1.College of Mathematics, Physics and Electronic Information Engineering, Wenzhou University, Wenzhou 325035, China 2.Department of Information, Wenzhou Vocational and Technical College, Wenzhou 325035, China 3.Department of Physics, Zhejiang University, Hangzhou 310027, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant Nos. 11775161, 61874078), the Natural Science Foundation of Zhejiang Province, China (Grant No. LY17A040007), and the Research Foundation of Education Bureau of Zhejiang Province, China (Grant No. Y201738867).
Received Date:29 April 2018
Accepted Date:25 July 2018
Available Online:01 October 2019
Published Online:20 October 2019
Abstract:Traditional Monte Carlo simulation requires a large number of samples to be employed for calculating various physical parameters, which needs much time and computer resources due to inefficient statistical cases rather than mining data features for each example. Here, we introduce a technique for digging information characteristics to study the phase transition of polymer generated by Monte Carlo method. Convolutional neural network (CNN) and fully connected neural network (FCN) are performed to study the critical adsorption phase transition of polymer adsorbed on the homogeneous cover and stripe surface. The data set (conformations of the polymer) is generated by the Monte Carlo method, the annealing algorithm (including 48 temperatures ranging from T = 8.0 to T = 0.05) and the Metropolis sampling method, which is marked by the state labeling method and the temperature labeling method and used for training and testing of the CNN and the FCN. The CNN and the FCN network can not only recognize the desorption state and adsorption state of the polymer on the homogeneous surface (the critical phase transition temperature TC = 1.5, which is close to the critical phase transition temperature TC = 1.625 of the infinite chain length of polymer adsorbed on the homogeneous surface regardless of the size effect), but also recognize the desorption state, the single-stripe adsorption state and the multi-stripe adsorption state of polymer on the stripe surface(the critical phase transition temperature T1 = 0.55 and T2 = 1.1, which are consistent respectively with T1 = 0.58 and T2 = 1.05 of polymer adsorbed on the stripe-patterned surface derived from existing research results). We obtain almost the same critical adsorption temperature by two different labeling methods. Through the study of the relationship between the size of the training set and the recognition rate of the neural network, it is found that the deep neural network can well recognize the conformational state of polymer on homogeneous surface and stripe surface of a small set of training samples (when the number of samples at each temperature is greater than 24, the recognition rate of the polymer is larger than 95.5%). Therefore, the deep neural network provides a new calculation method for polymer simulation research with the Monte Carlo method. Keywords:deep neural network/ adsorption phase transition/ polymer/ Monte Carlo method
这里的$\Delta E$表示每一次运动前后的能量变化, ${k_{\rm{B}}}$为玻尔兹曼常数, T为温度. 本文采用卷积神经网络和全连接神经网络研究高分子链的吸附相变, 在每个温度下抽取了9600个样本用于神经网络的训练和测试. 神经网络的梯度更新采用累积更新算法, 并使用滑动平均以及正则化来防止过拟合. 本文所采用的神经网络模型如图1所示. 图 1 神经网络结构示意图 (a) 卷积神经网络, INPUT表示输入层, Convolution表示卷积层, MAXPOOL表示池化层, Full connection表示全连接层, OUTPUT表示输出层, PADDING方式均为SAME; (b) 全连接网络的一般结构, 其中hidden layer表示隐藏层, 使用正则化和dropout来防止过拟合, DIM表示输入张量的维度 Figure1. Schematic diagram of the neural network structure: (a) Convolutional neural network, INPUT is the data entry, OUTPUT is the learning result, and the padding way is SAME; (b) the general structure of a full-connected network, where regularization and dropout are used to prevent overfitting, and DIM represents the dimension of the tensor.