bluuebunny/crossref_metadata_2025 huggingface dataset:
An investigation of the effect of stratification stability and saltation sand flux on the anisotropy of atmospheric surface layer wall turbulence
Authors: Mei Ao , Zhu Yulin , Zhou Shanlin , Liao Yongan , Huang Chentao , Li Mingyang , Leng Tingting
Published: March 2024

In the atmospheric surface layer (ASL), the anisotropic characteristics of turbulence become more complex due to the strong influence of heat flux and particle motion. In this paper, the effects of stratification stability and total saltation sand flux on turbulent anisotropy of ASL wall turbulence are systematically analyzed by using high-frequency 3D velocity, temperature, and saltation sand flux measured in the field. Our results show that the temperature gradient intensifies the spanwise turbulent motion and enhances the vertical motion asymmetry. Although the buoyancy-driven turbulence enhances the spanwise variation, the momentum transfer mode between the streamwise–vertical and spanwise–vertical does not change. With the increase in instability, the large-scale motions (LSM) of the spanwise velocity may be destroyed and more spanwise small-scale motions (SSM) formed. In addition, saltation increases the sharpness, randomness, and extreme frequency of spanwise velocity distribution, but does not change the momentum transfer mode. Saltation may enlarge the fluctuation range and scale of the spanwise velocity, but may not be the main factor affecting the anisotropy of SSM. These results can deepen people's understanding of wind-blown sand movement and turbulence properties in ASL, and provides empirical data and insights that can significantly contribute to the development and refinement of turbulence models, particularly those that need to account for the complex interplay between stratification stability, saltation sand flux, and turbulence anisotropy.
Aerodynamic center of a wing at low Reynolds number
Authors: Maji Arnesh , Pandi Jawahar Sivabharathy Samuthira , Mittal Sanjay
Published: March 2024

The location of the aerodynamic center, with respect to the center of gravity, determines the longitudinal static stability of an aerial vehicle. While most studies in the past focused on high Reynolds number (Re) flows, we consider flows at low Re (100≤Re≤6000) past an end-to-end wing and a finite wing of various semi-aspect ratio (0.25≤sAR≤5). It is shown that two-dimensional computations, even for an end-to-end wing, are inadequate for accurate prediction of aerodynamic coefficients. The chordwise pressure distribution as well as the variation of aerodynamic coefficients with angle of attack (α) at low Re are significantly different from that at high Re. Beyond a certain α, the flow is associated with a large recirculation zone, resulting in a non-linear variation of the aerodynamic coefficients with α. The conventional definition of the aerodynamic center is too restrictive at low Re. Owing to the non-linear variation of the pitching moment with change in α, it is not possible to determine one single location where it is invariant over a large range of α. The aerodynamic center is, therefore, determined over various sub-regimes of α. It varies significantly over the sub-regimes. The wing-tip vortex significantly affects the vortex shedding, flow structures, and pressure distribution on a finite wing. The locations of the aerodynamic center and center of pressure move fore, toward the leading edge, with a decrease in aspect ratio compared to that for an end-to-end wing.
Combustion of a nanoparticles-laden chemical in a vented cavity
Authors: Roy Nepal Chandra
Published: March 2024

Mixed convective characteristics of the combustion of a nanoparticles-laden fuel (n-butanol nanofluid) in a vented cavity are investigated. The nanofluid and the oxidizer enter the cavity through the inlets on the left and right vertical walls, respectively. However, the resulting product produced from the oxidation process of the fuel exits the cavity through the outlet at the bottom wall. Heat generated from the oxidation process causes natural convection within the cavity. The conjugate effect of natural and forced convection finally gives rise to mixed convection phenomena. In this regard, a mathematical model for mixed convection flow in a vented cavity is formulated with no-slip and isothermal boundary conditions. Having transformed the model into a dimensionless form, the stream function-vorticity formulation is used. The resulting equations are then solved numerically using the finite difference method. Numerical results are illustrated with the streamlines, isotherms, and isolines of fuel and oxidizer concentrations. The maximum values of the stream function (ψmax) and the temperature (θmax) are found to increase with an increase in the Frank–Kamenetskii number (Λ), volume fraction of nanoparticles (φ), and stoichiometric ratio (χ). On the contrary, they decrease with the increase in the Reynolds number (Re). When the Grashof number (Gr) is increased, ψmax increases and θmax decreases. The remaining concentrations of fuel, (CF)min, and oxidizer, (CO)min, are higher for an increase in Gr, whereas the opposite is recognized for increasing Λ. With the increase in Gr and Λ, the steady-state flow in the cavity tends to be oscillating and then chaotic.
Tutorial: The equations of electron emission and their evaluation
Authors: Jensen Kevin L.
Published: March 2024

