In this paper,the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of fragments.Attention is paid to eluc...In this paper,the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of fragments.Attention is paid to elucidating the influences of rod cross-section dimensions,structure height,structure layer,and rod inclination angle on the deformation mode,ballistic performances,and ability to change the ballistic direction of fragments.The results show that the ballistic performances of hourglass lattice sandwich structures are mainly affected by their structural parameters.In this respect,structural parameters optimization of the hourglass lattice sandwich structures enable one to effectively improve their ballistic limit velocity and,consequently,ballistic performances.展开更多
This paper presents the design optimization of composite submersible cylindrical pressure hull subjected to 3 MPa hydrostatic pressure.The design optimization study is conducted for cross-ply layups[0_(s)/90_(t)/0_(u)...This paper presents the design optimization of composite submersible cylindrical pressure hull subjected to 3 MPa hydrostatic pressure.The design optimization study is conducted for cross-ply layups[0_(s)/90_(t)/0_(u)],[0_(s)/90_(t)/0_(u)]s,[0_(s)/90_(t)]s and[90_(s)/0_(t)]s considering three uni-directional composites,i.e.Carbon/Epoxy,Glass/Epoxy,and Boron/Epoxy.The optimization study is performed by coupling a Multi-Objective Genetic Algorithm(MOGA)and Analytical Analysis.Minimizing the buoyancy factor and maximizing the buckling load factor are considered as the objectives of the optimization study.The objectives of the optimization are achieved under constraints on the Tsai-Wu,Tsai-Hill and Maximum Stress composite failure criteria and on buckling load factor.To verify the optimization approach,optimization of one particular layup configuration is also conducted in ANSYS with the same objectives and constraints.展开更多
The dynamic response of a multi-cabin protective structure subjected to impact load directly affects the protective performance of materials;thus,studying the dynamic response and communication law of wave effect of t...The dynamic response of a multi-cabin protective structure subjected to impact load directly affects the protective performance of materials;thus,studying the dynamic response and communication law of wave effect of the load plays an important role in the prediction of protective performance.In this study,the protection experiments of box-structure under air-and/or water-medium are conducted,the dynamic response of the structure subjected to low-impact load is analyzed,and the corresponding numerical simulations are analyzed using the theory of finite element method(FEM).Combined with experimental and FEM simulations,the shock strain distribution,acceleration attenuation,and signal energy in defensive materials are determined.Based on the results,the metal structure exhibits good absorption characteristics for shock vibration.Using the experimental data,we also show that the attenuation of shock wave in water medium should be significantly better than that in air medium,and the protective structure should be designed for a combination of water and air mediums.Meanwhile,the numerical simulation can provide a quantitative analysis process for dynamic analysis of defensive materials.展开更多
The vibration control in the frequency domain is significant.Therefore,an active vibration control in frequency domain is studied in this paper.It is generally known that piezo-intelligent structures possess satisfact...The vibration control in the frequency domain is significant.Therefore,an active vibration control in frequency domain is studied in this paper.It is generally known that piezo-intelligent structures possess satisfactory performances in the area of vibration control,and macro-fiber composites(MFCs)with high sensitivity and deformability are widely applied in engineering.So,this paper uses the MFC patches and designs a control method based on the pole placement method,and the natural frequency of the beam can be artificially designed.MFC patches are bonded on the top and bottom surfaces of the beam structure to act as the actuators and sensors.Then,the finite element method(FEM)is used to formulate the equation of motion,and the pole placement based on the out-put feedback method is used to design the active controller.Finally,the effectiveness of the active control method is verified.展开更多
Thermal-electric bilayer invisibility cloak can prevent the heat flux and electric current from touching the object without distorting the external temperature and electric potential fields simultaneously.In this pape...Thermal-electric bilayer invisibility cloak can prevent the heat flux and electric current from touching the object without distorting the external temperature and electric potential fields simultaneously.In this paper,we design an omnidirectional thermal-electric invisibility cloak with anisotropic geometry.Based on the theory of neutral inclusion,the anisotropic effective thermal and electric conductivities of confocal elliptical bilayer core-shell structure are derived,thus obtaining the anisotropic matrix material to eliminate the external disturbances omnidirectionally.The inner shell of the cloak is selected as an insulating material to shield the heat flux and electric current.Then,the omnidirectional thermal-electric cloaking effect is verified numerically and experimentally based on the theoretical anisotropic matrix and manufactured composite structure,respectively.Furthermore,we achieve the thermal-electric cloaking effect under a specific direction of heat flux and electric current using the isotropic natural materials to broaden the selection range of materials.The method proposed to eliminate anisotropy and achieve the omnidirectional effect could also be expanded to other different physical fields for the metadevices with different functions.展开更多
