就业与居住空间关系是城市规划与管理研究的热点问题。已有研究主要基于传统宏观模型对就业—居住空间结构进行现状分析或对城市理论进行实证研究,在微观尺度的机制探讨与过程模拟方面较为缺乏。本文基于多智能体自下而上的建模思想,提...就业与居住空间关系是城市规划与管理研究的热点问题。已有研究主要基于传统宏观模型对就业—居住空间结构进行现状分析或对城市理论进行实证研究,在微观尺度的机制探讨与过程模拟方面较为缺乏。本文基于多智能体自下而上的建模思想,提出基于就业市场的人口居住区位选择模型(Labor Market Based Model of Residential Location-LMBMRL)。以典型的快速工业化地区—东莞市主城区为实验区,通过多情景模拟对就业与居住空间的互动关系进行机制探讨与过程分析。模拟结果充分反映了就业选择对人口居住区位决策的影响,定量评估了住房与交通对职住空间均衡性与职住分离的影响规律。当住房成本提高时,城市职住均衡性降低;当交通可达性提高时,城市空间结构可能出现较为显著的职住分离现象。最后通过多情景模拟揭示不同行业劳动人口群体的就业—居住空间特征与组织模式。研究结果有助于深刻理解城市就业—居住空间互动关系及其内部因果,能够为城市规划与管理提供决策参考。展开更多
An automated method to optimize the definition of the progress variables in the flamelet-based dimension reduction is proposed. The performance of these optimized progress variables in coupling the flamelets and flow ...An automated method to optimize the definition of the progress variables in the flamelet-based dimension reduction is proposed. The performance of these optimized progress variables in coupling the flamelets and flow solver is presented. In the proposed method, the progress variables are defined according to the first two principal components （PCs） from the principal component analysis （PCA） or kernel-density-weighted PCA （KEDPCA） of a set of flamelets. These flamelets can then be mapped to these new progress variables instead of the mixture fraction/conventional progress variables. Thus, a new chemistry look-up table is constructed. A priori validation of these optimized progress variables and the new chemistry table is implemented in a CH4/N2/air lift-off flame. The reconstruction of the lift-off flame shows that the optimized progress variables perform better than the conventional ones, especially in the high temperature area. The coefficient determinations （R2 statistics） show that the KEDPCA performs slightly better than the PCA except for some minor species. The main advantage of the KEDPCA is that it is less sensitive to the database. Meanwhile, the criteria for the optimization are proposed and discussed. The constraint that the progress variables should monotonically evolve from fresh gas to burnt gas is analyzed in detail.展开更多
Traffic simulators are utilized to solve a variety of traffic-related problems.For such simulators,origin-destination(OD)traffic volumes as mobility demands are required to input,and we need to estimate them.The autho...Traffic simulators are utilized to solve a variety of traffic-related problems.For such simulators,origin-destination(OD)traffic volumes as mobility demands are required to input,and we need to estimate them.The authors regard an OD estimation as a bi-level programming problem,and apply a microscopic traffic simulation model to it.However,the simulation trials can be computationally expensive if full dynamic rerouting is allowed,when employing multi-agent-based models in the estimation process.This paper proposes an efficient OD estimation method using a multi-agent-based simulator with restricted dynamic rerouting to reduce the computational load.Even though,in the case of large traffic demand,the restriction on dynamic rerouting can result in heavier congestion.The authors resolve this problem by introducing constraints of the bi-level programming problem depending on link congestion.Test results show that the accuracy of the link traffic volume reproduced with the proposed method is virtually identical to that of existing methods but that the proposed method is more computationally efficient in a wide-range or high-demand context.展开更多
Mathematical and computational approaches are important tools for understanding epidemic spread patterns and evaluating policies of disease control. In recent years, epidemiology has become increasingly integrated wit...Mathematical and computational approaches are important tools for understanding epidemic spread patterns and evaluating policies of disease control. In recent years, epidemiology has become increasingly integrated with mathematics, sociology, management science, complexity science, and computer science. The cross of multiple disciplines has caused rapid development of mathematical and computational approaches to epidemic modeling. In this article, we carry out a comprehensive review of epidemic models to provide an insight into the literature of epidemic modeling and simulation.We introduce major epidemic models in three directions, including mathematical models, complex network models, and agent-based models. We discuss the principles, applications, advantages, and limitations of these models. Meanwhile, we also propose some future research directions in epidemic modeling.展开更多
Over the forty-year history of interactive computer graphics, there have beencontinuous advances, but at some stage this progression must terminate with images beingsufficiently realistic for all practical purposes. H...Over the forty-year history of interactive computer graphics, there have beencontinuous advances, but at some stage this progression must terminate with images beingsufficiently realistic for all practical purposes. How much detail do we really need? Polygon countsover a few million imply that on average each polygon paints less than a single pixel, making useof polygon shading hardware wasteful. We consider the problem of determining how much realism isrequired for a variety of applications. We discuss how current trends in computer graphics hardware,and in particular of graphics cards targeted at the computer games industry, will help or hinderachievement of these requirements. With images now being so convincingly realistic in many cases,critical faculties are often suspended and the images are accepted as correct and truthful althoughthey may well be incorrect and sometimes misleading or untruthful. Display resolution has remainedlargely constant in spatial terms for the last twenty years and in terms of the number of pixels hasincreased by less than an order of magnitude. If the long-promised breakthroughs in displaytechnology are finally realised, how should we use the increased resolution?展开更多
