Full-Text Search:
Home|Journal Papers|About CNKI|User Service|FAQ|Contact Us|中文
《Chinese Journal of Geophysics》 2008-02
Add to Favorite Get Latest Update

Hilbert-Huang transformation and noise suppression of magnetotelluric sounding data

TANG Jing-Tian~1, HUA Xi-Rui~ 1, 2 , CAO Zhe-Min~2, REN Zheng-Yong~1, DUAN Sheng-Long+21 School of Info-physics and Geomatics Engineering, Central South University, Changsha 410083, China2 The Fourth Survey and Design Institute of China Railway, Wuhan 430063, China  
Magnetotelluric signals are nonlinear, non-stationary, non-minimum phase, they do not meet the basic requirements of the Fourier transform based on the traditional power spectrum estimation. Hilbert-Huang Transformation is an entirely local time-frequency analysis method developed in recent years for dealing with non-linear, non-stationary signals. This paper briefly introduced the Hilbert-Huang Transform basic principles and algorithms. Based on the analysis of actual data examples, we discussed its application in magnetotelluric signal processing and noise suppression. It has been founded that selecting magnetotelluric signal sessions using Hilbert time-frequency energy spectrum is helpful to improve signal quality and enhance the quality of data processing and information interpretability. Using empirical mode decomposition method and multi-scale filter characteristics can effectively analyze the noise distribution of MT signal and suppress interference.
【Fund】: 国家863计划(2006AA06Z105);; 湖南省自然科学基金项目(07553087)资助
【CateGory Index】: P631.3
Download(CAJ format) Download(PDF format)
CAJViewer7.0 supports all the CNKI file formats; AdobeReader only supports the PDF format.
【References】
Chinese Journal Full-text Database 10 Hits
1 CHEN Xue-hua1,HE Zhen-hua2,HUANG De-ji1(1.College of Information Engineering,Chengdu University of Technology,Chengdu 610059,China;2.State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China);Seismic data edge detection based on higher-order pseudo Hilbert transform[J];Progress in Geophysics;2008-04
2 HUA Xi-rui1,2,TANG Jing-tian2,ZHU Zheng-guo1,REN Zheng-yong21.The Forth Survey & Design Institute of China Railway,Wuhan,4300632.Central South University,Changsha,410083;The improvement and applications of EH-4 system data processing technique[J];Progress in Geophysics;2008-04
3 LIN Hong-bo1,LI Yue1*,YE Wen-hai2,Pan Wei 3(1.College of Communication Engineering,Jilin University,Changchun 130012,China;2.Alcatel Shanhai Bell co.Ltd Changchun Branch,Changchun 130021,China3.College of Information and Technology,Hainan University,Haikou 570228,China);Denoising technique based on Time-Frequency Peak Filtering and its application[J];Progress in Geophysics;2008-06
4 Yang Zhenzhong1,Hua Xirui2(1.Hydro China Guiyang Engineering Corporation,Guiyang 550081,China; 2.China Railway Siyuan Survey and Design Group Co.,Ltd,Wuhan 430063,China);Application of EH-4 System to Salt Mine Detection in Mangkang County of Tibet[J];Chinese Journal of Engineering Geophysics;2009-02
5 Hua Xirui,Cao Zhemin,Liu Tie,Duan Shenglong(The forth survey & design institute of China railway,Wuhan 430063,China);The Research on High-frequency Magnetotelluric System's Data Processing Technique[J];Chinese Journal of Engineering Geophysics;2009-S1
6 Yang Yiming,Hua Xirui(The Fourth Railway Survey and Design Institute Group Corporation,Wuhan 430063,China);Application of High-Frequency Magnetotelluric Sounding to Deep Buried Tunnels[J];Chinese Journal of Engineering Geophysics;2009-S1
