To address the challenges of supply-demand imbal-ance in rail transit and the complex passenger flow interactions among multiple hub stations under high-passenger-volume scenarios,this study proposes an optimized rail...To address the challenges of supply-demand imbal-ance in rail transit and the complex passenger flow interactions among multiple hub stations under high-passenger-volume scenarios,this study proposes an optimized rail transit scheduling method based on a flexible train formation strat-egy(FTFS).By constructing interaction parameters that characterize the coupling effects of high passenger flow across multiple hubs,a multiobjective optimization model is developed to minimize passenger waiting time at hub sta-tions and operational costs.An improved nondominated sorting genetic algorithm incorporating chaotic mapping and adaptive evolutionary parameters is designed for efficient so-lution optimization.This method overcomes the limitations of fixed train formations by supporting diversified modular unit detachment and reconnection,enabling dynamic capac-ity adjustment and efficient rolling stock circulation.A case study on Nanjing Metro Line 1 demonstrates that the FTFS reduces the average waiting time at hub stations by 47.2%,alleviates train congestion by approximately 18.6%,and re-duces the operational costs under low-demand scenarios by 44.8%.Pareto frontier analysis further reveals the trade-off mechanism between transport capacity elasticity and opera-tional costs.These findings validate the effectiveness of the flexible train formation model in mitigating platform conges-tion and enhancing passenger flow evacuation efficiency at transport hubs,providing multiobjective decision-making support for managing extreme passenger flow during holi-days and peak events.展开更多
A mathematical optimal model is developed to address the problem of logistics hubs location.The method integrates nonlinear programming models and fuzzy comprehensive evaluation,and handles both quantitative and quali...A mathematical optimal model is developed to address the problem of logistics hubs location.The method integrates nonlinear programming models and fuzzy comprehensive evaluation,and handles both quantitative and qualitative factors that influence the location of logistics hubs.A mathematical programming model is used to find the optimal candidate sites of the logistics hub based on profit-maximizing criteria.Then a fuzzy comprehensive evaluation method is adopted to determine the final optimal location of those candidate sites by taking account of criteria including stability of policy environment,convenience of transportation(e.g.,easy access to highways/expressways,etc.),rationality of economy,competition and sustainability.Finally,the methodology is demonstrated by a case study of the Transfar Logistics Base in Zhejiang Province.The results verify the method application for logistics hub locations and show how to locate a logistics hub in practice from the case of Transfar Logistics Base.展开更多
Functional hubs with disproportionately extensive connectivities play a crucial role in global information integration in human brain networks.However,most resting-state functional magnetic resonance imaging(R-fMRI)st...Functional hubs with disproportionately extensive connectivities play a crucial role in global information integration in human brain networks.However,most resting-state functional magnetic resonance imaging(R-fMRI)studies have identified functional hubs by examining spontaneous fluctuations of the blood oxygen level-dependent signal within a typical low-frequency band(e.g.,0.01–0.08 Hz or 0.01–0.1 Hz).Little is known about how the spatial distributions of functional hubs depend on frequency bands of interest.Here,we used repeatedly measured R-fMRI data from 53 healthy young adults and a degree centrality analysis to identify voxelwise frequency-resolved functional hubs and further examined their test-retest reliability across two sessions.We showed that a wide-range frequency band(0.01–0.24 Hz)accessible with a typical sampling rate(fsample=0.5 Hz)could be classified into three frequency bands with distinct patterns,namely,low-frequency(LF,0.01–0.06 Hz),middle-frequency(MF,0.06–0.16 Hz),and high-frequency(HF,0.16–0.24 Hz)bands.The functional hubs were mainly located in the medial and lateral frontal and parietal cortices in the LF band,and in the medial prefrontal cortex,superior temporal gyrus,parahippocampal gyrus,amygdala,and several cerebellar regions in the MF and HF bands.These hub regions exhibited fair to good test-retest reliability,regardless of the frequency band.The presence of the three frequency bands was well replicated using an independent R-fMRI dataset from 45 healthy young adults.Our findings demonstrate reliable frequency-resolved functional connectivity hubs in three categories,thus providing insights into the frequency-specific connectome organization in healthy and disordered brains.展开更多
Size distribution characteristics of intercity bus hubs in China from 1997 to 2（104 were analyzed regarding highway passenger volume as a size index of intercity bus hubs. Yearly fractal dimensions of intercity bus h...Size distribution characteristics of intercity bus hubs in China from 1997 to 2（104 were analyzed regarding highway passenger volume as a size index of intercity bus hubs. Yearly fractal dimensions of intercity bus hub sizes were exactly calculated by a novel model. Fractal dimensions of the 200 biggest intercity bus hubs from 2000 to 2004 were 1. 486 2 to 1. 511 8, and that is consistent with fractal dimensions of Chinese urban system sizes. It showed that the size distribution of intercity bus hubs had fractal structure. Fractal dimensions from 1997 to 2004 indicated that intercity bus hub size distribution grew from bi-fractal to single fractal. It is concluded that the intercity bus hub system is in evolutionary progress, and the Central Government should support large intercity bus hubs more to optimize system structure.展开更多
