The dynamic model of a novel electric power steering （EPS） system integrated with active front steering function （the novel EPS system） is built. The concepts and quantitative expressions of the steering road feel...The dynamic model of a novel electric power steering （EPS） system integrated with active front steering function （the novel EPS system） is built. The concepts and quantitative expressions of the steering road feel, steering sensibility, and steering operation stability are introduced. Based on quality engineering theory, the optimization algorithm is proposed by integrating the Monte Carlo descriptive sampling, elitist non-dominated sorting genetic algorithm （NSGA-II） and 6-sigma design method. With the steering road feel and the steering portability as optimization targets, the system parameters are optimized by the proposed optimization algorithm. The simulation results show that the system optimized based on quality engineering theory can improve the steering road feel, guarantee steering stability and steering portability and thus provide a theoretical basis for the design and optimization of the novel electric power steering system.展开更多
An artificial molecular machine consists of molecule or substituent components jointed together in a specific way so that their mutual displacements could be initiated using appropriate outside stimuli. Such an abilit...An artificial molecular machine consists of molecule or substituent components jointed together in a specific way so that their mutual displacements could be initiated using appropriate outside stimuli. Such an ability of performing mechanical motions by consuming external energy has endowed these tiny machines with vast fascinating potential applications in areas such as actuators, manipulating atoms/molecules, drug delivery, molecular electronic devices, etc. To date, although vast kinds of molecular machine archetypes have been synthesized in facile ways, they are inclined to be defined as switches but not true machines in most cases because no useful work has been done during a working cycle. More efforts need to be devoted on the utilization and amplification of the nanoscale mechanical motions among synthetic molecular machines to accomplish useful tasks. Here we highlight some of the recent advances relating to molecular machines that can perform work on different length scales, ranging from microscopic levels to macroscopic ones.展开更多
The model of the differential steering system(DSS) of electric vehicle with motorized wheels and the three-degree-of-freedom dynamic model of vehicle are built.Based on these models,the concepts and quantitative expre...The model of the differential steering system(DSS) of electric vehicle with motorized wheels and the three-degree-of-freedom dynamic model of vehicle are built.Based on these models,the concepts and quantitative expressions of steering road feel,steering portability and steering stability are proposed.Through integrating the Monte Carlo descriptive sampling,elitist non-dominated sorting genetic algorithm(NSGA-II) and Taguchi robust design method,the system parameters are optimized with steering road feel and steering portability as optimization targets,and steering stability and steering portability as constraints.The simulation results show that the system optimized based on quality engineering can improve the steering road feel,guarantee steering stability and steering portability and thus provide a theoretical basis for the design and optimization of the electric vehicle with motorized wheels system.展开更多
Reservoir sedimentation is an unsolved problem.In this paper,based on measured data,theoretical analysis and numerical computations,we prove that a proportion of the sediment coarser than 0.1 mm(CS) is sorted and depo...Reservoir sedimentation is an unsolved problem.In this paper,based on measured data,theoretical analysis and numerical computations,we prove that a proportion of the sediment coarser than 0.1 mm(CS) is sorted and deposited in specific reaches in the upper backwaters or in run-of-river reservoirs.The ratio of CS is usually small but it impacts the slope of deposition delta greatly and raises the backwater in later stages for a river shaped reservoir(RSR).Based on these facts,we propose to remove such CS from a fixed basin(FB) in