Abstract
Cobalt-rich manganese crusts (CRCs) are important as a potential mineral source that could occur throughout the Pacific on seamounts, ridges, and plateaus. We built a prototype parametric acoustic probe to complete the task of in-situ thickness measurements to estimate the volumetric distribution of deep-sea mineral. The prototype is designed with dual-channels for receiving the primary and secondary signal, which lays a foundation for improving the thickness extraction algorithm. Considering that the signal quality is degraded by the system interference and ambient noise, some improvements to the algorithm are proposed by including the wavelet-based envelope extraction method and the adaptive estimation strategy based on the dual-channel information. Additionally, wavelet regression is applied to reduce the measuring noise assuming that the CRCs have local thickness invariability. The algorithm is suitable for the CRCs with the structure of the multilayers at the top surface and one single layer at the bottom surface. A laboratory experiment is performed to validate the effectiveness of the algorithm. The experiments carried out on the China Ocean 51th voyage in the Western Pacific Ocean on Aug 30, 2018, are described and the data obtained by using the sit-on-bottom stationary measurement are processed to validate the design of the prototype.
Highlights
Cobalt-rich manganese crusts (CRCs) are important as a mineral resource on the seafloor for copper, cobalt, nickel, platinum, manganese, thallium, tellurium, and other metals [1]
We emphasize on the work for improving the performance of the thickness measurements, considering that PPPAAP17 is a parametric array acoustic probe designed for the application of estimating the resources of CRCs
This paper described the importance of the CRCs as a potential mineral necessity source and the necessity of mapping and estimating the volumetric distribution of deep-sea mineral
Summary
Cobalt-rich manganese crusts (CRCs) are important as a mineral resource on the seafloor for copper, cobalt, nickel, platinum, manganese, thallium, tellurium, and other metals [1]. Considering that CRCs have extremely uneven distribution and thin geometrical features, it remains a challenging task to collect the necessary information to measure the thickness by using such general acoustic devices at the aspect of resolution or the penetrating capability. We emphasize on the work for improving the performance of the thickness measurements, considering that PPPAAP17 is a parametric array acoustic probe designed for the application of estimating the resources of CRCs. In practice, the necessary parameters, i.e., the sound velocity, the arrival time of the top surface, and the arrival time of the bottom surface, are calculated by processing the received signal that contains complicated context with the top-bottom peak detection. The processing and analysis of the experiments are demonstrated, and the comparisons are given to verify the effectiveness of the system and the algorithm
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