The tearing mode instability plays a key role in the triggering process of reconnection. The triggering collisionless tearing mode instability has been theoretically and numerically analyzed by many researchers. Howev...The tearing mode instability plays a key role in the triggering process of reconnection. The triggering collisionless tearing mode instability has been theoretically and numerically analyzed by many researchers. However, due to the difficulty in obtaining the observational wave number, it is still unknown whether the tearing mode instability can be excited in an actual plasma sheet prior to reconnection onset. Using the data from four Cluster satellites prior to a magnetospheric reconnection event on 13 September 2002, we utilized the wave telescope technique to obtain the wave number which corresponds to the peak of power spectral density. The wavelength is about 18RE and is consistent with previous theoretic and numerical results. After substituting the wave vector and other necessary parameters of the observed current sheet into the triggering condition of tearing mode instability, we find that the near-Earth current sheet prior to reconnection is unstable to tearing mode.展开更多
Characteristics of ULF waves associated with the solar wind deceleration in the Earth＇s foreshock on 6-7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-ha...Characteristics of ULF waves associated with the solar wind deceleration in the Earth＇s foreshock on 6-7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-handed polarized and quasi anti-parallel propagating mode, with a power peak at about 18.63mHz. The wave vector in the GSE coordinates is estimated to be k = （-4.29, 2.28, 1.21）×10^-4 km^-1, In the solar wind frame, the frequency of waves becomes - 9.39 mHz after the Doppler shift correction. The propagation direction of the waves is thus reversed and correspondingly the polarization of the waves becomes right-handed. The above-mentioned characteristics of the ULF waves in the solar wind frame indicate that the ULF waves associated with the solar wind deceleration are the Alfven-whistler waves, which have been frequently reported in both the observations and computer simulations.展开更多
Specific activity of primordial radionuclides and associated radiation hazards due to 40K, 226Ra, and 232Th have been measured in backed red brick samples, collected from five highly populated areas of the North West ...Specific activity of primordial radionuclides and associated radiation hazards due to 40K, 226Ra, and 232Th have been measured in backed red brick samples, collected from five highly populated areas of the North West Frontier Province of Pakistan. For the detection, analysis and data acquisition, a high purity germanium detector was used. Associated external doses were calculated using a Monte Carlo neutron photon transport code. A theoretical model to determine the gamma dose rate at 1 m height from the floor, made of bricks, was employed for the calculation of mass attenuation coefficient and self-absorption in the floor for the gamma energies of these radionuclides and their progeny. Monte Carlo simulation shows that in this study the floor, having more than an effective thickness of 15 cm, contributes very little to the external gamma dose rate. The values of the external dose rate and annual effective dose are found to be much lower than the world average as well as from other countries of the world.展开更多
Empirical observations indicate that the interevent time distribution of human actions exhibits heavy-tailed features. The queuing model based on task priorities is to some extent successful in explaining the origin o...Empirical observations indicate that the interevent time distribution of human actions exhibits heavy-tailed features. The queuing model based on task priorities is to some extent successful in explaining the origin of such heavy tails, however, it cannot explain all the temporal statistics of human behavior especially for the daily entertainments. We propose an interest-driven model, which can reproduce the power-law distribution of interevent time. The exponent can be analytically obtained and is in good accordance with the simulations. This model well explains the observed relationship between activities and power-law exponents, as reported recently for web-based behavior and the instant message communications.展开更多
We propose a new two-type-player prisoner＇s dilemma game based on the division of work on a square lattice, in which a fraction of the population μ are assigned type A and the rest B. In a one-shot two-player game, ...We propose a new two-type-player prisoner＇s dilemma game based on the division of work on a square lattice, in which a fraction of the population μ are assigned type A and the rest B. In a one-shot two-player game, we let both of their original payoffs be scaled by a same multiplicative factor α 〉 1, if two neighboring players are of different types; however we leave the payoffs unchanged if they are of the same type. Then we show that combined with the two-type setup, the square lattice can assist to induce different social ranks according to players＇ abilities to collect payoffs. Simulation results show that the density of cooperation is significantly promoted for a wide range of the temptation to defection parameters and that there are optimal values for both α and μ leading to the maximal cooperation level. We reach these results by analyzing the distribution of the players in the social ranks and we also show some typical snapshots of the system.展开更多
