bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetoelastic characteristics and peculiarities of indirect exchange in antiferromagnetic manganese fluoride
Authors: Dudko K. L. , Eremenko V. V. , Semenenko L. M.
Published: November 2024

Magnetic and magnetoelastic properties of manganese fluoride were studied experimentally. The properties of this crystalline material in the antiferromagnetic range (T < 67°K) are mainly due to indirect exchange interaction between Mn2+ ions through F− ions. Most attention was paid in this study to establishing a relation between such an interaction and the interatomic distances. It has been revealed that the exchange interaction energy decreases as R−14 with increasing minimum distance between Mn2+ and F− ions. The test results conform to the simple cosine-law relating the energy and the angle between the bond lines in Mn2 - F−-Mn2+ chains. This relation agrees with the concept of interaction intensity due to a dumb-bell p state of the electron shell in F− ions.
Inertial model of enhanced plasticity at the superconductivity transition
Authors: Éstrin Yu. Z.
Published: November 2024

It is shown that in the model of low-temperature plasticity based on athermal depinning of the dislocations from local obstacles the inertial effects associated with the acceleration of the dislocations during their translatory motion between the obstacles form the definitive factor in the dynamic depinning force. Dependences of the discontinuity of the deforming stress at the N−S transition on the differences of the electronic drag constants ΔB=BN−BS in the N and S states, the mean distance between obstacles, their effective power, and the deforming stress are calculated.
Kinetic properties of bismuth thin films
Authors: Komnik Yu. F. , Andrievskii V. V.
Published: November 2024

A study was made of the temperature variation (in the 1.5–300°K range) of the resistance, magnetoresistance and Hall coefficient of epitaxial bismuth films of thickness 170–5000 Ǻ. A number of peculiarities and anomalies in the behavior of the kinetic properties were observed and studied: the complex character of the temperature variation of the parameters found, the presence of an initial quadratic section in the dependences of the variation of the resistance in a magnetic field with extremely high values of the magnetoresistance coefficient, the appearance of an anomalous dimensional effect in the conductivity, etc. By means of calculations using the equations for a two-band model of semimetals the temperature and “thickness” variations of the carrier concentration and mobility were distinguished. The results obtained could be explained by invoking the theory of resonance scattering of carriers in size-quantized films and a model of potential distortion close to the film surface.
Hebbian learning from first principles
Authors: Albanese L. , Barra A. , Bianco P. , Durante F. , Pallara D.
Published: November 2024

Recently, the original storage prescription for the Hopfield model of neural networks – as well as for its dense generalizations – has been turned into a genuine Hebbian learning rule by postulating the expression of its Hamiltonian for both the supervised and unsupervised protocols. In these notes, first, we obtain these explicit expressions by relying upon maximum entropy extremization à la Jaynes. Beyond providing a formal derivation of these recipes for Hebbian learning, this construction also highlights how Lagrangian constraints within entropy extremization force network’s outcomes on neural correlations: these try to mimic the empirical counterparts hidden in the datasets provided to the network for its training and, the denser the network, the longer the correlations that it is able to capture. Next, we prove that, in the big data limit, whatever the presence of a teacher (or its lacking), not only these Hebbian learning rules converge to the original storage prescription of the Hopfield model but also their related free energies (and, thus, the statistical mechanical picture provided by Amit, Gutfreund and Sompolinsky is fully recovered). As a sideline, we show mathematical equivalence among standard Cost functions (Hamiltonian), preferred in Statistical Mechanical jargon, and quadratic Loss Functions, preferred in Machine Learning terminology. Remarks on the exponential Hopfield model (as the limit of dense networks with diverging density) and semi-supervised protocols are also provided.
Fluid-structure interaction analysis of large-span air-supported membrane structures under typhoon conditions
Authors: Fang Yufei , Zhao Bing , Chen Wujun , Gao Chengjun , Li Xiongyan , Zhang Daxu , Li Chunxiang
Published: November 2024

Air-supported membrane structures, lauded for their flexibility and ease of construction, find increasing applications in large-span projects. However, their susceptibility to wind-induced damage, particularly under gusty conditions, necessitates advanced analysis techniques to ensure structural integrity. This paper introduces a bidirectional coupled fluid-structure interaction (FSI) method for large-span air-supported membrane structures, integrating a cable net and surrounding fluid domain. The method employs a two-way FSI coupling scheme, utilizing large eddy simulation for fluid dynamics and membrane-wire models for the solid structure, enhancing both accuracy and computational efficiency. A geometric model of an air-supported membrane coal shed was developed, and its dynamic response under typhoon conditions was simulated. In situ measurement data, including displacement, pressure, and cable strain, recorded during a typhoon event, were compared with numerical simulation results to validate the proposed FSI framework. Key findings reveal significant vertical displacement at the middle top of the structure, with obvious fluctuations on windward and leeward sides. Wind suction loads and cable strain measurements exhibit distinct patterns, with the highest pressures and cable strains observed on the windward side. This research bridges a critical gap in applying FSI analysis to practical engineering scenarios, offering a validated approach for designing and constructing large-span air-supported membrane structures resistant to wind-induced damage.
Kinetically blocked self-assembly of colloidal strings with tunable interactions in magnetic fields
Authors: Yakovlev Egor V. , Simkin Ivan V. , Shirokova Anastasia A. , Kohanovskaya Alexandra V. , Gursky Konstantin D. , Dragun Maksim A. , Nasyrov Artur D. , Yurchenko Stanislav O. , Kryuchkov Nikita P.
Published: November 2024

