from: http://en.wikipedia.org/wiki/Rectifier_(neural_networks)
In the context of artificial neural networks, the rectifier is an activation function defined as
Rectified linear units can be extended to include Gaussian noise, making them noisy ReLUs, giving[3]
Noisy ReLUs have been used with some success in restricted Boltzmann machines for computer vision tasks.[3]
原文：http://www.cnblogs.com/jianyingzhou/p/4056981.html