Known as laser trapping,optical tweezers,with nanometer accuracy and pico-newton precision,plays a pivotal role in single bio-molecule measurements and controllable motions of micro-machines.In order to advance the fl...Known as laser trapping,optical tweezers,with nanometer accuracy and pico-newton precision,plays a pivotal role in single bio-molecule measurements and controllable motions of micro-machines.In order to advance the flourishing applications for those achievements,it is necessary to make clear the three-dimensional dynamic process of micro-particles stepping into an optical field.In this paper,we utilize the ray optics method to calculate the optical force and optical torque of a micro-sphere in optical tweezers.With the influence of viscosity force and torque taken into account,we numerically solve and analyze the dynamic process of a dielectric micro-sphere in optical tweezers on the basis of Newton mechanical equations under various conditions of initial positions and velocity vectors of the particle.The particle trajectory over time can demonstrate whether the particle can be successfully trapped into the optical tweezers center and reveal the subtle details of this trapping process.Even in a simple pair of optical tweezers,the dielectric micro-sphere exhibits abundant phases of mechanical motions including acceleration,deceleration,and turning.These studies will be of great help to understand the particle-laser trap interaction in various situations and promote exciting possibilities for exploring novel ways to control the mechanical dynamics of microscale particles.展开更多
The natural dynamic characteristics of a circular cylindrical tube made of three-directional(3 D)functional graded material(FGM)based on the Timoshenko beam theory are investigated.Hamilton’s principle is utilized to...The natural dynamic characteristics of a circular cylindrical tube made of three-directional(3 D)functional graded material(FGM)based on the Timoshenko beam theory are investigated.Hamilton’s principle is utilized to derive the novel motion equations of the tube,considering the interactions among the longitudinal,transverse,and rotation deformations.By dint of the differential quadrature method(DQM),the governing equations are discretized to conduct the analysis of natural dynamic characteristics.The Ritz method,in conjunction with the finite element method(FEM),is introduced to verify the present results.It is found that the asymmetric modes in the tube are controlled by the 3 D FGM,which exhibit more complicated shapes compared with the unidirectional(1 D)and bi-directional(2 D)FGM cases.Numerical examples illustrate the effects of the axial,radial,and circumferential FGM indexes as well as the supported edges on the natural dynamic characteristics in detail.It is notable that the obtained results are beneficial for accurate design of smart structures composed from multi-directional FGM.展开更多
For safety reasons,in the automated dispensing medicines process,robots and humans cooperate to accomplish the task of drug sorting and distribution.In this dynamic unstructured environment,such as a humanrobot collab...For safety reasons,in the automated dispensing medicines process,robots and humans cooperate to accomplish the task of drug sorting and distribution.In this dynamic unstructured environment,such as a humanrobot collaboration scenario,the safety of human,robot,and equipment in the environment is paramount.In this work,a practical and effective robot motion planning method is proposed for dynamic unstructured environments.To figure out the problems of blind zones of single depth sensor and dynamic obstacle avoidance,we first propose a method for establishing offline mapping and online fusion of multi-sensor depth images and 3D grids of the robot workspace,which is used to determine the occupation states of the 3D grids occluded by robots and obstacles and to conduct real-time estimation of the minimum distance between the robot and obstacles.Then,based on the reactive control method,the attractive and repulsive forces are calculated and transformed into robot joint velocities to avoid obstacles in real time.Finally,the robot’s dynamic obstacle avoidance ability is evaluated on an experimental platform with a UR5 robot and two KinectV2 RGB-D sensors,and the effectiveness of the proposed method is verified.展开更多
