To improve traffic performance when on-ramp vehicles merge into the mainstream,a collaborative merging control strategy is proposed to determine the merging sequence and trajectory control of vehicles.Merging trajecto...To improve traffic performance when on-ramp vehicles merge into the mainstream,a collaborative merging control strategy is proposed to determine the merging sequence and trajectory control of vehicles.Merging trajectory planning takes the minimization of vehicle acceleration as the optimization objective.Either the variational method or the quadratic programming method is utilized to determine arrival time,optimal time and control variables for each vehicle.As a supplement,the adaptive cruise control(ACC)model is used to calculate each control variable in each time interval on special occasions.Simulation results show that the cooperative merging control strategy outperforms the optimal control strategy.The root mean square(RMS)of acceleration and the root mean square error(RMSE)of time headway are significantly decreased,with the reductions up to 90.1%and 25.2%,respectively.Under the cooperative control strategy,the difference between the average speed and desired speed consistently approaches zero.In addition,few or no collisions occur.To conclude,the proposed strategy favours the improvements in passenger comfort,traffic efficiency,traffic stability and safety around highway on-ramps.展开更多
Nowadays more and more people reside in metropolitan areas,and the impact of this phenomenon is clearly creating challenges for the environment,the economy and the society at large.It is therefore useful and instructi...Nowadays more and more people reside in metropolitan areas,and the impact of this phenomenon is clearly creating challenges for the environment,the economy and the society at large.It is therefore useful and instructive to consider the issue of optimal city size and review the literature over the past decades on optimal city size theory.Based on the progress in recent years of comparative analysis and inductive research,from both theoretical and empirical perspectives,this paper outlines the original definitions proposed for optimal city size and discusses some of the advantages and disadvantages of the various theories.The two prevailing models in the classical analysis of optimal city size,the Henry George Theorem(HGT)and the neoclassical approach,are examined later.This paper then introduces the supply oriented dynamic model(SOUDY model)and offers a plausible model for optimal city size based on the general equilibrium analysis,which is related to sustainable development.The results show that:(1)Simple optimal city size theories come from the cost-benefit analysis developed by main stream economics,and therefore cannot overcome the defect that the optimal size of cities is the same since the same production function;(2)The Henry George Theorem,which is one of the classical analysis paradigms of optimal city size,has been used more frequently in recent years to research the issues of optimal tax and public goods and has gradually lost its connection to the topic of optimal city size;(3)The neoclassical approach to optimal city size consists of externalities influencing optimal city size,the equilibrium and optimal models for city size,the optimal town,product variety and city size distribution.This kind of research is still in the mainstream of the study of optimal city size.Compared to single optimal city size,more attention is paid to the optimal distribution of city size;and(4)The supply-oriented dynamic model allows for the integration of a spatial dimension into the economic research of optimal city size,and the constraint between city level and city size is relaxed and this has more power to explain real-world problems.At the same time,the general equilibrium analysis,as a significant economic research method,provides a new perspective for the study of optimal city size.The supply-oriented dynamic model and general equilibrium analysis are two new research paradigms that deserve more attention in the analysis of optimal city size.展开更多
This paper studies the complete monotonicity of the probability of ruin in the the classical risk model and the classical risk model that is perturbed by a diffusion. As a byproduct, the authors give an alternative p...This paper studies the complete monotonicity of the probability of ruin in the the classical risk model and the classical risk model that is perturbed by a diffusion. As a byproduct, the authors give an alternative proof to a result on the optimal dividend problem due to Loeffen （2008）.展开更多
Classical simulations of quantum circuits are limited in both space and time when the qubit count is above 50, the realm where quantum supremacy reigns. However, recently, for the low depth circuit with more than 50 q...Classical simulations of quantum circuits are limited in both space and time when the qubit count is above 50, the realm where quantum supremacy reigns. However, recently, for the low depth circuit with more than 50 qubits, there are several methods of simulation proposed by teams at Google and IBM. Here,we present a scheme of simulation which can extract a large amount of measurement outcomes within a short time, achieving a 64-qubit simulation of a universal random circuit of depth 22 using a 128-node cluster, and 56-and 42-qubit circuits on a single PC. We also estimate that a 72-qubit circuit of depth 23 can be simulated in about 16 h on a supercomputer identical to that used by the IBM team. Moreover, the simulation processes are exceedingly separable, hence parallelizable, involving just a few inter-process communications. Our work enables simulating more qubits with less hardware burden and provides a new perspective for classical simulations.展开更多
In this paper, we investigate the global existence of nonnegative solutions of a two- species Keller-Segel model with Lotka-Volterra competitive source terms. By raising the regularity of a solution from L^1 to L^p（p...In this paper, we investigate the global existence of nonnegative solutions of a two- species Keller-Segel model with Lotka-Volterra competitive source terms. By raising the regularity of a solution from L^1 to L^p（p〉1）, the existence and uniqueness of the classical global in time solution to this chemotaxis model is proved for any chemotactic coefficients X1, X2 〉 0 when the space dimension is one. Furthermore, it is shown that the model has a unique classical global solution in two and three space dimensions if the chemotactic coefficients X1 and X2 are small as compared to the diffusion coefficient d3 of the chemoattractant.展开更多
基金The Scientific Innovation Research of Graduate Students in Jiangsu Province(No.KYCX17_0145,KYCX17_0141)
文摘To improve traffic performance when on-ramp vehicles merge into the mainstream,a collaborative merging control strategy is proposed to determine the merging sequence and trajectory control of vehicles.Merging trajectory planning takes the minimization of vehicle acceleration as the optimization objective.Either the variational method or the quadratic programming method is utilized to determine arrival time,optimal time and control variables for each vehicle.As a supplement,the adaptive cruise control(ACC)model is used to calculate each control variable in each time interval on special occasions.Simulation results show that the cooperative merging control strategy outperforms the optimal control strategy.The root mean square(RMS)of acceleration and the root mean square error(RMSE)of time headway are significantly decreased,with the reductions up to 90.1%and 25.2%,respectively.Under the cooperative control strategy,the difference between the average speed and desired speed consistently approaches zero.In addition,few or no collisions occur.To conclude,the proposed strategy favours the improvements in passenger comfort,traffic efficiency,traffic stability and safety around highway on-ramps.
