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Babak Mohammadzadeh Asl, Ali Mohades Deylami
In recent years, high resolution adaptive minimum variance-based beamformers have been successfully applied to medical ultrasound imaging to improve its resolution and contrast, simultaneously. However, these improvements come at the cost of much more computational complexity in comparison to the non-adaptive delay-and-sum beamformer. The computational overhead mainly results from the L×L covariance matrix inversion needed for computation of the adaptive weights, the complexity of which is cubic with the subarray size, O(L3)...
January 4, 2018: Ultrasonics
S Laureti, M Ricci, M N I B Mohamed, L Senni, L A J Davis, D A Hutchins
A pulse compression technique has been developed for the non-destructive testing of concrete samples. Scattering of signals from aggregate has historically been a problem in such measurements. Here, it is shown that a combination of piezocomposite transducers, pulse compression and post processing can lead to good images of a reinforcement bar at a cover depth of 55 mm. This has been achieved using a combination of wide bandwidth operation over the 150-450 kHz range, and processing based on measuring the cumulative energy scattered back to the receiver...
December 30, 2017: Ultrasonics
S B Gebrekidan, To Kang, Hak-Joon Kim, Sung-Jin Song
In this paper, a third harmonic was used to investigate microstructural changes in Al6061-T6 due to different fatigue cycles and a relationship between fatigue cycle and third order nonlinearity has been observed. Piezoelectric measurement harmonic generation technique was applied for the specimens with 0%, 55%, 75% and 85% fatigue cycles, respectively. The results shows that the third order harmonics gradually increased up to 55% and rapidly decreased after wards, it was attributed to the behavior of dislocation, dislocation-precipitation interaction and voids with increasing fatigue cycle...
December 30, 2017: Ultrasonics
B K Jung, J Ryue, C Hong, W B Jeong, K K Shin
For coupled structures surrounded by heavy fluids, it is difficult to obtain dispersion curves from an eigenvalue analysis, because the external fluid term in the coupled equation includes transcendental functions for frequency and wavenumber. Thus, in this study, the acoustic mass of the external fluid was approximated as a function of frequency or wavenumber only. The coupled equation can then be used to calculate eigenvalues, and can estimate dispersion curves from an eigenvalue analysis. Because of this assumption, those dispersion curves will contain errors...
December 29, 2017: Ultrasonics
Ehsan Dehghan-Niri, Helem Al-Beer
Fundamental understanding of ultrasound interaction with material discontinuities having closed interfaces has many engineering applications such as nondestructive evaluation of defects like kissing bonds and cracks in critical structural and mechanical components. In this paper, to analyze the acoustic field nonlinearities due to defects with closed interfaces, the use of a common technique in nonlinear physics, based on a phase-space topography construction of ultrasound waveform, is proposed. The central idea is to complement the "time" and "frequency" domain analyses with the "phase-space" domain analysis of nonlinear ultrasound waveforms...
December 14, 2017: Ultrasonics
Martin Pekař, Nenad Mihajlović, Harm Belt, Alexander F Kolen, Jeannet van Rens, Frank Budzelaar, Bas Jacobs, Johan G Bosch, Hendrik J Vos, Debbie Rem-Bronneberg, Gijs van Soest, Antonius F W van der Steen
Commercially available intracardiac echo (ICE) catheters face a trade-off between viewing depth and resolution. Frequency-tunable ICE probes would offer versatility of choice between penetration or resolution imaging within a single device. In this phantom study, the imaging performance of a novel, frequency-tunable, 32-element, 1-D CMUT array integrated with front-end electronics is evaluated. Phased-array ultrasound imaging with a forward-looking CMUT probe prototype operated beyond collapse mode at voltages up to three times higher than the collapse voltage (-65 V) is demonstrated...
December 14, 2017: Ultrasonics
Xiang Yan, Fuh-Gwo Yuan
Conversion of evanescent shear horizontal (SH) guided waves into propagating is presented in this paper. The conversion is exemplified by a time-harmonic SH evanescent displacement prescribed on a narrow aperture at an edge of a semi-infinite isotropic plate. The conversion efficiency in terms of the amplitude of the propagating SH mode converted from evanescent can be expressed in a very simple compact form. The magnitude of the conversion efficiency can be quantified through a derived semi-analytical form based on the complex reciprocity theorem in conjunction with a two-dimensional (2-D) finite element analysis (FEA)...
