We study the evolutionary snowdrift game in a heterogeneous Newman-Watts small-world network. The heterogeneity of the network is controlled by the number of hubs. It is found that the moderate heterogeneity of the ne...We study the evolutionary snowdrift game in a heterogeneous Newman-Watts small-world network. The heterogeneity of the network is controlled by the number of hubs. It is found that the moderate heterogeneity of the network can promote the cooperation best. Besides, we study how the hubs affect the evolution of cooperative behaviours of the heterogeneous Newman-Watts small-world network. Simulation results show that both the initial states of hubs and the connections between hubs can play an important role. Our work gives a further insight into the effect of hubs on the heterogeneous networks.展开更多
We investigate an evolutionary snowdrift game on a square N ： L × L lattice with periodic boundary conditions, where a population of no （no ≤ N） players located on the sites of this lattice can either coopera...We investigate an evolutionary snowdrift game on a square N ： L × L lattice with periodic boundary conditions, where a population of no （no ≤ N） players located on the sites of this lattice can either cooperate with or defect from their nearest neighbours. After each generation, every player moves with a certain probability p to one of the player＇s nearest empty sites. It is shown that, when p = 0, the cooperative behaviour can be enhanced in disordered structures. When p 〉 0, the effect of mobility on cooperation remarkably depends on the payoff parameter r and the density of individuals ρ （ρ = no/N）. Compared with the results of p = 0, for small r, the persistence of cooperation is enhanced at not too small values of p; whereas for large r, the introduction of mobility inhibits the emergence of cooperation at any p 〈 1; for the intermediate value of r, the cooperative behaviour is sometimes enhanced and sometimes inhibited, depending on the values of p and p. In particular, the cooperator density can reach its maximum when the values of p and p reach their respective optimal values. In addition, two absorbing states of all cooperators and all defectors can emerge respectively for small and large r in the case of p 〉 0.展开更多
We propose an evolutionary snowdrift game model for heterogeneous systems with two types of agents, in which the inner-directed agents adopt the memory-based updating rule while the copycat-like ones take the uncondit...We propose an evolutionary snowdrift game model for heterogeneous systems with two types of agents, in which the inner-directed agents adopt the memory-based updating rule while the copycat-like ones take the unconditional imitation rule; moreover, each＇agent can change his type to adopt another updating rule once the number he sequentially loses the game at is beyond his upper limit of tolerance. The cooperative behaviors of such heterogeneous systems are then investigated by Monte Carlo simulations. The numerical results show the equilibrium cooperation frequency and composition as functions of the cost-to-benefit ratio r are both of plateau structures with discontinuous steplike jumps, and the number of plateaux varies non-monotonically with the upper limit of tolerance VT as well as the initial composition of agents faO. Besides, the quantities of the cooperation frequency and composition are dependent crucially on the system parameters including VT, faO, and r. One intriguing observation is that when the upper limit of tolerance is small, the cooperation frequency will be abnormally enhanced with the increase of the cost-to-benefit ratio in the range of 0 〈 r 〈 1/4. We then probe into the relative cooperation frequencies of either type of agents, which are also of plateau structures dependent on the system parameters. Our results may be helpful to understand the cooperative behaviors of heterogenous agent systems.展开更多
[Objective] The dormancy characteristics of Malus ‘Snowdrift’ in long-day treatment were studied, and 6-BA was used to break the dormancy, with the aim to achieve the purpose of flowering in autumn. [Method] The new...[Objective] The dormancy characteristics of Malus ‘Snowdrift’ in long-day treatment were studied, and 6-BA was used to break the dormancy, with the aim to achieve the purpose of flowering in autumn. [Method] The new shoots of ‘Snowdrift’ in long-day treatment were conducted with hydroponics to investigate their dormancy time. And cytokinin 6-benzyladenine(6-BA)was used to treat the dormant shoots, to investigate the budding, flowering and flower bud differentiation. [Result] The shoots in long-day treatment entered endodormancy after August 7^(th) and the shoots in the natural daylight entered endodormancy before July 18^(th). In long-day treatment, 116 buds, 198 flowers were observed after 6-BA spraying. [Conclusion] The optimum concentration of 6-BA was 300 mg/L. And the flower bud differentiation of ‘Snowdrift’ in long-day treatment was faster than those in natural daylight after 6-BA spraying.展开更多
