With the explosive growth of the World-Wide Web,it is becoming increasingly difficult for users to collect and analyze Web pages that are relevant to a particular topic. In this paper,Topic-Driven Web Information Gath...With the explosive growth of the World-Wide Web,it is becoming increasingly difficult for users to collect and analyze Web pages that are relevant to a particular topic. In this paper,Topic-Driven Web Information Gathering system is presented,which can efficiently collects Web pages for a topic in relatively limited hardware and network resources ,and keeps the pages more up-to-date.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 challenges of energy shortage and environmen-tal protection motivate people to take various measures to use energy wisely,and integrated energy systems are such a measure to tackle this challenge.In this paper,an ...The challenges of energy shortage and environmen-tal protection motivate people to take various measures to use energy wisely,and integrated energy systems are such a measure to tackle this challenge.In this paper,an optimal expansion planning model for an integrated energy system consisting of power grid,gas network and multiple energy hubs is proposed,where the planning objective is to minimize operational fuel cost and capital investment cost covering carbon capture equipment and energy hubs among others.To demonstrate the advantage of the proposed planning model,six case studies are investigated,and 13.47%annual cost savings can be achieved compared with the baseline planning scenario,which does not consider bidirectional energy exchange and integrated demand response program.Index Terms-Bidirectional energy exchange,energy hubs,integrated energy system,integrated demand response.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
An optimization model for the regional comprehensive freight hub location problem was built up from the viewpoint of the minimum cost of freight system. The construction method for regional comprehensive intermodal fr...An optimization model for the regional comprehensive freight hub location problem was built up from the viewpoint of the minimum cost of freight system. The construction method for regional comprehensive intermodal freight network was put forward, and three constraints of the reasonable and feasible path of the intermodal transport, i. e. , reasonable sequence, reasonable freight distance, and reasonable conversion times, were proposed according to the general concepts of the intermodal freight. Then the method for solving the model was given based on the super network and genetic algorithm. Finally, the model and the solution were verified by case study.展开更多
Gas market in Europe is experiencing a radical change for different reasons, partially determined and accelerated by economic downturn of the last period. In the past few years, many European countries adopted energy ...Gas market in Europe is experiencing a radical change for different reasons, partially determined and accelerated by economic downturn of the last period. In the past few years, many European countries adopted energy policies largely based on the utilization of natural gas. In fact, a sharp increase of the demand was observed and, at the same time, a lot of infrastructures were developed to assure the necessary supply. In the last few years, due to the economic downturn, natural gas demand decreased, causing a consistent oversupply on the market, which altered the consolidated dynamics of the sector. Under- standing the changes currently under development in the European gas market is of paramount importance in order to design future strategies for the sector; in particular, it is necessary to understand if the present situation will cause a reshaping of the sector.展开更多
Green infrastructure (GI) is ecological supporting system for the sustainable development of urban construction,and plays an important role in promoting the urban ecological economic and social development.In this pap...Green infrastructure (GI) is ecological supporting system for the sustainable development of urban construction,and plays an important role in promoting the urban ecological economic and social development.In this paper,Suzhou Dushu Lake Higher Education District is taken as an example,and landscape ecological resources in Dushu Lake Higher Education District are analyzed on the basis of field investigation.Combining with the relevant theory of green infrastructure,structure of GI in Suzhou Dushu Lake Higher Education District is analyzed and evaluated from hubs,links and sites,and the corresponding optimization strategy is put forward.展开更多
Carbon capture and storage(CCS)technology is an imperative,strategic,and constitutive method to considerably reduce anthropogenic CO_(2)emissions and alleviate climate change issues.The ocean is the largest active car...Carbon capture and storage(CCS)technology is an imperative,strategic,and constitutive method to considerably reduce anthropogenic CO_(2)emissions and alleviate climate change issues.The ocean is the largest active carbon bank and an essential energy source on the Earth's surface.Compared to oceanic nature-based carbon dioxide removal(CDR),carbon capture from point sources with ocean storage is more appropriate for solving short-term climate change problems.This review focuses on the recent state-of-the-art developments in offshore carbon storage.It first discusses the current status and development prospects of CCS,associated with the chailenges and uncertainties of oceanic nature-based CDR.The second section outlines the mechanisms,sites,advantages,and ecologic hazards of direct offshore CO_(2)injection.The third section emphasizes the mechanisms,schemes,influencing factors,and recovery efficiency of ocean-based CO-CH_(4)replacement and CO_(2)-enhanced oil recovery are reviewed.In addition,this review discusses the economic aspects of offshore CCS and the preponderance of offshore CCs hubs.Finally,the upsides,limitations,and prospects for further investigation of offshore CO_(2)storage are presented.展开更多
文摘With the explosive growth of the World-Wide Web,it is becoming increasingly difficult for users to collect and analyze Web pages that are relevant to a particular topic. In this paper,Topic-Driven Web Information Gathering system is presented,which can efficiently collects Web pages for a topic in relatively limited hardware and network resources ,and keeps the pages more up-to-date.
