Technical Physics最新文献

The problems of the current stage of operation of hazardous industrial facilities and other complex technical systems are considered. A graphical analytical method for optimizing the periodicity (frequency) of control at various levels is proposed. The results of modeling a system safety program for ensuring safe operation of hazardous industrial facilities and other complex technical systems using the mathematical apparatus of semi-Markov processes are presented. An analysis of the results obtained was conducted, and substantiated conclusions were drawn.

A novel Ag+TiN/TiN/Al₂O₃ multilayer coating was developed via magnetron sputtering and investigated for its structural and infrared optical performance with and without vacuum annealing. The multilayer structure comprises a co-sputtered Ag+TiN base layer for enhanced reflectivity and conductivity, an intermediate TiN layer for thermal stability, and a top Al₂O₃ dielectric capping layer for environmental protection and optical modulation. Post-deposition annealing at 400°C for 1 h in high vacuum significantly improved the crystallinity and grain size, as confirmed by X-ray diffraction and field-emission scanning electron microscopy. Optical characterization revealed a substantial increase in visible reflectance (from ~22 to ~46%) and a marked decrease in infrared emissivity, particularly in the mid-wave (3–5 μm) and long-wave (8–14 μm) IR windows. The average emissivity was reduced from 0.163 to 0.102 (MWIR) and from 0.251 to 0.201 (LWIR) upon annealing. These results demonstrate that the tri-layer Ag+TiN/TiN/Al₂O₃ architecture, with thermal treatment, effectively suppresses IR emission while maintaining favorable optical properties, offering strong potential for thermal stealth, aerospace, and energy-efficient applications.

The efficiency of metal heat treatment production processes is measured according to various characteristics, including productivity, energy consumption, and quality of the end product. Each of them can be enhanced through optimization by the relevant integral criterion. The quality of the end product made from a high-iron alloy depends, after heat treatment, on metal loss to scale, which is inevitably formed during high-intensity heating in an induction installation. For this reason, to reduce the percentage of rejects, it is necessary to find an optimal operating mode of the inductor, which will minimize this loss. This paper is devoted to the optimization of static induction heating of steel cylindrical workpieces before subsequent plastic deformation operations. A 2D numerical mathematical model of the induction heating process, developed in Altair FLUX, is considered as a controlled object with distributed parameters. Control problems with respect to time-optimal, minimum energy consumption, and minimum metal scale loss criteria are formulated. A solution to the formulated control problems after their parametrization and reduction to semi-infinite optimization can be found using the alternance method of parametric optimization of objects with distributed parameters. A system of transcendental equations is written based on the alternance method as an example for the minimum scale formation problem. These equations are closed to all unknown parameters of the heating process. The system is solved using an automated procedure developed in the MATLAB software package. An analysis of numerical results shows that solving this one-criterion optimal control problem reduces the amount of scale significantly increasing heating time compared to time-optimal and minimum energy consumption problems. That is why it is planned to solve a multi-criteria optimization problem taking into account several typical goal functions simultaneously at the next stage of research.

Methodology for stochastic modeling of processes of resource distribution in industrial networks based on GERT networks is considered. This work is topical due to the need for efficient management tools for complex production systems that operate under conditions of uncertainty and dynamic changes in external factors. Compared to conventional methods for network planning, this approach makes it possible to take into account the probabilistic nature of operations, alternative implementation of processes, and the presence of feedback, which are especially important for modern production complexes with a high level of automation. This paper presents a comprehensive mathematical framework, including the formalization of GERT network using graph theory and probability theory, as well as the methods for numerical analysis of time parameters based on the modified Monte Carlo algorithm. Special attention is paid to computer implementation of the model. A Python software module is developed to provide simulation of production processes, visualization of results, including the construction of 3D network graphs and animated diagrams, and integration with the systems of Industrial Internet of Things (IoT). Practical significance of the study is confirmed by testing the methodology on real production facilities. In comparison with conventional approaches, an increase in resource efficiency of 15–20% has been achieved. Promising directions for further research include the development of adaptive control algorithms based on GERT networks and machine learning methods and the creation of digital twins of industrial systems using predictive analytics. The results are of interest for specialists in industrial engineering, logistics, and management of complex technical and economic systems.

