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In this study, a tracking and pointing control system with a dual-FSM (fast steering mirror) two-dimensional flexible turntable composite axis is proposed. It is applied to the target-tracking accuracy control in a GI LiDAR (ghost imaging LiDAR) system. Ghost imaging is a multi-measurement imaging method; the dual-FSM GI LiDAR tracking and pointing imaging control system proposed in this study mainly solves the problems of the high-resolution remote sensing imaging of high-speed moving targets and various nonlinear disturbances when this technology is transformed into practical applications. Addressing the detrimental effects of nonlinear disturbances originating from internal flexible mechanisms and assorted external environmental factors on motion control's velocity, stability, and tracking accuracy, a nonlinear active disturbance rejection control (NLADRC) method based on artificial neural networks is advanced. Additionally, to overcome the limitations imposed by receiving aperture constraints in GI LiDAR systems, a novel optical path design for the dual-FSM GI LiDAR tracking and imaging system is put forth. The implementation of the described methodologies culminated in the development of a dual-FSM GI LiDAR tracking and imaging system, which, upon thorough experimental validation, demonstrated significant improvements. Notably, it achieved an improvement in the coarse tracking accuracy from 193.29 μrad (3σ) to 87.21 μrad (3σ) and enhanced the tracking accuracy from 10.1 μrad (σ) to 1.5 μrad (σ) under specified operational parameters. Furthermore, the method notably diminished the overshoot during the target capture process from 28.85% to 12.8%, concurrently facilitating clear recognition of the target contour. This research contributes significantly to the advancement of GI LiDAR technology for practical application, showcasing the potential of the proposed control and design strategies in enhancing system performance in the face of complex disturbances. [ABSTRACT FROM AUTHOR]

Current low-light enhancement algorithms fail to suppress noise when enhancing brightness, and may introduces structural distortion and color distortion caused by halos or artifacts. This paper proposes a content-illumination coupling guided low-light image enhancement network (CICGNet), it develops a truss topology based on Retinex as backbone to decompose low-light image component in an end-to-end way. The preservation of content features and the enhancement of illumination features are carried out along with depth and width direction of the truss topology. Each submodule uses the same resolution input and output to avoid the introduction of noise. Illumination component prevents misestimation of global and local illumination by using pre- and post-activation features at different depth levels, this way could avoid possible halos and artifacts. The network progressively enhances the illumination component and maintains the content component stage-by-stage. The proposed algorithm demonstrates better performance compared with advanced attention-based low-light enhancement algorithms and state-of-the-art image restoration algorithms. We also perform extensive ablation studies and demonstrate the impact of low-light enhancement algorithm on the downstream task of computer vision. Code is available at: https://github.com/Ruini94/CICGNet. [ABSTRACT FROM AUTHOR]

High-resolution imaging has become a development trend and is widely used in military and civil fields. As the carrying equipment of imaging system, the speed stability of tracking turntable is the basis of high-resolution and stable imaging. At present, in the aerospace field, there are high requirements for peak power dissipation and holding torque, so flexible joints such as harmonic gear drive are mostly used to realize the function. The characteristics of flexible load have a great impact on the characteristics of motion control, which is easy to cause mechanical resonance, lead to system instability, and have a great impact on speed stability and position tracking accuracy. Therefore, it is necessary to study the servo system of flexible load. In order to solve the problems of high-precision position control and speed stability at low speed of flexible turntable with uncertain load, on the one hand, we comprehensively consider the advantages and disadvantages of semi-closed-loop and full closed-loop control and design a dual-position loop feedback control system combined with the analysis of dynamic equation to realize speed stability and high-precision position control. On the other hand, according to the requirements of the speed stability at low speed of the turntable, the tracking differentiator (TD) is designed innovatively through the language three-point interpolation subdivision and five-point pre-deduction calculation method. Finally, a dual-position loop LLADRC (language linear active disturbances rejection controller) control method based on harmonic gear drive is studied. By comparing the semi-closed loop, dual-position loop, dual-position loop LADRC (linear active disturbances rejection controller, ADRC), and dual-position loop LLADRC methods through simulation analysis, it can be shown that the double position LLADRC control method is obviously superior to other schemes in terms of rapidity, speed stability at low speed, and position tracking accuracy. The theoretical research is verified by experimental test. When the given speed is 0.1 ° / s , taking the pitch axis as an example, the pitch speed error is 0.0039 ° / s (3σ). When the maximum speed of the given curve is 20 ° / s and the maximum acceleration is 16 ° / s , the position tracking error is 0.0025° (3σ). This control method solves the problems of system instability and low-speed stability in high-precision control of turntable system based on harmonic gear drive and provides a method for high-precision control of high-resolution imaging turntable. [ABSTRACT FROM AUTHOR]