This paper describes a design optimization study of the composite egg-shaped submersible pressure hull employing optimization and finite element analysis(FEA)tools as a first attempt to provide an optimized design of ...This paper describes a design optimization study of the composite egg-shaped submersible pressure hull employing optimization and finite element analysis(FEA)tools as a first attempt to provide an optimized design of the composite egg-shaped pressure hull for manufacturing or further investigations.A total of 15 optimal designs for the composite egg-shaped pressure hull under hydrostatic pressure are obtained in terms of fibers’angles and the number of layers for 5 lay-up arrangements and 3 unidirectional(UD)composite materials.The optimization process is performed utilizing a genetic algorithm and FEA in ANSYS.The minimization of the buoyancy factor eB:FT is selected as the objective for the optimization under constraints on both material failure and buckling strength.Nonlinear buckling analysis is conducted for one optimal design considering both geometric nonlinearity and imperfections.A sensitivity study is also conducted to further investigate the influence of the design variables on the optimal design of the egg-shaped pressure hull.展开更多
This study focuses on the effect of lateral mass impact on ring-stiffened thin-walled cylindrical shell.Cylindrical shells were fabricated to validate the numerical modeling and analytical techniques,and drop tests we...This study focuses on the effect of lateral mass impact on ring-stiffened thin-walled cylindrical shell.Cylindrical shells were fabricated to validate the numerical modeling and analytical techniques,and drop tests were performed using a rigid spherical indenter.Next,stiffened-ring cylindrical shells with various structural size parameters were simulated using ABAQUS software.The relationships between the impact force,deformation displacement,and rebound velocity were established,on the basis of impact mechanics theory and simulation results.It derived fitting functions to analyse the relationship between the maximum load and maximum displacement of ring-stiffened cylindrical shell under dynamic mass impact.Based on the validation of the simulation model,the fitting function data were compared with the simulation results,and the functions showed a good accuracy.Besides,the parameters,mass ratio and stiffened-ring mass ratio were used to reflect the effect of the mass change in the ring-stiffened cylindrical shell.Furthermore,parametric studies on ring-stiffened cylindrical shell models were conducted to analyse the progressive impact responses.展开更多
Twin gold crystal nanowires, whose loading direction is parallel to the twin boundary orientation, are simulated.We calculate the nanowires under tensile or compressive loads, different length nanowires, and different...Twin gold crystal nanowires, whose loading direction is parallel to the twin boundary orientation, are simulated.We calculate the nanowires under tensile or compressive loads, different length nanowires, and different twin boundary nanowires respectively. The Young modulus of nanowires under compressive load is about twice that under tensile load.The compressive properties of twin gold nanowires are superior to their tensile properties. For different length nanowires,there is a critical value of length with respect to the mechanical properties. When the length of nanowire is greater than the critical value, its mechanical properties are sensitive to length. The twin boundary spacing hardly affects the mechanical properties.展开更多
Safety of underground ammunition storage is an important issue,especially during the accidental ignition of missiles.This work investigates the pressure and temperature distribution of the multi-layer underground ammu...Safety of underground ammunition storage is an important issue,especially during the accidental ignition of missiles.This work investigates the pressure and temperature distribution of the multi-layer underground ammunition storage with a pressure relief duct during the accidental ignition process of the missile.A large-scale experiment was carried out using a multi-layered restricted space with a pressure relief duct to simulate the underground ammunition store and a solid rocket motor to simulate the accidental ignition of the missile.The results show that when the motor gas mass flow increased by5.6 times,the maximum pressure of the ammunition storage increased by 5.87 times.At a certain motor flow rate,when the pressure relief exhaust area at the end of the relief duct was reduced by 1/2,the maximum pressure on the first layer did not change.But the rate of pressure relief was reduced and the time delayed for the pressure of ammunition store to drop to zero.In this experiment,when the motor ignition position was located in to the third layer ammunition chamber,the maximum pressure was reduced by 32.9%and also reduced the rate of change of pressure.In addition,for the experimental conditions,the theoretical analysis of the pressure relief of the ammunition storage is given by a simplified model.Based on the findings,some suggestions to the safety protection design of ammunition store are proposed.展开更多
Organic pollutants could be degraded by using bubble discharge in water with gas aeration in the discharge reactor and more plasma can be generated in the discharge process. When pulsed high voltage was applied betwee...Organic pollutants could be degraded by using bubble discharge in water with gas aeration in the discharge reactor and more plasma can be generated in the discharge process. When pulsed high voltage was applied between electrodes with gas aerated into the reactor, it showed that bubbles were broken, which meant that breakdown took place. It could also be observed that the removal rate of phenol increased with increasing discharge voltage or pulse frequency, and with reducing initial phenol concentration or solution electric conductivity. It could remove more amount of phenol by oxygen aeration. With increasing oxygen flow rate, the removal rate increased. There was little difference with air or nitrogen aeration for phenol removal. The solution temperature after discharge increased to a great extent. However, this part of energy consumption did not contribute to the reaction, which led to a reduction in the energy utilization efficiency.展开更多
