Search Results (287)

In this work, an ultrasonic relaxation spectroscopic study of aqueous ammonium Fe(II) sulfate, aqueous ammonium Fe(III) sulfate and the corresponding ternary system has been undertaken. A variety of acoustic parameters including relaxation frequency, relaxation amplitude and speed of sound were determined as a function of solution concentration. In addition, the adiabatic compressibility and the molar volume change during the ionic association in ammonium Fe(II) sulfate and ammonium Fe(III) sulfate aqueous solutions were also estimated from the acoustic data. This approach facilitated a comprehensive characterization of the three systems across different concentrations. In the two binary systems, the presence of an ion association mechanism was identified involving the divalent and trivalent iron ions, with the sulfate anions, respectively. Furthermore, in the ternary system, an internal sphere oxidation–reduction mechanism occurred between the divalent and trivalent iron ions. All ions within each solution play an active role in shaping the structure of water molecules, owing to the prevailing kosmotropic characteristics specific to each solution. The results are examined within the context of the current phenomenological understanding in the field. Full article

Laser-induced acoustic communication is a highly adaptable cross-medium technique that combines the advantages of optical transmission through air and acoustic transmission underwater. However, poor signal stability at high repetition frequencies currently hinders its widespread application. To address this, this paper proposes an innovative scanning focal-point method to enhance stability. Traditional methods such as beam scanning, focus control, and distributed interaction are primarily aimed at enhancing sound pressure in a specific direction, achieving near-field/far-field focusing, or improving the signal-to-noise ratio through coherent synthesis of ultrasonic intensity. In contrast, the method proposed in this paper is intended to avoid the interference of droplets and vapor generated by single-point breakdown under high repetition frequencies, which would otherwise degrade the laser-acoustic conversion efficiency. It is therefore an active defense strategy specifically targeting the stability of laser-induced acoustic communication. First, optical simulation software was used to analyze the effects of surface ripples and bubbles on focal spot displacement and size. Next, a single-pulse experimental system was developed to measure the range and duration of surface depressions caused by optical breakdown. Finally, a scanning focal-point system was constructed for comparative experiments, with results recorded via hydrophones and high-speed cameras. The maximum laser-induced acoustic signal generated by the scanning focal-point method is 7.4 times that produced by single-point breakdown. The experimental results demonstrate that the scanning focal-point method can effectively avoid the influence of water surface disturbance and steam on the optoacoustic conversion efficiency and significantly improve the amplitude and stability of the laser-induced acoustic signal. Full article

Accurate and reliable groundwater-level monitoring in deep observation wells remains difficult for conventional non-contact ultrasonic systems because narrow tubular geometries intensify multipath reflections, signal attenuation, and echo ambiguity. This study proposes a dual-signal direct time-of-flight (ToF) method that combines radiofrequency (RF) synchronization with one-way airborne ultrasonic propagation to a floating receiver located at the groundwater surface. In the proposed architecture, the RF signal provides a near-instantaneous time reference, whereas the ultrasonic signal defines the propagation delay, thereby eliminating dependence on echo-based ranging. The system integrates a wellhead surface unit for synchronized transmission and control, a floating unit for ToF acquisition and embedded processing, and an optional reference channel for in situ estimation of the effective sound speed. A duty-cycled power architecture is used to support low-power long-term deployment, while a multi-shot acquisition strategy with a median-like estimator improves robustness against startup transients, timing jitters, and false detections. Field validation was conducted over a 12-month period under actual groundwater-monitoring conditions, during which the groundwater depth varied between 14 m and 30 m below the wellhead datum. Within this field-validation interval, the proposed system achieved a mean absolute error of 0.048 m, a maximum absolute error of 0.050 m, and an overall valid detection rate of 99.4% over 358 valid cycles out of 360 scheduled cycles. In addition, a separate range-dependent confined-tubular propagation test was conducted to evaluate the extended detection capability of the RF-synchronized one-way ultrasonic ToF architecture. This test demonstrated stable acoustic-link ToF detection up to 300 m inside the tested 170 mm confined plastic pipeline. Therefore, the 300 m result should be interpreted as a range-dependent valid-detection result rather than as a 12-month groundwater-depth validation over the full 300 m interval. These results demonstrate that the proposed direct-ToF method provides an RF-synchronized one-way ultrasonic ToF framework with a floating receiver for groundwater-level monitoring in deep observation wells, while remaining compatible with low-power and IoT-based environmental monitoring systems. Full article

