bluuebunny/crossref_metadata_2025 huggingface dataset:
Anomalous behavior of the structural and thermodynamic characteristics of the ceramic La1.8Sr0.2CuO4 on going over into the superconducting state
Authors: Verkin B. I. , Prokhvatilov A. I. , Strzhemechnyĭ M. A. , Isakina A. P. , Barylnik A. S. , Khomenko V. G. , Gal’nitskaya Yu. L. , Demirskiĭ V. V.
Published: January 2025

X-ray investigations of the ceramic La1.8Sr0.2CuO4 have been carried out in the temperature range 5–293 °K. A lowering of the lattice symmetry from tetragonal to orthorhombic was established for T<200 °K. Singularities in the temperature dependence of the lattice parameters and molar volume and anomalies in the thermal expansion were found in the region of the superconducting transition, correlated in temperature with anomalies in the specific heat.
X-ray characteristic of the structure of metal–ceramic compounds based on yttrium and lanthanum and the spatial charge density in the copper–oxygen framework of their lattice
Authors: Mel’nikov V. S. , Pshentsova N. P. , Demenko D. P. , Sheludchenko I. M. , Zhalko-Titarenko A. V. , Antonov V. N. , Nemoshkalenko V. V. , Shushilova O. I. , Shcherbak E. A. , Shevchuk N. P. , Zyrin A. V.
Published: January 2025

The structure of lanthanum and yttrium metal-ceramics was studied by the methods of x-ray and electron diffraction. It was established that the yttrium metal ceramic has five phases: tetragonal, orthorhombic I, orthorhombic II, hexagonal, and body-centered tetragonal. The lattice parameters were determined. The charge density in the copper–oxygen framework was calculated by the methods of cluster modeling.
Temperature dependence of the ultrasound velocity in a lanthanum cermet
Authors: Bar’yakhtar V. G. , Pan V. M. , Taborov V. F. , Tarasov V. F. , Shevchuk N. V. , Shulishova O. I. , Shcherbak A. I.
Published: January 2025

The temperature dependence of the ultrasound velocity is measured in the compound La1.8Sr0.2O4 in the temperature range 4.2–280 K. The longitudinal and transverse wave velocity decreases as the temperature is lowered in the interval from 200 to 35 K and and increases at temperatures above 200 K and below 35 K. The change of sign of the slope of the velocity–temperature curve at 35 and 200 K is a possible indication of phase transitions of a structural or (and) some other nature.
ESR studies of superconducting metal-oxide ceramics
Authors: Lyfar’ D. L. , Moiseev D. P. , Motuz A. A. , Ryabchenko S. M. , Tolpygo S. K.
Published: January 2025

Our ESR studies (3 cm) of the metal-oxide ceramics La2CuO4, La1.8Sr0.2CuO4−y, Y1.2B0.8CuO4−y, and Y1Ba2Cu3O9−y, at 4.2 °K < T < 300 °K have shown that the Cu spin paramagnetism is strongly suppressed in the first two. The intensities of the ESR signals correspond to the preservation of only a few per cent of the copper in the uncompensated spin state. The last two compounds were observed to display strong Cu2+ ESR signals, which pertain to a phase that is not responsible for the superconductivity and does not vary with Tc. Our results may signify that the bulk of the Cu ions in the phases responsible for the superconductivity are in the spinless Cu+ state or in a state with higher valence but with antiferromagnetic order at TN < 300 °K.
Two-frequency superradiance of pyrene impurity centers in diphenyl
Authors: Andrianov S. N. , Zinov’ev P. V. , Malyukin Yu. V. , Rudenko E. N. , Samartsev V. V. , Silaeva N. B. , Sheĭbut Yu. E.
Published: January 2025

Dicke superradiance (SR) on the purely electronic (1B2u→1Ag) and electronic-vibrational (1B2u→1Ag × ag) transitions of pyrene molecules in a diphenyl host was studied theoretically and experimentally. The conditions for the appearance of SR on an electronic–vibrational transition were determined. It is shown that SR pulses propagate in the crystal in the form of simulton. The lifetime of the vibrational excitations in this crystal is evaluated by Dicke’s SR method.
Thermal conductivity of magnetic crystals in the neighborhood of phase transitions
Authors: Buchel’nikov V. D. , Kuzavko Yu. A. , Shavrov V. G.
Published: January 2025

The influence of magnon–phonon interaction on the thermal conductivity of ferro- and antiferromagnets with an easy-plane type of anisotropy near the spin reorientation phase transition has been investigated. Umklapp processes and scattering of the quasiparticles by point defects have been studied. It is shown that at temperatures below the temperature corresponding to the magnitude of the magnetoelastic gap, the phonon subsystem has an appreciable effect on the thermal conductivity of magnetic crystals in the region of the phase transition, as a result of which a significant change takes place in its temperature and field dependences.
Anomalies of the plastic deformation of solid parahydrogen
Authors: Aleksandrovskiĭ A. N. , Kir’yanova E. A. , Manzheliĭ V. G. , Soldatov A. V. , Tolkachev A. M.
Published: January 2025

