bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Efficiency in Municipalities
Authors: Boyko Е. Е. , Byk F. L. , Ilyushin P. V. , Myshkina L. S.
Published: April 2024

A complex analysis of heat supply systems from the standpoint of reliability, efficiency and environmental friendliness has been carried out. It has been revealed that in heat supply systems the weakest link in terms of reliability is heat networks. The main number of accidents accompanied by interruption of thermal energy supply occurs on them. The cost and availability are the basis for the efficiency of the primary energy resources used, including: the energy efficiency of technologies, their conversion into useful types of energy, as well as the amount of losses in the transfer of thermal energy to heat receivers. Environmental friendliness is determined by the volume of harmful emissions during the production and transmission of the heat conductor. Methods for improving the indicated properties of heat supply systems are proposed, which is especially important for small, medium and large cities, where boiler houses are the basis of heat supply systems. It is shown that the inclusion of cogeneration sources in the composition of heat supply systems contributes to the growth of their energy efficiency. Peak sources of thermal energy, located in close proximity to heat sinks, can reduce heat losses and increase the reliability of heat networks. With the increase in the availability of electricity, prerequisites arise for the use of electric boilers as peak sources of thermal energy. The proposed changes should be included in the Heat Supply Schemes developed by municipal authorities, which should be supported by the expert community in order to increase the investment attractiveness of the thermal power industry.
Commercialization of Construction and Operation Stages of Large-Scale Underground Accumulators of Gas and Liquid Energy Carriers
Authors: Kazaryan V. A.
Published: April 2024

The article describes the relevant issues associated with the reduction of capex and opex of large-scale underground accumulators of gas and liquid energy carriers by commercializing the stages of their construction and operation. It is shown that during the construction of underground storage, the generated construction brine, which is a waste product, can be a raw material for the creation of products of high consumer value for the country’s economy. Technological schemes for the production of economically useful products in cooperation with the process of constructing underground storage in rock salt deposits and the operation of an underground accumulator of natural gas are presented. All the technological schemes are developed based on highly efficient production of common and technical salt, calcined soda, chlorine, glass, hydrogen (methane-hydrogen mixture), ammonia, carbamide. It is shown that the implementation of the developed schemes of cooperation of technological complexes for the production of essential and useful for the country’s economy products significantly reduces total capital and operational costs and, consequently, the cost of the output product.
Method for Creating Mathematical Models of Heating Nuclear Power Units of Power Plants for Optimization Studies of Autonomous Electric Power Systems
Authors: Kler A. M. , Stepanova E. L. , Zharkov P. V.
Published: April 2024

The authors present a two-stage method for creating mathematical models of cogeneration nuclear power units for optimization studies of autonomous electric power systems. The first stage of the methodology includes the development of a detailed model of a nuclear power unit, which provides a satisfactory accuracy of the description of physical and technological processes, as well as optimization calculations of operating modes. At the second stage, the energy dependencies are built based on the results of optimization calculations of the first stage. Energy dependencies define the boundaries of the region of feasible solutions in the form of polynomials. A simplified mathematical model of a nuclear power unit for optimization studies of autonomous EPS is created using polynomials. To solve the problem of finding a polynomial, a two-step approach is proposed. At the first step, the polynomial coefficients are selected such that the minimum of the maximum value of the modulus of the difference between the function determined using the polynomial and the function determined using the detailed model of the power unit is reached. At the second step, the deviation modules are limited to the value found at the first step, and the sum of the deviation modules is minimized at all points. The two-stage technique developed by the authors is demonstrated on the example of a cogeneration nuclear power unit, which is supposed to be operated in the climatic conditions of the Far North.
New Analytical Solutions of Mathematical Models of Heat Shock of Local Non-Equilibrium Heat Transfer
Authors: Kartashov E. M. , Krylov S. S.
Published: April 2024

The article is devoted to practically new model representations of locally nonequilibrium heat transfer in terms of nonstationary heat conduction for hyperbolic type equations (wave equations), as well as dynamic models of heat shock based on wave equations. The results presented in the article practically open up an independent scientific direction in analytical thermal physics and in the theory of thermal shock, namely: the study of the thermal response of solids of a canonical form of finite sizes to intense heating and cooling under conditions of a locally nonequilibrium heat transfer process. This direction required the development of a special apparatus of operational calculus due to the appearance in analytical solutions of model problems in the image space according to Laplace of non-standard operational images, the originals of which are unknown and are not available in reference books on operational calculus. The presented images are typical for operational solutions of a wide class of generalized boundary value problems for equations of hyperbolic type in the theory of heat conduction, diffusion, hydrodynamics, vibrations, propagation of electricity, thermomechanics and other areas of science and technology. Illustrative examples of analytical solutions of specific model problems of locally nonequilibrium heat transfer and the theory of thermal shock for a finite region are given in both classical and generalized formulations (the latter taking into account the finite rate of heat propagation). The characteristic features of functional structures as analytical solutions of the considered mathematical models are revealed.
Organizing the Rotation of the Body of a Vibration Robot Around the Vertical
Authors: Garbuz M. A. , Dosaev M. Z. , Samsonov V. A.
Published: April 2024