December 11, 2017: Ultrasonics
Yibo Sun, Xiaodong Liu, Xinhua Yang
Ultrasonic bonding has been emerging paving the way in micro assembly, with the high demand in fusion quality control. Under this background a novel ultrasonic precise bonding method based on non-constant amplitude control is proposed. A two-step bonding process, including frictional heating and viscoelastic heating, divided by the vibration propagation is designed. In step I, initial melting of the contacting surfaces is achieved at the amplitude bigger than the critical value. In step II, the whole interfacial fusion is realized at smaller amplitude to weaken the ultrasonic cavitation effect...
December 9, 2017: Ultrasonics
Mojtaba Mobaraki, R Scott Semken, Aki Mikkola, Juha Pyrhönen
Interest in producing heat and power using municipal wastewater sewage sludge as a fuel is increasing worldwide. Since its water content is initially high, sludge must be dewatered and further dried if it is to serve as an effective fuel for combustion. However, to maximize net energy production, the drying processes must use as little energy as possible. The water content in sewage sludge comprises both unbound and bound water. Unbound water content is typically extracted using a number of mechanical dewatering techniques...
December 8, 2017: Ultrasonics
Ting Su, Dayu Li, Shi Zhang
Beamformer plays an important role in medical ultrasound imaging systems. The delay multiply and sum (DMAS) beamformer achieves better performance in contrast and resolution compared with the delay and sum (DAS) beamformer, but suffers from higher computational complexity and partial energy loss. The higher computational complexity mainly arises from the multiply and geometric average operation, which needs (N2-N)/2 computations at every point, where N denotes the number of array elements. The partial energy loss, mainly due to the autocorrelation component of the echo signals, has been neglected in the DMAS beamformer...
December 8, 2017: Ultrasonics
Brennan Dubuc, Arvin Ebrahimkhanlou, Salvatore Salamone
This paper investigates the effect of axial stress on higher order longitudinal guided modes propagating in individual wires of seven-wire strands. Specifically, an acoustoelastic theory for a rod is used to predict the effect of stress on the phase velocity of guided modes in a strand. To this end, the exact acoustoelastic theory for an axially stressed rod is adapted for small deformations. Aside from the exact theory, approximate phase velocity changes (derived from both theory and experiment) are proposed, without the need to solve for dispersion curves...
December 7, 2017: Ultrasonics
Mehdi Faraji, Irene Cheng, Iris Naudin, Anup Basu
Intravascular Ultrasound (IVUS) is an intra-operative imaging modality that facilitates observing and appraising the vessel wall structure of the human coronary arteries. Segmentation of arterial wall boundaries from the IVUS images is not only crucial for quantitative analysis of the vessel walls and plaque characteristics, but is also necessary for generating 3D reconstructed models of the artery. The aim of this study is twofold. Firstly, we investigate the feasibility of using a recently proposed region detector, namely Extremal Region of Extremum Level (EREL) to delineate the luminal and media-adventitia borders in IVUS frames acquired by 20 MHz probes...
December 6, 2017: Ultrasonics
Fushi Bai, Kai-Alexander Saalbach, Liang Wang, Xiaogeng Wang, Jens Twiefel
During ultrasonic cavitation peening, bubbles repeatedly form and collapse, which leads to high impact loads on the treated surface. At the initial stage of ultrasonic cavitation peening, the most obvious change is plastic deformation instead of mass loss on the treated specimen surface. Meanwhile the plastic deformation is beneficial for mechanical surface properties. As the cavitation exposure time increases, erosion and damage are inflicted on the metal surface due to the increase in the number of collapse events...
