https://dspace.mnau.edu.ua/jspui/handle/123456789/24986 Sat, 12 Sep 2026 07:25:00 GMT 2026-09-12T07:25:00Z https://dspace.mnau.edu.ua/jspui/handle/123456789/26628 Назва: Numerical and Experimental Analysis of Free Vibrations of Thick-Walled Cylindrical Shell Автори: Grigorenko, Alexander; Müller, Wolfgang; Borysenko, Maksym; Бойчук, Олена Володимирівна; Boychuk, Olena Короткий огляд (реферат): Free vibrations of an isotropic thick-walled circular cylindrical shell with one end rigidly clamped, and the other free, are investigated numerically and experimentally. The natural frequencies and corresponding mode shapes are determined using the finite element method within a three-dimensional elasticity formulation, employing solid finite elements. The article focuses on constructing a reliable finite element model, including selecting element types and mesh density based on accuracy, convergence, and computational efficiency. In the article, solve a test problem to verify the numerical model and present a detailed convergence analysis. An experimental study of free vibrations based on stroboscopic interferometry, which allows full-field visualization of vibration mode shapes and determination of natural frequencies with sufficient accuracy. A comparison between numerical and experimental results demonstrates good agreement, confirming the reliability of the proposed modeling approach. The research study has been used in the design and analysis of thick-walled cylindrical shell structures in engineering applications, as well as for validating numerical and analytical methods for the vibration analysis of shell systems. Thu, 01 Jan 2026 00:00:00 GMT https://dspace.mnau.edu.ua/jspui/handle/123456789/26628 2026-01-01T00:00:00Z https://dspace.mnau.edu.ua/jspui/handle/123456789/26350 Назва: Study of Deep Subsurface Fatigue Degradation in Rolling and Sliding Tribocontacts under Variable Loading Автори: Марченко, Дмитро Дмитрович; Marchenko, Dmytro Короткий огляд (реферат): The paper evaluates the effectiveness of soft gas nitriding of alloyed structural steels 38KhMYuA, 38KhN3MA, and 38KhN3MFA, used in highly loaded gear transmissions, and establishes the limits of application of thin nitrided layers in terms of contact fatigue. The studies are conducted after nitriding at a temperature of 580°C and a duration of 7 hours using microhardness testing, layer-by-layer chemical analysis by high-temperature gas analysis, X-ray structural analysis, and contact fatigue testing of rollers simulating rolling and sliding conditions, typical for helical gearing. It is found that soft nitriding ensures the formation of a hardened layer 0.18–0.25 mm thick with a microhardness of 4.8–5.5 GPa while maintaining a ductile core with a hardness of 240–260 HB. It is shown that under elevated contact stresses, failure of nitrided samples initiates in the subsurface layers and develops via a deep contact fatigue mechanism, accompanied by the formation of deep spalling and a so-called white etching area. The results obtained demonstrate the limited effectiveness of thin nitrided layers under high contact loads and point to the feasibility of using materials with thicker hardened layers (0.8–1.2 mm) or design and technological solutions aimed at reducing contact stress and increasing the service life of gears. Опис: Повний текст доступний з сайту видавця за посиланням: https://link.springer.com/article/10.3103/S1068366626700121 Thu, 01 Jan 2026 00:00:00 GMT https://dspace.mnau.edu.ua/jspui/handle/123456789/26350 2026-01-01T00:00:00Z https://dspace.mnau.edu.ua/jspui/handle/123456789/26314 Назва: Burst-Aware Cascade Detection of UAV Radio-Frequency Signals Using Energy and Cyclostationary Analysis Автори: Sova, Ivan; Kozlov, Oleksiy; Kondratenko, Yuriy; Кондратенко, Юрій Пантелійович; Атаманюк, Ігор Петрович; Atamanyuk, Igor; Aleksieieva, Anna Короткий огляд (реферат): The increasing activity of unmanned aerial vehicles (UAVs) has intensified the demand for reliable and computationally efficient methods for passive radio-frequency (RF) signal detection. In practical RF monitoring scenarios, the environment is often non-stationary and affected by varying noise conditions. Under such circumstances, classical energybased detectors are sensitive to noise uncertainty, while more robust approaches, such as cyclostationary analysis, require substantially higher computational resources. This