Employing flow space theory and multi-source data,this study examines the spatial net-work structure and factors influencing railway passenger flow,which is crucial for rail planning in densely populated megalopolises...Employing flow space theory and multi-source data,this study examines the spatial net-work structure and factors influencing railway passenger flow,which is crucial for rail planning in densely populated megalopolises.Focusing on China’s Yangtze River Delta(YRD)megalopolis,we utilize social network analysis(SNA)to explore the characteristics of various flow networks and their interactions with the railway passenger flow network.Key findings include:(1)a pronounced polarization effect and core-periphery structure exist in the YRD,notably within industry and railway flow networks;(2)industry and cor-poration flow significantly contributes to rail passenger flow,with corporation networks in commerce,technical services,and finance showing higher similarity to the railway passen-ger flow network;(3)there is significant heterogeneity in the correlation between rail pas-senger flow and other flows within sub-networks formed by connections among nodes of different levels;(4)enhancing railway services at lower-level nodes is essential to mitigate the disparity between population mobility and rail passenger flow and to promote rail transportation equity.This research offers valuable insights for policymakers in developing countries to strategically plan railroad networks in megalopolises.展开更多
With rapid development of air transportation,the airspace structure of the future will need to be flexible and dynamic to accommodate the increase in traffic demand.The corridors-in-the-sky has become a new technology...With rapid development of air transportation,the airspace structure of the future will need to be flexible and dynamic to accommodate the increase in traffic demand.The corridors-in-the-sky has become a new technology to support the full exploitation and utilization of airspace resources.This paper proposes a method of designing corridor,identifying congestion state,and analyzing the influence of air routes’traffic flow.From this,we have reached a number of conclusions.(1)The congestion periods present the multi-peak"wavy"scattered distributions and the peaks back-end agglomeration characteristics in the whole day.(2)The congestion segments present the structural characteristics of unbalanced coverage and concentrated distribution to the crossing points.The corridors with high congestion level present as an italic"N-shaped"frame,which presents incomplete penetration of short segments.(3)For the temporal and spatial interaction,there are two types of congestion segments,and there are some common congestion periods in different congestion segments of multiple corridors.The high-density air route plays a relatively decisive role in corridor congestion,and the influence of two directions is unbalanced.This research can provide a basis for the dynamic evaluation of China’s airspace resources and corridors construction in the future.展开更多
The intermediate link compression characteristics of e-commerce express logistics ne tworks influence the tradition al mode of circulation of goods and economic organization,and alter the city spatial pattern.Based on...The intermediate link compression characteristics of e-commerce express logistics ne tworks influence the tradition al mode of circulation of goods and economic organization,and alter the city spatial pattern.Based on the theory of space of flows,this study adopts China Smart Logistics Network relational data to build China's e-commerce express logistics network and explore its spatial structure characteristics through social network analysis(SNA),the PageRank technique,and geospatial methods.The results are as follows:the network density is 0.9270,which is close to 1;hence,indicating that e-commerce express logistics lines between Chinese cities are nearly complete and they form a typical network structure,thereby eliminating fragmented spaces.Moreover,the average minimum number of edges is 1.1375,which indicates that the network has a small world effect and thus has a high flow efficiency of logistics elements.A significant hierarchical diffusion effect was observed in dominant flows with the highest edge weights.A diamond-structured network was formed with Shanghai,Guangzhou,Chongqing,and Beijing as the four core nodes.Other node cities with a large logistics scale and importance in the network are mainly located in the 19 city agglomerations of China,revealing the fact that the development of city agglomerations is essential for promoting the separation of experience space and changing the urban spatial pattern.This study enriches the theory of urban networks,reveals the flow laws of modern logistics elements,and encourages coordinated development of urban logistics.展开更多
