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In order to improve the accuracy of the parameters during the process of rice straw shredding and returning to the field in discrete element simulation, the stubble straw in the field after rice harvest were taken as the research object, and the contact parameters between straw and steel, straw and straw were measured through the slope test. Then based on simulation model and through the stacking angle and shear test, the bonding radius between straw model particles, tangential critical stress, normal critical stress, coefficient of restitution, static friction coefficient and dynamic friction coefficient were taken as the test factors, taking the shear resistance and radial stacking angle of straw as evaluation indicators, a multi-objective optimization simulation calibration experiment were conducted using the Box-Behnken experimental scheme. The results showed that the bonding radius between straw particles was 1.06 mm, and the normal critical stress of straw was 4.77x1010 Pa, tangential critical stress was 4.67x106 Pa, the collision restitution coefficient between straw and straw was 0.21, the static Friction coefficient was 0.19, and the rolling friction coefficient was 0.09. The results of the simulation test results under the optimal parameter combination conditions and the physical test showed that the relative errors of the shear resistance and radial stacking angle of straw in the simulation test and physical test were 1.7% and 2.8%, respectively. This study could provide reference for the discrete element simulation analysis between straw and straw, as well as between straw and agricultural machinery. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics (CFD) is a method for systematic analysis based on computer numerical calculation and image display. It is often used to analyze the flow mechanisms of gas-solid and gas-liquid two-phase flow in agricultural equipment. It is a new method for digital design of agricultural equipment, which has good application prospects. The commonly used calculation models of CFD in simulating agricultural materials and its application in agricultural equipment were summarized. Combined with the application of agricultural engineering, the future development trend of CFD was proposed on how to adapt to the future development needs of agricultural engineering. The results indicated that, due to the complex types of operation objects and easy damage of agricultural equipment, it was necessary to fully consider the physical characteristics of the operation objects and the relationship among components. The multidisciplinary coupling analysis, fine modeling and real-time prediction of high fidelity simulation would be the future development trend of CFD. [ABSTRACT FROM AUTHOR]

ZnO@ZIF-8 anode materials are prepared by a simple hydrothermal method and characterized by XRD, SEM and TEM. Compared with pure ZnO, the morphology of the electrode material changes obviously. The electrochemical performance test shows the high reversible capacity and excellent cycling stability of the ZnO@ZIF-8 prepared by simple hydrothermal method with the first reversible specific capacity of 1136 mAh/g and 412.3 mAh/g after 50 cycles. The electrochemical performance of ZnO@ZIF-8 is obviously improved compared with that of pure ZnO. [ABSTRACT FROM AUTHOR]

In order to resolve some key issues about the machinery of transplanter for rape seedlings, a new type of transplanter with crawler planting hole forming tools for rape was designed based on the working characteristic in the dry land and agronomic requirement. Research on soil physical and mechanical characteristics were conducted to provide the technical parameters for the design of the hole forming device. First, we completed the whole structure design and analyzed the working principle of the device. The crawler was drove by power system to go forward, on which the hole forming device was installed and synchronously moving. The surface cam was mounted on the chassis. As the caterpillar moved forward, the pore forming device installed on the track vertically stabbed into the soil under the pressure of surface cam supplied by body weight. As the tracks moved forward, the hole forming device was out of the surface cam profiling. As such, a plant hole was formed. We analyzed the curve of surface cam limit, confirmed the limited point so that a coordinate system was established. We then chose the definition curve interpolation method to solve the parameter equation of surface cam profiling combining with Matlab7.0 software plot function in the program and generated surface cam outline curve. For the optimization of punch mechanism of structural design, the surface cam profiling and reset spring control capacity into hole device unearthed vertically. The cylindrical hole was pressured by shearing and extrusion soil. We analyzed the same track number, it had two tracks. Each of them had two linear holes. When the machine moved forward, each side could dig holes in four rows at one time. We installed rolling bearing in the hole forming device for rolling friction instead of sliding friction to reduce friction in the cylindrical hole and the friction between the surface cams. By use of the prototype machine in field, we recorded variables, such as the time, moving distance, distance between holes, the depth of effective planting hole, and the diameter of planting hole. We analyzed indexes such as the rate of qualified hole, hole forming frequency, efficiency, etc.. The result showed that if the machine at lower speed at 1.65-1.78 km/h, the efficiency was up to 0.231-0.249 hm2/h, and the rate of qualified hole up to 93.8% on average. The various performance indicator met the design requirement. The planting and hole forming machine can get holes at 1 400 mm in length each, 50 mm in diameter, 50 mm in depth, and 120000 holes/hm2 in hole density per area. This could get the planting hole to satisfy agronomic requirement. The research provided theoretical and technical references for design of the new type of transplanter. [ABSTRACT FROM AUTHOR]

