Acoustic Effects Research Articles

Evaluation of acoustic environmental effects and improvement method of ecological fish-nest bricks in the Yangtze River Basin: A model-based case study

With the rapid development of the Yangtze River Basin, the issue of underwater noise pollution has become increasingly severe, which has adversely affected aquatic creatures, particularly fish. Ecological fish-nest bricks (EFNBs), a new type of eco-friendly revetment, can provide a favorable habitat for fish. However, its effects on the acoustic environment remain unclear. The finite element numerical simulation method of acoustic-structure coupling is adopted to explore the acoustic environment of EFNBs, analyzing the impact of sound source frequency (within 300 Hz), structural forms, and arrangement of these bricks on the internal sound pressure level. The sound pressure level distribution of A-EFNBs were also analyzed at a distance of 0–0.5 m from the opening. A method of acoustic environment improvement is proposed, which utilizes porous polyurethane sponge (PPS) sound-absorbing material to establish a conducive acoustic environment for fish in EFNBs. The study results indicate that at low frequencies of sound source (f ≤ 150 Hz), the sound pressure level within EFNBs slightly decreases compared to the adjacent areas without EFNBs. The sound pressure level variation within the bricks increases with sound source frequency. The peak sound pressure increases with the number of openings. Interval arrangements can in general decrease sound pressure by less than 20 dB. At higher frequencies(f＞200 Hz), the sound pressure level at the opening of the A-EFNBs tends to increase. However, the PPS sound-absorbing material substantially reduces the sound pressure level by 15 –55 dB, rendering it an effective method for improving the acoustic environment for fish. The PPS sound-absorbing material is more suitable for habitat improvement of black carp (Mylopharyngodon piceus) and grass carp (Ctenopharyngodon idellus) with relatively low hearing thresholds among the four famous Chinese carps. The research findings can serve as a reference for designing and implementing river ecological restoration projects.

The acoustic importance of velaria in Roman amphitheaters: Investigations on the effects of different coverage percentages in Durres and Capua

Roman amphitheaters were studied from an architectural perspective, as the geometry of elliptical or oval construction was always under discussion. The Roman amphitheaters of Durres and Capua were analysed with particular attention to the effects of the velarium on the acoustic response of the spaces. The investigations were conducted for the original shapes of the amphitheaters with different coverage percentages of the awning: no shading; half shading along the major axis; half shading along the minor axis; fully open to shade the entire seating area. The four scenarios were selected based on the shadow projection that the Romans might have used in ancient times; therefore, an additional solar analysis was performed for a summer-seasoned day based on a solar path found for the cities of Durres and Capua. The simulated results show that the acoustic effect of velarium was more efficient with half awning cut along the minor axis, as seen from the spatial distribution maps. However, the radiation analysis supports the thesis that 100% displayed surface area of the awning was in place when the cavea was fully occupied. Further discussions have been addressed based on a solar-radiation analysis of the two sites. This research study represents a scientific support for the movie industry that would like to reproduce the environment as existing in ancient times.

Development of a pump-jet piezoelectric swimmer with acoustic radiation actuation

The acoustofluidic actuation produced by piezoelectric transducer is capable of propelling micro underwater robots forward, yet the motion pattern is relatively simplistic. To solve this problem, a pump-jet swimmer with a combination of the underwater acoustic radiation effect is proposed in this work. The absorption and discharge of internal piezoelectric pump provide the linear forward power, and turning is achieved under the acoustic propulsive force of the external dual piezoelectric actuators. The working mode and optimal driving frequency of the piezoelectric actuators are determined through finite element simulation and mechanical vibration characteristic tests. And the key dimensional parameters of the piezoelectric pump are optimized in the light of the output flow measurements. Finally, a prototype with the size of Ф3.1 cm × 12 cm is fabricated for underwater driving performance experiments, which demonstrated well functions in straight swimming, turning, and loading. The swimmer with 20 g of additional load achieves a maximum speed of 105 mm s−1at the voltage of 180 Vp-p, it also completes the obstacle avoidance in water along a certain path. The rationality of this conceived actuation mechanism is preliminarily verified, which shows a potential for fixed-point transportation in the complex underwater situations.

