地下流稳定问题的样条函数解法

提出求解地下流稳定问题的一种新方法——样条函数法,该法较其它算法有计算精度高,程序易于编制,边界处理灵活等优点。     

Storage-efficient reconstruction framework for planar contours

A storage-efficient reconstruction framework for cartographic planar contours is developed. With a smaller number of control points, we aim to calculate the area and perimeter as well as to reconstruct a smooth curve. The input data forms an oriented contour, each control point of which consists of three values: the Cartesian coordinates (x, y) and tangent angle θ. Two types of interpolation methods are developed, one of which is based on an arc spline while the other one is on a cubic Hermite spline. The arc spline-based method reconstructs a G¹ continuous curve, with which the exact area and perimeter can be calculated. The benefit of using the Hermite spline-based method is that it can achieve G² continuity on most control points and can obtain the exact area, whereas the resulting perimeter is approximate. In a numerical experiment for analytically defined curves, more accurate computation of the area and perimeter was achieved with a smaller number of control points. In another experiment using a digital elevation model data, the reconstructed contours were smoother than those by a conventional method.     

基于改进三次样条插值的探空资料质控研究

由于L波段探空资料存在缺测及稀疏、零散的数据,造成信息量在时空分布上的不均匀性。考虑到参与插补计算的权重因子个数和插补半径对探空观测数据影响较大,在三次样条插值基础上将插补半径和参与计算权重因子个数作为约束条件引入算法中,以被插值点±40 gpm为插值半径,取有效因子个数≥3个,提出了改进的三次样条插补算法。通过交叉验证分时段对插补结果进行检验评估,气温AE在±0.1℃之间,RMSE值小于0.08;相对湿度AE在-1.0%～+0.7%之间,RMSE值小于0.3;风速数据AE在±0.6 m/s之间,RMSE值小于0.2,表明改进三次样条插补算法对探空资料的质控效果在时间和空间上一致性较好。在晴空条件下相对湿度的插补效果优于有降水天气,气温和风速的插补效果不受晴空条件和降水条件的影响。     

精密卫星钟差的内插方法研究

分析了几种精密卫星钟差的内插方法,将插值结果和IGS提供的数据相比较,采用统计量和差值图表来显示不同方法的插值结果,得到0.11～0.38 ns的精度.结果表明,内插方案的最佳选择取决于不同卫星钟类型的钟差变化特性以及插值方法本身的特点.     

Identification of groundwater drought prone zones in Pedda vagu and Ookachetti vagu watersheds,tributaries of the Krishna River,India

The Pedda vagu and Ookachetti vagu watersheds located in the semi-arid regions of Mahabubnagar district are highly dependent on groundwater for irrigation owing to unreliable rainfall and over extraction of groundwater. The present study has been conducted to identify spatio-temporal groundwater droughts and drought-prone zones. Temporal groundwater droughts have been determined using a standardized water-level index along with spatial groundwater droughts using spline interpolation in Geographic Information Systems. The study shows that the groundwater droughts varied among the stations during the observation period, i.e. 1998–2011. However, the spatial assessment shows that the region as such experienced more mild groundwater droughts except during severe meteorological drought years (1998, 2002, 2004 and 2008); this indicates that the region has good scope for groundwater exploitation during dry spells and initial stages of droughts. Therefore, it is critical to have plans for the development of groundwater to cope with drought.     

How does carbon dioxide emission change with the economic development? Statistical experiences from 132 countries

Issues concerning what measures should be adopted to achieve a sustainable world with less carbon dioxide emission and in what magnitude should we reduce our emission have been on agenda in both international negotiations and countries’ policy making aimed at coping with potential global climate change. These issues cannot be easily addressed unless comprehensive understanding about the countries’ status quo as well as historical relationship between economic development and carbon dioxide emission are gained. In this paper, we examine the historical relationship between economic development and carbon dioxide emission; the ex ante restrictions on function forms and the poorly handled robustness issues rife in economics literature are synthetically addressed. Evidence from recent four decades indicates that per capita carbon dioxide emission first significantly and monotonously increase at low income level and flattens after per capita income reaches at about 22,000 $ (2005 constant price). We perform various robustness checks by employing different data sources, different model specifications and different econometric estimates. The captured development–emission relationship is robust. Our empirical results indicate factors such as urbanization, population density, trade, energy mix and economic environment impact the absolute level of carbon dioxide emission not the overall income elasticity structure of carbon dioxide emission.     

基于样条小波和Gabor小波的边缘检测

提供了对图像边缘的两步检测法.先利用样条小波变换模极大值法对图像进行处理,接着利用Otsu的阀值法把模值分为边缘点,非边缘点和待选边缘点.对待选边缘点进行Gabor小波分解,再对其系数进行单阀值处理,就可得到不同尺度下较精确的图像边缘.用小波变换对图像进行边缘检测可以很好地抑制噪声,但其缺点是边缘存在不连续的现象.提供的方法保留了小波变换的优点又进一步提高了检测的精确度和图像边缘的连续性.     

四种精密卫星钟差插值方法的比较

利用四种插值方法加密IGS网站下载的15 min和30 s卫星钟钟差改正,分别与IGS网站下载的30 s钟差数据以及CODE网站下载的5s钟差数据比较,试验表明,两种加密情况下宜选用线性分段插值。     

几种确定似大地水准面方法比较

利用GPS点水准联测数据,通过曲面拟合的方法得到高程异常值;重点探讨了在同一组数据下分别采用二次曲面、多面函数、神经网络和样条函数等拟合方法;通过实例验证这些方法的可行性,同时对各种方法的精度进行了比较。     

格林样条插值算法及其应用

新近发展起来了一种基于双调和算子格林函数计算的数据插值方法——格林样条插值法,这是用中心点位于各观测数据点的多个格林函数进行加权叠加而解析地计算出插值曲面(曲线)的全局插值方法.本文介绍了该方法的基本原理、插值方法和实用程序的发展概况及使用中可能出现的问题.利用格林样条插值法和另两种常用插值法处理了某地布格重力异常的实测数据,对比插值结果说明,格林样条法在抑制虚假异常、稳定显示局部异常和消除奇异边缘效应等方面,具有一定的优越性.