As the frontier of multidimensional transportation systems,urban air mobility(UAM)is receiving increasing attention from international organizations,governments,and stakeholders in industry and academia owing to its h...As the frontier of multidimensional transportation systems,urban air mobility(UAM)is receiving increasing attention from international organizations,governments,and stakeholders in industry and academia owing to its high efficiency,low carbon footprint,and operational flexibility.Vertical take-off and landing(VTOL)infrastructure is the core facility that enables UAM and is therefore essential for its safe,efficient,and large-scale commercial implementation.However,the key technologies for establishing low-altitude VTOL infrastructure are still nascent,and government,industry,and academia have yet to harmonize the corresponding construction,management,and operation standards.To address this gap,we herein systematically review the related progress and trends,comprehensively surveying the key technologies of establishing VTOL infrastructure serving unmanned aerial vehicles(UAVs)and electric VTOL aircraft from three complementary perspectives of ground-side,airspace-side,and communication,navigation,surveillance,and information services.In the light of future UAM operations characterized by diverse vehicle types and dense air traffic,we propose a conceptual design for a public multioperator VTOL site to provide constructive insights into the sustainable growth of the low-altitude economy.展开更多
This study addresses the maneuver evasion problem for medium-to-long-range air-to-air missiles by proposing a KAN-λ-PPO-based evasion algorithm.The algorithm introduces Kolmogorov-Arnold Networks(KAN)to mitigate the ...This study addresses the maneuver evasion problem for medium-to-long-range air-to-air missiles by proposing a KAN-λ-PPO-based evasion algorithm.The algorithm introduces Kolmogorov-Arnold Networks(KAN)to mitigate the catastrophic forgetting issue of Multilayer Perceptrons(MLP)in continual learning,while incorporatingλ-return to resolve sparse reward challenges in evasion scenarios.First,we model the evasion problem withλ-return and present the KAN-λ-PPO algorithm.Subsequently,we establish game environments based on the segmented ballistic characteristics of medium and long range missiles.During training,a joint reward function is designed by combining the miss distance and positional advantages to train the agent.Experiments evaluate four dimensions:(1)Performance comparison between KAN and MLP in value function approximation;(2)Catastrophic forgetting mitigation of KAN-λ-PPO in dual-task scenarios;(3)Continual learning capabilities across multiple evasion scenarios;(4)Quantitative analysis of agent strategy evolution and positional advantages.Empirical results demonstrate that KAN improves value function approximation accuracy by an order of magnitude compared with traditional MLP architectures.In continual learning tasks,the KAN-λ-PPO scheme exhibits significant knowledge retention,achieving performance improvements of 32.7% and 8.6%over MLP baselines in Task1→2 and Task2→3 transitions,respectively.Furthermore,the learned maneuver strategies outperform High-G Barrel Rolls(HGB)and S-maneuver tactics in securing positional advantages while accomplishing evasion.展开更多
Regional turbofan aircraft,which are used for medium-short distances,have a heightened risk of high-altitude Wake Vortices(VV)because of their tail-mounted engines and high horizontal tail configurations.For some regi...Regional turbofan aircraft,which are used for medium-short distances,have a heightened risk of high-altitude Wake Vortices(VV)because of their tail-mounted engines and high horizontal tail configurations.For some regional medium-short-range turbofan aircraft,this threat is higher than that for conventionally designed aircraft.To analyze the flight safety of turbofan aircraft during cruise,this study developed a model to assess wake vortex encounters based on evolutionary high-altitude wake flow patterns.First,the high-altitude wake vortex aircraft dissipation patterns were analyzed by combining Quick Access Recorder(QAR)flight data with the wake vortex evolution model.Then,to consider the uniqueness of the medium-short-range turbofan aircraft,the severity of the wake vortex encounters was simulated using an induced roll moment coefficient.The proposed high-altitude wake vortex encounter model was able to identify and assess the highaltitude wake vortex changes,the bearing moments at different altitudes,and the atmospheric pressure conditions.Using the latest wake separation standards from the International Civil Aviation Organization(ICAO),acceptable safety wake intervals for follower aircraft in different scenarios were determined for the safety assessment.The results indicate that compared to mid and low altitudes,the high-altitude aircraft wake vortex dissipation rate is faster,the ultimate bearing moment is weaker,and the roll moment coefficient is higher,which confirm that there is elevated wake vortex encounter severity for regional turbofan aircraft.As safety is found to deteriorate when encountering wake vortices at altitudes higher than 8 km,new medium-short-range turbofan regional aircraft require higher safety margins than the latest wake separation standards.展开更多
Passengers typically spend much time in commercial zones of terminals for retail,meals,and other services.Enhancing the study of thermal comfort in this local space is necessary.The climate in the Eastern China Region...Passengers typically spend much time in commercial zones of terminals for retail,meals,and other services.Enhancing the study of thermal comfort in this local space is necessary.The climate in the Eastern China Region is variable and complex,making it more challenging to maintain the indoor thermal environment.This study conducted field measurements in winter in a commercial zone of one terminal to assess the thermal environment.Numerical simulations and PMV-PPD analyses were performed using the Computational Fluid Dynamics(CFD)program The results showed that the overall humidity in the commercial zone was low.There were notable differences in the temperatures and velocities of supply air among different air vents on the commercial island.Based on these initial conditions obtained by measurements,the simulations showed that localized areas under the breathing plane are either too hot(24℃and above)or too cold(18℃and below).The dissatisfaction percentage of the population exceeds 27%.This paper proposed that through enhancements in the air vent dimensions,layout,and air supply conditions,the temperature can be maintained in the range of 20-24℃.Furthermore,the PMV could be controlled within the range of-0.5 to 0.5.PPD was below 10%,reflecting compliance with Class I heating standards.Overall,findings from this study provide a less costly modification for thermal comfort improvement in commercial zones,and serve as a reference for the design and operation of air-conditioning systems to ensure thermal comfort in airport terminals’commercial zones.展开更多
