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Shear-force acoustic near-field microscopy (SANM) is employed to monitor stochastic formation and post dynamic response of a water meniscus that bridges a tapered gold probe (undergoing lateral oscillations of a few nanometers amplitude at constant frequency) and a flat (gold or silicon oxide) substrate. As the probe further approaches the substrate, its amplitude decreases. Shear forces (of yet unknown precise origin) are typically invoked to explain the apparently pure damping effects affecting the probe's motion. Herein, SANM measurements underscore instead the role of near-field acoustic emission from the water meniscus as an elastic energy dissipation channel involved in shear interactions. A simplified thermodynamic argument is provided to justify the formation of a water meniscus between the probe and the sample once they are at sufficient separation distance. The reported measurements focus on the role played by the tip's geometry (by using probes of slender and chubby apex termination). The results shed some light on the potential origin of the so-called shear forces, invoked in many scanning probe microscopy applications, but not yet well understood. [ABSTRACT FROM AUTHOR]

Aiming at effectively utilizing recycled coarse aggregate (RCA) in sustainable construction, it is necessary to study the internal damage evolution of steel fiber–reinforced recycled-aggregate concrete (SFRAC) under dynamic tensile loads and the reinforced mechanism of steel fiber. The influences of the steel fiber content, the recycled-aggregate replacement ratio, and the loading rate on the mechanical properties and dynamic damage of SFRAC were studied using the Brazilian disc splitting test and acoustic emission (AE) technology. Then, the mechanism of crack evolution was investigated by means of the parameter analysis method. The results indicate that the existence of RCA makes the mechanical properties of recycled-aggregate concrete worse than those of normal concrete and weakens the strain rate effect of splitting tensile strength, whereas this negative influence can effectively be improved by steel fiber. The preferable steel fiber contents obtained from the splitting tensile strength and peak displacement are 1.0% and 1.5%, and under these conditions, the SFRAC replaced by 30% RCA has a mechanical performance superior to that of normal concrete. It is also found that the damage degree and energy absorbing capacity of SFRAC can be identified by analyzing the ring and energy counts of the AE signal. Furthermore, the evolution of the crack pattern of SFRAC under dynamic axial tensile load is well reflected by the rise angle and average frequency. Increased steel fiber content and recycled-aggregate replacement ratio can change the failure mode to a complex tensile-shear mixed failure, and the shear crack gradually becomes the main crack with increasing loading rates. Practical Applications: The public environment crisis from the greenhouse effect led to a series of measures from all industries worldwide. The widespread use of concrete has brought with it serious environmental and energy-saving problems. The construction industry preliminarily attempts to replace natural aggregate by recycled aggregate obtained by crushing construction solid waste in green low-carbon buildings, which shows considerable carbon sequestration and emission reduction. However, recycled aggregate has poor mechanical properties such as low strength and high porosity. When participating in concrete configuration, this defect seriously affects the strength of the material and limits its wide application in construction engineering. For a component with strength requirements or special purposes, fiber can be adopted to improve the mechanical properties of recycled-aggregate concrete. This study examines the damage process of fiber-reinforced recycled-aggregate concrete with the microscopic method and proposes a satisfactory mix proportion. Naturally, these analysis methods require more time and effort than a basic macroscopic analysis. Moreover, proper research on the mechanism of damage evolution under dynamic loading is crucial. [ABSTRACT FROM AUTHOR]

Rock-burst prediction is an important issue faced by deep coal mining operations and holds significant significance for ensuring the safety of workers and the sustainable development of mines. This study investigates the crack-propagation behavior of coal and magnetite under uniaxial compression, introduces the characteristic parameter γ within the framework of the flicker noise spectrum (FNS), analyzes the trends in the variation of acoustic emission (AE) b-value and γ-value, and explores the relationship between these two parameters. Experimental results reveal that the proportion of tensile cracks is significantly higher than shear cracks during the loading process, shear failure becomes the main factor as the specimen approaches failure. Both the b-value and γ-value are proven to effectively reflect the damage evolution process of coal and magnetite and exhibit noticeable changes prior to collapse. Specifically, the peak γ-value serves as a precursor indicator for coal and magnetite collapse. Furthermore, this study uncovers a negative linear relationship between the b-value and γ-value. By delving into the feature parameter γ of AE signals, this research offers a new perspective and approach for predicting the instability of coal and magnetite formations and monitoring dynamic hazards. It contributes to a better understanding of the damage evolution process of coal and magnetite formations and provides valuable guidance and reference for preventing and mitigating dynamic hazards associated with coal and magnetite. Highlights: A novel monitoring indicator for coal and magnetite dynamic hazards, known as the γ-value, was introduced within the framework of the Flicker Noise Spectroscopy method. The study revealed a notable negative linear correlation between the b-value and the γ-value derived from acoustic emission signals. Experimental and on-site data have demonstrated that b-value and γ-value can effectively prevent rock burst. [ABSTRACT FROM AUTHOR]

Understanding the acoustic repertoire of a species is crucial for comprehending its ecology and can also provide a valuable tool in the analysis of passive acoustic monitoring data. Despite being the most abundant seal species in the Arctic, the call repertoire of ringed seals (Pusa hispida) remains poorly studied. This paper aims to provide a comprehensive and quantitative description of the calls produced by ringed seals. Data collection occurred in May 2022 near Ulukhaktok in the Western Canadian Arctic. Acoustic recorders were deployed in cracks in the sea ice that were regularly used by ringed seals as haul-out areas. All calls were counted and classified into one of three categories: yelps, barks and growls. High-quality calls were further analysed with ten acoustic parameters calculated for each signal. Cluster and classification and regression tree (CART) analyses were used to assess if the visual classification of calls was supported by the acoustic parameters calculated. The cluster and CART analyses affirmed the presence of all three distinct call types in the ringed seal acoustic repertoire. Classification of unseen calls using the CART model demonstrated an accuracy of 98%. The findings presented here serve as foundational information on the acoustic repertoire of ringed seals. [ABSTRACT FROM AUTHOR]

The combination of acoustic emission and electrical potential monitoring methods holds promise for monitoring and warning of rock bursts due to its comprehensive reflection of the damage process. However, the response features during the creep failure process remain unclear. In this paper, a coal creep test was conducted using a combination of electric potential and acoustic emission monitoring. The response characteristics were analyzed, their multifractal characteristics were analyzed, and the joint response mechanism was explored. This research demonstrated a significant correlation among acoustic emission and electrical potential signals and creep deformation and failure. At the start of loading, a brief increase in both signals was observed. As deformation progressed, the signals became steady, and their intensity and fluctuation notably increased during accelerated creep failure. Quantitative analysis of acoustic emission count rates and electric potential intensity during creep processes revealed a quadratic relationship of acoustic emission count rates with stress and strain variations, in addition to an exponential correlation with mean electric potential intensity. Additionally, the statistical analysis of the multifractal characteristics before coal sample instability and failure revealed consistent trends in the characteristic values of Δα and Δf(α), with initial decrease followed by slight fluctuations, culminating in a sudden abnormal change preceding failure. Finally, leveraging the mechanisms of acoustic emission and electrification under load, this study discusses the multifractal characteristics of acoustic-electric signals and verifies their complementary roles in accurately predicting coal rock creep failure. These studies provide essential theoretical groundwork and references for improving dynamic disaster monitoring in coal mines. [ABSTRACT FROM AUTHOR]