The work hardening curves σ(ϵ) of special-purity parahydrogen single crystals are obtained in the temperature range 2−6 °K at very low stresses (σ = 5·10−2 g/mm2). Our study reveals a number of anomalies, in particular an effect whereby a sample recovers its dimensions after plastic deformation reaching 7%. The work hardening curves of solid neon are also obtained for comparison. The gravity-induced downward flow of parahydrogen single crystals at helium temperatures mentioned in the literature has not been observed.
Localization and inelastic scattering of electrons in point-contact electric conductivity
Authors: Itskovich I. F. , Kulik I. O. , Shekhter R. I.
Published: January 2025

Nonlinear electric conductivity of dirty point contacts between clean conductors is studied under the condition when the elastic scattering length is comparable with the de Broglie wavelength λF, of electrons. It is shown that the second derivative of the I–V characteristics has maxima whose positions coincide with the maxima of the electron–phonon interaction (EPI) function. However the sign of the point-contact (PC) spectrum is opposite to that in the ballistic or diffuse charge transport. Thus, the possibility of PC spectroscopy of EPI is established in highly disordered materials where the quantum localization of electrons is significant.
Superconductivity of quasi-one-dimensional systems
Authors: Davydov A. S. , Brizhik L. S.
Published: January 2025

A new idea of superconductivity in quasi-one-dimensional systems with electron-phonon interaction is proposed. The idea is based on the soliton concept. The process of pairing and the dynamics of the propagation of many electrosolitons, formed as a result of the coupling of excess quasiparticles (electrons or holes) with local lattice deformations, is investigated.
Photochemical pathways in astronomical ices: A computational study of singlet oxygen reactions with hydrocarbons
Authors: Daniely Amit , Zamir Alon , Eisenberg Helen R. , Livshits Ester , Piacentino Elettra , Bergner Jennifer B. , Öberg Karin I. , Stein Tamar
Published: January 2025

Complex organic molecules are widespread in different areas of the interstellar medium, including cold areas, such as molecular clouds, where chemical reactions occur in ice. Among the observed molecules are oxygen-bearing organic molecules, which are of high interest given their significant role in astrobiology. Despite the observed rich chemistry, the underlying molecular mechanisms responsible for molecular formation in such cold dilute areas are still not fully understood. In this paper, we study the unique chemistry taking place in astronomically relevant ices, where UV radiation is a central driving force for chemical reactions. Photofragmentation of ice components gives rise to highly reactive species, such as the O(1D) atom. These species provide a pathway for chemical complexity even in cold areas. Using quantum chemistry calculations, we demonstrate that O(1D) reacts barrierlessly with hydrocarbons. Moreover, photoprocessing of the reaction products (and other components of the ice), followed by radical recombination, is found to be an essential part of the overall mechanism. In ice containing O(1D) and hydrocarbons, the formation of formaldehyde in methane ice, acetaldehyde in ethane ice, and carbon monoxide in acetylene ice, and the consumption of alcohol in all systems, was predicted in agreement with experimental results.
Computational study of a novel microwave electrothermal thruster using dielectric resonators (DRs)
Authors: Lee Juyeon , Raja Laxminarayan L.
Published: January 2025

This paper presents the study of a novel microwave electrothermal thruster with a dielectric resonator based approach for the plasma localization and propellant gas heating. The study is purely computational in a two-dimensional planar geometry and establishes the concept and demonstrates feasibility as an electric propulsion device. The resonant structure consists of a two cylindrical high dielectric constant (ɛr = 172.5) resonator enclosed within a plasma chamber that terminates at a convergent-divergent nozzle. The plasma chamber is irradiated by an incoming microwave that experiences a large wave electric field amplification of about 25 000 at a resonant frequency of 18.5 GHz. The field amplification results in breakdown and establishment of a steady plasma in a helium propellant in close vicinity to the nozzle. With a microwave power input of 40 W mm−1 (depth) at 1 atm. discharge pressure, the peak gas temperature is about 1300 K, with an electron number density of approximately 1020 m−3, resulting in a peak specific impulse of 245 s. The corresponding cold gas specific impulse is 150. The high specific impulse is attributed to the plasma hot zone being located in close vicinity of the nozzle, which effectively increases thrust. However, the thrust increase is accompanied by significant heat conduction losses, particularly as the dielectric gap size increases, underscoring the importance of thermal management in the system.
Interpretation and prediction of the three-dimensional coherent structure and its dynamics of tornado-like vortex via delayed proper orthogonal decomposition
Authors: Zhou Lei , Noack Bernd R. , Tse Kam Tim , He Xuhui
Published: January 2025

This study proposes a three-dimensional mode-based surrogate framework to predict the tornado-like vortex (TLV) derived from the fuzzy neural network and delayed proper orthogonal decomposition method. First, near-break-down TLV is simulated via large-eddy simulation, and its mean, fluctuating and statistical flow feature is analyzed. Then, three-dimensional spatiotemporal features of coherent structure are extracted and interpreted. Next, the capability of the proposed framework to predict the future state of an unsteady chaotic TLV flow field is systematically evaluated, including the spatiotemporal variation of velocity, pressure, and vorticities as well as flow statistics. Finally, parametric analysis is also conducted to investigate the influence of three key parameters [i.e., Fuzzy rules of the state network or output network (K1 or K2), time delayed embedding number (d)] contained in the framework and the step number of forward prediction (K) on the predicted accuracy. Results show that for near-break-down TLV, vortex wandering effect largely affects its dynamical feature, and its three-dimensional characteristics are distinct, exhibiting the essence of the swirling jet flow. 3D mode-based surrogate model can correctly predict the tornado-like vortex with a relative error of less than 2% for the radial, tangential, and vertical velocity component. It is found that fuzzy rules and time-delayed embedding number has great effect on prediction accuracy. Thus, to achieve optimal predicting effect, it is suggested that d is taken as 8, K1, and K2 are taken as 18, and when making multi-step predictions, the largest K should not exceed 7.
Performance of vortex pump in CFD simulations with rough walls
Authors: Li Wenguang
Published: January 2025

