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Introduction: the paper considers the topical problem of teaching students – future engineers – by computational methods of mathematics. The focus is on developing students̓ necessary professional competencies. Competencies are described in accordance with the Russian Federal State Educational Standard and the international standard by the European Association for Engineering Education SEFI. In order for students to thoroughly study the subject and have a strong professional competence, it is proposed to use a computer-based tutor. The aim of this research is to develop the special methodology of creating the computer-based tutors for teaching mathematical and engineering disciplines to students of technical specialties within the framework of a competence-oriented approach, to compare the effectiveness of classical teaching computational methods by using manual calculations, and training with the involvement of computer-based tutors. The advantages of computer-based tutors were proved in this paper. Materials and Methods: the basis of the research was methods of system analysis and descriptive and analytical methods, primarily experimental. To identify advantages of the proposed approach the methods of empirical research were used (observation and comparison). To prove the efficiency, classical methods of measurement were used. Results: based on the competence approach, a methodology of creating a computer tutor has been developed. It covers most the professional competencies that need to be studied. Also, students are guaranteed to receive the necessary competencies in the right sequence. The research showed that the use of specially designed software, such as Computer-based tutors, in the process of mathematical methods studying connected with the computational procedures allows us to achieve: on the one hand, deep digestion by students (as in using manual calculations), on the other hand to accelerate learning process and increase students motivation. As a result of pedagogical experiment on the use the computer-based tutors the progress in studies has been recorded: the percentage of positive ratings increased from 65 to 88 %. Also, the motivation of students to study mathematics was increased by 12 percent on average. Discussion and Conclusions: the methodology of creation and use of computer-based tutors has high practical significance and allows increasing the effectiveness of teaching mathematics within the competence approach for students of technical specialties. The use of the interactive computer-based tutors focused on mastering professional competencies, is effective for studying mathematical and engineering disciplines by students of technical universities. In particular, a positive effect has been achieved with the introduction of computer-based tutors in the educational process of Kazan National Research Technical University named after A. N. Tupolev-KAI, Kazan, Russia (the University is aimed at training engineers-designers for aerospace industry), Saarland Technical University, Saarbrucken, Germany (the University is focused on training IT engineers), and a number of other Russian and foreign technical universities.

WENO schemes (weighted, essentially non oscillating) are currently having a wide range of applications as approximate high order schemes for discontinuous solutions of partial differential equations. These schemes are used for direct numerical simulation (DNS) and large eddy simmulation in the gas dynamic problems, problems for DNS in MHD and even neutron kinetics. This work is dedicated to clarify some characteristics of WENO schemes and numerical simulation of specific tasks. Results of the simulations can be used to clarify the field of application of these schemes. The first part of the work contained proofs of the approximation properties, stability and convergence of WENO5, WENO7, WENO9, WENO11 and WENO13 schemes. In the second part of the work the modified wave number analysis is conducted that allows to conclude the dispersion and dissipative properties of schemes. Further, a numerical simulation of a number of specific problems for hyperbolic equations is conducted, namely for advection equations (one-dimensional and two-dimensional), Hopf equation, Burgers equation (with low dissipation) and equations of non viscous gas dynamics (onedimensional and two-dimensional). For each problem that is implying a smooth solution, the practical calculation of the order of approximation via Runge method is performed. The influence of a time step on nonlinear properties of the schemes is analyzed experimentally in all problems and cross checked with the first part of the paper. In particular, the advection equations of a discontinuous function and Hopf equations show that the failure of the recommendations from the first part of the paper leads first to an increase in total variation of the solution and then the approximation is decreased by the non-linear dissipative mechanics of the schemes. Dissipation of randomly distributed initial conditions in a periodic domain for one-dimensional Burgers equation is conducted and a comparison with the spectral method is performed. It is concluded that the WENO7-WENO13 schemes are suitable for direct numerical simulation of turbulence. At the end we demonstrate the possibility of the schemes to be used in solution of initial-boundary value problems for equations of non viscous gas dynamics: Rayleigh-Taylor instability and the reflection of the shock wave from a wedge with the formation a complex configuration of shock waves and discontinuities.

