Purpose. Research aims on determining the dependence of the fractal dimension of partial geometric fractals on the degree of distortion of the fractal structure. Such analysis is important for understanding behavior of complex objects in cases of partial violation of self-similarity, which frequently occurs in real-world tasks of computer graphics, modeling of natural processes, biomedical imaging, and materials analysis. Methodology. Research employed fractal construction technique based on L-systems with intermediate multi-symbol representation and defect seeding by randomly removing a certain percentage of symbols from generated sequence. Analysis was performed using box-counting method: fractal structure was repeatedly overlaid with square grids of variable side lengths, after which number of squares required to cover figure was determined. Fractal dimension was calculated from logarithmic relationship between number of squares and side length of squares (slope method on logarithmic plot). Graphical representations of fractals were saved in high-resolution BMP format to minimize rasterization errors. To improve reliability, each structure was analyzed through tenfold repeated grid coverage with varying parameters. Findings. Proposed methodology was tested on well-known geometric fractals: Koch snowflake, Koch square island, Sierpinski curve, dragon curve, and Lévy curve without distortions. Obtained fractal dimension values corresponded to theoretical predictions. For these fractals, relationship between fractal dimension and degree of damage (percentage of removed elements) was determined. In particular, increasing number of defects generally led to decrease in fractal dimension, indicating loss of self-similarity and simplification of geometric structure. These results allow quantitative description of fractal structure degradation and identification of critical limits of self-similarity stability. Originality. Research introduces new objects of study, namely partial geometric fractals, and provides new data on self-similarity levels of partial fractals with varying degrees of damage. Practical value. Results can be applied in computer graphics, image processing, 3D modeling, as well as in materials science and other fields where complexity and structure of materials are important. Study expands current approaches to fractal structure analysis and proposes new methods for their investigation and application.
Purpose. To improve the quality of student learning through electronic accounting of student success and workload, which will provide students with prompt access to their own learning outcomes, automate the accounting of educational activities for teachers, increase student motivation through gamification, and guarantee continuity and reliability of work thanks to cross-platform architecture and fault-tolerant solutions. Methodology. To obtain relevant data, the authors analyzed modern LMS, electronic journals, and interactive educational platforms, including Moodle, Canvas, and Top Hat, as well as relevant scientific publications over the past five years. Functionality, cross-platform, fault-tolerant, integration with university databases, and means of motivating students were assessed. Findings. Based on this analysis, an integrated information system was developed with two interconnected modules – the student’s application «Success» and the teacher’s «Cabinet», which provides automation of accounting of educational activities and increases the efficiency of interaction between students and teachers. Integration with the university's internal databases was carried out to automatically update information on grades, attendance, and class schedules. The system uses MongoDB for data storage and Flutter for cross-platform interface development. Originality. For the first time, the proposed system combines two interconnected platforms for students and teachers, which provides uninterrupted access to educational data in real time. The use of gamification elements and motivational indicators transforms performance accounting into a system that stimulates student activity and independence. The architecture with high fault tolerance and cross-platform implementation ensures reliability and mobility of the system in various educational environments. Practical value. The ability to provide students and teachers with prompt access to current data on educational activities, which contributes to increased transparency and control of the educational process. The implementation of the system allows you to automate attendance and grades, reducing the administrative burden on teachers. Adding gamification elements stimulates student motivation and improves their engagement in learning. The system has already been implemented and successfully used for three semesters, which confirms its effectiveness and practical value for the university educational environment.
Purpose. Justification the selection of architecture and hyperparameters for an artificial neural network designed to classify Automatic Cab Signalling (ALSN) code signals under conditions of intense interference and temporal distortion. Methodology. To achieve the purpose, a comparative analysis of different types of artificial neural networks was performed. It was found that for the classification of ALSN codes, a one-dimensional convolutional network (1D-CNN ) is the most suitable, as it effectively detects the characteristic temporal features of signals, requires less data for training, is resistant to noise, and provides stable classification even with a signal shift in time. Calculations of the number of network parameters were performed based on its configuration, including the number of layers, convolutional filters, and the number of neurons in fully connected layers. For model training, synthetic data were generated by adding noise and stochastic timing variations to reference signals («Z», «Zh», and «ChZh»). 1000 implementations were synthesized for each ALSN code signal. The program code for data preparation, network training, and signal classification was written in Python using the TensorFlow, Keras, Scipy.signal, and NumPy libraries. Findings. Based on the observed correlation between network configuration and recognition accuracy for the ALSN codes, an optimized model was selected featuring three convolutional layers, a 16-neuron Dense layer, and a 3-neuron output layer. The robustness of the proposed network was validated against both heavily distorted synthetic waveforms with low signal-to-noise ratios and empirical ALSN signals. Originality. This work represents the first comprehensive study of artificial neural networks efficacy for ALSN code classification under severe interference and temporal distortions. It justifies the specific 1D-CNN configuration and establishes the dependencies between model structural parameters (number of layers, filters, and neurons) and classification accuracy. Practical value. Replacing legacy relay-based equipment with the proposed 1D-CNN-based digital receiver will reduce operational expenditures while significantly enhancing the noise immunity and reliability of the ALSN system through stable code recognition in adverse settings, i.e. intensive noise and temporal parameters disturbances of the code signals.