To achieve the actual situation of water pressure stabilization during underground and tunnel water inrush disasters, the team independently developed a stable water pressure test system and conducted fracture and failure tests on fissured rock masses under the coupling effect of 1MPa stable water pressure and stress and without water pressure. Combined with data collected by acoustic emission instruments, the mechanical characteristics of fracture and failure, crack propagation mechanism, and acoustic emission response mechanism of fissured rock masses under the coupling effect of stable hydraulic pressure and stress were studied. The results showed that throughout the entire experimental process, the hydraulic pressure remained continuously stable, with a decrease of only 0.14%; The variation pattern of peak strength of fissured rock mass with increasing crack inclination angle under stable hydraulic pressure changes from a decrease and then an increase in the absence of hydraulic pressure to an increasing trend; The crack propagation length of low angle fissured rock mass is generally higher than that of high angle fissured specimens. The longer propagation path increases the range and effect of hydraulic pressure, and the initial crack propagation length of fissured rock mass under hydraulic pressure is also significantly longer than that of specimens without hydraulic pressure; During the loading process, both the acoustic emission ringing count and damage variable can be divided into four stages. From the cumulative total number of acoustic emission ringing counts, it can be seen that during the loading process, the total number of acoustic emission ringing in fissured rock masses subjected to hydraulic pressure is significantly lower than that of specimens without hydraulic pressure, and the trend is also relatively stable. [ABSTRACT FROM AUTHOR]

The increased use of roller bearings in recent years has made it vital to develop techniques for Condition Monitoring (CM) of these valuable assets. Toroidal Roller Bearings (TRB) are one of the recent inventions that has revolutionised some industries because of its unique design. In this study, newly produced TRBs were tested using Acoustic Emission (AE), vibration and temperature, on a specially designed test rig. The AE signal was recorded, processed, and analysed using FFT-based methods to transform from the time domain to the frequency domain, and to specify the Dominant Frequency (DF) of each hit in the signal. The result of the analysis was a layout on the time domain of the DFs of all AE hits along with RMSAE and other parameters, this layout was called DF map. The test was divided into three phases, and the DF bands were divided horizontally into three band groups. The aim is to establish a correlation between the phases and DF bands. Knowing the type of defects that are typical for each phase in the test provided insights to what are the DFs of that type. Promising results can be achieved using this measuring method on other types of bearings. [ABSTRACT FROM AUTHOR]

The application of recycled aggregate is crucial for waste concrete recycling, while the loading rate significantly influences the fracture behavior of recycled aggregate concrete. Herein, we investigate the effect of loading rate on the flexural and fracture behaviors of recycled aggregate concrete, along with associated acoustic emission characteristics. Results show that the flexural strength and energy absorption capacity maximum increase by 15.18% and 38.39%, respectively, as the loading rate rises. As the loading rate increases from 0.05 to 1 mm/min, peak frequency is primarily clustered in 0 ~ 75 kHz and 75 ~ 225 kHz and tends to be dense, while the b value decreases by 19.28%, 23.30%, and 30.17%, respectively. Additionally, the proportion of shear failure also decreases, which relates to the high energy release rate. Further, the multifractal spectrum α − f(α) resembles a quadratic distribution, with both multifractal intensity ∆f and spectrum width ∆α showing a downward trend as the loading rate rises. [ABSTRACT FROM AUTHOR]

The rockburst risk prediction based on microseismic (MS) data is an important research task in deep mine safety prevention. However, the lack of systematic research on explicit prediction indexes and the waste of a large amount of unlabeled data are still two main problems that hinder the development of rockburst prediction. In this paper, the acoustic emission (AE) event distribution at each coal rock deformation and failure stage is studied based on the laboratory experiment. The spatial-temporal evolution of rockburst in MS data of coal mine fields is explored. Based on systematic research of the AE and MS distribution features considering the physical logic of coal rock mass failure, nine different rockburst prediction indexes are employed to describe the MS data features before rockburst. Then, according to the rockburst prediction indexes, a new self-supervision rockburst risk prediction algorithm is constructed, consisting of the pre-trained model and fine-tuning model with the same encoder and decoder structure. The pre-trained model is trained with unlabeled MS data to automatically learn rockburst prediction index features by reconstructing the masked indexes. Based on the pre-trained encoder and decoder parameters, the fine-tuning model is trained with the labeled MS data to predict rockburst risk. A large number of experiments show that the proposed rockburst prediction self-supervision algorithm is far superior to previous algorithms, by effectively utilizing unlabeled data. The ablation experiment also proves the validity of the studied rockburst prediction indexes. [ABSTRACT FROM AUTHOR]

Frequent mining operations significantly disturb the security of deep weakly cemented rock roadways in western mining areas, constituting one of the primary causes of deformation, instability, and failure within the coal‐rock body. In this paper, dynamic uniaxial compression tests of soft rock‐coal combinations under low‐frequency disturbance with different cyclic amplitudes were conducted based on acoustic emission to elucidate fracture modes. The findings are as follows: Different cycle amplitudes manifested significant degradation effects on the soft rock‐coal combination. With increasing cycle amplitude, the proportion of tensile cracks initially decreased before subsequently increasing, demonstrating a general upward trajectory. The sudden increase in the acoustic emission RA value, the large decrease in the b‐value, and AE counts reaching the peak mean that failure and destabilization of the specimen begin to occur. The results of this study will furnish theoretical direction for dynamic disaster monitoring and early warning in soft rock mines located in western mining regions. [ABSTRACT FROM AUTHOR]

This paper describes the Santos Basin Underwater Soundscape Monitoring Project (PMPAS-BS), a Brazilian ocean soundscape monitoring initiative. The main objective of the project is to quantify and assess hydroacoustic noise of anthropogenic origin in a large sedimentary basin extending from 23° S to 28° S on the southeastern Brazilian continental margin of the South Atlantic Ocean. Noise associated with oil and gas (O&G) exploration and production activities is the primary target, but this oceanic region also has busy shipping lanes for commercial, military, and fishing vessels. The two main hubs of Brazil’s export and import of goods by sea are located in this region: Santos and Rio de Janeiro ports. The project has three measurement components: mobile monitoring based on gliders and drifting acoustic profilers, fixed shallow-water monitoring based on acoustic measurements at coastal stations near shipping lanes associated with exploration and production activities in the Santos Basin, and fixed oceanic monitoring based on deep-water mooring lines equipped with passive autonomous acoustic recorders near production units, shipping lanes, and areas with lower intensity of O&G activities (pristine or reference sites). Numerical modeling of anthropogenic underwater acoustic noise has also been included as a fourth project component. The PMPAS-BS covers an area of more than 251,000 km² and uses several instruments with different methods and sensors for acoustic measurements. Its results provide current sound levels over a very large region of the western South Atlantic, both in areas more and less affected by anthropogenic activities. [ABSTRACT FROM AUTHOR]

The mechanical properties of fissured sandstone will deteriorate under water–rock interaction. It is crucial to extract the precursor information of fissured sandstone instability under water–rock interaction. The potential of each acoustic emission (AE) parameter as a precursor for instability in the failure process of fissured sandstone was investigated in this study. An experimental dataset comprising 586 acoustic emission experiments was established, and subsequent classification training and testing were conducted using three machine learning (ML) models: AdaBoost, MLP, and Random Forest (RF). The primary parameters for identifying the instability risk state of fissured sandstone include acoustic emission ringing count, energy (mV·ms), centroid frequency, peak frequency, Rise Angle (RA), Average Frequency (AF), b value, and the natural/saturated state of fissured sandstone: state. To enhance data utilization, a 10-fold cross-validation method was employed during the model training process. The machine learning models were developed and designed to identify the instability risk of fissured sandstone under the natural and saturated states. The results demonstrated that the established RF model was capable of identifying fissured sandstone instability risks with an accuracy of 97.87%. Feature importance analysis revealed that state and b value exerted the most significant influence on identification results. The Spearman correlation coefficient was utilized to assess the correlation between input features. This study can provide technical support to identify the risk of instability of fissured sandstones under both natural and saturated water conditions. Based on the models developed in this study, it is possible to implement an early warning method for instability in fissured sandstone that meets realistic working conditions. Compared with the traditional empirical and formulaic methods, the machine learning method can more quickly process huge amounts of AE data and accurately identify the damage state of fissured sandstone. [ABSTRACT FROM AUTHOR]

