Condensation technique of degree of freedom is first proposed to improve the computational efficiency of meshfree method with Galerkin weak form for elastic dy- namic analysis. In the present method, scattered nodes w...Condensation technique of degree of freedom is first proposed to improve the computational efficiency of meshfree method with Galerkin weak form for elastic dy- namic analysis. In the present method, scattered nodes with- out connectivity are divided into several subsets by cells with arbitrary shape. Local discrete equation is established over each cell by using moving Kriging interpolation, in which the nodes that located in the cell are used for approxima- tion. Then local discrete equations can be simplified by con- densation of degree of freedom, which transfers equations of inner nodes to equations of boundary nodes based on cells. The global dynamic system equations are obtained by as- sembling all local discrete equations and are solved by using the standard implicit Newmark＇s time integration scheme. In the scheme of present method, the calculation of each cell is carried out by meshfree method, and local search is imple- mented in interpolation. Numerical examples show that the present method has high computational efficiency and good accuracy in solving elastic dynamic problems.展开更多
To more accurately answer the questions “who will feed China?” and “whether Chinese people can feed themselves?”, we proposed a concept of agricultural support capacity, defined as the population that can be fed b...To more accurately answer the questions “who will feed China?” and “whether Chinese people can feed themselves?”, we proposed a concept of agricultural support capacity, defined as the population that can be fed by energy, protein and fat from food, respectively, according to nutritional intake standards. In this study, we established models to measure this, based on analysis of China’s agricultural support capacity and how this changes under self-sufficiency and open conditions, in addition to the degrees of external dependence. Our results show that, since 2007, even without foreign resources, the energy, protein, superior protein and fat obtained from domestic agriculture had been able to feed the Chinese. However, the use of foreign resources increased and strengthened China’s agricultural support capacity, in addition to improving food diversity, optimizing nutrition, assisting in the regulation of food surplus and deficiency, and providing feed for the animal breeding industry. For the past decade, China’s degree of external dependence on energy from cereals has been relatively low, however, the degrees external dependence on superior protein and fat has increased steadily at a certain rate and have been over the national food security warning level. Therefore, China still has great demand for agricultural products from other regions of the world.展开更多
This paper considers a class of ratio-dependent Holling-Taner model with infinite delay and prey harvest, which is of periodic coefficients. By means of the coincidence degree theory, a set of sufficient conditions fo...This paper considers a class of ratio-dependent Holling-Taner model with infinite delay and prey harvest, which is of periodic coefficients. By means of the coincidence degree theory, a set of sufficient conditions for the existence of at least two positive periodic solutions of this model is established.展开更多
A delayed semi-ratio-dependent predator-prey system in a periodic environment is investigated in this paper.By using a continuation theorem based on Gaines and Mawhin's coincidence degree,the global existence of p...A delayed semi-ratio-dependent predator-prey system in a periodic environment is investigated in this paper.By using a continuation theorem based on Gaines and Mawhin's coincidence degree,the global existence of positive periodic solution is studied.A set of easily verifiable sufficient conditions are obtained.展开更多
We study a non-autonomous ratio-dependent predator-prey model with exploited terms. This model is of periodic coefficients, which incorporates the periodicity of the varying environment. By means of the coincidence de...We study a non-autonomous ratio-dependent predator-prey model with exploited terms. This model is of periodic coefficients, which incorporates the periodicity of the varying environment. By means of the coincidence degree theory, we establish sufficient conditions for the existence of at least four positive periodic solutions of this model.展开更多
The distortion of GDP and foreign trade data has exaggerated China＇s foreign trade dependence degree and external imbalance degree. The distortion of GDP is mainly caused by the difference between the exchange rate m...The distortion of GDP and foreign trade data has exaggerated China＇s foreign trade dependence degree and external imbalance degree. The distortion of GDP is mainly caused by the difference between the exchange rate method and purchasing power parity （PPP） estimation. The distortion of trade data includes double counting of customs statistics as well as the discrepancy between the international trade flows of goods and of capital caused by the ownership issue. The re-estimation of China＇s trade dependence degree and external imbalance degree reveals that according to official statistics, in 2007 the dependence degree of China＇s foreign trade decreased to 31.59 percent from 68.02 percent and its imbalance degree decreased to 2.11 percent from 10.13 percent. Therefore, it is utterly groundless to accuse China of ＂manipulating the exchange rate.＂展开更多
