Enhancing extraction efficiency from GaN-based LED by using an omni-directional reflector and photonic crystal

To enhance the light extraction efficiency of traditional light-emitting diodes（LEDs） by reducing the total internal reflection,an omni-directional reflector（ODR） and photonic crystal are adopted in the paper.The structures of photonic crystal and the ODR are designed by diffraction theory and finite difference time domain（FDTD） method.The photonic crystal is employed in the p-GaN layer and the ODR composed of TiO2/SiO2 is designed between the active region and substrate.The simulation results indicate that the light extraction of LEDs can be enhanced by 11.6 times,and the external quantum efficiency of LEDs will be effectively improved.     

带有脉冲免疫和传染年龄的肝病模型的全局渐近稳定性

讨论了带有脉冲免疫的肝病模型，并在传染类中引入了传染年龄，且传染类的恢复率是依赖这个年龄的，最后给出了元病周期解全局渐近稳定性的条件．     

微弱GPS信号捕获算法的研究

GPS件接收机在低信噪比的环境中,普通捕获算法不能实现理想的捕获效果.采用增加相干积分时间、处理相干积分后的数据和改进传统非相干算法的方法,显著提高了信噪比,有效地消除了传统非相干算法中的平方损耗.通过对不同的捕获算法仿真比较得出,改进的算法有更强的信号检测能力,处理增益更高.