We investigate the effects of four different information feedback strategies on the dynamics of traffic, travelers＇ route choice and the resultant system performance in a signal controlled network with overlapped rou...We investigate the effects of four different information feedback strategies on the dynamics of traffic, travelers＇ route choice and the resultant system performance in a signal controlled network with overlapped routes. Simulation results given by the cellular automaton model show that the system purpose-based mean velocity feedback strategy and the congestion coefficient feedback strategy have more advantages in improving network utilization efficiency and reducing travelers＇ travel times. The travel time feedback strategy and the individual purposed-based mean velocity feedback strategy behave slightly better to ensure user equity.展开更多
We show that the heterogeneity index, which was proposed by Hu and Wang [Physica A 387 （2008） 3769], can be used to describe the disparity of the cooperation sharing or competition gain distributions, which is very ...We show that the heterogeneity index, which was proposed by Hu and Wang [Physica A 387 （2008） 3769], can be used to describe the disparity of the cooperation sharing or competition gain distributions, which is very important for understanding the dynamics of a cooperation/competition system. An analytical relation between the distribution parameters and the heterogeneity index is derived, which is in good agreement with the empirical results. Our theoretical and empirical analyses also show that the relation between the distribution parameters can be analytically derived from the so-called Zhang-Chang model [Physica A 360 （2006） 599; 383 （2007） 687）. This strongly recommends a possibility to create a general dynamic cooperation/competition model.展开更多
A cellular automaton model is proposed to consider the anticipation effect in drivers＇ behavior. It is shown that the anticipation effect can be one of the origins of synchronized traffic flow. With anticipation effe...A cellular automaton model is proposed to consider the anticipation effect in drivers＇ behavior. It is shown that the anticipation effect can be one of the origins of synchronized traffic flow. With anticipation effect, the congested traffic flow simulated by the model exhibits the features of synchronized flow. The spatiotemporal patterns induced by an on-ramp are also consistent with the three-phase traffic theory. Since the origin of synchronized flow is still controversial, our work can shed some light on the mechanism of synchronized flow.展开更多
We study the effect of mutation on the evolutionary prisoner＇s dilemma in highly clustered scale-free networks. It is found that cooperation is more sensitive and vulnerable to strategy mutation in more highly cluste...We study the effect of mutation on the evolutionary prisoner＇s dilemma in highly clustered scale-free networks. It is found that cooperation is more sensitive and vulnerable to strategy mutation in more highly clustered networks. For small mutation rates, high clustering coefficient promotes cooperation. For medium mutation rates, high clustering coefficient inhibits the emergence of cooperation. For large mutation rates, cooperation is insensitive to clustering property. We provide explanations for the effects of clustering on cooperation with varied mutation rates.展开更多
We investigate the game theory in a structured population with the assumption that the evolution of network structure is far faster than that of strategy update. We find that the degree distribution for the finM netwo...We investigate the game theory in a structured population with the assumption that the evolution of network structure is far faster than that of strategy update. We find that the degree distribution for the finM network consists of two distinct parts： the low degree part which is contributed to by defectors and a broadband in the regime with high degree which is formed by cooperators. The structure of the final network and the final strategy pattern have also been numerically proved to be independent of the game parameters.展开更多
The plant genus Metasequoia Miki,1941 and its sole living relict species Metasequoia glyptostroboides Hu et Cheng,1948 have been of special interest for both the public and scientists since 1941 when the genus was est...The plant genus Metasequoia Miki,1941 and its sole living relict species Metasequoia glyptostroboides Hu et Cheng,1948 have been of special interest for both the public and scientists since 1941 when the genus was established.Due to its unique discovery history（fossils discovered earlier than the living species） and incomparable scientific value in the research of plant evolution and its relationship with environmental and climatic changes, Metasequoia becomes arguably the most comprehensively studied higher plant in both fossil and living forms.This paper summarized recent advance in Metasequoia research by reviewing the research history of Metasequoia and the scientific value of this genus,while paid special attention to the application of new methods and techniques in the research field of Metasequoia in the recent decades.The application of biogeochemical（organic geochemistry and stable isotope） analysis as well as the new and innova ted methods of preparing large-sized cuticular membrane from leaves with originally thin and fragile cuticles further secure Metasequoia＇s super star status for the research of palaeoclimatic reconstruction.展开更多
基金Supported the National Natural Science Foundation of China under Grant Nos 40804045 and Innovation Fund of Center for Space Science and Applied Research under Grant No O82112A18S.
