bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of planar shear inflow on wake behind a normal flat plate
Authors: Poojary Deekshith I. , Narasimhamurthy Vagesh D.
Published: December 2024

This study employs a direct numerical simulation to analyze the effects of planar shear inflow on the flow characteristics around a normal flat plate. The influence of shear is examined by comparing it with a uniform inflow condition. Based on the centerline inflow velocity and plate height, the Reynolds number was taken as 170 and the non-dimensional shear rate as 0.1. Flow visualization shows that the wake from uniform inflow is experiencing a temporal beating phenomenon that switches between coherent and incoherent states, whereas the planar shear drives the flow toward a fully incoherent state. A comparison with the uniform inflow case shows that planar shear induces weaker vortex shedding, a lower drag coefficient, and a corresponding increase in the recirculation length. Furthermore, a phase-time analysis using the Hilbert transform revealed that the vortices are shed in-phase in the uniform inflow case, whereas they are mostly out-of-phase in the planar shear case. Reduction of coherent vortices and enhancement of incoherent fluctuations are evident in the planar shear case, thereby affecting the mean velocity and Reynolds stress symmetry and a modest increase in the magnitude of turbulent components.
Ultra-thin p-AlGaN insert layer for enhancing the electrical performance of AlGaN-based deep-ultraviolet light-emitting diodes
Authors: Ji Chen , Wang Jiaming , Zhang Lisheng , Xu Fujun , Lang Jing , Guo Xueqi , Zhang Ziyao , Tan Fuyun , Ji Chengzhi , Kang Xiangning , Yang Xuelin , Tang Ning , Chen Zhizhong , Wang Xinqiang , Ge Weikun , Shen Bo
Published: December 2024

A composite p-contact structure is proposed to enhance the electrical performance of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs). With the insertion of a 1 nm-thick p-AlGaN layer prior to the contact layer, the operating voltage at 100 mA is significantly reduced by 0.2–0.3 V in 277 nm DUV-LEDs, leading to a maximum wall-plug efficiency of 10.7%. It is experimentally demonstrated that the reduction of operating voltage is mainly attributed to the lower specific contact resistivity of p-contact. The improvement mechanism of contact property is further explored by the theoretical calculations of energy band, where the hole accumulation in the contact layer, owing to the greater valence band offset induced by the p-AlGaN insert one, is speculated to promote the tunneling at the metal/semiconductor interface. The composite p-contact structure in this study is compatible with the present commercial DUV-LED epitaxial structure, enabling it to promote further development of this field.
Two-dimensional FePS3 nanoelectromechanical resonators with local-gate electrostatic tuning at room temperature
Authors: Wang Yunong , Yousuf S M Enamul Hoque , Zhang Xiao-Xiao , Feng Philip X.-L.
Published: December 2024

Nanoelectromechanical systems (NEMS) enabled by two-dimensional (2D) magnetic materials are promising candidates for exploring ultrasensitive detection and magnetostrictive phenomena, thanks to their high mechanical stiffness, high strength, and ultralow mass. The resonance modes of such vibrating membrane NEMS can be probed optically and also manipulated mechanically via electrostatically induced strain. Electrostatic frequency tuning of 2D magnetic NEMS resonators is, thus, an important means of investigating magneto-mechanical coupling mechanisms. Toward realizing magneto-mechanical coupled devices, we build circular drumhead iron phosphorus trisulfide (FePS3) NEMS resonators with different diameters (3–7 μm). Here, we report on experimental demonstration of tunable antiferromagnet FePS3 drumhead resonators with the highest fractional frequency tuning range up to Δf/f0 = 32%. Combining experimental results and analytical modeling of the resonance frequency scaling, we attain quantitative understanding of the elastic behavior of FePS3, including the transition from “membrane” to “plate” regime, with built-in tension (γ) ranging from 0.1 to 2 N/m. This study not only offers methods for investigating mechanical properties of ultrathin membranes of magnetic 2D materials but also provides important guidelines for designing future high-performance magnetic NEMS resonators.
Investigation of wind tunnel experiments on nonlinear ground effect for flying cars
Authors: Zhang Xiaodong , Du Hai , Zhang Tonghao , Ma Junyu , He Yunao , Zhang Kaiyuan , Gui Hongping
Published: December 2024

This research investigates the nonlinear aerodynamic characteristics of ground effect for flying cars, utilizing high-precision balance measurements to determine the lift and drag of flying cars and particle image velocimetry (PIV) in a closed-circuit low-speed recirculating wind tunnel. The ground effect's lift enhancement mechanism was revealed through analysis of aerodynamic results and flow field structures. Force measurement experiments demonstrated that ground effect significantly improves aerodynamic performance, with the lift coefficient showing a nonlinear trend as altitude decreases, undergoing the gentle force phase, the force increase phase, and the force reduction phase. PIV results indicated that the narrowing flow channel between the flying car and the ground at lower heights reduces airflow speed beneath the wing, converting kinetic energy into pressure potential energy, similar to a high-pressure air cushion. Consequently, airflow speed over the upper wing surface increases, enhancing lift. Additionally, ground effect causes the wingtip vortex structure to move upward and outward along the wing span, reducing downward induced velocity, weakening vortex strength, and increasing the effective aspect ratio of the three-dimensional wing. These changes reduce induced drag, thereby improving the overall performance of the flying car.
Self-excited oscillations of three-dimensional collapsible tubes conveying both laminar and turbulent flows
Authors: Huang Qiuxiang , Ji Xueyu , Ma Jingtao , Wang Li , Young John , Lai Joseph C. S.
Published: December 2024

