Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport
ISSN / EISSN : 2307-3489 / 2307-6666
Current Publisher: Dnipropetrovsk National University of Railway Transport (10.15802)
Total articles ≅ 702
Latest articles in this journal
Published: 10 December 2020
Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport pp 45-67; doi:10.15802/stp2020/218603
Purpose. The purpose of the work is to determine the rational capacity and energy consumption of the onboard capacitive energy storages using a complex approach for estimating the parameters, which is based on the methods of theoretical research. Methodology. The article performs a comparative analysis of existing methodologies and approaches for determination of the onboard capacitive storages parameters for subway trains with recovery systems, formulates the advantages and disadvantages of each of them. It is determined that among the existing methodologies it is most reasonable to use a complex approach, the aim of which is to determine the rational capacity and energy consumption according to two parameters of the energy storage system – weight and payback period. A procedure for determining the rational parameters of the onboard capacitive energy storage using theoretical research methods is proposed: theoretical basis of electric traction, mathematical modeling of dynamic motion and energy processes, mathematical statistics, technical-economic and comparative analysis. Findings. According to the results of the complex theoretical researches, the economic expediency of implementation of onboard capacitive energy storages on the subway train is confirmed. The energy storage system with rational parameters of the onboard capacitive energy storage for established operating conditions in the Municipal Enterprise «Kyiv Metro» and selected experimental train of the subway is determined. The amount of saved electricity due to the implementation of the energy storage system with rational parameters is estimated. Originality. The methodology for determining the rational parameters of the onboard capacitive energy storage in terms of replacing the use of experimental research data with theoretical research, the purpose of which is to model the movement of subway trains with recovery systems using software to reduce financial costs, research time and increase their accuracy. The research on determination of quantitative indicators of recovery electricity for the analysis of energy saving reserves was further developed in the subway. Practical value. The results of theoretical research can be the basis for the creation of full-scale samples of subway trains with onboard capacitive energy storages. The researches will create recommendations for the design of innovative energy-saving subway trains with improved technical and economic characteristics that can increase the efficiency of the transportation process in the subway.
Published: 10 December 2020
Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport pp 32-44; doi:10.15802/stp2020/218609
Purpose. The work is aimed to assess the influence of locomotive service systems on the indicators of their use and operation organization of the locomotive depot. Methodology. To achieve this purpose the calculation of operational indicators of locomotives of series 2TE116 and TE33AS in the conditions of locomotive depot is performed. The simulation model of the locomotive repair shop has been improved. Using the methods of the queuing systems theory, simulation modeling of the locomotive repair shop with service and schedule preventive systems for locomotive service was performed. Findings. The program of locomotives repair at schedule preventive and service systems is calculated. Based on the simulation results of the repair shop operation, we compared the influence of operation and repair on the locomotive depot operation for two different approaches to the organization of locomotives maintenance. The simulation model of the locomotive repair shop allows further comparative analysis of the use of different series of locomotives in the depot. The analysis of the results obtained demonstrates that the proposed approach to modeling the maintenance and repair of a diesel locomotive fleet can be improved by determining the reliability indicators when locomotives arrive for scheduled and unscheduled repairs. Originality. We improved the simulation model of the locomotive repair shop, which allows analyzing the influence of operational factors on the system of locomotive repair, in order to select a rational system of the locomotive fleet maintenance. Practical value. The results obtained make it possible to analyze the influence of the operation and repair indicators of locomotives on the operation of the locomotive depot and to determine the feasibility of using the selected traction rolling stock at a given service area. The results obtained indicate that the use of TE33AS diesel locomotives with a service system should reduce the residence time for all types of maintenance and repairs.
