This article proposes an integral-based event-triggered attack-resilient control method for the aircraft-on-ground(AoG) synergistic turning system with uncertain tire cornering stiffness under stochastic deception att...This article proposes an integral-based event-triggered attack-resilient control method for the aircraft-on-ground(AoG) synergistic turning system with uncertain tire cornering stiffness under stochastic deception attacks. First, a novel AoG synergistic turning model is established with synergistic reverse steering of the front and main wheels to decrease the steering angle of the AoG fuselage, thus reducing the steady-state error when it follows a path with some large curvature. Considering that the tire cornering stiffness of the front and main wheels vary during steering, a dynamical observer is designed to adaptively identify them and estimate the system state at the same time.Then, an integral-based event-triggered mechanism(I-ETM) is synthesized to reduce the transmission frequency at the observerto-controller end, where stochastic deception attacks may occur at any time with a stochastic probability. Moreover, an attackresilient controller is designed to guarantee that the closed-loop system is robust L2-stable under stochastic attacks and external disturbances. A co-design method is provided to get feasible solutions for the observer, controller, and I-ETM simultaneously. An optimization program is further presented to make a tradeoff between the robustness of the control scheme and the saving of communication resources. Finally, the low-and high-probability stochastic deception attacks are considered in the simulations. The results have illustrated that the AoG synergistic turning system with the proposed control method follows a path with some large curvature well under stochastic deception attacks. Furthermore,compared with the static event-triggered mechanisms, the proposed I-ETM has demonstrated its superiority in saving communication resources.展开更多
The dynamics of turning system which is a nonlinear system normally has great impact on the transportation speed of the vehicle having heavy load and large size.The dynamics of turning system depends on control algori...The dynamics of turning system which is a nonlinear system normally has great impact on the transportation speed of the vehicle having heavy load and large size.The dynamics of turning system depends on control algorithm and its implementation,but the existing control algorithms which having high dynamics in the application of heavy transportation vehicle are complex for realization and high hardware requirement.So,the nonlinear turning system is analyzed for improving its dynamics by researching new efficient control algorithm.The models of electromagnetic valve,hydraulic cylinder and turning mechanical part are built individually to get the open-loop model of the turning system following characteristics analyzed.According to the model,a new control algorithm for heavy transportation vehicle which combined PID with Bang-Bang control is presented.Then the close-loop model of turning system is obtained under Matlab/Simulink environment.By comparing the step response of different control algorithms in the same conditions,the new algorithm＇s validity is verified.On the basis of the analysis results,the algorithm is adopted to implement the turning control system by using CAN field bus and PLC controllers.Furthermore,the turning control system has been applied in one type of heavy transportation vehicle.It reduces the response time of turning system from seconds level to 250 ms,and the speed of heavy transportation vehicle increases from 5 km/h to 30 km/h.The application result shows that the algorithm and turning control system have met all the turning requirements.This new type of turning control algorithm proposed is simple in implementation for fast response of nonlinear and large-scale turning system of heavy transportation vehicle.展开更多
An improved numerical method is used to simulate the dynamic behavior of a two part towing cable systems during turnings. In U turns and full turns, periodical heave motions are found both for the towed vehicle and fo...An improved numerical method is used to simulate the dynamic behavior of a two part towing cable systems during turnings. In U turns and full turns, periodical heave motions are found both for the towed vehicle and for the depressor. Periodic motions of the subsea units and of the cable surface tension are closely related to the turning parameters, such as turning velocity and turning radius. System parameters, such as length of the second cable and the vehicle bydrodynamics, also damp turning instability.展开更多
Vehicle turning movement data from signalized intersections is utilized for numerous applications in the field of transportation. Such applications include real-time adaptive signal control, dynamic traffic assignment...Vehicle turning movement data from signalized intersections is utilized for numerous applications in the field of transportation. Such applications include real-time adaptive signal control, dynamic traffic assignment, and traffic demand estimation. However, it is very time consuming and costly to obtain vehicle turning movement information manually. Previous efforts to simplify this process were focused on solving the problem using an O-D matrix, but this method proved to be inaccurate and unreliable with the existing data acquisition system. Another study involved the identification of vehicle turning movements from the detector information, but the presence of shared lanes led to uncertainties in vehicle matching, thus limiting application of the method only to intersections without shared lanes. In light of those unsuccessful attempts, this paper develops and tests a system called the Automatic Turning Movement Identification System (ATMIS), which estimates vehicle turning movements at a signalized intersection in real time, regardless of its geometry. The results from lab experiments as well as a field test show that the algorithm is very promising and may potentially be expanded for field applications.展开更多
