bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the rotation of type-II superconductors in a transverse magnetic field
Authors: Ashimov S. M. , Naskidashvili I. A.
Published: December 2024

The characteristic properties of the dynamic response of superconductors, having different defect structures, to a torque applied to them in a transverse magnetic field are investigated. It is shown that when a superconductor with quantized vortices frozen in it is rotated, the change in the torque has a sinusoidal character. A simple method is proposed for determining the counter-torque pinning and viscous forces acting on the vortex lines in a rotating superconductor.
Nonlinear stationary magnons in spin glass
Authors: Akhiezer I. A. , Belorozov D. P.
Published: December 2024

Uniformly moving nonlinear magnons in spin glass are considered. It is shown that besides ordinary solitons (as well as periodic waves), another type of solitary waves, viz., “screw” solitons can propagate in a spin glass.
Surface polaritons in antiferromagnetic media possessing metallic conduction
Authors: Ivanov N. B.
Published: December 2024

The properties of surface polaritons in antiferromagnetic media possessing metallic conduction were studied for H = 0 without allowance for spatial dispersion. It is shown that under appropriate conditions magnetic polaritons should propagate with anomalous dispersion on the surface.
Saturation of the Zeeman subsystem with inhomogeneous broadening of the EPR line
Authors: Pogrebnyak S. V. , Shadchin E. A.
Published: December 2024

The form of the inhomogeneous broadening is taken into account in examining the Zeeman temperature distribution under conditions of stationary saturation of the EPR line. It is shown that taking the form of the broadening into account increases the width of the trough in the Zeeman temperature distribution and leads to an asymmetry of this distribution relative to the point of application of the saturating field.
The theory of localized surface excitations in helium II adjacent to a substrate
Authors: Pikhitsa P. V.
Published: December 2024

Localized states corresponding to two-dimensional maxons are shown to exist in helium II adjacent to a solid substrate. These states were in fact observed experimentally by Lauter et al.1 and their existence supports the suggestion that localized rotons are present in helium II near a substrate.
Bifurcation under parametric excitation of spin waves
Authors: Frishman A. M.
Published: December 2024

Variation of external parameters is shown to cause a rearrangement of the stationary state of the spin system under the conditions of parametric excitation.
Magnetization of a one-dimensional Ising magnet
Authors: Vadyunina L. S. , Sterlin A. M. , Yurishchev M. A.
Published: December 2024

A calculation of the magnetization for a three-dimensional Ising magnet with strong spatial anisotropy of the interaction is carried out within a self-consistent cluster approximation in which the average magnetic moments of four- and five-chain clusters are required to be equal. The theoretical curves obtained agree well with data for the quasi-one-dimensional Ising magnet CoCl2 · 2NC5H5.
Pairing of electrosolitons in soft molecular chains
Authors: Brizhik L. S. , Davydov A. S.
Published: December 2024

A theory of efficient transport of paired electrons from donors to acceptors along soft molecular chains, which takes into account the local deformation of the chains, is developed based on nonlinear equations. The effective mass of a pair and the energy and momentum transported by each pair are calculated. Pairing of electrosolitons can play a large role in the explanation of the superconductivity of the molecular crystals TMTSF2ClO4 at a temperature of 1.2 K.
Transformation of sound at the solid helium–He II interface: features of the growth of quantum crystals
Authors: Dyumin N. E. , Grigor’ev V. N. , Svatko S. V.
Published: December 2024

The features of the growth of hcp 4He crystals have been studied under conditions when the basal plane is perpendicular to the crystal growth direction. Information on the kinetic crystal growth coefficient was obtained from results of measurements of the temperature dependence of the transformation coefficient of first into second sound at the hcp 4He–He II interface in the temperature range 1.4−0.9 K at an oscillation frequency ∼10 kHz. It was found that a transition from classical behavior of the crystal growth coefficient to quantum takes place at T ∼ 1.3 K. It was established that the area of the atomically smooth section on the basal plane below the faceting temperature increases linearly with decreasing temperature.
Nonlinear absorption of electromagnetic waves in superconducting alloys at low temperatures
Authors: Azovskii A. Yu. , Bezuglyi E. V. , Galaiko V. P.
Published: December 2024

We make a theoretical investigation of a nonlinear mechanism of electromagnetic absorption in superconducting alloys as a result of oscillations of the density of states and the boundary of the energy spectrum of quasiparticles in the Meissner skin layer. Excitation of oscillations of the quasiparticle distribution function is shown to disrupt the usual dissipationless nature of the superfluid component of the electric current, which at low temperatures T ≪ Δ makes the principal contribution to absorption. The maximum nonlinear absorption is attained in fields far from the critical value and can be two or three orders of magnitude higher than the value calculated in the linear theory.
Electronic band structure and electronic properties of hexagonal ruthenium
Authors: Kulikov N. I. , Magnitskaya M. V.
Published: December 2024

