The multi-point dynamic aggregation(MPDA)problem is a challenging real-world problem.In the MPDA problem,the demands of tasks keep changing with their inherent incremental rates,while a heterogeneous robot fleet is re...The multi-point dynamic aggregation(MPDA)problem is a challenging real-world problem.In the MPDA problem,the demands of tasks keep changing with their inherent incremental rates,while a heterogeneous robot fleet is required to travel between these tasks to change the time-varying state of each task.The robots are allowed to collaborate on the same task or work separately until all tasks are completed.It is challenging to generate an effective task execution plan due to the tight coupling between robots abilities and tasks'incremental rates,and the complexity of robot collaboration.For effectiveness consideration,we use the variable length encoding to avoid redundancy in the solution space.We creatively use the adaptive large neighborhood search(ALNS)framework to solve the MPDA problem.In the proposed algorithm,high-quality initial solutions are generated through multiple problem-specific solution construction heuristics.These heuristics are also used to fix the broken solution in the novel integrated decoding-construction repair process of the ALNS framework.The results of statistical analysis by the Wilcoxon rank-sum test demonstrate that the proposed ALNS can obtain better task execution plans than some state-of-the-art algorithms in most MPDA instances.展开更多
Sandwich structures are vulnerable to multi-point impacts,and such impacts can result in a reduction in residual strength even catastrophic accident.Therefore,the multi-point impact behaviors of PMI foam sandwich stru...Sandwich structures are vulnerable to multi-point impacts,and such impacts can result in a reduction in residual strength even catastrophic accident.Therefore,the multi-point impact behaviors of PMI foam sandwich structure are investigated and studied using experimental and numerical coupled methods.Three impact energy levels and five Distances Between Impact Positions(DBIP)are considered in details,and representative impact characteristics are compared to reveal the association between Compression After Impact(CAI)strength and DBIP.Results indicate that the interference between the multi-point impact events has a dominant effect on CAI strength when DBIP is small,and the variation in bending stiffness induced by the boundary effect is the dominant factor affecting CAI strength when DBIP ranges from 20 mm to 60 mm.In addition,matrix damage represents the primary damage mode in multi-point impact,and the calculated ratio of energy absorbed by the top face sheet and honeycomb core,in relation to the total absorbed energy,serves as a clear indicator of the damage severity experienced by both components.This work is enlightening for the structural design of impact-resistant composites.展开更多
Purpose – Straightness measurement of rail weld joint is of essential importance to railway maintenance. Dueto the lack of efficient measurement equipment, there has been limited in-depth research on rail weld joint ...Purpose – Straightness measurement of rail weld joint is of essential importance to railway maintenance. Dueto the lack of efficient measurement equipment, there has been limited in-depth research on rail weld joint with a5-m wavelength range, leaving a significant knowledge gap in this field.Design/methodology/approach – In this study, the authors used the well-established inertial referencemethod (IR-method), and the state-of-the-art multi-point chord reference method (MCR-method). Two methodshave been applied in different types of rail straightness measurement trollies, respectively. These instrumentswere tested in a high-speed rail section within a certain region of China. The test results were ultimatelyvalidated through using traditional straightedge and feeler gauge methods as reference data to evaluate the railweld joint straightness within the 5-m wavelength range.Findings – The research reveals that IR-method and MCR-method produce reasonably similar measurementresults for wavelengths below 1 m. However, MCR-method outperforms IR-method in terms of accuracy forwavelengths exceeding 3 m. Furthermore, it was observed that IR-method, while operating at a slower speed,carries the risk of derailing and is incapable of detecting rail weld joints and low joints within the track.Originality/value – The research compare two methods’ measurement effects in a longer wavelength rangeand demonstrate the superiority of MCR-method.展开更多
The centroid coordinate serves as a critical control parameter in motion systems,including aircraft,missiles,rockets,and drones,directly influencing their motion dynamics and control performance.Traditional methods fo...The centroid coordinate serves as a critical control parameter in motion systems,including aircraft,missiles,rockets,and drones,directly influencing their motion dynamics and control performance.Traditional methods for centroid measurement often necessitate custom equipment and specialized positioning devices,leading to high costs and limited accuracy.Here,we present a centroid measurement method that integrates 3D scanning technology,enabling accurate measurement of centroid across various types of objects without the need for specialized positioning fixtures.A theoretical framework for centroid measurement was established,which combined the principle of the multi-point weighing method with 3D scanning technology.The measurement accuracy was evaluated using a designed standard component.Experimental results demonstrate that the discrepancies between the theoretical and the measured centroid of a standard component with various materials and complex shapes in the X,Y,and Z directions are 0.003 mm,0.009 mm,and 0.105 mm,respectively,yielding a spatial deviation of 0.106 mm.Qualitative verification was conducted through experimental validation of three distinct types.They confirmed the reliability of the proposed method,which allowed for accurate centroid measurements of various products without requiring positioning fixtures.This advancement significantly broadened the applicability and scope of centroid measurement devices,offering new theoretical insights and methodologies for the measurement of complex parts and systems.展开更多
