bluuebunny/crossref_metadata_2025 huggingface dataset:
New low‐noise sensorless control strategy for permanent magnet synchronous motor drives based on variable‐frequency voltage signal injection
Authors: Zhu Haotian , Zhang Li , Peng Zhongfei , Tan Feixue , Xu Lei
Published: January 2025

This paper proposes a new low‐noise sensorless control strategy for the permanent magnet synchronous motor (PMSM) drives to tackle audible noise caused by high‐frequency injection method. The traditional noise reduction methods face limitation in improving estimated accuracy of rotor position due to the signal delay with fixed frequency signal. To overcome this issue, a low‐noise sensorless control strategy is developed, which consists of two parts. First, with the injection of the proposed variable‐frequency voltage signal, significant noise reduction can be achieved due to its characteristics of multi‐frequency switching and multi‐modal amplitude tuning. Secondly, a delayed effects‐aware demodulated signal is designed to reduce the impact of system delay, which can further improve the estimation accuracy of rotor position. As a result, the proposed low‐noise sensorless control scheme can suppress audible noise and further improve position estimation accuracy. Also, the steady‐state and dynamic performances of the motor drive system can be enhanced. Finally, comparative experiments under steady‐state and dynamic conditions demonstrate the superiority of the proposed method in PMSM.
Bayesian Robust Tensor Decomposition Based on MCMC Algorithm for Traffic Data Completion
Authors: Huang Longsheng , Zhu Yu , Shao Hanzeng , Tang Lei , Zhu Yun , Yu Gaohang
Published: January 2025

Data loss is a common problem in intelligent transportation systems (ITSs). And the tensor‐based interpolation algorithm has obvious superiority in multidimensional data interpolation. In this paper, a Bayesian robust tensor decomposition method (MBRTF) based on the Markov chain Monte Carlo (MCMC) algorithm is proposed. The underlying low CANDECOMP/PARAFAC (CP) rank tensor captures the global information, and the sparse tensor captures local information (also regarded as anomalous data), which achieves a reliable prediction of missing terms. The low CP rank tensor is modeled by linear interrelationships among multiple latent factors, and the sparsity of the columns on the latent factors is achieved through a hierarchical prior approach, while the sparse tensor is modeled by a hierarchical view of the Student‐t distribution. It is a challenge for traditional tensor‐based interpolation methods to maintain a stable performance under different missing rates and nonrandom missing (NM) scenarios. The MBRTF algorithm is an effective multiple interpolation algorithm that not only derives unbiased point estimates but also provides a robust method for the uncertainty measures of these missing values.
Towards a finite element model of a batch of experimental violins: validation on sub-structural components
Authors: Meza-Pérez Amaury , Stoppani George , Viala Romain , Gonzalez Sebastian , Igartua Unai , Jardón Rico Roberto , Fritz Claudia
Published: January 2025

During the Bilbao project, six violins were built with systematic geometry control in order to investigate the influence of the plate thickness on the dynamics, sound and playing characteristics of the complete instruments. To this end, three violins with medium backs, each paired with a thin, normal, or thick top and three with medium tops, each paired with a thin, medium, or thick back were made. Despite careful control and reduction of the influence of handwork by a numerically controlled machining cutting means on the outside of the plates, there remains various sources of variability, in particular in the wood properties. In order to separate the effect on the vibratory behavior of the intentional thickness variations from irreducible variability in wood properties and geometric tolerance, a complete finite element model is being developed using COMSOL software. This model takes into account the geometry of the Bilbao project violins while the wood properties are obtained by optimising the numerical vibratory behavior to match the experimental modal data of the free plates, just after they were CNC routed. This paper explains in detail this optimisation process and show the results for the six top and six back plates. The proposed approach enables the identification of material properties in multiple directions and ensures a step-by-step control of the accuracy of the modeled parts compared to the real ones.
IoT-based cloud monitoring system for building fires
Authors: Pan Guanhong , Xie Yanzhang , Yang Qingping
Published: January 2025

This paper presents an IoT (Internet of Things) based smart building fire cloud monitoring system to enhance fire safety in smart buildings. It integrates low-cost sensors and real-time video surveillance for real-time environmental data collection. Data are uploaded to the cloud for remote monitoring via a custom web interface. The system features an artificial neural network model that reduces computational complexity and response time, achieving >95% accuracy in fire prediction. It assists in planning evacuation routes based on fire location, enhancing safety and efficiency. Laboratory and field tests confirm reliable performance, and the novel system will find applications in smart fire detection and prevention.
Property (ω) and Hypercyclic Property for Operators
Authors: DAI Lei , YI Jialu
Published: January 2025

By means of the new spectrum defined with respect to the property of Consistence in Fredholm and Index (CFI) around an operator, we establish the necessary and sufficient conditions for a bounded linear opeator [see formula in PDF] defined on a Hilbert space satisfying the property [see formula in PDF] or hypercyclic property. Moreover, the relation between the operators which satisfy the property [see formula in PDF] and hypercyclic (supercyclic) property is discussed.
Complete Convergence for Moving Average Processes under m-WOD Random Variables
Authors: SONG Mingzhu , WU Yongfeng
Published: January 2025

