Acoustic Impedance Research Articles

Numerical Simulation and Experimental Research of Spatial Volume Distribution and Velocity Changes of Abrasive Suspension Jet Based on LES + VOF + DEM

The machining accuracy and cutting ability of abrasive suspension jet (ASJ) are affected by the spatial volume distribution and velocity changes of jet flow and abrasives in the free jet area outside the nozzle. In this paper, large eddy simulation (LES) flow model, volume of fluid (VOF) multiphase flow model and discrete element model (DEM) were used to simulate the flow field characteristics of ASJ. The spatial volume distribution and velocity changes of jet flow and abrasives under 10[Formula: see text]MPa jet pressure were studied and the model validation experiments were carried out. In the comparison between the numerical simulation results and the experimental results, it was found that the average error of the percentage of central jet flow is 3.4%, the percentage of central abrasive particles is 3.0% and the velocity of abrasive particles is 4.2%. The physical structure of the numerical model is fixed (so it does not support abrasive injection jet (AIJ)), and the material physical parameters, initial conditions and boundary conditions are editable. Therefore, it can be used to predict the degree of water divergence, abrasives divergence and abrasives velocity attenuation of ASJ with different jet pressure and abrasive types. This numerical model can provide guidance for the parameter setting of ASJ machining process in order to obtain better machining accuracy and cutting ability.

Radiation Impedance of Rectangular CMUTs.

Recently, capacitive micromachined ultrasound transducers (CMUTs) with long rectangular membranes have demonstrated performance advantages over conventional piezoelectric transducers; however, modeling these CMUT geometries has been limited to computationally burdensome numerical methods. Improved fast modeling methods, such as equivalent circuit models, could help achieve designs with even better performance. The primary obstacle in developing such methods is the lack of tractable methods for computing the radiation impedance of clamped rectangular radiators. This paper presents a method that approximates the velocity profile using a polynomial shape model to rapidly and accurately estimate radiation impedance. The validity of the approximate velocity profile and corresponding radiation impedance calculation was assessed using finite element simulations for a variety of membrane aspect ratios and bias voltages. Our method was evaluated for rectangular radiators with width:length ratios from 1:1 up to 1:25. At all aspect ratios, the radiation resistance was closely modeled. However, when calculating the radiation reactance, our initial approach was only accurate for low aspect ratios. This motivated us to consider an alternative shape model for high aspect ratios, which was more accurate when compared with FEM. To facilitate the development of future rectangular CMUTs, we provide a MATLAB script that quickly calculates radiation impedance using both methods.

Enhancing Thin Coal Seam Detection in Eastern Indian Coalfields Using ICWT-Decon-Based Seismic Attributes and Acoustic Impedance Inversion

A high-resolution seismic survey (HRSS) is often used in coal exploration to bridge the data gap between two consecutive boreholes and avoid ambiguity in geological interpretation. The application of high-resolution seismic surveys in the Indian context is challenging as the delineation of thin non-coal layers within the coal layer requires a very high seismic data resolution. However, conventional seismic processing techniques fail to resolve thin coal/non-coal layers and faults, which is crucial for the precise estimation of coal resources and mine economics. To address these issues, we applied the inverse continuous wavelet transform deconvolution (ICWT-Decon) technique to post-stack depth-migrated seismic sections. We examined the feasibility of the ICWT-Decon technique in both a synthetic post-stack depth-migrated model and 2D/3D seismic data from the North Karanpura and Talcher Coalfields in Eastern India. The results offered enhanced seismic sections, attributes (similarity and sweetness), and acoustic inversion that aided in the precise positioning of faults and the delineation of a thin non-coal layer of 4.68 m within a 16.7 m coal seam at an approximate depth of 450 m to 550 m. This helped in the refinement of the resource estimation from 74.96 MT before applying ICWT-Decon to 55.92 MT afterward. Overall, the results of the study showed enhancements in the seismic data resolution, the better output of seismic attributes, and acoustic inversion, which could enable more precise lithological and structural interpretation.