文摘The tearing mode instability plays a key role in the triggering process of reconnection. The triggering collisionless tearing mode instability has been theoretically and numerically analyzed by many researchers. However, due to the difficulty in obtaining the observational wave number, it is still unknown whether the tearing mode instability can be excited in an actual plasma sheet prior to reconnection onset. Using the data from four Cluster satellites prior to a magnetospheric reconnection event on 13 September 2002, we utilized the wave telescope technique to obtain the wave number which corresponds to the peak of power spectral density. The wavelength is about 18RE and is consistent with previous theoretic and numerical results. After substituting the wave vector and other necessary parameters of the observed current sheet into the triggering condition of tearing mode instability, we find that the near-Earth current sheet prior to reconnection is unstable to tearing mode.
基金Supported by the National Natural Science Foundation of China under Grant Nos 40931054 and 40523006, the National Basic Research Program of China under Grant No 2006CB806305, the National High-Tech Research and Development Program of China under Grant No 2008AA12A216, and the Specialized Research Fund for State Key Laboratories.
文摘Characteristics of ULF waves associated with the solar wind deceleration in the Earth＇s foreshock on 6-7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-handed polarized and quasi anti-parallel propagating mode, with a power peak at about 18.63mHz. The wave vector in the GSE coordinates is estimated to be k = （-4.29, 2.28, 1.21）×10^-4 km^-1, In the solar wind frame, the frequency of waves becomes - 9.39 mHz after the Doppler shift correction. The propagation direction of the waves is thus reversed and correspondingly the polarization of the waves becomes right-handed. The above-mentioned characteristics of the ULF waves in the solar wind frame indicate that the ULF waves associated with the solar wind deceleration are the Alfven-whistler waves, which have been frequently reported in both the observations and computer simulations.
文摘Specific activity of primordial radionuclides and associated radiation hazards due to 40K, 226Ra, and 232Th have been measured in backed red brick samples, collected from five highly populated areas of the North West Frontier Province of Pakistan. For the detection, analysis and data acquisition, a high purity germanium detector was used. Associated external doses were calculated using a Monte Carlo neutron photon transport code. A theoretical model to determine the gamma dose rate at 1 m height from the floor, made of bricks, was employed for the calculation of mass attenuation coefficient and self-absorption in the floor for the gamma energies of these radionuclides and their progeny. Monte Carlo simulation shows that in this study the floor, having more than an effective thickness of 15 cm, contributes very little to the external gamma dose rate. The values of the external dose rate and annual effective dose are found to be much lower than the world average as well as from other countries of the world.
基金Supported by the National Natural Science Foundation of China under Grant Nos 70871082, 10975126, 90924011, 70971089, 10635040 and 60973069, the China Postdoctoral Science Foundation under Grant No 20080431273, and the Sino-Swiss Science and Technology Cooperation （SSSTC） Project （EG 20-032009）. We acknowledge Xiaopu Han and Wei Hong for their useful discussions.
文摘Empirical observations indicate that the interevent time distribution of human actions exhibits heavy-tailed features. The queuing model based on task priorities is to some extent successful in explaining the origin of such heavy tails, however, it cannot explain all the temporal statistics of human behavior especially for the daily entertainments. We propose an interest-driven model, which can reproduce the power-law distribution of interevent time. The exponent can be analytically obtained and is in good accordance with the simulations. This model well explains the observed relationship between activities and power-law exponents, as reported recently for web-based behavior and the instant message communications.
基金Supported by the National Basic Research Program of China under Grant No 2006CB705500, the National Natural Science Foundation of China under Grant Nos 60744003, 10635040 and 10532060, the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No 20060358065, and the National Science Fund for Fostering Talents in Basic Science （J0630319）.