It is known that the most important affinor structures on smooth manifolds are almost complex structures, almost product structures, f-structures of Kentaro Yano, and some others. However, a new type of affinor structures was introduced and intensively discussed in differential geometry in the last decade. These are the so-called Golden structures first introduced by M. Crasmareanu and C.-E. Hretcanu using the well-known quadratic equation for the Golden ratio. Since then, a number of papers have been devoted to the study of the integrability of Golden structures, compatible Riemannian metrics and connections, submanifolds in such manifolds, etc. At the same time, invariant Golden structures on homogeneous manifolds have not appeared in these investigations. In this paper, a wide collection of invariant Golden structures on homogeneous generalized symmetric spaces is presented. More precisely, we obtained a complete description of all canonical Golden structures on homogeneous k-symmetric spaces. A remarkable feature of these structures is that all of them are invariant with respect to both the acting Lie group as well as the generalized symmetries of order k of homogeneous k-symmetric spaces., Известно, что наиболее важными аффинорными структурами на гладких многообразиях являются почти комплексные структуры, структуры почти произведения, f-структуры Кентаро Яно и некоторые другие. Однако в последнее десятилетие новый тип аффинорных структур был введен и интенсивно обсуждался в дифференциальной геометрии. Это так называемые золотые структуры, впервые введенные М. Красмареану и К.-Э. Хретчану с использованием хорошо известного квадратного уравнения для золотого сечения. С тех пор ряд работ был посвящен изучению интегрируемости золотых структур, согласованных римановых метрик и связностей, подмногообразий в таких многообразиях и т.д. В то же время инвариантные золотые структуры на однородных многообразиях в этих исследованиях не появлялись. В данной статье предъявлен обширный класс инвариантных золотых структур на однородных обобщенных симметрических пространствах. Более точно, мы получили полное описание всех канонических золотых структур на однородных k-симметричных пространствах. Примечательной особенностью этих структур является то, что все они инвариантны как относительно действующей группы Ли, так и относительно обобщенных симметрий порядка k однородных k-симметрических пространств.

One of the most important goals of the state is to increase the country’s economic growth rate, including achieving high economic growth indicators such as the level of inflation and unemployment. The current situation in the Russian Federation requires a comprehensive approach from the authorities: within the country to increase the level of welfare of citizens, outside its borders-to preserve and increase competitiveness. This paper presents a retrospective analysis of economic growth rates from 1992 to 2019. Having studied the Russian experience of applying measures and tools of budget policy, the authors identified the most effective tax and budget tools. Best practices have shown the most significant effectiveness in such tax instruments as moderately progressive taxation of personal income, reducing the basic tax rate for indirect taxes, and expanding the practice of applying the simplified tax system. Among the budgetary instruments, the following have shown high efficiency: an increase in expenditures of the budget system budgets for basic and applied scientific research, an increase in budget investments in the industry that contribute to subsequent multiplicative growth, and an increase in expenditures of the budget system budgets for vocational training, retraining and advanced training of the working population.

Social networks have firmly entered the lives of billions of global Internet users worldwide. They communicate in social networks, play online games, make purchases, organise online events — exchange content from all walks of life [1, 2]. The most popular and well-known services in Russia are Vkontakte (vk.com), Youtube.com, Facebook.com, Odnoklassniki (Ok.ru), etc. The interfaces of such platforms allo — fake accounts. In this paper, we propose an approach to detect bots using the LiveJournal social network as an example. For this, we investigated the characteristics of the user’s egograph and performed a comparative analysis of the results of the classification algorithms.

The aim of the article is to substantiate the possibility of using the performance indicator designed according to the author’s methodology along with other indicators characterizing functioning of socio-economic systems. The performance indicator is defined as the ratio of normalized and standardized actual results to expected values which are calculated by the model of the relationship of effective signs and state and impact factors. The model is a production function, whose parameters can be defined by factor analysis of dependencies. To substantiate the presented indicator the author carries out a comparative analysis of its statistical dependence with the indicators of technical efficiency calculated using the stochastic boundary method. The paper considers 12 different variants which differ in the type of distributing the random component, which characterizes the inefficiency of the system; methods of calculating technical efficiency, as well as the presentation of data (pooled and panel data). As a basic model, the power multiplicative model in the form of Cobb-Douglas is used, which includes the volume of gross regional product, the cost of fixed assets, the average annual number of employees in economy and the cost of technological innovation taking into account inflation. The information base of the research is data on regions of the Central Federal district for 2007–2016. For the considered variants the relationships between the proposed performance indicator and other indicators considered were statistically significant, which gives reason to use it as a private indicator for analyzing functioning of socio-economic systems. The performance indicator can be used as a tool to analyze and compare functioning of socio-economic systems operating in different conditions.