Mediating coherent acoustic phonon oscillation of a 2D semiconductor/3D dielectric heterostructure by interfacial engineering

Abstract Coherent acoustic phonon (CAP) oscillation of 2D layered semiconductor/3D dielectric heterostructure generated by femtosecond laser pulse excitation can realize ultrafast photoacoustic conversion, while the photoacoustic conversion efficiency suffers from interfacial phonon scatterings of simultaneously laser-induced lattice heat. Here, taking advantage of graphene’s high thermal conductivity and large acoustic impedance, we demonstrate that phonon scatterings can be markedly mediated in a MoS$_2$/graphene/glass heterostructure via femtosecond laser pump-probe measurements. Equilibrium temperatures of MoS$_2$ lattice have been cooled down by about 45 %. As a benefit, both lifetime of CAP oscillations and pump pulse-picosecond acoustic pulse energy conversion efficiency have been enhanced by a factor of about 2. Our results constitute insights into CAP manipulations via interfacial engineering, that are fundamentally important for ultrafast photoacoustics based on 2D layered semiconductors.

Statistical Metamodel of Liner Acoustic Impedance Based on Neural Network and Probabilistic Learning for Small Datasets

The main novelty of this paper consists of presenting a statistical artificial neural network (ANN)-based model for a robust prediction of the frequency-dependent aeroacoustic liner impedance using an aeroacoustic computational model (ACM) dataset of small size. The model, focusing on percentage of open area (POA) and sound pressure level (SPL) at a zero Mach number, takes into account uncertainties using a probabilistic formulation. The main difficulty in training an ANN-based model is the small size of the ACM dataset. The probabilistic learning carried out using the probabilistic learning on manifolds (PLoM) algorithm addresses this difficulty as it allows constructing a very large training dataset from learning the probabilistic model from a small dataset. A prior conditional probability model is presented for the PCA-based statistical reduced representation of the frequency-sampled vector of the log-resistance and reactance. It induces some statistical constraints that are not straightforwardly taken into account when training such an ANN-based model by classical optimizations methods under constraints. A second novelty of this paper consists of presenting an alternate solution that involves using conditional statistics estimated with learned realizations from PLoM. A numerical example is presented.

Full-duplex two-way no-relay cross-media communication method based on acoustic wave conversion

Abstract Due to the difference in acoustic impedance between water and air, the water interface becomes a natural barrier. Underwater sound waves will bounce when they propagate to the water surface. Electromagnetic waves and light waves in the air will rapidly attenuate after passing through the water surface and going underwater, making it difficult to complete air-water cross-media information transmission. In this article, we first analyze the theoretical characteristics and vibration model of the water surface after medium collision, and develop a new full-duplex communication method across the air-ocean medium, which does not rely on relay equipment and only uses three transmission media in the air. Propagate signals in the sea channel physical field to achieve two-way communication, using the mutual conversion between laser, acoustic, and radio frequency signals to fill the gap in cross-media communication technology that can simultaneously achieve two-way, full-duplex and non-relay. It has been verified through experimental installations carried out in laboratory water tanks and large comprehensive anechoic pools that it is able to achieve full-duplex communication links across the air-sea surface, indicating that the combination of laser acousticization and radio frequency-acoustic wave conversion can be used across medium full-duplex wireless communication provides a feasible method for communication that breaks through the water interface.

Abstract P450: A dual probe ultrasound vector Doppler method for a robust and reliable estimation of blood flow volume and pulse wave velocity on the carotid artery

Background: The arterial pulse wave velocity (PWV) is a strong marker of cardiovascular risk and hypertension. The development of devices enabling a robust and reliable assessment of PWV could play an important role in the early diagnosis and monitoring of those diseases. In this work, we propose an ultrasound technique to estimate blood flow volume (BFV) and PWV by simultaneously using two probes. Methods: Two linear arrays, held by a handle, image two cross-sections of the artery, on two planes intersecting at 40° at the vessel center (A). B-mode and color flow Doppler (CFD) images are reconstructed at high frame rate (HFR): the cross-section HFR CFDs, providing vector-Doppler imaging, avoid any assumptions on flow velocity direction and profile, thus enabling reliable BFV estimates; the HFR B-mode allows tracking the arterial wall, thus enabling robust and time-resolved estimates of the lumen area (B). PWV is estimated as the ratio between the change in flow and cross-sectional area during the early systole (C). The method was preliminary verified by repeating 12 times the BFV and PWV estimation on the carotid artery of 8 healthy volunteers. Results: PWV and BFV measures were in the physiological range of 4.0-6.6 m/s (D) and 4.2-10.8 cm 3 /s, respectively. Measures were repeatable as proved by narrow interquartile ranges and low average standard deviations (1.4 m/s and 1.1 cm 3 /s, for PWV and BFV), which confirm the method's robustness. Conclusions: The proposed technique is suitable for BFV and PWV estimations. Since it is robust to probe repositioning and does not rely on any assumption of flow direction and profile, it could be implemented on wearable cardio-vascular wellness monitoring devices.