We investigate the cooperative behavior and the phase separation in a coevolving system. Agents in the system constructed by a regular random network initially play the snowdrift game with their neighbors. They try to...We investigate the cooperative behavior and the phase separation in a coevolving system. Agents in the system constructed by a regular random network initially play the snowdrift game with their neighbors. They try to obtain a better competing environment by imitating a neighbor＇s more successful strategy or cutting the connection to a defective neighbor and randomly rewiring to another agent so as to seek a better neighborhood. The dynamic process of strategy imitation and relationship among agents due to rewiring neighbors may drive the system into different states. The simulation results show that there are three different phases in the q-r plane, where q is the rewiring probability and r is the cost-to-benefit ratio. One is a static phase of a pure cooperative cluster with a few isolated defectors. The other two belong to active phases with one of a main mixed-strategy cluster and the other of a pure defective state. We find that a simple mean field theory can predict correctly the static phase and the active phase of the main mixed-strategy cluster. The theoretical boundary line between the two phases is in good agreement with the simulation result.展开更多
The model for snowdrift wind tunnel test needs to be similar with the prototype. Based on detailed analysis in aspects of geometry, kinematics and dynamics, the major similarity parameters that need to be satisfied ar...The model for snowdrift wind tunnel test needs to be similar with the prototype. Based on detailed analysis in aspects of geometry, kinematics and dynamics, the major similarity parameters that need to be satisfied are gained. The contradiction between the Reynolds number and Froude number as well as the problem of time scale is introduced, and the selections of the model parameters are specified. Lastly, an example of snowdrift wind tunnel test by adoption of quartz sand as the model of snow grains is presented. The flow field and the snow distributions on a typical stepped roof were investigated. The results show that the flow filed characters are in good agreement with the field observations, and the stepped roof snow depth distributions are basically consistent with the observation results.展开更多
为给通过地形复杂,缺少气象资料的西南艰险山区的铁路研究风吹雪易发性提供方法,以位于该区域的四川省康定市为例,采用中尺度数值天气预报模式(The Weather Research and Forecasting Mode,WRF)对该区域气象要素的时空分布进行模拟.基于...为给通过地形复杂,缺少气象资料的西南艰险山区的铁路研究风吹雪易发性提供方法,以位于该区域的四川省康定市为例,采用中尺度数值天气预报模式(The Weather Research and Forecasting Mode,WRF)对该区域气象要素的时空分布进行模拟.基于WRF模式中各种参数的特点,设计4种参数方案进行计算,采用双层网格嵌套达到降尺度模拟,为了高精度解析大气边界层过程,在竖直方向、近地面1.5km高度内加密为15层,提取康定站计算结果与观测结果进行比较.结果表明,WRF模式的计算结果符合康定市气候特征,气象要素的相关系数均高于0.5;风吹雪发生概率从高到低的区域依次为康定市东部和南部边缘的贡嘎山区,内部的大雪山段,以及位于101.7°E~102.0°E位置处的铁路线路,概率分别为19%、14%和12%,其他区域的概率低于4%.展开更多
We propose a novel snowdrift game model with edge weighting mechanism to explore the cooperative behaviors among the players on the square lattice. Based on the assumption of three types of weight distribution includi...We propose a novel snowdrift game model with edge weighting mechanism to explore the cooperative behaviors among the players on the square lattice. Based on the assumption of three types of weight distribution including uniform, exponential and power-law schemes, the cooperation level is largely boosted in contrast with the traditional snowdrift game on the unweighted square lattice. Exten- sive numerical simulations indicate that the fraction of cooperators greatly augments, especially for the intermediate range of cost-to-benefit ratio r. Furthermore, we investigate how the cooperative behaviors are affected by the undulation amplitude of weight distribution and noise strength of strat- egy selection, respectively. The simulation results will be conducive to further understanding and analyzing the emergence of cooperation, which is a ubiquitous phenomenon in social and biological science.展开更多