目的探讨磁共振三维可变翻转角快速自旋回波成像技术(SPACE)在显示肺球形病灶内部血管的临床应用价值。方法搜集拟进行胸部CT增强扫描的患者30例,所有患者均在接受CT增强检查后24 h内进行MR检查。扫描序列包括T1WI 3D Star VIBE序列、T2...目的探讨磁共振三维可变翻转角快速自旋回波成像技术(SPACE)在显示肺球形病灶内部血管的临床应用价值。方法搜集拟进行胸部CT增强扫描的患者30例,所有患者均在接受CT增强检查后24 h内进行MR检查。扫描序列包括T1WI 3D Star VIBE序列、T2WI HASTE序列以及T2-SPACE FLOW序列。由2名具有10年以上工作经验的放射科医师采用盲法先对MRI图像上所有病灶中肺血管的显示度进行主观评价,再观察与之对应的CT增强图像上肺血管的显示能力(CT增强图像作为参考标准),评分标准采用4分法(4分:边缘非常清晰,3分:边缘较清晰,2分:边缘不清晰,1分:不可见)。结果 CT增强图像上共检出48个肺球形病灶(大小1.0~5.6 cm),69支肺血管,另于MRI T2-SPACE FLOW序列上,检出48个球形病灶64支肺血管,检出率为94.3%。两名医师对CT增强图像和MRI图像上对肺球形病变内部血管形态显示度的主观评分分别为(3.59±0.46)分和(3.42±0.39)分(医师1)、(3.61±0.22)分和(3.49±0.68)分(医师2),差异均无统计学意义(P>0.05)。结论在显示肺球形病变内部血管中,T2-SPACE FLOW序列具有较高的敏感度及准确率,同时可以提供和CT增强扫描同等效能的肺血管显示度,具有重要的临床价值。展开更多
A first experimental study on two-phase how patterns at a long-term, steady microgravity condition was conducted on board the Russian Space Station 'MIR' in August 1999. Carbogal and air are used as the liquid...A first experimental study on two-phase how patterns at a long-term, steady microgravity condition was conducted on board the Russian Space Station 'MIR' in August 1999. Carbogal and air are used as the liquid and the gas phase, respectively. Bubble, slug, slug-annular transitional, and annular hows are observed. A new region of annular how with lower liquid superficial velocity is discovered, and the region of the slug-annular transitional flow is wider than that observed by experiments on board the parabolic aircraft. The main patterns are bubble, slug-annular transitional and annular flows based on the experiments on board MIR space station. Some influences on the two-phase how patterns in the present experiments are discussed.展开更多
The equations governing incompressible and compressible inviscid flows and written in the physical frame ( t,x,y,z ) are known to be linearly well posed and exhibit elliptic or hyperbolic nature. The linear well posed...The equations governing incompressible and compressible inviscid flows and written in the physical frame ( t,x,y,z ) are known to be linearly well posed and exhibit elliptic or hyperbolic nature. The linear well posedness is considered here for these equations under a space time transformation ( t,x,y,z)→(τ,ξ,η,ζ ), where the pseudo time τ and the new space coordinate ( ξ,η,ζ ) all depend on ( t,x,y,z ). Such a transformation could be useful for uniformly treating problems in which the flow is fast unsteady somewhere and slow unsteady or steady elsewhere. It is found that the transformation may alter the ellipticity, the hyperbolicty, and even the well posedness of the original equations. In one dimension, the transformed incompressible flow equations become weakly hyperbolic and the compressible ones could degenerate to elliptical equations. In high dimensions there are conditions such that the transformed equations become ill posed.展开更多
The mobility and interaction between urban and rural areas are becoming more and more intensive,and their links and exchanges are increasingly closer due to constant flow of factors such as information,capital,personn...The mobility and interaction between urban and rural areas are becoming more and more intensive,and their links and exchanges are increasingly closer due to constant flow of factors such as information,capital,personnel and technology.In this context,the element integration of urban and rural“space of flows”can promote the integrated development of urban and rural areas,improve the consumption environment and experience,and promote the industrial upgrading and technological progress.To realize the element integration of urban and rural“space of flows”,it is necessary to explore and innovate in infrastructure construction,information technology application,industrial cooperation and cultural exchanges.Government departments,enterprises and social organizations also need to work together to give play to their respective advantages and jointly promote the process of element integration of urban and rural“space of flows”.展开更多
