title: [Co-author and keyword networks and their clustering appearance in preventive medicine fields in Korea: analysis of papers in the Journal of Preventive Medicine and Public Health, 1991~2006].
abstract: OBJECTIVE
  This study evaluated knowledge structure and its effect factor by analysis of co-author and keyword networks in Korea's preventive medicine sector.
  
  
  METHODS
  The data was extracted from 873 papers listed in the Journal of Preventive Medicine and Public Health, and was transformed into a co-author and keyword matrix where the existence of a 'link' was judged by impact factors calculated by the weight value of the role and rate of author participation. Research achievement was dependent upon the author's status and networking index, as analyzed by neighborhood degree, multidimensional scaling, correspondence analysis, and multiple regression.
  
  
  RESULTS
  Co-author networks developed as randomness network in the center of a few high-productivity researchers. In particular, closeness centrality was more developed than degree centrality. Also, power law distribution was discovered in impact factor and research productivity by college affiliation. In multiple regression, the effect of the author's role was significant in both the impact factor calculated by the participatory rate and the number of listed articles. However, the number of listed articles varied by sex.
  
  
  CONCLUSIONS
  This study shows that the small world phenomenon exists in co-author and keyword networks in a journal, as in citation networks. However, the differentiation of knowledge structure in the field of preventive medicine was relatively restricted by specialization.
authors.affiliation: Department of Medical Sociology, Graduate School of Public Health, Seoul National University, Korea.
authors.forename: Minsoo
authors.initials: M
authors.lastname: Jung
authors.forename: Dongjun
authors.initials: D
authors.lastname: Chung
mesh_terms: D001319:Authorship; D019058:Community Networks / Q000458:organization & administration*; D006801:Humans; D007723:Korea / Q000453:epidemiology; D010506:Periodicals as Topic; D011315:Preventive Medicine