Air traffic flow management has been a major means for balancing air traffic demandand airport or airspace capacity to reduce congestion and flight delays.However,unpredictable fac-tors,such as weather and equipment m...Air traffic flow management has been a major means for balancing air traffic demandand airport or airspace capacity to reduce congestion and flight delays.However,unpredictable fac-tors,such as weather and equipment malfunctions,can cause dynamic changes in airport and sectorcapacity,resulting in significant alterations to optimized flight schedules and the calculated pre-departure slots.Therefore,taking into account capacity uncertainties is essential to create a moreresilient flight schedule.This paper addresses the flight pre-departure sequencing issue and intro-duces a capacity uncertainty model for optimizing flight schedule at the airport network level.The goal of the model is to reduce the total cost of flight delays while increasing the robustnessof the optimized schedule.A chance-constrained model is developed to address the capacity uncer-tainty of airports and sectors,and the significance of airports and sectors in the airport network isconsidered when setting the violation probability.The performance of the model is evaluated usingreal flight data by comparing them with the results of the deterministic model.The development ofthe model based on the characteristics of this special optimization mechanism can significantlyenhance its performance in addressing the pre-departure flight scheduling problem at the airportnetwork level.展开更多
It is common that airlines encounter a disruption of a flight schedule,which is mainly caused by resource shortages.In case of a disruption,subject to scarce resources,most of airlines lose flexibility of performing a...It is common that airlines encounter a disruption of a flight schedule,which is mainly caused by resource shortages.In case of a disruption,subject to scarce resources,most of airlines lose flexibility of performing aircraft recovery on the basis of business interest priorities and need to delay,swap,and cancel flights.This paper proposes an air-rail inter-modal strategy to incorporate a High-Speed Rail(HSR)transport mode into an aviation network for aircraft recovery.The air-rail inter-modal strategy focuses on occasionally operational integration of existing airside and HSR infrastructure capacities.It is different from air-rail cooperation implemented in Europe which emphasizes a long-term strategy.In addition to modelling the air-rail inter-modal strategy,an inter-modal time-band network is presented.Modelling is applied to a pure aviation network and the inter-modal network.Comparison results show that the inter-modal air-rail strategy helps to reduce the number of cancelled flights and the total disruption cost.展开更多
It is an important issue to assess traffic situation complexity for air traffic management.There is a lack of systematic review of the existing air traffic complexity assessment methods,and there is no consideration o...It is an important issue to assess traffic situation complexity for air traffic management.There is a lack of systematic review of the existing air traffic complexity assessment methods,and there is no consideration of the role of airspace and traffic coordination mechanism.A new 3-D airspace complexity measurement method is proposed based on route structure constraints to evaluate the air traffic complexity objectively.Firstly,the model of the impact on horizontal and vertical direction for“aircraft pair”is established based on the route guidance.After that,the coupled complexity model for 3-D airspace is given according to the modification on the model in terms of flight standardization.Finally,the global model of the airspace traffic complexity is established.It is proved by the experimental data from the actual operation in airspace that the proposed model can reflect the space coupling situation and complexity of aircraft.At the same time,it can precisely describe the actual operation of civil aviation in China.展开更多
Policy training against diverse opponents remains a challenge when using Multi-Agent Reinforcement Learning(MARL)in multiple Unmanned Combat Aerial Vehicle(UCAV)air combat scenarios.In view of this,this paper proposes...Policy training against diverse opponents remains a challenge when using Multi-Agent Reinforcement Learning(MARL)in multiple Unmanned Combat Aerial Vehicle(UCAV)air combat scenarios.In view of this,this paper proposes a novel Dominant and Non-dominant strategy sample selection(DoNot)mechanism and a Local Observation Enhanced Multi-Agent Proximal Policy Optimization(LOE-MAPPO)algorithm to train the multi-UCAV air combat policy and improve its generalization.Specifically,the LOE-MAPPO algorithm adopts a mixed state that concatenates the global state and individual agent's local observation to enable efficient value function learning in multi-UCAV air combat.The DoNot mechanism classifies opponents into dominant or non-dominant strategy opponents,and samples from easier to more challenging opponents to form an adaptive training curriculum.Empirical results demonstrate that the proposed LOE-MAPPO algorithm outperforms baseline MARL algorithms in multi-UCAV air combat scenarios,and the DoNot mechanism leads to stronger policy generalization when facing diverse opponents.The results pave the way for the fast generation of cooperative strategies for air combat agents with MARLalgorithms.展开更多