We compare the space-time correlations calculated from direct numerical simulation （DNS） and large-eddy simulation （LES） of turbulent channel flows. It is found from the comparisons that the LES with an eddy-visco...We compare the space-time correlations calculated from direct numerical simulation （DNS） and large-eddy simulation （LES） of turbulent channel flows. It is found from the comparisons that the LES with an eddy-viscosity subgrid scale （SGS） model over-predicts the space-time corre- lations than the DNS. The overpredictions are further quantified by the integral scales of directional correlations and convection velocities. A physical argument for the overpre- diction is provided that the eddy-viscosity SGS model alone does not includes the backscatter effects although it correctly represents the energy dissipations of SGS motions. This argument is confirmed by the recently developed elliptic model for space-time correlations in turbulent shear flows. It suggests that enstrophy is crucial to the LES prediction of spacetime correlations. The random forcing models and stochastic SGS models are proposed to overcome the overpredictions on space-time correlations.展开更多
The definition and abnormality discriminatory criteria of earthquake flow function are introduced in this paper based on the algorithm of Space Increased Probability (SIP). Nine earthquake flow functions were defined ...The definition and abnormality discriminatory criteria of earthquake flow function are introduced in this paper based on the algorithm of Space Increased Probability (SIP). Nine earthquake flow functions were defined by the method. The retrospect test that applied the SIP algorithm with the nonlinear earthquake flow function to 7 earthquakes, which occurred from 1975 to 1989 in Eastern China, with a magnitude of 6 or greater depicted that 6 of the 7 strong earthquakes (86%) were located in the SIP areas, and the SIP covers about 32% of the total research time-space domain. These suggest that the R-value, an effective scale for earthquake forecast, is 54% and may imply that the nonlinear earthquake flow function introduced in this paper can be applied to the intermediate-term earthquake forecast research.展开更多
To make elevator group control system better follow the change of elevator traffic flow (ETF) in order to adjust the control strategy,the prediction method of support vector machine (SVM) in combination with phase spa...To make elevator group control system better follow the change of elevator traffic flow (ETF) in order to adjust the control strategy,the prediction method of support vector machine (SVM) in combination with phase space reconstruction has been proposed for ETF.Firstly,the phase space reconstruction for elevator traffic flow time series (ETFTS) is processed.Secondly,the small data set method is applied to calculate the largest Lyapunov exponent to judge the chaotic property of ETF.Then prediction model of ETFTS based on SVM is founded.Finally,the method is applied to predict the time series for the incoming and outgoing passenger flow respectively using ETF data collected in some building.Meanwhile,it is compared with RBF neural network model.Simulation results show that the trend of factual traffic flow is better followed by predictive traffic flow.SVM algorithm has much better prediction performance.The fitting and prediction of ETF with better effect are realized.展开更多
In this paper, the fluid flow differential equation based on the homogenous reservoirs model is first reviewed. Then a theorem about the formal similarity of solutions in the Laplace space with outer boundary conditio...In this paper, the fluid flow differential equation based on the homogenous reservoirs model is first reviewed. Then a theorem about the formal similarity of solutions in the Laplace space with outer boundary conditions and inner boundary condition is presented and proved. Lastly, a corollary of our theorem is given particularly on inner boundary. The obtained results are very helpful for understanding inherent laws of relevant engineering science and designing practical analysis software.展开更多
