The logarithmic model is often used to describe the relationships between factors.It often gives good statistical characteristics.Yet,in the process of modeling of soil and water conservation,we find out that this“g...The logarithmic model is often used to describe the relationships between factors.It often gives good statistical characteristics.Yet,in the process of modeling of soil and water conservation,we find out that this“good”model cannot guarantee good result.In this paper we make an inquiry into the intrinsic reasons.It is shown that the logarithmic model has the property of enlarging or reducing model errors,and the disadvantages of the logarithmic model are analyzed.展开更多
In this article, a law of iterated logarithm for the maximum likelihood estimator in a random censoring model with incomplete information under certain regular conditions is obtained.
基于2000—2020年我国北方一作区马铃薯的实际数据,探讨碳排放特征、脱钩效应及驱动因素。本文通过IPCC排放因子系数法对马铃薯碳排放量进行测算并分析其排放特征,采用Tapio模型分析北方一作区马铃薯碳排放脱钩特征,并根据LMDI(Logarith...基于2000—2020年我国北方一作区马铃薯的实际数据,探讨碳排放特征、脱钩效应及驱动因素。本文通过IPCC排放因子系数法对马铃薯碳排放量进行测算并分析其排放特征,采用Tapio模型分析北方一作区马铃薯碳排放脱钩特征,并根据LMDI(Logarithmic mean divisia index)模型明确马铃薯碳排放的驱动因素。结果表明:2000—2020年北方一作区马铃薯排放量呈现先上升后下降的趋势,西北地区碳排放量最高,华北地区碳排放量其次,东北地区碳排放量最低,研究时期内碳累积减排3.32×105t。化肥为马铃薯碳排放最主要的碳源,累积碳排放量占比为42.25%;其次是灌溉、农膜、柴油、农药,累计碳排放量占比分别为35.25%、10.34%、9.02%、4.14%。研究期间北方一作区马铃薯脱钩状态主要以强脱钩和弱脱钩为主,表明马铃薯产业的产值呈增长趋势且碳排放处于下降趋势,当存在碳排放增长时,其增速也小于马铃薯产业产值的增速,马铃薯产业与碳排放状况总体上处于良好发展态势。马铃薯生产措施、马铃薯生产效率、马铃薯生产占比因素对马铃薯碳排放具有正向影响,种植业生产产值因素则具有负向影响,总体形成了一种类似于“对冲”的平衡状态。优化水肥管理模式是北方一作区马铃薯重要的碳减排措施,优化种植业生产结构并加大马铃薯低碳化发展将是低碳农业的关键。展开更多
Permanent plots in the montane tropical rain forests in Xishuangbanna, southwest China, were established, and different empirical models, based on observation data of these plots in 1992, were built to model diameter ...Permanent plots in the montane tropical rain forests in Xishuangbanna, southwest China, were established, and different empirical models, based on observation data of these plots in 1992, were built to model diameter frequency distributions. The focus of this study is on predicting accuracy of stem number in the larger diameter classes, which is much more important than that of the smaller trees, from the view of forest management, and must be adequately considered in the modelling and estimate. There exist 3 traditional ways of modelling the diameter frequency distribution: the negative exponential function model, limiting line function model, and Weibull distribution model. In this study, a new model, named as the logarithmic J-shape function, together with the others, was experimented and was found as a more suitable model for modelling works in the tropical forests.展开更多
基金Supported by the Ministry of Educational,China(2003-58)the Research Fund for thr Doctoral Programs of the Ministry of Education,China(2002-173)
文摘The logarithmic model is often used to describe the relationships between factors.It often gives good statistical characteristics.Yet,in the process of modeling of soil and water conservation,we find out that this“good”model cannot guarantee good result.In this paper we make an inquiry into the intrinsic reasons.It is shown that the logarithmic model has the property of enlarging or reducing model errors,and the disadvantages of the logarithmic model are analyzed.
文摘In this article, a law of iterated logarithm for the maximum likelihood estimator in a random censoring model with incomplete information under certain regular conditions is obtained.
文摘基于2000—2020年我国北方一作区马铃薯的实际数据,探讨碳排放特征、脱钩效应及驱动因素。本文通过IPCC排放因子系数法对马铃薯碳排放量进行测算并分析其排放特征,采用Tapio模型分析北方一作区马铃薯碳排放脱钩特征,并根据LMDI(Logarithmic mean divisia index)模型明确马铃薯碳排放的驱动因素。结果表明:2000—2020年北方一作区马铃薯排放量呈现先上升后下降的趋势,西北地区碳排放量最高,华北地区碳排放量其次,东北地区碳排放量最低,研究时期内碳累积减排3.32×105t。化肥为马铃薯碳排放最主要的碳源,累积碳排放量占比为42.25%;其次是灌溉、农膜、柴油、农药,累计碳排放量占比分别为35.25%、10.34%、9.02%、4.14%。研究期间北方一作区马铃薯脱钩状态主要以强脱钩和弱脱钩为主,表明马铃薯产业的产值呈增长趋势且碳排放处于下降趋势,当存在碳排放增长时,其增速也小于马铃薯产业产值的增速,马铃薯产业与碳排放状况总体上处于良好发展态势。马铃薯生产措施、马铃薯生产效率、马铃薯生产占比因素对马铃薯碳排放具有正向影响,种植业生产产值因素则具有负向影响,总体形成了一种类似于“对冲”的平衡状态。优化水肥管理模式是北方一作区马铃薯重要的碳减排措施,优化种植业生产结构并加大马铃薯低碳化发展将是低碳农业的关键。
文摘Permanent plots in the montane tropical rain forests in Xishuangbanna, southwest China, were established, and different empirical models, based on observation data of these plots in 1992, were built to model diameter frequency distributions. The focus of this study is on predicting accuracy of stem number in the larger diameter classes, which is much more important than that of the smaller trees, from the view of forest management, and must be adequately considered in the modelling and estimate. There exist 3 traditional ways of modelling the diameter frequency distribution: the negative exponential function model, limiting line function model, and Weibull distribution model. In this study, a new model, named as the logarithmic J-shape function, together with the others, was experimented and was found as a more suitable model for modelling works in the tropical forests.
