With the continuous growth of air traffic flow, some airports in China or other countries begin to construct Closely Spaced Parallel Runways(CSPR) to meet the capacity requirement of civil aviation. In this paper, the...With the continuous growth of air traffic flow, some airports in China or other countries begin to construct Closely Spaced Parallel Runways(CSPR) to meet the capacity requirement of civil aviation. In this paper, the simulation and calculation method of flight trajectory is developed,as well as the collision risk calculation method and wake vortex encounter risk calculation method.New methods for departure and go-around procedures are proposed to achieve approximate segregated parallel operation in an attempt to obtain approximately the same results on closely spaced parallel runways as on widely spaced parallel runways. By comparing with the independent parallel departure and segregated parallel operation in ICAO Doc. 9643, it is found that the lateral separation between aircraft in this proposal is not less than the separations in the other two cases. Based on the simulation calculation of flight trajectories under different conditions, the probabilities of collision conflict and encountering wake vortex are lower than those in current operation plan.The proposed plan has no special requirements in pilot operation, control command procedures,airport facilities, or meteorological observation and prediction, so it is convenient to promote and implement at the airports with closely spaced parallel runways.展开更多
A scheduling model of closely spaced parallel runways for arrival aircraft was proposed,with multi-objections of the minimum flight delay cost,the maximum airport capacity,the minimum workload of air traffic controlle...A scheduling model of closely spaced parallel runways for arrival aircraft was proposed,with multi-objections of the minimum flight delay cost,the maximum airport capacity,the minimum workload of air traffic controller and the maximum fairness of airlines′scheduling.The time interval between two runways and changes of aircraft landing order were taken as the constraints.Genetic algorithm was used to solve the model,and the model constrained unit delay cost of the aircraft with multiple flight tasks to reduce its delay influence range.Each objective function value or the fitness of particle unsatisfied the constrain condition would be punished.Finally,one domestic airport hub was introduced to verify the algorithm and the model.The results showed that the genetic algorithm presented strong convergence and timeliness for solving constraint multi-objective aircraft landing problem on closely spaced parallel runways,and the optimization results were better than that of actual scheduling.展开更多
The tire spray produced by aircraft running on wet runways may enter the intake of engines,which may lead to the compressor stall,surge,or even combustion flameout.Therefore,it is necessary to do some research work on...The tire spray produced by aircraft running on wet runways may enter the intake of engines,which may lead to the compressor stall,surge,or even combustion flameout.Therefore,it is necessary to do some research work on the tire spray to help to solve this problem.Firstly,the mechanism of tire spray is analyzed,and some parameters are defined to describe the spray pattern.Secondly,the numerical model of tire spray is established by coupled Smoothed Particle Hydrodynamics(SPH)and Finite Element Method(FEM)in LS-DYNA software,and the model is validated by a simplified water spray experiment.Then some influence factors on the spray pattern are studied by numerical simulation.Finally,some suggestions are proposed on different types of aircraft to avoid too much tire spray being ingested into the engine intakes.展开更多
Pavement construction in permafrost regions is complicated by the fact that the permafrost properties are influenced by the temperature and are extremely unstable.The numerical model for runway structures in permafros...Pavement construction in permafrost regions is complicated by the fact that the permafrost properties are influenced by the temperature and are extremely unstable.The numerical model for runway structures in permafrost regions is applied to analyze the time–space characteristics of the temperature field and the depth of the frozen layer.The influence of the installation layer is studied to enable structural optimization of the runway.Numerical results show that the temperature stabilization depth,low-and high-temperature interlayer response ranges,and maximum depth of the frozen layer are greater in runway engineering than in highway and railway engineering.The time history curves for the pavement and natural surface are similar,and the development of freezing and thawing is approximately linear.The pavement and natural surface have similar thawing rates,but the freezing rate of the natural surface is faster than that of the pavement.The depth of the frozen layer and the time of the frozen are greater for the natural surface than for the pavement.The installation layer helps to stabilize the temperature of the subgrade and reduces the freezing and thawing rates.This study provides technical support for the design and maintenance of runways in permafrost regions.展开更多
