A ripple surface type pickup finger was designed to improve the performance of pickup finger precision maize seed metering device and to provide a solution for precision maize planter.The main structure and working pr...A ripple surface type pickup finger was designed to improve the performance of pickup finger precision maize seed metering device and to provide a solution for precision maize planter.The main structure and working principle of seed metering device were detailed in this paper.The dimension size distributions of maize seeds in different types were studied,the gestures of seeds clamped by pickup finger were analyzed,and the clamping dynamical model of pickup finger was established by theoretical analysis.To optimize the structural parameters of ripple surface type pickup finger,the discrete element method(DEM)model of pickup finger precision maize seed metering device was established by the discrete element software EDEM.The numerical simulations of orthogonal seeding performance experiments were conducted to analyze the influences of these factors on the quality of seeding.The rotational speed,wavelength of ripple surface and amplitude of ripple surface were selected as the experimental factors.The average seeding qualified index and the average seeding coefficient of variation on four different types of maize seeds were chosen for evaluating the seeding performance.The results showed that,the average seeding qualified index was 93.35%and the average seeding coefficient of variation was 11.23%under conditions of the 25 r/min rotational speed,8 mm wavelength of ripple surface and 2 mm amplitude of ripple surface.Under the same condition,the bench test was done which showed that the results of test and simulation were consistent.The maximum error of qualified index was 1.95%and the qualified index of improved seed metering device exceeded the original one by 12.34%.The working performance can meet the requirements of precision maize seeding.展开更多
Indirect methods to detect and evaluate inclusions in steel are extensively reviewed, which include total oxygen content measurement, nitrogen pickup, steel and slag composition measurement, lining refractory observat...Indirect methods to detect and evaluate inclusions in steel are extensively reviewed, which include total oxygen content measurement, nitrogen pickup, steel and slag composition measurement, lining refractory observation, tracer studies of determining exogenous inclusions from slag and lining erosion, SEN clogging and final prod- uct tests. There is no single ideal method of detecting and evaluating inclusions in steel, so it is better to use several methods simultaneously to give a more accurate evaluation. Total oxygen content and nitrogen pickup in low carbon aluminum-killed steel as criterion of clean steel in many plants are summarized.展开更多
In this paper, a hybrid genetic algorithm （GA） is proposed for the traveling salesman problem （TSP） with pickup and delivery （TSPPD）. In our algorithm, a novel pheromone-based crossover operator is advanced that...In this paper, a hybrid genetic algorithm （GA） is proposed for the traveling salesman problem （TSP） with pickup and delivery （TSPPD）. In our algorithm, a novel pheromone-based crossover operator is advanced that utilizes both local and global information to construct offspring. In addition, a local search procedure is integrated into the GA to accelerate convergence. The proposed GA has been tested on benchmark instances, and the computational results show that it gives better convergence than existing heuristics.展开更多
Previous studies focused on the bed load transport rate for the condition of turbulent flow,while the knowledge of sediment transport in laminar flow is very limited.As an extreme case to reflect the viscous effect on...Previous studies focused on the bed load transport rate for the condition of turbulent flow,while the knowledge of sediment transport in laminar flow is very limited.As an extreme case to reflect the viscous effect on sediment transport,sediment transport in laminar flow is considered in this paper.There are at least two factors affecting the transport rate of sediment under laminar flow conditions: (1) fluid forces;(2) particle to particle interactions.Together,these two factors represent the physical transport system.First,an exposure degree Probability Density Function (PDF) is developed to explore how the transport rate can be associated with characteristics of laminar flow and this factor reflects the particle to particle interactions,and the pickup probability equation in the absence of turbulence is developed based on the stochastic approach which reflects the exposure degree influence.Then,the formulas to calculate the critical shear stress of incipient motion and the bed load transport rate of fine uniform sediment are established.The derivation is made mainly based on Einstein’s bed load theory;we choose Einstein’s equation to model this system because we believe that the probabilistic approach taken is an appropriate way to account for the spatial and temporal variations in the forces causing sediment transport.These formulas have been tested against a wide range of existing laboratory data and compared with other existing empirical or semiempirical methods.The predictions by these newly proposed formulas are very good.展开更多