High-energy gas fracturing of shale is a novel,high efficacy and eco-friendly mining technique,which is a typical dynamic perturbing behavior.To effectively extract shale gas,it is important to understand the dynamic ...High-energy gas fracturing of shale is a novel,high efficacy and eco-friendly mining technique,which is a typical dynamic perturbing behavior.To effectively extract shale gas,it is important to understand the dynamic mechanical properties of shale.Dynamic experiments on shale subjected to true triaxial compression at different strain rates are first conducted in this research.The dynamic stress-strain curves,peak strain,peak stress and failure modes of shale are investigated.The results of the study indicate that the intermediate principal stress and the minor principal stress have the significant influence on the dynamic mechanical behaviors,although this effect decreases as the strain rate increases.The characteristics of compression-shear failure primarily occur in shale subjected to triaxial compression at high strain rates,which distinguishes it from the fragmentation characteristics observed in shale under dynamic uniaxial compression.Additionally,a numerical three-dimensional Split Hopkinson Pressure Bar(3D-SHPB),which is established by coupling PFC3D and FLAC3D methods,is validated to replicate the laboratory characteristics of shale.The dynamic mechanical characteristics of shale subjected to different confining stresses are systematically investigated by the coupling PFC3D and FLAC3D method.The numerical results are in good agreement with the experimental data.展开更多
Wire arc additive manufacturing(WAAM)has emerged as a promising technique for producing large-scale metal components,favoured by high deposition rates,flexibility and low cost.Despite its potential,the complexity of W...Wire arc additive manufacturing(WAAM)has emerged as a promising technique for producing large-scale metal components,favoured by high deposition rates,flexibility and low cost.Despite its potential,the complexity of WAAM processes,which involves intricate thermal dynamics,phase transitions,and metallurgical,mechanical,and chemical interactions,presents considerable challenges in final product qualities.Simulation technologies in WAAM have proven invaluable,providing accurate predictions in key areas such as material properties,defect identification,deposit morphology,and residual stress.These predictions play a critical role in optimising manufacturing strategies for the final product.This paper provides a comprehensive review of the simulation techniques applied in WAAM,tracing developments from 2013 to 2023.Initially,it analyses the current challenges faced by simulation methods in three main areas.Subsequently,the review explores the current modelling approaches and the applications of these simulations.Following this,the paper discusses the present state of WAAM simulation,identifying specific issues inherent to WAAM simulation itself.Finally,through a thorough review of existing literature and related analysis,the paper offers future perspectives on potential advancements in WAAM simulation strategies.展开更多
In this paper, the effect of green water impact on a flexible structure is studied based on three-step computational fluid dynamics(CFD)–boundary element method(BEM)–finite element method(FEM) approach. The impact d...In this paper, the effect of green water impact on a flexible structure is studied based on three-step computational fluid dynamics(CFD)–boundary element method(BEM)–finite element method(FEM) approach. The impact due to shipping of water on the deck of the vessel is computed using commercial CFD software and used as an external force in coupled BEM-FEM solver. Other hydrodynamic forces such as radiation, diffraction, and Froude-Krylov forces acting on the structure are evaluated using 3 D time domain panel method. To capture the structural responses such as bending moment and shear force, 1 D finite element method is developed. Moreover, a direct integration scheme based on the Newmark–Beta method is employed to get the structural velocity,displacement, etc., at each time step. To check the effect of the green water impact on the structure, a rectangular barge without forward speed is taken for the analysis. The influence is studied in terms of bending moment, shear force, etc. Results show that the effect of green water impact on the bow region can be severe in extreme seas and lead to various structural damages. Similarly,it is also verified that vessel motion affects green water loading significantly and therefore one must consider its effect while designing a vessel.展开更多