The m-widely orthant dependent (m-WOD) sequences are very weak dependent random variables. In the paper, the authors investigate the moving average processes, which is generated by m-WOD random variables. By using the tail cut technique and maximum moment inequality of the m-WOD random variables, moment complete convergence and complete convergence of the maximal partial sums for the moving average processes are obtained, the results generalize and improve some corresponding results of the existing literature.
An Improvement of the Quantitative Stability Analysis for the Two-Stage Stochastic Variational Inequality Problems
Authors: WANG Zhenlong , LIN Liqin , WANG Yiting , LIU Jianxun
Published: January 2025

This paper extends the quantitative stability results to a more general class of two-stage stochastic variational inequality problems (TSVIP). The existence of solutions to the TSVIP is discussed, and the quantitative relationship between the TSVIP and its distribution perturbed problem is derived.
Nonisomorphic Orientable Quadrangular Embeddings and Edge-Colorings of K12s+9
Authors: LI Zhaoxiang , LIU Jiahong
Published: January 2025

In this paper, by constructing the current graph of the complete graph [see formula in PDF] and a mapping function, we prove that [see formula in PDF] ([see formula in PDF] is an odd number) has at least [see formula in PDF] nonisomorphic orientable quadrangular embeddings, and the orientable genus is [see formula in PDF]. Every one of the nonisomorphic orientable quadrangular embeddings has at least twenty-four 4-edge-colors, and each color appears around each face of orientable quadrangular embeddings.
The Space-Time Semi-Analytical Meshless Methods for Coupled Burgers' Equations
Authors: ZHANG Zhiqiang , WANG Fuzhang
Published: January 2025

In this paper, a simple direct space-time semi-analytical meshless scheme is proposed for the numerical approximation of the coupled Burgers' equations. During the whole solution procedure, two different schemes are considered in terms of radial and non-radial basis functions. The time-dependent variable in the first radial scheme is directly considered as the normal space variables to formulate an "isotropic" space-time radial basis function. The second non-radial scheme considered relationship between time-dependent and space-dependent variables. Under such circumstance, we can get a one-step space-time meshless scheme. The numerical findings demonstrate that the proposed meshless schemes are precise, user-friendly, and effective in solving the coupled Burgers' equations.
Endoscopic mucosal resection defect inspection for predicting recurrences: International image-based survey
Authors: Kemper Gijs , Schreuder Ramon-Michel , Schrauwen R. W.M. , Terhaar sive Droste Jochim S. , Siersema Peter , van Geenen Erwin-Jan M.
Published: January 2025

Background and study aims Endoscopic mucosal resection (EMR) is a safe and minimally invasive procedure to remove colorectal non-pedunculated polyps. Recurrence rates are relatively high and differ among endoscopists. We aimed to evaluate whether endoscopists are able to predict recurrence based on thorough inspection of images of mucosal defects after an assumed complete EMR.

Methods We developed an online survey in which endoscopists were invited to indicate whether they expected recurrence to develop when inspecting 30 post-EMR defect images. All EMRs were considered to be complete resections by the performing endoscopist. Participating endoscopists were scored based on the number of correct answers regarding presence or absence of recurrence found at first surveillance colonoscopy.

Results A total of 140 endoscopists responded to the survey (response rate 25%). A total of 124 respondents with a mean age of 46.5 years evaluated the 30 images. The overall score in the cohort was 70%, indicating that respondents were able to correctly predict recurrence in three-quarters of cases with an overall level of certainty of 53.4%. When comparing results of experienced and less experienced endoscopists based on the number of endoscopic submucosal dissections and/or EMRs performed yearly, no difference (71% versus 69%, P = 0.23) was found.

Conclusions This study shows that recurrences after presumed complete EMR can reasonably well be predicted by both experienced and less experienced endoscopists when evaluating images with mucosal defects. Thorough inspection of the post-EMR defect may reduce recurrence rates by recognizing and subsequent treatment of suspect areas.
From paternalism to self-determination: examining evolving tribal-federal relationships and co-management arrangements through three case studies
Authors: Lefthand-Begay Clarita , Redmore Lauren , Armatas Christopher , Brisbois Jesse , Choden Kunsang , Craig Dara , Baca Angelo , Martin Jaime , Ross Michael , Lopez-Whiteskunk Regina , Lomahquahu Alfred , Mills Monte
Published: January 2025

