The objective of this research is to determine the effect earthquakes have on the performance of transportation network systems.To do this,bridge fragility curves,expressed as a function of peak ground acceleration(PG...The objective of this research is to determine the effect earthquakes have on the performance of transportation network systems.To do this,bridge fragility curves,expressed as a function of peak ground acceleration(PGA)and peak ground velocity(PGV),were developed.Network damage was evaluated under the 1994 Northridge earthquake and scenario earthquakes.A probabilistic model was developed to determine the effect of repair of bridge damage on the improvement of the network performance as days passed after the event.As an example,the system performance degradation measured in terms of an index,'Drivers Delay,'is calculated for the Los Angeles area transportation system,and losses due to Drivers Delay with and without retrofit were estimated.展开更多
Located in the western hinterland,Southwest China is a typical mountainous area covered by plateaus,mountains and hills.Its ruggedness hinders regional internal and external connections,and its poor transportation inf...Located in the western hinterland,Southwest China is a typical mountainous area covered by plateaus,mountains and hills.Its ruggedness hinders regional internal and external connections,and its poor transportation infrastructure has long constrained the socioeconomic development of Southwest China.Based on the GIS transportation database,this paper explored the spatiotemporal evolution and characteristics of the land transportation networks and the accessibility of Southwest China from 1917 to 2017.Regional accessibility in Southwest China has significantly improved,and transportation infrastructure has gradually integrated the transportation circles of the52 central cities.The transportation network has followed an evolutionary process from a"hub-spoke pattern"to a"network pattern",while the construction of a high-speed railway(HSR)has brought about significant spatial polarization.We argue that innovation in transportation technology is one of the most effective factors for promoting a significant change in regional accessibility.In addition,the spatial distribution and evolution of accessibility in Southwest China presents a verticalcharacteristic that distinguishes it from the plains,as the spillover effects of new transportation infrastructure on accessibility improvement are partly offset by the mountainous terrain.Additionally,in Southwest China,there is significant"path dependence"in the evolution of the transportation network,since a large portion of the population is concentrated along transportation corridors in mountainous areas.展开更多
The identification of key nodes plays an important role in improving the robustness of the transportation network.For different types of transportation networks,the effect of the same identification method may be diff...The identification of key nodes plays an important role in improving the robustness of the transportation network.For different types of transportation networks,the effect of the same identification method may be different.It is of practical significance to study the key nodes identification methods corresponding to various types of transportation networks.Based on the knowledge of complex networks,the metro networks and the bus networks are selected as the objects,and the key nodes are identified by the node degree identification method,the neighbor node degree identification method,the weighted k-shell degree neighborhood identification method(KSD),the degree k-shell identification method(DKS),and the degree k-shell neighborhood identification method(DKSN).Take the network efficiency and the largest connected subgraph as the effective indicators.The results show that the KSD identification method that comprehensively considers the elements has the best recognition effect and has certain practical significance.展开更多
It is very important to establish cooperative mechanism to guarantee allmembers to develop their e-conomies in the Yellow Sea Rim. In this paper, the development strategiesof shipping centers and transportation networ...It is very important to establish cooperative mechanism to guarantee allmembers to develop their e-conomies in the Yellow Sea Rim. In this paper, the development strategiesof shipping centers and transportation network are discussed based on economic globalizationtendency. The results argue that a united transportation network should be built in order to promotethe economic competition of Northeast Asia in the world. As a key component of the economiccooperation, a hierarchical shipping centers network should be established with Hong Kong, Shanghai,Pusan, Kobe, and Tokyo as cores. The authorities of China, Japan, R. 0. Korea and D. P. R. Koreashould make more efforts to build a set of cooperation institutions based on raising thetransportation efficiency.展开更多
The air transportation network, one of the common multilayer complex systems, is composed of a collection of individual airlines, and each airline corresponds to a different layer. An important question is then how ma...The air transportation network, one of the common multilayer complex systems, is composed of a collection of individual airlines, and each airline corresponds to a different layer. An important question is then how many airlines are really necessary to represent the optimal structure of a multilayer air transportation system. Here we take the Chinese air transportation network （CATN） as an example to explore the nature of multiplex systems through the procedure of network aggregation. Specifically, we propose a series of structural measures to characterize the CATN from the multilayered to the aggregated network level. We show how these measures evolve during the network aggregation process in which layers are gradually merged together and find that there is an evident structural transition that happened in the aggregated network with nine randomly chosen airlines merged, where the network features and construction cost of this network are almost equivalent to those of the present CATN with twenty-two airlines under this condition. These findings could shed some light on network structure optimization and management of the Chinese air transportation system.展开更多
A theoretical study was conducted on finding optimal paths in transportation networks where link travel times were stochastic and time-dependent(STD). The methodology of relative robust optimization was applied as mea...A theoretical study was conducted on finding optimal paths in transportation networks where link travel times were stochastic and time-dependent(STD). The methodology of relative robust optimization was applied as measures for comparing time-varying, random path travel times for a priori optimization. In accordance with the situation in real world, a stochastic consistent condition was provided for the STD networks and under this condition, a mathematical proof was given that the STD robust optimal path problem can be simplified into a minimum problem in specific time-dependent networks. A label setting algorithm was designed and tested to find travelers' robust optimal path in a sampled STD network with computation complexity of O(n2+n·m). The validity of the robust approach and the designed algorithm were confirmed in the computational tests. Compared with conventional probability approach, the proposed approach is simple and efficient, and also has a good application prospect in navigation system.展开更多
