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• Cochlear-implanted (CI) children have difficulty in extracting abstract auditory rules from a complex speech sound stream. • Sensory intelligence and everyday hearing abilities greatly vary in CI children and are closely related. • Sensory intelligence in speech may gradually develop during childhood and adolescence. Sensory intelligence in the brain helps listeners automatically extract abstract auditory rules formed by invariant acoustic features from complex speech sound streams, presumably serving as the neural basis for speech comprehension. However, whether this intelligence is deficient in children with cochlear implants (CIs) remains unclear. Mandarin Chinese monosyllables shared a flat lexical tone contour to form an abstract auditory rule but differed in other acoustic features to construct a complex speech sound stream. The abstract rule was occasionally violated by monosyllables with a rising or falling lexical tone. In normal hearing (NH) children, the abstract auditory rule could be extracted, as revealed by a mismatch negativity (MMN) and a late discriminative negativity (LDN). However, the MMN and LDN were only evoked in CI children with good hearing and speech performance. NH children with a higher speech perception or spatial hearing score had a greater MMN. The LDN was attenuated with increasing age in NH children. The sensory intelligence for extraction of auditory abstract rules, associated with speech perception, is deficient in CI children. This intelligence may gradually develop during childhood and adolescence. Deficient sensory intelligence in CI children may aid in understanding poor speech comprehension in complex environments. [ABSTRACT FROM AUTHOR]

Due to the poor surface characteristics of additively manufactured parts, the necessity for post-process surface enhancement is crucial. Among the prevalent post-processing techniques, the acoustic cavitation-based surface finishing technique has recently emerged. Despite a considerable amount of focused research on the material removal mechanisms of this technique, less attention has been devoted to addressing its limitations associated with enhancing the process capability towards achieving a better surface finish. The driving force behind the acoustic cavitation technique is the bubble implosion through cavitation streaming, and the cessation of the acoustic cavitation streaming beyond a certain length is the main limitation. It has restrained the process capability towards finishing both external and internal surfaces. Hence, this research aims to unravel novel ways of employing the acoustic cavitation-generating parameters and achieving better-quality surface finishing of additively manufactured (AM) components. A study has been conducted on different AM materials, including Inconel 625 and aluminum alloy, by introducing various methods associated with acoustic amplitude, working mediums, temperature, and external vibration. The results reveal a significant reduction in average surface roughness for both materials. The topographical and morphological observations confirm the qualitative improvement on the surfaces. In addition, the conical bubble structures that frame the acoustic cavitation streaming are elucidated by implementing high-speed imaging techniques, and their enhancement at different parametric conditions is delineated. Henceforth, the findings suggest a notable insight into the potential of the employed approaches in enhancing the acoustic cavitation streaming for achieving a better surface finish of AM components. [Display omitted] • Surface finishing of AM components by enhanced acoustic cavitation. • Overcoming the limitations of acoustic cavitation for surface quality improvement. • Acoustic cavitation: factors affecting acoustic streaming and AM surface quality. • Thermal effect on bubble structures in free-field and confined acoustic cavitation. • A study on parametric investigation of acoustic cavitation: a different approach. [ABSTRACT FROM AUTHOR]

Accurate simulation of nonlinear acoustic waves is essential for the continued development of a wide range of (high-intensity) focused ultrasound applications. In this article, we explore mixed finite element formulations of classical strongly damped quasilinear models of ultrasonic wave propagation, the Kuznetsov and Westervelt equations. Such formulations allow simultaneous retrieval of the acoustic particle velocity and either the pressure or acoustic velocity potential , thus characterizing the complete ultrasonic field at once. Using non-standard energy analysis and a fixed-point technique, we establish sufficient conditions for the well-posedness, stability, and optimal a priori errors in the energy norm for the semi-discrete equations. For the Westervelt equation, we also determine the conditions under which the error bounds can be made uniform with respect to the involved dissipation parameter. Additionally, we discuss convergence in the maximum error norm of the involved scalar quantities. Finally, computer experiments for Raviart–Thomas (RT) and Brezzi–Douglas–Marini (BDM) elements are performed to confirm the theoretical findings. [ABSTRACT FROM AUTHOR]

The effects of helical flow in a blood vessel are investigated in a dynamic flow generator using surface acoustic wave (SAW) in the microfluidic device. The SAW, generated by an interdigital transducer (IDT), induces acoustic streaming, resulting in a stable and consistent helical flow pattern in microscale channels. This approach allows rapid development of helical flow within the channel without directly contacting the medium. The precise design of the window enables the creation of distinct unidirectional vortices, which can be controlled by adjusting the amplitude of the SAW. Within this device, optimal operational parameters of the dynamic flow generator to preserve the integrity of endothelial cells are found, and in such settings, the actin filaments within the cells are aligned to the desired state. Our findings reveal that intracellular Ca2+ concentrations vary in response to flow conditions. Specifically, comparable maximum intensity and graphical patterns were observed between low-flow rate helical flow and high-flow rate Hagen-Poiseuille flow. These suggest that the cells respond to the helical flow through mechanosensitive ion channels. Finally, adherence of monocytes is effectively reduced under helical flow conditions in an inflammatory environment, highlighting the atheroprotective role of helical flow. Helical flow in blood vessels is well known to prevent atherosclerosis. However, despite efforts to replicate helical flow in microscale channels, there is still a lack of in vitro models which can generate helical flow for analyzing its effects on the vascular system. In this study, we developed a method for generating steady and constant helical flow in microfluidic channel using acoustofluidic techniques. By utilizing this dynamic flow generator, we were able to observe the atheroprotective aspects of helical flow in vitro, including the enhancement of calcium ion flux and reduction of monocyte adhesion. This study paves the way for an in vitro model of dynamic cell culture and offers advanced investigation into helical flow in our circulatory system. [Display omitted] [ABSTRACT FROM AUTHOR]

To numerically simulate the acoustic propagation in fluids, a third-order compact finite volume method (FVM) that is suitable for three-dimensional (3D) hybrid unstructured grids is developed. It is used to solve the linear Euler equations (LEEs). Furthermore, the corresponding linear lattice Boltzmann flux solver (LBFS) is constructed. The conservative form of LEEs is discretized according to the third-order Gaussian quadrature rules. Based on the stencils only involving the neighboring cells of the control volume, high-order polynomials are constructed. By ensuring that the variables and their derivatives are conserved in the stencil, the unknown coefficients are determined using the least-square method. To satisfy the moment relations, the distribution function expression is determined by solving the equation system. Finally, the mesoscopic flux calculation scheme for LEEs is constructed based on the derived lattice model. The proposed high-order FVM is suitable for 3D hybrid unstructured grids, which makes it highly adaptable. It makes the selection of stencils and disposal of ghost cells simple due to its compact characteristics. Moreover, the proposed FVM extends the application of LBFS from traditional fluid equations to 3D LEEs. Therefore, the proposed flux solver has the advantages of Boltzmann-based flux schemes. The proposed FVM is used to simulate 3D acoustic propagations and is validated through several numerical cases. [ABSTRACT FROM AUTHOR]

We propose a hybrid Finite Volume (FV) - Spectral Element Method (SEM) for modeling aeroacoustic phenomena based on the Lighthill's acoustic analogy. First the fluid solution is computed employing a FV method. Then, the sound source term is projected onto the acoustic grid and the inhomogeneous Lighthill's wave equation is solved employing the SEM. The novel projection method computes offline the intersections between the acoustic and the fluid grids in order to preserve the accuracy. The proposed intersection algorithm is shown to be robust, scalable and able to efficiently compute the geometric intersection of arbitrary polyhedral elements. We then analyze the properties of the projection error, showing that if the fluid grid is fine enough we are able to exploit the accuracy of the acoustic solver and we numerically assess the obtained theoretical estimates. Finally, we address two relevant aeroacoustic benchmarks, namely the corotating vortex pair and the noise induced by a laminar flow around a squared cylinder, to demonstrate in practice the effectiveness of the projection method when dealing with high order solvers. The flow computations are performed with OpenFOAM [50] , an open-source finite volume library, while the inhomogeneous Lighthill's wave equation is solved with SPEED [34] , an open-source spectral element library. [ABSTRACT FROM AUTHOR]