The weapon transportation support scheduling problem on aircraft carrier deck is the key to restricting the sortie rate and combat capability of carrier-based aircraft.This paper studies the problem and presents a nov...The weapon transportation support scheduling problem on aircraft carrier deck is the key to restricting the sortie rate and combat capability of carrier-based aircraft.This paper studies the problem and presents a novel solution architecture.Taking the interference of the carrier-based aircraft deck layout on the weapon transportation route and precedence constraint into consideration,a mixed integer formulation is established to minimize the total objective,which is constituted of makespan,load variance and accumulative transfer time of support unit.Solution approach is developed for the model.Firstly,based on modeling the carrier aircraft parked on deck as convex obstacles,the path library of weapon transportation is constructed through visibility graph and Warshall-Floyd methods.We then propose a bi-population immune algorithm in which a population-based forward/backward scheduling technique,local search schemes and a chaotic catastrophe operator are embedded.Besides,the randomkey solution representation and serial scheduling generation scheme are adopted to conveniently obtain a better solution.The Taguchi method is additionally employed to determine key parameters of the algorithm.Finally,on a set of generated realistic instances,we demonstrate that the proposed algorithm outperforms all compared algorithms designed for similar optimization problems and can significantly improve the efficiency,and that the established model and the bi-population immune algorithm can effectively respond to the weapon support requirements of carrier-based aircraft under different sortie missions.展开更多
An air-suction potato seed metering device was designed to improve the performance of the large-size seed crops planting equipment and provide a solution for problems on the mechanical potato seeder,such as high multi...An air-suction potato seed metering device was designed to improve the performance of the large-size seed crops planting equipment and provide a solution for problems on the mechanical potato seeder,such as high multiple-seeding index,high missing-seeding index,low qualified index,and limited versatility.The main structure and operation parameters in terms of rotating speed of the device,seeds height and pickup vacuum pressure were determined by theoretical analysis.Two orthogonal tests,conventional tuber(the triaxial average diameter is about 38-57 mm)test and mini-tuber(the triaxial average diameter is about 12-36 mm)test,were conducted to analyze the influences of these factors on the quality of seeding.The multiple-seeding index,missing-seeding index and qualified index were chosen for evaluating the working performance.The results of conventional tuber test showed that,the multiple-seeding index was 1.1%,the missing-seeding index was 0.8%and the qualified index was 98.1%under conditions of the 30 r/min rotating speed,25 cm seeds height and 10 kPa pickup vacuum pressure.The results of mini-tuber test showed that the multiple-seeding index was 0.5%,the missing-seeding index was 0.6%and the qualified index was 98.9%under conditions of 35 r/min rotating speed,17 cm seeds height and 3.5 kPa pickup vacuum.The working performances of the device can meet the requirements of precision seeding.展开更多
It is difficult to solve complete coverage path planning directly in the obstructed area. Therefore, in this paper, we propose a method of complete coverage path planning with improved area division. Firstly, the bous...It is difficult to solve complete coverage path planning directly in the obstructed area. Therefore, in this paper, we propose a method of complete coverage path planning with improved area division. Firstly, the boustrophedon cell decomposition method is used to partition the map into sub-regions. The complete coverage paths within each sub-region are obtained by the Boustrophedon back-and-forth motions, and the order of traversal of the sub-regions is then described as a generalised traveling salesman problem with pickup and delivery based on the relative positions of the vertices of each sub-region. An adaptive large neighbourhood algorithm is proposed to quickly obtain solution results in traversal order. The effectiveness of the improved algorithm on traversal cost reduction is verified in this paper through multiple sets of experiments. .展开更多
Accurate measurement of the transverse position of a beam is crucial in particle accelerators because it plays a key role in determining the beam parameters.Existing methods for beam-position measurement rely on the d...Accurate measurement of the transverse position of a beam is crucial in particle accelerators because it plays a key role in determining the beam parameters.Existing methods for beam-position measurement rely on the detection of image currents induced on electrodes or narrow-band wake field induced by a beam passing through a cavity-type structure.However,these methods have limitations.The indirect measurement of multiple parameters is computationally complex,requiring external calibration to determine the system parameters in advance.Furthermore,the utilization of the beam signal information is incomplete.Hence,this study proposes a novel method for measuring the absolute electron beam transverse position.By utilizing the geometric relationship between the center position of the measured electron beam and multiple detection electrodes and by analyzing the differences in the arrival times of the beam signals detected by these electrodes,the absolute transverse position of the electron beam crossing the electrode plane can be calculated.This method features absolute position measurement,a position sensitivity coefficient independent of vacuum chamber apertures,and no requirement for a symmetrical detector electrode layout.The feasibility of this method is validated through numerical simulations and beam experiments.展开更多
基金the National Science and Technology Support Plan Project(2014BAD06B04).
