AIM: To analyze whether wet-lab training(WLT) or surgical-simulator training(SST) is better for ophthalmology residents to master the chopping technique.METHODS: Sixty ophthalmology residents(in their second year) and...AIM: To analyze whether wet-lab training(WLT) or surgical-simulator training(SST) is better for ophthalmology residents to master the chopping technique.METHODS: Sixty ophthalmology residents(in their second year) and three cataract surgeons participated in the study. The residents were randomly separated into two groups, WLT group and SST group. The residents in WLT group were asked to perform 10 trials of chopping using pig eyes and scored by the surgeons, and then they performed and scored using simulator for one time. The residents in SST group underwent 10 trials of chopping using simulator, and the simulator scored each trail. Then, this group were asked to perform the chopping using pig eyes and scored by the surgeons. At last, we investigated the residents’ satisfaction about the training.RESULTS: The demographic characteristics had no significant differences between the two groups. Recorded by the simulator, the residents in SST group got significantly higher overall score(83.90±1.31) than WLT group(78.73±1.92, P=0.03). And the residents in SST group got less corner area injured, and they spend less time than WLT group(P<0.05). Moreover, the residents in WLT group used more ultrasonic energy value than SST group(P=0.03). However, scored by the surgeons, the residents in two groups got nearly the same overall score. The residents in WLT group performed better on the frequencies of posterior capsule torn and incisional stress(P=0.03, 0.008, respectively). In the survey, the residents in two groups held the same opinion that the training was helpful and they strongly recommended this training. And all of them enjoyed the training, and enjoyed being randomized in their own group. However, with respect to the realistic character, the residents thought that WLT was better than SST(P<0.001).CONCLUSION: Both of the Eyesi surgical-stimulator and the wet-lab improve the residents’ chopping ability and each has its own advantages. The combination of the two training ways could be considered to be a part of the training curriculum for new residents.展开更多
A onvel current chopping strategy for switched reluc-tance generator(SRG)-a full conducted current chopping(FCCC)scheme is presented,According to characteristics lf phase current wave of SRG generating operation,it ca...A onvel current chopping strategy for switched reluc-tance generator(SRG)-a full conducted current chopping(FCCC)scheme is presented,According to characteristics lf phase current wave of SRG generating operation,it can be generated under sensorless condition without an addi-tional circuit or a position signal algorithm.Simulational results show the feasibility of this scheme.Experimental results of a 6kW6/4configuration SRG show its simplic-ity and high reliability with little decrease in efficiency.Soit will be widely used.展开更多
A novel current chopping mode was used in a switched reluctance motor drive system to make full use of the characteristics of digital signal processor (DSP) TMS320F240. The necessity of this 180° phase-shift curr...A novel current chopping mode was used in a switched reluctance motor drive system to make full use of the characteristics of digital signal processor (DSP) TMS320F240. The necessity of this 180° phase-shift current control (PSCC) mode is introduced first and then the principle of PSCC covering both hardware requirement and software programming is described in detail. The analysis made indicated that with this mode, the chopping frequency in winding can reach 20 kHz with 10 kHz power switches and the control frequency can reach 40 kHz at the same time. Subsequently, based on the linear and nonlinear mathematical models of the switched reluctance motor (SRM), some simulation work has been done. The simulation results show that when this mode is applied to SRM drive (SRD) system, the current waveform becomes better. So the ripple of the torque is reduced simultaneously and the vibration and acoustic noise are reduced involuntarily. Stationary tests show that the acoustic noise is greatly diminished. Finally, some experiments were made using a 50 kW SRD system for electric vehicle (EV). Experimental results indicate that this mode can be implemented feasibly and it has a good action on the SRD system.展开更多
In this paper,we design a farm machine integrating the functions of chopping field straw,pressing field straw into soil,breaking stubble,and cleaning up plastic film,in order to improve the efficiency of plastic film ...In this paper,we design a farm machine integrating the functions of chopping field straw,pressing field straw into soil,breaking stubble,and cleaning up plastic film,in order to improve the efficiency of plastic film cleaning,enrich the function of straw chopping equipment,reduce the noise generated at work,and further realize the intelligent harmony. The remote control button is used to control the work of the entire system,and the bluetooth remote control module and matrix keyboard are used to control the vehicle. With STM32 microcontroller as the main control chip,the machine controls the motion of the electric motor by relay,and employs LCD screen to realize real-time display of system work. It is convenient and easy to operate,with good human-computer interaction.展开更多