Dependence among random input variables affects importantly the results of probabilistic load flow(PLF),system economic operation,and system security.To solve this problem,the main objectiveness of the paper is to ana...Dependence among random input variables affects importantly the results of probabilistic load flow(PLF),system economic operation,and system security.To solve this problem,the main objectiveness of the paper is to analyze the performance of several schemes for simulating correlated variables combined with the point estimate method(PEM).Unlike the existing works that considering one single scheme combined with Monte Carlo simulation(MCS) or PEM,by neglecting the correlation among random input variables,four schemes were presented for disposing the dependence of correlated random variables,including Nataf transformation /polynomial normal transformation(PINT) combined with orthogonal transformation(OT) / elementary transformation(ET).Combining with the 2m+1 approach of PEM,a space transformation-based formulation was proposed and adopted for solving the PLF.The proposed approach is applied in the modified IEEE 30-bus system while considering correlated wind generations and load demands.Numerical results show the effectiveness of the proposed approach compared with those obtained from the MCS.Results also show that the scheme of combining Nataf transformation and ET with PEM provides the best performance.展开更多
OpenFlow协议版本的更新带来流表项匹配域支持字段的增加,而表项匹配域支持的任意通配符依赖TCAM进行匹配处理,导致设备中的TCAM存储空间面临很大压力。为此,提出一种减小TCAM中流表存储空间的数学模型FICO(function-integral TCAM-savi...OpenFlow协议版本的更新带来流表项匹配域支持字段的增加,而表项匹配域支持的任意通配符依赖TCAM进行匹配处理,导致设备中的TCAM存储空间面临很大压力。为此,提出一种减小TCAM中流表存储空间的数学模型FICO(function-integral TCAM-saving compression model for flow table of OpenFlow)。FICO首先根据匹配域不同字段间的关系,将字段之间的冗余分为三种,基于冗余提出三种预压缩算法,分别为域间字段合并、字段映射、域内字段压缩,最终组合为更小位宽的表项被送往TCAM中进行流匹配。通过仿真表明在保持OpenFlow功能完整性的前提下,较未压缩流表,FICO可以节省60%TCAM存储空间。并且随着流表规模的增大,压缩性能保持稳定。展开更多
The use of multi-perspective and multi-scalar city networks has gradually developed into a range of critical approaches to understand spatial interactions and linkages. In particular, road linkages represent key chara...The use of multi-perspective and multi-scalar city networks has gradually developed into a range of critical approaches to understand spatial interactions and linkages. In particular, road linkages represent key characteristics of spatial dependence and distance decay, and are of great significance in depicting spatial relationships at the regional scale. Therefore, based on highway passenger flow data between prefecture-level administrative units, this paper attempted to identify the functional structures and regional impacts of city networks in China, and to further explore the spatial organization patterns of the existing functional regions, aiming to deepen our understanding of city network structures and to provide new cognitive perspectives for ongoing research. The research results lead to four key conclusions. First, city networks that are based on highway flows exhibit strong spatial dependence and hierarchical characteristics, to a large extent spatially coupled with the distributions of major megaregions in China. These phenomena are a reflection of spatial relationships at regional scales as well as core-periphery structure. Second, 19 communities that belong to an important type of spatial configuration are identified through community detection algorithm, and we suggest they are correspondingly urban economic regions within urban China. Their spatial metaphors include the administrative region economy, spatial spillover effects of megaregions, and core-periphery structure. Third, each community possesses a specific city network system and exhibits strong spatial dependence and various spatial organization patterns. Regional patterns have emerged as the result of multi-level, dynamic, and networked characteristics. Fourth, adopting a morphology-based perspective, the regional city network systems can be basically divided into monocentric, dual-nuclei, polycentric, and low-level equilibration spatial structures, while most are developing monocentrically.展开更多
基金funding support from NSFC grants(Grant No.52072263)Shanghai Collaborative Innovation Research Center for Multi-network&Multi-modal Rail Transit.