This study investigates self-excited oscillations of three-dimensional collapsible tubes conveying both laminar and turbulent flows, using an immersed boundary-lattice Boltzmann method. The effects of Reynolds number (Re) on these oscillations are explored, revealing that at Re = 200, periodic vortex shedding downstream of the tube throat induces small-amplitude, quasi-periodic self-excited oscillations. Notably, stress concentrations near the downstream end of the elastic tube lead to the formation of two regions of wall thickening, which may predispose the elastic tube to fatigue failure. At higher turbulent flow conditions (Re = 1000), flow bifurcation occurs, resulting in large-amplitude, quasi-periodic oscillations. These oscillations are similarly driven by vortex shedding, which imparts periodic perturbations onto the elastic tube wall. Additionally, analysis at two monitoring points within the downstream rigid tube reveals small secondary oscillations in pressure and streamwise velocity. These secondary oscillations are attributed to the merging jets and their interactions within the downstream rigid tube.
Photodissociation of the CH2Cl radical: A high-level ab initio study
Authors: Charfeddine F. , Yazidi O. , Zanchet A. , Bañares L. , García-Vela A.
Published: December 2024

Photodissociation of the CH2Cl radical is investigated by using high-level multireference configuration interaction ab initio methods, including the spin–orbit coupling. All possible fragmentation pathways, namely, CH2Cl + hν → CH2 + Cl, HCCl + H, and CCl + H2, have been analyzed. The potential-energy curves of the ground and several excited electronic states along the corresponding dissociating bond distance of each pathway have been calculated. Inclusion of the spin–orbit couplings is found to be crucial because it strongly determines the shape of the curves of the different excited states and, therefore, their photodissociation dynamics behavior. Analysis of the potential curves indicates that the pathways producing CH2 + Cl and HCCl + H can occur through a fast direct dissociation mechanism, while the pathway leading to CCl + H2 involves much slower dissociation mechanisms such as internal conversion between electronic states, predissociation, or tunneling through exit barriers. The main implications are that the two faster channels are predicted to be dominant, while the slower pathway is expected to be very unlikely and rather irrelevant. Appreciable actinic fluxes of solar irradiation are available at stratospheric altitudes where ozone is abundant, in the wavelength range where absorption of the first low-lying excited states of CH2Cl has been observed experimentally. Our results show that in this excitation energy range, the above-mentioned two dominant dissociation pathways are open and then could contribute to stratospheric ozone depletion.
Simulating waves induced by landslide using coupled smoothed particle hydrodynamics and discrete element method: Evaluating the impact of irregular rock shapes
Authors: Sun Jiazhao , Zou Li , Govender Nicolin , Martínez-Estévez Iván , Ning Daosheng , Domínguez José M. , Crespo Alejandro J. C.
Published: December 2024

The morphology of rock plays an important role in the process of landslide-induced wave, yet it is often neglected in current studies. This work aims to fill this gap by investigating the impact of irregular rock shapes on landslide-induced wave generation and propagation via coupling smooth particle fluid dynamics and discrete element method from a multi-scale perspective. Initially, the wave induced by particle column collapse is reproduced and validated against existing results. Subsequently, the influence of rock shapes, particularly the aspect ratio of particles on landslide-induced waves, is analyzed. The findings indicate that spherical particles, due to their low self-locking tendency and simple force chain structure, exhibit higher average velocities and more stable velocity changes during the landslide process. Spherical particles generate larger free surface waves with smoother and more regular waveforms when entering the water. In contrast, irregular polyhedral particles produce multiple secondary wave peaks alongside the main wave. The wave height induced by these particles is negatively correlated with aspect ratio. Specifically, the maximum run-up height of waves generated by elliptical particles with the highest aspect ratio is 11.7% lower than that of spherical particles. This research highlights the influence mechanism of particle morphology on landslide and tsunami dynamics, which provides a theoretical foundation for disaster prediction and assessment.
Numerical prediction of cavitation erosion with emphasis on investigating the influence of driving pressure definition
Authors: Geng Linlin , Zhang Qinghua , Fang Haiyuan , Cao Yantao , Yang Mengzi , Zhang Desheng
Published: December 2024