Continuous muscle pump activation by neuromuscular electrical stimulation of the common peroneal nerve in the treatment of patients with venous leg ulcers: A position paper.

The standard treatment for patients with confirmed Venous Leg Ulcers (VLUs) is compression therapy to improve the function of the calf muscle pump. There is a significant cohort of patients who are unable to tolerate optimal compression therapy or indeed any level of compression therapy. In addition, there is a cohort of patients who can tolerate compression whose ulcers show little or no evidence of healing. There is a need for ways to further improve calf muscle pump function and to improve venous ulcer healing in these patients. Published data were reviewed on the use of Muscle Pump Activation (MPA) using common peroneal nerve neuromuscular electrical stimulation (NMES) to improve calf muscle pump function. There is physiological evidence that MPA can improve calf muscle pump function and venous return in both control subjects and in patients with venous disease. The use of MPA has also been shown to improve venous flow volume and venous flow velocity on ultrasound scanning in patients with venous disease. MPA has been shown to improve microcirculation in the skin using Laser Doppler and laser Doppler Speckle Contrast Imaging, in both normal subjects as well as in patients with venous disease and VLU. A recent randomized controlled trial of MPA plus compression therapy compared with compression therapy alone, found significantly faster rates of healing with the use of MPA in addition to compression therapy. There are indications for the use of MPA as an adjunctive treatment to enhance calf muscle pump function in patients with VLU: who cannot tolerate compression therapy who can only tolerate suboptimal, low-level compression whose ulcer healing remains slow or stalled with optimal compression.

Ultrasonic Velocity of Acrylates with Decane-2-ol at 313.15 K

Thermodynamic data involving ultrasonic velocities of binary liquid mixtures of methyl acrylate, ethyl acrylate and butyl acrylate with decane-2-ol have been measured at 313.15 K and at atmospheric pressure. Study of thermodynamic properties involves challenges of interpreting the excess quantities as a means of understanding the nature of intermolecular interactions among the mixed components. Experimental values of ultrasonic velocities were correlated with recently proposed Jouyban-Acree model. Deviations in isentropic compressibility were calculated and have been fitted to Redlich-Kister polynomial equation. Excess parameters like specific acoustic impendence, intermolecular free length, available volume, intrinsic pressure, molecular association and molar sound velocity were also calculated. Graphical representations of excess derived thermodynamic parameters used to explain the type and extent of intermolecular interactions

An investigation of anisotropy in the bubbly turbulent flow via direct numerical simulations

We investigated the effects of bubble count, flow direction, and Eötvös number on deformable bubbles in turbulent channel flow. For a given shear Reynolds number Re = 180 and fixed bubble volume fractions (1.263% and 2.525%), we conducted a series of direct numerical simulations using a coupled level-set and volume-of-fluid solver to evaluate their impact on bubble volume fraction distribution, velocity fields, and turbulence characteristics. Each aspect was studied based on the microscopic equations of two-phase flow, and the accuracy of the modeling terms used in current Reynolds-averaged Navier–Stokes equation (RANS) models was assessed. The influence on the anisotropic state was analyzed using the Lumley triangle, and the anisotropy of Reynolds stresses was captured through the exact balance equations. The results indicate that in upward flow, bubbles tend to accumulate near the wall, with smaller Eötvös numbers leading to closer proximity to the wall and greater attenuation of the liquid-phase velocity. This distribution enhances energy dissipation and turbulence isotropy. In downward flow, bubbles cluster in the channel center, generating additional pseudo-turbulence and attenuating energy in the buffer layer. Moreover, the interfacial transfer of turbulent energy, as currently modeled in RANS, is found to be inadequate for upward flows.

