National Metallurgical Academy of Ukraine

This study investigates the hot deformation behavior of electroslag remelted (ESR) 25Cr2Ni2MoV steel, focusing on the effects of deformation temperature and strain rate on flow stress, microstructure evolution, and dynamic recrystallization (DRX) mechanisms. Hot compression tests were performed at temperatures ranging from 1120 °C to 1210 °C and strain rates from 0.01 s−1 to 10 s−1 to generate true stress–strain curves. The friction and adiabatic temperature effects were corrected to ensure accurate results. The data reveal that the material exhibits a single-peak true stress–strain curve, characteristic of dynamic recrystallization softening. The flow stress is negatively sensitive to temperature and positively sensitive to strain rate. An Arrhenius-type constitutive model was developed, and the activation energy for hot deformation was determined to be 371.3 kJ/mol. EBSD analysis show that the recrystallized grain size is highly dependent on strain rate, with finer grains formed at lower strain rates (0.01–0.1 s−1). A processing map constructed at a true strain of 0.5 identified an optimal hot-working window at deformation temperatures of 1160–1200 °C with strain rates below 0.37 s−1, providing guidance for the forging process of large 25Cr2Ni2MoV steel.

The relevance of this topic is due to the high level of importance of sustainable waste management and the need for effective decision-making tools. The purpose of the article is to justify the possibility and expediency of using the life cycle assessment method in managing the logistics of municipal waste management. The research was conducted using general scientific methods of cognition: system analysis, synthesis, generalization, deduction, abstraction, concretization, and formalization. Given the results of the conducted research, the meaning, and essence of the evaluation method life cycle are highlighted. It was determined that the life cycle assessment method is possible and advisable to be used for analyzing the impact of waste on the environment, namely on the quality of the ecosystem, state of health of the population, and use of natural resources. It is noted that this method is an effective tool for ensuring the rational use of natural resources and effective management of waste, allowing optimizing the process of management of logistics of waste according to the criteria of time and cost. Separate attention is assigned to considering the process of adopting management solutions in the part of optimizing logistic processes in the system of managing municipal waste, which is outlined as a choice of one option from several possible ones. It is proposed that the method of life cycle assessment be applied by local authorities in Poland to substantiate management decisions regarding the choice of alternative options for processing, disposal, or dumping of municipal waste based on the criterion of minimizing the harmful impact on the environment.

The coalification rank of the coal blend components and their caking properties initially impact the coke’s quality. In part, the quality of coke depends on the technological parameters of the coke production technology, such as the method of blend preparation, the coking condition, the design features of the coke ovens, and the technique used for post-oven treatment. Therefore, to improve the coke quality, the main attention is paid to the quality of the coal blend. The petrographic analysis is the simplest and most reliable way to control coal quality indicators under industrial conditions. In this paper, the effect of nine industrial blends on coke quality using petrographic analysis has been studied. Additionally, this paper addresses the efficient use of coals and the preparation of coal mixtures under industrial conditions, which contributes to the sustainability of cokemaking. For the preparation of blends, 17 coals were used, for which, in addition to petrographic and proximate analyzes, the maximum thickness of the plastic layer was determined. Industrially produced cokes were analyzed for coke reactivity index (CRI), coke strength after reaction with CO2 (CSR), and Micum indices (M25 and M10). It has been established that the petrographic properties of coal blends are reliable parameters for assessing the quality of coke under conditions of an unstable raw material base, multi-component blends, and changes in coking regimes. Moreover, the research results have shown that to ensure the rational use of coals in the preparation of coal blends to achieve the required coke quality and consequently the sustainability of cokemaking, it is necessary to consider not only the mean reflectance of vitrinite but the proximate and caking properties of coals.

In this paper the information technologies stack is presented. Thesetechnologies are used during network architecture deployment. The analysis of technological advantages and drawbacks under investigation for monolithic and network architectures will be useful during of cyber security analysis in telecom networks. The analysis of the main numeric characteristics was carried out with the aid of Kubectl. The results of a series of numerical experiments on the evaluation of the response speed to requests and the fault tolerance are presented. The characteristics of the of monolithic and microservice-based architectures scalability are under investigation. For the time series sets, which characterize the network server load, the value of the Hurst exponent was calculated.
 The research main goal is the monolithic and microservice architecture main characteristics analysis, time series data from the network server accruing, and their statistical analysis.
 The methodology of Kubernetes clusters deploying using Minikube, Kubectl, Docker has been used. Application deploy on AWS ECS virtual machine with monolithic architecture and on the Kubernetes cluster (AWS EKS) were conducted.
 The investigation results gives us the confirmation, that the microservices architecture would be more fault tolerance and flexible in comparison with the monolithic architecture. Time series fractal analysis on the server equipment load showed the presence of long-term dependency, so that we can treat the traffic implementation as a self-similar process.
 The scientific novelty of the article lies in the application of fractal analysis to real time series: use of the kernel in user space, kernel latency, RAM usage, caching of RAM collected over 6 months with a step of 10 seconds, establishing a long-term dependence of time series data.
 The practical significance of the research is methodology creation of the monolithic and microservice architectures deployment and exploitation, as well as the use of time series fractal analysis for the network equipment load exploration.

