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Land use change is a considerable representation of mutual effect between human and natural activities. Northern Shanxi is located in the northern agro pastoral ecotone, which the land use pattern changes violently. This paper focuses on the dynamic change characteristics of cultivated land and grassland in the agro pastoral ecotone of northern Shanxi from 2000 to 2015, and explores the main driving factors of their change. It can provide support for land planning and management and relevant policy-making in northern Shanxi and promote regional sustainable development. The results showed that: ➀ There was a close interrelation between the change of cultivated land and grassland I n northern Shanxi, and the whole showed the opposite dynamic change trend. ➁The main land transfer type of cultivated land and grassland is construction land. And grassland is also the main transfer type of cultivated land. And cultivated land contributes greatly to the growth of grassland area. ➂Economic factors are the main driving force which affecting the area change of cultivated land and grassland, followed by the benefit factors of agricultural development, and finally the labor factors. ➃Economic factors can explain the shift of cultivated land and grassland in different districts and counties in northern Shanxi. The benefit factor of cultivated land development plays a negative driving role on cultivated land, the benefit of grassland development plays a promoting role on the growth of grassland area, and the driving force of labor factor is relatively small.

The transport and deposition of particulate materials through fractures is widely involved in environmental engineering and resource development engineering. A 3D Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) coupling method was used to investigate the particle and fluid flow. The Gauss Model was applied to construct the rough surfaces. First, the numerical results were compared with the previous results and reasonable agreements were obtained. Second, the results indicated a novel flow pattern of particles in rough fractures. Then, a comprehensive particle sedimentary analysis indicated that the deposition distance of particles was inversely proportional to the particle size and density ratio. In addition, the particle deposition rates were increased by the mean roughness and there was an uneven sediment distribution impacted by roughness. Reasons for this uneven sediment distribution were analyzed in detail. Moreover, the bridge plugs of particles considering the closure of fractures were simulated as well. A part of particulate materials would be filtered at the inlet due to size effect and the transport distance of entered particles decreased significantly when the particle was large. A critical particle radius (R

Chloride-induced corrosion of steel in reinforced concrete structures is one of the major causes of their deterioration over time. The analysis and research on the diffusion mechanism of chloride ions in reinforced concrete structures is still insufficient, and it is necessary to calculate the path of chloride ions based on theoretical models. In this paper, the fick’s second law was used to describe the free chloride concentration evolution in concrete. The Monte Carlo simulation was used to predict the cumulative distribution of corrosion initiation of reinforcing steel.The results show that the calculated results of the established model are in good agreement with the measured results.