Now vibration isolation of ultra precision machine tool is usually achieved through air springs systems. As far as HCM I sub micro turning machine developed by HIT, an active vibration isolation system that consists o...Now vibration isolation of ultra precision machine tool is usually achieved through air springs systems. As far as HCM I sub micro turning machine developed by HIT, an active vibration isolation system that consists of air springs and electro magnetic actuators was presented. The primary function of air springs is to support the turning machine and to isolate the high frequency vibration. The electro magnetic actuators controlled by fuzzy neural networks isolate the low frequency vibration. The experiment indicates that active vibration isolation system isolates base vibration effectively in all the frequency range. So the vibration of the machine bed is controlled under 10 -6 g and the surface roughness is improved.展开更多
For virtually realizing the graphic realism display of DXF machine parts, in AutoCAD2007 graphic drawing environment, an interactive experimental method was taken to realize the display of graphic in DXF, which was ta...For virtually realizing the graphic realism display of DXF machine parts, in AutoCAD2007 graphic drawing environment, an interactive experimental method was taken to realize the display of graphic in DXF, which was taken as the data-exchanged interface and source. Based on depth analysis of DXF data structure, take one drawing of DXF lathe turning rotational part asthe test piece. By VC＋＋6.0 programming, part＇s geometry information could be obtained. Through data processing, 3D data of the test piece could be generated, which is based on 2D data of DXF test piece. Then, OpenGL graphic processing technologies （light, material, texture, map, et al.） were applied on the 3D display of test piece from DXF files or program modules. Finally based on the test report, results of the system functions were shared to prove the realization of system design, and the feasibility of algorithms used. In the developed software, Machine Designers could get a full view of machine parts, and do some proper modifications. The study content and results of our work have some theory and practical significance on the application of program design in the practical projects.展开更多
Making use of the Z2×Z2 symmetry,we could study the structure near multiple S-treaking turning points.In particular,we show that there exist two kinds of singular point path through double S breaking turning poin...Making use of the Z2×Z2 symmetry,we could study the structure near multiple S-treaking turning points.In particular,we show that there exist two kinds of singular point path through double S breaking turning points and triple S bieaking turning points,one ts quadratic turning pornt path and one is quadratic pitch fork bifurcation point path.Some simple regular extended systems to corn pute double and triple S-breaking turning points are proposed.Numerical examples are also展开更多
Prediction of surface finish in turning process is a difficult but important task. Artificial Neural Networks (ANN) can reliably pred ict the surface finish but require a lot of training data. To overcome this prob le...Prediction of surface finish in turning process is a difficult but important task. Artificial Neural Networks (ANN) can reliably pred ict the surface finish but require a lot of training data. To overcome this prob lem, an expert system approach is proposed, wherein it will be possible to predi ct the surface finish from limited experiments. The expert system contains a kno wledge base prepared from machining data handbooks and number of experiments con ducted by turning steel rods, over a wide range of cutting parameters. With this knowledge base, the expert system predicts surface finish for different tool-w ork-piece combinations, by carrying out few experiments for each case. The prop osed expert system model is validated by carrying out a number of experiments.展开更多
In this paper we consider the asymptotic behavior of boundary value problems of nonliner systems εy″= F(t,y,y′,ε) , -1<t<1, y(-1,ε)=A, y(1,ε)=B when F possesses a generalized turning point at t...In this paper we consider the asymptotic behavior of boundary value problems of nonliner systems εy″= F(t,y,y′,ε) , -1<t<1, y(-1,ε)=A, y(1,ε)=B when F possesses a generalized turning point at t=0. The interior layer phenomenon of the problem is discussed.展开更多
