Complex field environments,diverse crop conditions,and varying feed rate fluctuations commonly result in a decline in the threshing performance and the clogging of the threshing cylinder for maize harvesters.In order ...Complex field environments,diverse crop conditions,and varying feed rate fluctuations commonly result in a decline in the threshing performance and the clogging of the threshing cylinder for maize harvesters.In order to overcome these problems,an electric-hydraulic concave clearance automatic control system for the threshing unit was developed based on the maize feed rate monitoring,which can automatically realize the best match between the concave clearance and diverse feed rates during harvesting.The threshing performance of the electric-hydraulic control system was evaluated for varying and uneven maize feed rate fluctuations,such as the feed rate increased(6-8-10 kg/s),the feed rate decreased after an increase(6-10-8 kg/s,8-10-6 kg/s),the feed rate increased after a decrease(8-6-10 kg/s,10-6-8 kg/s),and the feed rate decreased(10-8-6 kg/s).In particular,the threshing rotor shaft peak torque,the range of threshing rotor shaft torque,the rate of broken grains(BGR),and the rate of unthreshed grains(UGR)with and without the electric-hydraulic control system were tested.Treatments with the electric-hydraulic control system were adjustable concave clearance with the value of 45 mm,50 mm,and 55 mm.Treatments without the electric-hydraulic control system were constant concave clearance(50 mm).Results demonstrate that the threshing unit with the electric-hydraulic control system outperformed the one without the electric-hydraulic control system,with threshing rotor peak torque,the range of threshing rotor axis torque,the BGR,and the UGR decreasing by 18.38%,38.27%,2.08%,and 0.10%,respectively.Moreover,the rate of broken grains was lower than 5.00%,better than the national standard.Thus,the feed rate fluctuations and timely adjustment of the concave clearance were able to avoid blocking the rotor and improve the threshing performance compared to the constant concave clearance.展开更多
As one of the important materials,nanocrystalline Au(n-Au)has gained numerous interests in recent decades owing to its unique properties and promising applications.However,most of the current n-Au thin films are suppo...As one of the important materials,nanocrystalline Au(n-Au)has gained numerous interests in recent decades owing to its unique properties and promising applications.However,most of the current n-Au thin films are supported on substrates,limiting the study on their mechanical properties and applications.Therefore,it is urgently desired to develop a new strategy to prepare nAu materials with superior mechanical strength and hardness.Here,a hard n-Au material with an average grain size of~40 nm is prepared by cold-forging of the unique Au nanoribbons(NRBs)with unconventional 4H phase under high pressure.Systematic characterizations reveal the phase transformation from 4H to face-centered cubic(fcc)phase during the cold compression.Impressively,the compressive yield strength and Vickers hardness(HV)of the prepared n-Au material reach~140.2 MPa and~1.0 GPa,which are 4.2 and 2.2 times of the microcrystalline Au foil,respectively.This work demonstrates that the combination of high-pressure cold-forging and the in-situ 4H-to-fcc phase transformation can effectively inhibit the grain growth in the obtained n-Au materials,leading to the formation of novel hard n-Au materials.Our strategy opens up a new avenue for the preparation of nanocrystalline metals with superior mechanical property.展开更多
With the continuous improvement of agricultural mechanization,soil compaction becomes more and more serious.Serious soil compaction has been considered as an important negative factor affecting crop growth and yield.T...With the continuous improvement of agricultural mechanization,soil compaction becomes more and more serious.Serious soil compaction has been considered as an important negative factor affecting crop growth and yield.The measurement of soil compactness is a common method to measure the soil compaction level.In order to solve the problems of discontinuous sampling,time-consuming and poor real-time soil compactness measurement,a real-time measurement method of soil compactness based on fertilizing shovel was proposed,and the mathematical model between fertilizing shovel arm deformation and soil compactness was established.Based on the interaction mechanism between fertilizing shovel and soil,through the force analysis of fertilizing shovel,it was found that the deformation of fertilizing shovel arm was positively correlated with the sum of soil compactness(SSC)within the range of tillage depth.In order to verify the theoretical analysis results and the detection accuracy of strain gauge,the static bench test was carried out.The test results showed that the strain gauge signal for measuring the deformation of the fertilizing shovel arm was significantly correlated with the applied force.The fitting curve of the linear correlation coefficient was 0.999,the maximum detection error was 0.68 kg,and the detecting accuracy was within the tolerance of 0.57%.Through field orthogonal experiments with four working depths and four compaction levels,a mathematical model of the strain gauge signal and the SSC within the range of tillage depth was established.The experiment showed that compared with the other three depths,the linear correlation coefficient at the tillage depth of 5 cm(TD5)was the lowest,and the slope of the fitting curve was obviously different from the other three depths,so the 5 cm data were excluded when modeling.The model between mean signal value and mean SSC within the range of tillage depth was established based on the data of sampling points with tillage depths of 7.5 cm(TD7.5),10 cm(TD10),and 12.5 cm(TD12展开更多
基金This study was financially supported by the China Agriculture Research System of MOF and MARA,Mount Tai Industry Leading Talents Project(LJNY201708)the Soil-Machine-Plant Key Laboratory of the Ministry of Agriculture of China.
