Based on the system dynamic model, a full system dynamics estimation method is proposed for a chain shell magazine driven by a permanent magnet synchronous motor(PMSM). An adaptive extended state observer(AESO) is pro...Based on the system dynamic model, a full system dynamics estimation method is proposed for a chain shell magazine driven by a permanent magnet synchronous motor(PMSM). An adaptive extended state observer(AESO) is proposed to estimate the unmeasured states and disturbance, in which the model parameters are adjusted in real time. Theoretical analysis shows that the estimation errors of the disturbances and unmeasured states converge exponentially to zero, and the parameter estimation error can be obtained from the extended state. Then, based on the extended state of the AESO, a novel parameter estimation law is designed. Due to the convergence of AESO, the novel parameter estimation law is insensitive to controllers and excitation signal. Under persistent excitation(PE) condition, the estimated parameters will converge to a compact set around the actual parameter value. Without PE signal, the estimated parameters will converge to zero for the extended state. Simulation and experimental results show that the proposed method can accurately estimate the unmeasured states and disturbance of the chain shell magazine, and the estimated parameters will converge to the actual value without strictly continuous PE signals.展开更多
To achieve full-surface strain measurement of variable curvature objects,a 360°3D digital image correlation(DIC)system is proposed.The measurement system consists of four double-camera systems,which capture the o...To achieve full-surface strain measurement of variable curvature objects,a 360°3D digital image correlation(DIC)system is proposed.The measurement system consists of four double-camera systems,which capture the object’s entire surface from multiple angles,enabling comprehensive full-surface measurement.To increase the stitching quality,a hierarchical coordinate matching method is proposed.Initially,a 3D rigid body calibration auxiliary block is employed to track motion trajectory,which enables preliminary matching of four 3D-DIC sub-systems.Subsequently,secondary precise matching is performed based on feature points on the test specimen’s surface.Through the hierarchical coordinate matching method,the local 3D coordinate systems of each double-camera system are unified into a global coordinate system,achieving 3D surface reconstruction of the variable curvature cylindrical shell,and error analysis is conducted on the results.Furthermore,axial compression buckling experiment is conducted to measure the displacement and strain fields on the cylindrical shell’s surface.The experimental results are compared with the finite element analysis,validating the accuracy and effectiveness of the proposed multi-camera 3D-DIC measuring system.展开更多
Since cannon drum of agile shell-feeding system rotates frequently and intermittently, its motion must be steady. Outline of driving cam determines the motion of cannon drum, so it is necessary to select the proper ou...Since cannon drum of agile shell-feeding system rotates frequently and intermittently, its motion must be steady. Outline of driving cam determines the motion of cannon drum, so it is necessary to select the proper outline of cam. Through analysis of parabolic outline and cycloid outline of the cams, the outline that combines the two curves is obtained. According to the demand of production,the value of the outline is revised, and then the method of fitting curve is used to get the expression of the angle of cam and the displacement of the driven part. Through analyzing the motion of the cannon drum, it is suggested that the angle of the cam is proportion to the displacement of the driven part. The cam with the specially derived outline can move steadily.展开更多
A mechanical system for quickfeeding shells in gunboat is particularly analyzed from a dynamic view. SD nonlinear structural simulation is completed by means of dynamic explicit finite element method. Analysis results...A mechanical system for quickfeeding shells in gunboat is particularly analyzed from a dynamic view. SD nonlinear structural simulation is completed by means of dynamic explicit finite element method. Analysis results prove that the mechanical structure is feasible substantially, the material of outer surfaces near striking and overstress position should be improved and measures should be taken to avoid parts high temperature. And all analysis results give a principal theoretical basis for further work.展开更多
