检索结果-南通市图书馆

The role of aerial algae in the formation of the landscape of the Yunnan Stone Forest,Yunnan Province, china

Science china Earth sciences 2004年第9期47卷 846-864页

作者： TIAN Youping1,3. ZHANG Jie2, SONG Linhua1 & BAO Haosheng2 1. Institute of Geographic sciences and Natural Resources Research, Chinese academy of sciences, {3. 100101, china 2. Department of Geography, Nanjing university, Nanjing 210093. china 3. School of Earth sciences and Resources, china university of Geosciences, {3. 100083. china Institute of Geographic sciences and Natural Resources Research Chinese Academy of Sciences Beijing China School of Earth sciences and Resources China University of Geosciences Beijing China Department of Geography Nanjing University Nanjing China

Aerial algae on the surface of carbonate rocks at the Stone Forest, Shilin County, Yunnan Province, china, and their bioerosion were investigated in the field and studied in the laboratory in detail. Through the observation, identification and statistics of more than one hun- dred algal samples and rock samples with the optical microscopes (stereomicroscope, biological microscope) and the scanning electronic microscope (SEM), the relationships between erosional forms on the surface of the Stone Forest and algae and/or algal communities and the genetic mechanism for the formation of erosional forms were analyzed. It is suggested that aerial algae play an active role in bioerosive processes that may affect the formation of karst erosional forms. These effects include both direct and indirect ones. The direct effect is the initiative control (algal shape-controlling role) of algae on the formation of karst forms of various scales, mostly mi- cro-scale (3.) and minor-scale (10-3.10-1m) erosional forms. The algal shape-controlling roles can be divided into the algal individual shape-controlling role and the algal community shape-controlling role. The former mostly controls the formation of micro-scale erosional forms, while the latter mostly controls the formation of micro-scale and smaller minor-scale erosional forms. The indirect effect refers to the promoting role of algae in the formation of karst forms, which may affect the formation of karst forms of all types and scales. The bioerosion of algae accelerates the weathering process of the whole Stone Forest karst landforms.

关键词： aerial algae, bioerosion, the Stone Forest, Yunnan Province, china.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Orbit determination and prediction accuracy analysis for a regional tracking network

引用

Science china(Physics,Mechanics & Astronomy) 2010年第6期53卷 1130-1138页

作者： ZHOU ShanShi 1,2,3.,HU XiaoGong 1 & WU Bin 1 1 Shanghai Astronomical Observatory,Chinese academy of sciences,Shanghai 20003.,china 2 {3. university of Chinese academy of sciences,beijing 100049,china 3.Research Center of GNSS,Wuhan 43.079,china Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai China graduate university of Chinese academy of {3. Beijing China Research Center of GNSS Wuhan China

china's COMPASS satellite navigation system relies on a regional tracking network to provide navigation services. Limited by its geographic border,the regional network is able to cover only 3.% of the medium-earth-orbits(MEO). Accuracy of determined and predicted orbits is not able to satisfy system requirements if the tracking data processing strategy for global tracking network processing is used for the regional network. Two major error sources for orbital prediction are accuracy of initial orbital elements and dynamical modeling. To achieve better prediction accuracy,we propose a two-step orbit determination and prediction strategy. For step 1,only solar radiation pressure(SRP) parameters are estimated along with the orbital elements and other parameters; for step 2,all parameters are estimated but the SRP parameters are tightly constrained to their step 1 estimates. Experimenting with data from a regional GPS network,we conclude for orbital prediction using the proposed two-step strategy,the average user range error(URE) for 24-h prediction arcs is better than 0.6 m.

