Accelerating urbanization and the rapid development of intelligent transportation systems have rendered shortterm traffic flow prediction an important research field.Accurate prediction of traffic flow is beneficial f...Accelerating urbanization and the rapid development of intelligent transportation systems have rendered shortterm traffic flow prediction an important research field.Accurate prediction of traffic flow is beneficial for the optimization of traffic planning,improvement of road utilization,reduction of traffic congestion,and reduction in the incidence of traffic accidents.However,data pertaining to traffic flow are typically influenced by a multitude of factors,resulting in data that exhibit a considerable degree of nonlinearity and complexity.To address the issue of noise in raw traffic flow data,this study proposes a hybrid model that combines variational mode decomposition(VMD),a bidirectional long short-term memory network(BiLSTM),and a gated recurrent unit(GRU)for short-term traffic flow prediction.To validate the effectiveness of the model,an experimental validation was conducted based on traffic flow data from UK highways,and the performance of the model was compared with common benchmark models.The experimental results demonstrate that the proposed method yields superior prediction results in terms of mean absolute error,coefficient of determination,and root-mean-square error compared to existing prediction techniques,thereby substantiating its efficacy in short-term traffic flow prediction.展开更多
以异辛醇改性三氯氧钒(VOCl_3·3(2-ethyl-hexanol))为催化剂前体,倍半乙基铝(EASC)为助催化剂,三氯乙酸乙酯(ETCA)为活化剂进行乙烯/丙烯共聚合,并与传统VOCl_3体系进行对比。考察了EASC和ETCA用量、反应温度对聚合的影响。随EASC...以异辛醇改性三氯氧钒(VOCl_3·3(2-ethyl-hexanol))为催化剂前体,倍半乙基铝(EASC)为助催化剂,三氯乙酸乙酯(ETCA)为活化剂进行乙烯/丙烯共聚合,并与传统VOCl_3体系进行对比。考察了EASC和ETCA用量、反应温度对聚合的影响。随EASC用量的增加,2种催化体系活性均先增加后下降,VOCl_3·3(2-ethyl-hexanol)和VOCl_3体系分别在[Al]/[V]比为40和30时达到最高催化活性6. 15 kg EPR/g V·h和4. 97 kg EPR/g V·h。2种催化体系活性均随聚合温度的升高呈下降的趋势,VOCl_3·3(2-ethyl-hexanol)体系的下降幅度低于VOCl_3体系,表明异辛醇有效地稳定了生成的活性中心。差示扫描量热分析和核磁共振碳谱分析表明以VOCl_3·3(2-ethyl-hexanol)体系所合成的共聚物较VOCl_3体系有更高的丙烯插入率和更为无规的结构。展开更多
We report a facile coagglomeration method for preparing graphene (G)/MgCl2‐supported Ti‐based Ziegler‐Natta catalysts. The effects of graphene feed ratio on catalyst morphology and ethylene polymerization behavior ...We report a facile coagglomeration method for preparing graphene (G)/MgCl2‐supported Ti‐based Ziegler‐Natta catalysts. The effects of graphene feed ratio on catalyst morphology and ethylene polymerization behavior were examined. The synthesized catalyst exhibited very high activity for ethylene polymerization. The resultant polyethylene (PE)/G nanocomposites showed a layered morphology, and the graphene fillers were well dispersed in the PE matrix. In addition, the thermal stability and mechanical properties of PE were significantly enhanced with the introduction of a very small amount of G fillers (0.05 wt%). This work provides a facile approach to the production o fhigh‐performance PE.展开更多
The collisional dynamics of two symmetric droplets with equal intraspecies scattering lengths and particle number density for each component is studied by solving the corresponding extended Gross–Pitaevskii equation ...The collisional dynamics of two symmetric droplets with equal intraspecies scattering lengths and particle number density for each component is studied by solving the corresponding extended Gross–Pitaevskii equation in two dimensions by including a logarithmic correction term in the usual contact interaction.We find the merging droplet after collision experiences a quadrupole oscillation in its shape and the oscillation period is found to be independent of the incidental momentum for small droplets.With increasing collision momentum the colliding droplets may separate into two,or even more,and finally into small pieces of droplets.For these dynamical phases we manage to present boundaries determined by the remnant particle number in the central area and the damped oscillation of the quadrupole mode.A stability peak for the existence of droplets emerges at the critical particle number Nc≃48 for the quasi-Gaussian and flat-top shapes of the droplets.展开更多
