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The Harris Hawks Optimization algorithm (HHO) is a sophisticated metaheuristic technique that draws inspiration from the hunting process of Harris hawks, which has gained attention in recent years. However, despite its promising features, the algorithm exhibits certain limitations, including the tendency to converge to local optima and a relatively slow convergence speed. In this paper, we propose the multi-strategy improved HHO algorithm (MSI-HHO) as an enhancement to the standard HHO algorithm, which adopts three strategies to improve its performance, namely, inverted S-shaped escape energy, a stochastic learning mechanism based on Gaussian mutation, and refracted opposition-based learning. At the same time, we conduct a comprehensive comparison between our proposed MSI-HHO algorithm with the standard HHO algorithm and five other well-known metaheuristic optimization algorithms. Extensive simulation experiments are conducted on both the 23 classical benchmark functions and the IEEE CEC 2020 benchmark functions. Then, the results of the non-parametric tests indicate that the MSI-HHO algorithm outperforms six other comparative algorithms at a significance level of 0.05 or greater. Additionally, the visualization analysis demonstrates the superior convergence speed and accuracy of the MSI-HHO algorithm, providing evidence of its robust performance. [ABSTRACT FROM AUTHOR]

Abstract: Core–shell Fe2O3 hollow micro-spheres have been fabricated by a simple two-step method. Firstly, compound of carbon and iron hydrate were synthesized by hydrothermal process. The obtained products were characterized by X-ray diffraction (XRD), which exhibit the diffraction peaks of orthorhombic phase of iron oxide hydroxide. Energy dispersive X-ray spectroscopy (EDS) measurement indicates the existence of carbon. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) results show flake-based urchin-like architecture. Secondly, core–shell hollow micro-spheres were obtained by subsequent annealing process. XRD pattern of the final sample is well in agreement with the standard pattern of the hexagonal rhomb-centered α-Fe2O3. FE-SEM and TEM images reveal that those hollow spheres are of core–shell architecture with holes on the surfaces. Magnetic hysteresis measurement carried out on vibrant sample magnetometer (VSM) shows weak ferromagnetic property at room temperature. On the basis of the obtained experimental results, the possible formation mechanism was discussed. [Copyright &y& Elsevier]

Abstract: Well-crystallized zinc vanadium oxide hydroxide hydrate Zn3(OH)2V2O7·nH2O nanobelts were successfully synthesized by a simple hydrothermal method. X-ray diffraction patterns of the samples are in agreement with the standard pattern of the hexagonal Zn3(OH)2V2O7·nH2O. Transmission electron microscopy images reveal that those belts are several micrometers in length and 80–100nm in width. The crispations of the as-synthesized nanobelts are probably duo to their thickness. The products are shown to be crystallized by selected area electron diffraction characterization. The morphologies of the products were tuned by simply changing the reaction temperature. Nanotubes and expanding nanobelts are obtained at 140°C and 160°C, respectively. Magnetic hysteresis measurements indicate that the as-synthesized nanobelts are of weak ferromagnetic property at room temperature. [Copyright &y& Elsevier]