焊接时,由于锰及化合物进入焊工体内,易引起() A.焊工尘肺 B.锰中毒 C.焊工“ 发布时间:2018-05-16 10:49 │ 来源:www.tikuol.com 题型:单项选择题 问题: 焊接时,由于锰及化合物进入焊工体内,易引起()A.焊工尘肺B.锰中毒C.焊工“金属热”
题型:单项选择题 超细晶粒的制备已成为提高材料强韧性的主要手段之一。通过凝固的快冷(即增加过冷度)是获得细晶铸件的重要方法。已知铜的凝固温度Tm=1356K,溶化热Lm=1628×106J/m2,比表面能σ=177×10-3J/m2, 1)试求欲在均匀形核条件下获得半径为2nm晶粒所需的过冷度; 2)试写出其他三种可能获得细晶的方法。 查看答案
题型:单项选择题 On the number line above, the segment from 0 to 1 has been divided into fifths, as indicated by the large tick marks, and also into sevenths, as indicated by the small tick marks. What is the least possible distance between any two of the tick marks 查看答案