The movement of a vibrating robot, consisting of a body, two homogeneous flywheels, and an unbalance, is considered. A mathematical model of plane-parallel motion is constructed. The principal possibility of unbalance control, which results in the rotation of the robot in the horizontal plane, is shown. The dependences of the body’s rotation angle on the system’s parameters are described. The conditions for a complete stop of the body after rotation are determined. The displacement of the body from the initial position is analyzed.
Synthesis of Parameters of Proportionally-Integral and Proportionally-Integral-Differential Controllers for Stationary Linear Objects with Nonzero Initial Conditions
Authors: Shatov D. V.
Published: April 2024

The problem of the synthesis of proportional-integrating (PI) and proportional-integral-differentiating (PID) controllers in a nonstandard formulation is considered. For a linear one-dimensional control object with nonzero initial conditions, it is required to find a controller that is optimal in the sense of a quadratic functional of the state of the object with a regularization additive in control. The synthesis procedure is a solution of the corresponding quadratic optimization problem using a method similar to the conjugate gradient method (the direction at each step is calculated by the conjugate gradient method, and the step length is calculated by the Armijo rule). Numerical examples illustrate the effectiveness of the proposed algorithm in the synthesis of controllers for models of control objects that are common in practice.
Reducing the Problem of the Modal Control by Output for Stationary Fourth-Order Systems with Two Inputs and Two Outputs to the Control by State for a System with a Single Input
Authors: Zubov N. E. , Lapin A. V.
Published: April 2024

A problem of modal control by output for fourth-order dynamical systems with two inputs and two outputs is presented. For a certain class of such systems, an approach is proposed for reducing the problem under consideration to a control (direct version) or observation (dual version) problem for a system with a single input. The approach is based on two successive similarity transformations of the closed-loop system with a controller by output, which make it possible to reset one of the rows of the controller matrix by state or one of the columns of the observer matrix. The class of systems for which the condition of such zeroing is simultaneously a condition for the existence of an output controller is studied. Theorems on the inequality of the indices of controllability and observability in the system under the conditions presented are proved. A variant of using the well-known Bass–Gura and Ackermann formulas is proposed, which significantly simplifies the symbolic expressions for the controller (observer) in the transformed system. Examples of the application of the proposed approach, both in the direct and in the dual version, are considered. Symbolic calculations in MATLAB validate the results.
Game-Based Interconnected Control of a Group of Unmanned Aerial Vehicles in Conditions of Informational Counteraction
Authors: Boldinov V. A. , Bukhalev V. A. , Skrynnikov A. A.
Published: April 2024

The problem of the game-based control of a group of unmanned aerial vehicles (UAVs) in the conditions of informational counteraction by a group of stationary objects is considered. Two recurrent information-control algorithms are obtained: an algorithm for the interconnected control of a group of UAVs and a jammer control algorithm based on the theory of stochastic multistage games and the theory of systems with a random jump structure (RJS).
Autooscillations of a Multlink Aerodynamic Pendulum
Authors: Golub A. P. , Klimina L. A. , Lokshin B. Ya. , Selyutskiy Yu. D.
Published: April 2024

A multilink pendulum located in a flow is considered. On the last link of the pendulum, a wing is installed, on which the interaction with the flow is concentrated. The dynamics of this system are studied as a potential working element of an oscillatory wind power plant. For different flow velocities, periodic modes are numerically investigated that occur under different numbers of links and different values of the external load. It is shown that the maximum power that can be obtained with a two-link pendulum is greater in a wide range of flow velocities than with pendulums with more than two links. At the same time, pendulums with a large number of links make it possible to obtain considerable power in a wider range of load values than a two-link one.
Methods and Models of Project Resource Management under Uncertainty
Authors: Kosorukov O. A. , Lemtyuzhnikova D. V. , Mishchenko A. V.
Published: April 2024

Methods for optimizing project schedules for the criterion of minimizing the weighted average time of their execution are considered. In the case when the durations of the jobs are given deterministically, an exact and approximate method for solving the problem of choosing the optimal schedule is proposed. If changes in the durations of the jobs are possible, an analytical tool for estimating the stability of the schedules is created both for the situation of interval setting of the durations of the jobs and for the situation of changes in the durations of the jobs under possible disturbances in the external environment. In the event that the durations of the jobs are given stochastically, a mechanism for evaluating the effectiveness of the schedule by two criteria is proposed, and a procedure for the quantitative assessment of the risk of the schedule is proposed.
Quantitative Analysis of Flow Distributions in a Multiuser Telecommunication Network
Authors: Malashenko Yu. E. , Nazarova I. A.
Published: April 2024

