A general model for collaboration networks
  In this paper, we propose a general model for collaboration networks. Depending on a single free parameter "{\bf preferential exponent}", this model interpolates between networks with a scale-free and an exponential degree distribution. The degree distribution in the present networks can be roughly classified into four patterns, all of which are observed in empirical data. And this model exhibits small-world effect, which means the corresponding networks are of very short average distance and highly large clustering coefficient. More interesting, we find a peak distribution of act-size from empirical data which has not been emphasized before of some collaboration networks. Our model can produce the peak act-size distribution naturally that agrees with the empirical data well. 
Tao Zhou, Ying-di Jin, Bing-Hong Wang, Da-Ren He, Pei-Pei Zhang, Yue   He, Bei-Bei Su, Kan Chen, and Zhong-Zhi Zhang