Electron emission and transport through and over potential barriers is an essential process requiring modeling and simulation to meet the design needs and characterization of an exceedingly broad range of technologically important devices and processes. The simulation and description of thermal, field, and photoemission, and the related concerns of space–charge affected electron flow, often make use of specialized formulations developed in the early days of quantum mechanics. Advancements in the utilization of electron sources and particularly the simulation of devices and applications using advanced particle-in-cell and trajectory methods for beam optics codes create a strong need for a pedagogical account of the emission models to ensure correct numerical evaluation of their equations. This Tutorial starts from simple phenomenological accounts and progressively builds to comprehensive models emphasizing straightforward and often rapid calculation. It recommends formulations to supplant the canonical Richardson–Laue–Dushman (thermal), Fowler–Nordheim (field), Fowler–DuBridge (photo), and Baroody (secondary) equations and provides a useful formulation of space–charge affected flow commonly described by the Child–Langmuir relation that takes into account cathode dependence on surface field.
Influence of swirl intensity on combustion dynamics and emissions in an ammonia-enriched methane/air combustor
Authors: Liu Chunyu , Yang Haojie , Ruan Can , Yu Liang , Lu Xingcai
Published: March 2024

Ammonia (NH3) has been widely considered as a promising carbon-free energy and hydrogen carrier for various applications. The large-scale direct utilization of NH3 as fuel in gas turbine engines is currently attracting significant interest, with strong focuses on improving the efficiency and stability of the system and reducing the emissions of pollutants. The present study experimentally examined the impacts of swirl intensity on combustion stability and emissions in an NH3-enriched premixed swirl-stabilized CH4/air combustor under a wide range of equivalence ratios. Simultaneous high-speed OH* chemiluminescence and particle image velocimetry measurements suggested that increasing swirl intensity resulted in more compact flame shapes and expanded the recirculation zone, which promoted flame stability at higher NH3 ratios. However, under specified conditions, enhancing swirl intensity could increase the instability frequency and amplitude of pressure oscillations. The flame dynamics exhibited different behaviors depending on the swirl intensity. At high swirl intensity, the flames underwent high-frequency, small-amplitude periodic motion. At low swirl intensity, the flames oscillated axially with large amplitude and low frequency. For flow dynamics, the stability of the vortex at high swirl intensity contrasted with the periodic vortex shedding at low swirl intensity. Furthermore, the two-dimensional Rayleigh index indicated that the dominant positive thermoacoustic coupling regions were located near the flame shear layers and flame tail at low and high swirl intensities, respectively. Finally, the experimental results showed that swirl intensity affected pollutant emissions by influencing the temperature of combustion chamber and gas mixing efficiency. The pathway of fuel-type NOx was found to be dominant in the NOx emission of the NH3/CH4/air flames.
Effect of penetrant–polymer interactions and shape on the motion of molecular penetrants in dense polymer networks
Authors: Lin Tsai-Wei , Sing Charles E.
Published: March 2024

The diffusion of dilute molecular penetrants within polymers plays a crucial role in the advancement of material engineering for applications such as coatings and membrane separations. The potential of highly cross-linked polymer networks in these applications stems from their capacity to adjust the size and shape selectivity through subtle changes in network structures. In this paper, we use molecular dynamics simulation to understand the role of penetrant shape (aspect ratios) and its interaction with polymer networks on its diffusivity. We characterize both local penetrant hopping and the long-time diffusive motion for penetrants and consider different aspect ratios and penetrant–network interaction strengths at a variety of cross-link densities and temperatures. The shape affects the coupling of penetrant motion to the cross-link density- and temperature-dependent structural relaxation of networks and also affects the way a penetrant experiences the confinement from the network meshes. The attractive interaction between the penetrant and network primarily affects the former since only the system of dilute limit is of present interest. These results offer fundamental insights into the intricate interplay between penetrant characteristics and polymer network properties and also suggest future directions for manipulating polymer design to enhance the separation efficiency.
Transformer ratio growth due to ion motion in plasma wakefield accelerators
Authors: Minakov V. A. , Lotov K. V.
Published: March 2024

We report a recently discovered counterintuitive effect where breaking of a Langmuir wave in a plasma wakefield accelerator leads to an increase in the accelerating field rather than wave dissipation. The effect relies on the ability of transversely breaking waves to draw wave energy from nearby regions due to the inflow of electrons oscillating collectively and the outflow of electrons moving individually.
Femtosecond fluorescence conical optical parametric amplification spectroscopy
Authors: Cui Ennan , Liu Heyuan , Wang Zhuan , Chen Hailong , Weng Yu-Xiang
Published: March 2024

Parametric superfluorescence (PSF), which originated from the optical amplification of vacuum quantum noise, is the primary noise source of femtosecond fluorescence non-collinear optical parametric amplification spectroscopy (FNOPAS). It severely affects the detection limit of FNOPAS to collect the femtosecond time-resolved spectra of extremely weak fluorescence. Here, we report the development of femtosecond fluorescence conical optical parametric amplification spectroscopy (FCOPAS), aimed at effectively suppressing the noise fluctuation from the PSF background. In contrast to traditional FNOPAS configurations utilizing lateral fluorescence collection and dot-like parametric amplification, FCOPAS employs an innovative conical fluorescence collection and ring-like amplification setup. This design enables effective cancellation of noise fluctuation across the entire PSF ring, resulting in an approximate order of magnitude reduction in PSF noise compared to prior FNOPAS outcomes. This advancement enables the resolution of transient fluorescence spectra of 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) dye molecules in ethanol, even at an optically dilute concentration of 10−6 mol/l, with significantly enhanced signal-to-noise ratios. This improvement will be significant for extremely weak fluorescence detection on the femtosecond time scale.
Piezoelectric metamaterial with digitally controlled nonlinear shunt circuit for broadband wave attenuation
Authors: Xia Dawei , Pu Xiaoqing , Tong Shiqi , Xu Jiawen
Published: March 2024

