According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high sp...According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high speed on-off valve by the output pressure signal of the a-type half bridge is proposed. Having analyzed the factors related to the dynamic characteristics of an a-type half bridge, a rule for designing the outlet chamber＇s volume is worked out. According to the rule, a test stand is built to test the self-developed high-speed on-off valve. From the test results, it can be seen that with the outlet chamber＇s volume controlled by the rule the rise time of the pressure signals driven by signals with different frequencies changes very little. The test results conform to the simulation results, which nroves the correctness of the method.展开更多
In order to obtain nozzle droplet deposition characteristics for sprayer mechanical design and variable spraying control algorithms,a nozzle droplet deposition characteristics test system for air-assisted spraying was...In order to obtain nozzle droplet deposition characteristics for sprayer mechanical design and variable spraying control algorithms,a nozzle droplet deposition characteristics test system for air-assisted spraying was designed.The test system can supply a stable wind site with precisely controlled air speed whose speed control ranges from 2 m/s to 16 m/s with maximum relative error of 4.5%.It can spray out a certain amount of liquid pesticide with adjustable spraying pressure which can be controlled with high precision while the maximum relative error is only 1.33%.The distribution of droplet deposition can be collected and measured by using the acquisition device and a pesticide deposition optical measurement system.The experiment of two-dimensional nozzle flow measurement was carried out.The results show that nozzle flow distribution is uniform and symmetric with“double-hump”shape in the spray range.Multi-nozzle overlapped droplet deposition ranges from 85%to 116%relative to the average.The nozzle droplet deposition experiment was completed.The experiment results show that in air-assisted spraying,the higher the wind speed,the less droplet deposition is affected by gravity.When the wind speed is higher than 12 m/s and spraying distance is 0.80 m,droplet deposition is concentrated on the originally designated point and hardly affected by gravity.The horizontal spray width becomes smaller with higher wind speed.When the wind speed is high,it can be considered that nozzle deposition only focuses on the nozzle center,if the position requirement is not very high in orchard spraying.展开更多
Fe40Ni40P14B6 bulk metallic glass rods have been prepared by water quenching the fluxed alloy. The deformation behavior was investigated by nanoindentation tests and compressing tests. The average hardness and elastic...Fe40Ni40P14B6 bulk metallic glass rods have been prepared by water quenching the fluxed alloy. The deformation behavior was investigated by nanoindentation tests and compressing tests. The average hardness and elastic modulus of the as-prepared Fe40Ni40P14B6 BMG (bulk metallic glass) measured by nanoindentation tests are 8.347 and 176.61 GPa respectively. The displace- ment-load curve shows “pop-in” characteristics which correspond to the loading rate bursts. Many shear bands around the indent were observed. The as-prepared Fe-based BMG exhibits a compressive plastic strain of 5.21%, which is much larger than that of other Fe-based glassy alloys and most of other BMGs.展开更多
Language testing is very important and necessary,and moreover as we all know,nowadays,in English language testing, the muhiple-choice item is most widely used and many users regard the multiple-choice item as the most...Language testing is very important and necessary,and moreover as we all know,nowadays,in English language testing, the muhiple-choice item is most widely used and many users regard the multiple-choice item as the most flexible and probably the most effective of the objective item types.The multiple-choice item has its characteristics,advantages and disadvantages.We should bring out its strengths to make up for its weaknesses and use it appropriately.Although it has its limitations,it is suitable for large-scale tests and tests dealing with wide-range knowledge.We should correctly ap- ply testing principles and methods in order to make testing more effective and reliable.展开更多
So far the magneto-rheological(MR) effect mechanism of MR damper has not been known completely, especially in the impact load,and the problem becomes more complicated and difficult for analyzing.A set of characteristi...So far the magneto-rheological(MR) effect mechanism of MR damper has not been known completely, especially in the impact load,and the problem becomes more complicated and difficult for analyzing.A set of characteristic tests and parameters' identification are made to the MR damper by the experimental platform. The dynamical model of the damper is constructed based on the Bingham plastic model,and the buffer control strategy of aircraft undercarriage based on MR technology is established.Finally,the fuzzy control algorithm is applied to the process of automatic control for landing buffer of aircraft undercarriage.The simulation results show that the proposed MR damper pulley buffer can effectively recognize the impact energy.The research has a better application in the engineering.展开更多
文摘According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high speed on-off valve by the output pressure signal of the a-type half bridge is proposed. Having analyzed the factors related to the dynamic characteristics of an a-type half bridge, a rule for designing the outlet chamber＇s volume is worked out. According to the rule, a test stand is built to test the self-developed high-speed on-off valve. From the test results, it can be seen that with the outlet chamber＇s volume controlled by the rule the rise time of the pressure signals driven by signals with different frequencies changes very little. The test results conform to the simulation results, which nroves the correctness of the method.
