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Jacinta E Browne, Deirdre King, Andrew J Fagan, Deepa Chari, Carmel M Moran
OBJECTIVE: The objective of the study was to investigate whether clinically used ultrasonic contrast agents improved the accuracy of spectral Doppler ultrasound in the detection of low grade (<50%) renal artery stenosis. Low grade stenoses in the renal artery are notoriously difficult to reliably detect using Doppler ultrasound due to difficulties such as overlying fat and bowel gas. METHODS: A range of anatomically-realistic renal artery phantoms with varying low degrees of stenosis (0, 30 and 50%) were constructed and peak velocity data was measured from within the pre-stenotic and mid-stenotic regions in each phantom, for both unenhanced and contrast-enhanced spectral Doppler data acquisitions...
April 11, 2019: Ultrasonics
Mingjie Zhao, Zhichao Nie, Kui Wang, Pan Liu, Xin Zhang
Second and third harmonic ratios method to evaluate initial damage in concrete have been extensively studied. However, some regularities of this technique still not clear in current stage. In order to better understand the regularity of nonlinear parameters β and γ on micro and macro damage in concrete, the cracks with different damage scales are induced in concrete specimens. Three levels of test voltage are applied to intact concrete specimens, with the purpose to demonstrate the excitation voltage has an unneglectable effect on nonlinear parameters...
April 3, 2019: Ultrasonics
Kentaro Tani, Koji Fujiwara, Daisuke Koyama
This paper investigated an ultrasound vibration cell patterning technique. The ultrasound cell culture dish consisted of a culture dish with a glass bottom and a glass disc with a piezoelectric ring that generated a resonance flexural vibration mode on the bottom of the dish. The growth of HeLa cells on the dish was observed under ultrasound excitation for 24 h. Large ultrasound vibrations on the dish inhibited the cell growth. The acoustic field was predicted with finite element analysis and it was found that the cell growth depended strongly on both the acoustic field in the culture medium and the vibration distribution of the dish...
March 28, 2019: Ultrasonics
Ji Yang, Mehdi Faraji, Anup Basu
A Fully Convolutional Network (FCN) based deep architecture called Dual Path U-Net (DPU-Net) is proposed for automatic segmentation of the lumen and media-adventitia in IntraVascular UltraSound (IVUS) frames, which is crucial for diagnosis of many cardiovascular diseases and also for facilitating 3D reconstructions of human arteries. One of the most prevalent problems in medical image analysis is the lack of training data. To overcome this limitation, we propose a twofold solution. First, we introduce a deep architecture that is able to learn using a small number of training images and still achieves a high degree of generalization ability...
March 23, 2019: Ultrasonics
Haidang Phan, Younho Cho, Quang Hung Le, Chi Vinh Pham, Hoai T-L Nguyen, Phuong Thuy Nguyen, Tinh Quoc Bui
This article is concerned with the application of reciprocity in computing guided wave motions generated by a time-harmonic load in a layer of uniform thickness joined to a half-space. Explicit expressions for free Rayleigh waves and Love waves propagating in the layered half-space are introduced. Exact solutions of Rayleigh waves and Love waves are derived from reciprocity relations between an actual state - guided waves generated by a time-harmonic line load and a virtual state - an appropriately chosen free wave traveling in the structure...
March 22, 2019: Ultrasonics
Longhai Zeng, Jun Zhang, Yaolu Liu, Youxuan Zhao, Ning Hu
In this work, we propose an asymmetric transmission structure (ATS) for elastic shear vertical (SV) waves in solids, which has been relatively unexplored. The ATS is constituted by a metasurface and a phononic crystal (PC) possessing a directional band gap. While the metasurface aims to redirect the incident wave, the PC acts as a directional filter. The metasurface is composed of a stacked array of composite plates with two connecting parts made of different materials. To examine the performance of the designed ATS, full numerical simulations have been conducted...
