With the rapid development of aviation industry and its increasing impact on the global climate change,the contributions of carbon emissions frominternational flights are attracting more and more attention worldwide.T...With the rapid development of aviation industry and its increasing impact on the global climate change,the contributions of carbon emissions frominternational flights are attracting more and more attention worldwide.This study,taking Macao as the aviation hub,established the cross-border aviation carbon emission evaluation model to explore dynamic carbon emissions and net-zero path of international flights.The aviation hubmainly covers 58 routes and five types of civil aircraft from 12 countries or regions during 2000-2022.The results show that the aviation transportation in Macao emitted about 1.44 million tons CO_(2)eq in 2019,which is high 3.6 times that of 2000.The COVID-19 has led to a rapid decline in aviation carbon emissions in a short period of time,carbon emissions in 2020 decreased by 80%compared to 2019.In terms of cumulative carbon emissions from 2000 to 2019,the A321 and A320 Airbus contribute to 80%of carbon emissions.And the Chinese mainland(37%)and Taiwan(29%)are the main sources of emissions.In 2000-2019,the proportion of carbon emissions from China(including Taiwan and Hong Kong)decrease from 91%to 53%,while the contribution from Southeast Asia(from 5% to 26%),Japan and South Korea(from 2% to 19%)keep the growth trends.In the optimal scenario(B3C3),net zero emissions of cross-border aviation in Macao can be not achieved,and there is still only by removing 0.3 million tons CO_(2)eq.Emission reduction technology and new energy usage are priorities for the aviation emission reduction.展开更多
In order to alleviate the flight congestion in terminal areas(TMAs),it is of great significance to develop an effective method.An arrival sequencing model based on the serial point merge systems(PMSs)is constructed to...In order to alleviate the flight congestion in terminal areas(TMAs),it is of great significance to develop an effective method.An arrival sequencing model based on the serial point merge systems(PMSs)is constructed to improve the operational benefits of arrival flights.The approach of first come first service(FCFS)combined with the method of constraint position shift(CPS)is used as the sequencing strategy.Through the simulated annealing algorithm,the results show that the arrival flights sequencing through serial PMSs has significant advantages in reducing delays and increasing runway throughput especially in the case of high traffic loads.The proposed approach is conducive in promoting the implementation and application of serial PMS.展开更多
At 8:30 on October 27, the first international flight from Shanghai to Singapore MU576 took off at Pudong Airport. Thus,all international flights and those to Hong Kong and Macao were all moved to Pudong Airport. Besi...At 8:30 on October 27, the first international flight from Shanghai to Singapore MU576 took off at Pudong Airport. Thus,all international flights and those to Hong Kong and Macao were all moved to Pudong Airport. Besides internationalflights and Hong Kong and Macao flights, the eastward moving also cover some domestic flights, namely flights fromSanya, Haikou, Guangzhou, Shenzhen, Zhuhai, Qingdao, Yantai, Weihai, Weifang and so on in Northwest China, Mid-South China,and East China to Shanghai. After the eastward moving, the flight distribution at two airports in Shanghai changed greatly.展开更多
A new analysis of a previously studied traveling agent model, showed that there is a relation between the degree of homogeneity of the medium where the agents move, agent motion patterns, and the noise generated from ...A new analysis of a previously studied traveling agent model, showed that there is a relation between the degree of homogeneity of the medium where the agents move, agent motion patterns, and the noise generated from their displacements. We proved that for a particular value of homogeneity, the system self organizes in a state where the agents carry out Lévy walks and the displacement signal corresponds to 1/f noise. Using probabilistic arguments, we conjectured that 1/f noise is a fingerprint of a statistical phase transition, from randomness (disorder) to predictability (order), and that it emerges from the contextuality nature of the system which generates it.展开更多
<div style="text-align:justify;"> This paper mainly studies the problem of irregular flights recovery under uncertain conditions. Based on the analysis of the uncertain factors affecting the flight, ta...<div style="text-align:justify;"> This paper mainly studies the problem of irregular flights recovery under uncertain conditions. Based on the analysis of the uncertain factors affecting the flight, taking the total delay time and the total cost of flight delay as the objective function, and considering the constraints of flight plan and passenger journey, an uncertain objective programming model is constructed. Finally, taking OVS airport temporarily closed due to bad weather as an example, the results show that better quality optimization scheme can be obtained by integrating passenger recovery with narrow sense flight recovery stage and implementing integrated recovery. </div>展开更多
