Abstract: The freeze-thaw conditions have a great influence on the mechanical properties of rock mass, and the freeze-thaw failure of rock mass physical properties is one of the main diseases commonly encountered in rock engineering in cold areas. This paper systematically analyzes the freezing-thawing of rocks affected by freeze-thaw cycles, which provides a reliable theoretical basis for the future study of rock freeze-thaw damage and freeze-thaw fractures. In addition, the thermal, hydraulic and mechanical characteristics of rock mass under freeze-thaw cycle conditions have very important guiding significance for the study of the failure mechanism of engineering freeze-thaw cycle and the design of cold protection and thermal insulation in cold areas. Read More

Abstract: To address the low utilization rates of discarded concrete and industrial solid wastes, this study developed a novel foam concrete (FC) incorporating ground granulated blast furnace slag (GGBS), steel slag (SS), and cement as binders, with natural river sand blended with carbonized recycled fine aggregate (CRFA) as fine aggregates, and reinforced with modified basalt fiber (MBF). FC can be used to backfill voids in underground projects, which not only reduces the overall weight of the building, but also insulates and saves energy. Initially, a univariate experiment determined the optimal CRFA replacement rate and MBF content. Subsequently, the effects of GGBS and SS on the mechanical and physical properties of FC were investigated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed a synergistic hydration mechanism between GGBS and SS. The results showed that a 20% CRFA replacement and 4 kg·m-3 MBF produced maximum compressive and flexural strengths while reducing thermal conductivity. Additionally, the simultaneous addition of GGBS and SS decreased CH content and refined the pore structure, yielding a more uniform distribution with fewer connected pores. When both GGBS and SS were incorporated at a 20% replacement level, the 28-day compressive and flexural strengths peaked, and thermal conductivity decreased with increasing slag ratios. These findings confirm the synergistic hydration phenomenon of GGBS and SS and offer theoretical guidance for the engineering application of FC. Read More

Abstract: To reveal the microstructure formation mechanism of Cu-Sn alloy and the synergistic effect law of composite energy fields in the ultrasonic-assisted laser soldering process, this study employed a combination of experimental and numerical simulation methods to systematically investigate the effects of laser power (5-20W) and ultrasonic frequency (0-40kHz) on the temperature field, flow field, growth of interfacial intermetallic compounds (IMC), and reliability of solder joints. The experiment utilized a semiconductor laser system and an ultrasonic auxiliary device, and combined with COMSOL multiphysics simulation to construct a laser-ultrasonic composite energy field model, focusing on analyzing molten pool convection, temperature distribution, creep strain, and failure cycle characteristics. The results show that laser power dominates heat input and determines the energy accumulation state of the molten pool; ultrasonic frequency regulates molten pool flow through acoustic streaming effect, with around 30kHz achieving optimal momentum transfer, significantly improving temperature uniformity and refining the IMC layer; the synergy of high power (15-20W) and ultrasound (30-40kHz) can enhance the wettability and spreadability of solder joints, but excessively high ultrasonic frequency (40kHz) easily causes solder splashing. Accelerated life test simulations indicate that the interfacial region experiences creep strain concentration due to thermal mismatch, which is the weak link of fatigue failure, and ultrasonic assistance can extend the service life of solder joints by reducing the energy dissipation rate. This study clarifies the matching mechanism of laser-ultrasonic parameters, providing a theoretical basis for optimizing high-reliability soldering processes in electronic packaging. Read More

Abstract: Activated carbon (AC) is widely used in water treatment and environmental pollution control due to its excellent adsorption properties. However, the regeneration of saturated AC remains a critical challenge. As an efficient and environmentally friendly regeneration technology, electrochemical regeneration drives redox reactions through applied electric fields to degrade adsorbed pollutants and restore AC's adsorption capacity. This paper reviews the mechanisms of electrochemical AC regeneration, including direct electron transfer, ·OH radical oxidation, and electrochemical desorption. It explores how key parameters such as electrode materials, current density, electrolyte type, and pH value affect regeneration efficiency. Research demonstrates that electrochemical regeneration offers advantages like low energy consumption, minimal secondary pollution, and high regeneration rates, making it particularly suitable for regenerating saturated AC with high-concentration organic pollutants. Future research should focus on optimizing reactor designs, developing stable electrode materials, and exploring application potential in complex real-world wastewater systems. Read More

Abstract: Two-dimensional (2D) carbon nitrides are attracting growing interest because of their structural diversities and distinctive electronic properties. A first principles investigation has been carried out on a new 2D carbon nitride C12N2 with orthorhombic lattice. The carbon nitride C12N2 shows medium electronic band gap of 1.01 eV, high carrier mobility about of 2.2×105 cm2V-1s-1, suggesting that it is a promising candidate used on short channel transistors. The strain behavior of C12N2 has been studied, revealing that it can endure a uni-axial strain or compression of up to ±10%. Furthermore, the band edge positions, effective masses and band gap are seriously changed under different level of strains. It suggests that appropriate tensile strain can effectively overcome the short channel effect in semiconductor device. Read More