The mechanical properties of copper nanocubes by molecular dynamics are investigated in this paper. The [100], [110], [111] nanocubes are created, and their energies, yield stresses, hydrostatic stresses, Mises stress...The mechanical properties of copper nanocubes by molecular dynamics are investigated in this paper. The [100], [110], [111] nanocubes are created, and their energies, yield stresses, hydrostatic stresses, Mises stresses, and the relation- ships between them and strain are analyzed. Some concepts of the microscopic damage mechanics are introduced, which are the basis of studying the damage mechanical properties by molecular dynamics. The [100] nanocube exhibits homo- geneity and isotropy and achieves a balance easily. The [110] nanocube presents transverse isotropy. The [111] nanocube shows the complexity and anisotropy because the orientation sizes in three directions are different. The broken point occurs on a surface, but the other two do not. The [100] orientation model will be an ideal model for studying the microscopic damage theory.展开更多
Indium selenide has garnered significant attention for high volumetric capacities,but is currently plagued by the sluggish charge transfer kinetics,severe volume effect,and rapid capacity degradation that hinder their...Indium selenide has garnered significant attention for high volumetric capacities,but is currently plagued by the sluggish charge transfer kinetics,severe volume effect,and rapid capacity degradation that hinder their practical applications.Herein,we design,synthesize,and characterize a multi-kernel-shell structure comprised of indium selenide encapsulated within carbon nanospheres(referred to as m-K-S In_(2)Se_(3)@C)through an integrated approach involving a hydrothermal method followed by a gaseous selenization process.Importantly,experimental measurements and density functional theory calculations confirm that the m-K-S In_(2)Se_(3)@C not only improve the adsorption capability for Li-ions but also lower the energy barrier for Li-ions diffusion.Profiting from numerous contact points,shorter diffusion distances and an improved volume buffering effect,the m-K-S In_(2)Se_(3)@C achieves an 800 mA h g^(−1)capacity over 1000 loops at 1000 mA g^(−1),a 520 mA h g^(−1)capacity at 5000 mA g^(−1)and an energy density of 270 Wh kg^(−1)when coupled with LiFePO4,surpassing most related anodes reported before.Broadly,the m-K-S structure with unique nano-micro structure offers a new approach to the design of advanced anodes for LIBs.展开更多
In the real-world situation,the lunar missions’scale and terrain are different according to various operational regions or worksheets,which requests a more flexible and efficient algorithm to generate task paths.A mu...In the real-world situation,the lunar missions’scale and terrain are different according to various operational regions or worksheets,which requests a more flexible and efficient algorithm to generate task paths.A multi-scale ant colony planning method for the lunar robot is designed to meet the requirements of large scale and complex terrain in lunar space.In the algorithm,the actual lunar surface image is meshed into a gird map,the path planning algorithm is modeled on it,and then the actual path is projected to the original lunar surface and mission.The classical ant colony planning algorithm is rewritten utilizing a multi-scale method to address the diverse task problem.Moreover,the path smoothness is also considered to reduce the magnitude of the steering angle.Finally,several typical conditions to verify the efficiency and feasibility of the proposed algorithm are presented.展开更多
Since the concept of invisible cloak was proposed by Pendry and Leonhardt in 2006, many researchers have applied the theory of coordinate transformation to thermodynamics and overcome the complexity of inhomogeneous a...Since the concept of invisible cloak was proposed by Pendry and Leonhardt in 2006, many researchers have applied the theory of coordinate transformation to thermodynamics and overcome the complexity of inhomogeneous and anisotropic of material parameters. However, only two-dimensional(2 D) thermal illusion devices are researched recently. According to this situation, our study focuses on three-dimensional(3 D) thermal illusion devices including shrinker(or invisible cloak),concentrator, amplifier, reshaper, and rotator with arbitrary shape in a general way. In this paper, the corresponding material parameters of thermal illusion devices mentioned above are derived based on the theory of transformation thermodynamics and the simulated results agree well with the theoretical derivations. In addition, the conventional invisible cloak just controls the temperature gradient rather than the temperature value which is more concerned in physical applications. Here,we find that the temperature value of the cloaked object can be controlled by adjusting the location of the original point of the coordinate system.展开更多