A flowchart for porosity and acoustic impedance mapping using seismic inversion with semi hybrid optimization combining simulated annealing and pattern search techniques

A flowchart for porosity and acoustic impedance mapping using seismic inversion with semi hybrid optimization combining simulated annealing and pattern search techniques

An integrated multichannel system for air-coupled CMUT array imaging and guided wave detection applications

Abstract Capacitive micromachined ultrasonic transducers (CMUTs) made by MEMS process have become a new choice for air-coupled ultrasonic transducers due to their high sensitivity, low acoustic impedance and easy arraying. At present, in the air coupling application of CMUT transducer, due to the weak signal strength of single element, the CMUT array usually works in a whole piece, limiting the advantage of the array. Therefore, a multi-channel air-coupled CMUT imaging system with high-voltage DC bias and low-noise high-gain current signal amplification is designed to realize the electronic scanning of our CMUT arrays. The imaging system has 16 transmit and receive channels, and each channel consists of pulse transmitting circuit, AC/DC coupling circuit, impedance matching circuit, low-noise transimpedance amplification circuit, controllable gain amplification circuit and AD circuit. The imaging chain and element control method of our CMUT array were developed to realize the electronic scanning imaging of air-coupled ultrasound. The feasibility of the system for non-destructive testing was also verified via the Lamb wave detection in a metal plate.…

Application of Reciprocity Principle in Ultrasound Bone Tomography

Abstract Full-matrix synthetic aperture imaging (FMSA) is a well-established and widely used modality for ultrasound imaging Nevertheless, the accompanying relatively large amount of data acquisition, storage, and process results in heavy costs of computation and memory, which further hinders FMSA from real-time implementation. Moreover, the most existing FMSAs employed the hypothesis uniform sound velocity to reconstruct the soft tissues, which is not suitable for hard tissue imaging, irrespective of the high acoustic impedance contrast (i.e., the difference of sound velocity) between the bone and soft tissues. To overcome these limitations, a half-matrix ultrasound bone tomography method combining the reciprocity principle and sound velocity estimation was proposed for cortical cross-section imaging. The travel-time inversion was firstly utilized for sound velocity prediction, and then half-matrix synthetic aperture (HMSA) with ray-tracing was conducted to image the cortical cross-section. An ex-vivo bovine femur was used to validate the effectiveness of the method. Compared to the full-matrix capture method, the proposed method was demonstrated to be an accurate and cost-effective modality for cortical bone tomography.

Sound speed imaging of cortical bone and soft tissue based on frequency-domain ultrasound waveform tomography

Abstract As one of the ultrasound computed tomography (UCT) algorithms, full-waveform inversion (FWI) can recover clear and detailed internal structures of bones by iteratively minimizing the misfit between observed and numerical data. However, time domain full-waveform inversion (TDFWI) often lacks sufficient low-frequency information, and the computation of full-time data imposes a significant computational burden. Besides, there are few studies on whole-medium reconstruction that jointly invert the bone and surrounding soft tissues. In this study, an FWI-based frequency-domain UCT (FD-UCT) is utilized for simultaneously imaging the sound speed of bones and soft tissues, which facilitates the inversion efficiency while ensuring the existence of low-frequency information. Simulated studies show that the FD-UCT can both reconstruct bones with large acoustic impedance and distinguish subtle impedance differences within soft tissues to reveal lesions.

Physics-Embedded Neural Networks for Enhanced Ultrasonic Brain Tomography

Abstract Ultrasound imaging, valued for its non-invasiveness and cost-effectiveness, faces challenges in brain imaging due to acoustic impedance differences. This study introduces PEN-UBT, a deep learning-based method, combining Convolutional Neural Network for Forward Propagation (CN-FP) and Subnetwork for Inversion (SNI). CN-FP simplifies wavefield calculations, while SNI facilitates mapping from wavefield to model. PEN-UBT achieves high-fidelity imaging of the skull and soft tissues, excelling in scenarios with varying thrombus velocities. It demonstrates exceptional tissue resolution in brain slices, reducing imaging time to 1.13 seconds. PEN-UBT’s success extends its applicability beyond brain imaging, contributing to the broader field of medical imaging technologies.