Over the last decade, the popularity of Transportation Network Companies (TNCs) as a mode of travel has been increasing at a steady pace. This trend <span style="font-family:Verdana;">highlights the im...Over the last decade, the popularity of Transportation Network Companies (TNCs) as a mode of travel has been increasing at a steady pace. This trend <span style="font-family:Verdana;">highlights the importance of identifying the determinants that influence transportati</span><span style="font-family:Verdana;">on users to adopt TNCs as a preferred mode choice and the impacts of su</span><span style="font-family:Verdana;">ch preferences on their travel patterns and transportation network o</span><span style="font-family:Verdana;">peration. This paper reports on a recent study undertaken in Birmingham, AL aiming at understanding and documenting the factors that influence transportation users to select TNCs (such as Uber/Lyft) for completing typical day trips. In </span><span style="font-family:Verdana;">doing so, a travel diary questionnaire survey was developed in accordance with</span> <span style="font-family:Verdana;">the Institute of Transportation Engineers (ITE) Manual on Transportation Engineering Studies using the Qualtrics Research Core platform. The que</span><span style="font-family:Verdana;">stionnair</span><span style="font-family:Verdana;">e was used to survey over 450 transportation users in the Birmingham Metro area. The survey participants provided detailed trip information for a </span><span style="font-family:Verdana;">typical 24-hr day along with demographic data and travel preference informatio</span><span style="font-family:Verdana;">n. The survey responses provide high-resolution micro-level indicators </span><span style="font-family:Verdana;">of travel preferences and behaviors in a TNC-served area, which is a much-needed </span><span style="font-family:Verdana;">type of information for researchers and transportation planning agencies.</span>展开更多
The idea of network splitting according to time delay and weight is introduced.Based on the cyber physical systems(CPS),a class of multi-weighted complex transportation networks with multiple delays is modeled.The fin...The idea of network splitting according to time delay and weight is introduced.Based on the cyber physical systems(CPS),a class of multi-weighted complex transportation networks with multiple delays is modeled.The finite-time synchronization of the proposed complex transportation networks model is studied systematically.On the basis of the theory of stability,the technique of adaptive control,aperiodically intermittent control and finite-time control,the aperiodically intermittent adaptive finite-time synchronization controller is designed.The controller designed in this paper is beneficial for understanding the synchronization in multi-weighted complex transportation networks with multiple delays.In addition,the conditions for the existence of finite time synchronization have been discussed in detail.And the specific value of the settling finite time for synchronization is obtained.Moreover,the outer coupling configuration matrices are not required to be irreducible or symmetric.Finally,simulation results of the finite-time synchronization problem are given to illustrate the correctness of the results obtained.展开更多
In this paper, we demonstrate that the eco-industrial network equilibrium model of link flow version previously introduced can be reformulated as a transportation network equilibrium problem of path flow version. Then...In this paper, we demonstrate that the eco-industrial network equilibrium model of link flow version previously introduced can be reformulated as a transportation network equilibrium problem of path flow version. Then, some methodological tools mainly applied in the field of transportation science can be used to discuss the eco-industrial chain network problem. What the highlighted contribution lies in is that the paper not only expands theory of supply chain model with reducing path flow but also generalizes the traditional transportation network equilibrium problem by new applications.展开更多
This paper shows a number of Problems in pure and applied mathematicsthat are solved by constructing transportation networks.Moreover,it also shows thatall the solutions are characterized by forbidden configurations w...This paper shows a number of Problems in pure and applied mathematicsthat are solved by constructing transportation networks.Moreover,it also shows thatall the solutions are characterized by forbidden configurations which are not minors.However,all the characterizations are much related to the graphic method which wasfound by Chinese for solving a kind of the transportation problem in the fifties.展开更多
From the perspective of domestic market integration,this paper systematically examines the impact of transportation infrastructure conditions on excess sensitivity of household consumption based on the China Family Pa...From the perspective of domestic market integration,this paper systematically examines the impact of transportation infrastructure conditions on excess sensitivity of household consumption based on the China Family Panel Survey(CFPS)and multi-level matching panel data of transportation network density.The results show that the fast-growing development of the transportation infrastructure network has a significant alleviating effect on excess sensitivity of household consumption along the route,and the conclusion is still robust after the use of the multi-dimensional instrumental variable method and a series of robustness tests.According to the heterogeneity tests,in terms of the alleviating effect of transportation infrastructure,railroads rank the first,highways the second,substandard roads the third,waterways the fourth,and roads of other grades at the bottom.The mechanism test reveals that the improvement of domestic market integration is an important channel for transportation infrastructure to alleviate excess sensitivity of household consumption.This paper confirms that improving the transportation infrustructure system is conducive to the construction of a unified national market,alleviating excess sensitivity of consumption and stimulating consumption.This paper provides suggestions for implementing the strategy of boosting domestic demand,and helps the government understand households'consumption decision-making from a broader perspective.This study also provides a theoretical basis for the economic spillover effect of transportation infrastructure.展开更多
This study develops a comprehensive framework to assess the resilience of transportation networks consisting of deteriorating bridges subjected to earthquake events.For this purpose,the structural capacity of highway ...This study develops a comprehensive framework to assess the resilience of transportation networks consisting of deteriorating bridges subjected to earthquake events.For this purpose,the structural capacity of highway bridges is estimated during their service life using a set of detailed finite-element models that simulate the progress of deterioration.The developed models take into consideration the main environmental stressors and determine the extent of capacity loss as a function of time.Based on the degraded state of structural components,seismic fragility analyses are performed to obtain a probabilistic evaluation of the extent of damageability of the existing bridges under seismic events.Since each transportation link normally consists of a number of bridges,the state of damage in the individual bridges is mapped to the corresponding links and a scenario-based approach is employed to estimate the resilience of the entire transportation network.To demonstrate how the consequences of structural degradation can be integrated into the developed framework,the large-scale transportation network of Los Angeles and Orange counties is investigated under a series of aging and earthquake scenarios.The outcome of this study indicates how the estimates associated with the functionality measures of a transportation network can be improved if the age factor is properly integrated into the framework used for resilience assessment.展开更多
