QuickBird影像的正射校正研究

根据现有的数据特点和项目要求,在Erdas软件中,对Quickbird影像提出了可行的正射校正流程,重点分析有理函数模型的数学推导和算法实现,最终解决在校正过程中遇到的问题。     

Gravitational clustering of galaxies in an expanding universe

We inquire the phenomena of clustering of galaxies in an expanding universe from a theoretical point of view on the basis of thermodynamics and correlation functions. The partial differential equation is developed both for the point mass and extended mass structures of a two-point correlation function by using thermodynamic equations in combination with the equation of state taking gravitational interaction between particles into consideration. The unique solution physically satisfies a set of boundary conditions for correlated systems and provides a new insight into the gravitational clustering problem.     

A method for averaging the perturbing function in Hill’s problem

A modified method for averaging the perturbing function in Hill’s problem is suggested. The averaging is performed in the revolution period of the satellite over the mean anomaly of its motion with a full allowance for a variation in the position of the perturbing body. At its fixed position, the semimajor axis of the satellite orbit during the revolution of the satellite is constant in view of the evolution equations, while the remaining orbital elements undergo secular and long-period perturbations. Therefore, when the motion of the perturbing body is taken into account, the semimajor axis of the satellite orbit undergoes the strongest perturbations. The suggested approach generalizes the averaging method in which only the linear (in time) term is included in the perturbing function. This method requires no expansion in powers of time. The described method is illustrated by calculating the perturbations of the semimajor axes for two distant satellites of Saturn, S/2000 S 1 and S/2000 S5. An approximate analytic solution is compared with the results of numerical integration of the averaged system of equations of motion for these satellites.     

A generalized additive model for the spatial distribution of snowpack in the Spanish Pyrenees

A generalized additive model (GAM) was used to model the spatial distribution of snow depth in the central Spanish Pyrenees. Statistically significant non‐linear relationships were found between distinct location and topographical variables and the average depth of the April snowpack at 76 snow poles from 1985 to 2000. The joint effect of the predictor variables explained more than 73% of the variance of the dependent variable. The performance of the model was assessed by applying a number of quantitative approaches to the residuals from a cross‐validation test. The relatively low estimated errors and the possibility of understanding the processes that control snow accumulation, through the response curves of each independent variable, indicate that GAMs may be a useful tool for interpolating local snow depth or other climate parameters. Copyright © 2005 John Wiley & Sons, Ltd.     

地理信息系统的社会公共功能

地理信息系统已经成为商品走进人们的生活 ,它所具有的社会公共功能正引起人们越来越多的关注。     

The origin of the initial mass function and its dependence on the mean Jeans mass in molecular clouds

We investigate the dependence of stellar properties on the mean thermal Jeans mass in molecular clouds. We compare the results from the two largest hydrodynamical simulations of star formation to resolve the fragmentation process down to the opacity limit, the first of which was reported by Bate, Bonnell & Bromm. The initial conditions of the two calculations are identical except for the radii of the clouds, which are chosen so that the mean densities and mean thermal Jeans masses of the clouds differ by factors of 9 and 3, respectively.
We find that the denser cloud, with the lower mean thermal Jeans mass, produces a higher proportion of brown dwarfs and has a lower characteristic (median) mass of the stars and brown dwarfs. This dependence of the initial mass function (IMF) on the density of the cloud may explain the observation that the Taurus star-forming region appears to be deficient in brown dwarfs when compared with the Orion Trapezium cluster. The new calculation also produces wide binaries (separations >20 au), one of which is a wide binary brown dwarf system.
Based on the hydrodynamical calculations, we develop a simple accretion/ejection model for the origin of the IMF. In the model, all stars and brown dwarfs begin with the same mass (set by the opacity limit for fragmentation) and grow in mass until their accretion is terminated stochastically by their ejection from the cloud through dynamically interactions. The model predicts that the main variation of the IMF in different star-forming environments should be in the location of the peak (due to variations in the mean thermal Jeans mass of the cloud) and in the substellar regime. However, the slope of the IMF at high masses may depend on the dispersion in the accretion rates of protostars.     

中国大陆水平地壳运动的数学模型

在获得中国区域1000个实测GPS台站速度场的基础上,利用多面函数法、滑动欧拉矢量法和滑动弹塑性模型法建立了中国大陆水平地壳运动模型,统计表明3种方法外部符合精度2～4mm/a,模型互差精度约为3mm/a。     

一类多物种生态模型的稳定性

应用李雅普诺夫直接法研究了一类多物种生态模型的稳定性，给出了系统的局部和全局稳定性的充分条件。     

浙江中生代浅成热液金银成矿作用的耗散结构模型

浙江中生代主要浅成热液金银矿床在蚀变-矿化过程中的一些物理化学特征参数(如T、P、St和ρ等)呈非线性的变化关系,其控制变量是P、T和PH值.推断条带(或环带)状构造的矿脉(石)是由减压沸腾作用造成的.据Drummond等(1985)沸腾的模拟计算和研究表明,[H+]浓度是决定沸腾热液中的Au、Ag等成矿元素命运的主要因素.因此,可以[H+]浓度(状态变量)作为序参量来反映成矿溶液中Au、Ag浓度的变化趋势;并建立其自组织过程的动力学方程与开放沸腾热液系统Au、Ag沉淀的耗散结构模型.