This article examines the approaches that are adopted by both Singapore and Hong Kong in developing themselves as ＂regional hubs of higher education＂ through different strategies on the development of their higher e...This article examines the approaches that are adopted by both Singapore and Hong Kong in developing themselves as ＂regional hubs of higher education＂ through different strategies on the development of their higher education systems, and via developing transnational higher education. The article starts off with a delineation on how the process of globalization has structurally altered the landscape of the global higher education market, upon which these changes drive both Singapore and Hong Kong to become more competitive in the global education marketplace. By examining and evaluating the recent education reforms in the two Asian city-states, the author argues that the two places have significant differences and are using rather different strategies in developing their higher education sectors, which can then reflect upon their fundamental differences in terms of the basic mindsets, underlying philosophies and style of governance of higher education by the two governments.展开更多
The route optimization problem for road networks was applied to pedestrian flow.Evacuation path networks with nodes and arcs considering the traffic capacities of facilities were built in metro hubs,and a path impedan...The route optimization problem for road networks was applied to pedestrian flow.Evacuation path networks with nodes and arcs considering the traffic capacities of facilities were built in metro hubs,and a path impedance function for metro hubs which used the relationships among circulation speed,density and flow rate for pedestrians was defined.Then,a route optimization model which minimizes the movement time of the last evacuee was constructed to optimize evacuation performance.Solutions to the proposed mathematical model were obtained through an iterative optimization process.The route optimization model was applied to Xidan Station of Beijing Metro Line 4 based on the actual situations,and the calculation results of the model were tested using buildingExodus microscopic evacuation simulation software.The simulation result shows that the proposed model shortens the evacuation time by 16.05%,3.15% and 2.78% compared with all or none method,equally split method and Logit model,respectively.Furthermore,when the population gets larger,evacuation efficiency in the proposed model has a greater advantage.展开更多
Gas trading hubs have been initially developed in the US in 1980s,UK in 1990s,more recently in European in the 2000s and mulled in East Asia now.Due to its freshness and diversification in nationality,governance and c...Gas trading hubs have been initially developed in the US in 1980s,UK in 1990s,more recently in European in the 2000s and mulled in East Asia now.Due to its freshness and diversification in nationality,governance and culture,the European hub experience can offer valuable lessons for East Asia.This paper seeks to advance understanding of gas hub development in Europe and provide lessons for East Asia.The European experience highlights that market liberalization and transition of gas pricing mechanism are necessary in creating the competitive markets that are needed for functional gas hubs.Political will and regulations further safeguard the competition environment needed for hub development.Natural factors,such as significant domestic production and culture could have a significant impact on the hub development and transition of pricing mechanism.In East Asia,the path to gas trading hubs might be more difficult than in Europe but a growing market creates an opportunity to start new terms with new contracts.Nevertheless,East Asian needs to work hard to development its indigenous gas or LNG trading hubs.展开更多
This paper is engaged in the research of urban rail transit hub integration and transfer.Firstly,this paper focuses on the space division,the aggregation form of hub subsystems,the spatial layout of hub subsystems,and...This paper is engaged in the research of urban rail transit hub integration and transfer.Firstly,this paper focuses on the space division,the aggregation form of hub subsystems,the spatial layout of hub subsystems,and the design of integrated functions to achieve an integrated layout.In addition,this study also conducted a selection of transfer classification and transfer station layout of urban rail transit hubs,with the aims to promote the improvement of the functions of urban rail transit hubs,the rationality of transfers,and to improve the service quality of the hub system which meet the demand of the public travel.展开更多
Coordinated scheduling of multimode plays a pivotal role in the rapid gathering and dissipating of passengers in transport hubs. Based on the survey data, the whole-day reaching time distribution at transfer points of...Coordinated scheduling of multimode plays a pivotal role in the rapid gathering and dissipating of passengers in transport hubs. Based on the survey data, the whole-day reaching time distribution at transfer points of passengers from the dominant mode to the connecting mode was achieved. A GI/M K/1 bulk service queuing system was constituted by putting the passengers' reaching time distribution as the input and the connecting mode as the service institution. Through queuing theory, the relationship between average queuing length under steady-state and headway of the connecting mode was achieved. By putting the minimum total cost of system as optimization objective, the headway as decision variable, a coordinated scheduling model of multimode in intermodal transit hubs was established. At last, a dynamic scheduling strategy was generated to cope with the unexpected changes of the dominant mode. The instance analysis indicates that this model can significantly reduce passengers' queuing time by approximately 17% with no apparently increase in departure frequency, which provides a useful solution for the coordinated scheduling of different transport modes in hubs.展开更多