To find the distribution patterns of dynamic amplification coefficients for dams subjected to earthquake, 3D seismic responses of concrete-faced rockfill dams with different heights and different shapes of river valle...To find the distribution patterns of dynamic amplification coefficients for dams subjected to earthquake, 3D seismic responses of concrete-faced rockfill dams with different heights and different shapes of river valley were analyzed by using the equivalent-linear model. Statistical analysis was also made to the seismic coefficient, and an empirical formula for calculating the maximum acceleration was provided. The results indicate that under the condition of the same dam height and the same base acceleration excitations, with the increase of the river valley width, the position of the maximum acceleration on the axis of the top of the dam moves from the center to the riversides symmetrically. For the narrow valleys, the maximum acceleration occurs in the middle of the axis at the top of the dam; for wide valleys the maximum acceleration appears near the riversides. The result negates the application of 2D dynamical computation for wide valleys, and shows that for the seismic response of high concrete-faced rockfill dams, the seismic coefficient along the axis should be given, except for that along the dam height. Seismic stability analysis of rockfill dams using pseudo-static method can be modified according to the formula.展开更多
Modeling has become phenomenal in developing new products.In the case of filters,one of the mos applied procedures is via the construction of idealized physical computational models bearing close semblance to real fil...Modeling has become phenomenal in developing new products.In the case of filters,one of the mos applied procedures is via the construction of idealized physical computational models bearing close semblance to real filter media.It is upon these that multi-physics tools were applied to analvze the fow of fuid and the resulting typical performance parameters.In this work,two 3D filter membranes were constructed with MATLAB:one had a random distribution of unimodal nanofibers,and the other,a novel modification,formed.a bimodal distribution:both of them had similar dimensions and solid volume fractions.A comparison of their performance in a dust-loading environment was made by using computational fluid dynamic-discrete elemen method(CED-DEM)coupling technique in STAR-CCM+.It was found that the bimodal nanofiber membrane greatly improved the particle capture efficiencv.Whereas this increased the pressure drop,the gain was not toosignificant.Thus.overall,the results of the figure of merit ptoved that adopting a bimodal formation improved the filter's quality.展开更多
Tunnel deformation is a direct manifestation of the stress redistribution of rock and soil masses,and high-precision monitoring of it is an important challenge in the eld of geophysical engineering.This study applies ...Tunnel deformation is a direct manifestation of the stress redistribution of rock and soil masses,and high-precision monitoring of it is an important challenge in the eld of geophysical engineering.This study applies the improved PS-InSAR technology to tunnel deformation monitoring,overcoming the limitations of traditional methods(such as total stations)with limited spatial coverage and poor continuity.Four core innovations enable millimeter-level precision breakthroughs:adaptive quality map fusion of coherence coefficientγand phase derivative variance for dynamic reliable area partitioning;branch-cutting method optimization using residual point clustering and Canny forbidden-zone constraints reduces invalid paths by 40%while suppressing lining joint phase jumps;dynamic weighted least squares(WLS)model integrating weighted coherence with blast disturbance gradient achieves 52%high-frequency noise suppression and precise separation of short-period construction disturbance signals;3D integral correction introduces DEM dynamic calibration projection coefcient k(improving by 30%in curved sections),reducing axial projection error from 15%-30%to<5%.In the Yunnan Amai Tunnel eld test,spatial resolution reaches 0.1m in sensitive zones with deformation inversion error<5%,successfully capturing instantaneous blasting deformation(0.46-0.49mm)and structural trend displacement at the face.The monitoring accuracy is more than three times higher than traditional methods,providing reliable technical support for safety warnings in high-risk sections.展开更多
结合东坪金矿南山采区1号空区的工程实际,采用Plaxis 3D Tunnel对其建立三维数值模型,并对其不同开挖顺序的开挖过程进行数值模拟。通过对开采过程中的地压活动规律和围岩稳定性进行分析,论证了地下采空区开挖方案的可行性,揭示了采空...结合东坪金矿南山采区1号空区的工程实际,采用Plaxis 3D Tunnel对其建立三维数值模型,并对其不同开挖顺序的开挖过程进行数值模拟。通过对开采过程中的地压活动规律和围岩稳定性进行分析,论证了地下采空区开挖方案的可行性,揭示了采空区不同开挖阶段应力的集中部位和围岩的潜在破坏部位。计算表明该空区由上向下开挖顺序较为有利,其开挖过程总体可以保持稳定,但也存在不安全隐患。计算结果对该矿山的安全生产具有指导意义。展开更多
基金This work is supported by the National Natural Science Foundation of China(Grant No.11974119 and No.11804399)the Guangdong Innovative and Entrepreneurial Research Team Program(Grant No.2016ZT06C594)+1 种基金the Fundamental Research Funds for the Central Universities,South-Central University for Nationalities(Grant No.CZQ20018)National Key R&D Program of China(No.2018YFA 0306200).
