Photoluminescence studies of GaAs/AlAs short period superlattices

Low-temperature pressure-dependent photoluminescence measurements on short-period GaAs/AlAs superlattice structures are presented. Measurements show that the lowest energy conduction-band states are in the AlAs layers and the highest energy valence-band states are located in the GaAs layers. This result is supported by the following three experimental observations: (1) the observed pressure coefficient for the conduction-band to valence-band transition energy is negative, (2) the magnetic mass of this transition is “heavy”, and (3) the band-to-band absorption coefficient appears to be small. These experimental observations are in agreement with predictions of tight-binding calculations.     

反相高效液相色谱-增敏化学发光同时测定VB1和VC

本文基于维生素B1(VB1)、维生素C(VC)对鲁米诺(Luminol)和铁氰化钾(K3[Fe(CN)6])化学发光反应的增敏作用原理,建立了反相高效液相色谱(RP-HPLC)分离、柱后化学发光检测VB1与VC的新方法。当在鲁米诺中加入KBr时可以大大增敏该反应。本法已成功运用于蜂蜜和复合维生素片中VB1与VC的测定。     

软材料粘接结构界面破坏研究综述

软材料已经在软机器人、生物医学及柔性电子等各个领域得到广泛的应用. 实际应用中, 软材料多需要粘附于不同类型的基底上, 与之共同组成工程构件进而实现特定的功能, 粘接界面性能对构件的结构完整性与功能可靠性起着关键性作用. 本文对目前软材料粘接结构界面破坏行为方面的研究进行了系统总结. 首先通过与传统粘接结构的对比, 指出了“软界面”与“软基体”两种软材料粘接结构界面破坏行为的独特性及其物理本质. 接着分别总结了“软界面”与“软基体”两种粘接结构界面破坏行为的实验表征方面的研究成果, 对界面及基体黏弹性耗散对界面破坏机理的影响分别进行了分析. 然后从理论角度, 介绍了针对两种软材料粘接结构界面破坏行为的理论分析方法, 并对已建立的相关理论模型进行了总结. 之后以内聚力模型方法为基础, 介绍了软材料粘接结构界面破坏行为数值模拟方面的相关研究进展. 最后基于已有的研究成果, 提出了目前研究所面临的挑战, 并对可能的软材料粘接结构界面破坏的未来研究方向进行了讨论和展望.      

光助Fenton试剂氧化降解染料直接耐晒黑G的研究

文章研究了影响Fenton试剂氧化降解持久性有机污染物直接耐晒黑G的因素,如光源的选择、初始pH值、H₂O₂的用量、Fe2+的用量、阳离子交换树脂载体的引入等,通过研究确定了各因素的优化条件。研究结果表明：太阳光照能有效的促进直接耐晒黑G染料的降解脱色,大大缩短反应时间;引入阳离子交换树脂后,可增强Fenton氧化反应的活性,降解效果更好。     

Correction to: Interlaboratory Reproducibility of Contour Method Data Analysis and Residual Stress Calculation

Experimental Mechanics - The original version of this article has been corrected to include authors middle initials in the author list. The details given in this correction are correct.     

Experimental study on wake flow structures of screen cylinders using PIV

Experiments were conducted in a water flume using Particle Image Velocimetry (PIV) to study the evolution of the vortical structures in the wakes of four types of screen cylinders at a Reynolds number of about 3200. The results were compared with that of a bare cylinder. The screen cylinders were made of stainless steel screen meshes of various porosities (37%, 48%, 61% and 67%) rolled into cylindrical shapes. Smoke wire flow visualisations in a wind tunnel were also conducted in support of the PIV tests. Depending on the porosity of the screen mesh, two vortex formation mechanisms for the screen cylinder wakes were identified. One was associated with wake instability and the other was associated with shear-layer (Kelvin-Helmholtz) convective instability which involved merging through pairing and tripling of small-scale vortices within the shear layers. The former was responsible for the formation of large-scale vortices in the bare cylinder and the screen cylinder wakes with 37% and 48% porosities, while the latter was responsible for the screen cylinder wakes with 61% and 67% porosities. The results also showed that with increasing porosity, the vortex formation region was extended farther downstream and the Reynolds shear stress, the Turbulent Kinetic Energy (TKE) and vortex intensity were decreased constantly.     

Twin-field quantum key distribution based on twisted photon

Quantum key distribution (QKD) is a promising application to establish unconditional secure communications by quantum mechanics. However, its widespread application still faces a great challenge, that is, the fundamental linear key-rate constraint called Pirandola-Laurenza-Ottaviani-Banchi (PLOB) bound. Recently, twin-field QKD (TF-QKD) was proposed (Lucamarini et al., 2018 [4]), it overcomes the constraint mentioned above. However, the original TF-QKD is based on the phase-encoding strategy, which requires active alignment. In this paper, we improve the original TF-QKD with the photon orbital angular momentum (OAM), and propose a novel reference frame independent protocol to overcome the reference frame dependence. No more alignment procedure is needed, and the intrinsic misalignment errors are eliminated by utilizing the rotation-invariance of OAM photons. Besides, the security performance is also improved.     

Thermal fluctuations of dyadosphere of Reissner-Nordström,Janis-Newman-Winicour and f(R) global monopole black holes

In this paper, we study the effects of thermal fluctuations on Dyadosphere of Reissner-Nordström, Janis-Newman-Winicour and the fragmentation of f(R) global monopole black holes. In the presence of these fluctuations, we obtain various thermodynamic quantities like pressure, entropy, specific heat, Canonical and Grand Canonical ensembles. We discuss the stability of these black holes using the γ (the ratio of heat capacities). We also discuss the phase transition and range of local and global stability. It is demonstrated that in Dyadoshpere of Reissner-Nordström, Janis-Newman-Winicour and fragmentation of f(R) global monopole black holes become locally and globally stable due to logarithmic correction term and large horizon radius.     

Electronic and optical properties of Ho-doped BYF crystal

First-principles methods have been applied to explore the electronic and optical properties of BYF single crystals heavily doped with the Ho³⁺ ion (16.33 and 30.36 mol%). The electronic properties calculations manifest that the top of the valence band is dominated by 2p-orbitals of the F atoms and 4f-orbitals of the Ho atoms. The new defect states are dominated by 4f-orbitals of the Ho atoms which exist in the forbidden band. The principal absorptionat around 5.13 eV (241.7 nm) and 5.75 eV (215.7 nm) occurs in ultra-violet range owing to the electronic transitions from the occupied 2p-orbitalsof the F atoms as well as 4f-orbitals of the Ho atoms to empty 4f-orbitals of neighboring Ho atoms. Moreover, the influence of crystal field will split the energy levels of rare earth ions and easily release the parity forbidden condition of free rare earth ions resulting in f-f transition. Therefore, there may be a 2 μm luminescence in the Ho-doped BYF crystal.     

Dynamics of combined soliton solutions of unstable nonlinear Schrodinger equation with new version of the trial equation method

In this article, a new version of the trial equation method is suggested. With this method, it is possible to find the new exact solutions of the nonlinear partial differential equations. The developed method is applied to unstable nonlinear Schrödinger equation. New exact solutions are expressed with Jacobi elliptic function solutions, 1-soliton solutions and rational function solutions. When the obtained results are examined, we can say the unstable nonlinear Schrödinger equation shows different dynamic behaviors. In addition, the physical behaviors of these new exact solution are given with two and three dimensional graphs.