Most existing path planning approaches rely on discrete expansions or localized heuristics that can lead to extended re-planning,inefficient detours,and limited adaptability to complex obstacle distributions.These iss...Most existing path planning approaches rely on discrete expansions or localized heuristics that can lead to extended re-planning,inefficient detours,and limited adaptability to complex obstacle distributions.These issues are particularly pronounced when navigating cluttered or large-scale environments that demand both global coverage and smooth trajectory generation.To address these challenges,this paper proposes a Wave Water Simulator(WWS)algorithm,leveraging a physically motivated wave equation to achieve inherently smooth,globally consistent path planning.In WWS,wavefront expansions naturally identify safe corridors while seamlessly avoiding local minima,and selective corridor focusing reduces computational overhead in large or dense maps.Comprehensive simulations and real-world validations-encompassing both indoor and outdoor scenarios-demonstrate that WWS reduces path length by 2%-13%compared to conventional methods,while preserving gentle curvature and robust obstacle clearance.Furthermore,WWS requires minimal parameter tuning across diverse domains,underscoring its broad applicability to warehouse robotics,field operations,and autonomous service vehicles.These findings confirm that the proposed wave-based framework not only bridges the gap between local heuristics and global coverage but also sets a promising direction for future extensions toward dynamic obstacle scenarios and multi-agent coordination.展开更多
Accuracy allocation is crucial in the accuracy design of machining tools.Current accuracy allocation methods primarily focus on positional deviation,with little consideration for tool direction deviation.To address th...Accuracy allocation is crucial in the accuracy design of machining tools.Current accuracy allocation methods primarily focus on positional deviation,with little consideration for tool direction deviation.To address this issue,we propose a geometric error cost sensitivity-based accuracy allocation method for five-axis machine tools.A geometric error model consisting of 4l error components is constructed based on homogeneous transformation matrices.Volumetric points with positional and tool direction deviations are randomly sampled to evaluate the accuracy of the machine tool.The sensitivity of each error component at these sampling points is analyzed using the Sobol method.To balance the needs of geometric precision and manufacturing cost,a geometric error cost sensitivity function is developed to estimate the required cost.By allocating error components affecting tool direction deviation first and the remaining components second,this allocation scheme ensures that both deviations meet the requirements.We also perform numerical simulation of a BC-type(B-axis and C-axis type)five-axis machine tool to validate the method.The results show that the new allocation scheme reduces the total geometric error cost by 27.8%compared to a uniform allocation scheme,and yields the same positional and tool direction machining accuracies.展开更多
A simulation system for five axis NC machining using general cutting tools is presented This system differs from other simulation system in that it not only focuses on the geometric simulation but also focuses on t...A simulation system for five axis NC machining using general cutting tools is presented This system differs from other simulation system in that it not only focuses on the geometric simulation but also focuses on the collision detection which is usually not included in NC machining simulation Besides all of these, estimating cutting forces is also discussed In order to obtain high efficiency, all algorithms use swept volume modeling technique, so the simulation system is compact and can be performed efficiently展开更多
Recent progress in microwave absorption materials stimulates the extensive exploration of rare earth oxide materials.Herein,we report the synthesis of a hollow sphere-based carbon material compounded with rare earth o...Recent progress in microwave absorption materials stimulates the extensive exploration of rare earth oxide materials.Herein,we report the synthesis of a hollow sphere-based carbon material compounded with rare earth oxides.Hollow N-doped carbon nano-spheres loaded ceria composites(H-NC@CeO_(2))were designed and prepared by the template method,combined with in-situ coating,pyrolysis and chemical etching.By controlling the loading content of H-NC@CeO_(2)and adjusting the impedance matching of the material,the H-NC@CeO_(2)/PS(polystyrene)composite exhibited a minimum reflection loss(RL)of-50.8 dB and an effective absorption band-width(EAB)of 4.64 GHz at a filler ratio of 