Tunable self-assembly driven by external electric or magnetic fields is of significant interest in modern soft matter physics. While extensively studied in two-dimensional systems, it remains insufficiently explored in three-dimensional systems. In this study, we investigated the formation of vertical strings from an initial monolayer system of particles deposited on a horizontal substrate under the influence of an external magnetic field using experiments, computer simulations, and theoretical frameworks. We demonstrated that the main mechanism of string self-assembly is merging, driven by the interplay between gravity and induced tunable interparticle interactions. During this process, the system has to overcome a saddle point on the energy landscape, whose height increases with the string height. At a certain point, further self-assembly becomes kinetically blocked in a metastable state, far from equilibrium. This contrasts sharply with the typical scenario for tunable self-assembly in two dimensions, where the resulting structures usually correspond to the equilibrium state. Therefore, this finding opens up opportunities for more detailed control of three-dimensional tunable self-assembly by designing and tuning various potential barriers along the kinetic pathways.
Model of Faraday waves in a cylindrical container with force detuning
Authors: Ding D. , Bostwick J. B.
Published: November 2024

Recent experiments by Shao et al. [“Surface wave pattern formation in a cylindrical container,” J. Fluid Mech. 915, A19 (2021)] have revealed complex wave dynamics on the surface of a liquid bath in a vertically vibrated cylindrical container that are related to the presence of a meniscus on the container sidewall. We develop a corresponding theoretical model for this system by detuning the driving acceleration of the container, which results in an inhomogeneous Mathieu equation that governs the wave dynamics whose spatial structure is defined by the mode number pair (n,m), with n and m the radial and azimuthal mode numbers, respectively. Asymmetric m≠0 modes are unaffected by the detuning parameter, which is related to the meniscus shape and satisfy a homogeneous Mathieu equation with the shape of the instability tongues computed by the Floquet theory. The Poincaré–Lindstedt method is used to compute the instability tongues for the axisymmetric m=0 modes, which have a lower threshold acceleration and larger bandwidth that depend upon the detuning parameter. Our model results explicitly show how the shape of the meniscus and spatial structure of the wave determine the temporal response and are in good agreement with prior experimental observations for both pure modes and mixed modes.
Optimization of hydrogel extrusion printing process parameters based on numerical simulation
Authors: Wei Qinghua , Li Mingyang , An Yalong , Zhao Xudong , Sun Daocen
Published: November 2024

The printing quality of biological scaffold is not only affected by the fluidity of bio-ink but also by the printing process parameters, such as the size of the needle, printing height, extrusion speed, and printing speed. Therefore, optimizing the printing process parameters can further improve the molding quality of the biological scaffold. In this study, the printing and deposition process of sodium alginate hydrogel was modeled and analyzed based on the Herschel–Bulkley model by the finite element simulation method. The orthogonal experiment method, control variable method, and response surface method were used to design experiments, and the influences of different printing process parameters on the hydrogel deposition process were investigated. Finally, the optimal combination of printing process parameters was obtained by taking the molding degree and offset of the hydrogel line as optimization objectives. The results show that the strength relationship of the factors affecting the molding degree of the hydrogel line is as follows: printing height > needle diameter > printing speed > extrusion speed, and the strength relationship of the factors affecting the printing offset is as follows: printing height > needle diameter > extrusion speed > printing speed. The optimal combination of printing process parameters is d = 0.34 mm, H = 0.51 mm, v1 = 10 mm/s, and v2 = 7.91 mm/s. Compared with the printing experiment results of the hydrogel line molding degree under the optimal process parameters, the error range is within −11.55%–1.27%, which further demonstrates the reliability of the optimization method of hydrogel extrusion printing process parameters based on numerical simulation and response surface method.
Dynamics of sphere entry into dilute viscoelastic polymer solutions
Authors: Guo Weining , Yu Liufang , Zhang Beichen , Liu Jianghai , Liu Shuhong , Zuo Zhigang
Published: November 2024

This study experimentally investigates the effects of viscoelastic dilute aqueous polyethylene oxide solutions on the water entry of spheres. The solutions are modified to manipulate viscoelastic properties which influence cavity dynamics and the behavior of the Worthington jet. The effects of viscoelasticity and impact velocity are quantified using dimensionless numbers, including the Deborah number (De), the Reynolds number (Re), and the Froude number (Fr). Three distinct cavity patterns are identified, and transitions between these patterns occur as De and Re change. As Re increases, the cavity patterns emerge sequentially in a specific order, with the critical transition points between patterns dependent on De. The combined influence of De and Fr determines the dimensionless pinch-off time and depth of the deep seal cavity. Higher De or Fr values result in increased dimensionless pinch-off time and depth. Furthermore, energy analysis of the Worthington jet reveals that kinetic energy transforms into potential, surface tension, and elastic energy, with the Deborah number (De) influencing this conversion. In viscoelastic solutions, unlike in filtered water, elastic energy constitutes a significant portion of the total mechanical energy, leading to a much more complex energy conversion process.
Data Mining-Based optimization study on T-shaped multiple groove casing treatment for axial compressor stability
Authors: Li Qinghan , Chu Wuli , Dong Jiezhong , Ji Tianyuan
Published: November 2024

