In order to objectively and reasonably evaluate the actual and potential value of cultivated land, both social and ecological values are introduced into the classification and grading index system of cultivated land b...In order to objectively and reasonably evaluate the actual and potential value of cultivated land, both social and ecological values are introduced into the classification and grading index system of cultivated land based on the viewpoint of sustainable development, after considering the natural and economic values of cultivated land. Index system construction of the sustainable utilization of cultivated land should follow the principles of economic viability, social acceptability, and ecological protection. Classification of cultivated land should take into account the soil fertility of cultivated land. Then, grading of cultivated land is carried out from the practical productivity (or potential productivity) of cultivated land. According to the existing classification index system of cultivated land, the soil, natural and environmental factors in plains, mountains and hills are mainly modified in the classification index system of cultivated land. And index systems for the cultivated land classification in plains, mountains and hills are set up. The grading index system of cultivated land is established based on the economic viability (economic value), social acceptability (social value) and protection of cultivated land (ecological value). Quantitative expression of cultivated land grading index is also carried out.展开更多
In this paper,the superposition rule of the residence time distribution functions for the general systemhaving multiple inlet and outlet streams has been described and proved rigorously.For the cascade ves-sels system...In this paper,the superposition rule of the residence time distribution functions for the general systemhaving multiple inlet and outlet streams has been described and proved rigorously.For the cascade ves-sels system where the processed material in separate stages may be nonideally mixed in various degrees andthe volumes of separate stages may not be equal,the overall residence time distribution function E(t)and eachE(t)of the flow systems have been derived.The applications of these results to various flow systems havebeen discussed.展开更多
基金Supported by the Key Project of Chinese Ministry of Education ( 108098)the National Natural Science Foundation of China ( 40671078,40771088)the Dangui Plan of Huazhong Normal University
文摘In order to objectively and reasonably evaluate the actual and potential value of cultivated land, both social and ecological values are introduced into the classification and grading index system of cultivated land based on the viewpoint of sustainable development, after considering the natural and economic values of cultivated land. Index system construction of the sustainable utilization of cultivated land should follow the principles of economic viability, social acceptability, and ecological protection. Classification of cultivated land should take into account the soil fertility of cultivated land. Then, grading of cultivated land is carried out from the practical productivity (or potential productivity) of cultivated land. According to the existing classification index system of cultivated land, the soil, natural and environmental factors in plains, mountains and hills are mainly modified in the classification index system of cultivated land. And index systems for the cultivated land classification in plains, mountains and hills are set up. The grading index system of cultivated land is established based on the economic viability (economic value), social acceptability (social value) and protection of cultivated land (ecological value). Quantitative expression of cultivated land grading index is also carried out.
文摘In this paper,the superposition rule of the residence time distribution functions for the general systemhaving multiple inlet and outlet streams has been described and proved rigorously.For the cascade ves-sels system where the processed material in separate stages may be nonideally mixed in various degrees andthe volumes of separate stages may not be equal,the overall residence time distribution function E(t)and eachE(t)of the flow systems have been derived.The applications of these results to various flow systems havebeen discussed.
