Laterally loaded piles,which are commonly used in sandy stratum foundations,are particularly susceptible to necking defects during cast-in-place installation due to borehole collapse risks.These construction-induced g...Laterally loaded piles,which are commonly used in sandy stratum foundations,are particularly susceptible to necking defects during cast-in-place installation due to borehole collapse risks.These construction-induced geometric imperfections substantially compromise pile safety under lateral loading conditions.To address this critical design challenge,we develop a reliability-based multi-objective optimization framework that simultaneously accounts for structural safety,construction economy,and design robustness.The proposed methodology integrates the p-y curve(where p is the soil pressure per unit length,and y is the lateral deflection of the pile)analysis with stochastic modeling,enabling efficient evaluation of pile performance considering uncertainties in soil parameters and depth and size variations of necking defects.A systematic design framework is implemented and validated through experimental case studies,successfully generating optimal designs along the Pareto front.The identified knee-point configurations serve as practical compromise solutions for engineering decisions.Parametric investigations further elucidate the influence of necking defect depth and sand friction angle variations on optimal design outcomes,offering insights into risk mitigation for pile construction.展开更多
With the goal of designing a biologically inspired robot that can hold a stable hover under internal and external disturbances.We designed a tailless Flapping-wing Micro Aerial Vehicle(FMAV)with onboard 3D velocity pe...With the goal of designing a biologically inspired robot that can hold a stable hover under internal and external disturbances.We designed a tailless Flapping-wing Micro Aerial Vehicle(FMAV)with onboard 3D velocity perception.In this way,the wind disturbance caused by the relative motion of the FMAV can be quantified in real time based on the established altitudinal dynamics model.For the rest of the total disturbance,an active disturbance rejection controller is proposed to estimate and suppress those disturbances.In comparison with the traditional PID controller,this proposed approach has been validated.The results show that,in the hovering flight with the internal unmodeled dynamics,the root-mean-square of height controlled is only 2.53 cm.Even with the different weights of loads mounting on the FMAV,the ascending trajectory of flights remains impressively consistent.In the forward flight with the external disturbance,the root-mean-square error of height controlled is 2.78 cm.When the FMAV flies over a ladder introducing an abrupt external disturbance,the maximum overshoot is only half of that controlled by the PID controller.To our best knowledge,this is the first demonstration of FMAVs with the capability of sensing motion-generated wind disturbance onboard and handling the internal and external disturbances in hover flight.展开更多
The development of a tailless Flapping Wing Micro Aerial Vehicle(FWMAV)inspired by the hummingbird is presented in this work.By implementing mechanical simplifications,it is possible to use planar machining technology...The development of a tailless Flapping Wing Micro Aerial Vehicle(FWMAV)inspired by the hummingbird is presented in this work.By implementing mechanical simplifications,it is possible to use planar machining technology for manufacturing of the FWMAV’s body,greatly reducing assembly errors.Traditionally,studies on flapping wing aircraft are limited to open-loop wing kinematics control.In this work,an instantaneous closed-loop wing trajectory tracking control system is introduced to minimize wings’trajectory tracking errors.The control system is based on Field-Oriented Control(FOC)with a loop shaping compensation technique near the flapping frequency.Through frequency analysis,the loop shaping compensator ensures the satisfactory bandwidth and performance for the closed-loop flapping system.To implement the proposed controller,a compact autopilot board integrated with FOC hardware is designed,weighing only 2.5 g.By utilizing precise wing trajectory tracking control,the hummingbird-inspired FWMAV demonstrates superior ability to resist external disturbances and exhibits reduced attitude tracking errors during hovering flight compared to the open-loop wing motion.展开更多
MnO_(2)-modified Pb_(0.9625)Sm_(0.025)(Mg_(1/3)Nb_(2/3))_(0.71)Ti_(0.2)9O_(3) ceramics were prepared via a solid-state reaction approach.Results of detailed characterizations revealed that the addition of MnO_(2) has ...MnO_(2)-modified Pb_(0.9625)Sm_(0.025)(Mg_(1/3)Nb_(2/3))_(0.71)Ti_(0.2)9O_(3) ceramics were prepared via a solid-state reaction approach.Results of detailed characterizations revealed that the addition of MnO_(2) has influence on the grain size,and all samples exhibit a pure perovskite structure.As the content of manganese increases,the volume of tetragonal phase increases.The ceramics with 1.5 mol.%MnO_(2) show a high electro-strain of 0.151%at 2 kV/mm.Therefore,this study provides a new insight into the role of MnO_(2) addition in tailoring the electrical properties of the Sm-PMN-PT ceramics by acceptor doping.展开更多
A series of(100−x)Pb(Mg_(1/3)Nb_(2/3))O_(3−x)PbTiO_(3)(PMN−xPT,x=24,25,26)ceramics were prepared by solid-state reaction technique using MgNb_(2)O_(6)precursor.The results of the detailed characterizations reveal that...A series of(100−x)Pb(Mg_(1/3)Nb_(2/3))O_(3−x)PbTiO_(3)(PMN−xPT,x=24,25,26)ceramics were prepared by solid-state reaction technique using MgNb_(2)O_(6)precursor.The results of the detailed characterizations reveal that the content of PT has negligible influence on the grain size,and all samples possess the perovskite structure.As the PT content increases,the samples changed from the normal ferroelectric phase to the ergodic relaxor state at room temperature.As a result,PMN-xPT ceramics are endowed with electro-strain of 0.08%at a relatively low electric field of 2 kV/mm,and effective piezoelectric coefficient of 320 pm/V was obtained.Simultaneously,the PMN-xPT ceramics have exceptional pyroelectric performance,exhibiting a high pyroelectric coef-ficient p~5.5-6.3×10^(−8)C·cm^(−2)·K^(−1).This study demonstrates the great potential of PMN-xPT for piezoelectric and pyroelectric device applications.展开更多
基金supported by the Fundamental Research Funds for the Central Universities of China(No.226-2024-00197)the National Natural Science Foundation of China(No.42277129)+1 种基金the Key R&D Project of Zhejiang Province(No.2021C03159)the Natural Science Foundation of Zhejiang Province(No.LR24E080004),China.