Casing treatment is a highly effective and promising technology for improving compressor stability. The study aims to enrich the casing treatment design method and reveal its mechanism for improving compressor stability and design guidelines. Focusing on Rotor37, we develop a multi-objective optimization platform that combines geometric parameterization, mesh generation, numerical calculations, optimization algorithms, and other relevant components. Five design variables are optimized to maximize stall margin improvement and minimize peak efficiency loss concurrently. The optimal T-shaped multi-groove casing treatment improved the stall margin by 11.49% and reduced peak efficiency loss to 0.13%. Furthermore, the impact of casing treatment on the flow field characteristic is quantified through three kinds of parameters. The quantification analysis demonstrates that the casing treatment enhances stability by improving the axial momentum of the mainstream flow through the radial momentum transport effect and reducing passage blockage. Additionally, Spearman correlation analysis and the Apriori algorithm are employed to investigate the relationships between seven T-shaped muti-groove geometric parameters and five flow field characteristic quantification parameters. The results validate the mechanism of casing treatment for improving compressor stability and obtain nine strongly associated rules. Finally, the linear correlation of the associated rules is evaluated to transform into design guidelines for casing treatment. The guidelines guide the design of T-shaped muti-groove geometry parameters for optimal performance. These guidelines stipulate that a single T-shaped groove should possess a minimum cross-sectional area of 10 mm2 and a depth of not less than 5 mm. Moreover, the cross-sectional area of the straight groove should exceed 4 mm2.
Study on vegetation drag coefficient in combined wave with following and opposing currents
Authors: Huang Yuming , Yang Xiaoyu , Yang Zhonghua , Wang Yifei , Chen Ben , Jiao Jian
Published: November 2024

Drag coefficients (CD) are a key metric in quantifying the vegetation effect on riverine and coastal modeling. However, drag coefficients determined using various approaches under combined wave-current flows have not been comprehensively explored. In the paper, a three-dimensional (3D) numerical model was developed to study the wave dissipation induced by submerged canopies in both following and opposing currents. The results reveal the characteristics of variation of vegetation drag force under pure wave and combined wave-unidirectional flow, as well as the relationship between drag force and flow velocity. The calibration and direct measurement methods were applied to conduct the drag coefficients under various wave-current combinations. The temporal variation in horizontal velocity U, drag force F, and the drag coefficient within the aligned canopy and staggered canopy considering the combined effects of wave and current show different patterns. Moreover, the empirical relations between drag coefficients derived using different methods with Reynolds number (Re) and Keulegan-Carpenter number (KC) are proposed. Comparison of the CD-Re and CD-KC relations would provide insight into the understanding of wave dissipation by vegetation under combined wave-current flow conditions.
Characterization of far-field wake instabilities of marine propellers with barnacles
Authors: Wang Zhengren , Luo Wanzhen , Wang Lianzhou , Cao Weitao , Wu Tiecheng
Published: November 2024

This study investigates the impact of barnacle attachment on the wake characteristics of marine propellers, focusing on the evolution from the near-field to the far-field regions. Using the improved delayed detached-eddy simulation (IDDES) method on an unstructured grid with 50.7 × 106 cells, the research explores the specific effects and mechanisms of barnacle structures on propeller wake evolution by examining vortex dynamics, Reynolds stresses distribution, and energy transfer mechanisms in the wake. The results indicate that barnacle attachment significantly disrupts the coherence of the wake flow field, leading to premature wake instability as coherent vortical structures break up and evolve into the far wake. The simulations also reveal the instability mechanism caused by barnacles, where barnacles induce small-scale vortices that interact with tip vortices, intensifying the mutual inductance process, promoting turbulence generation and coherent structure instability. These findings provide valuable insights into the impact of biofouling on propeller wake dynamics.
Chaotic dynamics in a class of generalized memristive maps
Authors: Hussan Iram , Zhao Manyu , Zhang Xu
Published: November 2024

The memory effects of the memristors in nonlinear systems make the systems generate complicated dynamics, which inspires the development of the applications of memristors. In this article, the model of the discrete memristive systems with the generalized Ohm’s law is introduced, where the classical Ohm’s law is a linear relationship between voltage and current, and a generalized Ohm’s law is a nonlinear relationship. To illustrate the rich dynamics of this model, the complicated dynamical behavior of three types of maps with three types of discrete memristances is investigated, where a cubic function representing a kind of generalized Ohm’s law is used, and this cubic function is a simplified characteristic of the famous tunnel diode. The existence of attractors with one or two positive Lyapunov exponents (corresponding to chaotic or hyperchaotic dynamics) is obtained, and the coexistence of (infinitely) many attractors is observable. A hardware device is constructed to implement these maps and the analog voltage signals are experimentally acquired.
The effect of variable-diameter ratio on the deformation characteristics of discrete oil droplet in the sudden contraction and expansion round pipe
Authors: Xing Lei , Zhou Xiaoqing , Jiang Minghu , Cai Meng , Zhao Lixin , Qi Hang
Published: November 2024