The results of calculations of the band structure, density of states, joint density of states, and also extremal cross-sections of the Fermi surface, including their pressure derivatives, are compared with experimental results. Reasons for the discrepancies between single-particle, self-consistent calculations and experiments are discussed. A semiquantitative interpretation of measurements of the de Haas–van Alphen effect and optical absorption is given.
Hall effect in the magnetic Kondo lattice of CeAI2
Authors: Brandt N. B. , Moshchalkov V. V. , Sluchanko N. E. , Savitskiĭ E. M. , Shkatova T. M.
Published: December 2024

The temperature and field dependences of the Hall coefficient R(T, H) and of the transverse magnetoresistance Δρ┴(H)/ρ(0) of the magnetic Kondo lattice of CeAl2 are studied. The measurements were performed on polycrystalline samples of CeAl2 in the temperature range 1.8 ≤ T ≤ 300 K in a magnetic field H ≤ 40 kOe. It was found that as the temperature is decreased from T ≃100 K to the temperature of the antiferromagnetic transition at T≃3.8 K the quantity R (T, H0) increases by more than a factor of 4 (H0 ≤ 8 kOe). As the magnetic field H0 is increased, the ratio r = R(T = 3.8 K, H0)/R (T = 100 K, H0) decreases and at H = H0 = 40 kOe it is equal to r∼2. The magnetoresistance Δρ┴(H)/ρ(0) is negative and assumes a maximum absolute magnitude at T = T0≃3.7 K in a field of H = 16 kOe; the temperature T0 decreases as H increases approximately at the rate dT0/dH∼0.058 K/kOe. The data obtained are analyzed within the framework of the model of the formation of the Abrikosov–Suhl resonance and the model of skew-scattering, leading to the anomalous Hall effect.
Superconductivity of gallium antimonide at pressures up to 12.0 GPa
Authors: Il’ina M. A.
Published: December 2024

The Tc(P) relation has been studied under pressures from 6.5 to 12.0 GPa for a p-type GaSb specimen with p = 2.5·1019 cm−3 and two n-type specimens with initial current carrier concentrations n = 1.5·1018 and 4·1017 cm−3. It was found that the critical temperature Tc of the GaSb II modification depends on the type and on the value of the initial concentration.
Hindered rotation of CO molecules in a solid Kr matrix. Specific heat
Authors: Sumarokov V. V. , Freĩman Yu. A. , Manzheliĩ V. G. , Popov V. A. , Konstantinov V. A.
Published: December 2024

The specific heat of a Kr−CO solid solution with a carbon monoxide concentration of 0.95 mol.% has been studied in the temperature range 2−12 K. In order that the experimental and calculated results should agree it is necessary to assume an appreciable renormalization of the effective rotational constant B/Beff≈2.5. It was found that the barrier hindering rotation of CO molecules in a Kr matrix is ∽10B≈27.5 K. The existence of a low-temperature peak in the specific heat with a maximum in the region of T∽0.3 − 0.4 K is predicted.
Exact solution of Leggett’s equations for the A phase of superfluid He3
Authors: Poluéktov Yu. M.
Published: December 2024

The Lagrangian and Hamiltonian formalisms of Leggett’s magnetic dynamics for superfluid He3-A are formulated. The spherical coordinates of the spin vector d are chosen as the generalized variables. The exact solution of Leggett’s equations are found for He3-A with a uniform texture, in which the orbital vector l is aligned with the constant magnetic field H. The possible regimes of motion of the magnetic system He3-A, produced by a jump in the magnetic field, are studied.
Specific heat of solid para-hydrogen
Authors: Bagatskii M. I. , Minchina I. Ya. , Manzhelii V. G.
Published: December 2024

We have developed a vacuum adiabatic calorimeter for studies of cryocrystals and their mixtures over the temperature range 0.4–300 K. We report the specific heat of hydrogen with an ortho concentration of 5 · 10−3 % over the temperature range 0.5–8 K. The limiting value of the Debye temperature obtained as T →0 is found to be Θ0 = 118.5 ±0.5 K. It is shown that the specific heat of solid para-hydrogen, the same as that of other cryocrystals with central-force interactions and close-packed lattices (4He, Ne, Ar, Kr, and Xe), is described at low temperatures by the universal curve Cv = AT3[1 + α1(T/Θ0)2 + α2(T/Θ0)4 + ...] proposed by Barron and Morrison. The influence of sample history on the experimental values of the specific heat of hydrogen is studied with an ortho concentration of x = 0.21 at.% and the time for configurational equilibration in this mixture is estimated.
Quantum diffusion in hydrogen, studied by calorimetric methods
Authors: Minchina I. Ya. , Bagatskii M. I. , Manzhelii V. G. , Krivchikov A. I.
Published: December 2024

Two methods, both employing an adiabatic calorimeter, were used experimentally to study dilute solid solutions of hydrogen over the temperature range 0.4–3 K, with ortho concentrations of x = 0.10, 0.21 0.50, and 1.10 at.%. The time-dependent specific heat was utilized to characterize the configurational relaxation time τ in the ortho subsystem, as well as the temperature dependence of the specific heat of the ortho subsystem for the equilibrium cluster concentration characteristic of the temperature of the experiment, which does not vary during a measurement of the specific heat. We compare the experimental results with values for the specific heat of the ortho subsystem calculated in terms of a simple statistical model. We propose and demonstrate a means of determining τ from data on the energy given up in solid hydrogen per unit time due to conversion and cluster formation. From the calorimetric results we find that within the limits of experimental uncertainty, the value of τ is independent of concentration. The temperature dependence of τ for T < 1 K is described by the expression τ ∼ T−1.
Radio-frequency impedance of a metallic plate taking into account the surface scattering of charge carriers
Authors: Kirichenko O. V. , Skobov V. G. , Chernov A. S.
Published: December 2024