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Superfine tailings-blast furnace slag backfill (SBB) has been designed for recycling solid waste in mines and decreasing the cost of the overall process. During the mining process, the decrease of adjacent ore rock causes backfills water loss and its exposure to air. The mechanical behavior of SBB was investigated by uniaxial compressive strength (UCS), acoustic emission (AE) characteristics, and numerical simulations. Wavelet transform and fast Fourier transform were used to obtain the frequency components of AE events during the whole loading. The results indicated that the main frequency components of AE signals in SBB were close to 100 kHz, while medium and high-frequency components could be also distinguished for specific specimens with certain water loss. Particle flow code (PFC), a typical discrete element method (DEM), could reproduce the stress–strain curves of SBB specimens with varied water loss and simulate AE events of SBB during the loading. For the whole loading process, both indoor experiments and numerical simulation showed that AE events and simulated AE clusters began in the early stage of loading, which indicated that the crack initiated from a low stress level. [ABSTRACT FROM AUTHOR]

In order to cope with climate change and achieve the goal of carbon neutrality, the use of carbonization technology to enhance the performance of cement-based materials and achieve the purpose of carbon sequestration has become a very promising research direction. This paper considers the use of CO2NBW as mixing water for cement-based materials, aiming to improve the carbonization efficiency of materials to achieve the goal of carbon neutrality. This time, the effect of CO2NBW on cementitious filling materials under different aggregate fractal dimensions was studied through uniaxial compression tests and acoustic emission technology. The effect of CO2NBW on the mechanical properties and crack evolution of the material was discussed. The results showed that CO2 nanobubbles significantly improved the strength of cemented filling materials under different fractal dimensions, and the uniaxial compressive strength was most significantly improved by 23.04% when the fractal dimension was 2.7824. In addition, the characteristics of acoustic emission ring counts and energy parameters indicate that CO2 nanobubbles help improve the overall pore structure of the sample, affecting the macroscopic strength. However, the addition of CO2 nanobubbles reduces the limit energy storage ratio of elastic strain energy, which indicates that excessive CO2 concentration may affect the hydration reaction of the cementing material. [ABSTRACT FROM AUTHOR]

Grey cast iron releases energy in the form of stress waves when damaged. To analyse the evolution of the physical and mechanical properties and acoustic emission characteristics of grey cast iron under uniaxial compression, acoustic emission signals were collected at different rates (0.5, 1, and 2 mm/s). Combined with load-time curves, damage modes were identified and classified using the parametric RA-AF correlation analysis method. The results indicate the loading rate effects on the strength, deformation, acoustic emission (AE), and energy evolution of grey cast iron specimens. The acoustic emission counts align with the engineering stress–strain response. To better illustrate the entire failure process of grey cast iron, from its internal microstructure to its macroscopic appearance, X-ray diffraction (XRD) and optical microscopy (OM) were employed for qualitative and quantitative analyses of the material's internal microstructural characteristics. The equivalent crystal model of grey cast iron was constructed using a Particle Flow Software PFC2D 6.00.30 grain-based model (GBM) to simulate uniaxial compression acoustic emission tests. The calibration of fine parameters with indoor test results ensured good agreement with numerical simulation results. Acoustic emission dynamically monitors the compression process, while discrete element particle flow software further analyses the entire damage process from the inside to the outside. It provides a new research method and idea for the study of crack extension in some metal materials such as grey cast iron. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the mechanics, acoustic emission (AE) and electromagnetic emission (EME) response law of bursting liability coal at different loading rates, uniaxial compression tests were carried out on coal mass from Konggu Coal Mine. The corresponding relations among mechanical properties, AE and EME signals in the process of coal failure under loading were analyzed, and the energy evolution law of coal failure with bursting liability under loading rate was discussed. The results show that within a certain range of loading rate, the higher the loading rate, the higher the compressive strength and peak load of bursting liability coal, and the shorter the time for coal to reach the peak load. Under different loading rates, the mechanics, AE and EME signals of coal samples can be well corresponded. When the loading rate is low, the number of blocks destroyed of coal sample is large and the block size is relatively small, and the blocks are mainly scattered around the test platform. When the loading rate is high, the number of damaged blocks is relatively small and the block size is relatively large, and the blocks are far away from the test bench. When loading at a low rate, the internal cracks in coal can be fully developed and connected, and the energy release rate is relatively uniform in the process of loading and failure of coal sample. In the case of high loading rate, the energy release rate of coal sample in the loading process is much smaller than that in the moment of failure. Combining the above test results with the actual situation of the working face, it can be concluded that the total energy stored in the coal of fast mining increases and the threshold of impact decreases compared with that of slow mining. Therefore, under the disturbance of external dynamic load, rapid mining is more likely to induce rock burst. [ABSTRACT FROM AUTHOR]

The main challenges of using fiberglass composites are poor impact resistance and understanding of damage mechanisms during loading. This work focuses on improving the indentation resistance of glass/epoxy composites by the incorporation of industrial waste iron fillers with maximum concentration of 50 µm in size. Moreover, the quasi-static indentation test with acoustic emission (AE) monitoring was employed to study the damage initiation and propagation of baseline and optimized 10 wt.% of filler-loaded composites. Post-indentation performance was evaluated by conducting compression after indentation test. The result reveals that the stiffness, absorbed energy and strain energy density were increased by 32%, 59.2% and 18.02% in filler-loaded composites, whereas the residual dent was reduced from 0.9 to 0.5 mm as compared with baseline. As compared with 3 mm indentation displacement, the % of AE hits related to delamination and fiber failure was significantly reduced to 3.6% and 1% during 6 mm, respectively. Further, the sentry function results that shown very small two PII functions indicate a better indentation resistance in filler-loaded composites, which were well correlated with rear side photographic images. Besides, the filler-loaded composites exhibited least reduction in the residual compressive strength of 3.71% and 4.33% for 3 mm and 6 mm indented displacements, respectively. However, the microstructural analysis was used to validate the effect of iron fillers on glass/epoxy composites. Finally, this study concludes that the impact resistance of fiberglass composites was greatly improved by the addition of industrial waste iron fillers. [ABSTRACT FROM AUTHOR]

The stability of the roof in coal mining plays a crucial role in ensuring safe excavation. After coal extraction, the roof experiences complex and unbalanced stress conditions, leading to diverse roof failure behaviors, particularly in the case of thick roofs. This study examines the failure behaviors of roofs with different thicknesses through a combination of on-site measurements, physical modeling, and numerical modeling. The on-site results indicate that the failure of thick roof leads to larger magnitudes, increased magnitude variance, and energy compared to thin roof. A self-developed three-dimensional roof fracture experimental platform was utilized to conduct loading experiments on roofs with different thicknesses. The experimental results reveal that roof thickness significantly impacts peak load, deformation characteristics, crack patterns, and acoustic emission (AE) signals. Thin roof failure only generates tensile cracks, while thick roof failure produces both tensile and shear cracks. This suggests that an increase in roof thickness leads to a transition in the roof's failure mode from pure tensile failure to tensile-shear mixed failure or shear failure. The energy of AE events has a threshold. When below this threshold, more AE events occur for thin roofs, and when above it, thick roofs exhibit more AE events. The digital image correlation (DIC) results and AE location indicate roof failure initiates from the upper surface of the roof, where "O" shaped cracks form around the periphery, followed by gradual development of cracks on the lower surface. Thin roofs exhibit regular "X" shaped crack on lower surface, while thick roofs display additional branching and inflection points based on "X" shaped crack on lower surface. Numerical modeling using four polygonal particle roof models confirms the influence of roof thicknesses on peak load, deformation, and crack distribution, aligning with experimental and on-site results. These findings offer valuable theoretical support for controlling the stability of surrounding rock conditions in the presence of different roof thicknesses. Highlights: Roof thickness significantly affects coal mine safety, leading to diverse roof failure behaviors. On-site measurements, physical experiments, and numerical simulations reveal insights into roof behaviors. An experimental platform was established to explore the correlation between roof thickness and failure behavior. Thicker roofs exhibit higher peak loads, reduced deflection, complex crack propagation, and a tensile-shear mixed failure or shear failure. Numerical models of polygonal particle roofs further corroborate the impact of roof thickness on failure behavior, offering practical support for coal mine stability. [ABSTRACT FROM AUTHOR]