20wt%and a thickness of 2 mm.In accordance with measured electromagnetic parameters,simulations using the high frequency structure simulator(HFSS)software were conducted to investigate the impact of the honeycomb structure on the electromagnetic wave performance of H-NC@CeO_(2)/PS.By calculating the surface electric field and the material’s bulk loss density,the mechanism of electromagnetic loss for the honeycomb structure was elaborated.A method for structural design and man-ufacturing of broadband absorbing devices was proposed and a broadband absorber with an EAB of 11.9 GHz was prepared.This study presents an innovative approach to designing advanced electromagnetic(EM)wave absorbing materials with broad absorption band-widths.展开更多
A sudden increase in the radial depth(SIRD)is a distinctive phenomenon in plunge milling.It is typically characterized by a sharp increase in cutting force at the end of the axial feed of the tool,accompanied by harsh...A sudden increase in the radial depth(SIRD)is a distinctive phenomenon in plunge milling.It is typically characterized by a sharp increase in cutting force at the end of the axial feed of the tool,accompanied by harsh machine vibration sounds,which can negatively impact the reliability of plunge milling.This paper proposes an optimization method to eliminate SIRD in five-axis plunge milling.Initially,a five-axis plunge milling experiment and an analysis of the spatial position relationship between the plunge tools and the workpiece revealed that the cause of SIRD is unreasonable tool path planning.Subsequently,using the cutter position and cutter axis vector as variables,an SIRD discrimination model was developed for adjacent cutter positions and extended to multiple cutter positions.Optimizing the plunge milling tool path is considered a multivariate optimization problem that involves determining the cutter point and cutter axis vector.The SIRD discrimination model was used as a constraint function to aid in solving for the variables.The simulation and experimental results indicate that with the remaining volume of material as the optimization target,the optimized plunge milling tool path results in a residual material volume that is less than 60%of the gradually decreasing plunge depth.This optimization decreases the subsequent semi-finishing time of the workpiece and enhances machining efficiency.Additionally,it does not rely on operator experience and facilitates efficient automated optimization of the tool path to exclude SIRD.展开更多
Compared with traditional open surgery,laparoscopic surgery significantly reduces bodily trauma,postoperative pain,and hospitalization duration.However,owing to the small size of incisions and the counterintuitive mot...Compared with traditional open surgery,laparoscopic surgery significantly reduces bodily trauma,postoperative pain,and hospitalization duration.However,owing to the small size of incisions and the counterintuitive motion of surgical tools,longer training cycles are required for surgeons to achieve fine operational skills.This paper presents a laparoscopic surgery simulator with haptic-feedback control(LSHC-6)that provides a reliable and cost-effective training alternative for surgeons.In addition to the structural diagram,kinematic analysis,and gravity compensation algorithm,a particle swarm optimization algorithm(PSO)is applied to optimize the structural parameters of the simulator by evaluating its workspace,global dexterity,and gravity compensation ability.A prototype system was developed and evaluated using two training experiments.The results demonstrate that the simulator exhibits good operational fluidity,workspace,and stable force output,effectively meeting the needs of laparoscopic surgical training.展开更多
BACKGROUND Although exposure therapy is a proven treatment for post-traumatic stress disorder(PTSD),empirical research is difficult due to ethical issues.Recently,virtual reality-based content that can provide space a...BACKGROUND Although exposure therapy is a proven treatment for post-traumatic stress disorder(PTSD),empirical research is difficult due to ethical issues.Recently,virtual reality-based content that can provide space and time similar to reality for exposure therapy techniques is increasing.AIM To examine exposure therapy using driving simulations in patients with PTSD due to traffic accidents with PTSD symptoms.METHODS The intervention was provided to two individuals who experienced PTSD symptoms after a traffic accident using a driving simulator.Among the singlesubject experimental designs,the ABA(baseline-intervention-baseline)design was used,and the PTSD checklist and brain wave frequency were used to measure the results.RESULTS In all participants,the standard category departure time of the electroencephalogram decreased from baseline,and PTSD symptoms decreased after the intervention.CONCLUSION These results suggest the potential use of a driving simulator as an exposure treatment tool for PTSD.展开更多
