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D Wang, S L Qu, Q Zhao, X Y Yin, F Zhou
Ultrasonic wave propagation in a synthetic medium with different scale fractures is investigated through the physics modeling research. The experiment model consisting of two layers, the first layer is divided into four fractured blocks with a constant fracture density but different dimension and a block without fractures as the reference region. The velocity and reflected amplitude of wave derived from the wide azimuth data processing are anisotropic due to the fractured layer. Coda wave characteristics versus offset and azimuth are obviously different for varying fracture scales...
May 13, 2017: Ultrasonics
Lan Ao, Na Hu, Hai Xia Hu, Qing Liu, Zi Hao Zhao, Long Xing Liu, Jun Ru Wu, Fa Qi Li, Liao Qiong Fang
To investigate the safety of focused ultrasound (FUS) partial ablation on the pancreas of Sprague Dawley® (SD) rats by histopathological examination of the outcome and investigation of glycometabolism function changes after local ablation. A total of 135 healthy SD rats were randomly divided into three groups (n=45 of each): FUS ½ group, FUS ¼ group, and control group. Levels of serum amylase was measured using the enzyme dynamics method, fasting blood glucose was measured by the glucose oxidase-peroxidase method, fasting serum insulin was measured by direct chemiluminescence assay, and an ELISA was used to measure fasting serum glucagon immediately after treatment, and at 2h, 3days, 1, 2, 3 and 4weeks, 3 and 6months after FUS ablation...
May 11, 2017: Ultrasonics
Anurupa Shaw, Damien Teyssieux, Vincent Laude
The measurement of the displacements caused by the propagation of a short pulse of surface acoustic waves on a solid substrate is investigated. A stabilized time-domain differential interferometer is proposed, with the surface acoustic wave (SAW) sample placed outside the interferometer. Experiments are conducted with surface acoustic waves excited by a chirped interdigital transducer on a piezoelectric lithium niobate substrate having an operational bandwidth covering the 200-400MHz frequency range and producing 10-ns pulses with 36nm maximum out-of-plane displacement...
May 10, 2017: Ultrasonics
Zheng Xu, Wei Xu, Menglu Qian, Qian Cheng, Xiaojun Liu
We report a flat acoustic lens with a periodical structure to transform a divergent beam into a Bessel-like beam. Using the Schlieren imaging technique, the propagation process of acoustic wave in the periodical structure was experimentally observed. The pressure distribution in the main lobe is in good agreement with the Bessel function and the positions of the side lobes are close to the peak of the Bessel function. To observe the directivity of the beam, simulations were performed using the finite-element method...
May 9, 2017: Ultrasonics
Yikuan Wang, Ruiqi Guan, Ye Lu
A nonlinear Lamb-wave-based method for fatigue crack detection in steel plates with and without carbon fibre reinforcement polymer (CFRP) reinforcement is presented in this study. Both numerical simulation and experimental evaluation were performed for Lamb wave propagation and its interaction with a fatigue crack on these two steel plate types. With the generation of the second harmonic, the damage-induced wave nonlinearities were identified by surface-bonded piezoelectric sensors. Numerical simulation revealed that the damage-induced wave component at the second harmonic was slightly affected by the existence of CFRP laminate, although the total wave energy was decreased because of wave leakage into the CFRP laminate...
May 6, 2017: Ultrasonics
Mohammad Hadi Hafezi, Reza Alebrahim, Tribikram Kundu
The objective of this paper is to introduce a novel fast modeling tool called peri-ultrasound for linear/nonlinear ultrasonic wave propagation modeling. This modeling approach is based on peridynamic theory. It does not require monitoring of the crack clapping phenomenon or artificially changing the stiffness of the element when two surfaces of the crack come in contact. Peri-ultrasound tool enables us to detect the material nonlinearity in very early stages of crack growth. Nonlinear ultrasonic behavior could be nicely modeled by the proposed peri-ultrasound tool...
