This study presents the results of an experimental investigation of the effect of electron-beam surface modification on heat transfer during nucleate pool boiling of distilled water at atmospheric pressure. The relevance of the research is driven by the need to improve the efficiency of cooling systems operating under high heat flux conditions. Copper surfaces with various microrelief geometries fabricated by electron-beam processing using the Surfi-Sculpt technique were employed as test specimens. Three types of modified surfaces were produced: star-shaped structures generated using both the forward and reverse electron-beam scanning modes, and a surface with a linear structure. Boiling curves and heat transfer coefficient versus heat flux relationships were obtained for all investigated samples. The results demonstrated that electron-beam surface modification significantly enhances boiling heat transfer compared with a smooth copper surface. For all modified specimens, the boiling curves shifted toward lower wall superheats, accompanied by an increase in the heat transfer coefficient and critical heat flux. It was shown that the heat transfer performance is strongly influenced by the geometry of the fabricated microrelief, which affects the density of active nucleation sites as well as the liquid supply and vapor removal mechanisms. The obtained results confirm the potential of electron-beam processing as an effective approach for the development of high-performance boiling heat transfer surfaces.
The paper considers the features of three-dimensional modeling of the thermal state of rotary piston engine (RPE) components in Ansys Fluent software. It is shown that a well-developed computational and experimental basis has been established for internal combustion piston engines (ICEs), whereas no unified methodology currently exists for RPEs that accounts for rotor motion and the nonuniform nature of heat transfer. A transient CFD modeling methodology is proposed using user-defined functions, a dynamic computational mesh, the Realizable k–ε turbulence model, the Finite Rate/Eddy Dissipation combustion model, and conjugate heat transfer between the gas, solid, and liquid domains. The methodology provides the pressure, temperature, and gas velocity fields, as well as temperature fields of engine components. Validation against experimental pressure and temperature data confirms the applicability of the proposed approach for engineering assessment of the thermal state and subsequent strength calculations.
A mathematical model based on solving Maxwell’s equations supplemented by the equation of motion of the magnetization vector in a ferromagnet taking into account the exchange interaction in the Landau–Lifshitz form has been constructed for magnetic nanostructures. An iterative computational algorithm for solving a nonlinear diffraction problem for an autonomous block containing magnetic nanoinclusions with virtual Floquet channels on the faces, which is reduced to solving a system of nonlinear algebraic equations, has been developed.
This paper presents a comprehensive study on the influence of coal particle concentration (0–50
In this paper, a new current equation of main discharge of transversely excited atmospheric (TEA) CO2 laser is introduced. The current equation is derived in consideration of the effects of electron collision with laser gas molecules on discharge current. Then, the collision-induced current equation is combined with the discharge circuit model and six-temperature model (6TM) to build theoretical model. Dynamic emission process of e-beam controlled TEA-CO2 laser is simulated using the model. The calculated result is in agreement with the experimental result in [33]. The power characteristics are analyzed for different initial electron densities. As a result, it has been found that there is a critical threshold of initial electron density that influences power characteristics to be deteriorated. The theoretical model can be used in the study of the behavior of gas laser discharge and designing of electron beam controlled TEA-CO2 laser.
The service life of an agricultural syringe depends on the sprayer material. To increase the wear resistance of polymer nozzles, disperse fillers are implanted into the composite. The composite for sprayers of agricultural syringes must possess a high chemical resistance to agrochemicals and mechanical strength, as well as low hydro-abrasive wear. To choose an optimal polymer composite for sprayers of agricultural syringes, three composites have been prepared based on polyoxymethylene of grade MASCON POM 27, in which glass fiber, graphite, and silicon carbide have been used with volumetric degrees of filling of 10, 15, and 20
Fluidic thrust vector control has emerged as an attractive alternative to conventional mechanical vectoring systems in modern rocket propulsion due to its reduced structural complexity, improved reliability, and rapid response capability. In a recent study, the authors proposed a novel elliptical cross-section dual-bell rocket nozzle and demonstrated its aerodynamic performance compared with conventional dual-bell configurations. Building upon that design, the present work investigates the application of fluidic thrust vectoring using the shock vector control (SVC) method in the proposed nozzle configuration. A secondary jet is injected into the divergent section of the nozzle to generate asymmetric shock structures and modify the internal pressure distribution, leading to controlled deflection of the exhaust plume. The three-dimensional compressible Reynolds–Averaged Navier–Stokes equations are solved using a finite-volume approach with the SST k–ω turbulence model to analyze the interaction between the injected jet and the primary supersonic flow. The effects of injection pressure ratio and mass flow rate on shock formation, flow separation, and thrust vector angle are systematically examined. Numerical results show that the injected jet induces a strong asymmetric shock system, producing significant jet deflection and effective thrust vectoring while maintaining acceptable propulsion performance. The findings demonstrate that the combination of the elliptical dual-bell nozzle and shock vector control provides a promising fluidic thrust vectoring mechanism for advanced altitude-adaptive rocket propulsion systems.