The ground-based experimental tests are crucial to verify the related technologies of the drag-free satellite.This work presents a design method of the ground simulator testbed for emulating the planar dynamics of the...The ground-based experimental tests are crucial to verify the related technologies of the drag-free satellite.This work presents a design method of the ground simulator testbed for emulating the planar dynamics of the space drag-free systems.In this paper,the planar dynamic characteristics of the drag-free satellite with double test masses are analyzed and nondimensionalized.A simulator vehicle composed of an air bearing testbed and two inverted pendulums is devised on the basic of equivalent mass and equivalent stiffness proposed firstly in this paper.And the dynamic model of the simulator equivalent to the sensitive axis motion of the test mass and the planar motion of the satellite is derived from the Euler-Lagrange method.Then,the dynamic equivalence conditions between the space prototype system and the ground model system are derived from Pi theorem.To satisfy these conditions,the scaling laws of two systems and requirements for the inverted pendulum are put forward.Besides,the corresponding control scaling laws and a closed-loop control strategy are deduced and applied to establishing the numerical simulation experiments of underactuated system.Subsequently,the comparative simulation results demonstrate the similarity of dynamical behavior between the scaled-down ground model and the space prototype.As a result,the rationality and effectiveness of the design method are proved,facilitating the ground simulation of future gravitational wave detection satellites.展开更多
Large-scale physical simulation is essential for advancing our understanding of natural gas hydrates exploitation mechanism.However,cylinder-shaped simulators often face challenges in balancing large volume,controllab...Large-scale physical simulation is essential for advancing our understanding of natural gas hydrates exploitation mechanism.However,cylinder-shaped simulators often face challenges in balancing large volume,controllability,and comprehensive monitoring.In this study,we developed a fan columnshaped hydrate simulator(FCHS)with an internal angle of 6°,a radius of 3 m,and an inner height of0.3 m,resulting in an effective volume of~142 L.Moreover,the FCHS is equipped with an integrated"thermal-pressure-acoustic"sensing system,enabling in-situ monitoring of temperature,pressure,and P-wave velocity evolution during hydrate formation and dissociation process.The experimental results indicate that a pressure gradient successfully established from the reservoir center toward its boundaries during depressurization stage,and pressure propagation is relatively slow,resulting in a radial pressure difference of 3-4 MPa within a 3 m range.Once the system reaches pressure equilibrium,the pressure difference decreases to 0.3-0.4 MPa.The depressurization at the wellbore promotes hydrate dissociation in the near-well region,resulting in the radial temperature difference reaches~1.5℃ along the radial direction.The acoustic data reveals that a radial gradient in hydrate saturation gradually forms from the center to the boundary during depressurization-induced gas production.The evolutions of spatio-temporal multi-fields obtained in the FCHS are consist with that of field production.The FCHS proves to be a cutting-edge platform for experimental simulation of NGH exploitation and carbon sequestration processes.展开更多
Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing addit...Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.展开更多
The size and shape effect(SSE)of components has become a critical issue for mechanical properties,application reliability,and processing.In this study,the creep rupture life(CRL)of components with different wall thick...The size and shape effect(SSE)of components has become a critical issue for mechanical properties,application reliability,and processing.In this study,the creep rupture life(CRL)of components with different wall thicknesses and positions in a combustion chamber casing simulator made of K439B superalloy was investigated.The intrinsic mechanisms of the SSE were explored from the dendrite structure,volume fraction and size of theγ'phase,and element segregation,etc.It is shown that this casting exhibits a strong SSE of creep rupture life,characterized by a significant difference in the CRL values up to 60%with the variation of wall thickness and position in the casing.In terms of casting technology,the influence of SSE on CRL is actually determined by the cooling rate.The SSE on the creep rupture life originates from the dendrite structure(such as the secondary dendrite arm spacing),volume fraction size of theγ'phase in the dendrite trunk,and elements segregation rate.This work may have implications for the design and application of engineering components with large sizes and complex structures.展开更多