Over the past century,the safety of dams has gradually attracted attention from all parties.Research on the dynamic response and damage evolution of dams under extreme loads is the basis of dam safety issues.In recent...Over the past century,the safety of dams has gradually attracted attention from all parties.Research on the dynamic response and damage evolution of dams under extreme loads is the basis of dam safety issues.In recent decades,scholars have studied the responses of dams under earthquake loads,but there is still much room for improvement in experimental and theoretical research on small probability loads such as explosions.In this paper,a 50-m-high concrete gravity dam is used as a prototype dam,and a water explosion model test of a 2.5-m-high concrete gravity dam is designed.The water pressure and the acceleration response of the dam body in the test are analysed.The pressure characteristics and dynamic response of the dam body are assessed.Taking the dam damage test as an example,a numerical model of concrete gravity dam damage is established,and the damage evolution of the dam body is analysed.By combining experiments and numerical simulations,the damage characteristics of the dam body under the action of different charge water explosions are clarified.The integrity of the dam body is well maintained under the action of a small-quantity water explosion,and the dynamic response of the dam body is mainly caused by the shock wave.Both the shock wave and the bubble pulsation cause the dam body to accelerate,and the peak acceleration of the dam body under the action of the bubble pulsation is only one percent of the peak acceleration of the dam body under the action of the shock wave.When subjected to explosions in large quantities of water,the dam body is seriously damaged.Under the action of a shock wave,the dam body produces a secondary acceleration response,which is generated by an internal interaction after the dam body is damaged.The damage evolution process of the dam body under the action of a large-scale water explosion is analysed,and it is found that the shock wave pressure of the water explosion causes local damage to the dam body facing the explosion.After the peak value of the shock wave,the impulse continues to act on the dam body,causing cumulative damage and damage inside the dam body.展开更多
A nonlinear sliding mode adaptive controller for a thin-film diffractive imaging system is designed to achieve accurate pointing direction over the attitude of subarrays in large-diameter mirror arrays.The kinematics ...A nonlinear sliding mode adaptive controller for a thin-film diffractive imaging system is designed to achieve accurate pointing direction over the attitude of subarrays in large-diameter mirror arrays.The kinematics and dynamics equations based on error quaternion and angular velocity are derived,and a diffractive thin-film sub-mirror array controller is designed to point precisely.Moreover,the global stability of the controller is proved by the Lyapunov method.Since the controller can adaptively identify the inertia matrix of each sub-mirror system,it is robust to bounded disturbances and changes in inertia parameters.At the same time,the continuous arctangent function is introduced,which is effectively anti-chattering.The simulation results show that the designed controller can ensure the accurate tracking of the diffractive film in each sub-mirror in the presence of rotational inertia matrix uncertainty and various disturbances.展开更多
In this paper, we adopt the modified Morozov secondary electron emission model to investigate the influence of the characteristic of a space-charge-saturated sheath near the insulated wall of the Hall thruster on the ...In this paper, we adopt the modified Morozov secondary electron emission model to investigate the influence of the characteristic of a space-charge-saturated sheath near the insulated wall of the Hall thruster on the near-wall conductivity, by the method of two-dimensional （2D） particle simulation （2Dq-3V）. The results show that due to the sharp increase of collision frequency between the electrons and the wall under the space-charge-saturated sheath, the near-wall transport current under this sheath is remarkably higher than that under a classical sheath, and equals the near-wall transport current under a spatially oscillating sheath in order of magnitude. However, the transport currents under a space-charge-saturated sheath and a spatially oscillating sheath are different in mechanism, causing different current density distributions under the above two sheaths, and a great influence of channel width on the near-wall transport current under a space-charge-saturated sheath.展开更多
Coding metasurfaces have attracted tremendous interests due to unique capabilities of manipulating electromagnetic wave.However,archiving transmissive coding metasurface is still challenging.Here we propose a transmis...Coding metasurfaces have attracted tremendous interests due to unique capabilities of manipulating electromagnetic wave.However,archiving transmissive coding metasurface is still challenging.Here we propose a transmissive anisotropic coding metasurface that enables the independent control of two orthogonal polarizations.The polarization beam splitter and the orbital angular momentum(OAM)generator have been studied as typical applications of the anisotropic 2-bit coding metasurface.The simulated far field patterns illustrate that the x and y polarized electromagnetic waves are deflected into two different directions,respectively.The anisotropic coding metasurface has been experimentally verified to realize an OAM beam with l=2 of right-handed polarized wave,resulting from both contributions from linear-to-circular polarization conversion and the phase profile modulation.This work is beneficial to enrich the polarization manipulation field and develop transmissive coding metasurfaces.展开更多
基金supported by the Defense Industrial Technology Development Program(Grant No.JCKY2018604B004)the National Natural Science Foundation of China(Grant No.11972007)。
文摘In this paper,the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of fragments.Attention is paid to elucidating the influences of rod cross-section dimensions,structure height,structure layer,and rod inclination angle on the deformation mode,ballistic performances,and ability to change the ballistic direction of fragments.The results show that the ballistic performances of hourglass lattice sandwich structures are mainly affected by their structural parameters.In this respect,structural parameters optimization of the hourglass lattice sandwich structures enable one to effectively improve their ballistic limit velocity and,consequently,ballistic performances.