The spatial spread of COVID-19 during early 2020 in China was primarily driven by outbound travelers leaving the epicenter,Wuhan,Hubei province.Existing studies focus on the influence of aggregated out-bound populatio...The spatial spread of COVID-19 during early 2020 in China was primarily driven by outbound travelers leaving the epicenter,Wuhan,Hubei province.Existing studies focus on the influence of aggregated out-bound population flows originating from Wuhan;however,the impacts of different modes of transportation and the network structure of transportation systems on the early spread of COVID-19 in China are not well understood.Here,we assess the roles of the road,railway,and air transportation networks in driving the spatial spread of COVID-19 in China.We find that the short-range spread within Hubei province was dominated by ground traffic,notably,the railway transportation.In contrast,long-range spread to cities in other provinces was mediated by multiple factors,including a higher risk of case importation associated with air transportation and a larger outbreak size in hub cities located at the center of transportation networks.We further show that,although the dissemination of SARS-CoV-2 across countries and continents is determined by the worldwide air transportation network,the early geographic dispersal of COVID-19 within China is better predicted by the railway traffic.Given the recent emergence of multiple more transmissible variants of SARS-CoV-2,our findings can support a better assessment of the spread risk of those variants and improve future pandemic preparedness and responses.展开更多
This paper proposes a security region of transporta-tion networks,which is defined as the set of flow states(operating points)satisfying the N-1 security in transportation networks.The boundary of the set is closed,in...This paper proposes a security region of transporta-tion networks,which is defined as the set of flow states(operating points)satisfying the N-1 security in transportation networks.The boundary of the set is closed,inside all the operating points are N-1 secure;oppositely,outside all the operating points are insecure.First,N-1 security of the transportation networks is defined,which means that when a road is blocked,vehicles on other roads within the networks can also reach their destination through different paths without being trapped on the road.Then,the security region of transportation networks is modeled.The algorithm of a boundary calculation is studied and the boundary equations of security distances are proposed.Finally,the proposed security of the transportation networks is presented in different examples.This paper demonstrates the following:1)the security region can be accurately predicted by the simulation of N-1;2)the boundary distance can show the necessary degree of security;3)security can be improved by a preventive control scheme.The simulation on TransCAD is used to verify the correctness of the results.Index Terms-Boundary distance,evolution,security region,transportation network,TransCAD.展开更多
The hybrid electric propulsion system(HEPS)holds clear potential to support the goal of sustainability in the automobile and aviation industry.As an important part of the three-dimensional transportation network,vehic...The hybrid electric propulsion system(HEPS)holds clear potential to support the goal of sustainability in the automobile and aviation industry.As an important part of the three-dimensional transportation network,vehicles and aircraft using HEPSs have the advantages of high fuel economy,low emission,and low noise.To fulfill these advantages,the design of their energy management strategies(EMSs)is essential.This paper presents an in-depth review of EMSs for hybrid electric vehicles(HEVs)and hybrid electric aircraft.First,in view of the main challenges of current EMSs of HEVs,the referenced research is reviewed according to the solutions facing real-time implementation problems,variable driving conditions adaptability problems,and multi-objective optimization problems,respectively.Second,the existing research on the EMSs for hybrid electric aircraft is summarized according to the hybrid electric propulsion architectures.In addition,with the advance in propulsion technology and mechanical manufacturing in recent years,flying cars have gradually become a reality,further enriching the composition of the three-dimensional transportation network.And EMSs also play an essential role in the efficient operation of flying cars driven by HEPSs.Therefore,in the last part of this paper,the development status of flying cars and their future prospects are elaborated.By comprehensively summarizing the EMSs of HEPS for vehicles and aircraft,this review aims to provide guidance for the research on the EMSs for flying cars driven by HEPS and serve as the basis for knowledge transfer of relevant researchers.展开更多
The couple between the power network and the transportation network(TN)is deepening gradually with the increasing penetration rate of electric vehicles(EV),which also poses a great challenge to the traditional voltage...The couple between the power network and the transportation network(TN)is deepening gradually with the increasing penetration rate of electric vehicles(EV),which also poses a great challenge to the traditional voltage control scheme.In this paper,we propose a coordinated voltage control strategy for the active distribution networks considering multiple types of EV.In the first stage,the action of on-load tap changer and capacitor banks,etc.,are determined by optimal power flow calculation,and the node electricity price is also determined based on dynamic time-of-use tariff mechanism.In the second stage,multiple operating scenarios of multiple types of EVs such as cabs,private cars and buses are considered,and the scheduling results of each EV are solved by building an optimization model based on constraints such as queuing theory,Floyd-Warshall algorithm and traffic flow information.In the third stage,the output power of photovoltaic and energy storage systems is fine-tuned in the normal control mode.The charging power of EVs is also regulated in the emergency control mode to reduce the voltage deviation,and the amount of regulation is calculated based on the fair voltage control mode of EVs.Finally,we test the modified IEEE 33-bus distribution system coupled with the 24-bus Beijing TN.The simulation results show that the proposed scheme can mitigate voltage violations well.展开更多
The development of energy storage devices with high energy density relies heavily on thick film electrodes,but it is challenging due to the limited ion transport kinetics inherent in thick electrodes.Here,we report on...The development of energy storage devices with high energy density relies heavily on thick film electrodes,but it is challenging due to the limited ion transport kinetics inherent in thick electrodes.Here,we report on the preparation of a directional vertical array of micro-porous transport networks on LTO electrodes using a femtosecond laser processing strategy,enabling directional ion rapid transport and achieving good electrochemical performance in thick film electrodes.Various three-dimensional(3D)vertically aligned micro-pore networks are innovatively designed,and the structure,kinetics characteristics,and electrochemical performance of the prepared ion transport channels are analyzed and discussed by multiple characterization and testing methods.Furthermore,the rational mechanisms of electrode performance improvement are studied experimentally and simulated from two aspects of structural mechanics and transmission kinetics.The ion diffusion coefficient,rate performance at 60 C,and electrode interface area of the laser-optimized 60-15%micro-porous transport network electrodes increase by 25.2 times,2.2 times,and 2.15 times,respectively than those of untreated electrodes.Therefore,the preparation of 3D micro-porous transport networks by femtosecond laser on ultra-thick electrodes is a feasible way to develop high-energy batteries.In addition,the unique micro-porous transport network structure can be widely extended to design and explore other high-performance energy materials.展开更多