The electromagnetic field distribution is found and the surface impedance is calculated for a plate consisting of a metal with an axisymmetrical Fermi surface, placed in a perpendicular magnetic field H, with an arbitrary indicatrix of scattering of charge carriers by the boundary of the sample. It is shown that different functionals of the scattering indicatrix, characterizing the interaction of the conduction electrons with the metal surface, can be determined from measurements of the smooth part of the impedance and the amplitude of its oscillation as function of H as well as from the distortions in the form of the oscillations.
Low temperature dislocation hysteresis losses in bismuth single crystals
Authors: Atencio E. Medrano , Pal’-Val’ P. P. , Platkov V. Ya. , Startsev V. I.
Published: December 2024

In order to establish the parameters that govern the thermally activated motion of dislocations, we have studied the amplitude-dependent dislocation internal friction in pure undeformed bismuth single crystals with a [111] orientation over the temperature range 6–300 K and over a wide range of deformation amplitudes. Measurements were performed using a double composite oscillator technique at a frequency of 88 KHz for the longitudinal vibrations. Lowering of the temperature in the range 90–6 K causes the amplitude dependence of the decrement and of the modulus defect to move toward larger values of the amplitude, due to the thermally activated nature of dislocation depinning. The results are compared with the theory of Indenbom and Chernov. Quantitative analysis of the data in terms of this theory provides the activation energy and the activation volume for the depinning of dislocations at trapping centers as a function of the deformation amplitude. The force law is found for the interaction, and the distribution function for the length of the dislocation segments released is found to be a power law with an exponent of –4.9.
Magnetic heat capacity of the antiferromagnets β-NiS and β-Ni0.97Fe0.03S
Authors: Kasumov M. T. , Guseinov N. G.
Published: December 2024

The heat capacities Cp of hexagonal β-NiS and β-Ni0.97Fe0.03S and rhombohedral nonmagnetic α-NiS were measured in the temperature range from 3 to 350 K. The magnetic part of the heat capacity of β-NiS and β- Ni0.97Fe0.03S has been separated. The value obtained is shown to be in satisfactory agreement with the result of spin-wave theory in the temperature range 15–40 K. Doping with iron has been found to cause a rise in the phase transition temperature and an increase in the magnetic part of the heat capacity. The results of the measurements are compared with the conclusions of spin-wave theory.
High-frequency conductivity of electrons on a helium film in the presence of localization at substrate potential nonuniformities
Authors: Kovdrya Yu. Z. , Mende F. F. , Nikolaenko V. A.
Published: December 2024

We have studied the superhigh frequency conductivity of surface electrons on a helium film wetting a dielectric substrate with a large dielectric constant (ϵs ≈9.6) in the temperature range 1.7−2.1 K with an electron density of 1010 cm−2. The conductivity was determined from the decrease in the Q of a superconducting resonator when the liquid helium film was charged with electrons. It is shown that the effective high-frequency mobility of electrons on a helium film, defined as μ(ω) = σ /ne (σ is the conductivity of the electron layer, n is the electron density, and e is the electron charge), is much lower than the mobility on bulk helium. The quantity μ (ω) increases as the temperature decreases, and in the region 1.7−2 K μ (ω)−1 is approximately proportional to the density N of atomic vapor. When positive ions are present on the substrate, μ (ω) decreases to about 70 cm2/V-sec, and its temperature dependence changes. When the temperature is in the range 1.9−2.1 K μ (ω) is approximately proportional to the density of rotons, μ (ω) increases with the thickness d of the helium film, growing in order of magnitude when d≈5×10−6 cm. These results are explained by localization of electrons on nonuniformities in the potential of the substrate caused by defects and roughness or positive charges present on its surface. Electron localization produces deformations of the underlying helium films and causes holes to form (a sort of additional self-localization). These effects produce a unique behavior in the superhigh frequency conductivity of the electron layer.
Study of phase transitions in the solid solutions CH4−CD4
Authors: Prokhvatilov A. I. , Isakina A. P.
Published: December 2024

The solid solutions CH4−CD4 were studied by the x-ray method over a wide range of temperatures and concentrations. The characteristics of the phase transitions were studied and it was established that in solutions with a “frozen” high-temperature composition of spin modifications a linear concentration dependence of the phase-transition temperatures holds. It is shown that in the region of weak solid solutions xCD4 < 15% the metastability of the phase III is a result of the spin-nuclear conversion of methane molecules. The change in the tetragonality of the lattice of the low-temperature phase of the solid solutions as a function of the concentration of deutero-methane was studied.
Unusual behavior of superconducting granular vanadium films for T≤T
c
Authors: Solov’ev A. L. , Dmitriev V. M. , Dmitrenko A. I.
Published: December 2024

