Load-sensing steering systems for articulated loaders are prone to large pressure shocks and oscillations during steering operations,affecting the system stability.An optimized structure of the redirector with bypass ...Load-sensing steering systems for articulated loaders are prone to large pressure shocks and oscillations during steering operations,affecting the system stability.An optimized structure of the redirector with bypass damping is proposed to improve this phenomenon.In this structure,orifices and throttle grooves are added to the traditional redirector.To control the steering load and working conditions,the steering load of the loader is replaced by a pressure regulating valve.Simulation and experimental results reveal that the redirector with bypass damping has better load-sensing characteristics than the traditional redirector.The peak output pressure shock caused by the load unit step signal decreases from 6.50 to 5.64 MPa,which means the pressure oscillation of the hydraulic system is reduced by 13.4%.The pressure fluctuation time can be reduced from 2.09 to 1.6 s,with a decrease rate of 23.4%.The output pressure oscillation decays swiftly,and the smoothness of the steering operation is improved significantly.展开更多
With the development and improvement of the hydraulic steering system,the articulated steering system became the research focus of numerous domestic and foreign scholars.The full hydraulic steering system with a compa...With the development and improvement of the hydraulic steering system,the articulated steering system became the research focus of numerous domestic and foreign scholars.The full hydraulic steering system with a compact structure and ease of operation,is widely used in articulated steering mode.Furthermore,its performance can directly impact the steering sensitivity and stability.This paper studies the working principle and actual structure of the priority valve and the steering control valve,which are very important.By setting up a mathematic model,the system’s load-sensing characteristics and the impact of steering control valve bypass throttle damping on steering stability can be analyzed.The Hydraulic Components Design(HCD)model was established for the hydraulic part of this system.It is proved that the model can reflect the system’s actual properties by comparing simulation and experimental results.The dynamic model is based on its actual prototype parameters by taking the tire and ground forces into account.The steering process’s dynamic characteristics are co-simulated in the 1D+3D system model by combining AMESim and Virtual.Lab Motion.The simulation results show that the system’s load-sensing characteristics ensure the sensitivity of the steering operation,and the bypass throttle damping has significantly improved the operation stability and lowered down the cylinder pressure fluctuations.This can improve the system performance by appropriate optimization.展开更多
Endovascular aortic repair(EVAR)has been increasingly used to treat abdominal aortic aneurysm(AAA)due to its lower mortality and shorter recovery time.However,the complications caused by renal artery coverage remained...Endovascular aortic repair(EVAR)has been increasingly used to treat abdominal aortic aneurysm(AAA)due to its lower mortality and shorter recovery time.However,the complications caused by renal artery coverage remained a major concern.In this study,three types of renal orientation and five types of partial renal coverage degree were adopted to numerically investigate the flow pattern,wall shear stress distribution,and blood perfusion during a cardiac cycle.The results show that as for the mild partial coverage(=<30%),the renal artery with a downward orientation suffered fewer unfavorable wall shear stress(WSS)distribution and more blood perfusion.It should be noted that the renal artery with horizontal orientation suffered more unfavorable WSS distribution.In terms of severe coverage(≥50%),all of the renal arteries displayed highly disturbed wall shear distribution,resulting in a significant reduction in blood perfusion It was interesting to note that the artery with an upward orientation had a smaller rate of reduction in blood perfusion.It can be concluded that as for the mild renal coverage after EVAR,renal arteries with downward orientation may have the advantage of reducing the possibility of renal occlusion,while renal arteries with horizontal orientation may increase the unfavorable wall shear distribution.On the other hand,as for serious coverage(≥50%),high risk of renal ischemia remains the main concern for all types of renal arteries due to highly disturbed wall shear distribution would significantly increase regardless of renal orientation.展开更多
A quantitative structure-activity relationship （QSAR） model on depuration rate constants （ka） of polychlorinated biphenyls （PCBs） in freshwater mussel Elliptio complanata was successfully constructed using elect...A quantitative structure-activity relationship （QSAR） model on depuration rate constants （ka） of polychlorinated biphenyls （PCBs） in freshwater mussel Elliptio complanata was successfully constructed using electrotopological state indices （ESI） and partial least squares （PLS） regression. The cross validated 2 Qcum and the correlation coefficient R for the model were determined to be 0.845 and 0.954, respectively. The satisfactory Q2cum and R values indicated significantly high robustness and good predictive ability for the model. The model was tested and found acceptable for the prediction of logkd （the logarithm of the deputation rate constants） by validation set. According to the model, an increase in the values of Saasc, S5＇, S4, S5 and S4＇, led to increased logkd, and a decrease in the values of Na, S2, and S6 also resulted in increased logkd. Among these descriptors, Ncl, S aasC, S5＇,, S4 and S5 made significant contributions to the value of logkd. These significant descriptors showed that the depuration of PCBs in Elliptio complanata may be mainly attributed to an equilibrium partitioning process among compartments with different lipid contents, while the reactivity of PCBs with enzymes or other molecules may play a subordinate role.展开更多
基金Supported by National Key Research and Development Program of China(Grant No.2018YFB2000900).
