Strong blue emission around 435 nm from porous silicon (PS) embedded in $\mathrm{Pb}({\mathrm{Zr}}_x,{\mathrm{Ti}}_{\text{1−x}}){\mathrm{O}}_3$ (PZT) is realized, which is stable and clearly visible to the naked eye even after exposure in an ambient atmosphere for a year. The sample is obtained by hydrothermal etching of (100)-oriented single crystal silicon wafers in an HF aqueous solution, followed by pulsed laser ablation deposition of a PZT thin layer on the surface of the PS. The electrons and holes excited from silicon nanocrystallites could be separated by the PZT-induced electrostatic field and migrate to the boundaries of PS/PZT along opposite directions, respectively. Therefore, the blue emission is interpreted in terms of the recombination of excited carriers from the silicon nanocrystallites in the interfacial region of PS/PZT.

Autonomous navigation for agricultural machinery has broad and promising development prospects. Kalman filter technology, which can improve positioning accuracy, is widely used in navigation systems in different fields. However, there has not been much research performed into navigation for sprinkler irrigation machines (SIMs). In this paper, firstly, a self-developed SIM is introduced. Secondly, the kinematics model is established on the platform of the self-developed SIM, and the updated Sage–Husa adaptive Kalman filter, which is an accurate and real-time self-adaptive filtering algorithm, is applied in the navigation of the SIM with the aim of improving the positioning accuracy. Finally, experiment verifications were carried out, and the results show that the self-developed SIM has good navigation performance. Besides this, the influence of abnormal observations on the positioning accuracy of the system can be restrained by using the updated Sage–Husa adaptive Kalman filter. After using the updated Sage–Husa adaptive Kalman filter for the SIM, the maximum deviation between the SIM and the predetermined path is 0.18 m, and the average deviation is 0.08 m; these deviations are within a reasonable range. This proves that the updated Sage–Husa adaptive Kalman filter is applicable for the navigation of sprinkler irrigation machines.

Larger diameter and velocity and smaller landing angle of sprinkler irrigation droplets are more likely to cause soil splash and erosion. However, the mechanism of crop canopy influence on the physical parameters of sprinkler droplets is unknown. In this study, with the landing angle of sprinkler irrigation droplets as the independent variable and maize plants (Zea mays L.) as the research object, an indoor sprinkler irrigation experiment was carried out. The effects of maize canopy and variation in sprinkler irrigation droplets landing angle on the value and spatial distribution pattern of size, the velocity, and the landing angle of throughfall droplets was analyzed. In addition, the spatial variation patterns of throughfall droplets size, velocities’ distribution, and individual droplet’s speed, kinetic energy were also explored. The results showed that maize canopy and the decreasing of the sprinkler irrigation droplet landing angle had a positive and obvious effect on reducing the size and velocity of penetrating rain droplets. However, the throughfall droplets’ landing angles were only small variations. When the landing angle of sprinkler irrigation droplets was >45°, the spatial distribution of throughfall droplets size and velocity corresponded well with the canopy structure and leaf projection area of maize, i.e., the further away from the maize stalk, the larger the size and velocity of throughfall droplets. Nevertheless, if the landing angle of sprinkler irrigation droplets was <45°, the spatial distribution mentioned above was mainly affected by droplets landing angle. The spatial variation of throughfall droplets’ size and velocities at different measurement points was attributed to the change of the larger droplets’ volume proportion and the equivalent velocity. Although the maize leaves had a certain degree of perturbation effect on the velocities and kinetic energy of the larger kinetic energy droplets, the flight path of these drops did not alter significantly. The results of this research will be of practical value in guiding the development of a new sprayer and the optimum selection of sprinkler heads.

Choosing reasonable design parameters for ceramic emitters used in subsurface irrigation is important for reducing the deep percolation of water and improving the water use efficiency. Laboratory experiments and numerical simulations with the HYDRUS-2D software were carried out to analyze the effect of soil texture on the infiltration characteristics of porous ceramic emitters used for subsurface irrigation. HYDRUS-2D predictions of emitter discharge in soil and wetting front are in agreement with experimental results, and the HYDRUS-2D model can be used to accurately simulate soil water movement during subsurface irrigation with ceramic emitters in different soil textures. Results show that soil texture has a significant effect on emitter discharge, soil matrix potential around the emitter, and wetting front. For 12 different soil textures, the aspect ratio of the wetting front is basically between 0.84–1.49. In sandy soil, the wetting front mainly appears as an ellipse; but in the clay, the wetting front is closer to a circle. As irrigation time increases, emitter discharge gradually decreases to a stable value; however, emitter discharge in different texture soils is quite different. In order to improve the crop water use efficiency in sandy soil, soil water retention can be improved by adding a clay interlayer or adding water retention agent, reducing the risk of deep percolation and improving the water use efficiency.