This study aimed at optimizing tillage depth and hitching length for optimal draft requirement in sandy clay loam soils for animal drawn subsoiler. Field experiments were conducted to collect draft datasets using the ...This study aimed at optimizing tillage depth and hitching length for optimal draft requirement in sandy clay loam soils for animal drawn subsoiler. Field experiments were conducted to collect draft datasets using the MSI 7300 digital dynamometer communicating remotely with MSI-8000 RF data logger connected to a laptop through the serial port. To determine the numeric values of soil parameters pertinent to subsoiling, field experiments, laboratory tests and numerical analysis techniques were employed. For a specified speed, a combination of three hitch lengths of 2.5 m, 3.0 m and 3.5 m and three depths from 0 cm to 30 cm with a range of 10 cm interval was used. Soil bulk density was found to vary between 1.52 to 1.37 g/cm3 and 1.44 to 1.67 g/cm3 for Machakos and Kitui experimental plots respectively. Soil moisture content increased with an increase in depth ranging from 3.53% to 9.94% for Machakos site and from 4.15% to 9.61% for Kitui site. Soil shear strength parameters ranged between 21.71 and 29.6 kPa between depths of 0 - 20 cm and decreased to 28.07 kPa for depths beyond 20 cm at Machakos experimental plot;while for Kitui experimental plot, it ranged between 30.02 and 39.29 kPa between depths of 0 - 30 cm. A second-order quadratic expression of the form y = ax2 + bx + c was obtained for the relationship between specific draft and depth at given hitching length as well as specific draft against hitching length at a given depth. The optimal hitching length and tillage depth for Machakos experimental plot were obtained as 2.9 m (~3 m) and 16.5 cm respectively. In Kitui experimental site, the optimal hitching length was obtained as 2.9 m (~3 m) and the optimal tillage depth was 15.4 cm.展开更多
Use of the da Vinci■surgical robotic system has expanded to numerous upper and lower urinary tract procedures.We describe our surgical technique and perioperative outcome of robotic distal ureterectomy with psoas hit...Use of the da Vinci■surgical robotic system has expanded to numerous upper and lower urinary tract procedures.We describe our surgical technique and perioperative outcome of robotic distal ureterectomy with psoas hitch and ureteroneocystostomy for distal ureteral pathologies.Eight patients with a median age of 69.5 years old underwent robotic distal ureterectomy with psoas hitch and ureteroneocystostomy between April 2009 and August 2014.The entirety of all cases was performed robotically by a single surgeon at a tertiary academic medical center.Median operative time was 285 min(range:210-360 min),estimated blood loss was 50 mL(range:50-75 mL)and median length of hospital stay was 2.5 days(range:1-6 days).There was one post-operative complication,a readmission for dehydration(Clavien Ⅰ).It suggests that robotic distal ureterectomy with psoas hitch and ureteroneocystostomy is a safe and effective minimally invasive alternative for patients with distal ureteral pathology.展开更多
Objective:To present our experience and technique with robot-assisted uretero-neocystos tomy(RAUN)procedure in adults.Methods:Between February 2015 and August 2018,a total of 30(34 ureters)patients who un-derwent RAUN...Objective:To present our experience and technique with robot-assisted uretero-neocystos tomy(RAUN)procedure in adults.Methods:Between February 2015 and August 2018,a total of 30(34 ureters)patients who un-derwent RAUN surgery under a single surgeon were retrospectively reviewed.Perioperative data such as age,sex,body mass index(BMI),American society of anesthes iologists score,esti-mated blood loss,surgical technique,operative time,complications,length of hospital stay,and stent removal time were recorded.During the follow-up,patients underwent renal func-tion test,urinalysis,and renal ultrasound examination for evaluation.Success was defined as symptomatic and radiologic relieve.Lastly,a literature search was conducted to review all published articles regarding RAUN surgery in adults.Results:The patients'mean age,BMI,EBL,operative time,and follow-up period were 45.4 years,23.1 kg/m^2,65.6 mL,182.9 min,and 21.3 months,respectively.The two most common indications for the surgery were benign ureteral strictures and ureteric injuries secondaryto a previous radical hysterectomy.Of the 34 cases,26(76.5%)and 8(23.5%)patients received pri-mary RAUN and RAUN with psoas hitch technique,respectively.Refluxing RAUN method was performed in all cases.No intraoperative complications were found.Two patients had a radio-logic and symptomatic recurrence;one was managed with a repeat surgery while the other received ureteral dilatation treatment.Conclusion:Both our study and the published literature showed that RAUN is a safe,less inva-sive,and effective surgical technique that can easily replicate the open ureteroneocystostomy for managing lower ureteral diseases.展开更多