In future optical transport networks,lightpath performance analysis is of great practical significance for fully automated management.In general,the quality of transmission(QoT)of lightpaths,measured by optical qualit...In future optical transport networks,lightpath performance analysis is of great practical significance for fully automated management.In general,the quality of transmission(QoT)of lightpaths,measured by optical quality factor or optical signal-to-noise ratio,has a complex time-varying process,along with the interactions of the other lightpath state parameters(LSPs),such as transmit power,chromatic dispersion,polarization mode dispersion.Current studies are mostly focused on lightpath QoT estimation,but ignoring lightpath-level data analytics.In this case,our article proposes a novel lightpath performance analysis method considering recurrence plot(RP)and cross recurrence plot(CRP).Firstly,we give a detailed interpretation on the recurrence patterns of LSPs via a qualitative 2-D RP representation and its quantitative measure.It can potentially enable the accurate and fast lightpath failure detection with a low computational burden.On the other hand,CRP is devoted to modeling the relationships between lightpath QoT and LSPs,and the correlation degree is determined by a geometric mean of multiple indexes of cross recurrence quantification analysis.From the view of application,such CRP analysis can provide the effective knowledge sharing to guarantee more credible QoT prediction.Extensive experiments on a real-world optical network dataset have clearly demonstrated the effectiveness of our proposal.展开更多
The robustness of cargo ship transportation networks is essential to the stability of the world trade system. The current research mainly focuses on the coarse-grained, holistic cargo ship transportation network while...The robustness of cargo ship transportation networks is essential to the stability of the world trade system. The current research mainly focuses on the coarse-grained, holistic cargo ship transportation network while ignoring the structural diversity of different sub-networks. In this paper, we evaluate the robustness of the global cargo ship transportation network based on the most recent Automatic Identification System（AIS） data available. First, we subdivide three typical cargo ship transportation networks（i.e., oil tanker, container ship and bulk carrier） from the original cargo ship transportation network. Then, we design statistical indices based on complex network theory and employ four attack strategies, including random attack and three intentional attacks（i.e., degree-based attack, betweenness-based attack and flux-based attack） to evaluate the robustness of the three typical cargo ship transportation networks. Finally, we compare the integrity of the remaining ports of the network when a small proportion of ports lose their function. The results show that 1） compared with the holistic cargo ship transportation network, the fine-grain-based cargo ship transportation networks can fully reflect the pattern and process of global cargo transportation; 2） different cargo ship networks behave heterogeneously in terms of their robustness, with the container network being the weakest and the bulk carrier network being the strongest; and 3） small-scale intentional attacks may have significant influence on the integrity of the container network but a minor impact on the bulk carrier and oil tanker transportation networks. These conclusions can help improve the decision support capabilities in maritime transportation planning and emergency response and facilitate the establishment of a more reliable maritime transportation system.Abstract： The robustness of cargo ship transportation networks is essential to the stability of the world trade system. The current research mainly focuses on the coarse-grained, holistic cargo ship transportation network while ignoring the structural diversity of different sub-networks. In this paper, we evaluate the robustness of the global cargo ship transporta- tion network based on the most recent Automatic Identification System （AIS） data available. First, we subdivide three typical cargo ship transportation networks （i.e., oil tanker, container ship and bulk carrier） from the original cargo ship transportation network. Then, we design statistical indices based on complex network theory and employ four attack strategies, in- cluding random attack and three intentional attacks （i.e., degree-based attack, between- ness-based attack and flux-based attack） to evaluate the robustness of the three typical cargo ship transportation networks. Finally, we compare the integrity of the remaining ports of the network when a small proportion of ports lose their function. The results show that 1） com- pared with the holistic cargo ship transportation network, the fine-grain-based cargo ship transportation networks can fully reflect the pattern and process of global cargo transportation 2） different cargo ship networks behave heterogeneously in terms of their robustness, with the container network being the weakest and the bulk carrier network being the strongest; and 3） small-scale intentional attacks may have significant influence on the integrity of the con- tainer network but a minor impact on the bulk carrier and oil tanker transportation networks.These conclusions can help improve the decision support capabilities in maritime transportation planning and emergency response and facilitate the establishment of a more reliable maritime transportation system.展开更多
To improve the resilience of distribution networks(DNs),a multi-stage dynamic recovery strategy is proposed in this paper,which is designed for post-disaster DN considering an integrated energy system(IES)and transpor...To improve the resilience of distribution networks(DNs),a multi-stage dynamic recovery strategy is proposed in this paper,which is designed for post-disaster DN considering an integrated energy system(IES)and transportation network(TN).First,the emergency response quickly increases the output of gas turbines(GTs)in the natural gas network(NGN),and responsively reconfigures the DN in microgrids,to maximize the amount of loads to be restored.The single-commodity flow model is adopted to construct spanning tree constraints.Then,in the second stage of energy storage recovery,mobile energy storage systems(MESSs)are deployed to cover the shortages of power demands,i.e.,to further restore the loads after evaluating the load recovery situation.The Floyd algorithm based dynamic traffic assignment(DTA)is selected to obtain the optimal path of the MESSs.In the third stage,the outputs of various post-disaster recovery measures are adjusted to achieve an economically optimized operation.Case studies demonstrate the effectiveness of the proposed dynamic post-disaster recovery strategy.展开更多
基金The Federal Highway Administration(FHWA)under Contract No.DTFH61-98-C-00094the California Department of Transportation(CALTRANS)
文摘The objective of this research is to determine the effect earthquakes have on the performance of transportation network systems.To do this,bridge fragility curves,expressed as a function of peak ground acceleration(PGA)and peak ground velocity(PGV),were developed.Network damage was evaluated under the 1994 Northridge earthquake and scenario earthquakes.A probabilistic model was developed to determine the effect of repair of bridge damage on the improvement of the network performance as days passed after the event.As an example,the system performance degradation measured in terms of an index,'Drivers Delay,'is calculated for the Los Angeles area transportation system,and losses due to Drivers Delay with and without retrofit were estimated.