Variable-diameter pipes are extensively used in the transportation of oil–water two-phase flow in long-distance pipelines. However, the lack of flow field characteristics and deformation of discrete-phase oil droplets in variable-diameter pipes makes them inefficient for efficient transportation. The variations of pressure, velocity, vorticity, and turbulent kinetic energy of the flow field in a sudden contraction and expansion pipe were studied using numerical simulation and experiment. Additionally, the effect of flow field characteristics on the movement and deformation of discrete oil droplets was investigated. The results showed that the larger the variable-diameter ratio, the greater the pressure drop in the sudden expansion region, and the turbulent kinetic energy decreased, while the sudden expanding shoulder vortex increased. Moreover, for the same droplet size and maximum inlet flow rate, the maximum deformation of an oil droplet gradually increased with the variable-diameter ratio. Meanwhile, with the same pipe diameter, the larger the inlet flow rate, the larger the maximum deformation of oil droplets in the thin pipe segment, the more discrete phase model particles generated in the pipe, and the smaller the critical breaking value. Furthermore, the diameter of discrete-phase oil droplets in the same pipe diameter did not affect the turbulent kinetic energy in the pipe. The reported results provide excellent theoretical guidance for improving the sequential transportation of oil products in pipe.
An improved immersed moving boundary-based curved wetting condition method for the pseudopotential multiphase lattice Boltzmann model
Authors: Li Chao-Sheng , Cai Rong-Rong , Zhang Li-Zhi
Published: November 2024

The wettability treatment of curved boundaries is crucial for multiphase flow simulations at high density ratio. The conventional curved boundary methods all suffer from the problem of mass leakage. The immersed moving boundary (IMB) method is naturally mass-conserving for handling curved boundary but is currently only applicable to multiphase flows of low density ratios. Herein, an improved IMB curved wetting condition method in the pseudopotential lattice Boltzmann (LB) model is proposed for simulating multiphase flows at high density ratios. The IMB method is employed to manage curved boundaries, and the calculation of intermolecular interaction forces is modified to adjust contact angles. A series of static and dynamic multiphase flow simulations are conducted to demonstrate the performance of this method. Compared with the conventional curved boundary methods, the improved IMB method achieves mass conservation in multiphase flow simulations naturally without additional correction. Meanwhile, it exhibits lower spurious currents at large density ratios and various contact angles and accurately reproduces the fluid density distribution near curved wall. This improved IMB method also effectively models the dynamic behavior of the droplet impact on curved surfaces. Finally, the improved IMB method is extended to the simulation of multi-component multiphase flows—the impact behavior of droplet on sinusoidal wall surface at low Weber numbers (0.78–8.65) and a high density ratio of 140. Three different droplet behaviors of deposition, rebound, and breakup are observed upon the impingement by adjusting the droplet's velocity, wall wettability, and wall width. Additionally, the relationship of the contact time follows the law: tc* ∼ We0.17 (We = 2.16–7.01). The present method is expected to be an alternative for complex curved wetting phenomena in pseudopotential LB multiphase flow simulations.
Brownian dynamics simulation of the structural evolution in monodisperse hard-sphere suspensions during drying and sedimentation processes
Authors: Kim Yeji , Lee Young Ki
Published: November 2024

The drying behavior of monodisperse colloidal films, with a focus on the influence of process variables on film microstructures, is explored via Brownian dynamics (BD) simulations. In our model, hard-sphere colloidal particles are dispersed in a Newtonian liquid with an initial particle volume fraction of 0.1. The effects of the drying rate and sedimentation on the evolving microstructures are systematically investigated using two dimensionless numbers: the Péclet number (Pe), which represents the competition between evaporation and diffusion, and the sedimentation number (Ns), which reflects the relative influence of sedimentation on evaporation. First, we analyze the local particle volume fraction and film structure at various Pe and Ns. As Pe increases, particle accumulation occurs near the liquid–gas interface, whereas a high Ns promotes dense packing near the substrate owing to sedimentation. The BD simulation results, viz. the local volume fraction profiles and drying regime maps, are in good agreement with those of the continuum model proposed by Wang and Brady. Structural analysis of the dried films reveals that at a low Pe (Pe = 0.1), a face-centered cubic (FCC) structure dominates, primarily independent of the sedimentation effects. In contrast, a high Pe leads to hexagonal close-packed or amorphous structure formation. Notably, at intermediate drying rates (Pe = 10), an increase in Ns promotes additional FCC ordering in the final film structure. Our study provides new insights into the hitherto underexplored role of sedimentation in the structural evolution of drying colloidal films, revealing the mechanisms of drying-induced assembly in colloidal systems.
Evolution of unstable explosion shock wave: Generation and transformation
Authors: Wang Han-cheng , Jiao Jun-jie , Pan Xu-chao , Mondal Joydip , Hao Yu , Qi Yan-jie , Shan Feng , Du Wei , Fang Zhong , Cheng Yu-bo , Liu Xing , He Xiaolan , He Yong
Published: November 2024