This Letter reports a nonlinear piezoelectric metamaterial with pure digital inductance shunt circuits for adjustable broadband wave attenuation. The proposed nonlinear piezoelectric metamaterial is comprised of arrayed piezoelectric unit-cells with individually connected digital nonlinear inductive shunt circuits. Taking advantage of the programmed nonlinear behavior of the shunt circuits, we can expand the frequency region of wave attenuation at an arbitrary frequency. This broadband wave attenuation mechanism is facilitated by modifying the poles, zeros, and nonlinearity in the control algorithm, whereas the mechanical and electrical configurations are not altered. Our experimental analysis confirmed the adjustability and broadband features of the proposed system. The results demonstrated 3.84 times enlargement of the bandwidth under negative nonlinear coefficient K of −3 × 10−12. This piezoelectric metamaterial shows promising potential for active control in broadband wave attenuation.
Revisiting the Luce diode in the context of recent research on multi-vircators with dielectric reflectors
Authors: Liziakin G. , Belozerov O. , Leopold J. G. , Hadas Y. , Krasik Ya. E.
Published: March 2024

Recently, in a series of articles Mumtaz, Choi, and others [i.e., S. Mumtaz and E. Choi, IEEE Electronic Device Lett. 43, 1756 (2022)] studied a relativistic gridded vircator with one or more dielectric anodes, in which considerable increase in the efficiency of high-power microwave (HPM) generation compared to ordinary vircators was observed. This is very important since the main disadvantage of vircators is their low efficiency. It was suggested that the repelling of electrons by the initial impacting electron charge collected on the dielectric reflectors forms a multi-vircator, which increases HPM production. The present article reports the results of experiments and numerical simulations, which show that this mechanism does not result in high multi-vircator efficiency. Similar dielectric anodes were investigated 50 years ago in a configuration known as the Luce diode, in which collective acceleration of ions was studied. It was also known that the operation of the Luce diode is accompanied by a HPM burst, which was never measured. Results of experiments and simulations in various configurations based on a gridded vircator and dielectric reflectors confirm the existence of high-energy ion acceleration. Unfortunately, none of these configurations produce HPM of higher efficiency than a regular gridded vircator.
Data-driven modal decomposition of R134a refrigerant cavitating flow in Venturi tube
Authors: Zhang Beile , Zhang Ze , Fang Xufeng , Xue Rong , Chen Shuangtao , Hou Yu
Published: March 2024

This study utilized high-speed camera and large eddy simulation methods to explore the cavitating flow mechanisms and turbulence structures of R134a refrigerant inside a Venturi tube under varying cavitation numbers (CNs). Data-driven modal analysis approaches, proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD), were introduced to identify and extract the energy hierarchy and transient characteristics within the cavitating flow. The analysis of grayscale images indicated that the cavitating flow gradually transitioned from quasi-periodic to unsteady flow as the CN decreased, and the severity of cavitation correlates with lower peak frequencies. The POD analysis facilitated the extraction of coherent structures in the cavity's temporal evolution, and the results indicate that the quasi-ordering shedding and collapse of large-scale cavity clouds predominantly occur under low cavitation intensity conditions. As the CN increases, the influence of small-scale cavity shedding becomes more significant. The first 30 most energetic modes occupied over 75% of the entire energy, and they were used to reconstruct the cavitating flow, achieving good consistency with transient flow snapshots. Additionally, the DMD results of the cavitating flow yield three frequency spans, including several prominent characteristic frequencies. These spans are closely linked to the cavity cloud structures of varying scales, unveiling the structural characteristics of unsteady cavitating flow.
Experimental study of the vortex-induced vibration of a circular cylinder considering coupling effect in along- and across-wind direction
Authors: Yang Qingshan , Li Chao , Guo Kunpeng , Shan Wenshan , Huang Shuai
Published: March 2024

Tower-like structures with circular section are prone to unexpected across-wind vortex-induced vibration (VIV), and the along-wind response is usually neglected due to its amplitude being much smaller than that of VIV. Recent research pertaining to tall buildings has revealed, nevertheless, that the structural responses in the along-wind and across-wind directions are coupled in a way that results in a decrease in the across-wind response at the wind speed of VIV along with an increased along-wind response. However, the impact of coupling on tower-like structures has not yet been examined. Moreover, tower-like structures with a circular cross section undergo tip-induced vibration at the wind speed higher than vortex-resonance wind speed. However, the impact of this coupling effect on the tip-induced vibration remains uncertain. In this paper, a two-degree-of-freedom rocking model wind tunnel test is carried out under low turbulence and turbulent flow to investigate the coupling effect of tower-like structures. Experiment results show that the coupling effect exists at both the vortex-resonance vibration wind speed and the tip-induced vibration wind speed. Besides, when the along-wind response is coupled with the across-wind responses, it illustrates a steady harmonic vibration with a hardened non-Gaussian characteristic, and its kurtosis decreases to 1.5. Finally, the measured tip-associated vortex shedding frequency suggests that there is a “lock-in” phenomenon of the tip-induced vibration, this new finding improves the understanding of the wind-induced response at high wind speeds.
High-entropy and compositionally complex battery materials
Authors: Strauss F. , Botros M. , Breitung B. , Brezesinski T.
Published: March 2024