The precise acquisition of the quality characteristic parameters of large aircraft directly affects its performance characteristics.For large aircrafts such as missiles and rockets with internal fillings,traditional m...The precise acquisition of the quality characteristic parameters of large aircraft directly affects its performance characteristics.For large aircrafts such as missiles and rockets with internal fillings,traditional measurement methods involving large-angle tilting or rotation may pose safety risks.In light of the characteristics of large aircraft and in combination with existing measurement methods,we design a mass and centroid measurement method based on four-point support and small-angle tilting,and develop a set of mass and centroid testing system.This method obtains the intersection point of the gravity action line in the product coordinate system through coordinate transformation in two postures,thereby obtaining the three-dimensional centroid of the aircraft.We first elaborate on the principle of this method in detail,then introduce the composition of the equipment,and analyze the structural stress of key components.Finally,experimental verification and uncertainty analysis are carried out.Experimental verification shows that the maximum deviation of the mass measurement accuracy is less than 0.02%,the centroid measurement accuracy in the X direction is±0.15 mm,in the Y direction it is±0.21 mm,and in the Z direction it is±0.19 mm.展开更多
Effluents from wastewater treatment plants(WWTPs)are recognized as an important source for microplastic(MP)pollution in the receiving waters.The removal efficiency of MPs in WWTPs and the discharge flux remain largely...Effluents from wastewater treatment plants(WWTPs)are recognized as an important source for microplastic(MP)pollution in the receiving waters.The removal efficiency of MPs in WWTPs and the discharge flux remain largely unknown.The present study measured the MP abundances in the influents,effluents,and activated sludge in four domestic and one industrial WWTPs in Guangzhou,China.The MP abundance detected in influent samples were approximately one order of magnitude higher than those found in effluents,resulting in high removal efficiencies of MPs(97.4%-98.7%)in these WWTPs.A significant amount of the removed MPs deposited in the activated sludge,with abundances of MPs ranging from 7 to 888 pieces/g dry weight sludge.Microplastics remaining in effluents were discharged into the receiving river with releasing rates of ranging from(1.1±1.0)×10^(7)to(4.54±3.92)×10^(9)pieces per day.Results obtained in the present study suggest that the contribution of MPs from WWTPs to the aquatic environment is non-negligible and the application of sludge in the agricultural environment may bring additional MP pollution to agricultural soils.展开更多
The design of wide-range high-efficiency aerodynamic configurations is one of the most important key technologies in the research of near-space hypersonic vehicles.A double-sided intake configuration with different in...The design of wide-range high-efficiency aerodynamic configurations is one of the most important key technologies in the research of near-space hypersonic vehicles.A double-sided intake configuration with different inlets on the upper and lower surfaces is proposed to adapt to widerange flight.Firstly,the double-sided intake configuration’s design method and flight profile are delineated.Secondly,Computational Fluid Dynamics(CFD)numerical simulation based on multi-Graphics Processing Unit(GPU)parallel computing is adopted to evaluate the vehicle’s performance comprehensively,aiming to verify the feasibility of the proposed scheme.This evaluation encompasses a wide-range basic aerodynamic characteristics,inlet performance,and heat flux at critical locations.The results show that the inlets of the designed integration configuration can start up across Mach number 3.5 to 8.The vehicle possesses multi-point cruising capability by flipping the fuselage.Simultaneously,a 180°rotation of the fuselage can significantly decrease the heat accumulation on the lower surface of the vehicle,particularly at the inlet lip,further decreasing the temperature gradient across the vehicle structure.This study has some engineering value for the aerodynamic configuration design of wide-range vehicles.However,further study reveals that the flow phenomena at the intersection of two inlets are complex,posing potential adverse impacts on propulsion efficiency.Therefore,it is imperative to conduct additional research to delve into this matter comprehensively.展开更多
基金supported in part by the National Outstanding Youth Talents Support Program(No.61822304)the Basic Science Center Program of the NSFC(No.62088101)+2 种基金the Project of Major International(Regional)Joint Research Program of NSFC(No.61720106011)the Shanghai Municipal Science and Technology Major Project(No.2021SHZDZX0100)the Shanghai Municipal Commission of Science and Technology Project(No.19511132101).