In this paper, a tracking and pointing control system with dual-FSM (fast steering mirror) composite axis is proposed. It is applied to the target-tracking accuracy control in a 3D GISC LiDAR (three-dimensional ghost imaging LiDAR via sparsity constraint) system. The tracking and pointing imaging control system of the dual-FSM 3D GISC LiDAR proposed in this paper is a staring imaging method with multiple measurements, which mainly solves the problem of high-resolution remote-sensing imaging of high-speed moving targets when the technology is transformed into practical applications. In the research of this control system, firstly, we propose a method that combines motion decoupling and sensor decoupling to solve the mechanical coupling problem caused by the noncoaxial sensor installation of the FSM. Secondly, we suppress the inherent mechanical resonance of the FSM in the control system. Thirdly, we propose the optical path design of a dual-FSM 3D GISC LiDAR tracking imaging system to solve the problem of receiving aperture constraint. Finally, after sufficient experimental verification, our method is shown to successfully reduce the coupling from 7% to 0.6%, and the precision tracking bandwidth reaches 300 Hz. Moreover, when the distance between the GISC system and the target is 2.74 km and the target flight speed is 7 m/s, the tracking accuracy of the system is improved from 15.7 μrad (σ) to 2.2 μrad (σ), and at the same time, the system recognizes the target contour clearly. Our research is valuable to put the GISC technology into practical applications. [ABSTRACT FROM AUTHOR]

It is of great significance to study on the shift of temperature zone boundaries for revealing the climate change pattern and its environmental effects. Based on daily average temperature data from 32 standard meteorological stations in the Qinling Mountains from 1964 to 2015, the growing season start and end (GSS and GSE) of the climatic growing season parameters were calculated based on a temperature threshold of 10 °C, and the growing season length (GSL) was obtained by subtracting GSE from GSS. We have analyzed the spatiotemporal variations of these parameters in the Qinling Mountains and the shift rules of the warm temperate zone and northern subtropics zone boundaries in China over the past 52 years. Our research generated three primary results. First, the spatial distribution and changing trends of the GSS, GSE, and GSL were significantly different before and after abrupt changes in temperature. After the abrupt change, the coverages of the three were all gradually expanding to the higher altitude areas. The change rates of the three were faster, the trends were more significant, and the differences between the north and the south were obvious, especially in the northern slope. Second, the boundaries of both the warm temperate zone and the northern subtropical zone in China showed upward position shifts, and the area coverage changed along the northern and southern slopes of the Qinling Mountains, and the change amplitudes were even greater after the abrupt change in temperature. Third, there was a significant north–south difference in the response of China's temperature zones to climate change. The temperature zone on the northern slope was more sensitive to climate warming. It is worth emphasizing that the shifts of the temperature zones did not change the fact that the Qinling Mountains are the boundary between China's subtropical and the warm temperate zones. The north subtropical zone is still located on the southern slope of the Qinling Mountains, and the northern slope is still in the warm temperate zone. [ABSTRACT FROM AUTHOR]

Rare-earth-doped luminescent thin films have been responsible for unprecedented positive impacts in optoelectronic devices with high lateral resolution, excellent thermal stability, and strong adhesion to the solid surface. However, limited emission intensity and high-cost fabrication routine deeply inhibit their practical and commercial applications. Here, we propose a grain orientation engineering strategy via simple and low-cost polymer-assisted deposition (PAD) to fabricate textured BaMoO 4 : Eu3+ thin films with highly improved emission intensity by reducing the lattice mismatch between the thin films and substrates. The high-quality <004>-textured BaMoO 4 : Eu3+ thin film mounted on the (001)-oriented Si substrate with the Lotgering factor F 004 of 94.6%, boosting up the emission intensity of which to 366% compared to their randomly oriented counterparts. Moreover, the as-fabricated BaMoO 4 : Eu3+ film shows strong red emission at 615 nm corresponding to the 5 D 0 →7 F 2 transition of Eu3+ with correlated color temperature (CCT) of 2922 °C and ultra-high color purity (nearly 100%). Furthermore, the geometry, size, and luminescence performance of the crystals can be precisely manipulated by tuning the growth temperature, layers of the film, and doping concentration. The present research offers a novel and low-cost route to engineer luminescent films with controllable orientation and enhanced emission intensity, which demonstrate great potentials towards practical applications and industrialization. [ABSTRACT FROM AUTHOR]

All-inorganic halide perovskites have attracted great attention by virtue of the merits of bright emission, tunable wavelength and narrow-band emission. Despite the excellent optical features, all-inorganic halide perovskite materials have suffered from intrinsic instability, which has limited their applications in various optoelectronic devices. To mitigate the intractable issue, we demonstrated the CsPbBr3 nanoparticles decorated with smaller SiO2 nanocrystals to passivate the surface defects; SiO2 nanoparticles were applied as a barrier layer to maintain the optical property and enhance environmental stability. A facile in situ method was proposed to prepare CsPbBr3/SiO2 nanocomposites, in which an environmental ethanol/water solvent system was needed with the addition of tetraethyl orthosilicate (TEOS) as a silicon precursor. The obtained CsPbBr3/SiO2 nanocomposites have better optical characteristic and stability than bare CsPbBr3 nanoparticles. Even 70% photoluminescence intensity of as-prepared CsPbBr3/SiO2 nanocomposites can be maintained after 168 h storage in ethanol. This newly developed synthesis will open up a new route for the fabrication of optoelectronic devices in an environmentally friendly way, and the as-obtained perovskite materials with improved stability will make them great potential for multifunctional optoelectronic devices. [ABSTRACT FROM AUTHOR]