As governments around the world seek to develop and implement co-management practices with Indigenous peoples and local communities, there are many questions about how to foster collaborative and just agreements that support self-determination. Despite policy advancements enabling more co-management and shared stewardship within the United States (U.S.), possibilities for co-management are complicated by historical injustices that have hindered Tribal access to ancestral land and cultural practices. We use a multiple case study approach, examining three case studies from the Western U.S. that illustrate challenges facing Tribes and interventions used to improve land management relationships. The first case study focuses on the relationship between the Oglala Sioux Tribe and the U.S. government and highlights that historical injustices continue to affect Tribal land management. The second case study explores the collaborative management of Bears Ears National Monument, showcasing a decolonized approach endorsed by Tribes seeking to reclaim their inherent rights to the land. The third case study examines the Snoqualmie Tribe as an example of a sovereign Tribe embodying the concept of “Land Back.” Tribes have utilized strategies, such as co-management, coalition building, and land reacquisition, to maintain control over lands important to their populations. These strategies promote power-sharing, resource distribution, trust-building, and the integration of Indigenous knowledge with Western science. Nonetheless, failure to recognize and account for the weight of broken treaties, discriminatory laws and policies, and the historical trauma caused by these injustices emphasizes the importance of understanding the dynamics surrounding Tribal land management. As government-led land management paradigms around the world shift to consider self-determination of Indigenous nations and communities as a critical piece of improved stewardship, decision makers have many historically-informed dynamics to consider when shaping future co-management practices. KEYWORDS: co-management, Indigenous, “Land Back”, stewardship, Tribes, and sovereignty.
Hysteresis phenomena in Cd2P2S6 layered crystals
Authors: Ban H. , Gal D. , Motrja S. , Molnar A.
Published: January 2025

The results of the study of the temperature dependence of the dielectric permittivity of Cd2P2S6 crystals are presented. It is shown that in the temperature range 80–420 K there are three regions in which hysteresis phenomena are observed. At high temperatures (T > 320 K) there is an activation change of the dielectric losses associated with the increased conductivity of Cd2P2S6 crystals. The transition from heating to cooling leads to a decrease in losses, which is manifested as a hysteresis in the dielectric constant. A jump-like change in dielectric permittivity is found at 228 K in the cooling mode and 265 K in the heating mode, which is due to the first-order phase transition in these crystals. The third hysteresis region appears at low temperatures of 80–90 K. When the temperature is cycled in this interval, the classical hysteresis behavior is observed with a decrease in both amplitude and temperature range with each cycle. The cause of this behavior will be the subject of further investigation.
Optical properties of assemblies of disc-shaped metallic nanoparticles
Authors: Pavlyshche N. I. , Korotun A. V. , Kurbatsky V. P.
Published: January 2025

The issue of the frequency dependence of optical characteristics for assemblies of metal nanoparticles of different shapes (disc, spheroid, sphere) is considered. Expressions for radiation efficiency, absorption, scattering, and reflection coefficients of assemblies of nanoparticles were obtained. Calculations for disk nanoparticles were performed in the approximation of an equivalent oblate spheroid. Spectral features of optical characteristics determined by the shape, size and material of nanoparticles are described.
Ab initio study of randomly disordered hexagonal close-packed (rhcp) phase in platinum
Authors: Burakovsky L. , Preston D. L. , Errandonea D.
Published: January 2025

Platinum is one of the most important technological materials, and one of the most studied transition metals. Yet, its phase diagram remains virtually unknown. The solid phase of Pt at ambient conditions is face-centered cubic (fcc). However, in a previous paper [L. Burakovsky et al., J. Phys. Conf. Ser. 500, 162001 (2014)], we predicted Pt to undergo a phase transformation from fcc to another solid phase, namely, randomly disordered hexagonal close-packed (hcp) or simply random hcp (rhcp), which spans a pressure interval of ∼35–300 GPa and exists at temperatures ∼>3000 K. Since then, rhcp-Pt has been widely discussed in the literature but has been neither confirmed experimentally nor completely ruled out theoretically. In this work, using the technique of three-phase ab initio quantum molecular dynamics (QMD) simulations, we demonstrate the appearance of rhcp-Pt and determine the phase boundary that separates rhcp from fcc on the Pt phase diagram. These three-phase simulations consist in evolving a system containing two different hexagonal polytypes separated by liquid until the system reaches its final equilibrium state. It then appears that the results of the most recent experimental study on Pt melting, by Geballe et al. [Phys. Rev. Mater. 5, 033803 (2021)], map out a curve identified by Geballe et al. as the Pt melting curve, which virtually coincides with the fcc-rhcp solid–solid phase boundary presented in our work. We discuss the reasons for misinterpreting the fcc-rhcp solid–solid phase transition as melting. We calculate the equation of state (EOS) of fcc-Pt and refine its melting curve via more accurate QMD simulations using the Z method implemented with Vienna Ab initio Simulation Package. We also calculate the EOS and melting curve of rhcp-Pt. The two melting curves, along with the fcc-rhcp phase boundary, define the ab initio phase diagram of Pt that we present here. Our results extend the pressure range of rhcp-Pt by more than twice compared to the original result of 2014, namely, to ∼50–650 GPa. Finally, we argue that, despite being polymorphic, Pt should be considered as reliable EOS and shock-wave standards.
Multicaloric effect in FeRh, exploiting the thermal hysteresis in a multi-stimuli cycle combining pulsed magnetic field and uniaxial load
Authors: Scheibel F. , Shayanfar N. , Pfeuffer L. , Gottschall T. , Dittrich S. , Taubel A. , Aubert A. , Radulov I. , Skokov K. P. , Gutfleisch O.
Published: January 2025