7 Cai Jianhua1,2 Wang Xianchun1 1 Information Institute,Hunan University of Arts and Science,Changde,Hunan 415000,China2 School of Info-Physics and Geomatics Enginerring,Central South University,Changsha,Hunan 410083,China;Near-Infrared Spectrum Pretreatment Based on Empirical Mode Decomposition[J];Acta Optica Sinica;2010-01
8 Li Yanjun1,Hu Xiangyun1,He Zhanxiang2 (1.Institute of Geophysics and Geomatics,China University of Geosciences,Wuhan 430074,China;2.BGP,CNPC,Zhuozhou 072751,China);Application Situation and Prospects of Hilbert-Huang Transform in Geophysics[J];Chinese Journal of Engineering Geophysics;2010-05
9 XIAO Xiao1),TANG Jingtian1),ZHOU Cong1),L Qingtian2) 1) School of geosciences and Info-physics,Central South University,Changsha,410083;2) MLR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing,100037;Magnetotelluric Sounding in the Lujiang-Zongyang Ore-district and Preliminary Study of Electrical Structure[J];Acta Geologica Sinica;2011-05
10 Cai Jian-hua1,2,Gong Yu-rong2 and Wang Xian-chun1.1.Department of physics and electronic,Hunan University of Arts and Science,Changde City,Hunan Province,415000,China2.School of Info-physics and Geomatics Engineering,Central South University,Changsha City,Hunan Province,410083,China;Magnetotelluric Data Processing Based on Hilbert-Huang Transform in Oil and Gas Exploration[J];Oil Geophysical Prospecting;2009-05
【Citations】
Chinese Journal Full-text Database 7 Hits
1 WANG Shu-ming,WANG Jia-ying(Applied Geophysics Department, China University of Geosciences, Wuhan 430074, China);Discussion on the non-minimum phase of magnetotelluric signals[J];Progress In Geophysics;2004-02
2 Shi Chunxiang Luo Qifeng (Research Institute of Structural Engineering and Disaster Reduction, Tongji University, Shanghai 200092,China);HILBERT-HUANG TRANSFORM AND WAVELET ANALYSIS OF TIME HISTORY SIGNAL[J];Acta Seismologica Sinica;2003-04
3 Wang Shuming Wang Jiaying (Institute of Geophysics and Geomatics,China University of Geosciences,Wuhan 430074 ,China);ANALYSIS ON STATISTIC CHARACTERISTICS OF MAGNETOTELLURIC SIGNAL[J];Acta Seismologica Sinica;2004-06
4 Lin Jun; Xiang Kuikui;Zhu Baolong; Li Tonglin;(Dept. of Instrument and Information Engineering,Changchun University of Earth Sciences Changchun, 130026);Study on Implementation of MT Signal Processing in Situ[J];JOURNAL OF DATA ACQUISITION & PROCESSING;1997-01
5 Liu Yang (Faculty of Resource and Information, University of Petroleum, Beijing 102200, China);Extraction and removal of strong power interference[J];Geophysical Prospecting For Petrole;2003-02
6 Li Liqing Yu Qinfan Li Hui (China University of Geosciences, Beijing);FRACTAL FEATURES OF THE MTS DATA[J];COMPUTING TECHNIQUES FOR GIOPHYSICAL AND GEOCHENICAL EXPLORATION;1997-04
7 Zhong Youming Qin Shuren Tang Baoping (The Test Center,Institute of Mechanical Engineering,Chongqing University,Chongqing 400044);STUDY ON THE THEORY OF HILBERT-HUANG TRANSFORM[J];Journal of Vibration and Shock;2002-04
【Co-citations】
Chinese Journal Full-text Database 10 Hits
1 ZHANG Guo-hong1,LI Ren-he1, ZHANG Ling-min2 (1. Institue of Geophysical and Geochemical Prospecting Technology of Anhui province,Hefei 230022,China; 2. Institue of Geological Exploration of Anhui Chemical Industry,Maanshan, 243031, China);DISCUSSION OF SEVERAL TECHNICAL ISSUES WITH CSAMT METHOD[J];Geology of Anhui;2009-02
2 LI Jian-wei, XU Bao-jie System, Beijing Institute of Machinery,Beijing 100085,China);Study on the analytic methods of non-stationary vibration signals of mechanical and electrical system[J];Journal of Beijing Institute of Machinery;2004-03