The paired approach is a kind of efficiency approach to closely spaced parallel runways(CSPRs),and the point merge system has the powerful interval management function,which is effective to realize the converge of tra...The paired approach is a kind of efficiency approach to closely spaced parallel runways(CSPRs),and the point merge system has the powerful interval management function,which is effective to realize the converge of traffic flows from different approach directions.In order to improve the operation efficiency of the airport terminal area,a model of paired approach sequencing based on point merge is proposed to investigate the problem of increasing the operation capacity of the closely spaced parallel runways.Taking the minimum average flight delay time as the objective,the flight distance on sequencing legs,wake turbulence separation and paired approach safety separation as constraints,the genetic algorithm is used to optimize the paired approach sequencing of arrival flights.Taking the closely parallel runways of Shanghai Hongqiao International Airport run south as an example,the point merge program is designed and the effect of model was analyzed.The results show that after optimization,the average delay time and average landing time are reduced by 40.6%and 51.8%respectively,the capacity of the closely spaced parallel runways are 1.1 times higher than the actual,the flight uptime rate can reach 100%.It is concluded that the proposed model is feasible,which can effectively reduce delay times and alleviate congestion in terminal areas.展开更多
This article presents a methodology to determine the risk of aircrafts lateral runway excursion during landing via mathematical risk modeling. In addition, the methodology is demonstrated by means of detailed calculat...This article presents a methodology to determine the risk of aircrafts lateral runway excursion during landing via mathematical risk modeling. In addition, the methodology is demonstrated by means of detailed calculation of the lateral runway excursion risk value during the landing of the aircraft Airbus A310-200, in view of the maximum landing weight and the appropriate range of landing velocities according to the International Civil Aviation Organization specification. Obviously, the calculation demonstrates that the developed math solutions and equations presented herein are powerful tools to evaluate the risk of lateral runway excursion of the majority of aircrafts and for any airport. The method is also applicable to assess the residual level of risk at any specific airport and its deviation compared to the recommended safety level. Consequently, the presented mathematical solutions to determine the risk rate of lateral runway excursion during landing offers airports’ operational and safety management departments a viable tool so that appropriate measurements could be adopted. Finally, it is a methodology not only to assess the risk but also to determine the appropriate runway width.展开更多
The aircraft antiskid braking system is an important hydraulic system for preventing tire bursts and ensuring safe take-off and landing. The brake system adjusts the force applied on the brake discs by controlling the...The aircraft antiskid braking system is an important hydraulic system for preventing tire bursts and ensuring safe take-off and landing. The brake system adjusts the force applied on the brake discs by controlling the brake pressure. Traditional aircraft antiskid braking systems achieve antiskid performance by controlling the braking pressure with an electrohydraulic servo valve.Because the pilot stage of an electrohydraulic servo valve is easily blocked by carbonized hydraulic oil, the servo valve would become a dangerous weak point for aircraft safety. This paper proposes a new approach that uses an on-off valve array to replace the servo valve for pressure control. Based on this new pressure control component, an efficient antiskid control algorithm that can utilize this discontinuous feature is proposed. Furthermore, the algorithm has the ability to identify the runway circumstances. To overcome the discontinuity in the process of using an on-off valve array, the Filippov framework is introduced. The conditions of convergence of the system are also discussed.The results of the digital simulations and the hardware-in-the-loop(HIL) braking experiments are used to verify the efficiency and stability of the proposed control algorithm. The method also proves that the on-off valve array can replace the servo valve perfectly as a new type of antiskid braking pressure control component.展开更多
In this paper,a three dimension model is built according to real surface cleaner in airport runway rubber mark cleaning vehicle and numerical simulation of this model is carried out using Ansys Fluent software.After c...In this paper,a three dimension model is built according to real surface cleaner in airport runway rubber mark cleaning vehicle and numerical simulation of this model is carried out using Ansys Fluent software.After comparison and analysis of the flow fields between high speed rotating waterjet and static waterjet formerly studied by other researchers,the influences of different standoff distances from nozzle outlet to runway surface and rotation speeds on rubber mark cleaning effect are simulated and analyzed.Results show the optimal operation parameters for the simulated model and quantitative advices are given for design,manufacture and operation of the airport runway rubber mark cleaning vehicle.展开更多
