Inverse data-space multiple elimination with 3D curvelet sparsity promotion     

Tong Wang  Deli Wang  Tiexing Wang  Mi Tian 《Acta Geophysica》2017,65(6):1197-1205

This paper describes an effective implementation of the inverse data-space multiple elimination method via the three-dimensional (3D) curvelet domain. The method can separate the surface-related operator (A) and primaries (P ₀) through seismic data matrix inversion. A 3D curvelet transform is introduced to sparsely represent the seismic data in the inverse data space. Hence, this approach is suitable for obtaining an accurate solution because of its multiscale and multidirectional analysis properties. The L1 norm is used to promote sparseness in the transform domain. Then, a high-fidelity separation of the operator (A) and the primaries (P ₀) is realized. The proposed method is applied to synthetic data from a model containing a salt structure. We compare the results with that of the traditional inverse data-space multiple elimination method and also with that of two-dimensional surface-related multiple elimination. The findings fully demonstrate the superiority of the proposed method over the traditional inverse method; moreover, the proposed method protects the primary energy more effectively than the SRME method.  相似文献   

Stratigraphic absorption compensation based on multiscale shearlet transform     

Chengming Liu  Deli Wang  Jialin Sun  Yibin Li  Fan Yang 《Acta Geophysica》2018,66(4):575-584

Seismic waves propagating through viscoelastic media experience stratigraphic absorption and attenuation effects, which directly affect the imaging resolution in seismic exploration. Without stratigraphic absorption, the ratio of deep reflection energy to shallow reflection energy (attenuation ratio) is invariable at different frequencies. If a seismogram is decomposed into different frequency bands, these signals will show similar time–energy distributions. Therefore, the attenuation ratios should be similar across different frequency bands, except for frequency-variable weights. Nevertheless, the frequency-variable weights for different frequency bands can be obtained by benchmarking against the time–energy distributions of low-frequency information because the loss of low-frequency information is relatively insignificant. In this light, we obtained frequency-variable weights for different frequencies and established a stratal absorption compensation (SAC) model. The anisotropic basis of the shearlet enables nearly optimal representation of curved-shape seismic signals, and shearlets at different scales can represent signals for different frequency bands. Then, we combined the SAC model with the shearlet transform and established the new compensation method. As the signal and noise have different distributions in the shearlet domain, we selectively compensated the signals using a thresholding algorithm. Hence, it was possible to avoid noise enhancement. This is the prominent advantage of the proposed method over other compensation methods.  相似文献   

Lack of mitochondrial genetic structure in the endangered giant clam populations of Tridacna maxima (Bivalvia: Cardiidae: Tridacninae) across the Saudi Arabian coast     

Ben Othmen Abdelwahe  Abhary Mohame  Deli Temim  Ouanes Zouhour  Alhuwaiti Nour  Dimassi Najet  Mansour Lamjed 《海洋学报(英文版)》2020,39(2):28-37

The present investigation focuses on population genetic structure analysis of the endangered giant clam species Tridacna maxima across part of the Red Sea,with the main aim of assessing the influence of postulated potential barriers to gene flow(i.e.,particular oceanographic features and marked environmental heterogeneity)on genetic connectivity among populations of this poorly dispersive bivalve species.For this purpose,a total of 44 specimens of T.maxima were collected from five sampling locations along the Saudi Arabian coast and examined for genetic variability at the considerably variable mitochondrial gene cytochrome c oxidase I(COI).Our results revealed lack of population subdivision and phylogeographic structure across the surveyed geographic spectrum,suggesting that neither the short pelagic larval dispersal nor the various postulated barriers to gene flow in the Red Sea can trigger the onset of marked genetic differentiation in T.maxima.Furthermore,the discerned shallow COI haplotype genealogy(exhibiting high haplotype diversity and low nucleotide diversity),associated with recent demographic and spatial expansion events,can be considered as residual effect of a recent evolutionary history of the species in the Red Sea.  相似文献   

台湾周遭之地下水入海     

陈镇东  张劲  彭宗仁  KANDASAMY Selvaraj  雷佳  林毅杰 《海洋学报(英文版)》2018,37(6):18-22

A preliminary study shows that the submarine groundwater discharge(SGD) exists around Taiwan even though groundwater overdrawing on the island is serious. Fifteen of the 20 sites studied for major anions and cations recorded a clear SGD signal with freshwater outflow. A total of 278 salinity and major ion measurements were made. Sixteen nearly freshwater SGD(salinity≤1.0) samples were obtained, providing strong and direct evidence for the existence of fresh meteoric groundwater entering the ocean from Taiwan. The total SGD flux is estimated to be 1.07×1010 t/a which is about 14% of the annual river output. The freshwater component of the SGD is3.85×109 t which is about 5.2% of the annual river discharge in Taiwan. The collected SGD has a composition similar to seawater with an addition of Ca, CO_3 and HCO_3 due to dissolution of calcareous rocks. Some samples with high Cl/(Na+K) may indicate pollution.  相似文献   

