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Abstract: This paper presents a methodological framework for building a digital shadow of an induction motor based on standardised tests and a two‑axis (dq) simulation model. The tests were carried out according to IEEE Std 112 and IEC 60034‑2‑1. The parameters of the equivalent circuit were identified and entered into the model. Validation was performed by comparing the torque–speed and current–speed curves at 180 V and 220 V, while the nominal behaviour at 400 V was estimated using the model and voltage scaling. The model was then calibrated to reduce the discrepancy between the simulation and measurements, and the error was quantified using the root‑mean‑square error (RMSE) and mean absolute percentage error (MAPE). An automated load‑simulation setup that reproduces the torque test is also presented, enabling rapid evaluation of parameter influence. The results show a very good match in the current channel, with larger deviations in the prediction of characteristic torque points, indicating the limitations of linearised parameters and motivating nonlinear model extensions. The approach enables summarised reliable estimates at nominal voltage when direct measurements are not feasible.
Keywords: induction motor, digital shadow, standardised tests, dq model, torque test, automated load simulation, model calibration
Published in DKUM: 01.10.2025; Views: 0; Downloads: 2
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Abstract: The question of fiscal sustainability of countries has become one of the central topics in economic policy, especially in times of increasing public debts. One way to assess fiscal sustainability is to examine compliance with the intertemporal budget constraint, which involves testing the stationarity of government revenues and expenditures, the primary budget balance, and the first differences of public debt. Part of this approach includes testing cointegration and causality among different pairs of variables. Under this approach, the paper is focused on both first- and second-generation panel unit root tests, cointegration, and Granger causality test. This paper focuses on assessing the fiscal sustainability of four panels of countries divided by continents: Europe, Asia and Oceania, Africa, and Latin America, the Caribbean, and North America. It has been found that fiscal sustainability is present in all the broader groups of countries considered but in a weak form. Fiscal sustainability was confirmed when considering a constant in calculations, while deviations were observed among groups of countries when both a constant and trend were considered. The study serves as a starting point for a more extensive analysis of fiscal sustainability. For more accurate findings, it would be necessary to categorize countries into smaller and economically more homogeneous groups and analyze them using other fiscal sustainability methods as well.
Keywords: cointegration tests, fiscal sustainability, Granger causality tests, intertemporal budgetary constraint, unit root tests
Published in DKUM: 27.05.2025; Views: 0; Downloads: 14
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Abstract: This paper studies the load-bearing capacity of various concrete tetrapods under quasistatic loading. The tetrapods were made of plain concrete and synthetic-polymer-fiber-reinforced concrete. Load tests of the tetrapods were performed. The maximum load-bearing capacity and the residual-load-bearing capacity of the tetrapods (the load-bearing capacity after the first crack or at different crack widths) were evaluated. The strength and residual-strength values were backcalculated from the load-bearing capacities, and compared with available data from the literature. The specimens with and without fibers achieved similar maximum load-bearing capacities, with cracks occurring at identical locations. However, the differences in residual-load-bearing capacity were more significant. The synthetic-polymer-fiber-reinforced concrete tetrapods exhibited relatively high residual-load-bearing capacities, even at higher displacements and crack widths. Two different calculation-procedures were used for the load-bearing-capacity evaluation. A load-displacement calculation based on the moment-versus-curvature relation and the plastic-hinge approach was performed, and additionally proved the applicability of the employed calculation-procedures for the concrete tetrapod load-bearing-capacity evaluation.
Keywords: tetrapods, concrete, synthetic-polymer fibers, load tests, load-bearing capacity, residual load-bearing capacity, load displacement, calculation
Published in DKUM: 12.03.2025; Views: 0; Downloads: 8
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Abstract: This study presents a comprehensive analysis of different coating materials on the POM substrate. Specifically, it investigated physical vapour deposition (PVD) coatings of aluminium (Al), chromium (Cr), and chromium nitride (CrN) of three various thicknesses. The deposition of Al was accomplished through a three-step process, particularly plasma activation, metallisation of Al by magnetron sputtering, and plasma polymerisation. The deposition of Cr was attained using the magnetron sputtering technique in a single step. For the deposition of CrN, a two-step process was employed. The first step involved the metallisation of Cr using magnetron sputtering, while the second step involved the vapour deposition of CrN, obtained through the reactive metallisation of Cr and nitrogen using magnetron sputtering. The focus of the research was to conduct comprehensive indentation tests to obtain the surface hardness of the analysed multilayer coatings, SEM analyses to examine surface morphology, and thorough adhesion analyses between the POM substrate and the appropriate PVD coating.
Keywords: POM, PVD coating, metal coating, adhesion analyses, indentation tests
Published in DKUM: 15.02.2024; Views: 304; Downloads: 44
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Abstract: The article includes the study and reconstruction of a fluid bed device with the purpose of separating the granular material from the grinding process of rapid antigen tests. The following techniques were performed, with the purpose of characterisation of the ground particles: sieve analysis, X-ray fluorescence spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. The paper includes experimental testing of a simplified separation process with zeolite spheres and paper strips, supported by a numerical model. The flow conditions’ impact on the behaviour and interactions of particles of the considered problem were simulated using coupled computational fluid dynamics (CFD) and the discrete element method (DEM) approach. The separation process of zeolite spheres and paper strips was found to be efficient. The simulation results showed the appropriate behaviour of the particles during the process. We explained the results’ deviations, and we also presented the shortcomings and possible improvements. Further research is required to define the adequacy of the process, while using actual ground material of rapid antigen tests.
Keywords: rapid antigen tests, nanomaterials, fluidised bed, computational fluid dynamics, discrete element method, characterisation
Published in DKUM: 05.01.2024; Views: 378; Downloads: 61
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