J Syst Sci Syst Eng (Jun 2014) 23(2): 212-230 ISSN: 1004-3756 (Paper) 1861-9576 (Online) DOI: 10.1007/s11518-014-5243-z CN11-2983/N © Systems Engineering Society of China and Springer-Verlag Berlin Heidelberg 2014 TOPICS AND TRENDS OF THE ON-LINE PUBLIC CONCERNS BASED ON TIANYA FORUM ∗ Lina Cao Xijin Tang Academy of Mathematics and Systems Science Chinese Academy of Sciences, Beijing, 100190, China {caolina, xjtang}@amss.ac.cn () Abstract Many social events spread fast through the Internet and arouse wide community discussions. Those on-line public opinions emerge into diverse topics along the time. Moreover, the strength of the topics is fluctuating. How to catch both primary topics and trend of topics over the shifting on-line discussions are not only of theoretical importance for scientific research, but also of practical importance for societal management especially in current China. To try the cutting-edge text analytic technologies to deal with unstructured on-line public opinions and provide support for social problem-solving in the big data era is worth an endeavour. This paper applies dynamic topic model (DTM) to explore the changing topics of new posts collected from Tianya Zatan Board of Tianya Club, the most influential Chinese BBS in mainland China. By analysis of the hot and cold terms trends, we catch the topics shift of main on-line concerns with illustrations of topics of school bus and environment in December of 2011. An algorithm is proposed to compute the strength fluctuation of each topic. With visualized analysis of the respective main topics in several months of 2012, some patterns of the topics fluctuation on the board are summarized. Keywords: Topic models, dynamic topic model, on-line topics evolution, Tianya Club, societal management ∗ This research is supported by National Basic Research Program of China under Grant No. 2010CB731405 and National Natural Science Foundation of China under Grant No.71171187 & 71371107. This paper is an extended version of the paper presented at the 14th International Symposium on Knowledge and Systems Sciences (KSS2013), held in Ningbo during October 25-27, 2013 . 1. Introduction Social media, such as blog, microblog, review sites, BBS, etc., are fundamentally changing the way people communicate (Wu, Sun & Tan, 2013). In China, more and more people treat social media as one way to express their opinions toward the daily phenomena and social events openly and freely. The on-line discussions which show fresh, diverse and evolving opinions bring