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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...
This paper presents the characterization of frequency response and mode shape at the 1st harmonic frequency of a Micro-Opto-Mechanical Acoustic Sensors (MOMAS) with a Mach-Zehnder Interferometer (MZI) readout system. In previous research, the static modeling and characterization has been demonstrated. In this paper, we investigate the capability of using MOMAS in ultrasound domain as a Micro-Opto-Mechanical...
This paper describes the design, fabrication, characterization and test of three sectorized array transducers: one for air-coupled operation (400 kHz, 25 mm diameter) and two for water-coupled operation (4 MHz, 10 mm diameter and 2 MHz, 5 mm diameter). The objective is to use these transducers in pulse-echo mode along with a conical reflector to generate a 2D cylindrical acoustic field with angular...
Capacitive Micromachined Ultrasonic Transducers (CMUTs) can be used as small, highly sensitive chemical sensors in air. Single CMUT chemical sensors lack selectivity, but arrays of multiple sensors can be used to allow selective chemical detection. In this work, we demonstrate the simultaneous operation of eight CMUT chemical sensors on a single chip. We then use seven sensors from this array to classify...
As one of the most important and well established tools, ultrasound imaging provides noninvasive valuable diagnostic information, especially in the form of cross-sectional images of soft tissues. In this work, we report the design, fabrication, and characterization of press-focused LiNbO3 transducer with one matching layer only. The performance of these transducers is in good agreement with the simulation...
Measurement of transducer impedance in ultrasound systems indicates both the performance of a transducer and the presence of damaged elements and cables. Load impedance analysis is typically performed with dedicated test equipment and is a time consuming and thus expensive process, especially for high channel count systems. This paper proposes a method for the measurement of channel source impedance...
We explore the frequency dependence of piezoceramic disc transducers bonded to plates. For some transducer dimensions, the frequency response shows a sharp peak. This behavior is inconsistent with the use of short pulses or broadband chirps for flaw localization. We use finite element simulation to show that the highly resonant behavior is caused by a high-strain region immediately beneath the transducer...
I.H.P. SAW (Incredible High-Performance SAW) has a novel multi-layered structure to confine SAW energy in substrate surface area, and it shows extremely high quality (Q) factor, low temperature coefficient of frequency (TCF) and improved electromechanical coupling coefficient (K2). This paper introduces its mechanism of the high acoustic Q factor, both theoretically and experimentally, and its applications...
Metallic glasses are a unique class of amorphous glassy materials whose mechanical properties lie between that of metals and ceramics. Owing to the random disorganized structure of metallic glasses, the characterization and determination of structure-property relationships is often difficult. Ultrasonic techniques have been previously used to characterize metallic glasses either by using the time-of-flight...
The control of acoustic fields in 3-D is vital in many areas of physical acoustics. Recently, a new approach for the generation of complex diffraction limited acoustic fields in 3-D was introduced. This works by calculating a phase hologram designed to generate a desired acoustic field. The output of a simple planar transducer is then mapped onto this phase distribution using a 3-D printed kinoform...
In order to study relaxation characteristics of viscoelasticity of the liquid, a wide frequency sweep in the range of MHz to GHz is desired. We, therefore, report a new type HBAR (High-overtone Bulk Acoustic Resonator: shear mode ScAlN film on AT-cut quartz plate) sensor which makes it possible to operate in a wide frequency range as shown in Fig. 1. When a thickness shear acoustic mode (TSM) resonator...
Modern industries need to monitor every step of the production process for a better efficiency and product quality. However, important parameters, like the rheological indexes of the fluids involved in the process, cannot easily be inspected inline, as they are typically analyzed through off-line laboratory tests on specimens. Recently, electronics sensors have been introduced capable to characterize...
A dual beam vector Doppler method was proposed (DOI: 10.1016/j.ultrasmedbio.2009.11.004), in which one beam is continuously tracked perpendicular to the flow direction, and the second one is used to perform velocity measurements with known Doppler angle. Since two consecutive transmission (TX) and reception (RX) events (one for each beam) are needed, the effective Doppler pulse repetition frequency...
Finite element method (FEM) has been extensively used for analyzing both static and dynamic behaviour of CMUTs. Typical parameters being evaluated include the pull-in voltage, pressure, sensitivity, bandwidth, and crosstalk. PZFlex is a commercial FEA software and has been optimized for the ultrasound industry and is commonly used to design piezo-electric ultrasound transducers. However, PZFlex is...
Surface acoustic wave (SAW) devices have been shown recently to be an appropriate technology for harsh-environment sensor applications, such as those in the automotive, aerospace, power plant, and metallurgic industries. Usages include temperature, pressure, torque, strain, gas, liquid, biochemical, and mass sensors in structural health monitoring, industrial process monitoring, environment checking...
Accurate measurement of acoustic dispersion has important applications in theoretical acoustics, ultrasound tissue characterization, ultrasound measurement systems, etc. Usually, the parameter of interest associated to dispersion is the variation in the propagation velocity as a function of the frequency or the temperature. Nevertheless, this work is focused on the study of the variation in the propagation...
Skin stiffening is an early biomarker of many systemic sclerosis or fibrosis diseases. The Modified Rodnan Skin Score (MRSS) is considered the gold standard measurement in the majority of clinical studies of scleroderma or systemic sclerosis (SSc). However, the MRSS is a subjective palpation method. We have developed a noninvasive ultrasound surface wave elastography (USWE) technique for measuring...
In this paper, single crystalline silicon (SCS) anisotropy is exploited to suppress support loss in side-supported breathing-mode thin-film piezoelectric-on-silicon (TPoS) disc resonators for the first time. Contrary to the case of isotropic materials, for an SCS breathing-mode disc resonator, displacement is not uniform at the outer edges of the resonator. It is shown that for high order harmonics,...
Shear wave (SW) propagation in viscoelastic materials is characterized by a complex, frequency-dependent shear modulus μ(f). Measurements of μ(f) typically require Fourier transform techniques to decompose an observed SW signal into discrete frequency components and two independent measurements such as the phase velocity c(f) and attenuation α(f) to determine the real and imaginary parts of μ(f).
Accurate characterization of ultrasound fields generated by diagnostic and therapeutic transducers is critical for patient safety. At high frequencies, spatial variations in the pressure over the surface of the measurement device will produce a different averaged value from that at the intended location. Using a small hydrophone as an idealised point device, this paper seeks to ascertain the spatial-averaging...
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