All-inorganic perovskite nanocrystals have held great promise as incredibly effective luminescent materials and also have been synthesized efficiently by room temperature approaches. Toluene, a high toxicity solvent, is often used as a valid antisolvent in ligand-assisted reprecipitation strategy, which badly restricts the commercial application of this convenient method. Here, aiming to address the toluene toxicity issue, the low toxic tetraethyl orthosilicate (TEOS) is employed as a new alternative antisolvent to achieve high uniform and composition dependent luminescent all-inorganic perovskite Cs 4 PbX 6 (X = I, Br, Cl) combined with CsPbX 3 (X = I, Br, Cl) nanocrystals with tunable emission large-span wavelengths (626–437 nm) and remarkably narrow full width at half-maximum (FWHM) monochromaticity (down to 19 nm). Meanwhile, the ratio of CsBr to PbBr 2 is proved to be a critical factor to control the crystalline phase of the resulting perovskite nanocrystals. Additionally, one monochromatic light-emitting diode (LED) lamp with brightly pure green emission is fabricated based on bromine-based perovskite nanocrystals. This newly developed low toxicity antisolvent synthesis (LTaS) is suitable candidate for commercial production in an environmentally-friendly way, and the as-obtained perovskite materials with superior optical merits will be brought to the forefront of lighting and displays. [ABSTRACT FROM AUTHOR]

For highly efficient photocatalytic remediation of organic pollutants, broad-spectrum light response and effective charge separation are two key goals. To achieve these goals, a novel biochar (BC) modified PbMoO 4 composite catalyst was successfully synthesized in situ by combining coprecipitation with pyrolysis treatment of poplar sawdust and the technical feasibility of degradation of tetracycline (TC) with compound photocatalyst prepared from recovered agricultural and forestry residues was preliminarily demonstrated. The characterization demonstrated that the presence of BC narrowed the bandgap, enhanced visible light absorption as well as facilitated charge separation. Three composites (with the mass ratio of PbMoO 4 to BC = 1:4; 1:1; and 4:1, respectively) displayed higher activity than pure PbMoO 4. The results showed that the composite with the PbMoO 4 to BC ratio of 1:4 exhibited the best photocatalytic activity, for 150 mg L−1 TC the removal rate was 61.0%, and the rate constant was 8.1 × 10−3 min−1, while the photocatalytic activity of PbMoO 4 was 26.0% and 3.9 × 10−3 min−1. The reactions in the presence of radical quenchers indicated that holes (h+) and superoxide radicals (O 2 −) were the dominant active species for photodegradation. In different water matrices, for 150 mg L−1 TC solution the photocatalytic activity of optimal photocatalyst decreased as follows: ultrapure water > artificial sewage > farm sewage > municipal sewage. Moreover, the catalyst exhibited good stability over five cycles. Therefore, BC doped PbMoO 4 provides a useful strategy for improving the photocatalytic ability of PbMoO 4 -based photocatalysts and offers a promising method for water purification. [Display omitted] • Using poplar sawdust as biochar source realized the rational application of waste. • In situ synthesis enhanced the adsorption and photocatalytic activity of PbMoO 4. • Superior electrical conductivity of BC helps transport of photogenerated carrier. • BC strengthened the visible light response of PbMoO 4 @BC-1. • PbMoO 4 @BC-1 showed promising visible-light photodegradation for TC degradation. [ABSTRACT FROM AUTHOR]

• Air-stable MAPbI 3 was fabricated by solvent dose control and ligand regulation. • The MAPbI 3 quantum dots exhibit high photoluminescence quantum yield up to 80%. • The quantum yield was still at 74% of its original value after 20 days. • The strategy is also suitable for preparing color-tunable MAPbX 3 (X = Cl, Br, I). Methyl-ammonium lead iodide (MAPbI 3) perovskite quantum dots (QDs) have emerged as a promising material for photoelectronic, however, they usually suffer intrinsically from the environmental instability and low photoluminescence quantum yield (PLQY), which will seriously impede their commercial applications. Here, we report an internal-external combination strategy by lowering the dose of good solvent and reducing the chain length of amine ligand to simultaneously enhance the air stability and PLQY of MAPbI 3 QDs. The low-dose solvent can effectively reduce internal iodine vacancies defects and external residual solvent molecules, meanwhile, the faster and denser assembly of nimble short-chain (SC) ligand on the MAPbI 3 QDs surface can helpfully enhance the external surface passivation. As a result, compared to MAPbI 3 QDs synthesized by traditional ligand-assisted reprecipitation (LARP) method, the air stability and PLQY of which are improved by more than four orders of magnitude (from a few minutes to dozens of days) and nearly two times (from 42% to 80%) prepared by our strategy. Besides, this strategy can widely tune the color of MAPbX 3 (X = Cl, Br, I) QDs from 388 to 735 nm through regulating components. This internal-external combination strategy can provide some beneficial enlightenment for preparing long-term air-stable hybrid perovskite QDs with high PLQY, which drastically driving their commercial applications. [ABSTRACT FROM AUTHOR]