Oral language is usually regarded as the important carrier of expressing people ' s thinking and emotion , while sound and breath serve as the media of oral language and they are characterized with abundant aesthetic shapes , for example , the harmonious combination of hardness and gentleness , falsity and trueness , lightness and darkness , coldness and warmness , noisiness and tranquility , and so on 摘要口头语言是人们表达思想和感情的重要载体，声音和气息则是口头语言的传播媒介，它们具有丰富的审美形态，如：刚柔相济、虚实相生、明暗相间、冷暖相衬、动静相谐等。
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Larger loading capacity under the same specification ; easily establishing lubricant oil film , smaller friction coefficient , higher transmission efficiency , saving energy ; highest accuracy up to grade 3 of din standard ; smoother functioning , lower noisiness and longer service life 平面包络环面蜗杆与普通圆柱蜗杆传动相比具有更大的承载能力，易于建立动压油膜摩擦系数小，传动效率高节省能源具有可磨削性，能达到din标准三级，面粗糙度优于ra0 . 4而且具有运行平稳噪音低寿命长等优点。