Resistive junctions and the current-voltage characteristics (IVC) of superconducting granular vanadium films are studied. The features observed for T ≤ Tc can be explained by the presence of thermal vortex–antivortex topological excitations in the samples, which is confirmed by studies in uhf fields. The change in the properties of the samples occurs both when the temperature passes through the pairing temperature of such vortices T2D and when the ratio of the coherence length ξ(T) and the average granule size g changes. The dependence of Tc on the normal resistance of samples and low-frequency generation in such fields are also studied.
Nonlinear absorption of a microwave field by an impurity atom in a spin chain
Authors: Vekslerchik V. E. , Zaslavskii O. B. , Tsukernik V. M.
Published: December 2024

We have studied the line shape for absorption of a microwave field by an impurity atom in a compound of the type PrCl3, described by a one-dimensional X–Y model. An exact expression is obtained for the absorbed power in the case of an arbitrary field amplitude. In the vicinity of the absorption maximum, in the general case, there are terms logarithmic in the frequency shift or there is a cusp associated with the behavior of the density of states near the edge of the elementary excitation spectrum. At the lowest temperatures, if the field frequency is ω < J/ℏ (where J is the exchange integral), then raising the temperature leads not to smoothing but to a sharpening of the maximum. This characteristic of the low temperature absorption is manifested in sufficiently strong transverse fields.
Electronic drag of dislocations in superconductors with a structural transition
Authors: Menyaĭlenko V. V. , Molotkov S. N.
Published: December 2024

The electronic component of the drag force acting on dislocations in a superconductor with a structural transition is studied. The interelectronic correlation of a dielectric type, giving rise to the structural transition, leads to a maximum in the temperature dependence of the drag force near the point of the superconducting transition. In addition, a hysteresis dependence of the drag force on the velocity of the dislocation, which must occur both in ordinary superconductors and in superconductors with a structural transformation, is qualitatively predicted.
Existence of normalized solutions to Kirchhoff–Choquard equation with critical Sobolev perturbation
Authors: Li Qi , Wang Rui , Mao Anmin
Published: December 2024

In this paper, we consider a class nonlocal Kirchhoff–Choquard equation. Firstly, with the help of Pohozaev identity and Hardy–Littlewood–Sobolev inequality, we show a nonexistence result. Furthermore, by new truncation and subadditivity, as a ∈ (0, a*), we prove the existence of a couple of solution (u0,λ0)∈S(c)×R+. Lastly, as μ > 0, p = 2α, and 143<q<6, combining the technology and ideas of Jeanjean [Nonlinear Anal. Theory Math. Appl. 28(10), 1633 (1997)], we obtain at least one couple of solution (uc,λc)∈H1(RN)×R+.
CFD-based research on fixed valve leakage of inclined well pumps
Authors: Lyu A. Fengxia , Han B. Saiyue , Yue C. Dan , He D. Yanfeng , Zhang E. Xintong , Tang F. Ming , Zhang G. Sheng
Published: December 2024

With the growing demand for oilfield development, the use of inclined and directional wells has gradually increased. However, due to limitations in the shaft structure of inclined wells, the efficiency of rod pumping is significantly compromised. To investigate the delayed closure of fixed valves, a numerical model was developed using computational fluid dynamics technology, by combining the standard k–ω turbulence model with the volume-of-fluid multiphase flow model. The SIMPLE algorithm was employed to calculate the valve closing process in inclined well pumps. The delayed closure of the valve ball, caused by changes in the well inclination angle and swabbing parameters (such as sinking pressure, pump diameter, and stroke speed), was investigated. The simulation results showed that inclined well pumps are most effective at inclination angles below the critical angle (which, in this study, was 59.036°). In addition, lower sinking pressures, larger pump diameters, longer strokes, or fewer stroke times can reduce the time taken for valve closure and minimize leakage. As the well inclination angle approaches the critical value, pump valve leakage increases sharply. By quantitatively analyzing the numerical calculation results, we established a fitting relationship for valve ball fall time. This improved the proposed calculation model for pump efficiency in inclined well pumps, offering valuable insights for their practical application.
Evolution of confined mixing layer under optimal excitation frequency
Authors: Zhao Wei , Wang Guiren
Published: December 2024

The exceptionally rapid fluid mixing that is achievable in confined mixing layers through external excitation is studied through both flow visualization and particle image velocimetry at a moderate Reynolds number. Compared with free mixing layers, confined mixing layers exhibit a twofold larger spreading rate in the absence of excitation. When they are excited, a significantly larger V component of the mean velocity can be generated. This broadens the mixing layer on large scales, meanwhile generating a large |∂V/∂y| around the centerline. This large |∂V/∂y| further stretches the spanwise vortices, induces earlier collapse, and indirectly promotes small-scale mixing. Thus, the mean flow field plays an important role in the evolution of a confined mixing layer with excitation. Under the optimal excitation frequency, the turbulent kinetic energy primarily attributed to acoustical excitation is rapidly consumed by inverse energy transport. This further explains the formation of the mean field from the perspective of kinetic energy transfer. The results obtained here can be potentially applied to the design of high-efficiency and compact active mixers/reactors for chemical engineering and biomedical applications.
Theoretical research on a large beam tunnel, coalesced-mode broadband traveling wave tube
Authors: Cui Zhongtao , Yuan Xuesong , Xue Qinwen , Le Yiwen , Zhu Yunze , Thomas Cole Matthew , Yan Yang
Published: December 2024