In mathematical modeling of crystallization process, we have used the results of numerical experiment, in which a striated structure of the initial stage of the process governed by diffusive foliation mechanism has been detected. This is in qualitative agreement with a natural experiment. In G.I. Barenblatt’s terminology, the process is associated with the converted state flux at the initial stage of crystallization up to the formation of a dendrite structure. The universality of mathematical modeling principles and the relation with the critical processes of destruction, sintering of materials, and crystallization of binary alloys has been demonstrated based on their physical generality.

This paper discusses a method of increasing the thermodynamic efficiency of a jet engine by modifying the engine nozzle of classic design. The modified engine has a dual-circuit nozzle. Hydrogen is supplied to its outer circuit as an additional heat carrier. Increased thermal efficiency is achieved by utilizing the heat released in the inner circuit of the nozzle. Numerical simulation has shown that the thermal efficiency is enhanced in this case by almost 10%, and the new nozzle design increases thrust as well. The paper compares classic and modified engine designs based on efficiency, thrust, specific impulse, and nozzle weight change.

The paper presents a fault localization algorithm for medium-voltage networks of electric power systems and complexes. This approach utilizes information derived from an analysis of the power direction of the zero-sequence components, ensuring high accuracy of fault location. The proposed method demonstrates resilience to the impact of distributed generation, making it a promising option for modern power systems with a high share of renewable energy sources. Its key advantage is reliance on minimal infrastructure, as the transmission of a single binary signal between relay protection devices is sufficient to ensure correct operation. The paper presents the theoretical foundations of the method, tests it using Sincal and MATLAB software, and suggests applications. A simulation confirmed the method’s effectiveness, reducing the time required to locate faults by 40–60% compared to traditional approaches.

A new thin-film transistor (TFT) structure based on hydrogenated amorphous silicon-germanium (a-SiGe:H) is proposed and analyzed, incorporating a double-layer gate dielectric. Silvaco TCAD simulations are employed to evaluate the electrical performance of a conventional single-layer silicon dioxide (SiO₂) dielectric compared to a novel bi-layer configuration combining hafnium dioxide (HfO₂) and SiO₂. The bi-layer design leverages the high permittivity of HfO₂ to enhance gate control while maintaining excellent interface quality through the inclusion of a thin interfacial SiO₂ layer. This structure effectively addresses common limitations of high-κ dielectrics, such as interface traps and gate leakage. Simulation results demonstrate that the proposed bi-layer dielectric significantly improves device characteristics, reducing the threshold voltage from 0.458 to 0.130 V, increasing the ON-state current from 1.85 × 10⁻⁷ to 3.24 × 10⁻⁵ A, and enhancing the ON/OFF current ratio from 1.71 × 10⁵ to 4.68 × 10⁶, with only a modest increase in subthreshold swing. Electric field and energy band analyses further confirm improved electrostatic control and reduced leakage current. These findings underscore the potential of the HfO₂/SiO₂ bi-layer dielectric structure for advancing the performance and scalability of a-SiGe:H TFTs in future electronic applications.

This paper explores the behavior of air inside a corona discharge reactor, specifically in a tip-plane configuration, subjected to an applied voltage. The ionization of the air by the electric field generates ionizing waves, leading to a dynamic motion of the air governed by Navier–Stokes equations for a viscous fluid. The two-dimensional Navier–Stokes equations are solved numerically using an implicit algorithm that combines the finite difference method (FDM) and the implicit Euler scheme with the Newton–Raphson method. Two situations are examined: a single discharge and a series of discharges. The results reveal the distinct formation of primary and secondary vortexes in the air stream. In the case of a single discharge, a transition to symmetrical vortexes is observed, followed by an oscillatory phase characterized by the intermittent appearance of tertiary vortices. In contrast, for a series of discharges, the flow profiles show a cyclic repetition with a gradual increase in flow velocity.

The effect of decorating the surface of submicron barium titanate particles with graphene nanoplatelets on the characteristics of its surface and dielectric constant of polymer composites based on it is studied. Nonlinearity of the dependence of the dielectric constant and surface characteristics on the amount of modifier is shown. The Lichtenecker formula is used to approximate the measured values of permittivity. The formula is supplemented with the dependence of the structural parameter on the number of surface centers, which improves the interphase interactions of the polymer with the filler in the composite. The experimental data are well approximated using the modified formula.