A fast tool servo (FTS) system is developed for the fabrication of non-rotationally symmetric micro-structured surfaces using single-point diamond turning machines.The constructed FTS employs a piezoelectric tube actu...A fast tool servo (FTS) system is developed for the fabrication of non-rotationally symmetric micro-structured surfaces using single-point diamond turning machines.The constructed FTS employs a piezoelectric tube actuator (PZT) to actuate the diamond tool and a capacitive probe as the feedback sensor.To compensate the inherent nonlinear hysteresis behavior of the piezoelectric actuator,Proportional Integral (PI) feedback control is implemented.Besides,a feed-forward control based on a simple feed-forward predictor has been added to achieve better tracking performance.Experimental results indicate that error motions in the performance of the system caused by hysteresis can be reduced greatly and the micro-structured surface is successfully fabricated by implementing the FTS.展开更多
We consider in this paper the boundary value problems of nonlinear systems the form εY″=F(t,Y,Y′,ε), -1<t<1, Y(-1,ε)=A(ε), Y(1,ε)=B(ε). Supoosing some or all of the components of F , that is, ...We consider in this paper the boundary value problems of nonlinear systems the form εY″=F(t,Y,Y′,ε), -1<t<1, Y(-1,ε)=A(ε), Y(1,ε)=B(ε). Supoosing some or all of the components of F , that is, f i satisfy 2 f y′ 2 i t =0 =0, we say that F possesses a generalized turning point at t =0. Our goal is to give sufficient conditions for the existence of solution of the problems and to study the asymptotic behavior of the solution when F possesses a generalized turning point at t =0. We mainly discuss regular singular crossings.展开更多
The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and ...The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and solves the unsteady axisymmetric Euler equation to study the characteristics of the Axisymmetric Inward Turning Curved Detonation Wave(AIT-CDW)flow field and the parameters affecting the stability of the wave system structure of AIT-CDW flow field.The numerical results demonstrate a radial compression effect in the AIT-CDW flow field.This effect causes the detonation wave to have a shorter initiation length than oblique detonation wave flow field and the detonation wave angle to gradually increase with the flow direction postdetonation.The AIT-CDW flow field is confined space,making it prone to normal detonation waves when the detonation wave reflects from the wall.This phenomenon is detrimental to the stability of the wave system structure in the flow field.It has been observed that increasing the center body radius and decreasing the fuel equivalent ratio can effectively reduce the height of the normal detonation wave or even eliminate it.Additionally,a well-designed generatrix shape of the center body can enhance airflow,reduce choked flow,and promote the stability of the wave structure in the flow field.展开更多
Single-point diamond turning (SPDT) is widely used in the machining of infrared materials and metal-based mirrors. Diamond tips can scratch material, replicate the shape of the tip, and create annular turning marks on...Single-point diamond turning (SPDT) is widely used in the machining of infrared materials and metal-based mirrors. Diamond tips can scratch material, replicate the shape of the tip, and create annular turning marks on optical surfaces, which can have unpredictable adverse effects on imaging. In order to predict the effect of turning marks diffraction on the degradation of imaging quality, a model of the influence of SPDT processing parameters on the reduction of system imaging MTF under the influence of ideal grating turning marks diffraction was established. The results show that the depth of the turning mark will lead to the decline of MTF, especially the low frequency information. Finally, a method is proposed to reduce the effect of turning marks diffraction through changing the processing parameters. .展开更多
The turning performance of a ship is an important aspect of its maneuverability,and accurately predicting the hydrodynamic forces during ship turning motion is of great significance for the safe maneuvering design of ...The turning performance of a ship is an important aspect of its maneuverability,and accurately predicting the hydrodynamic forces during ship turning motion is of great significance for the safe maneuvering design of ships.This paper investigated the hydrodynamic performance of a KRISO container ship in steady turning using experimental and numerical approaches.The rotating arm tests were carried out in rotating arm basin of Zhejiang University,while the numerical simulations were conducted in commercial computational fluid dynamics software.Hydrodynamic forces and moments,hull surface wave height,wave patterns,and vorticity are studied under different velocities,radii,and drift angles.The results show that the increase in velocity has a significant impact on the forces and moments of the hull.The changes in longitudinal and transverse forces reflect the complex fluid dynamic interactions between the hull and water.Under conditions of small radius and large drift angle,the hull experiences greater forces and moments,indicating that stability and maneuverability will be more challenged during sudden turns.This study can provide experimental data and numerical simulation references for the research of ship turning maneuvers.展开更多
