Search Results (89)

Background: Asthma is a well-known otolaryngological and immunological disorder that affects patients worldwide. Currently, the primary diagnosis relies on a combination of clinical history, physical examination findings consistent with asthma, and objective evidence of reversible airflow obstruction. However, the diagnostic process can be invasive and time-consuming, which limits clinical efficiency and accessibility. Objectives: In this study, an AI-based prediction system was developed, leveraging voice changes caused by respiratory contraction due to asthma to create a machine learning (ML)-based clinical decision support system. Methods: A total of 1500 speech samples—comprising high-pitch, normal-pitch, and low-pitch recitations of the phonemes [i, a, u]—were used. Long-Term Average Spectrum (LTAS) and Single-Frequency Filtering Cepstral Coefficients (SFCCs) were extracted as features for classification. Seven machine learning algorithms were employed to assess the feasibility of asthma prediction. Results: The Decision Tree, CNN, and LSTM models achieved average accuracies above 0.8, with results of 0.88, 0.80, and 0.84, respectively. Observational results indicate that the Decision Tree model performed best for high-pitch phonemes, whereas the LSTM model outperformed others in normal-pitch and low-pitch phonemes. Additionally, to validate model efficiency and enhance interpretability, feature importance analysis and overall average spectral analysis were applied. Conclusions: This study aims to provide medical clinicians with accurate and reliable decision-making support, improving the efficiency of asthma diagnosis through AI-driven acoustic analysis. Full article

Sensory evoked potentials (EPs), namely, somatosensory, visual, and brainstem acoustic EPs, are used in neurosurgery to monitor the corresponding functions with the aim of preventing iatrogenic neurological complications. Functional deficiency usually precedes structural defect, being initially reversible, and prompt alarms may help surgeons achieve this aim. However, sensory EP registration requires presenting multiple stimuli and averaging of responses, which significantly lengthen this procedure. As delays can make intraoperative neuromonitoring (IONM) ineffective, it is important to reduce EP recording time. The possibility of speeding up EP recording relies on differences between IONM and outpatient clinical neurophysiology (CN). Namely, in IONM, the patient is her/his own control, and the neurophysiologist is less constrained by norms and standards than in outpatient CN. Therefore, neurophysiologists can perform a personalized selection of optimal locations of recording electrodes, frequency filter passbands, and stimulation rates. Varying some or all of these parameters, it is often possible to significantly improve the signal-to-noise ratio (SNR) for EPs and accelerate EP recording by up to several times. The aim of this paper is to review how this personalized approach is or may be applied during IONM for recording sensory EPs of each of the abovementioned modalities. Also, the problems hindering the implementation and dissemination of this approach and options for overcoming them are discussed here, as well as possible future developments. Full article

Laboratory acoustic measurements of hydrate-bearing sediments serve as an important reference for the geological interpretation of seismic exploration data. Tetrahydrofuran (THF) hydrates are relatively easy to form with precise control of hydrate saturation, and they overcome the long time it takes for methane in sediments to form hydrate. However, when THF hydrates are used as a substitute for methane hydrate, their acoustic properties yield different results. This study reports the results of a series of laboratory experiments on the formation of methane and THF hydrate in quartz sand and the evaluation of their acoustic properties. It compares the experimental results with the results of calculations from micro-distribution models of the four hydrates using effective medium theory (EMT). Methane hydrate formed by the excess gas method has higher acoustic velocities than THF hydrate at 0–80% saturation, but at 80–100% saturation, the situation reverses, with THF hydrate having a higher wave velocity. The methane hydrate synthesis process follows a mixed micro-distribution, with grain coating predominating at low saturations, the pore-filling mixing mode dominating at medium saturations, and grain coating dominating at high saturations. In addition, THF hydrate has a slow-velocity growth at low saturation and is dominated by a pore-filling model and a load-bearing model at high saturation. We compared our experimental data with a compilation of similar published results to confirm their reliability and support our conclusions. Both hydrate types exhibit distinct micro-distributions across different saturations. Therefore, when testing the elastic characteristics of hydrate sediments, the distinct hydrate synthesis methods and micro-distribution should be considered, especially when using THF hydrate as an alternative to methane hydrate. Full article

