检索结果-南通市图书馆

fMRI time series analysis based on stationary wavelet and spectrum analysis

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2006年第11期16卷 1171-1176页

作者： ZHI Lianhe~ 1,2,3., ZHAO Xia~4. SHAN Baoci~1**, PENG Silong~5, YAN Qiang~1, YUAN Xiuli~1 and TANG Xiaowei~ 1,6 (1. Key Laboratory of Nuclear Analysis Techniques, institute of High Energy Physics, chinese Academy of Sciences, beijing 10004.,{3. 2. Graduate School of chinese Academy of Sciences, beijing 10004.,{3. 3. Department of Physics, Zhoukou Normal University, Zhoukou 4.6100,{3. 4. Research Imaging Center, University of Texas Health Science Center, San Antonio, Texas 78229, USA 5. National ASIC Design and Engineering Center, institute of Automation, chinese Academy of Sciences, beijing 10004.,{3. 6. Department of Physics, Zhejiang University, Hangzhou 3.0027,{3.) [a]Key Laboratory of Nuclear Analysis Techniques Institute of High Energy Physics Chinese Academy of Sciences Beijing China [b]Graduate School of chinese Academy of Sciences Beijing China [c]Department of Physics Zhoukou Normal University Zhoukou China [d]Research Imaging Center University of Texas Health Science Center San Antonio Texas USA [e]National ASIC Design and Engineering Center Institute of Automation Chinese Academy of Sciences Beijing China [f]Department of Physics Zhejiang University Hangzhou China

The low signal to noise ratio (SNR) of functional MRI (fMRI) prefers more sensitive data analysis methods. Based on stationary wavelet transform and spectrum analysis, a new method with high detective sensitivity was developed for analyzing fMRI time series, which does not require any prior assumption of the characteristics of noises. In the proposed method, every component of fMRI time series in the different time-frequency scales of stationary wavelet transform was discerned by the spectrum analysis, then the components from noises were removed using the stationary wavelet transform, finally the components of real brain activation were detected by cross-correlation analysis. The results obtained from both simulated and in vivo visual experiments illustrated that the proposed method has much higher sensitivity than the traditional cross-correlation method.

关键词： fMRI stationary wavelet transform spectrum analysis data analysis.

The gravitational gradient tensor’s invariants and the related boundary conditions

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china Earth Sciences 2010年第5期53卷 781-790页

作者： YU JinHai1,2,3.& ZHAO DongMing4.1 College of Earth Science, Graduate University of chinese Academy of Sciences, beijing 10004., china 2 {3. of Geodesy and Geophysics, chinese Academy of Sciences, Wuhan 4.0}077, china 3.State Key Laboratory of Astronautic Dynamics, Xi’an 71004.0} china 4.Zhengzhou {3. of Surveying and Mapping, Zhengzhou 4.0052, china 1. College of Earth Science Graduate University of Chinese Academy of Sciences Beijing 100049 China2. Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China3. State Key Laboratory of Astronautic Dynamics Xi’an 710043 China4. Zhengzhou Institute of Surveying and Mapping Zhengzhou 450052 China

Here we report new approaches of recovering the Earth gravitational field from GOCE (Gravity field and steady-state Ocean Circulation Explorer) gradiometric data with the help of the gradient tensor’s invariants. Our results only depend on GOCE satellite’s position and gradiometry, in other words, they are completely independent of the satellite attitude. First, starting from the invariants, linearization models are established, which can be referred as the general boundary conditions on the satellite’s orbit. Then, the spherical approximation expressions for the models are derived, and the corresponding solving methods for them are discussed. Furthermore, considering effects of J2-term, the spherical approximation models are improved so that the accuracies of the boundary conditions can be theoretically raised to O ( J 2/2 T), which is approximately equivalent to O(T2). Finally, some arithmetic examples are constructed from EGM96 model based on the derived theories, and the computational results illustrate that the spherical models have accuracies of 10-7 and the order recovering the gravitational field can reach up to 200, and the models with regard to effect of J2-term have accuracies of 10-8 and the order can reach up to 280.