Combustion instability is one of the main disadvantages of power generation systems. Indirect noise or acceleration of entropy waves are sound sources that cause the combustion chamber unstable. This subject, however, has been less investigated due to the complex nature of entropy waves. A deep understanding of the physics of entropy waves is crucially important in order to reduce noise and instability. This study considers entropy generation in premixed flame conditions. In this situation, the hydrodynamic and thermal effects on the entropy wave performance in a combustion chamber are studied. To model turbulent flow, the large eddy simulation has been used. The effects of adding hydrogen to the input fuel mixture on entropy wave generation and deterioration in thermal convective and adiabatic combustion have been investigated. Comparing the acoustic noise produced by entropy waves with the studied cases shows the thermo-hydrodynamic effects on the entropy wave in the low-order models of combustion instability prediction, which has been limitedly noticed so far. Although the combustion efficiency is improved by increasing the percentage of hydrogen in the fuel, significant instabilities may occur. • Convective heat transfer boundary condition emphasizes the destruction of the wave. • Adding hydrogen, leading to louder noise and subsequent stronger instabilities. • Increasing the amplitude increases the turbulence and thus destroys the wave more. [ABSTRACT FROM AUTHOR]

This study presents a numerical investigation of acoustic streaming motion (of the Rayleigh type) in a compressible gas inside two-dimensional rectangular enclosures. To numerically study the effects of the sound field intensity on the formation process of streaming structures, we propose to discretize the fully compressible form of the two-dimensional Navier-Stokes equations using a high-order (formally greater or equal to fourth-order) accurate numerical scheme in both space and time. The proposed numerical solver utilizes high-order compact schemes along each spatial dimension combined with a filtering procedure when it is necessary. Acoustic standing waves are excited inside the enclosures and the resulting acoustic streaming patterns are investigated for low and high-intensity waves, in both linear and nonlinear regimes following closely the work of Daru et al. (2013). An extended investigation indicates that without the incorporation of an appropriate filter, the application of the high-order compact schemes in case of fast streaming results in spurious oscillations which inhibit their applicability. Following the recent relevant literature, the numerical simulations performed demonstrate the ability of the proposed numerical approach to reproduce efficiently and robustly the transitions from regular acoustic streaming to irregular streaming and the relevant phenomena confirming results that have been previously presented. [ABSTRACT FROM AUTHOR]

This study analyzes the flow pattern and power consumption of mixing highly viscous fluids under vertical acoustic vibration, and investigates the effects of various process parameters on them. A numerical simulation of solid-liquid-gas multiphase flow has been created based on the Volume of Fluid (VOF) model and Discrete Phase Model (DPM), which has been verified through experimentation. When subjected to acoustic vibration, the fluids within the vessel and the wall interact dynamically, driven by a mixing force comprised of both pressure and viscous forces. Notably, the degree to which the fluids absorb mixing power is highly dependent on the mixing force itself, the vessel's velocity, as well as the phase difference between them. Throughout the mixing process, the amplitudes of the instantaneous mixing power and mixing force gradually diminish. Nevertheless, the effective mixing power indeed increases due to the phase effect. Increasing the frequency or amplitude of vibration can expedite the mixing process, leading to improved mixing uniformity and significantly enhancing the effective mixing power. However, the energy absorbed by the fluids is highly nonlinear with respect to the frequency or amplitude of vibration. Achieving higher mixing efficiency can be attained by selecting suitable vibration parameters without increasing power consumption. • A numerical model of the multiphase flow under acoustic vibration has been built. • Energy absorbed in the mixing time is highly nonlinear to the vibration parameters. • Higher mixing efficiency and lower input energy can be achieved. • It's more efficient to increase amplitude than frequency under a constant acceleration. [ABSTRACT FROM AUTHOR]

The formation of bacterial biofilm regulated by quorum sensing (QS) is a critical factor that contributes to infections of indwelling medical devices. Autoinducer-2 (AI-2), as a signal molecule in QS, plays a crucial role in mediating bacterial signaling and regulating their biological behavior. This study investigated the impact of ultrasonic vibration at varying frequencies on biofilm formation in a mixture of Staphylococcus aureus and Escherichia coli. By exciting ultrasound at different frequencies (20, 100 and 200 kHz), a vibration with an amplitude of 100 nm was generated on the material surface located at the bottom of the petri dish containing mixed bacteria. We measured the content of AI-2 and bacteria in the mixed bacterial solution and bioburden on material surfaces at different time points during culture. In addition, the relationships among AI-2 content, bacterial concentration and distribution were assessed through finite-element analysis of acoustic streaming under ultrasonic vibration. The AI-2 gradient is influenced by the diversity of acoustic streaming patterns on the material surface and in the mixed bacterial solution caused by ultrasonic vibration at different frequencies, thereby regulating biofilm formation. The experimental results showed that the optimal inhibition effect on AI-2 and minimal bacterial adhesion degree was achieved when applying an ultrasonic frequency of 100 kHz with a power intensity of 46.1 mW/cm2 under an amplitude of 100 nm. Ultrasound can affect the QS system of bacteria, leading to alterations in their biological behavior. Different species of bacteria exhibit varying degrees of chemotaxis toward different frequencies. [ABSTRACT FROM AUTHOR]

In this study, we develop a single-phase free-surface flow model with the improved lattice kinetic scheme (LKS) and the volume of fluid (VOF) method. We implement the piecewise linear interface calculation (PLIC) algorithm to reconstruct the interface. The gas phase velocity is extrapolated from the liquid phase velocity using a velocity extension method and the signed distance function (SDF) to advect the VOF function. We calculate the SDF with the level-set reinitialisation method, and the VOF function is used as the initial profile. We discuss the advantages of the improved LKS in terms of the free-surface boundary condition by means of distribution functions, which conflict in interface cells in conventional streaming and collision processes in the lattice Boltzmann method (LBM). The proposed free-surface model is verified with well-known advection benchmark problems. We also simulate a static water problem and dam break flow. The proposed model accurately calculates the dam break surge front. Although the surge front position depends on the spatial resolution in the conventional LBM free-surface model, the improved LKS results are approximately the same regardless of the resolution. This is a critical difference between the proposed and conventional LBM models and represents a unique feature of the improved LKS. • A single-phase free-surface flow model by the improved LKS is developed. • Conflicts of the distribution function do not arise because the boundary conditions are given as the macroscopic variables. • The velocity field is extended by the SDF and the advection of the VOF function is calculated by the PLIC approach. • The proposed model is stable without the turbulence model and agrees well with the experimental results. [ABSTRACT FROM AUTHOR]

Passive acoustic monitoring has become an effective and economically scalable solution for wildlife monitoring in recent years, especially for population monitoring of endangered birds in hardly accessible and high-elevation areas. As sound recorders are deployed on the field for extended periods (months), continuous sound streams are often complex in nature, with noises and intermittent signals. Generally, it is prohibitively expensive to label bird sounds with the exact onset and offset time, thus, during training, the data is often provided with only presence/absence labeling (weak labeling) that states which bird species are present in each long recording without temporal information. During test time, it is, however, desirable to provide fine-grained detection in short audio segments. To bridge the gap between the difference of weak labels used for training and strong labels used for testing, we propose a re-labeling approach with two stages: (1) we train a model with weak labeling; and (2) using the model obtained from stage 1, we generate labels for short audio segments and retrain the model on short audio segments with the newly generated labels. We applied our approach in both classification and sound event detection and achieved consistently good performance across multiple random seeds. In BirdCLEF 2022, our model ranked in the top 1.1%, the 9th best entry out of the total 807 entries in the competition. [ABSTRACT FROM AUTHOR]

Ultrasonic assisted solidification (UST), heat treatment and alloying are all effective methods to control the microstructure of materials and improve their properties. In this paper, the Nb-16Si-20Zr-2C- x W composites were prepared using ultrasonic assisted solidification technology of high temperature melt (≥1800℃) and heat treatment. The influence mechanism of ultrasonic, the W element, and the synergistic regulation mechanism of ultrasonic and heat treatment on the material were studied. Nb-16Si-20Zr-2C- x W(UST) alloys are mainly composed of Nbss phase and γNb 5 Si 3 phase, and their microstructures are mainly divided into strong active zone(SZ) and weak active zone(WZ). In the Nb-Si superalloy melt treated by ultrasonic wave, the area near the ultrasonic sound source is the strong active zone, while the area far away from the ultrasonic sound source is the weak active zone. The features of faceted primary phases and non-faceted primary phases in the SZ and WZ are explained by the equation of undercooling degree at different interfaces and effect of ultrasonic on component undercooling. As the W element content in the alloys (UST) increases, the content of the Nbss phase increases, the median diameter of the primary γNb 5 Si 3 phase decreases, and the room temperature fracture toughness and compressive strength show an upward trend. When the addition amount of W element reaches 2 at%, there are more crack deflections, crack bridging and secondary cracks in the crack propagation path. Through the special arrangement of primary γNb 5 Si 3 phase in the ultrasonic field, the energy density of ultrasonic waves in the melt is calculate to be 33.5 kW/m2. The microstructure of Nb-16Si-20Zr-2C- x W alloys(UST+HT) became more uniform and spheroidize. It is worth mentioning that there are plenty of long strip γNb 5 Si 3 phases with different orientations in the Nb-16Si-20Zr-2C-0.1W(UST+HT) alloy and the long strip γNb 5 Si 3 phases with the same orientation are arranged in a periodic manner. This special composite structure induces crack deflections and branching cracks when cracks propagation, so the room temperature fracture toughness of Nb-16Si-20Zr-2C-0.1 W (UST+HT) alloy reaches 15.66 MPa·m1/2. • Ultrasonic wave was introduced into ultra-high temperature melts. • Ultrasonic made the microstructure obviously divided into two zones. • The maximum melt acoustic streaming rate was calculated to be 1.82 m/s. • W has an inhibitory effect on the silicide phase under the action of ultrasonic. • Fracture toughness K Q value of Nb-16Si-20Zr-2C-0.1W(UST+HT) is 15.66 MPa·m1/2. [ABSTRACT FROM AUTHOR]