文摘Known as laser trapping,optical tweezers,with nanometer accuracy and pico-newton precision,plays a pivotal role in single bio-molecule measurements and controllable motions of micro-machines.In order to advance the flourishing applications for those achievements,it is necessary to make clear the three-dimensional dynamic process of micro-particles stepping into an optical field.In this paper,we utilize the ray optics method to calculate the optical force and optical torque of a micro-sphere in optical tweezers.With the influence of viscosity force and torque taken into account,we numerically solve and analyze the dynamic process of a dielectric micro-sphere in optical tweezers on the basis of Newton mechanical equations under various conditions of initial positions and velocity vectors of the particle.The particle trajectory over time can demonstrate whether the particle can be successfully trapped into the optical tweezers center and reveal the subtle details of this trapping process.Even in a simple pair of optical tweezers,the dielectric micro-sphere exhibits abundant phases of mechanical motions including acceleration,deceleration,and turning.These studies will be of great help to understand the particle-laser trap interaction in various situations and promote exciting possibilities for exploring novel ways to control the mechanical dynamics of microscale particles.
基金Project supported by the National Natural Science Foundation of China(Nos.11902001 and12072221)the China Postdoctoral Science Foundation(No.2018M641643)the Anhui Provincial Natural Science Foundation of China(Nos.1908085QA13 and 1808085ME128)。
文摘The natural dynamic characteristics of a circular cylindrical tube made of three-directional(3 D)functional graded material(FGM)based on the Timoshenko beam theory are investigated.Hamilton’s principle is utilized to derive the novel motion equations of the tube,considering the interactions among the longitudinal,transverse,and rotation deformations.By dint of the differential quadrature method(DQM),the governing equations are discretized to conduct the analysis of natural dynamic characteristics.The Ritz method,in conjunction with the finite element method(FEM),is introduced to verify the present results.It is found that the asymmetric modes in the tube are controlled by the 3 D FGM,which exhibit more complicated shapes compared with the unidirectional(1 D)and bi-directional(2 D)FGM cases.Numerical examples illustrate the effects of the axial,radial,and circumferential FGM indexes as well as the supported edges on the natural dynamic characteristics in detail.It is notable that the obtained results are beneficial for accurate design of smart structures composed from multi-directional FGM.
基金the Interdisciplinary Program of Shanghai Jiao Tong University(No.YG2019QNA25)。
文摘For safety reasons,in the automated dispensing medicines process,robots and humans cooperate to accomplish the task of drug sorting and distribution.In this dynamic unstructured environment,such as a humanrobot collaboration scenario,the safety of human,robot,and equipment in the environment is paramount.In this work,a practical and effective robot motion planning method is proposed for dynamic unstructured environments.To figure out the problems of blind zones of single depth sensor and dynamic obstacle avoidance,we first propose a method for establishing offline mapping and online fusion of multi-sensor depth images and 3D grids of the robot workspace,which is used to determine the occupation states of the 3D grids occluded by robots and obstacles and to conduct real-time estimation of the minimum distance between the robot and obstacles.Then,based on the reactive control method,the attractive and repulsive forces are calculated and transformed into robot joint velocities to avoid obstacles in real time.Finally,the robot’s dynamic obstacle avoidance ability is evaluated on an experimental platform with a UR5 robot and two KinectV2 RGB-D sensors,and the effectiveness of the proposed method is verified.
