【摘要】 以具有代表性的民勤绿洲为研究对象,以Matlab7.0为工作平台,对沙漠绿洲地下水埋深预测的三层前馈神经网络(BP神经网络)进行了改进。输入端因子选取民勤绿洲逐月灌溉量、红崖山水库下泄水量、月降水量、月蒸发量(Φ20 cm)、月平均气温、时间序列6项,输出因子为民勤绿洲地下水位。通过在模型的输入层增加时间序列引导因子的方法使BP神经网络对输入端数据具备时间敏感性;通过Levenberg-Marquardt算法使网络误差最小化,并配合Bayesian正则化使网络的误差平方和、网络权重以及阈值平方和实现最优组合,最后使用相关系数、相对误差、效率系数等指标对模型的模拟结果进行检验。结果表明,通过以上一系列改进可以有效提高模型的模拟精度,增强模型的稳定性,并使模型具有良好的"泛化性"。更多还原

【Abstract】 Based on the work platform of Matlab-7.0,the paper predicted the depth of groundwater in Minqin Oasis of Gansu Province with the improved three-layers Back-Propagation Neutral Network(BP Neutral Network) model.The inputting 6 factors include monthly irrigation water volume,outflow of Hongyashan reservoir,and monthly precipitation,evaporation,air temperature,and time sequence;the output factor is the groundwater level in Minqin Oasis.The BP Neural Network Model became more sensitive to the temporal evolution when the time sequence factor was input;The Levenberg-Marquardt algorithm could minimize the bias values,and the use of the Bayesian regularization could optimize the combination of squared errors,weights and the sum of the squared threshold.The modeling results were evaluated with the correlation coefficients,relative error,efficiency index,etc.The results showed that the improved model could improve model’s simulation precision and stability.更多还原