Located in the southeast corner of Norbulingka Palace Park in Lhasa,the Xizang Museum stands out as a facility integrating contemporary technology,design and practices with the regional characteristics of Xizang Auton...Located in the southeast corner of Norbulingka Palace Park in Lhasa,the Xizang Museum stands out as a facility integrating contemporary technology,design and practices with the regional characteristics of Xizang Autonomous Region,southwest China.The museum houses over 520,000 cultural relics,including silk pieces,religious instruments,ancient books and documents,porcelain and jade articles,enamel vessels,and silverware,as well as Thangka paintings.展开更多
Using early indica rice Zhongzao 39 and japonica rice Xiushui 134 as the experimental materials, the effects of 4 temperature levels after transplantation on turning green, leaf growth, tillering, dry matter accumulat...Using early indica rice Zhongzao 39 and japonica rice Xiushui 134 as the experimental materials, the effects of 4 temperature levels after transplantation on turning green, leaf growth, tillering, dry matter accumulation and nutrition absorption were studied using a greenhouse and an artificial climate chest. We found that （1） tillering did not occur and growth of one new leaf took over 15 days at 16℃. New leaf growth took over 10 days and tillering occurred after 15 days of transplanta- tion at 19 ℃. Tillering appeared 10 days after planting and new leaf growth took 5 days between 22 and 25 ℃. This showed that low temperature impeded the turn- ing green of rice seedlings and the temperature must reach above 19 ℃ to ensure timely appearance of new leaf, tillering and turning green in rice seedlings. （2） When the temperature was 10 increased, both 100-seedling dry weight and nitrogen absorption increased. At temperatures lower 11 than 19 ℃, both dry weight incre- ment and nitrogen absorption were low. Nitrogen absorption of all organs increased obviously between 19 and 22 ℃. Thus, 19 ℃ was found to be an minimum tem- perature for plant organs to absorb nutrients. （3）Tiller of seedling cultivated on dry- land soil and substrate grew quickly and tillering occurred about 7 days after trans- planting. After that, the growth rate was about 0.18 tiller per day. For seedlings cultivated in slurry, tillering occurred 10 days after transplanting and the tillers grew at a rate of 0.16 tiller per day. However, substrate choice during the seedling rais- ing stage had no significant influence on leaf age. （4） Japonica rice exhibited stronger resistance to low temperature than indica rice. Tillering began at about the same time after transplanting in both rice varieties, but japonica rice exhibited higher tillering speed than early indica rice. The speed of leaf growth was higher in japoni- ca rice before transplantation but higher in indica rice after transplantation.展开更多
In this paper, we study a class singular perturbed elliptic equation boundary value problem with a super surface of turning point in n-dimensional space by using the method of multiple scales and the comparison theore...In this paper, we study a class singular perturbed elliptic equation boundary value problem with a super surface of turning point in n-dimensional space by using the method of multiple scales and the comparison theorem. The uniformly valid asymptotic approxmations of solutions for the boundary value problem is constructed.展开更多
The microstructural changes in the machined surface layer of Ni-based super alloys essentially determine the final performance of the structural components of aerospace engines in which these alloys are used.In this w...The microstructural changes in the machined surface layer of Ni-based super alloys essentially determine the final performance of the structural components of aerospace engines in which these alloys are used.In this work,multiscale metallurgical observations using scanning electron microscopy,electron-backscatter diffraction microscopy,and transmission electron microscopy were conducted to quantitatively characterize the microstructure of the machined subsurface.Next,to elucidate the factors that affect the formation of the refinement microstructure,the distributions of the deformation parameters(strain,strain rate,and temperature) in the machined subsurface were analyzed.A dislocation–twin interaction dynamic recrystallization mechanism for grain refinement during machining of Inconel 718 is proposed.Furthermore,microhardness evolution induced by grain refinement in the machined surface is evaluated.The results suggest that the gradient microstructure and the work hardening can be optimized by controlling the cutting parameters during turning of Inconel 718.展开更多
Intersections are quite important and complex traffic scenarios,where the future motion of surrounding vehicles is an indispensable reference factor for the decision-making or path planning of autonomous vehicles.Cons...Intersections are quite important and complex traffic scenarios,where the future motion of surrounding vehicles is an indispensable reference factor for the decision-making or path planning of autonomous vehicles.Considering that the motion trajectory of a vehicle at an intersection partly obeys the statistical law of historical data once its driving intention is determined,this paper proposes a long short-term memory based(LSTM-based)framework that combines intention prediction and trajectory prediction together.First,we build an intersection prior trajectories model(IPTM)by clustering and statistically analyzing a large number of prior traffic flow trajectories.The prior trajectories model with fitted probabilistic density is used to approximate the distribution of the predicted trajectory,and also serves as a reference for credibility evaluation.Second,we conduct the intention prediction through another LSTM model and regard it as a crucial cue for a trajectory forecast at the early stage.Furthermore,the predicted intention is also a key that is associated with the prior trajectories model.The proposed framework is validated on two publically released datasets,next generation simulation(NGSIM)and INTERACTION.Compared with other prediction methods,our framework is able to sample a trajectory from the estimated distribution,with its accuracy improved by about 20%.Finally,the credibility evaluation,which is based on the prior trajectories model,makes the framework more practical in the real-world applications.展开更多