Atomistic simulations were adopted to study the solute segregation effect on dislocation transmutation across the{1012}twin boundaries in magnesium.For pure magnesium,the dislocation-twin reaction resulted in the form...Atomistic simulations were adopted to study the solute segregation effect on dislocation transmutation across the{1012}twin boundaries in magnesium.For pure magnesium,the dislocation-twin reaction resulted in the formation of sessile dislocations accompanied by the fast migration of the twin boundary,and no〈c+a〉dislocation occurred.With Al segregation,instead,two basal dislocations transmuted into one prismatic〈c+a〉dislocation in the twin.Twin migration was significantly impeded,and the resultant twin disconnections stayed localized and had a higher step character than in pure Mg.To reveal the mechanism of the effect of solute segregation,the Peierls barriers of twin disconnections were calculated,and the dynamic evolutions of twin disconnection dipoles were simulated.The results suggested that Al segregation softened the Peierls barrier of twin disconnections but imposed a high pinning force on twin disconnections,thus attenuating their mobility.Moreover,given the same Al segregation,the twin disconnection dipole with a higher step showed greater stability,which explained the presence of localized twin disconnections with a higher step in the cases with Al segregation than in pure magnesium.The solute segregation induced low mobility of twin disconnections contributed to the occurrence of〈c+a〉dislocations.展开更多
The F_(1)-ATPase and V_(1)-ATPase are rotary biomotors.Alignment of their amino acid sequences,which originate from bovine heart mitochondria(1BMF)and Enterococcus hirae(3VR6),respectively,demonstrates that the segmen...The F_(1)-ATPase and V_(1)-ATPase are rotary biomotors.Alignment of their amino acid sequences,which originate from bovine heart mitochondria(1BMF)and Enterococcus hirae(3VR6),respectively,demonstrates that the segment forming the ATP catalytic pocket is highly conserved.Single-molecule experiments,however,have revealed subtle differences in efficiency between the F_(1) and V_(1) motors.Here,we perform both atomistic and coarse-grained molecular dynamics simulations to investigate the mechanochemical coupling and coordination in F_(1) and V_(1) ATPase.Our results show that the correlation between conformational changes in F_(1) is stronger than that in V_(1),indicating that the mechanochemical coupling in F_(1) is tighter than in V_(1).Moreover,the unidirectional rotation of F_(1) is more processive than that of V_(1),which accounts for the higher efficiency observed in F_(1) and explains the occasional backward steps detected in single-molecule experiments on V_(1).展开更多
The rapid advancement of machine learning based tight-binding Hamiltonian(MLTB)methods has opened new avenues for efficient and accurate electronic structure simulations,particularly in large-scale systems and long-ti...The rapid advancement of machine learning based tight-binding Hamiltonian(MLTB)methods has opened new avenues for efficient and accurate electronic structure simulations,particularly in large-scale systems and long-time scenarios.This review begins with a concise overview of traditional tight-binding(TB)models,including both(semi-)empirical and first-principles approaches,establishing the foundation for understanding MLTB developments.We then present a systematic classification of existing MLTB methodologies,grouped into two major categories:direct prediction of TB Hamiltonian elements and inference of empirical parameters.A comparative analysis with other ML-based electronic structure models is also provided,highlighting the advancement of MLTB approaches.Finally,we explore the emerging MLTB application ecosystem,highlighting how the integration of MLTB models with a diverse suite of post-processing tools from linear-scaling solvers to quantum transport frameworks and molecular dynamics interfaces is essential for tackling complex scientific problems across different domains.The continued advancement of this integrated paradigm promises to accelerate materials discovery and open new frontiers in the predictive simulation of complex quantum phenomena.展开更多
