检索结果-南通市图书馆

Numerical simulation of seismic wavefields in TTI media using the rotated staggered-grid compact finite-difference scheme

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Earthquake Science 2018年第2期31卷 75-82页

作者： Bing Bai Bingshou He Kairui Li Huaigu Tang Jiajia Yang College of Marine geo-sciences Ocean University of China Qingdao 266100 China Evaluation and detection Technology laboratory of Marine Mineral Resources Qingdao National Laboratory for Marine Science and Technology Qingdao 266071 China Key laboratory of Submarine geoscience and Prospecting Techniques Ministry of Education Qingdao 266100 China Qingdao Institute of Marine geology China Geological Survey Qingdao 266071 China

Numerical simulation in transverse isotropic media with tilted symmetry axis（TTI） using the standard staggered-grid finite-difference scheme（SSG）results in errors caused by averaging or interpolation. In order to eliminate the errors, a method of rotated staggered-grid finite-difference scheme（RSG） is proposed. However, the RSG brings serious numerical dispersion. The compact staggered-grid finite-difference scheme（CSG） is an implicit difference scheme, which use fewer grid points to suppress dispersion more effectively than the SSG. This paper combines the CSG with the RSG to derive a rotated staggered-grid compact finite-difference scheme（RSGC）. The numerical experiments indicate that the RSGC has weaker numerical dispersion and better accuracy than the RSG.

关键词： TTI media rotated staggered-grid compact staggered-grid finite-difference

Detecting spatio-temporal urban surface changes using identified temporary coherent scatterers

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2021年第6期32卷 1304-1317页

作者： HU Fengming WU Jicang Key laboratory for Information Science of Electromagnetic Waves Fudan UniversityShanghai 200433China College of Surveying and geo-Informatics Tongji UniversityShanghai 200092China

Synthetic aperture radar(SAR) is able to detect surface changes in urban areas with a short revisit time, showing its capability in disaster assessment and urbanization *** presented change detection methods are conducted using couples of SAR amplitude images. However, a prior date of surface change is required to select a feasible image pair. We propose an automatic spatio-temporal change detection method by identifying the temporary coherent scatterers. Based on amplitude time series, χ^(2)-test and iterative single pixel change detection are proposed to identify all step-times: the moments of the surface change. Then the parameters, e.g., deformation velocity and relative height, are estimated and corresponding coherent periods are identified by using interferometric phase time series. With identified temporary coherent scatterers, different types of temporal surface changes can be classified using the location of the coherent periods and spatial significant changes are identified combining point density and F values. The main advantage of our method is automatically detecting spatio-temporal surface changes without prior information. Experimental results by the proposed method show that both appearing and disappearing buildings with their step-times are successfully identified and results by ascending and descending SAR images show a good agreement.

关键词： change detection temporary coherent scatterer multi-temporal interferometric synthetic aperture radar(InSAR) amplitude analysis

Love wave tomography in Italy from seismic ambient noise

在线全文

学校读者我要写书评

暂无评论

Earthquake Science 2010年第5期23卷 487-495页

作者： Hongyi Li Fabrizio Bernardi Alberto Michelini Key laboratory of geo-detection (China University ofgeosciences Beijing) Ministry of Education Beijing 100083 China School of geophysics andlnformation Technology China University of Geosciences Beijing 100083 China Istituto Nazionale di geofisica e Vulcanologia Via di Vigna Murata 605 Rome 00143 Italy

We estimate Love wave empirical Green＇s functions from cross-correlations of ambient seismic noise to study the crust and uppermost mantle structure in Italy. Transverse-component ambient noise data from October 2005 through March 2007 recorded at 114 seismic stations from the Istituto Nazionale di geofisica e Vulcanologia （INGV） national broadband network, the Mediterranean Very Broadband Seismographic Network （MedNet） and the Austrian Central Institute for Meteorology and geodynamics （ZAMG） yield more than 2 000 Love wave group velocity measurements using the multiple-filter analysis technique. In the short period band （5-20 s）, the cross-correlations show clearly one-sided asymmetric feature due to non-tmiform noise distribution and high local activities, and in the long period band （〉20 s） this feature becomes weak owing to more diffusive noise distribution. Based on these measurements, Love wave group velocity dispersion maps in the 8-34 s period band are constructed, then the SH wave velocity structures from the Love wave dispersions are inverted. The final results obtained from Love wave data are overall in good agreement with those from Rayleigh waves. Both Love and Rayleigh wave inversions all reveal that the Po plain basin is resolved with low velocity at shallow depth, and the Tyrrhenian sea is characterized with higher velocity below 8 km due to its thin oceanic crust.