The global demand for high energy density batteries, mostly for application in electric vehicles, offering increased durability, safety, and sustainability is growing rapidly. In the past, this demand has been met primarily by the development and/or improvement of new/established battery materials and technologies. The high-entropy design concept—aiming at increasing chemical complexity/occupational disorder—has recently been introduced into the field of electrochemical energy storage. Various high-entropy battery materials that are seemingly capable of outperforming low-entropy counterparts by offering desirable properties have been reported. However, future studies are required to explore if the concept is broadly applicable and can be extended to all types of battery materials, especially those that are of industrial relevance. Herein, we provide a brief overview of the existing high-entropy anodes, cathodes, and solid/liquid electrolytes for use in rechargeable Li- or Na-ion batteries and discuss potential research directions and opportunities.
Convergent ab initio analysis of the multi-channel HOBr + H reaction
Authors: Beck Ian T. , Lahm Mitchell E. , Douberly Gary E. , Schaefer Henry F.
Published: March 2024

High-level potential energy surfaces for three reactions of hypobromous acid with atomic hydrogen were computed at the CCSDTQ/CBS//CCSDT(Q)/complete basis set level of theory. Focal point analysis was utilized to extrapolate energies and gradients for energetics and optimizations, respectively. The H attack at Br and subsequent Br–O cleavage were found to proceed barrierlessly. The slightly submerged transition state lies −0.2 kcal mol−1 lower in energy than the reactants and produces OH and HBr. The two other studied reaction paths are the radical substitution to produce H2O and Br with a 4.0 kcal mol−1 barrier and the abstraction at hydrogen to produce BrO and H2 with an 11.2 kcal mol−1 barrier. The final product energies lie −37.2, −67.9, and −7.3 kcal mol−1 lower in energy than reactants, HOBr + H, for the sets of products OH + HBr, H2O + Br, and H2 + BrO, respectively. Additive corrections computed for the final energetics, particularly the zero-point vibrational energies and spin–orbit corrections, significantly impacted the final stationary point energies, with corrections up to 6.2 kcal mol−1.
Numerical investigation on the effect of bionic fish swimming on the vortex-induced vibration of a tandemly arranged circular cylinder
Authors: Zhu Hongjun , Li Yingmei , Zhong Jiawen , Zhou Tongming
Published: March 2024

The effect of bionic fish swimming on the vortex-induced vibration (VIV) of a circular cylinder arranged in tandem at a low Reynolds number of 150 is numerically investigated in this work. The bionic fish placed upstream of the cylinder with gap ratios of 1, 3, and 5 and that located downstream of the cylinder with gap ratios of 3 and 5 are examined in the simulations that were carried out in the reduced velocity range of Ur = 2–15. It is found that both the gap ratio and the reduced velocity have a significant influence on the VIV response and wake flow structure. When the bionic fish is placed upstream, the maximum response amplitude of the downstream cylinder is much greater than that of an isolated one. Two flow regimes are identified in terms of the shear layer reattachment, i.e., the continuous reattachment and the alternate reattachment. Comparing the vortex shedding frequencies of the cylinder and the swimming fish, it is found that the frequency of the cylinder is always locked in the fish swimming frequency, and multiple frequencies occur at Ur = 5. When the bionic fish is arranged downstream, four flow regimes are observed, including the extended-body, continuous reattachment, alternate attachment, and co-shedding regimes. Furthermore, the time-mean energy transfer coefficient of the cylinder is considerably higher at Ur = 5 than that when the fish is placed upstream of the cylinder.
Cellular signalling by SARS-CoV-2 spike protein
Authors: Gracie Nicholas P. , Lai Lachlan Y. S. , Newsome Timothy P.
Published: March 2024

Following the release of the SARS-CoV-2 genome, the spike protein was identified as the key viral protein mediating cell entry. In addition to its critical function in delivering the viral genome to the host cytoplasm, the spike protein is able to activate diverse cell signalling pathways, leading to notable cellular responses, including inflammation, cellular remodelling, and immune evasion. The spike protein is associated with the induction of a ‘cytokine storm’ characterised by elevated levels of proinflammatory cytokines like IL-6 and IL-1β. Moreover, the spike protein deregulates TGF-β and E-selectin, leading to fibrotic injury and tissue scarring in cellular remodelling, notably in pulmonary tissues. Finally, the spike protein plays a role in immune evasion, disrupting Type I interferon responses. Understanding these diverse interactions and effects is crucial for comprehending the pathogenesis of COVID-19 and developing effective therapeutic strategies.
IL7 increases targeted lipid nanoparticle–mediated mRNA expression in T cells in vitro and in vivo by enhancing T cell protein translation
Authors: Tilsed Caitlin M. , Sadiq Barzan A. , Papp Tyler E. , Areesawangkit Phurin , Kimura Kenji , Noguera-Ortega Estela , Scholler John , Cerda Nicholas , Aghajanian Haig , Bot Adrian , Mui Barbara , Tam Ying , Weissman Drew , June Carl H. , Albelda Steven M. , Parhiz Hamideh
Published: March 2024