Published: 8 December 2020
Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport pp 15-21; doi:10.15802/stp2020/218310
Purpose. Development of CFD model to evaluate the efficiency of wastewater treatment in a horizontal settler. The CFD model can be used to calculate flow hydrodynamics and mass transfer in settlers with complex geometric shape in the area of wastewater flow. Methodology. For numerical simulation of the process of wastewater movement in a horizontal settler, two mathematical models are used. The first model is based on the motion equations of a viscous incompressible fluid – the Navier-Stokes equations. The Navier-Stokes equations are written in the variables «vorticity - flow function». A two-dimensional mass transfer equation is used to calculate the concentration of a pollutant in a horizontal settler. To numerically integrate the two-dimensional mass transfer equation, a finite-difference splitting scheme is used. The splitting of the modeling equation of mass transfer is carried out so that at each fractional step to determine the unknown value of the pollutant concentration by an explicit formula. For numerical integration of the vortex transfer equation and the equation for the flow function (the Navier-Stokes system of equations), finite-difference splitting schemes are used. Findings. Based on the developed CFD model, a complex of computer programs has been developed, which makes it possible to determine the efficiency of water treatment in a horizontal settler with additional elements. The results of a computational experiment to assess the efficiency of water treatment in a horizontal settler with additional elements in the form of plates are presented. Originality. An efficient CFD model has been created, which allows to quickly evaluate the efficiency of wastewater treatment in a horizontal settler with additional elements. The developed CFD model takes into account the geometric shape of the facility and the most significant physical factors, that influence the efficiency of the waste water treatment in horizontal settler: non-uniform flow velocity, diffusion, different position of inlet and outlet openings. Practical value. The developed CFD model belongs to the class of «diagnostic models» and can be used to assess the efficiency of treatment facilities at the stage of their preliminary design.
Published: 8 December 2020
Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport pp 68-79; doi:10.15802/stp2020/218318
Purpose. The article is aimed at the development of a methodology for detecting attacks on a computer network. To achieve this goal the following tasks were solved: to develop a methodology for detecting attacks on a computer network based on an ensemble of neural networks using normalized data from the open KDD Cup 99 database; when performing machine training to identify the optimal parameters of the neural network which will provide a sufficiently high level of reliability of detection of intrusions into the computer network. Methodology. As an architectural solution of the attack detection module, a two-level network system is proposed, based on an ensemble of five neural networks of the multilayer perceptron type. The first neural network to determine the category of attack class (DoS, R2L, U2R, Probe) or the fact that there was no attack; other neural networks – to detect the type of attack, if any (each of these four neural networks corresponds to one class of attack and is able to identify types that belong only to this class). Findings. The created software model was used to study the parameters of the neural network configuration 41–1–132–5, which determines the category of the attack class on the computer network. It is determined that the optimal training speed is 0.001. The ADAM algorithm proved to be the best for optimization. The ReLU function is the most suitable activation function for the hidden layer, and the hyperbolic tangent function – for the output layer activation function. Accuracy in test and validation samples was 92.86 % and 91.03 %, respectively. Originality. The developed software model, which uses the Python 3.5 programming language, the integrated development environment PyCharm 2016.3 and the Tensorflow 1.2 framework, makes it possible to detect all types of attacks of DoS, U2R, R2L, Probe classes. Practical value. Graphical dependencies of accuracy of neural networks at various parameters are received: speed of training; activation function; optimization algorithm. The optimal parameters of neural networks have been determined, which will ensure a sufficiently high level of reliability of intrusion detection into a computer network.
Published: 8 December 2020
Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport pp 5-14; doi:10.15802/stp2020/218302
Purpose. Efficiency determination of the aeration tank at the stage of design or reconstruction of bioreactors in which biological wastewater treatment is carried out requires the use of special mathematical models and calculation methods. The main purpose of the article is to develop CFD models for evaluating the operation efficiency of aeration tanks. Methodology. A numerical model has been developed for the computer calculation of the biological wastewater treatment process in aerotanks, taking into account hydrodynamics. The model is based on two-level mass conservation equations for the substrate and activated sludge and the velocity potential equation. The process of biological transformation of the substrate is calculated based on the Monod model. For the numerical integration of the mass transfer equations of activated sludge and substrate, the alternating-triangular difference splitting scheme is used. In this case, the basic equations are divided into two equations of a more simplified form. For the numerical integration of the equations for the velocity potential, it is split into two one-dimensional equations. Further, each equation is solved according to explicit scheme. For the numerical integration of equations that describe the process of substrate transformation based on the Monod model, the Euler method is used. Findings. The software implementation of the constructed numerical model has been carried out. The results of a computational experiment on the study of the wastewater treatment process in an aeration tank with plates are presented. This leads to the conclusion that the quality control of wastewater treatment in aeration tanks is possible with the help of plates. Originality. A multivariate CFD model has been developed, which makes it possible to quickly assess the efficiency of the aeration tank. A feature of the model is the ability to evaluate the operation of the aeration tank, taking into account its geometric shape and location of additional plates in the construction. Practical value. The constructed numerical model can be used during calculations in the case of designing aeration tanks, or in determining the efficiency of wastewater treatment under new operating conditions.