文摘Most existing path planning approaches rely on discrete expansions or localized heuristics that can lead to extended re-planning,inefficient detours,and limited adaptability to complex obstacle distributions.These issues are particularly pronounced when navigating cluttered or large-scale environments that demand both global coverage and smooth trajectory generation.To address these challenges,this paper proposes a Wave Water Simulator(WWS)algorithm,leveraging a physically motivated wave equation to achieve inherently smooth,globally consistent path planning.In WWS,wavefront expansions naturally identify safe corridors while seamlessly avoiding local minima,and selective corridor focusing reduces computational overhead in large or dense maps.Comprehensive simulations and real-world validations-encompassing both indoor and outdoor scenarios-demonstrate that WWS reduces path length by 2%-13%compared to conventional methods,while preserving gentle curvature and robust obstacle clearance.Furthermore,WWS requires minimal parameter tuning across diverse domains,underscoring its broad applicability to warehouse robotics,field operations,and autonomous service vehicles.These findings confirm that the proposed wave-based framework not only bridges the gap between local heuristics and global coverage but also sets a promising direction for future extensions toward dynamic obstacle scenarios and multi-agent coordination.
基金supported by the Key R&D Program of Zhejiang Province(Nos.2023C01166 and 2024SJCZX0046)the Zhejiang Provincial Natural Science Foundation of China(Nos.LDT23E05013E05 and LD24E050009)the Natural Science Foundation of Ningbo(No.2021J150),China.
文摘Accuracy allocation is crucial in the accuracy design of machining tools.Current accuracy allocation methods primarily focus on positional deviation,with little consideration for tool direction deviation.To address this issue,we propose a geometric error cost sensitivity-based accuracy allocation method for five-axis machine tools.A geometric error model consisting of 4l error components is constructed based on homogeneous transformation matrices.Volumetric points with positional and tool direction deviations are randomly sampled to evaluate the accuracy of the machine tool.The sensitivity of each error component at these sampling points is analyzed using the Sobol method.To balance the needs of geometric precision and manufacturing cost,a geometric error cost sensitivity function is developed to estimate the required cost.By allocating error components affecting tool direction deviation first and the remaining components second,this allocation scheme ensures that both deviations meet the requirements.We also perform numerical simulation of a BC-type(B-axis and C-axis type)five-axis machine tool to validate the method.The results show that the new allocation scheme reduces the total geometric error cost by 27.8%compared to a uniform allocation scheme,and yields the same positional and tool direction machining accuracies.
文摘A simulation system for five axis NC machining using general cutting tools is presented This system differs from other simulation system in that it not only focuses on the geometric simulation but also focuses on the collision detection which is usually not included in NC machining simulation Besides all of these, estimating cutting forces is also discussed In order to obtain high efficiency, all algorithms use swept volume modeling technique, so the simulation system is compact and can be performed efficiently
基金supported by the Research Funding of Hangzhou International Innovation Institute of Beihang Uni-versity,China(No.2024KQ130)the National Natural Science Foundation of China(Nos.52073010 and 52373259).
文摘Recent progress in microwave absorption materials stimulates the extensive exploration of rare earth oxide materials.Herein,we report the synthesis of a hollow sphere-based carbon material compounded with rare earth oxides.Hollow N-doped carbon nano-spheres loaded ceria composites(H-NC@CeO_(2))were designed and prepared by the template method,combined with in-situ coating,pyrolysis and chemical etching.By controlling the loading content of H-NC@CeO_(2)and adjusting the impedance matching of the material,the H-NC@CeO_(2)/PS(polystyrene)composite exhibited a minimum reflection loss(RL)of-50.8 dB and an effective absorption band-width(EAB)of 4.64 GHz at a filler ratio of 20wt%and a thickness of 2 mm.In accordance with measured electromagnetic parameters,simulations using the high frequency structure simulator(HFSS)software were conducted to investigate the impact of the honeycomb structure on the electromagnetic wave performance of H-NC@CeO_(2)/PS.By calculating the surface electric field and the material’s bulk loss density,the mechanism of electromagnetic loss for the honeycomb structure was elaborated.A method for structural design and man-ufacturing of broadband absorbing devices was proposed and a broadband absorber with an EAB of 11.9 GHz was prepared.This study presents an innovative approach to designing advanced electromagnetic(EM)wave absorbing materials with broad absorption band-widths.
