Flexible ureteroscopy(FURS)has been widely used in the diagnosis and treatment of upper urinarytract diseases.The key operation of FURS is that the surgeon manipulates the distal shaft of flexible ureteroscopeto a spe...Flexible ureteroscopy(FURS)has been widely used in the diagnosis and treatment of upper urinarytract diseases.The key operation of FURS is that the surgeon manipulates the distal shaft of flexible ureteroscopeto a specific target for diagnosis and treatment.However,the hysteresis of flexible ureteroscope may be one ofthe most important factors that degrade the manipulation accuracy and the surgeon usually spends a long timenavigating the distal shaft during surgery.In this study,we obtained hysteresis curves of distal shaft deflectionfor the flexible ureteroscope through extensive repeated experiments.Then,two methods based on piecewiselinear approximation and long short-term memory neural network were employed to model the hysteresis curves.On this basis,we proposed two hysteresis compensation strategies for the distal shaft deflection.Finally,wecarried out hysteresis compensation experiments to verify the two proposed compensation strategies.Experimentalresults showed that the hysteresis compensation strategies can significantly improve position accuracy with meancompensation errors of no more than 5°.展开更多
The current research of wind turbine drivetrain is mainly concentrated in dynamic characteristics of gearbox with a specific suspension of main shaft, such as one-point and two-point suspension. However, little attent...The current research of wind turbine drivetrain is mainly concentrated in dynamic characteristics of gearbox with a specific suspension of main shaft, such as one-point and two-point suspension. However, little attention is paid to the e ects of these suspension configurations on the dynamic responses of wind turbine gearbox. This paper investigates the influences of suspension configurations of main shaft on the dynamic characteristics of drivetrain. For evaluating the dynamic behaviors of drivetrain with multi-stage transmission system more realistically, a dynamic modeling approach of drivetrain is proposed based on Timoshenko beam theory and Lagrange's equation. Considering the flexibility and di erent suspension configurations of main shaft, time-varying mesh sti ness excitation, time-varying transmission error excitation and gravity excitation, etc., a three-dimensional dynamic model of drivetrain is developed, and the dynamic responses of drivetrain are investigated. Results show that with the one-point suspension of main shaft, the resonance frequencies in gearbox, especially at the low-speed stage, obviously shift to the higher frequency range compared to the gearbox without main shaft, but this trend could be inversed by increasing main shaft length. Meanwhile, the loads in main shaft, main shaft bearing and carrier bearing are greatly sensitive to the main shaft length. Hence, the load sharing is further disrupted by main shaft, but this e ect could be alleviated by larger load torque. Comparing to the one-point suspension of main shaft, there occurs the obvious load reduction at the low-speed stage with two-point suspension of main shaft. However, those advantages greatly depend on the distance between two main bearings, and come at the expense of increased load in upwind main shaft unit and the corresponding main bearing. Finally, a wind field test is conducted to verify the proposed drivetrain model. This study develops a numerical model of drivetrain which is able to evaluate the e ects of di erent suspension configurations of main shaft on gearbox.展开更多
Background： Nowadays pediatric femoral fractures are more commonly managed with operative treatment rather than conservative treatment because of more rapid recovery and avoidance of prolonged immobilization. Childre...Background： Nowadays pediatric femoral fractures are more commonly managed with operative treatment rather than conservative treatment because of more rapid recovery and avoidance of prolonged immobilization. Children between the ages of 5-13 years are treated either by traction plus hip spica and flexible/elastic stable retrograde intramedullary nail, or external fixators in the case of open fractures. The aim of this study is to evaluate the outcome of pediatric femoral shaft fractures treated by stainless steel flexible intramedullary nail in children between 5 and 13 years of age. Methods： There were 32 cases of femoral shaft fractures which were all fixed with stainless steel flexible intramedullary nail under fluoroscopy. Long leg cast was applied at the time of fixation. Partial weight bearing was started 2 weeks after surgery. Patients were evaluated in follow-up study to observe the alignment of fracture, infection, delayed union, nonunion, limb length discrepancy, motion of knee joint, and time to unite the fracture. Results： We were able to follow up 28 out of 32 patients. The patients were 8.14 years of age on average. The mean hospital stay after operation was 4 days and fracture union time was 9.57 weeks. There were 3 cases of varus angulation, 2 cases of anterior angulation, and 4 cases of limb lengthening. Conclusion： Patients aged between 5 and 13 years treated with flexible intramedullary nail for closed femoral shaft fracture have rapid union and recovery, short rehabilitation period, less immobilization and psychological impact, and cost-effective.展开更多
基金the National Natural Science Foundation of China(Nos.61973211,62133009,51911540479 and M-0221)the Project of the Science and Technology Commission of Shanghai Municipality(Nos.21550714200 and 20DZ2220400)the Project of the Institute of Medical Robotics of Shanghai Jiao Tong University,and the Interdisciplinary Program of Shanghai Jiao Tong University(Nos.ZH2018QNB31 and YG2017MS27)。
文摘Flexible ureteroscopy(FURS)has been widely used in the diagnosis and treatment of upper urinarytract diseases.The key operation of FURS is that the surgeon manipulates the distal shaft of flexible ureteroscopeto a specific target for diagnosis and treatment.However,the hysteresis of flexible ureteroscope may be one ofthe most important factors that degrade the manipulation accuracy and the surgeon usually spends a long timenavigating the distal shaft during surgery.In this study,we obtained hysteresis curves of distal shaft deflectionfor the flexible ureteroscope through extensive repeated experiments.Then,two methods based on piecewiselinear approximation and long short-term memory neural network were employed to model the hysteresis curves.On this basis,we proposed two hysteresis compensation strategies for the distal shaft deflection.Finally,wecarried out hysteresis compensation experiments to verify the two proposed compensation strategies.Experimentalresults showed that the hysteresis compensation strategies can significantly improve position accuracy with meancompensation errors of no more than 5°.