This study is aimed at the development and designing of a combined heat exchange installation (generator of an absorption refrigeration machine (AHM)/heat pump condenser) in an air-conditioning complex combining a refrigeration machine, a heat pump, and solar collectors. We propose an original schematic decision ensuring the combination of functioning of the generator, the condenser, and the heat pump in a single complex. Flow diagrams of working regimes of the air-conditioning complex are calculated. The technical aspect of the AHM generator is developed and the method for calculating its thermal and technical characteristic is proposed, which makes it possible to take into account the simultaneously occurring processes of boiling of a dilute lithium bromide solution, steam evaporation, and condensation of superheated freon R600a vapor in a single hydraulic loop of solar collectors and heat pump. This decision allows us to refute traditional multiloop systems in which different working bodies circulate, and the heat-transfer processes are implemented with the help of intermediate devices. As a result, it becomes possible to optimize the mass and size characteristics of the entire complex, to reduce the number of basic devices, and to increase the energy efficiency of the entire air-conditioning system. We propose that one and the same freon R600a (isobutane) be used as the heating agent of the solar power plant, the cooling agent of the heat pump, and the heat-accumulating substance. We report on the results of thermal and checking calculations of the combined heat exchange installation. The sizes of the system and its operation conditions are evaluated; the heat-transfer coefficients, expenditures, and the working parameters of cooling agents as well as the thermal power of the apparatus are determined. The significance of the results lies in the development and formation of the technical aspect of the combined heat exchanger, the proof of its high energy and technological efficiency, and the development of recommendations for its designing in complex systems of centralized air-conditioning.
Previously published experimental data on the normal total emissivity εtn of tellurium and antimony revealed its negative jump upon melting, which lacked a physical explanation. This paper proposes an interpretation of this negative jump. The decrease in εtn is attributed to an increase in the electrical conductivity of the melt due to metallization. The differences in the behavior of tellurium and antimony are associated with the extent of change in the electronic structure upon melting.
This paper examines the self-breakdown of voltage effort in short gaps and mm of flat-out electrical electric poles filled with Freon gas at pressures ranging from 0.5–3 bar. The characterization of electrical breakdown in compressed Freon gas can be studied theoretically. Freon gas can be used as an electrical insulator alone or mixed with Sulphur hexafluoride gas, in order to reduce the cost and obtain a strong insulator at a lower cost, as Freon gas is less insulating compared to Sulphur hexafluoride gas. A proposed formulation of results is presented to make use of gas in the design, insulation, electrical appliances and equipment. Theoretical conclusions on the calculations of the breakdown voltage and the electric field of irregular fields were clarified in the research using non uniform electrodes (needle to plane) for different distances (in mm) and comparing this with Sulphur hexafluoride and air. The theoretical calculations obtained were compared with the practical results and there was a clear match indicated. Freon (R-12) is one of the famous known types of Freon and its name in the International Union of Research and Applied Chemistry is dichlorodifluoromethane. Its chemical shape is (CCL2F2). Freon has been used in many applications in homes, and including in the industrial field, Freon gas voltage is higher in varying electric fields in gaps of a few mm and above due to negative activation compared to positive energy. Negative stimulation reduces the field near the acute cathode, leading to a high breakdown voltage.
