Search

A novel intermolecular system D-π⋯π′-A was constructed with tetraphenylethylene (TPE) and borondipyrromethene (BODIPY), which had a synergistic effect on PDT and PTT (1 + 1 > 2). The PTT effect of TPD-BOA(D/A) was 1.7 times the sum of BOA + TPD; the effect of PDT(TPA+BOD) was 1.45 times the sum of TPA + BOD. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the task demand of intelligent unmanned fertilizer application in seedling stage of corn planted in full-film double-ditch seedbed, a film identification method based on improved DeepLabv3+ identification method for full-film double-ditch corn seedbed was proposed. The differences in performance indicators of the original Deeplabv3+ network taking Xception as the backbone network and the network model that replaced three lightweight backbone networks, MobileNetV2, MobileNetV3 and GhostNet were tested. At the same time, the network models, classical semantic segmentation was introduced to PSPNet and UNet for comparative test. The MIoU of DeepLabv3+ network model that replaced its backbone network increased by 5.01%, and FPS improved by 206% compared with original network, and the model size reduced by 90.3%. The three DeepLabv3+ models after replacing the backbone network were further compressed, and the two-layer expansion convolution with low expansion rate in ASPP was deleted, and the common convolution after feature fusion was replaced by the depthwise separable convolution to obtain a lightweight network model. After testing the improved network model, it was found that the average decline of precision indicators was only 0.17%, FPS raised to 66.5, with an average increase of 25.5%, and the size of the model was compressed to 10.53 MB. Test results showed that, the improved model showed excellent performance, and could provide important technology and method support for the research and development of intelligent topdressing and field management on full-film double-ditch corn seedbed during seedling stage. [ABSTRACT FROM AUTHOR]

In order to clarify and enhance the work performance of the threshing and cleaning machine for plot-bred wheat and further reduce the grain retention in all working areas in the machine, in this study, a discrete element model for the threshing material of plot-bred wheat and a gas-solid coupling simulation model for the machine were established by ensuring all the harvesting criteria for the machine. Then numerical simulation was completed on the movement process of the threshing material in the threshing and cleaning machine for plot-bred wheat, the movement law and motion trajectory of all components of the threshing material were explored, and the impact forms of unreasonable work parameters on the separating and cleaning process were analyzed. First, four working areas were divided in the threshing and cleaning machine for plot-bred wheat. Under gas-solid flow coupling effect, the number variation of threshing material in each working area was analyzed under the effect of gas-solid coupling, and the operation characteristics of "no retained seeds and convenient cleaning" of the threshing machine for plot-bred wheat were further improved. The verification test results showed that, when the feeding amount of wheat was 0.30 kg/s, the rotation speed of the shaft of the tooth-type threshing cylinder was set to 1350 r/min, the rotation speed of the winnower was set to 500 r/min, the rotation speed of the residue absorption fan was set to 1000 r/min, the average total loss rate in threshing of the sample machine was 0.56%, and average impurity rate of the threshing material was 5.26%, average damage rate in threshing was 0.68%. In the test, the status of material discharged from the residue absorption fan outlet and bottom of the cyclone separator was similar to that of the simulation results, showing that it was feasible to use the method of gas-solid coupling to simulate the movement law of threshing material in the threshing and cleaning machine for plot-bred wheat. [ABSTRACT FROM AUTHOR]

In order to further clarify and improve the working performance of separating cleaner for flax threshing materials, and study the migration law and characteristics of components of flax threshing materials during separating and cleaning, in this paper, a gas-solid coupling simulation model was established on the separation cleaner for flax threshing materials and a numerical simulation was carried out on the separating and cleaning process. Simulation results showed that, the separating and cleaning effect of the components of flax threshing materials was good under the air-and-screen gas-solid coupling flow field. Meanwhile, the form distribution and the vector distribution of air volume and velocity of flax threshing materials in the air-and-screen devices were obtained. By referring to the migration trajectories of the flax threshing materials in the vibration sieve device, double channel residue collection device and dust absorber, the volume variation, motion trajectories and variation of migration velocity of the components of flax threshing materials over time in different regions were explored. Verification test results showed that, the content impurity rate of the separation cleaner for flax threshing materials was 2.06%, and loss rate in cleaning was 3.08%. Compared with simulation results, the verification test results were 1.23% and 0.42% higher, showing that the established discrete element model on the flax threshing materials and parameter setting were basically feasible. The verification test also verified the correctness of the simulation results of the separating and cleaning process of the flax threshing materials based on gas-solid coupling theory and the feasibility of the research method. [ABSTRACT FROM AUTHOR]