To increase the passenger transferring efficiency, the bus coordination holding control for transit hubs, which is as an important dynamic dispatching method for improving the service level of transit hubs, was studie...To increase the passenger transferring efficiency, the bus coordination holding control for transit hubs, which is as an important dynamic dispatching method for improving the service level of transit hubs, was studied in the framework of bus coordination dispatching mode. Firstly, the bus coordination holding control flow was studied based on Advanced Public Transportation Systems (APTS) environment. Then a control model was presented to optimize the bus vehicle holding time, and a genetic algorithm was designed as the solving method. In the end, an example was given to illustrate the effectiveness of the control strategy and the algorithm.展开更多
This paper clarifies various concepts relevant to gas trading hubs and presents an innovative framework with key elements to create gas hubs.The nine key elements in the framework are further divided into basic elemen...This paper clarifies various concepts relevant to gas trading hubs and presents an innovative framework with key elements to create gas hubs.The nine key elements in the framework are further divided into basic elements for balancing hubs and advanced elements for benchmark hubs.The framework is applied to three East Asian case studies.The East Asian comparative case study shows that while Singapore is leading the way in establishing an LNG hub in Asia,the LNG hub concept is yet to be tested.Meanwhile,although China has the potential to host a gas hub,its current level of hub development is low.The paper suggests that these countries can advance their hub initiatives by strengthening the key elements as detailed in the proposed framework and create a more conducive environment through efforts such as market liberalization.展开更多
This paper proposes an IoT-Fog-Cloud distributed consensus algorithm for solving the energy hub(EH)dispatch problem with packet-dropping communication links and some of EH elements'uncertainties.Every generating a...This paper proposes an IoT-Fog-Cloud distributed consensus algorithm for solving the energy hub(EH)dispatch problem with packet-dropping communication links and some of EH elements'uncertainties.Every generating and consumption unit in this algorithm is required to estimate total power generated,total load,and power mismatches.Energy node coordination is accomplished using a distributed approach.Such a distributed approach wins in work sharing,enduring a single link failure,effective decision-making,quickest convergence,and autonomy for global power nodes.The method works with all grid types in connected and islanded modes.Minimizing total operation cost and emissions while meeting total demand and system constraints are the most crucial contributions of this paper.Two case studies are applied to explain performance and effectiveness of the proposed algorithm with different packet loss scenarios.Under uncertainty,sensitivity of the system was evaluated.Results show mismatch between generated and consumed power is improved by 100%in the electricity grid,99.94%in heating grid,and 99.91%in gas grid.Also,total operating cost,total emissions,and emissions cost decreased by 8.6%,13.48%,and 18.73%,respectively.展开更多
With the implementation of the integrated electricity and gas market(IEGM),the smart energy hubs(SEHs)tend to participate in the market clearing for the optimization of the energy purchase portfolio.Meanwhile,the rene...With the implementation of the integrated electricity and gas market(IEGM),the smart energy hubs(SEHs)tend to participate in the market clearing for the optimization of the energy purchase portfolio.Meanwhile,the renewable energy is mushrooming at different scales of energy systems,which can introduce utility-level and distribution-level uncertainties to the operation of the IEGM and SEHs,respectively.Considering the impacts of divergent uncertainties,there exist complicated interactions between the IEGM clearing and the robust bidding of SEHs.The lack of consideration of such interactions may lead to inaccurate modeling of the IEGM clearing and cause potential market inefficiency.To handle this,a bi-level robust clearing framework of the IEGM considering the robust bidding of SEHs is proposed,which simultaneously considers the impacts of utility-level and distribution-level uncertainties.The proposed framework is partitioned into two levels.The upper level is the robust clearing mechanism of the IEGM.At this level,the uncertainty locational marginal electricity and gas prices are derived considering the utility-level uncertainties and the uncertainty-based bidding of SEHs.Given the price signals deduced in the upper level,the lower-level robust bidding of the SEH seeks the optimal bidding strategies while hedging against distribution-level uncertainties.To address the proposed framework,an effective algorithm combining column-and-constraint generation(C&CG)algorithm with the best-response decomposition(BRD)algorithm is formulated.The devised algorithm can efficiently solve the individual robust optimization model and coordinate the interaction of two levels.Numerical experiments are carried out to verify the effectiveness of the proposed framework.Moreover,the impacts of uncertainties on the market clearing results along with the optimal biddings of SEHs are further demonstrated within the proposed framework.展开更多
