检索结果-南通市图书馆

Journal of Earth Science 2009年第6期20卷 1012-1016页

作者： Hamid Aghajani Ali Moradzadeh 曾华霖 Faculty of Mining Petroleum and GeophysicsShahrood University of Technology school of geophysics and information Technology China University of GeosciencesBeijing

We present an estimation of depth of anomalous bodies using normalized full gradient （NFG） of gravity anomaly. Maxima in the NFG map can locate the bodies and indicate their depth. Model calculation using a sphere and application of the NFG method to gravity anomalies over salt domes in the USA and Denmark shows effectiveness of the method. However, the accuracy of depth estimation strongly depends on the number of term N in the Fourier series used to calculate the NFG. An optimum N for the calculation can be given from a test.

关键词： depth estimation anomalous body normalized full gradient gravity anomaly Fourier series.

A tentative study for the prediction of the CME related geomagnetic storm intensity and its transit time

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2005年第6期48卷 648-668页

作者： ZHAO Xinhua1,2 & FENG Xueshang1,3 1. SIGMA Weather Group, Key Laboratory of space Weather, Center for space Science and applied Re-search, Chinese Academy of Sciences, Beijing 100080, china 2. Graduate school of the Chinese Academy of Sciences, Beijing 100039, china 3. school of geophysics and Geoinformation Systems, china University of Geosciences, Beijing 100083, china 1. SIGMA Weather Group Key Laboratory of Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences 100080 Beijing China 2. Graduate school of the Chinese Academy of Sciences 100039 Beijing China 3. school of geophysics and Geoinformation Systems China University of Geosciences 100083 Beijing China

Using 80 CME-ICME events during 1997.1―2002.9, based on the eruptive source locations of CMEs and solar magnetic field observation at the photosphere, a current sheet magnetic coordinate (CMC) system is established in order to study the propagation of CME and its geoeffectiveness. In context of this coordinate system, the effect of the eruptive source location and the form of heliospheric current sheet (HCS) at the eruptive time of CME on the geomagnetic storm intensity caused by CME and the CME’s transit time at the Earth is investigated in detail. Our preliminary conclusions are: 1) The geomagnetic disturbances caused by CMEs tend to have the so-called “same side-opposite side effect”, i.e. CMEs erupt from the same side of the HCS as the earth would be more likely to arrive at the earth and the geomagnetic disturbances associated with them tend to be of larger magnitude, while CMEs erupting from the opposite side would arrive at the earth with less probability and the corresponding geomagnetic disturbance magnitudes would be relatively weaker. 2) The angular separation between the earth and the HCS affect the corresponding disturbance intensity. That is, when our earth is located near the HCS, adverse space weather events occur most probably. 3) The erupting location of the CME and its nearby form of HCS will also affect its arrival time at the earth. According to these conclusions, in this context of CMC coordinate we arrive at new prediction method for estimating the geomagnetic storm intensity (Dstmin) caused by CMEs and their transit times. The application of the empirical model for 80 CME-ICME events shows that the relative error of Dst is within 30% for 59% events with Dstmin≤?50 nT, while the averaged absolute error of transit time is lower than 10 h for all events.

关键词： coronal mass ejections, current sheet magnetic coordinate system, geomagnetic storm intensity, transit time, prediction method.

A new Early Cretaceous lizard with well-preserved scale impressions from western Liaoning, china

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2005年第2期15卷 67-73页

作者： JI Shu’an*(school of Earth and space Sciences, Peking University, Beijing 100871, china) school of Earth and space Sciences Peking University Beijing 100871 China

A new small lizard, Liaoningolacerta brevirostra gen. et sp. nov., from the Early Cretaceous Yixian Formation of western Liaoning is described in detail. The new specimen was preserved not only by the skeleton, but also by the exceptionally clear scale impressions. This lizard can be included within the taxon Scleroglossa based on its 26 or more presacrals, cruciform interclavicle with a large anterior process, moderately elongated pubis, and slightly notched distal end of tibia. The scales vary evidently in size and shape at different parts of body: small and rhomboid ventral scales, tiny and round limb scales, and large and longitudinally rectangular caudal scales that constitute the caudal whorls. This new finding provides us with more information on the lepidosis of the Mesozoic lizards.