文摘We propose a new two-type-player prisoner＇s dilemma game based on the division of work on a square lattice, in which a fraction of the population μ are assigned type A and the rest B. In a one-shot two-player game, we let both of their original payoffs be scaled by a same multiplicative factor α 〉 1, if two neighboring players are of different types; however we leave the payoffs unchanged if they are of the same type. Then we show that combined with the two-type setup, the square lattice can assist to induce different social ranks according to players＇ abilities to collect payoffs. Simulation results show that the density of cooperation is significantly promoted for a wide range of the temptation to defection parameters and that there are optimal values for both α and μ leading to the maximal cooperation level. We reach these results by analyzing the distribution of the players in the social ranks and we also show some typical snapshots of the system.
基金Supported by the National Natural Science Foundation of China under Grant No 70521001, and the National Basic Research Program of China under Crant No 2006CB705503.
文摘We investigate the effects of four different information feedback strategies on the dynamics of traffic, travelers＇ route choice and the resultant system performance in a signal controlled network with overlapped routes. Simulation results given by the cellular automaton model show that the system purpose-based mean velocity feedback strategy and the congestion coefficient feedback strategy have more advantages in improving network utilization efficiency and reducing travelers＇ travel times. The travel time feedback strategy and the individual purposed-based mean velocity feedback strategy behave slightly better to ensure user equity.
基金Supported by the National Natural Science Foundation of China under grant Nos 10635040 and 70671089.
文摘We show that the heterogeneity index, which was proposed by Hu and Wang [Physica A 387 （2008） 3769], can be used to describe the disparity of the cooperation sharing or competition gain distributions, which is very important for understanding the dynamics of a cooperation/competition system. An analytical relation between the distribution parameters and the heterogeneity index is derived, which is in good agreement with the empirical results. Our theoretical and empirical analyses also show that the relation between the distribution parameters can be analytically derived from the so-called Zhang-Chang model [Physica A 360 （2006） 599; 383 （2007） 687）. This strongly recommends a possibility to create a general dynamic cooperation/competition model.
基金Supported by the National Basic Research Program of China under Grant No 2006CB705500, and the National Natural Science Foundation of China under Grant Nos 10532060, 10672160, 70601026 and 10872194.
文摘A cellular automaton model is proposed to consider the anticipation effect in drivers＇ behavior. It is shown that the anticipation effect can be one of the origins of synchronized traffic flow. With anticipation effect, the congested traffic flow simulated by the model exhibits the features of synchronized flow. The spatiotemporal patterns induced by an on-ramp are also consistent with the three-phase traffic theory. Since the origin of synchronized flow is still controversial, our work can shed some light on the mechanism of synchronized flow.
文摘We study the effect of mutation on the evolutionary prisoner＇s dilemma in highly clustered scale-free networks. It is found that cooperation is more sensitive and vulnerable to strategy mutation in more highly clustered networks. For small mutation rates, high clustering coefficient promotes cooperation. For medium mutation rates, high clustering coefficient inhibits the emergence of cooperation. For large mutation rates, cooperation is insensitive to clustering property. We provide explanations for the effects of clustering on cooperation with varied mutation rates.
基金Supported by the New Century Excellent Talent Project of the Ministry of Education of China under Grant No NECT-07-0112, and the National Natural Science Foundation of China under Grant No 10775022.
文摘We investigate the game theory in a structured population with the assumption that the evolution of network structure is far faster than that of strategy update. We find that the degree distribution for the finM network consists of two distinct parts： the low degree part which is contributed to by defectors and a broadband in the regime with high degree which is formed by cooperators. The structure of the final network and the final strategy pattern have also been numerically proved to be independent of the game parameters.
文摘The plant genus Metasequoia Miki,1941 and its sole living relict species Metasequoia glyptostroboides Hu et Cheng,1948 have been of special interest for both the public and scientists since 1941 when the genus was established.Due to its unique discovery history（fossils discovered earlier than the living species） and incomparable scientific value in the research of plant evolution and its relationship with environmental and climatic changes, Metasequoia becomes arguably the most comprehensively studied higher plant in both fossil and living forms.This paper summarized recent advance in Metasequoia research by reviewing the research history of Metasequoia and the scientific value of this genus,while paid special attention to the application of new methods and techniques in the research field of Metasequoia in the recent decades.The application of biogeochemical（organic geochemistry and stable isotope） analysis as well as the new and innova ted methods of preparing large-sized cuticular membrane from leaves with originally thin and fragile cuticles further secure Metasequoia＇s super star status for the research of palaeoclimatic reconstruction.
