Self-organized criticality(SOC) of forest fires in China from 1950 to 1989 is studied. The stability, scale-invariant character of SOC and external effects on SOC of forest fires in China are analyzed in detail. Fores...Self-organized criticality(SOC) of forest fires in China from 1950 to 1989 is studied. The stability, scale-invariant character of SOC and external effects on SOC of forest fires in China are analyzed in detail. Forest-fire cellular automata model is a typical model for the research of SOC. Based on the traditional forest-fire model, an improved model, in which effects of tree species, meteorological conditions and human efforts on forest fires are considered, is introduced. Actual forest fire data in China are compared with simulation results of the two models. It is shown that forest fire data in China have SOC behavior and simulation results of the improved model accord better with actual forest fire data than those of the traditional model.展开更多
In traffic system, a reasonable information feedback can improve road capacity. In this paper, we investigate an asymmetrical two-route scenario in which dynamic information can be generated and displayed on the board...In traffic system, a reasonable information feedback can improve road capacity. In this paper, we investigate an asymmetrical two-route scenario in which dynamic information can be generated and displayed on the board to guide drivers. Two improved feedbacks (i.e. improved mean velocity feedback and improved congestion coefficient feedback) are introduced. Simulations show that the average cost is dependent on the vehicle arrival rate and there exists a critical the dynamic vehicles ratio corresponding to the maximum flux. We find that improved con-gestion coefficient can better enhance the system capacity than that of improved mean velocity feedback.展开更多
Using homogenous partition of coarse graining process, the time series of Hang Seng Index (HSI) in Hong Kong stock market is transformed into discrete symbolic sequences S={S1S2S3…}, Si∈(R, r, d, D). Weighted networ...Using homogenous partition of coarse graining process, the time series of Hang Seng Index (HSI) in Hong Kong stock market is transformed into discrete symbolic sequences S={S1S2S3…}, Si∈(R, r, d, D). Weighted networks of stock market are con- structed by vertices that are 16 2-symbol strings (i.e. 16 patterns of HSI variations), and encode stock market relevant information about interconnections and interactions between fluctuation patterns of HSI in networks topology. By means of the measure- ments of betweenness centrality (BC) in networks, we have at least obtained 3 highest betweenness centrality uniform vertices in 2 order of magnitude of time subinterval scale, i.e. 18.7% vertices undertake 71.9% betweenness centrality of networks, showing statistical stability. These properties cannot be found in random networks; here vertices almost have iden- tical betweenness centrality. By comparison to ran- dom networks, we conclude that Hong Kong stock market, rather than a random system, is statistically stable.展开更多
<Abstract>We study the role of unbiased migration in cooperation in the framework of the spatial evolutionary game on a variety of spatial structures, namely a regular lattice, continuous plane and complex netwo...<Abstract>We study the role of unbiased migration in cooperation in the framework of the spatial evolutionary game on a variety of spatial structures, namely a regular lattice, continuous plane and complex networks. A striking finding is that migration plays a universal role in cooperation, regardless of the spatial structure. For a high degree of migration, cooperators cannot survive owing to their failure to form cooperator clusters that resist attacks by defectors. Meanwhile, for a low degree of migration, cooperation is considerably enhanced relative to that in the static spatial game, which is due to the strengthening of the boundaries of cooperator clusters by the occasional accumulation of cooperators along the boundaries. The cooperator cluster thus becomes more robust than that in the static game and defectors near the boundary can be assimilated by cooperators. The cooperator cluster thus expands, which facilitates cooperation. The general role of migration will be substantiated by sufficient simulations relating to heuristic explanations.展开更多
Starting with the self-organized evolution of the trader group’s structure, a parsimonious percolation model for stock market is established, which can be considered as a kind of betterment of the Cont-Bouchaud model...Starting with the self-organized evolution of the trader group’s structure, a parsimonious percolation model for stock market is established, which can be considered as a kind of betterment of the Cont-Bouchaud model. The return distribution of the present model obeys Lévy form in the center and displays fat-tail property, in accord with the styl-ized facts observed in real-life financial time series. Fur-thermore, this model reveals the power-law relationship be-tween the peak value of the probability distribution and the time scales, in agreement with the empirical studies on the Hang Seng Index.展开更多
基金This work was supported by theSpecial Fund for the Major National Basic Research Projects in China the National Basic Research Climbing Project and the National Natural Science Foundation of China (Grant Nos. 59936140 and 19932020).
