Papers by Keyword: Quadrat Method

Abstract: Quantitative data are essential in characterizing vegetation. Considerable attention has been paid to vegetation sampling techniques. A series of methods have been developed for tree density estimation which utilize spacing distances instead of fixed-area quadrats. In this paper, a new plotless sampling method was proposed which we denominated a Point-centred quadrangle method. With the new method and a conventional distance method (point-centred quarter method), we investigated Larix principis-rupprechtii population in larch forests at Xiaolongmen Forest Station of Donglingshan Mountain, Beijing. Compared the two methods with quadrat method, the distance estimated by the new method needs to multiply by a coefficient for accuracy, and the precision of the new method are not better than the old one. However, this novel method is still usable for tree density estimation and is easy to use in wood engineering and forest survey work.

Abstract: Quantitative data are essential in characterizing vegetation. Considerable attention has been paid to vegetation sampling techniques. A series of methods have been developed for tree density estimation which utilize spacing distances instead of fixed-area quadrats. In this paper, a new plotless sampling method was proposed which we denominated a triangle method. With the new method and a conventional distance method (point-centred quarter method), we investigated Larix principis-rupprechtii population in larch forests at Xiaolongmen Forest Station of Donglingshan Mountain, Beijing. Compared the two methods with quadrat method, not only the accuracy, but also the precision of the new method are better than the old one. The results indicate that the new method is adequate to estimate tree density and easy to use in wood engineering and forest survey work.

Abstract: Particulate reinforced Ti based metal matrix composites (MMCs) were made by in-situ synthesis using vacuum arc re-melting process. The microstructure of the Ti-6Al-4V base alloy and 10 vol.% (TiB+TiC)/Ti-6Al-4V metal matrix composites was examined. The particulate reinforcements were analysed and identified TiB and TiC particles. The particle distribution was analysed using the quadrat method over 1620 quadrats. A homogeneous particle distribution was found to establish in the composites. The experimental distribution of the reinforcements agreed well with the theoretical Poisson distribution. A skew factor, which characterizes the degree of asymmetry of a statistical distribution, of 1.108 was determined for the particle distribution in the material.

Abstract: Equal channel angular extrusion (ECAE) was employed in an attempt to develop nanostructural metal matrix composites with homogenized distribution of reinforcing particles. Zn- Al metal matrix composites reinforced with 5 μm SiC particulates were produced by casting method. A non-uniform distribution of the reinforcing particles was evident in the metal matrix. With repetitive shear deformation imposed via the ECAE process, substantial structural improvement was achieved and the reinforcing particulates were de-clustered into a finely dispersed distribution throughout the metal matrix. The homogeneity of the particle distribution was studied by the Quadrat method and the skew factors were determined. It was found that the skew factors were substantially reduced after 8 extrusion passes, showing the homogeneity of the particle distribution was greatly improved in the composites.