关键词： orbit determination and prediction regional tracking network URE

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Multi-channel SAR imaging based on distributed compressive sensing

引用

Science china(Information sciences) 2012年第2期55卷 245-259页

作者： LIN YueGuan1,2,3.ZHANG BingChen1,2,JIANG Hai1,2,3.HONG Wen1,2 & WU YiRong1,2 1National Key Laboratory of Science and Technology on Microwave Imaging,beijing 100190,china 2Institute of Electronics,Chinese academy of {3.,beijing 100190,china 3.6} university of Chinese academy of {3.,beijing 100049,china National Key Laboratory of Science and Technology on Microwave Imaging Beijing China Institute of Electronics Chinese Academy of Sciences Beijing China graduate university of Chinese academy of {3. Beijing China

The rapid development of compressive sensing(CS)shows that it is possible to recover a sparse signal from very limited *** aperture radar(SAR)imaging based on CS can reconstruct the target scene with a reduced number of collected samples by solving an optimization *** multi-channel SAR imaging based on CS,each channel requires sufficient samples for separate imaging and the total number of samples could still be *** propose an imaging algorithm based on distributed compressive sensing(DCS)that reconstructs scenes jointly under multiple ***-channel SAR imaging based on DCS not only exploits the sparsity of the target scene,but also exploits the correlation among *** requires significantly fewer samples than multi-channel SAR imaging based on *** multiple channels offer different sampling rates,DCS joint processing can reconstruct target scenes with a much more flexible allocation of the number of measurements offered by each channel than that used in separate CS processing.

关键词： synthetic aperture radar multi-channel synthetic aperture radar compressive sensing distributed compressive sensing

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Semi-analytical analysis of the response of the air temperature over the land surface to the global vegetation distribution

引用

Chinese Science Bulletin 2009年第14期54卷 2499-2505页

作者： LIU Fei1,2 & CHAO JiPing3.4 1 Institute of Atmospheric Physics, Chinese academy of sciences, beijing 100029,{3. 2 graduate university of Chinese academy of sciences, beijing 100049,{3. 3.National Marine Environmental Forecasting Center, beijing 100081,{3. 4 First Institute of Oceanography, State Oceanic Administration of{3., Qingdao 266061,{3. Institute of Atmospheric Physics Chinese academy of sciences Beijing China graduate university of Chinese academy of {3. Beijing China National Marine Environmental Forecasting Center Beijing China First Institute of Oceanography State Oceanic Administration of China Qingdao China

Response of the air temperature over the land surface to the global vegetation distribution is investigated, using a three-dimensional governing equation to simulate the steady, large-scale, limited amplitude perturbation of the free, inviscid and adiabatic atmosphere. The adoption of the static equation leads to a temperature governing equation in the terrain following coordinate. With the prescribed temperature as the upper boundary condition and the radiation balance as the lower boundary condition, the semi-analytical solution of the global circulation temperature can be calculated. In this article, only the air temperature (at 2 m height) over the land surface is analyzed, and the result suggests that this model can simulate the air temperature pattern over the land surface reasonably. A better simulation occurs when a simple feedback of the albedo on the temperature is included. Two sensitivity experiments are analyzed through this model. One suggests that the air temperature over the land surface descends obviously when the land surface is covered with ice all over, while another suggests that the air temperature rises a little when the land surface is covered with forest except the ice-covered area. This model appears to be a good tool to study the response of the air temperature to the vegetation distribution. Limitations of the model are also discussed.

关键词：空气温度植被分布陆地表面反应解析分析模拟模式控制方程边界条件

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Neogene eolian deposits within the West Qinling Mountains:Climatic and tectonic implications

引用

Chinese Science Bulletin 2010年第15期55卷 1483-1487页

作者： GE JunYi 1,2 & GUO ZhengTang 3.1 State Key Laboratory of Loess and Quaternary Geology (SKLLQG),Institute of Earth Environment,Chinese academy of sciences,Xi’an 710075,china 2 {3. university of Chinese academy of sciences,beijing 100049,china 3.Key Laboratory of Cenozoic Geology and Environment,Institute of Geology and Geophysics,Chinese academy of sciences,beijing 100029,china State Key Laboratory of Loess and Quaternary Geology (SKLLQG) Institute of Earth Environment Chinese Academy of Sciences Xi’an China graduate university of Chinese academy of {3. Beijing China Key Laboratory of Cenozoic Geology and Environment Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China