Source characterization of a ducted source using acoustic free velocity

A common method to characterize linear time invariant ducted acoustic sources is the electroacoustic analogy. The sources are typically defined by their internal source strength and source impedance. Various methods have emerged to determine the source characteristics, broadly categorized into direct and indirect methods. Direct methods involve using a secondary source with significantly higher amplitude to measure source impedance, but those methods are unable to determine source strength. Indirect methods vary acoustic loads to obtain both source strength and source impedance, but accuracy depends on appropriate load combinations. In this research, we propose an inverse method to determine the acoustic source strength from the measured acoustic transfer function and the operational acoustic pressure. This approach yields the “acoustic free velocity,” corresponding to a volume velocity source that characterizes the original sound source. Subsequently, the source impedance is obtained using the acoustic free velocity in conjunction with the load impedance and acoustic pressure in the acoustic circuit. The method is demonstrated using a compressor driver source attached to an impedance tube. Validation of the measured source strength and source impedance is conducted using a two-load method. Prediction of muffler insertion loss shows good correlation with experimental measurements.

A way to macroporous and alveolar geopolymer foams elaboration: Influence of operating parameters on porosity characteristics

Alveolar cellular foams are widely used in a wide range of applications, from aeronautics and filtration systems to chemical and transformation processes. Their porous characteristics make them a prime candidate for reactions, radiative transfer and flow. Geopolymeric foams, which have their origins in civil engineering, are materials with promising potential in terms of mechanical, thermal and acoustic resistance. As they are mainly used in civil engineering, the structures currently being developed are mainly closed-pore matrices. However, if they are to invert the field of photocatalytic oxidation processes, solar collectors or concentrated solar power plants, the supports need to develop a high exchange surface area. Metal alveolar foams have been identified as ideal but very costly supports. Geopolymeric foams could meet these requirements, but their surface areas are currently too limited for photoreactors. In this study, it is proposed to develop and optimize the operating conditions for geopolymer foam synthesis in order to impart macroporous properties and an interconnected alveolar structure. Based on two well-established synthesis methods (direct foaming and replication), operating conditions such as foaming agent and surfactant content, and drying and calcination conditions, are studied. Geopolymer foams are produced with different macroporous characteristics. We aim to define the synthesis conditions required to produce interconnected macroporous alveolar foams with milimetric pores. In civil engineering, these materials have the advantage of being easy to design, use and shape according to the application.

The long-term efficacy and safety of balloon dilation eustachian tuboplasty combined with tympanostomy tube insertion for patients with otitis media with effusion: study protocol for a prospective randomized controlled trial

BackgroundOtitis media with effusion (OME) is a common disease in ear, nose, and throat clinics characterized by aural fullness and hearing loss and mainly caused by eustachian tube dysfunction (ETD). Tympanostomy tube insertion (TTI) is a conventional surgical treatment option that can alleviate symptoms but does not provide a definitive cure, and it is prone to recurrence. Balloon dilation eustachian tuboplasty (BDET) has become a novel procedure for the treatment of ETD, demonstrating significant potential in addressing the aforementioned limitations. However, it is not widely available in the clinic and few high-quality randomized clinical trials was conducted to investigate its long-term efficacy and security in OME. Therefore, the purpose of this study is to verify the efficacy of BDET combined with TTI for patients with OME and its prospects for providing a definitive cure.Methods and analysisThis is a prospective, parallel-group, single-blind, randomized controlled prospective trial. Totally 124 patients with OME will be randomized into either group A or B. Group A will receive conventional therapy (TTI) while group B will use BDET therapy in addition to TTI. Outcome assessments will take place at baseline and at the 3rd, 6th, 12th, and 24th months after surgery. The primary outcome is eustachian tube function, which will be measured by the eustachian tube dysfunction questionnaire (ETDQ-7) and eustachian tube score (ETS). The secondary outcomes include middle ear function, hearing situation, and quality of life, which will be measured by acoustic impedance measurement, pure-tone audiometry, and Chinese-version Chronic Ear Survey (CCES). The main analysis of change in the outcomes will use mixed-model with repeated measures (MMRM) analyses of variance (ANOVAs).DiscussionThis is the first prospective trial in Chinese populations that aims to validate the long-term efficacy and safety of BDET-combined TTI therapy in patients with OME. This parallel-group, single-blind, randomized controlled trial may provide an opportunity to decrease the recurrence rate of OME and explore a definitive cure for patients with OME. This trial’s rigorous design enhances the reliability of the findings, ensuring a robust answer to the research question. In the future, the research team will further expand upon the clinical evidence and applications of the BDET combined therapy.Trial registrationChinese Clinical Trial Registry ChiCTR2400079632. Registered on 8 January 2024, https://www.chictr.org.cn/bin/project/edit?pid=214452.

