Based on the survey data of nine primitive broad-leaved Korean pine forest plots ranging from 1 to 10.4 ha in Heilongjiang Province,this study used the moving window method and GIS technology to analyze the variation ...Based on the survey data of nine primitive broad-leaved Korean pine forest plots ranging from 1 to 10.4 ha in Heilongjiang Province,this study used the moving window method and GIS technology to analyze the variation characteristics of the spatial distribution pattern of forest biomass in each plot.We explored the minimum area that can reflect the structural and functional characteristics of the primitive broad-leaved Korean pine forest,and used computer simulation random sampling method to verify the accuracy of the minimum area.The results showed that:(1)Through the analysis of the spatial distribution raster map of biomass deviation in the plots at various scales of 10−100 m,there is a minimum area(0.64 ha)for the critical range of biomass density variation in the primitive broad-leaved Korean pine forest.This minimum area based on biomass density can indirectly reflect the comprehensive characteristics of productivity level per unit area,structure,function,and environmental quality of the primitive broad-leaved Korean pine forest community.(2)Using computer simulation random sampling,it was found that only by sampling in a specific plot larger than or equal to the minimum area can equivalent or similar results be achieved as random sampling within the plot,indicating that the minimum area determined by the moving window method is accurate.(3)The minimum area determined in this paper is an excellent indicator reflecting the complexity of community structure,which can be used for comparing changes in community structure and function before and after external disturbances,and has a good evaluation effect.This minimum area can also be used as a basis for scientific and reasonable setting of plot size in the investigation and monitoring work of broad-leaved Korean pine forests in this region,thereby achieving the goals of improving work efficiency and saving work costs.展开更多
Riparian areas are unique although often small component of the overall watershed landscape. The structure of riparian forests along Erdaobai River on the north slope of Changbai Mountain were investigated by using fi...Riparian areas are unique although often small component of the overall watershed landscape. The structure of riparian forests along Erdaobai River on the north slope of Changbai Mountain were investigated by using field data collected from eight sampling transects perpendicular to the Erdaobai River channel. Two kinds of species-area saturation curves were used to examine the relationship between species number and minimum sampling area. The results showed that riparian gymnosperms accounted for a high proportion of all gymnosperms in the Changbai Mountain Nature Reserve while riparian ferns and angiosperms accounted for a relatively low proportion. The average minimum sampling areas of riparian forest that included 60%, 80%, and 90% of the community species pool were about 85, 185, and 328 m 2 , respectively; while those for nonriparian forest were about 275, 390, and 514 m 2 , correspondingly.展开更多
The problem of determining a minimum-area ellipse through three non-collinear points is discussed in this paper. We give the proof and construction of the minimum-area ellipse through three non-collinear points from t...The problem of determining a minimum-area ellipse through three non-collinear points is discussed in this paper. We give the proof and construction of the minimum-area ellipse through three non-collinear points from the geometric point of view, and present a new method of determining knots. This method replaces the chord length, which is closer to the arc length of the mini- mum-area ellipse with arc length, and avoids the occurrence of ＇oscillation＇ and ＇loops＇. We compare the new method with the uni- form method, chord length method and the centripetal method. The comparison is performed on the quality of cubic spline curves using these methods. In most cases, the result of our method is better than others.展开更多
Impacts of the minimum purchase price policy for grain on the planting area of rice in Hubei Province were analyzed based on a mixed linear model.After the indicator system containing the minimum purchase price policy...Impacts of the minimum purchase price policy for grain on the planting area of rice in Hubei Province were analyzed based on a mixed linear model.After the indicator system containing the minimum purchase price policy and other factors influencing the planting area of rice was constructed,principal component analysis of the system was conducted,and then a mixed linear model where the planting area of rice was as the dependent variable was established.The results show that after the exclusion of the interference from other factors,the minimum purchase price policy for grain had a positive impact on the planting area of rice in Hubei Province.That is,the minimum purchase price policy significantly stimulated the growth of rice planting area in Hubei Province.展开更多
为解决因排查效率低、数据更新不及时等因素导致低压配电网户变关系连接形式与实际不符的问题,提出一种基于角度分段线性近似(anglepiecewiselinearrepresentation,APLR)和改进密度峰值聚类(improved clustering by fast search find of...为解决因排查效率低、数据更新不及时等因素导致低压配电网户变关系连接形式与实际不符的问题,提出一种基于角度分段线性近似(anglepiecewiselinearrepresentation,APLR)和改进密度峰值聚类(improved clustering by fast search find of density peaks,ICFSFDP)相结合的户变关系识别方法。首先,根据电压曲线中相邻线段的角度变化量提取曲线的转折点,利用APLR对曲线进行自适应降维重构;随后,使用ICFSFDP算法对降维数据组展开聚类分析,在决策图中由拟合函数与坐标轴围成面积的最小值得到最优类簇数目,进而得到聚类和非聚类中心用户;最后,使用动态时间弯曲(dynamic time warping,DTW)距离计算聚类和非聚类中心用户之间的距离相似度,进而得到户变关系。将所提方法应用于模拟和真实数据中,均可证实所提方法的有效性。算例分析结果表明:该方法能够对时间间隔不同、不等维的序列进行分析,且不需要人为设定聚类算法的参数,户变关系识别准确率高。展开更多
基金supported by Science and Technology Foundation Project of Ministry of Science and Technology of China(2012FY112000).
