveraged temperatures and velocities in the control sensors and planes were obtained according to the test results. The article presents the system of partial differential equations used in the calculation describing the process of heat and mass transfer in a liquid using the Smagorinsky turbulence model. Boundary conditions are specified that allow setting the random velocity pulsations at the entrance to the computational domain. Distributions of time-averaged water velocity and temperature in control sections and sensors are obtained. The simulation is performed on various computational grids, for which the axes of the global coordinate system coincide with the directions of hot and cold water flows. The possibility for FlowVision PC to construct a computational grid in the simulation process based on changes in flow parameters is shown. The influence of such an algorithm for constructing a computational grid on the results of calculations is estimated. The results of calculations on a diagonal grid using a beveled scheme are given (the direction of the coordinate lines does not coincide with the direction of the tee pipes). The high efficiency of the beveled scheme is shown when modeling flows whose general direction does not coincide with the faces of the calculated cells. A comparison of simulation results on various computational grids is carried out. The numerical results obtained in the FlowVision PC are compared with experimental data and calculations performed using other computing programs. The results of modeling turbulent mixing of water flow of different temperatures in the FlowVision PC are closer to experimental data in comparison with calculations in CFX ANSYS. It is shown that the application of the LES turbulence model on relatively small computational grids in the FlowVision PC allows obtaining results with an error within 5%.

The paper presents the results of the fundamental research directed on the theoretical study and computer simulation of peculiarities of the quasi-harmonic signal’s phase statistical distribution. The quasi-harmonic signal is known to be formed as a result of the Gaussian noise impact on the initially harmonic signal. By means of the mathematical analysis the formulas have been obtained in explicit form for the principle characteristics of this distribution, namely: for the cumulative distribution function, the probability density function, the likelihood function. As a result of the conducted computer simulation the dependencies of these functions on the phase distribution parameters have been analyzed. The paper elaborates the methods of estimating the phase distribution parameters which contain the information about the initial, undistorted signal. It has been substantiated that the task of estimating the initial value of the phase of quasi-harmonic signal can be efficiently solved by averaging the results of the sampled measurements. As for solving the task of estimating the second parameter of the phase distribution, namely — the parameter, determining the signal level respectively the noise level — a maximum likelihood technique is proposed to be applied. The graphical illustrations are presented that have been obtained by means of the computer simulation of the principle characteristics of the phase distribution under the study. The existence and uniqueness of the likelihood function’s maximum allow substantiating the possibility and the efficiency of solving the task of estimating signal’s level relative to noise level by means of the maximum likelihood technique. The elaborated method of estimating the un-noised signal’s level relative to noise, i. e. the parameter characterizing the signal’s intensity on the basis of measurements of the signal’s phase is an original and principally new technique which opens perspectives of usage of the phase measurements as a tool of the stochastic data analysis. The presented investigation is meaningful for solving the task of determining the phase and the signal’s level by means of the statistical processing of the sampled phase measurements. The proposed methods of the estimation of the phase distribution’s parameters can be used at solving various scientific and technological tasks, in particular, in such areas as radio-physics, optics, radiolocation, radio-navigation, metrology.

Scheduling computational workflows represented by directed acyclic graphs (DAGs) is crucial in many areas of computer science, such as cloud/edge tasks with distributed workloads and data mining. The complexity of online DAG scheduling is compounded by the large number of computational nodes, data transfer delays, heterogeneity (by type and processing power) of executors, precedence constraints imposed by DAG, and the nonuniform arrival of tasks. This paper introduces the Multi-Agent Local Voting Protocol (MLVP), a novel approach focused on dynamic load balancing for DAG scheduling in heterogeneous computing environments, where executors are represented as agents. The MLVP employs a local voting protocol to achieve effective load distribution by formulating the problem as a differentiated consensus achievement. The algorithm calculates an aggregated DAG metric for each executor-node pair based on node dependencies, node availability, and executor performance. The balance of these metrics as a weighted sum is optimized using a genetic algorithm to assign tasks probabilistically, achieving efficient workload distribution via information sharing and reaching consensus among the executors across the system and thus improving makespan. The effectiveness of the MLVP is demonstrated through comparisons with the state-of-the-art DAG scheduling algorithm and popular heuristics such as DONF, FIFO, Min- Min, and Max-Min. Numerical simulations show that MLVP achieves makepsan improvements of up to 70% on specific graph topologies and an average makespan reduction of 23.99% over DONF (state-of-the-art DAG scheduling heuristic) across randomly generated diverse set of DAGs. Notably, the algorithm’s scalability is evidenced by enhanced performance with increasing numbers of executors and graph nodes.

In this paper we present a mathematical model and numerical results on a propagation of the combustion front of the SHS compound, where the rate of chemical reaction at each point of the SHS sample is determined by solving the problem of diffusion and chemical reaction in the reaction cell. We obtained the dependence of the combustion front on the size of the average element of a heterogeneous structure with different values of the diffusion intensity. These dependences agree qualitatively with the experimental data. We studied the effect of activation energy for diffusion on the propagation velocity of combustion front. It is revealed the propagation of the combustion front transforms to an oscillatory regime at increase in activation energy of diffusion. A transition boundary of the combustion front propagation from the steady-state regime to the oscillatory one is defined.

In this paper the problem of automated building of a citation graph from a collection of scientific documents is considered as a sequence of machine learning tasks. The overall data processing technology is described which consists of six stages: preprocessing, metainformation extraction, bibliography lists extraction, splitting bibliography lists into separate bibliography records, standardization of each bibliography record, and record linkage. The goal of this paper is to provide a survey of approaches and algorithms suitable for each stage, motivate the choice of the best combination of algorithms, and adapt some of them for multilingual bibliographies processing. For some of the tasks new algorithms and heuristics are proposed and evaluated on the mixed English and Russian documents corpora.