基金Supported by National Natural Science Foundation of China(Grant Nos.51775061,51575061)Chongqing Municipal Research Program of Frontier and Application Foundation of China(Grant No.cstc2018jcyj AX0087)
文摘The current research of wind turbine drivetrain is mainly concentrated in dynamic characteristics of gearbox with a specific suspension of main shaft, such as one-point and two-point suspension. However, little attention is paid to the e ects of these suspension configurations on the dynamic responses of wind turbine gearbox. This paper investigates the influences of suspension configurations of main shaft on the dynamic characteristics of drivetrain. For evaluating the dynamic behaviors of drivetrain with multi-stage transmission system more realistically, a dynamic modeling approach of drivetrain is proposed based on Timoshenko beam theory and Lagrange's equation. Considering the flexibility and di erent suspension configurations of main shaft, time-varying mesh sti ness excitation, time-varying transmission error excitation and gravity excitation, etc., a three-dimensional dynamic model of drivetrain is developed, and the dynamic responses of drivetrain are investigated. Results show that with the one-point suspension of main shaft, the resonance frequencies in gearbox, especially at the low-speed stage, obviously shift to the higher frequency range compared to the gearbox without main shaft, but this trend could be inversed by increasing main shaft length. Meanwhile, the loads in main shaft, main shaft bearing and carrier bearing are greatly sensitive to the main shaft length. Hence, the load sharing is further disrupted by main shaft, but this e ect could be alleviated by larger load torque. Comparing to the one-point suspension of main shaft, there occurs the obvious load reduction at the low-speed stage with two-point suspension of main shaft. However, those advantages greatly depend on the distance between two main bearings, and come at the expense of increased load in upwind main shaft unit and the corresponding main bearing. Finally, a wind field test is conducted to verify the proposed drivetrain model. This study develops a numerical model of drivetrain which is able to evaluate the e ects of di erent suspension configurations of main shaft on gearbox.
文摘Background： Nowadays pediatric femoral fractures are more commonly managed with operative treatment rather than conservative treatment because of more rapid recovery and avoidance of prolonged immobilization. Children between the ages of 5-13 years are treated either by traction plus hip spica and flexible/elastic stable retrograde intramedullary nail, or external fixators in the case of open fractures. The aim of this study is to evaluate the outcome of pediatric femoral shaft fractures treated by stainless steel flexible intramedullary nail in children between 5 and 13 years of age. Methods： There were 32 cases of femoral shaft fractures which were all fixed with stainless steel flexible intramedullary nail under fluoroscopy. Long leg cast was applied at the time of fixation. Partial weight bearing was started 2 weeks after surgery. Patients were evaluated in follow-up study to observe the alignment of fracture, infection, delayed union, nonunion, limb length discrepancy, motion of knee joint, and time to unite the fracture. Results： We were able to follow up 28 out of 32 patients. The patients were 8.14 years of age on average. The mean hospital stay after operation was 4 days and fracture union time was 9.57 weeks. There were 3 cases of varus angulation, 2 cases of anterior angulation, and 4 cases of limb lengthening. Conclusion： Patients aged between 5 and 13 years treated with flexible intramedullary nail for closed femoral shaft fracture have rapid union and recovery, short rehabilitation period, less immobilization and psychological impact, and cost-effective.