Acoustic emission (AE) source localization technology, since the early application to one-dimensional structures, has been extended to a wide range of applications to two-dimensional (2D) structures, including isotropic and anisotropic materials, which are currently the most widely studied and the most mature. With the development of AE source localization technology, more and more significant challenges have arisen for three-dimensional (3D) structures, which are mostly anisotropic and have complex propagation paths. This paper summarizes and discusses the AE source localization methods in different dimensions as well as their applications, including the main methods for 2D AE source localization, such as the triangulation method, beam forming, strain rosette technique, modal AE, artificial neural network, optimization and the time reversal technique, as well as state-of-the-art AE source localization methods in isotropic and anisotropic structures utilizing these methods. Recent advances in AE source localization in complex 3D structures are also reviewed. Full article

Orthogonal Time–Frequency Space (OTFS) is an innovative modulation method that ensures efficient and secure communication over a time-varying channel. This characteristic inspired us to integrate OTFS technology with underwater acoustic (UWA) communications to counteract the time-varying and overspread characteristics of UWA channels. However, implementing OTFS in UWA communications presents challenges related to overspread channels. To handle these challenges, we introduce a specialized OTFS system and offer frame design recommendations for UWA communications in this article. We propose a Doppler compensation method and a dual-domain joint channel estimation method to address the issues caused by severe Doppler effects in UWA communication. Additionally, we propose an OTFS system detection approach. This approach incorporates an iterative detection process which facilitates soft information exchange between a message passing (MP) detector and a low-density parity check (LDPC) decoder. By conducting simulations, we demonstrate that the proposed UWA OTFS system significantly outperforms Orthogonal Frequency-Division Multiplexing (OFDM), Initial Estimate Iterative Decoding Feedback (IE-IDF-MRC), and two-dimensional Passive Time Reversal Decision Feedback Equalization (2D-PTR-DFE) in UWA channels. Full article

Flexible ultrasonic devices represent a feasible technology for providing timely signal detection and even a non-invasive disease treatment for the human brain. However, the deformation of the devices is always accompanied by a change in the acoustic field, making it hard for accurate focusing. Herein, we report a stable and flexible transducer. This device can generate a high-intensity acoustic signal with a controllable acoustic field even when the device is bent. The key is to use a low-impedance piezoelectric material and an island-bridge device structure, as well as to design a unique time-reversal algorithm to correct the deviation of signals after transcranial propagation. To provide an in-depth study of the acoustic field of flexible devices, we also analyze the effects of mechanical deformation and structural parameters on the corresponding acoustic response. Full article

The shale oil reservoirs of the Lower Permian Fengcheng Formation in the northern Mahu Sag are promising targets. However, complex geology and strong heterogeneity in the area pose great difficulties in the numerical simulation of in situ stress fields, which have for a long time been poorly understood. This study provides a systematic and accurate 3D in situ stress numerical simulation workflow based on comprehensive data. In this research, optimized ant tracking was applied to construct refined geological models. Acoustic impedance is taken as what we refer to as “hard” data to reflect variations in geomechanical parameters. Logging and mechanical tests were taken as “soft” data to restrict the numerical range of the geomechanical parameters. With the integration of “hard” data and “soft” data, accurate 3D geomechanical models can be attained. The finite element method was ultimately utilized to simulate the 3D in situ stress field of the Fengcheng Formation. Numerical simulation results reveal that the stress state of the Fengcheng Formation is quite complicated. The magnitude of the horizontal principal stress, horizontal stress difference and horizontal stress difference coefficient are correlated with burial depth, faults, and geomechanical parameters to some degree. The parameter Aφ was introduced in this research to better analyze the stress regime, the result of which demonstrates that the main stress regime in the study region is the reverse faulting stress regime. By evaluating the fault stability, it was found that there is basically no possibility of slippage regarding the faults in northern Mahu Sag. The results of this research provide evidence for well deployment optimization, borehole stability, and so on, all of which are of great significance in hydrocarbon exploration and exploitation. Full article