In view of the problems in operation process of fixed rake-type residual recycling component, such as poor individual profiling effect in film picking, easy clogging of the compound of films, soil and corn stubbles, high power consumption in film picking, and strong disturbance to seedbed soil, in this study, an operation model of intermittent filmpicking on full-film mulched double ditches was proposed and an intermittent film picking component was designed. The DEMMBD coupled algorithm was adopted for numerical simulation on the operation process of the intermittent film-picking component on full-film mulched double ditches, and a comparative analysis was carried out on the seedbed disturbance effect and resistance variation characteristics in film-picking by fixed and intermittent film-picking components. By taking the forward speed in film-picking, cam arrangement angle of the film-picking component and rotating speed of the cam shaft as independent variables, film-picking rate as the response value, a mathematical model between test factors and the film-picking rate was established, to explore the influence order of the factors on film-picking rate, and the optimal working parameters of the intermittent film-picking component were obtained as follows: the forward speed in film-picking was 2 km/h, cam arrangement angle was 180°, rotating speed of the cam shaft was 120 r/min. Under the optimal parameter combination, the average film-picking rate of the simulation test was 96.1%. Field test showed that, the average film-picking rate of the intermittent film-picking component was 95.6%, and 0.5% higher than that of the simulation test. The working condition of the sample machine was basically consistent with the simulation process, and can accurately represent the operation mechanism of intermittent film-picking on full-film mulched double ditches, showing that the established discrete element simulation model and its parameters were accurate and reasonable. [ABSTRACT FROM AUTHOR]

In order to further reduce the damage rate in threshing seed corn, a seed corn threshing testbed with variable diameter and spacing that can realize dynamic adjustment of parameters, such as feed quantity, rotating speed of the threshing device, threshing spacing of the threshing units, was designed in this research. The software of finite element analysis ANSYS Workbench was applied to do modal analysis on the threshing axis designed for variable diameter and spacing of seed corn. The first 8 orders of natural frequencies were distributed in 201.12-1640.20 Hz, with corresponding vibration amplitude in 5.86-27.04 mm, showing reasonable structural design of the threshing axis, which could realize effective seed corn threshing and conveying. Discrete element method was applied to do simulation analysis on the seed corn threshing and conveying process with variable diameter and spacing. Under the condition of different feed quantity, different rotating speed of the thresher, the moving speed of corn clusters and contact force among clusters were measured through simulation, and the working characteristics of the threshing testbed for low-damage and dynamic threshing and conveying of seed corn with variable diameter and spacing were revealed. Working performance test results of the testbed of seed corn with variable diameter and spacing showed that, when the rotating speed of the threshing axis was 190-290 r/min, feed quantity was 1.80-3.80 kg/s, the damage rate of seed corn was 0.32%-0.63%, threshing rate was 99.20%-99.82%, and content impurity rate was 4.23%-5.86%, the mass of threshed corn grains first increased and then decreased along the axial direction. The test verification process was in line with the simulation results; thus, the test results could satisfy the requirements in design and actual operation. [ABSTRACT FROM AUTHOR]

In order to further improve the working performance and efficiency of mechanized tillage operation of a full-film double-ditch seedbed, under the working conditions of different parameters of the spiral push-type soil covering device with double-width filming, the dynamic soil covering characteristics and soil covering uniformity of the device were analyzed, the collaborative and interactive coupling mechanism of the horizontal pushing process of the mulching soil and horizontally two-way spiral soil transmission device were revealed, and the main reasons for the influence of different soil covering belts on the change of soil particle number distribution were analyzed. Based on the full-film double-ditch mode with double-width filming, the mechanized soil covering path was optimized. In order to further reduce the disturbance on mulching soil by two-way spiral pushing, a kind of parallel shunt type soil covering device with double-width filming was designed, then a discrete element method was adopted to make simulation analysis and optimize the parallel shunt type soil covering device with double-width filming. Field verification tests showed that after the operation of the full-film double-ditch combined machine with double-width filming and soil covering installed with the parallel shunt type soil covering device, the qualified rate of the film edge soil covering width was 96.1%, an increase of 1.6% compared to that before optimization; the qualified rate of soil covering width at the center of the big ridge was 93.5%, an increase of 1.9% compared to that before optimization; the qualified rate of the soil covering thickness was 97.7%, an increase of 0.2% compared to that before optimization. The test indicators reached the requirements of relevant national and industrial standards, showing that the test results met the design requirements, and the working conditions of verification tests were consistent with the simulation results. [ABSTRACT FROM AUTHOR]

In order to explore the aerodynamics characteristics of flax threshing material, and accurately obtain the movement trajectory of the material of each component in air-screen cleaning, the suspension velocities of flax grains, capsules, short stalks and capsule husks at different stages were measured by means of the suspension velocity device. The experimental results showed that the suspension velocity range was 4.55-8.64 m/s for flax grains, 6.46-10.90 m/s for flax capsules, 3.23-7.75 m/s for flax short stalks, and 1.06-4.21 m/s for flax capsule shells. Based on the experimental results, the overall interval distribution of each component of flax threshing material and the separation characteristics were discussed and the discrete element model of each component of the flax threshing material was established. Through simulation measurement of angle of repose of the material and the sliding friction angle with steel, the reliability of the established model was verified. The gas-solid coupling method was used to simulate the suspension velocity of each component of the flax threshing material, and the suspension velocity of the four components of flax threshing material was obtained. The simulation measurement results were within the actual measurement range, showing that the test results were basically in line with the simulation results. The simulation on the suspension velocity of different components of flax threshing material based on gas-solid coupling had high precision degree. Therefore, the feasibility of the suspension velocity of the flax threshing material measured in the simulation test based on CFD-DEM coupling was verified [ABSTRACT FROM AUTHOR]