At 22:41 Beijing time on April 20,a LM-3B launch vehicle lifted off from the Xichang Satellite Launch Center and successfully launched the 44th satellite of the BeiDou Navigation Satellite System into its preset orbit...At 22:41 Beijing time on April 20,a LM-3B launch vehicle lifted off from the Xichang Satellite Launch Center and successfully launched the 44th satellite of the BeiDou Navigation Satellite System into its preset orbit.This was the 100th flight of the LM-3A carrier rocket family and the 302nd flight of the Long March series launch vehicle.展开更多
In order to meet the needs of collaborative decision making,considering the different demands of air traffic control units,airlines,airports and passengers in various traffic scenarios,the joint scheduling problem of ...In order to meet the needs of collaborative decision making,considering the different demands of air traffic control units,airlines,airports and passengers in various traffic scenarios,the joint scheduling problem of arrival and departure flights is studied systematically.According to the matching degree of capacity and flow,it is determined that the traffic state of arrival/departure operation in a certain period is peak or off-peak.The demands of all parties in each traffic state are analyzed,and the mathematical models of arrival/departure flight scheduling in each traffic state are established.Aiming at the four kinds of joint operation traffic scenarios of arrival and departure,the corresponding bi-level programming models for joint scheduling of arrival and departure flights are established,respectively,and the elitism genetic algorithm is designed to solve the models.The results show that:Compared with the first-come-firstserved method,in the scenarios of arrival peak&departure off-peak and arrival peak&departure peak,the departure flight equilibrium satisfaction is improved,and the runway occupation time of departure flight flow is reduced by 38.8%.In the scenarios of arrival off-peak&departure off-peak and departure peak&arrival off-peak,the arrival flight equilibrium delay time is significantly reduced,the departure flight equilibrium satisfaction is improved by 77.6%,and the runway occupation time of departure flight flow is reduced by 46.6%.Compared with other four kinds of strategies,the optimal scheduling method can better balance fairness and efficiency,so the scheduling results are more reasonable.展开更多
Birds and bats retract and stretch their wings dynamically during each flap in level flights, implying intriguing mechanisms for the aerodynamic performance improvement of flapping wings. A numerical investigation int...Birds and bats retract and stretch their wings dynamically during each flap in level flights, implying intriguing mechanisms for the aerodynamic performance improvement of flapping wings. A numerical investigation into the aerodynamic effects of such bio-inspired concept in forward flights has been performed based on a three-dimensional wing in plunging motion and a twosection wing in flapping motion. The currently considered Reynolds number and Strouhal number are Re=1.5×10^(5) and St=0.3, respectively. During the research, the mean angle of attack is varied in relatively wide ranges to achieve lift-thrust interconversion for the wings. The conclusive results show that dynamical spanwise retraction and stretch has induced three absolutely desirable scenarios for the oscillating wings in forward flights, namely producing more lift and consuming less power for a given thrust generation, producing more thrust and consuming less power for a given lift generation, and producing more lift and more thrust while consuming less power. Furthermore,the morphing wings have alleviated periodical aerodynamic load fluctuations compared with the non-morphing baseline. The mechanism of the aerodynamic effects of the bionic morphing mode is analyzed with the aid of field visualization. The current article is the first to reveal the absolute advantages of the bionic spanwise morphing. Hopefully, it may help comprehend the behaviors of natural fliers and provide inspirations for performance enhancement of micro artificial flappingwing vehicles.展开更多
The best active twist schedules exploiting various waveform types are sought taking advantage of the global search algorithm for the reduction of hub vibration and/or power required of a rotor in high-speed conditions...The best active twist schedules exploiting various waveform types are sought taking advantage of the global search algorithm for the reduction of hub vibration and/or power required of a rotor in high-speed conditions. The active twist schedules include two non-harmonic inputs formed based on segmented step functions as well as the simple harmonic waveform input. An advanced Particle Swarm assisted Genetic Algorithm（PSGA） is employed for the optimizer. A rotorcraft Computational Structural Dynamics（CSD） code CAMRAD II is used to perform the rotor aeromechanics analysis. A Computation Fluid Dynamics（CFD） code is coupled with CSD for verification and some physical insights. The PSGA optimization results are verified against the parameter sweep study performed using the harmonic actuation. The optimum twist schedules according to the performance and/or vibration reduction strategy are obtained and their optimization gains are compared between the actuation cases. A two-phase non-harmonic actuation schedule demonstrates the best outcome in decreasing the power required while a four-phase non-harmonic schedule results in the best vibration reduction as well as the simultaneous reductions in the power required and vibration. The mechanism of reduction to the performance gains is identified illustrating the section airloads, angle-of-attack distribution, and elastic twist deformation predicted by the present approaches.展开更多
