Manipulating the Flipping of Water Dipoles in Carbon Nanotubes

Flipping of water dipoles in carbon nanotubes is of great importance in many physical and biological applications,such as signal amplification,molecular switches and nano-gates.Ahead of these applications,understanding and inhibiting the non-negligible thermal noise is essential.Here,we use molecular dynamics simulations to show that the flipping frequency of water dipoles increases with the rising temperature,and the thermal noise can be suppressed by imposed charges and external uniform electric fields.Furthermore,the water dipoles flip periodically between two equiprobable and stable states under alternating electric fields.These two stable states may be adopted to store 0 and 1 bits for memory storage or molecular computing.     

一种基于迭代振幅-相位恢复算法和非线性双随机相位编码的图像加密方法

提出了一种基于迭代振幅-相位恢复算法和非线性双随机相位编码的图像加密方法。该方法利用两个公开密钥和一幅"假图像"在非线性双随机相位加密系统中生成密文,接着利用迭代非线性双随机相位编码生成两个私有密钥。待加密图像和密文作为迭代加密方法中的两个限定值。解密过程则可以在经典的基于4f系统的线性的光学双随机相位编码系统中完成。该加密方法具有迭代收敛速度快、安全性高的优点。迭代该图像加密方法能够抵御最近提出的基于改进的振幅-相位恢复算法的攻击。理论分析和仿真实验都证明了此方法的有效性和可靠性。     

不同尺度的蛋白质在纯石墨烯及氧化石墨烯表面的吸附比较

Using all-atom molecular dynamics (MD) simulations, we have investigated the adsorption stability and conformation change of different proteins on the surface of pristine graphene (PG) and graphene oxide (GO). We find that: (i) with the cooperation of the electrostatic interactions between proteins and oxygen-containing groups, GO shows better adsorption stability than PG; (ii) the peptide loses its secondary structure on both PG and GO surface, and the a-helix structure of the protein fragment is partially broken on PG surface, but is well preserved on GO surface, while the secondary structure of globular protein has no distinct change on both PG and GO surface. In general, GO presents better biocompatibility than PG. Our results are of significant importance to understand the interactions between proteins and PG/GO and the applications of PG/GO in biotechnology and biomedicine.     

围绕培养学生思维能力设计教学流程——以流体的运动教学实践为例

以"流体的运动"的教学实践为例,紧紧围绕实现培养学生思维能力这一目的,确立授课思路和教学策略,从而设计具体的教学流程.     

Nonparaxial propagation of Hermite-Laguerre-Gaussian beams in uniaxial crystal orthogonal to the optical axis

Analytical expressions for the three components of the nonparaxial propagation of a Hermite-Laguerre-Gaussian （HLG） beam in uniaxial crystal orthogonal to the optical axis are derived. The intensity distribution of an HLG beam and its three components propagating in a uniaxial crystal orthogonal to the optical axis are demonstrated by numerical examples. Although the y and z components of an HLG beam in the incident plane are both equal to zero, they emerge upon propagation inside the uniaxial crystal. Moreover, the beam profile of the x component is relatively stable and the beam profiles of the y and z components have the same evolution law. If the ratio of the extraordinary refractive index to the ordinary refractive index is larger than unity, the beam profile of the HLG beam is elongated in the x direction and generally rotates clockwise. Otherwise, the beam profile of the HLG beam is elongated in the y direction and generally rotates anticlockwise. This research is beneficial to the optical trapping and nonlinear optics involved in the rotation of a beam profile.     

Deep-learning-based cryptanalysis of two types of nonlinear optical cryptosystems

The two types of nonlinear optical cryptosystems (NOCs) that are respectively based on amplitude-phase retrieval algorithm (APRA) and phase retrieval algorithm (PRA) have attracted a lot of attention due to their unique mechanism of encryption process and remarkable ability to resist common attacks. In this paper, the securities of the two types of NOCs are evaluated by using a deep-learning (DL) method, where an end-to-end densely connected convolutional network (DenseNet) model for cryptanalysis is developed. The proposed DL-based method is able to retrieve unknown plaintexts from the given ciphertexts by using the trained DenseNet model without prior knowledge of any public or private key. The results of numerical experiments with the DenseNet model clearly demonstrate the validity and good performance of the proposed the DL-based attack on NOCs.     

基于双随机相位编码的非线性双图像加密方法

提出了一种基于双随机相位编码技术的非线性双图像加密方法,并分析了其安全性。在该方法中,加密过程和解密过程以及加密密钥和解密密钥均不相同。加密过程具有非线性,解密过程则是线性的。将两幅待加密图像复合为复振幅图像,并利用双随机相位编码技术和切相傅里叶变换进行加密,加密过程中生成两个解密密钥,解密过程则在经典的基于4f系统的双随机相位编码系统中完成。相比经典的双随机相位加密技术和基于切相傅里叶变换的单图像加密技术,该加密方法的安全性更高,它能够抵御最近提出的基于两步振幅相位恢复算法的特定攻击。理论分析和仿真实验结果都证明了此加密方法的可行性和安全性。