Flow passages in vortex pumps usually have rough walls. Precise consideration of wall roughness is an important issue in pump flow simulations. Numerical studies of the effects of wall roughness on the performance of vortex pumps are quite rare, especially with different interface models. Turbulent flows of water in a vortex pump with a specific speed of 76 are simulated using 1/8 and whole impeller fluid domains with rough walls, using the three-dimensional Reynolds-averaged Navier–Stokes equations, the standard k-ɛ model, and a scalable wall function in Ansys CFX 2019 R2. Equivalent sand grain roughnesses ks = 0.586 and 9.38 μm are determined for the chamber casing, volute, and suction pipe, and ks = 18.47 and 36.94 μm for the impeller by using the arithmetic average roughness Ra of the materials used in the pump and the correlation between ks and Ra given in the literature. The mixing loss along the interface between impeller and volute in the transient rotor model is determined. The rates of change of the head, shaft-power, and efficiency of the pump due to wall roughness are calculated. The transient rotor model with whole impeller domain and the frozen rotor model with 1/8 impeller domain for rough walls with Ra = 0.1 μm in the suction pipe, volute, and chamber and 3.2 μm in the impeller give the most accurate predictions of pump performance compared with experimental data. The transient rotor model with whole impeller domain gives more accurate predictions of pump performance than the frozen rotor model with 1/8 impeller domain. The mixing loss rises quickly at high flow rates. The transient rotor model with whole impeller domain gives plausible predictions of the rates of change.
Machine learning based prediction of specific heat capacity for half-Heusler compounds
Authors: Chaudhary Laxman , Chaudhary Keshab , Shahi Ambika , Jaiswal Kedar Nath , Kalauni Dipendra Prasad , Kim Se-Hun , Ghimire Madhav Prasad
Published: January 2025

Half-Heusler alloys are among the most emerging families due to their different properties in topological insulators, superconductors, and magnetic behavior, which are directly applicable to developing low-cost and high-power spintronics devices. This study investigates the predictive performance of a stacked model for estimating the lattice parameters and specific heat capacity of 438 half-Heusler alloys with 28 columns in different properties. The stacked model, which incorporates gradient boosting and random forest as baseline models, was meticulously tuned for parameter optimization. Our calculated results demonstrate the robustness of our model, as evidenced by the high R-squared scores that indicate remarkable accuracy and consistency in predicting lattice parameters and specific heat capacity. The model also shows strong correlation coefficients, underscoring its reliability and precision. Comparative analysis reveals the superiority of the stacked model over alternative approaches, positioning it as the preferred model for both properties. This research highlights the stacked model’s efficacy in material property prediction, offering valuable insights for materials science research and development at a very low cost.
Noether symmetry of multi-delay Birkhoffian system and its conserved quantity
Authors: Du Xin-Yu , Zhai Xiang-Hua
Published: January 2025

The Birkhoffian system, an important mechanical system in analytical mechanics, is studied in the background of multiple time delays. Both the multi-delay Birkhoffian system and the Hamiltonian system are investigated. First, the more general framework is discussed. The Pfaff–Birkhoff action is presented with multiple time delays. The multi-delay differential equations of motion are derived for both Birkhoffian and Hamiltonian models. Second, the invariance and two different kinds of Noether symmetries of the multi-delay Pfaff action are studied. Third, due to the effects of different time delays, the corresponding Noether-type theorems of multi-delay Birkhoffian systems are obtained. Two examples are presented to demonstrate the applications of the results.
Influence of perpendicular uniaxial anisotropy on the switching of a magnetic vortex
Authors: Vigo-Cotrina H. , Urcia-Romero S. , P. Guimarães A.
Published: January 2025

Magnetic vortices are being considered for information storage in magnetic devices. In this study, we used micromagnetic simulations to explore the effect of a perpendicular uniaxial anisotropy (PUA) on switching the vortex core in Permalloy nanodisks. We studied how the presence of the perpendicular uniaxial anisotropy (PUA) changes the spatial profile of the magnetic vortex. We determined the diameters of the vortex core as the perpendicular uniaxial anisotropy constant Kz varied. Additionally, we determined the frequencies and spatial profiles of the radial modes of the spin waves. Our results show that the PUA affects the frequencies of the spin modes of a magnetic vortex in a nanodisk. We have also created phase diagrams demonstrating the areas where reversing the magnetic vortex core is possible by applying a sinusoidal field perpendicular to the nanodisk plane.
Study on the insulation performance of C5F10O gas mixture in cold climates
Authors: Zhang Runlong , Zhang Xiaohui , Xu Zhilei , Dong Keliang , Zheng Jinfeng , Feng Shicheng , Zhou Zhaolin , Zhu Hui
Published: January 2025