This research paper focuses on the thermo-hydro-mechanical (THM) modeling of brine migration in a heated borehole test conducted as part of the ongoing Brine Availability Test in Salt (BATS) at the Waste Isolation Pilot Plant (WIPP) in New Mexico. It is a component of the international collaboration project DECOVALEX-2023 (DEvelopment of COupled models and their VALidation against EXperiments), which aims to understand the THM processes governing brine flow in heated rock salt repositories through collaborative analysis by multiple research teams. Using the TOUGH–FLAC simulator, THM simulations were performed and compared with data from the BATS phase 1a. This experiment involved two identical horizontal-borehole arrays, one heated and one serving as a control, both equipped with sensor arrays. Analysis of measurements revealed water flow rate surges during heater power transitions, with the highest jump observed during cooling. Acoustic emission activity exhibited distinct patterns in response to heater power changes, suggesting that damage to rock salt is particularly pronounced during the cooling phase. The THM simulations successfully captured these phenomena, highlighting the significance of thermal effects, brine migration, and mechanical behavior in predicting brine availability in heated and damaged rock salt. Our modeling also revealed the critical interplay between heating and cooling-induced damage and its influence on flow properties, particularly affecting brine inflow estimation. Notably, we found that cooling-induced brine inflow spikes result from increased permeability due to tensile dilatancy. These findings have important implications for the development of robust containment strategies and enhance our understanding of the complex processes involved in repository performance. Highlights: Numerical modeling study accurately replicates the thermal-hydromechanical behavior of rock salt surrounding a heated borehole. Jumps in brine flow rate during transitions in heater power are observed, with the highest jump during cooling. Acoustic emission patterns suggest pronounced damage to rock salt during the cooling phase. Thermal pressurization and tensile-induced damage are identified as the primary contributors to brine inflow spikes. Findings improve predictions of brine availability, aiding the development of robust containment strategies for radioactive waste disposal. [ABSTRACT FROM AUTHOR]

This work aims to reveal the effect of cyclic disturbance frequency, i.e., 0.01, 0.1, 0.5, and 1.0 Hz, on damage cracking and energy dissipation characteristics of rock‐backfill composite structure specimens. Testing results show that fatigue volumetric strain and secant modulus increase with increasing disturbance frequency; low‐frequency disturbance leads to an earlier volume expansion. In addition, the strain energy density increases with increasing disturbance frequency. Most of the energy are dissipated for the specimen under high‐frequency disturbance. Finally, computed tomography scanning reveals the influence of disturbance frequency on failure modes; tensile‐splitting failure and shear failure are likely to occur at the surrounding rock subjected to high‐ and low‐ frequency disturbances. Low‐frequency‐disturbed stress seems easily to stimulate cracks at the rock‐backfill interfaces and the backfill; the backfill can absorb much more energy than high‐frequency circumstances. It is suggested that the role of backfill in energy absorption, contact support, and stress isolation is disturbance frequency dependent. Highlights: The effects of cyclic disturbance frequency on damage‐cracking are revealed.The energy dissipation magnitude is negatively correlated to the disturbance frequency.Cracking at interfaces and backfill is relatively severe under low frequency disturbance.The backfill can absorb much more energy under low‐frequency disturbance conditions. [ABSTRACT FROM AUTHOR]

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Rock fracture acoustic emission (AE) signals are commonly used non-destructive testing data in geological exploration, resource exploitation, and engineering fields. However, these signals are often accompanied by noise interference caused by environmental factors. In this study, we propose an enhanced model for denoising rock fracture AE signals, called simplified fully convolutional denoising autoencoder (SFCDAE). This model is based on the denoising autoencoder principle in the field of deep learning neural networks. The SFCDAE model consists of only seven layers, with minimal preprocessing of data input. By comparing denoising performance evaluation indicators, higher peak signal-to-noise ratio (PSNR) and lower root mean square error (RMSE) were achieved. On average, PSNR increased by 5.575% and RMSE decreased by 22.225%. Using simulated environmental noise to validate the model, it was found that the model has good robustness and can remove artefacts from sudden noise. The practical application value of the LSTM classification model was validated using data containing real experimental noise, resulting in a higher classification accuracy of 80.083%. These results indicate that the proposed model has better denoising performance compared to existing intelligent models and has certain practical value. [ABSTRACT FROM AUTHOR]

In order to study the damage properties of red sandstone under combined action of temperature, water and stress, the uniaxial compression test was carried out for red sandstone after immersing in water for 0.5 h, 1 h and 3 h at 25 ℃, 55 ℃, 85 ℃ and 95 ℃, the mechanical properties, characteristic stress points, acoustic emission RA-AF parameters and failure forms of red sandstone were analyzed, the damage constitutive equation was established, and the damage properties of red sandstone were studied. The results showed: (1) temperature could significantly improve the saturated water content percentage of red sandstone. With the increase of temperature, the saturated water content percentage showed a trend of increase first and then decrease, and was the largest at 55 ℃; with the increase of temperature, the mechanical parameters (peak intensity, elasticity modulus, and stress at start point of expansion) decreased first and then increased, and was the smallest at 55 ℃; (2) the ratio of crack initiation stress to peak stress (σci/σf) initially increases and then decreases with rising temperatures for the same soaking duration. Conversely, it initially decreases and then increases with extended soaking time at the same temperature. The RA-AF acoustic emission signals predominantly occur in the tensile region at each stage account for a relatively large proportion, with the proportion of signals in the shear region significantly increasing as soaking time extends, corresponding well with the observed damage patterns. (3) By considering the damage due to temperature and water as Initial damage to red sandstone and the damage due to stress as load-induced damage, a damage variable based on the Weibull distribution function was established. The comprehensive damage constitutive equation derived from this can be applied to water-saturated red sandstone below 100 ℃. The findings provide theoretical reference for practical engineering applications. [ABSTRACT FROM AUTHOR]

Range tests play a critical role in designing acoustic telemetry studies, guiding equipment configuration, deployment techniques, and the analysis of animal movement data. These studies often strive to capture the effects of environmental variation on detection efficiency over time but are frequently limited in spatial and temporal scale. This could lead to disparities between test results and the circumstances encountered during animal tracking studies. In this study, we evaluated detection range and efficiency at two distinct spatial and temporal scales in a dynamic intertidal ecosystem. Two range tests were conducted, the first being a small-scale study using 6 receivers deployed over 1 month. Using modern acoustic receivers with built-in transmitters and environmental sensors, we then conducted a large-scale range test with 22 receiver stations over a full year to approximate the area and duration of a typical animal movement study. Differences in detection range between the two studies occurred as a result of environmental variation and tag power output, with midpoint ranges estimated as 123 m (small scale, low power), 149 m (small scale, high power) and 311 m (large scale, very high power). At both scales, wind speed emerged as the most influential factor explaining temporal variation in predicted detection efficiency. However, this effect was modulated by wind direction which varied as a result of land sheltering and fetch between the two study scales. At the small scale, detection efficiency decreased with winds from the south and east, while at the large scale, northern and westerly winds were most detrimental. Water temperature had a positive effect on predicted detection efficiency at both scales, while relative water level was positive at the small scale and negative at the large scale. Additional factors, including precipitation and Topographic Position Index, were found to influence detection efficiency at a large scale. Moreover, sensors associated with receivers in the larger array revealed the significant influences of receiver tilt and ambient noise. These discrepancies in the outcomes of the two studies underscore the critical role of scale in range test design and emphasize the need for long-term, in situ range testing at relevant spatial scales. [ABSTRACT FROM AUTHOR]