Multimodal transportation hubs serve as transfer points with the function of collecting,transferring,and distributing passengers and play a significant role in the entire multimodal transportation network.In an emerge...Multimodal transportation hubs serve as transfer points with the function of collecting,transferring,and distributing passengers and play a significant role in the entire multimodal transportation network.In an emergency,the development of an effective and efficient emergency evacuation strategy to evacuate passengers from multimodal transportation hubs is very important.This paper aims to conduct a comprehensive review on passenger emergency evacuations from multimodal transportation hubs,summarize the achievements,identify gaps in existing literature,thus to lay a solid foundation for future studies.This paper first reviewed studies on evacuee behavior characteristics in emergency evacuations,including pedestrian characteristics,pedestrian behavior characteristics,and pedestrian flow characteristics.Then evacuation models,including pedestrian evacuation models and multimodal transportation evacuation models,were investigated.In addition,a retrospective analysis was carried out for evacuation simulation.It is found that while many studies have been conducted on passenger emergency evacuations from multimodal transportation hubs,most of them focus more on evacuating pedestrians from inside to outside of hub buildings;the studies on evacuation at multimodal transfer points are limited.It is also found that most existing studies tried to establish a general model to handle all types of emergency evacuations;in fact,a model would be more efficient if it is just established for a specific emergency and for a specific type of hubs.Also,existing data collection methods may collect biased data;new data collection methods need to be explored to increase the accuracy of data collection.Future study directions include the evacuation at multimodal transfer points,interactive effects between individual pedestrian behavior and pedestrian group behavior,more specific types of emergency evacuations,more accurate data collection methods,and tradeoffs between cost and benefit in emergency evacuations.展开更多
The issue of "missing baryons” is always an unsolved mystery in galaxy cosmology, and an important reason for the great uncertainty of the galaxies' formation and evolution. To find the "missing" b...The issue of "missing baryons” is always an unsolved mystery in galaxy cosmology, and an important reason for the great uncertainty of the galaxies' formation and evolution. To find the "missing" baryons, extra high-resolution spectral observation and imaging of the soft X-ray band (<1 kev) is required. However, the existing observation methods cannot meet this requirement. Therefore, Tsinghua University leads and proposes the Chinese "Hot Universe Baryon Surveyor (HUBS)" satellite program.展开更多
The accuracy of the simulation model has a pro-found impact on the optimal operation of the energy hubs(EHs).However,in many articles,the constant model of the efficiency of equipment is adopted to formulate the opera...The accuracy of the simulation model has a pro-found impact on the optimal operation of the energy hubs(EHs).However,in many articles,the constant model of the efficiency of equipment is adopted to formulate the operation system,which would probably lead to a simplification of the simulation models.But,EHs are typically operated under off-design condition due to the fluctuations in cooling,heating,electricity requirement.More-over,even though the off-design characteristics are considered,few studies have suggested comparing the differences between those two models by considering the operation cost.In order to assess the effect of the off-design characteristics of EH on the optimal operation accuracy in this paper,two test cases are performed on the fixed and variable load conditions,respectively.In addition,the individual effect of off-design characteristics of each equipment on the optimal operation cost of the EH is also investigated through four optimization runs.It is worth mentioning that the optimal operation problem of the EH considering the off-design characteristics and on-off status of the equipment is a mixed integer non-linear programming problem(MINLP).By testing the design and off-design models on the two cases,the results of simulation demonstrate that the optimal operation cost for the off-design model is larger than that for the design model.Nonetheless,in the aspect of the authenticity of the system operation strategy,the off-design model performs better than the design model.Furthermore,a larger relative error of the system operation cost between the two models can be observed when the EH is operated under a relatively lower load condition,revealing that the influence of off-design characteristic on the optimal operation of EHs is too significant to be neglected.展开更多
As the sunlight scattered on the sea of Guanyinshan in Xiamen,a space that bridges creativity and industry opened its door to the world.On December 15th,following a ribbon-cutting and unveiling ceremony,YKK Xiamen Gua...As the sunlight scattered on the sea of Guanyinshan in Xiamen,a space that bridges creativity and industry opened its door to the world.On December 15th,following a ribbon-cutting and unveiling ceremony,YKK Xiamen Guanyinshan Showroom,the brand's second and largest comprehensive showroom,was officially inaugurated.This showroom is more than a product display window,it is an"Inspiration Hub"integrating exhibition,co-creation,and service.Its launch signifies YKK's progression in the Chinese market from“building an efficient product proposal system”to a new stage of“deep collaborative co-creation.”展开更多
The book Yangzhou:The Biography,written by Wei Minghua,is part of the Biographies of 100 Cities Along the Silk Road series.Rather than writing a general history account of this millennia-old city,this book aims to ans...The book Yangzhou:The Biography,written by Wei Minghua,is part of the Biographies of 100 Cities Along the Silk Road series.Rather than writing a general history account of this millennia-old city,this book aims to answer one central question:What is Yangzhou’s relationship with the Silk Road?This requires examining several aspects:the significant historical facts about Yangzhou in China’s foreign exchanges,why Yangzhou became a renowned hub for such interaction,and the stories of ordinary people in today’s Yangzhou.展开更多