文摘Load-sensing steering systems for articulated loaders are prone to large pressure shocks and oscillations during steering operations,affecting the system stability.An optimized structure of the redirector with bypass damping is proposed to improve this phenomenon.In this structure,orifices and throttle grooves are added to the traditional redirector.To control the steering load and working conditions,the steering load of the loader is replaced by a pressure regulating valve.Simulation and experimental results reveal that the redirector with bypass damping has better load-sensing characteristics than the traditional redirector.The peak output pressure shock caused by the load unit step signal decreases from 6.50 to 5.64 MPa,which means the pressure oscillation of the hydraulic system is reduced by 13.4%.The pressure fluctuation time can be reduced from 2.09 to 1.6 s,with a decrease rate of 23.4%.The output pressure oscillation decays swiftly,and the smoothness of the steering operation is improved significantly.
基金This work was supported by the National Key Research and Development Program of China,No.2018YFB2000900。
文摘With the development and improvement of the hydraulic steering system,the articulated steering system became the research focus of numerous domestic and foreign scholars.The full hydraulic steering system with a compact structure and ease of operation,is widely used in articulated steering mode.Furthermore,its performance can directly impact the steering sensitivity and stability.This paper studies the working principle and actual structure of the priority valve and the steering control valve,which are very important.By setting up a mathematic model,the system’s load-sensing characteristics and the impact of steering control valve bypass throttle damping on steering stability can be analyzed.The Hydraulic Components Design(HCD)model was established for the hydraulic part of this system.It is proved that the model can reflect the system’s actual properties by comparing simulation and experimental results.The dynamic model is based on its actual prototype parameters by taking the tire and ground forces into account.The steering process’s dynamic characteristics are co-simulated in the 1D+3D system model by combining AMESim and Virtual.Lab Motion.The simulation results show that the system’s load-sensing characteristics ensure the sensitivity of the steering operation,and the bypass throttle damping has significantly improved the operation stability and lowered down the cylinder pressure fluctuations.This can improve the system performance by appropriate optimization.
基金This study was supported in part by the Applying Basic Research Project of Sichuan Province,China[No.2022NSFSC1369]Sichuan Foundation of Science and Technology[No.2020YFS0247]+1 种基金Sichuan Medical Research Youth Innovation Project[No.Q21075]the National Natural Science Foundation of China[No.11802253].
文摘Endovascular aortic repair(EVAR)has been increasingly used to treat abdominal aortic aneurysm(AAA)due to its lower mortality and shorter recovery time.However,the complications caused by renal artery coverage remained a major concern.In this study,three types of renal orientation and five types of partial renal coverage degree were adopted to numerically investigate the flow pattern,wall shear stress distribution,and blood perfusion during a cardiac cycle.The results show that as for the mild partial coverage(=<30%),the renal artery with a downward orientation suffered fewer unfavorable wall shear stress(WSS)distribution and more blood perfusion.It should be noted that the renal artery with horizontal orientation suffered more unfavorable WSS distribution.In terms of severe coverage(≥50%),all of the renal arteries displayed highly disturbed wall shear distribution,resulting in a significant reduction in blood perfusion It was interesting to note that the artery with an upward orientation had a smaller rate of reduction in blood perfusion.It can be concluded that as for the mild renal coverage after EVAR,renal arteries with downward orientation may have the advantage of reducing the possibility of renal occlusion,while renal arteries with horizontal orientation may increase the unfavorable wall shear distribution.On the other hand,as for serious coverage(≥50%),high risk of renal ischemia remains the main concern for all types of renal arteries due to highly disturbed wall shear distribution would significantly increase regardless of renal orientation.
基金supported by the Major State Basic Research Development Program(No. 2009CB421605)the National Natural Science Foundation of China(No.40871218)+1 种基金the Special Fund of State Key Laboratory(No.08ESPCT-Y)the Program for New Century Excellent Talents in Universities
文摘A quantitative structure-activity relationship （QSAR） model on depuration rate constants （ka） of polychlorinated biphenyls （PCBs） in freshwater mussel Elliptio complanata was successfully constructed using electrotopological state indices （ESI） and partial least squares （PLS） regression. The cross validated 2 Qcum and the correlation coefficient R for the model were determined to be 0.845 and 0.954, respectively. The satisfactory Q2cum and R values indicated significantly high robustness and good predictive ability for the model. The model was tested and found acceptable for the prediction of logkd （the logarithm of the deputation rate constants） by validation set. According to the model, an increase in the values of Saasc, S5＇, S4, S5 and S4＇, led to increased logkd, and a decrease in the values of Na, S2, and S6 also resulted in increased logkd. Among these descriptors, Ncl, S aasC, S5＇,, S4 and S5 made significant contributions to the value of logkd. These significant descriptors showed that the depuration of PCBs in Elliptio complanata may be mainly attributed to an equilibrium partitioning process among compartments with different lipid contents, while the reactivity of PCBs with enzymes or other molecules may play a subordinate role.