S-粗集(singular rough sets)存在三种形式:单向S-粗集(one direction singular rough sets),单向S-粗集对偶(dualof one direction singular rough sets)和双向S-粗集(two direction singular rough sets)。S-粗集具有动态特性,遗传特...S-粗集(singular rough sets)存在三种形式:单向S-粗集(one direction singular rough sets),单向S-粗集对偶(dualof one direction singular rough sets)和双向S-粗集(two direction singular rough sets)。S-粗集具有动态特性,遗传特性,记忆特性和隐藏特性。利用S-粗集,给出了f-隐藏知识,F-隐藏知识,隐藏度和隐藏-依赖度的概念,提出了关于隐藏知识的隐藏定理和隐藏-依赖定理,并给出应用。展开更多
基金supported by the National Natural Science Founda-tion of China(11272118)Open Found of State Key Laboratory of Explosion Science and Technology(KFJJ12-5M)
文摘Condensation technique of degree of freedom is first proposed to improve the computational efficiency of meshfree method with Galerkin weak form for elastic dy- namic analysis. In the present method, scattered nodes with- out connectivity are divided into several subsets by cells with arbitrary shape. Local discrete equation is established over each cell by using moving Kriging interpolation, in which the nodes that located in the cell are used for approxima- tion. Then local discrete equations can be simplified by con- densation of degree of freedom, which transfers equations of inner nodes to equations of boundary nodes based on cells. The global dynamic system equations are obtained by as- sembling all local discrete equations and are solved by using the standard implicit Newmark＇s time integration scheme. In the scheme of present method, the calculation of each cell is carried out by meshfree method, and local search is imple- mented in interpolation. Numerical examples show that the present method has high computational efficiency and good accuracy in solving elastic dynamic problems.
文摘To more accurately answer the questions “who will feed China?” and “whether Chinese people can feed themselves?”, we proposed a concept of agricultural support capacity, defined as the population that can be fed by energy, protein and fat from food, respectively, according to nutritional intake standards. In this study, we established models to measure this, based on analysis of China’s agricultural support capacity and how this changes under self-sufficiency and open conditions, in addition to the degrees of external dependence. Our results show that, since 2007, even without foreign resources, the energy, protein, superior protein and fat obtained from domestic agriculture had been able to feed the Chinese. However, the use of foreign resources increased and strengthened China’s agricultural support capacity, in addition to improving food diversity, optimizing nutrition, assisting in the regulation of food surplus and deficiency, and providing feed for the animal breeding industry. For the past decade, China’s degree of external dependence on energy from cereals has been relatively low, however, the degrees external dependence on superior protein and fat has increased steadily at a certain rate and have been over the national food security warning level. Therefore, China still has great demand for agricultural products from other regions of the world.
文摘This paper considers a class of ratio-dependent Holling-Taner model with infinite delay and prey harvest, which is of periodic coefficients. By means of the coincidence degree theory, a set of sufficient conditions for the existence of at least two positive periodic solutions of this model is established.
文摘A delayed semi-ratio-dependent predator-prey system in a periodic environment is investigated in this paper.By using a continuation theorem based on Gaines and Mawhin's coincidence degree,the global existence of positive periodic solution is studied.A set of easily verifiable sufficient conditions are obtained.
基金Supported by the China Postdoctoral Science Foundation (20060400267)
文摘We study a non-autonomous ratio-dependent predator-prey model with exploited terms. This model is of periodic coefficients, which incorporates the periodicity of the varying environment. By means of the coincidence degree theory, we establish sufficient conditions for the existence of at least four positive periodic solutions of this model.
基金supported by the National Natural Science Foundation of China(Grant No.70810107020)National Social Science Fund of China(Grant No.11CJL038)
文摘The distortion of GDP and foreign trade data has exaggerated China＇s foreign trade dependence degree and external imbalance degree. The distortion of GDP is mainly caused by the difference between the exchange rate method and purchasing power parity （PPP） estimation. The distortion of trade data includes double counting of customs statistics as well as the discrepancy between the international trade flows of goods and of capital caused by the ownership issue. The re-estimation of China＇s trade dependence degree and external imbalance degree reveals that according to official statistics, in 2007 the dependence degree of China＇s foreign trade decreased to 31.59 percent from 68.02 percent and its imbalance degree decreased to 2.11 percent from 10.13 percent. Therefore, it is utterly groundless to accuse China of ＂manipulating the exchange rate.＂
文摘S-粗集(singular rough sets)存在三种形式:单向S-粗集(one direction singular rough sets),单向S-粗集对偶(dualof one direction singular rough sets)和双向S-粗集(two direction singular rough sets)。S-粗集具有动态特性,遗传特性,记忆特性和隐藏特性。利用S-粗集,给出了f-隐藏知识,F-隐藏知识,隐藏度和隐藏-依赖度的概念,提出了关于隐藏知识的隐藏定理和隐藏-依赖定理,并给出应用。
