Aerospace engineering and technology

Two classes of nonlinear problems concerning wave and jet structures in steady flows of an inhomogeneous fluid are considered. One of them is related to the modeling of lee waves in atmospheric airflows over uneven terrain. The other group of problems concerns the description of internal waves in deep-ocean currents. A common feature of both cases is the combined use of analytical approaches and computer algebra methods to construct asymptotic solutions of the equations of motion of a stratified fluid. The first approximate model is employed for the numerical calculation of jet-flow patterns and the nonlinear interference of lee waves over complex topography. The second model is used to characterize the qualitative properties and parameters of solitary internal waves in layered weakly stratified near-bottom flows.

The article examines current approaches to enhancing the autonomy of unmanned aerial vehicles (UAVs) under emergency conditions. The importance of UAV autonomy for the effective execution of search-and-rescue, monitoring, and emergency recovery operations in disaster zones is substantiated, where traditional methods are often impractical due to high risk to personnel and limited access to incident sites. An analysis of modern technological solutions is conducted, including computer vision systems with AI algorithms, multi-sensor navigation complexes, onboard computing platforms, and algorithms for route and energy optimization. Based on studies from 2022–2025, the effectiveness of LiDAR systems, modular navigation interfaces, and edge-computing technologies is evaluated. Key limitations are identified, such as dependence on satellite navigation, vulnerability of communication channels, limited energy resources, and restricted computational capacity of onboard systems. The following development directions are proposed: integration of quantum sensors, adoption of hybrid power systems, and use of adaptive algorithms for collective swarm behavior of UAVs. Recommendations are formulated for standardizing autonomy requirements for UAVs in emergency situations and for establishing testing grounds to validate operational scenarios. It is shown that a comprehensive approach to enhancing autonomy can yield a manifold increase in the responsiveness and safety of emergency rescue operations.

The article substantiates two non-destructive testing methods — non-contact and contact — designed to determine the thermophysical properties of materials by locally heating a semi-infinite medium using a disk-shaped heat source. During processing of the heating thermogram obtained with a non-contact source, the homochronicity parameter is used, defined as the ratio of the average rates of surface temperature change taken from different sections of the heating thermogram. It is established that, for certain geometric dimensions of the heat source and temperature measurement points, the homochronicity parameter ε is functionally related to the product of the material's thermal diffusivity and the temperature measurement time. This makes it possible, using nomograms derived from preliminary numerical calculations for a series of materials with known thermophysical properties, to determine the thermal diffusivity and thermal conductivity coefficients of the test materials without employing complex methods for solving inverse heat conduction problems. The contact method involves time-resolved detection of the excess temperature at the center or at a certain distance from the disk-shaped heat source, and interpretation of the temperature profile using nomograms obtained with consideration of the heater's heat capacity and the homochronicity parameter values, or by means of a neural network that establishes a relationship between the heating thermogram parameters and the target thermophysical properties.