Plasma-Engraved Lattice-Matched NiO/NiFe2O4 Heterostructure with Ample Oxygen Vacancies for Efficient Water Electrolysis and Zn-Air Batteries.

Heterogeneous interface and defect engineering offer effective pathways to accelerate oxygen evolution reaction (OER) charge transfer kinetics and motivate optimal intrinsic catalytic activity. Herein, we report the lattice-matched NiO/NiFe2O4 heterostructure with ample oxygen vacancies (Vo-NiO/NiFe2O4) induced by a feasible hydrothermal followed by calcination and plasma-engraving assistant technique, which shows the unique porous microflower arrangement of intertwined nanosheets. Benefitting from the synergetic effects between lattice-matched heterointerface and oxygen vacancies induce the strong electronic coupling, optimized OH-/O2 diffusion pathway and ample active sites, thus-prepared Vo-NiO/NiFe2O4 presents a favorable OER performance with a low overpotential (261 mV @ 10 mA cm-2) and small Tafel slope (39.4 mV dec-1), even surpassing commercial RuO2 catalyst. Additionally, the two-electrode configuration water electrolyzer and rechargeable zinc-air battery assembled by Vo-NiO/NiFe2O4 catalyst show the potential practical application directions. This work provides an innovative avenue for strengthening OER performance toward water electrolysis and Zn-air batteries via the interface and vacancy engineering strategy.

Online learning resource recommendation method based on multi-similarity metric optimization under the COVID-19 epidemic.

With the continuous COVID-19 pneumonia epidemic, online learning has become a normal choice for many learners. However, the problems of information overload and knowledge maze have been aggravated in the process of online learning. A learning resource recommendation method based on multi similarity measure optimization is proposed in this paper. We optimize the user score similarity by introducing information entropy, and use particle swarm optimization algorithm to determine the comprehensive similarity weight, and determine the nearest neighbor user with both score similarity and interest similarity through secondary screening in this method. The ultimate goal is to improve the accuracy of recommendation results, and help learners learn more effectively. We conduct experiments on public data sets. The experimental results show that the algorithm in this paper can significantly improve the recommendation accuracy on the basis of maintaining a stable recommendation coverage.

Comparison of two internal fixation systems in lumbar spondylolysis by finite element methods.

BACKGROUND AND PURPOSE: Internal fixation surgeries are currently the most effective treatments for lumbar spondylolysis, but the optimal fixation method is still on debate. This study was designed to compare the biomechanical characteristics of two fixation methods for lumbar spondylolysis, the pedicle screw-U shape rod (PSUSR) internal fixation system, and the pedicle screw-vertebral plate hook (PSVPH) internal fixation system, through three-dimensional finite element analysis, expecting to provide clinical guidance. METHODS: Four finite element models (A, B, C, D) of L4-S1 vertebral body of a female patient were reconstructed by CT image segmentation. (A: intact model. B: spondylolysis model. C: spondylolysis model with PSUSR internal fixation. D: spondylolysis model with PSVPH internal fixation). Six physiological motion states were simulated by applying 500N concentrated force and 10Nm moment load to four models. The biomechanical advantages of the two internal fixation systems were evaluated by comparing the range of motion (ROM), maximum stress, maximum strain, and maximum displacement of the models. RESULTS: Compared to model B, the ROM decreased by 35.7%-57.1% in model C and 39.7%-64.8% in model D. The maximum displacements of model C and D both decreased. The maximum stresses in both vertebral and the internal fixation system are greater in model C than those in model D. The maximum stress and strain reduction of L5-S1 intervertebral disc in model D was greater than that in model C. Model D restores the articular cartilage stresses to the normal levels of model A. The maximum stress and maximum displacement of the bone graft in model C are greater than those in model D. CONCLUSIONS: The PSVPH internal fixation system has better biomechanical properties than PSUSR internal fixation system in several mechanical comparisons. Experimental results suggest that PSVPH internal fixation system can effectively treat lumbar spondylolysis while preserving segmental mobility, and can be the treatment of choice.