In China,the term“black flights”re-fers to unauthorized operations of drones,flying cars and other aircraft.This includes unregistered devices,as well as registered ones flown without approval or beyond permitted zo...In China,the term“black flights”re-fers to unauthorized operations of drones,flying cars and other aircraft.This includes unregistered devices,as well as registered ones flown without approval or beyond permitted zones.Chinese law stipulates clear penalties for such violations,ranging from warnings and fines to criminal liability in serious cases.Despite these regulations,black flights have grown increasingly common in recent years.展开更多
Starting June 28,passengers on Chinese domestic flights face stricter power bank regulations.The Civil Aviation Administration of China now bans power banks without valid 3C certification(China5s mandatory safety stan...Starting June 28,passengers on Chinese domestic flights face stricter power bank regulations.The Civil Aviation Administration of China now bans power banks without valid 3C certification(China5s mandatory safety standard)or those recalled for safety defects-a move triggered by rising incidents of lithium-ion battery fires and smoke emissions mid-flight.展开更多
Cross-regional tourism expenditure can stimulate market activity and meet the increasing demand for high-quality tourism experiences.Using UnionPay offline transaction data matched with flight route information from 2...Cross-regional tourism expenditure can stimulate market activity and meet the increasing demand for high-quality tourism experiences.Using UnionPay offline transaction data matched with flight route information from 2013 to 2018 in China,this study applied a difference-in-differences model to investigate the impact of direct flights on cross-city tourism expenditure.It found that,after the opening of new routes,the cross-city tourism expenditure between city pairs increased by approximately 3.2 percent.Direct flights also increased tourism expenditure on sightseeing,lodging,catering,and shopping,with the larger effects for city pairs separated by more than 400 km.Destinations with high-quality cultural and natural assets,such as national 5A-level tourist attractions,world cultural and natural heritage sites,and national tourist resorts,tended to experience increased tourist expenditure.Direct flights also produced spillover effects on expenditure in surrounding cities,which decreased with distance,and these effects occurred mainly in hub cities and origin nonhub cities.These findings have implications for urban growth policy.展开更多
While aircraft age has long been recognized as a critical factor influencing maintenance costs and safety out-comes,its operational consequences for on-time performance remain comparatively underexplored in empirical ...While aircraft age has long been recognized as a critical factor influencing maintenance costs and safety out-comes,its operational consequences for on-time performance remain comparatively underexplored in empirical research.This study addresses that gap by examining the relationship between aircraft age and departure delays in U.S.domestic aviation.Using the aircraft registry data from Federal Aviation Agency(FAA)and on-time performance data in 2023 from Bureau of Transportation Statistics(BTS).To estimate the impact of aircraft age on departure delays,the study employs both traditional econometric techniques,Ordinary Least Squares(OLS)regression,and advanced ensemble machine learning methods.In addition,SHapley Additive exPlanations(SHAP)analysis is applied to interpret model predictions and quantify the relative contribution of aircraft age in comparison with other explanatory factors at both carrier and aircraft series levels.The results indicate that aircraft age is a statistically significant predictor of departure delay.At the carrier level,most major carriers exhibit a consistent age-delay relationship.At the aircraft series level,Boeing aircraft display more uniform agerelated delay patterns,whereas some Airbus narrow-body models show mixed or less consistent results,potentially reflecting differences in design,maintenance practices,or fleet management strategies.These find-ings extend the literature on fleet aging by moving beyond safety and cost considerations to highlight its role in airline operation,as well as underscore the value of incorporating fleet age into aircraft assignment,scheduling decisions,and performance models.展开更多