The hotspot recognition algorithm is proposed based on a potential collision in order to study the aircraft taxi conflicts in large airports.The spatial and temporal distribution characteristics of hotspots are analyz...The hotspot recognition algorithm is proposed based on a potential collision in order to study the aircraft taxi conflicts in large airports.The spatial and temporal distribution characteristics of hotspots are analyzed based on the risk assessment model of hotspot constructed in this paper.Firstly,approaches for monitoring of the aerodrome movement were compared.The hotspot recognition algorithm taken into account of whether aircrafts'taxi track has spatial and temporal overlap based on the aerodrome surveillance radar(ASR)data was presented,by identifying the hotspots through analyzing whether the aircrafts'time of entering and exiting the same taxiway is overlap or not,and the heading difference and distance of the two aircrafts satisfy the specified threshold constraint condition.Then,the ASR data were divided into several parts,and then airport hotspots were recognized and the spatial and temporal distribution characteristics were analyzed.The risk assessment model of airport safety hotspots was constructed which is taken into account of the conflict probability and its severity consequence.Finally,based on the risk grade assessment criteria and hotspots'risk value,the risk grade ranking of hotspot in one airport of China was evaluated and designated.According to the result,the spatial and temporal distribution characteristics of airport hotspots were varied with the variation of airport traffic flow and operational mode of runway,which shows that the hotspots have the characteristics of dynamic periodicity and diurnal variation.And the risk assessment results were consistent with experts'opinions and actual operation condition,which verified the rationality of the hotspot recognition algorithm,risk assessment model as well as the risk grade ranking criteria.展开更多
The wheel brake system of an aircraft is the key to ensure its safe landing and rejected takeoff.A wheel’s slip state is determined by the brake torque and ground adhesion torque,both of which have a large degree of ...The wheel brake system of an aircraft is the key to ensure its safe landing and rejected takeoff.A wheel’s slip state is determined by the brake torque and ground adhesion torque,both of which have a large degree of uncertainty.It is this nature that brings upon the challenge of obtaining high deceleration rate for aircraft brake control.To overcome the disturbances caused by the above uncertainties,a braking control law is designed,which consists of two parts:runway surface recognition and wheel’s slip state tracking.In runway surface recognition,the identification rules balancing safety and braking efficiency are defined,and the actual identification process is realized through recursive least square method with forgetting factors.In slip state tracking,the LuGre model with parameter adaptation and a brake torque compensation method based on RBF neural network are proposed,and their convergence are proven.The effectiveness of our control law is verified through simulation and ground experiment.Especially in the experiments on the ground inertial test bench,compared to the improved pressure-biased-modulation(PBM)anti-skid algorithm,fewer wheel slips occur,and the average deceleration rate is increased by 5.78%,which makes it a control strategy with potential for engineering applications.展开更多
The transport of runaway electrons in a high-temperature plasma is relatively easy to measure in a steady state experiment and a perturbation experiment, which provides runaway electron diffusion coefficient Dr. This ...The transport of runaway electrons in a high-temperature plasma is relatively easy to measure in a steady state experiment and a perturbation experiment, which provides runaway electron diffusion coefficient Dr. This diffusion coefficient is determined by internal magnetic fluctuations, so it can be interpreted in terms of a magnetic fluctuation level. The internal magnetic fluctuation level （b^-r/BT） is estimated to be about （2-4）×^-4 in the HL-1M plasma. The results presented here demonstrate the effectiveness of using runaway electron transport techniques to determine internal magnetic fluctuations. A profile of magnetic fluctuation level in the HL-1M plasma can be estimated from Dr.展开更多
This paper presents a short contribution in air transportation, specifically in scheduling aircraft (plane) landings at Léopol Sédar Senghor (LSS) airport of Dakar. The safety of air navigation of LSS is man...This paper presents a short contribution in air transportation, specifically in scheduling aircraft (plane) landings at Léopol Sédar Senghor (LSS) airport of Dakar. The safety of air navigation of LSS is managed by ASECNA: Agency for Air Navigation Safety in Africa and Madagascar. Scheduling aircraft landing is the problem of deciding a landing time on an appropriate runway for each aircraft in a given set of aircraft such that each aircraft lands within a predetermined time window. The separation criteria between the landing of an aircraft, and the landing of all successive aircraft, are respected. Our objective is to minimize the cost of deviation from the target times. We present a mixed-integer 0 - 1 formulation for the single runway case. Numerical experiments and comparisons based on real datasets of LSS airport are presented.展开更多