This paper presents a localization method for an underwater multitonal source by using a vertically distributed system in deep water. The system is composed of two kinds of nodes. One is a node at large depth, and the other is a node covering most of the water column. The former and latter are utilized to estimate the source range and depth, respectively. Specifically, the proposed method estimates the source range by matching the spatial arrival angle measured by the first kind of node with the replicas calculated by the acoustic model. Based on the estimation value of the source range, the second kind of node is utilized to estimate the source depth by using an incoherent time reversal method. The effectiveness of the proposed method is demonstrated through numerical simulations. The effects of the measurement error and the sound speed profile mismatch on the performance of the proposed method are also analyzed. Full article

Ships navigating in channels with vortex fields face increased risks. However, these vortex fields can be monitored using acoustic methods. The key is to extract the phase characteristics of sound signals passing through the vortices. Using time-reversal mirrors, this paper studied the extraction method of characteristics both numerically and experimentally, aiming to verify the effectiveness of the numerical simulation method. Starting from this point, the impact of different movement forms and scale changes in vortex fields on the acoustic signal extraction method was further investigated. The results indicate that with the iterations of time reversal (N < 6), the method is effective for uniformly moving vortex fields, when the vortex center moving speed $V_w$ < 2.2 × 10⁻³ m/s and the radius diffusion speed $V_r$ < 2.5 × 10⁻³ m/s. On the other hand, for oscillating vortex fields, it is effective when the oscillation amplitude $L_D$ < 0.15 m and the radius diffusion speed $V_r$ < 2.4 × 10⁻³ m/s; meanwhile, the dynamic characteristics of the vortex field can be ignored by the phase extraction method based on time-reversal mirrors. Full article

We used the transfer matrix method to investigate the conditions supporting the existence of directional bulk waves in a two-dimensional (2D) phononic crystal. The 2D crystal was a square lattice of unit cells composed of rectangular subunits constituted of two different isotropic continuous media. We established the conditions on the geometry of the phononic crystal and its constitutive media for the emergence of waves, which, for the same handedness, exhibited a non-zero amplitude in one direction within the crystal’s 2D Brillouin zone and zero amplitude in the opposite direction. Due to time-reversal symmetry, the crystal supported propagation in the reverse direction for the opposite handedness. These features may enable robust directional propagation of bulk acoustic waves and topological acoustic technology. Full article

This study addresses the issue of vortex current fields near the islands and reefs in China’s straits, which pose significant challenges to engineering construction and navigation safety in the surrounding waters. To monitor these vortex fields, the study proposes an innovative method utilizing acoustic signals. The study utilizes the numerical simulation and phase feature extraction of acoustic signals in the vortex current field, based on ray acoustic theory and time-reversal mirror technology. The study successfully monitored the central position of the vortex core and characteristic radius of the vortex current field near Barley Straw Reef using HYCOM data for the first time. Furthermore, the performance of the method was analyzed under different acoustic phase perturbations and signal-to-noise ratios. The numerical simulation results demonstrate that the acoustic method is effective in monitoring near-shore vortex fields, and the time-reversal mirror technique is useful in extracting phase difference information from acoustic signals generated by vortex currents. Full article

This review provides unique insights to the scientific scope and clinical visions of the inventors and pioneers of the SoftVue breast tomographic ultrasound (BTUS). Their >20-year collaboration produced extensive basic research and technology developments, culminating in SoftVue, which recently received the Food and Drug Administration’s approval as an adjunct to breast cancer screening in women with dense breasts. SoftVue’s multi-center trial confirmed the diagnostic goals of the tissue characterization and localization of quantitative acoustic tissue differences in 2D and 3D coronal image sequences. SoftVue mass characterizations are also reviewed within the standard cancer risk categories of the Breast Imaging Reporting and Data System. As a quantitative diagnostic modality, SoftVue can also function as a cost-effective platform for artificial intelligence-assisted breast cancer identification. Finally, SoftVue’s quantitative acoustic maps facilitate noninvasive temperature monitoring and a unique form of time-reversed, focused US in a single theranostic device that actually focuses acoustic energy better within the highly scattering breast tissues, allowing for localized hyperthermia, drug delivery, and/or ablation. Women also prefer the comfort of SoftVue over mammograms and will continue to seek out less-invasive breast care, from diagnosis to treatment. Full article