基金The Scientific Research Project of Hunan Education Department(18C0964)The 2016 Scientific Research Fund Project for Young Teachers of Hunan University of Finance and Economics(Q201604)
文摘Nowadays more and more people reside in metropolitan areas,and the impact of this phenomenon is clearly creating challenges for the environment,the economy and the society at large.It is therefore useful and instructive to consider the issue of optimal city size and review the literature over the past decades on optimal city size theory.Based on the progress in recent years of comparative analysis and inductive research,from both theoretical and empirical perspectives,this paper outlines the original definitions proposed for optimal city size and discusses some of the advantages and disadvantages of the various theories.The two prevailing models in the classical analysis of optimal city size,the Henry George Theorem(HGT)and the neoclassical approach,are examined later.This paper then introduces the supply oriented dynamic model(SOUDY model)and offers a plausible model for optimal city size based on the general equilibrium analysis,which is related to sustainable development.The results show that:(1)Simple optimal city size theories come from the cost-benefit analysis developed by main stream economics,and therefore cannot overcome the defect that the optimal size of cities is the same since the same production function;(2)The Henry George Theorem,which is one of the classical analysis paradigms of optimal city size,has been used more frequently in recent years to research the issues of optimal tax and public goods and has gradually lost its connection to the topic of optimal city size;(3)The neoclassical approach to optimal city size consists of externalities influencing optimal city size,the equilibrium and optimal models for city size,the optimal town,product variety and city size distribution.This kind of research is still in the mainstream of the study of optimal city size.Compared to single optimal city size,more attention is paid to the optimal distribution of city size;and(4)The supply-oriented dynamic model allows for the integration of a spatial dimension into the economic research of optimal city size,and the constraint between city level and city size is relaxed and this has more power to explain real-world problems.At the same time,the general equilibrium analysis,as a significant economic research method,provides a new perspective for the study of optimal city size.The supply-oriented dynamic model and general equilibrium analysis are two new research paradigms that deserve more attention in the analysis of optimal city size.
基金supported by the National Natural Science Foundation of China under Grant No.11171179the Research Fund for the Doctoral Program of Higher Education of China under Grant No.20093705110002
文摘This paper studies the complete monotonicity of the probability of ruin in the the classical risk model and the classical risk model that is perturbed by a diffusion. As a byproduct, the authors give an alternative proof to a result on the optimal dividend problem due to Loeffen （2008）.
基金supported by the National Key Research and Development Program of China(2016YFA0301700)the National Natural Science Foundation of China(11625419)+1 种基金the Anhui Initiative in Quantum Information Technologies(AHY080000)supported by Yangzi Cloud Computing Data Centre and Gyrotech,Nanjing,China
文摘Classical simulations of quantum circuits are limited in both space and time when the qubit count is above 50, the realm where quantum supremacy reigns. However, recently, for the low depth circuit with more than 50 qubits, there are several methods of simulation proposed by teams at Google and IBM. Here,we present a scheme of simulation which can extract a large amount of measurement outcomes within a short time, achieving a 64-qubit simulation of a universal random circuit of depth 22 using a 128-node cluster, and 56-and 42-qubit circuits on a single PC. We also estimate that a 72-qubit circuit of depth 23 can be simulated in about 16 h on a supercomputer identical to that used by the IBM team. Moreover, the simulation processes are exceedingly separable, hence parallelizable, involving just a few inter-process communications. Our work enables simulating more qubits with less hardware burden and provides a new perspective for classical simulations.
基金This work is supported by the National Natural Science Foundation of China （Nos. 11361055, 11761063 and 11661051）, the Natural Science Foundation of Gansu Province （No. 1606RJZA038）, the National Statistical Scientific Research Projects （No. 2017LZ41）, and the Scientific Study Project for Gansu Province Institutes of Higher Learning （No. 2017B-41）.
文摘In this paper, we investigate the global existence of nonnegative solutions of a two- species Keller-Segel model with Lotka-Volterra competitive source terms. By raising the regularity of a solution from L^1 to L^p（p〉1）, the existence and uniqueness of the classical global in time solution to this chemotaxis model is proved for any chemotactic coefficients X1, X2 〉 0 when the space dimension is one. Furthermore, it is shown that the model has a unique classical global solution in two and three space dimensions if the chemotactic coefficients X1 and X2 are small as compared to the diffusion coefficient d3 of the chemoattractant.