Purpose. Plasma spraying is widely used to strengthen and restore the working surfaces of product parts, which is due to the combination of its technical and economic advantages and high process efficiency. The active use of this technology, in particular when processing a wide range of parts, imposes increased requirements on the level of equipment used and the quality of raw materials. At the same time, the plasma spraying method of coatings has a number of limitations, which at the same time serve as a potential reserve for further improvement of technological solutions. An effective method for solving such problems is the use of mathematical models. The main goal of the work consists in building a nonlinear mathematical model of coating hardening on the surface of the body, taking into account the temperature dependence of thermophysical characteristics. Methodology. The mathematical model for studying the process of coating solidification on the body surface includes heat conduction equations for the solid crust and the base. Numerical integration of the modeling equations is carried out using the implicit difference method with front trapping at the grid node. Findings. A computer program has been developed that allows for numerical studies of the solidification processes of titanium and aluminum coatings on a steel base. The results of numerical modeling are presented. Originality. A nonlinear mathematical model has been developed to study the process of solidification of a thin coating on the surface of a body. The model is based on the numerical integration of heat conduction equations for the solid crust and the base and allows determining the change in temperature over time at different points of the «base – coating» system. Practical value. The developed mathematical model can be useful in studying the hardening of a coating sprayed onto a body surface, as well as in selecting the operating parameters of the plasma spraying process. It provides a scientific justification for the process parameters and operating modes of the equipment used. The model allows us to evaluate the dynamics of the formation of thermal fields in the hardening process of coatings.
Purpose. The author aims to conduct a numerical analysis using the finite element method of the structure of a pylon-type station, which is being built in rock formations using the New Austrian tunneling method (NATM), and to conduct its substantiation when varying the width of the pylon part, determining the dependences of the components of the stress-strain state. Methodology. It was determined that the pylon-type metro station under study is a structure that has obvious structural heterogeneity. A detailed analysis of the structural solution of the «pylon – passage» system of a pylon-type metro station constructed by NATM was conducted. It was substantiated that the reflection of the heterogeneous structure of a pylon-type metro station with the reproduction of the «pylon – passage» system is a task of mathematical modeling based on the finite element method. Using the professional calculation complex Structure CAD, finite element models of a pylon-type station with varying the width of the pylon part were developed. Findings. The results of the stress-strain state of the combined lining of a pylon-type metro station were obtained using finite element models with varying the pylon width. It is proven that for a pylon-type metro station with varying the pylon width bpyl, the deformed state remains homogeneous. Qualitative analysis of the six components of the stress-strain state with variation in the pylon width proves that the effect of the pylon width is local and decays in the vicinity of 1.0 … 1.2 m. The analyzed dependencies are linear or polynomial, respectively, for different components of the stress and strain state and allow us to justify the width of the pylon, which ensures the strength of the station structure. Originality is characterized by the first-ever obtained dependences of the stress-strain state of the combined lining of the pylon-type metro station with variations in the width bpyl. Practical value lies in carrying out a series of calculations during mathematical modeling by the finite element method with the analysis of the strength of the station structure and the provision of recommendations for the selection of its dimensions.