基金Supported by National Natural Science Foundation of China(Grant Nos.52075076,U1908231)National Key R&D Program of China(Grant No.2019YFA0705304)。
文摘A sudden increase in the radial depth(SIRD)is a distinctive phenomenon in plunge milling.It is typically characterized by a sharp increase in cutting force at the end of the axial feed of the tool,accompanied by harsh machine vibration sounds,which can negatively impact the reliability of plunge milling.This paper proposes an optimization method to eliminate SIRD in five-axis plunge milling.Initially,a five-axis plunge milling experiment and an analysis of the spatial position relationship between the plunge tools and the workpiece revealed that the cause of SIRD is unreasonable tool path planning.Subsequently,using the cutter position and cutter axis vector as variables,an SIRD discrimination model was developed for adjacent cutter positions and extended to multiple cutter positions.Optimizing the plunge milling tool path is considered a multivariate optimization problem that involves determining the cutter point and cutter axis vector.The SIRD discrimination model was used as a constraint function to aid in solving for the variables.The simulation and experimental results indicate that with the remaining volume of material as the optimization target,the optimized plunge milling tool path results in a residual material volume that is less than 60%of the gradually decreasing plunge depth.This optimization decreases the subsequent semi-finishing time of the workpiece and enhances machining efficiency.Additionally,it does not rely on operator experience and facilitates efficient automated optimization of the tool path to exclude SIRD.
基金Supported by the National Key Research and Development Program of China(Grant No.2022YFB4500604)in part by the Natural Science Foundation of Guangdong Province,China(Grant No.2022A1515010100 and 2024A1515010140).
文摘Compared with traditional open surgery,laparoscopic surgery significantly reduces bodily trauma,postoperative pain,and hospitalization duration.However,owing to the small size of incisions and the counterintuitive motion of surgical tools,longer training cycles are required for surgeons to achieve fine operational skills.This paper presents a laparoscopic surgery simulator with haptic-feedback control(LSHC-6)that provides a reliable and cost-effective training alternative for surgeons.In addition to the structural diagram,kinematic analysis,and gravity compensation algorithm,a particle swarm optimization algorithm(PSO)is applied to optimize the structural parameters of the simulator by evaluating its workspace,global dexterity,and gravity compensation ability.A prototype system was developed and evaluated using two training experiments.The results demonstrate that the simulator exhibits good operational fluidity,workspace,and stable force output,effectively meeting the needs of laparoscopic surgical training.
文摘BACKGROUND Although exposure therapy is a proven treatment for post-traumatic stress disorder(PTSD),empirical research is difficult due to ethical issues.Recently,virtual reality-based content that can provide space and time similar to reality for exposure therapy techniques is increasing.AIM To examine exposure therapy using driving simulations in patients with PTSD due to traffic accidents with PTSD symptoms.METHODS The intervention was provided to two individuals who experienced PTSD symptoms after a traffic accident using a driving simulator.Among the singlesubject experimental designs,the ABA(baseline-intervention-baseline)design was used,and the PTSD checklist and brain wave frequency were used to measure the results.RESULTS In all participants,the standard category departure time of the electroencephalogram decreased from baseline,and PTSD symptoms decreased after the intervention.CONCLUSION These results suggest the potential use of a driving simulator as an exposure treatment tool for PTSD.
基金supported by the National Key Research and Development Program of China (Grant No.2021YFC2202604)the Strategy Priority Research Program of Chinese Academy of Sciences (Grant No.XDA1502110101).