Optimizing the Shape of Space-Constrained Silencers Composed of Multiple Straight/Reverse Chambers Using the Simulated Annealing Method

Abstract To address the issue of hearing health problems caused by the broadband noise emitted from space-constrained marine diesel engines on a ship, an efficient silencer equipped at the engine's venting outlet is necessary. In consideration of the space-constrained situation that often occurs in ships, a reverse silencer with multiple chambers is introduced. A mathematical model of eigenfunction is adopted to consider the acoustic effect in high frequencies. An optimization of the silencer will be performed using the acoustic model of an eigenfunction together with the Simulated Annealing (SA) method under space-constrained conditions to achieve the best design. To pursue an efficient silencer design, two types of reverse silencers (Silencers A and B) are adopted to reduce the engine's venting noise. Acoustical models for straight chamber and reverse chamber silencers are checked before optimization. To assure the reliability of the SA scheme, a pure tone optimization at 250 Hz is exemplified. Results in silencers A and B show that the Sound Transmission Loss is approximately maximized at the desired frequency. Thereafter, a broadband noise elimination of engine noise using silencers A and B is performed. Simulated results show that overall noise abatement can be improved when the number of inverse chambers increases. The optimization of space-constrained reverse silencers with multiple chambers using eigenfunction in cooperation with Simulated Annealing (SA) has been accomplished. The overall silencer system's four-pole matrix is used to predict the silencer's acoustical performance of STL, which is achieved by multiplying individual four-pole matrices. With the introduction of the reverse silencer, the hearing health of workers can be protected, and noise pollution can be reduced in industrial settings.

Dissociating prosodic from syntactic delta activity during natural speech comprehension

Decoding human speech requires the brain to segment the incoming acoustic signal into meaningful linguistic units, ranging from syllables and words to phrases. Integrating these linguistic constituents into a coherent percept sets the root of compositional meaning and hence understanding. One important cue for segmentation in natural speech is prosodic cues, such as pauses, but their interplay with higher-level linguistic processing is still unknown. Here, we dissociate the neural tracking of prosodic pauses from the segmentation of multi-word chunks using magnetoencephalography (MEG). We find that manipulating the regularity of pauses disrupts slow speech-brain tracking bilaterally in auditory areas (below 2Hz) and in turn increases left-lateralized coherence of higher-frequency auditory activity at speech onsets (around 25-45Hz). Critically, we also find that multi-word chunks-defined as short, coherent bundles of inter-word dependencies-are processed through the rhythmic fluctuations of low-frequency activity (below 2Hz) bilaterally and independently of prosodic cues. Importantly, low-frequency alignment at chunk onsets increases the accuracy of an encoding model in bilateral auditory and frontal areas while controlling for the effect of acoustics. Our findings provide novel insights into the neural basis of speech perception, demonstrating that both acoustic features (prosodic cues) and abstract linguistic processing at the multi-word timescale are underpinned independently by low-frequency electrophysiological brain activity in the delta frequency range.

Hydrodynamic and acoustic cavitation effects on properties of cellulose fibers

The cellulose pulp refining process is crucial for achieving high-quality paper characteristics. This research aims to enhance energy efficiency while maintaining good fiber quality using hydrodynamic and acoustic cavitation (HAC). Experiments were conducted with an in-house developed flow-through sonicator combined with a novel Venturi nozzle for hydrodynamic cavitation. The Venturi design was determined by analytical modeling and verified by CFD simulation with multi-phase turbulence models to balance cavitation intensity and turbulence against the acoustic cavitation effect. Experimental evaluation of two batches of CTMP fibers, pre-processed in different ways, showed significant improvements in paper strength and fiber properties. The best results for Batch 1 (HC and LC) were obtained with 386 kWh/bdt for AC and 350 kWh/bdt for HC (60 °C, 2 % concentration). The tensile strength index increased by 26 %, and the TEA-index, related to freeness, increased by 55 %. HAC treatment (750 kWh/bdt, 70 °C, 1.5 % concentration) of the less refined Batch2 (HC) yielded results better than the Batch 1 reference. These findings confirm the energy-efficient potential of the sonicator concept compared to traditional industrial processes. The conclusion is that HAC-refining of softwood pulp requires a proper balance between hydrodynamic and acoustic cavitation intensities. Both fiber concentration by weight and temperature are critical for an energy-efficient process.