Due to long stubble remained in farmland after harvesting as well as hardened and impervious soil in southern farmland of China, the tillage and land preparation parts of multifunctional rape-planting machine tend to wind grass and obstruct with mud, which impairs the working performance of ridging equipment and reduces the percentage of rapeseed seedling germination. In order to solve these problems, a rapeseed planting method is proposed, which combines the straw mulching cultivation with the direct seeding. The method is used to collect and cut the rice stubbles, and then the chopped rice stubbles are evenly covered on the inter-row spaces without involving the tillage apparatus. A multifunctional rape-planting device is mounted to a rice combine-harvester by replacing screening device, using the original harvester header to collect the rice stubbles and replacing the threshing cylinder to chop and scatter the rice stubbles. In this paper, an air-assisted chopping mechanism was designed, in which the moving knives and the transplanting blades were coaxially installed. The performance of the air-assisted chopping mechanism was evaluated by simulating the chopping operation of "stalk-standing" and "crop residue" in farmland through a bench test driven by an electric motor. A quadratic orthogonal rotating experiment was designed by Design-Expert software. Based on the variance analysis and regression fitting, a multiple regression equation was obtained, showing the effects of the rotating speed of feeding press rolls, the rotating speed of rotation shaft of moving knives and the gaps between moving knife and stationary knife on the qualified rate of chopped stalk length and the power attenuation. It was shown that the rotating speed of rotation shaft of moving knives had the most influential effect, followed by the gaps between moving knife and stationary knife, and the rotating speed of feeding press rolls had the least effect on the qualified rate of chopped stalk length and the power attenuation. The response surface method was applied to optimize the operation conditions. The optimum factors for "stalk-standing" and "crop residue" chopping operation were as follows: The rotating speeds of feeding press rolls were 399.2 and 401.64 r/min, the rotating speeds of rotation shaft of moving knives were 968.12 and 977.23 r/min, and the gaps between moving knife and stationary knife were 0.52 and 0.49 mm, respectively. Under the optimal condition, the corresponding qualified rates of chopped stalk length for "stalk-standing" and "crop residue" were 95.89% and 97.09%, as well as the power attenuations were 3.04 and 2.6 kW, respectively. The differences between the experimental and the software analytical value of the qualified rate of chopped stalk length for "stalk-standing" and "crop residue" were both 0.11% and those of power attenuation were 0.05 and 0.08 kW, respectively, which indicated that the software analytical value was in great agreement with the experiment value. Based on the theoretical analysis, the higher qualified rate of chopped stalk length could be achieved under the faster rotating speed of rotation shaft of moving knives and the smaller gaps between moving knife and stationary knife. Taking into consideration the existing form of rice straw in farmland, the rotating speed of feeding press roll was designed to be 401.64 r/min, the rotating speed of rotation shaft of moving knife 977.23 r/min, and the gap between moving knife and stationary knife 0.49 mm. It can provide technical support for the design of rapeseed planter with the combination of straw-mulching cultivation and direct seeding. [ABSTRACT FROM AUTHOR]