A positive-branch unstable resonator with a step reflectivity mirror used in high power CO_2 laser is presented.

本文提出了在高功率CO_2激光器上应用阶梯反射输出的虚共焦非稳腔。

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While technology doesn't change the physical environment by adding trails or gyms, it can make a positive impact, says competition judge Joan Dorn, branch chief for physical activity and health at the Centers for Disease Control and Prevention.

CNN: Schools given $25K to help kids move