bp改进，神经网络算法，对bp算法的改进，缩短收敛时间-bp

通过蚁群算法改进bp神经网络,有利于学习(The improvement of BP neural network by ant colony algorithm is beneficial to learning.)

用matlab实现的26个字母识别。基于BP算法的字母识别其容错性和识别率相对较高，在有噪声的情况下训练其识别出错率也相应增加，许进一步改进。(26 letter recognition implemented with MATLAB.The letter recognition based on BP algorithm has a relatively high fault tolerance and recognition rate, and the error rate of recog