文摘Based on the survey data of nine primitive broad-leaved Korean pine forest plots ranging from 1 to 10.4 ha in Heilongjiang Province,this study used the moving window method and GIS technology to analyze the variation characteristics of the spatial distribution pattern of forest biomass in each plot.We explored the minimum area that can reflect the structural and functional characteristics of the primitive broad-leaved Korean pine forest,and used computer simulation random sampling method to verify the accuracy of the minimum area.The results showed that:(1)Through the analysis of the spatial distribution raster map of biomass deviation in the plots at various scales of 10−100 m,there is a minimum area(0.64 ha)for the critical range of biomass density variation in the primitive broad-leaved Korean pine forest.This minimum area based on biomass density can indirectly reflect the comprehensive characteristics of productivity level per unit area,structure,function,and environmental quality of the primitive broad-leaved Korean pine forest community.(2)Using computer simulation random sampling,it was found that only by sampling in a specific plot larger than or equal to the minimum area can equivalent or similar results be achieved as random sampling within the plot,indicating that the minimum area determined by the moving window method is accurate.(3)The minimum area determined in this paper is an excellent indicator reflecting the complexity of community structure,which can be used for comparing changes in community structure and function before and after external disturbances,and has a good evaluation effect.This minimum area can also be used as a basis for scientific and reasonable setting of plot size in the investigation and monitoring work of broad-leaved Korean pine forests in this region,thereby achieving the goals of improving work efficiency and saving work costs.
基金supported by the Ministry of Science and Technology of the People's Republic of China (2006BAD03A09)the Special Fund of State Key Laboratory of Urban and Regional Ecology
文摘Riparian areas are unique although often small component of the overall watershed landscape. The structure of riparian forests along Erdaobai River on the north slope of Changbai Mountain were investigated by using field data collected from eight sampling transects perpendicular to the Erdaobai River channel. Two kinds of species-area saturation curves were used to examine the relationship between species number and minimum sampling area. The results showed that riparian gymnosperms accounted for a high proportion of all gymnosperms in the Changbai Mountain Nature Reserve while riparian ferns and angiosperms accounted for a relatively low proportion. The average minimum sampling areas of riparian forest that included 60%, 80%, and 90% of the community species pool were about 85, 185, and 328 m 2 , respectively; while those for nonriparian forest were about 275, 390, and 514 m 2 , correspondingly.
基金Supported by the National Research Foundation for the Doctoral Program of Higher Education of China(20110131130004)Independent Innovation Foundation of Shandong University,IIFSDU(2012TB013)Ji’nan Science and Technology Development Project(No.201202015)
文摘The problem of determining a minimum-area ellipse through three non-collinear points is discussed in this paper. We give the proof and construction of the minimum-area ellipse through three non-collinear points from the geometric point of view, and present a new method of determining knots. This method replaces the chord length, which is closer to the arc length of the mini- mum-area ellipse with arc length, and avoids the occurrence of ＇oscillation＇ and ＇loops＇. We compare the new method with the uni- form method, chord length method and the centripetal method. The comparison is performed on the quality of cubic spline curves using these methods. In most cases, the result of our method is better than others.
基金Supported by the Humanities and Social Sciences Foundation for Young Scholars of Ministry of Education of China(11y3jc630197)
文摘Impacts of the minimum purchase price policy for grain on the planting area of rice in Hubei Province were analyzed based on a mixed linear model.After the indicator system containing the minimum purchase price policy and other factors influencing the planting area of rice was constructed,principal component analysis of the system was conducted,and then a mixed linear model where the planting area of rice was as the dependent variable was established.The results show that after the exclusion of the interference from other factors,the minimum purchase price policy for grain had a positive impact on the planting area of rice in Hubei Province.That is,the minimum purchase price policy significantly stimulated the growth of rice planting area in Hubei Province.
文摘为解决因排查效率低、数据更新不及时等因素导致低压配电网户变关系连接形式与实际不符的问题,提出一种基于角度分段线性近似(anglepiecewiselinearrepresentation,APLR)和改进密度峰值聚类(improved clustering by fast search find of density peaks,ICFSFDP)相结合的户变关系识别方法。首先,根据电压曲线中相邻线段的角度变化量提取曲线的转折点,利用APLR对曲线进行自适应降维重构;随后,使用ICFSFDP算法对降维数据组展开聚类分析,在决策图中由拟合函数与坐标轴围成面积的最小值得到最优类簇数目,进而得到聚类和非聚类中心用户;最后,使用动态时间弯曲(dynamic time warping,DTW)距离计算聚类和非聚类中心用户之间的距离相似度,进而得到户变关系。将所提方法应用于模拟和真实数据中,均可证实所提方法的有效性。算例分析结果表明:该方法能够对时间间隔不同、不等维的序列进行分析,且不需要人为设定聚类算法的参数,户变关系识别准确率高。
