美国长期天气预报业务的新发展──发布气候展望   总被引：1，自引：0，他引：1  

李小泉 《气象》1995,21(9):49-52

从１９９５年元月份起，美国天气局正式发布预见期为一年的业务性气候展望，该文简要地介绍了美国天气局作出这些重大变更的科学依据、预报方法、预报制作与预报准确等方面的情况。  相似文献   

大型GIS与数字地球的空间数学基础研究   总被引：14，自引：3，他引：14  

胡鹏  吴艳兰  杨传勇  李国建 《武汉大学学报(信息科学版)》2001,26(4):296-302

将地图投影概念由传统的曲面到平面的变换扩展为曲面到曲面的变换，并提出一套适合于大型GIS和地球数字产品的实用“地图投影”模型。该模型的视图采用等距离切圆柱投影，度量空间是椭球面几何系统，符合计算机环境下GIS视图与度量空间分离的特性。鉴于全球多分辨率连续可视化，精密可视化量算，三维、多维地球数据统一，标准的空间定位框架和只有在统一的空间系统内，全球资源、生态环境数据才能进行精确的地理分析等4个方面的需要，从地图投影发展到本模型将是方向和技术趋势。  相似文献   

论地球系统科学与可持续发展战略科学基础（Ⅰ）   总被引：47，自引：4，他引：47  

黄秉维 《地理学报》1996,51(4):350-354

地球系统科学是可持续发展战略的科学。它脱胎于气候系统研究，跨越一系一自然与社会科学，将全球变化与区域变化冶为一炉，所涵差的时间数十年至一二百年，在此时间尺度内，所涵盖的对象基本上是大气、海洋与陆地以及介于其间的物质能量交换过程。陆地最重要、最复杂、受人类活动的影响亦最大，目前未知数亦最多。宜先在跨学科的综合工作上多下功夫，积极推动地系统研究。  相似文献   

Estimation of regionalized compositions: A comparison of three methods   总被引：1，自引：0，他引：1  

V. Pawlowsky  R. A. Olea  J. C. Davis 《Mathematical Geology》1995,27(1):105-127

A regionalized composition is a random vector function whose components are positive and sum to a constant at every point of the sampling region. Consequently, the components of a regionalized composition are necessarily spatially correlated. This spatial dependence—induced by the constant sum constraint—is a spurious spatial correlation and may lead to misinterpretations of statistical analyses. Furthermore, the cross-covariance matrices of the regionalized composition are singular, as is the coefficient matrix of the cokriging system of equations. Three methods of performing estimation or prediction of a regionalized composition at unsampled points are discussed: (1) the direct approach of estimating each variable separately; (2) the basis method, which is applicable only when a random function is available that can he regarded as the size of the regionalized composition under study; (3) the logratio approach, using the additive-log-ratio transformation proposed by J. Aitchison, which allows statistical analysis of compositional data. We present a brief theoretical review of these three methods and compare them using compositional data from the Lyons West Oil Field in Kansas (USA). It is shown that, although there are no important numerical differences, the direct approach leads to invalid results, whereas the basis method and the additive-log-ratio approach are comparable.  相似文献   

Groebner-basis solution of the three-dimensional resection problem (P4P)     

J. L. Awange  E. W. Grafarend 《Journal of Geodesy》2003,77(5-6):327-337

The three-dimensional (3-D) resection problem is usually solved by first obtaining the distances connecting the unknown point P{X,Y,Z} to the known points P_i{X_i,Y_i,Z_i}i=1,2,3 through the solution of the three nonlinear Grunert equations and then using the obtained distances to determine the position {X,Y,Z} and the 3-D orientation parameters {,, }. Starting from the work of the German J. A. Grunert (1841), the Grunert equations have been solved in several substitutional steps and the desire as evidenced by several publications has been to reduce these number of steps. Similarly, the 3-D ranging step for position determination which follows the distance determination step involves the solution of three nonlinear ranging (`Bogenschnitt') equations solved in several substitution steps. It is illustrated how the algebraic technique of Groebner basis solves explicitly the nonlinear Grunert distance equations and the nonlinear 3-D ranging (`Bogenschnitt') equations in a single step once the equations have been converted into algebraic (polynomial) form. In particular, the algebraic tool of the Groebner basis provides symbolic solutions to the problem of 3-D resection. The various forward and backward substitution steps inherent in the classical closed-form solutions of the problem are avoided. Similar to the Gauss elimination technique in linear systems of equations, the Groebner basis eliminates several variables in a multivariate system of nonlinear equations in such a manner that the end product normally consists of a univariate polynomial whose roots can be determined by existing programs e.g. by using the roots command in Matlab.Acknowledgments.The first author wishes to acknowledge the support of JSPS (Japan Society of Promotion of Science) for the financial support that enabled the completion of the write-up of the paper at Kyoto University, Japan. The author is further grateful for the warm welcome and the good working atmosphere provided by his hosts Professors S. Takemoto and Y. Fukuda of the Department of Geophysics, Graduate School of Science, Kyoto University, Japan.  相似文献   

