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Qingdao, China

Liu B.,National Deep Sea Center | Han T.,First Institute of Oceanography | Kan G.,First Institute of Oceanography | Li G.,First Institute of Oceanography
Journal of Asian Earth Sciences

Knowledge about the marine sediment acoustic properties is a key to understanding wave propagation in sediments and is very important for military oceanography and ocean engineering. We developed a hydraulic-drived self-contained in situ sediment acoustic measurement system, and measured for the first time the in situ acoustic properties of sediments on 78 stations in the Yellow Sea, China, by employing this system. The relationships between the in situ measured acoustic properties and the onboard or laboratory determined geotechnical parameters were analyzed. Porosity was found to be the dominant factor in reducing velocity in a quadratic fashion; velocity showed an increment with bulk density and a decrement with mean grain size and clay content both with a nonlinear dependence; acoustic attenuation showed a bell-shaped correlation with porosity and mean grain size but reduced with clay content of the sediments. The attenuation results indicate that intergrain friction rather than viscous interactions between pore fluid and solid grains is the dominant loss mechanism in our marine sediments. The relationships established would be used to predict the geotechnical parameters from in situ measured acoustic properties and vice versa, as well as being an indicator of the seafloor processes, potential gas bubbles hazard and gas hydrates resources or other suitable targets of acoustic surveys. © 2013 Elsevier Ltd. Source

Zhang T.-W.,National Deep Sea Center | Zhang T.-W.,Northwestern Polytechnical University | Yang K.-D.,Northwestern Polytechnical University
Wuli Xuebao/Acta Physica Sinica

Matched-field replica vector should be calculated using parabolic equation in a range-dependent waveguide, this means that the matched-field localization is too computationally intensive, hence its engineering application is seriously hindered. A virtual time-reversal method for passive source localization for a range-dependent waveguide is presented. The number of parabolic equation computational grids in virtual time-reversal method is much smaller than that in matched-field processing for a range-dependent waveguide. Thus, the computational cost can be greatly reduced. Different from the matched-field processing, the virtual time-reversal method is a back-propagation process, which explores and utilizes the properties of reciprocity and superposition. It can be realized by weighting the replica surface with the complex conjugate of the data received on the corresponding element, followed by a summation of the processed received data. This performance of virtual time-reversal method for source localization is validated through numerical simulations and data from the Mediterranean Sea. © 2014 Chinese Physical Society. Source

Ding Z.,National Deep Sea Center | Wang C.,Qingdao University of Science and Technology | Wang P.,Qingdao University of Science and Technology
Lecture Notes in Electrical Engineering

Deep-sea benthic image features are difficult to extract because of its large amounts of information, auxiliary light imaging, and complex environmental background. To solve these problems, current study presents an approach to get texture information of sponge image captured by Jiao Long DSV. First, linear grayscale transformation is used to remove the seamount background and enhance contrast based on the image histogram analysis. The noise introduced by the suspended particles impurities is suppressed by median filter. Subsequently, compared with Prewitt and LoG algorithm, Canny operator is sure to get better edge extraction. Sponge texture information is most complete and noise is further reduced. Finally, mathematical morphology processing is carried out to perfect the texture by connecting intermittent textures, and the size estimation of the sponge based on hypothetical laser ruler is reliable and applicable. © Springer-Verlag Berlin Heidelberg 2015. Source

Zhang T.-W.,National Deep Sea Center | Zhang T.-W.,Northwestern Polytechnical University | Yang K.-D.,Northwestern Polytechnical University | Ma Y.-L.,Northwestern Polytechnical University | Wang Y.,Northwestern Polytechnical University
Wuli Xuebao/Acta Physica Sinica

It is very difficult to estimate the relative arrival delay of the eigenrays for an unknown source in shallow water. The effects of a source position changing in the neighborhood and sound speed profile perturbation on arrival time of eigenvays are similar. In this paper, we present a robust localization method based on the auto-correlation function of wide-band signal of single hydrophone. By designing neighboring location constraints, a weighting function is constructed to change the peak cross-interference of the auto-correlation function to useful information that is conducible to the improving of targeting performance. In this method there is no need to estimate the relative arrival delay of the eigenray. Computer simulation shows that the robust method can achieve better localization performance, and even has tolerences of environment mismatch and searching grid mismatch. The performance of the robust method is validated through the broad-band data collected on a vertical line array during the Shallow Water 2006 experiments. © 2015 Chinese Physical Society. Source

Gao W.,National Deep Sea Center | Liu H.S.,Ocean University of China | Sun J.Y.,CAS Qingdao Institute of Oceanology
Applied Mechanics and Materials

Independent components analysis (ICA) with constraint of seismic wavelet estimated from bispectrum of seismic traces is combined with short time Fourier transforms (STFT) to improve the traditional frequency domain seismic deconvolution. Neglecting noise, the seismic record is changed from time domain to frequency domain with STFT in order to transform the common seismic model to the basic ICA model. By applying FastICA algorithm with constraint of seismic wavelet estimated from bispectrum of seismic traces, reflectivity series and the seismic wavelet can be produced in frequency domain and changed back to the time domain subsequently. The model and real seismic data numerical examples all show the algorithm valid. © (2013) Trans Tech Publications, Switzerland. Source

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