May 5, 2017: Ultrasonics
B D Zaitsev, A A Teplykh, I A Borodina, I E Kuznetsova, E Verona
It has been shown that by using piezoelectric lateral electric field excited resonators based on X - cut LiNbO3, one can determine the octane number of gasoline. The measured dependence of gasoline permittivity on its octane number has shown that there is an ambiguous connection between pointed parameters. We have demonstrated both theoretically and experimentally that the value of the real part of the electrical impedance on the frequency of parallel resonance uniquely associates with the octane number of gasoline contacting the free side of the resonator...
May 4, 2017: Ultrasonics
Ruinan Ji, Jiamei Jin, Liang Wang, Jianhui Zhang
With the rapid development of modern industrial technology and high performance technology products, ultra-precision machining technology becomes increasingly important. However, joint clearance of kinematic pairs, lack of feeding accuracy and overlarge contact stress still limit the further improvement of ultra-precision machining technology. In this study, a novel surface machining method utilizing structural elastic waves was proposed, and a machining tool using the piezoelectric actuating principle was presented for verifying the proposed method...
May 4, 2017: Ultrasonics
Yongfeng Song, Christopher M Kube, Joseph A Turner, Xiongbing Li
The spatial statistics of an ensemble of waveforms containing ultrasonic scattering from microstructure are investigated. The standard deviation of the waveforms is of primary interest, because it is related to the maximum scattering amplitudes in the extreme value statistics theory. Further statistical measures are employed to define theoretical confidence bounds, which bound the experimentally calculated maximum amplitude when a finite number of waveforms are included in the ensemble. These statistical measures are applied in conjunction with a previously developed ultrasonic backscatter model...
May 4, 2017: Ultrasonics
J-C Kastelik, S Dupont, K B Yushkov, V Ya Molchanov, J Gazalet
A new laser scanning system is presented based on two wide-band acousto-optic deflectors. The interaction medium is tellurium dioxide. Anisotropic interactions take place under two different tangential phase matching configurations in such a way that the acousto-optic bandwidths add up. We demonstrate the feasibility of such a cascade deflection system for the wavelength of λ=514nm. The total frequency bandwidth is Δf=100MHz, equally distributed between the two acousto-optic deflectors. The total angular scan at the output is Δθ=4...
May 2, 2017: Ultrasonics
Reza Malehmir, Nasser Kazemi, Douglas R Schmitt
The study of the reflected acoustic waves plays an important role in our understanding of media. We provide an algorithm to propagate the ultrasonic bounded beam source and study its reflection from any horizontal and homogenous water-solid boundary. This algorithm implements a hybrid combination of the phase-advance wavefield continuation in the frequency domain and the complex analytic solution for the acoustic reflectivity. The peak amplitude of the specularly reflected beam is in agreement with the laboratory measured acoustic reflection from water-Aluminum and water-Copper alloy boundaries...
April 29, 2017: Ultrasonics
Ke Zhai, Qing He, Liang Li, Yi Ren
Chemical mechanical polishing (CMP) is the primary method to realize the global planarization of silicon wafer. In order to improve this process, a novel method which combined megasonic vibration to assist chemical mechanical polishing (MA-CMP) is developed in this paper. A matching layer structure of polishing head was calculated and designed. Silicon wafers are polished by megasonic assisted chemical mechanical polishing and traditional chemical mechanical polishing respectively, both coarse polishing and precision polishing experiments were carried out...
April 26, 2017: Ultrasonics
Vitalyi E Gusev, Alexey M Lomonosov, Chenyin Ni, Zhonghua Shen
An analytical theory accounting for the influence of hysteretic nonlinearity of micro-inhomogeneous plate material on the Lamb waves near the S1 zero group velocity point is developed. The theory predicts that the main effect of the hysteretic quadratic nonlinearity consists in the modification of the frequency and the induced absorption of the Lamb modes. The effects of the nonlinear self-action in the propagating and standing Lamb waves are expected to be, respectively, nearly twice and three times stronger than those in the plane propagating acoustic waves...
April 25, 2017: Ultrasonics
Sharmin R Ara, Syed Khairul Bashar, Farzana Alam, Md Kamrul Hasan
Using a large set of ultrasound features does not necessarily ensure improved quantitative classification of breast tumors; rather, it often degrades the performance of a classifier. In this paper, we propose an effective feature reduction approach in the transform domain for improved multi-class classification of breast tumors. Feature transformation methods, such as empirical mode decomposition (EMD) and discrete wavelet transform (DWT), followed by a filter- or wrapper-based subset selection scheme are used to extract a set of non-redundant and more potential transform domain features through decorrelation of an optimally ordered sequence of N ultrasonic bi-modal (i...