文摘Self-organized criticality(SOC) of forest fires in China from 1950 to 1989 is studied. The stability, scale-invariant character of SOC and external effects on SOC of forest fires in China are analyzed in detail. Forest-fire cellular automata model is a typical model for the research of SOC. Based on the traditional forest-fire model, an improved model, in which effects of tree species, meteorological conditions and human efforts on forest fires are considered, is introduced. Actual forest fire data in China are compared with simulation results of the two models. It is shown that forest fire data in China have SOC behavior and simulation results of the improved model accord better with actual forest fire data than those of the traditional model.
基金Supported by the National Basic Research Program of China (Grant No. 2006CB 705500)National Natural Science Foundation of China (Grant No. 1053206)Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20060358065)
文摘In traffic system, a reasonable information feedback can improve road capacity. In this paper, we investigate an asymmetrical two-route scenario in which dynamic information can be generated and displayed on the board to guide drivers. Two improved feedbacks (i.e. improved mean velocity feedback and improved congestion coefficient feedback) are introduced. Simulations show that the average cost is dependent on the vehicle arrival rate and there exists a critical the dynamic vehicles ratio corresponding to the maximum flux. We find that improved con-gestion coefficient can better enhance the system capacity than that of improved mean velocity feedback.
基金partially supported by the National Key Basic Research Special Foundation of Chinathe National Natural Science Foundation of China(Grant Nos.70171053,70271070,70471033 and 10472116).
文摘Using homogenous partition of coarse graining process, the time series of Hang Seng Index (HSI) in Hong Kong stock market is transformed into discrete symbolic sequences S={S1S2S3…}, Si∈(R, r, d, D). Weighted networks of stock market are con- structed by vertices that are 16 2-symbol strings (i.e. 16 patterns of HSI variations), and encode stock market relevant information about interconnections and interactions between fluctuation patterns of HSI in networks topology. By means of the measure- ments of betweenness centrality (BC) in networks, we have at least obtained 3 highest betweenness centrality uniform vertices in 2 order of magnitude of time subinterval scale, i.e. 18.7% vertices undertake 71.9% betweenness centrality of networks, showing statistical stability. These properties cannot be found in random networks; here vertices almost have iden- tical betweenness centrality. By comparison to ran- dom networks, we conclude that Hong Kong stock market, rather than a random system, is statistically stable.
基金supported by the National Basic Research Program of China (2006CB705500)the National Important Research Project (91024026)+1 种基金the National Natural Science Foundation of China (10795016,10635040,11005001)the Specialized Research Fund for the Doctoral Program of Higher Education of China(20093402110032)
文摘<Abstract>We study the role of unbiased migration in cooperation in the framework of the spatial evolutionary game on a variety of spatial structures, namely a regular lattice, continuous plane and complex networks. A striking finding is that migration plays a universal role in cooperation, regardless of the spatial structure. For a high degree of migration, cooperators cannot survive owing to their failure to form cooperator clusters that resist attacks by defectors. Meanwhile, for a low degree of migration, cooperation is considerably enhanced relative to that in the static spatial game, which is due to the strengthening of the boundaries of cooperator clusters by the occasional accumulation of cooperators along the boundaries. The cooperator cluster thus becomes more robust than that in the static game and defectors near the boundary can be assimilated by cooperators. The cooperator cluster thus expands, which facilitates cooperation. The general role of migration will be substantiated by sufficient simulations relating to heuristic explanations.
基金Th is work was supported by the National Natural Science Foundation of China (Grant Nos． 70171053． 70271070，70471033& 10472ll61)the Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP No．20020358009) the Foundation for Graduate Students of University of Science and Tech—nology of China(Grant No．KD 200408)．
文摘Starting with the self-organized evolution of the trader group’s structure, a parsimonious percolation model for stock market is established, which can be considered as a kind of betterment of the Cont-Bouchaud model. The return distribution of the present model obeys Lévy form in the center and displays fat-tail property, in accord with the styl-ized facts observed in real-life financial time series. Fur-thermore, this model reveals the power-law relationship be-tween the peak value of the probability distribution and the time scales, in agreement with the empirical studies on the Hang Seng Index.
