As an S-shaped curve,the logistic curve has both high and low limit,which provides advantages in modelling the influences of environmental factors on biogeological processes.However,although the logistic curve and its...As an S-shaped curve,the logistic curve has both high and low limit,which provides advantages in modelling the influences of environmental factors on biogeological processes.However,although the logistic curve and its transformations have drawn much attention in theoretical modelling,it is often used as a classification method to determine a true or false condition,and is less often applied in simulating the real data set.Starting from the basic theory of the logistic curve,with observed data sets,this paper explored the new application scenarios such as modelling the time series of environmental factors,modelling the influence of environmental factors on biogeological processes and modelling the theoretical curve in ecology area.By comparing the performance of traditional model and the logistic model,the results indicated that logistic modelling worked as well as traditional equations.Under certain conditions,such as modelling the influence of temperature on ecosystem respiration,the logistic model is more realistic than the widely applied Lloyd-Taylor formulation under extreme conditions.These cases confirmed that the logistic curve was capable of simulating nonlinear influences of multiple factors on biogeological processes such as carbon dynamic.展开更多
In the study of complex networks almost all theoretical models have the property of infinite growth, but the size of actual networks is finite. According to statistics from the China Internet IPv4 （Internet Protocol ...In the study of complex networks almost all theoretical models have the property of infinite growth, but the size of actual networks is finite. According to statistics from the China Internet IPv4 （Internet Protocol version 4） addresses, this paper proposes a forecasting model by using S curve （logistic curve）. The growing trend of IPv4 addresses in China is forecasted. There are some reference values for optimizing the distribution of IPv4 address resource and the development of IPv6. Based on the laws of IPv4 growth, that is, the bulk growth and the finitely growing limit, it proposes a finite network model with a bulk growth. The model is said to be an S-curve network. Analysis demonstrates that the analytic method based on uniform distributions （i.e., Barabasi-Albert method） is not suitable for the network. It develops an approximate method to predict the growth dynamics of the individual nodes, and uses this to calculate analytically the degree distribution and the scaling exponents. The analytical result agrees with the simulation well, obeying an approximately power-law form. This method can overcome a shortcoming of Barabasi-Albert method commonly used in current network research.展开更多
The values of non-marketable forest products have largely been ignored, which made the conservation of the natural resources increasingly more economically difficult. Based on the previous studies, compensation subsid...The values of non-marketable forest products have largely been ignored, which made the conservation of the natural resources increasingly more economically difficult. Based on the previous studies, compensation subsidy for the values of non-marketable forest products was computed with a method of compensation coefficient that combines the Engel Coefficient and Logistic Curve. The method was applied in Changbai Mountain area. The total value of the compensation subsidy in 1999 was supposed to 637.93 Yuan·hm-2, of which 70% would be paid directly to the local stakeholders and is much higher than the compensation subsidy previously computed (75Yuan·hm-2·year-1). It is currently impossible for the central government to bear all the costs and investment of natural forest protection. A practical solution is that the local government should invest in forest and put the compensation subsidy into the current revenue.展开更多
基金This study was jointly funded by the National Key Research and Development Program of China(2016YFE0109600)China Geological Survey projects(1212010611402,DD20189503).
文摘As an S-shaped curve,the logistic curve has both high and low limit,which provides advantages in modelling the influences of environmental factors on biogeological processes.However,although the logistic curve and its transformations have drawn much attention in theoretical modelling,it is often used as a classification method to determine a true or false condition,and is less often applied in simulating the real data set.Starting from the basic theory of the logistic curve,with observed data sets,this paper explored the new application scenarios such as modelling the time series of environmental factors,modelling the influence of environmental factors on biogeological processes and modelling the theoretical curve in ecology area.By comparing the performance of traditional model and the logistic model,the results indicated that logistic modelling worked as well as traditional equations.Under certain conditions,such as modelling the influence of temperature on ecosystem respiration,the logistic model is more realistic than the widely applied Lloyd-Taylor formulation under extreme conditions.These cases confirmed that the logistic curve was capable of simulating nonlinear influences of multiple factors on biogeological processes such as carbon dynamic.
基金Project supported by the National Natural Science Foundation of China (Grant No. 70871082)the Shanghai Leading Academic Discipline Project (Grant No. S30504)
文摘In the study of complex networks almost all theoretical models have the property of infinite growth, but the size of actual networks is finite. According to statistics from the China Internet IPv4 （Internet Protocol version 4） addresses, this paper proposes a forecasting model by using S curve （logistic curve）. The growing trend of IPv4 addresses in China is forecasted. There are some reference values for optimizing the distribution of IPv4 address resource and the development of IPv6. Based on the laws of IPv4 growth, that is, the bulk growth and the finitely growing limit, it proposes a finite network model with a bulk growth. The model is said to be an S-curve network. Analysis demonstrates that the analytic method based on uniform distributions （i.e., Barabasi-Albert method） is not suitable for the network. It develops an approximate method to predict the growth dynamics of the individual nodes, and uses this to calculate analytically the degree distribution and the scaling exponents. The analytical result agrees with the simulation well, obeying an approximately power-law form. This method can overcome a shortcoming of Barabasi-Albert method commonly used in current network research.
文摘The values of non-marketable forest products have largely been ignored, which made the conservation of the natural resources increasingly more economically difficult. Based on the previous studies, compensation subsidy for the values of non-marketable forest products was computed with a method of compensation coefficient that combines the Engel Coefficient and Logistic Curve. The method was applied in Changbai Mountain area. The total value of the compensation subsidy in 1999 was supposed to 637.93 Yuan·hm-2, of which 70% would be paid directly to the local stakeholders and is much higher than the compensation subsidy previously computed (75Yuan·hm-2·year-1). It is currently impossible for the central government to bear all the costs and investment of natural forest protection. A practical solution is that the local government should invest in forest and put the compensation subsidy into the current revenue.
