Dmytro Obidin

This paper considers a numerically stable discrete-time representation of the three-dimensional Constant Turn (CT) motion model within the Interacting Multiple Model (IMM) framework for radar tracking of maneuvering aerial targets. Classical discrete CT models used in Kalman-filter-based tracking contain singular expressions in the vicinity of zero and near-zero turn rates, which may degrade estimation accuracy and impair numerical robustness. To address this problem, a Maclaurin-series-based discretization of the three-dimensional CT model is developed, in which the state transition matrix and the process-noise-related matrices are approximated in polynomial form. Linear, quadratic, and cubic approximations are constructed and analyzed. The proposed CT model is integrated into a three-model IMM algorithm together with the Constant Velocity (CV) and Constant Acceleration (CA) models. The study includes both an internal comparison of Maclaurin approximations of different orders and an external comparison with the classical CT discretization and a Padé-based reference discretization. Numerical experiments are performed for representative three-dimensional maneuvering scenarios under radar measurement conditions. The obtained results show that the proposed discretization eliminates singular behavior near zero turn rate while preserving the tracking capability of the IMM estimator. The comparative analysis demonstrates that the quadratic Maclaurin approximation provides the most favorable trade-off between modeling accuracy, numerical stability, and computational cost. It yields tracking performance close to higher-order approximations and competitive with the Padé-based reference approach, while remaining simpler for practical implementation in real-time radar tracking systems. These results indicate that the proposed quadratic approximation is a suitable solution for maneuvering aerial target tracking in three-dimensional radar applications.

This study explores heat and mass transfer processes in the structural elements of an umbrella-type hydrogenerator, as well as the ventilation and cooling system in the active components of the hydrogenerator. A vertical synchronous air-cooled hydrogenerator with a rated capacity of 60 MW has been investigated. The task addressed relates to the cooling efficiency of generator components. Conventional analytical calculation methods do not make it possible to identify local overheating zones and pressure distribution in complex ventilation channels. Therefore, it becomes necessary to use numerical methods and algorithms to calculate and analyze the cooling efficiency of the generator’s active parts. The main result of this study is the designed structure of the guide channels (blades) of the rotor, which provides the required air flow rate of 45 m3/s. At the same time, the maximum values of the winding temperature do not exceed the permissible values for class F insulation. The CFD calculation detailed the action of the superchargers and showed the real pressure in the channels and the volume of air passing through each section of the generator. The error between the results from CFD modeling and analytical calculations is less than 3%. The results are attributed to the detailed reproduction of the geometry of the ventilation channels in the 3D model, which made it possible to determine the real aerodynamic resistance and cooling medium consumption. The proposed method uses the boundary conditions of the third kind for a comprehensive calculation of the conjugate heat and mass transfer. The proposed structure could be implemented in the design and modernization of air-cooled hydrogenerators.

The article presents the findings of a study that employed intelligent components to model a hybrid network traffic load management system. Recent research indicates that forwarding a substantial volume of requests between network elements results in higher failure rates. Consequently, optimizing the allocation of network resources becomes crucial, especially when incorporating “smart” components during deployment. Innovative strategies in traffic engineering and baseline load prediction enable a more effective utilization of network components while maintaining operational stability.

In Ukraine, the challenges and threats to the efficient functioning of the transportation industry are intensifying during the war and infrastructure destruction. The need for emergency repairs of the ruined infrastructure hinders the reform of the Ukrainian transportation industry. Furthermore, developing an integrated EU-oriented multimodal transportation system within the "Eastern Partnership" regional network becomes more complicated. This article aims to identify the problems of efficiency and competitiveness of the Ukrainian transportation industry in the context of integration into the Trans-European Transport Network (TEN-T) and the construction of a multimodal transportation system. The research employs a systemic analysis methodology to assess the structural indicators of Ukraine's transportation system development. The structure of Ukrainian freight transportation by mode is compared with that in EU countries to reflect differences in a modal split in the context of Ukraine's accession to TEN-T. The results demonstrate a range of problems related to the competitiveness of the Ukrainian transportation industry, which act as barriers to its integration with TEN-T. Institutional, political, and managerial-administrative problems are identified as the leading issues associated with inefficient data collection and processing, management and control functions, decision-making, communication, and interaction among governing bodies. A separate group of issues in Ukraine's transportation industry is linked to the material-technical condition of various types of transportation infrastructure, which affects service quality. Consequently, other problems arise, including the low level of development of intermodal and multimodal transport, transportation logistics, decreased efficiency in capacity utilization, insufficient level of competition in the market for transportation services, and non-compliance with European requirements for access to the transportation services market.