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Many high-end power machines demand greater bearing performance in terms of running speed, precision, reliability, longevity, noise reduction, etc. An ultrasonic bearing based on Near-Field Acoustic Levitation (NFAL) effect is a kind of emerging noncontact gas bearing. Due to its self-aligning capability, the ultrasonic bearing can steadily run at a high speed under high precision. Actuated by piezoelectric...
Arranging microparticles into desired pattern is of particular importance for many applications in the field of micro-electronics-mechanical system, regenerative medicine, tissue engineering and composite fabricating. A variety of techniques for patterning microparticles on the substrate have been developed in recent years based on optic, magnetic and electric field. However, each above mentioned...
The image quality provided by current ultrasound (US) scanners can be increased by extending the effective bandwidth of the US transducers. In 2007, a promising technique, called Resolution Enhancement Compression (REC), was proposed. Combining chirp modulated signals in emission and Modified Wiener Filters (MTF) in reception, REC allows bandwidth enhancement by boosting the energy of the emitted/received...
Tumor growth requires formation of new angiogenic vessels, which differ in their morphology from those of healthy tissue. These vascular abnormalities result in altered blood flow dynamics, which can be assessed by dynamic contrast-enhanced ultrasound (DCE-US). Two distinct approaches are typically employed in DCE-US following an intravenous injection of ultrasound contrast agent: assessment of perfusion...
Cardiovascular disease, including atherosclerosis and critical limb ischemia, affects millions of people worldwide. There is a clinical need to base treatment decisions on quantitative analysis of the plaque composition. However, no reliable clinical methods to quantify the mechanical properties of plaque components and detect plaque vulnerability currently exist, particularly for coronary disease...
In most studies on vascular shear wave imaging (SWI), longitudinal section is mainly concerned, and the radial motion and reflected waves are not considered in cross section. It is important to investigate the SWI in cross section when evaluating the anisotropy of the vessel wall or the complete plaque composition. In our previous study, a novel method based on coordinate transformation and directional...
This paper presents an equivalent circuit model of a piezoelectric micromachined ultrasonic transducer (PMUT) array, combining an acoustic coupling model originally developed for capacitive micromachined ultrasonic transducer (CMUT) arrays and an electro-mechanical model of the individual PMUTs in the array. This model is experimentally validated with PMUT arrays of varied sizes and accurately predicts...
Acoustic streaming effects are usually treated using perturbation theory by writing the field variables as perturbation expansions utilizing a small scale parameter and solving the ensuing equation systems. When conducting numerical simulations, this approach can help reducing the computational effort drastically. In most cases, the zero-order velocity is assumed to be zero, which is an applicable...
Structure-property relationships in bulk materials can be important in establishing sensing methods to assess the state of material microstructure. This is particularly true for nuclear graphites since these materials can display anisotropy and can become oxidized under service conditions. Both anisotropy and oxidation-induced porosity can influence structural integrity and this must be confirmed...
I describe recent progress in machine learning in medical ultrasound imaging. At a high level, the two technologies appear to be well-matched as the former attempts to make sense of complex patterns, and the latter can generate images of complex acoustic patterns. Thus, the general challenge to the image analysis practitioner is to design machine learning architectures that model the patterns in real...
To prevent unauthorized access to ICs, encryption can be enabled via extremely small and practically invisible microscale chips that are embedded inside the packaging of ICs. The authors lately demonstrated an acoustic power link based on AlN HBAR-like structures operating at 500 MHz [1]. Enormous acoustic losses introduced by air at such large frequencies necessitate tight coupling between the transducers...
Flow cytometer plays a key role in cell sorting and analysis. For a higher detection precision, sheath flow is adopted to avoid the turbulent or vortex effect when the cell flowing through a capillary tube during the cell counting in many commercial cytometers. This method works well when the low flow velocity is relatively low. However, in order to have a higher analysis efficiency for clinical laboratories,...
Accurate diagnosis of non-alcoholic steatohepatitis (NASH) is a critical issue in current clinical practice. Non-invasive diagnosis of NASH can be achieved by quantitative ultrasound (QUS), which requires a detailed understanding tissue-specific acoustic microstructure at cellular scale (i.e., 10 μm). Therefore, QUS methods would benefit from the knowledge of the acoustic properties of organelles...
Ultrasonic guided wave inspection has been in use for more than two decades. Its main advantage is that large sections of pipes can rapidly be screened. However, large area coverage comes at the cost of reduced resolution. Higher resolution can be achieved at higher frequencies-thickness products (> 300 kHz∗mm in steel), where more wave modes are excited; however, this makes the received signals...
Elastic properties of the ocular tissues are significantly affected by intraocular pressure (IOP) in the eye. For example, the speed of the elastic wave in the cornea dramatically increases with IOP. In our previous studies using ultrasound shear wave imaging we demonstrated that, for the lens, the increase in IOP does not result significant changes in the wave velocity. Compared with ultrasound imaging,...
We have studied C-mode and B-mode imaging using high-frequency ultrasonic waves through a thin fiber for direct observation of the microscopic image of tissue. We reported previously that the C-mode images of the tissue on the glass and B-mode image of animal bone placed in water were obtained using a fused quartz fiber as the needle-type ultrasound probe. In this paper, we propose a method for the...
One of the primary motivations for using ultrasound reflectometry for fingerprint imaging is the promise of increased spoof resistance over conventional optical or capacitive sensing approaches due to the ability for ultrasound to determine the elastic impedance of the imaged material. A fake 3D printed plastic finger can therefore be easily distinguished from a real finger. However, ultrasonic sensors...
Piezoelectric ultrasonic motors (PUMs) are based on the concept of driving the runner by a mechanical vibration excited on the stator via the converse piezoelectric effect. They exhibit merits of small size, simple structure, quick response, high accuracy and resolution, self-locking when power off and a lack of electromagnetic radiation. The linear PUMs become the research focus in recent years as...
The k-Wave MATLAB toolbox is widely used to conduct medical ultrasound simulations. It uses a Fourier collocation method to numerically solve the governing model equations, and introduces sources by adding acoustic pressure at points on an orthogonal grid. This approach introduces two errors when sources don't exactly align with the grid. These are phase errors arising from shifting source points...
Rodents are used extensively in research to study disease and evaluate drugs. Preclinical imaging systems allow for non-invasive assessments of animals. High frequency ultrasound systems have emerged over the last 15 years as valuable tools for evaluating numerous diseases and organs. When compared against other anatomical imaging systems, such as MRI and CT, ultrasound is the most cost effective,...
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