March 21, 2019: Ultrasonics
Zhendong Xie, Yanjin Guan, Jun Lin, Jiqiang Zhai, Lihua Zhu
Establishing an accurate constitutive relation in ultrasonic vibration assisted metal forming, can provides a reliable theoretical basis for analyzing the mechanism of the ultrasonic vibration on materials. A constitutive model of 6063 aluminum alloy under the ultrasonic vibration upsetting at room temperature was constructed based on Johnson-Cook Model and experimental results. The influence of amplitude and frequency on the yield strength, hardening coefficient and exponent were analyzed quantitatively. Results showed that the yield strength was reduced due to the softening effect induced by the ultrasonic vibration...
March 21, 2019: Ultrasonics
Lilian D'Hondt, Matthieu Cavaro, Cédric Payan, Serge Mensah
Argon microbubbles will exist in the primary sodium of the next generation of sodium-cooled fast reactors (SFR). Due to its opacity, acoustic methods will be used for the in-service inspection in these reactors, but the presence of such bubbles will greatly affect ultrasonic wave propagation. Moreover, these bubbles can lead to the formation of gas pockets in the reactor and impact cavitation and boiling phenomena. It is therefore necessary to characterise what is called the 'microbubble cloud' by providing the volume fraction and the bubble size distribution...
March 16, 2019: Ultrasonics
Hala R Mahmoud, Sahar A El-Molla, Mona A Naghmash
Novel mesoporous MnO2 /SnO2 catalysts were successfully synthesized via traditional and ultrasonic co-precipitation methods. Moreover, their catalytic efficiencies were evaluated in decomposition of hydrogen peroxide (H2 O2 ). Interestingly, it was found that the mixing of MnO2 with SnO2 catalyst led to a significant improvement in their catalytic efficiencies compared with single oxides catalysts. However, the influence of ultrasonic power and irradiation time on MnO2 /SnO2 nanomaterials were compared to get optimum synthetic condition...
March 15, 2019: Ultrasonics
Olivier Lombard, Lilian D'Hondt, Matthieu Cavaro, Serge Mensah, Cédric Payan
We propose a technique to measure the velocity of a bubble cloud based on the coda correlation. The method is founded on successive recordings of multiple scattered waves from a bubble cloud. Our model predicts the dependence between the correlation coefficient of these coda waves and the velocity of the bubble cloud under diffusion approximation. The Acoustic experiments are validated by simultaneous optical measurements in a water tank, with a good agreement between the acoustical and the optical methods (relative difference smaller than 7%)...
March 15, 2019: Ultrasonics
Chen Zhang, Yun Song
The 3D elliptical vibration-assisted cutting (EVC) mechanism with arbitrary elliptical locus in space has a wide array of industrial applications for generating micro/nano-structured surface. However, the current 3D EVC mechanism are limited by their motion couplings, resonant frequencies and regulation of arbitrary elliptical locus. In order to improve the output properties, an innovative decoupled 3D ultrasonic EVC mechanism is proposed in the form of compliant parallel mechanism. First, the proposed 3D ultrasonic EVC mechanism is specifically designed to be capable of generating uniformly magnified output displacement in three directions and its 3D elliptical locus is obtained by the designed multi-axis flexure hinge structure with three orthogonal sub chains...
March 14, 2019: Ultrasonics
Dan Li, Xu Yan, Zheng Xu, Dean Ta
We achieved the shift of ultrasonic beam over a long distance by guided waves through a brass plate with two groups of periodical gratings on the surface. Using Schlieren imaging, we experimentally observed the propagation of ultrasonic waves through this structure. In addition, simulations were performed using the finite-element method. Both the experimental and simulation results revealed that the shift of ultrasonic beam can be realized in this structure. We further investigated the effect of the shift distance and the size of the gratings on the shift efficiency, and discussed the mechanism...
March 7, 2019: Ultrasonics
Aurélien Thon, Pierre Bélanger
Detection and sizing of corrosion are critical issues across many industries such as for the oil and gas industry or the petrochemical industry. Inspections may become difficult and time-consuming when the structures under inspection are only partially accessible such as for pipes under insulation or at pipe supports. It has been demonstrated in the literature that the cutoff frequency-thickness product of high order ultrasonic guided wave modes can be used in medium to long-range thickness gauging. As the thickness varies along an inspection line, the thickness variation acts as a low-pass filter for the high order ultrasonic guided wave modes...
