Fig. 4

Institutions relationship and collaboration density and the top 20 institutions. A The dense and complex lines between various research institutions in China indicate high correlation and close collaboration. B The edges with lighter colors (yellow) represent the period after 2016, during which more Chinese institutions were involved in the research. The darker-colored edges represent the earlier period when Chinese institutions were less involved. C The color depth represents the chronological order, with brighter colors indicating later periods. It can be observed that research from mainland China appeared later than that from other regions. The dense lines between South Korea and Taiwan represent a close collaboration. D. The top 20 institutions. GZUCM with the most publications of 85 (7.35%) articles, BUCM with 70 (6.05%) articles, and TUTCM with 64 (5.53%) articles