基金supported by the National Natural Science Foundation of China(Grants No.41671159)Fundamental Research Funds for the Central Universities for funding(Grants No.XDJK2018B011)Major Projects on Philosophy and Social Sciences of Chongqing Education Commission(Grants No.19SKZDZX08)。
文摘Located in the western hinterland,Southwest China is a typical mountainous area covered by plateaus,mountains and hills.Its ruggedness hinders regional internal and external connections,and its poor transportation infrastructure has long constrained the socioeconomic development of Southwest China.Based on the GIS transportation database,this paper explored the spatiotemporal evolution and characteristics of the land transportation networks and the accessibility of Southwest China from 1917 to 2017.Regional accessibility in Southwest China has significantly improved,and transportation infrastructure has gradually integrated the transportation circles of the52 central cities.The transportation network has followed an evolutionary process from a"hub-spoke pattern"to a"network pattern",while the construction of a high-speed railway(HSR)has brought about significant spatial polarization.We argue that innovation in transportation technology is one of the most effective factors for promoting a significant change in regional accessibility.In addition,the spatial distribution and evolution of accessibility in Southwest China presents a verticalcharacteristic that distinguishes it from the plains,as the spillover effects of new transportation infrastructure on accessibility improvement are partly offset by the mountainous terrain.Additionally,in Southwest China,there is significant"path dependence"in the evolution of the transportation network,since a large portion of the population is concentrated along transportation corridors in mountainous areas.
基金supported by the National Natural Science Foundation of China(Grant No.61961019)the Youth Key Project of the Natural Science Foundation of Jiangxi Province of China(Grant No.20202ACBL212003).
文摘The identification of key nodes plays an important role in improving the robustness of the transportation network.For different types of transportation networks,the effect of the same identification method may be different.It is of practical significance to study the key nodes identification methods corresponding to various types of transportation networks.Based on the knowledge of complex networks,the metro networks and the bus networks are selected as the objects,and the key nodes are identified by the node degree identification method,the neighbor node degree identification method,the weighted k-shell degree neighborhood identification method(KSD),the degree k-shell identification method(DKS),and the degree k-shell neighborhood identification method(DKSN).Take the network efficiency and the largest connected subgraph as the effective indicators.The results show that the KSD identification method that comprehensively considers the elements has the best recognition effect and has certain practical significance.
文摘It is very important to establish cooperative mechanism to guarantee allmembers to develop their e-conomies in the Yellow Sea Rim. In this paper, the development strategiesof shipping centers and transportation network are discussed based on economic globalizationtendency. The results argue that a united transportation network should be built in order to promotethe economic competition of Northeast Asia in the world. As a key component of the economiccooperation, a hierarchical shipping centers network should be established with Hong Kong, Shanghai,Pusan, Kobe, and Tokyo as cores. The authorities of China, Japan, R. 0. Korea and D. P. R. Koreashould make more efforts to build a set of cooperation institutions based on raising thetransportation efficiency.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11405118,11401448 and 11301403
文摘The air transportation network, one of the common multilayer complex systems, is composed of a collection of individual airlines, and each airline corresponds to a different layer. An important question is then how many airlines are really necessary to represent the optimal structure of a multilayer air transportation system. Here we take the Chinese air transportation network （CATN） as an example to explore the nature of multiplex systems through the procedure of network aggregation. Specifically, we propose a series of structural measures to characterize the CATN from the multilayered to the aggregated network level. We show how these measures evolve during the network aggregation process in which layers are gradually merged together and find that there is an evident structural transition that happened in the aggregated network with nine randomly chosen airlines merged, where the network features and construction cost of this network are almost equivalent to those of the present CATN with twenty-two airlines under this condition. These findings could shed some light on network structure optimization and management of the Chinese air transportation system.
基金Project(71001079)supported by the National Natural Science Foundation of China
文摘A theoretical study was conducted on finding optimal paths in transportation networks where link travel times were stochastic and time-dependent(STD). The methodology of relative robust optimization was applied as measures for comparing time-varying, random path travel times for a priori optimization. In accordance with the situation in real world, a stochastic consistent condition was provided for the STD networks and under this condition, a mathematical proof was given that the STD robust optimal path problem can be simplified into a minimum problem in specific time-dependent networks. A label setting algorithm was designed and tested to find travelers' robust optimal path in a sampled STD network with computation complexity of O(n2+n·m). The validity of the robust approach and the designed algorithm were confirmed in the computational tests. Compared with conventional probability approach, the proposed approach is simple and efficient, and also has a good application prospect in navigation system.
