National Deep Sea Center
National Deep Sea Center
Chen Y.-S.,Harbin Engineering University |
Chen Y.-S.,National Deep Sea Center |
Zheng X.,Harbin Engineering University |
Jin S.-Q.,Harbin Engineering University |
Duan W.-Y.,Harbin Engineering University
China Ocean Engineering | Year: 2017
Smoothed Particle Hydrodynamics method (SPH) has a good adaptability for simulating of free surface flow problems. However, there are some shortcomings of SPH which are still in open discussion. This paper presents a corrected solid boundary handling method for weakly compressible SPH. This improved method is very helpful for numerical stability and pressure distribution. Compared with other solid boundary handling methods, this corrected method is simpler for virtual ghost particle interpolation and the ghost particle evaluation relationship is clearer. Several numerical tests are given, like dam breaking, solitary wave impact and sloshing tank waves. The results show that the corrected solid boundary processing method can recover the spurious oscillations of pressure distribution when simulating the problems with complex geometry boundary. © 2017, Chinese Ocean Engineering Society and Springer-Verlag Berlin Heidelberg.
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 | Year: 2013
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.
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 | Year: 2013
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.
Gao W.,Ocean University of China |
Gao W.,National Deep Sea Center |
Liu H.-S.,Ocean University of China
Applied Geophysics | Year: 2013
The strong noise produced by the leakage of electricity from marine seismic streamers is often received with seismic signals during marine seismic exploration. Traditional denoising methods show unsatisfactory effects when eliminating strong noise of this kind. Assuming that the strong noise signals have the same statistical properties, a blind source separation (BSS) algorithm is proposed in this paper that results in a new denoising algorithm based on the constrained multi-user kurtosis (MUK) optimization criterion. This method can separate strong noise that shares the same statistical properties as the seismic data records and then eliminate them. Theoretical and field data processing all show that the denoising algorithm, based on multi-user kurtosis optimization criterion, is valid for eliminating the strong noise which is produced by the leakage of electricity from the marine seismic streamer so as to preserve more effective signals and increase the signal-noise ratio. This method is feasible and widely applicable. © 2013 Editorial Office of Applied Geophysics and Springer-Verlag Berlin Heidelberg.
Zhang T.,National Deep Sea Center |
Yang K.,Northwestern Polytechnical University |
Liu Y.,CAS Beijing Institute of Acoustics |
Yang B.,CAS Beijing Institute of Acoustics
2016 IEEE/OES China Ocean Acoustics Symposium, COA 2016 | Year: 2016
Ambient noise in the ocean has been measured and studied for over half a century. Due to multipath effects, the signal will not always arrive from the horizontal direction. The directional response of a vertical line array (VLA) to a distant source can be expressed in terms of the modal beams weighted by their normal mode amplitudes. This modal representation offers a physical interpretation of the vertical directionality of the source in terms of normal modes. When a short VLA lies at the lower sound speed portion of the water column and a high frequency source is located at the higher sound speed portion of the water column, there always exists a notch in the horizontal direction. The vertical directionality of the source has been validated using Mediterranean Sea data, and it is shown that the vertical directionalities of the ambient noise and the distant source are quite different. © 2016 IEEE.
Zhang Z.,Zhejiang University |
Pei Y.,State Oceanic Administration |
Liu Z.,Zhejiang University |
Wang K.,State Oceanic Administration |
And 2 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2012
In order to develop an efficient plasma drill, we experimentally researched rock breakdown under short high-voltage pulses in deionized water. Rocks were placed between a needle high-voltage electrode and a plate grounded electrode. The relationship between breakdown probability and electrical strength was evaluated by applying various voltage levels to the rocks. The results show that the electrical breakdown strength of yellow sandstone with 7% porosity is 70 kV/cm, and for white marble with 0.8% porosity it is 160 kV/cm. The porosity has a great influence on the breakdown strength. Moreover, experimental results show that the breakdown strength drops with increasing thickness of the rock.
Zhang T.-W.,National Deep Sea Center |
Zhang T.-W.,Northwestern Polytechnical University |
Yang K.-D.,Northwestern Polytechnical University
Wuli Xuebao/Acta Physica Sinica | Year: 2014
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.
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 | Year: 2015
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.
Shi X.,National Deep Sea Center |
Lembke C.,University of South Florida
Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment | Year: 2016
This article proposes a novel trial-and-error control strategy for buoyancy-driven underwater profilers that can be used for water column observation. The proposed strategy is based on the design of a characteristic function utilizing the profiler's buoyancy adjustment components by automatically triggering a pump and a valve. To facilitate the elaboration of the proposed control strategy, a Bottom Ocean Stationing Ocean Profiler and its buoyancy adjustment system are introduced. Based on this buoyancy adjustment system, a characteristic function uses the difference between the current depth and the desired depth to determine a target velocity. Then, the trial-and-error control strategy based on error in velocity is implemented on the control of the buoyancy engine by determining whether positive or negative buoyancy adjustment is needed and by how much. This method has been applied to the depth control for our profilers resulting in field application results to validate the analysis. © IMechE 2015.
Kan G.,State Oceanic Administration |
Su Y.,State Oceanic Administration |
Liu B.,National Deep Sea Center |
Li G.,State Oceanic Administration |
Meng X.,State Oceanic Administration
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2014
Based on the sediment cores collected in the middle area of the Southern Yellow Sea and the core data measured in the laboratory, the properties of the acoustic impedance of shallow seafloor sediments and the correlations between the acoustic impedance and the physical parameters of the sediments are analyzed. The data analysis demonstrates that the acoustic impedance is characterized with a zonal distribution pattern, and its distribution can be divided into three sub-zones: a low acoustic impedance sub-zone in the northeast, a high acoustic impedance sub-zone in the southwest and an acoustic impedance gradient band aligning from northwest to southeast. The empirical regression equations between the acoustic impedance and the physical-mechanical parameters of the sediments are established by means of regression analysis. The results indicate that the acoustic impedance is well correlated to the parameters such as density, percent moisture, porosity ratio, percent porosity, liquid limit, plastic limit, plasticity index and compression coefficient, with the coefficient R2 which is generally larger than 0.8, but poor correlated to the parameters such as sand content, clay content, median grain size and shear strength, with the correlation coefficient R2 which is commonly less than 0.7. Comparing the correlations between the acoustic impedance and the physical-mechanical parameters to that between the sound speed and the physical-mechanical parameters of the sediment shows that the former correlation coefficient R2 generally larger than the latter one. This result indicats the acoustic impedance could be a better sediment acoustic parameter that can reflect the relationships between the acoustic properties and the physical-mechanical parameters of the seafloor sediments.