Purpose. Timely detection and prevention of wheel slip in electric locomotives has always been one of the most pressing issues in rail transport. Wheel slip in electric locomotives increases wear on wheel tyres and rails, increases the likelihood of traction motor failure, and creates emergency situations during operation. The purpose of this scientific research is to determine the patterns of wheel slip development in electric locomotives under various operating conditions through simulation modeling of the wheel slip process. Methodology. The methodological basis of the study is the general principles of system analysis, mathematical analysis, modeling of electromechanical systems, theoretical mechanics, and the theory of electric traction. Computer simulation modeling of the wheel pair slip development process was performed using the «Simulink» environment. Finding. As a result of scientific research, a mathematical model of the wheel pair slip process of an electric locomotive was created, which takes into account the traction characteristics of the electric drive, the characteristics of adhesion, the physical and chemical state of the wheel-rail contact, the moments of inertia of the components of the traction electric drive, and the time parameters of the process of loss of adhesion qualities. An approximate expression was obtained, which describes the traction characteristics with a high degree of accuracy and is presented as a dependence of the dimensionless traction coefficient on the relative slip of the wheel surface on the rail. A simulation model was created that allows modeling the wheel slip process of an electric locomotive under various operating conditions. As a result of modeling, several variants of slip development were obtained for real parameters of the traction electric drive and operating conditions. The ratios were determined at which the temporary loss of traction qualities of the electric locomotive leads to differential slip. Originality. An analytical expression is proposed and approximation coefficients are determined for the dependence of the wheel-rail adhesion coefficient on the sliding speed of the wheel surfaces on the rails. Conditions are formulated that determine the nature of wheel pair slip development, which can be used in the development of principles for automatic control of traction electric drives with high resistance to slip. Practical value. The model created allows theoretical research into the process of wheel slip in electric locomotives under various operating conditions. The results of such research can be used to create an automatic traction electric drive control system that improves the electric locomotive's resistance to wheel slip.
Purpose. Research to determine the optimal, from a technical and economic point of view, option for replacing pumping equipment using the example of the second-lift pumping station VNS–45, operated in the city of Kryvyi Rih. Methodology. The study was implemented in several stages: analysis of the actual operating mode of the station, comparison of technical characteristics of alternative pumps, construction of graphs of the combined operation of pumps with the system, statistical processing of results and assessment of practical value. This approach allowed to ensure the complexity of the analysis and reliability of the conclusions. The work used methods of hydraulic calculation, graphic modeling and analysis of the passport characteristics of pumps. All parameters were analyzed at an average daily water flow of 83.07 m3/h. The results of the study showed that the most effective are the Grundfos NB 65–200/198 and MVAe.65–200 A.1100 pumps, which provide a reduction in average monthly electricity consumption by more than 30% compared to the existing unit of the D320–50 type. Findings. The issues of excessive energy consumption by centralized water supply system facilities have been resolved. A significant part of the costs of utility companies is the operation of pumping equipment, which in most cases is technically outdated and operates outside the optimal operating mode and is energy inefficient. The results obtained can become the basis for further research in the direction of implementing automatic control systems based on variable pump rotation speeds and optimization algorithms. Originality. A scientifically based approach has been developed to modernize pumping equipment units, which in most cases are technically outdated and operate outside their optimal operating range, in order to increase energy efficiency. Practical value. The practical value of the research lies in the creation of a universal engineering model for the selection of pumping equipment for urban water supply systems, which does not require changing the hydraulic scheme or implementing complex control algorithms. The model can be applied to similar facilities without additional capital investments in engineering (pipeline) infrastructure.
Purpose. This work is aimed at investigating the evolution of the refactoring concept – from a tool for optimizing program code to a powerful means of improving data structures, algorithms, and business processes. The main purpose of the study is to examine the historical development of software and ontology refactoring, as well as the possibilities of applying improvement methods to ontologies as a specific type of software structure that plays a key role in knowledge-oriented systems, the Semantic Web, and next-generation cyber-physical systems. Methodology. The methodological basis of the study consists of general scientific and specialized methods of analysis and synthesis. A systematic review of scientific publications in the fields of software refactoring and ontology engineering was conducted using full-text and abstract scientometric databases. Comparative analysis methods were applied to compare different refactoring approaches, structural and functional analysis was used to study changes in software and ontology models, and classification methods were employed to group existing refactoring techniques by level of abstraction and application domain. Finding. Within the scope of the study, a comprehensive analysis of scientific publications devoted to refactoring and ontology engineering was performed using full-text and abstract databases. The evolution of refactoring approaches was examined, including data schema transformations, conceptual refactoring, modification of integrity constraints, and the development of tools for assessing the quality of changes. Particular attention was paid to the application of refactoring to ontologies, including an analysis of its impact on modularity, coherence, and knowledge reuse. Originality. The scientific novelty of the work lies in the systematic study of existing refactoring methods and their classification by type. A comprehensive analysis of the strengths and weaknesses of each approach was carried out, enabling a well-founded selection of optimal strategies for software improvement. The proposed approach contributes to a deeper understanding of refactoring mechanisms in the context of various application domains. Practical value. The presented results can be used in the design, maintenance, and evolution of knowledge-oriented systems, where structural consistency and semantic support play an important role. Prospects for further research are outlined, including the automation of ontology refactoring processes using machine learning methods, the expansion of evaluation metric systems, and the adaptation of the proposed solutions to application domains characterized by a high degree of change dynamics.