关键词： ambient noise Love wave tomography crustal structure Italy

An extended processing scheme for coherent integration and parameter estimation based on matched filtering in passive radar

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science C(Computers and Electronics) 2014年第11期15卷 1071-1085页

作者： Xin GUAN Li-hua ZHONG Dong-hui HU Chi-biao DING Key laboratory of Technology in geo-spatial Information Processing and Application System Institute of Electronics Chinese Academy of Sciences University of Chinese Academy of Sciences

In passive radars, coherent integration is an essential method to achieve processing gain for target detection. The cross ambiguity function(CAF) and the method based on matched filtering are the most common approaches. The method based on matched filtering is an approximation to CAF and the procedure is:(1) divide the signal into snapshots;(2) perform matched filtering on each snapshot;(3) perform fast Fourier transform(FFT) across the snapshots. The matched filtering method is computationally affordable and can offer savings of an order of 1000 times in execution speed over that of CAF. However, matched filtering suffers from severe energy loss for high speed targets. In this paper we concentrate mainly on the matched filtering method and we use keystone transform to rectify range migration. Several factors affecting the performance of coherent integration are discussed based on the matched filtering method and keystone transform. Modified methods are introduced to improve the performance by analyzing the impacts of mismatching, precision of the keystone transform, and discretization. The modified discrete chirp Fourier transform(MDCFT) is adopted to rectify the Doppler expansion in a multi-target scenario. A novel velocity estimation method is proposed, and an extended processing scheme presented. Simulations show that the proposed algorithms improve the performance of matched filtering for high speed targets.

关键词： Keystone transform Matched filtering MDCFT Mismatching Passive radar Velocity estimation

Error matching detection and robust estimation adjustment approach for map conflation

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2008年第S1期51卷 48-61页

作者： TONG XiaoHua & DENG SuSu Department of Surveying and geo-informatics,Tongji University,Shanghai 200092,China Department of Surveying and geo-informatics Tongji University

The conflation of geographic datasets is one of the key technologies in the realm of spatial data capture and integration in geographic information system (GIS). Map conflation is a complex process of matching and merging spatial data. Due to various reasons such as errors in original data related to map data discrepancies,a great amount of uncertainties exists during the process and this will result in errors in featuring matching,especially point feature. Thus,it is vital to develop the method to detect the errors in feature matching and further the conflation results will not be affected. In this paper,error matching detection and robust estimation adjustment methods are proposed for map conflation. The characteristics of errors in feature matching are first analyzed,then a new approach for map conflation based on the least-squares adjustment is presented,and a robust estimation adjustment method is further proposed to detect and process matching errors. The results of the map conflation test show that the proposed method not only determines the errors in feature matching,but also obtains the optimal merging results in map conflation.

关键词： map conflation robust estimation error feature matching uncertainty

Moving target detection in the cepstrum domain for passive coherent location(PCL) radar

在线全文

学校读者我要写书评

暂无评论

Frontiers of Information Technology & Electronic Engineering 2015年第9期16卷 785-795页

作者： Ji-chuan LI Xiao-de LU Hui ZHANG Peng-cheng YANG Yu LIU Mao-sheng XIANG Science and Technology on Microwave Imaging laboratory Institute of Electronics Chinese Academy of Sciences University of Chinese Academy of Sciences Key laboratory of Technology in geo-spatial Information Processing and Application System Institute of ElectronicsChinese Academy of Sciences