Heating,Ventilation,andAir Conditioning(HVAC)systems are critical formaintaining thermal comfort in office environments which also crucial for occupant well-being and productivity.This study investigates the impact of...Heating,Ventilation,andAir Conditioning(HVAC)systems are critical formaintaining thermal comfort in office environments which also crucial for occupant well-being and productivity.This study investigates the impact of integrating ceiling fans with higher air conditioning setpoints on thermal comfort and energy efficiency in office environments.Field measurements and questionnaire surveys were conducted to evaluate thermal comfort and energysaving potential under varying conditions.Results show that increasing the AC setpoint from 25○C to 27○C,combined with ceiling fan operation,reduced power consumption by 10%,achieving significant energy savings.Survey data confirmed that 85%of participants reported consistent thermal sensations across all conditions,with ceiling fans effectively compensating for higher setpoints through enhanced air circulation.CFDsimulations revealed that mediumspeed ceiling fan operation produced the most uniformairflowdistribution,with an average air velocity of 0.45 m/s,and minimized temperature variations,ensuring balanced thermal conditions.Temperature analysis showed a reduction in hotspots and cold zones,maintaining an average temperature deviation of less than±0.5○C.Predicted Mean Vote(PMV)evaluations at a 27○C setpoint indicated improved thermal comfort,with average PMV values around−0.3,corresponding to a“neutral”thermal sensation.These findings demonstrate the effectiveness of integrating ceiling fans with HVAC systems in achieving energy efficiency and occupant comfort,offering a sustainable approach to reducing AC energy consumption in office environments.展开更多
Food systems are deeply affected by climate change and air pollution,while being key contributors to these environmental challenges.Understanding the complex interactions among food systems,climate change,and air poll...Food systems are deeply affected by climate change and air pollution,while being key contributors to these environmental challenges.Understanding the complex interactions among food systems,climate change,and air pollution is crucial for mitigating climate change,improving air quality,and promoting the sustainable development of food systems.However,the literature lacks a comprehensive review of these interactions,particularly in the current phase of rapid development in the field.To address this gap,this study systematically reviews recent research on the impacts of climate change and air pollution on food systems,as well as the greenhouse gas and air pollutant emissions from agri-food systems and their contribution to global climate change and air pollution.In addition,this study summarizes various strategies for mitigation and adaptation,including adjustments in agricultural practices and food supply chains.Profound changes in food systems are urgently needed to enhance adaptability and reduce emissions.This review offers a critical overview of current research on the interactions among food systems,climate change,and air pollution and highlights future research directions to support the transition to sustainable food systems.展开更多
LDACs(liquid desiccant air-conditioners)with heat pump can perform cooling dehumidification or heating humidification,and have high energy-saving and sterilization performance.Therefore,they are installed in hospitals...LDACs(liquid desiccant air-conditioners)with heat pump can perform cooling dehumidification or heating humidification,and have high energy-saving and sterilization performance.Therefore,they are installed in hospitals,nursing homes,and food factories,where humidity control is required.However,LiCl(lithium chloride),a conventional humidity control liquid,is highly corrosive to metals,requiring the use of highly corrosion-resistant materials for the pipes and the heat exchangers.These lead to the problem that the manufacturing cost of the air conditioner increases.Therefore,we developed an inexpensive and compact LDAC by adopting a novel IL(ionic liquid)that does not corrode the metals commonly used in air conditioners.In this study,we evaluated the metal solubilities and sterilizing properties of the IL.Based on the physical properties of the IL,the humidity control module was improved for the purpose of downsizing and cost reduction of the unit.Moreover,we conducted a performance evaluation of the LDAC in the environmental test room under the condition in which temperature and humidity change rapidly in short period of time to simulate the condition of sudden showers of rain in summer.Test results showed that processed air was supplied at very stable level.展开更多
Plasma-assisted combustion technology has been a hot spot in aero-engines andscramjet-engines.The electron density is a key discharge parameter related to the active-particledensity.The latter has been considered play...Plasma-assisted combustion technology has been a hot spot in aero-engines andscramjet-engines.The electron density is a key discharge parameter related to the active-particledensity.The latter has been considered playing an important role in the above applications bythe kinetic effect.In this work,an atmospheric pressure air plasma collisional-radiative model con-sidering the excited states of atomic nitrogen and oxygen is built based on previous widely kineticinvestigations of molecules and radicals,as well as their excited states.The excited states,especiallythe atomic nitrogen and oxygen states were less investigated in previous works.The emission inten-sity distributions from the model have a good agreement with those measured in the glide arcplasma with two discharge modes,as well as the microwave plasma.Based on the kinetics of molec-ular and atomic emitting states,the line-ratio method is presented to determine the electron density.The N_(2)(337 nm)/O(844 nm)and N_(2)(337 nm)/NO(γ)line ratios are used for the glide arc plasma andmicrowave plasma torch,respectively.Besides,the kinetics of the excited states involved with twoline-ratios are also investigated in the two types of discharges.Combined with the atmospheric pres-sure actinometry method,the kinetic effect of the plasma-assisted combustion can be revealed quan-titatively in the future.展开更多
Airborne microplastics(MPs)are important pollutants that have been present in the environment for many years and are characterized by their universality,persistence,and potential toxicity.This study investigated the e...Airborne microplastics(MPs)are important pollutants that have been present in the environment for many years and are characterized by their universality,persistence,and potential toxicity.This study investigated the effects of terrestrial and marine transport of MPs in the atmosphere of a coastal city and compared the difference between daytime and nighttime.Laser direct infrared imaging(LDIR)and polarized light microscopy were used to characterize the physical and chemical properties of MPs,including number concentration,chemical types,shape,and size.Backward trajectories were used to distinguish the air masses from marine and terrestrial transport.Twenty chemical types were detected by LDIR,with rubber(16.7%)and phenol-formaldehyde resin(PFR;14.8%)being major components.Three main morphological types of MPs were identified,and fragments(78.1%)are the dominant type.MPs in the atmosphere were concentrated in the small particle size segment(20-50μm).The concentration of MPs in the air mass from marine transport was 14.7 items/m^(3)-lower than that from terrestrial transport(32.0 items/m^(3)).The number concentration of airborne MPs was negatively correlated with relative humidity.MPs from terrestrial transport were mainly rubber(20.2%),while those from marine transport were mainly PFR(18%).MPs in the marine transport air mass were more aged and had a lower number concentration than those in the terrestrial transport air mass.The number concentration of airborne MPs is higher during the day than at night.These findings could contribute to the development of targeted control measures and methods to reduce MP pollution.展开更多