In this paper,we study the influence of the size of interaction neighbors(k) on the evolution of cooperation in the spatial snowdrift game.At first,we consider the effects of noise K and cost-to-benefit ratio r,the si...In this paper,we study the influence of the size of interaction neighbors(k) on the evolution of cooperation in the spatial snowdrift game.At first,we consider the effects of noise K and cost-to-benefit ratio r,the simulation results indicate that the evolution of cooperation depends on the combined action of noise and cost-to-benefit ratio.For a lower r,the cooperators are multitudinous and the cooperation frequency ultimately increases to 1 as the increase of noise.However,for a higher r,the defectors account for the majority of the game and dominate the game if the noise is large enough.Then we mainly investigate how k influences the evolution of cooperation by varying the noise in detail.We find that the frequency of cooperators is closely related to the size of neighborhood and cost-to-benefit ratio r.In the case of lower r,the augmentation of k plays no positive role in promoting the cooperation as compared with that of k = 4,while for higher r the cooperation is improved for a growing size of neighborhood.At last,based on the above discussions,we explore the cluster-forming mechanism among the cooperators.The current results are beneficial to further understand the evolution of cooperation in many natural,social and biological systems.展开更多
Railways built in cold,snowy,and lightly populated areas are subjected to wind and snow disasters.In this study,we selected a snow hazard prevention and control section of the Altay–Zhundong Railway in Xinjiang Uygur...Railways built in cold,snowy,and lightly populated areas are subjected to wind and snow disasters.In this study,we selected a snow hazard prevention and control section of the Altay–Zhundong Railway in Xinjiang Uygur Autonomous Region of China as the research object.We investigated the deposited snowfall variation characteristics on the two sides and in the embankment pavement area of snow fences with different porosities,fence heights,and arrangement distances using single-factor tests and orthogonal tests based on global atmospheric reanalysis climate data,field survey data,and a multi-phase flow analysis model.The results showed significant differences in the characteristics of snow cover distribution and snow cover thickness between the embankment and the cutting in the absence of snow protection measures.The maximum snow cover thickness of the embankment pavement decreased by 12.6%relative to the cutting pavement.The snow cover thickness of the embankment exhibited an increasing trend from windward shoulder to leeward shoulder,whereas the snow cover thickness of the cutting presented a declining trend from windward shoulder to leeward toe.In the collaborative prevention and control of snow fences and embankments,the three factors can be ranked in terms of their sensitivity to deposited snowfall within the influence scope of snow fences as follows:fence height>arrangement distance>porosity.At the same time,fence height yielded a significant relationship for the influence scope of snow fences(P<0.05).The three factors can also be ranked in terms of their sensitivity to deposited snowfall on the pavement as follows:porosity>fence height>arrangement distance.For the embankment protection of the Altay–Zhundong Railway against wind and snow,snow fence with a porosity of 75%,a fence height of 4.8 m,and an arrangement distance from the embankment of 60 m produced the best snow control effect.By revealing the characteristics of snow cover distribution along railway subgrade and the protective effect of snow fences,this study provides valuable references for the engineering applications of railway construction in areas prone to wind and snow disasters.展开更多
基金supported by the National Basic Research Program of China (No 2006CB705500)the National Natural Science Foundation of China (Grant Nos 60744003, 10635040, 10532060 and 10472116)the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘We study the evolutionary snowdrift game in a heterogeneous Newman-Watts small-world network. The heterogeneity of the network is controlled by the number of hubs. It is found that the moderate heterogeneity of the network can promote the cooperation best. Besides, we study how the hubs affect the evolution of cooperative behaviours of the heterogeneous Newman-Watts small-world network. Simulation results show that both the initial states of hubs and the connections between hubs can play an important role. Our work gives a further insight into the effect of hubs on the heterogeneous networks.
基金Project supported by the National Natural Science Foundation of China （Grant No 10775060）.
