摘要：Wind machines have been increasingly applied to prevent frost damage through airflow disturbance in tea fields and *** impeller is the most important component of the ***,there are few studies on customized impeller design or airflow disturbance *** objective of this study was to design a new impeller for frost protection wind machines based on reverse engineering and CFD *** characteristic parameters of an impeller include blade cross-section shape,installation angle,sweep angle,hub ratio and blade *** optimal combination of the above parameters was obtained through the simulation of the impeller’s aerodynamic *** tests were conducted in a tea field to evaluate airflow disturbance performance of the designed *** result shows that at a certain rotation speed and rotation diameter,the optimal combination of impeller parameters was:single arc cross-section ofϕ2400 mm,installation angle of 15°,sweep angle of 87°,hub ratio of 0.3 and blade number of 4,of which the impeller could achieve the highest usage of 0.56,the least consumed power of 1.363 kW and more uniform distribution of surface pressure on the windward *** with other commercial frost protection wind machines,the maximum airflow velocity of the developed impeller was higher at 12 m in front of *** probability of airflow velocity above 3.0 m/s within 30 min was the highest(71.7%),indicating its improvement of airflow *** swing the new impeller could cover an effective area of 300 m2,which was similar to that of the commercial ones.

摘要：The structural parameters of tine furrow openers have significant effects on soil property of seed furrow in no-till planting,thereby affecting crop growth and *** order to analyze the effects of key parameters of tine furrow openers on soil properties(soil bulk density,soil water-stable aggregates(WSA),and soil disturbance)of the surface soil layer of 0-10 cm and surface straw disturbance,the tine furrow openers with different structural parameters,including cutting edge thickness,cutting edge curve,penetration clearance angle and rake angle,were designed and tested under no-till *** test and single factor test were performed to analyze the effects of different *** showed that the rake angle,cutting edge thickness and cutting edge curve had significant effects on cross-sectional area of furrow(Af)and disturbance of surface straw;the rake angle had a significant effect on soil bulk *** types and operating depth had significant effects on soil disturbance caused by tine furrow *** concave type tine furrow opener produced the lowest soil disturbance and soil bulk density of seed furrow,the highest surface straw disturbance and the greatest content of WSA(>0.5 mm).With increasing rake angles of tine furrow opener,the width of seedbed(Wsb)and the Af decreased first and then increased,respectively,while the width of soil throw(Wst)and the height of ridge(Hr)*** Wsb and Af created by tine furrow opener with 60°rake angle were significantly lower than that with others,*** tine furrow opener with rake angle ranged from 45°to 60°created the lowest soil bulk *** the penetration clearance angle increased,the content of WSA(>0.5 mm)decreased,but the effect of penetration clearance angle on the content of WSA(<0.5 mm)was not *** cutting edge thickness(<2 mm)had no significant effects on soil properties of *** study could provide a reference for optimal design of the tine fu

摘要：The structure stiffness of presses has great effects on the forming precision of workpieces, especially in near-net or net shape forming. Conventionally the stiffness specification of presses is empirically determined, resulting in poor designs with insufficient or over sufficient stiffness of press structures. In this paper, an approach for the structure design of hydraulic presses is proposed, which is forming-precision-driven and can make presses costeffective by lightweight optimization. The approach consists of five steps:(1)the determination of the press stiffness specification in terms of the forming precision requirement of workpieces;(2)the conceptual design of the press structures according to the stiffness and workspace specifications, and the structure configuration of the press;(3)the prototype design of the press structures by equivalently converting the conceptual design to prototypes;(4)the selection of key structure parameters by sensitivity analysis of the prototype design; and(5)the optimization of the prototype design. The approach is demonstrated and validated through a case study of the structure design of a 100 MN hydraulic press.

摘要：An experimental platform was developed to investigate the effects of audible sound(20 Hz to 20 MHz)on plant growth promotion,which included a microcontroller-based embedded system for audible sound adjustment and *** direct digital frequency synthesis(DDFS)method was used to generate various waveforms of sound in the *** glass and mufflers were used to reduce background *** developed system was tested on various plants,including hydroponic tomatoes,celery and mung *** testing results showed that the developed platform could produce pure tone and mixing audible sound with high stability and accuracy,make octave analysis of the sound under experimental environments,and the background noise in the testing chamber of the platform was lower than 55 dB(A)when the compression engine was *** developed experimental platform has a great potential on facilitating scientific research on acoustic biology effects on plants and collecting real-time experimental data.

摘要：The orchards usually have rough terrain,dense tree canopy and *** is hard to use GNSS for autonomous navigation in orchard due to signal occlusion,multipath effect,and radio frequency *** achieve autonomous navigation in orchard,a visual navigation method based on multiple images at different shooting angles is proposed in this paper.A dynamic image capturing device is designed for camera installation and multiple images can be shot at different ***,the obtained orchard images are classified into sky and soil detection *** image is transformed to HSV space and initially segmented into sky,canopy and soil regions by median filtering and morphological ***,the sky and soil regions are extracted by the maximum connected region algorithm,and the region edges are detected and filtered by the Canny ***,the navigation line in the current frame is extracted by fitting the region coordinate *** the dynamic weighted filtering algorithm is used to extract the navigation line for the soil and sky detection stage,respectively,and the navigation line for the sky detection stage is mirrored to the soil ***,the Kalman filter algorithm is used to fuse and extract the final navigation *** test results on 200 images show that the accuracy of visual navigation path fitting is 95.5%,and single frame image processing costs 60 ms,which meets the real-time and robustness requirements of *** visual navigation experiments in Camellia oleifera orchard show that when the driving speed is 0.6 m/s,the maximum tracking offset of visual navigation in weed-free and weedy environments is 0.14 m and 0.24 m,respectively,and the RMSE is 30 mm and 55 mm,respectively.