Strategies are considered for the distribution of flows over various transmission routes in a multicommodity network model. Estimates of feasible network loads are formed based on the vector of jointly feasible internodal flows. Two distribution strategies are studied. When implementing the first one, the transmitted internodal flows are equal to each other. The second strategy assumes the search for a nondiscriminatory distribution of flows, during the transmission of which equal value resources are achieved. The load created by a certain pair of nodes is understood as the total capacity required to provide the given type of connection. To estimate the minimum specific resources for the transmission of a flow of a certain type, all the shortest paths between the corresponding pair of nodes are constructed. To obtain an upper estimate of resources when connecting each pair of nodes, the maximum single-product flow is calculated along all the network edges. Computational experiments were carried out for networks with different structures that make it possible to carry out a comparative analysis of equalizing distribution strategies when splitting internodal flows for transmission along different routes.
Motion Control of a Multipurpose Laboratory Module with the Use of a Propulsion Unit
Authors: Sumarokov A. V.
Published: April 2024

The motion control of the Nauka Multipurpose Laboratory Module (MLM) during its flight to the International Space Station (ISS) is considered. For maneuvering and angular stabilization, a propulsion system is used as an actuator. In order to ensure simultaneous control of the motion of the center of mass of the spacecraft (SC) and its stabilization with the help of engines at each moment of time, it is necessary to solve the problems of determining the required change in the speed of the SC, choosing the optimal configuration of the engines, and the problem of predicting the motion parameters of the SC. Methods for solving these problems, applied in the development of the control system of the Multipurpose Laboratory Module, are presented. The operability of the described algorithms is confirmed by the results of mathematical modeling on a ground test bench for onboard software and in the course of flight design tests directly during the flight and successful docking on the ISS.
Analytical Synthesis of an Aircraft’s Lateral Motion Control by Output at the Lack of Measurements of Slip and Roll Angles
Authors: Zubov N. E. , Zybin E. Yu. , Lapin A. V.
Published: April 2024

For a linearized fourth-order model describing the lateral motion of an aircraft with two controls, the stabilizing control laws analytical expressions are obtained at the lack of measurements of slip and roll angles. Analytical synthesis is based on a new approach of solving the problem of control by output. In contrast to the traditional Van der Woude approach using multilevel decomposition, the proposed approach is applicable to a wide class of systems with total dimension of control and observation vectors not exceeding the dimension of state vector. A compact formula is presented that determines the matrix of controller by output for a fourth-order dynamic system with two inputs and two outputs, provided that the indices of controllability and observability are not equal to each other. The results of simulation of control processes are given on the example of stabilization of the lateral motion of a hypothetical aircraft.
Direct Lyapunov Method in the Problem of Ensuring the Stability of a Compact Minimum Set of a Dynamic System and the Formation of a Halo-Orbit Near the Lagrange Point L2
Authors: Stepanyants G. A.
Published: April 2024

The efficiency of using the direct Lyapunov method for ensuring the stability of motion in compact invariant sets of finite-dimensional dynamical systems is shown. In the linear model of the restricted three-body problem, the possibility of ensuring the asymptotic stability of the periodic motion of a spacecraft (SC) in the vicinity of the collinear Lagrange point L2 using light pressure forces without the consumption of the working fluid is considered. The required area of control surfaces is estimated depending on the mass of the SC.
Rapid Goal-Setting in Hierarchical Groups of Active Objects: I. Selected Group
Authors: Galikhanov S. K. , Fedunov B. E. , Yunevich N. D.
Published: April 2024

This article studies the problems of rapid goal-setting in hierarchical groups of active (anthropocentric) objects, by which the authors mean, primarily, groups of aircraft, united by the initial and situationally arising missions. A group of objects are assigned a mission before they start functioning. When a group performs the given mission in a deliberately or passively antagonistic environment, the following collision occurs: “Mission stage in progress: immediate threat to the mission.” This forces the group to solve the problem of rapid goal setting. A methodology for solving such problems is created, which entails conducting a system analysis of the subject area to identify the composition and interaction of the tactical-level onboard intelligent systems necessary to solve these problems; the presence of previously developed subject-independent images of the knowledge bases of the identified intelligent systems; and saturation of the knowledge bases of these systems with specific information (the mission being performed, the threat that has arisen, and specific information of the means of counteracting it available at the facilities). The resulting solution to the problem of rapid goal setting at unmanned facilities is immediately sent for implementation, and at facilities with a crew, the solution is implemented only with their consent. An illustrative example of solving a practically significant task of rapid goal-setting in aviation problems is given.
Generalization of the Rutherford Formula and Synthesis of Trajectories with Gravity Assist Maneuvers
Authors: Golubev Yu. F. , Grushevskii A. V. , Koryanov V. V. , Tuchin A. G. , Tuchin D. A.
Published: April 2024

