ABSTRACT
Ultrasonic vibration-assisted con-rod fracture splitting (UV-CFS) was used to carry out the fracture experiment of 1045 quenched and tempered steel. The effect of ultrasonic vibration on the fracture properties was studied, the fracture microstructure and the evolution of dislocations near the fracture were analyzed and the microscopic mechanism was analyzed. The results show that in the case of conventional fracture splitting without amplitude, the dimple and the fracture belong to ductile fracture. With the increase in ultrasonic amplitude, the plasticity and pore deformation of the con-rod samples decrease at first and then increase; when the amplitude reaches a certain point, the load required for cracking is reduced to a minimum and the ultrasonic hardening effect is dominant, resulting in a decrease in the plasticity of the sample, a cleavage fracture, a brittle fracture, the minimum pore deformation and high cracking quality. The research results also show that with the increase in ultrasonic amplitude, the fracture dislocation density decreases at first, then increases, and dislocation entanglement and grain breakage appear, then decrease, and multiple dislocation slip trajectories appear. The changes in the dislocation density and microstructure are consistent with the above results.
ABSTRACT
In order to separate the colloidal in high-turbidity water, a kind of magnetic composite (Fe3O4/HBPN) was prepared via the functional assembly of Fe3O4 and an amino-terminal hyperbranched polymer (HBPN). The physical and chemical characteristics of Fe3O4@HBPN were investigated by different means. The Fourier Transform infrared spectroscopy (FTIR) spectra showed that the characteristic absorption peaks positioned at 1110 cm-1, 1468 cm-1, 1570 cm-1 and 1641 cm-1 were ascribed to C-N, H-N-C, N-H and C=O bonds, respectively. The shape and size of Fe3O4/HBPN showed a different and uneven distribution; the particles clumped together and were coated with an oil-like film. Energy-dispersive spectroscopy (EDS) displayed that the main elements of Fe3O4/HBPN were C, N, O, and Fe. The superparamagnetic properties and good magnetic response were revealed by vibrating sample magnetometer (VSM) analysis. The characteristic diffraction peaks of Fe3O4/HBPN were observed at 2θ = 30.01 (220), 35.70 (311), 43.01 (400), 56.82 (511), and 62.32 (440), which indicated that the intrinsic phase of magnetite remained. The zeta potential measurement indicated that the surface charge of Fe3O4/HBPN was positive in the pH range 4-10. The mass loss of Fe3O4/HBPN in thermogravimetric analysis (TGA) proved thermal decomposition. The -C-NH2 or -C-NH perssad of HBPN were linked and loaded with Fe3O4 particles by the N-O bonds. When the Fe3O4/HBPN dosage was 2.5 mg/L, pH = 4-5, the kaolin concentration of 1.0 g/L and the magnetic field of 3800 G were the preferred reaction conditions. In addition, a removal efficiency of at least 86% was reached for the actual water treatment. Fe3O4/HBPN was recycled after the first application and reused five times. The recycling efficiency and removal efficiency both showed no significant difference five times (p > 0.05), and the values were between 84.8% and 86.9%.
ABSTRACT
The use of magnetic composites in wastewater treatment has become widespread due to their high flocculating characteristics and ferromagnetism. This review provides an analysis and summary of the preparation and application of magnetic composites through controllable assembly for use in wastewater treatment. The applications of magnetic composites include the treatment of dye wastewater, heavy metal wastewater, microalgae suspensions, and oily wastewater. Additionally, the recycling and regeneration of magnetic composites have been investigated. In the future, further research could be focused on improving the assembly and regeneration stability of magnetic composites, such as utilizing polymers with a multibranched structure. Additionally, it would be beneficial to explore the recycling and regeneration properties of these composites.
ABSTRACT
Exploring the topological surface state of a topological semimetal by the transport technique has always been a big challenge because of the overwhelming contribution of the bulk state. In this work, we perform systematic angular-dependent magnetotransport measurements and electronic band calculations on SnTaS2 crystals, a layered topological nodal-line semimetal. Distinct Shubnikov-de Haas quantum oscillations were observed only in SnTaS2 nanoflakes when the thickness was below about 110 nm, and the oscillation amplitudes increased significantly with decreasing thickness. By analysis of the oscillation spectra, together with the theoretical calculation, a two-dimensional and topological nontrivial nature of the surface band is unambiguously identified, providing direct transport evidence of drumhead surface state for SnTaS2. Our comprehensive understanding of the Fermi surface topology of the centrosymmetric superconductor SnTaS2 is crucial for further research on the interplay of superconductivity and nontrivial topology.
ABSTRACT
The past few decades witness a typical urbanization era in large developing countries such as China. In line with the urbanization process, land resources have inevitably presented a series of changes. The evolution of urban land carrying capacity (ULCC) is appreciated as a yardstick for guiding towards sustainable urban development. This paper therefore proposes an alternative method from carrier-load perspective for investigating the evolution of ULCC performance in China during the rapid urbanization era of 2012-2017. The data employed for analysis is collected from 290 Chinese prefectural-level cities. Results indicate that ULCC performance in the urbanizing China has been evolving towards a better state, for which 94% of the surveyed cities have made progress. However, significant disparity exists between cities on ULCC evolution performance, in particular, mega cities tend to have better ULCC evolution performance. Some cities may have better evolution performance although they have a poor average ULCC value. Contrarily, some cities may present poor evolution performance but they carry a better average ULCC value. The research findings provide valuable references not only for policy-makers to better understand the state of ULCC across the country, and appreciate inspiring experiences and lessons for implementing effective tailor-made measures to improve the ULCC performance, but also for enriching the literature in land resource management.
ABSTRACT
Urbanization has prompted a dramatic social and economic development during the past decades in China. As a long-term national strategy, urbanization can only be implemented effectively with sufficient and sustainable ecological environment resources. By appreciating that the ecological environment carrying capacity (EECC) is a yardstick for guiding the practice of sustainable urban development, it is therefore pressing to examine the change of EECC adequately, so that the sustainable urbanization can be addressed appropriately. This paper develops a new method from load-carrier perspective to explore the change of EECC performance in the rapid urbanizing China. The EECC performance on water, land, atmosphere and overall perspectives were measured for 30 provinces in China based on the established method. The results show that most provinces in China are experiencing an improving EECC performance during the urbanization process, particularly with an obvious progress in land dimension. In referring to the spatial difference of overall EECC performance, the gap between 30 provinces has been narrowing during surveyed years. However, few provinces including Chongqing, Shandong and Jiangxi have undergone a degradation in overall EECC performance. The EECC performance in atmosphere dimension is still considered as a challenge faced by most provinces, evidenced by high level of PM2.5 concentration. These research findings provide valuable references not only for Chinese governments to formulate effective policy instruments and strategy measures for improving ecological environmental carrying status, but also for researchers to further study in the ecological environment carrying capacity in the context of other countries.