关键词： new genus Squamata skeleton lepidosis Early Cretaceous western Liaoning

Autonomous Path Planning For Robot Manipulators in Manufacturing Environment

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 1998年第2期12卷 104-107页

作者： Wei Wang Yang Yang Kui Yuan information Engineering school, UST Beijing, Beijing 100083, china information Engineering school UST Beijing Beijing 100083 China

A robot intelligent path planning system(RIPPS), which can be used as a robot off-line programming tool was introduced in this paper. C-space modeling and path search are key parts of the system. A fast C-space modeling is presented based on critical collision joint angle(CCJA), C-obstacle boundary can be computed by the feature points of obstacles. A modified A* algorithm is used for path search, although the path is slightly sub-optimal, a tremendous speed increase is achieved. RIPPS runs on a Silicon Graphic 4D/70 workstation, simulation results show that the system is efficient and practical for robot collision-free autonomous path planning in a structured and known environment.

关键词： robot path plalanning A~* algorithm

Source time-function as discriminant using empirical Green's function

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2005年第12期48卷 2118-2122页

作者： HE Yongfeng1,2 & CHEN Xiaofei1 1. Department of geophysics, school of Earth & space Sciences, Peking University, Beijing 100871, china 2. North-West Institute of Nuclear Technology, Xi’an 710024, china 1. Department of geophysics School of Earth & Space Sciences Peking University 100871 Beijing China 2. North-West Institute of Nuclear Technology 710024 Xi’an China

The source mechanism of underground nuclear explosions is remarkably different from that of earthquakes in both spatial radiation pattern and source time-function (STF). Small underground nuclear explosions can be used as empirical Green’s functions (EGF) to isolate the source-time spectrum of a large suspected earthquake occurred in a Nuclear Test Site (target area) by the spectral division method. As this study shows, with high-quality data, the quotient spectrum can be transformed to the time domain, yielding the apparent far-field source-time function of the large suspected event. The relative source time-function (RSTF) of a nuclear ex-plosion is usually a simple pulse with a duration of about 1 s., while an earthquake’s is more complicated with a series of pulses and a longer duration. The RSTF can be used as a nice dis-criminant to distinguish the nature earthquakes from underground nuclear explosions in target areas.

关键词： target-area, empirical Green's function, RSTF.

The crustal structure under Sanjiang and its dynamic implications:Revealed by seismic reflection/refraction profile between Zhefang and Binchuan,Yunnan

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2005年第9期48卷 1329-1336页

作者： ZHANG Zhongjie1, BAI Zhiming1, WANG Chunyong2, TENG Jiwen1, Lü Qingtian3, LI Jiliang1, LIU Yifeng1 & LIU Zhenkuan4 1. Institute of Geology and geophysics, Chinese Academy of Sciences, Beijing 100029, china 2. Institute of geophysics, china Seismological Bureau, Beijing 100085, china 3. Institute of Deposition Resource, Chinese Academy of Geosciences, Beijing 100037, china 4. school of Exploration and information, china University of Geosciences, Beijing 100083, china 1. Institute of Geology and geophysics Chinese Academy of Sciences 100029 Beijing China 2. Institute of geophysics China Seismological Bureau 100085 Beijing China 3. Institute of Deposition Resource Chinese Academy of Geosciences 100037 Beijing China 4. school of Exploration and information China University of Geosciences 100083 Beijing China

The fault belts in Sanjiang mainly include Jinshajiang-Honghe fault, Lancangjiang fault and Nujiang fault (called Sanjiang faults) in western Yunnan Province, china. By interpreting the wide-angle seismic reflection/refraction profile between Zhefang and Binchuan, which crosses Tengchong and Baoshan blocks in Dianxi (western Yunnan) tectonic zone, we recon- struct the crustal structure with seismic traveltime tomography for crustal P-wave velocity and the seismic scattering image for crustal seismic reflection structure. In this paper, we firstly present the crustal structure images of P-wave velocity and seismic reflection under the wide-angle seismic profile. These results demonstrate that, the crustal velocity structure and seismic reflec- tion structure along the profile can be divided into 3 segments, and there is an obvious difference of crustal structure among the eastern, the western and the middle segment. Generally, crustal P-wave velocities in the Baoshan segment are 0.1―0.2 km/s slower and seismic reflection am- plitudes from Moho discontinuity are stronger than the other 2 segments. In the studied area, crustal thickness is about 40 km, and shows the thickening tendency from west to east along the profile. Additionally, it can be seen that there is one strong-amplitude seismic reflection event as bright points at the depths of 8―10 km, along the segment of 80―115 km of the profile (south- ward of Tengchong); and seismic reflection wave-field from Moho discontinuity varies obviously along the lateral direction. Finally, we make some discussions on the crustal thickening pattern in the Sanjiang fault belt, structural environment of earthquake development and the contact rela- tionship between the Tengchong block, Banshan block and Luxi trough.

关键词： Sanjiang area wide-angle seismic profile crustal structure.