the upper backwater by dredging and we prove that the removal of CS is effective in reducing sediment deposition and in preserving the long-term capacity of reservoirs.A numerical model computation of the Three Gorges Project(TGP) reservoir indicates that dredging 30×106-50×106 t/a of CS could reduce 20% total deposition by the end of 100th year,so that the slope of deposition can be slowed down by 25%-30%.This would be remarkable for a long extended RSR.This method of removing CS can also be applied to the Xiaolangdi reservoir(XLD) on the Yellow River(YR) to not only limit reservoir deposition but also filter out the CS from entering the Lower Yellow River(LYR) to slow down the rise of the perched LYR.It provides a new alternative to postpone the continuous siltation of the LYR.展开更多
As the running speed of high-speed trains increases, aerodynamic drag becomes the key factor which limits the further increase of the running speed and energy consumption. Aerodynamic lift of the trailing car also bec...As the running speed of high-speed trains increases, aerodynamic drag becomes the key factor which limits the further increase of the running speed and energy consumption. Aerodynamic lift of the trailing car also becomes the key force which affects the amenity and safety of the train. In the present paper, a simplified CRH380A high-speed train with three carriages is chosen as the model in order to optimize aerodynamic drag of the total train and aerodynamic lift of the trailing car. A constrained mul- ti-objective optimization design of the aerodynamic head shape of high-speed trains based on adaptive non-dominated sorting genetic algorithm is also developed combining local function three-dimensional parametric approach and central Latin hypercube sampling method with maximin criteria based on the iterative local search algorithm. The results show that local function parametric approach can be well applied to optimal design of complex three-dimensional aerodynamic shape, and the adaptive non-dominated sorting genetic algorithm can be more accurate and efficient to find the Pareto front. After optimization the aerodynamic drag of the simplified train with three carriages is reduced by 3.2%, and the lift coefficient of the trailing car by 8.24%, the volume of the streamlined head by 2.16%; the aerodynamic drag of the real prototype CRH380A is reduced by 2.26%, lift coefficient of the trailing car by 19.67%. The variation of aerodynamic performance between the simplified train and the true train is mainly concentrated in the deformation region of the nose cone and tail cone. The optimization approach proposed in the present paper is simple yet efficient, and sheds lights on the constrained multi-objective engineering optimization design of aerodynamic shape of high-speed trains.展开更多
基金Projects(51005115,51205191)supported by the National Natural Science Foundation of ChinaProject(QC201101)supported by the Visiting Scholar Foundation of the Automobile Engineering Key Laboratory of Jiangsu Province,China+1 种基金Project(SKLMT-KFKT-201105)supported by the Visiting Scholar Foundation of the State Key Laboratory of Mechanical Transmission in Chongqing University,ChinaProjects(NS2013015,NS2012086)supported by the Funds from the Postgraduate Creative Base in Nanjing University of Areonautics and Astronautics,and NUAA Research Funding,China
文摘The dynamic model of a novel electric power steering （EPS） system integrated with active front steering function （the novel EPS system） is built. The concepts and quantitative expressions of the steering road feel, steering sensibility, and steering operation stability are introduced. Based on quality engineering theory, the optimization algorithm is proposed by integrating the Monte Carlo descriptive sampling, elitist non-dominated sorting genetic algorithm （NSGA-II） and 6-sigma design method. With the steering road feel and the steering portability as optimization targets, the system parameters are optimized by the proposed optimization algorithm. The simulation results show that the system optimized based on quality engineering theory can improve the steering road feel, guarantee steering stability and steering portability and thus provide a theoretical basis for the design and optimization of the novel electric power steering system.