Microwave rock fracturing has a wide range of application prospect in deep resource development due to its advantages of high efficiency and energy saving, and the study of damage in the fracturing process is of great importance in guiding the safety and high efficiency of rock fracturing. However, damage characterisation during microwave rock fracturing has not been sufficiently investigated. Therefore, studying the characteristics of crack propagation and evolution during microwave heating is of great significance. This paper investigates the crack evolution characteristics and failure mechanism of granite under microwave irradiation by collecting the real-time acoustic emission signals during heating using the self-developed microwave hot rock damage real-time dynamic monitoring system. The results indicate similar change characteristics of the real-time acoustic emission counts, energy, and RA/AF values of rock samples with corresponding stages after 900 s of microwave power irradiation at 0.3 kW, 0.6 kW, and 0.9 kW under the same temperature range and the most active acoustic emission range is 200–310 °C. The degree of thermal damage to rock samples and the power show a positive correlation under similar temperature ranges. The characteristics of real-time RA/AF values reflect the tensile failure of granite during microwave heating, accounting for more than 65%. However, the shear crack ratio increases with irradiation time or power, with the highest ratio of 33.3%. In addition, the real-time acoustic emission curve in the microwave heating process reaches the acoustic emission active point at 200 °C, which is far less than 300 °C and 350 °C of the traditional conduction heating method, with 1/2th and 1/15th of the heating time of the traditional conduction heating method, indicating the superiority of microwave rock breaking. [ABSTRACT FROM AUTHOR]

Highlights Fiber‐reinforced polymers (FRP) feature high strength‐to‐weight ratio amongst the emerging class of natural composites. This paper presents the impact of the glass fiber on the tensile strength of the flax epoxy laminate. The mechanical behavior and damping characteristics of flax fiber reinforced polymer (FFRP) and the hybrid flax‐glass fiber reinforced polymer (HFRP) are experimentally investigated. Both the flax and hybrid FRPs are made using vacuum infusion process. The specimens without and with holes of 4, 5, and 6 mm in diameter are subjected to tensile test using acoustic emission monitoring and free vibration test. In the former testing, HFRP resulted in higher peak frequencies and cumulative counts. Also, the natural frequency and damping factor of HFRP vary proportionately with the hole size, as identified in the latter tests. Different damage mechanisms during the tensile test revealed that the presence of glass fibers in HFRP increased resistance for certain damage mechanisms. Adding glass fiber to flax fiber reinforced polymer (FFRP) creates a hybrid FRP (HFRP) with increased resistance to damage and improved damping characteristics. HFRP exhibits a distinction in failure mechanisms compared to FFRP. The study utilizes acoustic emission (AE) to identify various damage mechanisms in the material, providing a more detailed information. The addition of glass fibers in HFRP leads to a more pronounced increase in damping factors. [ABSTRACT FROM AUTHOR]

This work presents particle-based numerical simulations on coal pillars in a coal mine based underground water reservoir (CMUWR). We aim to replicate the stress–strain characteristics and present the acoustic emission behavior of the coal under complex dynamic stress paths. The study reveals failure characteristics of coal exposed to monotonic/cyclic shear load under constant/cyclic normal loads. Based on the evolution of stress-time-dependent bond diameter implemented in particle model, different damage paths are established for dry and water-immersed samples under two loading frequencies. Furthermore, the numerical Gutenberg–Richter's b-value was calculated from the released energy emanating from bond failure, and this work presents the evolution of numerical Gutenberg–Richter's b-value. The numerical simulation contributes to a micromechanical understanding of the failure mechanisms of coal under water-immersion and cyclic stress, providing valuable insights for strength prediction of CMUWR. [ABSTRACT FROM AUTHOR]

Moisture content of rock/coal can change its mechanical properties and absorption capacities, which can directly affect gas diffusivity, change the stress distribution and hence cause significant impacts on the overall gas or coal extraction process. Observation of the water penetration process and water distribution in the coal matrix will be beneficial for the understanding of the fluid-solid coupling mechanism in hydraulic fracturing, aquifer cracking and coal seam infusion. However, the observation of water penetration process and the determination of water distribution mode were hard to be non-destructively achieved as coal is a non-uniform, inhomogeneous and un-transparent material. µ-CT imaging, which is based on variation of X-ray attenuation related to the density and atomic composition of the scanned objects, enables a four-dimensional (spatial-temporal) visualise of the heterogeneous and anisotropic coal samples. The primary aim of this paper is extending the application of µ-CT imaging to explore the moisture penetration and distribution within coal samples during water infusion process, which has been reported by very little literature. The working principle and procedures of CT imaging was firstly introduced. Then, the determination equation of moisture distribution based on density profile was established. The CT determined moisture content has been compared with weighting method for verification. The paper has demonstrated that µ-CT can be used for non-destructively imaging the moisture distribution within coal samples. [ABSTRACT FROM AUTHOR]

This paper investigates a 1.7 mm diameter ultra-weak fiber Bragg grating (UWFBG) hydrophone towed array cable for acoustic direction finding. The mechanism of the underwater acoustic waves received by this integrated-coating sensitizing optical cable is deduced, and it is shown that the amplitude of its response varies with the direction of the sound wave. An anechoic pool experiment is carried out to test the performance of such a hydrophone array. The test array is a selection of six sensing fibers, each of which is coiled into 9 cm diameter fiber ring suspended in the water to receive acoustic signals. An average sensitivity of −141.2 dB re rad/μPa at frequencies from 2.5 kHz to 6.3 kHz was achieved, validating the detection of the azimuth of underwater acoustic waves. The ultra-thin towing cable system, with free structure, high sensitivity, and underwater target-detection capability has demonstrated great potential for future unmanned underwater vehicle (UUV) applications. [ABSTRACT FROM AUTHOR]

Water inrush represents a significant hazard in karst tunnels, and the water-resistant rock mass plays a pivotal role in water inrush incidents. It is of great significance to explore the coupled hydro-mechanical failure process of water-resistant rock mass under excavation. A series of triaxial compression tests with different pressure conditions and loading rates were conducted in this study to investigate progressive failure characteristics and permeability evolution of limestone specimens. The experimental findings demonstrate that loading rate and confining pressure significantly influence progressive failure characteristics and permeability evolution. Additionally, a decreasing-then-increasing trend is observed in the crack initiation threshold (σci), and the crack damage threshold (σcd) exhibits a decreasing tendency. The resulting σci/σp ratio increases while the σcd/σp ratio decreases, indicating a diminishing stable fracture development stage. In general, permeability experiences an increase within an order of magnitude during the progressive failure of rock specimens, and the permeability of the rock mass decreases with rising initial confining pressure. The rate of deformation induced over the duration of permeability measurement exhibits a positive correlation with the stress ratio. Lastly, we propose a potential hysteresis water inrush mechanism, drawing upon the aforementioned observations. It is deduced that the creation, expansion, and ultimate penetration of fractures within the rock mass, resulting from the combined effects of excavation stress disturbance and changed pore pressure, give rise to water inrush events in karst tunnels. Highlights: Study of progressive failure characteristics and permeability evolution of limestone. Loading rate and confining pressure significantly influence progressive failure characteristics. Permeability experiences an increase within an order of magnitude. Deformation induced by permeability measurement exhibits a positive correlation with the stress ratio. Investigation of water inrush mechanism linking construction disturbance and pore pressure. [ABSTRACT FROM AUTHOR]