Let $M$ be a compact two-dimensional manifold and, $f \in C^{\infty}(M,\mathbb{R})$ be a Morse function, and $\Gamma_f$ be its Kronrod-Reeb graph. Denote by $\mathcal{O}_{f}=\{f \circ h \mid h \in \mathcal{D}\}$ the orbit of $f$ with respect to the natural right action of the group of diffeomorphisms $\mathcal{D}$ on $C^{\infty}(M,\mathbb{R})$, and by $\mathcal{S}(f)=\{h\in\mathcal{D} \mid f \circ h = f\}$ the corresponding stabilizer of this function. It is easy to show that each $h\in\mathcal{S}(f)$ induces a homeomorphism of $\Gamma_f$. Let also $\mathcal{D}_{\mathrm{id}}(M)$ be the identity path component of $\mathcal{D}(M)$, $\mathcal{S}'(f)= \mathcal{S}(f) \cap \mathcal{D}_{\mathrm{id}}(M)$ be group of diffeomorphisms of $M$ preserving $f$ and isotopic to identity map, and $G_f$ be the group of homeomorphisms of the graph $\Gamma_f$ induced by diffeomorphisms belonging to $\mathcal{S}'(f)$. This group is one of the key ingredients for calculating the homotopy type of the orbit $\mathcal{O}_{f}$. Recently the authors described the structure of groups $G_f$ for Morse functions on all orientable surfaces distinct from $2$-torus $T^2$ and $2$-sphere $S^2$. The present paper is devoted to the case $M=S^{2}$. In this situation $\Gamma_f$ is always a tree, and therefore all elements of the group $G_f$ have a common fixed subtree $\mathrm{Fix}(G_f)$, which may even consist of a unique vertex. Our main result calculates the groups $G_f$ for all Morse functions $f:S^{2}\to\mathbb{R}$ whose fixed subtree $\mathrm{Fix}(G_f)$ consists of more than one point., Comment: 5 pages

We consider an application of the Message Passing Interface (MPI) technology for parallelization of the program code which solves equation of the linear elasticity theory. The solution of this equation describes the propagation of elastic waves in demormable rigid bodies. The solution of such direct problem of seismic wave propagation is of interest in seismics and geophysics. Our implementation of solver uses grid-characteristic method to make simulations. We consider technique to reduce time of communication between MPI processes during the simulation. This is important when it is necessary to conduct modeling in complex problem formulations, and still maintain the high level of parallelism effectiveness, even when thousands of processes are used. A solution of the problem of effective communication is extremely important when several computational grids with arbirtrary geometry of contacts between them are used in the calculation. The complexity of this task increases if an independent distribution of the grid nodes between processes is allowed. In this paper, a generalized approach is developed for processing contact conditions in terms of nodes reinterpolation from a given section of one grid to a certain area of the second grid. An efficient way of parallelization and establishing effective interprocess communications is proposed. For provided example problems we provide wave fileds and seismograms for both 2D and 3D formulations. It is shown that the algorithm can be realized both on Cartesian and on structured (curvilinear) computational grids. The considered statements demonstrate the possibility of carrying out calculations taking into account the surface topographies and curvilinear geometry of curvilinear contacts between the geological layers. Application of curvilinear grids allows to obtain more accurate results than when calculating only using Cartesian grids. The resulting parallelization efficiency is almost 100% up to 4096 processes (we used 128 processes as a basis to find efficiency). With number of processes larger than 4096, an expected gradual decrease in efficiency is observed. The rate of decline is not great, so at 16384 processes the parallelization efficiency remains at 80%.