Horizontal feeding devices and plate hob chopping devices are the key component of silage maize harvester.To solve the problem of feeding blockage,reduce energy consumption,and improve the chopping quality of the chop...Horizontal feeding devices and plate hob chopping devices are the key component of silage maize harvester.To solve the problem of feeding blockage,reduce energy consumption,and improve the chopping quality of the chopping device a horizontal different diameter five-rollers device(HDDFD)was designed and the plate hob chopping device was simultaneously optimized and analyzed.Through the dynamic analysis,the feeding conveying speed was determined to be 2.0-4.5 m/s.The distance equation of the actual and theoretical cutting-edge curve and the position of the fixed blade were finally obtained.Single factor and response surface orthogonal tests in the bench site were carried out with feeding speed,rotating speed of chopping cylinder,feeding amount,and feeding direction as influencing factors,standard grass length rate(SGLR),and energy consumption per unit mass(ECPUM)as evaluation indexes.The optimal working parameters for chopping performance could be concluded as a feeding speed of 3.39 m/s,rotating speed of the chopping cylinder of 1016.17 r/min,feeding amount of 8.04 kg/s,and feeding direction of 52.2°.In addition,the SGLR and ECPUM were obtained as 95.35%and 37.63 kJ/kg,respectively.The relative error between the experimental results with round parameter combination and the predicted value was verified to be less than 5%.Field tests verified the reliability of the optimized feeding and chopping device.It can be seen that the HDDFD and optimized plate hob chopping device can meet the requirements of mechanized silage harvesting which obviously improves the working quality and reduce the energy consumption of chopping.展开更多
In order to address the problems of large chop length,high energy consumption and poor chopping effect that were associated with a horizontal total mixed rations(TMR)mixer,a straw chopping device was designed;further,...In order to address the problems of large chop length,high energy consumption and poor chopping effect that were associated with a horizontal total mixed rations(TMR)mixer,a straw chopping device was designed;further,its structure and working principle were analyzed.In this study,wheat straw was chosen as the test object.The number of processing times,number of fixed blades,cutting speed,number of tooth plates and the inclined angle of the box were considered as the test factors.The standard straw length rate and average power were used as evaluation indices for conducting the orthogonal rotation combination experiment with five factors and five levels of quadratic regression.The experimental results denoted that the order of influencing factors on the standard straw length rate can be given as follows:the number of processing times,number of fixed blades,cutting speed,number of tooth plates and inclined angle of the box.The order of the influence of each factor on the average power can be given as follows:the cutting speed,number of fixed blades and number of tooth plates.Further,the optimum structural and working parameters of the device can be determined as follows:linear cutting speed of 17-20 m/min,box inclined angle of 70°-80°,20-23 fixed blades,5-6 processing times and 4-7 tooth plates.Under such a circumstance,the standard straw length rate reached up to 70.5%-77.4%and the average power was low at 5.8-7 kW.The results can be used as reference for designing a chopping device for a TMR mixer.展开更多
Chopped and spread maize stalks improve soil structure and fertility. However, because of the absence of research on airflow distribution in the chopping chamber, improvement of the spreading uniformity of chopped sta...Chopped and spread maize stalks improve soil structure and fertility. However, because of the absence of research on airflow distribution in the chopping chamber, improvement of the spreading uniformity of chopped stalks has been limited. Therefore, in this study, computational fluid dynamics (CFD) technology was applied to analyze the influence of structural and operational parameters of the chopping and spreading machine on the velocity, pressure, and turbulent kinetic energy distribution of airflow in the chopping chamber. The experimental factors considered were the relative position angle (RPA) between the collecting-chopping shaft and the sliding-supporting shaft, working velocity (WV) of the chopping chamber, and rotational velocity of the collecting-chopping blade (RVCCB). The results revealed that RPA and RVCCB had a significant influence on the maximum negative pressure in the inlet (MNPI), the proportion of negative pressure area at inlet (PNPAI), and the maximum pressure drop at inlet and outlet (MPDIO). Additionally, RVCCB had a strong influence on the maximum velocity, average velocity, and velocity variation coefficient of airflow at the outlet. Moreover, maximum turbulence (MT) and maximum turbulent kinetic energy dissipation rate (MTKEDR) showed a positive relationship with RVCCB. To determine the values of RPA, RVCCB, and WV, a multivariate parameters optimization regression model was constructed, which yielded the optimal values of 15°, 1800 r/min, and 0.50 m/s, respectively. Subsequently, a hyperbolic spiral-type guiding shell with an arc length of 90° was designed to enhance the uniform distribution of airflow in the chopping chamber. Finally, a validation experiment of airflow distribution was conducted. The results showed that the velocity difference between the simulation and the validation experiment was less than 15%, indicating the accuracy of CFD simulation, and the spreading uniformities of the chopped stalks were better than national standards. These findings can serve as technical and theoretical support for the design and optimization of chopping and spreading machines.展开更多