文摘The multi-point dynamic aggregation(MPDA)problem is a challenging real-world problem.In the MPDA problem,the demands of tasks keep changing with their inherent incremental rates,while a heterogeneous robot fleet is required to travel between these tasks to change the time-varying state of each task.The robots are allowed to collaborate on the same task or work separately until all tasks are completed.It is challenging to generate an effective task execution plan due to the tight coupling between robots abilities and tasks'incremental rates,and the complexity of robot collaboration.For effectiveness consideration,we use the variable length encoding to avoid redundancy in the solution space.We creatively use the adaptive large neighborhood search(ALNS)framework to solve the MPDA problem.In the proposed algorithm,high-quality initial solutions are generated through multiple problem-specific solution construction heuristics.These heuristics are also used to fix the broken solution in the novel integrated decoding-construction repair process of the ALNS framework.The results of statistical analysis by the Wilcoxon rank-sum test demonstrate that the proposed ALNS can obtain better task execution plans than some state-of-the-art algorithms in most MPDA instances.
基金Supported by the National Key R&D Program of China(2023YFB3709602,2023YFB3709603)National Natural Science Foundation of China(12372141)the Key R&D Program in Shaanxi Province(2024GH-ZDXM-27).
文摘Sandwich structures are vulnerable to multi-point impacts,and such impacts can result in a reduction in residual strength even catastrophic accident.Therefore,the multi-point impact behaviors of PMI foam sandwich structure are investigated and studied using experimental and numerical coupled methods.Three impact energy levels and five Distances Between Impact Positions(DBIP)are considered in details,and representative impact characteristics are compared to reveal the association between Compression After Impact(CAI)strength and DBIP.Results indicate that the interference between the multi-point impact events has a dominant effect on CAI strength when DBIP is small,and the variation in bending stiffness induced by the boundary effect is the dominant factor affecting CAI strength when DBIP ranges from 20 mm to 60 mm.In addition,matrix damage represents the primary damage mode in multi-point impact,and the calculated ratio of energy absorbed by the top face sheet and honeycomb core,in relation to the total absorbed energy,serves as a clear indicator of the damage severity experienced by both components.This work is enlightening for the structural design of impact-resistant composites.
文摘Purpose – Straightness measurement of rail weld joint is of essential importance to railway maintenance. Dueto the lack of efficient measurement equipment, there has been limited in-depth research on rail weld joint with a5-m wavelength range, leaving a significant knowledge gap in this field.Design/methodology/approach – In this study, the authors used the well-established inertial referencemethod (IR-method), and the state-of-the-art multi-point chord reference method (MCR-method). Two methodshave been applied in different types of rail straightness measurement trollies, respectively. These instrumentswere tested in a high-speed rail section within a certain region of China. The test results were ultimatelyvalidated through using traditional straightedge and feeler gauge methods as reference data to evaluate the railweld joint straightness within the 5-m wavelength range.Findings – The research reveals that IR-method and MCR-method produce reasonably similar measurementresults for wavelengths below 1 m. However, MCR-method outperforms IR-method in terms of accuracy forwavelengths exceeding 3 m. Furthermore, it was observed that IR-method, while operating at a slower speed,carries the risk of derailing and is incapable of detecting rail weld joints and low joints within the track.Originality/value – The research compare two methods’ measurement effects in a longer wavelength rangeand demonstrate the superiority of MCR-method.
基金supported by National Natural Science Foundation of China(No.52176122).