The study of non-stationary rarefied gas flows is, currently, attracting a great deal of attention. Such an interest arises from creating the pulsed jets used for deposition of thin films and special coatings on the solid surfaces. However, the problems of non-stationary rarefied gas flows are still understudied because of their large computational complexity. The paper considers the computational aspects of investigating non-stationary movement of gas reflected from a wall and flowing through a suddenly formed gap. The study objective is to analyse the possible numerical kinetic approaches to solve such problems and identify the difficulties in their solving. When modeling the gas flows in strong rarefaction one should consider the Boltzmann kinetic equation, but its numerical implementation is rather time-consuming. In order to use more simple approaches based, for example, on approximation kinetic equations (Ellipsoidal-Statistical model, Shakhov model), it is important to estimate the difference between the solutions of the model equations and of the Boltzmann equation. For this purpose, two auxiliary problems are considered, namely reflection of the gas flow from the wall and outflow of the free jet into the rarefied background gas.A numerical solution of these problems shows a weak dependence of the solution on the type of the collision operator in the rarefied region, but at the same time a strong dependence of a behavior of the macro-parameters on the velocity grid step. The detailed velocity grid is necessary to avoid a non-monotonous behavior of the macro-parameters caused by so-called ray effect. To reduce computational costs of the detailed velocity grid solution, a hybrid method based on the synthesis of model equations and the Boltzmann equation is proposed. Such an approach can be promising since it reduces the domain in which the Boltzmann collision integral should be used.The article presents the results obtained using two different software packages, namely a Unified Flow Solver (UFS) [13] and a Nesvetay 3D software complex [14-15]. Note that the UFS uses the discrete ordinate method for velocity space on a uniform grid and a hierarchical adaptive mesh refinement in physical space. The possibility to calculate both the Boltzmann equation and the model equations is realized. The Nesvetay 3D software complex was created to solve the Shakhov model equation (S-model) for calculations based on non-structured non-uniform grids, both in velocity space and in physical one.

A numerically stable direct multiplicative method for solving systems of linear equations that takes into account the sparseness of matrices presented in a packed form is considered. The advantage of the method is the calculation of the Cholesky factors for a positive definite matrix of the system of equations and its solution within the framework of one procedure. And also in the possibility of minimizing the filling of the main rows of multipliers without losing the accuracy of the results, and no changes are made to the position of the next processed row of the matrix, which allows using static data storage formats. The solution of the system of linear equations by a direct multiplicative algorithm is, like the solution with LU-decomposition, just another scheme for implementing the Gaussian elimination method. The calculation of the Cholesky factors for a positive definite matrix of the system and its solution underlies the construction of a new mathematical formulation of the unconditional problem of quadratic programming and a new form of specifying necessary and sufficient conditions for optimality that are quite simple and are used in this paper to construct a new mathematical formulation for the problem of quadratic programming on a polyhedral set of constraints, which is the problem of finding the minimum distance between the origin ordinate and polyhedral boundary by means of a set of constraints and linear algebra dimensional geometry. To determine the distance, it is proposed to apply the known exact method based on solving systems of linear equations whose dimension is not higher than the number of variables of the objective function. The distances are determined by the construction of perpendiculars to the faces of a polyhedron of different dimensions. To reduce the number of faces examined, the proposed method involves a special order of sorting the faces. Only the faces containing the vertex closest to the point of the unconditional extremum and visible from this point are subject to investigation. In the case of the presence of several nearest equidistant vertices, we investigate a face containing all these vertices and faces of smaller dimension that have at least two common nearest vertices with the first face.

We consider one of the problems of transport modelling - searching the equilibrium distribution of traffic flows in the network. We use the classic Beckmans model to describe time costs and flow distribution in the network represented by directed graph. Meanwhile agents behavior is not completely rational, what is described by the introduction of Markov logit dynamics: any driver selects a route randomly according to the Gibbs distribution taking into account current time costs on the edges of the graph. Thus, the problem is reduced to searching of the stationary distribution for this dynamics which is a stochastic Nash - Wardrope equilibrium in the corresponding population congestion game in the transport network. Since the game is potential, this problem is equivalent to the problem of minimization of some functional over flows distribution. The stochasticity is reflected in the appearance of the entropy regularization, in contrast to non-stochastic case. The dual problem is constructed to obtain a solution of the optimization problem. The universal primal-dual gradient method is applied. A major specificity of this method lies in an adaptive adjustment to the local smoothness of the problem, what is most important in case of the complex structure of the objective function and an inability to obtain a prior smoothness bound with acceptable accuracy. Such a situation occurs in the considered problem since the properties of the function strongly depend on the transport graph, on which we do not impose strong restrictions. The article describes the algorithm including the numerical differentiation for calculation of the objective function value and gradient. In addition, the paper represents a theoretical estimate of time complexity of the algorithm and the results of numerical experiments conducted on a small American town.