Fluidic thrust vectoring (FTV) has emerged as an effective technique for controlling exhaust flow in propulsion systems, with shock vector control (SVC) representing one of its most efficient implementations. Dual-bell nozzles (DBNs), known for their altitude-compensating capability, provide a promising configuration for integrating such control strategies. However, previous studies of SVC in DBNs have been largely restricted to cold-flow simulations using air, which do not accurately represent the high-temperature, chemically reacting environments encountered in rocket propulsion. To address this limitation, the present study investigates the influence of chemical reactions on SVC performance using the ANSYS Fluent computational fluid dynamics (CFD) solver. A kinetic reaction mechanism for LH2/LO2 is employed to account for high-temperature dissociation and recombination processes. The analysis is conducted on a novel subscale DBN geometry designed using an in-house method of characteristics (MoC) code, with the resulting contour validated through CFD simulations. Calculated species molar fractions from CFD are further validated against those obtained using NASA’s chemical equilibrium with applications (CEA) code, showing good agreement. Comparative analyses between cold-flow (air) and reacting-flow (LH2/LO2) conditions reveal significant differences in SVC performance, highlighting the critical role of thermodynamic and thermochemical effects on vectoring efficiency. These findings demonstrate that cold-flow assumptions may lead to inaccurate predictions, emphasizing the necessity of incorporating reacting-flow models for realistic assessment and design of SVC systems in DBNs.
In this article, we carry out a theoretical investigation of the self-focusing and propagation characteristics and terahertz (THz) radiation generation of Laguerre–Gaussian (LG) laser beams in an inhomogeneous plasma channel, considering the effects of relativistic and ponderomotive nonlinearities. The analysis is carried out by the method of moments to derive the equation for the evolution of the width of LG laser beams propagating in a preformed parabolic plasma channel. From the results, it is observed that the overall effect of relativistic mass variation and intensity-dependent ponderomotive force results in a significant modification in the plasma refractive index, which in turn affects self-focusing and confinement. The self-focusing is observed to be sensitive to various parameters such as intensity, plasma density, channel depth, and order of LG modes. It is also noted that the most efficient generation of THz radiation occurs in the regime where self-focusing is strongest, which suggests an intrinsic connection between beam confinement effects and plasma low-frequency responses. It is also noted that the THz signal increases with increasing laser intensity and channel depth, which suggests that relativistic ponderomotive effects are key to understanding the overall efficiency of the process. It is also noted that the presence of a preformed parabolic plasma channel enhances the guiding effects, which supports the interaction process. On the whole, the study suggests that structured LG beam modes, especially of higher orders, can be a promising way of controlling self-focusing and boosting THz generation in plasmas, and this may have implications for the creation of a new generation of radiation sources.
The emission of axion a by a classical alternating electromagnetic field F, which is accompanied by the emission of photon γ (F → a + γ) and caused by the contribution of three-pole diagrams, is considered for the first time. Simultaneously, the similar process of neutrino production F → νν̅ + γ is also discussed for the first time.
An explanation of the dependence of the resistance of metals on the atomic number is proposed. Based on experimental data borrowed from the Encyclopedia of Physics, a table is given, in which the relationship between the resistance of various metals and their atomic number is clearly traced. With its help, an empirical illustration of this dependence is constructed, which has the form of a pronounced parabola. It is proved that such a dependence can be explained with the help of three main mechanisms of interaction of electrons, arranged in a hierarchical order in relaxation time: the electron–electron, electron–phonon (fluctuation), and electron–dipole interactions. A comparison of theoretical dependence and empirical dependence showed their quite satisfactory agreement.
The article substantiates the requirements for the formation of a digital elevation model (DEM) for simulating the transport of suspended sediments using the example of the Terek River. It is shown that the hydrological regime (flood, high water, mean water) determines the migration of suspended matter and the accumulation of fine-dispersed fractions in the delta. A conceptual model scheme is proposed, which provides for the joint use of the one-dimensional Hydrologic Engineering Center–River Analysis System (HEC-RAS) module for the entire channel network (from the Pavlodolsk hydroelectric power station to the mouth) and the three-dimensional MIKE 3 module for critical sections. Requirements for the initial DEM data have been formulated, and analysis of factors for erosion and accumulation of bottom sediments has been performed.