Atom-level modulation of the coordination environment for single-atom catalysts(SACs)is considered as an effective strategy for elevating the catalytic performance.For the MNxsite,breaking the symmetrical geometry and...Atom-level modulation of the coordination environment for single-atom catalysts(SACs)is considered as an effective strategy for elevating the catalytic performance.For the MNxsite,breaking the symmetrical geometry and charge distribution by introducing relatively weak electronegative atoms into the first/second shell is an efficient way,but it remains challenging for elucidating the underlying mechanism of interaction.Herein,a practical strategy was reported to rationally design single cobalt atoms coordinated with both phosphorus and nitrogen atoms in a hierarchically porous carbon derived from metal-organic frameworks.X-ray absorption spectrum reveals that atomically dispersed Co sites are coordinated with four N atoms in the first shell and varying numbers of P atoms in the second shell(denoted as Co-N/P-C).The prepared catalyst exhibits excellent oxygen reduction reaction(ORR)activity as well as zinc-air battery performance.The introduction of P atoms in the Co-SACs weakens the interaction between Co and N,significantly promoting the adsorption process of ^(*)OOH,resulting in the acceleration of reaction kinetics and reduction of thermodynamic barrier,responsible for the increased intrinsic activity.Our discovery provides insights into an ultimate design of single-atom catalysts with adjustable electrocatalytic activities for efficient electrochemical energy conversion.展开更多
Longitudinal and horizontal vibration must both be reduced in an effective vibration isolation system. We present a cylindrical shell vibration isolator as a dynamic system composed of four springs and dampers. Vibrat...Longitudinal and horizontal vibration must both be reduced in an effective vibration isolation system. We present a cylindrical shell vibration isolator as a dynamic system composed of four springs and dampers. Vibration is directly produced by the motion of machinery, and more is subsequently generated by harmonic frequencies within their structure. To test the effectiveness of our isolator, we first determined equations for the transmission of vibration from the machine to its cylindrical shell. Damping effects produced by the vibration parameters of our system are then analyzed.展开更多
The medium -large caliber naval gun is still playing an important role in modern war. The development of highly automatic Shell Raising and Feeding System (SRFS) in the world has been briefly outlined. Several typical...The medium -large caliber naval gun is still playing an important role in modern war. The development of highly automatic Shell Raising and Feeding System (SRFS) in the world has been briefly outlined. Several typical SRFS of medium-large caliber naval guns have been analyzed. A re-design of the system is introduced, in which systematic design method has been used to demonstrate its feasibility. The design goal of the system is to realize rapid shell feeding, with application to many types of shells, quick change of shell types , accurate and reliable feeding operation, simple mechanical structure and easy realization of shell withdrawing.展开更多
The main goal of this study is to use higher-order isogeometric analysis(IGA)to study the dynamic response of sandwich shells with an auxetic honeycomb core and two different functionally graded materials(FGM)skin lay...The main goal of this study is to use higher-order isogeometric analysis(IGA)to study the dynamic response of sandwich shells with an auxetic honeycomb core and two different functionally graded materials(FGM)skin layers(namely honeycomb-FGS shells)subjected to dynamic loading.Touratier's non-polynomial higher-order shear deformation theory(HSDT)is used due to its simplicity and performance.The governing equation is derived from Hamilton's principle.After verifying the present approach,the effect of input parameters on the dynamic response of honeycomb-FGS shells is carried out in detail.展开更多
A model with three-layer structure is introduced to explore the acoustic radiation force(ARF)on composite particles with an elastic thin shell.Combing acoustic scattering of cylinder and the thin-shell theorem,the ARF...A model with three-layer structure is introduced to explore the acoustic radiation force(ARF)on composite particles with an elastic thin shell.Combing acoustic scattering of cylinder and the thin-shell theorem,the ARF expression was derived,and the longitudinal and transverse components of the force and axial torque for an eccentric liquid-filled composite particle was obtained.It was found that many factors,such as medium properties,acoustic parameters,eccentricity,and radius ratio of the inner liquid column,affect the acoustic scattering field of the particle,which in turn changes the forces and torque.The acoustic response varies with the particle structures,so the resonance peaks of the force function and torque shift with the eccentricity and radii ratio of particle.The acoustic response of the particle is enhanced and exhibits higher force values due to the presence of the elastic thin shell and the coupling effect with the eccentricity of the internal liquid column.The decrease of the inner liquid density may suppress the high-order resonance peaks,and internal fluid column has less effects on the change in force on composite particle at ka>3,while limited differences exist at ka<3.The axial torque on particles due to geometric asymmetry is closely related to ka and the eccentricity.The distribution of positive and negative force and torque along the axis ka exhibits that composite particle can be manipulated or separated by ultrasound.Our theoretical analysis can provide support for the acoustic manipulation,sorting,and targeting of inhomogeneous particles.展开更多