The use of lipid nanoparticles (LNP) to encapsulate and deliver mRNA has become an important therapeutic advance. In addition to vaccines, LNP-mRNA can be used in many other applications. For example, targeting the LNP with anti-CD5 antibodies (CD5/tLNP) can allow for efficient delivery of mRNA payloads to T cells to express protein. As the percentage of protein expressing T cells induced by an intravenous injection of CD5/tLNP is relatively low (4-20%), our goal was to find ways to increase mRNA-induced translation efficiency. We showed that T cell activation using an anti-CD3 antibody improved protein expression after CD5/tLNP transfection in vitro but not in vivo. T cell health and activation can be increased with cytokines, therefore, using mCherry mRNA as a reporter, we found that culturing either mouse or human T cells with the cytokine IL7 significantly improved protein expression of delivered mRNA in both CD4
+
and CD8
+
T cells in vitro. By pre-treating mice with systemic IL7 followed by tLNP administration, we observed significantly increased mCherry protein expression by T cells in vivo. Transcriptomic analysis of mouse T cells treated with IL7 in vitro revealed enhanced genomic pathways associated with protein translation. Improved translational ability was demonstrated by showing increased levels of protein expression after electroporation with mCherry mRNA in T cells cultured in the presence of IL7, but not with IL2 or IL15. These data show that IL7 selectively increases protein translation in T cells, and this property can be used to improve expression of tLNP-delivered mRNA in vivo.
Effets du feedback correctif écrit direct et indirect sur la réécriture du texte et les subséquentes
productions d’apprenants de l’italien LV3 au lycée
Authors: La Russa Francesca
Published: March 2024

Ce travail compare les effets du feedback correctif (FC) direct et indirect sur la réécriture du texte et les
subséquentes productions de 26 apprenants francophones de l’italien LV3. L’impact de leur engagement lors du
traitement du FC est également évalué. Les apprenants ont été répartis en trois groupes (feedback direct, feedback indirect et
groupe contrôle). Le protocole d’enquête a prévu un pré-test, une phase d’administration du FC, ainsi
qu’un post-test immédiat et différé. Les groupes expérimentaux obtiennent de meilleurs résultats par rapport au groupe
contrôle dans la réécriture du texte et dans les productions subséquentes. À un niveau d’engagement plus élevé lors du
traitement du FC correspondent de meilleurs résultats dans la réécriture du texte. Le FC indirect conduit les apprenants à
s’engager davantage dans le traitement, ce qui leur permet de corriger leurs erreurs dans la réécriture. Cet effort serait
atténué, dans le plus long terme, par le fait de ne pas savoir si leurs hypothèses de résolution sont correctes. Le FC direct, qui
donne de l’input en langue cible et la possibilité de le traiter immédiatement, porte les apprenants à améliorer davantage
la correction de leurs subséquentes productions.
Interaction between Surface Acoustic Wave and Quantum Hall Effects
Authors: Liu 刘 Xiao 萧 , Wu 吴 Mengmeng 蒙蒙 , Wang 王 Renfei 任飞 , Wang 王 Xinghao 兴豪 , Zhang 张 Wenfeng 文锋 , Dong 董 Yujiang 昱江 , Du 杜 Rui-Rui 瑞瑞 , Liu 刘 Yang 阳 , Lin 林 Xi 熙
Published: March 2024

Surface acoustic wave (SAW) is a powerful technique for investigating quantum phases appearing in two-dimensional electron systems. The electrons respond to the piezoelectric field of SAW through screening, attenuating its amplitude, and shifting its velocity, which is described by the relaxation model. In this work, we systematically study this interaction using orders of magnitude lower SAW amplitude than those in previous studies. At high magnetic fields, when electrons form highly correlated states such as the quantum Hall effect, we observe an anomalously large attenuation of SAW, while the acoustic speed remains considerably high, inconsistent with the conventional relaxation model. This anomaly exists only when the SAW power is sufficiently low.
Study on the mechanism of glass-SiC-glass anodic bonding process
Authors: Cheng Xiao , Hu Lifang , Liu Wei , Chou Zhao , Jia Weijie , Mu Wenjin
Published: March 2024

The connection of silicon carbide (SiC) to glass is important for the development of microelectromechanical systems. In the study, glass-SiC-glass with SiC as common anode was effectively bonded by using anodic bonding technology in atmosphere. The interfacial microstructure of bonded joints was analyzed by using scanning electron microscope, energy-dispersive spectrometer and transmission electron microscope. The effect of the bonding voltages and bonding temperatures on the interfacial microstructure and mechanical property of glass/SiC/glass was investigated. The results indicated that a Na+ depletion layer formed in the glass adjacent to the SiC/glass interface due to the decomposition of Na2O compound in the glass and the migration of Na+ towards the upper surface of glass during anodic bonding. With elevating bonding temperatures or bonding voltages, the thickness of Na+ depletion layer was gradually increased and more O2− accumulated at the SiC/depletion layer interface, which was beneficial for the tensile strength of joints. But owing to the increased residual thermal stress, the tensile strength of the joints dropped with enhanced bonding temperature. The maximum tensile strength of the joint was about ∼12.8 MPa when bonding at 450 °C/1000 V/1 min. The joint mainly ruptured in the glass with a brittle fracture mode.
Experimental investigation of micro-machining of borosilicate glass using an ultrasonic assisted rotary electrochemical discharge machining (UA-RECDM) process
Authors: Grover Sahil , Mangal S K , Singh Sarbjit , Singh Manpreet , Rajput Viveksheel , Sharma Shubham , Kumar Abhinav , Abbas Mohamed
Published: March 2024