Pavements of airport runway and apron are subjected to stern stresses imposed by landing and ground movements of aircraft. The stresses are primarily concentrated in touchdown zone and wheel path areas of the pavement...Pavements of airport runway and apron are subjected to stern stresses imposed by landing and ground movements of aircraft. The stresses are primarily concentrated in touchdown zone and wheel path areas of the pavement structure. This paper proposes that this area can be designed using geosynthetic layer reinforcement to minimise deflection and deterioration of the structure. The reinforcement can reduce the vertical stresses on the underground fuel pipes in the apron area, if used. The concept of ditch conduit reinforcement is suggested where a geosynthetic layer is used within a soil backfill to redistribute load over a conduit leading to stress redistribution. It is observed that the vertical load is significantly reduced by the arching action of the soil mass overlying the conduit. The load can be reduced further by placing a geosynthetic reinforcement layer within the soil backfill above the conduit. It is suggested that the inclusion of a geosynthetic layer in the granular backfill reduces the vertical load on a ditch conduit and the amount of reduction depends upon the tensile modulus, deflection of the geosynthetic and soil arching action. This leads to believe that a reinforced pavement structure for runway and aerodrome apron area improves the load carrying capacity of the pavement to sustain the operations of heavy transport aircraft, including occasional overloading of the pavement. Hence, this paper explores a possibility of using a geosynthetic layer under the runway pavement to provide reinforcement.展开更多
The area of operations management has had a substantial effect on the today’s air transportation management.Having moved with huge demand from management to obtain a competitive advantage in the market,the airlines a...The area of operations management has had a substantial effect on the today’s air transportation management.Having moved with huge demand from management to obtain a competitive advantage in the market,the airlines are utilizing advanced optimization techniques to develop decision support systems for operations management and control.In order to provide a service with high quality and low cost,airlines spend a tremendous amount of resources and effort to generate profitable and cost-effective fare classes,flight schedules,fleet plans,aircraft routes,crew scheduling,gate assignment,etc.In this paper,the techniques and operations management applications that are used in the air transportation industry are reviewed including demand forecasting,fleet assignment,aircraft routing,crew scheduling,runway scheduling problem and gate assignment.展开更多
In this paper,numeric simulations are performed for three dimension models built according to actual surface cleaner in airport runway rubber mark cleaning vehicle using ANSYS FLUENT software on the basis of previous ...In this paper,numeric simulations are performed for three dimension models built according to actual surface cleaner in airport runway rubber mark cleaning vehicle using ANSYS FLUENT software on the basis of previous research finished by the authors.After analyzing the simulated flow fields under different standoff distances between nozzle outlet and runway surface and different discharge pressures at nozzle outlet,the relationships of normal stress and shear stress at striking point to outlet pressure and standoff distance are obtained.Finally,the most appropriate discharge pressure at nozzle outlet for the studied surface cleaner model is found,and this will provide theoretical basis for future rubber mark cleaning process in airports and equipment model selection in subsequent design of airport runway rubber mark cleaning vehicles.展开更多
The influence of self-heating on the millimeter-wave(mm-wave)and terahertz(THz)performance of double-drift region(DDR)impact avalanche transit time(IMPATT)sources based on silicon(Si)has been investigated in this pape...The influence of self-heating on the millimeter-wave(mm-wave)and terahertz(THz)performance of double-drift region(DDR)impact avalanche transit time(IMPATT)sources based on silicon(Si)has been investigated in this paper.The dependences of static and large-signal parameters on junction temperature are estimated using a non-sinusoidal voltage excited(NSVE)large-signal simulation technique developed by the authors,which is based on the quantum-corrected drift-diffusion(QCDD)model.Linear variations of static parameters and non-linear variations of large-signal parameters with temperature have been observed.Analytical expressions representing the temperature dependences of static and large-signal parameters of the diodes are developed using linear and 2nd degree polynomial curve fitting techniques,which will be highly useful for optimizing the thermal design of the oscillators.Finally,the simulated results are found to be in close agreement with the experimentally measured data.展开更多
