Kaufmanbrink7340

9%. For a receive line spacing equivalent to transducer pitch, averaging estimates from three parallel lines produced peak SNRe at the focal zone (25 mm), while, at the shallower regions (7) were needed. Increasing the beamforming line density by a factor of 8 increased the focal zone SNRe only by 13.2%. When SWS quantification was desirable at a fixed depth (such as within the push focal depth), using a deeper tracking focal zone enabled higher parallel line count and improved the peak SNRe by 33%. The multifocusing strategy produced a lower SNRe than the single-focus configurations. For a fixed tracking focal zone, a depth-dependent averaging based on the simulated transmit intensity adequately accounted for the transmit beamwidth. The results in this work demonstrated that STL-SWEI can be implemented using focused transmit beams with robust noise-suppression capability.Ferroelectric materials based on lead zirconate titanate (PZT) are widely used as sensors and actuators because of their strong piezoelectric activity. However, their application is limited because of the high processing temperature, brittleness, lack of conformal deposition, and a limited possibility to be integrated with the microelectromechanical systems (MEMS). Recent studies on the piezoelectricity in the 2-D materials have demonstrated their potential in these applications, essentially due to their flexibility and integrability with the MEMS. In this work, we deposited a few layer graphene (FLG) on the amorphous oxidized Si3N4 membranes and studied their piezoelectric response by sensitive laser interferometry and rigorous finite-element modeling (FEM) analysis. Modal analysis by FEM and comparison with the experimental results show that the driving force for the piezoelectric-like response can be a polar interface layer formed between the residual oxygen in Si3N4 and the FLG. The response was about 14 nm/V at resonance and could be further enhanced by adjusting the geometry of the device. These phenomena are fully consistent with the earlier piezoresponse force microscopy (PFM) observations of the piezoelectricity of the graphene on SiO2 and open up an avenue for using graphene-coated structures in the MEMS.In synthetic aperture (SA) imaging reported in the ultrasound imaging literature, typically, the delay and sum (DAS) beamformer is used; however, it is computationally expensive due to the pixel-by-pixel processing performed in the time domain. Recently, the adaptation of frequency-domain beamformers for medical ultrasound SA imaging, particularly to single-element/multielement synthetic transmit aperture (STA/MSTA) schemes, has been reported. In such reports, usually, less attention is paid to reducing system complexity. Recently, a sparse-transmit sparse-receive version of diverging beam-based synthetic aperture technique (DBSAT) was shown to achieve a reduction in system complexity by using fewer parallel receive channels, yet it achieves better quality and higher frame rate than conventional focused beamforming. However, this was also demonstrated using the DAS beamformer. In this work, we aim at achieving a reduction in computational cost, in addition to a reduction in system complexity, by implementing a fast and efficient frequency-wavenumber ( ω - k ) algorithm for the sparse DBSAT scheme. In doing so, an additional novel step of recovering missing frame data due to sparse transmit is introduced, namely, projection onto elliptical sets (POES). The results from this novel combination of ω - k with POES recovery showed that it is feasible to achieve several orders of magnitude faster reconstruction compared with the standard DAS beamforming, without any compromise in the image quality and, in some cases, with improved image quality. The average value of the contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) calculated from cyst at 15-mm depth obtained using the different schemes was 4.94 and 5.73 dB better when ω - k was employed instead of DAS, respectively. In addition, for the sparse data set acquired with a 50% overlap during transmit and 64 active receive elements, DAS reconstruction takes as long as ~647 s, whereas the ω - k algorithm takes only ~2 s when programmed and executed in MATLAB.There is an increasing need for ultrasonic transducers able to operate continuously at high temperatures in many industrial sectors. Operating temperatures may be 600 °C and higher. There is not any commercial solution to deal with such applications, and only a few ultrasonic prototype probes exist. It is, therefore, important to find new materials suitable for the manufacture of high-temperature ultrasonic probes. One important element of ultrasonic probes is the backing as it enables the control of both sensitivity and bandwidth. The goal of this article is to explore the possibility of using particulate metal composite as a high-temperature backing elements. Several tin-tungsten composites with different tungsten volume fractions were produced by uniaxial pressing. The backings were characterized by ultrasonic spectroscopy. The backings have an impedance ranging from 25 to 31 MRayl with attenuation at least equal to 20 dB/cm and up to 191 dB/cm. In order to operate at 600 °C, a sample of Al/W composite was produced. selleck compound Its impedance ranged from 8 to 10 MRayl with a mean attenuation of around 156 dB/cm at 4.5 MHz. The metallic composites, therefore, have ultrasonic properties suitable for use as backing. Moreover, they are relatively easy to manufacture. These are, therefore, very interesting materials for high-temperature ultrasonic probe applications.A series of Aurivillius phase materials, Bi5Ti 3 - 2x Fe 1 + x NbxO15 ( [Formula see text], 0.1, 0.2, 0.3, and 0.4), was fabricated by chemical solution deposition. The effects of aliovalent substitution for the