This work devoted to analyzing the influence of the definition of driving pressure on the erosion prediction. For that, the density-corrected shear stress transfer turbulence model and the Sauer cavitation model are used to simulate the unsteady cavitating flow around a twisted hydrofoil. The numerical results were verified by compared to the cavitation shedding rate and the transient cavity behaviors in the experiment. The erosion energy in the flow field was defined based on the transient pressure and time-averaged pressure field, respectively, and the wall erosion load was predicted by mapping the erosion energy to the hydrofoil surface. It is found that using the time-averaged pressure as the driving pressure can predict more reasonable and more agreeable erosion simulation results, the instantaneous wall erosion load is more consistent with the transient evolution of cavity structures, and the distribution of accumulated wall erosion load is comparable to the erosion region in the experiment. Meanwhile, it is found that the main eroded area on the middle of the hydrofoil is caused by the continuous collapse of the small vapor structures shedding from the sheet cavity closure region, and the scattered pitting area in the middle of the trailing edge is mainly related to the ultimate collapse of cloud cavity.
Two-phase radial ejector for transcritical CO2 refrigeration
Authors: Chandran Ramachandran Jishnu , Sadasivan Sreeja , Arumugam Senthil Kumar , Chen Fei
Published: December 2024

Transcritical refrigeration systems using natural refrigerants like CO2 operate on the ejector–expansion cycle to achieve high operating efficiency. The variability of ejector geometry dictates the adjustability of refrigerating capacity in such systems. Traditional spindle-controlled axial-flow ejectors significantly obstruct the high-pressure motive flow to regulate mass flow rate by controlling flow area. This study introduces the first radial-flow ejector geometry for transcritical CO2 refrigeration systems, designed to operate at high mass flow rates and entrainment ratios with minimal obstruction to motive flow. The study numerically investigates the performance of a radial-flow two-phase ejector for CO2, comparing it with an axial-flow ejector of similar dimensions under the same conditions. It explores the impact of applied compression ratio, motive nozzle throat spacing, and other geometries on radial ejector performance. An increase in the motive throat spacing improves the range of operable discharge pressures and achievable compression ratios, with a slight reduction in the secondary flow entrainment. A nozzle throat spacing of 0.6 mm allows a wider range of operable discharge pressures, and beyond this, the operable discharge pressure range drops. The addition of a diffuser section of sufficient length also improves the flow entrainment in the radial ejector. The radial ejector allows substantially high mass flow rates of even 15 times that of the axial ejector. This high mass flow capacity in the radial configuration can significantly compact ejector designs for large-capacity transcritical CO2 refrigeration and air-conditioning systems.
Mitigation of train-tunnel aerodynamics through active airflow control at front and rear noses: Impact of slit area
Authors: Li Wenhui , Gu Yifan , Su Hongzhou , Zhao Weifeng , Deng Yelin , Fan Xueliang
Published: December 2024

As railway transportation advances toward higher speeds, traditional passive measures may struggle to meet the stringent aerodynamic criteria in tunnels, necessitating the exploration of novel active flow control techniques. This study employs three-dimensional, compressible, unsteady Reynolds-averaged Navier–Stokes simulations to investigate the aerodynamic effects of the suction and blowing slit area (S) positioned on the front and rear noses of the train. The results indicate that suction and blowing activation is particularly effective in alleviating pressure on the narrower side of the tunnel. Specifically, with a 4 m2 slit, the original 4.8% pressure difference between symmetrical points on the train body is fully eliminated. The influence of suction and blowing on the positive pressures is confined to the front and rear noses where the slits are located. Notably, only suction at the front nose mitigates pressure gradients, while blowing at the rear is unrelated. The peak-to-peak pressure (ΔP) on both the train surface and tunnel wall exhibits a linear decline, with reductions of 17.4% and 16.6%, respectively, as S increases from 0 to 4 m2. Similarly, the slipstreams on both sides of the tunnel decrease linearly with increasing slit area: with u/Umax = −0.008S + 0.24 for the near side, and u/Umin = 0.014S − 0.265 for the far side. Additionally, expanding the slit area further boosts the stability and safety of the train during tunnel exit by reducing lateral forces and rolling moments, while also decreasing overall drag, thereby partially compensating for the energy input. Although the maximum lift on the head car increases with slit area, the lift on the tail car initially rises and then decreases, helping to mitigate instability upon tunnel exit. Overall, the hybrid suction and blowing technique offers promising potential for enhancing the tunnel aerodynamics in the future.
An investigation on the flow structures of the intermittent flow in a helically coiled tube
Authors: Liu Gang , Ren Wanlong , Wang Yue , Hua Zhili , Hao Zongrui
Published: December 2024

In this work, a series of numerical investigations are carried out to explore the flow structures of intermittent flow in a helically coiled tube. The distributions of velocity magnitude and turbulence kinetic energy for several cross sections along the flow process of plug flow, slug flow, and slug-annular flow are compared to reveal the asymmetric characteristics of intermittent flow. For the elongated bubble zone of slug-annular flow, the maximum turbulence kinetic energy at the middle part of the pipe can reach nearly three times the maximum turbulence kinetic energy at the bottom part of the pipe. In addition, the tangent vectors are extracted to reflect the rotational flow of the fluids. The Dean vortex induced by centrifugal force is found in the liquid slug zone and as well as in the gas region of the body part of the elongated bubble zone. The directions of the tangent vectors with larger components would develop from gas to liquid at the nose part while develop from liquid to gas at the tail part due to the increased turbulence fluctuations of liquid phase at the tail part of the elongated bubble.
Migration and catalytic viscosity reduction of biochar-based catalyst fluid in heavy oil reservoir pores
Authors: Wang Yiya , Zhang Liqiang , Han Xinlu , Xie Kunlun , Liu Ruiqi , Huang Chenxing , Li Huanan , Lin Riyi
Published: December 2024

