In the context of globalization, the interests of countries are intertwined and complicated, thus leads to multiple types of trade frictions. In order to protect domestic industries, some countries frequently set up trade protection barriers to restrict Chinese exports, which has a significant impact on China's economic development. Therefore, it is crucial for us to clarify the impact of trade protection barriers on regional export expanding processes in China. Based on the data of the China Customs Database from 2002 to 2016, this article focuses on the expanding path of Chinese export products by integrating the supply and demand perspectives into the same framework. In addition to the introduction to trade barriers set in the demand market as external forces, we also take the external market relatedness effect into consideration, which enriches traditional export spillover mechanisms. The main findings are as follows: (1) With the process of product upgrading, Chinese export destination structure is gradually leaning to emerging economies. Eastern and Central China, which expand their exporting portfolio by exporting more technology-intensive and capital-intensive products, are main contributors to this process. (2) The evolution path of Chinese export products presents typical path dependence characteristics composed of market linkages and technological linkages. In comparison, market linkages, which have been formerly neglected, are more vital to the expanding process of Chinese export market. (3) Multiple trade barriers will inhibit export expanding by cutting off channels for products entry, thereby breaking the region's original export expanding routes. (4) External shocks have a common effect on expanding mechanisms of regional export products by weakening the path dependence of technological linkages and market linkages. In conclusion, absorbing foreign investment, regional economic cooperation and diversification of export product and destination structure are effective countermeasures against external shocks like trade barriers.

Based on the data released by UNESCO on international student mobility in tertiary education from 2001 to 2015, this paper draws on network science to construct a multidimensional weighted directed network heterogeneity model. This model combines the GIS spatial analysis method and the negative binomial regression model to study spatiotemporal evolution and factors influencing international student mobility networks. The results are as follows. First, in terms of the evolutionary characteristics of time series, the linkages of international student mobility networks have increased from 4921 to 9137, and its average weighted degree centrality has rapidly increased from 8004 to 20,834, which indicates that both the number of international students and the choices of overseas routines are mounting. Second, in terms of the topological structure, it has evolved from a single core comprising the United States into dual cores comprising the United States and China. Gradually, Asian countries have become the main body of international student mobility networks, while the centrality of European countries has reduced. Thirdly, in terms of spatial structure, the international student mobility network has a significant core-periphery structure and hierarchical characteristics. The countries in the core, strong semi-periphery and semi-periphery alternate with countries from other tiers. The spatial patterns of the international student mobility network "from east to west, and from south to north" are changing. China and Australia have become the new regional centers of international student mobility networks, meaning that regionalization has become an important trend. Finally, regression analysis shows that the flow of international students correlates positively with the quality of higher education in destination countries, the number of students in colleges and universities, the per capita GDP, the historical links connection between the destination country and the country of origin, and the level of globalization. Geographical distance and linguistic proximity have a significant negative correlation with the flow of international students, indicating that the impediment of language is rapidly weakening, while geographical distance still hinders student mobility.

Exploring the relationship between urban spatial growth and population density change is the basis of urban sustainable development research, which is of great significance for formulating effective land policies to promote urban compact development. The research selected 23 cities with a population of more than 1 million in China and Europe as the study areas. Based on the land use and population data in the study areas in 1990, 2000, and 2014, the research calculated the growth rate of sample urban space during each period, and the urban compactness index was then established to divide the urban spatial growth mode into compact type, maintenance type and spread type. The characteristics of spatial growth, population density change, and their relationship were further discussed. The results are as follows: (1) Population density decline is widespread in cities of China and Europe. Population density in cities of China is relatively high, and the rate of decline is fast, whereas population density in cities of Europe is relatively low and the rate of decline is slow. From 1990 to 2014, the growth rate of urban spatial radius in China was significantly higher than that in Europe. There is a strong negative correlation between the growth rate of urban space and the change rate of population density (with a Pearson's r of -0.693). (2) From 1990 to 2000, most of the sample cities' spatial growth mode were compact. From 2000 to 2014, most Chinese cities' spatial growth mode transformed into spread type and rate of population density decline increased. By contrast, European cities' spatial growth mode maintained to be compact or transformed into maintenance, and the rate of population density decline decreased. (3) Compact spatial growth does not necessarily lead to an increase in population density, but it tends to lower the rate of population density decline, relative to spread spatial growth. The comparative analysis of Chinese and European cities shows that if cities maintain a compact spatial growth mode, the rate of population density will be lowered. If cities' spatial growth mode transforms from compact to spread, it will intensify the decline of urban population density over time.