We present our discovery of unstable shock trains induced by transmission of unsteady detonation wave with electromagnetic and optical measurements. It reveals that transmission of explosion shock wave is essentially a transfer of state between matter with high energy densities and disturbed medium, and the wave structure depends on the uniformity of energy densities. The generation of transmitted shock wave differs generation of shock wave in the piston problem. This study could form theoretical and experimental basis of unsteady shock wave structure and foster further understanding the mechanism for generation of shock wave.
Magnetic metamaterials by ion-implantation
Authors: Vantaraki Christina , Ström Petter , Tran Tuan T. , Grassi Matías P. , Fevola Giovanni , Foerster Michael , Sadowski Jerzy T. , Primetzhofer Daniel , Kapaklis Vassilios
Published: November 2024

We present a method for the additive fabrication of planar magnetic nanoarrays with minimal surface roughness. Synthesis is accomplished by combining electron-beam lithography, used to generate nanometric patterned masks, with ion implantation in thin films. By implanting 56Fe+ ions, we are able to introduce magnetic functionality in a controlled manner into continuous Pd thin films, achieving 3D spatial resolution down to a few tens of nanometers. Our results demonstrate the application of this technique in fabricating square artificial spin ice lattices, which exhibit well-defined magnetization textures and interactions among the patterned magnetic elements.
Flow over a sphere at elevated pressures: An analysis of the near-wake using spectral proper orthogonal decomposition
Authors: Chavez R. , Anand N. K. , Hassan Yassin A. , Girimaji Sharath
Published: November 2024

This study advances the understanding of temporal dynamics in flow over a sphere in the near-wake by applying spectral proper orthogonal decomposition (SPOD) to time resolved particle image velocimetry experimental data collected at elevated pressures (3–6 MPa) over a wide range of Reynolds numbers (19 200–49 500). From the acquired velocity vector fields, the statistical values of mean and fluctuating velocities were computed along with their associated uncertainties. The work uniquely characterizes flow structures using SPOD spectra, showing that as Reynolds numbers increase, energetic peaks shift to lower frequencies, highlighting larger, slower-evolving structures. At higher Reynolds numbers, spectral peaks converge, suggesting previously distinct peaks merge into a broader one. Visualizing SPOD modes revealed large eddies at low frequencies and smaller structures in the wake at high frequencies. The investigation covers various aspects, including point-wise spectral analysis of the Reynolds decomposed streamwise and spanwise velocity components inside and outside the wake region using power spectral density, flow reconstruction using SPOD modes, and fills gaps in the literature regarding the relationship of the flow separation angle at these Reynolds numbers. The findings support Kolmogorov's theory of turbulence and offer insights into the oscillatory nature and energy dynamics of flow around a sphere. This characterization of flow dynamics at elevated pressures fills a gap in the literature, offering insights that enhance understanding of turbulence in engineering applications like pebble bed gas-cooled reactors, providing the nuclear industry with valuable data at prototypical conditions through advanced measurement and analysis techniques.
Wake dynamics of side-by-side hydrokinetic turbines in open channel flows
Authors: Dong Guodan , Zhao Zhenzhou , Xu Chang , Qin Jianhua
Published: November 2024

Lateral placement of hydrokinetic turbines is an interesting topic, as the blockage effect can increase the flow speed and increase the power coefficient (CP) for neighboring turbines. This study investigates wake dynamics in hydrokinetic turbine arrays with single- (1T), double- (2T), and triple-turbine (3T) configurations under various tip speed ratios (λ = 3.5, 5.8, and 7.1) using large eddy simulation coupled with the actuator line (AL) model. Results indicate that CP increases as lateral spacing decreases, which highlights the advantages of tighter lateral placement. The CP of the 3T-S turbine (the side turbine in the 3T configuration) is larger than those of the other configurations, following the trend CP,3T−S>CP,3T−M>CP,2T>CP,1T, which reflects a growing blockage effect with more turbines. Wake dynamics are analyzed using time-averaged and instantaneous methods. In 3T scenarios, blockage enhances turbulence kinetic energy, facilitating faster wake recovery, aided by turbine interference. Mean kinetic energy budget analysis shows that 3T-S wakes recover fastest due to increased turbulent convection. For instantaneous analysis, pre-multiplied power spectral density reveals vertical meandering begins at approximately 3D (D is the rotor diameter) and horizontal meandering starts near 4D, with a dominant frequency of St=0.28. Integral length scales show an initial increase followed by a downstream decrease, with minima marking the onset of wake meandering. Dynamic mode decomposition analysis reveals that high-frequency disturbance amplitudes increase with the number of turbines. At the optimal λ, wake effects dominate over inflow effects.
A method for evaluating the effect induced by vortices on the moment and efficiency of the fluid machinery
Authors: Huang Xianbei , Jin Guanqi , Guo Qiang , Liu Xiaodong , Lu Jiaxing
Published: November 2024

