Piao Sheng-chun

Research on chaotic character of ship-radiated noise based on phase space reconstruction

The phase space reconstruction is an important method of chaotic time series analysis. In this paper, the method is applied to ship radiated noise obtained through both onshore acquisition system and underwater hydrophones. Utilizing the delay coordinate reconstruction method, the two primary parameters, delay time and embedding dimension are determined. By optimizing these two parameters, the reconstructed attractor is gained with prominent structure of nonlinear dynamics. The largest Lyapunov exponent and correlation dimension of the data have also been obtained, both of which exhibit chaotic behavior. Comparing with those of data acquired via hydrophones, it proves that the phase space reconstruction and chaotic time series analysis method is effective to seismic-acoustic signal processing.

The study of Normal Modes dispersion extraction based on F-K transform

At present, dispersion curves are usually extracted through temporal-spatial analysis methods. To obtain more dispersion information relating to waveguides, the F-K transform is introduced in this paper. Based on Normal Mode theory, the feasibility analysis of the F-K transform employed in dispersion extraction has been provided with deduction and numerical simulation at first. Then, an anechoic tank measurement based on scale model has been carried out so as to demonstrate the research mentioned above, while at the same time the validity of the scale model applied to sound propagation has also been proved by normal mode theory. As for the accuracy and efficiency of measurement, they are further verified by the agreement between the numerical simulation and the analysis results of the measured data.

Experimental study of sound propagationusing a deep-water vector hydrophone

Vector hydrophone can synchronously receive the sound scalar field and the vector field information at a single point, which increases the variety and the quantity of the received sound information. Vector field information is beneficial to improve the performance of underwater acoustic devices or systems. In summer of 2014, a Long-Range Ocean Acoustic Propagation Experiment was carried out in deep sea. A deep-water vector hydrophone designed by Harbin Engineering University was located at the depth of 3146 m, which measured all the three components of particle velocities as well as the sound pressure in the acoustic field. The scalar and vector receptions of convergence zone arrivals and deep shadow zone arrivals were acquired for hundreds of kilometers in the experiment. The analyzed transmission loss results of the experimental data are described and compared with the predictions by a 2-D parabolic equation (PE) model, which is also called RAM. The comparisons show that the RAM-PE model is efficient to simulate both scalar field and vector field in deep water. Moreover, experiment results demonstrate that the deep-water vector hydrophone performs well to measure sound pressure signal and sound vector signal in deep water.

Review of long-range bottom reverberation in shallow water

Theoretical models of long range bottom reverberation in shallow water are reviewed. Firstly, several classical models are summarized based on the empirical scattering function and physical scattering mechanism. Then, the development of theoretical model and experimental measurement about bi-static shallow water reverberation are outlined in the second part. During summarization, the researching work of the group from HEU is also introduced. Bi-static reverberation in range dependent waveguide is the emphasis of their research, and the decaying rule of reverberation intensity in wedged environment is presented in paper.

Separation of overlapped Rayleigh and SH waves using intrinsic coherence function

This paper focuses on passive polarized wave separation. A new approach is proposed against overlapped Rayleigh and SH waves. The information given by the two three-component sensors is sufficient for the identification of mixing matrix and the estimation of target parameters, such as incident angle, time-delay and the axial ratio of particle motion trajectory. Although the two polarized waves may be coherent, wave separation is realized with the help of intrinsic coherence function based on second order statistics. The feasibility of this algorithm is verified by applying it to emulation continuous Rayleigh and SH waves.