【单选题】金属材料抵抗疲劳能力的大小,可以用疲劳强度(疲劳极限)衡量。疲劳强度越大,( )。
【单选题】直齿圆柱齿轮主要是进行接触疲劳强度计算和弯曲疲劳强度计算,其强度条件分别为 齿面接触疲劳强度和齿根弯曲疲劳强度, 其中为两齿轮中较小的许用接触应力,与接触疲劳极限有关,为许用( ),它与其疲劳极限有关。
【单选题】Russian-born Max Weber grew up in New York, studied art there, and then went back to Europe to familiarize himself with contemporary artistic developments, on returning to the United States, Weber wor...
C.
Works of the National Gallery of Art
D.
An Innovative American Artist
【单选题】Though Professor Liu ____ in New York for seven years, he has never regretted moving back to Shanghai, his hometown.
【单选题】对称循环的交弯应力作用下,构件的疲劳强度条件为:【图片】;若按非对称循环的构件的疲劳强度条件,【图片】进行了疲劳强度校核,则 。
C.
( C )是等价的,即非对称循环构件的疲劳强度条件式也可以用来校核对称循环下的构件疲劳强度;
D.
( D )不以说明问题,必须按对称循环情况重新校核。
【简答题】A、B、W、D、E为原子序数依次增大的五种短周期元素,已知:五种元素的原子质子数之和为39,且B、W同周期,A、D同主族,A、W能形成两种液态化合物A 2 W和A 2 W 2 ,E元素的周期数与主族序数相等. (1)E元素在周期表中的位置为______周期______族. (2)经测定A 2 W 2 为二元弱酸,其酸性比碳酸的还要弱.请写出:A 2 W 2 的电子式______;其第一步电离的电离...