December 5, 2017: Ultrasonics
Diya Wang, Mengnan Xiao, Hong Hu, Yu Zhang, Zhe Su, Shanshan Xu, Yujin Zong, Mingxi Wan
This study aimed to develop a focal microvascular contrast-enhanced ultrasonic parametric perfusion imaging (PPI) scheme to overcome the tradeoff between the resolution, contrast, and accuracy of focal PPI in the tumor. Its resolution was limited by the low signal-to-clutter ratio (SCR) of time-intensity-curves (TICs) induced by multiple limitations, which deteriorated the accuracy and contrast of focal PPI. The scheme was verified by the in-vivo perfusion experiments. Single-pixel TICs were first extracted to ensure PPI with the highest resolution...
December 2, 2017: Ultrasonics
Zheng Jiang, Liang Wang, Jiamei Jin
In this work, a novel robotic arm driven by sandwich piezoelectric transducers is proposed. The proposed robotic arm is composed of three arms and four joints. Each arm consists of a sandwich piezoelectric transducer and an H-shaped hollow frame. The sandwich piezoelectric transducer utilizes frictional force to drive the joints on its both sides to rotate simultaneously. The joint between two arms can be driven to rotate in two perpendicular directions by two sandwich piezoelectric transducers. The rotation of joints results in the arm motion...
December 2, 2017: Ultrasonics
Dengjiang Wang, Jingjing He, Xuefei Guan, Jinsong Yang, Weifang Zhang
This paper presents a study on model assessment for predicting structural fatigue life using Lamb waves. Lamb wave coupon testing is performed for model development. Three damage sensitive features, namely normalized energy, phase change, and correlation coefficient are extracted from Lamb wave data and are used to quantify the crack size. Four data-driven models are proposed. The average relative error and the probability of detection (POD) are proposed as two measures to evaluate the performance of the four models...
December 2, 2017: Ultrasonics
A N Darinskii, M Weihnacht, H Schmidt
The paper numerically investigates the transmission of harmonic surface acoustic waves (SAWs) across the perfectly bonded and perfectly sliding contacts between two 90°-wedges, at least one of which possessing piezoelectric properties. The finite element method in frequency domain is used. The structures are constructed of lithium niobate, fused quartz, silicon and gallium arsenide. The SAW is always incident from lithium niobate. The dependences of the transmission coefficient on the combination of materials and the orientation of the lithium niobate, as well as on the height of the step at the interface between the two parts of the structure are computed and analyzed...
November 27, 2017: Ultrasonics
Philip W Loveday, Craig S Long, Dineo A Ramatlo
Accurate computation of dispersion characteristics of guided waves in rails is important during the development of inspection and monitoring systems. Wavenumber versus frequency curves computed by the semi-analytical finite element method exhibit mode repulsion and mode crossing which can be difficult to distinguish. Eigenvalue derivatives, with respect to the wavenumber, are used to investigate these regions. A term causing repulsion between two modes is identified and a condition for two modes to cross is established...
November 24, 2017: Ultrasonics
Masahiro Kusano, Hideki Hatano, Makoto Watanabe, Shunji Takekawa, Hisashi Yamawaki, Kanae Oguchi, Manabu Enoki
Laser ultrasonic testing (LUT) can realize contactless and instantaneous non-destructive testing, but its signal-to-noise ratio must be improved in order to measure carbon fiber reinforced plastics (CFRPs). We have developed a mid-infrared (mid-IR) laser source optimal for generating ultrasonic waves in CFRPs by using a wavelength conversion device based on an optical parametric oscillator. This paper reports a comparison of the ultrasonic generation behavior between the mid-IR laser and the Nd:YAG laser. The mid-IR laser generated a significantly larger ultrasonic amplitude in CFRP laminates than a conventional Nd:YAG laser...
November 24, 2017: Ultrasonics
Jaydev K Dave, Maureen E Mc Donald, Praveen Mehrotra, Andrew R Kohut, John R Eisenbrey, Flemming Forsberg
About 92.1 million Americans suffer from at least one type of cardiovascular disease. Worldwide, cardiovascular diseases are the number one cause of death (about 31% of all global deaths). Recent technological advancements in cardiac ultrasound imaging are expected to aid in the clinical diagnosis of many cardiovascular diseases. This article provides an overview of such recent technological advancements, specifically focusing on tissue Doppler imaging, strain imaging, contrast echocardiography, 3D echocardiography, point-of-care echocardiography, 3D volumetric flow assessments, and elastography...
November 23, 2017: Ultrasonics
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