Large magnetocaloric effects can be observed in materials with first-order magneto-structural phase transition. However, materials with large thermal hysteresis show a reduced effect in moderate fields (∼2 T) because the external field is insufficient to induce a fully reversible transformation. The hysteresis can be overcome or even exploited by applying a second external stimulus. A multi-stimuli test bench has been built to demonstrate the multicaloric effect in FeRh alloy using a pulsed magnetic field up to 9 T and a uniaxial stress of up to 700 MPa. A cyclic multicaloric effect of ±2.5 K could be observed for a sequential application of a pulsed field of 3 T and a uniaxial stress of 700 MPa. The interplay among external field strength, thermal hysteresis, and the transition width enables the use of pulsed magnetic fields and allows a decoupling of the applied magnetic field and the heat transfer process in the multi-stimuli cycle.
Sliding ferroelectricity-induced triple barrier modulation in van der Waals boron arsenide tunnel junctions
Authors: Zhao Hongyuan , Yun Jiangni , Yao Linwei , Zhang Lin , Liu Jinyuan , Yan Junfeng , Zheng Lei , Kang Peng , Zhao Wu , Zhang Zhiyong
Published: January 2025

To develop low-power, miniature, nonvolatile memory resistor integrated devices for in-memory computing technologies, the exploration of atomic-scale ferroelectric channel semiconductor devices is necessary. We theoretically designed tunnel junction devices based on two-dimensional ferroelectric semiconductors, with two-dimensional metal TaSe2 used as the top electrode and van der Waals bilayer boron arsenide (BAs) as the ferroelectric semiconductor channel, aiming to achieve high-performance, low-power, two-dimensional ferroelectric memory resistors. Our findings demonstrate that the bilayer BAs, upon contact with metal electrodes, can achieve two stable and switchable ferroelectric states. Interlayer relative sliding enables stable and alternating two-dimensional ferroelectric domains, altering the types of triple potential barriers at interfaces from Schottky contacts to Ohmic contacts. Thus, under the modulation of the “triple barrier” mechanism, control over channel carrier switching is achieved, resulting in a tunneling electroresistance of 104%. Additionally, non-equilibrium Green's function results indicate nonlinear changes in the I–V curve when switching between the two stable ferroelectric states, highlighting the multi-resistive state nature of channel resistance. Our research underscores the potential of sliding ferroelectric tunnel junctions in integrating nonvolatile storage and computing units, emphasizing their innovative applications in in-memory computing technologies.
Fully coupled dynamic analysis of novel floating dual-rotor wind turbines
Authors: Chen Siqi , Wang Kai , Wen Yihan , Le Conghuan , Gao Zhen
Published: January 2025

This paper employs a fully coupled aero-hydro-servo-elastic approach to develop numerical models for the 10 MW floating single-rotor wind turbine (SRWT) and the 5 MW-5 MW floating dual-rotor wind turbine (DRWT). A series of numerical simulations was conducted to investigate the aerodynamic characteristics, wake characteristics, dynamic response, and tower base force characteristics of two types of wind turbines. The results under three conditions—wind only, wave only, and combined wind and wave were analyzed and compared. The results indicate that the rated wind speeds of the floating SRWT and DRWT are 11.4 and 14 m/s, respectively. Under wind-only conditions, the aerodynamic force of DRWT is greater than that of SRWT when the wind speed reaches the rated speed of DRWT. However, when the wind speed is below the rated speed of DRWT, the results are the opposite. Regarding aerodynamic wake recovery, the DRWT demonstrates greater advantages due to the mutual interaction and mixing of the wakes. In terms of platform motion and tower base forces, the DRWT not only exhibits greater stability in sway, heave, roll, and yaw degrees of freedom but also shows lower average values for both the force and bending moment at the tower base. Under combined wind and wave conditions, the DRWT exhibits more complex high-frequency response characteristics compared to the SRWT. This paper offers a comprehensive analysis of the floating DRWT in comparison with the floating SRWT and provides insight for future design optimizations of DRWTs.
Driven by Brownian motion Cox–Ingersoll–Ross and squared Bessel processes: Interaction and phase transition
Authors: Mishura Yuliya , Ralchenko Kostiantyn , Kushnirenko Svitlana
Published: January 2025

This paper studies two related stochastic processes driven by Brownian motion: the Cox–Ingersoll–Ross (CIR) process and the Bessel process. We investigate their shared and distinct properties, focusing on time-asymptotic growth rates, distance between the processes in integral norms, and parameter estimation. The squared Bessel process is shown to be a phase transition of the CIR process and can be approximated by a sequence of CIR processes. Differences in stochastic stability are also highlighted, with the Bessel process displaying instability while the CIR process remains ergodic and stable.
Stability investigation of tunnel surrounding rock by coupling peridynamics, finite element method, and finite volume method
Authors: Zhang Daosheng , Zhou Zongqing , Gao Chenglu , Bai Songsong , Bu Fanlin , Chen Xiaochu , Chen Jinbo
Published: January 2025

