利用无序获得更低折射率比范围内的全向反射

讨论了如何获得较低折射率比 (nH/nL)下的全向反射 .在 1/4波长膜系基础上 ,采用非周期结构 ,设计了在高低折射率分别为 2 .16和 1.4 4下的可见光波段范围内的全向高反膜 ,并对非周期膜系和 1/4波长膜系进行了比较 ,最后实验制备了 5 95～ 6 10nm波段的全向高反膜 .     

口语测试及评价

外语测试是外语教学过程的重要环节,但是大规模的口语测试一直处于劣势,所以英语教学界对口语测试的呼声越来越高.本文从话语运用、设计口试类型、考查学生能力等方面谈了口语测试及评价应注重的东西,争取对大学英语口语教学起到一定作用.     

Average modeling of Single Stage Flyback PFC ＋ Flyback DC／DC converter

With the use of this novel average model for Single Stage Flyback PFC Flyback DC/DC converter, voltage control mode, peak current control mode and average current control mode can be simulated easily by changing the model‘s parmneters. It can be used to do various analysis not only for small signal and static behavior but also for large signal and dynamic behavior of the converter. By using this average model the simulation speed can be improved by 2 orders of rrmgnitude above that obtained by using the conventional switched model. It can be applied to optimize the trade-off between high power factor, voltage stress, current stress and good output performance while designing this kind of single stage PFC converter. A 60W single stage power factor corrector was built to verify the proposed model. The modeling principle can be applied to other Single Stage PFC topologies.