Up to now, there is no appropriate method to quantitatively evaluate the effect of local flow on the fluid machinery's performance, especially the moment and efficiency. In this paper, a moment decomposition method (MDM) is developed for this purpose. The major advantage of this method is the ability to calculate the contribution of local flow to the blade's moment and the applicability to simulations with non-constant density flows. The method is applied to a centrifugal pump under different flow rates. The relative error is around 10% under 0.5Qd∼1.0Qd (Qd is the design flow rate), showing satisfying accuracy. By analyzing the flow angle, it is found that the flow impact at blade inlet triggers the flow rate imbalance and alternative vortex generation in adjacent passages. The MDM results show that vorticity effect dominates under different flow rates. Negative kinematic effect in the passage with stronger vortices leads to lower moment contribution compared to another passage. By decomposing the passages, it is found that the wake region is the main source of moment. In addition, the hydraulic efficiency decrease in the impeller due to flow rate decrease is the result of wake suppression in the passage with weaker vortices.
On cavitation caused by tip clearance of a flat-plate hydrofoil
Authors: Han Huan , Geng Da , Qian Zhaohui , Ren Zibo , Zuo Zhigang , Liu Shuhong
Published: November 2024

This research integrates experimental visualization via high-speed photography with numerical simulations, leveraging large eddy simulation and the Schnerr–Sauer (S-S) cavitation model, to examine cavitation dynamics on a flat-plate hydrofoil across a range of tip clearance settings. We identify three distinct cavitation patterns caused by tip clearance (CT) in terms of the flow structures and interactions of tip leakage vortex cavitation, tip separation vortex cavitation (TSVC), and shear layer cavitation. The flat-plate hydrofoil demonstrates stronger TSVC and more pronounced vortex interactions compared to National Advisory Committee for Aeronautics 0009 hydrofoils. A phase diagram is established to predict the cavitation patterns of CT under different operational conditions of the cavitation number σ and the angle of attack α. We also observe a downwash effect from the vortices, influencing the cavitation length on the suction side of the hydrofoil. The findings are significant for optimizing hydrofoil designs in fluid machinery where effective cavitation management is critical.
Research on a 220-GHz modified staggered double corrugated waveguide backward wave oscillator
Authors: Ge Weihua , Yu Sheng
Published: November 2024

The output power of a backward wave oscillator (BWO) is limited by the low interaction impedance of a slow wave structure (SWS) when the frequency is in the THz band. A BWO based on modified staggered double corrugated waveguide (MSDCW) SWS is researched as a high-power source operating at THz band to break through the coupling impedance limitation in this paper. The MSDCW-SWS designed for BWO with wide electronic tunable band is optimized by numerical Eigenmode simulation to obtain higher coupling impedance. The simulation results show that the coupling impedance of MSDCW-SWS at 211.5 GHz is 42% higher than that of the original staggered double corrugated waveguide (SDCW) SWS when the dispersion conditions are the same for both SWSs. The sheet beam MSDCW-BWO with a broadband output structure is designed to operate under voltage between 23 and 49 kV and an electron beam current of 160 mA. The 3-D interaction simulation results reveal that more than 80.6 W of average output power can be produced from 210 to 238 GHz and the highest electron efficiency of 2.5% can be obtained at 211.5 GHz. The MSDCW-BWO can be considered a promising high-power THz source.
Electrical and structural characterization of YAlN at high alloy concentrations
Authors: Afshar N. , Yassine M. , Yassine A. , Maier N. , Ambacher O.
Published: November 2024

YxAl1−xN in its wurtzite phase has been identified as a prospective wide bandgap semiconductor and a promising competitor of ScxAl1−xN in application devices. Notwithstanding theoretical predictions of the high stability of YxAl1−xN in the wurtzite structure even at high alloy concentrations, experimental studies have revealed significant challenges in achieving the requisite high concentration films. This study demonstrates that strain is an effective parameter on the growth of wurtzite YxAl1−xN, which can be tuned by engineering growth methods, such as the introduction of different buffer layers. Conversely, difficulties have been encountered in achieving Y concentrations above x = 0.4, despite the incorporation of Y atoms into the layers, with the formation of amorphous structures occurring prior to the predicted structural phase transition to the rock salt crystal. A comprehensive grasp of the structural characteristics of YxAl1−xN thin films offers invaluable insight that will prove to be beneficial for future research on this material system.
Cotranslational molecular condensation of cochaperones and assembly factors facilitates axonemal dynein biogenesis
Authors: Li Yuanyuan , Xu Wenyan , Cheng Yubao , Djenoune Lydia , Zhuang Chuzhi , Cox Andrew Lee , Britto Clemente J. , Yuan Shiaulou , Wang Siyuan , Sun Zhaoxia
Published: November 2024