Electrochemical discharge machining is an advanced micro-machining process for machining of conductive as well as non-conductive hard and brittle materials, e.g. glass, ceramics, silicon wafer, etc. The present work explores the machining of glass using an in-house developed novel ultrasonic assisted rotary electrochemical discharge machining setup. The setup has specialized features, such as using ultrasonic vibrations to tool the electrode and incorporating rotary motion for manipulating the workpiece. Experiments were conducted using a one factor at a time approach by varying the tool feed rate, the amplitude of the vibrations and the rotation of the workpiece as process parameters. The quality of the machining output was evaluated by observing two key parameters: the overcut and the circularity of the hole. It was observed that as the workpiece rotation speed increased from 40 rpm to 60 rpm, the overcut in the machined samples decreased from 181.378 μm to 163.564 μm. The rotary motion of the workpiece caused a seeping action of the electrolyte in the hydrodynamic regime, leading to the formation of a thin gas film and the stabilization of the discharging process. The morphology of the machined hole exhibits better circularity, low heat-affected zones, minimum micro-cracks and smooth edges at its periphery due to stable discharge formation.
Double-layer coated particles formed by one-step method based on microfluidic technology
Authors: Hu Jian , Chen Xinyu , Lin Jiayu , Xu Zekai , Luo Minzhuo , Tsui Gary Chi-Pong , Deng Yu
Published: March 2024

This study used a microfluidic device with a focus-wrapping structure to create double-layer calcium alginate hydrogel drug particles in a one-step process. We validated the double-layer structure of the particles using both a fluorescence and regular light microscope. Curcumin and catalase were distributed independently in each layer, and we expected that such structure could play a role in the slow release of drugs. This scheme greatly reduces the need of hydrophilic and hydrophobic modification treatment, therefore greatly simplifies the experimental process. In the meantime, the requirement for injecting drugs into osteoarthritis and other diseases is expected to be realized, expanding the use of hydrogel in the medical field, because the microsphere is easy to generate, inexpensive, and strong in internal drug substitutability.
Comprehensive material study of Ge grown by aspect ratio trapping on Si substrate
Authors: Stanchu Hryhorii , Kryvyi Serhii , Margiotta Stephen , Cook Matthew , Grant Joshua , Tran Huong , Acharya Sudip , de Oliveira Fernando M , Mazur Yuriy I , Benamara Mourad , King Clifford A , Du Wei , Li Baohua , Salamo Gregory , Yu Shui-Qing
Published: March 2024

High-quality monolithic Ge-on-Si is sought for CMOS-compatible optoelectronic devices. We examine the structural characteristics of Ge-on-Si grown by the aspect ratio trapping (ART) method on a SiO2/Si(001) template in pre-patterned holes. Transmission electron microscopy and surface topography analysis revealed high-quality Ge islands overgrown from the ART holes in SiO2. The superior crystal quality of Ge ART growth was also confirmed by comparing x-ray diffraction (XRD) data of Ge ART and Ge planar epilayer samples. The XRD and micro-Raman data additionally show a small residual strain in the islands which vanishes by reducing the hole diameter from 280 nm to 180 nm, while leading to only a minor increase in the crystallographic inclinations of the Ge islands from 0.34 deg to 0.54 deg. With finite element method simulations, we find that the small residual strain in Ge originates during the cool-down from growth to room temperature because of thermal expansion coefficient mismatch between Ge and SiO2. A tensile force develops along the [001] axis of the Ge pillar whose faster shrinkage to the room temperature volume is restricted by the oversized surface island.
A semi-supervised learning method based on pseudo-label iterative purification for intelligent fault diagnosis of rolling bearing
Authors: Yue Wenbo , Zhang Li , Yang Jianwei , Wang Dongpo
Published: March 2024

Bearing fault diagnosis based on semi-supervised learning shows good results in solving the scarcity of data in industrial scenarios. Pseudo-label samples can be used to expand labeled datasets, thereby to solve the shortage of training samples. However, when pseudo-labeling is employed to improve the performance of the model, the low confidence level of pseudo-labels will have a negative impact on the model. To solve this problem, the pseudo-label iterative purification method is proposed. Firstly, the graph neural network is employed to aggregate samples in order to increase the degree of dissimilarity among target domain data belonging to distinct categories. Subsequently, the pseudo-labeled samples are purified, while multiple positive-negative discriminators are trained on particular data from the source domain to accurately identify the target domain samples containing the pseudo-labels. Finally, the backbone network is fine-tuned by the purified pseudo-labeled samples. Results of experiments on the self-built bearing dataset and the Paderborn University bearing dataset validate that the method proposed in this article exhibits outstanding performance.
A hybrid fault diagnosis method for rolling bearings based on GGRU-1DCNN with AdaBN algorithm under multiple load conditions
Authors: Sun Lirong , Zhu Xiaomin , Xiao Jiannan , Cai Wei , Ma Qianxia , Zhang Runtong
Published: March 2024