Gas-insulated switchgear (GIS) is essential for the safe, stable, and efficient operation of high-voltage power systems. Insulating gas plays a critical role in achieving electrical insulation and stable operation in GIS equipment. Perfluoropentanone (C5F10O), a novel environmentally friendly insulating gas, has gained significant attention as a potential replacement for SF6. However, C5F10O is susceptible to liquefaction in sudden drops in environmental temperature, which leads to a decrease in its insulating properties. In order to determine the parameter information that satisfies both the liquefaction temperature and insulating properties of C5F10O gas mixtures in cold climates, this paper establishes a simulation model for C5F10O gas mixtures. The model investigates the impact of temperature on the insulating properties of C5F10O gas mixtures and analyzes the physical mechanisms underlying their insulating performance in cold climates. In addition, experiments are conducted with C5F10O gas mixtures at different temperatures to observe the variation patterns of breakdown voltage at various temperatures. The insulating mechanism of C5F10O gas mixtures in cold climates is theoretically analyzed, and the characteristics of breakdown field strength with changes in buffer gas and pressure are discussed. The research findings provide theoretical data support for the application of C5F10O gas mixtures in cold climates and offer valuable references for the research and development of SF6 replacement gases.
Wave transformation in transmission lines with rapid connection and disconnection of reactive elements
Authors: Maslov A. V.
Published: January 2025

Rapid switching of transmission line parameters has emerged as a way to manipulate signals and as a testbed for various electromagnetic processes in time-varying media, including metamaterials. In general, the switching results in wave reflection and transmission similar to that for a spatial interface but at new frequencies. Here, various realizations of parameter switching are studied: connection and disconnection of reactive elements (capacitors and inductors) in series and in parallel. The temporal boundary conditions for the current and voltage distributions are derived rigorously based on the telegrapher’s equations that explicitly model additional elements, instead of taking the equivalent values. It is shown that the temporal boundary conditions depend not only on the parameter values before and after switching but on its specific realization. Connecting or disconnecting reactive elements always involves energy losses. When new elements are added, two types of losses are identified. The first type is related to the creation of static magnetic and electric fields in the elements after switching. The second type is related to a very rapid energy dissipation during switching even for a vanishingly small resistivity in the line. When elements are removed, their energy is also removed from the waves. The effects of finite switching times are discussed. This study defines some serious constraints in using switchable transmission lines for the realization of photonic time crystals and efficient wave manipulation without externally added energy. The results are also applicable to wave propagation phenomena in other media with time-varying parameters.
An enhanced interface-sharpening algorithm for accurate simulation of underwater explosion in compressible multiphase flow on complex grids
Authors: Jiang Mingtao , Tao Xingrui , Chen Wei , Dai Zili
Published: January 2025

In underwater explosion simulations, the accuracy is critically affected by numerical diffusion and the quality of the computational grid. An enhanced interface-sharpening algorithm, based on the five-equation model and an anti-diffusion source term, is proposed to simulate the strongly compressible multiphase flow with an arbitrary number of phases in underwater explosions. To enhance the precision of interface and maintain computational stability on nonuniform and unstructured grids, an adaptive factor algorithm and a continuous interface capture function are developed. Furthermore, a redesigned fractional step method incorporating a special iteration stop criteria is proposed to solve the volume fraction equation. A pressure–density cutoff model is used to calculate the mixture density at the saturation pressure to account for the effect of cavitation. The quadratic monotone upstream-centered scheme for conservation laws reconstruction scheme and the improved advection upstream splitting method (AUSM+-up) flux scheme are also adopted to compute the flux across the grid interfaces. The overall computational framework is constructed upon a density-based explicit finite volume method. To assess the accuracy and robustness of the proposed numerical model, four representative test cases were chosen. The results reveal that the model refines the phase interface, adeptly capturing the complexities inherent in underwater explosion scenarios with both precision and efficiency across a diverse array of conditions.
Serration of the impeller trailing edge to affect the hydrodynamics and non-cavitating noise generation for a pump jet
Authors: Xu Longlong , Wang Xianzhong , Wang Weiwei , He Junze , Qi Wenchao , Huang Weibei
Published: January 2025

Bionics is an emerging scientific discipline that investigates the structures, functions, and regulatory mechanisms of biological systems, with the aim of providing novel design concepts and operational principles for engineering applications. This study initially takes the axial flow pump jet as the research object. Based on bionic principles, the trailing edges of the impeller blades are subjected to bionic noise reduction designs, including conventional serrations, flat-tipped serrations, and curved serrations. Using a hybrid computational fluid dynamics/computational aeroacoustics (CFD/CAA) computational method, the hydrodynamic performance and flow noise of the pump jet are numerically calculated before and after the bionic design. By analyzing and comparing the results, it is observed that the efficiency of the bionically modified impeller is lower than that of the original pump. However, it exhibits superior noise reduction capabilities, with a maximum reduction in the overall sound pressure level of flow noise within the 25–4000 Hz frequency range by 4.96 dB. Finally, using a self-constructed experimental platform for assessing the hydrodynamics and flow noise of pump jets, experimental measurements were conducted on both the original pump jet and the bionic pump. The experimental results indicate that the bionic pump exhibits a 3.84 dB reduction in the overall sound pressure level of flow noise compared to the original pump within the 10–4000 Hz frequency range. This validates the practical noise reduction effectiveness of the bionic design and offers a novel approach for the development of low-noise pump-jet systems.
Impact of foam metal hoods on pressure waves generated by high-speed trains traversing tunnels
Authors: Wang Kai-Wen , Xiong Xiao-Hui , Wen Chih-Yung , Chen Guang , Liang Xi-Feng , Zhang Lei , Li Xiao-Bai
Published: January 2025