Urban combat environments pose complex and variable challenges for UAV path planning due to multidimensional factors,such as static and dynamic obstructions as well as risks of exposure to enemy detection,which threat...Urban combat environments pose complex and variable challenges for UAV path planning due to multidimensional factors,such as static and dynamic obstructions as well as risks of exposure to enemy detection,which threaten flight safety and mission success.Traditional path planning methods typically depend solely on the distribution of static obstacles to generate collision-free paths,without accounting for constraints imposed by enemy detection and strike capabilities.Such a simplified approach can yield safety-compromising routes in highly complex urban airspace.To address these limitations,this study proposes a multi-parameter path planning method based on reachable airspace visibility graphs,which integrates UAV performance constraints,environmental limitations,and exposure risks.An innovative heuristic algorithm is developed to balance operational safety and efficiency by both exposure risks and path length.In the case study set in a typical mixed-use urban area,analysis of airspace visibility graphs reveals significant variations in exposure risk at different regions and altitudes due to building encroachments.Path optimization results indicate that the method can effectively generate covert and efficient flight paths by dynamically adjusting the exposure index,which represents the likelihood of enemy detection,and the path length,which corresponds to mission execution time.展开更多
Air pollution,a critical environmental issue,necessitates urgent action.It originates from both human activities,like industrial emissions and vehicle pollution,and natural events such as sandstorms,leading to increas...Air pollution,a critical environmental issue,necessitates urgent action.It originates from both human activities,like industrial emissions and vehicle pollution,and natural events such as sandstorms,leading to increased atmospheric pollutants such as sulfur dioxide(SO_(2)),nitrogen dioxide(NO_(2)),ammonia ion(NH_(4)^(+)),black carbon,ozone,and fine particulate matter(PM_(2.5)).Leveraging China's extensive air quality monitoring data,artificial intelligence(AI)was used in this study to enhance air quality prediction and management.The study aims to utilize the vast air monitoring data more effectively by developing advanced air quality assessment methods and AI models.An AI-based method presented in this study was applied to train extensive air quality data,enabling an intelligent air quality index(AQI)that swiftly and accurately reflects air quality status,to assess impacts on sensitive groups,and to predict future trends.This smart prediction and optimization(SPO)approach not only utilizes existing monitoring network data efficiently but also offers precise future air quality forecasts,providing valuable strategies for pollution prevention and air quality improvement.Data on various pollutants were collected from four regions in China between August 2021 and July 2022,using diverse modeling techniques and machine learning methodologies.The models achieved a high accuracy level of around 99%,indicating the significant portion of air quality that falls into the unhealthy category,especially impacting sensitive groups and reflecting the adverse atmospheric conditions in the studied regions.展开更多
Tuberculosis(TB)remained the first leading cause of death from a single infectious agent worldwide in 2023,resulting in nearly twice as many deaths as those caused by the human immunodeficiency virus/acquired immune d...Tuberculosis(TB)remained the first leading cause of death from a single infectious agent worldwide in 2023,resulting in nearly twice as many deaths as those caused by the human immunodeficiency virus/acquired immune deficiency syndrome.An estimated 10.8 million TB cases were reported globally in 2023,with approximately 1.25 million associated deaths.In China,which ranks third in the global TB burden,there were approximately 741,000 new cases and 25,000 deaths in 2023^([1]).TB poses a significant threat to human health worldwide.展开更多
This paper presents an air quality simulation model that incorporates shipping activities and weather conditions,with a case study of Hainan Island to examine the impact of ship emissions on air quality.The findings r...This paper presents an air quality simulation model that incorporates shipping activities and weather conditions,with a case study of Hainan Island to examine the impact of ship emissions on air quality.The findings reveal that the density of automatic identification system(AIS)signals is particularly high in the southern coastal regions.The results showed that the annual ship emissions recorded the highest density of 896.7 tons/0.01°,49.8 tons/0.01°,1139.7 tons/0.01°,and 122,000 tons/0.01°for sulfur oxides(SO_(x)),particulate matter(PM),nitrogen oxides(NOx),and carbon dioxide(CO_(2)),respectively.Furthermore,the partial distributions of these emissions were not significantly affected by the seasons.Ships within twelve nautical miles of Hainan coastlines emit approximately 2817.7 tons of SO_(x),14,686.4 tons of NO_(x),630.4 tons of PM_(2.5),and 416.9 tons of hydrocarbons(HC)annually.These emissions are primarily concentrated in the sea areas surrounding the ports of Haikou,Yangpu,Basuo,and Sanya.Ships manufactured between 2000 and 2010 have contributed significantly to air pollution,with SO_(x) and HC emissions accounting for approximately 51%and 56% of total emissions,respectively.However,for shipsmanufactured after 2016,these proportions have dropped to approximately 10%.In terms of air pollutants fromship emissions in Hainan Island,the spatial distribution of their contributions is significantly uneven.The impact of PM2.5 differs significantly depending on the season,with the concentrations being substantially higher during Spring.However,the proportions of O3 and other pollutants do not vary significantly,except during Spring.展开更多
基金supported by the National Natural Science Foundation of China(No.U2333214).