The method for reducing heavy oil viscosity through catalysts has remained experimental. Catalyst aggregation in reservoirs is a challenging issue. This study prepares catalyst fluids with both hydrophilic and oleophilic properties and uses dispersants to inhibit aggregation. Stability is assessed using direct observation and an ultraviolet-visible spectrophotometer, with results showing that a dispersant concentration of 0.05 wt. % stabilizes catalyst fluids. Micromodel experiments are conducted to investigate the catalytic performance and dispersion characteristics of catalyst fluids under various conditions. A post-processing method based on the hue, saturation, and value color space for image recognition and error calculation is proposed to analyze the migration and sweeping effects of catalyst fluids. This method involves identifying images captured by a digital camera, calculating area ratios, and determining recognition errors. The results show that catalyst fluids exhibit the best viscosity reduction ratio (80.0%) and the largest dispersion area ratio (55.7%) when the catalyst concentration is 4 wt. %, the injection velocity is 0.01 ml/min, the reaction temperature is 200 °C, and the reaction time is 24 h. With the increase in injection velocity, the viscosity reduction effect becomes worse. The viscosity reduction effect is improved with the increase in reaction temperature. With the growth of reaction time, the viscosity reduction effect increases and then becomes gentle. The combined mechanism of catalytic viscosity reduction and sweeping effects of catalyst fluids in porous media is proposed. This study provides a theoretical foundation for the large-scale development of heavy oil catalytic viscosity reduction.
Huge effects of hydrogen absorption on the magnetic properties of ScFe2
Authors: El Bidaoui S. , Diop L. V. B. , Isnard O.
Published: December 2024

The effects of both hydrogen and deuterium absorption are investigated in the ScFe2 intermetallic compound by comparing its intrinsic magnetic properties with those of ScFe2H2.8 and ScFe2D3.2 compounds. It is found that H/D insertion into the hexagonal MgZn2-type crystal lattice of ScFe2 induces a huge increase in spontaneous magnetization, attributed to the volume expansion caused by H/D insertion. The increase in spontaneous magnetization amounts to 104% for ScFe2D3.2. We report for the first time the Curie point of the hydride and deuteride compounds from the analysis of the temperature dependence of the spontaneous magnetization in the frame of Kuz'min's model. Unlike spontaneous magnetization, the magnetic ordering temperature remains almost unaltered upon H insertion for the studied compositions. The ferromagnetic state is robust for all the studied compounds, none of which present antiferromagnetic behavior. No significant difference is observed in the magnetic properties for the two H/D isotopes, the dominant factor being the H/D concentration.
An experimental study on flame propagation and combustion characteristics of multiple emulsified diesel and biodiesel fuel droplets
Authors: Cheng Cheng , Hu Yong , Yu Ke , Jiang Yong , Wang Zhen
Published: December 2024

To unravel the interaction mechanism between droplets that is relevant for practical liquid fueled burners, the flame propagation characteristics of multi-droplet of emulsified diesel and biodiesel (FAME) fuels were studied using a suspended line droplet array. It was found that when S/d0 ≤ 3 (ratio of droplet spacing to initial droplet diameter), the double droplets were ignited simultaneously and surrounded by a single flame, and as the droplet spacing increased, two independent flames were formed around each droplet. The highest flame propagation rate was attained at S/d0 = 3, which was attributed to the consistent values of flame standoff ratio limited by the dominant heat conduction and finite evaporating rate. The droplet interaction, such as oxygen competition effect, enhanced with smaller droplet distance, can result in the reduction in the droplet combustion rate and flame propagation rate; the latter one, however, showed an increasing trend when small droplet or the size non-uniformity of droplet cloud was considered. In addition, the child droplet ejected from the emulsified droplets showed three burning modes and was an important factor promoting the flame spread, and the results showed that compared with the FAME emulsified fuels, the child droplets in diesel cases were more prone to ignition, expanding the burning regime.
Influence of intermediate principal stress on the fault strength
Authors: Liang Qinming , Huang Gun , Song Zhenlong , Geng Weile , Lu Yu , Huang XinYu , Yao Jingming , Cheng Guojian , Xiong Yangtao
Published: December 2024

Earthquake risk assessment of fault often overlooks the influence of intermediate principal stress (σ2) on fault. However, recent studies have shown that σ2 can alter the internal friction angle, which in turn affects the friction coefficient and strength of rock. In this study, we conducted slip experiments on granite fault to investigate the effect of σ2 on the maximum static friction coefficient (μ0). Our results revealed that as σ2 increased, μ0 also increased, leading to a higher fault strength. Similarly, direct shear tests with varying σ2 yielded consistent observations. The simulation results indicate that an increases in σ2 changes the roughness of fault plane, resulting in variations in the friction coefficient. Furthermore, the fault strength can be described using a true triaxial strength criterion. Our findings emphasize the significance of higher σ2 in the potential risk of major earthquake.
Highly enhanced reactivity of HCl on the Ag/Au(111) alloy surface via rotational quantum state excitation
Authors: Liu Tianhui , Fu Bina , Zhang Dong H.
Published: December 2024