Over the past months,a southern Chinese harbor serving as a pivotal gateway to regions around the world has come into the spotlight after the launching of special customs operations on Hainan Island.LOCATED on the nor...Over the past months,a southern Chinese harbor serving as a pivotal gateway to regions around the world has come into the spotlight after the launching of special customs operations on Hainan Island.LOCATED on the northwest tip of HainanIsland,the Yangpu Port is a scene ofbustling activity with towering gantrycranes busily loading containers on andoff large cargo vessels.Port orders here have surgedas a result of a slew of special customs policiesthat went into force last December.展开更多
基金Key Project of the National Natural Science Foundation of China (No. 52432011)the National Natural Science Foundation of China (No. 524B2153)。
文摘To address the challenges of supply-demand imbal-ance in rail transit and the complex passenger flow interactions among multiple hub stations under high-passenger-volume scenarios,this study proposes an optimized rail transit scheduling method based on a flexible train formation strat-egy(FTFS).By constructing interaction parameters that characterize the coupling effects of high passenger flow across multiple hubs,a multiobjective optimization model is developed to minimize passenger waiting time at hub sta-tions and operational costs.An improved nondominated sorting genetic algorithm incorporating chaotic mapping and adaptive evolutionary parameters is designed for efficient so-lution optimization.This method overcomes the limitations of fixed train formations by supporting diversified modular unit detachment and reconnection,enabling dynamic capac-ity adjustment and efficient rolling stock circulation.A case study on Nanjing Metro Line 1 demonstrates that the FTFS reduces the average waiting time at hub stations by 47.2%,alleviates train congestion by approximately 18.6%,and re-duces the operational costs under low-demand scenarios by 44.8%.Pareto frontier analysis further reveals the trade-off mechanism between transport capacity elasticity and opera-tional costs.These findings validate the effectiveness of the flexible train formation model in mitigating platform conges-tion and enhancing passenger flow evacuation efficiency at transport hubs,providing multiobjective decision-making support for managing extreme passenger flow during holi-days and peak events.
基金The National Key Technology R&D Program of China during the 11th Five-Year Plan Period(No.2006BAH02A06)Program for New Century Excellent Talents in China(No.NCET-05-0529)
文摘A mathematical optimal model is developed to address the problem of logistics hubs location.The method integrates nonlinear programming models and fuzzy comprehensive evaluation,and handles both quantitative and qualitative factors that influence the location of logistics hubs.A mathematical programming model is used to find the optimal candidate sites of the logistics hub based on profit-maximizing criteria.Then a fuzzy comprehensive evaluation method is adopted to determine the final optimal location of those candidate sites by taking account of criteria including stability of policy environment,convenience of transportation(e.g.,easy access to highways/expressways,etc.),rationality of economy,competition and sustainability.Finally,the methodology is demonstrated by a case study of the Transfar Logistics Base in Zhejiang Province.The results verify the method application for logistics hub locations and show how to locate a logistics hub in practice from the case of Transfar Logistics Base.
基金The study was supported by the National Key R&D Program of China(2018YFA0701402)the National Natural Science Foundation of China(82021004,81971690,81620108016,and 11835003)the Fundamental Research Funds for the Central Universities of China(2019NTST24).
文摘Functional hubs with disproportionately extensive connectivities play a crucial role in global information integration in human brain networks.However,most resting-state functional magnetic resonance imaging(R-fMRI)studies have identified functional hubs by examining spontaneous fluctuations of the blood oxygen level-dependent signal within a typical low-frequency band(e.g.,0.01–0.08 Hz or 0.01–0.1 Hz).Little is known about how the spatial distributions of functional hubs depend on frequency bands of interest.Here,we used repeatedly measured R-fMRI data from 53 healthy young adults and a degree centrality analysis to identify voxelwise frequency-resolved functional hubs and further examined their test-retest reliability across two sessions.We showed that a wide-range frequency band(0.01–0.24 Hz)accessible with a typical sampling rate(fsample=0.5 Hz)could be classified into three frequency bands with distinct patterns,namely,low-frequency(LF,0.01–0.06 Hz),middle-frequency(MF,0.06–0.16 Hz),and high-frequency(HF,0.16–0.24 Hz)bands.The functional hubs were mainly located in the medial and lateral frontal and parietal cortices in the LF band,and in the medial prefrontal cortex,superior temporal gyrus,parahippocampal gyrus,amygdala,and several cerebellar regions in the MF and HF bands.These hub regions exhibited fair to good test-retest reliability,regardless of the frequency band.The presence of the three frequency bands was well replicated using an independent R-fMRI dataset from 45 healthy young adults.Our findings demonstrate reliable frequency-resolved functional connectivity hubs in three categories,thus providing insights into the frequency-specific connectome organization in healthy and disordered brains.