In view of the problems of poor working quality and low efficiency caused by traditional hitch mechanisms,which cannot make farm implements adapt to hillside fields for terrain-adaptive working after leveling the body...In view of the problems of poor working quality and low efficiency caused by traditional hitch mechanisms,which cannot make farm implements adapt to hillside fields for terrain-adaptive working after leveling the body of hilly tractors,a new type of terrain-adaptive hitch mechanism was designed which can adjust the transverse posture of farm implements to meet the ploughing requirements of complicated terrain in hilly and mountainous areas.The mechanism was mainly composed of the original hitch device and the newly added rotating device.The kinematic model of each sub-mechanism was established,as well as the mathematical relation of significant performance indexes of the whole mechanism,such as lifting capacity,transverse inclination angle and tillage depth.Genetic algorithm was used to optimize the lifting performance of this hitch mechanism in Matlab,so that the minimum vertical lifting force at the center of gravity of farm implements increased by 14.1%,which met the requirements of national standards.Through ADAMS simulation calculation,it was found that different working slopes had a certain influence on the external load of each component,and terrain-adaptive hitch mechanism had little effect on the vibration characteristics of hilly tractors.The fatigue analysis and optimization design of the key component,rotating shaft,were carried out in ANSYS Workbench,and the mass of this part reduced by 64%.A real vehicle test platform was set up to test and verify the power lifting range and working slope range of terrain-adaptive hitch mechanism.The test results showed that the actual power lifting ranged in 185-857 mm,and the maximum error from the theoretical range was only 3.1%,while the actual working slope range was from–25.9°to+23.2°,and the maximum error from the theoretical range was only 4.5%.Therefore,the terrain-adaptive hitch mechanism can meet the requirements of power lifting performance,and simultaneously can adjust the transverse posture of farm implements for adapting to hillside fields of no less than 20°.展开更多
The real-time monitoring of the load in farming by the sensor installed on the tractor's three-point hitch can effectively improve the farming efficiency and force-position combined control,reduce the compaction r...The real-time monitoring of the load in farming by the sensor installed on the tractor's three-point hitch can effectively improve the farming efficiency and force-position combined control,reduce the compaction risk of the wheel on the soil and reduce the fuel consumption in farming process.However,the measurement and quantification of the loads on the three-point hitch have some problems remaining unresolved:testing the accuracy and reliability of a load measuring system is hard when the tractor works in a field,the mathematical model of spatial forces usually lacks a practical and effective validation,and the calibration process of the measurement system is inconvenient and incomplete while easily causing a low accuracy.Specifically,this paper builds a new spatial-force mathematical model based on the geometry of a three-point hitch.To eliminate the discrepancy of the geometric model with the actual structure and to refine the mathematical model,a calibration process is conducted by developing a calibration bench,which is equipped with a data acquisition system and a multi-parameter monitoring interface.The three-point hitch installed on this calibration bench is subject to steady-state loading.The loading force,angle of the lower drawbar,and three-component forces(three shaft pin sensors’forces)of the three-point hitch are well measured.With applying for the measured data to calibrate the theoretical mathematic model eventually derives the resultant force from all the three-component forces,a dynamical loading bench was developed to test the calculated resultant force for the three-point hitch during the sinusoidal and randomly variant dynamical loadings tests.A hitch force measurement system is also developed to collect real-time data and calculate the resultant force of measured three-component forces through the calibrated mathematical model.The results of the dynamical loading tests show that the average relative error MRE=1.09%with an average force measurement time delay beingΔt=0.5 s,the root mean square error RMSE=59.3 N,and the coefficient of determination R2=0.9903.As observed,the shape and the trend of the generated resultant force curve are basically the dynamical loading force.The dynamical loading test proves the high efficacy and reliability of the proposed indoor calibration method for calculating the load based on the three-component forces as measured on the three-point hitch.Besides,the preliminary study of the proposed method on the hitch load provides great potential to improve the indoor six-component measurement and quantification of both the force and momentum acting on the three-point hitch.展开更多