Rotational excitations of reactants are often considered to have little impact on chemical reactivity compared to the excitations of vibrational modes and translational motion. Here, we reveal a significant influence of the rotational excitation of HCl on its dissociation on an Ag/Au(111) alloy surface. This finding is based on six-dimensional time-dependent wave packet calculations performed on an accurately fitted machine learning potential energy surface. Rotational energy is found to be 90 times more effective in driving the reaction than an equivalent amount of translational energy. The reactivity of HCl on Ag/Au(111) is diminished due to a charge transfer effect, which induces a strongly non-monotonic dependence of the minimum energy path on molecular orientation, resulting in the HCl molecule deviating from the minimum barrier. We identify and detail two underlying mechanisms by which rotationally excited HCl can overcome the charge transfer effect between Au and Ag atoms, leading to enhanced reactivity and an intriguing rotational-alignment phenomenon. This finding underscores the profound impact that rotational excitations can exert on molecular reactivity, emphasizing a delicate interplay between various forms of molecular energy and their respective contributions to the reaction mechanism.
Biogenic CO2 flux uncertainty: numerical experiments and validation over south-eastern South America
Authors: Bautista Nahuel E. , Ruiz Juan J. , Salio Paola V. , Burgos Lucas J. , Gassmann María I.
Published: December 2024

Understanding carbon dioxide (CO2) surface fluxes is essential in the context of a changing climate. In particular, agriculture significantly contributes to CO2 fluxes. Recently, some studies have focused on understanding how synoptic-scale variability modulates CO2 fluxes associated with vegetation and agriculture, finding that frontal passages and precipitation events exert a strong influence on these fluxes. This variability is particularly relevant in the Argentinean Pampas, where large CO2 fluxes associated with extensive agriculture combine with strong synoptic variability. Numerical modelling provides a valuable tool for investigating surface CO2 fluxes and their variability, despite the uncertainties associated with the model’s limitations. In this work, we investigate simulated CO2 fluxes in the Argentinean Pampas using the Weather Research and Forecasting Model (WRF) coupled with the Vegetation, Respiration and Photosynthesis Model (VPRM) over three case studies representing different synoptic-scale conditions. In addition, we estimate the uncertainty in the simulations by comparing simulated CO2 fluxes using various WRF configurations and the ERA5 reanalysis. We found that the synoptic-scale conditions have a considerable impact on the magnitude of fluxes as well as the simulation uncertainty. Uncertainties in simulated CO2 fluxes can be as high as 60%, being larger at sunrise and sunset. Also, the largest uncertainty is associated with a case with a cold frontal passage and widespread precipitation. These results allow a more accurate estimation of CO2 flux uncertainty, which is key to understanding the effects of climate change.
A proteome-wide yeast degron collection for the dynamic study of protein function
Authors: Valenti Rosario , David Yotam , Edilbi Dunya , Dubreuil Benjamin , Boshnakovska Angela , Asraf Yeynit , Salame Tomer-Meir , Sass Ehud , Rehling Peter , Schuldiner Maya
Published: December 2024

Genome-wide collections of yeast strains, known as libraries, revolutionized the way systematic studies are carried out. Specifically, libraries that involve a cellular perturbation, such as the deletion collection, have facilitated key biological discoveries. However, short-term rewiring and long-term accumulation of suppressor mutations often obscure the functional consequences of such perturbations. We present the AID library which supplies “on demand” protein depletion to overcome these limitations. Here, each protein is tagged with a green fluorescent protein (GFP) and an auxin-inducible degron (AID), enabling rapid protein depletion that can be quantified systematically using the GFP element. We characterized the degradation response of all strains and demonstrated its utility by revisiting seminal yeast screens for genes involved in cell cycle progression as well as mitochondrial distribution and morphology. In addition to recapitulating known phenotypes, we also uncovered proteins with previously unrecognized roles in these central processes. Hence, our tool expands our knowledge of cellular biology and physiology by enabling access to phenotypes that are central to cellular physiology and therefore rapidly equilibrated.
Ambient-Pressure Anisotropic Single-Gap Superconductivity in La-Trapped B26 Cages with Superior Hardness
Authors: Chen 陈 Haoqi 浩琦 , Tang 唐 Yushan 玉山 , Jiang 姜 Haowen 皓文 , Jiang 姜 Xuehui 雪辉 , Wang 王 Jialin 佳琳 , Zhang 张 Chengyao 铖瑶 , Duan 段 Defang 德芳 , Ma 马 Yanbin 艳斌 , Dong 董 Jing 晶
Published: December 2024

