Analysis of forest canopy hemisphere images is one of the most important methods for measuring forest canopy structure parameters. In this study, our main focus was on using circular image region segmentation, which i...Analysis of forest canopy hemisphere images is one of the most important methods for measuring forest canopy structure parameters. In this study, our main focus was on using circular image region segmentation, which is the basis of forest canopy hemispherical photography. The boundary of a forest canopy hemisphere image was analyzed via histogram, rectangle, and Fourier descriptors. The image boundary characteristics were defined and obtained based on the following：（1） an edge model that contains three parts, i.e., step, ramp, and roof;（2） boundary points of discontinuity;（3） an edge that has a linear distribution of scattering points. On this basis, we proposed a segmentation method for the circular region in a forest canopy hemisphere image, fitting the circular boundary and computing the center and radius by the least squares method. The method was unrelated to the parameters of the image acquisition device. Hence, this study lays a foundation for automatically adjusting the parameters of high-performance image acquisition devices used in forest canopy hemispherical photography.展开更多
By using the generalized PoincarE index theorem it is proved that if the n2 critical points of an n-polynomial system form a configuration of type (2n -1) - (2n - 3) +(2n- 5) -…+ (- 1 )n- 1, and the 2n -1 outmost ant...By using the generalized PoincarE index theorem it is proved that if the n2 critical points of an n-polynomial system form a configuration of type (2n -1) - (2n - 3) +(2n- 5) -…+ (- 1 )n- 1, and the 2n -1 outmost anti-saddles form the venices of a convex (2n -1)-polygon, then among these 2n-1 anti-saddles at least one must be a node.展开更多
基金Project supported by the Fundamental Research Funds for the Central Universities,China（No.2572014BB04） the National Natural Science Foundation of China（No.31370710） the Specialized Research Fund for the Doctoral Program of Higher Education of China（No.20110062110002）
文摘Analysis of forest canopy hemisphere images is one of the most important methods for measuring forest canopy structure parameters. In this study, our main focus was on using circular image region segmentation, which is the basis of forest canopy hemispherical photography. The boundary of a forest canopy hemisphere image was analyzed via histogram, rectangle, and Fourier descriptors. The image boundary characteristics were defined and obtained based on the following：（1） an edge model that contains three parts, i.e., step, ramp, and roof;（2） boundary points of discontinuity;（3） an edge that has a linear distribution of scattering points. On this basis, we proposed a segmentation method for the circular region in a forest canopy hemisphere image, fitting the circular boundary and computing the center and radius by the least squares method. The method was unrelated to the parameters of the image acquisition device. Hence, this study lays a foundation for automatically adjusting the parameters of high-performance image acquisition devices used in forest canopy hemispherical photography.
文摘By using the generalized PoincarE index theorem it is proved that if the n2 critical points of an n-polynomial system form a configuration of type (2n -1) - (2n - 3) +(2n- 5) -…+ (- 1 )n- 1, and the 2n -1 outmost anti-saddles form the venices of a convex (2n -1)-polygon, then among these 2n-1 anti-saddles at least one must be a node.