The beneficial effect of transparent surgical masks on the communication of adults with hearing loss within clinical settings

Purpose: The study examined the benefits of transparent versus non-transparent surgical masks on the speech intelligibility in quiet of adult cochlear implant (CI) users, in conjunction with patient preferences and the acoustic effects of the different masks on the speech signal. Methods: Speech tracking test (STT) scores and acoustical characteristics were measured in quiet for live speech in three different conditions, without mask, with a non-transparent surgical mask and with a transparent surgical mask. Patients were asked about their experience with the face masks. The study sample consists of 30 patients using a cochlear implant. Results: We found a significant difference in speech perception among all conditions, with the speech tracking scores revealing a significant advantage when switching from the non-transparent surgical mask to the transparent one. The transparent surgical mask, although it does not transmit high frequencies effectively, seems to have minimal effect on speech comprehension in practice when lip movements are visible. This substantial benefit is further emphasized in the questionnaire, where 82% of the patients express a preference for the transparent surgical mask. Conclusion: The study highlights significant benefits for patients in speech intelligibility in quiet with the use of medically safe transparent facemasks. Transitioning from standard surgical masks to transparent masks demonstrates highly significant effectiveness and patient satisfaction for patients with hearing loss. This research strongly advocates for the implementation of transparent masks in broader hospital and perioperative settings.

Mathematical Modeling of Multi-Physics Phenomena in Smart Materials and Structures

Smart materials and buildings show interesting multi-physics effects, where the interaction of different physical fields like mechanics, electromagnetics, thermodynamics, and sound is very important. This essay gives an in-depth look at different mathematical modeling methods used to understand and predict how smart materials and buildings will behave in various situations. At its core, the modeling framework combines guiding equations from various physical fields. This calls for a comprehensive method that takes into account how these events interact with each other in complex ways. The basis is mechanics, which includes fundamental equations that show how materials react to mechanical forces, including elasticity, viscoelasticity, and flexibility. Electromagnetic effects are very important in materials like magnetostrictives and piezoelectrics, where the way electrical and mechanical fields combine determines how they work. To correctly describe this electrical connection, Maxwell's equations are linked to mechanical equations. This lets devices like sensors, motors, and energy harvesters be designed and improved. Thermodynamics is used for shape memory metals and phase change materials, whose behavior is controlled by changes in temperature. Adding heat transfer equations to mechanical and electromagnetic equations helps us fully understand how these materials interact with heat, motion, and electricity, which is important for many uses, from medical devices to spacecraft structures. Structures with active shaking control systems that use piezoelectric materials have interesting acoustic effects. With the help of mechanical and electrical algorithms and acoustic wave transmission models, it is possible to study and create smart structures that can reduce noise and shocks while also improving their performance and integrity. The study also talks about numerical methods, like finite element methods and multiphysics modeling tools, that can be used to quickly solve the linked equations. These tools help us learn more about how complicated materials behave in various working situations.

Phase-tuned acousto-optic spatial filter.

An acousto-optic (AO) tunable filter with a phase-controlled dual-section piezoelectric transducer is designed and created for laser beam shaping (LBS). Owing to the acoustic beam steering effect, we experimentally observe splitting of the two-dimensional transfer function. As a result, we demonstrate generation of tunable bottle laser beams and dual-ring intensity distributions for the diffracted beam.

Design and Optimization of One Special Microperforated Plate-Labyrinth Coupled Structure (MPPS-LS): From the View of Numerical Simulation

Controlling large-wavelength acoustic waves via small-size structures is an important direction for the field of noise control. Since porous acoustic material can only absorb low-frequency sound waves when their thickness is approximately one-fourth of the wavelength, such acoustic material is not effective when controlling the large-wavelength acoustic waves with small-size structures. Therefore, the resonant acoustic material has been usually chosen to absorb low-frequency sound waves instead. As a typical resonant acoustic material, microperforated plate structures (MPPS), need one large cavity with low space utilization to absorb the low-frequency acoustic waves. The microperforated plate-labyrinth coupled structure (MPPS-LS) has been proposed with the goal of improving low-frequency sound absorption ability, which is consisted of a MPPS and three separated second-order LS coupled together. The mathematical model has been established using the acousto-electric analogy method and transfer matrix method to examine the impact of the structural parameters of each part on the acoustic characteristics. According to this study, the coupled structure is compact in size and has a good low and medium-frequency acoustic absorption effect, combining low and medium-frequency acoustic absorption characteristics of both the MPPS and LS. The sound absorption of the structure after optimized design is testing using impedance tube.