基金supported in part by the National Science Fund for Excellent Young Scholars of China (62222317)the National Natural Science Foundation of China (61973319)+4 种基金the Funds for International Cooperation and Exchange of the National Natural Science Foundation of China (61860206014)111 Project of China (B17048)Science and Technology Innovation Program of Hunan Province (2022WZ1001)the Natural Science Foundation of Changsha (kq2208287)the Postdoctoral Fund of Central South University (22022136)。
文摘This article proposes an integral-based event-triggered attack-resilient control method for the aircraft-on-ground(AoG) synergistic turning system with uncertain tire cornering stiffness under stochastic deception attacks. First, a novel AoG synergistic turning model is established with synergistic reverse steering of the front and main wheels to decrease the steering angle of the AoG fuselage, thus reducing the steady-state error when it follows a path with some large curvature. Considering that the tire cornering stiffness of the front and main wheels vary during steering, a dynamical observer is designed to adaptively identify them and estimate the system state at the same time.Then, an integral-based event-triggered mechanism(I-ETM) is synthesized to reduce the transmission frequency at the observerto-controller end, where stochastic deception attacks may occur at any time with a stochastic probability. Moreover, an attackresilient controller is designed to guarantee that the closed-loop system is robust L2-stable under stochastic attacks and external disturbances. A co-design method is provided to get feasible solutions for the observer, controller, and I-ETM simultaneously. An optimization program is further presented to make a tradeoff between the robustness of the control scheme and the saving of communication resources. Finally, the low-and high-probability stochastic deception attacks are considered in the simulations. The results have illustrated that the AoG synergistic turning system with the proposed control method follows a path with some large curvature well under stochastic deception attacks. Furthermore,compared with the static event-triggered mechanisms, the proposed I-ETM has demonstrated its superiority in saving communication resources.
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2007AA04Z215)Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111102110007)
文摘The dynamics of turning system which is a nonlinear system normally has great impact on the transportation speed of the vehicle having heavy load and large size.The dynamics of turning system depends on control algorithm and its implementation,but the existing control algorithms which having high dynamics in the application of heavy transportation vehicle are complex for realization and high hardware requirement.So,the nonlinear turning system is analyzed for improving its dynamics by researching new efficient control algorithm.The models of electromagnetic valve,hydraulic cylinder and turning mechanical part are built individually to get the open-loop model of the turning system following characteristics analyzed.According to the model,a new control algorithm for heavy transportation vehicle which combined PID with Bang-Bang control is presented.Then the close-loop model of turning system is obtained under Matlab/Simulink environment.By comparing the step response of different control algorithms in the same conditions,the new algorithm＇s validity is verified.On the basis of the analysis results,the algorithm is adopted to implement the turning control system by using CAN field bus and PLC controllers.Furthermore,the turning control system has been applied in one type of heavy transportation vehicle.It reduces the response time of turning system from seconds level to 250 ms,and the speed of heavy transportation vehicle increases from 5 km/h to 30 km/h.The application result shows that the algorithm and turning control system have met all the turning requirements.This new type of turning control algorithm proposed is simple in implementation for fast response of nonlinear and large-scale turning system of heavy transportation vehicle.
文摘An improved numerical method is used to simulate the dynamic behavior of a two part towing cable systems during turnings. In U turns and full turns, periodical heave motions are found both for the towed vehicle and for the depressor. Periodic motions of the subsea units and of the cable surface tension are closely related to the turning parameters, such as turning velocity and turning radius. System parameters, such as length of the second cable and the vehicle bydrodynamics, also damp turning instability.
