Anisimkin V.I., Verona E., Kuznetsova A.S., Osipenko V.A. «Acoustic Wave Propagation Along Piezoelectric Plate Coated with Piezoelectric Films» Акустический журнал, 65, № 2, с. pp. 171-177 (2019)

A novel solid state structure consisting of piezoelectric plate sandwiched between two piezoelectric films is suggested as propagation medium for acoustic waves. Considering, as an example, quartz plate coated with AlN film and with AlN film together with ZnO film, the main characteristics of the Lamb and SH acoustic modes are numerically calculated and compared with each other. It is shown that i) the range of acoustic parameters achievable in structures is wider than that is for an uncoated plate, ii) generation of waves in the plate with one film is accomplished by 12 transducer configurations, while there are 32 configurations to excite the same waves in two film structure, iii) dispersion of the wave velocities and coupling constants depend on the mode order, mode type, film thickness, plate thickness, and transducer configuration. This property makes selection of appropriate modes more flexible. Results of calculations are partially verified experimentally.

Zhai J.X., Chen C. «Low-loss Floating Electrode Unidirectional Transducer for SAW Sensor» Акустический журнал, 65, № 2, с. pp. 178-184 (2019)

Two types of interdigital transducer (IDT) structures of SAW devices have been investigated; one type consists in a classical single electrode transducer where the unit cell has two electrodes, and the other type has a design of floating electrode unidirectional transducer (FEUDT) where the unit cell has six electrodes per period. By taking the Fourier transform of the corresponding time response, the insertion loss (IL) of the SAW device with FEUDT is calculated as –2.6 (forward) and –20.5 dB (backward). At the same time, the device with conventional IDT exhibits an IL value of –8.4 (forward) and –7.8 dB (backward). It turns out that the design of a novel FEUDT type SAW device can efficiently reduce the insertion loss of the SAW device.

Jurkonis R., Sakalauskas A., Lukoševičius A., Maciulevičius M., Tamoši~-unas M., Šatkauskas S. «Mapping Microbubble and Ultrasound Spatio-temporal Interaction by M-mode Imaging: The Study of Feasibility» Акустический журнал, 65, № 2, с. pp. 216-225 (2019)

Ultrasound (US) and microbubble (MB) interaction is an important factor in the research of bioacoustics, as well as targeted drug and gene delivery. In this study, we demonstrate the feasibility of pulse–echo M-mode imaging system to be used for the visualization and quantification of US–MB interaction in both spatial and temporal dimensions. The system incorporates an exposure chamber with the cell–MB suspension, a 2.7 MHz focused US transducer, a US pulser–receiver and the customized LabView software. The results of cell and MB interaction obtained after M-mode image analysis have showed the US–MB interaction to be non-uniform in space and non-stationary in time. In order to quantify the spatio-temporal US–MB interaction, we have introduced the time function of spatial homogeneity dynamics. We have observed that the effective duration of interaction can be characterized at the predefined threshold of spatial homogeneity. For example, at the US excitation of 360 kPa peak negative pressure (15 bursts transmitted at 80 Hz pulse repetition frequency), the US–MB interaction persists for more than 5 seconds in the range at 4 mm depth of the exposure chamber with more than 50% of homogeneity. The system proposed in this assay is feasible for the characterization of US–MB interaction and can be exploited to optimize the MB concentration and/or the US excitation parameters.

Wang Q., Zhou B., Chen Y., Quan H. «Subarray Beam-space Adaptive Beamforming Combined with Array Shape Estimation based on Non-Acoustic Sensor» Акустический журнал, 65, № 2, с. pp. 226-233 (2019)

To address the issue of serious decline in performance of the array signal processing caused by the towed array shape distortion during maneuvering, this paper presents a new method of subarray beam-space adaptive beamforming combined with an array shape estimation method based on non-acoustic sensor. Firstly, the array shape through the approximate circular arc structure of the array segment between the adjacent sensor during maneuvering is preliminary calculated. Next, the final estimated array shape through a smooth processing method on the entire array shape by means of a calibration method using spline interpolation technique is achieved. This method is able to estimate the array shape in real time. The array steering vector based on the real-time estimation of the array shape is updated, using a subarray beam-space adaptive beamforming (SBABF) to reduce the demand of the number of the snapshots. And the beam-space covariance matrix converges fast within a few snapshots. The SBABF method combined with array shape estimation (AE-SBABF) was verified by simulation data and sea trial data processing results. During maneuvering, the AE-SBABF can not only improve the array processing gain of the target effectively, but also solve the left/right ambiguity problem well.