Sonodynamic and sonomechanical effect on cellular stemness and extracellular physicochemical environment to potentiate chemotherapy

BackgroundHypoxia-activated prodrug (HAP) is a promising candidate for highly tumor-specific chemotherapy. However, the oxygenation heterogeneity and dense extracellular matrix (ECM) of tumor, as well as the potential resistance to chemotherapy, have severely impeded the resulting overall efficacy of HAP.ResultsA HAP potentiating strategy is proposed based on ultrasound responsive nanodroplets (PTP@PLGA), which is composed of protoporphyrin (PpIX), perfluoropropane (PFP) and a typical HAP, tirapazamine (TPZ). The intense vaporization of PFP upon ultrasound irradiation can magnify the sonomechanical effect, which loosens the ECM to promote the penetration of TPZ into the deep hypoxic region. Meanwhile, the PpIX enabled sonodynamic effect can further reduce the oxygen level, thus activating the TPZ in the relatively normoxic region as well. Surprisingly, abovementioned ultrasound effect also results in the downregulation of the stemness of cancer cells, which is highly associated with drug-refractoriness.ConclusionsThis work manifests an ideal example of ultrasound-based nanotechnology for potentiating HAP and also reveals the potential acoustic effect of intervening cancer stem-like cells.Graphical

Research on enhanced mass transfer using audible acoustic agglomeration technology

Currently, tail flues of coal-fired power plants are treated using wet desulfurization process to remove pollutants. But, the treated flue gas has a significant moisture loss and this process also contributes to environmental pollution. Acoustic agglomeration is a non-contact treatment process that can effectively solve the problem of moisture loss in flue gas; however, there are few theoretical and experimental studies on acoustic droplet agglomeration applied to coal-fired power generation. In this paper, an experimental platform for acoustic droplet agglomeration is demonstrated to recover moisture. Further, the effects of important factors such as acoustic frequency, sound pressure level and droplet flow rate on the agglomeration efficiency are investigated. The experimental results show that there are two optimal frequencies exist, namely 500 Hz and 1200 Hz, for the droplets used in this experiment with acoustic droplet agglomeration. A highest efficiency of 58% is achieved at 500 Hz. The acoustic action differs between the 500 Hz and 1200 Hz cases. The analysis suggests that the primary force driving droplet agglomeration at 500 Hz is likely the acoustic flow effect. On the other hand, the main mechanism behind acoustic agglomeration at 1200 Hz could be related to the acoustic wake effect. Sound pressure level is the primary factor affecting droplet agglomeration, and the agglomeration efficiency increases with sound pressure, reaching 96.7% at 150 dB. Furthermore, the agglomeration effect shows a positive correlation with droplet flow rate, while the agglomerated particle size also increases simultaneously. This research provides a new idea for moisture recovery, which could offer valuable insights for implementing acoustic droplet agglomeration and moisture recovery in power plants.

High-sensitivity narrow‑band T-shaped cantilever Fabry-perot acoustic sensor for photoacoustic spectroscopy

Photoacoustic spectroscopy (PAS) has been rapidly developed and applied to different detection scenarios. The acoustic pressure detection is an important part in the PAS system. In this paper, an ultrahigh sensitivity Fabry-Perot acoustic sensor with a T-shaped cantilever was proposed. To achieve the best acoustic pressure effect, the dimension of the cantilever structure was designed and optimized by finite element analysis using COMSOL Multiphysics. Simulation results showed that the sensitivity of such T-shaped cantilever was 1.5 times higher than that based on a rectangular cantilever, and the resonance frequency of T-shaped cantilever were able to modulate from 800 Hz to 1500 Hz by adjusting the multi-parameter characteristics. Experimental sensing results showed that the resonance frequency of T-shaped Fabry-Perot acoustic sensor was 1080 Hz, yielding a high sensitivity of 1.428 μm/Pa, with a signal-to-noise ratio (SNR) of 84.8 dB and a detectable pressure limit of 1.9 μPa/Hz1/2@1 kHz. We successfully used such acoustic sensor to measure acetylene (C2H2) concentration in the PAS. The sensitivity of PAS for C2H2 gas was 3.22 pm/ppm with a concentration range of 50 ppm ∼100 ppm, and the minimum detection limit was 24.91ppb.

A novel smart hybrid multimorph piezoelectric spherical shell cloak for broadband near-perfect underwater acoustic camouflage applications