文摘Vehicle turning movement data from signalized intersections is utilized for numerous applications in the field of transportation. Such applications include real-time adaptive signal control, dynamic traffic assignment, and traffic demand estimation. However, it is very time consuming and costly to obtain vehicle turning movement information manually. Previous efforts to simplify this process were focused on solving the problem using an O-D matrix, but this method proved to be inaccurate and unreliable with the existing data acquisition system. Another study involved the identification of vehicle turning movements from the detector information, but the presence of shared lanes led to uncertainties in vehicle matching, thus limiting application of the method only to intersections without shared lanes. In light of those unsuccessful attempts, this paper develops and tests a system called the Automatic Turning Movement Identification System (ATMIS), which estimates vehicle turning movements at a signalized intersection in real time, regardless of its geometry. The results from lab experiments as well as a field test show that the algorithm is very promising and may potentially be expanded for field applications.
文摘Now vibration isolation of ultra precision machine tool is usually achieved through air springs systems. As far as HCM I sub micro turning machine developed by HIT, an active vibration isolation system that consists of air springs and electro magnetic actuators was presented. The primary function of air springs is to support the turning machine and to isolate the high frequency vibration. The electro magnetic actuators controlled by fuzzy neural networks isolate the low frequency vibration. The experiment indicates that active vibration isolation system isolates base vibration effectively in all the frequency range. So the vibration of the machine bed is controlled under 10 -6 g and the surface roughness is improved.
文摘For virtually realizing the graphic realism display of DXF machine parts, in AutoCAD2007 graphic drawing environment, an interactive experimental method was taken to realize the display of graphic in DXF, which was taken as the data-exchanged interface and source. Based on depth analysis of DXF data structure, take one drawing of DXF lathe turning rotational part asthe test piece. By VC＋＋6.0 programming, part＇s geometry information could be obtained. Through data processing, 3D data of the test piece could be generated, which is based on 2D data of DXF test piece. Then, OpenGL graphic processing technologies （light, material, texture, map, et al.） were applied on the 3D display of test piece from DXF files or program modules. Finally based on the test report, results of the system functions were shared to prove the realization of system design, and the feasibility of algorithms used. In the developed software, Machine Designers could get a full view of machine parts, and do some proper modifications. The study content and results of our work have some theory and practical significance on the application of program design in the practical projects.
基金This work is supported by NSFC amd Slate Major Key Project for Baslc Research
文摘Making use of the Z2×Z2 symmetry,we could study the structure near multiple S-treaking turning points.In particular,we show that there exist two kinds of singular point path through double S breaking turning points and triple S bieaking turning points,one ts quadratic turning pornt path and one is quadratic pitch fork bifurcation point path.Some simple regular extended systems to corn pute double and triple S-breaking turning points are proposed.Numerical examples are also
文摘Prediction of surface finish in turning process is a difficult but important task. Artificial Neural Networks (ANN) can reliably pred ict the surface finish but require a lot of training data. To overcome this prob lem, an expert system approach is proposed, wherein it will be possible to predi ct the surface finish from limited experiments. The expert system contains a kno wledge base prepared from machining data handbooks and number of experiments con ducted by turning steel rods, over a wide range of cutting parameters. With this knowledge base, the expert system predicts surface finish for different tool-w ork-piece combinations, by carrying out few experiments for each case. The prop osed expert system model is validated by carrying out a number of experiments.
文摘In this paper we consider the asymptotic behavior of boundary value problems of nonliner systems εy″= F(t,y,y′,ε) , -1<t<1, y(-1,ε)=A, y(1,ε)=B when F possesses a generalized turning point at t=0. The interior layer phenomenon of the problem is discussed.
基金Funded by the National High-tech R&D Program ("863" Program) of China (No.2006AA04Z314)
文摘A fast tool servo (FTS) system is developed for the fabrication of non-rotationally symmetric micro-structured surfaces using single-point diamond turning machines.The constructed FTS employs a piezoelectric tube actuator (PZT) to actuate the diamond tool and a capacitive probe as the feedback sensor.To compensate the inherent nonlinear hysteresis behavior of the piezoelectric actuator,Proportional Integral (PI) feedback control is implemented.Besides,a feed-forward control based on a simple feed-forward predictor has been added to achieve better tracking performance.Experimental results indicate that error motions in the performance of the system caused by hysteresis can be reduced greatly and the micro-structured surface is successfully fabricated by implementing the FTS.