A coalesced-mode, wide bandwidth traveling wave tube (TWT) with a large beam tunnel is herein investigated for use in millimeter-wave and terahertz amplification sources. The high frequency structure and input–output circuits of the TWT are designed to operate in both mode 1 (coalesced TE10-like mode) and mode 3 (coalesced TM11-like mode) at a same operating voltage, allowing a significant increase in the bandwidth. The gain difference between the two modes is reduced to less than 3 dB as the energy transmission is optimized with a large circular beam tunnel. Particle-in-cell simulations are performed at 24 kV with a beam current of 350 mA, and the coalesced-mode TWT is predicted to operate in two atmospheric windows, with a maximum output power of 530 W and a peak linear gain of 36 dB. The 3 dB bandwidth is predicted to be 41.6 GHz, ranging from 103.1 to 144.7 GHz, corresponding to a relative bandwidth of over 33%.
Investigation of RF behavior in a MW-level, frequency-multiplying, W-Band gyroklystron amplifier for linear accelerator applications
Authors: Debnath Ankhi , Swati M. V. , Baghel G. S.
Published: December 2024

The proposed work presents the design of the RF interaction structure for MW-level, three-cavity, frequency-doubling gyroklystron amplifier for W-Band linear accelerator applications. The input cavity is driven by a driver signal of 47.5 GHz frequency. It operates in the fundamental harmonic TE01 mode, while the buncher and output cavities operate in the second harmonic TE02 mode at twice the input signal frequency. The interaction circuit has been designed using a combination of both analytical studies and particle-in-cell simulations. The optimized gyroklystron delivers the peak RF output power of ∼6.6MW, with an interaction efficiency of ∼29% at 95 GHz when driven by a 500 kV, 45 A gyrating electron beam. The corresponding device's gain and 3 dB bandwidth are obtained as around 46 dB, 1.872 GHz.
Use of current-potential patches to obtain fundamental improvements to the coils of magnetic fusion devices
Authors: Boozer Allen H.
Published: December 2024

A central issue in the design of tokamaks or stellarators is the coils that produce the external magnetic fields. The freedom that remains unstudied in the design of coils is enormous. This freedom could be quickly studied computationally at low cost with high reliability. In particular, the space between toroidal field and modular coils that blocks access to the plasma chamber could be increased by a large factor. The concept of current-potential patches, which was developed in Todd Elder's thesis, provides a method for separating the study of the feasibility of coils with attractive physics properties from the engineering design of specific coils. In addition to enhanced accessibility, coils can be designed for increased plasma-coil separation, insensitivity to coil position errors, and plasma control.
The impact of electron inertia on collisional laser absorption for high energy density plasmas
Authors: Young James R. , Gourdain Pierre-Alexandre
Published: December 2024

High-power lasers are at the forefront of science in many domains. While their fields are still far from reaching the Schwinger limit, they have been used in extreme regimes, to successfully accelerate particles at high energies, or to reproduce phenomena observed in astrophysical settings. However, our understanding of laser–plasma interactions is limited by numerical simulations, which are very expensive to run as short temporal and spatial scales need to be resolved explicitly. Under such circumstances, a non-collisional approach to model laser–plasma interactions becomes numerically expensive. Even a collisional approach, modeling the electrons and ions as independent fluids, is slow in practice. In both cases, the limitation comes from a direct computation of electron motion. In this work, we show how the generalized Ohm's law captures collisional absorption phenomena through the macroscopic interactions of laser fields, electron flows, and ion dynamics. This approach replicates several features usually associated with explicit electron motion, such as cutoff density, reflection, and absorption. As the electron dynamics are now solved implicitly, the spatial and temporal scales of this model fit well between multi-fluid and standard magnetohydrodynamics scales, enabling the study of a new class of problems that would be too expensive to solve numerically with other methods.
Optimizing aerodynamic stability in compressible flow around a vibrating cylinder with deep reinforcement learning
Authors: Barzegar Gerdroodbary M. , Shiryanpoor Iman , Salavatidezfouli Sajad , Abazari Amir Musa , Pascoa J. C.
Published: December 2024

This paper explores the use of Deep Reinforcement Learning (DRL) to improve the aerodynamic stability of compressible flow around a vibrating cylinder. In uncontrolled conditions, the cylinder experiences a drag coefficient of 1.35 and an oscillatory lift coefficient with an amplitude of 0.35. By applying a classic Deep Q-Network (DQN), the lift oscillation amplitude is significantly reduced to ±0.025, marking an improvement of over 100%. The study further investigates the effects of episode count, neural network architecture, and DQN variants on performance, demonstrating the robustness of the approach. While changes to the neural network structure within the classic DQN yield limited improvements in reducing lift oscillations, both the classic and dueling DQN variants effectively control lift oscillations. Notably, the dueling DQN provides greater stability, reducing lift oscillation amplitude to as low as ±0.001. The paper also examines the effect of varying jet positions, offering valuable insights into the adaptability and generalization of the proposed DRL-based control strategy.
Analysis and experiment of conductive rod of high voltage casing considering creep condition
Authors: Zhou Xiu , Tian Tian , Li Liang , Bai Jin , Luo Yan , Ma Kui , Zhang Heng , Jiang Kaiji , Chen Dezhi
Published: December 2024