A cepstrum moving target detection （CEPMTD） algorithm based on cepstrum techniques is proposed for passive coherent location （PCL） radar systems. The primary cepstrum techniques are of great success in recognizing the arrival times of static target echoes. To estimate the Doppler frequencies of moving targets, we divide the radar data into a large number of seg- ments, and reformat these segments into a detection matrix. Applying the cepstrum and the Fourier transform to the fast and slow time dimensions respectively, we can obtain the range information and Doppler information of the moving targets. Based on the CEPMTD outlined above, an improved CEPMTD algorithm is proposed to improve the detection performance. Theoretical analyses show that only the target＇s peak can be coherently added. The performance of the improved CEPMTD is initially vali- dated by simulations, and then by experiments. The simulation results show that the detection performance of the improved CEPMTD algorithm is 13.3 dB better than that of the CEPMTD algorithm and 6.4 dB better than that of the classical detection algorithm based on the radar cross ambiguity function （CAF）. The experiment results show that the detection performance of the improved CEPMTD algorithm is 1.63 dB better than that of the radar CAF.

关键词： Moving target detection Cepstrum techniques Cross ambiguity fimction (CAF) Passive coherent location (PCL)radar

Analysis of seasonal signals and long-term trends in the height time series of IGS sites in China

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2016年第6期59卷 1283-1291页

作者： MING Feng YANG YuanXi ZENG AnMin JING YiFan Institute of geospatial Information Information Engineering University National Key laboratory of geo-information Engineering Xi'an Institute of Surveying and Mapping Institute of Navigation and Aerospace Engineering Information Engineering University

The seasonal signal and long-term trend in the height time series of 10 IGS sites in China are investigated in this paper. The offset detection and outlier removal as well as the removal of common mode error are performed on the raw GPS time-series data developed by the Scripps Orbit and Permanent Array Center(SOPAC). The seasonal-trend decomposition procedure based on LOESS(STL) is utilized to extract precise seasonal signals, followed by an estimation of the long-term trend with the application of maximum likelihood estimation(MLE) to the seasonally adjusted time series. The Up-compo- nents of all sites are featured by obvious seasonal variations, with significant phase and amplitude modulation on some sites. After Kendall's tau test, a significant trend(99% confidence interval) for all sites is achieved. Furthermore, the trends at sites TCMS and TNML have significant changes at epochs 2009.5384 and 2009.1493(95% confidence interval), respectively, using the Breaks For Additive Seasonal and Trend test. Finally, the velocities and their uncertainties for all sites are estimated using MLE with the white noise plus flicker noise model. And the results are analyzed and compared with those announced by SOPAC. The results obtained in this paper have a higher precision than the SOPAC results.

关键词： GPS Height time series Seasonal signal Long-term trend STL filter Colored noise

Supermode analysis of the 18-core photonic crystal fiber laser

在线全文

学校读者我要写书评

暂无评论

中国激光 2012年第9期39卷 10-13页

作者：王远姚建铨郑一博温午麒陆颖王鹏 Institute of Laser & Otpoelectronics College of Precision Instruments and Opto-Electronic EngineeringKey Laboratory of Opto-Electronics Information and Technical Science(Ministry of Education)Tianjin University Hebei Key laboratory of Optoelectronic Information and geo-detection Technology Shijiazhuang University of Economics

The modal of 18-core photonic crystal fiber laser is discussed and *** corresponding far-field distribution of the supermodes is given by Fresnel diffraction *** improving beam quality,the mode selection method based on the Talbot effect is *** reflection coefficients are calculated,and the result shows that an in-phase supermode can be locked better at a large propagation distance.

关键词：光子晶体光纤激光器超模 Talbot效应菲涅耳衍射积分远场分布光束质量反射系数传播距离

Edge detection of remote sensing image based on nonlinear intensity of curved surface

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 2003年第3期13卷 739-742页

作者：张连蓬刘国林江涛 College of geo information Science and Engineering

A new edge detector based on the nonlinear intensity of curved surface was proposed. The edge detector describes the largest curvature and the smallest curvature of curved surface, therefore it can reflect the real largest direction of image edge jump. By the new edge detector, it is convenient to calculate the curvature in any direction of the curved surface and the curvature can be used in the identification of edge direction and the feature extraction of objects on remote sensing image.

关键词：遥感图象处理边缘检测曲面非线形