This article studies the development of new effective methods for designing spacecraft (SC) trajectories for missions using the generalization of the Rutherford formula for the scattering of charged particles proposed by the authors for the case of gravitational scattering. For controlled gravity assist maneuvers of SC, a rule is formulated that makes it possible to purposefully create beams of trajectories with specified properties as a result of a gravity assist maneuver. Modifications of this rule are presented that make it possible to implement efficient and reliable beam recurrent procedures for searching for the ballistic scenarios of interplanetary flights. Of particular importance is the synthesis of sequences of gravity assist maneuvers that provide the given change in the asymptotic velocity of the SC relative to the target planet.
Privileged Learning Using Regularization in the Problem of Evaluating the Human Posture
Authors: Kaprielova M. S. , Neichev R. G. , Tikhonova A. D.
Published: April 2024

The problem of evaluating a person’s posture from video data is solved. Various key points of the human body are analyzed. We study the change in the accuracy of a fixed model when using different proportions in the regularization term of the loss function. It is shown that for a fixed number of training epochs, the accuracy of the model differs depending on the selected proportions. In addition, it is shown that the linear correlation between the trajectories of the key points that are part of the regularization term is not the main criterion for predicting the effectiveness of applying the regularization term of the loss function.
On the Skating Motion of a Robot Controlled by an Internal Flywheel
Authors: Klimina L. A. , Shalimova E. S.
Published: April 2024

The motion of an axisymmetric robot controlled by a flywheel mounted on it is considered. It is assumed that the body of the robot is in contact with the plane at three points, while the force of dry anisotropic friction acts at two points, and at the third point the friction is isotropic. The control of the internal flywheel, which ensures the movement of the object in the given direction, is built. The dependence of the average velocity of the center of mass of the robot on the parameters of the system is studied.
New Two-Level Machine Learning Method for Evaluating the Real Characteristics of Objects
Authors: Dokukin A. A. , Sen’ko O. V.
Published: April 2024

A new two-level ensemble regression method, as well as its modifications and application in applied problems, are considered. The key feature of the method is its focus on constructing an ensemble of predictors that approximate the target variable well and, at the same time, consist of algorithms that, if possible, differ from each other in terms of the calculated predictions. The ensemble with the indicated properties at the first stage is constructed through the optimization of a special functional, whose choice is theoretically substantiated in this study. At the second stage, a collective solution is calculated based on the forecasts formed by this ensemble. In addition, some heuristic modifications are described that have a positive effect on the quality of the forecast in applied problems. The effectiveness of the method is confirmed by the results obtained for specific applied problems.
On the Implementation of Information Technology for Refining the Ephemerides of GLONASS Spacecraft Based on the Use of Advanced Intersatellite Measurement Hardware
Authors: Krasil’schikov M. N. , Kruzhkov D. M. , Pasynkov V. V.
Published: April 2024

The necessary conditions for the implementation of information technology, which ensure the autonomy of operation while improving the accuracy of the ephemerides and clocks of the existing midaltitude segment of GLONASS, are substantiated. The discussed technology includes methods and algorithms for improving the accuracy of forecasting and refining the ephemerides of navigation spacecraft (NSC) in an inertial coordinate system, predicting and refining the evolution of the Earth’s rotation parameters, and precise synchronization of onboard clocks. Attention is paid to creation of the necessary conditions for the implementation of the first of these components of the proposed technology, which provides prediction and refinement of the ephemerides in an inertial coordinate system, including in the autonomous mode of satellite constellations. The component is implemented in the form of a block of special procedures for using equipment for measuring distances between satellites. In this case, a number of technical problems and related limitations arise that prevent the successful use of such equipment in solving the problem of NSC ephemerides refinement. The approaches and methods proposed by the authors, which are designed to overcome some of the problems and limitations and, ultimately, to improve the accuracy of the formed estimates of NSC ephemerides based on processing the intersatellite measurements formed using the onboard hardware, are described.
Optimal Finite-Dimensional Controller of the Stochastic Differential Object’s State by Its Output. I. Incomplete Precise Measurements
Authors: Rudenko E. A.
Published: April 2024

The well-known problem of synthesizing the optimal on the average and on given time interval of the inertial control law for a continuous stochastic object if only a part of its state variables are accurately measured is considered. Due to the practical unrealizability of its classical infinite-dimensional Stratonovich-Mortensen solution, it is proposed to limit ourselves to optimizing the structure of a finite-dimensional dynamic controller, whose order is chosen by the user. This finiteness allows using a truncated version of the a posteriori probability density that satisfies a deterministic partial differential integrodifferential equation. Using the Krotov extension principle, sufficient optimality conditions for the structural functions of the controller and the Lagrange–Pontryagin equation for finding their extremals are obtained. It is shown that in particular cases of the absence of measurements, complete measurements and taking into account only the values of incomplete measurements, the proposed controller turns out to be static (inertialess), and the relations for its synthesis coincide with the known ones. For a dynamic controller, algorithms for finding each of its structural functions are given.
Optimization of Longitudinal Motions of an Elastic Rod Using Periodically Distributed Piezoelectric Forces
Authors: Gavrikov A. A. , Kostin G. V.
Published: April 2024

