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Data on pressure signals and gas flow rate signals was collected under various experimental conditions. A comparative analysis was conducted to investigate the gradient changes of the fluidizing gas, the supplemental gas, and the pressurizing gas. A three‐factor three‐level orthogonal experiment was carried out. The results demonstrated that the proper use of the fluidizing gas can enhance the steady...
This paper presents the theory of passive localization for underwater sources based on multipath arrival structures. The principles of channel modelling in Ray-theory, determination of eigenrays which connect source and receiver, the information of source range and source depth is included primarily in arrival angles and time delays. The weighted-subspace-fitting (WSF) technique is used to minimize...
The received wind driven noise field can be described as a sum of fields radiated from many random sources on the sea surface. Wind driven noise source levels can be modeled by empirical relationship with local wind speed. A method for modeling wind-driven ambient noise based on ray approach in deep ocean is presented. Simulations are performed to demonstrate the validity of the method. The wind-driven...
The internal solitary waves propagating over the shelf slope fluctuating the acoustic energy in shallow water has been widely studied. In this paper, this process is broadened into the continental slope with different gradient at different range which is linked with the shallow water and the deep water. The temporal and spatial structures of the acoustic field with the internal solitary wave passing...
This paper presents an inversion scheme that uses two wideband explosive sources based on modal dispersion characteristics to synchronously obtain sound speed profile and bottom parameters. The signal received on a single hydrophone in a vertical line array is decomposed into a series of propagation modes within the framework of normal mode theory, and the dispersive characteristics of the modes are...
A model is developed for bistatic bottom reverberation in the deep ocean, which includes the propagation and scattering processes. The two-way propagations from the source to scatterer and the scatterer to receiver are described by ray theory. The sound speed profile in the deep ocean is taken into account for the accuracy. The scattering intensity is assumed to be a sum of the roughness-scattering...
Inversion of modal dispersion curves is an effective method for obtaining underwater acoustic parameters. In this paper, an inversion scheme for synchronously obtaining the sound speed profile and bottom parameters using two wideband explosive sound sources is proposed based on modal dispersion characteristics. First, the first three orders of empirical orthogonal functions were determined and used...
A formula is developed in this paper to calculate array gain when the plane-wave assumption is not applied. The formula is developped based on the assumption that the noise in the deep water is Gassian white and isotropic. The performance of a vertical linear is analyzed in the range-independent ocean, and also in a weak range-dependent ocean perturbed by random internal waves. Simulation results...
An ensemble Kalman filter (EnKF) approach is proposed to perform sequential tracking of water column sound speed profile (SSP) using a moving acoustic source. First, the SSPs are discretized in depth and range, and are expressed by the empirical orthogonal functions (EOFs). Second, the acoustic source state information and the first three orders of EOF coefficients are expressed as the state variable,...
This paper studies and discusses robust minimum variance distortionless response (MVDR) beamformer with subarray multistage processing for circular hydrophone arrays, which is an extension of the multistage MVDR beamformer with line microphone arrays for noise reduction. The basic theory is to divide the hydrophones into a certain number of groups with each group only having two hydrophones for MVDR...
Underwater sensors will diverge from the initial position because of the ocean current when the underwater sensors are deployed in the deep ocean. Assuming that the xy-plane coincides with the sea surface, a local Cartesian x-y coordinates system is set up in such a way that, when the sensors and sources are projected onto the local xy-plane, its origin coincides with the initial point of the sensors...
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