The impact of rapid urbanization on food security of China has received considerable attention. It is not clear whether China can strike a balance between urbanization and food security, especially grain security. There have been numerous studies examining the effects of urbanization on grain production or consumption, but few studies have yet analyzed grain balances. Based on the Chinese World Agricultural Regional Market Equilibrium Model (CWARMEM), this paper explores the impacts of urbanization on national and regional grain balances through different scenarios. The CWARMEM is a global partial equilibrium multimarket model which captures the differences between urban and rural residents as well as the effects of globalization. The results show that urbanization has a small negative effect on maintaining grain self-sufficiency. Despite of that, China is able to achieve the objective of grain security set by its policymakers. Moreover, urbanization changes regional grain balances across China: the position of Northeast China and North China, as two dominant grain suppliers of China, will be weaken; Central China and East China will increase dependence on other grain suppliers; the grain surplus of Northwest China will increase slightly. Besides, in terms of grain category, urbanization helps China achieve self-sufficiency in food grain (rice and wheat), while expands deficit of feed grain (maize).

Various types of porous media materials inherently contain pore structures of different scales, ranging from nanoscale to millimeter scale. Due to the limitations of the existing imaging technology, it is challenging and intractable for any single method to obtain and characterize the multiscale pore structure features of porous media accurately and comprehensively. To address the issue, according to the inherent logical correspondence and mutual conversion relationship between different‐scale image pixels, we propose an improved universal fusion algorithm for constructing three‐dimensional (3D) multiscale porous media. We successfully applied this algorithm to the construction of multiscale pore structure model of carbonate rock, sandstone and coal, and subsequently made quantitative extractions and characterizations of their pore structure characteristics. In addition, the finite element method (FEM) was used to calculate their absolute permeability. The results show that the improved fusion algorithm can effectively solve the problem of pore bias of the existing algorithm, which reduces the porosity of the multiscale model to a certain extent, while maintaining good pore interconnectivity. Besides, the multiscale model obtained by the improved fusion algorithm has a wider pore size distribution interval than that of the existing algorithm, and the absolute permeability of the former, computed using the FEM, is closer to the laboratory‐measured value than that of the latter.

This paper selects ten national reference climatologic stations and two national basic stations in Xinjiang, respectively Urumqi Station, Turpan Station, Qitai Station, Usu Station, Altay Station, Ili Station, Hami Station, Khotan Station, Minfeng Station, Aksu Station, Ruoqiang Station and Yanqi Station. According to the surface observation data of the stations during 1961-2019, complete E 20 sequence for the period 1961-2019 is acquired. This paper analyzes spectral characteristics and periodic changes of annual E 20 in each station. Results show: (1) The complete daily E 20 sequence during 1961-2019 after run-in in 12 stations experiences typical changes on a yearly basis, and at present, the entire Xinjiang enters a new high evaporation period; (2) The main period of annual E 20 in the 12 stations shows 23~32a periodic oscillation, and the evaporation level in each station is the most active on that dimension; secondly, Yanqi Station, Aksu Station, Khotan Station, Minfeng Station and Hami Station have obvious and universal periodic oscillation on the longer scale of 14~22a; Altay Station, Usu Station, Qitai Station, Urumqi Station and Ruoqiang Station show obvious periodic oscillation on the scale of 10a; this study sufficiently confirms the larger periodic change trend of evaporation sequence in Xinjiang during 1961-2019.