The automatic and intelligent degree of tractor hitch system determines the operations quality,efficiency,tractor power output and energy consumption,and automatic control of electro-hydraulic hitch is one of the key ...The automatic and intelligent degree of tractor hitch system determines the operations quality,efficiency,tractor power output and energy consumption,and automatic control of electro-hydraulic hitch is one of the key technical problems in the realization of automated tractor.In this study,the adjustment methods and characteristics of electro-hydraulic hitch system were summarized.The development of electro-hydraulic hitch control technologies was elaborated and analyzed from both the electro-hydraulic control strategy and slip control strategy perspectives.The implementation methods and control characteristics were discussed.A new idea for the development of automated tractor was put forward that integrating cutting-edge technologies such as big data,fusion control and artificial intelligence.In addition,based on the precise and efficient control of electro-hydraulic hitch system,a high reliability of the control system of the tractor with intelligent application of the control algorithm was obtained.The results can provide a reference for the precise operation of automated tractors under the big data in agriculture.展开更多
文摘This study aimed at optimizing tillage depth and hitching length for optimal draft requirement in sandy clay loam soils for animal drawn subsoiler. Field experiments were conducted to collect draft datasets using the MSI 7300 digital dynamometer communicating remotely with MSI-8000 RF data logger connected to a laptop through the serial port. To determine the numeric values of soil parameters pertinent to subsoiling, field experiments, laboratory tests and numerical analysis techniques were employed. For a specified speed, a combination of three hitch lengths of 2.5 m, 3.0 m and 3.5 m and three depths from 0 cm to 30 cm with a range of 10 cm interval was used. Soil bulk density was found to vary between 1.52 to 1.37 g/cm3 and 1.44 to 1.67 g/cm3 for Machakos and Kitui experimental plots respectively. Soil moisture content increased with an increase in depth ranging from 3.53% to 9.94% for Machakos site and from 4.15% to 9.61% for Kitui site. Soil shear strength parameters ranged between 21.71 and 29.6 kPa between depths of 0 - 20 cm and decreased to 28.07 kPa for depths beyond 20 cm at Machakos experimental plot;while for Kitui experimental plot, it ranged between 30.02 and 39.29 kPa between depths of 0 - 30 cm. A second-order quadratic expression of the form y = ax2 + bx + c was obtained for the relationship between specific draft and depth at given hitching length as well as specific draft against hitching length at a given depth. The optimal hitching length and tillage depth for Machakos experimental plot were obtained as 2.9 m (~3 m) and 16.5 cm respectively. In Kitui experimental site, the optimal hitching length was obtained as 2.9 m (~3 m) and the optimal tillage depth was 15.4 cm.
文摘Use of the da Vinci■surgical robotic system has expanded to numerous upper and lower urinary tract procedures.We describe our surgical technique and perioperative outcome of robotic distal ureterectomy with psoas hitch and ureteroneocystostomy for distal ureteral pathologies.Eight patients with a median age of 69.5 years old underwent robotic distal ureterectomy with psoas hitch and ureteroneocystostomy between April 2009 and August 2014.The entirety of all cases was performed robotically by a single surgeon at a tertiary academic medical center.Median operative time was 285 min(range:210-360 min),estimated blood loss was 50 mL(range:50-75 mL)and median length of hospital stay was 2.5 days(range:1-6 days).There was one post-operative complication,a readmission for dehydration(Clavien Ⅰ).It suggests that robotic distal ureterectomy with psoas hitch and ureteroneocystostomy is a safe and effective minimally invasive alternative for patients with distal ureteral pathology.
文摘Objective:To present our experience and technique with robot-assisted uretero-neocystos tomy(RAUN)procedure in adults.Methods:Between February 2015 and August 2018,a total of 30(34 ureters)patients who un-derwent RAUN surgery under a single surgeon were retrospectively reviewed.Perioperative data such as age,sex,body mass index(BMI),American society of anesthes iologists score,esti-mated blood loss,surgical technique,operative time,complications,length of hospital stay,and stent removal time were recorded.During the follow-up,patients underwent renal func-tion test,urinalysis,and renal ultrasound examination for evaluation.Success was defined as symptomatic and radiologic relieve.Lastly,a literature search was conducted to review all published articles regarding RAUN surgery in adults.Results:The patients'mean age,BMI,EBL,operative time,and follow-up period were 45.4 years,23.1 kg/m^2,65.6 mL,182.9 min,and 21.3 months,respectively.The two most common indications for the surgery were benign ureteral strictures and ureteric injuries secondaryto a previous radical hysterectomy.Of the 34 cases,26(76.5%)and 8(23.5%)patients received pri-mary RAUN and RAUN with psoas hitch technique,respectively.Refluxing RAUN method was performed in all cases.No intraoperative complications were found.Two patients had a radio-logic and symptomatic recurrence;one was managed with a repeat surgery while the other received ureteral dilatation treatment.Conclusion:Both our study and the published literature showed that RAUN is a safe,less inva-sive,and effective surgical technique that can easily replicate the open ureteroneocystostomy for managing lower ureteral diseases.
基金supported by the National Key R&D Program of China(Grant No.2016YFD0700504).
