Zhuo Chen

Food security is crucial to world peace. Economic development has posed a great threat to the protection of cultivated land. Considering 20 cities in the lower Yellow River (AALYR) as the study area, this study explored the spatial evolution of cultivated land pressure (CLP) and economic development from 1998 to 2018, revealing the spatiotemporal coupling characteristics of the CLP index and economic development. The main results are as follows: we discerned that CLP and economic development have an obvious spatiotemporal consistency during 1998–2018. The CLP showed a spatial pattern of overall stability, as well as local changes. Most prefecture-level cities experienced decreased significantly in CLP and improvements in food security. Overall, there were regional differences in the coupling relationships between CLP and economic development in the study area. The explanatory power of the proportion of secondary and tertiary industries were significantly higher than other driving factors. Therefore, while developing the economy rapidly, we should also protect cultivated land resources and improve the coordination level between them, which is essential to guarantee food security and a steady economic development.

China’s energy consumption in urban areas accounts for a large proportion of total energy consumption, and many pollutants are emitted with the energy consumption. Considering the requirement for green development of economy, it is necessary to study the green total factor productivity (GTFP) in cities. In this study, the Malmquist index, spatial autocorrelation analysis and convergence analysis are used to analyze the GTFP for 263 prefectural or higher-level cities in China. The results show a growing trend of values measured by the GTFP in Chinese cities, indicating an increase in efficiency. In addition. the eastern region has the highest efficiency, followed by the central region while the lowest being the western region. The calculated values of GTFP show a relatively strong overall spatial clustering with some local high-high clusters of high index values. GTFP also shows relatively weak divergence and no sign of convergence. Thus, we propose that, to improve GTFP and narrow the gap between regions, it would be necessary to enhance technological progress and restructuring industrial productivity in cities.

Online social networks have become a new channel for urban citizens to acquire information. The efficient information diffusion in their communities ensures wide awareness of updated special events. With agent-based models built on the NetLogo platform, I study information diffusion on online social networks with different simulated network structures. Outcomes from simulated networks and from a case study of real-world Twitter networks show that there exist a range of paired optimal propagation parameters that could mimic real-world information diffusion. It is found that the physical space and the process of information diffusion on the real retweet network over time still demonstrate a geographic pattern showing that a local city or a related city is more involved in a special event in the area.