基金supported by the National Natural Science Foundation of China(Nos.51839009 and 52027814)the Natural Science Foundation of Hubei Province(No.2023AFB589).
文摘High-energy gas fracturing of shale is a novel,high efficacy and eco-friendly mining technique,which is a typical dynamic perturbing behavior.To effectively extract shale gas,it is important to understand the dynamic mechanical properties of shale.Dynamic experiments on shale subjected to true triaxial compression at different strain rates are first conducted in this research.The dynamic stress-strain curves,peak strain,peak stress and failure modes of shale are investigated.The results of the study indicate that the intermediate principal stress and the minor principal stress have the significant influence on the dynamic mechanical behaviors,although this effect decreases as the strain rate increases.The characteristics of compression-shear failure primarily occur in shale subjected to triaxial compression at high strain rates,which distinguishes it from the fragmentation characteristics observed in shale under dynamic uniaxial compression.Additionally,a numerical three-dimensional Split Hopkinson Pressure Bar(3D-SHPB),which is established by coupling PFC3D and FLAC3D methods,is validated to replicate the laboratory characteristics of shale.The dynamic mechanical characteristics of shale subjected to different confining stresses are systematically investigated by the coupling PFC3D and FLAC3D method.The numerical results are in good agreement with the experimental data.
基金supported in part by China Scholarship Council under Grant 202208200010。
文摘Wire arc additive manufacturing(WAAM)has emerged as a promising technique for producing large-scale metal components,favoured by high deposition rates,flexibility and low cost.Despite its potential,the complexity of WAAM processes,which involves intricate thermal dynamics,phase transitions,and metallurgical,mechanical,and chemical interactions,presents considerable challenges in final product qualities.Simulation technologies in WAAM have proven invaluable,providing accurate predictions in key areas such as material properties,defect identification,deposit morphology,and residual stress.These predictions play a critical role in optimising manufacturing strategies for the final product.This paper provides a comprehensive review of the simulation techniques applied in WAAM,tracing developments from 2013 to 2023.Initially,it analyses the current challenges faced by simulation methods in three main areas.Subsequently,the review explores the current modelling approaches and the applications of these simulations.Following this,the paper discusses the present state of WAAM simulation,identifying specific issues inherent to WAAM simulation itself.Finally,through a thorough review of existing literature and related analysis,the paper offers future perspectives on potential advancements in WAAM simulation strategies.
基金supported by Naval Research Board,India under Project No.NRB-344/HYD/14-15
文摘In this paper, the effect of green water impact on a flexible structure is studied based on three-step computational fluid dynamics(CFD)–boundary element method(BEM)–finite element method(FEM) approach. The impact due to shipping of water on the deck of the vessel is computed using commercial CFD software and used as an external force in coupled BEM-FEM solver. Other hydrodynamic forces such as radiation, diffraction, and Froude-Krylov forces acting on the structure are evaluated using 3 D time domain panel method. To capture the structural responses such as bending moment and shear force, 1 D finite element method is developed. Moreover, a direct integration scheme based on the Newmark–Beta method is employed to get the structural velocity,displacement, etc., at each time step. To check the effect of the green water impact on the structure, a rectangular barge without forward speed is taken for the analysis. The influence is studied in terms of bending moment, shear force, etc. Results show that the effect of green water impact on the bow region can be severe in extreme seas and lead to various structural damages. Similarly,it is also verified that vessel motion affects green water loading significantly and therefore one must consider its effect while designing a vessel.