The construction environment of subsea tunnels is highly complex. Revealing the influencing factors and governing laws of surrounding rock stability as well as ensuring the stability of the surrounding rock during the construction process is crucial for the safe construction of the tunnel. Based on the coupling of peridynamics (PD) with finite element method (FEM) and finite volume method (FVM), the PD-FEM coupling method describes solid deformation and damage, while FVM solves the fluid seepage field. Data exchange is performed through a transition layer to achieve efficient fluid–solid coupling calculations. Using the Shantou Bay Subsea Tunnel as the engineering background, an engineering-scale simulation of the subsea tunnel excavation process was conducted. The results were validated by comparison with COMSOL simulation results and field monitoring data. Furthermore, 15 additional simulations were conducted. Through comparing and analyzing the distribution characteristics of excavation damage zones, displacement fields, and seepage fields in the surrounding rock under various influencing factors, this study unveils the influence patterns of tunnel burial depth (in situ stress conditions), seawater depth (groundwater pressure), rock mass elastic modulus (surrounding rock properties), and tunnel excavation methods on the stability of surrounding rock in Shantou Bay Subsea Tunnel. This provides a scientific basis for predicting the stability of subsea tunnel surrounding rock and ensuring safe construction.
Dissecting inertial clustering and sling dynamics in high-Reynolds number particle-laden turbulence
Authors: Codispoti Lukas A. , Meyer Daniel W. , Jenny Patrick
Published: January 2025

We advance the understanding of inertial clustering and the role of sling events in high-Reynolds number (Re) particle-laden turbulence. To this end, we perform one-way coupled particle tracking in flow fields obtained from direct numerical simulations (DNS) of forced homogeneous isotropic turbulence. Additionally, we examine the impact of filtering utilized in large eddy simulations by applying a sharp spectral filter to the DNS fields. Our analysis reveals that while instantaneous clustering through the centrifuge mechanism explains clustering at early times, the path history effect—the sampling of fluid flow along particle trajectories—becomes important later on. The filtered fields expose small-scale fractal clustering that cannot be predicted by the instantaneous flow field. We show that there exists a filter-effective Stokes number that governs the degree of fractal clustering and preferential sampling, revealing scale-similarity in the spatial distributions and fractal dimensions. Sling events are prevalent throughout our simulations and impose prominent patterns on the particle fields. In pursuit of investigating the sling dynamics, we compute the relative velocity, averaged over proximal neighboring particles, to identify particles undergoing caustics. As postulated in recent theories, we find that in fully resolved, high-Re turbulence, sling events occur in thin sheets of high strain, situated between turbulent vortices. This behavior is driven by rare, extreme events of compressive straining, manifested by characteristic fluctuations of the flow velocity gradients.
DeepONet-embedded physics-informed neural network for production prediction of multiscale shale matrix–fracture system
Authors: Chen JiaXuan , Yu Hao , Li Bo , Zhang HouLin , Jin Xu , Meng SiWei , Liu He , Wu HengAn
Published: January 2025

As a rising method for reservoir-scale production analysis, machine learning (ML) models possess high computational efficiency with robust capability of nonlinear mapping. However, their accuracy and interpretability are commonly limited owing to the absence of intrinsic physical mechanisms, solely by the data fitting. This work proposes a novel DeepONet-embedded physics-informed neural network (DE-PINN), which comprises a forward network to connect the matrix/fracture characteristics and production performance, and a sampling network to acquire the location of sampling points within shale reservoirs. DeepONets are constructed by the selected layers of these networks to output the field variables in governing equations that include mass/momentum conservation equations coupled with multiscale transport mechanisms. Through the automatic differentiation method, these equations are solved by the obtained field variables, and the residuals generated during the solution are integrated into the loss function as physical constraints. Compared with traditional data-driven machine learning models, the DE-PINN exhibits better performance in forecasting the production rate and cumulative production, achieving the mean absolute percentage error (MAPE) of approximately 3% and adjusted R2 values in the test set exceeding 0.98. This model demonstrates the advantage by realizing superior predictive precision with fewer production data samples under complex geological conditions of the shale reservoirs.
Alginate biopolymer viscoelasticity from sol to gel: Linear and nonlinear rheology, and Brownian motion of tracer particles embedded in the polymer network
Authors: López-Santiago Ricky F. , Castillo Rolando
Published: January 2025

The linear and nonlinear rheological behavior of alginate/Ca2+ gels made through slow solubilization of CaCO3 using gluconic acid-δ-lactone was studied. Rheological modulus follows a power law at the critical point; exponents (n = 0.60–0.65) decrease slightly, increasing Ca2+ ions. These values agree with those reported in the literature with similar mannuronic/guluronic residue ratios and total polymer concentration. The strain-hardening behavior of matured gels was investigated using large amplitude oscillatory shear. The Blatz–Sharda–Tschoegl scaling model was used to estimate their fractal dimension, whose values were 1.23–1.31; the fractal dimension is not sensible to Ca2+ concentration. The Lissajous–Bowditch curves show a higher nonlinearity and constitute a rheological fingerprint of these gels. The geometrical decomposition of intracycle strain in terms of strain thickening and stiffening ratios shows a weak formation of temporary network junctions during the breaking process due to the convexity of their curves. Diffusion wave spectroscopy was used to determine the mean square displacement of microspheres embedded in polymer solution exhibiting a subdiffusive process, with two slopes: m ∼ 0.3 at short times and m ∼ 1 at long times. The diffusive region section decreases as the gelation progresses due to Ca2+ and disappears when gels are formed. Gelation time was estimated to identify a terminal relaxation time, whose evolution follows almost the same exponential curve for gels with high Ca2+ concentration due to the formation of many multiple egg-box structures. After 24 h of gelation, mean square displacement curves show an apparent plateau, indicating important particle confinement.
Wall pressure amplification of shock-collapsed multi-bubble arrays near a rigid wall
Authors: Eric Goncalves da silva , Parnaudeau Philippe
Published: January 2025