On March 25th, our designer Hu Sheguang, with an unconstrained yet quite unique style, presented creative patterns during a fashion show for another new season. He made use of various uniform elements and with the fas...On March 25th, our designer Hu Sheguang, with an unconstrained yet quite unique style, presented creative patterns during a fashion show for another new season. He made use of various uniform elements and with the fashion detachment of women, brought us a charming show. The models for the show were selected from all over the world.They wore fitted military green uniforms;exuding dominance from head to toe.Hu fully integrated Chinese and Western elements while using fur, tulle, taffeta and other materials to create a stunning astehtic.展开更多
In order to resolve the safety problem of the existing crane runway gir-ders(CRGs)with defects,the constraint-based R6 criterion is proposed to assess their structural integrity.The ex isting steel CRGs with defects a...In order to resolve the safety problem of the existing crane runway gir-ders(CRGs)with defects,the constraint-based R6 criterion is proposed to assess their structural integrity.The ex isting steel CRGs with defects at the weld joint between the upper flange and web plate,are characterized to three-dimensional finite element models with a semi-ellipse surface crack.The R6 criterion has been modified by considering the constraint effect which is represented by T-stress.The analysis results ilustrate that working condition of the cracked CRGs leads to high constraint level along the crack front.The crack aspect ratio(a/c)and run-way eccentricity(e)have significant influence on the integrity of the cracked CRGs.The integrity assessment results based on modified constraint-based R6 failure criterion enable to more effectively protect the cracked CRGs from brittle fracture failure.展开更多
基金funded by the National Natural Science Foundation of China (Nos. U1533116, U1633125)Project Foundation of Civil Aircraft for MIIT of China (No. MJ-2016-Y76)the Fundamental Research Funds for the Central Universities of CAUC of China (No. 3122017067)
文摘With the continuous growth of air traffic flow, some airports in China or other countries begin to construct Closely Spaced Parallel Runways(CSPR) to meet the capacity requirement of civil aviation. In this paper, the simulation and calculation method of flight trajectory is developed,as well as the collision risk calculation method and wake vortex encounter risk calculation method.New methods for departure and go-around procedures are proposed to achieve approximate segregated parallel operation in an attempt to obtain approximately the same results on closely spaced parallel runways as on widely spaced parallel runways. By comparing with the independent parallel departure and segregated parallel operation in ICAO Doc. 9643, it is found that the lateral separation between aircraft in this proposal is not less than the separations in the other two cases. Based on the simulation calculation of flight trajectories under different conditions, the probabilities of collision conflict and encountering wake vortex are lower than those in current operation plan.The proposed plan has no special requirements in pilot operation, control command procedures,airport facilities, or meteorological observation and prediction, so it is convenient to promote and implement at the airports with closely spaced parallel runways.
文摘A scheduling model of closely spaced parallel runways for arrival aircraft was proposed,with multi-objections of the minimum flight delay cost,the maximum airport capacity,the minimum workload of air traffic controller and the maximum fairness of airlines′scheduling.The time interval between two runways and changes of aircraft landing order were taken as the constraints.Genetic algorithm was used to solve the model,and the model constrained unit delay cost of the aircraft with multiple flight tasks to reduce its delay influence range.Each objective function value or the fitness of particle unsatisfied the constrain condition would be punished.Finally,one domestic airport hub was introduced to verify the algorithm and the model.The results showed that the genetic algorithm presented strong convergence and timeliness for solving constraint multi-objective aircraft landing problem on closely spaced parallel runways,and the optimization results were better than that of actual scheduling.
基金supported by the Aeronautical Science Foundation of China(No.2016ZD53038)the support of the Commercial Aircraft Corporation of China Ltd.
文摘The tire spray produced by aircraft running on wet runways may enter the intake of engines,which may lead to the compressor stall,surge,or even combustion flameout.Therefore,it is necessary to do some research work on the tire spray to help to solve this problem.Firstly,the mechanism of tire spray is analyzed,and some parameters are defined to describe the spray pattern.Secondly,the numerical model of tire spray is established by coupled Smoothed Particle Hydrodynamics(SPH)and Finite Element Method(FEM)in LS-DYNA software,and the model is validated by a simplified water spray experiment.Then some influence factors on the spray pattern are studied by numerical simulation.Finally,some suggestions are proposed on different types of aircraft to avoid too much tire spray being ingested into the engine intakes.
基金the National Natural Science Foundation of China(Grant No.52108333)the Natural Science Foundation of Tianjin(Grant Nos.18JCQNJC08300,18JCYBJC90800,20JCQNJC01320)the Key Laboratory of Road Structure and Materials Transportation Industry(Grant No.310821171114)for providing the funding that made this study possible.