文摘The centroid coordinate serves as a critical control parameter in motion systems,including aircraft,missiles,rockets,and drones,directly influencing their motion dynamics and control performance.Traditional methods for centroid measurement often necessitate custom equipment and specialized positioning devices,leading to high costs and limited accuracy.Here,we present a centroid measurement method that integrates 3D scanning technology,enabling accurate measurement of centroid across various types of objects without the need for specialized positioning fixtures.A theoretical framework for centroid measurement was established,which combined the principle of the multi-point weighing method with 3D scanning technology.The measurement accuracy was evaluated using a designed standard component.Experimental results demonstrate that the discrepancies between the theoretical and the measured centroid of a standard component with various materials and complex shapes in the X,Y,and Z directions are 0.003 mm,0.009 mm,and 0.105 mm,respectively,yielding a spatial deviation of 0.106 mm.Qualitative verification was conducted through experimental validation of three distinct types.They confirmed the reliability of the proposed method,which allowed for accurate centroid measurements of various products without requiring positioning fixtures.This advancement significantly broadened the applicability and scope of centroid measurement devices,offering new theoretical insights and methodologies for the measurement of complex parts and systems.
基金supported by National Natural Science Foundation of China-Youth Program(No.62303420)。
文摘The precise acquisition of the quality characteristic parameters of large aircraft directly affects its performance characteristics.For large aircrafts such as missiles and rockets with internal fillings,traditional measurement methods involving large-angle tilting or rotation may pose safety risks.In light of the characteristics of large aircraft and in combination with existing measurement methods,we design a mass and centroid measurement method based on four-point support and small-angle tilting,and develop a set of mass and centroid testing system.This method obtains the intersection point of the gravity action line in the product coordinate system through coordinate transformation in two postures,thereby obtaining the three-dimensional centroid of the aircraft.We first elaborate on the principle of this method in detail,then introduce the composition of the equipment,and analyze the structural stress of key components.Finally,experimental verification and uncertainty analysis are carried out.Experimental verification shows that the maximum deviation of the mass measurement accuracy is less than 0.02%,the centroid measurement accuracy in the X direction is±0.15 mm,in the Y direction it is±0.21 mm,and in the Z direction it is±0.19 mm.
基金Supported by the National Natural Science Foundation of China(No.21936004)the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.SML2021SP208)the Fundamental Research Funds for the Central Universities(No.21623118)。
文摘Effluents from wastewater treatment plants(WWTPs)are recognized as an important source for microplastic(MP)pollution in the receiving waters.The removal efficiency of MPs in WWTPs and the discharge flux remain largely unknown.The present study measured the MP abundances in the influents,effluents,and activated sludge in four domestic and one industrial WWTPs in Guangzhou,China.The MP abundance detected in influent samples were approximately one order of magnitude higher than those found in effluents,resulting in high removal efficiencies of MPs(97.4%-98.7%)in these WWTPs.A significant amount of the removed MPs deposited in the activated sludge,with abundances of MPs ranging from 7 to 888 pieces/g dry weight sludge.Microplastics remaining in effluents were discharged into the receiving river with releasing rates of ranging from(1.1±1.0)×10^(7)to(4.54±3.92)×10^(9)pieces per day.Results obtained in the present study suggest that the contribution of MPs from WWTPs to the aquatic environment is non-negligible and the application of sludge in the agricultural environment may bring additional MP pollution to agricultural soils.
基金co-supported by the Foundation of National Key Laboratory of Science and Technology on Aerodynamic Design and Research,China(No.614220121020114)the Key R&D Projects of Hunan Province,China(No.2023GK2022)。
文摘The design of wide-range high-efficiency aerodynamic configurations is one of the most important key technologies in the research of near-space hypersonic vehicles.A double-sided intake configuration with different inlets on the upper and lower surfaces is proposed to adapt to widerange flight.Firstly,the double-sided intake configuration’s design method and flight profile are delineated.Secondly,Computational Fluid Dynamics(CFD)numerical simulation based on multi-Graphics Processing Unit(GPU)parallel computing is adopted to evaluate the vehicle’s performance comprehensively,aiming to verify the feasibility of the proposed scheme.This evaluation encompasses a wide-range basic aerodynamic characteristics,inlet performance,and heat flux at critical locations.The results show that the inlets of the designed integration configuration can start up across Mach number 3.5 to 8.The vehicle possesses multi-point cruising capability by flipping the fuselage.Simultaneously,a 180°rotation of the fuselage can significantly decrease the heat accumulation on the lower surface of the vehicle,particularly at the inlet lip,further decreasing the temperature gradient across the vehicle structure.This study has some engineering value for the aerodynamic configuration design of wide-range vehicles.However,further study reveals that the flow phenomena at the intersection of two inlets are complex,posing potential adverse impacts on propulsion efficiency.Therefore,it is imperative to conduct additional research to delve into this matter comprehensively.
