百度知道 - 信息提示

Chinese people attach much importance to reunion, family relationship and filial piety, espacially the harmony of family. The most expected thing for them is the harmony of family. When something unhappy happen in a family, they are always unwilling to expose it to others, which means "do not wash your dirty linen in public". Chinese people also regard the suggestions given by parents and the elders. An old saying goes "If you don't listen to the elders, you will loose a lot",which is to emphasis the importance of the elders' experience to the youth. Chinese people also pay much attention to the influence of family education to the children's personality formation. Just as the proverb goes, the lack of education is the fault of father. 语法应该没问题，不过中国谚语翻译成英文都会变味很多。

剪切应力和弯曲应力的大小沿着梁的长度方向发生变化，并与到中性轴的距离有关。因而可以得出，主平面的弯曲和主压应力的大小也会不同。在中性轴上，主压应力的方向呈45度角。这可以从等式4-3得到验证，将f=0代入，可得到tan 2α = ∞，因此α = 45. 我们可以在梁的中性轴处（f=0）取一正方形隔离体，如图4-1所示。在两个垂直的面上，垂直剪切应力大小相等方向相反，这是由平衡得到的。如果只有这两个应力存在，那么隔离体不能保持平衡，将会旋转。因此，在两个水平面上，必然存在大小相等的方向相反的水平剪切应力，且它们的大小与垂直面上的垂直剪切应力的大小相等。（在梁上任意一点处，水平剪切应力的大小与垂直剪切应力的大小相等这个概念，几乎可以在任何材料力学文章中找到）。