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Exponential growth of information generated by online social networks demands effective and scalable recommender systems to give useful results. Traditional techniques become unqualified because they ignore social relation data; existing social recommendation approaches consider social network structure, but social contextual information has not been fully considered. It is significant and challenging to fuse social contextual factors which are derived from users’ motivation of social behaviors into social recommendation. In this paper, we investigate the social recommendation problem on the basis of psychology and sociology studies, which exhibit two important factors: individual preference and interpersonal influence. We first present the particular importance of these two factors in online behavior prediction. Then we propose a novel probabilistic matrix factorization method to fuse them in latent space. We further provide a scalable algorithm which can incrementally process the large scale data. We conduct experiments on both Facebook style bidirectional and Twitter style unidirectional social network data sets. The empirical results and analysis on these two large data sets demonstrate that our method significantly outperforms the existing approaches. [ABSTRACT FROM AUTHOR]

Knowledge contribution in virtual communities is an important issue in the field of knowledge management. Based on Ames's theoretical framework on motivation, we propose a model for knowledge contribution in problem-solving virtual communities (PSVCs). The model includes two second-order individual motivations, with four major mechanisms in PSVCs that are associated with these motivations. Results confirm that only egoistic motives affect members' knowledge contribution in PSVCs. Further, knowledge repository and social identity are found to be important mechanisms for promoting knowledge contribution through egoistic motives. This paper concludes with theoretical and practical implications and provides insights for future research. [ABSTRACT FROM PUBLISHER]