In orthopedic surgery, cortical bone cutting usually involves washing and cooling with physiological saline. However, how the saline changes the cutting behaviors of bone ultrasonic vibration cutting remains challenging. Hence, this paper simulates the clinical ultrasonic cutting condition in orthopedics to reveal the cutting behaviors of bone ultrasonic vibration orthogonal cutting immersed in physiological saline. The dynamic equation and motion process curves of ultrasonic cavitation bubbles were established. The results showed that the bone cutting immersed in physiological saline significantly improved the surface quality, reduced surface roughness and mechanical damage, and avoided large brittle cracks propagation. In saline immersed cutting, the physiological saline changes the mechanical behaviors of bone materials, resulting in plastic behaviors for the material removal and crack deflection. This study establishes the influence of physiological saline on the ultrasonic vibration cutting performance, providing guidance for orthopedic bone cutting surgery methods. [ABSTRACT FROM AUTHOR]

The solidification process of FeCoNiCu 1.5 Al 0.2 high-entropy alloy (HEA) with two FCC phases was modulated by three-dimensional (3D) ultrasounds with 20 kHz frequency and 22 μm amplitude. The statically solidified alloy was composed of a primary γ 1 phase growing into coarse dendrites and a Cu-rich γ 2 phase dispersed in interdendritic spacings. Once 3D ultrasounds were applied, the primary γ 1 phase was refined into small equiaxed grains and the secondary γ 2 phase was distributed around their grain boundaries. Based on the estimation of local sound pressure and undercooling, as well as acoustic spectra examination, it is concluded that transient cavitation was the dominant reason for the formation of tiny equiaxed γ 1 phase by remarkably increasing local nucleation rate, which also promoted the generation of connected γ 2 phase together with acoustic streaming effect. The yield strength, ultimate strength and total elongation for ultrasonically solidified alloy sample were simultaneously enhanced by 73 %, 54 % and 13 %, which were up to 605 MPa, 845 MPa and 35 % respectively. According to LUR tests and dislocation characterization, both hetero-deformation induced (HDI) strengthening and grain refinement strengthening contributed to the increase of yield strength, while the former mainly enhanced ultimate strength and ductility synergistically. This indicates that 3D ultrasonic solidification provides an effective approach to overcoming the strength-ductility trade-off for Cu-containing HEAs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Directional clearance of bacteria on submerged surfaces is achieved. • A system dominated by acoustic radiation force for material transport was designed. • The antibacterial adhesion efficiency for multiple bacteria reached over 90%. • The applicability on surfaces of different materials and morphologies was validated. • The system solely directs the removal of bacteria without causing in situ bacterial death. The process of bacterial film formation on submerged surfaces commences with the attachment of bacteria to the substrate. Appropriate combinations of topology and surface chemistry have been explored to prevent biofilm anchoring at the solid–liquid interface. However, the failure to actively remove bacteria from solid surfaces within a fluid in a directional manner results in bacterial backflow onto those surfaces, thus leading to secondary contaminations. Herein, inspired by the biology broom of the ciliary beating system, we propose an active surface sweeper mechanism assisted by charged particles and surface acoustic waves (SAW) to facilitate the directional clearance of bacteria. Through the synergistic effect of charge trapping and acoustic propelling, the sweeper system demonstrates an effective inhibition of bacterial adhesion in the initial stage of biofilm formation. Utilizing SAW for twenty seconds yields a remarkable 94.8% efficiency in bacterial clearance, with antibacterial adhesion efficiency up to 92.4% and 98.8% for Escherichia coli and Staphylococcus aureus, respectively. Moreover, the accompanying theoretical force modeling offers a comprehensive mechanistic insight into the relationship between acoustic streaming and bacteria repelling. The motion analysis of bacteria-loaded particles suggests that the acoustic radiation force, rather than the Strokes force, determines the clearance direction of bacteria. [ABSTRACT FROM AUTHOR]

Technologies based on surface acoustic waves (SAWs) find widespread use in wireless communications, signal processing, and sensing applications. In this study, we present an innovative dual-mode SAW configuration using a 64° Y-cut lithium niobate (LN) substrate. The conventional setup, employing interdigital transducers (IDTs) oriented along the crystal X-axis, is known for generating the shear horizontal mode (SH-SAW) with in-plane polarization. Conversely, by utilizing IDTs oriented perpendicular to the X-axis, we introduce effective excitation of a Rayleigh-like SAW (R-SAW), a novel achievement in our research. Through finite element simulations and electro-mechanical analyses, we comprehensively characterize these modes in terms of frequencies, polarizations, propagation losses, and temperature coefficients. Furthermore, we investigate their interaction with liquids by analyzing damping characteristics and acoustic streaming effects using particle image velocimetry (PIV). SH-SAWs exhibit a leaky displacement during propagation with minimal damping in liquids, resulting in weak acoustic streaming—ideal for real-time sensing applications in wet environments. In contrast, non-leaky R-SAWs, characterized by a strong displacement component normal to the surface, exhibit enhanced acoustic streaming, facilitating microfluidic operations. Additionally, R-SAWs demonstrate high sensitivity to mass loading, making them optimal for real-time sensing in dry environments. The ability to generate both SAW modes on the same substrate offers the potential to develop fully electrical-driven, multifunctional integrated sensing platforms with SAW-driven microfluidic capabilities. This unique capability promises novel solutions in bio-sensing, leveraging the complementary strengths of the two acoustic modes in detection and sample handling. [Display omitted] • Dual-mode SAW excitation in 64° Y-cut Lithium Niobate. • New IDT orientations enable SH-SAW and R-SAW modes in 64° Y-cut Lithium Niobate. • Analyses of mode characteristics for sensor applications. • Coupling of SAW modes with liquids was demonstrated and characterized. • Enables multi-functional, SAW-driven microfluidics. [ABSTRACT FROM AUTHOR]

Microfluidics heating has significant applications in the biological reaction and materials science. In this research, we demonstrate the acoustothermal effects in a microliter droplet driven by 1 MHz Lamb waves on a non-piezoelectric substrate. The two forms of droplet energy, kinetic and thermal effects, which are converted from the input power of Lamb waves, have been investigated in this study. The temperature increase of the droplets is not only determined by thermal conduction of the substrate, but also by viscous dissipation of the radiated longitudinal waves within the droplets. Theoretical and experimental analyses on the influence of acoustic input power on acoustothermal heating in a droplet are studied. The thermal effects induced by Lamb waves are prominent when the acoustic input power is >0.8 W. Besides, the volume of the droplet can affect the temperature distribution gradient in the droplet. The heat source distribution characterized by infrared thermography is mainly in the area where Lamb waves encounter the droplet. A better uniformity and greater temperature rise achieved with the higher viscosity are observed. A model for the acoustic streaming effects and thermal effects of droplets to demonstrate the rapid temperature increase of the droplets during the later stage of heating is demonstrated. The corresponding measurements with a high-speed camera and an infrared camera reveal a rapid enhancement of acoustothermal heating along with the acoustic flow and an increase in temperature at the top of the droplets resulting from the interaction with acoustic force and thermal energy dissipation induced by viscosity, which are reproduced by the numerical simulations. [ABSTRACT FROM AUTHOR]