This numerical study investigates the collapse of various arrangements of gas bubbles immersed in water in the vicinity of a rigid wall and impacted by a planar shock wave. Multiple bubble configurations, from 2 to 5 bubbles, are compared, focusing primarily on the pressure loads on the wall and the potential amplification in comparison with the single-bubble case. The three-dimensional simulations are performed using a massively parallel compressible diffuse interface solver. The effects of the grid resolution and the mass transfer term are discussed. The main characteristics of the flows are described, and the dynamic behaviors in pressure wave propagation are illustrated. A power-law is proposed for the evolution of the maximum pressure peak on the wall as a function of the density ratio of the bubble array. An amplification of a factor 30 is highlighted for a pyramidal arrangement.
Deep Opt: A structure optimization framework based on deep learning, and its application to micromixer optimization
Authors: Bu Tao , Li Quanjiang , Wang Jingtao
Published: January 2025

In this work, a new structural optimization framework, Deep Opt, is developed. The framework was built based on deep learning and multi-objective genetic algorithm (NSGA-II) for a simple, novel micromixer optimization process of geometrical structures and operational conditions. First, the process of generating signed distance field (SDF) and computational fluid dynamics (CFD) datasets for different structural micromixers was automated based on Python scripts. Then, the two datasets were reconstructed separately using two encoder–decoder convolutional neural networks (ED-CNN), termed ED-SDF and ED-CFD. The surrogate model for subsequent optimization was created by connecting two neural networks in series. Finally, the optimal micromixer and its flow field distribution were determined by utilizing NSGA-II to perform a multi-objective (minimum pressure drop, maximum mixing index, and minimum mixing energy cost) optimization of the micromixer with two structural variables, the sum of the obstacle radius (Rsum), the ratio of the obstacle radius (Rratio), and a CFD variable Re. Compared with conventional optimization methods, Deep Opt is able to generate high-fidelity flow field for the corresponding structures while optimizing the structural parameters and CFD parameters. In addition, Deep Opt improves the scalability of the optimization process, enabling the customization of optimization targets without the need to reconstruct the dataset, improving the utilization of CFD data. In practice, the framework is not only limited to micromixer optimization but can also be applied to CFD optimization problems with general geometrical configurations, such as the design and optimization of airfoils, stirred tanks, and so on.
Effect of leading-edge cavitation of a hydrofoil on the near-field sound pressure
Authors: Qian Zhaohui , Zeng Yongshun , Yao Zhifeng , Wu Qin , Luo Xianwu
Published: January 2025

Leading-edge (LE) cavitation of a blade is a frequent occurrence in hydraulic machinery during off-design operation, often accompanied by unsteady flow and high-amplitude noise. To quantitatively assess the noise caused by cavitation, the Powell vortex sound theory was refined to consider the non-uniform distribution of sound speed and the compressibility effect resulting from mass transfer near the vapor–liquid interface. This led to the development of a new model capable of visualizing the spatiotemporal distribution of sound pressure in cavitating flows. Unsteady simulations were conducted on a hydrofoil at various cavitation numbers and were validated using experimental data. Three different types of sound sources were identified: unbalanced vortex force, non-uniform kinetic energy, and compressibility effect, with the compressibility effect being the dominant source under LE cavitation conditions. The sound pressure during cavitation exhibited dramatic fluctuations over time and was closely related to the spatial position, particularly peaking during the transient moments of LE cavitation break-off, with the highest sound pressure observed near the vapor–liquid interface. There was a strong correlation between sound pressure and vapor volume fraction, suggesting that cavitation noise is a result of the dynamic evolution of cavitation. As the cavitation number decreased from 2.02 to 1.04, the sound pressure level substantially increased, with an increment of up to 17 dB. This paper presents a method for simulating and visualizing near-field sound pressure considering cavitation, providing valuable insights into the relationship between LE cavitation and sound pressure levels.
Baffle angle optimization of a typical shell and tube heat exchanger
Authors: Dogan Sercan
Published: January 2025