Generally, logic locking technique is used to safeguard the intellectual property (IP) of integrated circuit (IC) designs across the world’s supply chain. To overcome security issues, the nano digital circuits exhibit greater strength than the traditional CMOS security methods. An advanced nano technology of Quantum dot Cellular Automata (QCA) based hardware security is domineering in this era that rising a greater cyber security from a threat and safeguarding sensitive data within ICs. In this work, the QCA based Enhanced Majority Voter (EMV) gate is presented in a logic locking technique to enhance its security by reducing complexity. In this proposed method, the EMV is performed and execute the correct key only when the exact key is given. This process can be highly safeguarded from thwarting tampering and reverse engineering attempts. The validation result of proposed EMV logic locking revealed as a marginal increase in complexity (measured by dots) that is compared to benchmarks while preserving identical execution times. Therefore, this proposed EMV locking strengthens hardware security without compromising circuit performance.
The aim of the study is to comparatively evaluate the strength and mass characteristics of the all-metal and metal–composite versions of the helicopter fuselage design. The main emphasis is laid on the possibility of modernizing existing structures by partially replacing metal elements with polymer composite materials (PCMs). The research methodology includes the development of a standard fuselage design, the construction of finite-element models, and strength calculations. The study is based on a comparison of two configurations: an all-metal structure made of D16 alloy and a hybrid design with selective use of composite materials. For the analysis, the maneuverable calculation cases “pull-up” and “side-slip” are used. The main results show that replacing some of the metal elements with composite materials makes it possible • to maintain the required static safety factor (η ≥ 1.01); • to achieve a 24
We consider the influence of oscillations of the vapor–liquid interface on the stability of a hot liquid–metal drop in a cold liquid. For the first time, four different mechanisms of impact of the vapor film oscillations on the liquid–metal drop are proposed, which lead to instability (vapor explosion). For one of the described mechanisms, the boundary of the instability, i.e., of explosive fragmentation of the drop is obtained, which depends on the material, the metal drop temperature, and the drop radius.
A new universal classification of components of heterogeneous media (liquids, gases, and plasma) flows includes traditional waves and families of ligaments describing the fine structure of distributions of observable physical quantities. The mathematical basis of the classification includes the sets of complete solutions to the system of fundamental equations of fluid mechanics constructed taking into account macro- and microscopic mechanisms of transfer and conversion of energy components. A fluid medium is characterized by equations of state for the Gibbs potential and its derivatives. When solving problems using the algebra of complex numbers, the frequency, which is a measure of energy, preserves its real-valuedness and positive definiteness, and the wave number is chosen to be complex-valued. Complete solutions to linearized and weakly nonlinear equations are found using united perturbation theory. The spatiotemporal parameters of the solutions describing waves and ligaments determine the requirements to experimental techniques as regards the choice of observable physical quantities that permit the assessment of error, the size of the observation area, the sensitivity, as well as the spatial and temporal resolution of instruments. The paper presents complete dispersion relations of propagating periodic surface and internal gravity waves in stratified media. Schlieren methods for visualizations of periodic internal wave beams and ligaments in the depth of a continuously stratified fluid are also considered.
A combined experimental and computational research on the influence of plasma torch geometry on the thermophysical parameters of combustion of brown coal from the Transbaikal Krai has been carried out. It has been shown that the torch shape in direct-flow and vortex plasmatrons sets a law of adding a tempering coal−air mixture to the high-temperature zone. Based on a developed analytical model that takes into account the torch geometry and the kinetics of thermodynamic transformations, the quantitative dependences of the gas phase temperature and degree of carbon gasification on flow swirl parameters and pulverized coal concentration have been derived. It has been shown experimentally that the vortex plasmatron, which forms a cardioid torch with a developed contact surface, makes it possible to achieve stable burning at a carbon dust concentration of 0.6 kg/kg and a power of 120 kW. Under such conditions, the degree of carbon drop increases by 20–25