3 XU Bao-jie~(1,2),ZHANG Jian-min~1,XU Xiao-li~2,LI Jian-wei~2(1.School of Mechanical and Vehicular Engineering,Beijing Institute of Technology,Beijing 100081,China;2.Measurement and Control of Mechanical and Electrical System Key Lab of Beijing,Beijing Institute of Machinery,Beijing 100085,China);A Study on the Method of Restraining the Ending Effect of Empirical Mode Decomposition (EMD)[J];Transactions of Beijing Institute of Technology;2006-03
4 JIN Wen-biao,YOU Jun(College of Computer Science and Technology,Chongqing University of Posts and Telecommunications,Chongqing 400065,P.R.China);Velocity determination of single sound source based on Doppler effect[J];Journal of Chongqing University of Posts and Telecommunications(Natural Science);2007-06
5 SHANG Tong-xiao1,LI Tong-lin1,GUAN Yi-xiao1,LI Jianping1,LIN Pin-rong2 1.College of GeoExploration Science and Technology,Jilin University,Changchun 130026,China 2.Institute of Gcophysical and Geochemical Exploration CAGS,Langfang,Hebei 065000,China;Full-Region Inversion of 1-D CASMT[J];Journal of Jilin University(Earth Science Edition);2007-S1
6 WANG Li-qun1,LIU Guo-xing2,HAN Jiang-tao2,JIN Zhong-bao21.Jilin Geological Exploration Bureau for Nonferrous Metals,Jilin City,Jilin Province 132000,China2.College of GeoExploration Science and Technology,Jilin University,Changchun 130026,China;Application of High-power Induced Polarization Method and CSAMT Profile Measurement Find Tin and Molybdenum Ore Occurrence in Tuanbei of Dunhua[J];Journal of Jilin University(Earth Science Edition);2008-S1
7 SHAN Chun-ling,LIU Guo-xing,HAN Jiang-taoCollege of GeoExploration of Science and Technology,Jilin University,Changchun 130026,China;Numerical Simulation in Great Depth Resolving Power of Magnetotelluric Sounding[J];Journal of Jilin University(Earth Science Edition);2008-S1
8 FAN Cui-song,LI Tong-lin,WANG Da-yongCollege of GeoExploration Science and Technology,Jilin University,Changchun 130026,China;Treatment of Watelet Transform for Square Wave Noise in MT Date[J];Journal of Jilin University(Earth Science Edition);2008-S1
9 WANG Yan-zhang1,2,CHENG De-fu1,2,WANG Jun1,LIN Jun11.Key Laboratory for Geophysical Instrumentation of Ministry of Education,Jilin University,Changchun 130061,China;2.Texas Instrument-Jilin University DSPs Laboratory,Changchun 130061,China;Research of Broad Frequency Difference Magnetic Field Sensor Based on Nanocrystalline Alloy[J];Chinese Journal of Sensors and Actuators;2007-09
10 XIE Xing-bing,YAN Liang-jun(Key Laboratory of Exploration Technologies for Oil and Gas Resources Ministry of Education,Yangtze University,Jingzhou 434023) Meng Fan-jun(The First Survey and Design Institute of Ministry of Railways,Lanzhou 730000);Application of CSAMT Technique in Foundation Exploration of Baoshen Railway[J];;2007-03
China Proceedings of conference Full-text Database 10 Hits
1 ZHANG Quan-sheng~(1,2) WANG Jia-ying~1 YE Jing-yan~2 WANG Lei~2 (1.Institue of Geophysics & Geomatics,China University of Geosciences,Wuhan 430074,China; 2.No.814 Party of East China Geological Exploration Bureau of Nonferrous Metals,Jiangsu Province,Zhenjiang 212005,Jiangsu);A feasibility study of offshore telluric-magnetotelluric method in Leiqiong area[A];[C];2005
2 QIAN Zhenhua SONG Hanwen (Department of Mechanics and Engineering Science, Fudan University, Shanghai 200433);Studies on Empirical Mode Decomposition (EMD)[A];[C];2005
