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In order to investigate the contact characteristics of the mechanical parts of the brewing robot with wine lees particles, it is essential to calibrate the parameters of the discrete elemental model of wine lees particles. This paper proposes a method based on tests of the angle of repose. The simulation test is conducted to establish a regression model and combined with physical tests to find optimization. The contact model used in simulation modeling is Hertz-Mindlin with Johnson-Kendall-Roberts. Not all discrete element model parameters of wine lees particles have a significant impact on the angle of repose, so screening through Plackett-Burman Design is performed. The results indicate that the restitution coefficient between wine lees particles and restitution coefficient between wine lees particle and steel plate have a significant impact on angle of repose. Additionally, another parameter that is difficult to obtain, namely surface energy (JKR), also plays a crucial role. The optimal value interval for these three parameters is determined by the steepest ascent test, and a linear regression model for angle of repose is built through Box-Behnken Design. The optimal values obtained are as follows: restitution coefficient between wine lees particles—0.603; restitution coefficient between wine lees particle and steel plate—0.595; JKR—0.083. Finally, in order to verify the accuracy of calibrated parameters, simulation verification tests are carried out which show that there is only a relative error rate at 0.18% between simulated angle of repose and actual angle of repose, indicating that accurate calibration parameters were achieved. This study can provide reference for selecting discrete element model parameters for wine lees particles in future research endeavors. [ABSTRACT FROM AUTHOR]

Ecological ditches (eco-ditches) are being recognized as a green method for treating wastewater from domestic sewage sources. However, the relationship between the efficiency of nutrient removal from wastewater and N2O emissions is unclear given that a higher nutrient removal efficiency might result in more N2O emissions. Therefore, we constructed an eco-ditch system with three combinations of different plants (local wetland species) to treat rural sewage in the mountainous regions of China and monitored water quality and N2O emissions. Eco-ditches are important sources of atmospheric N2O, with nutrient removal efficiencies of 22–84% and 23–87% for total nitrogen (TN) and total phosphorus (TP), respectively, and emissions of N2O ranging from 16 to 243 µg m−2 h−1. The seasonal variations in pollutant removal efficiency and N2O emissions followed similar patterns—both were considerably greater in summer than in the other seasons, with the lowest values observed in winter. Among the three plant configurations tested, ditch sections containing Acorus calamus L. and Phyllostachys heteroclada Oliv. had the highest nutrient removal efficiency and the lowest N2O emissions, with removal efficiencies of 24% and 32%, respectively, for TN and TP, and a 16% average reduction in N2O emissions, which was positively associated with NO3–N. This study highlights the importance of selecting appropriate combination of plant species for eco-ditches to efficiently remove nutrients from rural domestic sewage and reduce N2O emissions. [ABSTRACT FROM AUTHOR]

China stands as one of the world's largest agricultural powerhouses, boasting abundant crop resources. Nonetheless, there remains a lack of clarity regarding the extensive scale of crop residue return in the fields. Drawing from direct field measurements and comprehensive survey data, this paper pioneers the reporting of residues from the five primary crops, shedding light on the associated nutrient components, including carbon (C), nitrogen (N), and phosphorus (P) replenishment via crop roots, stubble, and straw in the Southwest China region for the year 2012. The results showed that the total amount of the main crop residue resources was 97.4 Mt, which was composed of 17.8 Mt, 12.6 Mt, and 67 Mt for crop root, stubble, and straw, respectively. After crops harvested, there were 7165.8 kilotonne nutrient C, 132.2 kilotonne nutrient N, and 9.8 kilotonne nutrient P of crop residues returned to the fields through crop root, respectively, accounting for 44.6%, 48.2%, and 43.4% of the total nutrient returned, which was the main part of crop nutrients return to fields. The amount of nutrient C, N, and P returned through stubbles were 5017.3 kilotonne, 75.9 kilotonne, and 6.8 kilotonne, respectively, accounting for 31.3%, 27.6%, and 30.6% of the total return of crops. From the composition proportion of residues nutrients return to field, the orders were all expressed as follows: root > stubble > straw. According to the optimum fertilization amount of the main crops in Southwest China, the returned of crop residues nutrient N in maize, rice, rapeseed, and wheat can replace approximately 5.6%, 18.4%, 11.2%, and 14.8% of nitrogen fertilizer, and 2.4%, 8.3%, 3%, and 9.2% of phosphate fertilizer, respectively. This conclusion is beneficial for regulating the practice of returning crop residues to the fields and the use of agricultural fertilizers, aiming to achieve sustainable development in agricultural production. [ABSTRACT FROM AUTHOR]