Recently, a breakthrough in the high-pressure synthesis of sp
3-bonded clathrate-like R-3m-LaB8 featuring La-trapped B26 cages was achieved. Although the superconducting critical temperature (T
c) and Vickers hardness (H
v) of LaB8 were estimated, the anisotropic superconductivity and superconducting gap nature remain unclear. The stability of pure B26 cages under ambient conditions is of interest for exploring the B26 hardness and the role of La atoms in the LaB8 hardness. By resolving the Allen–Dynes modified McMillan equation and the anisotropic Eliashberg equations, it was found that LaB8 exhibits anisotropic single-gap superconductivity with T
c = 19.0 ∼ 26.5 K, and the superconducting gap anisotropic ratio reaches 48.50% at 5 K. Most significantly, our work fundamentally validated the coupling of B-2p orbitals with the optical double-degenerate E
g phonon modes and A
g phonon mode from a novel perspective. The H
v of B26 cages was determined to be 18.6 GPa, which is lower than that of La-trapped B26 cages (i.e., LaB8), indicating that La acts as a hardness enhancer for LaB8.
Novel variant transformer-based method for aluminum profile surface defect detection
Authors: Ye Shixiong , Wu Jiling , Jin Yuzhen , Cui Jingyu
Published: December 2024

The detection of surface defects on metals plays a pivotal role in the evaluation of aluminum profile product quality. To date, the most prevalent approach for detecting metal surface defects is via the use of conventional neural networks (CNNs). However, in recent years, transformer-based methods have achieved notable improvements in computer vision and exhibited superiority over traditional CNNs in most tasks. Regarding aluminum surface defect image characteristics, such as intricate textures, few defect samples, and large-scale differences in various defects, it is difficult to further improve the performance of traditional CNNs. Hence, this study proposes a novel variant transformer-based method for aluminum profile surface defect detection that combines a traditional CNN and transformer architecture with a deformable attention module (DAM). The DAM focuses on a subset of the critical sampling points around the reference point to alleviate the intractable complexity associated with high-resolution feature maps and enhances the recognition effect of small target defects. The proposed image-stitching method uses defect-free samples to generate new samples, which partially mitigates the issue of class imbalance. Moreover, we performed supplementary experiments to confirm the effectiveness of transfer learning in training small-scale datasets. Compared with a baseline, the mean average precision (mAP) improved by 3.32%. Extensive experimental results demonstrate the efficacy of our method in accurately detecting surface defects in aluminum profiles and significantly improving the detection of small target defects.
Study on the mechanical properties of the thin-walled double circular tube filled with a novel NPR lattice core based on the concave rotating mechanism
Authors: Wang Caihua , Lv Weitao , Li Dong
Published: December 2024

This study presents a thin-walled double circular tube filled with a novel negative Poisson’s ratio (NPR) lattice core based on the concave rotating mechanism. The unit cell of the NPR lattice core is constructed by replacing each inclined side of a concave hexagon with a smaller concave hexagon with an identical geometry aspect ratio. The single cell is arrayed to obtain a two-dimensional honeycomb structure, and then curling and mirroring operations are utilized to get a circular tube structure. Compressive deformation and load–displacement response of NPR lattice core with different concave angles are analyzed by FEM. To validate with numerical results, the NPR lattice core samples are prepared using 3D printing technology and subjected to quasi-static uniaxial compression experiments. Then, the thin-walled double circular tube filled with the NPR lattice core (FDCT) is established. The load–displacement relationship and energy absorption characteristics are analyzed, and the effects of two angle parameters on the specific energy absorption of the structure are discussed. The results show that an increase in the concave angle decreases the rigidity of the NPR lattice core. When subject to compression, all models show NPR effects, with minimum and maximum Poisson’s ratios of −0.29 and −0.5, respectively. For FDCT, it is found that the interaction between the core layer and the tube wall enhances the structure’s energy absorption performance. Changes in the core layer angle parameters affect the energy absorption of the FDCT structure, where increasing the concave angle improves the energy absorption efficiency of the structure. In contrast, the effect of the rotational angle is not significant.
Xm–EOP/PDEM connection for Scarf I potentials and their coherent states revivals
Authors: Yahiaoui Sid-Ahmed , Cherroud Othmane
Published: December 2024

The revival structures for X

m
-exceptional orthogonal polynomials (EOP) of Scarf I potentials endowed with position-dependent effective mass (PDEM) are studied in the context of the generalized Gazeau-Klauder coherent states. It is shown that the deduced coherent states mimic full and fractional revivals phenomena in the case of the constant-mass. However, in the case of position-dependent effective mass, although full revivals take place during their time evolution, there is no trace of fractional revivals as defined in the common sense. These properties are illustrated numerically by means of some specific profiles of the mass-function, with and without singularities. We have also observed a close connection between the coherence time

τ

coh

[
m
]

and the mass-parameter λ. We suspect the effect that a larger mass-parameter λ contributes significantly to a longer coherence time

τ

coh

[
m
]

.
Low-loss weakly coupled four-mode hollow-core antiresonant fiber based on centrosymmetric nested structure
Authors: Wang Shuaihang , Tian Feng , Li Li , Li Zhipei , Zhang Qi , Tian Qinghua , Wang Yongjun , Wang Fu
Published: December 2024