文摘We consider in this paper the boundary value problems of nonlinear systems the form εY″=F(t,Y,Y′,ε), -1<t<1, Y(-1,ε)=A(ε), Y(1,ε)=B(ε). Supoosing some or all of the components of F , that is, f i satisfy 2 f y′ 2 i t =0 =0, we say that F possesses a generalized turning point at t =0. Our goal is to give sufficient conditions for the existence of solution of the problems and to study the asymptotic behavior of the solution when F possesses a generalized turning point at t =0. We mainly discuss regular singular crossings.
基金supported by the National Natural Science Foundation of China(Nos.U20A2069,62376234 and 123B2037)the Advanced Aero-Power Innovation Workstation,China(No.HKCX2024-01-017)。
文摘The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and solves the unsteady axisymmetric Euler equation to study the characteristics of the Axisymmetric Inward Turning Curved Detonation Wave(AIT-CDW)flow field and the parameters affecting the stability of the wave system structure of AIT-CDW flow field.The numerical results demonstrate a radial compression effect in the AIT-CDW flow field.This effect causes the detonation wave to have a shorter initiation length than oblique detonation wave flow field and the detonation wave angle to gradually increase with the flow direction postdetonation.The AIT-CDW flow field is confined space,making it prone to normal detonation waves when the detonation wave reflects from the wall.This phenomenon is detrimental to the stability of the wave system structure in the flow field.It has been observed that increasing the center body radius and decreasing the fuel equivalent ratio can effectively reduce the height of the normal detonation wave or even eliminate it.Additionally,a well-designed generatrix shape of the center body can enhance airflow,reduce choked flow,and promote the stability of the wave structure in the flow field.
文摘Single-point diamond turning (SPDT) is widely used in the machining of infrared materials and metal-based mirrors. Diamond tips can scratch material, replicate the shape of the tip, and create annular turning marks on optical surfaces, which can have unpredictable adverse effects on imaging. In order to predict the effect of turning marks diffraction on the degradation of imaging quality, a model of the influence of SPDT processing parameters on the reduction of system imaging MTF under the influence of ideal grating turning marks diffraction was established. The results show that the depth of the turning mark will lead to the decline of MTF, especially the low frequency information. Finally, a method is proposed to reduce the effect of turning marks diffraction through changing the processing parameters. .
基金supported by the China Scholarship Council(Grant No.202306320084).
文摘The turning performance of a ship is an important aspect of its maneuverability,and accurately predicting the hydrodynamic forces during ship turning motion is of great significance for the safe maneuvering design of ships.This paper investigated the hydrodynamic performance of a KRISO container ship in steady turning using experimental and numerical approaches.The rotating arm tests were carried out in rotating arm basin of Zhejiang University,while the numerical simulations were conducted in commercial computational fluid dynamics software.Hydrodynamic forces and moments,hull surface wave height,wave patterns,and vorticity are studied under different velocities,radii,and drift angles.The results show that the increase in velocity has a significant impact on the forces and moments of the hull.The changes in longitudinal and transverse forces reflect the complex fluid dynamic interactions between the hull and water.Under conditions of small radius and large drift angle,the hull experiences greater forces and moments,indicating that stability and maneuverability will be more challenged during sudden turns.This study can provide experimental data and numerical simulation references for the research of ship turning maneuvers.
文摘Located in the southeast corner of Norbulingka Palace Park in Lhasa,the Xizang Museum stands out as a facility integrating contemporary technology,design and practices with the regional characteristics of Xizang Autonomous Region,southwest China.The museum houses over 520,000 cultural relics,including silk pieces,religious instruments,ancient books and documents,porcelain and jade articles,enamel vessels,and silverware,as well as Thangka paintings.