An optimization study was conducted with the objective of enhancing the performance of a prevalent shell-and-tube heat exchanger model by modifying the baffle angles. The initial step was to verify the turbulence model results with numerical studies and analytical approaches documented in the literature. Subsequently, an investigation was conducted to address the contributions identified in the literature by determining the optimal angle for a shell-and-tube heat exchanger with six baffles. In the extant literature, the 36% baffle cut case, which is typically observed to provide the optimal heat transfer result, was selected for further analysis. A genetic algorithm optimization model embedded in a program was employed to evaluate the heat transfer and pressure drop jointly, thereby determining the optimal angles for all baffles. According to the performance evaluation criteria that considered both heat and flow results, the optimal angles were found to be 315°, 195°, 80°, 340°, 250°, and 95° from the first to the last baffle, respectively. Additionally, a comparison was conducted between the cross-arrangement baffle and the optimized baffle, which demonstrated superior performance by 5.5% and 19.5%, respectively, contingent on the increasing flow rate. Moreover, the novel configuration enabled enhanced mixing of the flow, which exhibited periodic movement in the staggered baffle configuration within the shell. This resulted in a notable enhancement of the heat transfer process.
Rank-two tensorial shape descriptors: Insights into anisotropic permeability tensor characterization
Authors: Zhang Zihan , Li Changdong , Ye Yang , Lu Sha
Published: January 2025

The permeability of an anisotropy porous microstructure is expressed as a symmetric tensor of rank two. Compared with a specific scalar or a combination of several scalars, a homogeneous and symmetric tensorial descriptor is more suitable for characterizing the anisotropy permeability tensor. Unlike prior work, our method integrates advanced three-dimensional pore mesh generation from X-ray computed tomography images of sand-packing sample and desiccation cracked soil, creating twenty-seven representative elementary volume meshes. Using the finite element method, we numerically simulate the permeability tensor for each mesh and validate our results by showing strong correlations between Minkowski tensor (MT) descriptor W20,2 and permeability tensor: Pearson correlation coefficients of 0.763 for sand-packing sample and 0.854 for desiccation cracked soil. Additionally, we compare our approach with conventional permeability prediction methods and demonstrate that MTs provide a more detailed understanding of permeability anisotropy. This approach offers new insights into the anisotropy of permeability and provides a more robust framework for characterizing heterogeneous porous materials in both geophysical and engineering applications.
Transport of lithium droplets between two nonparallel iron plates: A molecular dynamics study
Authors: Liu Songchang , Liu Jiaxin , Lee Jin Yong
Published: January 2025

The use of bionic structures for the efficient and passive directional transportation of liquid droplets is crucial in numerous industrial applications. Compared with conventional fluids, liquid metals are stable under a wide range of environmental conditions owing to their excellent physicochemical properties. However, the directional transportation of liquid metals remains challenging. Herein, inspired by the pecking feeding mode of shorebirds, we performed a series of systematic molecular dynamics simulations to study the directional transport of liquid lithium (Li) between non-parallel iron (Fe) plates. The simulations demonstrate that cyclically closing and opening the Fe plates induces the movement of Li droplets toward the tip of the beak-shaped plate. Increasing the opening angle and applying a positive strain of the Fe plates can increase the transport velocity of the Li droplets. Nevertheless, the dissolution of Fe atoms in the liquid Li due to corrosion hinders the transportation of Li droplet across the Fe plate. We simulated the impact of two surface nanostructures on Li transport behavior and found that saw-tooth nanostructures decrease transport efficiency and lead to droplet breakup, whereas nanogrooves improve transport capacity by promoting the capillary effect. This work indicates that understanding the mechanism and influencing factors of liquid Li transport between non-parallel plates is essential for the design of bionic structures for the efficient transport of liquid metals.
Ultralow-Vertical-Current Magnetization Switching Effect in an All Van Der Waals 2D Heterostructure
Authors: Wu 武 Hao 浩 , Yang 杨 Li 丽 , Zhang 张 Gaojie 高节 , Jin 靳 Wen 雯 , Yu 虞 Jie 杰 , Xiao 肖 Bichen 碧晨 , Annas 王 Ahmed 绍凌 , Zhang 张 Wenfeng 文峰 , Chang 常 Haixin 海欣
Published: January 2025

The manipulation of magnetization and spin polarization using electrical currents represents a fundamental breakthrough in spintronics. It has formed the foundation for data storage and next-generation computing systems. Spin-transfer torque (STT) and spin-orbit torque (SOT) have emerged as prominent mechanisms in current-driven magnetization switching. However, these approaches typically require critical current densities in the range of 106 to 109 A⋅cm−2, resulting in significant heat generation during data writing processes. Herein, we report the discovery of an ultralow-vertical-current magnetization switching effect in a van der Waals ferromagnetic/ferroelectric heterostructure based on the modulation of the critical magnetic field (H
C) using small vertical currents, with a critical current density as low as 1.81 A⋅cm−2 and an average effective field (H
eff/J
C) as high as 150.3 mT⋅A−1⋅cm2. This unique magnetization switching effect with ultralow-critical-vertical-current densities typically six to nine orders of magnitude lower than those of the STT and SOT provides a new transformative and viable pathway for developing next-generation spintronic and quantum technologies.
Controllable and multi-band acoustic metamaterial topological insulators
Authors: Wang Yuanbo , Di Muchun , Ding Changlin , Dong Yibao , Zhai Shilong , Luo Chunrong , Zhao Xiaopeng
Published: January 2025