The longitudinal vibrations of an elastic rod controlled by a distributed force, which is applied to individual sections of the rod, are studied. It is assumed that the force varies in space in a piecewise constant manner. Such a mechanical system can be implemented using piezoactuators attached along the rod. The dynamics of the system is determined from the solution of the variational problem following the method of integrodifferential relations. The variational problem is solved analytically. To do this, traveling waves of the d’Alembert type are introduced on the space-time mesh, which determine continuous displacements and a dynamic potential. The latter relates the momentum density and stresses. A control problem is posed under the condition of the weighted minimization of the vibrational energy stored by the rod at the terminal time instant, and the mean potential energy generated by the control actions. The extremal motion and the corresponding control law are found explicitly by solving the Euler–Lagrange equations. As an example, the control capabilities for certain configurations of piezoelectric elements are studied.
Improvement of Intersatellite Measurements Scheduling to Refine the Accuracy of the Ephemerides of Modern and Prospective GLONASS Orbital Segments
Authors: Krasilshchikov M. N. , Kruzhkov D. M. , Marareskul T. A. , Martynov E. A. , Muratov D. S.
Published: April 2024

The information technology developed by the authors to ensure the possibility of operation without downloading information by the ground control complex while improving the accuracy of the ephemerides of the existing global navigation satellite systems (GLONASS) midaltitude segment and its promising additions is described. Achieving the stated goals within the framework of the technology under discussion involves the formation of precise ephemerides by solving the following interrelated tasks: improving the accuracy of determining and predicting the ephemerides of navigation satellites in the inertial coordinate system; improvement of methods and algorithms for forecasting and updating the evolution of the Earth’s rotation parameters onboard satellites; and precise synchronization of onboard clocks. The primary attention is paid to the first of the listed tasks, i.e., prediction and refinement of the ephemerides of navigation satellites in the inertial coordinate system, including in the mode of operation of satellite constellations without updating the ephemerides-temporal information. As a base for its solution, it is proposed to use advanced onboard hardware for intersatellite measurements. The basic limitations related to the implementation of intersatellite measurements and their subsequent processing for both midaltitude and advanced space segments of the GLONASS are discussed. The results of the design-ballistic analysis and processing of real and simulated measurements, as well as the preliminary characteristics of the accuracy of the ephemerides estimates obtained in this case onboard, are presented.
Controlling the Process of Formation of the Scientific and Technological Background in Aircraft Construction Based on the Assessment of a Deficit of Functional Properties of Promising Aircraft
Authors: Anisimov K. S. , Evdokimenkov V. N. , Krasil’shchikov M. N. , Sypalo K. I. , Toporov N. B.
Published: April 2024

The existing experience of the design of aviation technology proves that in a number of cases a promising aircraft (AC) that satisfies the set of requirements cannot be created within the framework of the accumulated scientific and technical groundwork in the field of AC manufacturing. As a result, there is a need to determine priority scientific and technical solutions, whose implementation, under time and financial constraints, will ensure the creation of an AC that meets the stated requirements. It is shown that such a problem can be interpreted as a so-called generalized optimization problem, whose difference from the classical mathematical programming problem lies in the fact that the set of permissible values of flight performance characteristics (FPC) is an additional object of optimization. A constructive algorithm for solving such a problem is proposed, whose capabilities are illustrated using the example of designing a transport ramp aircraft
Analysis of Nodal Multiflows in a Multiuser System with Equalizing Control Strategies
Authors: Malashenko Yu. E. , Nazarova I. A.
Published: April 2024

Within the framework of computational experiments on a mathematical model of a multiuser network communication system, the dynamics of changes in the indicators of the functioning of a telecommunications network are studied. The proposed algorithmic scheme makes it possible to sequentially form component-by-component nondecreasing vectors of permissible outgoing nodal multiflows. The model assumes that the transmission of interstitial flows of different types is carried out simultaneously from all nodes by all nodes along all routes with the minimum number of edges. During the calculations, resources are distributed in equal shares at each step until the network is fully loaded. The results obtained during the experiments make it possible to trace changes in the values of quotas distributed to the nodes for transmitting a certain type of flow. The found vectors of allowable outgoing nodal multiflows can be considered as guaranteed multicriterial estimates of the functioning of a multiuser system. Networks with different structural features and equal total capacity are analyzed. Special diagrams are provided.
On the Prevention of Vibrations in the Problem of the Time-Optimal Control of a System with Two Degrees of Freedom
Authors: Selyutskiy Yu. D. , Formalskii A. M.
Published: April 2024