Safer,smarter,faster...In China,people prefer high-speed trains to flights if the journey time is under five hours.High-speed train travel is set to become even more attractive with the addition of a new member to the...Safer,smarter,faster...In China,people prefer high-speed trains to flights if the journey time is under five hours.High-speed train travel is set to become even more attractive with the addition of a new member to the high-speed train family:the CR450,the world’s fastest electric multiple unit(EMU).展开更多
Particle distribution in the cross-section of the flighted rotating drum(FRD)is critical to the analysis of heat and mass transfer between gas and solids.In this work,the particle tracking velocimetry(PTV)method is ap...Particle distribution in the cross-section of the flighted rotating drum(FRD)is critical to the analysis of heat and mass transfer between gas and solids.In this work,the particle tracking velocimetry(PTV)method is applied to study the influence of the number of flights on the particle motion in FRDs.The drum,installed with 1,4,8,or 12 rectangular flights,is filled with plastic balls to 15%and operated at various rotating speeds ranging from 10 rpm to 30 rpm.The results show that the number of flights has different effects on the holdup ratio and cascading rate of single flight and active flights.With 8 and 12 flights,the FRD produces a larger and more stable particle ratio of the dilute phase.Moreover,DEM simulations agree with PTV measurements,whereas literature models show significant deviations.展开更多
Most of the previous works ignore the fact that equilibrium flights in self-profit maximization scenario are totally different from that in joint profit(social welfare)maximization scenario and take price difference(f...Most of the previous works ignore the fact that equilibrium flights in self-profit maximization scenario are totally different from that in joint profit(social welfare)maximization scenario and take price difference(flight fare difference)between the two scenarios as congestion price,which is a passenger-based method.Most of all,the function of congestion pricing is to alleviate congestion by making airlines reduce flights at peak time.Therefore,the equilibrium flights under self-profit maximization should be the same as the ones under joint profit maximization after congestion prices are tolled.Flight-based congestion pricing method is provided in our paper.The analysis suggests no role for congestion pricing when total real flight production of all airlines is less than the equilibrium flights under joint profit maximization scenario.Otherwise,congestion tolls should be levied to all airlines.Furthermore,congestion price can be determined by solving the corresponding equations system.展开更多
Changsha has played a pioneering role in reshaping cross-continental trade and cooperation.From the 50,000 pieces of Changsha Kiln ceramics recovered from the Tang Dynasty shipwreck“Black Stone”to today’s weekly ca...Changsha has played a pioneering role in reshaping cross-continental trade and cooperation.From the 50,000 pieces of Changsha Kiln ceramics recovered from the Tang Dynasty shipwreck“Black Stone”to today’s weekly cargo flights between China and Africa,Changsha’s trade with the African continent has spanned over a thousand years.This historic cultural city is playing an increasingly vital role in China-Africa economic and trade cooperation,with a spirit of innovation and openness.展开更多
基金supported by the Science and Technology Development Fund,Macao SAR,China(Nos.0033/2022/AFJ and 0011/2023/AMJ)Guangdong Basic and Applied Basic Research Foundation(No.2023A1515012017).
文摘With the rapid development of aviation industry and its increasing impact on the global climate change,the contributions of carbon emissions frominternational flights are attracting more and more attention worldwide.This study,taking Macao as the aviation hub,established the cross-border aviation carbon emission evaluation model to explore dynamic carbon emissions and net-zero path of international flights.The aviation hubmainly covers 58 routes and five types of civil aircraft from 12 countries or regions during 2000-2022.The results show that the aviation transportation in Macao emitted about 1.44 million tons CO_(2)eq in 2019,which is high 3.6 times that of 2000.The COVID-19 has led to a rapid decline in aviation carbon emissions in a short period of time,carbon emissions in 2020 decreased by 80%compared to 2019.In terms of cumulative carbon emissions from 2000 to 2019,the A321 and A320 Airbus contribute to 80%of carbon emissions.And the Chinese mainland(37%)and Taiwan(29%)are the main sources of emissions.In 2000-2019,the proportion of carbon emissions from China(including Taiwan and Hong Kong)decrease from 91%to 53%,while the contribution from Southeast Asia(from 5% to 26%),Japan and South Korea(from 2% to 19%)keep the growth trends.In the optimal scenario(B3C3),net zero emissions of cross-border aviation in Macao can be not achieved,and there is still only by removing 0.3 million tons CO_(2)eq.Emission reduction technology and new energy usage are priorities for the aviation emission reduction.
