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From the aspect of bibliometrics and social network analysis, this paper studies the content characteristics and network evolution of service quality in China, form visual analysis charts and summarizes the research hotspots and development trends. Taking CNKI database as the data source, data mining and association analysis of sample data were carried out by means of manual judgment, keyword co-occurrence, bibliometric software BICOMB and Pajek. 872 related literatures were retrieved from 1999 to 2019, and the tendency of the number of published papers in each year was close to the inverted U type. This study expands the application fields of bibliometrics and social network software, and analyzes the development trend of service quality. The theoretical and practical research on service quality has achieved rapid development in the past 20 years. The library service quality and service quality satisfaction have always gotten a high level of attention, and the characteristics of network platforms for service quality have gradually become apparent because of the development of the Internet and computer technology.

To investigate the small-signal stability of automatic generation control (AGC) system with constant communication delay, this paper establishes its state-space based on Padé approximation and conducts eigenvalue calculation. Then, by tracking the change of eigenvalues with time delay, the time-delay margin can be confirmed. Different controller parameters have complex influence on time delay margin and damping performance, so this paper utilizes particle swarm optimization (PSO) to obtain the optimal PI controller parameters to derive delay margin largest and an ideal damping performance. Finally, the simulation studies verify the correctness of time-delay margin calculation and indicate the AGC system has an ideal damping performance with optimal PI controller parameters