[Display omitted] The electrodeposition process confronts significant challenges arising from mass transfer limitation and residual stress. To address these issues, an innovative method, combining megasonic agitation with coaxial jet electrodeposition, is introduced. This approach aims to enhance mass transfer and mitigate residual stress. First, an electrodeposition nozzle device was designed, and the liquid-phase mass transfer during electrodeposition was analyzed through finite element simulation. Simulation results indicate that the mass transfer coefficient increases with rising megasonic power density. Notably, when the megasonic power density reached 20 W/cm2, the mass transfer coefficient increased from 0.45 × 10−7 m/s to 18.63 × 10−7 m/s, compared to electrodeposition without megasonic agitation. Secondly, electrodeposition experiments were conducted both with and without megasonic assistance. X-ray diffraction (XRD) was employed to measure the residual stress values of the electrodeposited layers. The results reveal that samples processed with megasonic assistance exhibit lower residual stress values compared to those without. Specifically, at a megasonic power density of 10 W/cm2, the residual stress was 94.3 MPa, representing a 37.7 % reduction compared to the residual stress of 151.5 MPa observed in samples without megasonic agitation. Overall, the findings demonstrate that coaxial megasonic agitation can effectively enhance the liquid-phase mass transfer capability during electrodeposition and reduce the residual stress of the electroplated layer. This innovative method presents a promising avenue for improving electrodeposition processes and achieving superior material properties. [ABSTRACT FROM AUTHOR]

The impulsive live streaming consumption intentions of the Southeast Asian market are examined in this study. Online live streaming transactions, a new form of social media, are becoming popular due to their real-time communication and innovative business concept. Though little attention has been dedicated to it, a theoretical knowledge of Live Streaming Transaction (LST) is crucial given its broad application and unique features. The analysis of 8613 respondents from Southeast Asia in this study, based on flow, temperament, and personality theories, offers fresh perspectives on the mediating role of flow and the moderating effect of temperament in a cross-national setting. Cluster sampling was used to construct a mixed-method conditional indirect effects model. Since introverted temperament types look for voices that echo within them, our findings revealed that LSTs are more intriguing to this market segment. Theoretical and practical elements, as well as implications for future directions, are presented. [ABSTRACT FROM AUTHOR]

As an emerging form of marketing, live streaming has a positive effect on the ability of e-Commerce platforms to attract traffic and increase sales. It has become another important competitive area in the industry. Based on an alternative learning theory model, the influencing factors of live streaming on e-Commerce platforms are studied, and the data findings can be applied to brand marketing and platform performance improvement. Quantitative and qualitative analyses were conducted using tens of thousands of live-streaming data, and the findings show that live interaction and live streamer follower accumulation have a significant positive effect on the number of sold users. Through the empirical study of real data, this paper inspires participants to fully embrace the effect of live streaming and enhance the consumer shopping experience. [ABSTRACT FROM AUTHOR]

Mechanosensitive channels (MSCs) play an important role in how cells transduce mechanical stimuli into electrical or chemical signals, which provides an interventional possibility through the manipulation of ion channel activation using different mechanical stimulation conditions. With good spatial resolution and depth of penetration, ultrasound is often proposed as the tool of choice for such therapeutic applications. Despite the identification of many ion channels as mechanosensitive in recent years, only a limited number of MSCs have been reported to be activated by ultrasound with substantial evidence. Furthermore, although many therapeutic implications using ultrasound have been explored, few offered insights into the molecular basis and the biological effects induced by ultrasound in relieving pain and accelerate tissue healing. In this review, we examined the literature, in particular studies that provided evidence of cellular responses to ultrasound, with and without the target ion channels. The ultrasound activation conditions were then summarized for these ion channels, and these conditions were related to their mode of activation based on the current biological concepts. The overall goal is to bridge the results relating to the activation of MSCs that is specific for ultrasound with the current knowledge in molecular structure and the available physiological evidence that may have facilitated such phenomena. We discussed how collating the information revealed by available scientific investigations helps in the design of a more effective stimulus device for the proposed translational purposes. Traditionally, studies on the effects of ultrasound have focused largely on its mechanical and physical interaction with the targeted tissue through thermal-based therapies as well as non-thermal mechanisms including ultrasonic cavitation; gas body activation; the direct action of the compressional, tensile and shear stresses; radiation force; and acoustic streaming. However, the current review explores and attempts to establish whether the application of low-intensity ultrasound may be associated with the activation of specific MSCs, which in turn triggers relevant cell signaling as its molecular mechanism in achieving the desired therapeutic effects. Non-invasive brain stimulation has recently become an area of intense research interest for rehabilitation, and the implication of low-intensity ultrasound is particularly critical given the need to minimize heat generation to preserve tissue integrity for such applications. [ABSTRACT FROM AUTHOR]

Thermoacoustics is about conversion between thermal and acoustical energies to provide alternative green technology for power cycle and cooling system. The oscillatory flow across porous structure inside the system is playing the role of energy conversion between the acoustic wave and the surface of the porous structure. Better understanding of fluid dynamics of oscillatory flow inside thermoacoustic system is therefore important for the thermoacoustic based energy conversion system. This paper presents the 'entrance' and 'exit' effects of the oscillatory flow within a parallel-plate structure that is placed inside a standing-wave thermoacoustic environment. Two-dimensional SST k-ω CFD models which were validated using experimental data and theoretical predictions were used for this investigation. Two different operating frequencies of 14.2 Hz and 23.6 Hz were studied for flow with five different amplitudes that were represented using drive ratios of 0.3%, 0.83%, 1.5%, 2.1% and 3%. These correspond to cases with Reynolds numbers between 5936 and 62926. Due to the cyclic nature of the flow, a region defined as an 'exit' region was observed in addition to the usual 'entrance' region and the fully developed region for flow inside a channel. The change of shape of velocity profiles from the 'm' shape profile, to the 'slug-like' profile and 'parabolic-like' profile was discussed in relation to the 'entrance' and 'exit' effects on flow inside the channel. The 'entrance' and 'exit' effects become bigger as drive ratio increases. The effect of 'entrance' and 'exit' are slightly reducing as frequency increases from 14.2 Hz to 23.6 Hz. This may be related to the shorter travel distance of fluid as the frequency increases. The results shown in this paper suggest that the flow within a 200 mm parallel-plate structure should be treated as developing flow especially for flow with low resonance frequency at drive ratio higher than 1%. [ABSTRACT FROM AUTHOR]

Microfluidic-based nucleic acid testing (NAT) has been proven as an alternative approach for in-situ and rapid NA detection. However, these on-chip methods still require complex peripherals, which contradict the purpose of point-of-care (POC) applications. One of the major challenges is the integration of NA purification and amplification in a miniaturized setup with high mass and heat transfer efficiency. Here, we propose a hand-held in-situ nucleic acid detection device featuring a dual-functional GHz acoustofluidic resonator. The device is designed to utilize GHz acoustic streaming and acoustothermal effects to address both liquid mixing and heating issues, ensuring uniform reaction conditions and consistent thermal management in the microfluidic channel. By replacing traditional magnetic beads with polystyrene beads as matrix for solid-phase microextraction, the redundant washing and elution steps are eliminated, thereby simplifying the NA extraction process. The mixing and heating functions can be seamlessly switched by adjusting the applied power, thereby enhancing NA processing without the need for additional peripherals. The developed hand-held NAT apparatus achieved a detection limit of 10³ copies per milliliter in complex plasma samples within 35 min. Our method simplifies workflows, improves NA retention, and is suitable for processing complex biological samples, making it ideal for POC and in-field testing applications. [ABSTRACT FROM AUTHOR]

Ultrasound-assisted hydration (UAH) stands out as a potent strategy, offering multiple advantages over conventional thermal hydration methods. It is an energy efficient, cost and time effective, easily scalable and relatively greener approach. Acoustic cavitation is the major working mechanism in aqueous phase sonication. Cavitation creates immense localised heat and pressure, which ultimately ends up heating the liquid media. To the best of our knowledge, no study dealing with the synergistic relationship between the physical effects of ultrasound and the consequent temperature rise during UAH is available in open literature. This work investigates this complex interplay with aim to identify the dominant working mechanism leading to the hydration of the pinto beans (Phaseolus vulgaris), a variety of common beans. Three different hydration protocols were devised to discern these effects, normal hydration (N) at 25 °C, temperature-controlled UAH (TC) between 18 and 20 °C using an ice bath, and temperature-uncontrolled UAH (TuC). Additionally, the post sonication residual effects of ultrasound treatment were examined. Our findings reveal that sonication induces changes in both TC and TuC treated beans, but more pronounced effects were observed in the absence of temperature control. During TC, acoustic streaming emerged as the predominant sonic action mechanism. Conversely, during TuC, temperature itself emerged as the dominant force, leading to irreversible alterations in the bean's physical and chemical structures. • Ultrasound assisted hydration (UAH) enhances the rate of hydration. • Acoustic streaming is the dominant mechanism when temperature is controlled during UAH. • Ultrasound induced changes are reversible when temperature is controlled. • Temperature dominates the physical effects of ultrasounds when temperature is not controlled. • Ultrasound induced changes are irreversible when temperature is not controlled. [ABSTRACT FROM AUTHOR]