The April 14th, 2010 Yushu earthquake, a devastating earthquake with foreshocks

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2010年第6期53卷 791-793页

作者： NI SiDao1, WANG WeiTao2 & LI Li3 1 school of Earth and space Sciences, University of Science and Technology of china, Hefei 230026, china 2 Institute of geophysics, china Earthquake Administration, Beijing 100081, china 3 National Earthquake Infrastructure Service, china Earthquake Administration, Beijing 100036, china 1. school of Earth and space Sciences University of Science and Technology of China Hefei 230026 China2. Institute of Geophysics China Earthquake Administration Beijing 100081 China3. National Earthquake Infrastructure Service China Earthquake Administration Beijing 100036 China

In the early morning of April 14th, 2010, a strong earth- quake (Ms7.1, http://***; Mw6.9, http://neic. ***) occurred in Yushu district, Qinghai Province, china. More than 2000 lives were lost and over 100000 injured,

关键词： Figure Yushu earthquake a devastating earthquake with foreshocks The April 14th 2010 very than

Numerical study of the auroral particle transport in the polar upper atmosphere

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2008年第10期51卷 1759-1771页

作者： CAI HongTao1,2, MA ShuYing1,2 & PU ZuYin3 1 school of Electronic information, Wuhan University, Wuhan 430079, china 2 Key Laboratory of Geospace Environment and Geodesy, Ministry of Education of PRC, Wuhan 430079, china 3 school of Earth and space Sciences, Peking University, Beijing 100871, china 1. school of Electronic information Wuhan University Wuhan 430079 China 2. Key Laboratory of Geospace Environment and Geodesy Ministry of Education of PRC Wuhan 430079 China 3. school of Earth and space Sciences Peking University Beijing 100871 China

Starting from the Boltzmann equation and with some reasonable assumptions, a one-dimensional transport equation of charged energetic particles is derived by taking account of major interactions with neutral species in the upper atmosphere, including the processes of elastic scattering, the excitation, the ionization and the secondary electron production. The transport equation is numerically solved, for a simplified atmosphere consisting only of nitrogen molecules (N2), to obtain the variations of incident electron fluxes as a function of altitude, energy and pitch angle. The model results can describe fairly the transport characteristics of pre-cipitating auroral electron spectra in the polar upper atmosphere; meanwhile the N2 ionization rates calculated from the modeled differential flux spectra also exhibit good agreements with existing empirical models in terms of several key parameters. Taking the energy flux spectra of precipitating electrons observed by FAST satellite flying over EISCAT site on May 15, 1997 as model inputs, the model-calculated ionization rate profile of neutral atmosphere consists reasonably with that recon-structed from electron density measurements by the radar.

关键词： aurora particle precipitation polar upper atmosphere electron transport equation numerical simulation

2.5-D modeling of cross-hole electromagnetic measurement by nite element method

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2008年第2期5卷 126-134页

作者： Shen Jinsong Sun Wenbo Department of geophysics School of Resources and Information Technology China University of Petroleum Beijing 102249 China CNPC Key Lab of Geophysical Exploration China University of Petroleum Beijing 102249 China

A finite element method is developed for simulating frequency domain electromagnetic responses due to a dipole source in the 2-D conductive structures. Computing costs are considerably minimized by reducing the full three-dimensional problem to a series of two-dimensional problems. This is accomplished by transforming the problem into y-wave number （Ky） domain using Fourier transform and the y-axis is parallel to the structural strike. In the Ky domain, two coupled partial differential equations for magnetic field Hy and electric field Ey are derived. For a specific value of Ky, the coupled equations are solved by the finite element method with isoparametric elements in the x-z plane. Application of the inverse Fourier transform to the Ky, domain provides the electric and magnetic fields in real space. The equations derived can be applied to general complex two-dimensional structures containing either electric or magnetic dipole source in any direction. In the modeling of the electromagnetic measurement, we adopted a pseudo-delta function to distribute the dipole source current and circumvent the problem of singularity at the source point. Moreover, the suggested method used isoparametric finite elements to accommodate the complex subsurface formation. For the large scale linear system derived from the discretization of the Maxwell＇s equations, several iterative solvers were used and compared to select the optimal one. A quantitative test of accuracy was presented which compared the finite element results with analytic solutions for a dipole source in homogeneous space for different ranges and different wave numbers Ky. to validate the addressed the effects of the distribution range τ of the homogeneous medium. code and check its effectiveness. In addition, we pseudo-delta function on the numerical results in

关键词： 2.5-D electromagnetic modeling frequency domain isoparametric finite element pseudo-delta function