文摘We investigate an evolutionary snowdrift game on a square N ： L × L lattice with periodic boundary conditions, where a population of no （no ≤ N） players located on the sites of this lattice can either cooperate with or defect from their nearest neighbours. After each generation, every player moves with a certain probability p to one of the player＇s nearest empty sites. It is shown that, when p = 0, the cooperative behaviour can be enhanced in disordered structures. When p 〉 0, the effect of mobility on cooperation remarkably depends on the payoff parameter r and the density of individuals ρ （ρ = no/N）. Compared with the results of p = 0, for small r, the persistence of cooperation is enhanced at not too small values of p; whereas for large r, the introduction of mobility inhibits the emergence of cooperation at any p 〈 1; for the intermediate value of r, the cooperative behaviour is sometimes enhanced and sometimes inhibited, depending on the values of p and p. In particular, the cooperator density can reach its maximum when the values of p and p reach their respective optimal values. In addition, two absorbing states of all cooperators and all defectors can emerge respectively for small and large r in the case of p 〉 0.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11175131 and 10875086)
文摘We propose an evolutionary snowdrift game model for heterogeneous systems with two types of agents, in which the inner-directed agents adopt the memory-based updating rule while the copycat-like ones take the unconditional imitation rule; moreover, each＇agent can change his type to adopt another updating rule once the number he sequentially loses the game at is beyond his upper limit of tolerance. The cooperative behaviors of such heterogeneous systems are then investigated by Monte Carlo simulations. The numerical results show the equilibrium cooperation frequency and composition as functions of the cost-to-benefit ratio r are both of plateau structures with discontinuous steplike jumps, and the number of plateaux varies non-monotonically with the upper limit of tolerance VT as well as the initial composition of agents faO. Besides, the quantities of the cooperation frequency and composition are dependent crucially on the system parameters including VT, faO, and r. One intriguing observation is that when the upper limit of tolerance is small, the cooperation frequency will be abnormally enhanced with the increase of the cost-to-benefit ratio in the range of 0 〈 r 〈 1/4. We then probe into the relative cooperation frequencies of either type of agents, which are also of plateau structures dependent on the system parameters. Our results may be helpful to understand the cooperative behaviors of heterogenous agent systems.
文摘[Objective] The dormancy characteristics of Malus ‘Snowdrift’ in long-day treatment were studied, and 6-BA was used to break the dormancy, with the aim to achieve the purpose of flowering in autumn. [Method] The new shoots of ‘Snowdrift’ in long-day treatment were conducted with hydroponics to investigate their dormancy time. And cytokinin 6-benzyladenine(6-BA)was used to treat the dormant shoots, to investigate the budding, flowering and flower bud differentiation. [Result] The shoots in long-day treatment entered endodormancy after August 7^(th) and the shoots in the natural daylight entered endodormancy before July 18^(th). In long-day treatment, 116 buds, 198 flowers were observed after 6-BA spraying. [Conclusion] The optimum concentration of 6-BA was 300 mg/L. And the flower bud differentiation of ‘Snowdrift’ in long-day treatment was faster than those in natural daylight after 6-BA spraying.
文摘We investigate the cooperative behavior and the phase separation in a coevolving system. Agents in the system constructed by a regular random network initially play the snowdrift game with their neighbors. They try to obtain a better competing environment by imitating a neighbor＇s more successful strategy or cutting the connection to a defective neighbor and randomly rewiring to another agent so as to seek a better neighborhood. The dynamic process of strategy imitation and relationship among agents due to rewiring neighbors may drive the system into different states. The simulation results show that there are three different phases in the q-r plane, where q is the rewiring probability and r is the cost-to-benefit ratio. One is a static phase of a pure cooperative cluster with a few isolated defectors. The other two belong to active phases with one of a main mixed-strategy cluster and the other of a pure defective state. We find that a simple mean field theory can predict correctly the static phase and the active phase of the main mixed-strategy cluster. The theoretical boundary line between the two phases is in good agreement with the simulation result.
文摘The model for snowdrift wind tunnel test needs to be similar with the prototype. Based on detailed analysis in aspects of geometry, kinematics and dynamics, the major similarity parameters that need to be satisfied are gained. The contradiction between the Reynolds number and Froude number as well as the problem of time scale is introduced, and the selections of the model parameters are specified. Lastly, an example of snowdrift wind tunnel test by adoption of quartz sand as the model of snow grains is presented. The flow field and the snow distributions on a typical stepped roof were investigated. The results show that the flow filed characters are in good agreement with the field observations, and the stepped roof snow depth distributions are basically consistent with the observation results.