文摘The ground-based experimental tests are crucial to verify the related technologies of the drag-free satellite.This work presents a design method of the ground simulator testbed for emulating the planar dynamics of the space drag-free systems.In this paper,the planar dynamic characteristics of the drag-free satellite with double test masses are analyzed and nondimensionalized.A simulator vehicle composed of an air bearing testbed and two inverted pendulums is devised on the basic of equivalent mass and equivalent stiffness proposed firstly in this paper.And the dynamic model of the simulator equivalent to the sensitive axis motion of the test mass and the planar motion of the satellite is derived from the Euler-Lagrange method.Then,the dynamic equivalence conditions between the space prototype system and the ground model system are derived from Pi theorem.To satisfy these conditions,the scaling laws of two systems and requirements for the inverted pendulum are put forward.Besides,the corresponding control scaling laws and a closed-loop control strategy are deduced and applied to establishing the numerical simulation experiments of underactuated system.Subsequently,the comparative simulation results demonstrate the similarity of dynamical behavior between the scaled-down ground model and the space prototype.As a result,the rationality and effectiveness of the design method are proved,facilitating the ground simulation of future gravitational wave detection satellites.
基金support received from the National Natural Science Foundation of China(22127812,22578482,22278433)the National Key Research and Development Program of China(2021YFC2800902)。
文摘Large-scale physical simulation is essential for advancing our understanding of natural gas hydrates exploitation mechanism.However,cylinder-shaped simulators often face challenges in balancing large volume,controllability,and comprehensive monitoring.In this study,we developed a fan columnshaped hydrate simulator(FCHS)with an internal angle of 6°,a radius of 3 m,and an inner height of0.3 m,resulting in an effective volume of~142 L.Moreover,the FCHS is equipped with an integrated"thermal-pressure-acoustic"sensing system,enabling in-situ monitoring of temperature,pressure,and P-wave velocity evolution during hydrate formation and dissociation process.The experimental results indicate that a pressure gradient successfully established from the reservoir center toward its boundaries during depressurization stage,and pressure propagation is relatively slow,resulting in a radial pressure difference of 3-4 MPa within a 3 m range.Once the system reaches pressure equilibrium,the pressure difference decreases to 0.3-0.4 MPa.The depressurization at the wellbore promotes hydrate dissociation in the near-well region,resulting in the radial temperature difference reaches~1.5℃ along the radial direction.The acoustic data reveals that a radial gradient in hydrate saturation gradually forms from the center to the boundary during depressurization-induced gas production.The evolutions of spatio-temporal multi-fields obtained in the FCHS are consist with that of field production.The FCHS proves to be a cutting-edge platform for experimental simulation of NGH exploitation and carbon sequestration processes.
基金National Key Research and Development Program of China(2022YFB4600902)Shandong Provincial Science Foundation for Outstanding Young Scholars(ZR2024YQ020)。
文摘Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.
基金financially supported by the National Science and Technology Major Project of China (No.J2019-VI-0004-0117)a Laboratory Fund Project (6142903220101)。
文摘The size and shape effect(SSE)of components has become a critical issue for mechanical properties,application reliability,and processing.In this study,the creep rupture life(CRL)of components with different wall thicknesses and positions in a combustion chamber casing simulator made of K439B superalloy was investigated.The intrinsic mechanisms of the SSE were explored from the dendrite structure,volume fraction and size of theγ'phase,and element segregation,etc.It is shown that this casting exhibits a strong SSE of creep rupture life,characterized by a significant difference in the CRL values up to 60%with the variation of wall thickness and position in the casing.In terms of casting technology,the influence of SSE on CRL is actually determined by the cooling rate.The SSE on the creep rupture life originates from the dendrite structure(such as the secondary dendrite arm spacing),volume fraction size of theγ'phase in the dendrite trunk,and elements segregation rate.This work may have implications for the design and application of engineering components with large sizes and complex structures.
