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Based on the equal strain model of composite materials, the material properties of 1-3 piezoelectric composites are studied, and the active sound absorption property of 1-3 piezoelectric composites is studied by using piezoelectric shunt damping technology. According to the electromechanical relationship of the piezo-composites layer in vibration state and the sound transfer matrix of the medium, the research model is established. In this paper, the relationship between the material properties and the sound absorption property of 1-3 piezoelectric composites is studied, and the active sound absorption property of 1-3 piezoelectric composites is studied by using the negative capacitance and resistance circuit. The results show that: the material parameters of polymer phase in 1-3 piezoelectric composites and the thickness of the composite can affect the sound absorption property of 1-3 piezoelectric composites layer. However, due to the limitation of thickness in practical application, the effect of passive sound absorption of 1-3 piezoelectric composites in low frequency range is worse. The sound absorption property of 1-3 piezoelectric composites can be increased by external negative capacitance and resistance circuit. The absorption coefficient of 1-3 piezoelectric composites layer in low frequency and wide band range can be improved by piezoelectric shunt damping technology.

The hydrophone installed on the platform is the core component of the sonar equipment, and the surrounding vibration environment has an impact on the acoustic performance of the hydrophone at all times. There are two main ways for the vibration and noise of the platform to affect the hydrophone: one is that mechanical vibration is transmitted to the sensitive components of the hydrophone through the platform and the installation structure, which belongs to the direct transmission of vibration; the other is that the bending wave propagates along the platform to the vicinity of the hydrophone, which stimulates the flow around the hydrophone to produce the pressure wave decaying along the normal direction of the platform. In this paper, the influence of vibration excitation on the acoustic environment and voltage output performance of hydrophone with different structure and different installation state is studied by simulation modeling, the research results can provide references for hydrophone design and array.

The working environment of platform has put forward many requirements on the performance of hydrophone, and the sound pressure sensitivity and acceleration sensitivity are the most important, especially the acceleration sensitivity, which determines whether the hydrophone can effectively resist the vibration noise interference caused by platform vibration and eddy current. Reducing the acceleration sensitivity can improve the signal to noise ratio of hydrophone and reduce the minimum detectable signal. In this paper, the acceleration sensitivity mechanism of hydrophone is analyzed theoretically, and four methods to reduce the acceleration sensitivity of hydrophone are put forward. The four cases are analyzed by COMSOL finite element software.

In this paper, the performances of 1-3 piezoelectric composites based on a single crystal ferroelectric PIN-PMN-PT as underwater projectors are simulated by finite element method. The harmonic vibration modes and transmitting voltage responses are investigated. The potential advantages and values of single crystal ferroelectrics based composite transducers are presented compared with PZT based composites. The basic principle of designing 1-3 piezoelectric composites for projectors is discussed.

In this paper, a finite element model of a plane hydrophone mounted on a sound barrier plate is established, and the vibration damping performance of the sound barrier plate on the hydrophone is simulated. The influences of different size and different structural sound barriers on the vibration attenuation performance of the hydrophone are discussed. By comparing and analyzing the simulation results of the finite element model of the plane hydrophone mounted on the sound barrier, the influence law of acoustic baffle on the vibration absorption performance of hydrophone is concluded.

A small-sized flextensional transducer is introduced which uses piezoelectric single crystal as driving material to achieve low-frequency and high-power emission. By analyzing the influence of structure for CLASS IV flextensional transducer on the radiation capacity and the vibrator stress, ratio for major axis length/minor axis length, shell height, shell thickness, the position of vibrators and so on are reasonably selected, which can reduce the energy loss caused by the bending deformation of the vibrator, and radiation capacity of the transducer is designed to improve. The maximum size of the single crystal CLASS IV flextensional transducer is 270mm, the quality factor is 248 W/(m3•Hz), and sound source level is 7.4 dB higher than the piezoelectric ceramic transducer of the same size and structure.