Purpose. To conduct a comparative analysis of the technical condition of the bodies of universal and specialized gondolas (with a blind body) owned by state and private operators. To determine the structural elements of the bodies that fail most often and pose a threat to traffic safety. Methodology. The study was conducted using statistical data on failures of universal gondolas owned by JSC «Ukrzaliznytsia» and private operators during operation over the period 2022-2024. For this purpose, data on wagons of various models and different service lives entering scheduled types of maintenance and repair were analyzed. During the study, classical methods of mathematical statistics and the well-known Microsoft Excel application package were used. The analysis made it possible to determine which models of gondolas prevail in the general fleet of cars and to establish which main structural elements of universal gondolas bodies fail most often. Findings. A statistical analysis of failures and damage to the bodies of both universal gondolas and specialized gondolas with a solid body of different models was carried out, taking into account the service life. The results obtained made it possible to compare the technical condition of universal gondolas bodies of different models, as well as to compare the technical condition of universal gondolas and specialized gondolas with a solid body. It was established that the most common types of damage to universal open-top freight wagons include failures of welded joints of vertical posts, damage to the covers of unloading hatches and their locks, cracks and fractures of the vertical sheets of the transverse beams of the frame. Originality. For the first time, a comparative analysis of damage occurrence of different models of gondolas was carried out and the dependence of the number of failures on the service life was determined. Practical value. The results obtained make it possible to determine the directions of development of new technical solutions for improving gondola bodies. Based on the analysis conducted, taking into account the actual technical condition of the gondolas and the level of their damage depending on the model and service life, it is possible to form an improved strategy for restoring the operability of gondolas by optimizing the timing of repairs and maintenance.
Purpose. To determine the performance indicators of the vertical dynamic behavior of the EKr–1 «Tarpan» electric train under the influence of random railway track irregularities on a straight track section at operating speeds of up to 250 km/h. Methodology. The study employs a comprehensive three-dimensional mathematical model of the EKr–1 «Tarpan» electric train in interaction with the railway track, which incorporates a thermodynamic model of the pneumatic suspension system. The model consists of a system of 54 differential equations. Railway track irregularities are modeled as a random process and generated by applying white noise followed by filtering with a Butterworth filter, which ensures the specified spectral characteristics in terms of wavelength and amplitude. As indicators of the dynamic performance of the rolling stock, the coefficients of vertical dynamics of the primary and secondary suspension stages, as well as the vertical accelerations of the car body, are investigated. The vertical dynamic coefficients are determined based on the forces arising in the suspension system. Findings. The relationships between the coefficients of vertical dynamics of the primary and secondary suspension stages and the maximum values of the car body vertical acceleration as functions of operating speed have been obtained. These relationships exhibit a nonlinear behavior, on the basis of which the maximum permissible operating speeds of the EKr–1 «Tarpan» electric train under the specified railway track maintenance conditions have been determined. The dynamic performance indicators of the high-speed EKr–1 «Tarpan» electric train were obtained for both tare (empty) and gross (loaded) vehicle conditions. Originality. Based on an improved comprehensive mathematical model describing the dynamic behavior of high-speed rolling stock–track interaction, theoretical values of dynamic performance indicators have been substantiated for operating regimes representative of service conditions, taking into account the rolling stock design features, wheel–rail interaction conditions, and operating speeds of up to 250 km/h. Practical value. The obtained dynamic performance indicators of the EKr–1 «Tarpan» electric train, as well as the established maximum permissible operating speeds, can be used to substantiate the conditions for its safe operation in high-speed service regimes. The results of the study are advisable for application in the design, modernization, and improvement of suspension systems of high-speed rolling stock, as well as in the development of regulatory and operational documentation.