文摘Pavement construction in permafrost regions is complicated by the fact that the permafrost properties are influenced by the temperature and are extremely unstable.The numerical model for runway structures in permafrost regions is applied to analyze the time–space characteristics of the temperature field and the depth of the frozen layer.The influence of the installation layer is studied to enable structural optimization of the runway.Numerical results show that the temperature stabilization depth,low-and high-temperature interlayer response ranges,and maximum depth of the frozen layer are greater in runway engineering than in highway and railway engineering.The time history curves for the pavement and natural surface are similar,and the development of freezing and thawing is approximately linear.The pavement and natural surface have similar thawing rates,but the freezing rate of the natural surface is faster than that of the pavement.The depth of the frozen layer and the time of the frozen are greater for the natural surface than for the pavement.The installation layer helps to stabilize the temperature of the subgrade and reduces the freezing and thawing rates.This study provides technical support for the design and maintenance of runways in permafrost regions.
基金supported by the National Key Research and Development Program(No.211221210054)the Fundamental Research Funds for the Central Universities of Chang’an University(No.300102210117)。
文摘The paired approach is a kind of efficiency approach to closely spaced parallel runways(CSPRs),and the point merge system has the powerful interval management function,which is effective to realize the converge of traffic flows from different approach directions.In order to improve the operation efficiency of the airport terminal area,a model of paired approach sequencing based on point merge is proposed to investigate the problem of increasing the operation capacity of the closely spaced parallel runways.Taking the minimum average flight delay time as the objective,the flight distance on sequencing legs,wake turbulence separation and paired approach safety separation as constraints,the genetic algorithm is used to optimize the paired approach sequencing of arrival flights.Taking the closely parallel runways of Shanghai Hongqiao International Airport run south as an example,the point merge program is designed and the effect of model was analyzed.The results show that after optimization,the average delay time and average landing time are reduced by 40.6%and 51.8%respectively,the capacity of the closely spaced parallel runways are 1.1 times higher than the actual,the flight uptime rate can reach 100%.It is concluded that the proposed model is feasible,which can effectively reduce delay times and alleviate congestion in terminal areas.
文摘This article presents a methodology to determine the risk of aircrafts lateral runway excursion during landing via mathematical risk modeling. In addition, the methodology is demonstrated by means of detailed calculation of the lateral runway excursion risk value during the landing of the aircraft Airbus A310-200, in view of the maximum landing weight and the appropriate range of landing velocities according to the International Civil Aviation Organization specification. Obviously, the calculation demonstrates that the developed math solutions and equations presented herein are powerful tools to evaluate the risk of lateral runway excursion of the majority of aircrafts and for any airport. The method is also applicable to assess the residual level of risk at any specific airport and its deviation compared to the recommended safety level. Consequently, the presented mathematical solutions to determine the risk rate of lateral runway excursion during landing offers airports’ operational and safety management departments a viable tool so that appropriate measurements could be adopted. Finally, it is a methodology not only to assess the risk but also to determine the appropriate runway width.
基金the Science and Technology on Aircraft Control Laboratorythe National Nature Science Foundation of China (Nos. 51775014 and 51890882)
文摘The aircraft antiskid braking system is an important hydraulic system for preventing tire bursts and ensuring safe take-off and landing. The brake system adjusts the force applied on the brake discs by controlling the brake pressure. Traditional aircraft antiskid braking systems achieve antiskid performance by controlling the braking pressure with an electrohydraulic servo valve.Because the pilot stage of an electrohydraulic servo valve is easily blocked by carbonized hydraulic oil, the servo valve would become a dangerous weak point for aircraft safety. This paper proposes a new approach that uses an on-off valve array to replace the servo valve for pressure control. Based on this new pressure control component, an efficient antiskid control algorithm that can utilize this discontinuous feature is proposed. Furthermore, the algorithm has the ability to identify the runway circumstances. To overcome the discontinuity in the process of using an on-off valve array, the Filippov framework is introduced. The conditions of convergence of the system are also discussed.The results of the digital simulations and the hardware-in-the-loop(HIL) braking experiments are used to verify the efficiency and stability of the proposed control algorithm. The method also proves that the on-off valve array can replace the servo valve perfectly as a new type of antiskid braking pressure control component.