Concrete wall cavities are common hidden defects in construction engineering that seriously reduce structural safety, durability, and construction quality, especially in old buildings and projects without complete design documents. Traditional detection methods have obvious limitations: the manual tapping method relies heavily on subjective experience and lacks quantitative standards, while advanced non-destructive testing methods such as ultrasonic testing and infrared thermography are expensive, complex to operate, and difficult to apply on a large scale. At present, the quantitative correlation between acoustic signal characteristics and cavity defects has not been fully studied. To address these problems, this study combines literature analysis, controlled experiments, and acoustic signal processing to propose a quantitative identification method for concrete wall cavities based on autocorrelation analysis of sound signals. Tapping signals from normal and cavity walls are collected and processed using band-pass filtering and amplitude normalization. The autocorrelation function (ACF) is then used to extract characteristic parameters. The results show that the proposed method exhibits significantly improved accuracy and efficiency compared with traditional manual detection. Obvious differences in autocorrelation characteristics can be observed between normal and cavity walls. The method realizes the transformation from subjective auditory judgment to objective quantitative identification, with low cost, strong anti-interference ability, and high sensitivity to small defects. It provides a reliable technical tool for the rapid and quantitative non-destructive testing of concrete wall cavities in engineering practice. Full article

We report on a novel approach for the monitoring of tangential laser turning with ultrashort laser pulses. By using an ultra-sonic sensor consisting of a membrane-free optical microphone, the current state of the ablation process can be analyzed, potentially enabling a real-time automated regulation. With its high sensitivity, bandwidth, and sampling rate, it is an ideal tool for process monitoring. The material ablation caused by focused femtosecond laser pulses produces distinct sound waves, which can be detected by the optical microphone. The diameter reduction of a rotating cylindrical workpiece during the laser turning process with ultrashort laser pulses results in a variation in the acoustic emissions. From this, properties like the state of the machining progress can be inferred. Full article

Moth auditory systems, evolutionarily adapted and structurally diverse with ultrasonic sensitivity, underpin the development of acoustic-based pest management strategies. Here, based on hypotheses derived from previous findings, we tested whether and how audible sounds (music, bird chirp, noise; 0.25–1 kHz, 80/120 dB) affect the development, survival, behavior and fecundity, as well as the molecular responses, using both short-term and long-term exposure (three successive generations) experimental designs. Behavioral assays showed dose-specific responses: high-intensity (120 dB) bird chirp and noise suppressed larval and adult activity, while low-intensity (80 dB) counterparts promoted larval crawling. Long-term exposure revealed that bird chirp and noise significantly impaired fitness, reducing larval/pupal body weight, pupation/eclosion rates, and egg hatching rate, with 120 dB noise exerting the strongest effects; 80 dB music showed neutral or positive impacts. Transcriptomic analysis identified 71–235 differentially expressed genes (DEGs) across treatment groups, with bird chirp and noise inducing more downregulated DEGs related to metabolism, immunity, and development. Notably, all cuticle-related DEGs in the 80 dB noise group and 53.2% in the 120 dB noise group were upregulated, suggesting stress-induced cuticular remodeling. GO/KEGG enrichment indicated distinct patterns: 80 dB music, bird chirp and 120 dB noise groups only had downregulated DEGs enriched in certain terms/pathways, mainly associated with cellular components; the 80 dB noise group had upregulated DEGs enriched in sensory, cuticle, metabolism and longevity-related terms/pathways, and downregulated DEGs in metabolism and human disease-related terms/pathways. Analysis of the expression patterns of all the longevity pathway-related genes suggested that sound stress induces lifespan regulation in this insect. These findings clarify S. frugiperda’s multidimensional responses to audible sound, providing a foundation for sound-based pest management. Full article

This paper addresses the challenge of accurately measuring liquid level interfaces in multiphase mixed media by proposing a detection method based on ultrasonic transmission. First, a mathematical model of the ultrasonic measurement system was established, and the acoustic field characteristics of transducers with different frequencies and diameters in slurry were simulated and analyzed to determine the optimal excitation frequency and probe diameter. On this basis, an echo sound pressure calculation model based on the side-incidence method was constructed, and a formula for calculating the liquid level interface height was derived. Finally, an experimental test platform with a multi-layer steel container was built to measure the propagation velocity, attenuation coefficient, and acoustic impedance coefficient of ultrasound in the slurry, verifying the feasibility of the liquid level interface measurement method. Full article

By applying nonlinear vibration-to-sound modulation technology to bolt loosening detection, this paper proposes a new experimental setup and signal-processing method. A linear swept-frequency signal is used to excite low-frequency vibrations, while a fixed-frequency sine wave is used for high-frequency ultrasonic excitation. First, a fractional Fourier transform is applied to the vibration-acoustic modulation signal to transform it into the optimal fractional domain where the energy of the swept-frequency signal is concentrated; next, the swept-frequency signal undergoes a masking filter, and the filtered signal is transformed back to the time domain; finally, the time-domain signal is transformed back to the frequency domain, and the amplitudes of the sum and difference frequency components of the high-frequency signal are extracted as damage parameters. The effectiveness of this method in bolt loosening detection was verified through bolt connection tests, with the applied tightening torque ranging from 10 to 30 N·m. This method is simple to operate and highly robust, making it a reliable approach for detecting the degree of loosening in bolt connections. Full article