We study a mechanical system with two degrees of freedom, consisting of two absolutely rigid bodies (material points) connected to each other by a weightless rectilinear viscoelastic rod that can be stretched or compressed. The bodies can move translationally along a fixed straight line. A control force limited in absolute value is applied to one of them, whose vector is directed along the rod. A continuous piecewise-linear control in time, which transfers the system from one equilibrium position to another in a length of time close to the minimum possible time, is constructed. In the absence of viscosity, with the constructed quasi time-optimal control, unwanted vibrations of the bodies are not excited either during the transition process or when it ends. In contrast to the time-optimal relay control, the constructed continuous control is also robust with respect to the uncertainty of the design parameters.
Structural Models for Failure Detection of Moore Finite-State Machines
Authors: Solov’ev V. V.
Published: April 2024

Fault detection is an important task in the design of fault-tolerant state machines. Structural models of Moore finite-state machines are proposed to detect multiple faults in various elements of the finite-state machine and prevent their negative impact on the controlled object. The structural models under consideration make it possible to detect invalid input and output vectors both in each state and for the entire automaton, invalid code of the current and next state of the automaton, and invalid transitions between states. The costs of implementing the proposed structures by area range on average from 3 to 26%, and the speed of the machine either does not change or even increases by an average of 24–30%. Estimates of the area and performance of the proposed structural models of finite-state machines are given, and recommendations for their practical use are given. It is shown that the choice of a suitable structure allows us not to increase the area, and in some cases even leads to an increase in the performance of the finite-state machine.
Optimal Suppression of Oscillations in the Problem of a Spin-Up of a Two-Mass System
Authors: Vasenin S. A. , Reshmin S. A.
Published: April 2024

We consider a controlled mechanical system of many bodies, consisting of a load-bearing disk that rotates around its axis fixed in space, and a carried disk attached to it using weightless elastic elements. The presented bodies are in the same plane. The problem of minimizing the amplitude of radial oscillations is studied. To solve this problem over a sufficiently large interval, two numerical methods are used: the method of successive approximations in the control space and Newton’s method. The properties of the phase trajectories of the system are studied depending on the initial states of the disks. Various disk spin-up modes are detected. Using the smoothing procedure for optimal control, a continuous control is constructed that reduces the amplitude of radial oscillations.
Neural Network Approaches for Recommender Systems
Authors: Zharova M. A. , Tsurkov V. I.
Published: April 2024

Recommender systems are special algorithms that allow users to receive personalized recommendations on topics that interest them. Systems of this kind are widely used in various fields, for example, in e-commerce, provider services, social networks, etc. Together with classical approaches, neural networks have also become popular in recommender systems in recent years, which are gradually replacing traditional methods of collaborative filtering and content-based algorithms. However, neural networks require large computing resources, which often raises questions on whether an increase in quality will be justified and whether there be one at all. The neural network approach in recommender systems—the self-attentive sequential recommendation (SASRec) transformer model from Microsoft Recommenders—is studied and compared with the classic algorithm, the LightFM hybrid model. For training and validation, the data taken from a housing search application are used. It is proposed to use the hit rate as the main metric for comparison. The results of the experiments will help to understand which algorithms have higher accuracy in terms of predictions and recommendations. As an additional part, the clustering of user and object embeddings is considered.
Statistical and Wavelet Transform-Based Study of the Latitudinal Ionospheric Response to an Annular Solar Eclipse on June 21, 2020
Authors: Pundhir Devbrat , Singh Birbal , Singh Rajpal
Published: April 2024

The ionosphere is a very complex and variable part of the atmosphere and it is controlled by solar activity. A solar eclipse is one of the phenomena which depicts a major impact on the ionosphere. In this study, we have analyzed the TEC data of 11 IGS-TEC stations (including one GPS station namely Agra) corresponding to a solar eclipse of June 21, 2020 for the duration of June 07–21, 2020. The TEC variations show lower values on the eclipse’s day in comparison to the other days from the mean of each station except some of the stations like Agra (≈2 TECU), BHR4 (≈1TECU), IISC (≈0.5TECU) have shown the enhanced TEC variations. These results are examined by applying wavelet transform techniques such as continuous wavelet transforms (CWTs), and wavelet decomposition over the average, addition, and multiplication of TEC data of 11 stations for the duration of 9:30 AM to 3:30 PM on the eclipse’s day. These results match very well with our statistical results and depict a better representation of the TEC variations during the solar eclipse. The wavelet decomposition of TEC variation has provided that TEC is affected by solar eclipse globally. These TEC variations are interpreted in terms of the mechanisms available in the literature.
Generation of an Intense Subsurface Current by a Squeal Passing over the Sea
Authors: Serebryany A. N. , Svadkovskiy A. N.
Published: April 2024