This paper designs a novel centrosymmetric double-layer nested antiresonant fiber (CDNAF) with few-mode transmission characteristics. The cladding structure of the CDNAF incorporates glass plates and multilayer capillaries, effectively mitigating the coupling between various core modes and cladding modes. Simulation results show that the CDNAF can support four modes of low-loss transmission from LP01 to LP02 at 1550 nm. The confinement loss (CL) of the four modes is less than 0.008 dB km−1, 0.07 dB km−1, 0.42 dB km−1, and 4.8 dB km-1, respectively, and the CDNAF has a sizeable differential group delay (DGD) and weak bending sensitivity. The loss of high-order modes is much greater than that of the other four transmission modes, ensuring high-purity transmission of the four modes. In the wavelength range of 1200–1700 nm, the CDNAF ensures few-mode characteristics with at least two low-loss transmission modes. Furthermore, the effective refractive index difference (Δn

eff
) between adjacent modes is much greater than 10–4, eliminating or significantly reducing the need for multiple-input multiple-output digital signal processing (MIMO-DSP) techniques in optical communication systems. Additionally, the results demonstrate that CDNAF can transmit three modes at an ultimate bending radius of 5 cm and can transmit four modes like a straight fiber at a bending radius of 18 cm, which demonstrates that CDNAF has excellent bending performance. These excellent characteristics give the CDNAF great potential for application in large-capacity optical communication systems.
Dispersion and dissipation of shear horizontal wave in magneto-electro-elastic material loaded with complex magnetic viscous fluid
Authors: SINGH RAVINDRA , . Ramnarayan , Yadav Priyanka , prasad surendra
Published: December 2024

The present study outlines the theoretical analysis of Shear horizontal (SH) wave propagation on magneto-electro-elastic (MEE) material lying on an elastic half-space and subjected to magnetic fluid loading. Using an exact analytical approach, complex dispersion relations for SH waves are derived under both electric short and electric open boundary conditions. To validate these derived relations, specific cases are considered where the MEE material behaves as piezoelectric and piezomagnetic. The complex dispersion relations are separated into real and imaginary components, revealing nonlinear relationships between phase velocity and attenuation of SH waves in relation to geometric parameters, frequency, and the physical properties of the magnetic fluid. Five different magnetic fluids are examined to illustrate the phase velocity and attenuation characteristics graphically. The effects of geometric and physical parameters of the magnetic fluids, the thickness of the MEE material, and the frequency and density of the elastic half-space on the phase velocity and attenuation of SH waves are discussed. Additionally, the finite element method (FEM) is employed to validate the results, ensuring the accuracy of the analytical findings. The results of this study are fundamental and can be used to design and development of surface acoustic wave (SAW) liquid sensors as well as magnetic field sensors.
Composite material from polylactic acid and modified fire flax: synthesis and properties
Authors: Cherkashina N I , Pavlenko Z V , Ryzhikh D A , Serebryakov S V , Silchenko D V
Published: December 2024

The paper presents data on the synthesis of a composite material based on polylactic acid and fire flax powder. To improve adhesion between the polymer matrix and the plant filler, the fire flax powder was modified (acylated) with acetic anhydride. The IR Fourier spectroscopy method established the acylation reaction of fire flax powder. After modification with acetic anhydride, an increase in the intensity of the following peaks is observed in the IR Fourier spectrum: at 1747 cm−1, at 1374 cm−1 and at 1234 cm−1. Composites based on polylactic acid were manufactured, which contained the modified filler in concentrations of 30%, 40% and 50% by weight. Physicomechanical, electron microscopic and thermal studies of the developed polymer composites are presented. The tensile strength of the studied composites was determined using standard methods according to ISO 527–2:2012. The composite containing 50 wt% modified fire flax powder has the following characteristics: tensile strength—6.53 MPa, relative elongation −13.89%, density −1.247 g cm−3, maximum permissible operating temperature (sample weight loss up to 5 wt%) −254 °C. This study promotes the development of biodegradable materials by offering polylactide-based composites with the addition of fire flax as an alternative to non-degradable synthetic fillers. The use of agricultural waste not only reduces the cost of production, but also solves the problem of biomass utilization, which opens up prospects for the creation of environmentally friendly composites in various industries. The research methodology also makes it possible to modify natural components, expanding their use and potentially replacing traditional plastics.
Generative modeling and augmentation of EEG signals using improved diffusion probabilistic models
Authors: Torma Szabolcs , Szegletes Luca
Published: December 2024

Objective. The development of deep learning models for electroencephalography (EEG) signal processing is often constrained by the limited availability of high-quality data. Data augmentation techniques are among the solutions to overcome these challenges, and deep neural generative models, with their data synthesis capabilities, are potential candidates. Approach. The current work investigates enhanced diffusion probabilistic models (DPM) and sampling methods for brain signal generation and data augmentation. We used implicit sampling and progressive distillation to shorten the inference and subsequently analyzed the effects of these methods on the generated data. To assess the feasibility of our method, four classification models were trained and evaluated in an inter-subject setting on datasets augmented with synthetic signals. Main results. Our analysis of generative metrics and statistical evaluations, including subject- and group-level tests, showed that our DPMs could generate visual evoked potentials and motor imagery signals. Distilled, single-step DPMs were trained on two publicly available datasets and were used to synthesize relatively high-quality EEG samples. The performance of the classifiers was improved by the application of the synthesized signals. The present work demonstrates that DPMs are capable of augmenting data with high fidelity and improving the diversity of EEG signals. Although samples can be generated in a single step, there is a significant trade-off between the data quality and sampling steps. Significance. The findings and results of this study demonstrate the promising capability of diffusion models for EEG synthesis, which marks progress toward an efficient and generalizable augmentation method for various EEG decoding tasks.
Multi-dimensional hybrid bilinear CNN-LSTM models for epileptic seizure detection and prediction using EEG signals
Authors: Liu Shan , Wang Jiang , Li Shanshan , Cai Lihui
Published: December 2024