Published: 8 December 2020
Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport pp 105-115; doi:10.15802/stp2020/218353
Purpose. The main purpose of the work is to improve the safety of railway transport operation. The implementation of this purpose is provided by assessing and preventing the negative influence of petroleum products on the structural elements of the railway infrastructure. Methodology. The main criterion for assessing the residual life of technical elements of equipment is their strength characteristics. One of the key factors affecting the suitability of technical devices during operation is corrosion damage to the metal. Therefore, the influence of various combinations of the mineralization degree and concentration of petroleum products on the corrosion rate of metals most often used in the design of cooling systems for diesel engines and other transport objects was studied. Thus, for carrying out static and dynamic laboratory tests, model working solutions with different salinity (demineralization model) and different concentrations of dissolved petroleum products (model of standard solutions with organic impurities) were selected. Dynamic and static studies of corrosion damage were carried out by the gravimetric method and the method of polarization resistance using standard samples and solutions. Findings. Based on the results of experimental studies of the authors and analytical data processing, generalizing model dependences of the corrosion rate on the mineralization degree of the working solution of the fractional composition of petroleum products were obtained. A study was carried out and the influence of the water demineralization degree on the corrosion rate of materials of diesel cooling systems was established. Originality. Based on a wide range of author's experimental data, the presence of generalizing dependences of the corrosion rate on temperature, the mineralization degree of the working solution and the fraction of the petroleum products composition has been shown and proven. The obtained dependences form the basis of the developed mathematical model of corrosion, which is a set of relationships linking the characteristics of the corrosion process with various factors influencing its development. Practical value. The obtained experimental and analytical data can be widely used for non-destructive testing procedures, detailed prediction of the state of structural elements and the selection of effective inhibitors to reduce the corrosive aggressiveness of the environment and protect structures.
Published: 3 December 2020
Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport pp 22-31; doi:10.15802/stp2020/217765
Purpose. Identification and methodological substantiation of ways to increase the unitized cargo transportation efficiency, which would increase the trucking company profits and the manufacturer quality customer service. Methodology. In the course of the research the following methods were used: the method of theoretical generalization and systematization to determine the peculiarities of formation of the rational routes of cargo transportation in different conditions; the analytical method to determine the factors influencing the feasibility of adopting a certain strategy of the trucking company to improve the transportation efficiency; comparison to analyze strategies to increase the cargo transportation efficiency of the trucking company when using routes of different types. Findings. The relationship between the organizational structure effectiveness of the production enterprise management and the probable problems in choosing the type of route for goods delivery to customers is defined. The authors proved that the efficiency of unitized cargo transportation depends on a well-defined strategy of increasing the road transport efficiency. Based on the conducted research the influence of economic and organizational factors on expediency of the decision concerning rational strategy of transportation efficiency maintenance is estimated. Three types of strategies are proposed, the content of which is reflected in the receipt of additional profit by the transport company from the production enterprise, when using pendulum routes by saving its resources (return of returnable packaging) and by finding cargo on the way back, as well as using delivery-assembling routes while minimizing fines for late goods delivery. The dependence visualization of the amount of the trucking company profit on the type of strategy adopted allows us to assess the prospects for the introduction of certain types of freight vehicles routes. Originality. Methodical approaches to ways substantiation of the trucking company profit increase, choosing their rational route according to the efficiency increase strategy of unitized cargo transportations from the manufacturer to clients have received further development. Practical value. The obtained results are aimed at improving the methodological approaches to optimizing the unitized cargo routes, based on the choice of two types of routes in certain conditions, the first is the pendulum route with simultaneous receipt of applications for goods delivery, the second – the delivery-assembling routes, taking into account fines for late delivery.
Published: 3 December 2020
Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport pp 134-141; doi:10.15802/stp2020/217771
Purpose. The purpose of the work is to determine and analyze the technical parameters of the bench for railway wheels complex tests, providing for the combination of fatigue and contact strength tests, their simultaneous performing on same test-bench. Methodology. Determination of the technical parameters of the test-bench was carried out based on comparing the characteristics of fatigue and contact strength tests of railway wheels. Requirements for fatigue tests and related equipment are determined based on an analysis of the current regulations and patent review. A model of the contact strength test-bench with the introduction of necessary changes in terms of ensuring the cyclicity of the working effort application was adopted as the basic model for the development of a complex test-bench. The criterion for the possibility of complex tests, involving the simultaneous testing of railway wheels for fatigue and contact strength, was the dependence of the test-bench roller diameter on the parameters of the tested wheel, the wheelset axle load, which includes the tested wheel and the wheel material endurance limit. Findings. The analysis of the obtained dependence showed that the roller diameter as a function of the load in the contact zone of the “wheel – roller” pair has second order discontinuity in the section where this load changes from the minimum to the maximum value. Analytical dependence is also presented and analyzed in graphical form. The generalization of the results obtained made it possible to conclude that it is impossible to carry out complex tests of railway wheels, which provide for the combination of fatigue strength tests with contact strength tests, subject to their simultaneous holding at the same test-bench. Originality. For the proposed scheme of the bench for complex tests of railway wheels, for the first time, we obtained the dependence linking the parameters of the test wheel, the parameters of the bench, the wheel pair axle load and the wheel material endurance limit. Practical value. The results obtained can be used as a basis for the development of new test-benches for railway wheels.
