Then the authors divide the outside of the circle further into many small circles. By doing so, the authors transform the irregular loop EM field solving problem into the circle loop EM field problem.

然后再将回线内圆外的部分划成众多的小圆形，此时就将求解不规则回线的电磁场转化为求解圆形回线的电磁场。

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They divide their time between the historic Loop district, on the edge of Lake Michigan, and Uptown, further north.

BBC: Jack Kerouac��s US road trip