文摘Over the last decade, the popularity of Transportation Network Companies (TNCs) as a mode of travel has been increasing at a steady pace. This trend <span style="font-family:Verdana;">highlights the importance of identifying the determinants that influence transportati</span><span style="font-family:Verdana;">on users to adopt TNCs as a preferred mode choice and the impacts of su</span><span style="font-family:Verdana;">ch preferences on their travel patterns and transportation network o</span><span style="font-family:Verdana;">peration. This paper reports on a recent study undertaken in Birmingham, AL aiming at understanding and documenting the factors that influence transportation users to select TNCs (such as Uber/Lyft) for completing typical day trips. In </span><span style="font-family:Verdana;">doing so, a travel diary questionnaire survey was developed in accordance with</span> <span style="font-family:Verdana;">the Institute of Transportation Engineers (ITE) Manual on Transportation Engineering Studies using the Qualtrics Research Core platform. The que</span><span style="font-family:Verdana;">stionnair</span><span style="font-family:Verdana;">e was used to survey over 450 transportation users in the Birmingham Metro area. The survey participants provided detailed trip information for a </span><span style="font-family:Verdana;">typical 24-hr day along with demographic data and travel preference informatio</span><span style="font-family:Verdana;">n. The survey responses provide high-resolution micro-level indicators </span><span style="font-family:Verdana;">of travel preferences and behaviors in a TNC-served area, which is a much-needed </span><span style="font-family:Verdana;">type of information for researchers and transportation planning agencies.</span>
基金Project supported by the National Natural Science Foundation of China(Grant No.61803275)Liaoning Provincial Department of Education Scientific Research Fund Project,China(Grant Nos.lnjc202018 and lnzd202007)+1 种基金Liaoning BaiQianWan Talents Program(Grant No.2017076)Liaoning Province Doctor Starting Foundation(Grant No.20170520283).
文摘The idea of network splitting according to time delay and weight is introduced.Based on the cyber physical systems(CPS),a class of multi-weighted complex transportation networks with multiple delays is modeled.The finite-time synchronization of the proposed complex transportation networks model is studied systematically.On the basis of the theory of stability,the technique of adaptive control,aperiodically intermittent control and finite-time control,the aperiodically intermittent adaptive finite-time synchronization controller is designed.The controller designed in this paper is beneficial for understanding the synchronization in multi-weighted complex transportation networks with multiple delays.In addition,the conditions for the existence of finite time synchronization have been discussed in detail.And the specific value of the settling finite time for synchronization is obtained.Moreover,the outer coupling configuration matrices are not required to be irreducible or symmetric.Finally,simulation results of the finite-time synchronization problem are given to illustrate the correctness of the results obtained.
基金Sponsored by the Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China(Grant No.13XNH169)
文摘In this paper, we demonstrate that the eco-industrial network equilibrium model of link flow version previously introduced can be reformulated as a transportation network equilibrium problem of path flow version. Then, some methodological tools mainly applied in the field of transportation science can be used to discuss the eco-industrial chain network problem. What the highlighted contribution lies in is that the paper not only expands theory of supply chain model with reducing path flow but also generalizes the traditional transportation network equilibrium problem by new applications.
文摘This paper shows a number of Problems in pure and applied mathematicsthat are solved by constructing transportation networks.Moreover,it also shows thatall the solutions are characterized by forbidden configurations which are not minors.However,all the characterizations are much related to the graphic method which wasfound by Chinese for solving a kind of the transportation problem in the fifties.
文摘From the perspective of domestic market integration,this paper systematically examines the impact of transportation infrastructure conditions on excess sensitivity of household consumption based on the China Family Panel Survey(CFPS)and multi-level matching panel data of transportation network density.The results show that the fast-growing development of the transportation infrastructure network has a significant alleviating effect on excess sensitivity of household consumption along the route,and the conclusion is still robust after the use of the multi-dimensional instrumental variable method and a series of robustness tests.According to the heterogeneity tests,in terms of the alleviating effect of transportation infrastructure,railroads rank the first,highways the second,substandard roads the third,waterways the fourth,and roads of other grades at the bottom.The mechanism test reveals that the improvement of domestic market integration is an important channel for transportation infrastructure to alleviate excess sensitivity of household consumption.This paper confirms that improving the transportation infrustructure system is conducive to the construction of a unified national market,alleviating excess sensitivity of consumption and stimulating consumption.This paper provides suggestions for implementing the strategy of boosting domestic demand,and helps the government understand households'consumption decision-making from a broader perspective.This study also provides a theoretical basis for the economic spillover effect of transportation infrastructure.
基金partially sponsored by the National Science Foundation(NSF)under Grants No.2125426.
文摘This study develops a comprehensive framework to assess the resilience of transportation networks consisting of deteriorating bridges subjected to earthquake events.For this purpose,the structural capacity of highway bridges is estimated during their service life using a set of detailed finite-element models that simulate the progress of deterioration.The developed models take into consideration the main environmental stressors and determine the extent of capacity loss as a function of time.Based on the degraded state of structural components,seismic fragility analyses are performed to obtain a probabilistic evaluation of the extent of damageability of the existing bridges under seismic events.Since each transportation link normally consists of a number of bridges,the state of damage in the individual bridges is mapped to the corresponding links and a scenario-based approach is employed to estimate the resilience of the entire transportation network.To demonstrate how the consequences of structural degradation can be integrated into the developed framework,the large-scale transportation network of Los Angeles and Orange counties is investigated under a series of aging and earthquake scenarios.The outcome of this study indicates how the estimates associated with the functionality measures of a transportation network can be improved if the age factor is properly integrated into the framework used for resilience assessment.
基金supported by the National Natural Science Foundation of China[61773091 and 62173065 to X.-K.X.,11975025 to L.W.,11875005 to Y.W.,72025405 and 82041020 to X.L.,71974029 to X.W.]the Grand Challenges ICODA pilot initiative,delivered by Health Data Research UK and funded by the Bill&Melinda Gates Foundation and the Minderoo Foundation[to X.F.L.]+1 种基金US CDC Grant 20U01CK000592[to S.P.]US CDC and CSTE Grant NU38OT00297[to S.P.].