文摘Laterally loaded piles,which are commonly used in sandy stratum foundations,are particularly susceptible to necking defects during cast-in-place installation due to borehole collapse risks.These construction-induced geometric imperfections substantially compromise pile safety under lateral loading conditions.To address this critical design challenge,we develop a reliability-based multi-objective optimization framework that simultaneously accounts for structural safety,construction economy,and design robustness.The proposed methodology integrates the p-y curve(where p is the soil pressure per unit length,and y is the lateral deflection of the pile)analysis with stochastic modeling,enabling efficient evaluation of pile performance considering uncertainties in soil parameters and depth and size variations of necking defects.A systematic design framework is implemented and validated through experimental case studies,successfully generating optimal designs along the Pareto front.The identified knee-point configurations serve as practical compromise solutions for engineering decisions.Parametric investigations further elucidate the influence of necking defect depth and sand friction angle variations on optimal design outcomes,offering insights into risk mitigation for pile construction.
基金Supporting Foundation of the Ministry of Education of the People’s Republic of China(6141A02022607,6141A02022627).
文摘With the goal of designing a biologically inspired robot that can hold a stable hover under internal and external disturbances.We designed a tailless Flapping-wing Micro Aerial Vehicle(FMAV)with onboard 3D velocity perception.In this way,the wind disturbance caused by the relative motion of the FMAV can be quantified in real time based on the established altitudinal dynamics model.For the rest of the total disturbance,an active disturbance rejection controller is proposed to estimate and suppress those disturbances.In comparison with the traditional PID controller,this proposed approach has been validated.The results show that,in the hovering flight with the internal unmodeled dynamics,the root-mean-square of height controlled is only 2.53 cm.Even with the different weights of loads mounting on the FMAV,the ascending trajectory of flights remains impressively consistent.In the forward flight with the external disturbance,the root-mean-square error of height controlled is 2.78 cm.When the FMAV flies over a ladder introducing an abrupt external disturbance,the maximum overshoot is only half of that controlled by the PID controller.To our best knowledge,this is the first demonstration of FMAVs with the capability of sensing motion-generated wind disturbance onboard and handling the internal and external disturbances in hover flight.
基金support by the National Natural Science Foundation of China(No.62073217,No.61871266)the Fund of the Ministry of Education of the People’s Republic of China(6141A02022607,6141A020227)the Fund of the Professional Technical Service Platform of Shanghai(19DZ2291103).
文摘The development of a tailless Flapping Wing Micro Aerial Vehicle(FWMAV)inspired by the hummingbird is presented in this work.By implementing mechanical simplifications,it is possible to use planar machining technology for manufacturing of the FWMAV’s body,greatly reducing assembly errors.Traditionally,studies on flapping wing aircraft are limited to open-loop wing kinematics control.In this work,an instantaneous closed-loop wing trajectory tracking control system is introduced to minimize wings’trajectory tracking errors.The control system is based on Field-Oriented Control(FOC)with a loop shaping compensation technique near the flapping frequency.Through frequency analysis,the loop shaping compensator ensures the satisfactory bandwidth and performance for the closed-loop flapping system.To implement the proposed controller,a compact autopilot board integrated with FOC hardware is designed,weighing only 2.5 g.By utilizing precise wing trajectory tracking control,the hummingbird-inspired FWMAV demonstrates superior ability to resist external disturbances and exhibits reduced attitude tracking errors during hovering flight compared to the open-loop wing motion.
基金supported by State Grid Corporation of China Co.,Ltd.(Grant No.5500-202024252A-0-0-00).
文摘MnO_(2)-modified Pb_(0.9625)Sm_(0.025)(Mg_(1/3)Nb_(2/3))_(0.71)Ti_(0.2)9O_(3) ceramics were prepared via a solid-state reaction approach.Results of detailed characterizations revealed that the addition of MnO_(2) has influence on the grain size,and all samples exhibit a pure perovskite structure.As the content of manganese increases,the volume of tetragonal phase increases.The ceramics with 1.5 mol.%MnO_(2) show a high electro-strain of 0.151%at 2 kV/mm.Therefore,this study provides a new insight into the role of MnO_(2) addition in tailoring the electrical properties of the Sm-PMN-PT ceramics by acceptor doping.
基金This work was supported by the State Grid Corporation of China through the Project No.5500-202058320A-0-0-00.
文摘A series of(100−x)Pb(Mg_(1/3)Nb_(2/3))O_(3−x)PbTiO_(3)(PMN−xPT,x=24,25,26)ceramics were prepared by solid-state reaction technique using MgNb_(2)O_(6)precursor.The results of the detailed characterizations reveal that the content of PT has negligible influence on the grain size,and all samples possess the perovskite structure.As the PT content increases,the samples changed from the normal ferroelectric phase to the ergodic relaxor state at room temperature.As a result,PMN-xPT ceramics are endowed with electro-strain of 0.08%at a relatively low electric field of 2 kV/mm,and effective piezoelectric coefficient of 320 pm/V was obtained.Simultaneously,the PMN-xPT ceramics have exceptional pyroelectric performance,exhibiting a high pyroelectric coef-ficient p~5.5-6.3×10^(−8)C·cm^(−2)·K^(−1).This study demonstrates the great potential of PMN-xPT for piezoelectric and pyroelectric device applications.