关键词： the Earth’s gravitational field gravitational gravidiometry tensor’s invariant

Growth characteristics and response to climate change of Larix Miller tree-ring in china

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 871-879页

作者： SUN Yu1,4. WANG LiLi1,2,3. CHEN Jin5, DUAN JianPing1,4. SHAO XueMei1,2 & CHEN KeLong6 1 institute of Geographic Sciences and Natural resources Research, chinese Academy of Sciences, {3. 100101, china 2 institute of Tibetan Plateau Research, chinese Academy of Sciences, {3. 100085, china 3.institute of Desert and Meteorology, china Meteorological Administration, Urumqi 83.002, china 4.Graduate University of chinese Academy of Sciences, {3. 10004., china 5 institute of Vertebrate Paleontology and Paleoanthropology, chinese Academy of Sciences, {3. 10004., china 6 School of Life and Geography Sciences, Qinghai Normal University, Xining 810008, china 1. institute of Geographic Sciences and Natural resources Research Chinese Academy of Sciences Beijing 100101 China4. Graduate University of Chinese Academy of Sciences Beijing 100049 China2. Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China3. Institute of Desert and Meteorology China Meteorological Administration Urumqi 830002 China5. Institute of Vertebrate Paleontology and Paleoanthropology Chinese Academy of Sciences Beijing 100044 China6. School of Life and Geography Sciences Qinghai Normal University Xining 810008 China

As one of the earliest species used in dendrochronological studies, Larix responds sensitively to climate change. In this study, nine larch species and one variety from eleven sites were collected to study the growth characteristics of tree-ring width using dendrochronological methods. Ten residual tree-ring chronologies were developed to analyze their relationships with regional standardized anomaly series by Pearson’s correlation analysis. The results suggest that most of the chronologies had significantly positive correlations with the mean temperature and mean maximum temperature in May. The spring temperature evidently limited the radial growth of the larch species without precipitation control. The largest mean tree-ring width was found in Himalayan Larch in Jilong, whereas Master Larch in Si’er reflected the smallest mean value. Both species presented little climate information in this study. chinese, Potanin, and Tibetan larches are significantly correlated with climate change, implying a huge potential for climate history reconstruction. The elevation of the sampling sites appears to be an important condition for tree-ring growth of larches responding to climate factors.

关键词： Larix Miller tree-ring climate change mean temperature in May

Paleomagnetic dating of the Cenjiawan Paleolithic site in the Nihewan Basin, northern china

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2006年第3期49卷 295-303页

作者： WANG Hongqiang1,2, DENG Chenglong1, ZHU Rixiang1 & XIE Fei3.1. Paleomagnetism and Geochronology Laboratory (SKL-LE), institute of Geology and Geophysics, chinese Academy of Sci- ences, beijing 100029,{3. 2. School of the Earth Sciences and resources,{3. University of geosciences, beijing 100083.{3. 3. Hebei Province institute of Cultural Relics, Shijiazhuang 050000,{3. 1. Paleomagnetism and Geochronology Laboratory (SKL-LE) Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China 2. School of the Earth Sciences and resources China University of Geosciences Beijing 100083 China 3. Hebei Province institute of Cultural Relics Shijiazhuang 050000 China

Rock magnetic and magnetostratigraphic investigations on a lacustrine sequence in the Nihewan Basin, northern china, which bears the Cenjiawan Paleolithic site, indicate that the dominant magnetic mineral and remanence carrier contained in the sediments is magnetite. While hematite co-exists with magnetite in some portions of the Cenjiawan sequence, where characteristic remanent magnetizations are carried by both magnetite and hematite. Measurements of anisotropy of magnetic susceptibility confirm that the Cenjiawan sequence has preserved the original sedimentary features and is suitable for magnetostratigraphic study. Paleomagnetic results indicate that the Cenjiawan Paleolithic site is formed just posterior to the Punaruu normal event, which is dated at about 1.1 Ma. Combined with the paleomagnetic results of the Donggutuo, Xiaochangliang and Majuangou sections, it is concluded that early humans were occupying the Nihewan Basin around 1.6, 1.3.and 1.1 Ma. This integrated result is significant to understanding the ability of migration and adaptation to the envi- ronment of early humans.