The two-dimensional (2D) cross-hole seismic computed tomography (CT) imaging acquisition method has the potential to characterize the target zone optimally compared to surface seismic surveys. It has wide applications in oil and gas exploration, engineering geology, etc. Limited to 2D hole velocity profiling, this method cannot acquire three-dimensional (3D) information on lateral geological structures outside the profile. Additionally, the sensor data received by cross-hole seismic exploration constitute responses from geological bodies in 3D space and are potentially affected by objects outside the well profiles, distorting the imaging results and geological interpretation. This paper proposes a 3D cross-hole acoustic wave reverse-time migration imaging method to capture 3D cross-hole geological structures using sensor settings in multi-cross-hole seismic research. Based on the analysis of resulting 3D cross-hole images under varying sensor settings, optimizing the observation system can aid in the cost-efficient obtainment of the 3D underground structure distribution. To verify this method’s effectiveness on 3D cross-hole structure imaging, numerical simulations were conducted on four typical geological models regarding layers, local high-velocity zones, large dip angles, and faults. The results verify the model’s superiority in providing more reliable and accurate 3D geological information for cross-hole seismic exploration, presenting a theoretical basis for processing and interpreting cross-hole data. Full article

Ensuring the reliability of process gas compressors is critical for underground gas storage, as piston rod fractures can lead to serious accidents, such as natural gas leaks or explosions. On-time monitoring and early detection play a vital role in preventing catastrophic consequences, minimising costs, and reducing production losses due to unplanned downtime. This study presents a novel accelerated life-testing method designed to replicate the fracture events of reciprocating compressor piston rods. By accelerating the induced crack initiation and propagation to the final fracture, comprehensive analyses of the fracture results are performed to reveal the piston rod fracture mechanism and the resulting secondary damage to the unit. The research further presents an innovative approach for identifying piston rod crack propagation by means of acoustic emission. Through kinetic analysis and time–frequency domain analysis, the study elucidates two mechanisms responsible for triggering crack signals during the compressor operation: the contact impact between the crosshead pin and the bearing due to the piston rod load reversal, and crack propagation occurring before the maximum tensile load is reached. In addition, the study identifies the piston rod crack expansion signal frequency band and achieves a high-sensitivity identification of crack dynamic growth by extracting signal sub-band features associated with crack propagation. Then, a prediction model of the fatigue crack growth rate was established based on the AE energy release rate, which provides a quantitative assessment of dynamic crack propagation during compression. This method aims to provide a maintenance strategy for piston rod fractures, thereby increasing the operational safety of critical dynamic equipment in underground gas storage. Full article

Brain neurodegenerative diseases are central nervous system (CNS) affections typically common in older adults. A new therapeutic approach for them consists of providing specific drugs to the CNS through blood circulation; however, the Blood–Brain Barrier (BBB) prevents almost 100% of neurotherapeutics from reaching the brain. There are indications that Focused Ultrasound (FUS), temporarily placed in the BBB, can achieve a controlled increase in temperature at its focus, allowing temporary, localized, and reversible opening of this barrier, which facilitates the temporary delivery of specific drugs. This work presents a FUS-based protocol for the local, temporary, and reversible opening of the BBB in Wistar rats. The proposed protocol specifies certain power, treatment times, and duty cycle to controllably increase the temperature at the region of interest, i.e., the substantia nigra. Numerical simulations using commercial software based on the finite element method were carried out to determine the optimal size of the craniotomies for nearly full-acoustic transmission. Experiments in rats were performed with the parameters used during computational simulations to determine the adequate opening of the BBB. For this, craniotomies of different sizes were made at coordinates of the substantia nigra, and FUS was applied from the exterior. The opening of the BBB was evaluated using Evans Blue (EB) as an indicator of the crossing of the dye from the blood vessels to brain tissue. Numerical simulations demonstrated a major distance reached by the ultrasound focus with a bigger diameter. Experimental results show the local, temporary, and reversible opening of the BBB through a 10 mm diameter craniotomy, which effectively allowed placing the ultrasound focus over the substantia nigra, unlike a 6 mm diameter craniotomy in which there is a deviation of the focus through that window. Moreover, from these results, it was also determined that the disruption of the BBB was reversible, with an opening duration of 6 h after FUS application. The experimental work developed in this study resulted in a minimally invasive method for the temporary opening of the BBB. Full article