传统的期权定价都是假设波动率为固定常数，而这与实际不太相符。

In traditional option pricing method the volatility is assumed as a constant, but this is contradicted to the fact.

youdao

绝对常数是固定而不可以改变的。

An absolute constant is fixed and can not be changed.

youdao

同时，实践证明，用固定若干基本物理常数的数值来重新定义基本单位，可以进一步提高基本单位的准确性。

At the same time, the practice shows that the accuracy of fundamental si units could be improved further by redefinition of some fundamental physical constants.

youdao

Obviously-- and that's a bad way of saying it, I said constant the previous time-- in the linear case, it's subtract by certain amount.

这么描述很不准确，我之前在，线性算法中也说了常数,它是每次减少固定的量。

麻省理工公开课 - 计算机科学及编程导论课程节选

We can also do a similar thing, and I'll keep my distance from the board, but we can instead be holding x constant, for example, putting x to be equal to zero, and then all we're doing is considering the electric field as a function of t.

我们也可以做类似的事情,把x固定为一个常数,例如令x等于零，然后,考虑电场作为时间的函数,这种情况下，我们划掉。

麻省理工公开课 - 化学原理课程节选