We consider a numerically stable direct multiplicative algorithm of solving linear equations systems, which takes into account the sparseness of matrices presented in a packed form. The advantage of the algorithm is the ability to minimize the filling of the main rows of multipliers without losing the accuracy of the results. Moreover, changes in the position of the next processed row of the matrix are not made, what allows using static data storage formats. Linear system solving by a direct multiplicative algorithm is, like the solving with $LU$-decomposition, just another scheme of the Gaussian elimination method implementation. In this paper, this algorithm is the basis for solving the following problems: Problem 1. Setting the descent direction in Newtonian methods of unconditional optimization by integrating one of the known techniques of constructing an essentially positive definite matrix. This approach allows us to weaken or remove additional specific difficulties caused by the need to solve large equation systems with sparse matrices presented in a packed form. Problem 2. Construction of a new mathematical formulation of the problem of quadratic programming and a new form of specifying necessary and sufficient optimality conditions. They are quite simple and can be used to construct mathematical programming methods, for example, to find the minimum of a quadratic function on a polyhedral set of constraints, based on solving linear equations systems, which dimension is not higher than the number of variables of the objective function. Problem 3. Construction of a continuous analogue of the problem of minimizing a real quadratic polynomial in Boolean variables and a new form of defining necessary and sufficient conditions of optimality for the development of methods for solving them in polynomial time. As a result, the original problem is reduced to the problem of finding the minimum distance between the origin and the angular point of a convex polyhedron, which is a perturbation of the $n$-dimensional cube and is described by a system of double linear inequalities with an upper triangular matrix of coefficients with units on the main diagonal. Only two faces are subject to investigation, one of which or both contains the vertices closest to the origin. To calculate them, it is sufficient to solve $4n - 4$ linear equations systems and choose among them all the nearest equidistant vertices in polynomial time. The problem of minimizing a quadratic polynomial is $NP$-hard, since an $NP$-hard problem about a vertex covering for an arbitrary graph comes down to it. It follows therefrom that $P = NP$, which is based on the development beyond the limits of integer optimization methods.

In this paper we consider the controlled motion of a helical body with three blades in an ideal fluid, which is executed by rotating three internal rotors. We set the problem of selecting control actions, which ensure the motion of the body near the predetermined trajectory. To determine controls that guarantee motion near the given curve, we propose methods based on the application of hybrid genetic algorithms (genetic algorithms with real encoding and with additional learning of the leader of the population by a gradient method) and artificial neural networks. The correctness of the operation of the proposed numerical methods is estimated using previously obtained differential equations, which define the law of changing the control actions for the predetermined trajectory. In the approach based on hybrid genetic algorithms, the initial problem of minimizing the integral functional reduces to minimizing the function of many variables. The given time interval is broken up into small elements, on each of which the control actions are approximated by Lagrangian polynomials of order 2 and 3. When appropriately adjusted, the hybrid genetic algorithms reproduce a solution close to exact. However, the cost of calculation of 1 second of the physical process is about 300 seconds of processor time. To increase the speed of calculation of control actions, we propose an algorithm based on artificial neural networks. As the input signal the neural network takes the components of the required displacement vector. The node values of the Lagrangian polynomials which approximately describe the control actions return as output signals . The neural network is taught by the well-known back-propagation method. The learning sample is generated using the approach based on hybrid genetic algorithms. The calculation of 1 second of the physical process by means of the neural network requires about 0.004 seconds of processor time, that is, 6 orders faster than the hybrid genetic algorithm. The control calculated by means of the artificial neural network differs from exact control. However, in spite of this difference, it ensures that the predetermined trajectory is followed exactly.

The paper deals with the optimal control problem, including the linear parabolic equation as a state problem. Pointwise constraints are imposed on the control function. The objective functional involves the observation function in the entire space-time domain. The optimal control problem is approximated by a finite dimensional problem with mesh approximation of the state equation by the explicit (forward Euler) mesh scheme with variable time steps. The existence of unique solutions for the continuous and mesh optimal control problems is proved. The Uzawa-type iterative method is used for solving the finite dimensional optimal control problem. The results of numerical experiments are presented.