Grouser height and soil moisture content have a significant effect on the tractive performance of tracked vehicles. Paddy soil has the mechanical properties of both clay soil and sandy soil and can have a wide range of water content values, and it has a considerable influence on the tractive performance of tracked agricultural machinery. To study the influence of grouser height on the tractive performance of a single-track shoe under different soil moisture contents, a three-dimensional shearing model of the single-track shoe and the contact soil was established based on the ground vehicle mechanics theory, and an experimental platform with a soil bin, sensors, and a control system was established. Six preset levels of moisture contents (7%, 12%, 17%, 22%, 27%, and 32%) of paddy soil were prepared for the research experiment. The mechanical properties of the soil with different moisture contents were obtained through the use of a direct shear test, penetration test, and compaction test. The obtained physical parameters of the soil have special characteristics that are different from typical soil. Combined with the three-dimensional model and the obtained soil parameters, the parameters of the tractive performance, such as thrust, running resistance, and traction with different moisture contents were analyzed and calculated. The test results revealed that the thrust at different grouser heights shows a regular waveform growth trend with an increase in soil moisture content. The minimum value and the maximum value of thrust were obtained at moisture contents of 7% and 12%, respectively. The curve of different grouser heights of the running resistance shows similar changes with different moisture contents. The two peak points and inflection points of the fluctuation curve are for moisture contents of 17% and 27%. The change curve of the traction is highly similar to the curve of thrust. The maximum value of the traction was found at a moisture content of 12%, and the minimum value at 22% or 27%. Under different moisture conditions, tracked vehicles with higher grousers have better tractive performances.

Design and test of the key components for a combing-type tobacco harvester

A differential separation trommel screener was developed to solve the problems of the impurity content in insects and the high rate of insect impurities in the separation of black soldier fly (BSF) sand mixture. Moreover, the mechanical and physical properties of the BSF sand and its bonding contact model were examined. With the rotational speed of the trommel and the spikes and the inclination of the trommel as the experimental factors, their motion characteristics were analyzed and their value ranges were determined. In addition, the impurity content in the insects and the rate of insect impurities were selected as the test indicators. The Box–Behnken test was performed, the response surface regression model was built, and the parameters were optimized. The results indicated that the respective test factors, the impurity content and the insect rate, followed the following order of significance: the trommel rotation speed, spike teeth rotation speed, and trommel screener inclination. At the trommel rotation speed of 47.37 r/min, the speed of the spike teeth reached 24.16 r/min, the inclination angle of the trommel was 5°, the impurity content was 6.0%, and the insect rate reached 1.2%. The results of the bench test indicated that the average impurity content was 5.87% and the average insect rate was 1.20%. The results of this study provide a reference for the improvement and optimization of the separation structure of the BSF sand mixture.

Discrete element modeling and verification of the simulation parameters for chopped hybrid Broussonetia papyrifera stems

The input of exogenous organic matter could affect the transformation of soil carbon (C) and nitrogen (N), and their C- and N-priming effects (CPE and NPE) play a key role in the balance of soil C and N. However, little is known about how the interaction effect between straw and straw biochar regulates CPE and NPE. Therefore, we conducted a 90-day incubation experiment, which included five treatments: no straw and straw biochar (CK), 1.5% straw (S), 0.53% straw biochar (B), 1.5% straw + 0.53% straw biochar (SB), and 1.5% straw + 1.06% straw biochar (SB1). Our findings revealed that cumulative soil CO₂ emissions were increased by 95.52–216.53% through the short-term input of exogenous organic matter input; however, this trend gradually weakened with decreasing dissolved organic C (DOC) content. The cumulative NPE generated by the addition of exogenous organic matter was much smaller than the cumulative CPE. Under the B and S treatments, the cumulative CPE and NPE were negative throughout the entire incubation period. The SB treatment remarkably boosted the microbial biomass nitrogen (MBN) content; however, the SB1 treatment was more effective in inhibiting soil C and N mineralization processes than SB treatment. Moreover, the cumulative CPE and NPE were mainly regulated by N. We conclude that the combination of straw and straw biochar preferentially stimulated soil C mineralization, but that this effect decreased with time, which may be due to the consumption of labile DOC caused by the initial positive CPE, while soil N mineralization had a lag effect.