基金supported by the National Natural Science Foundation of China(No.U1933119)the Foundation of Graduate Innovation Center in Nanjing University of Aeronautics and Astronautics(No.xcxjh20210703)
文摘In order to alleviate the flight congestion in terminal areas(TMAs),it is of great significance to develop an effective method.An arrival sequencing model based on the serial point merge systems(PMSs)is constructed to improve the operational benefits of arrival flights.The approach of first come first service(FCFS)combined with the method of constraint position shift(CPS)is used as the sequencing strategy.Through the simulated annealing algorithm,the results show that the arrival flights sequencing through serial PMSs has significant advantages in reducing delays and increasing runway throughput especially in the case of high traffic loads.The proposed approach is conducive in promoting the implementation and application of serial PMS.
文摘At 8:30 on October 27, the first international flight from Shanghai to Singapore MU576 took off at Pudong Airport. Thus,all international flights and those to Hong Kong and Macao were all moved to Pudong Airport. Besides internationalflights and Hong Kong and Macao flights, the eastward moving also cover some domestic flights, namely flights fromSanya, Haikou, Guangzhou, Shenzhen, Zhuhai, Qingdao, Yantai, Weihai, Weifang and so on in Northwest China, Mid-South China,and East China to Shanghai. After the eastward moving, the flight distribution at two airports in Shanghai changed greatly.
文摘A new analysis of a previously studied traveling agent model, showed that there is a relation between the degree of homogeneity of the medium where the agents move, agent motion patterns, and the noise generated from their displacements. We proved that for a particular value of homogeneity, the system self organizes in a state where the agents carry out Lévy walks and the displacement signal corresponds to 1/f noise. Using probabilistic arguments, we conjectured that 1/f noise is a fingerprint of a statistical phase transition, from randomness (disorder) to predictability (order), and that it emerges from the contextuality nature of the system which generates it.
文摘<div style="text-align:justify;"> This paper mainly studies the problem of irregular flights recovery under uncertain conditions. Based on the analysis of the uncertain factors affecting the flight, taking the total delay time and the total cost of flight delay as the objective function, and considering the constraints of flight plan and passenger journey, an uncertain objective programming model is constructed. Finally, taking OVS airport temporarily closed due to bad weather as an example, the results show that better quality optimization scheme can be obtained by integrating passenger recovery with narrow sense flight recovery stage and implementing integrated recovery. </div>
文摘At 22:41 Beijing time on April 20,a LM-3B launch vehicle lifted off from the Xichang Satellite Launch Center and successfully launched the 44th satellite of the BeiDou Navigation Satellite System into its preset orbit.This was the 100th flight of the LM-3A carrier rocket family and the 302nd flight of the Long March series launch vehicle.
基金supported by Nanjing University of Aeronautics and Astronautics Graduate Innovation Base(Laboratory)Open Fund(No.kfjj20200717).
文摘In order to meet the needs of collaborative decision making,considering the different demands of air traffic control units,airlines,airports and passengers in various traffic scenarios,the joint scheduling problem of arrival and departure flights is studied systematically.According to the matching degree of capacity and flow,it is determined that the traffic state of arrival/departure operation in a certain period is peak or off-peak.The demands of all parties in each traffic state are analyzed,and the mathematical models of arrival/departure flight scheduling in each traffic state are established.Aiming at the four kinds of joint operation traffic scenarios of arrival and departure,the corresponding bi-level programming models for joint scheduling of arrival and departure flights are established,respectively,and the elitism genetic algorithm is designed to solve the models.The results show that:Compared with the first-come-firstserved method,in the scenarios of arrival peak&departure off-peak and arrival peak&departure peak,the departure flight equilibrium satisfaction is improved,and the runway occupation time of departure flight flow is reduced by 38.8%.In the scenarios of arrival off-peak&departure off-peak and departure peak&arrival off-peak,the arrival flight equilibrium delay time is significantly reduced,the departure flight equilibrium satisfaction is improved by 77.6%,and the runway occupation time of departure flight flow is reduced by 46.6%.Compared with other four kinds of strategies,the optimal scheduling method can better balance fairness and efficiency,so the scheduling results are more reasonable.