In order to realize the image fusion of multi focus and multi-source acquisition, in this paper a method based on deep learning model and DT-CWT image fusion is proposed. Firstly, the base parts and detail features of the image were separated, the base parts was denoised and filtered by DT-CWT, and the fusion base parts were obtained; depth learning model VGG-S was selected to extract the detail features of the image, and then the fusion details were obtained by multi-layer fusion strategy. Finally, the maximum gradient value is used to select the detail features to obtain the fusion details. The fusion base parts and details features were overlapped and reconstructed to obtain the fusion image. The algorithm not only retains the significant features of the image, but also makes the fused image obtain more detailed feature information. In the process, the noise was reduced. The subjective and objective evaluation results are improved obviously.

The dielectric and piezoelectric properties of tetragonal PIN-PMN-PT single crystal under dc voltage have been systematically investigated. The dielectric constant and piezoelectric coefficient decreased, and dielectric loss remained basically invariable with increasing of the dc voltage(0~2000V). Although the dc voltage ensures the single crystal is not depolarized, a balance need to be found between the applied voltage and the electrical properties of the single crystal.

There is a growing demand for wearable electronic devices in recent years. In particular, stretchable strain sensors with large strain range, high sensitivity, good linearity and remarkable stability have attracted much attention in wearable electronics field for applications in the real-time human motion detection. However, the simultaneous realization of high stretchability and good sensitivity is still a critical challenge, especially in the consideration of the conformability on the curved surfaces. In this work, a fully-stretchable and highly- sensitive strain sensor with outstanding profile conformability was developed by using a novel liquid-state conductive composite composed of carbon nanotubes and liquid silicone rubber. This liquid-state conductive composite exhibits a remarkable stretchability and stability compared with traditional stretchable electrodes, which endows the strain sensor a 400% length deformation with a gauge factor of 43.84. Moreover, the proposed strain sensor was systematically studied and proven to possess the unique features of high linearity, low hysteresis and good stability. The strain sensor can endure various mechanical deformations without any damage, including 4-folded, and 360° twisted. It was also demonstrated that the developed sensor can monitor the gesture and motion of joint activities, which shows an attractive future vision for applications in health detection.

In this paper, a design of a mid-frequency planar PVDF hydrophone is proposed. The FEM is utilized to simulate the performance of the hydrophone. The effects of the stiffening substrate and the compliant layers on the hydrophone sensitivity are analyzed in detail. Under the guidance of the theoretical analysis, a prototype of the mid-frequency planar PVDF hydrophone is manufactured, and the actual performance is measured in an anechoic tank. The theoretical analysis and experimental results indicate that the planar hydrophone has the advantages both in signal sensing and noise suppressing, and can be widely used in the underwater target detection.

This paper, based on acoustic radiation, is focued on volume array. By using the finite element simulation software, the actual volume array model and the equivalent point source model are both established. Contrast and analysis of effect for mutual radiation to directivity of volume array. Mutual radiation impedance of the two models is calculated, which is varying with distance and frequency. Effect of mutual radiation is analyzed on resonance frequency, array work efficiency, bandwidth and so on. The results show that the point source model can predict the array property well and shorten the design cycle. Volume array of $\lambda /4$ gets severe mutual radiation influence. The radiation capability of the array is affected by the spacing of the array elements, the size of the array elements, the array configuration and the structure of the radiation surface.

A design of broadband underwater transducer with several piezoelectric ceramic rings is presented. These rings have different size and polarization direction as a result have different resonant frequency. Fluid cavity resonance mode is also adopted to extend low frequency bandwidth. FEM calculation results showed that, the transducer possesses a bandwidth of two octaves as long as the structure sizes were reasonably designed. This new structure transducer has the characteristics of low frequency working and broadband.

In this paper, the design of a flexural cylinder transducer based on magnetostrictive material is proposed. The FEM is utilized to simulate the performance of the transducer. Two driving mechanism are analyzed, and one of them is chosen for parametric simulation in detail. Several design parameters are studied, and the effects of the shell dimension, the shell material and active material on transducer transmitting voltage response are analyzed. According to the theoretical results, the flexural cylinder transducer can radiate significant acoustical power at ultra low frequency with a compact dimension.