Axonemal dynein, the macromolecular machine that powers ciliary motility, assembles in the cytosol with the help of dynein axonemal assembly factors (DNAAFs). These DNAAFs localize in cytosolic foci thought to form via liquid–liquid phase separation. However, the functional significance of DNAAF foci formation and how the production and assembly of multiple components are so efficiently coordinated, at such enormous scale, remain unclear. Here, we unveil an axonemal dynein production and assembly hub enriched with translating heavy chains (HCs) and DNAAFs. We show that mRNAs encoding interacting HCs of outer dynein arms colocalize in cytosolic foci, along with nascent HCs. The formation of these mRNA foci and their colocalization relies on HC translation. We observe that a previously identified DNAAF assembly, containing the DNAAF Lrrc6 and cochaperones Ruvbl1 and Ruvbl2, colocalizes with these HC foci, and is also dependent on HC translation. We additionally show that Ruvbl1 is required for the recruitment of Lrrc6 into the HC foci and that both proteins function cotranslationally. We propose that these DNAAF foci are anchored by stable interactions between translating HCs, ribosomes, and encoding mRNAs, followed by cotranslational molecular condensation of cochaperones and assembly factors, providing a potential mechanism that coordinates HC translation, folding, and assembly at scale.
Inverse problems for a generalized fractional diffusion equation with unknown history
Authors: Janno Jaan
Published: November 2024

Solutions of equations governing nonlocal in time processes depend on history of the processes that may be unknown in various situations. In this paper, a method to exclude the unknown history in identification problems making use of non-analyticity of an input is proposed. The method is applied to inverse problems for a diffusion equation containing a generalized fractional derivative. It is assumed that a source f is unknown for time values t in

(
0
,

t
0

)

, vanishes for

t
∈
(

t
0

,

t
1

)

and has nonzero (generated) values for

t
∈
(

t
1

,
T
)

. Provided that

f

|

(

t
1

,
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)

satisfies certain restrictions, it is proved that product of a kernel of the derivative with an elliptic operator as well as the history of f for

t
∈
(
0
,

t
0

)

are uniquely recovered by a measurement of a state u in

(

t
0

,
T
)

. In case of less restrictions on f the uniqueness of the kernel and the history of f is shown. Moreover, in a case when a functional of u in

(

t
0

,
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)

is given the uniqueness of the kernel is proved under unknown history.
Electronic properties of polyaniline–graphene nanocomposites synthesized via solution mixing method
Authors: Thakur Soumyasuravi , Rathee Neeraj , Ray Nirat
Published: November 2024

A key advantage of combining the exceptional properties of graphene with conducting polymers, lies in their remarkable property tunability through filler additions into polymer matrices, with synthesis routes playing a crucial role in shaping their characteristics. In this work, we examine the electronic properties of polyaniline and graphene nanocomposites synthesized via a simple solution mixing method, which offers advantages such as ease of use and efficiency. Increasing graphene content enhances nanocomposite conductivity, and a percolation effect is observed. The percolation threshold is high and is consistent with a strong role played by voids in the structure. Temperature-dependent conductivity measurements highlight three distinct conduction regimes: insulating, critical, and metallic. These findings underscore the significant influence of synthesis method and structural disorder on shaping electronic properties, paving the way for engineering multifunctional nanocomposites with exceptional versatility and performance.
Quantitative Eliashberg theory of the superconductivity of thin films
Authors: Ummarino Giovanni Alberto , Zaccone Alessio
Published: November 2024

A quantitative theory of the superconductivity of materials confined at the nanoscale in parameter-free agreement with experimental data has been missing so far. We present a generalization, in the Eliashberg framework, of a BCS theory of superconductivity in good metals which are confined along one of the three spatial directions, such as thin films. In this formulation of the Eliashberg equations the approximation of taking the normal density of states as its value at the Fermi level has been removed. By numerically solving these new Eliashberg-type equations, we find the dependence of the superconducting critical temperature

T

c

on the confinement size L, in quantitative agreement with experimental data of Pb and Al thin films with no adjustable parameters. This quantitative agreement provides an indirect confirmation that, upon increasing the confinement, a crossover from a spherical-like Fermi surface, which contains two growing hole pockets caused by the confinement, to a strongly deformed Fermi surface, occurs. This topology of the Fermi sea is implemented in the new Eliashberg-type equations to reproduce the experimentally observed maximum in the critical superconducting temperature vs film thickness of ultra-thin Pb films.
Generalized pole-residue method for dynamic analysis of nonlinear systems based on Volterra series
Authors: Cao Qianying , Chang Anteng , Du Junfeng , Lu Lin , Qin Jianmin
Published: November 2024

Prediction of remaining useful life (RUL) is very important in health management across the fields of civil engineering, ocean engineering and energy. Monitoring and analyzing the dynamic response can provide valuable insights into the RUL of the dynamic systems. To calculate the response of such systems, time-consuming step-by-step numerical integration methods and convolution methods based on Volterra series in the time domain have been widely used. In contrast, this work develops an efficient generalized pole-residue method based on the Volterra series performed in the Laplace domain. The proposed method involves two steps: (1) the Volterra kernels are decoupled in terms of Laguerre polynomials, and (2) the partial response related to a single Laguerre polynomial is obtained analytically in terms of the pole-residue method. Compared to the traditional pole-residue method for a linear system, one of the novelties of the pole-residue method in this paper is how to deal with the higher-order poles and their corresponding coefficients. Because the proposed method derives an explicit, continuous response function of time, it is much more efficient than traditional numerical methods. Unlike the traditional Laplace domain method, the proposed method is applicable to arbitrary irregular excitations. Because the natural response, forced response and cross response are naturally obtained in the solution procedure, meaningful mathematical and physical insights are gained. In numerical studies, systems with a known equation of motion and an unknown equation of motion are investigated. For each system, regular excitations and complex irregular excitations with different parameters are studied. Numerical studies validate the good accuracy and high efficiency of the proposed method by comparing it with the fourth-order Runge–Kutta method.
Abrikosov clusters in chiral liquid crystal droplets
Authors: Fernandez-Gonzalez V , Clerc M G , González-Cortés G , Hidalgo P I , Vergara J
Published: November 2024