• Ultrasonic vibration-assisted laser cladded Fe-based amorphous coatings were fabricated. • The mechanism of ultrasonic vibration on amorphous coatings was elucidated. • The evolution pattern of ultrasonic vibration on crystal and amorphous was investigated. In order to investigate the influence of ultrasonic vibration (UV) on microstructural evaluation of amorphous coating, the Fe-based amorphous (Fe 41.5 Co 12.2 Cr 7.4 Mo 37.3 C 0.3 B 0.5 Y 0.4 Al 0.4) coatings with and without UV were fabricated by laser cladding technology. The microstructure and corrosion resistance of the coatings were studied in detail to understand the mechanism of the UV on amorphous coatings. It can be found that the cavitation effect generated by UV refines and breaks the columnar crystals at the interface. Compared to the coatings without UV, the average length of columnar crystals of coatings with UV decreases by 57.52 %, reducing from 25.26 ± 5.89 μm to 10.73 ± 3.91 μm. In addition, the sound pressure gradient drives the accelerated flow of the molten pool, resulting in a flow velocity of up to 0.134 m/s. The acoustic streaming effect of UV promotes the uniform distribution of elements and inhibits the segregation of the intermetallic compounds, which increases the amorphous content from 68.5 % to 75.3 %. The acoustic streaming and cavitation effects refine the microstructure and increase the amorphous content by using of UV, which contributes to improve the corrosion resistance. [ABSTRACT FROM AUTHOR]

• A deep learning framework for identifying flow boiling regimes is developed. • An acoustic dataset of flow boiling is built by performing experiments. • A highly accurate CNN model based on boiling acoustic spectrograms is constructed. • A transfer learning strategy is proposed to adapt the CNN to noise interference. • A decision logic is added to enable the CNN to achieve real-time identification. Monitoring two-phase cooling systems and identifying corresponding boiling regimes are vital to avoid device failure owing to thermal runaway. Boiling acoustic characteristics can be used to develop a nonintrusive monitoring tool because of its close relation to the bubble behavior. Compared with bubble image-based techniques, acoustic sensing is cheaper and easier to implement. However, the acoustic data available is very limited, especially for flow boiling. Also, real-time strategies are still lacking since the prediction models based on boiling acoustics are usually offline. Additionally, noise interference typically degrades model prediction performance. To promote the implementation of an automated boiling system amidst these challenges, we present a deep learning framework for real-time identification of boiling regimes using acoustic signals of flow boiling. Flow boiling experiments are first performed using HFE7100 under different conditions and then combined with deionized water data from our previous experiments to construct the acoustic dataset. We use the corresponding acoustic spectrograms to train and test a convolutional neural network which shows a prediction accuracy of 99.97 % without noise interference. A transfer learning strategy is further employed to improve the original model performance under noise interference. Finally, we add a decision logic to adapt the CNN model to acoustic data streams for real-time identification of boiling regimes. The CNN model with the decision logic can accurately identify the boiling regimes in real-time by scanning the corresponding spectrograms irrespective of working fluids and conditions. In practice, our strategy can be utilized to initiate the necessary precautions to avoid overheating-induced failure. [ABSTRACT FROM AUTHOR]

• Boundary-driven acoustic streaming (AS) induced by both flat and curved walls is studied experimentally and numerically. • The Chladni figures formed in a semi-circular channel are similar to those observed in a circular channel. • PIV accurately measures the AS fields generated by the motion of 1 µm particles, which aligns with simulations. • The ratio of AS velocity generated by the curved wall and that by the flat wall depends on the acoustic modes. While boundary-driven acoustic streaming in fluids surrounded by flat walls has been extensively studied in the literature, theoretical studies on boundary-driven acoustic streaming generated by curved walls have recently emerged. This paper aims to present a quantitative analysis of acoustic streaming fields driven by forces induced by both flat and curved walls. A semi-circular channel made of stainless steel was designed to serve as a model channel with both flat and curved boundaries. A multi-layered glass-steel-glass device, actuated by a piezoelectric transducer, was assembled for experimental characterization of boundary-driven acoustic streaming in such scenarios. First, the various standing acoustic modes in the semi-circular channel were measured through the acoustophoretic patterning of 20 µm polystyrene particles. Next, the acoustic radiation force fields and boundary-driven acoustic streaming patterns under various resonant acoustic modes were characterized through micro-particle-image-velocimetry measurements of the motion of 20 µm and 1 µm polystyrene particles, respectively. Finally, the experimental results were explained using efficient finite element simulations of acoustofluidics and acoustophoresis in a semi-circular reduced-fluid model, with a focus on analyzing the streaming velocities driven by the flat and curved walls. Both experimental and numerical results demonstrated that the ratio of streaming velocities induced by the flat wall and the curved wall in this semi-circular channel depends on the resonant acoustic modes. This research highlights the diverse boundary-driven acoustic streaming patterns that arise in irregular channels and provides a theoretical foundation for choosing strategies for shape optimization to suppress acoustic streaming in acoustofluidic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Induced the acoustic streaming to accelerate gas bubbles to escape the molten pool. • Drag force causes the significant differences in the motion trajectories of bubbles under acoustic streaming. • Using acoustic streaming to concentrate non-escape bubbles at the molten pool edge. • The hybrid processing methods has enhanced the porosity reduction effect by ultrasonic effect. Pore defect plays an important factor on leading to a decrease in the strength performance and reliability of deposition layers manufactured by directed energy deposition (DED). The ultrasonic energy field assistant method usually improves the structure of materials, now is induced to reduce porosity by acoustic streaming driven effect in directed energy deposition process. In this work, 1Cr12Ni3MoVN powder (29% hollow particles) was used to controllable generate bubbles in the molten pool to induce the imperfect deposition conditions in the experiments. The distribution of pores with different laser processing parameters under ultrasonic vibration (UV) was investigated, and the principle that ultrasonic vibration drives the bubble motion under the complex physical environment was also analyzed by numerical simulation. The results show that acoustic streaming lead by UV effect, in competition with other flows (Marangoni flow and non-isothermal flow), makes the small bubbles to escape or large bubbles to move toward the edge of the molten pool. In general, UV reduces porosity from an average of 0.61% to 0.31%. Combined with the subtractive method, the porosity reduction rate has been improved from 45% to 82%. UV finally resulted in an average increase of 17% in the elongation of the material. This work provides the understanding on the driving effect of acoustic streaming on bubble motion and guide a novel way to reduce the porosity of DED technology. [ABSTRACT FROM AUTHOR]

• Innovative AI-based approach to designing an acoustofluidic micromixer is proposed. • Response Surface Methodology is used to mathematically model the system. • Metaheuristic algorithms and RSM are employed to for data-driven optimization. • DE outperformed NSGA-II in finding optimal solutions with better functionalities. • Number of sharp edges significantly influences mixing efficiency in high voltages. Micro-mixing is an essential step in various biological and chemical analyses and synthesis processes. In the present study, an acoustofluidic micromixer is designed, modeled, and its functionality has been investigated. Intelligent acoustofluidic is proposed as an evaluation-optimization method, based on Machine Learning algorithms. The first step involves designing a parametric geometry with multiple sharp edges. Following that, mathematical modeling of the system is carried out using Response Surface Methodology (RSM) and computational fluid dynamics (CFD). Geometrical parameters including the sharp edge tip angle and the channel thickness, along with the peak-to-peak actuation voltage were investigated. It was revealed that, due to the inherent nonlinearity of acoustic streaming, each design parameter could significantly impact the flow patterns and mixing performance of the acoustofluidic mixer. The mathematical surrogate model obtained from data-based modeling procedure is then employed for the artificial intelligence multi-objective optimization algorithms, i.e. Differential Evolution (DE) and Non-dominated Sorting Genetic Algorithm two (NSGA-II). The two objective functions are the mixing index and the mechanical energy consumption index (ME). The derived optimum solutions had low Mehcanical Energy (ME) values while yielding homogeneity in a wide range of applied voltages. This ensures the controllability of the proposed system, which is an invaluable feature in synthesis processes to determine the critical physical properties of the nanoparticles. Through the algorithm evaluation process, which was conducted to distinguish the more accurate and robust optimization method, it was revealed that the DE algorithm outperformed NSGA-II in generating optimum solutions with superior functionalities. In the final section, three optimum models, operating under three different V p - p values, 10, 20, 30, were selected, and their acoustofluidic characteristics were analyzed. It was concluded that utilizing baffles with three sharp edges at low V p - p values results in a 96% Mixing Index and 48% decrease in the power consumption of the system. However, at high V p - p values, baffles with one sharp edge demonstrated superior mixing functionality, with a MI of 98%. Moreover, it is revealed that utilizing baffles with three-sharp edges results in an 80% increase of Mixing Index of the acoustofluidic micromixer. [ABSTRACT FROM AUTHOR]

