基于边优先的任意多边形最优三角剖分   总被引：1，自引：0，他引：1  

翟仁健  武芳  薛本新 《测绘科学》2008,33(1):122-125

针对现有多边形三角剖分算法不能同时兼顾算法的简单有效性、适用性以及剖分三角网质量的问题,提出一种基于边优先的任意多边形最优化三角剖分算法:首先直接对多边形的边进行构网,最后再对生成的非约束边进行构网,最终完成整个多边形的三角剖分。剖分得到的三角网为约束Delaunay三角网,网形稳定、最优,算法简单,执行效率较高,且适用于任意复杂多边形。实验证明了该算法的合理性和有效性,较好地解决了现有多边形三角剖分算法存在的问题。  相似文献   

顾及地貌特征的矿区地表塌陷DEM的生成方法   总被引：2，自引：0，他引：2  

王京卫  王倩  李法理  马东岭 《测绘科学》2008,33(2):127-129,136

地下煤炭资源开采导致矿区地表塌陷和矿区地形的变化,直接由开采沉陷下沉预计数据生成的DEM不能表现矿区地表塌陷后的地形状况。通过在开采沉陷下沉预计程序中增加高程修正计算功能,对矿区原始地貌高程进行下沉修正计算,生成矿区地表塌陷高程数据文件,由该数据文件可以生成顾及地貌特征的矿区地表塌陷DEM。该方法操作和实现简单,生成的DEM精度可靠,能够表现矿区地表塌陷后的地形状况,可以作为矿区地理信息系统的基础数据,对于指导开采沉陷的防治和治理具有重要意义。  相似文献   

基于矿物学方法评价浙江省土壤中Pb污染状况     

郑喜珅  鲁安怀  汪庆华  郑佳  朱朝晖  于芳 《地质科技情报》2008,27(3):77-82

利用土壤重金属元素环境质量矿物学评价方法,对淅江省全境土壤中不同土壤类型(或亚类)表层、不同母质表层和剖面中的Pb进行环境质量评价的结果表明,土壤中Pb的实测量和土壤对Pb的固持量决定了土壤中Pb的环境质量,浙江省土壤中Pb的污染度有正负值,说明土壤中的Pb对有些地区产生了污染,而对有些地区则没有产生污染.研究结果揭示,土壤矿物对Pb具有一定的固定与容纳能力,超过其固定与容纳能力,土壤中的Pb会对环境造成污染.这一旨在揭示土壤中重金属元素与各种矿物之间环境平衡关系的方法,可为评价土壤环境质量提供科学依据和技术支撑.  相似文献   

Benthic nutrient fluxes in the intertidal flat within the Changjiang （Yangtze River） Estuary   总被引：1，自引：0，他引：1  

GAO Lei    LI Daoji  WANG Yanming  YU Lihua  KONG Dingjiang  LI Mei  LI Yun  and FANG Tao State Key Laboratory of Marine Geology  Tongji University  Shanghai  China State Key Laboratory of Estuarine  Coastal Research  East China Normal University  Shanghai  China 《中国地球化学学报》2008,27(1):58-71

In an annual cycle from March 2005 to February 2006, benthic nutrient fluxes were measured monthly in the Dongtan intertidal flat within the Changjiang （Yangtze River） Estuary. Except for NH4^＋, there always showed high fluxes from overlying water into sediment for other four nutrients. Sediments in the high and middle marshes, covered with halophyte and consisting of macrofauna, demonstrated more capabilities of assimilating nutrients from overlying water than the low marsh. Sampling seasons and nutrient concentrations in the overlying water could both exert significant effects on these fluxes. Additionally, according to the model provided by previous study, denitrification rates, that utilizing NO3- transported from overlying water （Dw） in Dongtan sediments, were estimated to be from -16 to 193 μmol·h^-1·m^-2 with an average value of 63 μmol·h^-1·m^-2 （n=18）. These estimated values are still underestimates of the in-situ rates owing to the lack of consideration of DN, i.e., denitrification supported by the local NO3^- production via nitrification.  相似文献   

Changes in nutrient uptake of phytoplankton under the interaction between sunlight and phosphate in the Changjiang （Yangtze） River Estuary     