基金Supported by Natural Science Foundation Grant from Jiangxi Science and Technology Department (No.20192BAB205049)Young Talent Scholar Grant (No.2016KJXX-12)from Shaanxi Science and Technology Department, Teaching Reform Grant (No.JC2020-0309,No.JG20190330)。
文摘AIM: To analyze whether wet-lab training(WLT) or surgical-simulator training(SST) is better for ophthalmology residents to master the chopping technique.METHODS: Sixty ophthalmology residents(in their second year) and three cataract surgeons participated in the study. The residents were randomly separated into two groups, WLT group and SST group. The residents in WLT group were asked to perform 10 trials of chopping using pig eyes and scored by the surgeons, and then they performed and scored using simulator for one time. The residents in SST group underwent 10 trials of chopping using simulator, and the simulator scored each trail. Then, this group were asked to perform the chopping using pig eyes and scored by the surgeons. At last, we investigated the residents’ satisfaction about the training.RESULTS: The demographic characteristics had no significant differences between the two groups. Recorded by the simulator, the residents in SST group got significantly higher overall score(83.90±1.31) than WLT group(78.73±1.92, P=0.03). And the residents in SST group got less corner area injured, and they spend less time than WLT group(P<0.05). Moreover, the residents in WLT group used more ultrasonic energy value than SST group(P=0.03). However, scored by the surgeons, the residents in two groups got nearly the same overall score. The residents in WLT group performed better on the frequencies of posterior capsule torn and incisional stress(P=0.03, 0.008, respectively). In the survey, the residents in two groups held the same opinion that the training was helpful and they strongly recommended this training. And all of them enjoyed the training, and enjoyed being randomized in their own group. However, with respect to the realistic character, the residents thought that WLT was better than SST(P<0.001).CONCLUSION: Both of the Eyesi surgical-stimulator and the wet-lab improve the residents’ chopping ability and each has its own advantages. The combination of the two training ways could be considered to be a part of the training curriculum for new residents.
文摘A onvel current chopping strategy for switched reluc-tance generator(SRG)-a full conducted current chopping(FCCC)scheme is presented,According to characteristics lf phase current wave of SRG generating operation,it can be generated under sensorless condition without an addi-tional circuit or a position signal algorithm.Simulational results show the feasibility of this scheme.Experimental results of a 6kW6/4configuration SRG show its simplic-ity and high reliability with little decrease in efficiency.Soit will be widely used.
文摘A novel current chopping mode was used in a switched reluctance motor drive system to make full use of the characteristics of digital signal processor (DSP) TMS320F240. The necessity of this 180° phase-shift current control (PSCC) mode is introduced first and then the principle of PSCC covering both hardware requirement and software programming is described in detail. The analysis made indicated that with this mode, the chopping frequency in winding can reach 20 kHz with 10 kHz power switches and the control frequency can reach 40 kHz at the same time. Subsequently, based on the linear and nonlinear mathematical models of the switched reluctance motor (SRM), some simulation work has been done. The simulation results show that when this mode is applied to SRM drive (SRD) system, the current waveform becomes better. So the ripple of the torque is reduced simultaneously and the vibration and acoustic noise are reduced involuntarily. Stationary tests show that the acoustic noise is greatly diminished. Finally, some experiments were made using a 50 kW SRD system for electric vehicle (EV). Experimental results indicate that this mode can be implemented feasibly and it has a good action on the SRD system.
基金Supported by Key Major Production Accident Prevention and Control Technology Project of State Administration of Work Safety in 2015(shandong-0075-2015AQ)
文摘In this paper,we design a farm machine integrating the functions of chopping field straw,pressing field straw into soil,breaking stubble,and cleaning up plastic film,in order to improve the efficiency of plastic film cleaning,enrich the function of straw chopping equipment,reduce the noise generated at work,and further realize the intelligent harmony. The remote control button is used to control the work of the entire system,and the bluetooth remote control module and matrix keyboard are used to control the vehicle. With STM32 microcontroller as the main control chip,the machine controls the motion of the electric motor by relay,and employs LCD screen to realize real-time display of system work. It is convenient and easy to operate,with good human-computer interaction.
基金The research program is supported by the Key Science and Technology Innovation Project of Shandong Province,China(Grant No.2019JZZY020615)the Shandong Province Agricultural major application technology innovation project(Grant No.SD2019NJ005).