关键词： Nihewan Basin, Early Pleistocene, Cenjiawan, Paleolithic site, paleomagnetism.

Two possible mechanisms for vortex self-organization

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2006年第2期49卷 202-211页

作者： LUO Zhexian2, ZHOU Xiuji1 & GAO Shouting3.1. chinese Academy of Meteorological Sciences, beijing 100081, china 2. Department of Space Information Science, Nanjing University of Information Science and Technology, Nanjing 21004., china 3. institute of Atmospheric Physics, chinese Academy of Sciences, beijing 100029, china 2. Department of Environmental Science Nanjing University of Information Science and Technology Nanjing 210044 China 1. chinese Academy of Meteorological Sciences Beijing 100081 China 3. institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

The vortex self-organization is investigated in this paper by four groups of numerical experiments within the framework of quasi-geostrophic model, and based on the experimental results two types of possible mechanisms for vortex self-organization are suggested. The meso-scale to-pography may enable separated vortices to merge into a larger scale vortex; and the interaction of meso-γ and meso-β scale systems may make separated vortices to self organize a typhoon-like vor-tex circulation.

关键词： vortex, self-organization, meso-scale topography, interaction of different scales.

Interannual variability of Antarctic Oscillation and its influence on East Asian climate during boreal winter and spring

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2006年第5期49卷 554-560页

作者： FAN Ke1,2,3.& WANG Huijun2 1. Nansen-Zhu International Research Center, institute of Atmospheric Physics, chinese Academy of Sciences, beijing 100029,{3. 2. Department of Atmospheric Science, Yunnan University, Kunming 650091,{3. 3. Graduate University of the chinese Academy of Sciences, beijing 10004.,{3. 1. Nansen-Zhu International Research Center Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China 2. Department of Atmospheric Science Yunnan University Kunming 650091 China 3. Graduate University of the chinese Academy of Sciences Beijing 100049 China

The interannual variability of Antarctic Oscillation (AAO) and its influence on East Asian climate during both boreal winter and spring are addressed. The results show that the positive AAO anomaly decreases the cold activity over East Asia during both boreal winter and spring. AAO-related barotropic meridional teleconnection from Antarctic to Arctic is found through analysis of mean me- ridional circulations. This meridional teleconnection is remarkable over Eurasia during boreal winter and over the Pacific Ocean during boreal spring. The results also show that zonal mean zonal wind at high latitudes in Southern Hemisphere has well positive correlation with that of Eurasia during boreal winter and has negative correlation with Pacific North American teleconnection (PNA) during boreal spring, which again display the meridional teleconnection. Thus, local meridional teleconnection is a possible linkage for interaction of circulations at mid-high latitudes between both hemispheres.

关键词： Antarctic Oscillation, Eurasian west wind, meridional teleconnection, mean meridional circulation.

Chronology of Holocene lacustrine sediments in Co Ngoin, central Tibetan Plateau

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2006年第9期49卷 991-1001页

作者： WU Yanhong1, WANG Sumin1& HOU Xinhua1,3.1. Key Laboratory of Lake Sedimentation and Environment, Nanjing institute of Geography and Limnology, chinese Academy of Sciences, Nanjing 210008, china 2. institute of Tibetan Plateau Research, chinese Academy of Sciences, beijing 10085, china 3. Graduate University of chinese Academy of Sciences, beijing 10003., china 1. Key Laboratory of Lake Sedimentation and Environment Nanjing Institute of Geography and Limnology Chinese Academy of Sciences Nanjing 210008 China 2. institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 10085 China 3. Graduate University of chinese Academy of Sciences Beijing 100039 China