Non-visual auditory camouflage plays a major role in the art of underwater deception. In this work, a hybrid active/semi-active omnidirectional cloaking shell structure composed of alternate complementary piezoelectric and smart viscoelastic (PZT/SVE) actuator layers is proposed that can effectively conceal a three dimensional underwater macroscopic object from broadband incident sound waves. The smart hybrid structure incorporates a finite sequence of fully active parallel-connected multimorph PZT constraining layers inter-stacked with semi-active SVE core layers both of which are collaboratively operative in the framework of a Particle Swarm Optimized (PSO) multiple-input multiple-output active damping control (MIMO-ADC) scheme. The elasto-acoustic modeling of the problem is conducted by coupling the spatial state space methodology based on the classical three-dimensional exact piezoelasticity theory with the wave equations for the inner and outer acoustic domains. The acoustic cloaking performance of proposed configuration is evaluated for four distinct classes of highly functional SVE interlayer materials with tunable (field-dependent) rheological properties, namely, magnetorheological elastomer (MRE), shape memory polymer (SMP), electrorheological fluid (ERF), and magnetorheological shear thickening polishing fluid (MRSTPF). Extensive numerical results reveal significant broadband reductions of the far-field backscattering amplitude in the (f∞θ=π,kexRex)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left|{f}_{\\infty }\\left(\ heta =\\pi ,{k}_{\ ext{ex}}{R}_{\ ext{ex }}\\right)\\right|)$$\\end{document} as well as the percentage error of external cloaked field (%Err)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(\\%\ ext{Err})$$\\end{document} by incorporating a sufficient number of smart multimorph PZT/SVE material layers. Furthermore, it is concluded that comparable low frequency acoustic cloaking effects is possible without expenditure of any external energy just by employing the entirely inactive MRSTPF-based cloak as an alternative to the semiactive or fully active multimorph PZT/SVE cloaks. The outcome of proposed study can advantageously serve as the first step towards practical development and experimental implementation of future high performance smart acoustic cloaking devices with expanded broadband near-perfect omnidirectional invisibility for three dimensional objects of diverse geometries.

Robustness analysis and prediction of topological edge states in topological elastic waveguides

Topological elastic waveguides constructed using acoustic topological insulators have garnered significant attention due to their exceptional wave modulation properties. While the existence of these edge states is guaranteed by topology, their robustness to defects is unclear. In this paper, topological edge states based on the acoustic pseudo-spin Hall effect are constructed, and the robustness of the topological edge states is quantitatively studied by analyzing displacement fields of phononic crystal (PnC) plates with various defects. Our robustness assessment considers nearly all possible defect scenarios, focusing on the influence of defects on three primary indicators: transmittance, maximum displacement and its specific location on the PnC plate. The results indicate that the topological edge states formed by this structure are highly robust to defects with varying rotation angles, but exhibit limited robustness to defects of different dimensions or positions. Furthermore, a Light Gradient Boosting Machine (LightGBM) model is employed to predict the displacement along the wave transmission path in the presence of diverse lattice defects. The model emerges as an accurate predictor of displacement distribution changes, and thus can provide potential optimization strategies for topologically elastic waveguide-based energy harvesting systems and self-powered sensors.

Local defect resonance and nonlinearity of porosity air bubbles in solids

Acoustics of bubbles is quite developed field mainly due to multiple cavitation-related ultrasonic applications in liquids. New applications, which require detailed studies of ultrasound encounter with bubble in solid materials, have become apparent recently and are concerned with detectability of porosity in advanced solid materials based on layered technology, like composite and additive manufactured structures. To elucidate the transition from liquids to solids the present paper starts from theoretical similarity between both and proceeds to experimental study of the resonance acoustic effects of air bubbles in epoxy resin. The LDR frequencies are shown to be reciprocal to the bubble radius so that the latter can be evaluated if the frequency is known. The bubbles excited at the LDR frequencies and their subharmonics (superharmonic resonance) manifest extraordinary wide higher harmonic spectra that implies a nonlinear means for nondestructive testing of porosity in composites and other materials.

Computational study of gas-dynamic approach for noise reduction in atwo-stroke engine’s exhaust system

