按照逐段增加技术元素、动作数量和难度制定出的段位标准，不仅便于习练者明确段级间的差异；

The Duan level standards are set according to the principle of gradually increasing the technical elements and the total number and difficulty of the movements level by level.

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布莱亚·邓纳姆是马萨诸塞州萨默维尔的一位母亲，她在她一年级的孩子和幼子一起洗澡时，激动地见证了兄弟间的亲情时刻，拍下几张照片。

Bria Dunham, a mother in Somerville, Massachusetts, was so excited to watch a moment of brotherly bonding while her first-grader and baby took a bath together that she snapped a few photos.

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There are some relative, the notion that the energy gap between n equals one and n equals two is greater than that for n equals two to n equals three. That is correctly represented.

还有很多与之相关的内容，比如说这个观点，第一能量级和第二能量级,之间的能量差要大于第二和第三能量级间的,能量差，而这已经被正确地表示出来了。

麻省理工公开课 - 固态化学导论课程节选