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Understanding of the propagation of ultrasound through a bubbly medium is a challenging task because of the nonlinear dynamics of the bubbles and their effect on the attenuation and sound speed of the medium. The majority of the studies on this subject apply linear models, which will generate inaccurate results, especially at higher-pressure excitations. These studies have also ignored the effect...
Parameters derived from the acoustic backscatter coefficient (BSC) represent quantification on an absolute scale and have been used to characterize tissue microstructure. This motivates their use to detect and quantify microstructural remodeling and ripening of the uterine cervix during pregnancy. This work systematically assessed the ex vivo human cervix microstructure and the effects of cervical...
Quantum Spin Hall Effects(QSHE) underpins most of the design in topological insulators. The intrinsic spin-0 of the phononics, yet, continue to be the main barrier in designing acoustic topological insulators. Previous research proposed a solution using external fields such as clockwise and counter-clockwise circulating fluids to create artificial acoustic spin-1/2 states. Most recently, several papers...
In cortical bone, osteoporosis impacts both pore size and porosity. A theoretical model predicting ultrasonic parameters based on cortical micro-architectural parameters remains to be developed, and the independent effect of pore size and porosity on ultrasonic parameters remains unclear. Here, we propose a model predicting the attenuation, phase velocity and scattering mean free path (SMFP) in cortical...
Design of side edges is one of the most important tasks for realization of high performance RF SAW/BAW devices. For the purpose, the authors proposed an FEM based technique where the specified mode is injected to the border under concern through a damping mechanism, and scattering coefficients are estimated from calculated BAW field [1]. Even though this technique is effective, its setup is too complicated...
Irregular patterns of microcalcifications in the breast may indicate a malignant cancer tumor. The gold standard for early detection is X-ray mammography. However, high density of connective tissue of the breast can limit detection. Improved suppression of the connective tissue can be achieved with ultrasound. However detecting the weak signals from microcalcifications in a highly echoic background...
Imaging using the total focusing method (TFM) is a popular tool in nondestructive evaluation and it becomes a standard. From full matrix capture, this method consists in focusing at each point of a defined reconstruction zone. It is generally more efficient than conventional phased array focusing that can focus at only a few points. Despite the good quality of TFM images, TFM suffers from a lack of...
Power Doppler (PD) is the preferred technique for accessing weakly scattering blood cells with low-velocity flow. However, strong clutter decreases sensitivity of the blood signals, which degrades micro-vasculature imaging. Eigen-based filtering methods have been developed to separate the independent scattering sources using both spatial and slow-time statistics of echo data. We recently found that...
A new toolbox for the simulation of acoustic wave fields is described. The toolbox, USim, is designed to make an acoustic modeling of ultrasound propagation in tissues reliable and fast. The forward simulations of the wave field are based on the Born-Neumann single scattering approximation of the solution of Sturm-Liouville equation. The toolbox allows simulating the ultrasound wave propagation in...
This article investigates a flow-free, pseudospin-based acoustic topological insulator. Zone folding, a strategy originated from photonic crystal, is used to form double Dirac cones in phononic crystal. The lattice symmetry of the phononic crystal is broken by tuning the size of the center “atom” of the unit cell in order to open the nontrivial topological gap. Robust sound one-way propagation is...
Recently, ultrasound imaging of muscle contractions has been used by several research groups to infer volitional motor intent of the user, and has shown promise as a novel muscle computer interface. Learning spatiotemporal features from ultrasound image sequences is challenging because of deformations introduced by probe repositioning. The image features are sensitive to probe placement and even small...
One of the major cause for the attenuation of ultrasonic waves in polycrystalline materials is the random scattering at the grain boundaries — grain boundary scattering (GBS) —, whereby the acoustic mismatch is the result of the random orientation of the mechanical properties of the single crystals within the individual grains. Various analytical models, such as the unified theory, have been developed...
In order to achieve better performance of bulk and surface acoustic wave resonators operating at several GHz, it is crucial to dispose of advanced techniques and methods to provide information about the elastic constants of the constituent layered materials and to image the spatial profile of the acoustic field, both inside and outside the resonator.
To understand physiologic state in diseased liver e.g. non-alcoholic steatohepatitis, this study aims to analyze the acoustic impedance (Z) of hepatic cells using a scanning acoustic microscopy (SAM). Ultrasound scattering sources in cells, however, cause the multi-reflection and prevent from analyzing the precious value of Z although it provides the useful information of structure in cells (M. N...
Grain-boundary scattering of acoustic waves in polycrystalline materials is studied with analytical and numerical methods in the presented paper. In particular, the attenuation of Surface Acoustic Waves (SAWs) propagating through a polycrys-talline microstructure is investigated. A three dimensional timedomain finite-element method (FEM) is utilized for the numerical simulation, whereby the granular...
The nondestructive quantification of grain feature information in polycrystalline aerospace materials is an important area of recent research, where information related to mean grain size, grain size distribution, and crystallographic orientation is needed for engineering analysis and remaining life predictions in aerospace engine components. In the present effort, the interaction of surface acoustic...
Linear reconstruction techniques based on the Born approximation are known to be unable to reconstruct speed of sound quantitatively. Recently, it was shown that non-linear reconstructions based on the Kaczmarz method can overcome this limitation (Hesse, Salehi, and Schmitz 2013). However, a fundamental problem towards its practical application is the convergence. As described by Natterer (Natterer...
The production and the characterization of high-quality ScAlN films, whose electromechanical coupling is larger than those of traditional AlN films, is attracting interest to develop the next generation of bulk acoustic wave resonators for mobile communications. We have exploited the Brillouin light scattering technique (BLS) to achieve a detailed elastic characterization of both AlN and ScAlN films...
The resolution of ultrasound images is limited by the bandwidth of the imaging system and the features of the propagating medium. Using certain assumptions, image restoration can recover out-of-bandwidth data and improve resolution. Several resolution improvement methods have been reported in the literature. Due to the lack of ground truth, their evaluation remains an open issue. Indeed, to evaluate...
Nondestructive evaluation of material microstructure has become increasingly relevant with the surge of advanced manufacturing methods. Because factors such as grain size and shape dictate material properties, accurate characterization of these features is crucial when implementing novel production methods. Previous ultrasonic approaches to measure grain size in complex media have been hindered by...
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