This paper presents a miniaturized and highly accurate saltwater concentration monitoring system based on Capacitive Micromachined Ultrasonic Transducer (CMUT) array technology. The system incorporates a highly integrated CMUT array with a compact footprint of 5 mm × 5 mm, capable of both transmitting and receiving ultrasonic signals, which significantly contributes to the system’s miniaturization and portability. To ensure accurate compensation for temperature-dependent variations in sound velocity, a TA610A temperature sensor is integrated for continuous real-time monitoring of the salt solution temperature. By acquiring ultrasonic echo signals, the system calculates the time-of-flight (TOF) of the acoustic waves. Based on the TOF and real-time temperature data, the sound velocity is determined, and the salt concentration is subsequently derived with temperature compensation applied to enhance measurement accuracy. Experimental results show a measurement precision of 0.1% and a maximum absolute error of 0.02%, confirming the system’s high accuracy and robustness. Combining stability, reliability, and a compact real-time sensing design, the proposed CMUT-based system holds significant promise for practical deployment in various industrial and environmental monitoring scenarios. Full article

Ultrasonic testing is a prevalent method for non-destructive evaluation of railway rails; however, conventional Time-of-Flight (ToF) approaches applied in practical dry-coupled inspections often rely on simplified assumptions regarding wave propagation velocity and neglect complex waveform characteristics. This paper presents a robust depth estimation framework for surface-breaking cracks that enhances sizing accuracy through effective velocity calibration and Hilbert envelope extraction. Unlike standard methods that assume the free-space speed of sound in air (343 m/s) for wave propagation within the air-filled gap of a surface-breaking crack, we propose an effective velocity model derived from in situ calibration to account for the boundary layer viscosity and thermal conduction effects within narrow crack geometries. The signal processing chain incorporates spectral analysis, band-pass filtering, and Hilbert Transform-based envelope detection to mitigate noise and resolve phase ambiguities. Experimental validation on steel specimens with controlled defects (0.2–10.0 mm) demonstrates that the proposed method achieves an exceptional linear correlation (R² ≈ 0.9976). The calibrated effective velocity was determined to be 289.3 m/s, approximately 15.6% lower than the speed of sound in air, confirming the significant influence of confinement effects. Furthermore, excitation parameters were optimized, identifying that high-voltage excitation (≥110 V) and a tuned pulse width (≈150 ns) are critical for maximizing the signal-to-noise ratio. The results confirm that combining physical model calibration with advanced signal analysis significantly reduces systematic errors, paving the way for portable, high-precision rail inspection systems. Full article

Reducing the carbon footprint of cement based materials requires approaches beyond replacing cement alone. Mineral carbonation of aggregates offers a simple route to store carbon dioxide permanently while improving material performance. In this study, four steel slag aggregates were evaluated as sand replacements in mortar after pre carbonation, including basic oxygen furnace slag, blast furnace slag, skim slag, and Rockport slag. The aggregates were treated using moisture assisted carbonation with carbon dioxide and then used in mortar made under the same mix design and curing conditions. Bulk chemistry was determined by X-ray fluorescence, carbon uptake was quantified by thermogravimetric analysis, and performance was evaluated using compressive strength, ultrasonic pulse velocity, chemical soundness, freeze thaw resistance, and scanning electron microscopy. Pre-carbonation stored approximately 14–19 wt% CO₂ relative to the dry mass of the slag aggregates, depending on slag type. Mortars with carbonated basic oxygen furnace slag and carbonated blast furnace slag showed clear strength gains at 28 days, along with higher ultrasonic pulse velocity and improved chemical durability. Rockport slag showed modest improvement, while skim slag showed a reduction in strength after carbonation. Microstructural observations indicate that carbonate precipitation filled pores and densified the aggregate paste interface, which explains the strength and durability improvements in the more responsive slags. These laboratory-scale results show that, under the specific moisture-assisted pre-carbonation conditions investigated, pre-carbonation of slag aggregates can combine permanent CO₂ storage with improved mortar performance. However, the magnitude of these benefits depends strongly on slag chemistry and particle structure, highlighting the need for slag-specific carbonation design and further validation under practical conditions. Full article