Chronology is the basis for using lacustrine sediments to reconstruct the history of en-vironmental change. Radioactive-nuclides such as 14., 210Pb and 13.Cs dating are mainly used to establish the chronology for recent several ten thousand years. Because of being mixed with “dead carbon”, the measured 14. age is always older than the actual age which is recognized as “reservoir effect”. Cs is a kind of active metal element, and easy to migrate vertically in the sediment that leads to the error of the time marker. 210Pb dating should make sure to select CIC model or CRS model. On the Tibetan Plateau, most of the lakes are alkaline closed lake where Cs is more moveable in the sediment and the reservoir effect caused by “dead carbon” on 14. dating is stronger. Based on the analysis on results of 14., 210Pb and 13.Cs of the lacustrine sediments from Co Ngoin, central Tibetan Plateau, we use the simple regression method to re-calculate the 14. calendar ages, and establish the time sequence for cores CE-1 and CE-2 with result of 210Pb CRS model for the upper 3. cm and re-calculated 14. calendar age for sediments bellow 3. cm. Since 14.0 cal. a BP, sedimentation inter-rupted for more than 1000 years. According to this time sequence, variations of environmental proxies confidently reflect the major climatic events in Holocene.

关键词： 14., 210Pb and 13.Cs, chronology, lacustrine sediments, climatic event, Co Ngoin, central Tibetan Plateau.

Isolation, characterization and functional analysis of a cdc4. homologue from tobacco BY-2 cells

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2007年第2期17卷 156-162页

作者： CHEN Zhiling, YU Yi, LIU Lina and XIA Guixian ( College of Life Science, Capital Normal University, beijing 100037, china institute of Microbiology, {3. Academy of Sciences, {4. 100080, china) [a]College of Life Science Capital Normal University Beijing China [b]institute of Microbiology Chinese Academy of Sciences Beijing China

The fission yeast Schizosaccharomyces pombe was used to identify genes from tobacco BY-2 cells that may play roles in cell cycle regulation. A cDNA encoding a protein homologous to the yeast CDC4. was isolated and the gene was designated as NtCDC4. . The cDNA contains an open reading frame coding for a predicted protein of 808 amino acids which comprises of two typical ATPase modules (aa 24.-3.4.and aa 518-64.) . Overexpression of NtCDC4. in tobacco BY-2 cells led to an increase in the mitotic index as well as to the formation of diffused mitotic spindles. NtCDC4.-GFP fusion proteins are distributed ubiquitously through Gl to M phases, yet their subcellular localization varied regularly along with the cell cycle progression. These results indicate that NtCDC4. may play an important role in the regulation of cell cycle in BY-2 cells.

关键词： tobacco BY-2 suspension cells NtCDC4. spindle cell cycle.

Identification and removal of block ambiguities in sea surface wind field with scatterometers

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china Earth Sciences 2009年第2期52卷 242-249页

作者： CHEN KeHai1,2, XIE XueTong3.& FANG Yu4.1 South china Sea institute of Oceanology, chinese Academy of Sciences, Guangzhou 5103.1, china 2 Graduate University of chinese Academy of Sciences, beijing 10004., china 3.School of Electronic Science and Engineering, National University of Defense Technology, Changsha 4.0073. china 4.The institute of Remote Sensing and GIS, Peking University, beijing 100871, china 1. South china Sea institute of Oceanology Chinese Academy of Sciences Guangzhou 510301 China 2. Graduate University of chinese Academy of Sciences Beijing 100049 China 3. School of Electronic Science and Engineering National University of Defense Technology Changsha 410073 China 4. The institute of Remote Sensing and GIS Peking University Beijing 100871 China

The solution of the current wind retrieval algorithm for scatterometers has several wind vector ambi-guities, due to the bi-harmonic relationship between normalized backscattering cross section and the relative wind direction and the existence of the measurement error. In order to remove the ambiguities for a unique wind field, a circular median filter approach (CMF) is usually adopted. But under the con-dition for clustering distribution of the false ambiguities in some local areas, the CMF fails and thus engenders block ambiguities, which degrade the precision of the retrieved wind field. For such a situation, a technique of identification and removal of the block ambiguities is presented to further optimize the retrieved wind field after CMF. It is demonstrated in experiment that this technique can identify and remove most of the block ambiguities.

关键词： scatterometer block ambiguity identification and removal