Multi-threshold image segmentation using an enhanced fruit fly optimization for COVID-19 X-ray images.

Since the outbreak of COVID-19, it has seriously endangered the health of human beings. Computer automatic segmentation of COVID-19 X-ray images is an important means to assist doctors in rapid and accurate diagnosis. Therefore, this paper proposes a modified FOA (EEFOA) with two optimization strategies added to the original FOA, including elite natural evolution (ENE) and elite random mutation (ERM). To be specific, ENE and ERM can effectively speed up the convergence and deal with the problem of local optima, respectively. The outstanding performance of EEFOA was confirmed by experimental results comparing EEFOA with the original FOA, other FOA variants, and advanced algorithms at CEC2014. After that, EEFOA is implemented for multi-threshold image segmentation (MIS) of COVID-19 X-ray images, where a 2D histogram consisting of the original greyscale image and the non-local means image is used to represent the image information, and Rényi's entropy is used as the objective function to find the maximum value. The evaluation results of the MIS segmentation experiments show that, whether high or low threshold, EEFOA can achieve higher quality segmentation results and greater robustness than other advanced segmentation methods.

Direct Atomic Observation of Reversible Orientation Switch in Monoatomic-Layered Gold Membrane Conducted by Dynamic Vortex.

Controlling the material structure at an atomic scale to tune their physicochemical and nanoengineering properties is a major driving force of nanotechnology. However, manipulating the structural variation in monoatomic-layered metals remains a challenge, hindering the full application of their novel properties. Here, we show by experiments and simulations that a reversible orientation rotation of monoatomic-layered gold membrane embedded in the gold crystal is performed through dynamic vortexing that is comprised of the circular motion of atoms. A pair of dynamic vortices are successively generated and together span the entire gold membrane to accomplish the orientation switch. Density functional theory calculations demonstrate that the gold membrane exhibits a Rashba-type spin splitting, while the spin direction reversibly flips with the switching orientation of the gold membrane. The results provide a conceptual approach for constructing a novel electronic system with monoatomic-layered metals and the reversible spin-flip has inspiring applications for future spintronics.