文摘In this paper,a three dimension model is built according to real surface cleaner in airport runway rubber mark cleaning vehicle and numerical simulation of this model is carried out using Ansys Fluent software.After comparison and analysis of the flow fields between high speed rotating waterjet and static waterjet formerly studied by other researchers,the influences of different standoff distances from nozzle outlet to runway surface and rotation speeds on rubber mark cleaning effect are simulated and analyzed.Results show the optimal operation parameters for the simulated model and quantitative advices are given for design,manufacture and operation of the airport runway rubber mark cleaning vehicle.
基金the Joint Funds of the National Science Foundation of China and the Civil Aviation Administration(Nos.U1733105 and U1733203)the Sichuan Science and Technology Program(No.2019YFG0308)
文摘The hotspot recognition algorithm is proposed based on a potential collision in order to study the aircraft taxi conflicts in large airports.The spatial and temporal distribution characteristics of hotspots are analyzed based on the risk assessment model of hotspot constructed in this paper.Firstly,approaches for monitoring of the aerodrome movement were compared.The hotspot recognition algorithm taken into account of whether aircrafts'taxi track has spatial and temporal overlap based on the aerodrome surveillance radar(ASR)data was presented,by identifying the hotspots through analyzing whether the aircrafts'time of entering and exiting the same taxiway is overlap or not,and the heading difference and distance of the two aircrafts satisfy the specified threshold constraint condition.Then,the ASR data were divided into several parts,and then airport hotspots were recognized and the spatial and temporal distribution characteristics were analyzed.The risk assessment model of airport safety hotspots was constructed which is taken into account of the conflict probability and its severity consequence.Finally,based on the risk grade assessment criteria and hotspots'risk value,the risk grade ranking of hotspot in one airport of China was evaluated and designated.According to the result,the spatial and temporal distribution characteristics of airport hotspots were varied with the variation of airport traffic flow and operational mode of runway,which shows that the hotspots have the characteristics of dynamic periodicity and diurnal variation.And the risk assessment results were consistent with experts'opinions and actual operation condition,which verified the rationality of the hotspot recognition algorithm,risk assessment model as well as the risk grade ranking criteria.
基金supported by the National Natural Science Foundation of China(Grant No.52205045)the National Key Research and Development Program of China(Grant No.2021YFB2011300)the Young Elite Scientists Sponsorship Program by CAST(Grant No.YESS20200063)。
文摘The wheel brake system of an aircraft is the key to ensure its safe landing and rejected takeoff.A wheel’s slip state is determined by the brake torque and ground adhesion torque,both of which have a large degree of uncertainty.It is this nature that brings upon the challenge of obtaining high deceleration rate for aircraft brake control.To overcome the disturbances caused by the above uncertainties,a braking control law is designed,which consists of two parts:runway surface recognition and wheel’s slip state tracking.In runway surface recognition,the identification rules balancing safety and braking efficiency are defined,and the actual identification process is realized through recursive least square method with forgetting factors.In slip state tracking,the LuGre model with parameter adaptation and a brake torque compensation method based on RBF neural network are proposed,and their convergence are proven.The effectiveness of our control law is verified through simulation and ground experiment.Especially in the experiments on the ground inertial test bench,compared to the improved pressure-biased-modulation(PBM)anti-skid algorithm,fewer wheel slips occur,and the average deceleration rate is increased by 5.78%,which makes it a control strategy with potential for engineering applications.
基金Project supported by the Nuclear Industry Science Foundation of China （Grant No 19675013）.
文摘The transport of runaway electrons in a high-temperature plasma is relatively easy to measure in a steady state experiment and a perturbation experiment, which provides runaway electron diffusion coefficient Dr. This diffusion coefficient is determined by internal magnetic fluctuations, so it can be interpreted in terms of a magnetic fluctuation level. The internal magnetic fluctuation level （b^-r/BT） is estimated to be about （2-4）×^-4 in the HL-1M plasma. The results presented here demonstrate the effectiveness of using runaway electron transport techniques to determine internal magnetic fluctuations. A profile of magnetic fluctuation level in the HL-1M plasma can be estimated from Dr.