Zircon U-Pb geochronology and geological implications of granitoids from Sawuer Mountains in North Xinjiang, NW China     

Chengdong QI  Guohua QIAO  Hongchen DONG  Dayei LUI  Xing ZHANG  Deli YU 《世界地质(英文版)》2008,11(4)

LA-ICP MS zircon U-Pb dating results of granites from Sawuer Mountains in North Xinjiang, NW China, are reported based on 1:50 000 regional geologic surveys. Zircon U-Pb dating shows that the granitoids have magmatic crystallization age of 320 ±2 Ma. In addition, zircons with ages of 341 ～358 Ma could be subdi- vided into two groups, i.e. , Group 1 with a weighted mean age of 342 + 3 Ma and Group 2 with a weighted mean age of 354 + 2 Ma. The petrology and geochemistry of granitoids from Sawuer Mountains suggest their mixed origin. The granite from Sawuer Mountains occurred in an extensional setting, most probably related to post-orogenic processes during the closure of the Peo-Asian Ocean; namely, represent the tectonic setting shif- ted from compress to post-collisional setting.  相似文献   

A review on rill erosion process and its influencing factors   总被引：8，自引：0，他引：8  

SUN Liying  FANG Haiyan  QI Deli  LI Junlan  CAI Qiangguo 《中国地理科学(英文版)》2013,23(4):389-402

Rills are frequently observed on slope farmlands and rill erosion significantly contributes to sediment yields. This paper focuses on reviewing the various factors affecting rill erosion processes and the threshold conditions of rill initiation. Six factors, including rainfall, runoff, soil, topography, vegetation and tillage system, are discussed. Rill initiation and network are explored. Runoff erosivity and soil erodibility are recognized as two direct factors affecting rill erosion and other types of factors may have indirect influences on rill erosion through increasing or decreasing the effects of the direct factors. Certain conditions are necessary for rill initiation and the critical conditions are different with different factors. Future studies should be focused on 1) the dynamic changes of rill networks; 2) the combined effect of multiple factors; and 3) the relationships of threshold values with other related factors.  相似文献   

基于主波峰的自适应波形重跟踪算法研究     

莫德丽  赵银军  陈国清  梁珊  童凯  梁玉莲 《大地测量与地球动力学》2021,41(10):1051-1056

构建基于主波峰的自适应波形重跟踪算法（AMWRT）。首先提取主波峰,然后对主波峰分别应用经典的重心偏移法（OCOG）及阈值法（threshold）进行波形重跟踪,并进行精度比较,得到最优的观测水位。将AMWRT、OCOG和threshold法应用于长江中游地区,结果表明：1）测高卫星观测的长时间水位序列与水文站实测数据趋势较为一致;2）AMWRT算法相较于OCOG法及threshold法表现良好,比其中表现最好的经典threshold_0.5法的精度提高了30%,其绝对平均误差（MAE）和均方根误差（RMSE）分别降低至0.55 m和0.72 m。  相似文献   

我国煤系石墨研究现状及开发利用制约因素探讨     

任辉  刘兴旺  祁才吉  王淑丽  张必欣  王畅  李艳  王德利  屈云燕  栾俊霞  刘宬宇  王鹏昊 《地质论评》2024,70(3):2024030024-2024030024

近年来,我国煤系石墨研究工作在成因机制、控矿因素、鉴定指标、选矿加工等方面取得一系列新进展和新发现,勘查找矿工作也取得显著成效,但在资源探获和开发利用方面仍然存在较多问题,以致其资源战略保障能力得不到充分发挥,导致过度利用于低附加值领域而形成资源浪费等现象。笔者等通过成矿模式规律认识不深、演化机制研究不足、物化性质研究不清、保护性开发程度不足、选矿技术工艺落后和高端产品创新技术研发不够6个方面对我国煤系石墨开发利用制约因素进行了探讨,并给出相应对策建议,对我国煤系石墨产业健康发展具有促进作用。  相似文献