基金This work is supported by the National Natural Science Foundation of China research grant“Study on the characteristic motion and load of bubbles near a solid boundary in shear flows”(51679056)Natural Science Foundation of Heilongjiang Province of China(E2016024).
文摘This paper presents the design optimization of composite submersible cylindrical pressure hull subjected to 3 MPa hydrostatic pressure.The design optimization study is conducted for cross-ply layups[0_(s)/90_(t)/0_(u)],[0_(s)/90_(t)/0_(u)]s,[0_(s)/90_(t)]s and[90_(s)/0_(t)]s considering three uni-directional composites,i.e.Carbon/Epoxy,Glass/Epoxy,and Boron/Epoxy.The optimization study is performed by coupling a Multi-Objective Genetic Algorithm(MOGA)and Analytical Analysis.Minimizing the buoyancy factor and maximizing the buckling load factor are considered as the objectives of the optimization study.The objectives of the optimization are achieved under constraints on the Tsai-Wu,Tsai-Hill and Maximum Stress composite failure criteria and on buckling load factor.To verify the optimization approach,optimization of one particular layup configuration is also conducted in ANSYS with the same objectives and constraints.
基金supported by the Natural Science Foundation of Heilongjiang Province,China(LH2019A008)the National Natural Science Foundation of China(51508123,named‘Study on blast response of floating roof storage tank in material point method’).
文摘The dynamic response of a multi-cabin protective structure subjected to impact load directly affects the protective performance of materials;thus,studying the dynamic response and communication law of wave effect of the load plays an important role in the prediction of protective performance.In this study,the protection experiments of box-structure under air-and/or water-medium are conducted,the dynamic response of the structure subjected to low-impact load is analyzed,and the corresponding numerical simulations are analyzed using the theory of finite element method(FEM).Combined with experimental and FEM simulations,the shock strain distribution,acceleration attenuation,and signal energy in defensive materials are determined.Based on the results,the metal structure exhibits good absorption characteristics for shock vibration.Using the experimental data,we also show that the attenuation of shock wave in water medium should be significantly better than that in air medium,and the protective structure should be designed for a combination of water and air mediums.Meanwhile,the numerical simulation can provide a quantitative analysis process for dynamic analysis of defensive materials.
基金supported by the National Natural Science Foundation of China(Nos.11802069,11761131006)the China Postdoctoral Science Foundation(No.3236310534)+1 种基金the Heilongjiang Provincial Postdoctoral Science Foundation(Nos.002020830603,LBHTZ2008)the China Fundamental Research Funds for the Central Universities(No.GK2020260225).
文摘The vibration control in the frequency domain is significant.Therefore,an active vibration control in frequency domain is studied in this paper.It is generally known that piezo-intelligent structures possess satisfactory performances in the area of vibration control,and macro-fiber composites(MFCs)with high sensitivity and deformability are widely applied in engineering.So,this paper uses the MFC patches and designs a control method based on the pole placement method,and the natural frequency of the beam can be artificially designed.MFC patches are bonded on the top and bottom surfaces of the beam structure to act as the actuators and sensors.Then,the finite element method(FEM)is used to formulate the equation of motion,and the pole placement based on the out-put feedback method is used to design the active controller.Finally,the effectiveness of the active control method is verified.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.11572090)the Fundamental Research Funds for the Central Universities(Grant No.3072022GIP0202).
文摘Thermal-electric bilayer invisibility cloak can prevent the heat flux and electric current from touching the object without distorting the external temperature and electric potential fields simultaneously.In this paper,we design an omnidirectional thermal-electric invisibility cloak with anisotropic geometry.Based on the theory of neutral inclusion,the anisotropic effective thermal and electric conductivities of confocal elliptical bilayer core-shell structure are derived,thus obtaining the anisotropic matrix material to eliminate the external disturbances omnidirectionally.The inner shell of the cloak is selected as an insulating material to shield the heat flux and electric current.Then,the omnidirectional thermal-electric cloaking effect is verified numerically and experimentally based on the theoretical anisotropic matrix and manufactured composite structure,respectively.Furthermore,we achieve the thermal-electric cloaking effect under a specific direction of heat flux and electric current using the isotropic natural materials to broaden the selection range of materials.The method proposed to eliminate anisotropy and achieve the omnidirectional effect could also be expanded to other different physical fields for the metadevices with different functions.