The application of sonoelectrochemical (SEC) oxidation technique involving the incorporation of ultrasound irradiation into an electrochemical oxidation system has found enormous success for various purposes, especially for organic synthesis and water treatment. Although its industrial application towards the removal of organic contaminants in water is not popular, its success on the laboratory scale is often attributed to the physical and chemical effects. These effects arise from the influence of ultrasound irradiation, thus eliminating electrode passivation or fouling, improving mass transfer and enhancing reactive oxygen species (ROS) generation. The continuous activation of the electrode surface, improved reaction kinetics and other associated advantages are equally occasioned by acoustic streaming and cavitation. This review hereby outlines common ROS generated in SEC oxidation and pathways to their generation. Furthermore, classes of materials commonly employed as anodes and the influence of prominent operational parameters on the performance of the technique for the degradation of organic pollutants in water are extensively discussed. Hence, this study seeks to broaden the significant promises offered by SEC oxidation to environmentally sustainable technology advances in water treatment and pollution remediation. [Display omitted] • Generation of reactive oxygen species (ROS) in sonoelectrochemical oxidation systems. • Common and emerging classes of anodic materials in sonoelectrochemical oxidation. • Influence of operating parameters on ROS generation and overall efficiency of sonoelectrochemical oxidation. [ABSTRACT FROM AUTHOR]

• The acoustic wave effects on array flow field forces and turbulence are evaluated. • The sound intensity effect on array surface vortex shedding frequency is clarified. • The effects of sound frequency and pressure level on the Nusselt number are examined. • Acoustic waves can enhance convective heat transfer on the surface of arrays. In this paper, a combination of numerical simulation and experimental investigation is carried out. A study on the effect of low-frequency acoustic waves on the flow field and convective heat transfer in the unit structure of a staggered heat exchanger is presented. Air is considered as background free flow, with a Reynolds number of 200. The range of the pipe pitch ratio is 2.2–5, the frequency range of the sound wave is 50–200 Hz, and the range of the sound pressure level is 115–135 dB. The results highlighted that the reattachment phenomenon on the downstream cylindrical surface gradually disappeared with the addition of external acoustic perturbation. Additionally, the lift coefficient increases with an increase in the sound pressure level, and the larger the pitch ratio, the greater the vortex shedding frequency. At the same time, the drag coefficient also increases. As both the sound frequency and pressure level increase, the array surface localization and average Nusselt number increase. In particular, when S/D = 5, multiple acoustic incidences and reflections occurred on the wall at the array gap. According to the acoustic superposition principle, it is noted that the acoustic energy reinforced the fluid flow at the gap. This leads to an improvement of 75 % in the array surface-averaged convective heat transfer compared to the acoustic perturbation case with no sound. The findings of the experiments demonstrated the ability of acoustic waves to enhance convective heat transfer on the surface of cylindrical arrangements. [ABSTRACT FROM AUTHOR]

A novel approach was proposed to prepare carbides reinforced Inconel 718 alloy composites by ultrasonicating graphite mold to introduce carbon element into liquid phase. The graphite mold was designed to resonate with three-dimensional (3D) power ultrasounds, which stimulated cavitation effect and acoustic streaming to promote uniform carbon dispersion and the subsequent incorporation of various carbides with alloy solidification process. It was found that the carbon content infiltrated into liquid alloy increased with ultrasound amplitude and dimension, which attained the maximum of 2.64 wt% C. Ultrasound accelerated the peritectic L+TiC→NbC reaction, forming a blocky (Ti, Nb)C phase instead of shell-core structured (TiC+NbC) phases. A new (Cr, Fe) 7 C 3 phase was produced due to the extended carbon solubility into liquid alloy under 3D ultrasounds. Meanwhile, the synergistic orientation relationships between γ(Ni) and carbide phases were enhanced by high-frequency vibration. The ultrasonically solidified composites exhibited excellent wear resistance and hardness as compared with other IN718 alloy-based composites. • The carbides/IN718 composites are firstly prepared by power ultrasound. • Ultrasound induces formation and dispersion of (Nb,Ti)C and (Cr,Fe) 7 C 3 carbides. • Coherence of interfaces between γ(Ni) and (Nb,Ti)C phases is enhanced by ultrasound. • Ultrasound significantly improves both wear resistance and hardness of composites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acoustic wave-aided particle filter multiphysics modeling. • Capture efficiency of fiber filters soars through external standing acoustic waves. • Suspended particles are attracted to fibers by radiation forces and acoustic streaming. • The average acoustic radiation force scales linearly with the average scattered pressure. • The solid fraction influences the scattered pressure more than disorder. Indoor air pollution affects millions of people worldwide. Conventional air purification techniques struggle to balance between safety, power consumption, efficacy, and cost. Acoustics have previously been leveraged to improve air purification with fiber filters, but little is known about how the arrangement of the fibers influences the acoustic effects, particularly for non-agglomerative purification performance relevant to fine and ultrafine pollutants. Here, we explore performance enhancements to fiber filters by applying external standing acoustic waves. We investigate the effects of the porous media arrangement in ordered (aligned and staggered) and disordered fiber media by building a multiphysics model, incorporating thermos-viscous acoustics, laminar flow, and particle tracing. Particles are modeled as point forces to isolate acoustic radiation forces and streaming. Attractive acoustic radiation forces dominate in the porous domain, leading to increased particle/boundary interactions. We find that the average acoustic radiation forces scale linearly with the average scattered acoustic pressure by the fiber medium. The scattered pressure varies depending on the fiber arrangement, indicating that there is an optimal design to increase the performance of acoustic-induced effects. We show a dramatic increase in performance efficiency, up to two orders of magnitude (123 times) for a staggered domain. This work has important applications to further advance acoustically enhanced filtration as a compelling solution for micro/nanoparticle separation processes. [ABSTRACT FROM AUTHOR]

Accurate measurement of flue gas velocity is of great significance for the safe production, energy saving, and emission reduction of coal-fired power plants. In this paper, a method of flue gas velocimetry based on a hyperbolic chirp-modulating acoustic source was proposed, and its superiority was verified by numerical simulations and field experiments. For an acoustic velocimeter, it is crucial to ensure the accuracy of the acoustic Time-of-Flight (TOF), which directly affects the flue gas velocity measurements. The improvement of the accuracy of estimation of the TOF directly determines the accuracy of the flue gas velocity measurement. Simulation on the different types of acoustic sources at different signal-to-noise ratios (SNRs) was conducted, and the results proved that the hyperbolic chirp signal is more accurate in the measurement of TOF. In the strong noise range of − 10 dB to − 20 dB, the average relative root mean square error (RRMSE) obtained using this hyperbolic chirp modulating acoustic source is 0.60 dB and 0.36 dB lower than obtained using the linear and logarithmic modulating modes, respectively. The average relative error (RE) is approximately 0.87 times that of the linear chirp. Power plant flue field experiments show that the measurement error using this hyperbolic modulating mode is about 0.52 times and 0.74 times that of using linear and logarithmic modulating modes, respectively. In harsh measurement environments with strong noise, the proposed acoustic source modulation scheme can significantly improve the measurement SNR and effectively enhance the accuracy and robustness of flue gas velocimetry. [Display omitted] • The proposed method is a flue gas velocimetry method based on a hyperbolic chirp modulating acoustic source. • This method can be applied to the non-contact measurement of velocity of gaseous media in coal-fired power plants. • The proposed method is able to iomprove the estimation accuracy of acoustic TOF. • The proposed method offers better noise resistance, and reduced attenuation. [ABSTRACT FROM AUTHOR]

The accurate and efficient manipulation of particles and droplets is crucial for the fields of disease diagnosis, target drug delivery, and sample purification, specific microstructure-based particle and droplet manipulation have been widely utilized in bioassays. However, current techniques are mainly based on the fixed microstructures, which is extremely difficult to achieve dynamic modulation by adjusting microstructure morphology and excitation conditions. Herein, we present a novel particle capture and droplet manipulation methodology by using morphologically reconfigurable magnetic micropillar arrays incorporate with acoustic streaming effects, which enables reconfigurable particle capturing, cargo transportation, and droplet manipulation. The mechanism is to assemble NdFeB magnetic powders by magnetic gradient fields to form morphologically variable magnetic micropillar arrays with porous surfaces, and the localized acoustic streaming effects generated by surface acoustic waves (SAWs) enable micropillar arrays to capture nearby particles onto the surfaces or to drive perturbations in droplets in the vicinity. To demonstrate the capabilities of this technology, we have achieved the high-volume acoustofluidic particle capture and loading (0.214 MCF), targeted complex maze navigation, efficient droplets manipulation (≤ 3.96 mm/s), and acoustofluidic mixing acceleration (≤ 2.5 s). Therefore, this technique enables reconfigurable and versatile manipulation of particles and droplets in biomedical applications. [Display omitted] • A manipulation method using magnetic micropillars with acoustic streaming effects. • The technique enables reconfigurable capturing, transportation, and manipulation. • Magnetic micropillars are morphologically reconfigurable by modulating magnetic fields. [ABSTRACT FROM AUTHOR]