基金Project(90815024) supported by the National Natural Science Foundation of China
文摘To find the distribution patterns of dynamic amplification coefficients for dams subjected to earthquake, 3D seismic responses of concrete-faced rockfill dams with different heights and different shapes of river valley were analyzed by using the equivalent-linear model. Statistical analysis was also made to the seismic coefficient, and an empirical formula for calculating the maximum acceleration was provided. The results indicate that under the condition of the same dam height and the same base acceleration excitations, with the increase of the river valley width, the position of the maximum acceleration on the axis of the top of the dam moves from the center to the riversides symmetrically. For the narrow valleys, the maximum acceleration occurs in the middle of the axis at the top of the dam; for wide valleys the maximum acceleration appears near the riversides. The result negates the application of 2D dynamical computation for wide valleys, and shows that for the seismic response of high concrete-faced rockfill dams, the seismic coefficient along the axis should be given, except for that along the dam height. Seismic stability analysis of rockfill dams using pseudo-static method can be modified according to the formula.
基金the Chang Jiang Youth Scholars Program of China(No.51773037)the National Natural Science Foundation of China(Nos.51803023 and 61771123)+2 种基金the Shanghai Sailing Program(No.18YF1400400)the China Postdoctoral Science Foundation(No.2018M640317)the Fundamental Hesearch Funds for the Central Universities(No.2232018A3-11)。
文摘Modeling has become phenomenal in developing new products.In the case of filters,one of the mos applied procedures is via the construction of idealized physical computational models bearing close semblance to real filter media.It is upon these that multi-physics tools were applied to analvze the fow of fuid and the resulting typical performance parameters.In this work,two 3D filter membranes were constructed with MATLAB:one had a random distribution of unimodal nanofibers,and the other,a novel modification,formed.a bimodal distribution:both of them had similar dimensions and solid volume fractions.A comparison of their performance in a dust-loading environment was made by using computational fluid dynamic-discrete elemen method(CED-DEM)coupling technique in STAR-CCM+.It was found that the bimodal nanofiber membrane greatly improved the particle capture efficiencv.Whereas this increased the pressure drop,the gain was not toosignificant.Thus.overall,the results of the figure of merit ptoved that adopting a bimodal formation improved the filter's quality.
基金supported by the Science and Technology Innovation and Demonstration Project of the Department of Transport of Yunnan Province(Project No.2023-166).
文摘Tunnel deformation is a direct manifestation of the stress redistribution of rock and soil masses,and high-precision monitoring of it is an important challenge in the eld of geophysical engineering.This study applies the improved PS-InSAR technology to tunnel deformation monitoring,overcoming the limitations of traditional methods(such as total stations)with limited spatial coverage and poor continuity.Four core innovations enable millimeter-level precision breakthroughs:adaptive quality map fusion of coherence coefficientγand phase derivative variance for dynamic reliable area partitioning;branch-cutting method optimization using residual point clustering and Canny forbidden-zone constraints reduces invalid paths by 40%while suppressing lining joint phase jumps;dynamic weighted least squares(WLS)model integrating weighted coherence with blast disturbance gradient achieves 52%high-frequency noise suppression and precise separation of short-period construction disturbance signals;3D integral correction introduces DEM dynamic calibration projection coefcient k(improving by 30%in curved sections),reducing axial projection error from 15%-30%to<5%.In the Yunnan Amai Tunnel eld test,spatial resolution reaches 0.1m in sensitive zones with deformation inversion error<5%,successfully capturing instantaneous blasting deformation(0.46-0.49mm)and structural trend displacement at the face.The monitoring accuracy is more than three times higher than traditional methods,providing reliable technical support for safety warnings in high-risk sections.
文摘结合东坪金矿南山采区1号空区的工程实际,采用Plaxis 3D Tunnel对其建立三维数值模型,并对其不同开挖顺序的开挖过程进行数值模拟。通过对开采过程中的地压活动规律和围岩稳定性进行分析,论证了地下采空区开挖方案的可行性,揭示了采空区不同开挖阶段应力的集中部位和围岩的潜在破坏部位。计算表明该空区由上向下开挖顺序较为有利,其开挖过程总体可以保持稳定,但也存在不安全隐患。计算结果对该矿山的安全生产具有指导意义。