基金This work is supported by the National Natural Science Foundation of China research grant#51679056Natural Science Foundation of Heilongjiang Province of China grant#E2016024.
文摘This paper describes a design optimization study of the composite egg-shaped submersible pressure hull employing optimization and finite element analysis(FEA)tools as a first attempt to provide an optimized design of the composite egg-shaped pressure hull for manufacturing or further investigations.A total of 15 optimal designs for the composite egg-shaped pressure hull under hydrostatic pressure are obtained in terms of fibers’angles and the number of layers for 5 lay-up arrangements and 3 unidirectional(UD)composite materials.The optimization process is performed utilizing a genetic algorithm and FEA in ANSYS.The minimization of the buoyancy factor eB:FT is selected as the objective for the optimization under constraints on both material failure and buckling strength.Nonlinear buckling analysis is conducted for one optimal design considering both geometric nonlinearity and imperfections.A sensitivity study is also conducted to further investigate the influence of the design variables on the optimal design of the egg-shaped pressure hull.
基金supported by the National Natural Science Foundation of China(Grant No.51508123,named“Study on blast response of floating roof storage tank in material point method”)Natural Science Foundation of Heilongjiang Province,China(LH2019A008)to provide fund for conducting experiments and research.The authors would like to acknowledge Professor Wei Wang in Harbin Institute of Technology for instructions and help in experiment design.
文摘This study focuses on the effect of lateral mass impact on ring-stiffened thin-walled cylindrical shell.Cylindrical shells were fabricated to validate the numerical modeling and analytical techniques,and drop tests were performed using a rigid spherical indenter.Next,stiffened-ring cylindrical shells with various structural size parameters were simulated using ABAQUS software.The relationships between the impact force,deformation displacement,and rebound velocity were established,on the basis of impact mechanics theory and simulation results.It derived fitting functions to analyse the relationship between the maximum load and maximum displacement of ring-stiffened cylindrical shell under dynamic mass impact.Based on the validation of the simulation model,the fitting function data were compared with the simulation results,and the functions showed a good accuracy.Besides,the parameters,mass ratio and stiffened-ring mass ratio were used to reflect the effect of the mass change in the ring-stiffened cylindrical shell.Furthermore,parametric studies on ring-stiffened cylindrical shell models were conducted to analyse the progressive impact responses.
基金supported by the National Science and Technology Pillar Program,China(Grant No.2015BAK17B06)the Earthquake Industry Special Science Research Foundation Project,China(Grant No.201508026-02)+1 种基金the Natural Science Foundation of Heilongjiang Province,China(Grant No.A201310)the Scientific Research Starting Foundation for Post Doctorate of Heilongjiang Province,China(Grant No.LBHQ13040)
文摘Twin gold crystal nanowires, whose loading direction is parallel to the twin boundary orientation, are simulated.We calculate the nanowires under tensile or compressive loads, different length nanowires, and different twin boundary nanowires respectively. The Young modulus of nanowires under compressive load is about twice that under tensile load.The compressive properties of twin gold nanowires are superior to their tensile properties. For different length nanowires,there is a critical value of length with respect to the mechanical properties. When the length of nanowire is greater than the critical value, its mechanical properties are sensitive to length. The twin boundary spacing hardly affects the mechanical properties.
基金supported by the Natural Science Foundation of China(Grant number:NSFC11572095)。
文摘Safety of underground ammunition storage is an important issue,especially during the accidental ignition of missiles.This work investigates the pressure and temperature distribution of the multi-layer underground ammunition storage with a pressure relief duct during the accidental ignition process of the missile.A large-scale experiment was carried out using a multi-layered restricted space with a pressure relief duct to simulate the underground ammunition store and a solid rocket motor to simulate the accidental ignition of the missile.The results show that when the motor gas mass flow increased by5.6 times,the maximum pressure of the ammunition storage increased by 5.87 times.At a certain motor flow rate,when the pressure relief exhaust area at the end of the relief duct was reduced by 1/2,the maximum pressure on the first layer did not change.But the rate of pressure relief was reduced and the time delayed for the pressure of ammunition store to drop to zero.In this experiment,when the motor ignition position was located in to the third layer ammunition chamber,the maximum pressure was reduced by 32.9%and also reduced the rate of change of pressure.In addition,for the experimental conditions,the theoretical analysis of the pressure relief of the ammunition storage is given by a simplified model.Based on the findings,some suggestions to the safety protection design of ammunition store are proposed.