To explore the wide-frequency damping and vibration-attenuation performances in the application of aerospace components,the cylindrical sandwich shell structure with a gradient core of entangled wire mesh was proposed...To explore the wide-frequency damping and vibration-attenuation performances in the application of aerospace components,the cylindrical sandwich shell structure with a gradient core of entangled wire mesh was proposed in this paper.Firstly,the gradient cores of entangled wire mesh in the axial and radial directions were prepared by using an in-house Numerical Control weaving machine,and the metallurgical connection between skin sheets and the gradient core was performed using vacuum brazing.Secondly,to investigate the mechanical properties of cylindrical sandwich shells with axial or radial gradient cores,quasi-static and dynamic mechanical experiments were carried out.The primary evaluations of mechanical properties include secant stiffness,natural frequency,Specific Energy Absorption(SEA),vibration acceleration level,and so on.The results suggest that the vibration-attenuation performance of the sandwich shell is remarkable when the high-density core layer is at the end of the shell or abuts the inner skin.The axial gradient material has almost no influence on the vibration frequencies of the shell,whereas the vibration frequencies increase dramatically when the high-density core layer approaches the skin.Moreover,compared to the conventional sandwich shells,the proposed functional grading cylindrical sandwich shell exhibits more potential in mass reduction,stiffness designing,and energy dissipation.展开更多
This work uses refined first-order shear theory to analyze the free vibration and transient responses of double-curved sandwich two-layer shells made of auxetic honeycomb core and laminated three-phase polymer/GNP/fib...This work uses refined first-order shear theory to analyze the free vibration and transient responses of double-curved sandwich two-layer shells made of auxetic honeycomb core and laminated three-phase polymer/GNP/fiber surface subjected to the blast load.Each of the two layers that make up the double-curved shell structure is made up of an auxetic honeycomb core and two laminated sheets of three-phase polymer/GNP/fiber.The exterior is supported by a Kerr elastic foundation with three characteristics.The key innovation of the proposed theory is that the transverse shear stresses are zero at two free surfaces of each layer.In contrast to previous first-order shear deformation theories,no shear correction factor is required.Navier's exact solution was used to treat the double-curved shell problem with a single title boundary,while the finite element technique and an eight-node quadrilateral were used to address the other boundary requirements.To ensure the accuracy of these results,a thorough comparison technique is employed in conjunction with credible statements.The problem model's edge cases allow for this kind of analysis.The study's findings may be used in the post-construction evaluation of military and civil works structures for their ability to sustain explosive loads.In addition,this is also an important basis for the calculation and design of shell structures made of smart materials when subjected to shock waves or explosive loads.展开更多
For the first time, the isogeometric analysis(IGA) approach is used to model and analyze free and forced vibrations of doubly-curved magneto-electro-elastic(MEE) composite shallow shell resting on the visco-Pasternak ...For the first time, the isogeometric analysis(IGA) approach is used to model and analyze free and forced vibrations of doubly-curved magneto-electro-elastic(MEE) composite shallow shell resting on the visco-Pasternak foundation in a hygro-temperature environment. The doubly-curved MEE shallow shell types include spherical shallow shell, cylindrical shallow shell, saddle shallow shell, and elliptical shallow shell subjected to blast load are investigated. The Maxwell equation and electromagnetic boundary conditions are used to determine the vary of the electric and magnetic potentials. The MEE shallow shell's equations of motion are derived from Hamilton's principle and refined higher-order shear theory. Then, the IGA method is used to derive the laws of natural frequencies and dynamic responses of the shell under various boundary conditions. The accuracy of the model and method is verified through reliable numerical comparisons. Aside from this, the impact of the input parameters on the free and forced vibration of the doubly-curved MEE shallow shell is examined in detail. These results may be useful in the design and manufacture of military structures such as warships, fighter aircraft, drones and missiles.展开更多