文摘A ripple surface type pickup finger was designed to improve the performance of pickup finger precision maize seed metering device and to provide a solution for precision maize planter.The main structure and working principle of seed metering device were detailed in this paper.The dimension size distributions of maize seeds in different types were studied,the gestures of seeds clamped by pickup finger were analyzed,and the clamping dynamical model of pickup finger was established by theoretical analysis.To optimize the structural parameters of ripple surface type pickup finger,the discrete element method(DEM)model of pickup finger precision maize seed metering device was established by the discrete element software EDEM.The numerical simulations of orthogonal seeding performance experiments were conducted to analyze the influences of these factors on the quality of seeding.The rotational speed,wavelength of ripple surface and amplitude of ripple surface were selected as the experimental factors.The average seeding qualified index and the average seeding coefficient of variation on four different types of maize seeds were chosen for evaluating the seeding performance.The results showed that,the average seeding qualified index was 93.35%and the average seeding coefficient of variation was 11.23%under conditions of the 25 r/min rotational speed,8 mm wavelength of ripple surface and 2 mm amplitude of ripple surface.Under the same condition,the bench test was done which showed that the results of test and simulation were consistent.The maximum error of qualified index was 1.95%and the qualified index of improved seed metering device exceeded the original one by 12.34%.The working performance can meet the requirements of precision maize seeding.
文摘Indirect methods to detect and evaluate inclusions in steel are extensively reviewed, which include total oxygen content measurement, nitrogen pickup, steel and slag composition measurement, lining refractory observation, tracer studies of determining exogenous inclusions from slag and lining erosion, SEN clogging and final prod- uct tests. There is no single ideal method of detecting and evaluating inclusions in steel, so it is better to use several methods simultaneously to give a more accurate evaluation. Total oxygen content and nitrogen pickup in low carbon aluminum-killed steel as criterion of clean steel in many plants are summarized.
文摘In this paper, a hybrid genetic algorithm （GA） is proposed for the traveling salesman problem （TSP） with pickup and delivery （TSPPD）. In our algorithm, a novel pheromone-based crossover operator is advanced that utilizes both local and global information to construct offspring. In addition, a local search procedure is integrated into the GA to accelerate convergence. The proposed GA has been tested on benchmark instances, and the computational results show that it gives better convergence than existing heuristics.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50739002 and 50979064)
文摘Previous studies focused on the bed load transport rate for the condition of turbulent flow,while the knowledge of sediment transport in laminar flow is very limited.As an extreme case to reflect the viscous effect on sediment transport,sediment transport in laminar flow is considered in this paper.There are at least two factors affecting the transport rate of sediment under laminar flow conditions: (1) fluid forces;(2) particle to particle interactions.Together,these two factors represent the physical transport system.First,an exposure degree Probability Density Function (PDF) is developed to explore how the transport rate can be associated with characteristics of laminar flow and this factor reflects the particle to particle interactions,and the pickup probability equation in the absence of turbulence is developed based on the stochastic approach which reflects the exposure degree influence.Then,the formulas to calculate the critical shear stress of incipient motion and the bed load transport rate of fine uniform sediment are established.The derivation is made mainly based on Einstein’s bed load theory;we choose Einstein’s equation to model this system because we believe that the probabilistic approach taken is an appropriate way to account for the spatial and temporal variations in the forces causing sediment transport.These formulas have been tested against a wide range of existing laboratory data and compared with other existing empirical or semiempirical methods.The predictions by these newly proposed formulas are very good.