基金The Ph.D.Programs Foundation of Ministry of Edu-cation of China(No20050710006)
文摘Size distribution characteristics of intercity bus hubs in China from 1997 to 2（104 were analyzed regarding highway passenger volume as a size index of intercity bus hubs. Yearly fractal dimensions of intercity bus hub sizes were exactly calculated by a novel model. Fractal dimensions of the 200 biggest intercity bus hubs from 2000 to 2004 were 1. 486 2 to 1. 511 8, and that is consistent with fractal dimensions of Chinese urban system sizes. It showed that the size distribution of intercity bus hubs had fractal structure. Fractal dimensions from 1997 to 2004 indicated that intercity bus hub size distribution grew from bi-fractal to single fractal. It is concluded that the intercity bus hub system is in evolutionary progress, and the Central Government should support large intercity bus hubs more to optimize system structure.
文摘This article examines the approaches that are adopted by both Singapore and Hong Kong in developing themselves as ＂regional hubs of higher education＂ through different strategies on the development of their higher education systems, and via developing transnational higher education. The article starts off with a delineation on how the process of globalization has structurally altered the landscape of the global higher education market, upon which these changes drive both Singapore and Hong Kong to become more competitive in the global education marketplace. By examining and evaluating the recent education reforms in the two Asian city-states, the author argues that the two places have significant differences and are using rather different strategies in developing their higher education sectors, which can then reflect upon their fundamental differences in terms of the basic mindsets, underlying philosophies and style of governance of higher education by the two governments.
基金Project(51078086)supported by the National Natural Science Foundation of China
文摘The route optimization problem for road networks was applied to pedestrian flow.Evacuation path networks with nodes and arcs considering the traffic capacities of facilities were built in metro hubs,and a path impedance function for metro hubs which used the relationships among circulation speed,density and flow rate for pedestrians was defined.Then,a route optimization model which minimizes the movement time of the last evacuee was constructed to optimize evacuation performance.Solutions to the proposed mathematical model were obtained through an iterative optimization process.The route optimization model was applied to Xidan Station of Beijing Metro Line 4 based on the actual situations,and the calculation results of the model were tested using buildingExodus microscopic evacuation simulation software.The simulation result shows that the proposed model shortens the evacuation time by 16.05%,3.15% and 2.78% compared with all or none method,equally split method and Logit model,respectively.Furthermore,when the population gets larger,evacuation efficiency in the proposed model has a greater advantage.
文摘Gas trading hubs have been initially developed in the US in 1980s,UK in 1990s,more recently in European in the 2000s and mulled in East Asia now.Due to its freshness and diversification in nationality,governance and culture,the European hub experience can offer valuable lessons for East Asia.This paper seeks to advance understanding of gas hub development in Europe and provide lessons for East Asia.The European experience highlights that market liberalization and transition of gas pricing mechanism are necessary in creating the competitive markets that are needed for functional gas hubs.Political will and regulations further safeguard the competition environment needed for hub development.Natural factors,such as significant domestic production and culture could have a significant impact on the hub development and transition of pricing mechanism.In East Asia,the path to gas trading hubs might be more difficult than in Europe but a growing market creates an opportunity to start new terms with new contracts.Nevertheless,East Asian needs to work hard to development its indigenous gas or LNG trading hubs.
文摘This paper is engaged in the research of urban rail transit hub integration and transfer.Firstly,this paper focuses on the space division,the aggregation form of hub subsystems,the spatial layout of hub subsystems,and the design of integrated functions to achieve an integrated layout.In addition,this study also conducted a selection of transfer classification and transfer station layout of urban rail transit hubs,with the aims to promote the improvement of the functions of urban rail transit hubs,the rationality of transfers,and to improve the service quality of the hub system which meet the demand of the public travel.
基金Projects(51278221,51378076)supported by the National Natural Science Foundation of China
文摘Coordinated scheduling of multimode plays a pivotal role in the rapid gathering and dissipating of passengers in transport hubs. Based on the survey data, the whole-day reaching time distribution at transfer points of passengers from the dominant mode to the connecting mode was achieved. A GI/M K/1 bulk service queuing system was constituted by putting the passengers' reaching time distribution as the input and the connecting mode as the service institution. Through queuing theory, the relationship between average queuing length under steady-state and headway of the connecting mode was achieved. By putting the minimum total cost of system as optimization objective, the headway as decision variable, a coordinated scheduling model of multimode in intermodal transit hubs was established. At last, a dynamic scheduling strategy was generated to cope with the unexpected changes of the dominant mode. The instance analysis indicates that this model can significantly reduce passengers' queuing time by approximately 17% with no apparently increase in departure frequency, which provides a useful solution for the coordinated scheduling of different transport modes in hubs.