中国古代地图的数学基础与地理空间维度认知     

AN Min  ZHANG Chun-ling 《测绘学院学报》2007,(Z1)

从几个典型的中国古地图的数学基础出发,结合相关的数学方法,探讨了中国古人在地理空间维度认知方面走过的历程。认为,当中国古代地图发展到以"计里画方"进行地图绘制时,已经实现了3维地理空间的科学认知。这也是"计里画方"的制图方法可以持续1 000多年的理论依据。  相似文献   

Reservoir induced earthquakes analyzed via radial basis function networks     

Ghassem Habibagahi 《Soil Dynamics and Earthquake Engineering》1998,17(1):53-56

Estimation of the magnitude of reservoir induced seismicity is essential for seismic risk analysis of dam sites. Different geological and empirical methods dealing with the mechanism or magnitude of such earthquakes are available in the literature. In this study, a method based on an artificial neural network utilizing radial basis functions (RBF network) was employed to analyze the problem. The network has only two input neurons, one representing the maximum depth of the reservoir and the other being a comprehensive parameter representing reservoir geometry. Magnitudes of the induced earthquakes predicted using the RBF network were compared with the actual recorded data. Compared with the conventional statistical approach, the proposed method gives a better prediction, both in terms of coefficients of correlation and error rates.  相似文献   

Multi-resolution adaptive modeling of groundwater flow and transport problems     

H. Gotovac  R. Andricevic  B. Gotovac 《Advances in water resources》2007

Many groundwater flow and transport problems, especially those with sharp fronts, narrow transition zones, layers and fingers, require extensive computational resources. In this paper, we present a novel multi-resolution adaptive Fup approach to solve the above mentioned problems. Our numerical procedure is the Adaptive Fup Collocation Method (AFCM), based on Fup basis functions and designed through a method of lines (MOL). Fup basis functions are localized and infinitely differentiable functions with compact support and are related to more standard choices such as splines or wavelets. This method enables the adaptive multi-resolution approach to solve problems with different spatial and temporal scales with a desired level of accuracy using the entire family of Fup basis functions. In addition, the utilized collocation algorithm enables the mesh free approach with consistent velocity approximation and flux continuity due to properties of the Fup basis functions. The introduced numerical procedure was tested and verified by a few characteristic groundwater flow and transport problems, the Buckley–Leverett multiphase flow problem, the 1-D vertical density driven problem and the standard 2-D seawater intrusion benchmark–Henry problem. The results demonstrate that the method is robust and efficient particularly when describing sharp fronts and narrow transition zones changing in space and time.  相似文献   

Robust and reliable metamodels for mechanized tunnel simulations     

《Computers and Geotechnics》2014

The main objective of this paper is to construct a robust and reliable metamodel for the mechanized tunnel simulation in computationally expensive applications. To accomplish this, four metamodeling approaches have been implemented and their performance has been systematically evaluated through a comparative study utilizing pure mathematical test functions. These metamodels are quadratic polynomial regression, moving least squares, proper orthogonal decomposition with radial basis functions, and an extended version of the latest approach. This extended version has been proposed by the authors and named proper orthogonal decomposition with extended radial basis functions. After that, a system identification study for mechanized tunneling has been conducted through the back analysis of synthetic measurements. In this study, the best performing metamodel, that is the one suggested by the authors, has been employed to surrogate a complex and computationally expensive 3D finite element simulation of the mechanized tunnel. The obtained results demonstrate that the proposed metamodel can reliably replace the finite element simulation model and drastically reduce the expensive computation time of the back analysis subroutine.  相似文献   

建设工程基础验线与竣工规划测量的研究     

黄心一  陶利  秦政国 《现代测绘》2014,(4):11-13

基础验线与竣工规划测量是城市规划管理的重要环节,其成果是规划过程监督管理与竣工验收审核的重要依据。无锡市自2012年1月1日起正式实施建设工程基础验线与竣工规划测量工作。本文介绍了无锡市建设工程基础验线与竣工规划测量的作业依据与资料准备、工作内容及提交的成果,并结合工程实例对成果进行分析,为今后工作提供参考。  相似文献