文摘The spatial spread of COVID-19 during early 2020 in China was primarily driven by outbound travelers leaving the epicenter,Wuhan,Hubei province.Existing studies focus on the influence of aggregated out-bound population flows originating from Wuhan;however,the impacts of different modes of transportation and the network structure of transportation systems on the early spread of COVID-19 in China are not well understood.Here,we assess the roles of the road,railway,and air transportation networks in driving the spatial spread of COVID-19 in China.We find that the short-range spread within Hubei province was dominated by ground traffic,notably,the railway transportation.In contrast,long-range spread to cities in other provinces was mediated by multiple factors,including a higher risk of case importation associated with air transportation and a larger outbreak size in hub cities located at the center of transportation networks.We further show that,although the dissemination of SARS-CoV-2 across countries and continents is determined by the worldwide air transportation network,the early geographic dispersal of COVID-19 within China is better predicted by the railway traffic.Given the recent emergence of multiple more transmissible variants of SARS-CoV-2,our findings can support a better assessment of the spread risk of those variants and improve future pandemic preparedness and responses.
基金supported by National Key Research and Development Program of China(2016YFB0900100)National Natural Science Foundation of China(51877144)China Postdoctoral Science(2020M6700668).
文摘This paper proposes a security region of transporta-tion networks,which is defined as the set of flow states(operating points)satisfying the N-1 security in transportation networks.The boundary of the set is closed,inside all the operating points are N-1 secure;oppositely,outside all the operating points are insecure.First,N-1 security of the transportation networks is defined,which means that when a road is blocked,vehicles on other roads within the networks can also reach their destination through different paths without being trapped on the road.Then,the security region of transportation networks is modeled.The algorithm of a boundary calculation is studied and the boundary equations of security distances are proposed.Finally,the proposed security of the transportation networks is presented in different examples.This paper demonstrates the following:1)the security region can be accurately predicted by the simulation of N-1;2)the boundary distance can show the necessary degree of security;3)security can be improved by a preventive control scheme.The simulation on TransCAD is used to verify the correctness of the results.Index Terms-Boundary distance,evolution,security region,transportation network,TransCAD.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51975048,52102449).
文摘The hybrid electric propulsion system(HEPS)holds clear potential to support the goal of sustainability in the automobile and aviation industry.As an important part of the three-dimensional transportation network,vehicles and aircraft using HEPSs have the advantages of high fuel economy,low emission,and low noise.To fulfill these advantages,the design of their energy management strategies(EMSs)is essential.This paper presents an in-depth review of EMSs for hybrid electric vehicles(HEVs)and hybrid electric aircraft.First,in view of the main challenges of current EMSs of HEVs,the referenced research is reviewed according to the solutions facing real-time implementation problems,variable driving conditions adaptability problems,and multi-objective optimization problems,respectively.Second,the existing research on the EMSs for hybrid electric aircraft is summarized according to the hybrid electric propulsion architectures.In addition,with the advance in propulsion technology and mechanical manufacturing in recent years,flying cars have gradually become a reality,further enriching the composition of the three-dimensional transportation network.And EMSs also play an essential role in the efficient operation of flying cars driven by HEPSs.Therefore,in the last part of this paper,the development status of flying cars and their future prospects are elaborated.By comprehensively summarizing the EMSs of HEPS for vehicles and aircraft,this review aims to provide guidance for the research on the EMSs for flying cars driven by HEPS and serve as the basis for knowledge transfer of relevant researchers.
基金supported by the Science and Technology Project of North China Electric Power Research Institute,which is“Research on Key Technologies for Power Quality Evaluation and Improvement of New Distribution Network Based on Collaborative Interaction of Source-Network-Load-Storage”(KJZ2022016).
文摘The couple between the power network and the transportation network(TN)is deepening gradually with the increasing penetration rate of electric vehicles(EV),which also poses a great challenge to the traditional voltage control scheme.In this paper,we propose a coordinated voltage control strategy for the active distribution networks considering multiple types of EV.In the first stage,the action of on-load tap changer and capacitor banks,etc.,are determined by optimal power flow calculation,and the node electricity price is also determined based on dynamic time-of-use tariff mechanism.In the second stage,multiple operating scenarios of multiple types of EVs such as cabs,private cars and buses are considered,and the scheduling results of each EV are solved by building an optimization model based on constraints such as queuing theory,Floyd-Warshall algorithm and traffic flow information.In the third stage,the output power of photovoltaic and energy storage systems is fine-tuned in the normal control mode.The charging power of EVs is also regulated in the emergency control mode to reduce the voltage deviation,and the amount of regulation is calculated based on the fair voltage control mode of EVs.Finally,we test the modified IEEE 33-bus distribution system coupled with the 24-bus Beijing TN.The simulation results show that the proposed scheme can mitigate voltage violations well.
基金supported by the National Natural Science Foundation of China(52275463,51772240)the National Key Research and Development Program of China(2021YFB3302000)the Key Research and Development Projects of Shaanxi Province,China(2018ZDXM-GY-135)。
文摘The development of energy storage devices with high energy density relies heavily on thick film electrodes,but it is challenging due to the limited ion transport kinetics inherent in thick electrodes.Here,we report on the preparation of a directional vertical array of micro-porous transport networks on LTO electrodes using a femtosecond laser processing strategy,enabling directional ion rapid transport and achieving good electrochemical performance in thick film electrodes.Various three-dimensional(3D)vertically aligned micro-pore networks are innovatively designed,and the structure,kinetics characteristics,and electrochemical performance of the prepared ion transport channels are analyzed and discussed by multiple characterization and testing methods.Furthermore,the rational mechanisms of electrode performance improvement are studied experimentally and simulated from two aspects of structural mechanics and transmission kinetics.The ion diffusion coefficient,rate performance at 60 C,and electrode interface area of the laser-optimized 60-15%micro-porous transport network electrodes increase by 25.2 times,2.2 times,and 2.15 times,respectively than those of untreated electrodes.Therefore,the preparation of 3D micro-porous transport networks by femtosecond laser on ultra-thick electrodes is a feasible way to develop high-energy batteries.In addition,the unique micro-porous transport network structure can be widely extended to design and explore other high-performance energy materials.