The high-speed trains traveling at 400 km/h will generate severe alternating pressure and potential sonic boom when passing through tunnels. This paper proposed foam metal hoods (FMH) to mitigate the pressure waves induced by trains traversing tunnels. 1:20 scaled moving-model experiments were conducted to investigate the mitigation mechanisms of FMH on micro-pressure waves (MPW), residual pressure, and aerodynamic loads on the train and tunnel. The impact of FMH's installation position and length on MPW and residual pressure were discussed. The results indicate that the entrance FMH can weaken the expansion wave generated by the tail train entering the tunnel, thereby reducing the pressure amplitude on the train surface and tunnel wall. FMH can reduce the reflection intensity of pressure waves, effectively lowering the root mean square (RMS) of residual pressure. Installing FMH at both ends can reduce the RMS of residual pressure in the middle of the tunnel by 25%. The exit FMH enables the initial wavefront to gradually release pressure outward, thereby reducing MPW intensity. The radiation range of the MPW iso-surface is narrowed by energy consumption as the wavefront passes through the porous structures. The mitigation ratio of MPW intensifies as the length of the exit FMH increases. Using a 4-m-long exit FMH can decrease the MPW amplitude by 83.2% at 20 m from the FMH exit. The FMH facilitates a low-noise environment near tunnel portals, reducing the aerodynamic loads on the tunnel structures, and mitigating the train aerodynamic loads.
Formation of high-quality SiO2/β-Ga2O3(001) MOS structures: The role of post-deposition annealing
Authors: Kobayashi Takuma , Maeda Kensei , Hara Masahiro , Nozaki Mikito , Watanabe Heiji
Published: January 2025

We investigated the effect of post-deposition annealing on the electrical characteristics of SiO2/β-Ga2O3(001) MOS structures. While oxygen annealing effectively improves the interface properties, it induces acceptor defects in Ga2O3, leading to a decrease in net donor density. With the combination of oxygen and nitrogen annealing, carrier compensation was suppressed, and a low interface state density of about 1 × 1011 cm−2 eV−1 was obtained near the conduction band edge of Ga2O3. High immunity against positive gate bias stress was also confirmed.
Two-phase flow characteristics within the ionic liquid compression chamber under different Mach numbers of the self-acting valve
Authors: Wang Lingzi , Liao Yiling , Niu Junyu , Guo Yi , Feng Jianmei , Peng Xueyuan
Published: January 2025

The emerging ionic liquid compressor represents advanced compression technology for high-pressure hydrogen refueling stations. The self-acting valve is the core component in the cylinder of the reciprocating compressor, as it directly affects the operational performance of the ionic liquid compressor; however, the influence of the valve structure on the two-phase flow and compressor performance is unknown. This study combined a two-phase flow model with valve motion to explore the two-phase compression characteristics influenced by self-acting valves. The liquid fluctuation and gas velocity field in the compression chamber were analyzed when different structural self-acting valves that have different valve Mach numbers were arranged on the compression chamber, and then the valve motion and fluid suction and discharge performance were investigated. The results indicated that considering the pressure loss through the valve and the accuracy of opening and closing of the valve disk, the lowest possible Mach number is preferable; however, in terms of hydrogen exhaust temperature and loss of ionic liquid in the discharge procedures, larger Mach number is better. This research provides a foundation for optimizing the valve design of the ionic liquid compressor suitable for two-phase compression and guides future research on improving compressor performance and energy efficiency.
Molecular dynamics simulation study on the pressure and temperature evolution of ultrasonic cavitation bubbles
Authors: Suo Yibo , Zhu Xijing , Zhao Chunmiao , Gong Tai , Li Zuoxiu , Gao Guodong , Bi Chenglong
Published: January 2025

This study uses molecular dynamics simulations to examine how varying frequencies and amplitudes of ultrasonic vibration affect the temperature and pressure of cavitation bubbles at the atomic scale. A three-dimensional model of water, gas molecules, and metal atoms was developed using LAMMPS code. The microcanonical ensemble (NVE) and isothermal-isobaric ensemble (NPT) were employed to track the evolution of cavitation bubble temperature and pressure in response to tool head vibrations. The findings show that cavitation bubbles experience significant temperature and pressure increases during oscillation, with these parameters varying noticeably across different vibration amplitudes and frequencies. At lower amplitudes, pressure fluctuations are more intense and erratic, while at higher amplitudes, pressure peaks are higher but exhibit smoother changes. Further analysis indicates that a specific combination of amplitude and frequency can optimize pressure and temperature outputs, highlighting the mechanisms of thermal and mechanical softening in ultrasonic cavitation. This study offers valuable atomic-scale insights into the cavitation effects that occur in ultrasonic machining.
A gradient method for solving the boundary value problem of the underwater large deformation cable
Authors: Wang Zhen , Ye Yuyan , Zou Li , Zhong Houyang , Li Dejun , Mao Guiting
Published: January 2025