work presents a burst-aware cascade method for UAV RF signal presence detection that explicitly addresses this trade-off. The proposed framework combines fast energy-based screening with temporal burst aggregation, applying spectral correlation function (SCF) analysis selectively and only when sustained signal activity is indicated. Detection is performed on fixed-length RF signal chunks, while additional segment-level duration constraints are used to characterize sustained transmissions. The method is evaluated using the publicly available DroneRF dataset and compared against six baseline detectors, including fixed-threshold energy, wavelet-based, blind cyclostationary, two adaptive energy detector variants, and a lightweight convolutional neural network. Experimental results confirm that chunk-level detection remains difficult for all considered methods. Temporal aggregation across longer intervals yields a substantial improvement: the cascade achieves Pd = 1.000 and AUC = 1.000 at the segment level, matching exhaustive cyclostationary detection while reducing per-segment processing time by a factor of 2.46. An additional result is that burst-level concatenation prior to SCF estimation provides implicit coherent integration, preserving Pd = 1.000 at signal amplitude reductions of up to −20 dB where standalone detectors degrade to Pd = 0.995. Overall, burst-aware cascade architectures offer a practical and interpretable approach to RF-based UAV monitoring, providing a well-grounded compromise between detection reliability and computational efficiency under realistic operating conditions. Thu, 01 Jan 2026 00:00:00 GMT https://dspace.mnau.edu.ua/jspui/handle/123456789/26314 2026-01-01T00:00:00Z https://dspace.mnau.edu.ua/jspui/handle/123456789/26310 Назва: Effect of Intake Water Injection on Fuel Efficiency and Performance of an Agricultural Diesel Engine Автори: Калініченко, Антоніна; Kalinichenko, Antonina; Марченко, Дмитро Дмитрович; Marchenko, Dmytro; Грубань, Василь Анатолійович; Hruban', Vasyl'; Hovorukha, Vira Короткий огляд (реферат): The article presents the results of experimental investigations and regression-based analysis on the influence of a water injection system on the fuel efficiency and performance of diesel engines used in agricultural machine–tractor units. The need to improve fuel economy and operating efficiency is driven by increasing energy costs and the growing demand for more efficient agricultural machinery. The study focuses on the application of water injection into the intake manifold as a method for improving fuel consumption and engine operating performance under laboratory and field conditions. Experimental investigations were carried out on a Deutz 1000.3 W diesel engine under laboratory and field conditions. The engine was tested on a dynamometer, and field tests were performed using a Deutz-Fahr Agrolux 80 (SDF Group, Treviglio, Italy) tractor powered by the tested Deutz engine and coupled with an Amazone D9-20 Super (AMAZONEN-WERKE H. DREYER SE & Co., KG, Hasbergen-Gaste, Germany) seeder. The seeder was used as a trailed agricultural implement and did not have its own engine. The optimal water-to-fuel ratio was found to be 27–32%, ensuring a balance between increased engine power and reduced fuel consumption. The use of water injection reduced fuel consumption by 10–15%, increased effective engine power by up to 19%, and improved traction performance under field conditions. The novelty of this study lies in the adaptation and experimental evaluation of intake water injection for an agricultural diesel engine operating as part of a machine–tractor unit. Particular attention was paid to the relationship between the water-to-fuel ratio, fuel consumption, engine performance, and traction characteristics under laboratory and field conditions. The results demonstrate that water injection provides a cost-effective and technically feasible solution for improving fuel economy and operating performance of agricultural diesel engines without requiring significant modifications to existing designs. Potential environmental benefits may be associated with reduced diesel fuel consumption. However, emissions were not the main experimental focus of the present study and should be investigated separately in future work. Thu, 01 Jan 2026 00:00:00 GMT https://dspace.mnau.edu.ua/jspui/handle/123456789/26310 2026-01-01T00:00:00Z