基金supported by the Fundamental Research Funds for the Central Universities of China(HEUCFZ1124,HEUCFR1005)the Open Research Fund Program of State Key Laboratory of Water Resources and Hydropower Engineering Science of China(2010B077)
文摘Organic pollutants could be degraded by using bubble discharge in water with gas aeration in the discharge reactor and more plasma can be generated in the discharge process. When pulsed high voltage was applied between electrodes with gas aerated into the reactor, it showed that bubbles were broken, which meant that breakdown took place. It could also be observed that the removal rate of phenol increased with increasing discharge voltage or pulse frequency, and with reducing initial phenol concentration or solution electric conductivity. It could remove more amount of phenol by oxygen aeration. With increasing oxygen flow rate, the removal rate increased. There was little difference with air or nitrogen aeration for phenol removal. The solution temperature after discharge increased to a great extent. However, this part of energy consumption did not contribute to the reaction, which led to a reduction in the energy utilization efficiency.
文摘The mechanical properties of copper nanocubes by molecular dynamics are investigated in this paper. The [100], [110], [111] nanocubes are created, and their energies, yield stresses, hydrostatic stresses, Mises stresses, and the relation- ships between them and strain are analyzed. Some concepts of the microscopic damage mechanics are introduced, which are the basis of studying the damage mechanical properties by molecular dynamics. The [100] nanocube exhibits homo- geneity and isotropy and achieves a balance easily. The [110] nanocube presents transverse isotropy. The [111] nanocube shows the complexity and anisotropy because the orientation sizes in three directions are different. The broken point occurs on a surface, but the other two do not. The [100] orientation model will be an ideal model for studying the microscopic damage theory.
基金supported by the National Natural Science Foundation of China(22101065 and 51972075)the Heilongjiang Provincial Natural Science Foundation of China(YQ2021B001)+1 种基金the Project funded by China Postdoctoral Science Foundation(2023T160153 and 2020M681075)the Fundamental Research Funds for the Central Universities.
文摘Indium selenide has garnered significant attention for high volumetric capacities,but is currently plagued by the sluggish charge transfer kinetics,severe volume effect,and rapid capacity degradation that hinder their practical applications.Herein,we design,synthesize,and characterize a multi-kernel-shell structure comprised of indium selenide encapsulated within carbon nanospheres(referred to as m-K-S In_(2)Se_(3)@C)through an integrated approach involving a hydrothermal method followed by a gaseous selenization process.Importantly,experimental measurements and density functional theory calculations confirm that the m-K-S In_(2)Se_(3)@C not only improve the adsorption capability for Li-ions but also lower the energy barrier for Li-ions diffusion.Profiting from numerous contact points,shorter diffusion distances and an improved volume buffering effect,the m-K-S In_(2)Se_(3)@C achieves an 800 mA h g^(−1)capacity over 1000 loops at 1000 mA g^(−1),a 520 mA h g^(−1)capacity at 5000 mA g^(−1)and an energy density of 270 Wh kg^(−1)when coupled with LiFePO4,surpassing most related anodes reported before.Broadly,the m-K-S structure with unique nano-micro structure offers a new approach to the design of advanced anodes for LIBs.
基金supported by the National Natural Science Foundations of China(No.11772185)Fundamental Research Funds for the Central Universities(No.3072022JC0202)。
文摘In the real-world situation,the lunar missions’scale and terrain are different according to various operational regions or worksheets,which requests a more flexible and efficient algorithm to generate task paths.A multi-scale ant colony planning method for the lunar robot is designed to meet the requirements of large scale and complex terrain in lunar space.In the algorithm,the actual lunar surface image is meshed into a gird map,the path planning algorithm is modeled on it,and then the actual path is projected to the original lunar surface and mission.The classical ant colony planning algorithm is rewritten utilizing a multi-scale method to address the diverse task problem.Moreover,the path smoothness is also considered to reduce the magnitude of the steering angle.Finally,several typical conditions to verify the efficiency and feasibility of the proposed algorithm are presented.
基金Project supported by the National Natural Science Foundation of China(Grant No.11702069)the Fundamental Research Funds for the Central Universities,China(Grant No.HEUCFM180203)
文摘Since the concept of invisible cloak was proposed by Pendry and Leonhardt in 2006, many researchers have applied the theory of coordinate transformation to thermodynamics and overcome the complexity of inhomogeneous and anisotropic of material parameters. However, only two-dimensional(2 D) thermal illusion devices are researched recently. According to this situation, our study focuses on three-dimensional(3 D) thermal illusion devices including shrinker(or invisible cloak),concentrator, amplifier, reshaper, and rotator with arbitrary shape in a general way. In this paper, the corresponding material parameters of thermal illusion devices mentioned above are derived based on the theory of transformation thermodynamics and the simulated results agree well with the theoretical derivations. In addition, the conventional invisible cloak just controls the temperature gradient rather than the temperature value which is more concerned in physical applications. Here,we find that the temperature value of the cloaked object can be controlled by adjusting the location of the original point of the coordinate system.
