No abstract

In this work, we have investigated the structural, electrical, magnetic and optical properties of Ni-Nb co-doped BaTiO3 ceramics. The compositions of BaTi1 − x(Ni1/2Nb1/2)xO3 were prepared through conventional solid-state reaction method. All the samples exhibit a gradual phase transition behavior from the tetragonal to a cubic structure with the increase of Ni-Nb co-doping concentration. The temperature dependence of the dielectric constant reveals that the transition temperature gradually decreased with an increase in Ni2+ and Nb5+ concentrations. The ferroelectric studies show these doping samples have relatively full ferroelectric hysteresis loops at room temperature, but exhibit a decreasing ferroelectric property with the increasing level of doping. The magnetic measurement suggests that these samples have ferromagnetic ordering at room temperature with an increase in the Ni-Nb doping. Moreover, band gaps of these samples are obviously reduced through the strategy of co-doping.

this paper used ERDAS and ARCGIS software to collect the different land use information on the experimental, buffer and core areas for more than 30 years. By combining the social and economic data and selecting the index which is about the ecological risk of land use to built the system of land utilization evaluation index on ecological risk. On this basis, the AHP and expert commonly were used to determine the weight of index and establish the assessment model on ecological risk of the land use by using the method of fuzzy mathematics. With reference to the ecological risk index which was calculated, and adopting the interpolation and three regression methods to built a forecasting model .Finally, the computer simulation was used to establish the early warning for ecological risk of the land use.

No abstract