March 6, 2019: Ultrasonics
Yan Liu, Hui Zhang, Jian Yang, Xiang Zhang, Shu-Yi Zhang, Li Fan, Gen Gu
Traditional acoustic regulations in practice are used to have major obstacles in low frequency range, for which absorbers or suppressors have thicknesses that are comparable to their working wavelength. We present an acoustic structure-based "coiling-up space" to achieve outstanding sound regulation of acoustic waves in the extremely low frequency region. The structure is composed of an open waveguide and with a spiral throat tube and a cavity. The acoustic structure excites Helmholtz and Fabry-Pérot resonances in labyrinth cavity structures, coupling of an open waveguide, which produce Fano-like resonances respectively and a broadband low-transmission spectrum in the 120-3100 Hz range...
March 6, 2019: Ultrasonics
Yu G Sokolovskaya, N B Podymova, A A Karabutov
The aim of this work is to verify applicability of the Kramers-Kronig relations between the attenuation coefficient and phase velocity of longitudinal acoustic waves in carbon fiber reinforced plastic (CFRP) composites in a finite megahertz frequency range. To measure these characteristics, the method of broadband acoustic spectroscopy with a laser source of ultrasound is used. We have experimentally shown that absolute attenuation in CFRPs is determined by both absorption in a polymer matrix and scattering on carbon fibers and gas pores of several tenths of microns in size...
March 5, 2019: Ultrasonics
P D Pupyrev, I A Nedospasov, A P Mayer
In numerical calculations, guided acoustic waves, localized in two spatial dimensions, have been shown to exist and their properties have been investigated in three different geometries, (i) a half-space consisting of two elastic media with a planar interface inclined to the common surface, (ii) a wedge made of two elastic media with a planar interface, and (iii) the free edge of an elastic layer between two quarter-spaces or two wedge-shaped pieces of a material with elastic properties and density differing from those of the intermediate layer...
March 4, 2019: Ultrasonics
He Li, Weishan Chen, Xinqi Tian, Junkao Liu
The temperature characteristics of a T-shaped linear ultrasonic motor using longitudinal vibration transducers are reported. When the ultrasonic motor is excited by different voltages, the surface temperatures at the driving foot, PZT ceramic and end cap are tested by a thermal imager for obtaining the thermal characteristics of the motor under no-load condition. PZT ceramic shows the maximum temperature increase. Then, the variations of resonant frequencies, electromechanical coupling factors and mechanical Q-factors versus time, as well as the effect of the temperature on the resonance frequencies, electromechanical coupling factors and mechanical Q-factors, is measured and analysed under the long-term running...
March 2, 2019: Ultrasonics
Natalya F Naumenko
Multilayered substrates for Surface Acoustic Wave (SAW) devices are able to combine SAW characteristics that cannot coexist in a single crystal substrate and, thus, meet the strong requirements of the new class of SAW devices developed for the next generations of communication systems. Recently, high performance resonators arranged on LiTaO3 /quartz bonded wafers and utilizing shear horizontally polarized acoustic waves were reported. Leaky SAWs with quasi-longitudinal polarization propagate faster and can facilitate fabrication of high frequency SAW devices but generally leak strongly into the substrate...
March 2, 2019: Ultrasonics
Elena Jasiūnienė, Liudas Mažeika, Vykintas Samaitis, Vaidotas Cicėnas, David Mattsson
Ultrasonic inspection is widely used for non-destructive evaluation of composite adhesive joints. However, there are serious challenges in applying ultrasonic testing on metal to composite hybrid joints, because they are multi-layered, made out of dissimilar materials and relatively thin. The ultrasonic signals reflected by different layers are overlapped, scattered and attenuated. The aim of this research was to develop an ultrasonic inspection technique suitable for defect detection in hybrid metal to composite joints where the metal part has pin arrays, which entangle with the composite part...
February 28, 2019: Ultrasonics
Alberto González-Mohino, Antonio Jiménez, M Jesús Paniagua, Trinidad Perez-Palacios, Montaña Rufo
No abstract text is available yet for this article.
February 25, 2019: Ultrasonics
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