The valley degrees of freedom, representing quantum states of energy extremes in momentum space, are introduced into the acoustic system, and the valley topological insulator analogs of the quantum valley Hall effect can control the sound wave to observe topological valley transport against backscattering in domain walls of different valley topological phase structures. However, most of the earlier acoustic topological insulators are based on Bragg scattering and topological states only work in a single frequency band, which limits the design of applications for multiband communications. Here, we propose multiband acoustic valley Hall topological metamaterials based on weak interaction of local resonance subunits with isolated modulation. Valley topological phase transitions exists at two separated frequency bands by combining acoustic meta-atoms and meta-molecules and simply rotating the scatterers. Both the simulated and experimental results demonstrate structure-dependent dual-band topological edge states. Such a design may provide new ideas for multi-channel acoustic communications and subwavelength acoustic energy harvesting.
Effect of different glide planes of dislocations on radiative and nonradiative recombination in terms of the open circuit voltage of InGaAs solar cells
Authors: Harada Tomoki , Harada Shogo , Suzuki Hidetoshi , Endo Soma , Ogura Akio , Imaizumi Mitsuru , Ikari Tetsuo , Fukuyama Atsuhiko
Published: January 2025

To reduce fluctuations in the performance of lattice-mismatched solar cells within a wafer, it is necessary to characterize and quantify the effect of misfit dislocations, caused by strain relaxation, on the performance of a solar cell. To this end, the relationship between the preferential glide planes (GPs) and the carrier generation-recombination process in InGaAs solar cells with low (LowV) and high (HighV) open-circuit voltages has been investigated in this study. The GPs of the β dislocations in the HighV cells were uniformly controlled in the wafer plane. However, the LowV cells contained a mixture of two in-plane regions, in which the GPs of the β dislocations were controlled by the surface atomic steps during their growth on a vicinal substrate (LowV-sub region) or by the InGaP ordering effect (LowV-ord region). The results of the microwave photoconductivity decay method and our newly-developed laser heterodyne photothermal displacement method suggested that the photoexcited carrier concentration was low in the LowV-ord region. A photoluminescence measurement as a function of temperature further revealed that indium fluctuations occurred due to the presence of the GPs of the β dislocation. The LowV cells exhibited high indium composition and reduced bandgap. Thus, a small photoexcited carrier concentration and reduced bandgap energy decreased the difference between the quasi-Fermi levels of electrons and holes, resulting in a small V
OC. The photovoltaic performance could be determined by the density of the threading dislocations and the corresponding fluctuations in the indium composition owing to the different GPs of the β dislocations.
Effect of dopants and surface oxides on the electronic properties of dislocations in p-type SiC
Authors: Cheng Ziyang , Cao Rui , Xu Lingbo , Cui Can , Pi Xiaodong , Yang Deren , Wang Rong
Published: January 2025

Understanding the electronic properties of dislocations is key to tailoring their properties in silicon carbide (SiC)-based electronic devices. By combining the Kelvin probe force microscopy analysis and first-principles calculations, we investigate the effect of aluminum (Al) dopants and surface oxides on the electronic properties of dislocations in p-type SiC. It is found that dislocations, including threading screw dislocations (TSDs), threading edge dislocations (TEDs), and basal plane dislocations (BPDs) create deep acceptor-like states in p-type SiC. The defect levels move upwards in the order of BPD, TED and TSD, which closely relates with the lattice distortion of dislocations. Interestingly, we find that the defect levels of dislocations are higher than that of Al dopants in p-type SiC. First-principles calculations indicate that the defect formation energies of Al dopants at the cores of dislocations are higher than those in the perfect region of p-type SiC, as a result of the steric effect. This indicates that the concentration of Al acceptors at the dislocation cores is lower than that in the perfect region, resulting in the higher defect level positions of dislocations in p-type SiC. Additionally, we find that surface oxidation reduces the difference of defect-level positions between dislocations and the perfect region of p-type SiC, which paves the way for tailoring the electronic properties of dislocations in p-type SiC.
A direct conversion model from ZTD to PWV based on the random forest
Authors: Jiang Chunhua , Chen Shaoni , Gao Xiang , Zhu Huizhong , Gao Meng , Wang Shuaimin , Liu Guangsheng
Published: January 2025

Precipitable water vapor (PWV) is crucial for weather forecasting and climate change research. However, accurate PWV estimation is challenging, especially in the absence of measured meteorological data. In this study, we develop a conversion model based on the random forest algorithm, called RPWV, which can directly derive PWV from zenith total delay without measured meteorological data. The results indicate that the RPWV model demonstrates high accuracy and reliability for PWV retrieval across North America. Specifically, using global navigation satellite system PWV as a reference, the bias and root mean square (RMS) values for RPWV are 0.01 mm and 1.87 mm, respectively. Moreover, compared with the conventional linear model and backpropagation neural network model, the accuracy of the RPWV is improved by 81.3% and 13.4%, respectively. In contrast to radiosonde PWV, the bias and RMS values of the RPWV are 1.85 mm and 3.40 mm, respectively. This model provides a straightforward and efficient method for estimating PWV and has potential for weather forecasting and climate research in environments where meteorological data is scarce.