基金China National 863 Project(2012AA101904)project 31201128 supported by NSFC,project KFZN2012W13-013IEA and project 2452013QN070 supported by Northwest A&F University.
文摘In order to obtain nozzle droplet deposition characteristics for sprayer mechanical design and variable spraying control algorithms,a nozzle droplet deposition characteristics test system for air-assisted spraying was designed.The test system can supply a stable wind site with precisely controlled air speed whose speed control ranges from 2 m/s to 16 m/s with maximum relative error of 4.5%.It can spray out a certain amount of liquid pesticide with adjustable spraying pressure which can be controlled with high precision while the maximum relative error is only 1.33%.The distribution of droplet deposition can be collected and measured by using the acquisition device and a pesticide deposition optical measurement system.The experiment of two-dimensional nozzle flow measurement was carried out.The results show that nozzle flow distribution is uniform and symmetric with“double-hump”shape in the spray range.Multi-nozzle overlapped droplet deposition ranges from 85%to 116%relative to the average.The nozzle droplet deposition experiment was completed.The experiment results show that in air-assisted spraying,the higher the wind speed,the less droplet deposition is affected by gravity.When the wind speed is higher than 12 m/s and spraying distance is 0.80 m,droplet deposition is concentrated on the originally designated point and hardly affected by gravity.The horizontal spray width becomes smaller with higher wind speed.When the wind speed is high,it can be considered that nozzle deposition only focuses on the nozzle center,if the position requirement is not very high in orchard spraying.
文摘Fe40Ni40P14B6 bulk metallic glass rods have been prepared by water quenching the fluxed alloy. The deformation behavior was investigated by nanoindentation tests and compressing tests. The average hardness and elastic modulus of the as-prepared Fe40Ni40P14B6 BMG (bulk metallic glass) measured by nanoindentation tests are 8.347 and 176.61 GPa respectively. The displace- ment-load curve shows “pop-in” characteristics which correspond to the loading rate bursts. Many shear bands around the indent were observed. The as-prepared Fe-based BMG exhibits a compressive plastic strain of 5.21%, which is much larger than that of other Fe-based glassy alloys and most of other BMGs.
文摘Language testing is very important and necessary,and moreover as we all know,nowadays,in English language testing, the muhiple-choice item is most widely used and many users regard the multiple-choice item as the most flexible and probably the most effective of the objective item types.The multiple-choice item has its characteristics,advantages and disadvantages.We should bring out its strengths to make up for its weaknesses and use it appropriately.Although it has its limitations,it is suitable for large-scale tests and tests dealing with wide-range knowledge.We should correctly ap- ply testing principles and methods in order to make testing more effective and reliable.
基金the National Natural Science Foundation of China(No.61074090)the Program for Liaoning Excellent Talents in University of China (No.LR2011005)the Innovation Funds of Aviation Industry Corporation of China(No.cxy2011SH)
文摘So far the magneto-rheological(MR) effect mechanism of MR damper has not been known completely, especially in the impact load,and the problem becomes more complicated and difficult for analyzing.A set of characteristic tests and parameters' identification are made to the MR damper by the experimental platform. The dynamical model of the damper is constructed based on the Bingham plastic model,and the buffer control strategy of aircraft undercarriage based on MR technology is established.Finally,the fuzzy control algorithm is applied to the process of automatic control for landing buffer of aircraft undercarriage.The simulation results show that the proposed MR damper pulley buffer can effectively recognize the impact energy.The research has a better application in the engineering.