文摘As the frontier of multidimensional transportation systems,urban air mobility(UAM)is receiving increasing attention from international organizations,governments,and stakeholders in industry and academia owing to its high efficiency,low carbon footprint,and operational flexibility.Vertical take-off and landing(VTOL)infrastructure is the core facility that enables UAM and is therefore essential for its safe,efficient,and large-scale commercial implementation.However,the key technologies for establishing low-altitude VTOL infrastructure are still nascent,and government,industry,and academia have yet to harmonize the corresponding construction,management,and operation standards.To address this gap,we herein systematically review the related progress and trends,comprehensively surveying the key technologies of establishing VTOL infrastructure serving unmanned aerial vehicles(UAVs)and electric VTOL aircraft from three complementary perspectives of ground-side,airspace-side,and communication,navigation,surveillance,and information services.In the light of future UAM operations characterized by diverse vehicle types and dense air traffic,we propose a conceptual design for a public multioperator VTOL site to provide constructive insights into the sustainable growth of the low-altitude economy.
文摘This study addresses the maneuver evasion problem for medium-to-long-range air-to-air missiles by proposing a KAN-λ-PPO-based evasion algorithm.The algorithm introduces Kolmogorov-Arnold Networks(KAN)to mitigate the catastrophic forgetting issue of Multilayer Perceptrons(MLP)in continual learning,while incorporatingλ-return to resolve sparse reward challenges in evasion scenarios.First,we model the evasion problem withλ-return and present the KAN-λ-PPO algorithm.Subsequently,we establish game environments based on the segmented ballistic characteristics of medium and long range missiles.During training,a joint reward function is designed by combining the miss distance and positional advantages to train the agent.Experiments evaluate four dimensions:(1)Performance comparison between KAN and MLP in value function approximation;(2)Catastrophic forgetting mitigation of KAN-λ-PPO in dual-task scenarios;(3)Continual learning capabilities across multiple evasion scenarios;(4)Quantitative analysis of agent strategy evolution and positional advantages.Empirical results demonstrate that KAN improves value function approximation accuracy by an order of magnitude compared with traditional MLP architectures.In continual learning tasks,the KAN-λ-PPO scheme exhibits significant knowledge retention,achieving performance improvements of 32.7% and 8.6%over MLP baselines in Task1→2 and Task2→3 transitions,respectively.Furthermore,the learned maneuver strategies outperform High-G Barrel Rolls(HGB)and S-maneuver tactics in securing positional advantages while accomplishing evasion.
基金supported by the National Natural Science Foundation of China(Nos.U2333209,U1733203)the National Key R&D Program of China(No.2021YFF0603904)the Civil Aviation Administration of China(No.AQ20200019)。
文摘Regional turbofan aircraft,which are used for medium-short distances,have a heightened risk of high-altitude Wake Vortices(VV)because of their tail-mounted engines and high horizontal tail configurations.For some regional medium-short-range turbofan aircraft,this threat is higher than that for conventionally designed aircraft.To analyze the flight safety of turbofan aircraft during cruise,this study developed a model to assess wake vortex encounters based on evolutionary high-altitude wake flow patterns.First,the high-altitude wake vortex aircraft dissipation patterns were analyzed by combining Quick Access Recorder(QAR)flight data with the wake vortex evolution model.Then,to consider the uniqueness of the medium-short-range turbofan aircraft,the severity of the wake vortex encounters was simulated using an induced roll moment coefficient.The proposed high-altitude wake vortex encounter model was able to identify and assess the highaltitude wake vortex changes,the bearing moments at different altitudes,and the atmospheric pressure conditions.Using the latest wake separation standards from the International Civil Aviation Organization(ICAO),acceptable safety wake intervals for follower aircraft in different scenarios were determined for the safety assessment.The results indicate that compared to mid and low altitudes,the high-altitude aircraft wake vortex dissipation rate is faster,the ultimate bearing moment is weaker,and the roll moment coefficient is higher,which confirm that there is elevated wake vortex encounter severity for regional turbofan aircraft.As safety is found to deteriorate when encountering wake vortices at altitudes higher than 8 km,new medium-short-range turbofan regional aircraft require higher safety margins than the latest wake separation standards.
基金supported by the National Natural Science Foundation of China(52478098)the Natural Science Foundation of Shanghai Municipality(21ZR1444800)the Shanghai Sailing Program(21YF1430700).
文摘Passengers typically spend much time in commercial zones of terminals for retail,meals,and other services.Enhancing the study of thermal comfort in this local space is necessary.The climate in the Eastern China Region is variable and complex,making it more challenging to maintain the indoor thermal environment.This study conducted field measurements in winter in a commercial zone of one terminal to assess the thermal environment.Numerical simulations and PMV-PPD analyses were performed using the Computational Fluid Dynamics(CFD)program The results showed that the overall humidity in the commercial zone was low.There were notable differences in the temperatures and velocities of supply air among different air vents on the commercial island.Based on these initial conditions obtained by measurements,the simulations showed that localized areas under the breathing plane are either too hot(24℃and above)or too cold(18℃and below).The dissatisfaction percentage of the population exceeds 27%.This paper proposed that through enhancements in the air vent dimensions,layout,and air supply conditions,the temperature can be maintained in the range of 20-24℃.Furthermore,the PMV could be controlled within the range of-0.5 to 0.5.PPD was below 10%,reflecting compliance with Class I heating standards.Overall,findings from this study provide a less costly modification for thermal comfort improvement in commercial zones,and serve as a reference for the design and operation of air-conditioning systems to ensure thermal comfort in airport terminals’commercial zones.
