The environment evolution of Wuliangsuhai wetland since 1986 is analyzed based on the remote sensing principle. The total water area of Wuliangsuhai lake has been increased during the past 17 years. T
The distribution of soil organic matter (SOM) and nitrogen on Gongga Mountain was studied in this paper. The results showed that the content of SOM and nitrogen (N) of A horizon had an ascending trend
A detailed record of sea level changes during the last 2500 years is preserved in the northernwest coast of Fildes Peninsula in Antarctica. Fourteen marine alga layers were deposited in the beach with
本文介绍了一种利用AutoLISP语言来实现表面粗糙度代号标注的基本原理、具体方法。采用这种方法,可以有效提高机械图样的绘图效率。
针对由独立同分布误差膨胀而成的独立不等精度误差,根据未知参数的M估计的Ba hadur型线性表达式,本文导出了由观测量、残差向量、参数估计量和观测量平差向量组成的基本向量的Bahadur型表达式。进一步地,根据方差传播定律导出了M估计的基本向量的渐近方差 协方差矩阵,该矩阵由3个多余参数决定,第三多余参数由本文定义。对Lq范估计, 收稿日期:2003 06 03;修回日期:2004 05 12基
Direction is a common spatial concept that is used in our daily life. It is frequently used as a selection condition in spatial queries. As a result, it is important for spatial databases to provide a
美国Autodest公司推出的AutoCAD图形软件包是通用的图形支撑软件,使用面广、通用性强。现以AutoCAD2002为基础,就本人在使用过程中的所得与大家分享,希能对提高绘图速度有所帮助。 1 建立标准样板图 AutoCAD用户都知道,在AutoCAD的缺省绘图环境中,缺省图层为0层,线形为细实线。我们在绘图时,每次都要逐一创建图层、线形及相应的颜色,在绘完1个图形,新建1个文件再绘另一张图