The data of an unusual case of measuring the current that occurred during the passage of a squally wind over the sea are presented. The measurements were carried out on October 12, 2011 in the waters of the Black Sea shelf near Gelendzhik within the boundaries from the Golubaya Bay beam to Cape Tolstoy on a yacht equipped with ADCP “Rio Grande 600 kHz”. An unusual intense subsurface current (up to 1 m/s) was revealed, penetrating 8 m deep, generated by a strong squall that passed over the shelf zone.
Evaluation of the Effectiveness and Impact of Wetting the Surface of the Collector Mesh on the Process of Collecting Atmospheric Fog
Authors: Ukolov A. I. , Popova T. N.
Published: April 2024

Fog collectors can be an efficient source of fresh water in areas with constant air advection. A key feature of any collection device is the mesh used to capture the fog droplets. In this paper, we combine a fog collection experiment performed in natural field conditions for meshes with different degrees of wetting of the fibers with a theoretical analysis of the aerodynamics of air near the collector, carried out on the basis of computer simulation of the flow. The obtained overall collection efficiency of a collector grid with a shading coefficient s = 0.2 for the weather conditions of the Kerch Peninsula was ηcoll = 0.045 for a hydrophilic and ηcoll = 0.022 for a superhydrophobic surface. This phenomenon is confirmed by the analysis of the forces acting on the drop and the calculation of the drainage coefficient for two types of coatings. It has been shown that droplets with a volume of up to 1 μL will not fall into the collection trough, but will overcome the cohesion force and return back to the atmosphere. In general, the described technology is simple, economical and does not require energy consumption. Based on the experience of several countries, the effectiveness of a technology can be guaranteed if technical, social and managerial factors are taken into account in its planning and implementation.
Parameterization of Interaction between the Atmosphere and the Urban Surface: Current State and Prospects
Authors: Tarasova M. A. , Varentsov M. I. , Stepanenko V. M.
Published: April 2024

Cities have a significant impact on the environment, forming such microclimatic features as an urban heat island, an increase in the intensity of convective weather events, etc. Numerical models of the atmosphere with an integrated block that describes the interaction between the urbanized surface and the atmosphere – urban parameterization – reproduce well the meteorological features of the urban environment. The review studies on urban parameterizations are mostly outdated, and the recent ones do not fully cover aspects of the methods used in the models to describe physical processes. The paper is devoted to updating information on urban parameterizations, comparing the approaches used in them to describe physical processes and forming proposals for their improvement. Based on the most common urban parameterizations of various levels of complexity, the main groups of physical processes describing “urban surface – atmosphere” interaction are identified. They are the surface energy balance, radiation heat transfer, surface moisture balance, turbulent heat and moisture exchange in the urban canopy, anthropogenic influence on heat and moisture fluxes, radiation and turbulent interaction with urban vegetation. The main approaches to parameterization of physical processes defined within each block are described. Modern trends in the development of urban parameterizations are highlighted: 1) over the past 10 years, parameterizations have become more complicated due to the addition of the building energy model, a three-dimensional structure of urban vegetation, and vertical resolution when calculating turbulent fluxes; 2) at the same time, little attention is paid to revising the original empirical formulas, often obtained on the basis of single field or laboratory e-xperiments. Ways to improve urban parameterizations are proposed by clarifying the basic dependencies used mainly in the calculation of turbulent fluxes, particularly, using the results of highly detailed Large-eddy simulation modeling, which, with growing computational power, is increasingly used to simulate explicit heat transfer between the atmosphere and individual elements of the urban environment.
Two-Layer Ocean Circulation Model with Variational Control of Turbulent Viscosity Coefficient
Authors: Zalesny V. B.
Published: April 2024

The development of a variational method for solving the problem of quasi-geostrophic dynamics in a two-layer periodic channel is considered. The development of the method is as follows. First, the formulation of the variational problem is generalized: the turbulent exchange coefficient of a quasi-geostrophic potential vorticity (QGPV) is included in the control vector. Secondly, the solution area more accurately describes the size of the Antarctic Circumpolar Current (ACC). Using the selection of linear meridional transport and the expansion of the solution in a Fourier series, the problem is reduced to a nonlinear system of ordinary differential equations (ODEs) in time. The doubly connected domain leads to the fact that the solution of the ODE must satisfy an additional stationary relation that determines the transport of the ACC. The variational algorithm is reduced to solving a system of forward and adjoint equations minimizing the mean squared error of the stationary relation. The QGPV turbulent exchange coefficient is determined in the process of solving the optimal problem. The numerical runs are carried out for a periodic channel simulating the water area of the ACC in the Southern Ocean. The characteristics of stationary current regimes are studied for different values of the model parameters. Typical is a sinusoidal circulation in both layers with a linear transfer with the wind, depending on the bottom topography. In some cases, under the sinusoidal, in the lower layer, a cellular circulation is formed, and sometimes an undercurrent occurs. In this case, the solution of the optimal problem is characterized by a low value of the turbulent viscosity coefficient and a low transport in the lower layer.
Variability of Jet Streams in the Atmosphere of the Northern Hemisphere in Recent Decades (1980–2021)
Authors: Bezotecheskaya Е. А. , Chkhetiani О. G. , Mokhov I. I.
Published: April 2024