Abstract The accumulation of impurities in the recycling of steel impacts the quality of secondary steel. Understanding impurity levels is crucial in the context of the proliferation of circular economy policies, expected high recycling rates, and growth of scrap consumption. By assuming the accumulation of impurities to be equal worldwide, the understanding of the extent and variation of the mixing and accumulation was limited in previous studies, and the factors influencing those variations were not considered. This is a first cross‐national comparison of impurity accumulation in recycled steel. In this study, the copper, tin, nickel, chromium, and molybdenum content was analyzed in over 500 samples of electric arc furnace rebars from China, Japan, Vietnam, Ukraine, and the Netherlands (representing northwestern Europe) with an optical emission spectrometer. The impurity content in rebars represents the content of impurities accumulated in steel scrap in the countries studied. The measured content of impurities was then used to determine the factors influencing the accumulation of those impurities. It was revealed that the recycling technology, the presence of a market for recovered metals, the quality of the material input, steelmaking practices, and the management of byproducts derived from a legislative or economic context played a role in the impurities content. By communicating on scrap chemical content, the collaboration between the recycling and steel industries could be enhanced in terms of matching the demand and supply and facilitating an increase in the scrap share in steelmaking.

Mining power complexes can significantly reduce the cost of production of mining enterprises and increase their competitive position in the relevant market. To solve the urgent problem of further improving the operation of mine energy complexes, it is proposed to include in their composition installations for the useful use of energy from low-potential sources with a freon-steam turbine, which implement the thermodynamic Rankine cycle. The article considers the features of the organization of the Rankine cycle depending on the properties of freons. When choosing freons, the emphasis is placed on the use of strictly ozone-safe freons that meet modern requirements for normalizing the value of the global warming potential. The previously proposed method for calculating the thermodynamic parameters necessary for evaluating useful action’s coefficient of using specific freons in a useful energy recovery equipment has been improved. The calculation of the energy efficiency of the equipment with a freon-steam turbine for the selected options for the use of freons is performed. The analysis of the obtained results showed that the use of ozone-safe freons with low values of the global warming potential in installations for the utilization of energy from low-potential sources will improve the operation of mine energy complexes.

Abstract A study of waste heat recovery systems for robust ship power systems (tens of MW) and installations of relatively low power (1…3 MW) of diesel locomotives has been carried out. A method for calculating the power of gas and steam turbines as part of the waste heat recovery systems has been developed. Based on simple calculations for two operating points, the method allows you to get the amount of the waste heat recovery system generated energy in other modes, different from those given in the instructions for technical operation. Preference for one or another type of turbine generator or their combination should be provided based on a feasibility study, taking into account capital investments and the power of energy consumers in the vehicle, as well as long-term prospects in fuel-saving and reducing greenhouse gas emissions. The waste heat recovery system's energy characteristics can be used to confirm the compliance of the main power plant with the requirements of the MARPOL 73/78 convention in terms of improving energy efficiency design index and reducing greenhouse gas emissions at loads of 50%, 75%, 100%. KeywordsWaste heat recovery systemMain engineHeat balanceEnergy efficiency design index

Impact of high temperatures on slag bowls causes considerable elastoplastic deformations resulted in appearance of cracks in them. To prevent destruction of the bowls casing, it is necessary to undertake measures for stabilization of thermostressed state of slag carriage bowls and increasing their thermostability. Results of experimental and computer studies of temperature fields and thermostressed state of slag carriage bowls of various design presented. The study of the thermostressed state of slag carriage bowls was carried out by a tensometric method based on standard equipment. The measuring of temperature and thermal stresses was carried out in the most critical bowls sections. To study the thermostressed state of bowls, a methodology of computer simulation and engineer analysis based on Solid Works/Cosmos Works software was proposed. Results of comparative evaluation of the thermostressed state and thermostability of the forming bowl casing, used in the domestic industry and abroad presented. Basic measures to stabilize the thermostressed state of slag carriage bowls and ways of their thermostability increasing were proposed. Reliability of the results obtained was confirmed by results of experimental studies.