文摘Employing flow space theory and multi-source data,this study examines the spatial net-work structure and factors influencing railway passenger flow,which is crucial for rail planning in densely populated megalopolises.Focusing on China’s Yangtze River Delta(YRD)megalopolis,we utilize social network analysis(SNA)to explore the characteristics of various flow networks and their interactions with the railway passenger flow network.Key findings include:(1)a pronounced polarization effect and core-periphery structure exist in the YRD,notably within industry and railway flow networks;(2)industry and cor-poration flow significantly contributes to rail passenger flow,with corporation networks in commerce,technical services,and finance showing higher similarity to the railway passen-ger flow network;(3)there is significant heterogeneity in the correlation between rail pas-senger flow and other flows within sub-networks formed by connections among nodes of different levels;(4)enhancing railway services at lower-level nodes is essential to mitigate the disparity between population mobility and rail passenger flow and to promote rail transportation equity.This research offers valuable insights for policymakers in developing countries to strategically plan railroad networks in megalopolises.
基金National Natural Science Foundation of China,No.41671121
文摘With rapid development of air transportation,the airspace structure of the future will need to be flexible and dynamic to accommodate the increase in traffic demand.The corridors-in-the-sky has become a new technology to support the full exploitation and utilization of airspace resources.This paper proposes a method of designing corridor,identifying congestion state,and analyzing the influence of air routes’traffic flow.From this,we have reached a number of conclusions.(1)The congestion periods present the multi-peak"wavy"scattered distributions and the peaks back-end agglomeration characteristics in the whole day.(2)The congestion segments present the structural characteristics of unbalanced coverage and concentrated distribution to the crossing points.The corridors with high congestion level present as an italic"N-shaped"frame,which presents incomplete penetration of short segments.(3)For the temporal and spatial interaction,there are two types of congestion segments,and there are some common congestion periods in different congestion segments of multiple corridors.The high-density air route plays a relatively decisive role in corridor congestion,and the influence of two directions is unbalanced.This research can provide a basis for the dynamic evaluation of China’s airspace resources and corridors construction in the future.
基金Under the auspices of National Natural Science Foundation of China(No.42071165,41801144)GDAS’Project of Science and Technology Development(No.2023GDASZH-2023010101,2021GDASYL-20210103004)。
文摘The intermediate link compression characteristics of e-commerce express logistics ne tworks influence the tradition al mode of circulation of goods and economic organization,and alter the city spatial pattern.Based on the theory of space of flows,this study adopts China Smart Logistics Network relational data to build China's e-commerce express logistics network and explore its spatial structure characteristics through social network analysis(SNA),the PageRank technique,and geospatial methods.The results are as follows:the network density is 0.9270,which is close to 1;hence,indicating that e-commerce express logistics lines between Chinese cities are nearly complete and they form a typical network structure,thereby eliminating fragmented spaces.Moreover,the average minimum number of edges is 1.1375,which indicates that the network has a small world effect and thus has a high flow efficiency of logistics elements.A significant hierarchical diffusion effect was observed in dominant flows with the highest edge weights.A diamond-structured network was formed with Shanghai,Guangzhou,Chongqing,and Beijing as the four core nodes.Other node cities with a large logistics scale and importance in the network are mainly located in the 19 city agglomerations of China,revealing the fact that the development of city agglomerations is essential for promoting the separation of experience space and changing the urban spatial pattern.This study enriches the theory of urban networks,reveals the flow laws of modern logistics elements,and encourages coordinated development of urban logistics.
基金The project supported by the National Natural Science Foundation of China (19789201)the Ministry of Science and Technology of China (95-Yu-34)The Post-doctoral Science Foundation of China
文摘A first experimental study on two-phase how patterns at a long-term, steady microgravity condition was conducted on board the Russian Space Station 'MIR' in August 1999. Carbogal and air are used as the liquid and the gas phase, respectively. Bubble, slug, slug-annular transitional, and annular hows are observed. A new region of annular how with lower liquid superficial velocity is discovered, and the region of the slug-annular transitional flow is wider than that observed by experiments on board the parabolic aircraft. The main patterns are bubble, slug-annular transitional and annular flows based on the experiments on board MIR space station. Some influences on the two-phase how patterns in the present experiments are discussed.