基金supported in part by the Science and Technology Project of Hebei Education Department,Grant ZD2021088in part by the S&T Major Project of the Science and Technology Ministry of China,Grant 2017YFE0135700。
文摘In future optical transport networks,lightpath performance analysis is of great practical significance for fully automated management.In general,the quality of transmission(QoT)of lightpaths,measured by optical quality factor or optical signal-to-noise ratio,has a complex time-varying process,along with the interactions of the other lightpath state parameters(LSPs),such as transmit power,chromatic dispersion,polarization mode dispersion.Current studies are mostly focused on lightpath QoT estimation,but ignoring lightpath-level data analytics.In this case,our article proposes a novel lightpath performance analysis method considering recurrence plot(RP)and cross recurrence plot(CRP).Firstly,we give a detailed interpretation on the recurrence patterns of LSPs via a qualitative 2-D RP representation and its quantitative measure.It can potentially enable the accurate and fast lightpath failure detection with a low computational burden.On the other hand,CRP is devoted to modeling the relationships between lightpath QoT and LSPs,and the correlation degree is determined by a geometric mean of multiple indexes of cross recurrence quantification analysis.From the view of application,such CRP analysis can provide the effective knowledge sharing to guarantee more credible QoT prediction.Extensive experiments on a real-world optical network dataset have clearly demonstrated the effectiveness of our proposal.
基金Key Project of the Chinese Academy of Sciences,No.ZDRW-ZS-2016-6-3National Natural Science Foundation of China,No.41501490
文摘The robustness of cargo ship transportation networks is essential to the stability of the world trade system. The current research mainly focuses on the coarse-grained, holistic cargo ship transportation network while ignoring the structural diversity of different sub-networks. In this paper, we evaluate the robustness of the global cargo ship transportation network based on the most recent Automatic Identification System（AIS） data available. First, we subdivide three typical cargo ship transportation networks（i.e., oil tanker, container ship and bulk carrier） from the original cargo ship transportation network. Then, we design statistical indices based on complex network theory and employ four attack strategies, including random attack and three intentional attacks（i.e., degree-based attack, betweenness-based attack and flux-based attack） to evaluate the robustness of the three typical cargo ship transportation networks. Finally, we compare the integrity of the remaining ports of the network when a small proportion of ports lose their function. The results show that 1） compared with the holistic cargo ship transportation network, the fine-grain-based cargo ship transportation networks can fully reflect the pattern and process of global cargo transportation; 2） different cargo ship networks behave heterogeneously in terms of their robustness, with the container network being the weakest and the bulk carrier network being the strongest; and 3） small-scale intentional attacks may have significant influence on the integrity of the container network but a minor impact on the bulk carrier and oil tanker transportation networks. These conclusions can help improve the decision support capabilities in maritime transportation planning and emergency response and facilitate the establishment of a more reliable maritime transportation system.Abstract： The robustness of cargo ship transportation networks is essential to the stability of the world trade system. The current research mainly focuses on the coarse-grained, holistic cargo ship transportation network while ignoring the structural diversity of different sub-networks. In this paper, we evaluate the robustness of the global cargo ship transporta- tion network based on the most recent Automatic Identification System （AIS） data available. First, we subdivide three typical cargo ship transportation networks （i.e., oil tanker, container ship and bulk carrier） from the original cargo ship transportation network. Then, we design statistical indices based on complex network theory and employ four attack strategies, in- cluding random attack and three intentional attacks （i.e., degree-based attack, between- ness-based attack and flux-based attack） to evaluate the robustness of the three typical cargo ship transportation networks. Finally, we compare the integrity of the remaining ports of the network when a small proportion of ports lose their function. The results show that 1） com- pared with the holistic cargo ship transportation network, the fine-grain-based cargo ship transportation networks can fully reflect the pattern and process of global cargo transportation 2） different cargo ship networks behave heterogeneously in terms of their robustness, with the container network being the weakest and the bulk carrier network being the strongest; and 3） small-scale intentional attacks may have significant influence on the integrity of the con- tainer network but a minor impact on the bulk carrier and oil tanker transportation networks.These conclusions can help improve the decision support capabilities in maritime transportation planning and emergency response and facilitate the establishment of a more reliable maritime transportation system.
基金supported by the Science and Technology Project of the State Grid Corporation of China“Research on resilience technology and application foundation of intelligent distribution network based on integrated energy system”(No.52060019001H).
文摘To improve the resilience of distribution networks(DNs),a multi-stage dynamic recovery strategy is proposed in this paper,which is designed for post-disaster DN considering an integrated energy system(IES)and transportation network(TN).First,the emergency response quickly increases the output of gas turbines(GTs)in the natural gas network(NGN),and responsively reconfigures the DN in microgrids,to maximize the amount of loads to be restored.The single-commodity flow model is adopted to construct spanning tree constraints.Then,in the second stage of energy storage recovery,mobile energy storage systems(MESSs)are deployed to cover the shortages of power demands,i.e.,to further restore the loads after evaluating the load recovery situation.The Floyd algorithm based dynamic traffic assignment(DTA)is selected to obtain the optimal path of the MESSs.In the third stage,the outputs of various post-disaster recovery measures are adjusted to achieve an economically optimized operation.Case studies demonstrate the effectiveness of the proposed dynamic post-disaster recovery strategy.