基金supported by the National Natural Science Foundation of China(Nos.U2033203,U1833126,61773203,61304190)。
文摘Air traffic flow management has been a major means for balancing air traffic demandand airport or airspace capacity to reduce congestion and flight delays.However,unpredictable fac-tors,such as weather and equipment malfunctions,can cause dynamic changes in airport and sectorcapacity,resulting in significant alterations to optimized flight schedules and the calculated pre-departure slots.Therefore,taking into account capacity uncertainties is essential to create a moreresilient flight schedule.This paper addresses the flight pre-departure sequencing issue and intro-duces a capacity uncertainty model for optimizing flight schedule at the airport network level.The goal of the model is to reduce the total cost of flight delays while increasing the robustnessof the optimized schedule.A chance-constrained model is developed to address the capacity uncer-tainty of airports and sectors,and the significance of airports and sectors in the airport network isconsidered when setting the violation probability.The performance of the model is evaluated usingreal flight data by comparing them with the results of the deterministic model.The development ofthe model based on the characteristics of this special optimization mechanism can significantlyenhance its performance in addressing the pre-departure flight scheduling problem at the airportnetwork level.
基金co-supported by the Tianjin Natural Science Foundation, China (No. 18JCQNJC04300)the National Natural Science Foundation of China (No. 71801215)the Foundation for University Key Teacher by the Ministry of Education of China (Nos. 3122018C033, 3122015L010)
文摘It is common that airlines encounter a disruption of a flight schedule,which is mainly caused by resource shortages.In case of a disruption,subject to scarce resources,most of airlines lose flexibility of performing aircraft recovery on the basis of business interest priorities and need to delay,swap,and cancel flights.This paper proposes an air-rail inter-modal strategy to incorporate a High-Speed Rail(HSR)transport mode into an aviation network for aircraft recovery.The air-rail inter-modal strategy focuses on occasionally operational integration of existing airside and HSR infrastructure capacities.It is different from air-rail cooperation implemented in Europe which emphasizes a long-term strategy.In addition to modelling the air-rail inter-modal strategy,an inter-modal time-band network is presented.Modelling is applied to a pure aviation network and the inter-modal network.Comparison results show that the inter-modal air-rail strategy helps to reduce the number of cancelled flights and the total disruption cost.
基金supported by the National Natural Science Foundation of China (No. 61573181)the Civil Aviation Joint Fund Key Projects of National Natural Science Foundation of China (No.U1333202)
文摘It is an important issue to assess traffic situation complexity for air traffic management.There is a lack of systematic review of the existing air traffic complexity assessment methods,and there is no consideration of the role of airspace and traffic coordination mechanism.A new 3-D airspace complexity measurement method is proposed based on route structure constraints to evaluate the air traffic complexity objectively.Firstly,the model of the impact on horizontal and vertical direction for“aircraft pair”is established based on the route guidance.After that,the coupled complexity model for 3-D airspace is given according to the modification on the model in terms of flight standardization.Finally,the global model of the airspace traffic complexity is established.It is proved by the experimental data from the actual operation in airspace that the proposed model can reflect the space coupling situation and complexity of aircraft.At the same time,it can precisely describe the actual operation of civil aviation in China.
文摘Policy training against diverse opponents remains a challenge when using Multi-Agent Reinforcement Learning(MARL)in multiple Unmanned Combat Aerial Vehicle(UCAV)air combat scenarios.In view of this,this paper proposes a novel Dominant and Non-dominant strategy sample selection(DoNot)mechanism and a Local Observation Enhanced Multi-Agent Proximal Policy Optimization(LOE-MAPPO)algorithm to train the multi-UCAV air combat policy and improve its generalization.Specifically,the LOE-MAPPO algorithm adopts a mixed state that concatenates the global state and individual agent's local observation to enable efficient value function learning in multi-UCAV air combat.The DoNot mechanism classifies opponents into dominant or non-dominant strategy opponents,and samples from easier to more challenging opponents to form an adaptive training curriculum.Empirical results demonstrate that the proposed LOE-MAPPO algorithm outperforms baseline MARL algorithms in multi-UCAV air combat scenarios,and the DoNot mechanism leads to stronger policy generalization when facing diverse opponents.The results pave the way for the fast generation of cooperative strategies for air combat agents with MARLalgorithms.
基金support by the National Science and Technology Council under Grant No.NSTC 112-2221-E-167-017-MY3.
文摘Heating,Ventilation,andAir Conditioning(HVAC)systems are critical formaintaining thermal comfort in office environments which also crucial for occupant well-being and productivity.This study investigates the impact of integrating ceiling fans with higher air conditioning setpoints on thermal comfort and energy efficiency in office environments.Field measurements and questionnaire surveys were conducted to evaluate thermal comfort and energysaving potential under varying conditions.Results show that increasing the AC setpoint from 25○C to 27○C,combined with ceiling fan operation,reduced power consumption by 10%,achieving significant energy savings.Survey data confirmed that 85%of participants reported consistent thermal sensations across all conditions,with ceiling fans effectively compensating for higher setpoints through enhanced air circulation.CFDsimulations revealed that mediumspeed ceiling fan operation produced the most uniformairflowdistribution,with an average air velocity of 0.45 m/s,and minimized temperature variations,ensuring balanced thermal conditions.Temperature analysis showed a reduction in hotspots and cold zones,maintaining an average temperature deviation of less than±0.5○C.Predicted Mean Vote(PMV)evaluations at a 27○C setpoint indicated improved thermal comfort,with average PMV values around−0.3,corresponding to a“neutral”thermal sensation.These findings demonstrate the effectiveness of integrating ceiling fans with HVAC systems in achieving energy efficiency and occupant comfort,offering a sustainable approach to reducing AC energy consumption in office environments.