3 SUN Yanzheng, HUANG Wei, YU Bo (School of Communication and Information, University of Electronic Science and Technology of China , Chengdu 610054, China);Analysis of Non-stationary Signal Based on HHT[A];[C];2006
4 LI Jian-hua~(1,2) LIN Pin-rong~2 HE Wei~3 ZHENG Cai-jun~2 (1.Guilin University of Technology,Guilin 541004,China;2.Institute of Geophysical and Geochemical Exploration,Langfang 065000,China;3.China University of Mining and Technology,Beijing 100083,China);A FIR DIGITAL FILTER ANALYSIS OF MT TIME SERIES[A];[C];2007
5 ZHAO Guo-ze, CHEN Xiao-bin, TNAG Ji (Institute of Geology,China Earthquake Administration, Beijing 100029,China);Advanced geo-electromagnetic methods in China[A];[C];2007
6 Xie Xingbing Yan Liangjun Xu Jianfeng 1 Key Laboratory of Exploration Technologies for Oil and Gas Resources,Ministry of Education,Yangtze University,JingZhou 434023; 2 JiLin research institute of exploration geophysics,ChangChun 130000;Magnetic field correction in the array CSAMT data acquisition with large interval[A];[C];2007
7 YAO Xiong-liang, ZHANG A-man, XUWei-jun (School of Shipbuilding Engineering, Harbin Engineering University, Harbin 150001, China);Hilbert-Huang transform based on EMD and its application on analysis explosion signal[A];[C];2005
8 Gao Qiang Duan Chendong Automobile School,Chang'an University,Xi'an,China,710064 Meng QingFeng Mechanical Engineering School,Xi'an Jiaotong University,Xi'an,China,710049;RESEARCH ON END EFFECTS OF EMPIRICAL MODE DECOMPOSITION[A];[C];2008
9 He Jishan Bao Lizhi Zhu Ziqiang (Central South University of Technology,Changsha,410083);INTRODUCTION TO THE MARINE ELECTROMAGNETIC(EM) METHODS[A];[C];1998
10 Qin Yi , Mao Yong-fang, Qin Shu-ren (Test Center, Mechanical Department, Chongqing University, Chongqing,400044, China);Orthogonal Empirical Mode Decomposition and its Fast implement[A];[C];2007
【Co-references】
Chinese Journal Full-text Database 10 Hits
1 GAO Xiang-ping,WU Xiao-pei,SHEN Qian(School of Computer Science and Technology,Anhui University,Hefei 230039,China);Mental task classification based on adaptive autoregressive model and support vector machine[J];Journal of Anhui University(Natural Sciences);2006-02
2 LI Xi-bing,ZHANG Yi-ping,LIU Zhi-xiang,ZUO Yu-jun,WANG Wei-hua(School of Resources and Safety Engineering,Central South University,Changsha410083,Hunan,China);Wavelet analysis and Hilbert-Huang transform of blasting vibration signal[J];Explosion and Shock Waves;2005-06
3 LI Tong_lin, LIU Fu_chun, HAN Ying_jie, ZHAO Hai_zhen (Changchun University of Science and Technology, Changchun 130026, China);THE STUDY OF ELECTROMAGNETIC NOISE CREATED BY HIGH VOLTAGE TRANSMISSION LINE[J];JOURNAL OF CHANGCHUN UNIVERSITY OF SCIENCE AND TECHNOLOGY;2000-01
4 WANG Zhu-wen1,LIU Jing-hua1,NIE Chun-yan21.College of GeoExploration Science and Technology,Jilin University,Changchun 130026,China2.Electronic Information Institute,Changchun University,Changchun 130022,China;The Reassignment Method Based on Time-Frequency Analysis and Its Application in the Array Acoustic Logging Data Processing[J];Journal of Jilin University(Earth Science Edition);2007-05
5 GUAN Yi-xiao1,LI Tong-lin1,LI Jian-ping1,SHANG Tongxiao1,LIN Pin-rong2 1.College of GeoExploration Science and Technology,Jilin University,Changchun 130026,China 2.Institute of Geophysical and Geochemical Exploration CAGS,Langfang,Hebei 065000,China;Research of 2D Magnetotelluric Interactive Interpretation System[J];Journal of Jilin University(Earth Science Edition);2007-S1