The interactive relationships between cities in the knowledge economy era have attracted much attention. Researchers have applied a range of methods to explore intercity innovative relationships and associated network characteristics. It nevertheless remains unclear just how intercity innovative relationships can be theoretically constructed based on knowledge flow space and how further scientific simulation methods can be designed. Research questions in this area have rarely been explored in detail, an issue which has inevitably placed obstacles on further exploration. A framework for the theoretical construction of intercity innovative relationships is presented in this study; the basis for this research is that an intercity innovation network is essentially a 'soft network', distinct from a 'hard network'. These interconnections are founded on a subjective relationship construction process and therefore necessitate scale transformation from 'point-point' connections between innovative subjects in different cities with respect to 'city-city' interactions. At the same time, this transformation process is prone to exaggerations and deviations from objective intercity innovative relationships and therefore exerts considerable influence on the accuracy of results such that constructions must be entirely theoretical. Four construction methods for intercity innovative relationships and network simulation are summarized in this study, including an intercity undirected network based on cross-city co-operations between scientific and technological achievements, an intercity directed network based on the cross-city transfer of scientific and technological achievements, an intercity innovation network based on the cross-city flow of high-end talents, and an intercity innovation network based on the multi-city distribution of innovative enterprises and institutions. Simulation tests were then undertaken using relevant data to reflect aspects of these relationships. The results of this analysis are conducive to further exploration of global and regional innovative spatial patterns from the perspective of urban geography and intercity relationships and provide a theoretical and methodological foundation for further research on intercity innovation networks.

In the era of "internet society" premised upon new telecommunications and information technologies, there is a perennial debate on whether geographical distance still plays a role in spatial phenomena, and this has been deemed as a cornerstone of geographical research. To empirically tackle this recurring conundrum, this paper proposes an analytical framework to interpret how geographical distance affects information dissemination, which has always been portrayed to be instantaneous spreading across space by information technique. To be specific, we suggest that closer geographical distance could lead to better information dissemination through two entwined paths: geographical proximity is related to geographical and cultural homogeneity on the one hand, and lowers the cost of physical transport and non-physical links, which would facilitate intercity dissemination, on the other hand. As the former has been widely recognized in previous studies, in this paper we mainly focus on testing the latter path. That is, the influence of geographical distance on the attention to information still remains, after controlling regional characteristics and socio-economic attributes of the audiences. Taking two Chinese TV shows as examples, this paper measures the degree of information attention based on the Baidu Index, as well as maps its spatio-temporal changes. To understand the impact of the changing role of geographical distance over time, we perform OLS regressions at four phases from the first broadcasting of the two programs. The result verifies that geographical distance still plays a significant role in the attention and reception of information during the entire period. The degree of audience's attention decreases as the distance from programs' birthplaces increases. The resistance of geographical distance, however, gradually decays over time. Furthermore, these results are robust at both provincial and city scales, with two different programs having similar findings. The retained effects of geographical distance on the cost of information attention and reception helps explain our results. In other words, the law of geographical distance decay and geographical embeddedness is remaining, even though internet technique enables instant information transition. We therefore argue that the prognosis of "death of distance" or "end of geography" is far from the reality - at least from our empirical analysis, albeit in the internet society.