The Fourier transform spectrometer (FTS) is a core instrument for solar observation with high spectral resolution, especially in the infrared. The Infrared System for the Accurate Measurement of Solar Magnetic Field (AIMS), working at 10–13 μm, will use an FTS to observe the solar spectrum. The Bruker IFS-125HR, which meets the spectral resolution requirement of AIMS but simply equips with a point source detector, is employed to carry out preliminary experiment for AIMS. A sun-light feeding experimental system is further developed. Several experiments are taken with them during 2018 and 2019 to observe the solar spectrum in the visible and near infrared wavelength, respectively. We also proposed an inversion method to retrieve the solar spectrum from the observed interferogram and compared it with the standard solar spectrum atlas. Although there is a wavelength limitation due to the present sun-light feeding system, the results in the wavelength band from 0.45–1.0 μm and 1.0–2.2 μm show a good consistency with the solar spectrum atlas, indicating the validity of our observing configuration, the data analysis method and the potential to work in longer wavelength. The work provided valuable experience for the AIMS not only for the operation of an FTS but also for the development of its scientific data processing software.
Dynamic degradation occurs when chaotic systems are implemented on digital devices, which seriously threatens the security of chaos-based pseudorandom sequence generators. The chaotic degradation shows complex periodic behavior, which is often ignored by designers and seldom analyzed in theory. Not knowing the exact period of the output sequence is the key problem that affects the application of chaos-based pseudorandom sequence generators. In this paper, two cubic chaotic maps are combined, which have symmetry and reconfigurable form in the digital circuit. The dynamic behavior of the cubic chaotic map and the corresponding digital cubic chaotic map are analyzed respectively, and the reasons for the complex period and weak randomness of output sequences are studied. On this basis, the digital cubic chaotic map is optimized, and the complex periodic behavior is improved. In addition, a reconfigurable pseudorandom sequence generator based on the digital cubic chaotic map is constructed from the point of saving consumption of logical resources. Through theoretical and numerical analysis, the pseudorandom sequence generator solves the complex period and weak randomness of the cubic chaotic map after digitization and makes the output sequence have better performance and less resource consumption, which lays the foundation for applying it to the field of secure communication.
Image sticking in liquid crystal display (LCD) is related to the residual direct current (DC) voltage (RDCV) on the cell and the dynamic response of the liquid crystal materials. According to the capacitance change of the liquid crystal cell under the DC bias, the saturated RDCV (SRDCV) can be obtained. The response time can be obtained by testing the optical dynamic response of the liquid crystal cell, thereby evaluating the image sticking problem. Based on this, the image sticking of vertical aligned nematic (VAN) LCD (VAN-LCD) with different cell thicknesses (3.8 μm and 11.5 μm) and different concentrations of γ-Fe 2 O 3 nanoparticles (0.017 wt.%, 0.034 wt.%, 0.051 wt.%, 0.068 wt.%, 0.136 wt.%, 0.204 wt.%, and 0.272 wt.%) was evaluated, and the effect of nano-doping was analyzed. It is found that the SRDCV and response time decrease firstly and then increase with the increase of the doping concentration of γ-Fe 2 O 3 nanoparticles in the VAN cell. When the doping concentration is 0.034 wt.%, the γ-Fe 2 O 3 nanoparticles can adsorb most of the free impurity ions in liquid crystal materials, resulting in 70% reduction in the SRDCV, 8.11% decrease in the decay time, and 15.49% reduction in the rise time. The results show that the doping of γ-Fe 2 O 3 nanoparticles can effectively improve the image sticking of VAN-LCD and provide useful guidance for improving the display quality.
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