6 WANG Zhu-wen1,LIU Jing-hua1,NIE Chun-yan21.College of GeoExploration Science and Technology,Jilin University,Changchun 130026,China2.Electronic Information Institute,Changchun University,Changchun 130022,China;Array Acoustic Logging Signal Analysis Based on the Local Correlation Energy[J];Journal of Jilin University(Earth Science Edition);2008-02
7 FAN Cui-song,LI Tong-lin,WANG Da-yongCollege of GeoExploration Science and Technology,Jilin University,Changchun 130026,China;Treatment of Watelet Transform for Square Wave Noise in MT Date[J];Journal of Jilin University(Earth Science Edition);2008-S1
8 DUAN Sheng-quan, HE Zhen-hua, HUANG De-jiCollege of Information Engineering, Chengdu University of Technology, Chengdu 610059, China;Application of the Hilbert-Huang transform to the analysis of seismic signal[J];Journal of Chengdu University of Technology(Science & Technology Edition);2005-04
9 He Lanfang, Wang Xuben, Wang Chengxiang (Chengdu University of Technology, China);IMPROVING THE S/N RATIO OF MT DATA BY WAVELET ANALYSIS[J];JOURNAL OF CHENGDU UNIVERSITY OF TECHNOLOGY;1999-03
10 SONG Li-xin 1*,WANG Qi1,WANG Yu-Jing2 1.Department of Automation Measurement and Control,Harbin Institute of Technology,Harbin 150001,China;2.Department of electronic and information engineering,Harbin university of science and technology,Harbin 150040,China;ECG Signal Noise Reduction Using Hilbert-Huang Transform[J];Chinese Journal of Sensors and Actuators;2006-06
【Secondary References】
Chinese Journal Full-text Database 10 Hits
1 CHEN Suo-cheng1,LUO Wei-bin2(1.Xinjiang Huiyou Mining Group Co.Ltd.,Hami 839000,China;2.School of Geological Engineering and Geomatics,Changan University,Xi′an 710054,China);Time-Frequency Analysis on The High Frequency Magnetotelluric Sounding Data[J];Gansu Metallurgy;2009-03
2 Lin Jiayong~(1,2,3),Din Maobin~1,Tang Jingtian~1,Wang Ye~1,Xiao Xiao~1(1.School of Info-physics and Geomatics Engineering,Central South University,Changsha 410083,China;2.Geophysics and Geochemistry Institute of Yunnan Geology Survey Academy,Yunnan Yiliang 652100,China;3.Geophysical and Geochemical Exploration Team,Yunnan Geology and Mineral Resources Bureau,Yunnan Yiliang 652100,China);EH-4 electromagnetic imaging systems to detect the accumulation of body applied research[J];Geotechnical Investigation & Surveying;2009-12
3 Li Yanjun1,Hu Xiangyun1,He Zhanxiang2 (1.Institute of Geophysics and Geomatics,China University of Geosciences,Wuhan 430074,China;2.BGP,CNPC,Zhuozhou 072751,China);Application Situation and Prospects of Hilbert-Huang Transform in Geophysics[J];Chinese Journal of Engineering Geophysics;2010-05
4 Chen Zhiping,Chen Dejiu,Zhang Zhaoxiu,Ye Xingjun (Chongqing Civicism Exploration and Design Research Institute,Chongqing 400015,China);Application of High Frequency Magnetotelluric Method in Chimushan Tunnels[J];Chinese Journal of Underground Space and Engineering;2010-S2
5 CHEN Jian-guo1,2,XIAO Fan1,2,CHANG Tao1,2 1.State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China 2.Faculty of Earth Resources,China University of Geosciences,Wuhan 430074,China;Gravity and Magnetic Anomaly Separation Based on Bidimensional Empirical Mode Decomposition[J];Earth Science(Journal of China University of Geosciences);2011-02
6 CHEN Jun,CUI Xiang-xia,XIAO Jing,YANG Zhao-hua,LIU Ting-ting(Department of Physics and Electronic Engineering,Taishan University,Taian,Shandong 271021,China);Properties of Image Edge Enhancement Using Radial Hilbert Transform[J];Acta Photonica Sinica;2011-03
