The temperature distribution characteristics of a moving annular hollow laser beam irradiated on the substrate are studied in this paper. First, through the linear superposition property of potential function, we derive the analytical solution of temperature distribution and the cooling rate of the moving ideal annular hollow heat source. The entransy dissipation rate per unit volume of the annular hollow laser beam is more uniform than that of the Gaussian laser beam. The “ω”-shaped profile of the cross-sectional melt temperature is predicted. Second, we set up an actual annular hollow heat source expression, and two parameters (hollow ratio and heat source hollow area) are defined to describe the heat transfer characteristics of the actual annular hollow heat source. Experiments are carried out to validate transient numerical results. The maximum relative error between the experiments and the simulations is 6.39%, and the average relative error is 3.16%. In the simulation, we compare the profile temperature field of the annular hollow heat source with that of the Gaussian heat source. The profile temperature field in simulation for the actual annular hollow heat source is in agreement with that predicted in the analytical solution for the ideal annular hollow heat source. The effects of scanning speed, power intensity, hollow ratio, and heat source hollow area on the temperature field are demonstrated. The obtained characteristics provide theoretical support for laser materials engineering applications.

Soil erosion is a serious geo-environmental issue causing land degradation in China. Developing new techniques based on remote sensing data to assess soil erosion will assist in the comprehensive treatment of environment and the sustainable management of soil resources. In this paper, land cover and Normalized Difference Vegetation Index (NDVI) were derived from Landsat Thematic Mapper (TM) images to assess the soil erosion with DEM. These techniques will assist in the sustainable development of Guanting reservoir.