successful inclusion of Fe 3+ and Nb 5+ by replacing Ti 4+ were explored as a potential mechanism for increasing magnetic ion content within the material. The structural, optical, piezoelectric, and magnetic properties of the materials were investigated. It was found that a limit of x = 0.1 was achieved before the appearance of secondary phases as determined by the X-ray diffraction. Absorption in the visible region increased with increasing values of x corresponding to the transition from the valence band to the conduction band of the Fe- [Formula see text] energy level. Piezoresponse force microscopy measurements demonstrated that the lateral piezoelectric response increased with increasing values of x . Magnetic measurements of Bi5Ti2.8Fe1.1Nb0.1O15 exhibited a weak ferromagnetic response at 2, 150, and 300 K of 2.2, 1.6, and 1.5 emu/cm3 with Hc of ∼ 40 , 36, and 34 Oe, respectively. The remanent magnetization MR of this sample was found to be higher than the range of reported values for the Bi5Ti3Fe1O15 parent phase. Elemental analysis of this sample by energy-dispersive X-ray analysis did not provide any evidence for the presence of iron-rich secondary phases. However, it is noted that a series of measurements at varying sample volumes and instrument resolutions is still required in order to put a defined confidence level on the Bi5Ti2.8Fe1.1Nb0.1O15 material being a single-phase multiferroic.Thêo1 is a frequency stability statistic that is similar to the Allan variance but can provide stability estimates at longer averaging factors and with higher confidence. However, the calculation of Thêo1 is significantly slower than that of the Allan variance, particularly for large data sets, due to a worse computational complexity. A faster algorithm for calculating the "all- τ " version of Thêo1 is developed by identifying certain repeated sums and removing them with a recurrence relation. The new algorithm has a reduced computational complexity, which is equal to that of the Allan variance. Computation time is reduced by orders of magnitude for many data sets. The new, faster algorithm does introduce an error due to accumulated floating-point errors in very large data sets. The error can be compensated for by increasing the numerical precision used at critical steps. The new algorithm can also be used to increase the speed of ThêoBr and ThêoH that are more sophisticated statistics derived from Thêo1.The finite-element analysis (FEA) is used in this work to study the impedance curves and modes of motion at resonance of nonstandard shear plates, thickness poled, and longitudinally excited. An ecological, lead-free, piezoelectric ceramic of ( 1-x )(Bi0.5Na0.5)TiO3- x BaTiO3 with x =0.06 (BNBT6) composition is studied. The FEA modeling is based on the full matrix of the material coefficients. These are obtained from complex impedance measurements on two-thickness poled resonators. A study as a function of the variations of the dimensions of the plate was accomplished ( t = thickness for poling and L and w = lateral dimensions, where w is the distance between electrodes for the electrical excitation). We aimed to a further understanding, and, thus, the ability to control, the coupling of the main shear resonance and the lateral modes. The use of uncoupled shear modes to obtain the material parameters is a key issue for their determination as complex quantities, thus considering all material losses, electromechanical, dielectric, and elastic.We present a new transmit pulse encoding scheme for ultrafast phased-array imaging called sparse orthogonal diverging wave imaging (SODWI). In SODWI, Hadamard encoding is used to selectively invert transmit pulse phases beamformed with a diverging wave delay profile. This approach has the advantage of delivering energy to a much wider field of view than conventional Hadamard-encoded multielement synthetic transmit aperture (HMSTA), making it more suitable for phased-array applications. With SODWI, we use a synthetic transmit element delay insertion (STEDI) approach which produces significant improvements in resolution, grating lobe level, and signal-to-noise ratio (SNR) over HMSTA. We also show how in SODWI a subset of the Hadamard codes can be sparsely selected to increase the imaging frame rate at the expense of image quality. SODWI is then compared with a variety of beamforming schemes for phased-array applications, including HMSTA, STEDI-HMSTA, diverging wave imaging (DWI), synthetic aperture (SA), and focused imaging. We present the results by implementing this technique on a 64-channel custom beamforming platform with a 40-MHz phased array. When a full set of codes is used, SODWI outperforms focused imaging contrast and SNR by 2.7 and 1.8 dB in addition to an 8× increase in frame rate, respectively.Studies of medical flow imaging have technical limitations for accurate analysis of blood flow dynamics and vessel wall interaction at arteries. We propose a new deep learning-based boundary detection and compensation (DL-BDC) technique in ultrasound (US) imaging. It can segment vessel boundaries by harnessing the convolutional neural network and wall motion compensation in the analysis of near-wall flow dynamics. The network enables training from real and synthetic US images together. The performance of the technique is validated through synthetic US images and tissue-mimicking phantom experiments. The neural network performs well with high Dice coefficients of over 0.94 and 0.9 for lumens and walls, outperforming previous segmentation techniques. Then, the performance of the wall motion compensation is examined for compliant phantoms. When DL-BDC is applied to flow influenced by wall motion, root-mean-square errors are less than 0.07%. The technique is utilized to analyze flow dynamics and wall interaction with varying elastic moduli of the phantoms.