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(No.61873225)and(No.52130702).
文摘The challenges of energy shortage and environmen-tal protection motivate people to take various measures to use energy wisely,and integrated energy systems are such a measure to tackle this challenge.In this paper,an optimal expansion planning model for an integrated energy system consisting of power grid,gas network and multiple energy hubs is proposed,where the planning objective is to minimize operational fuel cost and capital investment cost covering carbon capture equipment and energy hubs among others.To demonstrate the advantage of the proposed planning model,six case studies are investigated,and 13.47%annual cost savings can be achieved compared with the baseline planning scenario,which does not consider bidirectional energy exchange and integrated demand response program.Index Terms-Bidirectional energy exchange,energy hubs,integrated energy system,integrated demand response.
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 National Natural Science Foundation of China (No.50708020)Provincial Natural Science Fund of Jiangsu (BK2007566)
文摘An optimization model for the regional comprehensive freight hub location problem was built up from the viewpoint of the minimum cost of freight system. The construction method for regional comprehensive intermodal freight network was put forward, and three constraints of the reasonable and feasible path of the intermodal transport, i. e. , reasonable sequence, reasonable freight distance, and reasonable conversion times, were proposed according to the general concepts of the intermodal freight. Then the method for solving the model was given based on the super network and genetic algorithm. Finally, the model and the solution were verified by case study.
文摘Gas market in Europe is experiencing a radical change for different reasons, partially determined and accelerated by economic downturn of the last period. In the past few years, many European countries adopted energy policies largely based on the utilization of natural gas. In fact, a sharp increase of the demand was observed and, at the same time, a lot of infrastructures were developed to assure the necessary supply. In the last few years, due to the economic downturn, natural gas demand decreased, causing a consistent oversupply on the market, which altered the consolidated dynamics of the sector. Under- standing the changes currently under development in the European gas market is of paramount importance in order to design future strategies for the sector; in particular, it is necessary to understand if the present situation will cause a reshaping of the sector.
文摘Green infrastructure (GI) is ecological supporting system for the sustainable development of urban construction,and plays an important role in promoting the urban ecological economic and social development.In this paper,Suzhou Dushu Lake Higher Education District is taken as an example,and landscape ecological resources in Dushu Lake Higher Education District are analyzed on the basis of field investigation.Combining with the relevant theory of green infrastructure,structure of GI in Suzhou Dushu Lake Higher Education District is analyzed and evaluated from hubs,links and sites,and the corresponding optimization strategy is put forward.
基金the financial support from the Science and Technology Commission of Shanghai Municipality(No.21DZ1206200)the Shanghai Agriculture Science and Technology Program(No.2022-02-08-00-12-F01176)the financial support from the National Natural Science Foundation of China(Nos.52006135 and 72140008),respectively.
文摘Carbon capture and storage(CCS)technology is an imperative,strategic,and constitutive method to considerably reduce anthropogenic CO_(2)emissions and alleviate climate change issues.The ocean is the largest active carbon bank and an essential energy source on the Earth's surface.Compared to oceanic nature-based carbon dioxide removal(CDR),carbon capture from point sources with ocean storage is more appropriate for solving short-term climate change problems.This review focuses on the recent state-of-the-art developments in offshore carbon storage.It first discusses the current status and development prospects of CCS,associated with the chailenges and uncertainties of oceanic nature-based CDR.The second section outlines the mechanisms,sites,advantages,and ecologic hazards of direct offshore CO_(2)injection.The third section emphasizes the mechanisms,schemes,influencing factors,and recovery efficiency of ocean-based CO-CH_(4)replacement and CO_(2)-enhanced oil recovery are reviewed.In addition,this review discusses the economic aspects of offshore CCS and the preponderance of offshore CCs hubs.Finally,the upsides,limitations,and prospects for further investigation of offshore CO_(2)storage are presented.