The Qinling Mountains constitute a key climate barrier between southern and northern *** recent investigations revealed widely spread eolian deposits of Neogene age mantling the piedmont highlands of the intermountain basins within West ***-mammalian fossils dated a 150.2 m section (NL-VI) near Xihe for the late Miocene to Pliocene (～10-4 Ma).Soil micromorphology,grain-size and geochemical analysis consistently define typical loess-soil alternations for the upper (0-66 m) and lower (98-150.2 m) parts of the section,with the middle section (66-98 m) having been affected by episodic slope *** results add important insights to the earlier studies about the widespread eolian deposition in northern china during the Miocene,prior to 8 *** also suggest that the basic configuration of the ridges and inter-ridge basins of West Qinling has already formed by ～10 *** well-preserved eolian deposits are unlikely to support intense substratum deformation and rapid uplift of West Qinling since the late Miocene.

关键词：秦岭山脉风尘堆积构造意义气候新近纪晚中新世地球化学分析风尘沉积

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

fMRI time series analysis based on stationary wavelet and spectrum analysis

引用

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 100049,{3. 2. graduate School of Chinese academy of sciences, beijing 100049,{3. 3. Department of Physics, Zhoukou Normal university, Zhoukou 466100,{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 100049,{3. 6. Department of Physics, Zhejiang university, Hangzhou 3.0027,{3.) Key Laboratory of Nuclear Analysis Techniques Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China graduate School of Chinese academy of sciences Beijing 100049 China Department of Physics Zhoukou Normal University Zhoukou 466100 China Research Imaging Center University of Texas Health Science Center San Antonio TX 78229 United States National ASIC Design and Engineering Center Institute of Automation Chinese Academy of Sciences Beijing 100049 China Department of Physics Zhejiang University Hangzhou 310027 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.

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

On designated-weight Boolean functions with highest algebraic immunity

引用

Science china Mathematics 2010年第11期53卷 2847-2854页

作者： LIU MeiCheng1,3. DU YuSong2, PEI DingYi2 & LIN DongDai1 1The State Key Laboratory of Information Security, Institute of Software of Chinese academy of sciences, beijing 100190,{3. 2College of Mathematics and Information sciences, Guangzhou university, Guangzhou 510006,{3. 3.7} university of Chinese academy of sciences, beijing 100049,{3. The State Key Laboratory of Information Security Institute of Software of Chinese Academy of Sciences Beijing China graduate university of Chinese academy of {3. Beijing China College of Mathematics and Information sciences Guangzhou University Guangzhou China

Algebraic immunity has been considered as one of cryptographically significant properties for Boolean functions. In this paper, we study ∑d-1 i=0 (ni)-weight Boolean functions with algebraic immunity achiev-ing the minimum of d and n - d + 1, which is highest for the functions. We present a simpler sufficient and necessary condition for these functions to achieve highest algebraic immunity. In addition, we prove that their algebraic degrees are not less than the maximum of d and n - d + 1, and for d = n1 +2 their nonlinearities equalthe minimum of ∑d-1 i=0 (ni) and ∑ d-1 i=0 (ni). Lastly, we identify two classes of such functions, one having algebraic degree of n or n-1.

关键词： cryptography Boolean function algebraic immunity algebraic degree nonlinearity

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

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

引用

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 {3., beijing 100049, china 2 Institute of Geodesy and Geophysics, Chinese academy of {3., Wuhan 43.077, china 3.State Key Laboratory of Astronautic Dynamics, Xi’an 710043. china 4 Zhengzhou Institute of Surveying and Mapping, Zhengzhou 450052, china College of Earth Science Graduate University of Chinese Academy of Sciences Beijing China Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan China State Key Laboratory of Astronautic Dynamics Xi’an China Zhengzhou Institute of Surveying and Mapping Zhengzhou 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

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

An improved method for evaluating the seasonal variability of total suspended sediment flux field in the Yellow and East china Seas