In order to achieve the construction standard of high mechanized performance of the seedbed with whole plastic-film mulching on double ridges, in this study, the forms of suppression failure were analyzed, and the key factors influencing the suppression performance were determined based on the structure of the seedbed suppression device and its working principles. The discrete element method was adopted for numerical simulation on the suppression process of the seedbed with whole plastic film mulching on double ridges; the parameters during the interaction between the suppression device and seedbed soil were extracted and analyzed, such as contact area, sinkage and horizontal traction resistance trend of press wheels on big ridges and furrows of small ridge. Taking the suppression load on big ridges, suppression load on furrows of small ridge, and advancing velocity of the combined operation machine as the independent variables, qualified rate of suppression as the response value, a mathematical model between the test factors and qualified rate of suppression was established, to explore the influence sequence of the factors on suppression qualified rate. The optimal working parameters of the suppression device were finally obtained: the suppression load on big ridges was 40 N, suppression load on furrows of small ridge was 69.8 N and the machine advancing velocity was 0.98 m/s, and the achieved mean value of suppression qualified rate was 92.6%. Field verification test showed that the mean value of suppression qualified rate was 90.3%, a mere difference of 2.3% compared with the simulation result. The actual operation of the sample machine was basically consistent with the simulation process and could reveal the mechanized suppression operation mechanism of the seedbed with whole plastic film mulching on double ridges, indicating that the established DEM model and its parameter setting were relatively accurate and reasonable. [ABSTRACT FROM AUTHOR]

In order to achieve high-performance and mechanization construction standard of whole plastic mulched double ridge seedbed, and to meet its forming process and corresponding agronomic requirements of the mechanized double ridge seedbed, the key working parameters such as the speed of rotary blade group, the thickness of upturned sod and the power consumption of rotary blade group under different parameters were analyzed based on related working performance in ridge forming. Also, the test factors and their range of values were finally determined in this study. Discrete element method (DEM) simulation was applied in the numerical simulation of the mechanized ridge forming process of whole plastic mulched double ridges, and the ridge forming effect and digging resistance variation characteristics of different types of shovels were compared. Taking the forward speed of the combined machine, the penetration angle of the arc-shaped shovel and the depth of rotary tillage as independent variables, and the qualified rate of seedbed tillage as the response value, the mathematical model between the test factors and the qualified rate of the seedbed tillage was established, to explore the influence sequence of the factors on the qualified rate of seedbed tillage, and obtained the following optimal working parameters of the ridge forming device: the advancing velocity of the combined machine of 0.50 m/s, penetration angle of the arc-shaped shovel of 31°, rotary tillage depth of 140 mm, and average qualified rate 95.20% of seedbed tillage in corresponding simulation verification test. Field test showed that the average qualified rate of seedbed tillage in ridge forming device was 93.60%, which was close to that of the simulation results. The actual working condition of the sample machine was basically in line with the simulation process and could relatively precisely reflect the mechanized ridge forming mechanism of whole plastic double ridges. The results showed that the established DEM model and its parameter setting were relatively accurate and reasonable. [ABSTRACT FROM AUTHOR]

In order to realize seedbed mechanization of whole plastic-film mulching on double ridges and to overcome the difficulty in crosswise belt type soil covering by whole plastic-film, a kind of crosswise belt type whole plastic-film ridging-mulching corn seeder on double ridges was designed in this study. The key components of the sample machine was designed and its working parameters of seedbed soil covering device, crosswise-belt soil covering mechanism and profiling sowing depth adjustment device were determined. After numerical simulation on the film edge and crosswise soil covering by whole plastic-film on double ridges by discrete element method, the velocity and displacement of the oscillating plate, and the variation rule of amount of covered soil with time were explored. Field test results show that, when the advancing velocity of the machine was 0.50 m/s, the qualified rate of soil width covered on film edge of the seedbed reached 96.1%, qualified rate of crosswise soil belt width was 94.5%, qualified rate of soil thickness on seedbed was 95.3%, qualified rate of sowing depth was 89.3%, qualified rate of spacing between crosswise soil belts reached 93.6%, which all met related standards in China and satisfied design requirements, and could realize seedbed mechanization of whole plastic-film mulching on double ridges. Comparison tests on working performances of practical soil covering show a basic consistence with the seedbed soil covering simulation, and verified the effectiveness of the soil covering model built by using discrete element method. [ABSTRACT FROM AUTHOR]