The characterization of mechanical properties in heat-treated carbon steels, which is crucial for quality control, traditionally relies on destructive testing. This study evaluated the reliability of the non-destructive ultrasonic technique as a metrological alternative for AISI 1045 steel. Samples subjected to six heat treatment conditions (Annealing, Normalizing, Quenching, and Tempering) were characterized by hardness, metallography, and ultrasound. Through linear regression analyses, the multiparametric model combining sound velocity, attenuation, and FWHM demonstrated exceptional metrological precision, resulting in a coefficient of determination of (R² = 96.687%). The metrological robustness of the model was validated by quantifying the Expanded Uncertainty (U), following the GUM (Guide to the Expression of Uncertainty in Measurement). It is concluded that the multiparametric ultrasonic methodology is an accurate, robust, and non-destructive alternative for the quantitative determination of Vickers Hardness in AISI 1045 steels, contributing to the optimization of industrial processes and metrological rigor. Full article

Plastic shrinkage and self-desiccation, along with the associated early-age cracking, are still among the most important factors that influence long-term performance of concrete structures, including durability. Superabsorbent polymers (SAPs) have been widely researched for application in concrete to mitigate shrinkage through facilitating effective internal curing by releasing water into the mixture to promote continuous hydration of cement. The acoustic emission (AE) monitoring technique, due to its high sensitivity, has proven very effective in tracking the process of water release by SAPs in concrete during early-stage curing. Typically, AE parameters such as cumulative activity, amplitude and energy are utilized to characterize the kinetics of curing processes. While these parameters indicate well the internal activity of SAPs in time, they do not offer information on the precise location of the active sources within the material’s volume, leaving a crucial gap in the understanding of the ongoing microstructural changes caused by internal water distribution and cement hydration. In this sense, AE event source localization can offer information about the active zones of water hydration activity in the material 3D domain, allowing detection of their evolution during concrete curing. Meanwhile, Acoustic Emission Tomography (AET) computes ultrasonic velocity distributions in different periods of monitoring, which are governed by acoustic characteristics of the concrete mixtures, to visualize material stiffness development spatially and temporally. This level of insight is particularly important for SAP concrete, where uniformity of internal water curing is essential for ensuring long-term durability and material soundness. By visualizing how the hydration sources evolve in real time, these methods offer an effective, non-destructive, and cost-effective solution for early-age concrete quality control, which would be challenging to achieve through other techniques. Full article

This study presents a comparative analysis of cylindrical lithium-ion cell architectures, tracing the evolution from the conventional tabbed design (18650/21700) to the large-format 4680 cell with its tabless current collectors. This architectural shift is driven by the imperative to minimise internal ohmic resistance and enhance thermal management in high-power automotive battery applications. Forensic investigation reveals that the 4680 design replaces localised, high-resistance tab connections with a distributed, low-impedance interface, necessitating the adoption of advanced manufacturing techniques, including long ultrasonic torsional welding and highly controlled high-power density laser welding. Crucially, the welding of external aluminium busbars to the cell relies on sophisticated microstructural engineering, particularly for the challenging dissimilar Aluminium-Steel (Al-Steel) anode weld. This weld format employs a spiral laser path to limit the formation of brittle aluminium-iron (Al-Fe) intermetallic compounds (IMCs), leveraging the steel cell casing’s nickel plating to promote a more ductile Al-Fe-Ni phase for improved joint reliability. Furthermore, the 4680 cell incorporates a significantly thicker casing (≈0.54 to 0.7 mm) for enhanced mechanical strength. In conclusion, the 4680 cell achieves superior performance through robust mechanical design and advanced welding processes that prioritise microstructurally sound, low-resistance interfaces. Full article

To mitigate acoustic beam drift, which degrades the signal-to-noise ratio (SNR) and limits the measurement range in ultrasonic gas flowmeters (USFMs), we present a miniaturized transit-time USFM that integrates a single piezoelectric micromachined ultrasonic transducer (PMUT) with a non-axisymmetric conical cavity. This design increases acoustic transmission gain and produces anisotropic directivity across orthogonal radiation planes, thereby broadening acoustic coverage along the flow direction and reducing beam steering. With an optimized cavity angle combination of (50°, 70°), the system achieves a 7.4 dB transmission gain and a half-power beamwidth (HPBW) of 29.1°. Experimental validation demonstrates a sound pressure attenuation of only 0.72 dB at 18.74 m/s. Within the 0.06–12 m³/h flow range, the USFM exhibits indication errors of ±2% (<1 m³/h) and ±1.5% (≥1 m³/h), with repeatability below 0.5%. The performance meets the Class 1.5 accuracy standard specified in CJ/T 477-2015, offering an innovative solution for wide-range miniaturized gas flow measurement. Full article