Self-organizing triangular lattices of topological vortices have been observed in type-II superconductors, Bose–Einstein condensates, and chiral magnets under external forcing. Liquid crystals exhibit vortex self-organization in dissipative media. In this study, we experimentally investigate the formation of vortex clusters, analogous to Abrikosov lattices, in temperature-driven chiral liquid crystal droplets. Based on a Ginzburg–Landau-like equation, we derive the interaction laws underlying the formation of these Abrikosov clusters of chiral domains. The origin of these is elucidated due to the competition between the repulsive interaction and the spatial effect of the confinement within the droplet. Our results advance the theoretical understanding of localized vortex self-organization in liquid crystals and open up possibilities for controlling the clustering of these topological defects.
Study in Murine Model: Is There a Relationship Between Presbycusis and Frailty?
Authors: Heredia-Molina, Rosalía Fátima , Riestra-Ayora Juan Ignacio , Yanes-Díaz Joaquín , Thuissard Vasallo Israel John , Andreu-Vázquez Cristina , de la Osa Subtil Iria , Sanz-Fernández Ricardo , Sánchez-Rodríguez Carolina
Published: November 2024

Age-related hearing loss, or Presbycusis, is the most frequent sensory deficiency in older adults and is associated with comorbidities such as falls, cognitive decline, and frailty. Frailty is related to poor health outcomes in old age. Recent research suggested that age-related hearing loss may be a potentially modifiable risk factor for frailty, although inconclusive. The use of animal models to study the correlation between age-related hearing loss and frailty is important to test future interventions to be translated into clinical practice. The aim of this study was to determine if there is an association between age-related hearing loss and frailty in experimental animals based on the human frailty phenotype. This research studied male and female C57Bl/6J mice at different ages (6, 14, and 22 months). Auditory steady-state response threshold shifts were measured at different frequencies. To assess frailty status, we were based on the “Valence Score,” which consists of measuring: weakness, weight loss, low level of activity, slowness, and little resistance. We found that hearing is significantly lower in older age groups. The mice become frail as they age. The worsening in auditory steady-state responses threshold shifts with age correlates significantly with an increasing frailty. No significant differences were found between both sexes. Our research is, to our knowledge, the first carried out in experimental animals to establish the association between age-related hearing loss and frailty, which would provide a useful tool to evaluate future interventions in mice before translating them into clinical practice.
Co- and post-seismic deformation of the 2022 Menyuan Mw6.6 earthquake from InSAR and GPS observations
Authors: Liu Tai , Hong Shunying , She Yawen , Fu Guangyu , Meng Guojie , Zou Zhenyu , Wu Weiwei
Published: November 2024

This study combines InSAR (Interferometric Synthetic Aperture Radar) and GPS (Global Positioning System) data to examine the coseismic slip and post-seismic deformation of the 2022 Menyuan Mw 6.6 earthquake, shedding light on the fault structure, slip distribution and rheology of the northeastern Tibetan Plateau. InSAR coseismic deformation revealed fault dip angle of 82° for the Lenglongling fault and 84° for the Tuolaishan fault. The optimal coseismic slip model, derived from InSAR, GPS and near-field pixel-offset data, indicates a maximum slip of 3.3 m, concentrated in the upper 3 km of the fault. We propose a three-step procedure to comprehensively invert the post-seismic deformation, accounting for both afterslip and viscoelastic relaxation, constrained by the InSAR and GPS observations. The optimal afterslip model indicates a cumulative afterslip of 9 cm over two years, primarily concentrated in the deeper sections of the coseismic slip zone. Incorporating viscoelastic relaxation improved the spatial distribution of the afterslip on the Tuolaishan fault. The afterslip released a seismic moment of 1.96 × 10¹⁸ N·m, accounting for approximately 15 per cent of the coseismic moment release. The viscosity of the lower crust in the region was estimated to range from 1.5 to 5 × 1018 Pa·s, with an optimal value of 2 × 10¹⁸ Pa·s. As the distance from the epicentre increased, viscoelastic relaxation became the dominant post-seismic mechanism, contributing up to 80 per cent of the deformation observed at the QHGC and GSMI stations. Additionally, the earthquake increased Coulomb stress on the ‘Tianzhu Seismic Gap’ and nearby faults, raising seismic hazard in the region. These findings highlight the importance of simultaneously considering both afterslip and viscoelastic relaxation mechanisms in post-seismic deformation analysis, and accounting for post-seismic effects when evaluating seismic stress changes.