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Copyright © The Author(s) 2021. The particle breakage of calcareous sands plays a key role in determining the particle shape and shear strength. This process has been analysed in the current study by employing the ring shear tests on calcareous sands sampled from the South China Sea. In this study, a set of parameters, e.g. roundness and aspect ratio, have been employed to quantify the geometrical properties of calcareous sands pre- and after the breakage. These two parameters have been found to correlate well with the vertical loading stress level, shear strain and shear strength. The particle breakage leads to the change of micro-structure during the shear test, as illustrated by the Scanning Electron Microscopy (SEM) images. It is found that during the shearing deformation, particle breakages can effectively reduce, while particle rearrangements can increase the shear strength of the calcareous sands. Strategic Priority Research Program of the Chinese Academy of Sciences; National Natural Science Foundation of China

Porcelain-veneered Y-TZP fixed dental prostheses often fail from fracture and wear. Zirconia with its exceptional homogenous properties contributes to alleviate the failure. Powder injection molding (PIM) has long been found to enable a much more homogeneous microstructure to components when compared to those from die pressing. However, PIM parts, however, may have a slight difference in properties for different areas due to the nature of the injection process of the feedstock. In this study, zirconia dental ceramic parts were fabricated by the powder injection molding technique that utilizes a multi-component binder system consisting of paraffin, high density polyethylene, polypropylene, and stearic acid aiming to improve the behavior in the densification of powder shaping. The nano ZrO2 powders were firstly granulated before mixing to ensure good dispersion in the feedstock. The homogeneity of sintered zirconia was characterized by determining density and hardness of ten equally thick-section zirconia and four bars. The result showed that TZ-3YS-E zirconia obtained a sintering density of 6.05 g·cm− 3 and a hardness of 1300 HV0.5 with a small fluctuation sintered at 1475 °C. The homogeneity in the region away-from- gate was superior to the nearer-gate region based on evaluation of density, hardness, flexural strength and observation of microstructure, as well as the simulation of the mold filling of the feedstock. The average absolute deviation of hardness of slices 1 to 5 near the injection gate was 27.0 while that of slices 6 to 10 away from the injection gate was 14.0. The differences on the homogeneity and performances were regarded as the results of the drop of temperature and pressure in the final stage of mold filling of feedstock.

Chinese Academy of Sciences, National Natural Science Foundation of China, Youth Innovation Promotion Association of CAS

The construction of concrete-filled steel tube (CFST) pouring is a key process in the building of CFST arch bridges, directly affecting engineering quality and structure safety. However, the construction of CFST pouring has complex procedures and multiple risk sources, and major engineering problems often arise from incorrect risk assessment. In order to reasonably analyze the hazards of various risk sources to engineering, avoid major engineering problems, and improve engineering quality, risk assessment is conducted on the construction of CFST pouring in this paper. First, As Low As Reasonably Practicable (ALARP) and risk assessment matrix are introduced, and statistics are made of the occurrence probability and risk loss rating of three major risks in the construction of CFST pouring, resulting in one I-level risk, two II-level risks, five III-level risks, and two IV-level risks. Finally, seven unacceptable events requiring special attention from decision-makers are obtained through ALARP. The results of risk assessment can be used as a basis for the construction management of practical projects, and major risks are strictly controlled through strengthening management and other methods, which will effectively reduce risk levels, providing a powerful guarantee for increasing the span of CFST arch bridges.

National Natural Science Foundation of China; Key Laboratory of Geotechnical and Underground Engineering (Tongji University); Ministry of Education; The Strategic Priority Research Program of the Chinese Academy of Sciences; Youth Innovation Promotion Association of CAS

The organic-inorganic lead halide perovskites are attractive materials for photovoltaic application. The most widely studied perovskites based on methyl ammonium organic cation are less likely to form an ideal high-symmetry configuration at room temperature, leading to the appearance of local lattice strain. Herein, this study reports a strategy for the construction of thermally stable cubic perovskites at room temperature through the incorporation of the larger organic cation dimethyl ammonium. Detailed characterization on the single crystals and thin films reveals the formation of cubic phase with the addition of a certain amount of dimethyl ammonium at room temperature. With the presence of dimethyl ammonium, the nonradiative recombination in perovskite is suppressed, showing a longer PL lifetime and hole diffusion length. The more efficient charge extraction leads to an improvement in the photocurrent density, and then the device efficiency from 17.1% to 18.6%, together with an enhanced thermal stability at 85 °C. The influence of incorporating a larger organic cation on the structural configuration, optical properties, charge extraction, as well as the photovoltaic performance is systematically investigated, which offers an alternative way to improve the intrinsic stability of hybrid perovskites. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version