A nonlinear large deformation cable equation system based on arc length is employed to determine the configuration of the cable under current and buoyancy loads. Different from a traditional initial method and a shooting method, we have solved this nonlinear problem as a boundary value problem with nonlinear and global boundary conditions directly. A finite difference scheme is proposed to solve the large deformation cable equation, and the Newton–Raphson iteration is used to search for numerical approximate solution. We demonstrate that this system degenerates into the catenary equation in the case of vanishing bending stiffness for the first time. The solution of the catenary equation serves as the initial guess for the three-section cable problem. This method overcomes the disadvantages of the initial value method and step method, avoiding the need to adjust the boundary location. The spatial shapes of the large deformation cable and the effects of the length and position of the buoyancy section are discussed. The impact of ocean currents is also analyzed using Morison's formula.
A
γ
-based compressible multiphase model with cavitation based on discontinuous Galerkin method
Authors: Kong Qi , Liu Yun-Long , Li Yu-Ke , Ma Shan , Hao Qi-Hang , Zhang A-Man
Published: January 2025

The treatment of material interface and cavitation in compressible flow brings difficulties and challenges for numerical simulation, which is also a research field of great significance. Therefore, we present a discontinuous Galerkin (DG) method to simulate cavitation in multiphase flow by combining the γ-based model and a cutoff cavitation model. The DG scheme is adopted for the spatial discretization on an unstructured mesh, and the positivity-preserving limiter is extended to the γ-based model to ensure the parabolicity of the system. Then the eigenvectors of the Jacobian matrices obtained by replacing the total energy in the conservative variables with the pressure are provided for the weighted essentially non-oscillatory reconstruction. In addition, the cutoff model is introduced to suppress the non-physical negative pressure and maintain the accuracy of the peak pressure at the boundary of cavitation. Finally, some numerical results also verify the feasibility of the simple scheme proposed to deal with the cavitation problems and show high accuracy and robustness.
The influence of streamwise curvature on supersonic flow over backward-facing step
Authors: Zhang Zhen , Yi Shihe , Liu Xiaolin , Ye Zihao
Published: January 2025

Curvature plays a pivotal role in the evolution of supersonic boundary layer flows. Under the inflow condition of Ma = 3.8, the influence of curvature on the flow over a backward-facing step (BFS) was investigated using the nanotracer-based planar laser scattering technique and numerical simulations. The results indicate that concave curvature (CC) promotes flow instability, whereas convex curvature (CV) suppresses it. For CC, the wall pressure and volume compression impulse (Ip) increase along the streamwise direction, while CV decreases along the streamwise direction. The trends become more pronounced as the curvature radius (RC) decreases. The sudden increases and decreases in Ip observed on both CC and CV surfaces occur earlier by 20 mm as RC decreases. Curvature significantly alters the velocity profile of supersonic flow over a BFS, with more pronounced effects closer to the downstream and smaller RC values. In the case of CC, as one moves further downstream, the trend of ΔU/U∞ shows a deceleration, and ΔU/U∞ gradually increases with the increase in y/h until it approaches zero near the main flow region. For CV, the rate of decrease in ΔU/U∞ is greater upstream for y/h < 0.15 and downstream for y/h > 0.15. Beyond y/h > 2, ΔU/U∞ remains nearly constant near the main flow region. On the CV surface, as one approaches the wall, ΔU/U∞ changes more significantly with the decrease in RC, while moving away from the wall, the change in ΔU/U∞ slows down, and further attenuation occurs with increasing distance from the wall.
Single resonant cavity enhances the second harmonic generation of layered ferroelectric NbOCl2
Authors: Jia Mengyuan , Chen Junyang , Wu Xiaohua , Qu Xuexuan , Huang Mingyuan
Published: January 2025

Second harmonic generation (SHG) is a common nonlinear optical process with wide applications. Recent studies have found that the van der Waals crystal material NbOCl2 has a high efficiency in SHG, and this material does not undergo any change in electronic structure or weakening of excitonic effect during stacking, making it a scalable SHG crystal. Here, we designed and fabricated a single resonant Fabry–Pérot (FP) microcavity to enhance the SHG of NbOCl2 by amplifying the local electric field of the excitation light. The cavity was fabricated by plasma-enhanced chemical vapor deposition, and the deposition process was optimized to avoid the damage of the NbOCl2 sample. Our measurements confirmed that the SHG of the NbOCl2 sample can be amplified more than 30 times on the distributed Bragg reflector (half of the FP cavity), and more than 200 times inside the FP cavity. This method provides ideas for efficiently enhancing harmonics and directions for on-chip integrated photonic devices.
Microscopic regulation mechanisms of pore heterogeneity and flow conditions on CO2 residual trapping and sequestration capacity
Authors: Song Hongqing , Lao Junming , Zhou Yiyang , Xie Zhenhuan , Wang Yuhe , Yue Ming
Published: January 2025

