• Grain boundary engineering for enhancing intergranular damage resistance of ferritic/martensitic steel P92

    分类: 核科学技术 >> 核科学技术其他学科 分类: 物理学 >> 核物理学 提交时间: 2024-02-28

    摘要: Ferritic/martensitic (F/M) steels have been widely used as structural material for thermal and nuclear power plants. However, it is susceptible to intergranular damage in service conditions, which is expected to be critical issues. In order to improve the intergranular damage resistance of F/M steel, thermomechanical process (TMP) was employed to achieve a grain boundary engineering (GBE) microstructure in a kind of F/M steel P92 in this study. TMP, including cold rolling to 6%, 9%, and 12% thickness reduction, respectively, followed by austenization at 1323 K for 40 min plus tempering at 1053 K for 45 min, were applied on as-received (AR) P92 steel. Both prior austenite grain (PAG) size, prior austenite grain boundary character distribution (GBCD), and the connectivity of prior austenite grain boundaries (PAGBs) were investigated. Compared with AR specimen, the PAG size does not change significantly. The fraction of coincident site lattice boundaries (CSLBs, 3 ≤ Σ ≤ 29) and Σ3n boundaries along PAGBs decreases with increasing reduction ratio due to the recrystallization fraction increases with increasing reduction ratio. The PAGBs connectivity of the 6%-deformed specimen deteriorates compared with that of AR specimen slightly. Moreover, the potentiodynamic polarization studies revealed that the intergranular damage resistance of studied steel could be improved by enhancing the fraction of CSLBs along PAGBs, indicating that TMP, involving low deformation, could enhance the intergranular damage resistance.

  • Speckle-based optical cryptosystem and its application for human face recognition via deep learning

    分类: 光学 >> 量子光学 提交时间: 2023-02-19

    摘要: Face recognition has recently become ubiquitous in many scenes for authentication or security purposes. Meanwhile, there are increasing concerns about the privacy of face images, which are sensitive biometric data that should be carefully protected. Software-based cryptosystems are widely adopted nowadays to encrypt face images, but the security level is limited by insufficient digital secret key length or computing power. Hardware-based optical cryptosystems can generate enormously longer secret keys and enable encryption at light speed, but most reported optical methods, such as double random phase encryption, are less compatible with other systems due to system complexity. In this study, a plain yet high-efficient speckle-based optical cryptosystem is proposed and implemented. A scattering ground glass is exploited to generate physical secret keys of gigabit length and encrypt face images via seemingly random optical speckles at light speed. Face images can then be decrypted from the random speckles by a well-trained decryption neural network, such that face recognition can be realized with up to 98% accuracy. The proposed cryptosystem has wide applicability, and it may open a new avenue for high-security complex information encryption and decryption by utilizing optical speckles.