An ultrasonic-assisted resistance spot welding process, which can improve the quality of aluminum/steel spot-welded joints, has been developed. However, the mechanism of the thermal-electrical-mechanical behavior caused by the ultrasonic longitudinal vibration to welding process has not been clarified. In this study, the role and impact mechanisms of ultrasonic longitudinal vibration during the welding process to form joints were confirmed by combining the microstructural characterization of the formed joints with the signal analysis of the process, as well as the analysis of the independent finite element numerical calculation results. Additionally, the interface metallurgical reaction behavior, welding defects, fracture behavior, and joint strength characteristics of ultrasonic-assisted aluminum/steel resistance spot welding joints were comprehensively analyzed, and the results indicated that the sizes of the aluminum/steel nuggets decreased. It could be attributed to the competition among multiple ultrasonic effects. Specifically, ultrasonic vibration decreased the contact resistance between the aluminum/steel sheets, whereas the acoustic cavitation and acoustic streaming effects increased the electrical conductivity of molten steel and thermal conductivity of molten aluminum, respectively. Moreover, ultrasonic vibration promoted the radial creep of molten and near-molten aluminum, which expanded in the effective bonding area between the two workpieces. Furthermore, ultrasonic vibration effectively reduced the thickness of the intermetallic compound layer (<3.0 µm), concurrently inhibited the formation of interfacial welding defects. Finally, the peak tensile-shear load of aluminum/steel joints is significantly increased under multiple ultrasonic optimization mechanisms. [Display omitted] • The ultrasonic effects are introduced into the computational model for aluminum/steel resistance spot welding process. • The effect mechanisms of ultrasonic vibration on the aluminum/steel resistance spot welding process were explored. • Ultrasonic vibration facilitates the radial creep of molten and near-molten aluminum, which can expand the bonding area. • Ultrasonic vibration decreases nugget sizes by reducing contact resistance, increasing thermal and electrical conductivity. [ABSTRACT FROM AUTHOR]

Ultrasonic microneedle patches, a class of ultrasound-driven transdermal drug delivery systems, are promising in addressing bacterial biofilms. This device has been proven to be more effective in treating Staphylococcus aureus biofilms than drug in free solution. However, there exists a notable gap in understanding how various excitation conditions and material parameters affect drug delivery efficiency. This study aims to fill this void by conducting an comprehensive multi-physics numerical analysis of ultrasonic microneedle patches, with the ultimate goal of enhancing drug delivery. First, we investigate the impact of various ultrasound frequencies on drug penetration depths. The findings reveal that local resonance can accelerate drug release within a shorter time window (first 1.5 h), whereas non-resonant frequencies enable more profound and prolonged diffusion. This information is crucial for medical professionals in selecting the most effective frequency for optimal drug administration. Furthermore, our investigation extends to the effects of applied voltage on temperature distribution, a critical aspect for ensuring medical safety during the application of these patches. Additionally, we examine how particles of different sizes respond to acoustic pressure and streaming fields, providing valuable insights for tailoring drug delivery strategies to specific therapeutic needs. Overall, our findings offer comprehensive guidelines for the effective use of ultrasonic microneedle patches, potentially shifting the paradigm in patient care and enhancing the overall quality of life. [Display omitted] • Numerical simulations of drug diffusion reveal the effect of acoustic streaming and pressure fields, both at resonant and non-resonant frequencies. Our findings indicate that at resonant frequencies, the microneedle can create multiple localized streaming vortices, leading to an accelerated drug delivery within a short time window. On the other hand, non-resonant frequencies help drug to penetrate deeper tissues. • Drug delivery efficiencies under different excitation voltages are examined. More importantly, temperature distributions of different voltages are numerically simulated, which helps to prevent overheating and ensure medical safety during administration. • The dynamic behaviors of drug particles of different sizes under acoustic forces are investigated, and particles trajectories in response to acoustic streaming drag and acoustic radiation forces are simulated. We found that motions of small-size particles are dominated by streaming drag force, while large-size ones follow the distribution of Gor'kov potential induced by acoustic radiation force. [ABSTRACT FROM AUTHOR]

• Transfer thickness space size to length space. • Gradient thickness synergistic broadband noise reduction. • Axial and radial coordinated ultra-thin noise reduction coating. • Achieve low-frequency broadband noise reduction for pipeline ventilation. This paper proposes a method of designing a metasurface muffling coating for pipeline ventilation and noise reduction, which realises low-frequency broadband noise reduction by laying ultra-thin labyrinth-channel acoustic absorbing metasurface structures on the inner wall surface of the pipeline. With the advantage of relatively loose size constraints in the length direction of the fluid conveying pipeline, the thickness dimensions required for low-frequency broadband sound absorption are transferred to the length direction, which significantly increases the effective ventilation area, and the ventilatable area is as high as 55.5 % of the overall structural section area. Since sound waves can be gradually attenuated in the pipeline as the fluid medium flows along the length of the pipeline rather than needing to be attenuated at the same time as in a flat plate acoustic structure, the performance requirements of the acoustic structure are substantially reduced, enabling a significant increase in the operating bandwidth. We have tried the arrangement method of coating layers with gradient thickness, which shows that the combination of different thicknesses of metasurface coating layers can broaden the muffling frequency band and improve the transmission loss of the muffling structure. The design is equally suitable for the noise reduction of liquid-filled piping systems, and the peak transmission loss can be as high as 54.6 dB, which represents a pleasing combination of low-frequency muffling and lightweight design, as well as excellent ventilation capability, and embraces a promising future for application. [ABSTRACT FROM AUTHOR]

• The effect of oscillating flow induced by acoustic waves is greatly influenced by the natural convection effect. • The relative Nusselt numbers decrease exponentially with the increase of Strouhal number. • Acoustic waves can not only enhance the convective heat exchange process but also hinder the heat transfer process. • Low-frequency acoustic streaming and high-frequency oscillatory flow are the main mechanisms affecting heat transfer. This study has experimentally investigated the heat transfer characteristics of a heated steel pipe (diameter = 20 mm) placed horizontally in a vertical experimental cylindrical pipe under longitudinal sound waves. The ranges of sound parameters used in this study are as follows: sound frequency f = 210–1000 Hz, and sound pressure level SPL = 125–135 dB. The heat transfer coefficient and Nusselt number of the cross- section of the heated pipe are used to describe the influence of different sound parameters on the heat transfer behavior of the heated pipe. The results show that under the action of low-frequency strong sound wave (f < 230 Hz), the distribution of local Nusselt number of heated pipe decreases (0-90°) at first and then increases (90-180°), while under the action of high-frequency strong sound wave (f > 500 Hz), the distribution of local Nusselt number first increases and then decreases. The relative Nusselt number decreases exponentially with the increase of the Strouhal number. In addition, the oscillating flow induced by sound waves is greatly influenced by the natural convection. The local enhancing or weakening effects of strong sound waves with different parameters on the heat transfer in a hot steel pipe are related to the characteristics of local flow. [ABSTRACT FROM AUTHOR]

Compared with the conventional method of transcranial focused ultrasound stimulation using a single transducer or a focused beam, the compression and tensile forces are generated from the high-pressure gradient of a standing wave that can generate increased stimulation. We experimentally verified a neuromodulation system using patterned interference radiation force (PIRF) and propose a method for obtaining the magnitude of the radiation force, which is considered the main factor influencing ultrasound neuromodulation. The radiation forces generated using a single focused transducer and a standing wave created via two focused transducers were compared using simulations. Radiation force was calculated based on the relationship between the acoustic pressure, radiation force and time-averaged second-order pressure obtained using an acoustic streaming simulation. The presence of the radiation force was verified by measuring the time-averaged second-order pressure generated due to the radiation force, by using a glass tube. [ABSTRACT FROM AUTHOR]

