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The detachment of railway tunnel lining constitutes a grave danger to train operation safety and drastically curtails the tunnel's service life. This study endeavors to efficiently detect the void defects in railway tunnel lining by creating a finite element model of tunnel lining structures. Utilizing this model, the study simulates the nonlinear acoustic wave propagation cloud maps for three representative tunnel lining structures: void-free, air void, and water void. This facilitates a thorough examination of the acoustic signal characteristics in the wavefield, time domain, and frequency domain. To satisfy the precision and efficiency demands of tunnel lining void detection, this study has devised and developed a portable acoustic detector that incorporates automatic analysis and processing capabilities and is furnished with a high-performance rare-earth magneto-strictive acoustic excitation device. This detection system can swiftly detect and assess typical void defects in tunnel lining. To further validate the effectiveness of this system, this study conducted lining defect detection in the Pingdao Railway Tunnel in the eastern Qinling Mountains. The test results show that the detection rate of this system for both air-filled and water-filled voids with a width of 1 m reached 100%, demonstrating its extremely high application value. [ABSTRACT FROM AUTHOR]

4H‐SiC based devices have garnered significant interest within the realm of high‐voltage and high‐frequency electronic equipment. Schottky barrier heights (SBHs) play a pivotal role in determining the properties of metal/4H‐SiC contacts and holding significance for electrical performance of 4H‐SiC devices. Herein, the first‐principles method is utilized to investigate the interface properties between various metals (Sc, Mg, Zr, Ag, Al, Ru, Rh, Pd, Ni, Au, Ir, and Pt) and 4H‐SiC. The results reveal an approximate linear relationship between SBH and work function of these metals. Fermi‐level pinning factors are determined to be 0.27 and 0.32 for the Si‐face and C‐face interfaces, respectively. The disparity in pinning factors arises from polarization differences between the two interfaces, which stem from uneven net charge distribution on the Si‐face and C‐face. Meanwhile, the SBH values indicate a strong pinning effect, due to the charge transfer occurring at the metal/4H‐SiC interface. Through further analysis of layer density and differential charge density, the interatomic interaction and charge transfer between metal and SiC atoms are analyzed. This work offers fundamental insights into the structural changes in metal/4H‐SiC interfaces and provides valuable guidance in the potential prediction and optimization of device performance. [ABSTRACT FROM AUTHOR]

The introduction of strain InxGa1-xAs channel with high In content increases the confinement of the two-dimensional electron gas (2DEG) and further improves the high-frequency performance of InGaAs/InAlAs/InP HEMTs. The effect of InxGa1-xAs channel with different In contents on electron irradiation tolerance of InP-based HEMT structures in terms of 2DEG mobility and density has been investigated. The experiment results show that, after the same high electron irradiation dose, the 2DEG mobility and density in InP-based HEMT structures with strain InxGa1-xAs (x＞0.53) channel decrease more dramatically than that without strain In0.53Ga0.47As channel. Moreover, the degradation of 2DEG mobility and density becomes more severe as the increase of In content and strain in the InxGa1-x As channel. The research results can provide some suggestions for the design of radiation-resistant InP-based HEMTs. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskite nanocrystals have become a very widely used as semiconductor light-emitting materials. However, perovskite nanocrystals face stability challenges, which is a key factor hindering their application. In this paper, by introducing water into the synthesis of formamidinium lead bromide (FAPbBr3) perovskite, ultra-stable FAPbBr3@PbBr(OH) fluorescent material was prepared. The photoluminescence intensity of the material after the addition of water increased 2.9 times compared with that before the addition of water. The excellent green fluorescence emission was still maintained after four cycles of wash–dry treatment. Meanwhile, it also exhibits good ultraviolet and thermal stability. The above enhanced performance of FAPbBr3 nanocrystals is attributed the protection of PbBr(OH). In addition, the prepared material can be used in anti-counterfeit patterns. The anti-counterfeit patterns have good color rendering and the luminous color has a high dependence on temperature. Both of these features make it very valuable for various fluorescent anti-counterfeiting labels. [ABSTRACT FROM AUTHOR]