Transformer bushings are used in large quantities in substations, and their operational reliability directly affects the operational safety of equipment and the power grid. The conductor rod is a crucial component of a high-voltage (HV) casing, and any breakage can trigger line protection actions and lead to significant economic losses. Since the conductive rod is subjected to the tension exerted by the compression spring for a long time and the influence of other external tensions, it is in a state of slow creep, and thus the conductive rod gradually fails. Therefore, this paper investigates the stress and deformation of the conductor rod in a 750 kV HV casing under service conditions that take creep characteristics into account. First, a finite element model of the rod connector considering creep characteristics is established. Second, stress and deformation experiments of the sample are carried out, considering the effect of creep characteristics. Finally, the experimental results are compared with the simulation results to verify the accuracy of the simulation.
Effects of suction/injection and surface curvature on aerodynamically slender bodies of revolution with uniform heat transfer
Authors: Shah Babar Hussain , Tang Zhili
Published: December 2024

Controlling the boundary layer has been a topic of interest for a long time due to its practical application, especially in the field of aerospace engineering. In a real-world scenario, it is often needful to prevent flow separation to minimize the drag to get a lift. One of the important methods to control the boundary layer is suction and injection which often give useful information inside the boundary layer. Therefore, the current analysis has been presented theoretically investigating the effects of suction/injection (mass transfer) on aerodynamically slender bodies of revolution generated with a variable radius of power-law shape function. The self-similar flow has been recovered under consideration of some particular form of variable radius that forms a paraboloid body of revolution together with mass transfer velocity and compares the results with those body of revolution that kills the criterion of self-similarity. The particular shapes are considered due to the resemblance of most high-speed aero vehicles to quantify the transport phenomenon along these sophisticated shapes which are considered challenging theoretically in general. The non-similar boundary layer equation is solved with the implicit finite difference technique with second order accuracy, and results are reported through graphs and tables. The impact of convex curvature of the surface has also been highlighted under the mass transfer. The results reported help us to understand the behavior of particular aero vehicles under the heat and mass transfer which can be meaningful for the designing of such practical shapes.
Performance of CO2 decomposition in water-cooling DBD plasma reactor
Authors: He Lin , Yue Xiaofeng , Liu Xiaoping , Wu Zhengwei
Published: December 2024

Low-temperature plasma is recognized as a CO2 decomposition technology with substantial sustainable potential. Enhancing energy efficiency remains a critical challenge for plasma technology to achieve broader industrial adoption. This study developed two water electrode reactors—one with a stationary water electrode and the other with a flowing water electrode—designed to enhance energy efficiency in the CO2 decomposition process. A systematic performance comparison was subsequently made with a conventional aluminum mesh electrode reactor. The findings revealed that water electrode reactors significantly enhanced both heat transfer efficiency and power factor, thereby improving CO2 conversion performance. The stationary water reactor achieved a peak energy efficiency of 20.64%. The effects of input power, feed flow rate, and N2 content on dielectric barrier discharge plasma performance under high flow rate conditions were also explored in this study. The results indicated that as the input power increased, discharge intensity in all three reactors were intensified, leading to higher CO2 conversion. However, a portion of the energy was dissipated as heat, which gradually diminished overall energy efficiency. When the feed flow rate increased from 150 sccm to 600 sccm, the shorter residence time resulted in decreased CO2 conversion, while overall energy efficiency improved significantly. Increasing the N2 content caused an exponential rise in CO2 conversion, while the effective conversion rate and energy efficiency did not improve accordingly. Compared to previous studies, this research demonstrates a clear advantage in energy efficiency, offering useful insights for the industrial application of plasma technology in CO2 decomposition.
Stay cable tension estimation using a vision-based monitoring system under complex environments
Authors: Wang Lusheng , Gao Xin , Zhao Chen , Lan Chunguang
Published: December 2024

Cables are the primary load-bearing component of cable-stayed bridges, the accurate monitoring of cable tension is essential for evaluating cable service reliability and bridge safety. Addressing the challenges faced by existing vision monitoring technologies in complex environments, such as limited camera resolution, low-light conditions, adverse weather and camera vibration, a non-contact vision-based monitoring system based on computer vision technology has been developed and applied to cable tension monitoring in cable-stayed bridges. The monitoring system addresses the challenges under low-light and adverse weather by utilizing an industrial camera equipped with an infrared filter and an infrared light source. A sub-pixel template matching algorithm is employed to enhance measurement accuracy under limited resolution. Furthermore, a camera vibration cancellation algorithm is introduced to mitigate the impact of external vibrations, significantly improving measurement stability. Both model experiments and field test were conducted to validate the monitoring system. Results from the model experiments demonstrate high measurement accuracy and stability under limited resolution, low-light, and adverse weather, with a maximum frequency recognition error of only 0.4%. The field test further demonstrates a significant improvement in measurement accuracy through the camera vibration cancellation method, achieving a cable tension error of only 0.86% compared to the design tension. These results highlight the system’s potential for reliable cable tension monitoring in complex environments.
Comparative analysis of real-time PPP time transfer performance of BDS-3 based on SSR/PPP-B2b corrections
Authors: Chen Shi , Liu Ya , Li Xiaohui , Zhang Huijun , Qin Weijin , Fan Duosheng , Zhao Zhixiong
Published: December 2024