AucoreCoshell nanoparticles with different shell thicknesses were prepared by using chemical reduction method and characterized by scanning electron microscopy（SEM） and cyclic voltammetry（CV）. The results reveal t...AucoreCoshell nanoparticles with different shell thicknesses were prepared by using chemical reduction method and characterized by scanning electron microscopy（SEM） and cyclic voltammetry（CV）. The results reveal that the prepared core-shell nanoparticles were covered by Co shell and exhibited the similar electrochemistry property with the Co nanoparticles surface. Surface enhanced Raman spectroscopy（SERS） activities of these nanoparticles were studied by using pyridine as a probe molecule. It was found that the SERS intensity depended on the Co shell thickness of the core-shell nanoparticles and was weakened with the increasing shell thickness. The SERS intensity of these AucoreCoshell nanoparticles is found to be about twenty times higher than that obtained on an electrochemically roughened cobalt electrode.展开更多
文摘Based on the system dynamic model, a full system dynamics estimation method is proposed for a chain shell magazine driven by a permanent magnet synchronous motor(PMSM). An adaptive extended state observer(AESO) is proposed to estimate the unmeasured states and disturbance, in which the model parameters are adjusted in real time. Theoretical analysis shows that the estimation errors of the disturbances and unmeasured states converge exponentially to zero, and the parameter estimation error can be obtained from the extended state. Then, based on the extended state of the AESO, a novel parameter estimation law is designed. Due to the convergence of AESO, the novel parameter estimation law is insensitive to controllers and excitation signal. Under persistent excitation(PE) condition, the estimated parameters will converge to a compact set around the actual parameter value. Without PE signal, the estimated parameters will converge to zero for the extended state. Simulation and experimental results show that the proposed method can accurately estimate the unmeasured states and disturbance of the chain shell magazine, and the estimated parameters will converge to the actual value without strictly continuous PE signals.
基金funded by the National Natural Science Foundations of China(Nos.12272176,U2037603).
文摘To achieve full-surface strain measurement of variable curvature objects,a 360°3D digital image correlation(DIC)system is proposed.The measurement system consists of four double-camera systems,which capture the object’s entire surface from multiple angles,enabling comprehensive full-surface measurement.To increase the stitching quality,a hierarchical coordinate matching method is proposed.Initially,a 3D rigid body calibration auxiliary block is employed to track motion trajectory,which enables preliminary matching of four 3D-DIC sub-systems.Subsequently,secondary precise matching is performed based on feature points on the test specimen’s surface.Through the hierarchical coordinate matching method,the local 3D coordinate systems of each double-camera system are unified into a global coordinate system,achieving 3D surface reconstruction of the variable curvature cylindrical shell,and error analysis is conducted on the results.Furthermore,axial compression buckling experiment is conducted to measure the displacement and strain fields on the cylindrical shell’s surface.The experimental results are compared with the finite element analysis,validating the accuracy and effectiveness of the proposed multi-camera 3D-DIC measuring system.
文摘Since cannon drum of agile shell-feeding system rotates frequently and intermittently, its motion must be steady. Outline of driving cam determines the motion of cannon drum, so it is necessary to select the proper outline of cam. Through analysis of parabolic outline and cycloid outline of the cams, the outline that combines the two curves is obtained. According to the demand of production,the value of the outline is revised, and then the method of fitting curve is used to get the expression of the angle of cam and the displacement of the driven part. Through analyzing the motion of the cannon drum, it is suggested that the angle of the cam is proportion to the displacement of the driven part. The cam with the specially derived outline can move steadily.
文摘A mechanical system for quickfeeding shells in gunboat is particularly analyzed from a dynamic view. SD nonlinear structural simulation is completed by means of dynamic explicit finite element method. Analysis results prove that the mechanical structure is feasible substantially, the material of outer surfaces near striking and overstress position should be improved and measures should be taken to avoid parts high temperature. And all analysis results give a principal theoretical basis for further work.
