The reaction pathways from phenyl radicals to phenanthrene (A3) and pyrene (A4) via C2H3 and C4H4 additions were investigated using the G3(MP2, CC) method.

Given the lack of accurate parameter values in discrete element simulation of sweet potato seedling mechanized recovery, a direct measurement and virtual calibration method was used to study the Discrete Element Method (DEM) simulation parameters of broken sweet potato stems and leaves. The intrinsic parameters, collision recovery coefficient and static friction coefficient of broken seedlings were acquired by physical experiments. Different parameter combinations were designed for DEM simulation. The intrinsic parameters of sweet potato leaves and other unmeasurable DEM simulation parameters were determined by stacking angle optimization simulation. Plackett-Burman test shows that the static friction coefficients of stem-stem and stem-steel and the rolling friction coefficients of stem-stem and stem-leaf all significantly influence the accumulation angle. The parameters that significantly influence the stacking angle of broken seedlings were sent to steepest ascent test and Box-Behnken test. The average stacking angle of 40.51° and the relative error of 0.972% indicate it feasible to calibrate DEM parameters by physical test and optimization simulation and the calibrated parameters can be used in DEM simulation of broken sweet potato stems and leaves.

The yield of sweet potato vines is large, making it a good source of food. However, it is difficult to harvest sweet potato vines due to creeping and intertwining. Therefore, according to the domestic sweet potato planting model, this paper designed a double roll sweet potato vine harvester which can complete the operations of vine picking, vine killing, conveying and header harvesting at one time. The machine adopts the process of front roll vine picking, rear roll vine killing and rod bar lifting. The key components of the vine picking device, vine killing device and lifting device were designed and calculated. A numerical simulation test of the vine harvesting process was carried out by using the discrete element numerical simulation method. It was determined that the length of the vine picking rod from the outside to the inside is 175 mm, 150 mm and 105 mm, respectively, and the inclination angle of the end is 160°. There are six vine killing knives on each vine killing knife plate. The inclination of the lifting device is 50°and the conveying speed is 3 m/s. Using the box Behnken experimental design method, taking the vine picking roller speed, vine killing roller speed and ground clearance as the experimental factors, and taking the sweet potato vine harvest rate, stubble height and potato injury rate as the evaluation indexes, a quadratic regression orthogonal test was carried out, the effects of various factors on the evaluation indexes were analyzed, and the experimental factors were optimized and verified. The experimental results showed that the optimal parameter combination is as follows: the rotation speed of vine picking roller should be 716 r/min, the rotation speed of vine killing roller should be 1960 r/min and the ground clearance should be 16 mm. With these parameters, the harvest rate of sweet potato vines is 93.1%, the stubble height is 29.5 mm and the potato injury rate is 0.174%. As such, the harvester meets the requirements for the mechanized harvesting of sweet potato vines and is of great significance as a light and simplified product for the sweet potato industry.

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