Purpose. The authors set the goal of determining the principles of the concept of reverse conversion to substantiate the use of underground metro structures as shelters for critical infrastructure facilities. Methodology. The laboratory test program consisted of obtaining the characteristics of soil cement and analyzing the results obtained in the case of use as a railway track base. During construction work, soil cement samples were taken. After selection, the samples were cut with special equipment, and the cut points were ground to ensure full contact with the press plates. After the soil cement samples were placed in the compaction device under a load of 0.03 MPa and left under this load for 72 hours. The loading of the samples was carried out in stages with a holding time of at least 5 minutes until stabilization. The tests were processed, analyzed and considered within the framework of the analysis of elastic properties. Findings. When the pressure reached 1.12 MPa, the sample was kept for 30 minutes, the settlement was 0.093 mm. After that, unloading was carried out in stages to a pressure of 0.03 MPa with stabilization of each stage. Analysis of the constructed graph shows that the residual deformation is 0.03 mm, and the total at a pressure of 1.12 MPa is 0.093 mm. Analysis of the graph shows the creation of a hysteresis loop, which characterizes the operation of soil cement in the elastic mode. At the same time, the deformation modulus E at different loading stages is in the range of 560…750 MPa. Soil cement demonstrates stable elastic properties, which makes it an effective material for use in civil, industrial and railway construction. Originality. The article, based on the results of laboratory tests of soil cement, finally proves its high elastic properties under the action of cyclic loads, which simulate the action of the rail-sleeper grid on the ballast and the railway subgrade. Practical value lies in obtaining the values of the modulus of elasticity of soil cement, which can be further used for practical calculations of predicting the settlements of soil bases.
Purpose. The purpose of the article is to determine the parameters of a plug-in hybrid power plant for a shunting and haulage locomotive for industrial enterprises. Methodology. An analysis of the parameters of the operating modes of diesel locomotives used for shunting operations and haulage work at domestic industrial enterprises was carried out. Data from the on-board systems of diesel locomotives operated by PJSC Poltava Mining and Processing Plant and PJSC DTEK Pavlogradvuhillya were used for the analysis. Finding. It was determined that during shunting operations, energy consumption does not exceed 600 kWh at a maximum power of 350 kW. During haulage operations, energy consumption is 850–1200 kWh at a maximum power of 650 kW. A comparison of fuel consumption, fuel and energy costs, and CO2 emissions for different power plant options was carried out. The fuel characteristics of Cummins QST30–L2 diesel engines with a power of 895 kW and Cummins QSZ13 diesel engines with a power of 401 kW were used for a comparative assessment of hybrid power plant options. It was found that it is rational to use plug-in power plants in which the energy storage device must be charged from an energy source with a low cost per kilowatt-hour of energy. This allows reducing fuel and energy costs by 30–35% compared to diesel fuel costs when performing maneuvering operations. To ensure export operation, the plug-in hybrid power plant must include a diesel engine with a capacity of about 400 kW. In this case, the traction electric drive and auxiliary systems are powered jointly, and the possible reduction in fuel and energy costs can be 12–14%. It has been shown that the type of storage cell should be selected taking into account their service life. For the plug-in power plant under study, it is rational to use CALB L194F130B lithium iron phosphate cells. Originality. The use of a plug-in hybrid power plant on shunting and haulage locomotives used in industrial enterprises has been justified, and the parameters of the power plant have been determined. Practical value. The results obtained can be used in the creation of hybrid power units for shunting and haulage locomotives for industrial enterprises. The proposed method for determining the parameters of a hybrid power unit can be used for other rolling stock.