文摘为给通过地形复杂,缺少气象资料的西南艰险山区的铁路研究风吹雪易发性提供方法,以位于该区域的四川省康定市为例,采用中尺度数值天气预报模式(The Weather Research and Forecasting Mode,WRF)对该区域气象要素的时空分布进行模拟.基于WRF模式中各种参数的特点,设计4种参数方案进行计算,采用双层网格嵌套达到降尺度模拟,为了高精度解析大气边界层过程,在竖直方向、近地面1.5km高度内加密为15层,提取康定站计算结果与观测结果进行比较.结果表明,WRF模式的计算结果符合康定市气候特征,气象要素的相关系数均高于0.5;风吹雪发生概率从高到低的区域依次为康定市东部和南部边缘的贡嘎山区,内部的大雪山段,以及位于101.7°E~102.0°E位置处的铁路线路,概率分别为19%、14%和12%,其他区域的概率低于4%.
文摘We propose a novel snowdrift game model with edge weighting mechanism to explore the cooperative behaviors among the players on the square lattice. Based on the assumption of three types of weight distribution including uniform, exponential and power-law schemes, the cooperation level is largely boosted in contrast with the traditional snowdrift game on the unweighted square lattice. Exten- sive numerical simulations indicate that the fraction of cooperators greatly augments, especially for the intermediate range of cost-to-benefit ratio r. Furthermore, we investigate how the cooperative behaviors are affected by the undulation amplitude of weight distribution and noise strength of strat- egy selection, respectively. The simulation results will be conducive to further understanding and analyzing the emergence of cooperation, which is a ubiquitous phenomenon in social and biological science.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 60904063 and 60673046Tianjin municipal Natural Science Foundation under Grant No. 11JCYBJC06600the Development Fund of Science and Technology for the Higher Education in Tianjin under Grant No. 20090813
文摘In this paper,we study the influence of the size of interaction neighbors(k) on the evolution of cooperation in the spatial snowdrift game.At first,we consider the effects of noise K and cost-to-benefit ratio r,the simulation results indicate that the evolution of cooperation depends on the combined action of noise and cost-to-benefit ratio.For a lower r,the cooperators are multitudinous and the cooperation frequency ultimately increases to 1 as the increase of noise.However,for a higher r,the defectors account for the majority of the game and dominate the game if the noise is large enough.Then we mainly investigate how k influences the evolution of cooperation by varying the noise in detail.We find that the frequency of cooperators is closely related to the size of neighborhood and cost-to-benefit ratio r.In the case of lower r,the augmentation of k plays no positive role in promoting the cooperation as compared with that of k = 4,while for higher r the cooperation is improved for a growing size of neighborhood.At last,based on the above discussions,we explore the cluster-forming mechanism among the cooperators.The current results are beneficial to further understand the evolution of cooperation in many natural,social and biological systems.
基金supported by the National Natural Science Foundation of China(52168065).
文摘Railways built in cold,snowy,and lightly populated areas are subjected to wind and snow disasters.In this study,we selected a snow hazard prevention and control section of the Altay–Zhundong Railway in Xinjiang Uygur Autonomous Region of China as the research object.We investigated the deposited snowfall variation characteristics on the two sides and in the embankment pavement area of snow fences with different porosities,fence heights,and arrangement distances using single-factor tests and orthogonal tests based on global atmospheric reanalysis climate data,field survey data,and a multi-phase flow analysis model.The results showed significant differences in the characteristics of snow cover distribution and snow cover thickness between the embankment and the cutting in the absence of snow protection measures.The maximum snow cover thickness of the embankment pavement decreased by 12.6%relative to the cutting pavement.The snow cover thickness of the embankment exhibited an increasing trend from windward shoulder to leeward shoulder,whereas the snow cover thickness of the cutting presented a declining trend from windward shoulder to leeward toe.In the collaborative prevention and control of snow fences and embankments,the three factors can be ranked in terms of their sensitivity to deposited snowfall within the influence scope of snow fences as follows:fence height>arrangement distance>porosity.At the same time,fence height yielded a significant relationship for the influence scope of snow fences(P<0.05).The three factors can also be ranked in terms of their sensitivity to deposited snowfall on the pavement as follows:porosity>fence height>arrangement distance.For the embankment protection of the Altay–Zhundong Railway against wind and snow,snow fence with a porosity of 75%,a fence height of 4.8 m,and an arrangement distance from the embankment of 60 m produced the best snow control effect.By revealing the characteristics of snow cover distribution along railway subgrade and the protective effect of snow fences,this study provides valuable references for the engineering applications of railway construction in areas prone to wind and snow disasters.
