During the baling operation, the wheat stalks are subjected to various mechanisms in the baler and the main form is compression. After the wheat stem is forced by a combination of the threshing cylinder, it needs to be formed under the action of straw baler and meet transport requirements. This paper mainly studies the properties of wheat stalks when baling, and proposes the application of the creep after-effect theory during the baling process. The tension-compression tester was used to perform a 50 mm stalk mechanical test, 50 mm stalk static pressure test, 35 mm×40 mm×50 mm stalk module static pressure test and bale static pressure test. The measured elastic modulus of the stem sample was 7.59 MPa, and the elastic modulus of the inner core of the stem was 8.24 MPa. The return curve of the single stalk and the bale is consistent with the initial creep and steady-state creep in the creep after-effect theory. A logarithmic function was used for fitting of the first stage with coefficient of determination R 2 = 0.8364, and a linear function was used for fitting of the second stage with coefficient of determination R 2 = 0.9921. The high water content static pressure test suggests that the load in the loading direction is the coupled load of the working load of the hydraulic cylinder and the internal stress of the bale. When harvesting wheat stalks with high moisture content, the density parameter of the bale can be appropriately increased while the load parameter of the hydraulic cylinder can be considered unchanged or even reduced. The adjustment of density and load can still ensure the forming quality of the bale.

With the advancement of agricultural mechanization and the development of combine harvesters, cleaning devices play a very important role in the grain harvesting process. In this study, the DFPF-25 type material floating velocity measuring device was used to measure the suspension velocity of each component of the grain material. Secondly, the DFQX-3 cleaning device was used to conduct the airflow field test, then the fluid simulation of the cleaning shoe was carried out. The results showed that the simulation and experimental results were in a good agreement under the conditions of single fan and double fan. The high-speed flow velocity formed by the double fan system at the tail of the cleaning shoe was 4.76 m/s (simulation) and 4.03 m/s (experiment), which had outstanding cleaning effects on unfilled grains, long stems, and short stems. To sum up, the installation of the cross-flow fan at the rear of the cleaning shoe has a positive effect on the cleaning effect of the combine harvester, and the double-fan cleaning structure composed of the cross-flow fan and the centrifugal fan can significantly improve the cleaning effect.

No abstract

Studying the early changes in post-fire vegetation communities may improve the overall resilience of forests. The necessity for doing so was demonstrated by the Bobcat Fire, which seriously threatened the central San Gabriel Mountains and the Angeles National Forest in California. This study aimed to monitor and quantify the effects of climatological and topographic conditions along with burn severity on early (within 1 year) post-fire forests and shrubs community regeneration. In this study, we used Sentinel-2(MSI) intensive time-series imagery (July 2020–October 2021) to make a confusion matrix combined with 389 vegetation sample points on Google Earth Pro. The overall accuracy (OA) and the Kappa coefficient, calculated from the confusion matrix, were used as evaluation parameters to validate the classification results. With multiple linear regression models and Environmental Systems Research Institute (ESRI) historical images, we analyzed the effects of climate and slope aspects on the regeneration of post-fire forest and shrub communities. We also quantitatively analyzed the regeneration rates based on five burn severity types. The results show that the normalized burning rate (NBR) was the most accurate vegetation classification indicator in this study (OA: 92.3–99.5%, Kappa: 0.88–0.98). The vegetation classification accuracy based on SVM is about 6.6% higher than K-Means. The overall accuracy of the burn area is 94.87%. Post-fire climate factors had a significant impact on the regeneration of the two vegetation communities (R2: 0.42–0.88); the optimal regeneration slope was 15–35°; and the fire severity changed the original competition relationship and regeneration rate. The results provide four main insights into the regeneration of post-fire vegetation communities: (1) climate factors in the first regenerating season have important impacts on the regeneration of forest and shrub communities; (2) daytime duration and rainfall are the most significant factors for forests and shrubs regeneration; (3) tolerable low burn severity promotes forests regeneration; and (4) forests have a certain ability to resist fires, while shrubs can better tolerate high-intensity fire ecology. This study could support the implementation of strategies for regionalized forest management and the targeted enhancement of post-fire vegetation community resilience.

No abstract