The fault diagnosis of rolling bearings is a critical aspect of rotating machinery, as it significantly contributes to the overall operational safety of the mechanical equipment. In the practical engineering environment, the complex and variable working conditions, along with the presence of overlapping noise, contribute to intricate frequency information in the acquired signals and their highly time-dependent characteristics, which makes it difficult to extract the available fault features hidden in the signal. Based on this, a hybrid fault diagnosis method named GGRU-1DCNN-AdaBN is introduced, which combines improved gap-gated recurrent unit network (GGRU), one-dimensional convolutional neural network (1DCNN), and adaptive batch normalization (AdaBN). The proposed approach involves several parts to enhance fault diagnosis accuracy in vibration signals under constant load conditions and variable load conditions. Firstly, the end-layer structure of the traditional GRU is replaced with a one-dimensional global average pooling layer to aggregate the influence components of defects and reduce model training parameters. Secondly, the fusion of different types of frequency and sequence features is achieved by combining 1DCNN, addressing the limitation of a single network’s feature extraction capability and the loss of temporal features in a cascaded hybrid model. Subsequently, the fused features are input into a softmax multi-classifier to obtain fault type identification results. Lastly, the GGRU-1DCNN method is further improved by incorporating the AdaBN algorithm, enhancing the model’s domain adaptive capability under variable load conditions and noisy environments. The method is validated using datasets obtained from Case Western Reserve University, aero-engine bearings, Xi’an Jiaotong University, and the Changxing Sumyoung Technology. The findings suggest that the proposed method demonstrates superior accuracy and robustness in fault diagnosis, as well as excellent generalization capability and universal applicability.
Study of partial discharges measurement cycles effect on defect recognition for underground cable joints
Authors: Chang Chien-Kuo , Boyanapalli Bharath Kumar
Published: March 2024

This study investigates the influence of various partial discharge (PD) measurement durations on defect recognition in high voltage power cable joints, aiming to address a crucial challenge in the field of insulation assessment. The main objective is to determine the optimal measurement cycle duration for accurate defect recognition, thereby enhancing the reliability of PD-based diagnostic techniques. Totally 14 cable joints, each containing three different types of prefabricated artificial defects, were analyzed across five different measurement cycle durations: 40, 80, 120, 200, and 1200 cycles. Subsequently, convolutional neural networks (CNNs) were employed for defect recognition analysis. The results reveal a significant impact of measurement cycle duration on defect recognition accuracy. Particularly, a CNN based on 200 measurement cycles demonstrates superior performance compared to models with fewer cycles, achieving a total defect recognition accuracy of 100%. This finding underscores the importance of sufficient measurement cycles for obtaining comprehensive PRPD patterns and accurate defect classification. Furthermore, the study highlights the significance of setting a threshold value to mitigate false conditions in defect type recognition, offering valuable insights for practical applications in power system maintenance and diagnostics. Overall, this research contributes to advancing the understanding of PD-based insulation assessment techniques and provides practical recommendations for optimizing measurement cycle duration to enhance defect recognition accuracy in high voltage power cable joints.
Vibration characteristics of defective axle box bearings in high-speed trains under track irregularity excitation
Authors: Wang Min , Yang Shaopu , Liu Yongqiang , Guo Tao , Chen Yanhong , Wang Baosen
Published: March 2024

Track irregularity is a type of excitation source for the wheel-rail system, and it is also the major cause of vibration and wheel-rail forces on the axle box bearings of vehicles, and it is commonly found on in-service lines. Therefore, this paper mainly focuses on the dynamic characteristics of high-speed train axle box bearings under track irregularity. Firstly, a nonlinear system containing a faulty double-row tapered roller bearings is established, the obtained equations of motion are solved numerically using the Runge–Kutta and comparing it with the varying compliance vibration frequency and fault characteristic frequency obtained by formula, the comparison results verify the effectiveness of the model. Then, the track irregularity is coupled to the above bearing system, the model is also verified by using the rolling and vibrating test rig of single wheelset. Secondly, the eigenvalue of covariance matrix is introduced as an index to analyze the influence trend of different fault sizes, loads, and inner rotational speeds on the axial trajectory. Finally, the influence trend of track irregularity on the stability of vertical acceleration is analyzed by simulating different operating conditions.
End-to-end information fusion method for transformer-based stereo matching
Authors: Xu Zhenghui , Wang Jingxue , Guo Jun
Published: March 2024