基金supported by the National Natural Science Foundation of China(51872115,12234018 and 52101256)Beijing Synchrotron Radiation Facility(BSRF,4B9A)。
文摘Atom-level modulation of the coordination environment for single-atom catalysts(SACs)is considered as an effective strategy for elevating the catalytic performance.For the MNxsite,breaking the symmetrical geometry and charge distribution by introducing relatively weak electronegative atoms into the first/second shell is an efficient way,but it remains challenging for elucidating the underlying mechanism of interaction.Herein,a practical strategy was reported to rationally design single cobalt atoms coordinated with both phosphorus and nitrogen atoms in a hierarchically porous carbon derived from metal-organic frameworks.X-ray absorption spectrum reveals that atomically dispersed Co sites are coordinated with four N atoms in the first shell and varying numbers of P atoms in the second shell(denoted as Co-N/P-C).The prepared catalyst exhibits excellent oxygen reduction reaction(ORR)activity as well as zinc-air battery performance.The introduction of P atoms in the Co-SACs weakens the interaction between Co and N,significantly promoting the adsorption process of ^(*)OOH,resulting in the acceleration of reaction kinetics and reduction of thermodynamic barrier,responsible for the increased intrinsic activity.Our discovery provides insights into an ultimate design of single-atom catalysts with adjustable electrocatalytic activities for efficient electrochemical energy conversion.
基金the National Nature Science Foundation under Grant No.50375121.
文摘Longitudinal and horizontal vibration must both be reduced in an effective vibration isolation system. We present a cylindrical shell vibration isolator as a dynamic system composed of four springs and dampers. Vibration is directly produced by the motion of machinery, and more is subsequently generated by harmonic frequencies within their structure. To test the effectiveness of our isolator, we first determined equations for the transmission of vibration from the machine to its cylindrical shell. Damping effects produced by the vibration parameters of our system are then analyzed.
文摘The medium -large caliber naval gun is still playing an important role in modern war. The development of highly automatic Shell Raising and Feeding System (SRFS) in the world has been briefly outlined. Several typical SRFS of medium-large caliber naval guns have been analyzed. A re-design of the system is introduced, in which systematic design method has been used to demonstrate its feasibility. The design goal of the system is to realize rapid shell feeding, with application to many types of shells, quick change of shell types , accurate and reliable feeding operation, simple mechanical structure and easy realization of shell withdrawing.
基金funded by Le Quy Don Technical University Research Found (Grant No.2023QHT.03)。
文摘The main goal of this study is to use higher-order isogeometric analysis(IGA)to study the dynamic response of sandwich shells with an auxetic honeycomb core and two different functionally graded materials(FGM)skin layers(namely honeycomb-FGS shells)subjected to dynamic loading.Touratier's non-polynomial higher-order shear deformation theory(HSDT)is used due to its simplicity and performance.The governing equation is derived from Hamilton's principle.After verifying the present approach,the effect of input parameters on the dynamic response of honeycomb-FGS shells is carried out in detail.
基金the National Natural Science Foundation of China(Grant Nos.12374441 and 11974232)the Fund from Yulin Science and Technology Bureau(Grant No.CXY-2022-178).
文摘A model with three-layer structure is introduced to explore the acoustic radiation force(ARF)on composite particles with an elastic thin shell.Combing acoustic scattering of cylinder and the thin-shell theorem,the ARF expression was derived,and the longitudinal and transverse components of the force and axial torque for an eccentric liquid-filled composite particle was obtained.It was found that many factors,such as medium properties,acoustic parameters,eccentricity,and radius ratio of the inner liquid column,affect the acoustic scattering field of the particle,which in turn changes the forces and torque.The acoustic response varies with the particle structures,so the resonance peaks of the force function and torque shift with the eccentricity and radii ratio of particle.The acoustic response of the particle is enhanced and exhibits higher force values due to the presence of the elastic thin shell and the coupling effect with the eccentricity of the internal liquid column.The decrease of the inner liquid density may suppress the high-order resonance peaks,and internal fluid column has less effects on the change in force on composite particle at ka>3,while limited differences exist at ka<3.The axial torque on particles due to geometric asymmetry is closely related to ka and the eccentricity.The distribution of positive and negative force and torque along the axis ka exhibits that composite particle can be manipulated or separated by ultrasound.Our theoretical analysis can provide support for the acoustic manipulation,sorting,and targeting of inhomogeneous particles.
