The optical absorption properties of the two-dimensional (2D) MoSi2N4 monolayer is often a focus of research. By semi doping Cr and W at M sites, the influence of M-site atoms on the optical absorption properties of MA2Z4 series materials was investigated. The results show that the atomic layer spacing of 2D materials has some changes after the semi doping of the Cr and W elements, but the entire crystal structure is not significantly different. The semi doping of Cr atoms makes the MoSi2N4 monolayer have an additional absorption peak, the highest absorption peak of the Mo0.5Cr0.5Si2N4 monolayer has a large red shift corresponding to the wavelength, and the width of the absorption peak is also greatly improved. The semi doping of W element results in a red shift of the strongest absorption peak and an increase of the maximum absorption intensity of the Mo0.5W0.5Si2N4 monolayer.
We propose a visible light positioning system based on four-quadrant photodetector and improved genetic algorithm, where single light-emitting diode lamp and four-quadrant photodetector are adopted as light source transmitter and receiver. The improved genetic algorithm and the illuminance values received by the light source receiver are employed to accurately locate the position of measured points. The improved genetic algorithm has a better performance in accuracy and convergence speed. The experimental results indicate that the average positioning error of the proposed scheme is 4.0230 cm. Compared with the indoor visible light positioning system using standard genetic algorithm, the proposed scheme can obtain higher positioning accuracy and robustness under the condition of shorter average positioning time.
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