福建省不同景观资源分布特征的比较分析

采用最近邻点距离法，对福建省省级以上风景名胜区、自然保护区及森林公园空间分布特征进行研究，同时对3种景观资源的号源现状及特征进行了比较。研究表明，福建省总体景观资源空间分布为显著的聚集分布，其中风景名胜区、森林公园及自然保护区等3种景观资源均为随机分布，3种景观资源的景源特征差异比较大，建议在案观较稀疏的区域增加新的景区，通过各种廊道连接构成全省景观网络系统，以保证全省景观资源系统的健康有序发展。     

两种基于灰度位图的缩放技术之对比研究

在计算机数字图像处理过程中为满足不同的计算需要,要对图像进行不同的变换,其中一个很重要也是经常需要的变换就是对图像进行压缩与放大。对常用的两种位图的缩放技术"最近邻域内插法"和"双线性内插法"进行了较详细的验证与推导,并通过实验对比,寻找出两种方法之间的差距和优劣。实验结果表明"双线性内插法"不仅方法简单,计算量小,较适合在位图的缩放处理中使用。     

几种常用文本分类算法性能比较与分析

分析了几种典型的文本分类算法的特点,并基于中文文本数据集和英文文本数据集对算法性能进行了综合评价.实验结果表明:对于英文文本数据,支持向量机具有最优的性能,但时间开销最大,贝叶斯算法速度较快;对于中文文本数据,由于分词的困难,使得算法性能普遍低于同等规模下在英文数据集上的性能.几种算法性能均随训练集规模的增大而有改善.     

平分最近点算法与Fisher判别分类算法的关系

在线性可分情况下,对平分最近点算法和Fisher判别法构造的判别函数进行了对比研究,得出两类模式在特定的分布和一定的条件下,两种算法是等价的。     

基于Voronoi cell的RNN_k近似查询与计算

在空间数据索引与查询研究领域中,反向k最近邻(RNNk)问题作为反向最近邻问题的泛化扩展近来受到更多关注.所谓RNNk查询就是找到所有以给定查询点为k个最近邻之一的对象点.为了有效地进行RNNk查询,利用分级的Voronoi cell和空间区域划分方法对查询结果进行有效过滤,避免了过多次最近邻查找计算.在初步得到的RNNk结果中,有针对性地分别利用平行于分割线的扫描线和局部扩展的查询区域Q进一步限定了RNN候选点.近似最小平均距离(AMAD)计算则可由近似的RNNk查询结果得到且不受k取值限制.实验结果表明了在3种不同数据分布情况下,本文算法与近似方法的效率和有效性.因此,通过充分利用对数据的过滤与查询空间修剪的近似方法,得到了具有较高查全率和准确率的近似查询和计算.     

石羊河流域居民地空间分布类型研究

本文采用最近邻点指数计算方法,运用G IS空间分析技术,通过对石羊河流域居民地分布类型的研究,划分了适合于干旱区内陆河流域的居民地空间分布的5种类型,并对该流域居民地分布类型的空间格局进行分析,揭示其一般规律。     

Path analysis of spatial predictors of front-yard landscape in an anthropogenic environment

Contagious spatial patterns were shown to exist in the landscape of front-yards in street sections of Hochelaga-Maisonneuve, Montréal. Neighbour mimicry was hypothesized as the mechanism behind this pattern (Zmyslony and Gagnon 1998). To assess the role of spatial environmental factors in structuring this pattern, we carried out a path analysis on the front-yard landscape with five spatial factors: relative distance, street side, width, depth and type of front-yard. We removed all non-significant factors from our model with simple Mantel tests and untangled the common spatial component from the relationship between spatial factors and front-yard landscape with partial Mantel tests. We then used path analysis to evaluate the relative importance of all significant spatial factors in structuring front-yard landscape and to determine the r ² (% of landscape variation explained by spatial factors). Results showed that (1) among all spatial environmental factors, distance (proximity) remained the best predictor of front-yard vegetation – distance alone explained an average of 20% of the landscape variation of a street section, (2) depth, width and type of front-yard also structured the front-yard landscape independently of distance, (3) front-yard landscape expresses greater similarity within the same side of a street section, and (4) in two street sections of Hochelaga-Maisonneuve, spatial factors predicted over 40% of the landscape variation. This suggests (1) that landscape contagion exists also in highly humanized environments and (2) that the mimicry phenomenon was induced not only by proximity, but also by similar environmental conditions in same side street sections and whole street sections. Finally, we suggest that street sections are a very useful and appropriate unit of analysis of urban ecosystems.     

Environmental similarity is more important than distance in the community structuring processes of ammonia-oxidizing archaea in agricultural soils

Ammonia-oxidizing archaea(AOA) are important in converting ammonia into nitrate in soils. While many aspects of their community structure have been studied, the relative importance of stochastic versus deterministic processes has poorly been understood. We compared AOA communities across the North China Plain, targeting the amoA gene. A phylogenetic null modelling approach was used to calculate the beta nearest taxon index to quantify the influence of stochastic and deterministic processes. We f...