基金supported by the National Natural Science Foundation of China(42277087,42130708,42471021,42277482,and 42361144876)the Natural Science Foundation of Guangdong Province(2024A1515012550)+3 种基金the Hainan Institute of National Park grant(KY-23ZK01)the Tsinghua Shenzhen International Graduate School Cross-disciplinary Research and Innovation Fund Research Plan(JC2022011)the Shenzhen Science and Technology Program(JCYJ20240813112106009 and ZDSYS20220606100806014)the Scientific Research Start-up Funds(QD2021030C)from Tsinghua Shenzhen International Graduate School。
文摘Food systems are deeply affected by climate change and air pollution,while being key contributors to these environmental challenges.Understanding the complex interactions among food systems,climate change,and air pollution is crucial for mitigating climate change,improving air quality,and promoting the sustainable development of food systems.However,the literature lacks a comprehensive review of these interactions,particularly in the current phase of rapid development in the field.To address this gap,this study systematically reviews recent research on the impacts of climate change and air pollution on food systems,as well as the greenhouse gas and air pollutant emissions from agri-food systems and their contribution to global climate change and air pollution.In addition,this study summarizes various strategies for mitigation and adaptation,including adjustments in agricultural practices and food supply chains.Profound changes in food systems are urgently needed to enhance adaptability and reduce emissions.This review offers a critical overview of current research on the interactions among food systems,climate change,and air pollution and highlights future research directions to support the transition to sustainable food systems.
文摘LDACs(liquid desiccant air-conditioners)with heat pump can perform cooling dehumidification or heating humidification,and have high energy-saving and sterilization performance.Therefore,they are installed in hospitals,nursing homes,and food factories,where humidity control is required.However,LiCl(lithium chloride),a conventional humidity control liquid,is highly corrosive to metals,requiring the use of highly corrosion-resistant materials for the pipes and the heat exchangers.These lead to the problem that the manufacturing cost of the air conditioner increases.Therefore,we developed an inexpensive and compact LDAC by adopting a novel IL(ionic liquid)that does not corrode the metals commonly used in air conditioners.In this study,we evaluated the metal solubilities and sterilizing properties of the IL.Based on the physical properties of the IL,the humidity control module was improved for the purpose of downsizing and cost reduction of the unit.Moreover,we conducted a performance evaluation of the LDAC in the environmental test room under the condition in which temperature and humidity change rapidly in short period of time to simulate the condition of sudden showers of rain in summer.Test results showed that processed air was supplied at very stable level.
基金supported by the National Key Lab of Aerospace Power System and Plasma Technology Foundation,China(No.6142202210101)the National Science and Technology Major Project,China(No.J2019-Ⅲ-0013-0056)+2 种基金the National Natural Science Foundation of China(No.52025064)supported by the National Natural Science Foundation of China(Nos.52350072 and 52277167)the Beijing Natural Science Foundation,China(No.1242030)。
文摘Plasma-assisted combustion technology has been a hot spot in aero-engines andscramjet-engines.The electron density is a key discharge parameter related to the active-particledensity.The latter has been considered playing an important role in the above applications bythe kinetic effect.In this work,an atmospheric pressure air plasma collisional-radiative model con-sidering the excited states of atomic nitrogen and oxygen is built based on previous widely kineticinvestigations of molecules and radicals,as well as their excited states.The excited states,especiallythe atomic nitrogen and oxygen states were less investigated in previous works.The emission inten-sity distributions from the model have a good agreement with those measured in the glide arcplasma with two discharge modes,as well as the microwave plasma.Based on the kinetics of molec-ular and atomic emitting states,the line-ratio method is presented to determine the electron density.The N_(2)(337 nm)/O(844 nm)and N_(2)(337 nm)/NO(γ)line ratios are used for the glide arc plasma andmicrowave plasma torch,respectively.Besides,the kinetics of the excited states involved with twoline-ratios are also investigated in the two types of discharges.Combined with the atmospheric pres-sure actinometry method,the kinetic effect of the plasma-assisted combustion can be revealed quan-titatively in the future.
基金supported by the National Natural Science Foundation of China (No.42075107)the Fundamental Research Funds for the Central Universities (No.2022YJSDC05)+1 种基金the China Scholarship Council (No.202206430058)the Yueqi Scholar Fund of China University of Mining and Technology (Beijing).
文摘Airborne microplastics(MPs)are important pollutants that have been present in the environment for many years and are characterized by their universality,persistence,and potential toxicity.This study investigated the effects of terrestrial and marine transport of MPs in the atmosphere of a coastal city and compared the difference between daytime and nighttime.Laser direct infrared imaging(LDIR)and polarized light microscopy were used to characterize the physical and chemical properties of MPs,including number concentration,chemical types,shape,and size.Backward trajectories were used to distinguish the air masses from marine and terrestrial transport.Twenty chemical types were detected by LDIR,with rubber(16.7%)and phenol-formaldehyde resin(PFR;14.8%)being major components.Three main morphological types of MPs were identified,and fragments(78.1%)are the dominant type.MPs in the atmosphere were concentrated in the small particle size segment(20-50μm).The concentration of MPs in the air mass from marine transport was 14.7 items/m^(3)-lower than that from terrestrial transport(32.0 items/m^(3)).The number concentration of airborne MPs was negatively correlated with relative humidity.MPs from terrestrial transport were mainly rubber(20.2%),while those from marine transport were mainly PFR(18%).MPs in the marine transport air mass were more aged and had a lower number concentration than those in the terrestrial transport air mass.The number concentration of airborne MPs is higher during the day than at night.These findings could contribute to the development of targeted control measures and methods to reduce MP pollution.