基金mainly supported by the National Natural Science Foundation of China (No. 52175277, 52275293)Resources provided by the Basic Research Program of Shenzhen, China (No. JCYJ 20190806142816524)the Guangdong Basic and Applied Basic Research Foundation, China (No. 2023A1515010774)。
文摘Birds and bats retract and stretch their wings dynamically during each flap in level flights, implying intriguing mechanisms for the aerodynamic performance improvement of flapping wings. A numerical investigation into the aerodynamic effects of such bio-inspired concept in forward flights has been performed based on a three-dimensional wing in plunging motion and a twosection wing in flapping motion. The currently considered Reynolds number and Strouhal number are Re=1.5×10^(5) and St=0.3, respectively. During the research, the mean angle of attack is varied in relatively wide ranges to achieve lift-thrust interconversion for the wings. The conclusive results show that dynamical spanwise retraction and stretch has induced three absolutely desirable scenarios for the oscillating wings in forward flights, namely producing more lift and consuming less power for a given thrust generation, producing more thrust and consuming less power for a given lift generation, and producing more lift and more thrust while consuming less power. Furthermore,the morphing wings have alleviated periodical aerodynamic load fluctuations compared with the non-morphing baseline. The mechanism of the aerodynamic effects of the bionic morphing mode is analyzed with the aid of field visualization. The current article is the first to reveal the absolute advantages of the bionic spanwise morphing. Hopefully, it may help comprehend the behaviors of natural fliers and provide inspirations for performance enhancement of micro artificial flappingwing vehicles.
基金supported by Basic Science Research Program through the National Research Foundation of Korea (NRF)funded by the Ministry of Education (No. 2017R1D1A1A09000590)
文摘The best active twist schedules exploiting various waveform types are sought taking advantage of the global search algorithm for the reduction of hub vibration and/or power required of a rotor in high-speed conditions. The active twist schedules include two non-harmonic inputs formed based on segmented step functions as well as the simple harmonic waveform input. An advanced Particle Swarm assisted Genetic Algorithm（PSGA） is employed for the optimizer. A rotorcraft Computational Structural Dynamics（CSD） code CAMRAD II is used to perform the rotor aeromechanics analysis. A Computation Fluid Dynamics（CFD） code is coupled with CSD for verification and some physical insights. The PSGA optimization results are verified against the parameter sweep study performed using the harmonic actuation. The optimum twist schedules according to the performance and/or vibration reduction strategy are obtained and their optimization gains are compared between the actuation cases. A two-phase non-harmonic actuation schedule demonstrates the best outcome in decreasing the power required while a four-phase non-harmonic schedule results in the best vibration reduction as well as the simultaneous reductions in the power required and vibration. The mechanism of reduction to the performance gains is identified illustrating the section airloads, angle-of-attack distribution, and elastic twist deformation predicted by the present approaches.
文摘In China,the term“black flights”re-fers to unauthorized operations of drones,flying cars and other aircraft.This includes unregistered devices,as well as registered ones flown without approval or beyond permitted zones.Chinese law stipulates clear penalties for such violations,ranging from warnings and fines to criminal liability in serious cases.Despite these regulations,black flights have grown increasingly common in recent years.
文摘Starting June 28,passengers on Chinese domestic flights face stricter power bank regulations.The Civil Aviation Administration of China now bans power banks without valid 3C certification(China5s mandatory safety standard)or those recalled for safety defects-a move triggered by rising incidents of lithium-ion battery fires and smoke emissions mid-flight.
基金supported by the National Natural Science Foundation of China(Nos.72233002 , 72173104)the Major Program of National Fund of Philosophy and Social Science of China(No.24ZDA087)the Postdoctoral Fellowship Program of CPSF(No.GZC20233140).