基金National Natural Science F oundation of China(No.10 0 2 5 2 10 )
文摘The equations governing incompressible and compressible inviscid flows and written in the physical frame ( t,x,y,z ) are known to be linearly well posed and exhibit elliptic or hyperbolic nature. The linear well posedness is considered here for these equations under a space time transformation ( t,x,y,z)→(τ,ξ,η,ζ ), where the pseudo time τ and the new space coordinate ( ξ,η,ζ ) all depend on ( t,x,y,z ). Such a transformation could be useful for uniformly treating problems in which the flow is fast unsteady somewhere and slow unsteady or steady elsewhere. It is found that the transformation may alter the ellipticity, the hyperbolicty, and even the well posedness of the original equations. In one dimension, the transformed incompressible flow equations become weakly hyperbolic and the compressible ones could degenerate to elliptical equations. In high dimensions there are conditions such that the transformed equations become ill posed.
基金General Program of Beijing Natural Science Foundation(8212009)2023 Organized Scientific Research Project of North China University of Technology(110051360023XN278).
文摘The mobility and interaction between urban and rural areas are becoming more and more intensive,and their links and exchanges are increasingly closer due to constant flow of factors such as information,capital,personnel and technology.In this context,the element integration of urban and rural“space of flows”can promote the integrated development of urban and rural areas,improve the consumption environment and experience,and promote the industrial upgrading and technological progress.To realize the element integration of urban and rural“space of flows”,it is necessary to explore and innovate in infrastructure construction,information technology application,industrial cooperation and cultural exchanges.Government departments,enterprises and social organizations also need to work together to give play to their respective advantages and jointly promote the process of element integration of urban and rural“space of flows”.
基金supported by the National Basic Research Program of China (973 Program) (2007CB814800)the National Natural Science Foundation of China (10325211 and 10628206)
文摘We compare the space-time correlations calculated from direct numerical simulation （DNS） and large-eddy simulation （LES） of turbulent channel flows. It is found from the comparisons that the LES with an eddy-viscosity subgrid scale （SGS） model over-predicts the space-time corre- lations than the DNS. The overpredictions are further quantified by the integral scales of directional correlations and convection velocities. A physical argument for the overpre- diction is provided that the eddy-viscosity SGS model alone does not includes the backscatter effects although it correctly represents the energy dissipations of SGS motions. This argument is confirmed by the recently developed elliptic model for space-time correlations in turbulent shear flows. It suggests that enstrophy is crucial to the LES prediction of spacetime correlations. The random forcing models and stochastic SGS models are proposed to overcome the overpredictions on space-time correlations.
基金This project was sponsored by the Joint Earthquake Science Foundation of China.
文摘The definition and abnormality discriminatory criteria of earthquake flow function are introduced in this paper based on the algorithm of Space Increased Probability (SIP). Nine earthquake flow functions were defined by the method. The retrospect test that applied the SIP algorithm with the nonlinear earthquake flow function to 7 earthquakes, which occurred from 1975 to 1989 in Eastern China, with a magnitude of 6 or greater depicted that 6 of the 7 strong earthquakes (86%) were located in the SIP areas, and the SIP covers about 32% of the total research time-space domain. These suggest that the R-value, an effective scale for earthquake forecast, is 54% and may imply that the nonlinear earthquake flow function introduced in this paper can be applied to the intermediate-term earthquake forecast research.
基金Sponsored by the National Eleventh Five year Plan Key Project of Ministry of Science and Technology of China (Grant No. 2006BAJ03A05-05)
文摘To make elevator group control system better follow the change of elevator traffic flow (ETF) in order to adjust the control strategy,the prediction method of support vector machine (SVM) in combination with phase space reconstruction has been proposed for ETF.Firstly,the phase space reconstruction for elevator traffic flow time series (ETFTS) is processed.Secondly,the small data set method is applied to calculate the largest Lyapunov exponent to judge the chaotic property of ETF.Then prediction model of ETFTS based on SVM is founded.Finally,the method is applied to predict the time series for the incoming and outgoing passenger flow respectively using ETF data collected in some building.Meanwhile,it is compared with RBF neural network model.Simulation results show that the trend of factual traffic flow is better followed by predictive traffic flow.SVM algorithm has much better prediction performance.The fitting and prediction of ETF with better effect are realized.
