the online social network has served as a critical medium for information dissemination, diffusion of epidemics and spread of behavior. In this paper, we proposed a model of opinion spreading and evolution based on online social network, where the social temperature is taken into account. First, the forms and features of the opinion spreading and evolution in social network are analyzed. Then a model of opinion spreading and evolution is established, in which social temperature as an external factor participate the opinion evolution of nodes and then affect the opinion spreading. Simulation results show that social temperature has an important impact on the opinion spreading and evolution.

Risk assessment is the key and core technologies ensuring IT system security. Based on the comprehensive analysis to complex information systems, this paper first summarizes the typical characters of complex information systems and then gives new risk factors that complex system need to face. Furthermore, a new risk assessment method is proposed to evaluate the complex information systems. The method takes full account of the effect of complexity of complex information systems in each process of risk assessment, and utilizes multi-level risk views to carry out in-depth analysis to the risk of complex system.