Published: 2 December 2020
Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport pp 93-104; doi:10.15802/stp2020/217611
Purpose. The authors propose to develop a mathematical model for the calculated determination of residual stresses in arbitrary layer of a thermal gas coating based on the change magnitude in the base geometry (sample deflection) and the variation law of the layer thickness derivative, further regulation of these stresses by changing the technological parameters of spraying for each type of sprayed coating. Methodology. Based on known works on stress detection of in welded joints, the approach of determination of samples deflection after layer-by-layer spraying was developed. These deflection parameters are the basis for the developed mathematical model of influence on the stress state. The data on the study of the main types of residual (internal) stresses, as I type, distributed in the volume of the whole part (sample) with coating, and II type, localized in the volume of sprayed particles, are systematized. Findings. We presented investigations of the residual stresses arising in the applied layer, the magnitude and nature of the distribution of which depend on the type, base and sprayed materials, methods and parameters of spraying, the rigidity of the part, and other factors. The important role of evaluating residual stresses in a thermal gas coating by the calculation method is shown in connection with the complexity of the experimental determination of the kinetics of stress development in the coating-base composite. Originality. The authors of this work, on the basis of the first created mathematical model and software product Mathcad-Prime 6 2020, conducted a study of the level and principles of the formation of residual stresses in the coating during gas-thermal layer-by-layer spraying with various material, including the possibility of using a pulsating spraying air flow. Analytical studies have shown that the attention in the literature over the past five to seven years has been paid only to the study of residual stresses and deformations in welded joints, and only the growing interest in spraying technology opens up wide possibilities for studying the formation of stress fields in a thermal gas coating. Practical relevance. The results obtained in this paper confirm the formation of residual stresses in coatings and can be used as computational programs to solve design tasks, as well as for educational purposes during experts training in engineering fields.
Published: 2 December 2020
Science and Transport Progress. Bulletin of Dnipropetrovsk National University of Railway Transport pp 142-159; doi:10.15802/stp2020/217649
Purpose. An integral and essential feature of the modern wagon fleet is its large scale. For the entire fleet of rolling stock, even the smallest structural changes take on enormous proportions. The aim of the work is a theoretical study of the influence of the inertial characteristics of bodies of various types of freight rolling stock, taking into account the loading mode and the movement speed, on their main dynamic and interaction indicators with the track structure. Methodology. Theoretical studies were carried out by the method of mathematical and computer modeling of the dynamic load during the movement of some types of freight cars: gondola cars model 12-532, hopper cars for transporting coal model 12-4034 and flat wagons model 13-401 on standard bogies 18-100 at speeds in the range from 50 to 90 km/h on curves of small and medium radii. Findings. The analysis of theoretical studies of the dynamic qualities and interaction indicators of freight rolling stock and the railway track is presented. In the course of theoretical studies and after modeling taking into account the oscillation processes of freight cars at different loading modes the dependences of the main dynamic indicators on the movement speed were obtained. Originality. The influence of inertial characteristics of bodies of various types of freight rolling stock and loading modes on the dynamic load of a car was first explored in order to solve the problem of predicting the rolling stock dynamics and indicators of its interaction with the track. The results of theoretical studies taking into account the movement speed along curved track sections of small and medium radius were obtained. Practical value. The presented calculation results make it possible to determine the optimal values of such parameters as dead weight, height of the mass center and car base length when solving the problems of modernizing the operated car fleet and determining the reserves for increasing their carrying capacity. They make it possible to solve the problems of finding the optimal directions for modernizing the rail vehicle; contribute to the creation of technical conditions for the manufacture of new and modernization of the operated freight cars and are aimed at increasing the level of reliability and safety of the transportation process in modern conditions on the railway transport.