Previous studies at the field and core scales suggest that pore heterogeneity can enhance CO2 trapping but may reduce storage efficiency during sequestration in saline aquifers; however, a fundamental understanding of the underlying microscale mechanisms is lacking. Here, we elucidate the microscale regulation mechanisms of pore heterogeneity and flow conditions on CO2 residual trapping and sequestration capacity by employing microfluidics validated models and simulations. First from uniform structures, we reveal that low pore–throat ratio (PTR) excels at trapping residual CO2, whereas high PTR stands out at generating residual CO2. The median PTR performs poorly in both respects. Then, from heterogeneous structures, we discover small heterogeneous order coupled with low Ca (capillary number) and We (Weber number), or large heterogeneous order coupled with high Ca and We, is beneficial for residual CO2 trapping. In specific, the median–low–high pore–throat ratio structure traps 15% pore volume of CO2 at low Ca and We. We also find that small heterogeneous order or high Ca and We enhances the sequestration capacity. Particularly, the low–median–high pore–throat ratio structure at high Ca and We maximally sequestrates 77% PV of CO2. These microscale findings enhance the knowledge of how pore heterogeneity and reservoir conditions regulate CO2 trapping and sequestration capacity. Last but not least, we establish state diagrams correlating residual CO2 trapping or sequestration capacity to reservoir conditions and pore heterogeneity, to benefit site selection and operation optimization during actual CO2 sequestration in saline aquifers.
Aeroacoustic impact of triply periodic minimal surface porous casings on axial flow fans
Authors: Mozafari Mostafa , Masdari Mehran , Zhang Qiang , Tahani Mojtaba
Published: January 2025

This study investigates the effectiveness of porous casing treatments in reducing noise in axial flow fans, using various triply periodic minimum surface (TPMS) configurations. All TPMS-based casings outperform solid casings in minimizing radial fan noise and enhancing the casing's sound absorption capabilities. Among the structures, the primitive type is less effective compared to the diamond and gyroid designs. Experimental results demonstrate that the gyroid and diamond casings reduce overall sound pressure levels by 6 dB (11%) and 8 dB (14%), respectively. They also decrease accumulated sound energy by 36% and 60%, respectively. Additionally, increasing porosity from 20% to 50% further enhances accumulated sound energy reduction by 27%. TPMS structures significantly lower sound pressure levels at blade passing frequencies (BPF), with maximum noise reductions observed at BPF4 and BPF10, where noise drops by 6 and 7 dB, respectively. This innovative casing treatment has a marked impact on the aeroacoustic performance of axial flow fans, and the findings offer valuable insights for future noise reduction strategies using TPMS-based porous casings.
The effects of jet Lorentz factor on a relativistic astrophysical jet
Authors: Pal Ribhu , Roy Arnab , Halder Pabitra
Published: January 2025

In this Letter, the numerical simulation of axisymmetric hydrodynamic relativistic jet propagation was performed by solving the hydrodynamic relativistic Euler equation using the computer code PLUTO [Mignone et al., Astrophys. J. Suppl. Ser. 170, 228 (2007)]. The detailed flow features involved in this relativistic jet propagation has been thoroughly discussed in this present numerical study. The effect of the jet Lorentz factor (Γj) on the shock–turbulence interaction has been studied by analyzing the divergence of the Lamb vector (L=ω×U). The strong coexistence of two layers ∇·L<0 and ∇·L>0 enhances the momentum transfer due to energy difference, causing turbulence amplification.
Investigation on striped heat transfer characteristics of turbine blade tips
Authors: Lu Shaopeng , Gu Huanyu , Jiang Hongmei , Jin Yun , Wang Yifan , Lu Gaoqian , Han Xingsi , Zhang Qian , Guo Haoyan
Published: January 2025

The formation mechanism of high thermal load at the blade tip plays an important role in effective cooling design and persistent operation of turbine blades. In this study, experimental investigation was conducted in a blow-down transonic wind tunnel to enable full optical access of a high-pressure turbine blade tip surface. Spatially resolved tip heat transfer coefficient was obtained for a flat tip by infrared transient thermal measurement. Combined with closely coupled unsteady self-adaptive turbulence eddy simulation numerical analysis, this paper first reveals alternating bands of high and low heat transfer coefficients (HTC) of the tip surface. Experimental data and computational fluid dynamics results consistently show this striped distribution of HTC, which indicates variations in the local heat transfer intensity. This phenomenon is linked to the formation of different types of vortices within the blade tip clearance. The clockwise (along flow direction) vortices originated from the detachment of the separation bubble, driven by the pressure gradient cross the clearance. As the clockwise vortices move cross the clearance, they induce low-energy fluid near the wall to form counterclockwise vortices, which alternate with the clockwise vortices in space. This alternating vortex pattern directly causes the high HTC stripes observed on the blade tip.
Double stress overshoot in startup shear flow and failure of Cox–Merz rule of pom-pom polymers
Authors: Schußmann Max G. , Song Hyeong Yong , Hyun Kyu , Wilhelm Manfred , Hirschberg Valerian
Published: January 2025