Water content is an important factor affecting the rock-breaking efficiency of tunnel boring machine (TBM) disc cutters. However, limited efforts have been made to study the fracturing mechanism of sandstone excavation by TBM disc cutters under varying water content conditions. To investigate the breakage behavior of water-soaked sandstone by TBM disc cutters, five sets of penetration tests on sandstone specimens with different water content levels were performed. The tests were conducted using a modified RYL-600 computer-controlled rock shear rheometer. An acoustic emission (AE) monitoring system was utilized throughout the entire process to track the AE activity of the specimens. The force–depth curves of the penetration process at various water content levels were investigated. The effects of water content on AE characteristics, rock fracture properties, and specific energy were analyzed. The results indicate that AE activity can be divided into three stages: quiet period, slow rise period, and active period. With increasing water content, peak penetration force, consumed energy, and specific energy decrease gradually, while chip volume increases. Water promotes mutual penetration of surface and internal cracks of the specimen, resulting in the formation of larger chip volumes. These findings provide theoretical guidance for designing and improving TBM cutter head parameters in water-rich soft rock formations. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of the cement-tailings ratio (CTR) on the fatigue properties, acoustic emission (AE) activities, energy dissipation, and fracture patterns of rock-backfill composite structure (RBCS) samples. The investigation employed multi-level cyclic loading tests combined with acoustic emission monitoring and post-test CT scanning. The results indicated that the fatigue strength and fatigue lifetime of the RBCS samples initially increased and then decreased as the CTR was reduced from 1:4 to 1:12. The energy dissipation characteristics reflected the optimal energy absorption effect of the backfill at a CTR of 1:8. The AE ring counts/energy apparent skip phenomenon corresponded to the stress-strain curve from a dense to sparse pattern. The samples with CTRs of 1:4 and 1:8 showed a more significant increase in the peak frequency band at failure and released more energy. The fracture of the RBCS specimen was dominated by tensile cracking signals accompanied by some shear cracking signals. However, the proportion of shear signals was higher for samples with CTRs of 1:4 and 1:8. Similarly, the b value was smaller at failure. The 3D visualization images revealed that the fracture pattern of the RBCS was a mixed tensile-shear fracture, including shear fracture within the backfill, tensile cracking in the interface, and tensile-shear fracture within the rock. The volume and complexity of cracks increased and then decreased with decreasing CTR, i.e., from 1:4 to 1:12. The evolution of cracks probably involves internal backfill fracturing first, and then the fracture extends into the surrounding rock. A recommendation for the design of CTB was presented in this study to ensure the safety and stability of mine excavations. [ABSTRACT FROM AUTHOR]

Bedload transport is a natural process that strongly affects the Earth's surface system. An important component of quantifying bedload transport flux and establishing early warning systems is the identification of the onset of bedload motion. Bedload transport can be monitored with high temporal resolution using passive acoustic methods, for example, hydrophones. Yet, an efficient method for identifying the onset of bedload transport from long‐term continuous acoustic data is still lacking. Benford's Law defines a probability distribution of the first‐digit of data sets and has been used to identify anomalies. Here, we apply Benford's law to continuous acoustic recordings from Baiyang hydrometric station, a tributary of Liwu River, Taroko National Park, Taiwan at the frequency of 32 kHz from stationary hydrophones deployed for 3 years since 2019. We construct a workflow to parse sound combinations of bedload transportation and analyze them in the context of hydrometric sensing constraining the onset, and recession of bedload transport. We identified three separate sound classes in the data related to the noise produced by the motion of pebbles, water flow, and air. We identify two bedload transport events that lasted 17 and 45 hr, respectively, covering about 0.35% of the total recorded time. The workflow could be transferred to other different catchments, events, or data sets. Due to the influence of instrument and background noise on the regularity of the residuals of the first‐digit, we recommend identifying the first‐digit distribution of the background noise and ruling it out before implementing this workflow. Plain Language Summary: Long‐term, high‐frequency monitoring of Earth surface processes brings huge data sets that can be of high quality. Benford's Law defines the specific probability distribution of the first‐digit of the data sets and has been used to identify anomalies and high‐energy events. We provide a workflow for applying Benford's Law to identify the onset of the motion of coarse sediment along the river bed at a time resolution of seconds. Since Benford's Law has demonstrated usefulness in acoustic amplitude analysis in this study, it could serve as a tool for identifying anomalous events in any kind of real‐time data series, which could be beneficial for generating event samples for machine learning applications. Key Points: Long‐term, high‐frequency acoustic monitoring constitutes huge‐volume data sets with a low signal‐to‐noise ratioThe distinct first‐digit distribution between signal and noise can used to filter out 99% of background noise from acoustic recordingsWe applied the method to a three‐year‐long acoustic data set in Baiyang, identifying two bedload transportation events [ABSTRACT FROM AUTHOR]

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This document presents the findings of a study on the occurrence and distribution of Rice's whales in the Gulf of Mexico. The study used acoustic recordings to detect the presence of Rice's whale calls at three different sites in the Gulf of Mexico. The results showed that Rice's whales were present in both U.S. and Mexican waters, indicating a transboundary range for the species. The study also highlighted the threats faced by Rice's whales, including vessel strikes, oil and gas exposure, entanglement in fishing gear, and habitat degradation. The authors emphasized the need for collaborative management and conservation efforts between U.S. and Mexican environmental agencies to protect the critically endangered species. Further research is needed to determine the full extent of the Rice's whale range and estimate the population abundance in the Gulf of Mexico. [Extracted from the article]

Passive acoustic telemetry can be used within cooperative networks to track migratory species over great distances at a relatively low cost. However, the non‐uniform distribution of fixed receivers within networks often results in sporadic detection data.Here, we propose a novel combination of methods to measure the reliability of hot spot analysis results derived from track reconstructions of passive telemetry data. We use an iterative process to simulate tracks of animals, derive detection data from these tracks, and reconstruct tracks from these derived data using a movement model. We then compare quadrat count residuals from the simulated and reconstructed tracks for different grid resolutions. The methodological framework is outlined in detail and tested on the acoustic telemetry cooperative arrays off the US East Coast. Our methods are applied to a subset of blacktip shark, Carcharhinus limbatus, acoustic telemetry detection data collected off the US East Coast. We then apply the resultant quadrat count to a hot spot analysis to determine the distribution of animals derived from these track reconstruction methods. We integrate the results of our methods process with the hot spot analysis results to determine the reliability of this distribution information.The track reconstruction methods performed well in coastal regions, from Palm Beach County, FL to Long Island, NY, minimized the clustering effect of high densities of receivers, and closed the gaps in some regions that were lacking receiver coverage. This performance was primarily affected by the presence/absence of receivers, and to a lesser extent by receiver density and water depth, depending on the grid resolution.Our method combination demonstrates a means by which passive telemetry data can be regularized to determine the spatial distribution of animals across regions with non‐uniform sampling coverage. These methods also allow the user to determine the reliability of animal distribution products in a telemetry array and the factors that contribute to high accuracy and precision. Our iterative process enables managers to infer the reliability of ecological results in decision‐making processes and could be leveraged for use as a gap analysis to develop a national strategy for telemetry assets. [ABSTRACT FROM AUTHOR]