BACKGROUND: The traditional approach to designing exhaust mufflers relies heavily on energy dissipation. In the "gas-dynamic" approach, the flow of exhaust gases is equalized by introducing long channel(s) into the muffler to separate impulses and shift them in time. It is assumed that such mufflers will provide noise reduction without creating significant backpressure. AIMS: To evaluate the potential of the "gas-dynamic" approach to reducing the noise level of two-stroke internal combustion engines. MATERIALS AND METHODS: The study was carried out using computational models. The processes in the gas-air tract of the piston engine were calculated using a one-dimensional (1D) model. The noise characteristic was the effective sound pressure at a specified point in the environment, calculated using 2D model of propagation of disturbances in elastic medium. The object of study was a two-stroke gasoline two-cylinder engine RMZ-551i, with a resonator (providing gas-dynamic supercharging) and a muffler. Initially, the parameters and sound pressure level of the engine with the stock muffler at full load and close to nominal engine speed were calculated. Then, the structure of the stock muffler was modified by adding a "tuned" channel between its two chambers. The parameters of the modified muffler were optimized based on the criterion of reducing gas pulsations at the outlet to the atmosphere. The noise reduction of the muffler implementing the gas-dynamic approach was evaluated relative to the stock muffler and expressed in terms of sound pressure levels in dB. Performance and levels of sound pressure were finally calculated over a wide range of engine speeds. RESULTS: According to the computational estimate, the optimal implementation of the gas-dynamic approach in the muffler reduces exhaust noise by 7 dB, while engine power decreases by 2.5%. Calculation of the sound pressure level based on the external speed characteristic showed that at an engine speed of 3000 rpm, the calculated sound pressure exceedsby 8 dB the minimum (99 dB) obtained for the optimally "tuned" muffler at an engine speed of 5000 rpm. It is suggested that the gas-dynamic approach with optimization is also applicable for uniform noise reduction over a wide range of engine speeds, with a more complex structure of the exhaustmuffler. CONCLUSIONS: Theoretical evaluation of a muffler with a tuned channel connecting its two chambers was carried out, with a two-stroke engine RMZ-551i with a stock muffler as a basis for comparison. At the optimum point on the speed characteristic, the exhaust noise was reduced by 7 dB, while the calculated power decrease was insignificant. The authorsnote the suitability of the methodology for rapid assessments and automated computational optimization of mufflers that utilize wave effects. They also point out the limitations of the models used, which require validation or rather calibration based on experimental data, and the need for the development of applied models of acoustic effects and measuring devices for domestic CAE packages.

Magneto-acoustic Fusion Sensing for Surface and Subsurface Defect Differentiation in the Ferromagnetic Material

The conventional periodic permanent magnet (PPM) shear horizontal (SH0) guided wave electromagnetic acoustic transducer (EMAT) has a good detection capability for defects on both the surface and subsurface of the material. However, it is difficult to distinguish between surface and subsurface defects in the material using only the amplitude of the defect echo. In this paper, SH0 guided wave is excited using the SH0 guided wave EMAT with PPM configuration, which is used to achieve the detection and evaluation of defects on the surface and subsurface of ferromagnetic metal; on the other hand, the local magnetic field perturbation (MFP) effect of the PPM configuration on ferromagnetic material is fully exploited to achieve the identification of surface defects by picking up the MFP of the material at the defects. The proposed magneto-acoustic fusion effect sensor has an improved spatial magnetic field at both the mechanical construction and the magnetic sensor compared to the traditional magnetic flux leakage (MFL) detection method. Both simulation and experiment show that the proposed magneto- acoustic fusion effect sensing method based on the PPM configuration is capable of detecting the defects on the surface and subsurface of metal material, while the MFP effect in the fusion sensor can be used to help differentiate between the surface and subsurface defects in the material.

Starch nanoparticles with predictable size prepared by alternate treatments of ball milling and ultrasonication

In this study, starch nanoparticles (SNPs) were prepared by alternate treatments of liquid nitrogen ball milling and ultrasonication. The impact, shear and friction forces produced by ball milling, and acoustic cavitation and shear effects generated by ultrasonication disrupted starch granules to prepare SNPs. The SNPs possessed narrow particle size distribution (46.91–210.52 nm) and low polydispersity index (0.28–0.45). Additionally, the SNPs exhibited the irregular fragments with good uniformity. The relative crystallinity decreased from 34.91 % (waxy corn starch, WCS) to 0–25.91 % (SNPs), and the absorbance ratios of R1047/1022 decreased from 0.81 (WCS) to 0.60–0.76 (SNPs). The SNPs had lower thermal stability than that of WCS, characterized by a decrease in Td (temperature at maximum weight loss) from 309.39 °C (WCS) to 300.39–305.75 °C (SNPs). Furthermore, the SNPs exhibited excellent swelling power (3.48–28.02 %) and solubility (0.34–0.97 g/g). Notably, oil absorption capacity of the SNPs (9.77–15.67 g/g) was rather greater than that of WCS (1.33 g/g). Furthermore, the SNPs possessed the lower storage modulus (G′), loss modulus (G″) and viscosity than that of WCS. The SNPs with predictable size and high dispersion capability prepared in this study lay a foundation for expanding the application of SNPs.

Wave propagation in a honeycomb sandwich panel of variable thickness: model and characterisation of the Black Hole Acoustic effect

Wave propagation in a honeycomb sandwich panel of variable thickness: model and characterisation of the Black Hole Acoustic effect