基金supported by the Ministry of Industry and Information Technology(No.23100002022102001)。
文摘Urban combat environments pose complex and variable challenges for UAV path planning due to multidimensional factors,such as static and dynamic obstructions as well as risks of exposure to enemy detection,which threaten flight safety and mission success.Traditional path planning methods typically depend solely on the distribution of static obstacles to generate collision-free paths,without accounting for constraints imposed by enemy detection and strike capabilities.Such a simplified approach can yield safety-compromising routes in highly complex urban airspace.To address these limitations,this study proposes a multi-parameter path planning method based on reachable airspace visibility graphs,which integrates UAV performance constraints,environmental limitations,and exposure risks.An innovative heuristic algorithm is developed to balance operational safety and efficiency by both exposure risks and path length.In the case study set in a typical mixed-use urban area,analysis of airspace visibility graphs reveals significant variations in exposure risk at different regions and altitudes due to building encroachments.Path optimization results indicate that the method can effectively generate covert and efficient flight paths by dynamically adjusting the exposure index,which represents the likelihood of enemy detection,and the path length,which corresponds to mission execution time.
基金supported by the National Key R&D Program of China(No.2023YFC3707201)the National Natural Science Foundation of China(No.52320105003)+2 种基金the Informatization Plan of Chinese Academy of Sciences(No.CASWX2023PY-0103)CAS-ANSO Co-funding Research Project(No.CAS-ANSO-CF-2024)the Fundamental Research Funds for the Central Universities(No.E3ET1803)。
文摘Air pollution,a critical environmental issue,necessitates urgent action.It originates from both human activities,like industrial emissions and vehicle pollution,and natural events such as sandstorms,leading to increased atmospheric pollutants such as sulfur dioxide(SO_(2)),nitrogen dioxide(NO_(2)),ammonia ion(NH_(4)^(+)),black carbon,ozone,and fine particulate matter(PM_(2.5)).Leveraging China's extensive air quality monitoring data,artificial intelligence(AI)was used in this study to enhance air quality prediction and management.The study aims to utilize the vast air monitoring data more effectively by developing advanced air quality assessment methods and AI models.An AI-based method presented in this study was applied to train extensive air quality data,enabling an intelligent air quality index(AQI)that swiftly and accurately reflects air quality status,to assess impacts on sensitive groups,and to predict future trends.This smart prediction and optimization(SPO)approach not only utilizes existing monitoring network data efficiently but also offers precise future air quality forecasts,providing valuable strategies for pollution prevention and air quality improvement.Data on various pollutants were collected from four regions in China between August 2021 and July 2022,using diverse modeling techniques and machine learning methodologies.The models achieved a high accuracy level of around 99%,indicating the significant portion of air quality that falls into the unhealthy category,especially impacting sensitive groups and reflecting the adverse atmospheric conditions in the studied regions.
文摘Tuberculosis(TB)remained the first leading cause of death from a single infectious agent worldwide in 2023,resulting in nearly twice as many deaths as those caused by the human immunodeficiency virus/acquired immune deficiency syndrome.An estimated 10.8 million TB cases were reported globally in 2023,with approximately 1.25 million associated deaths.In China,which ranks third in the global TB burden,there were approximately 741,000 new cases and 25,000 deaths in 2023^([1]).TB poses a significant threat to human health worldwide.
基金supported by the National Key Research and Development Program of China(No.2022YFC3704200)the National Natural Science Foundation of China(No.52306128)+5 种基金the Major Program of Science and Technology of Hainan Province,China(No.ZDKJ202007)the Innovation Platform for Academicians of Hainan Province(No.YSPTZX202205)the Youth Innovation Foundation of Hainan Research Academy of Environmental Sciences,China(No.QNCX2021002)the Central Guiding Local Science and Technology Development Fund Projects(No.236Z4001G)the Natural Science Basic Research Program of Shaanxi(No.2023-JC-QN-0517)the support from Energy Foundation China.
文摘This paper presents an air quality simulation model that incorporates shipping activities and weather conditions,with a case study of Hainan Island to examine the impact of ship emissions on air quality.The findings reveal that the density of automatic identification system(AIS)signals is particularly high in the southern coastal regions.The results showed that the annual ship emissions recorded the highest density of 896.7 tons/0.01°,49.8 tons/0.01°,1139.7 tons/0.01°,and 122,000 tons/0.01°for sulfur oxides(SO_(x)),particulate matter(PM),nitrogen oxides(NOx),and carbon dioxide(CO_(2)),respectively.Furthermore,the partial distributions of these emissions were not significantly affected by the seasons.Ships within twelve nautical miles of Hainan coastlines emit approximately 2817.7 tons of SO_(x),14,686.4 tons of NO_(x),630.4 tons of PM_(2.5),and 416.9 tons of hydrocarbons(HC)annually.These emissions are primarily concentrated in the sea areas surrounding the ports of Haikou,Yangpu,Basuo,and Sanya.Ships manufactured between 2000 and 2010 have contributed significantly to air pollution,with SO_(x) and HC emissions accounting for approximately 51%and 56% of total emissions,respectively.However,for shipsmanufactured after 2016,these proportions have dropped to approximately 10%.In terms of air pollutants fromship emissions in Hainan Island,the spatial distribution of their contributions is significantly uneven.The impact of PM2.5 differs significantly depending on the season,with the concentrations being substantially higher during Spring.However,the proportions of O3 and other pollutants do not vary significantly,except during Spring.