基金the financial support of the National Natural Science Foundation of China(No.52102453)。
文摘The weapon transportation support scheduling problem on aircraft carrier deck is the key to restricting the sortie rate and combat capability of carrier-based aircraft.This paper studies the problem and presents a novel solution architecture.Taking the interference of the carrier-based aircraft deck layout on the weapon transportation route and precedence constraint into consideration,a mixed integer formulation is established to minimize the total objective,which is constituted of makespan,load variance and accumulative transfer time of support unit.Solution approach is developed for the model.Firstly,based on modeling the carrier aircraft parked on deck as convex obstacles,the path library of weapon transportation is constructed through visibility graph and Warshall-Floyd methods.We then propose a bi-population immune algorithm in which a population-based forward/backward scheduling technique,local search schemes and a chaotic catastrophe operator are embedded.Besides,the randomkey solution representation and serial scheduling generation scheme are adopted to conveniently obtain a better solution.The Taguchi method is additionally employed to determine key parameters of the algorithm.Finally,on a set of generated realistic instances,we demonstrate that the proposed algorithm outperforms all compared algorithms designed for similar optimization problems and can significantly improve the efficiency,and that the established model and the bi-population immune algorithm can effectively respond to the weapon support requirements of carrier-based aircraft under different sortie missions.
基金the China Agriculture Research System Special Foundation CARS-10-P22National Science and Technology Support Project 2014BAD06B03+1 种基金Yunnan Province Winter Pollution-free Yield Technology System Construction and Application Projects Funded 2014YNC001Heilongjiang Province Key Science and Technology Project GA15B401.
文摘An air-suction potato seed metering device was designed to improve the performance of the large-size seed crops planting equipment and provide a solution for problems on the mechanical potato seeder,such as high multiple-seeding index,high missing-seeding index,low qualified index,and limited versatility.The main structure and operation parameters in terms of rotating speed of the device,seeds height and pickup vacuum pressure were determined by theoretical analysis.Two orthogonal tests,conventional tuber(the triaxial average diameter is about 38-57 mm)test and mini-tuber(the triaxial average diameter is about 12-36 mm)test,were conducted to analyze the influences of these factors on the quality of seeding.The multiple-seeding index,missing-seeding index and qualified index were chosen for evaluating the working performance.The results of conventional tuber test showed that,the multiple-seeding index was 1.1%,the missing-seeding index was 0.8%and the qualified index was 98.1%under conditions of the 30 r/min rotating speed,25 cm seeds height and 10 kPa pickup vacuum pressure.The results of mini-tuber test showed that the multiple-seeding index was 0.5%,the missing-seeding index was 0.6%and the qualified index was 98.9%under conditions of 35 r/min rotating speed,17 cm seeds height and 3.5 kPa pickup vacuum.The working performances of the device can meet the requirements of precision seeding.
文摘It is difficult to solve complete coverage path planning directly in the obstructed area. Therefore, in this paper, we propose a method of complete coverage path planning with improved area division. Firstly, the boustrophedon cell decomposition method is used to partition the map into sub-regions. The complete coverage paths within each sub-region are obtained by the Boustrophedon back-and-forth motions, and the order of traversal of the sub-regions is then described as a generalised traveling salesman problem with pickup and delivery based on the relative positions of the vertices of each sub-region. An adaptive large neighbourhood algorithm is proposed to quickly obtain solution results in traversal order. The effectiveness of the improved algorithm on traversal cost reduction is verified in this paper through multiple sets of experiments. .
基金supported by the National Key R&D Program of China(No.2022YFA1602201)。
文摘Accurate measurement of the transverse position of a beam is crucial in particle accelerators because it plays a key role in determining the beam parameters.Existing methods for beam-position measurement rely on the detection of image currents induced on electrodes or narrow-band wake field induced by a beam passing through a cavity-type structure.However,these methods have limitations.The indirect measurement of multiple parameters is computationally complex,requiring external calibration to determine the system parameters in advance.Furthermore,the utilization of the beam signal information is incomplete.Hence,this study proposes a novel method for measuring the absolute electron beam transverse position.By utilizing the geometric relationship between the center position of the measured electron beam and multiple detection electrodes and by analyzing the differences in the arrival times of the beam signals detected by these electrodes,the absolute transverse position of the electron beam crossing the electrode plane can be calculated.This method features absolute position measurement,a position sensitivity coefficient independent of vacuum chamber apertures,and no requirement for a symmetrical detector electrode layout.The feasibility of this method is validated through numerical simulations and beam experiments.