文摘Over the past century,the safety of dams has gradually attracted attention from all parties.Research on the dynamic response and damage evolution of dams under extreme loads is the basis of dam safety issues.In recent decades,scholars have studied the responses of dams under earthquake loads,but there is still much room for improvement in experimental and theoretical research on small probability loads such as explosions.In this paper,a 50-m-high concrete gravity dam is used as a prototype dam,and a water explosion model test of a 2.5-m-high concrete gravity dam is designed.The water pressure and the acceleration response of the dam body in the test are analysed.The pressure characteristics and dynamic response of the dam body are assessed.Taking the dam damage test as an example,a numerical model of concrete gravity dam damage is established,and the damage evolution of the dam body is analysed.By combining experiments and numerical simulations,the damage characteristics of the dam body under the action of different charge water explosions are clarified.The integrity of the dam body is well maintained under the action of a small-quantity water explosion,and the dynamic response of the dam body is mainly caused by the shock wave.Both the shock wave and the bubble pulsation cause the dam body to accelerate,and the peak acceleration of the dam body under the action of the bubble pulsation is only one percent of the peak acceleration of the dam body under the action of the shock wave.When subjected to explosions in large quantities of water,the dam body is seriously damaged.Under the action of a shock wave,the dam body produces a secondary acceleration response,which is generated by an internal interaction after the dam body is damaged.The damage evolution process of the dam body under the action of a large-scale water explosion is analysed,and it is found that the shock wave pressure of the water explosion causes local damage to the dam body facing the explosion.After the peak value of the shock wave,the impulse continues to act on the dam body,causing cumulative damage and damage inside the dam body.
基金supported by the Central University Basic Research Fund of China(No.3072022CFJ0202)the Central University Basic Research Fund of China(No.3072022CFJ0204)。
文摘A nonlinear sliding mode adaptive controller for a thin-film diffractive imaging system is designed to achieve accurate pointing direction over the attitude of subarrays in large-diameter mirror arrays.The kinematics and dynamics equations based on error quaternion and angular velocity are derived,and a diffractive thin-film sub-mirror array controller is designed to point precisely.Moreover,the global stability of the controller is proved by the Lyapunov method.Since the controller can adaptively identify the inertia matrix of each sub-mirror system,it is robust to bounded disturbances and changes in inertia parameters.At the same time,the continuous arctangent function is introduced,which is effectively anti-chattering.The simulation results show that the designed controller can ensure the accurate tracking of the diffractive film in each sub-mirror in the presence of rotational inertia matrix uncertainty and various disturbances.
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. HEUCF100212)the National Natural Science Foundation of China (Grant Nos. 51007013,10875024,and 10975026)
文摘In this paper, we adopt the modified Morozov secondary electron emission model to investigate the influence of the characteristic of a space-charge-saturated sheath near the insulated wall of the Hall thruster on the near-wall conductivity, by the method of two-dimensional （2D） particle simulation （2Dq-3V）. The results show that due to the sharp increase of collision frequency between the electrons and the wall under the space-charge-saturated sheath, the near-wall transport current under this sheath is remarkably higher than that under a classical sheath, and equals the near-wall transport current under a spatially oscillating sheath in order of magnitude. However, the transport currents under a space-charge-saturated sheath and a spatially oscillating sheath are different in mechanism, causing different current density distributions under the above two sheaths, and a great influence of channel width on the near-wall transport current under a space-charge-saturated sheath.
基金Project supported by the National Natural Science Foundation of China(Grant No.U1931121)the Natural Science Foundation of Heilongjiang Province in China(Grant No.ZD2020F002)+2 种基金111 Project to the Harbin Engineering University(Grant No.B13015)the Fundamental Research Funds for the Central Universities(Grant Nos.3072021CFT2501 and 3072021CF2508)the Postdoctoral Scientific Research Developmental Fund of Heilongjiang Province,China(Grant No.LBH-Q9097).
文摘Coding metasurfaces have attracted tremendous interests due to unique capabilities of manipulating electromagnetic wave.However,archiving transmissive coding metasurface is still challenging.Here we propose a transmissive anisotropic coding metasurface that enables the independent control of two orthogonal polarizations.The polarization beam splitter and the orbital angular momentum(OAM)generator have been studied as typical applications of the anisotropic 2-bit coding metasurface.The simulated far field patterns illustrate that the x and y polarized electromagnetic waves are deflected into two different directions,respectively.The anisotropic coding metasurface has been experimentally verified to realize an OAM beam with l=2 of right-handed polarized wave,resulting from both contributions from linear-to-circular polarization conversion and the phase profile modulation.This work is beneficial to enrich the polarization manipulation field and develop transmissive coding metasurfaces.