文摘Complex field environments,diverse crop conditions,and varying feed rate fluctuations commonly result in a decline in the threshing performance and the clogging of the threshing cylinder for maize harvesters.In order to overcome these problems,an electric-hydraulic concave clearance automatic control system for the threshing unit was developed based on the maize feed rate monitoring,which can automatically realize the best match between the concave clearance and diverse feed rates during harvesting.The threshing performance of the electric-hydraulic control system was evaluated for varying and uneven maize feed rate fluctuations,such as the feed rate increased(6-8-10 kg/s),the feed rate decreased after an increase(6-10-8 kg/s,8-10-6 kg/s),the feed rate increased after a decrease(8-6-10 kg/s,10-6-8 kg/s),and the feed rate decreased(10-8-6 kg/s).In particular,the threshing rotor shaft peak torque,the range of threshing rotor shaft torque,the rate of broken grains(BGR),and the rate of unthreshed grains(UGR)with and without the electric-hydraulic control system were tested.Treatments with the electric-hydraulic control system were adjustable concave clearance with the value of 45 mm,50 mm,and 55 mm.Treatments without the electric-hydraulic control system were constant concave clearance(50 mm).Results demonstrate that the threshing unit with the electric-hydraulic control system outperformed the one without the electric-hydraulic control system,with threshing rotor peak torque,the range of threshing rotor axis torque,the BGR,and the UGR decreasing by 18.38%,38.27%,2.08%,and 0.10%,respectively.Moreover,the rate of broken grains was lower than 5.00%,better than the national standard.Thus,the feed rate fluctuations and timely adjustment of the concave clearance were able to avoid blocking the rotor and improve the threshing performance compared to the constant concave clearance.
基金supported by the National Natural Science Foundation of China(Nos.52090020,51722209,and 51525205)the National Key Research and Development Program of China(No.2018YFA0305900)+3 种基金Z.S.Z.acknowledges the NSF for Distinguished Young Scholars of Hebei Province of China(No.E2018203349)M.D.M.acknowledges the China Postdoctoral Science Foundation(No.2021M691051)Z.X.F.and H.Z.thank the support from ITC via Hong Kong Branch of National Precious Metals Material Engineering Research Center(NPMM),the Start-Up Grants(Nos.9380100,9610480,and 7200651)grants(Nos.9610478,1886921,7020013,and 7005512)from City University of Hong Kong.
文摘As one of the important materials,nanocrystalline Au(n-Au)has gained numerous interests in recent decades owing to its unique properties and promising applications.However,most of the current n-Au thin films are supported on substrates,limiting the study on their mechanical properties and applications.Therefore,it is urgently desired to develop a new strategy to prepare nAu materials with superior mechanical strength and hardness.Here,a hard n-Au material with an average grain size of~40 nm is prepared by cold-forging of the unique Au nanoribbons(NRBs)with unconventional 4H phase under high pressure.Systematic characterizations reveal the phase transformation from 4H to face-centered cubic(fcc)phase during the cold compression.Impressively,the compressive yield strength and Vickers hardness(HV)of the prepared n-Au material reach~140.2 MPa and~1.0 GPa,which are 4.2 and 2.2 times of the microcrystalline Au foil,respectively.This work demonstrates that the combination of high-pressure cold-forging and the in-situ 4H-to-fcc phase transformation can effectively inhibit the grain growth in the obtained n-Au materials,leading to the formation of novel hard n-Au materials.Our strategy opens up a new avenue for the preparation of nanocrystalline metals with superior mechanical property.
基金supported in part by the earmarked fund for CARS(CARS-02)the Soil-Machine-Plant Key Laboratory of the Ministry of Agriculture of Chinathe Project of introducing talents in urgent need in Key Supporting Areas of Shandong Province in 2021.
文摘With the continuous improvement of agricultural mechanization,soil compaction becomes more and more serious.Serious soil compaction has been considered as an important negative factor affecting crop growth and yield.The measurement of soil compactness is a common method to measure the soil compaction level.In order to solve the problems of discontinuous sampling,time-consuming and poor real-time soil compactness measurement,a real-time measurement method of soil compactness based on fertilizing shovel was proposed,and the mathematical model between fertilizing shovel arm deformation and soil compactness was established.Based on the interaction mechanism between fertilizing shovel and soil,through the force analysis of fertilizing shovel,it was found that the deformation of fertilizing shovel arm was positively correlated with the sum of soil compactness(SSC)within the range of tillage depth.In order to verify the theoretical analysis results and the detection accuracy of strain gauge,the static bench test was carried out.The test results showed that the strain gauge signal for measuring the deformation of the fertilizing shovel arm was significantly correlated with the applied force.The fitting curve of the linear correlation coefficient was 0.999,the maximum detection error was 0.68 kg,and the detecting accuracy was within the tolerance of 0.57%.Through field orthogonal experiments with four working depths and four compaction levels,a mathematical model of the strain gauge signal and the SSC within the range of tillage depth was established.The experiment showed that compared with the other three depths,the linear correlation coefficient at the tillage depth of 5 cm(TD5)was the lowest,and the slope of the fitting curve was obviously different from the other three depths,so the 5 cm data were excluded when modeling.The model between mean signal value and mean SSC within the range of tillage depth was established based on the data of sampling points with tillage depths of 7.5 cm(TD7.5),10 cm(TD10),and 12.5 cm(TD12