The BeiDou Navigation Satellite System (BDS) precise point positioning (PPP) service, PPP-B2b, is broadcasted by BDS-3 geostationary earth orbit (GEO) satellites, which provides high-precision positioning and timing services to users in China and neighboring regions. This paper presents an analysis of real-time PPP time transfer experiments utilizing PPP-B2b corrections from BDS-3 satellites and compares the results with real-time time transfer performance based on the state space representation (SSR) corrections broadcast by the International Global Navigation Satellite System Service Data Center of Wuhan University. PPP-B2b/SSR corrections were applied to the broadcast ephemeris to derive precise satellite positions and clock biases. The BDS-3 B1I + B3I and B1C + B2a combinations were analyzed under short baseline conditions using real-time PPP processing software. The results demonstrated that the standard deviation (STD) of real-time PPP time transfer for the B1C + B2a dual-frequency combination of BDS-3 using PPP-B2b/SSR corrections were consistently below 0.2 ns, while the STD for the B1I + B3I dual-frequency combination remained under 0.3 ns. The 10 000 s Allan Deviations for all combinations were better than 1.322 × 10−14. The findings confirmed that the PPP-B2b of BDS-3 is capable of achieving sub-nanosecond time transfer, comparable to SSR-based methods. PPP-B2b is more accessible and offers a broader range of applications compared to SSR, making it suitable for long-term, reliable real-time time transfer operations in network-restricted environments.
Electroisomerization blinking of an azobenzene derivative molecule
Authors: Godey Sylvie , Therssen Hugo , Guérin David , Mélin Thierry , Lenfant Stéphane
Published: December 2024

We report here the reversibility and bistability of the switching behavior in an azobenzene derivative induced by the bias applied by a scanning-tunneling microscopy (STM) tip, at low temperature and in ultra-high vacuum environment. This cis-to-trans and trans-to-cis switching were observed during STM imaging in either polarity at +2 V or −2 V, on a sub-second time scale. This results in a blinking effect visible on STM images, corresponding to the reversible switching of the azobenzene molecule under the applied STM bias through an electric field induced process.
Impact of Flat-Surfaced Pins on Material Flow and Particle Distribution in Friction Stir Processing: A CEL Method Analysis
Authors: Akbari Mostafa , Asadi Parviz , Abdollahzadeh Amin , Esfandiar Milad , Moghanian Amirhossein
Published: December 2024

This study investigates the impact of Flat-Surfaced Pin geometry on temperature, strain, particle distribution, and material flow during Friction Stir Processing (FSP) using a Coupled Eulerian-Lagrangian (CEL) formulation. Various models incorporating different pin shapes—cylindrical, square, and hexagonal—were developed for this purpose. To investigate material flow during the FSP, Tracer particles were employed as a methodological tool. A comparison between experimental and numerical results concerning the distribution of reinforcing particles in the base metal reveals a strong correlation, highlighting the model's effectiveness in accurately predicting material flow patterns. The findings indicate that the circular tool was less effective in achieving a uniform distribution of particles, with a significant accumulation observed on the retreating side. In contrast, both square and hexagonal tools demonstrated improved performance regarding particle distribution. Quantitative measurements show that the areas occupied by the reinforcing particles are 14.3 mm² for the circular pin, 34.4 mm² for the square pin, and 37.9 mm² for the hexagonal pin. This variation can be attributed to the design of the pin profiles, as the flat surfaces facilitate a pulsating effect that enhances material flow. Moreover, in samples processed with square and hexagonal pins, particles located near the upper surface of the plate tend to rotate with the pin, subsequently stretching toward the advancing side. Finally, the square and hexagonal tools exhibited higher average hardness values of 68.88 HV and 66.84 HV, respectively, compared to the circular tool, which yielded an average hardness of 57.17 HV.
Global Analysis of a Monkeypox Virus Model Considering Government Interventions
Authors: Gümüş Mehmet , Türk Kemal
Published: December 2024

Monkeypox is an infectious disease that threatens human life. The recent spread of the virus has increased global health concerns and risks. In this paper, an innovative mathematical modeling approach is presented to investigate the transmission dynamics of monkeypox virus. The mathematical model is constructed considering the spread of the virus in both human and rodent populations. It also provides a more realistic approach by including a saturated incidence rate. The model is usable by including potential interventions that governments can adopt. The local and global asymptotic stability of the equilibrium points with the basic reproduction number $\mathfrak{R}_0$ is examined. In addition, a bifurcation analysis is conducted to reveal significant changes in the dynamics of the model. Sensitivity analysis is given to evaluate the effects of potential measures that can be taken to eliminate the disease. Finally, the obtained theoretical results are supported by numerical simulations.
Statistical and sensitivity analysis of MHD Casson Nanofluid with convective boundary conditions on a stretching surface
Authors: Deebani Wejdan , RAZA JAWAD , Lund Liaquat Ali , Shah Zahir , Shutaywi Meshal
Published: December 2024