In stereo matching, the application of transformers can overcome the limitations of disparity range and capture long-range matching information. However, the lack of cross-epipolar context information often leads to numerous mismatches, especially in low-texture regions. An end-to-end information fusion stereo matching method is proposed to address this issue. In the proposed method, a feature extraction method that combines dense connections and a residual block is proposed. Global and local semantic information can be effectively fused by incorporating dense connections among multiscale feature maps. Additionally, the inclusion of a residual block helps extract more representative feature maps. The idea of criss-cross attention is introduced in the transformer implicit matching process. Criss-cross attention enables the capture of cross-epipolar context information by combining horizontal and vertical attention mechanisms. This method improves the matching accuracy from the perspective of multi-path information fusion. According to the matching results, the disparity regression layer and the context adjustment layer are used to generate the initial and final disparity maps, respectively. The proposed method is evaluated on the Scene Flow, KITTI 2012, and Middlebury 2014 datasets. Experimental results indicate that the proposed method effectively enhances matching accuracy. Moreover, the proposed method exhibits strong generalization ability, allowing for direct application to synthetic, real outdoor, and real indoor scene images.
Transient N-GQDs/PVA nanocomposite thin film for memristor application
Authors: Pisal Deshmukh Akshaya , Patil Kalyanee , Barve Kanchan , Bhave Tejashree
Published: March 2024

In recent years quantum dot (QDs) based resistive switching devices(memristors) have gained a lot of attention. Here we report the resistive switching behavior of nitrogen-doped graphene quantum dots/Polyvinyl alcohol (N-GQDs/PVA) degradable nanocomposite thin film with different weight percentages (wt.%) of N-GQDs. The memristor device was fabricated by a simple spin coating technique. It was found that 1 wt% N-GQDs/PVA device shows a prominent resistive switching phenomenon with good cyclic stability, high on/off ratio of ~102 and retention time of ∼104 s. From a detailed experimental study of band structure, we conclude that memristive behavior originates from the space charge controlled conduction (SCLC) mechanism. Further transient property of built memristive device was studied. Within three minutes of being submerged in distilled water, the fabricated memory device was destroyed. This phenomenon facilitates the usage of fabricated memristor devices to develop memory devices for military and security purposes.
A study of turbulent filaments in the edge plasma of the Wendelstein 7-X stellarator
Authors: Buzás A. , Kocsis G. , Biedermann C. , Cseh G. , Szepesi T. , Szűcs M. ,   the W7-X Team
Published: March 2024

Filaments are studied by examining fast camera images on the Wendelstein 7-X stellarator. Fast cameras offer a unique perspective, revealing the complex 3D structure of filaments in the entire poloidal cross-section of the plasma. By correlating individual pixels, their location, shape, and movement are analyzed in standard and high-ι configurations. The presence of filaments is not uniform poloidally around. The number of active areas matches the number of magnetic islands in both configurations. Filaments are found to extend to multiple toroidal turns in standard configuration. No time delay is observed between the different toroidal sections. Such behavior is not seen in high-ι configuration. Filaments are observed within and without the edge shear layer, indicated by the direction of their poloidal rotation. Inside the shear layer, their velocity scatters around 1.25 km s−1, accompanied by a lifetime between 80 and 120 µs. Outside, their velocity shows greater absolute values and variance, but still in a few km s−1 range. The similarities and differences between the two configurations are discussed and compared to previous results.
Classical stochastic approach to quantum mechanics and quantum thermodynamics
Authors: Oliveira Mário J de
Published: March 2024

We derive the equations of quantum mechanics and quantum thermodynamics from the assumption that a quantum system can be described by an underlying classical system of particles. Each component φ

j
of the wave vector is understood as a stochastic complex variable whose real and imaginary parts are proportional to the coordinate and momentum associated with a degree of freedom of the underlying classical system. From the classical stochastic equations of motion, we derive a general equation for the covariance matrix of the wave vector, which turns out to be of the Lindblad type. When the noise changes only the phase of φ

j
, the Schrödinger and the quantum Liouville equations are obtained. The component ψ

j
of the wave vector obeying the Schrödinger equation is related to the stochastic wave vector by

|

ψ
j

|

2

=
⟨

|

ϕ
j

|

2

⟩

.
Classroom architectural design evolution: Acoustic evaluation of public-school classrooms in Malaysia
Authors: Razali A W , Che Din N , Yahya M N , Sulaiman R
Published: March 2024

Education transformation greatly emphasises curriculum modification to produce impactful future generations and yet often disregards the impact of classroom design in achieving desired education outcomes. The prioritisation of optimal acoustic quality in classroom design is crucial due to the inherent reliance on auditory abilities in the process of teaching and learning. Therefore, a comprehensive acoustic standard guideline for classrooms, ANSI Standard 12.60, was launched in 2002 and adopted for school classrooms in the USA. However, the scenario might be different in Malaysia, as there is no acoustic standard guideline established. Therefore, this study seeks to identify the actual acoustic conditions of classrooms that were constructed in the post-independence era. On-site acoustic measurements were performed to evaluate significant acoustic parameters, including reverberation time (RT), background noise level (BNL), speech transmission index (STI), and sound pressure level (SPL). The findings revealed that the RT for both classrooms was within the recommended value, while the BNL and STI of both classrooms failed to comply with the established recommended guidelines. In a similar vein, these findings translate the degree of awareness among the education institutions and construction sector of the importance of classroom acoustics in providing a better learning experience among students.