To reveal the influence mechanism of mining speed on roof fracture-type rockburst, the Brazilian split technique combined with acoustic emission monitoring technology was employed to study the effects of loading rates on the tensile failure characteristics and acoustic emission parameters of coal series sandstone. The linear relationship between the tensile strength of the samples and the change rate of tensile stress was determined. The mining speed was introduced into the mechanical model of initial and cyclic fracture of the hard roof, and the quantitative relationship between the maximum rate of change of tensile stress within the hard roof and the mining speed was derived. Based on this, a computational model for the bending elastic energy of the hard roof during initial and cyclic fractures, considering the mining speed, was established. The main findings are as follows: As the loading rate increases, the distribution range of acoustic emission energy in sandstone Brazilian split samples before failure widens, with a significant rise in acoustic emission ring-down counts and energy at failure. At lower loading rates, acoustic emission events primarily occur near sample failure, whereas at higher rates, they mostly happen in the early loading stage. The higher the mining speed, the less opportunity there is for internal micro-fractures to develop and expand before the hard roof fractures, which macroscopically results in increased tensile strength and a larger amount of energy released at the moment of fracture. Bending elastic energy rises approximately linearly with mining speed, and the thicker the hard roof, the more sensitive the bending elastic energy is to changes in mining speed. This effect is even more pronounced during cyclic fractures. Optimizing mining speed is crucial for preventing roof fracture-type rockbursts, especially in mining workfaces with thick and hard roofs. [ABSTRACT FROM AUTHOR]

The present work investigates the treatment of wastewater containing an antibiotic, ciprofloxacin (CIP), using acoustic cavitation (AC) coupled with other advanced oxidation processes (AOPs). For the laboratory scale degradation study, operating parameters like drug concentration, operating pH, and initial temperature were initially optimized and then used in hybrid approach of AC in combination with AOPs. At 15 m/L initial drug concentration, neutral pH of 7, and ambient temperature of 30°C, optimum CIP degradation of 13.66% was obtained within 120 min of operation. The intensification of the AC‐based approach was subsequently achieved using other oxidants like H2O2, potassium persulphate (KPS), and O3. The combination of AC with H2O2 and KPS resulted in 44.30% and 35.41% CIP degradation, respectively, while AC combined with ozone resulted in almost complete degradation of CIP within 90 min of treatment with a maximum cavitational yield of 4.761 × 10−6 mg/J. The cost estimation for the optimized treatment approaches revealed that AC combined with ozone is the best process for degradation with the least operational cost of 8.7 Rs/L (105 US $/m3). Complete degradation of CIP with AC + O3 based approach at much lower costs opens a window for implementation in the pharmaceutical industries. [ABSTRACT FROM AUTHOR]

Measuring the temperature changes of the deep ocean will be critical to understanding how the earth system will respond to climate change. In this work, we present a method for measuring the depth‐averaged, deep ocean temperature at local (∼3 km) spatial scales using passive estimates of acoustic propagation. These passive acoustic estimates of deep ocean temperature can be used with existing and future passive acoustic monitoring infrastructure to provide complimentary observations of the ocean to in situ measurements, and could be particularly useful in areas of poor ocean observation coverage. Using 8 years of ambient sound data, we demonstrate that the passive estimates agree with global ocean models and measurements by ARGO floats. The rms difference between the HYCOM ocean model is shown to be 0.13°C, and the rms difference between ARGO measurements is shown to be 0.086°C. Plain Language Summary: In this work, we demonstrate that the ambient sound in the ocean can be used to measure local, depth‐averaged, deep ocean temperature. Using 8 years of ambient sound, we compare the estimate of ocean temperature to a global ocean model and ocean temperature measurements. The observations of deep‐ocean temperature estimated from ambient sound are shown to be consistent with the ocean model and direct measurements. This technique could eventually be used as a method for observing the deep ocean and be used as data assimilation into global ocean models. Key Points: Using coherent ambient sound, surface reflection acoustic arrival times are estimated with a high accuracy (∼1 ms)These estimates of acoustic travel time are then used to estimate the depth‐averaged water temperature in the deep oceanIn this work, we demonstrate the feasibility of using passive acoustic monitoring infrastructure to observe deep ocean temperature [ABSTRACT FROM AUTHOR]

Evaporation duct anomalies are always present above various oceanic processes, and their response to ubiquitous mesoscale eddies in the Kuroshio Extension region is quantitatively analyzed for the first time in this study using a synthetic analysis method based on reanalysis data sets and eddy trajectory data sets. The results indicated that the spatial distribution of evaporation duct anomalies is characterized by a monopole pattern, mainly modulated by the amplitude of anticyclonic eddies (AEs) and by the radius of cyclonic eddies (CEs). For AEs, the coupling strength is 0.7 m (2.9 M) per meter increase in amplitude, while for CEs, the coupling strength is 0.2 m (0.6 M) per 100 km increase in radius for the average evaporation duct height anomalies (evaporation duct strength anomalies) within the radius range. The modulation of evaporation duct anomalies by eddies is further examined. Plain Language Summary: Mesoscale eddies typically carry water with different characteristics from the surrounding environment, allowing them to transport moisture and energy at the ocean–atmosphere interface, thereby influencing the characteristic properties of evaporation ducts over the sea. To date, researchers have focused on the effects of various oceanic and atmospheric processes on evaporation ducts. However, there has been a persistent lack of research on the properties of evaporation ducts under the impact of mesoscale eddies. In this study, the variability in the evaporation duct environment under the influence of eddies and the underlying mechanisms are statistically analyzed. The results showed that ubiquitous mesoscale eddies could moderately modulate evaporation duct properties, which in turn could influence the effectiveness of shipborne radar technology, such as electromagnetic propagation, communication, and target detection. Key Points: The response of evaporation ducts to different eddy parameters is quantitatively determinedAnticyclonic (cyclonic) eddies with larger amplitudes (radii) exhibit stronger evaporation ductsAnticyclonic (cyclonic) eddies explain 5% (10%) of the total variance in evaporation duct properties [ABSTRACT FROM AUTHOR]

AbstractTo quantitatively study the failure evolution characteristics of raw coal and briquette under triaxial compression, an acoustic emission (AE) experiment was conducted on both materials. The failure evolution of raw coal and briquette was quantitatively characterized based on AE energy. A constitutive model accurately describing the failure evolution process of raw coal and briquette was constructed. Using the Logistic function, a constitutive model of failure evolution under triaxial compression was constructed by combining failure mechanics theory with effective medium theory. The effects of parameters a and r on the failure evolution process and constitutive relationship were further analyzed. The study results show that the compaction stage of raw coal is more typical but shorter, exhibiting an obvious stress fallback characteristic. The briquette exhibits an obvious linear increase in stress before reaching peak stress, with no obvious residual strength. The failure evolution curves of raw coal based on AE energy characterization can be divided into three stages: initial almost no failure, slow start of failure, and sharp, steep increase in failure. In contrast, the failure evolution curves of briquette do not have obvious stage change characteristics. The failure evolution equations and the constitutive model obtained by fitting the Logistic function yielded correlation coefficients ranging from 0.9704 to 0.9987. This indicates that the Logistic function effectively express the characteristics of failure evolution and the failure deformation process based on AE energy characterization. The theoretical failure evolution curves of raw coal and briquette are jointly determined by parameters a and r. Parameters a and r significantly affect the ontological relationship of raw coal and have a smaller effect on that of briquette. The research results are of great theoretical significance for the stability evaluation of deep coal mining. [ABSTRACT FROM AUTHOR]

A comprehensive analysis of aerosol characteristics over Saudi Arabia from 2005 to 2022, utilizing high-resolution satellite-based observations and reanalysis datasets, examining the distribution of aerosols and their subtypes across the three dimensions (temporal, spatial, and altitude based) for March, April, and May. This study focuses on the analysis of parameters such as aerosol optical depth (AOD), angstrom exponent (AE), absorption aerosol optical depth (AAOD), and Ultraviolet Aerosol Index (UVAI), revealing significant spatial disparities, with elevated aerosol concentrations in the central and eastern regions and comparatively lower concentrations along the western coastal areas. In this study, the spatial patterns and temporal trends are analyzed through trajectory modeling. The study also investigates the composition of aerosols in various Saudi cities. Aerosols prevailing in a dozen Saudi Arabian cities were systematically categorized into six sub-types, considering their particle size and UV-absorbing properties. Notably, two major aerosol sub-types, absorbing coarse (AC) aerosols (UVAI > 0.25, AE < 0.70) treated as mineral dust and absorbing mixed (AM) aerosols (0.70 < AE < 1.25) along with neutral fine (NF) particles (− 0.5 < UVAI < 0.25, AE > 1.25) treated as urban, predominate across the Kingdom of Saudi Arabia. [ABSTRACT FROM AUTHOR]