文摘In this paper, the fluid flow differential equation based on the homogenous reservoirs model is first reviewed. Then a theorem about the formal similarity of solutions in the Laplace space with outer boundary conditions and inner boundary condition is presented and proved. Lastly, a corollary of our theorem is given particularly on inner boundary. The obtained results are very helpful for understanding inherent laws of relevant engineering science and designing practical analysis software.
基金National Science Foundation of China(No.61533010)the Science and Technology Commission of Shanghai Municipality,China(No.14ZR1415300)
文摘Dependence among random input variables affects importantly the results of probabilistic load flow(PLF),system economic operation,and system security.To solve this problem,the main objectiveness of the paper is to analyze the performance of several schemes for simulating correlated variables combined with the point estimate method(PEM).Unlike the existing works that considering one single scheme combined with Monte Carlo simulation(MCS) or PEM,by neglecting the correlation among random input variables,four schemes were presented for disposing the dependence of correlated random variables,including Nataf transformation /polynomial normal transformation(PINT) combined with orthogonal transformation(OT) / elementary transformation(ET).Combining with the 2m+1 approach of PEM,a space transformation-based formulation was proposed and adopted for solving the PLF.The proposed approach is applied in the modified IEEE 30-bus system while considering correlated wind generations and load demands.Numerical results show the effectiveness of the proposed approach compared with those obtained from the MCS.Results also show that the scheme of combining Nataf transformation and ET with PEM provides the best performance.
文摘OpenFlow协议版本的更新带来流表项匹配域支持字段的增加,而表项匹配域支持的任意通配符依赖TCAM进行匹配处理,导致设备中的TCAM存储空间面临很大压力。为此,提出一种减小TCAM中流表存储空间的数学模型FICO(function-integral TCAM-saving compression model for flow table of OpenFlow)。FICO首先根据匹配域不同字段间的关系,将字段之间的冗余分为三种,基于冗余提出三种预压缩算法,分别为域间字段合并、字段映射、域内字段压缩,最终组合为更小位宽的表项被送往TCAM中进行流匹配。通过仿真表明在保持OpenFlow功能完整性的前提下,较未压缩流表,FICO可以节省60%TCAM存储空间。并且随着流表规模的增大,压缩性能保持稳定。
基金National Natural Science Foundation of China,No.41530751,No.41471113,No.41601165
文摘The use of multi-perspective and multi-scalar city networks has gradually developed into a range of critical approaches to understand spatial interactions and linkages. In particular, road linkages represent key characteristics of spatial dependence and distance decay, and are of great significance in depicting spatial relationships at the regional scale. Therefore, based on highway passenger flow data between prefecture-level administrative units, this paper attempted to identify the functional structures and regional impacts of city networks in China, and to further explore the spatial organization patterns of the existing functional regions, aiming to deepen our understanding of city network structures and to provide new cognitive perspectives for ongoing research. The research results lead to four key conclusions. First, city networks that are based on highway flows exhibit strong spatial dependence and hierarchical characteristics, to a large extent spatially coupled with the distributions of major megaregions in China. These phenomena are a reflection of spatial relationships at regional scales as well as core-periphery structure. Second, 19 communities that belong to an important type of spatial configuration are identified through community detection algorithm, and we suggest they are correspondingly urban economic regions within urban China. Their spatial metaphors include the administrative region economy, spatial spillover effects of megaregions, and core-periphery structure. Third, each community possesses a specific city network system and exhibits strong spatial dependence and various spatial organization patterns. Regional patterns have emerged as the result of multi-level, dynamic, and networked characteristics. Fourth, adopting a morphology-based perspective, the regional city network systems can be basically divided into monocentric, dual-nuclei, polycentric, and low-level equilibration spatial structures, while most are developing monocentrically.