April 24, 2017: Ultrasonics
Patrik Fröjd, Peter Ulriksen
This study contributes to the establishment of frequency recommendations for use in coda wave interferometry structural health monitoring (SHM) systems for concrete structures. To this end, codas with widely different central frequencies were used to detect boreholes with different diameters in a large concrete floor slab, and to track increasing damage in a small concrete beam subjected to bending loads. SHM results were obtained for damage that can be simulated by drilled holes on the scale of a few mm or microcracks due to bending...
April 23, 2017: Ultrasonics
Konstantinos Diamantis, Alan Greenaway, Tom Anderson, Jørgen Arendt Jensen, Vassilis Sboros
Recent progress in adaptive beamforming techniques for medical ultrasound has shown that current resolution limits can be surpassed. One method of obtaining improved lateral resolution is the Minimum Variance (MV) beamformer. The frequency domain implementation of this method effectively divides the broadband ultrasound signals into sub-bands (MVS) to conform with the narrow-band assumption of the original MV theory. This approach is investigated here using experimental Synthetic Aperture (SA) data from wire and cyst phantoms...
April 21, 2017: Ultrasonics
Ehsan Kozegar, Mohsen Soryani, Hamid Behnam, Masoumeh Salamati, Tao Tan
Automated 3D breast ultrasound (ABUS) is a new popular modality as an adjunct to mammography for detecting cancers in women with dense breasts. In this paper, a multi-stage computer aided detection system is proposed to detect cancers in ABUS images. In the first step, an efficient despeckling method called OBNLM is applied on the images to reduce speckle noise. Afterwards, a new algorithm based on isocontours is applied to detect initial candidates as the boundary of masses is hypo echoic. To reduce false generated isocontours, features such as hypoechoicity, roundness, area and contour strength are used...
April 20, 2017: Ultrasonics
Rafatou Takpara, Marc Duquennoy, Mohammadi Ouaftouh, Christian Courtois, Frédéric Jenot, Mohamed Rguiti
Surface acoustic waves (SAW) are particularly suited to effectively monitoring and characterizing structural surfaces (condition of the surface, coating, thin layer, micro-cracks…) as their energy is localized on the surface, within approximately one wavelength. Conventionally, in non-destructive testing, wedge sensors are used to the generation guided waves but they are especially suited to flat surfaces and sized for a given type material (angle of refraction). Additionally, these sensors are quite expensive so it is quite difficult to leave the sensors permanently on the structure for its health monitoring...
April 19, 2017: Ultrasonics
Youxuan Zhao, Feilong Li, Peng Cao, Yaolu Liu, Jianyu Zhang, Shaoyun Fu, Jun Zhang, Ning Hu
Since the identification of micro-cracks in engineering materials is very valuable in understanding the initial and slight changes in mechanical properties of materials under complex working environments, numerical simulations on the propagation of the low frequency S0 Lamb wave in thin plates with randomly distributed micro-cracks were performed to study the behavior of nonlinear Lamb waves. The results showed that while the influence of the randomly distributed micro-cracks on the phase velocity of the low frequency S0 fundamental waves could be neglected, significant ultrasonic nonlinear effects caused by the randomly distributed micro-cracks was discovered, which mainly presented as a second harmonic generation...
April 12, 2017: Ultrasonics
Che-Chou Shen, Hsiao-Chi Yang
Ultrasound array imaging systems rely on a presumed beamforming sound velocity to calculate the time compensation of each element for receive focusing. The mismatch between the tissue sound velocity and the beamforming sound velocity can degrade the focusing quality due to loss of phase coherence. Since the tissue sound velocity cannot be known in prior, an adaptive optimization of beamforming sound velocity is required to improve the image quality. Differential phase gradient of channel data is proposed to estimate the optimal sound velocity for beamforming...
April 12, 2017: Ultrasonics
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