[Display omitted] The application of ultrasound and acoustic cavitation in liquid exfoliation of bulk layered materials is a widely used method. However, despite extensive research, the fundamental mechanisms remain far from being fully understood. A number of theories have been proposed to interpret the interactions between cavitation and bulk layered materials and hence to explain the mechanisms of ultrasound assisted exfoliation. Unfortunately, most of the research reported to date is ambiguous or inconclusive due to lack of direct real-time experimental evidence. In this paper, we report systematic work characterising cavitation emissions and observing the exfoliation of graphite in situ, in deionised water under the dynamic interaction with laser and ultrasound induced cavitation bubbles. Using ultra-high-speed optical imaging, we were able to determine the dynamic sequence of graphite exfoliation events on a time scale never reported before. Real-time observations also revealed that shock waves with a pressure magnitude up to 5 MPa and liquid-jets in the range of 80 ms−1, from transient cavitation bubble implosions, were essential for the initiation and propagation of the exfoliation process. On the other hand, bubble oscillations associated with stable cavitation were beneficial for promoting a gentler delamination of graphite layers. [ABSTRACT FROM AUTHOR]

The effect of acoustic streaming generated due to a standing wave over a flat plate in the presence of a magnetic field has been discussed. Due to this unsteadiness, the flow is divided into two regions: the boundary layer region and the core flow region. Invoking successive approximation method, we found the velocity expression for the core region confirming that the velocity is independent of viscosity but depends on a magnetic field and is used to demonstrate the Couette flow. [ABSTRACT FROM AUTHOR]

Future wearable technology may provide for enhanced communication in noisy environments and for the ability to pick out a single talker of interest in a crowded room simply by the listener shifting their attentional focus. Such a system relies on two components, speaker separation and decoding the listener's attention to acoustic streams in the environment. To address the former, we present a system for joint speaker separation and noise suppression, referred to as the Binaural Enhancement via Attention Masking Network (BEAMNET). The BEAMNET system is an end-to-end neural network architecture based on self-attention. Binaural input waveforms are mapped to a joint embedding space via a learned encoder, and separate multiplicative masking mechanisms are included for noise suppression and speaker separation. Pairs of output binaural waveforms are then synthesized using learned decoders, each capturing a separated speaker while maintaining spatial cues. A key contribution of BEAMNET is that the architecture contains a separation path, an enhancement path, and an autoencoder path. This paper proposes a novel loss function which simultaneously trains these paths, so that disabling the masking mechanisms during inference causes BEAMNET to reconstruct the input speech signals. This allows dynamic control of the level of suppression applied by BEAMNET via a minimum gain level, which is not possible in other state-of-the-art approaches to end-to-end speaker separation. This paper also proposes a perceptually-motivated waveform distance measure. Using objective speech quality metrics, the proposed system is demonstrated to perform well at separating two equal-energy talkers, even in high levels of background noise. Subjective testing shows an improvement in speech intelligibility across a range of noise levels, for signals with artificially added head-related transfer functions and background noise. Finally, when used as part of an auditory attention decoder (AAD) system using existing electroencephalogram (EEG) data, BEAMNET is found to maintain the decoding accuracy achieved with ideal speaker separation, even in severe acoustic conditions. These results suggest that this enhancement system is highly effective at decoding auditory attention in realistic noise environments, and could possibly lead to improved speech perception in a cognitively controlled hearing aid. [ABSTRACT FROM AUTHOR]

Modulation of intra-cellular calcium by ultrasound offers a possible means for therapeutic applications. One such possibility is the modulation of nucleus pulposus cells as a preventive measure for inter-vertebral disc degeneration. We report a cellular stimulation device (micro-pipette ultrasound) using a glass micro-pipette as a waveguide to deliver ultrasound through the pipette tip and to elevate intra-cellular calcium in nucleus pulposus cells. The device generates two relevant stimuli at the cellular level: ultrasound propagation throughout the cell and acoustic streaming on the apical side. Ultrasound is radiated from a tip of a few microns, and its amplitude is proportional to the input voltage; acoustic streaming can be controlled by the duty factor. The novelty of the device is to impose a unique cellular loading: shear stress on cell apical surfaces combined with compressional waves propagating through the cells. G protein-coupled receptors and acid-sensing ion channel 3 were shown to play a role in calcium elevation by micro-pipette ultrasound in nucleus pulposus cells. Our results demonstrate that micro-pipette ultrasound can be an effective tool to elevate intra-cellular calcium levels in different cells, facilitating the identification of different mechanoreceptors in action. [ABSTRACT FROM AUTHOR]

In order to calculate the noise field distribution in the main transformer room of an indoor substation accurately, a thermal-acoustic coupling idea was introduced, and a noise field solving the algorithm based on thermal-acoustic coupling was proposed in view of the noise quality loss caused by the effect of ambient temperature changes. Firstly, the fluid-structure coupling model of the main transformer room is established, and the computational fluid dynamics method is used to calculate the flow field distribution and temperature boundary conditions under the action of the heat source; Then, extracting the rheological equation of the environmental boundary conditions in the flow field calculation, and use the difference function to couple the rheological equation to the sound grid to obtain the sound field coupling model under the condition of variable temperature; Finally, the modified parameter acoustic integral equation under the sound field coupling model is calculated based on the conventional Gauss numerical integration method, and the sound field of the main transformer room considering the effect of variable temperature is obtained. The algorithm has been successfully applied in the analysis of the noise field of Xi'an 110 kV Zhenxing Substation, and the error with the measured value is 2.083%. • Thermoacoustic coupling should be considered in the noise field of main transformer room. • Thermoacoustic coupling is calculated by bidirectional hysteresis coupling method. • The introduction of temperature rise parameters can improve the accuracy of acoustic FEM. • Thermoacoustic coupling should be considered in noise reduction of main transformer room. [ABSTRACT FROM AUTHOR]

Flow noise, part of hydrodynamic noise, significantly impacts the stealth capabilities of submarines. Investigating the noise source location and formation mechanism of flow noise is crucial for enhancing submarine stealth performance. This study uses large eddy simulation to examine the evolution of vortex structure in the SUBOFF submarine. The propagation of far-field noise from dipole and quadrupole noise sources of the SUBOFF is calculated, by rationally constructing a permeable integral surface in conjunction with the Ffowcs-Williams and Hawkings and "Collapsing-Sphere" formulations. The numerical results for both flow and acoustic fields are consistent with experimental data and previous numerical findings. Sail and rudder are the predominant dipole noise sources, due to turbulence effects from vortex shedding. The permeable integral surface effectively captures the quadrupole noise source. The quadrupole noise in the 2 kHz frequency range contributes 17 % to 26 % of the total noise energy. The location of the quadrupole noise source and its generation mechanism is explored, through the evolution of the vortex structure and the Lamb vector amplitude. Approximate scaling laws for far-field dipole and quadrupole noise spectra are given, thus illustrating the general laws in the frequency domain of the far-field noise. • The quadrupole noise source of the SUBOFF is captured using a permeable integral surface combined with a "collapsing-sphere" formulation. • Propagation characteristics of far-field noise from the SUBOFF dipole and quadrupole noise sources are investigated. • The location of the primary dipole and quadrupole noise sources of the SUBOFF are explored, first explaining its formation mechanism. • Approximate scaling laws for far-field dipole and quadrupole noise spectra are given. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) and three-dimensional (3D) ultrasounds were introduced into the solidification process of ternary Cu-2.8wt%Ni-0.7wt%Si alloy together with the in-situ measurements of acoustic fields. In the case of 1D ultrasound, stable cavitation was the main form of acoustic energy transmission. The grain size of α-Cu dendrites was reduced because stable cavitation improved the wetting between impurities and alloy melt, which further promoted nucleation process. When 3D ultrasounds were applied, transient cavitation was the dominant mode of acoustic energy dissipation. This induced local high undercooling in alloy melt, causing a significant increase in bulk nucleation rates and the formation of numerous tiny α-Cu equiaxed grains. Meanwhile, as ultrasonic dimension increased, the strengthened acoustic streaming accelerated solute and thermal diffusion and weakened the preferred orientation of growing α-Cu grains. The proportion of low-angle grain boundaries (LAGBs) increased consequently, which suppressed the nucleation and growth of δ-Ni 2 Si discontinuous precipitates (DPs) during subsequent annealing treatment. The tensile strength and electrical conductivity of 3D ultrasonically solidified alloy after annealing reached 688.2 MPa and 2.7×107 S/m respectively, showing obvious advantages in synergetic mechanical and electrical performances. [Display omitted] • The cavitation intensities inside liquid alloy were measured quantitatively. • Tiny equiaxed grains were obtained by 3D ultrasounds. • Ultrasonic solidification suppressed the δ-Ni 2 Si discontinuous precipitates. • The mechanical and electrical performances were improved synergistically. [ABSTRACT FROM AUTHOR]