Based on the reanalysis data quantitative estimates of the kinetic energy of the high-altitude jet streams of the Northern Hemisphere (EK JS NH) and its changes in the annual cycle and interannual variability for the period 1980–2021 were obtained under different conditions for the minimum wind speed Vm in the JS area. Adequate estimates are made for the share of the total kinetic energy of the atmosphere of the Northern Hemisphere associated with JS (PEк JS). The share of the volume of atmospheric layers in the JS area in the NH in the total analyzed atmospheric layer of 500–100 hPa (PV JS) was also estimated. Significant changes were noted in summer including significant weakening trends of EК, PEк and PV in July and August at Vm ≥ 20 and Vm ≥ 30 m/s. In winter significant changes were noted only for PV – a decreasing trend at Vm ≥ 20 and Vm ≥ 30 m/s. Seasonal features of JS connection with El Niño phenomena are noted which are most significantly manifested from January to April.
Methane Emission from Lakes in the North of Western Siberia
Authors: Kazantsev V. S. , Krivenok L. A. , Dvornikov Yu. A. , Lomov V. A. , Sabrekov A. F.
Published: April 2024

The paper presents the results of field measurements of methane fluxes into the atmosphere from thermokarst lakes located on the Russian Federation territory on the three key sites: foothills of the Polar Urals, coast of the Kara Sea and the northwestern part of the Yamal Peninsula. A total of 13 lakes were studied and about 500 methane fluxes were measured by the floating chamber method. The results showed most of the fluxes does not exceed 8 mg CH4 m–2 h–1. For more significant values, a statistically significant correlation with the wind speed was revealed, which largely determines the intensity of gas exchange on the “water-atmosphere” boundary. The exceptions are measurements in zone of lake methane seeps. For most lakes, the greatest scatter of measured fluxes was observed in the shallow part. The diurnal dynamics of methane fluxes was approximated by a sinusoidal function. For the lakes presented in the work, the range of emission assessment is 0.23–775.38 g CH4 h–1. Obtained results are important material for estimating regional methane emission from the surface of thermokarst lakes in the tundra zone.
Symmetric Stability of Vertical Baroclinic Vortices with a Warm Core
Authors: Kurgansky M. V.
Published: April 2024

An attempt has been made to relate the morphological characteristics of intense convective vortices, such as waterspouts and dust devils, to their hydrodynamic stability. The symmetric stability of cyclostrophically balanced vertical baroclinic vortices, whose radius of maximum wind depends on height, is considered. It shows the stability of narrow vortices, nearly cylindrical at the bottom, with a radius that then increases with height at an increasing rate and becomes infinite at a finite level above the Earth’s surface. On the contrary, wider conical vortices satisfy the necessary condition of instability, and it is hypothesized that this partly explains the more diffuse, disorganized nature of this kind of dust devils. The possibility of taking into account the general rotation in the problem is considered.
Analysis of Long-Term Measurements of Tropospheric Ozone at the SPBU Observational Site in Peterhof
Authors: Virolainen Ya. A. , Ionov D. V. , Polyakov A. V.
Published: April 2024

Tropospheric ozone (TO) is one of the major greenhouse gases and a toxic air pollutant. It plays a key role in various chemical and photochemical processes in the troposphere. Ozone concentrations both at surface level and in free troposphere are measured by various local and remote-sensing methods. The SPBU observational site in Peterhof (NDACC site St. Petersburg) is equipped with the Bruker IFS 125HR Fourier spectrometer used for TO measurements and the Thermo Scientific Model 49i gas analyzer for monitoring surface ozone concentrations (SOC). The temporal variability of TO in the 0–8 km layer for the period from April 2009 to October 2022 and of SOC for the period from 2013 to 2021 has been analyzed. Seasonal cycle of TO and SOC is similar to that of total ozone columns, but it is shifted in time by about 1 and 1.5 months, respectively. The maximum variation of TO from the average value for the period falls on the first half of April ~+16%; a minimum of about –(12–14)% is observed from mid-October to the end of December. In the middle of summer, there is also a slight increase in the TO variation at the level of +(7–8)%. A statistically significant decrease in the TO content by 0.34 ± 0.22% per year was also obtained. Comparison of hourly averaged data on TO with synchronized data of SOC measurements revealed an increase in the correlation coefficient (up to 0.5 or more) between the two values 3–4 hours after local noon in the warm season, accompanied by an increase in SOC. The increase in correlations is in good agreement with the increase in the height of the planet boundary layer.