文摘Horizontal feeding devices and plate hob chopping devices are the key component of silage maize harvester.To solve the problem of feeding blockage,reduce energy consumption,and improve the chopping quality of the chopping device a horizontal different diameter five-rollers device(HDDFD)was designed and the plate hob chopping device was simultaneously optimized and analyzed.Through the dynamic analysis,the feeding conveying speed was determined to be 2.0-4.5 m/s.The distance equation of the actual and theoretical cutting-edge curve and the position of the fixed blade were finally obtained.Single factor and response surface orthogonal tests in the bench site were carried out with feeding speed,rotating speed of chopping cylinder,feeding amount,and feeding direction as influencing factors,standard grass length rate(SGLR),and energy consumption per unit mass(ECPUM)as evaluation indexes.The optimal working parameters for chopping performance could be concluded as a feeding speed of 3.39 m/s,rotating speed of the chopping cylinder of 1016.17 r/min,feeding amount of 8.04 kg/s,and feeding direction of 52.2°.In addition,the SGLR and ECPUM were obtained as 95.35%and 37.63 kJ/kg,respectively.The relative error between the experimental results with round parameter combination and the predicted value was verified to be less than 5%.Field tests verified the reliability of the optimized feeding and chopping device.It can be seen that the HDDFD and optimized plate hob chopping device can meet the requirements of mechanized silage harvesting which obviously improves the working quality and reduce the energy consumption of chopping.
基金The authors acknowledge that this work was financially supported by the National Natural Science Foundation of China(No.51775358)the Young and Middle-aged Leaders in Science and Technology Innovation(No.2016BC001)+1 种基金Third Division Meat Sheep Breeding Mechanized Science and Technology Commissioner Innovation and Entrepreneurship Demonstration(No.2016CA002)and the Shihezi University Science and Technology Achievements Transformation Project(No.CGZH201601).
文摘In order to address the problems of large chop length,high energy consumption and poor chopping effect that were associated with a horizontal total mixed rations(TMR)mixer,a straw chopping device was designed;further,its structure and working principle were analyzed.In this study,wheat straw was chosen as the test object.The number of processing times,number of fixed blades,cutting speed,number of tooth plates and the inclined angle of the box were considered as the test factors.The standard straw length rate and average power were used as evaluation indices for conducting the orthogonal rotation combination experiment with five factors and five levels of quadratic regression.The experimental results denoted that the order of influencing factors on the standard straw length rate can be given as follows:the number of processing times,number of fixed blades,cutting speed,number of tooth plates and inclined angle of the box.The order of the influence of each factor on the average power can be given as follows:the cutting speed,number of fixed blades and number of tooth plates.Further,the optimum structural and working parameters of the device can be determined as follows:linear cutting speed of 17-20 m/min,box inclined angle of 70°-80°,20-23 fixed blades,5-6 processing times and 4-7 tooth plates.Under such a circumstance,the standard straw length rate reached up to 70.5%-77.4%and the average power was low at 5.8-7 kW.The results can be used as reference for designing a chopping device for a TMR mixer.
基金supported by Natural Science Foundation of Henan Province(Grant No.242300421560)Science and Technology Research Project of Henan(Grant No.232102110273)+2 种基金the Scientific Research Foundation for Advanced Talents of Henan University of Technology(Grant No.2022BS077)Training Plan of Young Backbone Teachers in Colleges and Universities in Henan Province(Grant No.2020GGJS088)the Cultivation Programme for Young Backbone Teachers in Henan University of Technology(Grant No.0503/21420191).
文摘Chopped and spread maize stalks improve soil structure and fertility. However, because of the absence of research on airflow distribution in the chopping chamber, improvement of the spreading uniformity of chopped stalks has been limited. Therefore, in this study, computational fluid dynamics (CFD) technology was applied to analyze the influence of structural and operational parameters of the chopping and spreading machine on the velocity, pressure, and turbulent kinetic energy distribution of airflow in the chopping chamber. The experimental factors considered were the relative position angle (RPA) between the collecting-chopping shaft and the sliding-supporting shaft, working velocity (WV) of the chopping chamber, and rotational velocity of the collecting-chopping blade (RVCCB). The results revealed that RPA and RVCCB had a significant influence on the maximum negative pressure in the inlet (MNPI), the proportion of negative pressure area at inlet (PNPAI), and the maximum pressure drop at inlet and outlet (MPDIO). Additionally, RVCCB had a strong influence on the maximum velocity, average velocity, and velocity variation coefficient of airflow at the outlet. Moreover, maximum turbulence (MT) and maximum turbulent kinetic energy dissipation rate (MTKEDR) showed a positive relationship with RVCCB. To determine the values of RPA, RVCCB, and WV, a multivariate parameters optimization regression model was constructed, which yielded the optimal values of 15°, 1800 r/min, and 0.50 m/s, respectively. Subsequently, a hyperbolic spiral-type guiding shell with an arc length of 90° was designed to enhance the uniform distribution of airflow in the chopping chamber. Finally, a validation experiment of airflow distribution was conducted. The results showed that the velocity difference between the simulation and the validation experiment was less than 15%, indicating the accuracy of CFD simulation, and the spreading uniformities of the chopped stalks were better than national standards. These findings can serve as technical and theoretical support for the design and optimization of chopping and spreading machines.
