An Improved Reduced-Dimension Robust Capon Beamforming Method Using Krylov Subspace Techniques.

A reduced-dimension robust Capon beamforming method using Krylov subspace techniques (RDRCB) is a diagonal loading algorithm with low complexity, fast convergence and strong anti-interference ability. The diagonal loading level of RDRCB is known to become invalid if the initial value of the Newton iteration method is incorrect and the Hessel matrix is non-positive definite. To improve the robustness of RDRCB, an improved RDRCB (IRDRCB) was proposed in this study.

Origin of Reliable High-Power Performances of PbZrTiO-Pb(MnNb)O-Based Piezoelectric Ceramics.

High-power piezoelectric ceramics typically operate under severe conditions. This makes the accurate evaluation of their high-power performances through pure quasi-static parameters challenging. The 0.

A primary wideband calibration method for noise hydrophones based on three-transducer spherical wave reciprocity in the frequency domain.

A primary wideband calibration method for noise hydrophones is developed, which can be applied to obtain noise acoustic spectral density sensitivity in the free-field. In this method, a wideband three-transducer spherical wave reciprocity calibration method is proposed in the frequency domain. A lowpass spatial domain filter is utilized to eliminate the reflecting acoustic waves from boundaries and water surface, and the wideband frequency responses of the transducer pair are calculated.

A self-reciprocity calibration of spherical transducers using boundary reflection in a spherical shell.

A self-reciprocity method is described for calibrating a spherical transducer in a spherical shell. The reciprocity constant is calculated using Green's function and the electroacoustic reciprocal principle in the spherical shell. A sensitivity correction is developed by calculating the transducer's receiving force in different fields.

Well-balanced performance achieved in PZT piezoceramics a multiscale regulation strategy.

Emerging high-power piezoelectric applications demand the development of piezoelectric materials featuring both a high mechanical quality factor () and a large piezoelectric coefficient (). However, it is widely accepted that an increase in is usually accompanied with a decrease in , and . Herein, a multiscale regulation strategy is proposed to improve and simultaneously from the perspectives of phase structure, ferroelectric domains, and lattice defects.

Construction of a Soft Antifouling PAA/PSBMA Hydrogel Coating with High Toughness and Low Swelling through the Dynamic Coordination Bonding Provided by Al(OH) Nanoparticles.

Marine biofouling, resulting from the adhesion of marine organisms to ship surfaces, has long been a significant issue in the maritime industry. In this paper, we focused on utilizing soft and hydrophilic hydrogels as a potential approach for antifouling (AF) coatings. Acrylic acid (AA) with a polyelectrolyte effect and -(3-sulfopropyl)--(methacryloxyethyl)-,-dimethylammonium betaine (SBMA) with an antipolyelectrolyte effect were selected as monomers.

Nearly Perfect Transmission of Lamé Modes in a Rectangular Beam with Part and Through-Thickness Vertical Cracks.

The guided waves in the uniform waveguide of rectangular cross-section exhibit complicated propagation and scattering characteristics due to the diversity of vibration modes. This paper focuses on the mode conversion of the lowest Lamé mode at a part-through or through-thickness crack. Firstly, the Floquet periodicity boundary condition is applied to derive the dispersion curves in the rectangular beam, which relates the axial wavenumber to the frequency.

Distinguishing multiple surface ships using one acoustic vector sensor based on a convolutional neural network.

A direction of arrival (DOA) estimation method based on a convolutional neural network (CNN) using an acoustic vector sensor is proposed to distinguish multiple surface ships in a selected frequency band. The cross-spectrum of the pressure and particle velocity are provided as inputs to the CNN, which is trained using data obtained by employing an acoustic propagation model under different environmental and source parameters. By learning the characteristics of acoustic propagation, the multisource distinguishing performance of the CNN is improved.

An Underwater Acoustic Network Positioning Method Based on Spatial-Temporal Self-Calibration.

The emergence of underwater acoustic networks has greatly improved the potential capabilities of marine environment detection. In underwater acoustic network applications, node location is a basic and important task, and node location information is the guarantee for the completion of various underwater tasks. Most of the current underwater positioning models do not consider the influence of the uneven underwater medium or the uncertainty of the position of the network beacon modem, which will reduce the accuracy of the positioning results.

Calibration methods and facilities for vector receivers using a laser Doppler vibrometer in the frequency range 20 Hz to 10 kHz.

Calibration methods and facilities have been employed to directly obtain sensitivities of an underwater acoustic vector receiver using two methods based on laser Doppler vibrometry. The vector receiver was first calibrated in a standing wave tube over the frequency range 20 Hz to 2 kHz, where the oscillatory velocity of the water-air interface was measured to determine the sound particle velocity at the position of vector receiver based on waveguide theory. In the frequency range 2.

Deep learning-based direction-of-arrival estimation for multiple speech sources using a small scale array.

A high resolution direction-of-arrival (DOA) approach is presented based on deep neural networks (DNNs) for multiple speech sources localization using a small scale array. First, three invariant features from the time-frequency spectrum of the input signal include generalized cross correlation (GCC) coefficients, GCC coefficients in the mel-scaled subband, and the combination of GCC coefficients and logarithmic mel spectrogram. Then the DNN labels are designed to fit the Gaussian distribution, which is similar to the spatial spectrum of the multiple signal classification.

A simple method for moving source depth estimation applied to the SWellEx96 data.

Existing methods for source localization in an ocean waveguide generally require simultaneous range and depth estimation as they are intrinsically coupled in the acoustic field. Using beam intensities averaged over ranges longer than the mode cycle distances, it is shown that the range-averaged vertical beam distribution is insensitive to the source range and sensitive to the source depth. An incoherent matched beam processing method is presented and applied to the SWellEx96 moving source data to estimate source depth based on the 127 and 130 Hz signals with good results.

Matched beam-intensity processing for a deep vertical line array.

A vertical line array can be deployed in deep water below the critical depth, the depth where the sound speed equals the sound speed at the surface, to take advantage of the lower ambient noise level (compared with above the critical depth) for target detection. To differentiate a submerged source from a surface source, a Fourier transform based method [McCargar and Zurk, J. Acoust.

A method of velocity estimation using composite hyperbolic frequency-modulated signals in active sonar.

This paper proposes a method to estimate the target velocity using a combination of two hyperbolic frequency-modulated (HFM) signals. The Doppler-shifted time-delay between the two signals compared with the original time-delay is used to estimate the target velocity. One finds that a HFM with an increasing frequency sweep (positive HFM) and one with a decreasing frequency sweep (negative HFM) yield a different time.

Perception of visual apparent motion is modulated by a gap within concurrent auditory glides, even when it is illusory.

Auditory and visual events often happen concurrently, and how they group together can have a strong effect on what is perceived. We investigated whether/how intra- or cross-modal temporal grouping influenced the perceptual decision of otherwise ambiguous visual apparent motion. To achieve this, we juxtaposed auditory gap transfer illusion with visual Ternus display.

Measurement of focused ultrasonic fields using a scanning laser vibrometer.

With the development of optical techniques, scanning laser vibrometers have been applied successfully in measuring particle velocities and distributions in ultrasonic fields. In this paper, to develop the optical interferometry in measuring focused fields with small amplitude, the "effective" refractive index used for plane waves and extended for spherical waves is presented, the piezo-optic effect as a function of the incident angle of the laser beam is simulated, and the ultrasonic field produced by a concave spherical transducer is calculated numerically around its focal region. To verify the feasibility of the optical method in detecting focused ultrasonic fields, a measurement system was set up that utilized both a scanning laser vibrometer and a membrane hydrophone.