基金supported by the National Natural Science Foundation of China(52071039 and 52301156)National Natural Science Foundation of Jiangsu Province of China(BK20241873)Natural Science Foundation of Jiangsu Province(BK20232025 and BK20243005)are greatly acknowledged.
文摘Atomistic simulations were adopted to study the solute segregation effect on dislocation transmutation across the{1012}twin boundaries in magnesium.For pure magnesium,the dislocation-twin reaction resulted in the formation of sessile dislocations accompanied by the fast migration of the twin boundary,and no〈c+a〉dislocation occurred.With Al segregation,instead,two basal dislocations transmuted into one prismatic〈c+a〉dislocation in the twin.Twin migration was significantly impeded,and the resultant twin disconnections stayed localized and had a higher step character than in pure Mg.To reveal the mechanism of the effect of solute segregation,the Peierls barriers of twin disconnections were calculated,and the dynamic evolutions of twin disconnection dipoles were simulated.The results suggested that Al segregation softened the Peierls barrier of twin disconnections but imposed a high pinning force on twin disconnections,thus attenuating their mobility.Moreover,given the same Al segregation,the twin disconnection dipole with a higher step showed greater stability,which explained the presence of localized twin disconnections with a higher step in the cases with Al segregation than in pure magnesium.The solute segregation induced low mobility of twin disconnections contributed to the occurrence of〈c+a〉dislocations.
基金supported by the National Natural Science Foundation of China(Grant Nos.22193032 and 32401033)the Research Fund of Wenzhou Institute,Chinese Academy of Sciences(Grant Nos.WIUCASQD2020009,WIUCASQD2023005,XSZD2024004,2021HZSY0061,and WIUCASICTP2022)。
文摘The F_(1)-ATPase and V_(1)-ATPase are rotary biomotors.Alignment of their amino acid sequences,which originate from bovine heart mitochondria(1BMF)and Enterococcus hirae(3VR6),respectively,demonstrates that the segment forming the ATP catalytic pocket is highly conserved.Single-molecule experiments,however,have revealed subtle differences in efficiency between the F_(1) and V_(1) motors.Here,we perform both atomistic and coarse-grained molecular dynamics simulations to investigate the mechanochemical coupling and coordination in F_(1) and V_(1) ATPase.Our results show that the correlation between conformational changes in F_(1) is stronger than that in V_(1),indicating that the mechanochemical coupling in F_(1) is tighter than in V_(1).Moreover,the unidirectional rotation of F_(1) is more processive than that of V_(1),which accounts for the higher efficiency observed in F_(1) and explains the occasional backward steps detected in single-molecule experiments on V_(1).
基金supported by the Advanced Materials-National Science and Technology Major Project(Grant No.2025ZD0618401)the National Natural Science Foundation of China(Grant No.12504285)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20250472)NFSG grant from BITS-Pilani,Dubai campus。
文摘The rapid advancement of machine learning based tight-binding Hamiltonian(MLTB)methods has opened new avenues for efficient and accurate electronic structure simulations,particularly in large-scale systems and long-time scenarios.This review begins with a concise overview of traditional tight-binding(TB)models,including both(semi-)empirical and first-principles approaches,establishing the foundation for understanding MLTB developments.We then present a systematic classification of existing MLTB methodologies,grouped into two major categories:direct prediction of TB Hamiltonian elements and inference of empirical parameters.A comparative analysis with other ML-based electronic structure models is also provided,highlighting the advancement of MLTB approaches.Finally,we explore the emerging MLTB application ecosystem,highlighting how the integration of MLTB models with a diverse suite of post-processing tools from linear-scaling solvers to quantum transport frameworks and molecular dynamics interfaces is essential for tackling complex scientific problems across different domains.The continued advancement of this integrated paradigm promises to accelerate materials discovery and open new frontiers in the predictive simulation of complex quantum phenomena.
