Is a zero mean white noise source.

是一个零均值的白噪声源。

What does write(2) return of zero mean and will I eventually make progress (non-zero result)?

怎么写（2）零均值回归，最终我取得进步（非零结果）？

In this study, those remaining effects are treated as stochastic noise and are assumed white Caussian distributed with zero mean.

在这项研究中，那些未被考虑的各影响因素被作为随时噪声加以处理，并假设其具有零均值白高斯分布。