Purpose. The objective of this study is to develop approaches for the objective investigation of the inventory structure of the NZhM–56 floating railway bridge. It involves selecting a computational model for the floating bridge to facilitate further substantiated research into load-carrying capacity and formulating recommendations for the deployment of NZhM–56 equipment to accommodate railway, vehicular, and tracked loads. Methodology. Variational modeling of NZhM–56 floating (pontoon) bridges using diverse configurations (varying in length and number of pontoon supports) for analysis via the influence line method. Analysis of the obtained results and substantiation of the bridge crossing computational model proposed for further research. Application of software implementing the Finite Element Method (FEM) to conduct the investigations. Findings. Development of approaches for recalculating the load-carrying capacity of inventory floating (pontoon) bridge systems using the finite element method. The study identifies the specific length and assembly configuration of the NZhM–56 floating bridge that exerts the greatest impact on internal forces generated under live loads. This configuration is selected for further research and for providing substantiated recommendations regarding live load passage. Furthermore, the most critical (unfavorable) scenarios and positions for live load placement have been proposed to investigate the stress-strain state of the structure. Originality. The scientific significance of this work lies in the selection of a methodology for recalculating the load-carrying capacity of floating (pontoon) bridge systems, specifically focusing on the NZhM–56 bridge. A comprehensive investigation is conducted into the relationship between the critical length, the assembly configuration of the NZhM–56 bridge, and the magnitude of internal forces generated under live loads. Furthermore, the research focuses on the specific behavior of the transition section of the pontoon bridge, analyzed both as an independent subsystem and in its structural interaction with the river (main) span elements. Practical value. Definition of approaches and methodologies for recalculating the load-carrying capacity of inventory floating (pontoon) bridge systems, necessitated by contemporary challenges. The research is aimed at ensuring the safe passage of temporary railway, tracked, and wheeled loads over the NZhM–56 floating bridge. Furthermore, the study identifies specific features of investigating floating bridge systems through the application of software implementing the Finite Element Method (FEM).
Purpose. The purpose of the study is to develop a diagnostic system for assessing the hazard level of railway level crossings based on a multifactor risk analysis within a structured set of criteria. To achieve this purpose, domestic and international regulatory documents governing the design and operation of at-grade railway–road crossings were reviewed, and their operational and economic characteristics were assessed. Methodology. The proposed methodology is aimed at increasing the level of detail and the informativeness of hazard assessment at the stage of practical application. Its diagnostic value lies in providing a basis for planning targeted, site-specific safety measures intended to eliminate particular hazard factors. It is shown that incorporating the cognitive factor enables more accurate ranking of level crossings and forms a rationale for substantiating targeted measures to improve traffic safety. Finding. The proposed comprehensive hazard assessment methodology, which incorporates the cognitive factor, was tested on a sample of railway level crossings. Based on aggregated tabular results, two crossings were classified as high-risk, one as elevated-risk, and one as moderate-risk, according to the assessment indicator structure (MSZ, KD, cognitive hazard coefficient, and integrated hazard index). Comparative analysis confirmed that inclusion of the cognitive factor significantly affects the integrated hazard index and enables identification of facilities with increased risk under moderate traffic dynamics, taking into account the influence of drivers’ cognitive dissonance and cognitive load. The high-risk class is associated with information-environment overload and contradictory signals as factors that contribute to hazardous situations. The results justify prioritizing measures such as improving signalling logic, unifying signal indications, increasing conspicuity, and reducing visual noise, and indicate that these measures can be implemented without substantial capital expenditure. Originality. For the first time, a multifactor methodology for assessing cognitive hazard at railway level crossings has been developed, based on integrating driver psychophysiological factors (cognitive load, cognitive dissonance, fatigue) into the overall risk calculation system. Unlike existing regulatory approaches, the proposed methodology makes it possible to diagnose specific causes of cognitive risk and to determine the priority of targeted measures aimed at reducing the probability of driver error. Practical value. In situations where the physical parameters of a railway level crossing (number of tracks, spatial layout, pavement type, presence and type of signalling) are technically or economically difficult to change, the methodology provides a tool for optimizing the information environment within the existing infrastructure. This makes it possible to address traffic-safety aspects that are not covered by current regulatory documents.
Purpose. The study is aimed at obtaining indicators of computational complexity for the formation of spatial graph fractals, which in turn requires developing a software application for the formation of spatial graph fractals, which allows them to be visually viewed, as well as creating tools for calculating indicators of computational complexity. Methodology. The approach of constructive-synthesizing modeling is used to form spatial graph fractals, which is based on the rules of production inherent in formal grammars. Constructive- synthesizing modeling involves a number of transformations, such as: specialization, interpretation and concretization. Structural transformations describe how a spatial graph fractal can be formed, which includes the definition of the subject area, attributes, operations on attributes, substitution rules, conditions and restrictions on operations, description of algorithms, and implementation in the form of software. The indicators of basic operations performed at the assembler level are determined, such as: arithmetic, assignment, comparison and transition. To calculate the indicators of the iteration of the formation of a graph fractal at the code level, special counters are added. The operation counters are located only in those sections of the code that are directly executed during the iteration. Findings. A program was developed in C# with a graphical interface. The indicators of the experimental computational complexity for the formation of spatial graph fractals by means of constructive-synthesizing modeling based on the use of different types of crystal lattices have been determined. The found dependencies have a correlation ratio close to unity. Originality. The experimental computational complexity of the formation of spatial graph fractals by means of constructive-synthesizing modeling has been determined. As the basis for the formation of spatial graph fractals, various types of crystal lattices are used, which describe the arrangement of atoms of crystalline substances. Practical value. Determining the indicators of basic operations makes it possible to predict the execution time of an iteration of forming spatial graph fractals, as well as to optimize the algorithms for performing this iteration. Analysis of the indicators of basic operations makes it possible to find bottlenecks in the algorithms for forming spatial graph fractals.
