thermodynamic identity的用法和樣例：
例句
- An identity is true regardless of the values of its variables.
恒等式中的變量變化不影響恒等式的成立。 - After that, people found the identity has many different applications, especially on regularity and non-existence of solutions about PDEs.
自此以后，人們發(fā)現該恒等式有很多用途，尤其是在研究偏微分方程中解的存在性和唯一性方面。