基金Supported by Special Scientific Research Funds for Commonweal Section(Agriculture)(201203029,201003016)China Rice Industry System Project(2011-2015)Special Funding for Basic Scientific Research and Zhejiang Provincial Natural Science Foundation(LY13C130004)~~
文摘Using early indica rice Zhongzao 39 and japonica rice Xiushui 134 as the experimental materials, the effects of 4 temperature levels after transplantation on turning green, leaf growth, tillering, dry matter accumulation and nutrition absorption were studied using a greenhouse and an artificial climate chest. We found that （1） tillering did not occur and growth of one new leaf took over 15 days at 16℃. New leaf growth took over 10 days and tillering occurred after 15 days of transplanta- tion at 19 ℃. Tillering appeared 10 days after planting and new leaf growth took 5 days between 22 and 25 ℃. This showed that low temperature impeded the turn- ing green of rice seedlings and the temperature must reach above 19 ℃ to ensure timely appearance of new leaf, tillering and turning green in rice seedlings. （2） When the temperature was 10 increased, both 100-seedling dry weight and nitrogen absorption increased. At temperatures lower 11 than 19 ℃, both dry weight incre- ment and nitrogen absorption were low. Nitrogen absorption of all organs increased obviously between 19 and 22 ℃. Thus, 19 ℃ was found to be an minimum tem- perature for plant organs to absorb nutrients. （3）Tiller of seedling cultivated on dry- land soil and substrate grew quickly and tillering occurred about 7 days after trans- planting. After that, the growth rate was about 0.18 tiller per day. For seedlings cultivated in slurry, tillering occurred 10 days after transplanting and the tillers grew at a rate of 0.16 tiller per day. However, substrate choice during the seedling rais- ing stage had no significant influence on leaf age. （4） Japonica rice exhibited stronger resistance to low temperature than indica rice. Tillering began at about the same time after transplanting in both rice varieties, but japonica rice exhibited higher tillering speed than early indica rice. The speed of leaf growth was higher in japoni- ca rice before transplantation but higher in indica rice after transplantation.
文摘In this paper, we study a class singular perturbed elliptic equation boundary value problem with a super surface of turning point in n-dimensional space by using the method of multiple scales and the comparison theorem. The uniformly valid asymptotic approxmations of solutions for the boundary value problem is constructed.
基金financial support from the National Natural Science Foundation of China (No.51425503)the Major Science and Technology Program of High-end CNC Machine Tools and Basic Manufacturing Equipment of China (No.2014ZX04012014)supported by a grant from the Taishan Scholar Foundation of Shandong province (No.TS20130922)
文摘The microstructural changes in the machined surface layer of Ni-based super alloys essentially determine the final performance of the structural components of aerospace engines in which these alloys are used.In this work,multiscale metallurgical observations using scanning electron microscopy,electron-backscatter diffraction microscopy,and transmission electron microscopy were conducted to quantitatively characterize the microstructure of the machined subsurface.Next,to elucidate the factors that affect the formation of the refinement microstructure,the distributions of the deformation parameters(strain,strain rate,and temperature) in the machined subsurface were analyzed.A dislocation–twin interaction dynamic recrystallization mechanism for grain refinement during machining of Inconel 718 is proposed.Furthermore,microhardness evolution induced by grain refinement in the machined surface is evaluated.The results suggest that the gradient microstructure and the work hardening can be optimized by controlling the cutting parameters during turning of Inconel 718.
基金partly supported by the National Natural Science Foundation of China(61903034,U1913203,61973034,91120003)the Program for Changjiang Scholars and Innovative Research Team in University(IRT-16R06,T2014224)+1 种基金China Postdoctoral Science Foundation funded project(2019TQ0035)Beijing Institute of Technology Research Fund Program for Young Scholars。
文摘Intersections are quite important and complex traffic scenarios,where the future motion of surrounding vehicles is an indispensable reference factor for the decision-making or path planning of autonomous vehicles.Considering that the motion trajectory of a vehicle at an intersection partly obeys the statistical law of historical data once its driving intention is determined,this paper proposes a long short-term memory based(LSTM-based)framework that combines intention prediction and trajectory prediction together.First,we build an intersection prior trajectories model(IPTM)by clustering and statistically analyzing a large number of prior traffic flow trajectories.The prior trajectories model with fitted probabilistic density is used to approximate the distribution of the predicted trajectory,and also serves as a reference for credibility evaluation.Second,we conduct the intention prediction through another LSTM model and regard it as a crucial cue for a trajectory forecast at the early stage.Furthermore,the predicted intention is also a key that is associated with the prior trajectories model.The proposed framework is validated on two publically released datasets,next generation simulation(NGSIM)and INTERACTION.Compared with other prediction methods,our framework is able to sample a trajectory from the estimated distribution,with its accuracy improved by about 20%.Finally,the credibility evaluation,which is based on the prior trajectories model,makes the framework more practical in the real-world applications.
