In this paper, we describe the basic principle of polarization maintaining optical fiber and the method to measure the beat length of PM optical fiber.

本文叙述了保偏光纤能够保证传输光波偏振特性的基本原理，介绍了测量保偏光纤拍长的基本方法。

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PM is an effective method to settle the problem.

项目管理是解决这一问题的有效的管理方法。

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This paper introduced working principle of PM Claw-pole stepping motors, including magnetic circuits analysis and torque calculation method.

本文介绍永磁爪极步进电机的工作原理、磁路分析及转矩计算方法。

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Speaking to Radio 4's PM programme, Tom Steinberg director of Mysociety, said he was drawn to this method of collecting data because HotOrNot style rating systems are "incredibly sophisticated clever ways of doing online polling".

BBC: Hunt begins for most scenic spots