基金Sponsored by the National Natural Science Foundation of China (Grant No. 70601022)the National Basic Research Program of China (Grant No.2006CB705505)
文摘To increase the passenger transferring efficiency, the bus coordination holding control for transit hubs, which is as an important dynamic dispatching method for improving the service level of transit hubs, was studied in the framework of bus coordination dispatching mode. Firstly, the bus coordination holding control flow was studied based on Advanced Public Transportation Systems (APTS) environment. Then a control model was presented to optimize the bus vehicle holding time, and a genetic algorithm was designed as the solving method. In the end, an example was given to illustrate the effectiveness of the control strategy and the algorithm.
文摘This paper clarifies various concepts relevant to gas trading hubs and presents an innovative framework with key elements to create gas hubs.The nine key elements in the framework are further divided into basic elements for balancing hubs and advanced elements for benchmark hubs.The framework is applied to three East Asian case studies.The East Asian comparative case study shows that while Singapore is leading the way in establishing an LNG hub in Asia,the LNG hub concept is yet to be tested.Meanwhile,although China has the potential to host a gas hub,its current level of hub development is low.The paper suggests that these countries can advance their hub initiatives by strengthening the key elements as detailed in the proposed framework and create a more conducive environment through efforts such as market liberalization.
文摘This paper proposes an IoT-Fog-Cloud distributed consensus algorithm for solving the energy hub(EH)dispatch problem with packet-dropping communication links and some of EH elements'uncertainties.Every generating and consumption unit in this algorithm is required to estimate total power generated,total load,and power mismatches.Energy node coordination is accomplished using a distributed approach.Such a distributed approach wins in work sharing,enduring a single link failure,effective decision-making,quickest convergence,and autonomy for global power nodes.The method works with all grid types in connected and islanded modes.Minimizing total operation cost and emissions while meeting total demand and system constraints are the most crucial contributions of this paper.Two case studies are applied to explain performance and effectiveness of the proposed algorithm with different packet loss scenarios.Under uncertainty,sensitivity of the system was evaluated.Results show mismatch between generated and consumed power is improved by 100%in the electricity grid,99.94%in heating grid,and 99.91%in gas grid.Also,total operating cost,total emissions,and emissions cost decreased by 8.6%,13.48%,and 18.73%,respectively.
基金supported by the Science and Technology Project of State Grid Corporation(No.5108-202218280A-2-449-XG)。
文摘With the implementation of the integrated electricity and gas market(IEGM),the smart energy hubs(SEHs)tend to participate in the market clearing for the optimization of the energy purchase portfolio.Meanwhile,the renewable energy is mushrooming at different scales of energy systems,which can introduce utility-level and distribution-level uncertainties to the operation of the IEGM and SEHs,respectively.Considering the impacts of divergent uncertainties,there exist complicated interactions between the IEGM clearing and the robust bidding of SEHs.The lack of consideration of such interactions may lead to inaccurate modeling of the IEGM clearing and cause potential market inefficiency.To handle this,a bi-level robust clearing framework of the IEGM considering the robust bidding of SEHs is proposed,which simultaneously considers the impacts of utility-level and distribution-level uncertainties.The proposed framework is partitioned into two levels.The upper level is the robust clearing mechanism of the IEGM.At this level,the uncertainty locational marginal electricity and gas prices are derived considering the utility-level uncertainties and the uncertainty-based bidding of SEHs.Given the price signals deduced in the upper level,the lower-level robust bidding of the SEH seeks the optimal bidding strategies while hedging against distribution-level uncertainties.To address the proposed framework,an effective algorithm combining column-and-constraint generation(C&CG)algorithm with the best-response decomposition(BRD)algorithm is formulated.The devised algorithm can efficiently solve the individual robust optimization model and coordinate the interaction of two levels.Numerical experiments are carried out to verify the effectiveness of the proposed framework.Moreover,the impacts of uncertainties on the market clearing results along with the optimal biddings of SEHs are further demonstrated within the proposed framework.
