The origin of power-law distributions in self-organized criticality is investigated by treating the variation of the number of active sites in the system as a stochastic process. An avalanche is then regarded as a fir...The origin of power-law distributions in self-organized criticality is investigated by treating the variation of the number of active sites in the system as a stochastic process. An avalanche is then regarded as a first-return random walk process in a one-dimensional lattice. We assume that the variation of the number of active sites has three possibilities in each update： to increase by 1 with probability f1, to decrease by 1 with probability f2, or remain unchanged with probability 1 - f1 - f2. This mimics the dynamics in the system. Power-law distributions of the lifetime are found when the random walk is unbiased with equal probability to move in opposite directions. This shows that power-law distributions in self-organized criticality may be caused by the balance of competitive interactions.展开更多
We study the self-gravitating stars with a linear equation of state, P = aρ, in AdS space, where a is a constant parameter. There exists a critical dimension, beyond which the stars are always stable with any central...We study the self-gravitating stars with a linear equation of state, P = aρ, in AdS space, where a is a constant parameter. There exists a critical dimension, beyond which the stars are always stable with any central energy density; below which there exists a maximal mass configuration for a certain central energy density and when the central energy density continues to increase, the configuration becomes unstable. We find that the critical dimension depends on the parameter a, it runs from d = 11.1429 to 10.1291 as a varies from a = 0 to 1. The lowest integer dimension for a dynamically stable self-gravitating configuration should be d = 12 for any a E [0, 1] rather than d = 11, the latter is the case of self-gravitating radiation configurations in AdS space.展开更多
Energy harvesting is an area of substantial and increasing research attention, and vibration-based devices dominate this research. The primary goal of most researchers is producing maximum electrical output from the h...Energy harvesting is an area of substantial and increasing research attention, and vibration-based devices dominate this research. The primary goal of most researchers is producing maximum electrical output from the harvester systems. However, there have been little metrological considerations for circumstances under which the energy harvester devices are characterized. This makes comparison of different device prototypes very difficult. It is the focus of this paper to highlight the need for metrological considerations to energy harvesting so that a universal metric can be developed. An attempt is also made to discuss the critical parameters that are essential in establishing an international standard on vibration-based energy harvesting. Finally, a simple standard for energy harvesting is proposed.展开更多
基金The project supported in part by National Natural Science Foundation of China under Grant Nos.10635020 and 10475032the Major Project of the Ministry of Education of China under Grant No.306022.
文摘The origin of power-law distributions in self-organized criticality is investigated by treating the variation of the number of active sites in the system as a stochastic process. An avalanche is then regarded as a first-return random walk process in a one-dimensional lattice. We assume that the variation of the number of active sites has three possibilities in each update： to increase by 1 with probability f1, to decrease by 1 with probability f2, or remain unchanged with probability 1 - f1 - f2. This mimics the dynamics in the system. Power-law distributions of the lifetime are found when the random walk is unbiased with equal probability to move in opposite directions. This shows that power-law distributions in self-organized criticality may be caused by the balance of competitive interactions.
基金Supported partially by National Natural Science Foundation of China under Grant Nos.10821504 and 10525060Chinese Academy of Sciences under Grant No.KJCX3-SYW-N2
文摘We study the self-gravitating stars with a linear equation of state, P = aρ, in AdS space, where a is a constant parameter. There exists a critical dimension, beyond which the stars are always stable with any central energy density; below which there exists a maximal mass configuration for a certain central energy density and when the central energy density continues to increase, the configuration becomes unstable. We find that the critical dimension depends on the parameter a, it runs from d = 11.1429 to 10.1291 as a varies from a = 0 to 1. The lowest integer dimension for a dynamically stable self-gravitating configuration should be d = 12 for any a E [0, 1] rather than d = 11, the latter is the case of self-gravitating radiation configurations in AdS space.
文摘Energy harvesting is an area of substantial and increasing research attention, and vibration-based devices dominate this research. The primary goal of most researchers is producing maximum electrical output from the harvester systems. However, there have been little metrological considerations for circumstances under which the energy harvester devices are characterized. This makes comparison of different device prototypes very difficult. It is the focus of this paper to highlight the need for metrological considerations to energy harvesting so that a universal metric can be developed. An attempt is also made to discuss the critical parameters that are essential in establishing an international standard on vibration-based energy harvesting. Finally, a simple standard for energy harvesting is proposed.