The purpose of this paper is to analyze the optimization of MHD Casson Nanofluid with convective boundary conditions over a stretching sheet by Response Surface Methodology. The governing equations transformed into the system of nonlinear ODEs (Ordinary differential equations) using similarity transformation and then solved by 3-stage Lobatto IIIA in Matlab routine bvp4c. The response of different physical parameters on the skin friction, reduced Nusselt number, reduced Sherwood number, velocity profile, temperature profile and nanoparticle concentration profile are examined through graphs. The enhancement in the values of stretching parameter, Casson parameter caused the decrement in temperature profile and Conversely, for increment in magnetic parameter, radiation parameter, local Eckert number, thermophoresis and Brownian motion parameters. The maximum value of skin friction occurred for increased value of stretching parameter. The value of response function (reduced Nusselt number) decreased at the values of local Eckert number, thermophoresis and Brownian motion parameters increased and decrement in radiation parameter. Skin friction show negative sensitivity towards Casson parameter and positive sensitivity towards magnetic parameter and stretching parameter.
Nanocrack in MoS2 manipulated by T-stress in modified boundary layer model
Authors: Yang Xing , Zhang Bin
Published: December 2024

MoS2 is expected to replace silicon-based field-effect transistors and continue Moore’s law. However, thin-film MoS2 transistors on flexible substrates are prone to nanocracking under bending conditions. Although classical fracture mechanics provides a broad understandings of its crack tip field, how the higher-order T-stress term influences the nanofracture remains to be investigated. Using molecular dynamic simulations and modified boundary layer models, we show that T-stress regulates the nonlinear stress, plastic zones, and distortion around the crack tip, thereby changes fracture toughness and cracking direction. Under mode I loading, fracture toughness increases monotonically with rising T-stress. With the introduction of mode II loading (K
II), the interplay between T-stress and K
II can decrease fracture toughness as T-stress exceeds a critical value. Furthermore, negative T-stress tends to impedes crack deflection, whereas positive T-stress tends to promote it. However, owing to the local anisotropy in MoS2 lattices, crack deflection always occurs in the discrete zigzag lattice orientations. Our study might provide new insights into the fracture of MoS2 transistors under complex loads.
Experimental Investigation on Effects of Thermal And Physical Properties of Biodegradable Hybrid Nanofluid Using Two Step Method.
Authors: Dattatraya Popat Kshirsagar , Venkatesh M A
Published: December 2024

The hybrid nanoparticle was most crucial material used in the green technology and biodegradable oils may emerging as substitute for mineral oil as base oils because to their high thermal conductivity, viscosity, density and physical properties. In work carried out the examination of nanofluids the creation and evaluation of hybrid nanofluids that are biodegradable, together with the basic fusing material. Using the SiC and TiO2 as a Nanoparticle with base fluid as a bio oil, surfactant used as Sodium Dodecyl Sulfate (SDS) to maintain the stability of fluids. It was made using palm oil in both individual and hybrid modes (Hybrid combination such as Palm oil + SiC+TiO2, nanoparticle (1%, 2%, 3% Vol), Base fluid and Palm oil + Sic, and Palm oil and TiO2, nanoparticle (1%, 2%, 3% Vol). The results shows that biodegradable Hybrid nano fluids is better than the pure nanofluids. The zeta potential results shows that the highest stability was observed that biodegradable Hybrid nanofluids is 70%. (Palm Oil + SiC +TiO2) 3% vol. The findings indicate that using industrial applications, bio oil-based hybrid nanofluids can have their thermal characteristics increased.
Effect of rotation on the onset of convection in magnetic nanofluids containing gyrotactic microorganisms
Authors: Arora Monika , Danesh Mustafa , Kumar Sharma Mahesh
Published: December 2024

The focus of this work is on employing linear stability analysis to investigate the initiation of the bioconvection (Bconvec
) phenomenon in the presence of rotational influence. In this study, we examine a water based magnetic nanofluids (Wb-MgNf
) that contains gyrotactic microorganisms, taking into account the influence of gravity. The motion of the microorganisms is considered to be motile and of small size, rendering the inertial effects negligible. The employed model incorporates the combined impact of two slip mechanisms, namely Brownian motion and thermophoresis, as suggested by J. Buongiorno in his article ”Convective transport in nanofluids” in addition to magnetophoresis. To solve the resulting eigenvalue problem, a numerical method utilizing MATLAB’s EIG function is utilized. The critical Rayleigh number Rac
is determined through neutral stability curves (NsCurves
) to analyze the system, considering the governing parameters. The Taylor number Ta
is employed to investigate the influence of rotation, revealing that it stabilizes the system. The onset of convection is advanced by the parameters nanoparticle concentration Rayleigh number Rn and bioconvection Lewis number Lb.