The ongoing global energy shift from fossil fuels to renewable sources highlights the importance of underground hydrogen storage (UHS) as a sustainable mechanism to counterbalance the seasonal inconsistencies of renewable energy. Comparable to geological CO2 sequestration, UHS necessitates precise subsurface imaging and a thorough understanding of hydrogen behavior within geological formations, including its location and migration patterns. Since direct subsurface measurement is unattainable, there is a pronounced need for robust subsurface characterization and monitoring techniques. This research focuses on UHS feasibility in enduring storage scenarios, employing seismic monitoring strategies adapted from CO2 storage practices. Specifically, we integrate Continuous Active Source Seismic Monitoring (CASSM) and Time-Lapse Full Waveform Inversion (TLFWI) to scrutinize UHS. The study employs synthetic crosshole surveys that initially model the coexistence of hydrogen and water within fractured reservoirs, aiming to pinpoint hydrogen-related velocity alterations in acoustic waveforms. Subsequently, we utilize a time-lapse synthetic model of hydrogen injection to emulate CASSM observations. Utilizing TLFWI in conjunction with White's model, we successfully process the CASSM data to discern and quantify temporal variations in velocity and saturation, which effectively maps the spatial and temporal distribution of mobile hydrogen. The results affirm the capabilities of TLFWI and CASSM as proficient monitoring systems for UHS. This study aspires to offer a dependable methodology for the administration of large-scale and long-term geological hydrogen storage. • New method links seismic monitoring with waveform inversion. • Imaging shows changes in underground hydrogen storage. • Monitoring accurately pinpoints hydrogen in fractured reservoirs. • Patchy White's model tracks hydrogen saturation through velocity changes. [ABSTRACT FROM AUTHOR]

This study introduced a mode II fracture energy approximation based on scratch test results and a phase field modeling approach. Using a length-insensitive approach, an analytical solution to in-plane shear (mode II) fractures was derived based on the phase field model for quasi-brittle fractures. Thereafter, the analytical solutions were related to the experimental data collected from the scratch testing to estimate the shear fracture energy, wherein the stress–strain degradation observed during fracture formation was compared. Panoramic pictures acquired after the test and the observed acoustic emission activity aided in identifying the evolution of shear fractures. The resulting shear fracture energy predicted for the reference material was consistent with results published in the literature. Subsequently, the developed methodology was applied to the shale rock samples in which mode II fractures were identifiable. This study demonstrated a cost- and time-effective approach to evaluating fracture properties of materials from small samples, which is valuable when limited samples are available and time/cost are of constraint. [ABSTRACT FROM AUTHOR]

Frost weathering is a key mechanism of rock failure in periglacial environments and landscape evolution. In high-alpine rock walls, freezing regimes are a combination of diurnal and sustained seasonal freeze–thaw regimes, and both influence frost cracking processes. Recent studies have tested the effectiveness of freeze–thaw cycles by measuring weathering proxies for frost damage in low-strength and in grain-supported pore space rocks, but detecting frost damage in low-porosity and crack-dominated alpine rocks is challenging due to small changes in these proxies that are close to the detection limit. Consequently, the assessment of frost weathering efficacy in alpine rocks may be flawed. In order to fully determine the effectiveness of both freezing regimes, freeze–thaw cycles and sustained freezing were simulated on low-porosity, high-strength Dachstein limestone with varying saturation. Frost-induced rock damage was uniquely quantified by combining X-ray computed microtomography (µ CT), acoustic emission (AE) monitoring, and frost cracking modelling. To differentiate between potential mechanisms of rock damage, thermal- and ice-induced stresses were simulated and compared to AE activity. Our results underscore the significant impact of initial crack density on frost damage, with µ CT scans revealing damage primarily through crack expansion. Discrepancies between AE signals and visible damage indicate the complexity of damage mechanisms. The study highlights frost cracking as the main driver of rock damage during freezing periods. Notably, damage is more severe during repeated freeze–thaw cycles compared to extended periods of freezing, a finding that diverges from field studies. This discrepancy could stem from limited water mobility due to low porosity or from the short duration of our experimental setup. [ABSTRACT FROM AUTHOR]

The use of ocean sensors is crucial for exploration of the ocean and harnessing the potential of its resources. However, conventional ocean sensors are limited by their fabrication techniques, which result in sensors that are large in size, have high-power consumption requirements, and involve complex deployment processes. However, fulfilling observation requirements in the harsh marine environment presents a formidable challenge for these devices. Microelectromechanical system (MEMS) technologies offer a promising solution that will enable development of a new generation of ocean sensors that offer superior performance. This paper focuses on MEMS-based ocean sensors that have been designed to measure both essential physical parameters and fundamental processes within the marine environment, including the ocean's conductivity, temperature, and depth, ocean currents, ocean turbulence, earthquakes, seafloor deformation, and ocean acoustic signals. The fundamental designs of these sensors, including their working principles, structures, properties, and fabrication procedures, are illustrated in the individual sections. The paper also discusses the important challenges that MEMS ocean sensors may encounter, along with their prospects for future development. By highlighting the potential of MEMS-based ocean sensors, this review aims to contribute to the development of more efficient and reliable ocean observation systems. [ABSTRACT FROM AUTHOR]

Carbon Fiber Reinforced Polymer (CFRP), a novel high-performance material, has found extensive use across various domains. Due to the intricate structure of CFRP and variability in its manufacturing process, such as differences in resin curing speeds or carbon fiber alignment, defects including voids and inclusions can inevitably occur. These defects can compromise the material's performance and reliability, making Non-Destructive Testing (NDT) essential for early defect detection and real-time monitoring. This paper reviews existing NDT technologies like visual inspection, computed tomography (CT), ultrasonic testing, acoustic emission testing, infrared thermal imaging, eddy current testing, and Raman spectroscopy. To facilitate performance comparison, we use spider charts to illustrate key aspects of each technique, including detection accuracy, damage localisation, interface details, and online monitoring capabilities. These charts specifically highlight the superior overall performance of CT. The principles, applications, and cutting-edge advancements in NDT techniques and Structural Health Monitoring systems (SHM) are systematically discussed. This review delves into the principles, strengths, and limitations of CFRP damage detection methods, includes detailed examples and provides a selection criterion for the work of NDT researchers. [ABSTRACT FROM AUTHOR]

In-depth investigations into the effect of water saturation on the damage and failure mechanisms of rock have significance for analyzing the stability of the surrounding rock in water-rich rock masses. Uniaxial compression tests were carried out on two types of sandstone to explore the influence and mechanism of water saturation on their strength and deformation, stress thresholds, energy evolution, and acoustic emission (AE) characteristics. The deduced the following after water saturation: (1) water saturation had an obvious softening effect on both types of sandstone, manifested by a reduction in uniaxial compressive strength and elastic modulus, and an increase in the Poisson's ratio; (2) the normalized crack initiation stress (σci/σf) increased and the normalized crack damage stress (σcd/σf) decreased; (3) the total energy (U), elastic energy (Ue), and dissipated energy (Ud) at the peak strength decreased and the ratio of elastic energy to total energy (Ue/U) decreased; and (4) the peak values of AE count and AE cumulative count decreased in both types of sandstone. Based on our analysis of the AE b-values, the proportion of small-scale ruptures increased. An analysis based on the AE ratio of the rise time to amplitude (RA) value and average frequency (AF) value showed that the proportion of shear fracture increased after water saturation. Our findings provide an indication of the significance of determining the failure mechanism of water-saturated rocks. [ABSTRACT FROM AUTHOR]