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Gao J.,CAS Qingdao Institute of Oceanology | Gao J.,University of Chinese Academy of Sciences | Wu S.,Chinese Academy of Sciences | McIntosh K.,University of Texas at Austin | And 6 more authors.
Tectonophysics | Year: 2015

The northern margin of the South China Sea (SCS) has particular structural and stratigraphic characteristics that are somewhat different from those described in typical passive margin models. The differences are attributable to poly-phase tectonic movements and magmatic activity resulting from the interaction among the Eurasian, Philippine Sea and Indo-Australian plates. Based on several crustal-scale multi-channel seismic reflection profiles and satellite gravity data across the northern SCS margin, this paper analyzes the structures, volcanoes and deep crust of the continent-ocean transition zone (COT) at the mid-northern margin of the SCS to study the patterns and model of extension there.The results indicate that the COT is limited landward by basin-bounding faults near Baiyun sag and is bounded by seaward-dipping normal faults near the oceanic basin in our seismic lines. The shallow anatomy of the COT is characterized by rift depression, structural highs with igneous rock and/or a volcanic zone or a zone of tilted fault blocks at the distal edge. Gravity modeling revealed that a high velocity layer (HVL) with a 0.8-6-km thickness is frequently present in the slope below the lower crust. Our study shows that the HVL is only located in the eastern portion of the northern SCS margin based on the available geophysical data. We infer from this that the presence of an HVL is not required in the COT at the northern SCS margin. The magmatic intrusions and HVL may be related to partial melting caused by the decompression of a passive, upwelling asthenosphere, which resulted primarily in post-rifting underplating and magmatic emplacement or modification of the crust. Based on this study, we propose that an intermediate mode of rifting was active in the mid-northern margin of the SCS with characteristics that are closer to those of the magma-poor margins than those of volcanic margins. © 2015 Elsevier B.V.

Lv S.,South China University of Technology | Wang Z.,South China University of Technology | Sheng Y.,Guangzhou Marine Geological Survey Bureau | Feng J.,South China University of Technology
2012 International Conference on Systems and Informatics, ICSAI 2012 | Year: 2012

Based on fractional Fourier transform and optical Fresnel diffraction, this paper proposes a new image transforming method called fractional Fresnel transform (FFNT). The transformed image can be restored without distortion, and the modification of the transform-domain coefficients can satisfy asymmetry. Using FFNT and Arnold scrambling technique, we conduct some experiments to test the validity of this new transform method. Experimental results show that the new watermarking scheme can achieve excellent performance to JPEG compression and Gaussian low-pass filtering attacks. © 2012 IEEE.

Ma D.,Changan University | Zhao H.,Changan University | Wu Z.,Guangzhou Marine Geological Survey Bureau
Shiyou Diqiu Wuli Kantan/Oil Geophysical Prospecting | Year: 2013

When the traditional three-point positioning method is used to calculate ocean bottom seismograph (OBS) based on the travel-time of direct wave, it is often found that calculated OBS positions are not unique, and sometimes they have great errors. To solve this problem, a mixed positioning method based on the travel-time of direct wave is proposed in this paper. Jointly using the three-point locating method, the least square method and searching method, the non-unique problem caused by direct wave travel-time errors, shotpoint errors of and sound wave velocity errors is solved. The optimal OBS position and the optimal sound wave velocity are found. Application results show this method is an efficient and simple way for improving OBS positioning precision.

Lu S.-X.,South China University of Technology | Wang Z.-S.,South China University of Technology | Sheng Y.,Guangzhou Marine Geological Survey Bureau | Feng J.-C.,South China University of Technology
Guangzi Xuebao/Acta Photonica Sinica | Year: 2012

A novel image transforming method called Reconstruction Transform is proposed, which can make the double random phase encryption image become non-negative integer value. Reconstruction transform includes two stages, pre-processing and spectral shifting. It's major characteristic is that, compress the interger image to become complex image of half-sized before applying spectral transform to the original image, thus reducing the calculation space in the following steps. The proposed method has the advantage of joint image compression and encryption. Compared with the chaotic image encryption scheme, the cipher-text image of the proposed scheme has lower information entropy. Experimental results show that this method has high security, the decrypted image of this method has little distortion and the cipher-text image has a certain degree of robustness to additive noise attack.

Luo W.-D.,Guangzhou Marine Geological Survey Bureau
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2011

Concerning about problems appearing in the procedure of the data acquisition and post-processing of the multibeam bathymetric measurement. The security safeguard of equipment, the place and key points of parameter testing, on-site quality control of data acquisition were discussed, the processing points and corresponding measures were described. The method completed the work flow of the multibeam bathymetric measurement, improved the level of the on-site quality control and the quality of data acquisition, make the ocean survey better and promote the development of the multibeam bathymetric measurement.

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