Study on the phase transition of the fractal scale-free networks

Based on the Ising spin, the phase transition on fractal scale-free networks with tree-like skeletons is studied, where the loops are generated by local links. The degree distribution of the tree-like skeleton satisfies the power-law form P(k)～ k~(-δ).It is found that when δ≥3, the renormalized scale-free network will have the same degree distribution as the original network. For a special case of δ = 4.5, a ferromagnetic to paramagnetic transition is found and the critical temperature is determined by the box-covering renormalization method. By keeping the structure of the fractal scale-free network constant, the numerical relationship between the critical temperature and the network size is found, which is the form of power law.     

基于机器视觉的自然环境下作物行识别与导航线提取

针对基于机器视觉的农业导航机器人在图像处理时易受光照变化影响和常规导航线检测算法实时性、稳健性不高等问题,提出了YCrCg颜色模型,选择该颜色模型中与光照无关的Cg分量进行后续图像处理,采用基于二维直方图的模糊C均值聚类法(FCM)进行图像分割,并根据图像中作物行的特点,提出了基于直线扫描的作物行直线检测算法。该算法将图像底边和顶边像素点作为直线的两个端点,通过移动上下端点位置产生不同斜率直线,选择包含目标点最多的直线作为作物行中心线。实验表明,不同光照下基于YCrCg颜色模型的图像分割可以有效地识别出作物行,处理一幅640pixel×480pixel图片耗时约为16.5ms,直线扫描算法能快速准确的检测出导航线,与最小二乘法、Hough变换等算法相比具有速度快、抗干扰性强等优点。     

Self-Organization of Weighted Networks in Connection with the Misanthrope Process

Prom an undirected random graph, by the weight redistribution of the edges, we obtain a weighted network. The weight redistribution of the edges can be connected to the well-known Misanthrope process, in which distinguishable particles hop among different urns. Under specific conditions, the condensation phenomena can be observed, i.e., nearly all the edges connect to one vertex in the network. When there is no condensation, by adjusting the parameters, the strength distribution can be scale-free or exponentially decreasing. The numerical results fit well with the analytical ones.     

Phase transition in a two-dimensional Ising ferromagnet based on the generalized zero-temperature Glauber dynamics

At zero temperature, based on the Ising model, the phase transition in a two-dimensional square lattice is studied using the generalized zero-temperature Glauber dynamics. Using Monte Carlo （MC） renormalization group methods, the static critical exponents and the dynamic exponent are studied; the type of phase transition is found to be of the first order.     

Traffic of indistinguishable particles in complex networks

In this paper,we apply a simple walk mechanism to the study of the traffic of many indistinguishable particlesin complex networks.The network with particles stands for a particle system,and every vertex in the network standsfor a quantum state with the corresponding energy determined by the vertex degree.Although the particles areindistinguishable,the quantum states can be distinguished.When the many indistinguishable particles walk randomlyin the system for a long enough time and the system reaches dynamic equilibrium,we find that under different restrictiveconditions the particle distributions satisfy different forms,including the Bose-Einstein distribution,the Fermi-Diracdistribution and the non-Fermi distribution(as we temporarily call it).As for the Bose-Einstein distribution,we findthat only if the particle density is larger than zero,with increasing particle density,do more and more particles condensein the lowest energy level.While the particle density is very low,the particle distribution transforms from the quantumstatistical form to the classically statistical form,i.e.,transforms from the Bose distribution or the Fermi distributionto the Boltzmann distribution.The numerical results fit well with the analytical predictions.