文摘Cross-regional tourism expenditure can stimulate market activity and meet the increasing demand for high-quality tourism experiences.Using UnionPay offline transaction data matched with flight route information from 2013 to 2018 in China,this study applied a difference-in-differences model to investigate the impact of direct flights on cross-city tourism expenditure.It found that,after the opening of new routes,the cross-city tourism expenditure between city pairs increased by approximately 3.2 percent.Direct flights also increased tourism expenditure on sightseeing,lodging,catering,and shopping,with the larger effects for city pairs separated by more than 400 km.Destinations with high-quality cultural and natural assets,such as national 5A-level tourist attractions,world cultural and natural heritage sites,and national tourist resorts,tended to experience increased tourist expenditure.Direct flights also produced spillover effects on expenditure in surrounding cities,which decreased with distance,and these effects occurred mainly in hub cities and origin nonhub cities.These findings have implications for urban growth policy.
文摘While aircraft age has long been recognized as a critical factor influencing maintenance costs and safety out-comes,its operational consequences for on-time performance remain comparatively underexplored in empirical research.This study addresses that gap by examining the relationship between aircraft age and departure delays in U.S.domestic aviation.Using the aircraft registry data from Federal Aviation Agency(FAA)and on-time performance data in 2023 from Bureau of Transportation Statistics(BTS).To estimate the impact of aircraft age on departure delays,the study employs both traditional econometric techniques,Ordinary Least Squares(OLS)regression,and advanced ensemble machine learning methods.In addition,SHapley Additive exPlanations(SHAP)analysis is applied to interpret model predictions and quantify the relative contribution of aircraft age in comparison with other explanatory factors at both carrier and aircraft series levels.The results indicate that aircraft age is a statistically significant predictor of departure delay.At the carrier level,most major carriers exhibit a consistent age-delay relationship.At the aircraft series level,Boeing aircraft display more uniform agerelated delay patterns,whereas some Airbus narrow-body models show mixed or less consistent results,potentially reflecting differences in design,maintenance practices,or fleet management strategies.These find-ings extend the literature on fleet aging by moving beyond safety and cost considerations to highlight its role in airline operation,as well as underscore the value of incorporating fleet age into aircraft assignment,scheduling decisions,and performance models.
文摘Safer,smarter,faster...In China,people prefer high-speed trains to flights if the journey time is under five hours.High-speed train travel is set to become even more attractive with the addition of a new member to the high-speed train family:the CR450,the world’s fastest electric multiple unit(EMU).
文摘Particle distribution in the cross-section of the flighted rotating drum(FRD)is critical to the analysis of heat and mass transfer between gas and solids.In this work,the particle tracking velocimetry(PTV)method is applied to study the influence of the number of flights on the particle motion in FRDs.The drum,installed with 1,4,8,or 12 rectangular flights,is filled with plastic balls to 15%and operated at various rotating speeds ranging from 10 rpm to 30 rpm.The results show that the number of flights has different effects on the holdup ratio and cascading rate of single flight and active flights.With 8 and 12 flights,the FRD produces a larger and more stable particle ratio of the dilute phase.Moreover,DEM simulations agree with PTV measurements,whereas literature models show significant deviations.
基金This work was supported by the National Natural Science Foundation of China(No.71571182)the Social Science and Humanity Fund of the Ministry of Education of China(No.14YJC630185)the Fundamental Research Funds for the Central Universities(No.3122013C001).
文摘Most of the previous works ignore the fact that equilibrium flights in self-profit maximization scenario are totally different from that in joint profit(social welfare)maximization scenario and take price difference(flight fare difference)between the two scenarios as congestion price,which is a passenger-based method.Most of all,the function of congestion pricing is to alleviate congestion by making airlines reduce flights at peak time.Therefore,the equilibrium flights under self-profit maximization should be the same as the ones under joint profit maximization after congestion prices are tolled.Flight-based congestion pricing method is provided in our paper.The analysis suggests no role for congestion pricing when total real flight production of all airlines is less than the equilibrium flights under joint profit maximization scenario.Otherwise,congestion tolls should be levied to all airlines.Furthermore,congestion price can be determined by solving the corresponding equations system.
文摘Changsha has played a pioneering role in reshaping cross-continental trade and cooperation.From the 50,000 pieces of Changsha Kiln ceramics recovered from the Tang Dynasty shipwreck“Black Stone”to today’s weekly cargo flights between China and Africa,Changsha’s trade with the African continent has spanned over a thousand years.This historic cultural city is playing an increasingly vital role in China-Africa economic and trade cooperation,with a spirit of innovation and openness.
