The taper functions of Kozak （1988）, Bi （2000） and Fang et al. （2000） were comparatively analyzed in the present paper to develop a system for calculating the merchantable volume of oaks in the northwestern regi...The taper functions of Kozak （1988）, Bi （2000） and Fang et al. （2000） were comparatively analyzed in the present paper to develop a system for calculating the merchantable volume of oaks in the northwestern region of the state of Chihuahua （Mexico）. Taper data corresponding to 298 trees were collected in mixed and uneven-aged pine-oak stands located throughout the study area, and covering the cxisting range of ages, stand densities and sites. Results show that the compatible segmented model developed by Fang et al. （2000） best described the experimental data and is therefore recommended for estimating tree diameter at a specific height, height to a specific diameter, merchantable volume, and total volume for oaks. The equation developed in this study is a fundamental tool for use in forest surveys in the study region and is simple enough to ensure its operational implementation. The results of the statistical analysis show that the equation can be recommended for other regions, although some local adaptations may be needed.展开更多
A model based on a thermodynamic approach is proposed for predicting the dynamics of communicable epidemics assumed to be governed by controlling eforts of multiple scales so that an entropy is associated with the sys...A model based on a thermodynamic approach is proposed for predicting the dynamics of communicable epidemics assumed to be governed by controlling eforts of multiple scales so that an entropy is associated with the system.All the epidemic details are factored into a single and time-dependent coefcient,the functional form of this coefcient is found through four constraints,including notably the existence of an inflexion point and a maximum.The model is solved to give a log-normal distribution for the spread rate,for which a Shannon entropy can be defined.The only parameter,that characterizes the width of the distribution function,is uniquely determined through maximizing the rate of entropy production.This entropy-based thermodynamic(EBT)model predicts the number of hospitalized cases with a reasonable accuracy for SARS in the year 2003.This EBT model can be of use for potential epidemics such as avian influenza and H7N9 in China.展开更多
基金supported by El Fondo de Cooperación Internacional en Cienciay Tecnología entre la UE-México (project: 92739)
文摘The taper functions of Kozak （1988）, Bi （2000） and Fang et al. （2000） were comparatively analyzed in the present paper to develop a system for calculating the merchantable volume of oaks in the northwestern region of the state of Chihuahua （Mexico）. Taper data corresponding to 298 trees were collected in mixed and uneven-aged pine-oak stands located throughout the study area, and covering the cxisting range of ages, stand densities and sites. Results show that the compatible segmented model developed by Fang et al. （2000） best described the experimental data and is therefore recommended for estimating tree diameter at a specific height, height to a specific diameter, merchantable volume, and total volume for oaks. The equation developed in this study is a fundamental tool for use in forest surveys in the study region and is simple enough to ensure its operational implementation. The results of the statistical analysis show that the equation can be recommended for other regions, although some local adaptations may be needed.
文摘A model based on a thermodynamic approach is proposed for predicting the dynamics of communicable epidemics assumed to be governed by controlling eforts of multiple scales so that an entropy is associated with the system.All the epidemic details are factored into a single and time-dependent coefcient,the functional form of this coefcient is found through four constraints,including notably the existence of an inflexion point and a maximum.The model is solved to give a log-normal distribution for the spread rate,for which a Shannon entropy can be defined.The only parameter,that characterizes the width of the distribution function,is uniquely determined through maximizing the rate of entropy production.This entropy-based thermodynamic(EBT)model predicts the number of hospitalized cases with a reasonable accuracy for SARS in the year 2003.This EBT model can be of use for potential epidemics such as avian influenza and H7N9 in China.