Transportation systems serve as a crucial foundation for maintaining the normal operation of cities and satisfying the requirements of public life.With the development of next-generation information technologies,autom...Transportation systems serve as a crucial foundation for maintaining the normal operation of cities and satisfying the requirements of public life.With the development of next-generation information technologies,automated driving technologies have brought new opportunities to improve the performance of traffic systems and the intelligence level of cities.Currently,significant research efforts have been conducted to develop automated driving systems in three major industries,i.e.,automobile,roadway,and telecommunication.However,the collaboration and integration of automated driving systems among automobile,roadway,and telecommunications are still lacking,especially for collaborative development of system architecture and objectives.To address the need,this study first proposes a system architecture of vehicle-road-cloud collaborative automated driving system(VRC-CADS).Three levels of collaborative development,i.e.,collaborative sensing,collaborative decision-making,and collaborative control,are designed for the VRC-CADS.Based on that,the typical scenarios of automated driving for each level of the system are further defined and interpreted.Moreover,feasible and systematic suggestions for the collaborative development of the VRC-CADS are provided,considering the cross-cutting collaboration among government agencies,academia,and industry.The proposed system architecture of the VRC-CADS will facilitate the optimization of urban lifelines and the evolution of intelligent cities.展开更多
Effective task assignment decisions are paramount for ensuring reliable task execution in multi-UAV systems.However,in the development of feasible plans,challenges stemming from extensive and prolonged task requiremen...Effective task assignment decisions are paramount for ensuring reliable task execution in multi-UAV systems.However,in the development of feasible plans,challenges stemming from extensive and prolonged task requirements are encountered.This paper establishes a decision-making framework for multiple unmanned aerial vehicles(multi-UAV)based on the well-known pigeon-inspired optimization(PIO)algorithm.By addressing the problem from a hierarchical structural perspective,the initial stage involves minimizing the global objective of the flight distance cost after obtaining the entire task distribution and task requirements,utilizing the global optimization capability of the classical PIO algorithm to allocate feasible task spaces for each UAV.In the second stage,building upon the decisions made in the preceding stage,each UAV is abstracted as an agent maximizing its own task execution benefits.An improved version of the PIO algorithm modified with a sine-cosine search mechanism is proposed,enabling the acquisition of the optimal task execution sequence.Simulation experiments involving two different scales of UAVs validate the effectiveness of the proposed methodology.Moreover,dynamic events such as UAV damage and task changes are considered in the simulation to validate the efficacy of the two-stage framework.展开更多
基金supported by the Enterprise Innovation Consortium Project under the Major Special Science and Technology Project of Gansu Province(Grant No.22ZD6GA010).
文摘Accelerating urbanization and the rapid development of intelligent transportation systems have rendered shortterm traffic flow prediction an important research field.Accurate prediction of traffic flow is beneficial for the optimization of traffic planning,improvement of road utilization,reduction of traffic congestion,and reduction in the incidence of traffic accidents.However,data pertaining to traffic flow are typically influenced by a multitude of factors,resulting in data that exhibit a considerable degree of nonlinearity and complexity.To address the issue of noise in raw traffic flow data,this study proposes a hybrid model that combines variational mode decomposition(VMD),a bidirectional long short-term memory network(BiLSTM),and a gated recurrent unit(GRU)for short-term traffic flow prediction.To validate the effectiveness of the model,an experimental validation was conducted based on traffic flow data from UK highways,and the performance of the model was compared with common benchmark models.The experimental results demonstrate that the proposed method yields superior prediction results in terms of mean absolute error,coefficient of determination,and root-mean-square error compared to existing prediction techniques,thereby substantiating its efficacy in short-term traffic flow prediction.