基金financially supported by the National Natural Science Foundation of China (21572063, 21372076)the Science Fund for Creative Research Groups (21421004)+1 种基金the Programme of Introducing Talents of Discipline to Universities (B16017)the Fundamental Research Funds for the Central Universities (222201717003)
文摘An artificial molecular machine consists of molecule or substituent components jointed together in a specific way so that their mutual displacements could be initiated using appropriate outside stimuli. Such an ability of performing mechanical motions by consuming external energy has endowed these tiny machines with vast fascinating potential applications in areas such as actuators, manipulating atoms/molecules, drug delivery, molecular electronic devices, etc. To date, although vast kinds of molecular machine archetypes have been synthesized in facile ways, they are inclined to be defined as switches but not true machines in most cases because no useful work has been done during a working cycle. More efforts need to be devoted on the utilization and amplification of the nanoscale mechanical motions among synthetic molecular machines to accomplish useful tasks. Here we highlight some of the recent advances relating to molecular machines that can perform work on different length scales, ranging from microscopic levels to macroscopic ones.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51005115 and 51005248)the Science Fund of State Key Laboratory of Automotive Safety and Energy (Grant No. KF11201)
文摘The model of the differential steering system(DSS) of electric vehicle with motorized wheels and the three-degree-of-freedom dynamic model of vehicle are built.Based on these models,the concepts and quantitative expressions of steering road feel,steering portability and steering stability are proposed.Through integrating the Monte Carlo descriptive sampling,elitist non-dominated sorting genetic algorithm(NSGA-II) and Taguchi robust design method,the system parameters are optimized with steering road feel and steering portability as optimization targets,and steering stability and steering portability as constraints.The simulation results show that the system optimized based on quality engineering can improve the steering road feel,guarantee steering stability and steering portability and thus provide a theoretical basis for the design and optimization of the electric vehicle with motorized wheels system.
基金supported by the State Key Laboratory of Hydroscience and Engineering, Tsinghua University (Grant No. 2011-KY-2)the Independent Research Plans of Tsinghua University (Grant No. 20101081780)
文摘Reservoir sedimentation is an unsolved problem.In this paper,based on measured data,theoretical analysis and numerical computations,we prove that a proportion of the sediment coarser than 0.1 mm(CS) is sorted and deposited in specific reaches in the upper backwaters or in run-of-river reservoirs.The ratio of CS is usually small but it impacts the slope of deposition delta greatly and raises the backwater in later stages for a river shaped reservoir(RSR).Based on these facts,we propose to remove such CS from a fixed basin(FB) in the upper backwater by dredging and we prove that the removal of CS is effective in reducing sediment deposition and in preserving the long-term capacity of reservoirs.A numerical model computation of the Three Gorges Project(TGP) reservoir indicates that dredging 30×106-50×106 t/a of CS could reduce 20% total deposition by the end of 100th year,so that the slope of deposition can be slowed down by 25%-30%.This would be remarkable for a long extended RSR.This method of removing CS can also be applied to the Xiaolangdi reservoir(XLD) on the Yellow River(YR) to not only limit reservoir deposition but also filter out the CS from entering the Lower Yellow River(LYR) to slow down the rise of the perched LYR.It provides a new alternative to postpone the continuous siltation of the LYR.
基金supported by the Major State Basic Research Development Program of China ("973" Program) (Grant No. 2011CB711100) National Key Technology R&D Program (Grant No. 2009BAQG12A03)
文摘As the running speed of high-speed trains increases, aerodynamic drag becomes the key factor which limits the further increase of the running speed and energy consumption. Aerodynamic lift of the trailing car also becomes the key force which affects the amenity and safety of the train. In the present paper, a simplified CRH380A high-speed train with three carriages is chosen as the model in order to optimize aerodynamic drag of the total train and aerodynamic lift of the trailing car. A constrained mul- ti-objective optimization design of the aerodynamic head shape of high-speed trains based on adaptive non-dominated sorting genetic algorithm is also developed combining local function three-dimensional parametric approach and central Latin hypercube sampling method with maximin criteria based on the iterative local search algorithm. The results show that local function parametric approach can be well applied to optimal design of complex three-dimensional aerodynamic shape, and the adaptive non-dominated sorting genetic algorithm can be more accurate and efficient to find the Pareto front. After optimization the aerodynamic drag of the simplified train with three carriages is reduced by 3.2%, and the lift coefficient of the trailing car by 8.24%, the volume of the streamlined head by 2.16%; the aerodynamic drag of the real prototype CRH380A is reduced by 2.26%, lift coefficient of the trailing car by 19.67%. The variation of aerodynamic performance between the simplified train and the true train is mainly concentrated in the deformation region of the nose cone and tail cone. The optimization approach proposed in the present paper is simple yet efficient, and sheds lights on the constrained multi-objective engineering optimization design of aerodynamic shape of high-speed trains.
