3. Results and discussion
3.1. Descriptive analysis of word frequency
The keywords for an article can express its main content, and the keyword frequency of academic journal articles can
measure the importance of its related themes in a specific field. In this study, records of 2861 articles were retrieved, and
314 of them were manually excluded or removed because they did not represent regular articles, but notifications, news
reports, etc. As a result, records of 2547 articles were selected for subsequent analysis. With the aid of SATI, 10,768 keywords
were extracted from these article records (4.22 keywords per article). The keyword frequency distribution displays a powerlaw
distribution with an exponent 1.07, as shown in Fig. 1.