FANG Tao LI Daoji YU Lihua LI Yun 《中国地球化学学报》2008,27(2):161-170

We conducted ship-board incubation experiments to investigate changes in nutrient uptake of phytoplankton under different phosphate concentrations and irradiances in the Changjiang River Estuary and its adjacent waters in China. Under 100% natural irradiance the uptake rates of phosphate, silicate, and nitrate were accelerated at high phosphate levels （1.84 μM）, while under low irradiance （about 50% natural irradiance） their uptake rates were restrained at the high but stimulated greatly at the intermediate phosphate concentrations （1.26 μM）, as the growth of phytoplankton, changes in nitrite and ammonium uptake didn＇t follow an obvious pattern. Our results also showed that there were linear relationships between nitrate, silicate and phosphate uptake at different phosphate concentrations under low and high irradiances, and the growth period of phytoplankton was prolonged both at the high phosphate concentrations under high irradiance and at the intermediate concentrations under low irradiance, suggesting that the limitation of phytoplankton growth mainly reflected changes in its growth period, and because no such environment （low irradiance and low phosphate concentrations） actually existed in a high turbidity zone, phytoplankton blooms hardly occurred there. In the absence of irradiance, denitrification occurred readily and phytoplankton was kept decreasing, which resulted in phosphate regeneration.  相似文献   

层次分析法在生态环境综合评价应用中的优化     

郭谦 《国土资源遥感》2008,19(3):104-107

层次分析法（Analytical Hierarchy Process,AHP）,是一种常用的系统分析与决策方法,但在应用于青藏高原区域生态环境综合评价时,由于因素的权重值只能为正数,影响了表达效果。为此,本文对其进行了优化,改进了构造判断矩阵时的赋值方法,在评价过程中引入了负数。实验证明,优化后的方法能准确地评价青藏高原的生态环境。  相似文献   

区域似大地水准面确定的最小二乘支持向量机方法     

范千  张宁 《测绘工程》2008,17(5)

支持向量机(SVM)是近年来发展起来的机器学习的新方法,它较好地解决小样本、非线性、高维数、局部极小点等实际问题.文中研究支持向量机的拓展算法--最小二乘支持向量机(LSSVM),并将其应用于确定大面积复杂似大地水准面.通过工程实例并与神经网络模型和二次曲面多项式拟合模型相比较,验证确定区域似大地水准面的LSSVM方法的有效性.  相似文献   

天宝GEOXT数据采集模式及精度研究     

谢宏全  周立  马迁  吴少辉 《测绘工程》2008,17(4):1-3

随着经济的不断发展,移动GIS越来越受到人们的关注,而GEOXT的出现正是符合这一发展趋势的产物。GEOXT这一款仪器将GPS与GIS结合在一起,利用GPS技术得出GIS的成果。文中在说明天宝GEOXT数据采集系统配置及特点的基础上,通过实验总结了数据采集的3种模式：单机码相位测距、后差分改正和实时差分改正数据采集,并对数据采集的技术流程、点位精度、特点和应用范围进行了阐述。最后对不同采集时间间隔对精度的影响进行了试验研究。  相似文献   

Automated Target Detection and Discrimination Using Constrained Kurtosis Maximization   总被引：1，自引：0，他引：1  

Qian Du Kopriva  I. 《Geoscience and Remote Sensing Letters, IEEE》2008,5(1):38-42

Exploiting hyperspectral imagery without prior information is a challenge. Under this circumstance, unsupervised target detection becomes an anomaly detection problem. We propose an effective algorithm for target detection and discrimination based on the normalized fourth central moment named kurtosis, which can measure the flatness of a distribution. Small targets in hyperspectral imagery contribute to the tail of a distribution, thus making it heavier. The Gaussian distribution is completely determined by the first two order statistics and has zero kurtosis. Consequently, kurtosis measures the deviation of a distribution from the background and is suitable for anomaly/target detection. When imposing appropriate inequality constraints on the kurtosis to be maximized, the resulting constrained kurtosis maximization (CKM) algorithm will be able to quickly detect small targets with several projections. Compared to the widely used unconstrained kurtosis maximization algorithm, i.e., fast independent component analysis, the CKM algorithm may detect small targets with fewer projections and yield a slightly higher detection rate.  相似文献   

石笋流体包裹体中的惰性气体及其在重建长江中游古温度变化中的作用   总被引：2，自引：0，他引：2  

方念乔  胡超涌 《地学前缘》2008,15(4):132-137

文中讨论了一种评估古气温变化的新方法。我们成功地利用石笋流体包裹体所捕获的Xe/Ar比值,重建了末次冰盛期以来盛行东亚季风的长江中游地区的气候演化。一种表达成ln(CXe/CAr)的对数式被证明与冷暖周期变化具有密切的关系。从研究的石笋中所提出的δ13C与Mg/Ca曲线一般随区域古气温波动而变化,但不能排除其中有另类气候信号的叠加。我们的工作则明确地指出,流体包裹体所记录的Xe/Ar在各种反映温度变化的替代指标中可能是最好的一种。整体而言,ln(CXe/CAr)曲线与那些基本随暖期和冷期振荡的曲线保持一致。将稀有气体曲线与δ13C和Mg/Ca信号整合对比之后,我们在研究区划分出末次冰盛期以来8组暖/冷旋回。整合后的气温变化模式合理地解释了过去20000年里的区域环境变化。  相似文献