Purpose. The energy efficiency of traction electric motors of mainline electric locomotives with a supply voltage of 25 kV is characterized by the efficiency factor (EFC). Traction motors are powered by a multi-arm single-phase half-controlled thyristor rectifier, the arms of which are connected to separate sections of the traction transformer. The purpose is to determine the influence of the current ripple coefficient on the efficiency of the motor. Methodology. The efficiency determination methodology is based on the law of energy conservation, methods of harmonic analysis and computer modeling to obtain the dependences of the armature current ripple coefficient on the thyristor control angle, armature circuit inductance and load current. Finding. An analytical expression for the efficiency of the motor with a pulsating armature current was obtained based on the calculation of relative electrical losses from the harmonic components of the current, which are equal to the square of the current ripple coefficient. A computer model was developed, based on which graphical dependences of the armature current ripple coefficient were obtained separately from the thyristor control angle, armature circuit inductance and load current. The results of the experiments were processed by the experiment planning method and an analytical expression was obtained for calculating the current ripple coefficient. The method for calculating the efficiency of a traction motor is as follows: for the given ohmic resistance and armature circuit inductance, load current and average thyristor control angle, the current ripple coefficient is calculated, the value of which is inserted into the expression for calculating the engine efficiency. Originality. The author improved the analytical expression for determining the efficiency of a DC motor when powered by a single-phase half-controlled thyristor rectifier, which, unlike the known ones, takes into account the armature winding current ripple coefficient. For the first time, an analytical dependence of the current ripple coefficient for a single-phase thyristor DC electric drive was obtained as a function of the thyristor control angle, armature circuit inductance and load current. Practical value. The analytical expression for determining the efficiency of a DC motor when powered by a single-phase half-controlled thyristor rectifier allows: 1) to calculate the load capacity of the motor by mechanical power on the shaft, taking into account the permissible heating by the effective value of the current with harmonic components; 2) to calculate the inductance of the smoothing reactor to increase the efficiency of the motor by reducing the current ripple coefficient.
Purpose. To provide a coherent and accessible assessment of changes in Ukraine’s construction sector during the crisis period; to show how these shifts affected output, demand structure, the labor market, and firms’ financial performance; and to derive practical guidance for organizing reconstruction. Methodology. The study combines general scientific approaches with transparent statistical procedures. Comparisons are conducted on a harmonized, fixed territorial basis, excluding temporarily occupied territories and areas of active hostilities. We employ fixed-base and chain indices to track dynamics, a structural analysis of shares by construction product type, and a decomposition of sub-sector contributions to changes in aggregate indicators. Sensitivity checks are performed for the choice of base period and weighting choices, complemented by logical cross-checks of totals. Findings. We identify a sequence of contraction, adaptation, and gradual recovery. Evidence shows a persistent shift in demand from residential building towards engineering infrastructure and industrial facilities. The role of small and micro enterprises in employment increases, while financial outcomes diverge notably across activity types and firm-size groups. The findings also underline reliance on public reconstruction programs and the importance of transparent management of schedules, costs, and logistics. Originality. We propose a concise yet rigorous analytical framework that separates organic recovery from statistical base effects and changes in coverage. The nature of structural shifts is clarified; quantitative estimates of sub-sector contributions are produced; and the use of a fixed territorial basis is justified for correct intertemporal comparison. Practical value. The results support the prioritization of critical-infrastructure projects, realistic planning of resources and supply chains, and the design of contracting models with strengthened control of risk and cost. The analysis further substantiates the deployment of building information modelling with time and cost dimensions, the use of modular and industrialized solutions, flexible subcontracting arrangements, and digital monitoring—measures that enhance project controllability and coordination among stakeholders in a volatile environment.