基金Supports from the National Natural Science Foundation of China(Grant No.12272094,No.52205185 and No.51975123)the Natural Science Foundation of Fujian Province of China(Grant No.2022J01541 and No.2020J05102)the Key Project of National Defence Innovation Zone of Science and Technology Commission of CMC(Grant No.XXX-033-01)。
文摘To explore the wide-frequency damping and vibration-attenuation performances in the application of aerospace components,the cylindrical sandwich shell structure with a gradient core of entangled wire mesh was proposed in this paper.Firstly,the gradient cores of entangled wire mesh in the axial and radial directions were prepared by using an in-house Numerical Control weaving machine,and the metallurgical connection between skin sheets and the gradient core was performed using vacuum brazing.Secondly,to investigate the mechanical properties of cylindrical sandwich shells with axial or radial gradient cores,quasi-static and dynamic mechanical experiments were carried out.The primary evaluations of mechanical properties include secant stiffness,natural frequency,Specific Energy Absorption(SEA),vibration acceleration level,and so on.The results suggest that the vibration-attenuation performance of the sandwich shell is remarkable when the high-density core layer is at the end of the shell or abuts the inner skin.The axial gradient material has almost no influence on the vibration frequencies of the shell,whereas the vibration frequencies increase dramatically when the high-density core layer approaches the skin.Moreover,compared to the conventional sandwich shells,the proposed functional grading cylindrical sandwich shell exhibits more potential in mass reduction,stiffness designing,and energy dissipation.
文摘This work uses refined first-order shear theory to analyze the free vibration and transient responses of double-curved sandwich two-layer shells made of auxetic honeycomb core and laminated three-phase polymer/GNP/fiber surface subjected to the blast load.Each of the two layers that make up the double-curved shell structure is made up of an auxetic honeycomb core and two laminated sheets of three-phase polymer/GNP/fiber.The exterior is supported by a Kerr elastic foundation with three characteristics.The key innovation of the proposed theory is that the transverse shear stresses are zero at two free surfaces of each layer.In contrast to previous first-order shear deformation theories,no shear correction factor is required.Navier's exact solution was used to treat the double-curved shell problem with a single title boundary,while the finite element technique and an eight-node quadrilateral were used to address the other boundary requirements.To ensure the accuracy of these results,a thorough comparison technique is employed in conjunction with credible statements.The problem model's edge cases allow for this kind of analysis.The study's findings may be used in the post-construction evaluation of military and civil works structures for their ability to sustain explosive loads.In addition,this is also an important basis for the calculation and design of shell structures made of smart materials when subjected to shock waves or explosive loads.
文摘For the first time, the isogeometric analysis(IGA) approach is used to model and analyze free and forced vibrations of doubly-curved magneto-electro-elastic(MEE) composite shallow shell resting on the visco-Pasternak foundation in a hygro-temperature environment. The doubly-curved MEE shallow shell types include spherical shallow shell, cylindrical shallow shell, saddle shallow shell, and elliptical shallow shell subjected to blast load are investigated. The Maxwell equation and electromagnetic boundary conditions are used to determine the vary of the electric and magnetic potentials. The MEE shallow shell's equations of motion are derived from Hamilton's principle and refined higher-order shear theory. Then, the IGA method is used to derive the laws of natural frequencies and dynamic responses of the shell under various boundary conditions. The accuracy of the model and method is verified through reliable numerical comparisons. Aside from this, the impact of the input parameters on the free and forced vibration of the doubly-curved MEE shallow shell is examined in detail. These results may be useful in the design and manufacture of military structures such as warships, fighter aircraft, drones and missiles.
文摘AucoreCoshell nanoparticles with different shell thicknesses were prepared by using chemical reduction method and characterized by scanning electron microscopy（SEM） and cyclic voltammetry（CV）. The results reveal that the prepared core-shell nanoparticles were covered by Co shell and exhibited the similar electrochemistry property with the Co nanoparticles surface. Surface enhanced Raman spectroscopy（SERS） activities of these nanoparticles were studied by using pyridine as a probe molecule. It was found that the SERS intensity depended on the Co shell thickness of the core-shell nanoparticles and was weakened with the increasing shell thickness. The SERS intensity of these AucoreCoshell nanoparticles is found to be about twenty times higher than that obtained on an electrochemically roughened cobalt electrode.