Oxygen vacancy modulated optical and dielectric properties of photoactive γ-Fe2WO6

Ferrite compounds have gained scientific attention for their multifunctional attributes. This investigation explores the structural, optical, dielectric and conductivity properties of polycrystalline γ-Fe2WO6 synthesized by the solid state route. The X-ray diffraction confirmed the orthorhombic structure and single-phase formation, while the electron microscopy showed uniform distribution of dense micrometer-sized grains in γ-Fe2WO6. The FTIR spectroscopy analysis validated the presence of active stretching and bending modes, signifying oxygen anion vibration at both Fe and W sites. The simultaneous presence of Fe2+ and Fe3+ ions in the matrix, as confirmed by X-ray photoelectron spectroscopy (XPS), results in an augmented optical energy band gap and contributes to dielectric permittivity due to the charge carrier hopping mechanism between the trap sites. The compound manifests semiconductor attributes, evident in its indirect optical band gap measuring 1.7 eV. It is observed that the compound has effectively degraded the Methylene Blue (MB) under the visible light within 40 min with a degradation efficiency up to 63 %. The material's electrical conductivity, follows the Jonscher's power law, signifies its semiconductor nature and adheres to the Small Polaron tunneling model for charge conduction between neighboring sites. The impedance (Z′) curves exhibit dielectric relaxation (≤ 10 kHz) with a similar activation energy to the dc conductivity study. The activation energy, determined from both the impedance and conductivity analyses, indicates a connection with the migration of oxygen vacancies within the material. Our observation reveals the presence of oxygen vacancies, which possibly act as in-gap electron traps, enhancing the correlated optical and ac conductivity properties, making it an appealing material for diverse multifunctional applications.

Tuning effect in time-lapse seismic inversion for CO2 plume monitoring at Sleipner field

Over 20 million tons of CO2‌ have been injected into the sandy Utsira formation of the Sleipner field in the North Sea basin. The thin layering of sands, CO2-saturated sands, and intra-formation thin shales cause interference effects in the seismic response of the monitor surveys. Initial analysis of the amplitude change suggests over 60 % change in the relative acoustic impedance of the reservoir between the 1996 and 2010 surveys. This study follows a multi-stage inversion scheme applied to time-lapse seismic monitoring of the Sleipner field. At each stage, the errors and uncertainties caused by noise and tuning are deeply analyzed. Time-shift estimation from seismic data shows spurious features caused by tuning, specifically using the window-based methods. The time-strain inversion builds a low-frequency initial model for the subsequent model-based inversion but is contaminated by remnants of noise and interference. The synthetic wedge modelling and analysis provides the origins and severity of the tuning error in time-shift and time-strain estimations at the Sleipner field. The model-based inversion removes noise and injects high-frequency components into the results, improving the outcome of time-strain inversion. However, it fails to fully eliminate the tuning imprints and leaves strong traces of error on the results. Afterward, the time-lapse Bayesian seismic inversion slightly adjusts the outcome and shows how deep the influence of interference effect on the time-lapse inversion is. In addition, the complementary discussion on rock physical models in estimating the saturation changes highlights how the tuning error can lead to flawed quantitative interpretation.