Purpose. The purpose of the study is to conduct a substantive comparative analysis of the state of occupational injuries related to the official activities of military personnel during the transportation of military cargo by rail and to justify the prevention of accidents, fatal accidents involving military personnel, and accidents resulting in serious injuries to military personnel. Methodology. Problematic issues during the loading of military trains and transports in modern conditions are highlighted. Comprehensive measures aimed at optimizing and implementing safety measures during loading and unloading operations are identified. Based on the analysis, proposals are made for the organized loading (unloading) of trains and transport in compliance with safety measures. The study uses the practical experience of officers of the military transport service of the Logistics Command of the Armed Forces of Ukraine. Military units that are transported as part of military echelons and send military cargo to ensure the fulfillment of tasks to provide troops with everything they need for life and operations during wartime. Findings. During a special period, the transportation of military units by rail is one of the main methods of strategic and tactical movement of troops, weapons, equipment, and material resources, as well as the evacuation of the wounded, equipment, and supplies. Originality. Development of recommendations and reference and analytical material for military units, military command bodies, heads of military transport departments on railways, and military commandants. Systematization of the work of commanders (chiefs) to ensure and enforce the rules for providing first aid to victims, safety while on the tracks of railway stations, the use of fire extinguishing equipment, as well as signals used in railway transport by military echelon personnel and guards. Practical value. Ensuring the preservation of life and strengthening the health of military echelon personnel and guards during the protection and escort of military transports with dangerous cargo (ammunition) in areas of operations (combat actions).
Purpose. Development of a CFD model that makes it possible to quickly predict the level of dust pollution of atmospheric air after an explosion in a quarry, development of a fast CFD calculation model. Methodology. To solve the aerodynamics and mass transfer problem, the fundamental equations of continuum mechanics are used. The air flow velocity field is modeled using the Laplace equation for the velocity potential. Numerical integration of the Laplace equation is carried out using the splitting method. After splitting, difference equations are constructed that can be solved by an explicit formula. The G. Marchuk model is used to model the distribution of dust in atmospheric air. Difference splitting schemes are used for numerical integration of the mass transfer equation. At the first stage, physical splitting is carried out into the equations of diffusion and convective dust transport. Then, alternating triangular difference splitting schemes are constructed. The terrain is modeled on a rectangular difference grid using markers. Findings. A set of numerical models has been developed to solve the problems of aerodynamics and mass transfer of a significant impurity in atmospheric air. Finite-difference splitting schemes have been used to build numerical models, which allow obtaining simple calculation dependencies. The constructed numerical models make it possible to quickly calculate the dynamics of dust pollution in conditions of complex terrain. Originality. Numerical models have been built to analyze the dynamics of dust pollution of atmospheric air after an explosion in a quarry. The model makes it possible to take into account the geometric shape of the relief, weather conditions, the rate of gravitational dust deposition, atmospheric diffusion, and the shape of the dust cloud after the explosion. The model can be used for rapid assessment of the impact of explosions on the environment. Practical value. A specialized package of computer programs has been developed to conduct a computational experiment based on the constructed numerical models. The results of the numerical experiment are presented.
Purpose. To conduct a structured analysis and classification of modern methods and models used to work with time series of various nature. Attention was paid not only to typical features and types of calculations, but also to identifying the subject area of application, comparing and highlighting strengths and weaknesses when working with different data sets, with relevant examples of areas of use and an emphasis on advantages. Methodology. A step-by-step and detailed review of existing methods and models based on their main characteristics, areas of use, and features of working with approaches of different nature that use different properties of time series. Findings. Analysis of the most common methods for processing time series and a separate review of their representatives. Particular attention is paid to hybrid models that can combine methods of one or different classes, as well as atypical approaches based on the specific properties of time series, in particular their fractality. Originality. It consists in a comprehensive and fundamental consideration of methods for analyzing time series, ranging from classical linear and nonlinear statistical models and artificial intelligence methods to hybrid and fractal approaches, with an emphasis on identifying their areas of application and comparing their advantages and disadvantages. The practical value of the research lies in the systematization of material that can be used for preliminary analysis of the subject area and selection of tools based on their effectiveness, which, in turn, simplifies the search for analogues and reduces the time required to prepare for research. In addition, the work highlights lesser-known and atypical methods that are of interest for further research and may be promising candidates for future scientific developments in the field of time series analysis.