文摘以异辛醇改性三氯氧钒(VOCl_3·3(2-ethyl-hexanol))为催化剂前体,倍半乙基铝(EASC)为助催化剂,三氯乙酸乙酯(ETCA)为活化剂进行乙烯/丙烯共聚合,并与传统VOCl_3体系进行对比。考察了EASC和ETCA用量、反应温度对聚合的影响。随EASC用量的增加,2种催化体系活性均先增加后下降,VOCl_3·3(2-ethyl-hexanol)和VOCl_3体系分别在[Al]/[V]比为40和30时达到最高催化活性6. 15 kg EPR/g V·h和4. 97 kg EPR/g V·h。2种催化体系活性均随聚合温度的升高呈下降的趋势,VOCl_3·3(2-ethyl-hexanol)体系的下降幅度低于VOCl_3体系,表明异辛醇有效地稳定了生成的活性中心。差示扫描量热分析和核磁共振碳谱分析表明以VOCl_3·3(2-ethyl-hexanol)体系所合成的共聚物较VOCl_3体系有更高的丙烯插入率和更为无规的结构。
基金supported by the National Research Foundation of Korea (NRF-2015R1D1A1A0161012)the National Natural Science Foundation of China (U1462124)~~
文摘We report a facile coagglomeration method for preparing graphene (G)/MgCl2‐supported Ti‐based Ziegler‐Natta catalysts. The effects of graphene feed ratio on catalyst morphology and ethylene polymerization behavior were examined. The synthesized catalyst exhibited very high activity for ethylene polymerization. The resultant polyethylene (PE)/G nanocomposites showed a layered morphology, and the graphene fillers were well dispersed in the PE matrix. In addition, the thermal stability and mechanical properties of PE were significantly enhanced with the introduction of a very small amount of G fillers (0.05 wt%). This work provides a facile approach to the production o fhigh‐performance PE.
基金supported by the National Natural Science Foundation of China(Grant No.12074340)the Science Foundation of Zhejiang Sci-Tech University(ZSTU)under Grant Nos.20062098-Y and 21062339-Y.
文摘The collisional dynamics of two symmetric droplets with equal intraspecies scattering lengths and particle number density for each component is studied by solving the corresponding extended Gross–Pitaevskii equation in two dimensions by including a logarithmic correction term in the usual contact interaction.We find the merging droplet after collision experiences a quadrupole oscillation in its shape and the oscillation period is found to be independent of the incidental momentum for small droplets.With increasing collision momentum the colliding droplets may separate into two,or even more,and finally into small pieces of droplets.For these dynamical phases we manage to present boundaries determined by the remnant particle number in the central area and the damped oscillation of the quadrupole mode.A stability peak for the existence of droplets emerges at the critical particle number Nc≃48 for the quasi-Gaussian and flat-top shapes of the droplets.
文摘Transportation systems serve as a crucial foundation for maintaining the normal operation of cities and satisfying the requirements of public life.With the development of next-generation information technologies,automated driving technologies have brought new opportunities to improve the performance of traffic systems and the intelligence level of cities.Currently,significant research efforts have been conducted to develop automated driving systems in three major industries,i.e.,automobile,roadway,and telecommunication.However,the collaboration and integration of automated driving systems among automobile,roadway,and telecommunications are still lacking,especially for collaborative development of system architecture and objectives.To address the need,this study first proposes a system architecture of vehicle-road-cloud collaborative automated driving system(VRC-CADS).Three levels of collaborative development,i.e.,collaborative sensing,collaborative decision-making,and collaborative control,are designed for the VRC-CADS.Based on that,the typical scenarios of automated driving for each level of the system are further defined and interpreted.Moreover,feasible and systematic suggestions for the collaborative development of the VRC-CADS are provided,considering the cross-cutting collaboration among government agencies,academia,and industry.The proposed system architecture of the VRC-CADS will facilitate the optimization of urban lifelines and the evolution of intelligent cities.
文摘Effective task assignment decisions are paramount for ensuring reliable task execution in multi-UAV systems.However,in the development of feasible plans,challenges stemming from extensive and prolonged task requirements are encountered.This paper establishes a decision-making framework for multiple unmanned aerial vehicles(multi-UAV)based on the well-known pigeon-inspired optimization(PIO)algorithm.By addressing the problem from a hierarchical structural perspective,the initial stage involves minimizing the global objective of the flight distance cost after obtaining the entire task distribution and task requirements,utilizing the global optimization capability of the classical PIO algorithm to allocate feasible task spaces for each UAV.In the second stage,building upon the decisions made in the preceding stage,each UAV is abstracted as an agent maximizing its own task execution benefits.An improved version of the PIO algorithm modified with a sine-cosine search mechanism is proposed,enabling the acquisition of the optimal task execution sequence.Simulation experiments involving two different scales of UAVs validate the effectiveness of the proposed methodology.Moreover,dynamic events such as UAV damage and task changes are considered in the simulation to validate the efficacy of the two-stage framework.