引用

International Journal of Sediment Research 2011年第1期26卷 1-14页

作者： PANG Chongguang~1,YU Wei~2,YANG Yang~3.and HAN Danxiu~4 Institute of Oceanology,Chinese academy of sciences,Qingdao 266071,china, 2 Institute of Oceanology,Chinese academy of sciences,Qingdao 266071,china,graduate School of Chinese academy of sciences,beijing 10003.,china 3.Institute of Oceanology,Chinese academy of sciences,Qingdao 266071,china,graduate School of Chinese academy of sciences,beijing 10003.,china 4 china university of Petroleum,beijing 102249,china Doctor Researcher Institute of Oceanology Chinese Academy of Sciences Qingdao 266071 China Institute of Oceanology Chinese Academy of Sciences Qingdao 266071 China Graduate School of Chinese Academy of Sciences Beijing 100039 China china university of Petroleum Beijing 102249 China

The suspended sediment flux field in the Yellow and East china Seas(YECS) displays its seasonal variability.A new method is introduced in this paper to obtain the flux field via retrieval of ocean color remote sensing data,statistical analysis of historical suspended sediment concentration data,and numerical simulation of three-dimensional(3.) flow *** components of the sediment flux field include(i) surface suspended sediment concentration inverted from ocean color remote sensing data;(ii) vertical distribution of suspended sediment concentration obtained by statistical analysis of historical observation data;and(iii) 3. flow field modeled by a numerical *** the improved method,the 3. suspended sediment flux field in the YECS has been *** comparison with the suspended sediment flux field solely based on the numerical simulation of a suspended sediment transport model,the suspended sediment flux field obtained by the improved method is found to be more *** 3. suspended sediment flux field from ocean colour remote sensing and in situ observation are more closer to the ***,by quantitatively analyzing the newly obtained suspended sediment flux field,the quantity of sediment erosion and deposition within the different regions can be *** sediment exchange between the Yellow Sea and the East china Sea can be *** mechanism of suspended sediment transport in the YECS can be better *** particular,it is suggested that the long-term transport of suspended sediment is controlled mainly by the circulation pattern,especially the current in winter.

关键词： Suspended sediment flux field Seasonal variability Yellow and East china Seas Regression equation Numerical simulation

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Intrafloral differentiation of stamens in heterantherous flowers

引用

Journal of Systematics and Evolution 2009年第1期47卷 43-56页

作者： 1,2Zhong-Lai LUO 1,2Lei GU 1Dian-Xiang ZHANG 1(South china Botanical Garden, Chinese academy of sciences, Guangzhou 510650, china) 2(graduate university of Chinese academy of sciences, beijing 100049, china) South china Botanical Garden Chinese Academy of Sciences Guangzhou 510650 China graduate university of Chinese academy of {3. Beijing 100049 China

Flowers that have heteromorphic stamens (heterantherous flowers) have intrigued many researchers ever since the phenomenon was discovered in the 19th century. The morphological differentiation in androecia has been suggested as a reflection of "labor division" in pollination in which one type of stamens attracts pollinators and satisfies their demand for pollen as food and the other satisfies the plant’s need for safe gamete dispersal. The extent and patterns of stamen differentiation differ notably among taxa with heterantherous flowers. Seven species with heteromorphic stamens in three genera were sampled from Leguminosae and Melastomataceae, and the morphological difference of androecia, pollen content, pollen histochemistry and viability, pollen micro-morphology, as well as the main pollinators were examined and compared. Pollen number differs significantly between stamen sets of the same flower in most species investigated, and a correlation of pollen number and anther size was substantiated. Higher pollen viabilities were found in the long (pollinating) stamens of Senna alata (L.) Roxb. and S. bicapsularis (L.) Roxb. Dimorphic pollen exine ornamentation is reported here for the first time in Fordiophyton faberi Stapf. The height of stigma and anther tips of the long stamens in natural conditions was proved to be highly correlated, supporting the hypothesis that they contact similar areas of the pollinator’s body.

关键词： buzz pollination heteranthery labor division pollen micro-morphology pollen number pollination stamen differentiation

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：