Reference group is an important factor influencing users’ purchase in the network communities. The reference group’s influences involve informative influence and normative influence, and users’ purchases are divided into the trial purchase and upgrade purchase. In different purchases, users have different product information, consumer experience, and purchase attitudes, making different responses to the reference group. Thus, a research model of reference groups’ influences on users’ purchase intentions from the perspective of trial purchase and upgrade purchase is constructed. The model and hypotheses are tested by analyzing 349 valid questionnaires. The results indicate that both informative and normative influences have significant positive effects on users’ trial purchase intentions. Informative influence has a significant positive effect on users’ upgrade intentions, while the normative influence on users’ upgrade purchase intentions is not significant. Both informative influence and normative influence have significant positive effects on trust in the product. Trust in the product has a significant positive effect on trial purchase intentions, but its effect on upgrade purchase intentions is not significant. Purchase involvement positively regulates the relationship between informative influence and trial purchase intentions and negatively regulates the relationship between informative influence and upgrade purchase intentions. The results further enrich the theoretical system of users’ purchase behaviors in a virtual environment. The research can also have important implications for network communities wishing to improve online marketing.

Metro station plays crucial social and economic roles in easing metropolitan traffic congestion. To ensure the safe operation of metro station and obtain the real-time risk status of metro station, it is necessary to study dynamic risk assessment of metro station. Based on the real-time data collected by data acquisition equipments and research on metro station risk assessment, the dynamic risk assessment index system is established by considering people, equipments, environments, managements and accidents factors together. Considering the fuzzy uncertainty in the process of risk assessment, a new decision model combining interval type-2 fuzzy set and TOPSIS method is proposed and applied to the metro station dynamic risk assessment. The results can reflect the actual risk status of metro stations objectively and are consistent with the real situation. A numerical example case of the metro station in Beijing is used to illustrate the effectiveness and practicality of our methods, which can provide effective decision support for decision-makers.

Mobile application innovation diffusion can be used to enhance the reputation and competitiveness of Internet enterprises. However, few works have explored the process of mobile application innovation diffusion from the individual perspective. Therefore, this paper employs multi-agent methods to simulate the innovation diffusion of mobile applications from the perspective of social networks. Specifically, we combine psychology, sociology, game theory and network effect theory to model user behaviors of adoption and rejection decisions for mobile applications. The multi-agent model was built in Anylogic 8 to simulate the communication and interaction between individual users. Then, this paper discusses the evolution of decision-making of social network user groups with different network structures and network effects. We also investigate the impact of different firms’ promotion on innovation diffusion. Our findings suggest firms could make better strategies and achieve better diffusion effects from mobile applications.

In an orthogonal frequency division multiplexing (OFDM) communication system, the reduction of peak-to-mean envelope power ratio (PMEPR) is one of crucial issues. It is all known that in an OFDM system, Golay complementary sequence (CS) pairs result in lowest upper bound 2 of PMEPR. Hence, this letter focuses on constructions of 16-QAM Golay CS sets. The proposed two constructions can produce the required sequences with arbitrary lengths, including lots of unknown ones in the existing references, if there exist the quaternary Golay CS sets of such lengths, and the PMEPRs of the Golay CS pairs from both are at most 2. As a consequence, the resultant sequences by this letter can be used as the inputs of using non-radix-2 inverse fast Fourier transform (IFFT) in the time domain OFDM signals.