7 XIAO Xiao1),TANG Jingtian1),ZHOU Cong1),L Qingtian2) 1) School of geosciences and Info-physics,Central South University,Changsha,410083;2) MLR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing,100037;Magnetotelluric Sounding in the Lujiang-Zongyang Ore-district and Preliminary Study of Electrical Structure[J];Acta Geologica Sinica;2011-05
8 Cai Jianhua Wang Xianchun Hu Weiwen(Information Institute,Hunan University of Arts and Science,Changde 415000,China);Near-infrared Spectrum Detection of Soil Organic Matter Content Based on Empirical Mode Decomposition[J];Transactions of the Chinese Society for Agricultural Machinery;2010-09
9 LI Jin,WANG Jing-fang,GAO Jin-ding College of Electric Information Engineering,Hunan International Economics University,Changsha 410205,China;Speech endpoint detection algorithm based on EMD and RP[J];Computer Engineering and Applications;2010-34
10 ZHOU Changyou~1,LI Rui~1,YANG Fan~2,XU Min~2,WANG Yongsheng~3 (1.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu Sichuan 610059,China;2.Sichuan Petroleum Geophysical Peospecting Comoany, CNPC Chuangqing Drilling Engineering Co.,Ltd,Chengdu Sichuan 610213,China;3.Qinghai Oilfield Company Exploration Division,Dunhuang Gansu 136202,China);Frequency attenuation gradient attribute of hydrocarbon potential detection based on wavelet transform[J];Petrochemical Industry Application;2010-11
【Secondary Citations】
Chinese Journal Full-text Database 10 Hits
1 LIU SHI-DA(Department of Geophysics, Peking University, Beijing);EARTH SYSTEM MODELING AND CHAOTIC TIME SERIES[J];Chinese Journal of Geophysics;1990-02
2 XU YI XIAN\ WANG JIA YING (China University of Geosciences, Wuhan 430074, China)[;POWER SPECTRUM ESTIMATION FOR MAGNETOTELLURIC SIGNAL BASED ON CONTINUOUS WAVELET TRANSFORM[J];Chinese Journal of Geophysics;2000-05
3 TANG BIN (University of Electronic and Science Technology of China, Chengdu 610054, China)YIN CHENG (Southwest Petroleum Institute, Nanchong 637001, China) [;NON-MINIMUM PHASE SEISMIC WAVELET RECONSTRUCTION BASED ON HIGHER ORDER STATISTICS[J];Chinese Journal of Geophysics;2001-03
4 LIU JIANXIN YAN JIABIN HE JISHAN LIU CHUNMING School of Info-Geophysics and Geomatics Engineering,Central South University, Changsha 410083, China;ROBUST ESTIMATION METHOD OF SEA MAGNETOTELLURIC IMPEDANCE BASED ON CORRELATIVE COEFFICIENT[J];Chinese Journal of Geophysics;2003-02
5 WANG CHI;CHEN JIN-BO;WANG SHUI(Department of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026);FRACTAL AND CHAOTIC FEATURES FOR VARYING COMPONENT OF THE EARTH'S MAGNETIC FIELD[J];Chinese Journal of Geophysics;1995-01
6 YANG Sheng,BAO Guang-shu,ZHANG Shao-yun;THE CORRECTION TO ABERRANT APPEARANCE RESISTIVITY CURVE BY USING IMPEDANCE PHASE DATA IN MAGENETOTELLURIC METHOD[J];Geology and Prospecting;2001-06
7 ;Adaptive Filtering Method to Eliminate the Interference of 50Hz In Transient Electromagnetic Instument[J];MEASUREMENT & CONTROL TECHNOLOGY;1999-06
8 Yan Liangjun Hu Wenbao Chen Qinli Zhang Xiang Hu Jiahua (Jianghan Petroleum Institute, Jingzhou 434102);Application of Remote Reference MT to Noisy Area[J];JOURNAL OF JIANGHAN PETROLEUM INSTITUTE;1998-04
9 MEI Tie min,YU Chuang,YU Guo Wei(Dept.of Automatic Control,Shenyang Institute of Technology,Shenyang 110015,China);The Elimination of 50 Hz Noise from ECG Signals[J];JOURNAL OF SHENYANG INSTITUTE OF TECHNDOGY;2000-02
10 Gao Shaowu,Zhou Xingyuan and Cai Jiaming. Gao Shaowu, GRI,BGP,Zhuozhou City,Hebei Province,072751,China;Suppression of single-frequency interference wave in time domain.[J];Oil Geophysical Prospecting;2001-01
©2006 Tsinghua Tongfang Knowledge Network Technology Co., Ltd.(Beijing)(TTKN) All rights reserved