文摘In view of the problems of poor working quality and low efficiency caused by traditional hitch mechanisms,which cannot make farm implements adapt to hillside fields for terrain-adaptive working after leveling the body of hilly tractors,a new type of terrain-adaptive hitch mechanism was designed which can adjust the transverse posture of farm implements to meet the ploughing requirements of complicated terrain in hilly and mountainous areas.The mechanism was mainly composed of the original hitch device and the newly added rotating device.The kinematic model of each sub-mechanism was established,as well as the mathematical relation of significant performance indexes of the whole mechanism,such as lifting capacity,transverse inclination angle and tillage depth.Genetic algorithm was used to optimize the lifting performance of this hitch mechanism in Matlab,so that the minimum vertical lifting force at the center of gravity of farm implements increased by 14.1%,which met the requirements of national standards.Through ADAMS simulation calculation,it was found that different working slopes had a certain influence on the external load of each component,and terrain-adaptive hitch mechanism had little effect on the vibration characteristics of hilly tractors.The fatigue analysis and optimization design of the key component,rotating shaft,were carried out in ANSYS Workbench,and the mass of this part reduced by 64%.A real vehicle test platform was set up to test and verify the power lifting range and working slope range of terrain-adaptive hitch mechanism.The test results showed that the actual power lifting ranged in 185-857 mm,and the maximum error from the theoretical range was only 3.1%,while the actual working slope range was from–25.9°to+23.2°,and the maximum error from the theoretical range was only 4.5%.Therefore,the terrain-adaptive hitch mechanism can meet the requirements of power lifting performance,and simultaneously can adjust the transverse posture of farm implements for adapting to hillside fields of no less than 20°.
基金This work was financially supported by the project of agricultural machinery R&D,manufacturing,promotion,application,and integrationand the 13th Five-Year Plan National Key Research and Development Program of China(Grant No.2016YFD0700102).
文摘The real-time monitoring of the load in farming by the sensor installed on the tractor's three-point hitch can effectively improve the farming efficiency and force-position combined control,reduce the compaction risk of the wheel on the soil and reduce the fuel consumption in farming process.However,the measurement and quantification of the loads on the three-point hitch have some problems remaining unresolved:testing the accuracy and reliability of a load measuring system is hard when the tractor works in a field,the mathematical model of spatial forces usually lacks a practical and effective validation,and the calibration process of the measurement system is inconvenient and incomplete while easily causing a low accuracy.Specifically,this paper builds a new spatial-force mathematical model based on the geometry of a three-point hitch.To eliminate the discrepancy of the geometric model with the actual structure and to refine the mathematical model,a calibration process is conducted by developing a calibration bench,which is equipped with a data acquisition system and a multi-parameter monitoring interface.The three-point hitch installed on this calibration bench is subject to steady-state loading.The loading force,angle of the lower drawbar,and three-component forces(three shaft pin sensors’forces)of the three-point hitch are well measured.With applying for the measured data to calibrate the theoretical mathematic model eventually derives the resultant force from all the three-component forces,a dynamical loading bench was developed to test the calculated resultant force for the three-point hitch during the sinusoidal and randomly variant dynamical loadings tests.A hitch force measurement system is also developed to collect real-time data and calculate the resultant force of measured three-component forces through the calibrated mathematical model.The results of the dynamical loading tests show that the average relative error MRE=1.09%with an average force measurement time delay beingΔt=0.5 s,the root mean square error RMSE=59.3 N,and the coefficient of determination R2=0.9903.As observed,the shape and the trend of the generated resultant force curve are basically the dynamical loading force.The dynamical loading test proves the high efficacy and reliability of the proposed indoor calibration method for calculating the load based on the three-component forces as measured on the three-point hitch.Besides,the preliminary study of the proposed method on the hitch load provides great potential to improve the indoor six-component measurement and quantification of both the force and momentum acting on the three-point hitch.
基金This work was financially supported by the Thirteen Fifth National Key Research and Development Program of China(Grant No.2016YFD0700102)National Natural Science Foundation of China(Grant No.31801783),and China Scholarship Council.
文摘The automatic and intelligent degree of tractor hitch system determines the operations quality,efficiency,tractor power output and energy consumption,and automatic control of electro-hydraulic hitch is one of the key technical problems in the realization of automated tractor.In this study,the adjustment methods and characteristics of electro-hydraulic hitch system were summarized.The development of electro-hydraulic hitch control technologies was elaborated and analyzed from both the electro-hydraulic control strategy and slip control strategy perspectives.The implementation methods and control characteristics were discussed.A new idea for the development of automated tractor was put forward that integrating cutting-edge technologies such as big data,fusion control and artificial intelligence.In addition,based on the precise and efficient control of electro-hydraulic hitch system,a high reliability of the control system of the tractor with intelligent application of the control algorithm was obtained.The results can provide a reference for the precise operation of automated tractors under the big data in agriculture.