The understanding of long chain branched homopolymer melts in shear flow is of significant interest to polymer science and critical to ensure stable processing. We report on the startup shear flow at a constant shear rate of well-defined pom-pom shaped polymer melts. Pom-poms consist of two stars covalently connected by a single backbone. For low-arm numbers and short arms, a single stress overshoot followed by a steady state is observed, similar to linear and star shaped melts. For one highly branched pom-pom with entangled branches, a double stress overshoot during the startup shear flow could be observed before reaching the steady state viscosity. Additionally, we find that the Cox–Merz rule, which relates the complex viscosity η*ω to the steady state shear viscosity ηγ̇, fails at high-shear rates, if the backbone is not self-entangled.
A new forcing approach for wall-modeled simulation of rough-wall turbulent flows
Authors: Niu Yuting , Xiao Zuoli
Published: January 2025

The effect of rough surface on turbulent flows is usually investigated using direct numerical simulation (DNS) with either body-fitted grids or immersed boundary method. Both methods, however, require a significant number of grids to resolve all rough scales, resulting in intolerable computational cost. In this paper, a new volume forcing approach is developed to simulate wall-bounded turbulent flows with surface roughness at the same computational cost as that with smooth walls. Specifically, two extra forcing terms are introduced in the Navier–Stokes equations to mimic roughness effects. One is the feedback force operating within the roughness cell and ensuring zero velocity at the grid points located therein. The other represents the vortex force around the roughness surface. A direct comparison with the model proposed in literature shows a significant improvement in the prediction of mean flow and Reynolds stresses. To further validate the new forcing model, simulation of channel flow with cubical roughnesses is implemented, which shows a good agreement with fully resolved DNS.
Complemento directo dislocado y escala de afectación
Authors: Repiso Isabel
Published: January 2025

En español, el complemento directo dislocado (e.g., A él lo atropellaron) forma
parte de las construcciones que tematizan un participante distinto del agente. En este sentido, son construcciones que expresan el
contenido proposicional desde una perspectiva pasiva. Sin embargo, a diferencia de la pasiva con ‘ser’, el complemento directo
dislocado no ha sido objeto de estudios empíricos destinados a repertoriar su combinatoria con distintos tipos de verbos. El
presente estudio explora los usos y frecuencias del complemento directo dislocado con referente humano y agente no explícito
(e.g., A ella la premiaron). Un total de 164 construcciones del corpus CORPES XXI fueron analizadas atendiendo a
las siguientes variables: contexto (violento vs. neutro), grado de afectación (con contacto vs. sin contacto), tipo de cambio
experimentado (estado o propiedad / ubicación / psicológico / benéfico). Los resultados indican que esta construcción es
significativamente productiva en contextos violentos y combinada con verbos de contacto físico para marcar cambios de estado o
relativos a una propiedad del argumento afectado. Estos resultados ponen en evidencia la prominencia de esta construcción en
español para expresar la afectación física y violenta con verbos de valencia psicológica negativa en predicados regidos por el
primitivo semántico [CAUSE].
Revisiting the reported speech as a mitigation device in the PRESEEA-Seville oral corpus
Authors: Repede Doina
Published: January 2025

This article aims to describe the use of mitigating reported speech concerning three general mitigation functions
— self-protection, prevention, and repair — identified in the works of Albelda et al. (2014, 2021). This goal will be achieved through a review of relevant
literature on this phenomenon and an analysis of 72 semi-structured interviews taken from the PRESEEA-Seville oral corpus. From a
sociolinguistic perspective, we will also examine how the employ of mitigating reported speech functions is affected by three
fundamental social criteria: gender, age, and level of education. Additionally, we will provide information on how frequently they
are used. Generally, we observe a prevalence of the self-protection function, especially in the use of direct quotations. This
helps to preserve the speaker’s face, resulting in a positive impact. In terms of social factors, this function is notable in both
male and female participants with low levels of education, particularly among first-generation individuals.
Innovative lightweight flexibility test platform for RV reducer with topology optimization and 3-D printing
Authors: Qian Rundong , Qiao Haiyu , Ni Chenyi , Liu Yayun , Wang Chuanyang , Jiang Ning
Published: January 2025

The majority of existing mechanical devices are only capable of measuring a single parameter. They are constructed primarily from metal processing, resulting in a substantial weight, elevated manufacturing costs, and a fixed and inflexible accuracy and assembly methodology. Accordingly, this paper presents the design of a lightweight RV reducer test platform, which enhances the flexibility of high-precision measurement. The test platform employs topology optimization lightweight structure design and 3D printing technology. Static simulation is used to lightweight the structure and add an adjustable structure. It significantly reduces cost and weight while having an adjustable self-connection structure and a wide range of application scenarios. It improves the flexibility of high-precision measurement while ensuring sufficient strength. In order to verify the measurement performance of the platform, the wavelet threshold method with excellent denoising effect was used to analyze the acceleration power spectral density of each part of the test platform at different rotation speeds. The results show that the wavelet threshold method could effectively filter noise and extract key experimental data. The accelerometer results show that the test bench has superior stability at both 0.5 r min−1 and 120 r min−1 speeds, and has practical application value. The simulation also verifies that the test platform has sufficient rigidity to meet the working conditions.