Design and development of orchard autonomous navigation spray system.

Driven by the demand for efficient plant protection in orchards, the autonomous navigation system for orchards is hereby designed and developed in this study. According to the three modules of unmanned system "perception-decision-control," the environment perception and map construction strategy based on 3D lidar is constructed for the complex environment in orchards. At the same time, millimeter-wave radar is further selected for multi-source information fusion for the perception of obstacles. The extraction of orchard navigation lines is achieved by formulating a four-step extraction strategy according to the obtained lidar data. Finally, aiming at the control problem of plant protection machine, the ADRC control strategy is adopted to enhance the noise immunity of the system. Different working conditions are designed in the experimental section for testing the obstacle avoidance performance and navigation accuracy of the autonomous navigation sprayer. The experimental results show that the unmanned vehicle can identify the obstacle quickly and make an emergency stop and find a rather narrow feasible area when a moving person or a different thin column is used as an obstacle. Many experiments have shown a safe distance for obstacle avoidance about 0.5 m, which meets the obstacle avoidance requirements. In the navigation accuracy experiment, the average navigation error in both experiments is within 15 cm, satisfying the requirements for orchard spray operation. A set of spray test experiments are designed in the final experimental part to further verify the feasibility of the system developed by the institute, and the coverage rate of the leaves of the canopy is about 50%.

Effect of environmental regulation policy synergy on carbon emissions in China under consideration of the mediating role of industrial structure.

A comprehensive understanding of the effect of environmental regulation policy synergy on carbon emissions is essential for the design and decision-making of the other policy combinations. In this paper, the panel data from 30 provinces in China during 2000-2019 are used as samples to investigate the heterogeneity of different policy combinations and compare the differences using a Bayesian non-parametric generalized additive quantile method. The research results imply that the environmental regulation policy synergy has a significant heterogeneous effect on carbon emissions on different levels. Specifically, the effect of environmental regulation policy synergy on carbon emissions has an inverted U-shape trend at the low quintiles, i.e., before the turning point, it shows a "green paradox" effect, and after the turning point, it shows an "emission reduction" effect. However, the effect of environmental regulation policy synergy on carbon emissions shows a significant N-shape trend at the high quintiles, i.e., before the second turning point, it shows an "emission reduction" effect, and after the second turning point, it shows a "green paradox" effect. Moreover, the effect of environmental regulation policy combinations on carbon emissions reduction has been found to vary significantly across regions.

Water-Triggered Stiffening of Shape-Memory Polyurethanes Composed of Hard Backbone Dangling PEG Soft Segments.

Shape-memory polymers (SMPs) induced by heat or water are commonly used candidates for biomedical applications. Shape recovery inevitably leads to a dramatic decrease of Young's modulus due to the enhanced flexibility of polymer chains at the transition temperature. Herein, the principle of phase-transition-induced stiffening of shape-memory metallic alloys (SMAs) is introduced to the design of molecular structures for shape-memory polyurethane (SMPUs), featuring all-hard segments composed of main chains that are attached with poly(ethylene glycol) (PEG) dangling side chains. Different from conventional SMPs, they achieve a soft-to-stiff transition when shape recovers. The stiffening process is driven by water-triggered segmental rearrangement due to the incompatibility between the hard segments and the soft PEG segments. Upon hydration, the extent of microphase separation is enhanced and the hard domains are transformed to a more continuous morphology to realize more effective stress transfer. Meanwhile, such segmental rearrangement facilitates the shape-recovery process in the hydrated state despite the final increased glass transition temperature (Tg ). This work represents a novel paradigm of simultaneously integrating balanced mechanics, shape-memory property, and biocompatibility for SMPUs as materials for minimally invasive surgery such as endoluminal stents.

Blocking the formation of bromate in γ-Fe-Ti-Al2O3 catalytic ozonation of ibuprofen in bromide-containing water.