基金supported by The National Key Research and Development Program of China(No.2018YFB1601200)
文摘Multimodal transportation hubs serve as transfer points with the function of collecting,transferring,and distributing passengers and play a significant role in the entire multimodal transportation network.In an emergency,the development of an effective and efficient emergency evacuation strategy to evacuate passengers from multimodal transportation hubs is very important.This paper aims to conduct a comprehensive review on passenger emergency evacuations from multimodal transportation hubs,summarize the achievements,identify gaps in existing literature,thus to lay a solid foundation for future studies.This paper first reviewed studies on evacuee behavior characteristics in emergency evacuations,including pedestrian characteristics,pedestrian behavior characteristics,and pedestrian flow characteristics.Then evacuation models,including pedestrian evacuation models and multimodal transportation evacuation models,were investigated.In addition,a retrospective analysis was carried out for evacuation simulation.It is found that while many studies have been conducted on passenger emergency evacuations from multimodal transportation hubs,most of them focus more on evacuating pedestrians from inside to outside of hub buildings;the studies on evacuation at multimodal transfer points are limited.It is also found that most existing studies tried to establish a general model to handle all types of emergency evacuations;in fact,a model would be more efficient if it is just established for a specific emergency and for a specific type of hubs.Also,existing data collection methods may collect biased data;new data collection methods need to be explored to increase the accuracy of data collection.Future study directions include the evacuation at multimodal transfer points,interactive effects between individual pedestrian behavior and pedestrian group behavior,more specific types of emergency evacuations,more accurate data collection methods,and tradeoffs between cost and benefit in emergency evacuations.
基金supported by the National Natural Science Foundation of China (51706233, U1831203, 51427806)Strategic Pilot Projects in Space Science of China (XDA15010400)Key Research Program of Frontier Sciences, CAS (QYZDYSSW-JSC028)
文摘The issue of "missing baryons” is always an unsolved mystery in galaxy cosmology, and an important reason for the great uncertainty of the galaxies' formation and evolution. To find the "missing" baryons, extra high-resolution spectral observation and imaging of the soft X-ray band (<1 kev) is required. However, the existing observation methods cannot meet this requirement. Therefore, Tsinghua University leads and proposes the Chinese "Hot Universe Baryon Surveyor (HUBS)" satellite program.
基金The work was supported by the State Key Program of National Natural Science Foundation of China(Grant No.51437006)the Natural Science Foundation of Guangdong Province,China(2018A030313799).
文摘The accuracy of the simulation model has a pro-found impact on the optimal operation of the energy hubs(EHs).However,in many articles,the constant model of the efficiency of equipment is adopted to formulate the operation system,which would probably lead to a simplification of the simulation models.But,EHs are typically operated under off-design condition due to the fluctuations in cooling,heating,electricity requirement.More-over,even though the off-design characteristics are considered,few studies have suggested comparing the differences between those two models by considering the operation cost.In order to assess the effect of the off-design characteristics of EH on the optimal operation accuracy in this paper,two test cases are performed on the fixed and variable load conditions,respectively.In addition,the individual effect of off-design characteristics of each equipment on the optimal operation cost of the EH is also investigated through four optimization runs.It is worth mentioning that the optimal operation problem of the EH considering the off-design characteristics and on-off status of the equipment is a mixed integer non-linear programming problem(MINLP).By testing the design and off-design models on the two cases,the results of simulation demonstrate that the optimal operation cost for the off-design model is larger than that for the design model.Nonetheless,in the aspect of the authenticity of the system operation strategy,the off-design model performs better than the design model.Furthermore,a larger relative error of the system operation cost between the two models can be observed when the EH is operated under a relatively lower load condition,revealing that the influence of off-design characteristic on the optimal operation of EHs is too significant to be neglected.
文摘As the sunlight scattered on the sea of Guanyinshan in Xiamen,a space that bridges creativity and industry opened its door to the world.On December 15th,following a ribbon-cutting and unveiling ceremony,YKK Xiamen Guanyinshan Showroom,the brand's second and largest comprehensive showroom,was officially inaugurated.This showroom is more than a product display window,it is an"Inspiration Hub"integrating exhibition,co-creation,and service.Its launch signifies YKK's progression in the Chinese market from“building an efficient product proposal system”to a new stage of“deep collaborative co-creation.”
文摘The book Yangzhou:The Biography,written by Wei Minghua,is part of the Biographies of 100 Cities Along the Silk Road series.Rather than writing a general history account of this millennia-old city,this book aims to answer one central question:What is Yangzhou’s relationship with the Silk Road?This requires examining several aspects:the significant historical facts about Yangzhou in China’s foreign exchanges,why Yangzhou became a renowned hub for such interaction,and the stories of ordinary people in today’s Yangzhou.
文摘Over the past months,a southern Chinese harbor serving as a pivotal gateway to regions around the world has come into the spotlight after the launching of special customs operations on Hainan Island.LOCATED on the northwest tip of HainanIsland,the Yangpu Port is a scene ofbustling activity with towering gantrycranes busily loading containers on andoff large cargo vessels.Port orders here have surgedas a result of a slew of special customs policiesthat went into force last December.