文摘就业与居住空间关系是城市规划与管理研究的热点问题。已有研究主要基于传统宏观模型对就业—居住空间结构进行现状分析或对城市理论进行实证研究,在微观尺度的机制探讨与过程模拟方面较为缺乏。本文基于多智能体自下而上的建模思想,提出基于就业市场的人口居住区位选择模型(Labor Market Based Model of Residential Location-LMBMRL)。以典型的快速工业化地区—东莞市主城区为实验区,通过多情景模拟对就业与居住空间的互动关系进行机制探讨与过程分析。模拟结果充分反映了就业选择对人口居住区位决策的影响,定量评估了住房与交通对职住空间均衡性与职住分离的影响规律。当住房成本提高时,城市职住均衡性降低;当交通可达性提高时,城市空间结构可能出现较为显著的职住分离现象。最后通过多情景模拟揭示不同行业劳动人口群体的就业—居住空间特征与组织模式。研究结果有助于深刻理解城市就业—居住空间互动关系及其内部因果,能够为城市规划与管理提供决策参考。
基金Project supported by the National Natural Science Foundation of China(Nos.50936005,51576182,and 11172296)
文摘An automated method to optimize the definition of the progress variables in the flamelet-based dimension reduction is proposed. The performance of these optimized progress variables in coupling the flamelets and flow solver is presented. In the proposed method, the progress variables are defined according to the first two principal components （PCs） from the principal component analysis （PCA） or kernel-density-weighted PCA （KEDPCA） of a set of flamelets. These flamelets can then be mapped to these new progress variables instead of the mixture fraction/conventional progress variables. Thus, a new chemistry look-up table is constructed. A priori validation of these optimized progress variables and the new chemistry table is implemented in a CH4/N2/air lift-off flame. The reconstruction of the lift-off flame shows that the optimized progress variables perform better than the conventional ones, especially in the high temperature area. The coefficient determinations （R2 statistics） show that the KEDPCA performs slightly better than the PCA except for some minor species. The main advantage of the KEDPCA is that it is less sensitive to the database. Meanwhile, the criteria for the optimization are proposed and discussed. The constraint that the progress variables should monotonically evolve from fresh gas to burnt gas is analyzed in detail.
基金supported by JSPS KAKENHI (Grant Nos.15H01785 and 19H02377).
文摘Traffic simulators are utilized to solve a variety of traffic-related problems.For such simulators,origin-destination(OD)traffic volumes as mobility demands are required to input,and we need to estimate them.The authors regard an OD estimation as a bi-level programming problem,and apply a microscopic traffic simulation model to it.However,the simulation trials can be computationally expensive if full dynamic rerouting is allowed,when employing multi-agent-based models in the estimation process.This paper proposes an efficient OD estimation method using a multi-agent-based simulator with restricted dynamic rerouting to reduce the computational load.Even though,in the case of large traffic demand,the restriction on dynamic rerouting can result in heavier congestion.The authors resolve this problem by introducing constraints of the bi-level programming problem depending on link congestion.Test results show that the accuracy of the link traffic volume reproduced with the proposed method is virtually identical to that of existing methods but that the proposed method is more computationally efficient in a wide-range or high-demand context.
基金Acknowledgements The authors would like to thank editors and three anonymous referees for their valuable comments and suggestions. This work was supported by the National Natural Science Foundation of China （Grant Nos. 91024030, 61374185 and 61403402）.
文摘Mathematical and computational approaches are important tools for understanding epidemic spread patterns and evaluating policies of disease control. In recent years, epidemiology has become increasingly integrated with mathematics, sociology, management science, complexity science, and computer science. The cross of multiple disciplines has caused rapid development of mathematical and computational approaches to epidemic modeling. In this article, we carry out a comprehensive review of epidemic models to provide an insight into the literature of epidemic modeling and simulation.We introduce major epidemic models in three directions, including mathematical models, complex network models, and agent-based models. We discuss the principles, applications, advantages, and limitations of these models. Meanwhile, we also propose some future research directions in epidemic modeling.
文摘Over the forty-year history of interactive computer graphics, there have beencontinuous advances, but at some stage this progression must terminate with images beingsufficiently realistic for all practical purposes. How much detail do we really need? Polygon countsover a few million imply that on average each polygon paints less than a single pixel, making useof polygon shading hardware wasteful. We consider the problem of determining how much realism isrequired for a variety of applications. We discuss how current trends in computer graphics hardware,and in particular of graphics cards targeted at the computer games industry, will help or hinderachievement of these requirements. With images now being so convincingly realistic in many cases,critical faculties are often suspended and the images are accepted as correct and truthful althoughthey may well be incorrect and sometimes misleading or untruthful. Display resolution has remainedlargely constant in spatial terms for the last twenty years and in terms of the number of pixels hasincreased by less than an order of magnitude. If the long-promised breakthroughs in displaytechnology are finally realised, how should we use the increased resolution?