Objective. Automatic detection and prediction of epilepsy are crucial for improving patient care and quality of life. However, existing methods typically focus on single-dimensional information and often confuse the periodic and aperiodic components in electrophysiological signals. Approach. We propose a novel deep learning (DL) framework that integrates temporal, spatial, and frequency information of EEG signals, in which periodic and aperiodic components are separated in the frequency domain. Specifically, we calculated the periodic and aperiodic components in single channel and the synchronization index of each component between channels. A self-attention mechanism is employed to filter single-channel features by selectively focusing on the most distinguishing features. Then, a hybrid bilinear DL network is utilized to capture the spatiotemporal features by combining a convolutional neural network and a long short-term memory network. Finally, a bilinear pooling layer is employed to extract second-order features based on interactions between these spatiotemporal features. Main results. The model achieves exceptional performance, with a detection accuracy of 98.84% on the CHB-MIT dataset, and a prediction accuracy of 98.44% on CHB-MIT and 97.65% on the Kaggle dataset, both with an false positive rate of 0.02. Significance. This work paves the way for developing real-time, wearable epilepsy prediction devices to improve patient care.
The ‘Brussels 4’: essential requirements for implantable brain–computer interface user autonomy
Authors: Oxley Thomas J , Deo Darrel R , Cernera Stephanie , Sawyer Abbey , Putrino David , Ramsey Nick F , Fry Adam
Published: December 2024

Objective. Implantable brain–computer interfaces (iBCIs) hold great promise for individuals with severe paralysis and are advancing toward commercialization. The features required for successful clinical translation and patient adoption of iBCIs may be under recognized within traditional academic iBCI research and deserve further consideration. Approach. Here we consider potentially critical factors to achieve iBCI user autonomy, reflecting the authors’ perspectives on discussions during various sessions and workshops across the 10th International BCI Society Meeting, Brussels, 2023. Main results. Four key considerations were identified: (1) immediate use, (2) easy to use, (3) continuous use, and (4) stable system use. Significance. Addressing these considerations may enable successful clinical translation of iBCIs.
Longitudinal changes in electrophysiology and widefield calcium imaging following electrode implantation
Authors: Robbins Constance , Eles James , Zheng X Sally , Kozai Takashi , Cui X Tracy , Vazquez Alberto
Published: December 2024

Objective. Intracortical microelectrode arrays often fail to deliver reliable signal quality over chronic recordings, and the effect of an implanted recording array on local neural circuits is not completely understood. Approach. In this work we examined the degree of correlation and the spatial dependence of that relationship between widefield calcium imaging and electrophysiology in awake mice from 4 to 44 d post-implantation. Both correlation maps and spike-triggered averaging (STA) are used to characterize the relationship. Main results. We find that calcium imaging and electrophysiological signal are highly correlated in all animals, however, spatial variability in the correlation is affected by inherent correlation in the calcium imaging signal. Some animals exhibit a high degree of apparent neuronal synchrony in the vicinity of the probe at 4 d, while more diversity of response is detected at later time points. Significance. Degree of synchrony appears to be related to the acute injury response to the implanted electrode, with later time points displaying less synchrony. STA may be used to uncover the diverse cortical connections of spiking units.
Forecasting Strategies in Retail: Utilizing Advanced Machine Learning Methods while Safeguarding Privacy
Authors: Naskinova Irina , Kolev Mikhail , Lazarova Meglena
Published: December 2024

Demand forecasting is critical to optimizing retail inventory management, pricing, and operations. This study compares several time series forecasting models on a publicly available retail dataset, including traditional stats like ARIMA and SARIMA, smoothing techniques, and new ones from Facebook, such as Prophet and Neural Prophet. We evaluate each model using metrics like Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), and R2. The results show that NeuralProphet and hybrid models outperform traditional models like ARIMA and SARIMA. We also look at the computational efficiency and practicality of the models and provide insights into how they can be used in real-world demand forecasting scenarios. The results show that traditional models are robust. Still, advanced models like NeuralProphet and hybrids, which combine machine learning with time series forecasting, have a lot of potential to improve forecast accuracy and operational decision-making.
Minimization Principle for Analytical Solution of Turbulent Flow in Channel
Authors: Fedoseyev Alex
Published: December 2024

The analytical solution for turbulent flow in a channel, presented in Fedoseyev (2023), described the mean turbulent flow velocity as a superposition of the parabolic and superexponential solutions. In this study, the coefficients of superposition are obtained through the minimization principle, the principle of minimum viscous dissipation. The laminar flow showed a significantly larger dissipation rate. The obtained analytical solutions agreed well with turbulent flow experiments.