Iron and titanium doped γ-Al2O3 (γ-Fe-Ti-Al2O3) mesoporous catalysts were synthesized by evaporation-induced self-assembly using glucose as template, and applied to ozonation of ibuprofen in bromide-containing water. X-ray diffraction (XRD), nitrogen adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS) results showed that iron and titanium successfully doped into the skeleton of γ-Al2O3, uniform distribution, maintain the ordered mesoporous structure of γ-Al2O3, with larger specific surface area. The valence of titanium coexists with Ti4+ and Ti3+, and the valence of iron was Fe3+. Infrared spectra of chemisorbed pyridine (Py-FTIR) results showed that the doped titanium and iron into the framework position of γ-Al2O3 altered the surface acidity of the alumina surface, especially increasing the medium Lewis acid sites, which was conducive to the effective decomposition of ozone into active oxygen species. The γ-Fe-Ti-Al2O3 catalyst (Al/Fe = 25, Al/Ti = 75) enhanced the removal rate of ibuprofen in ozonation of bromide-containing water, and effectively blocked the formation of bromate. After the reaction of 60 min, the removal rate of TOC was increased from 54% of γ-Al2O3/O3 to 86% with γ-Fe-Ti-Al2O3/O3, while the ozonation alone was only 13%. Electron Paramagnetic Resonance (EPR) spectra showed that hydroxyl and superoxide radicals were reactive oxygen species, which was beneficial to the mineralization of organic matter. The capture experiment of Fe2+ ion confirmed that the electronic cycle of Fe2+ ion and Fe3+ ion was beneficial to block the formation of bromated. The addition of ibuprofen and humic acid can enhance the reduction of Fe3+ in the catalytic ozonation of γ-Fe-Ti-Al2O3, which further strengthened the blocking of bromate formation.

Heterogeneity and threshold effects of environmental regulation on health expenditure: Considering the mediating role of environmental pollution.

A comprehensive understanding of the heterogeneity and threshold effects of environmental regulation on health expenditure is essential for policy design and decision-making. This case study seeks to analyze the heterogeneity and threshold effects using panel data, which covers 30 Chinese provinces from 2007 to 2017. We examine the linear and nonlinear impacts of environmental regulation on health expenditure by using the Bayesian quantile regression and panel threshold regression, respectively. The empirical research results indicate a significant heterogeneous effect of environmental regulation on health expenditure in provinces where health expenditure falls in different quintiles. It shows mainly two effects: a positive effect of environmental regulation on health expenditure in provinces in the low quintiles and high quintiles of health expenditure; and a negative interrelationship between environmental regulation and health expenditure for provinces in the medium quintiles of health expenditure. A single threshold effect of environmental regulation on health expenditure is found to be different among three regions: the eastern, central and western regions. Specifically, in eastern and western China, the environmental regulations are stricter, and this helps reduce the health expenditures relating to environmental pollution. However, it was found that stricter environmental regulations do not reduce health expenditures in central China.

Mechanically robust enzymatically degradable shape memory polyurethane urea with a rapid recovery response induced by NIR.

Biodegradable shape memory polymers have great potential for use in minimally invasive surgical procedures. Herein, a series of shape memory polyurethanes (SMPUs) containing a chymotrypsin-inspired chain extender with adjustable mechanical properties and excellent shape memory effect (SME) was prepared successfully. The chemical structure, mechanical properties, SME and in vitro degradation of the PUs were systematically characterized by proton nuclear magnetic resonance spectroscopy, tensile testing, dynamic mechanical analysis under controlled force mode, and scanning electronic microscopy. By increasing the molecular weight of poly(ε-caprolactone) (PCL) and hard segment content, a PCL4000-based SMPU with a modulus value of 115 MPa was obtained, which is three times that of a PCL2000-based sample. Further, the modulus of the PCL4000-based SMPU was increased by 50% while that of the PCL2000-based SMPU was significantly reduced when temperature increased from 23 °C to 37 °C. In addition, the PCL4000-based SMPU exhibited excellent SME with the shape fixity ratio and recovery ratio almost reaching 100%. Gold nanorods were further incorporated into the PU matrix, endowing the materials with a fast near-infrared (NIR) response in 23 s for shape recovery (NIR wavelength of 808 nm, 1.5 W). Combined with enzymatic degradability, these PU/gold-nanorod composites exhibit great potential to be used in biodegradable shape memory expanding stents.

The behavior of ozone on different iron oxides surface sites in water.

A transformation process of ozone on different iron oxides suspensions, including α-Fe2O3, α-FeOOH, Fe3O4, was carried out using FTIR of adsorbed pyridine, ATR-FTIR and electron paramagnetic resonance (EPR) spectra with isotope 18O3. It was verified that on the surface isolated hydroxyl groups and the surface hydroxyl groups without acid sites of these iron oxides, ozone was electrostatically adsorbed and did not interact with the surface of these oxides, stably existed as ozone molecule. In contrast, ozone could replace the surface hydroxyl groups on Lewis acid sites of oxides, and directly interacted with the surface metal ions, decomposing into reactive oxygen species (ROS) and initiating the surface metal redox. The results indicate that Lewis acid sites were active center while the electronic cycle of the Fe2+/Fe3+ is advantageous to promote ozone decomposition into O2•- and •OH radicals. The mechanism of catalytic ozonation in different surface acid sites of iron oxides aqueous suspension was proposed on the basis of all experimental information.