By analyzing mechanism of premature phenomenon in particle swarm optimization (PSO), we found nature of premature convergence and proposed a "leap" strategy to jump out of local minimum, making halted particles "renewed" when they are trapped into a local optimum. The strategy is applied to nonlinear programming and results are encouraging. The improved PSO solves efficiently premature convergence of the algorithm applying in nonlinear optimizations and improves global search ability of PSO.

The electron structure of the Na_1/2Bi_1/2TiO₃ system with ABO₃ type perovskite structure is studied by using self-consult charge-discrete variation-X_α (SCC-DV-X_α) method, and the effect of A, B position substitute on poling characteristic is also analyzed. The calculational results show that spontaneous polarization exists in the NBT piezoceramics system, the piezoelectric properties are enhanced because of the displacement of the B position ions, in addition, the compound substituent of Ba, Sr and Mn ion can decrease coercive field, and increase the strength of spontaneous polarization, so the dielectric properties get improved.