文摘This paper presents a short contribution in air transportation, specifically in scheduling aircraft (plane) landings at Léopol Sédar Senghor (LSS) airport of Dakar. The safety of air navigation of LSS is managed by ASECNA: Agency for Air Navigation Safety in Africa and Madagascar. Scheduling aircraft landing is the problem of deciding a landing time on an appropriate runway for each aircraft in a given set of aircraft such that each aircraft lands within a predetermined time window. The separation criteria between the landing of an aircraft, and the landing of all successive aircraft, are respected. Our objective is to minimize the cost of deviation from the target times. We present a mixed-integer 0 - 1 formulation for the single runway case. Numerical experiments and comparisons based on real datasets of LSS airport are presented.
文摘Pavements of airport runway and apron are subjected to stern stresses imposed by landing and ground movements of aircraft. The stresses are primarily concentrated in touchdown zone and wheel path areas of the pavement structure. This paper proposes that this area can be designed using geosynthetic layer reinforcement to minimise deflection and deterioration of the structure. The reinforcement can reduce the vertical stresses on the underground fuel pipes in the apron area, if used. The concept of ditch conduit reinforcement is suggested where a geosynthetic layer is used within a soil backfill to redistribute load over a conduit leading to stress redistribution. It is observed that the vertical load is significantly reduced by the arching action of the soil mass overlying the conduit. The load can be reduced further by placing a geosynthetic reinforcement layer within the soil backfill above the conduit. It is suggested that the inclusion of a geosynthetic layer in the granular backfill reduces the vertical load on a ditch conduit and the amount of reduction depends upon the tensile modulus, deflection of the geosynthetic and soil arching action. This leads to believe that a reinforced pavement structure for runway and aerodrome apron area improves the load carrying capacity of the pavement to sustain the operations of heavy transport aircraft, including occasional overloading of the pavement. Hence, this paper explores a possibility of using a geosynthetic layer under the runway pavement to provide reinforcement.
文摘The area of operations management has had a substantial effect on the today’s air transportation management.Having moved with huge demand from management to obtain a competitive advantage in the market,the airlines are utilizing advanced optimization techniques to develop decision support systems for operations management and control.In order to provide a service with high quality and low cost,airlines spend a tremendous amount of resources and effort to generate profitable and cost-effective fare classes,flight schedules,fleet plans,aircraft routes,crew scheduling,gate assignment,etc.In this paper,the techniques and operations management applications that are used in the air transportation industry are reviewed including demand forecasting,fleet assignment,aircraft routing,crew scheduling,runway scheduling problem and gate assignment.
文摘In this paper,numeric simulations are performed for three dimension models built according to actual surface cleaner in airport runway rubber mark cleaning vehicle using ANSYS FLUENT software on the basis of previous research finished by the authors.After analyzing the simulated flow fields under different standoff distances between nozzle outlet and runway surface and different discharge pressures at nozzle outlet,the relationships of normal stress and shear stress at striking point to outlet pressure and standoff distance are obtained.Finally,the most appropriate discharge pressure at nozzle outlet for the studied surface cleaner model is found,and this will provide theoretical basis for future rubber mark cleaning process in airports and equipment model selection in subsequent design of airport runway rubber mark cleaning vehicles.
文摘The influence of self-heating on the millimeter-wave(mm-wave)and terahertz(THz)performance of double-drift region(DDR)impact avalanche transit time(IMPATT)sources based on silicon(Si)has been investigated in this paper.The dependences of static and large-signal parameters on junction temperature are estimated using a non-sinusoidal voltage excited(NSVE)large-signal simulation technique developed by the authors,which is based on the quantum-corrected drift-diffusion(QCDD)model.Linear variations of static parameters and non-linear variations of large-signal parameters with temperature have been observed.Analytical expressions representing the temperature dependences of static and large-signal parameters of the diodes are developed using linear and 2nd degree polynomial curve fitting techniques,which will be highly useful for optimizing the thermal design of the oscillators.Finally,the simulated results are found to be in close agreement with the experimentally measured data.
文摘On March 25th, our designer Hu Sheguang, with an unconstrained yet quite unique style, presented creative patterns during a fashion show for another new season. He made use of various uniform elements and with the fashion detachment of women, brought us a charming show. The models for the show were selected from all over the world.They wore fitted military green uniforms;exuding dominance from head to toe.Hu fully integrated Chinese and Western elements while using fur, tulle, taffeta and other materials to create a stunning astehtic.
基金The works described in this paper are financially supported by the National Program on Key Research Project(2016YFC0701301-02),to which the authors are most grateful.
文摘In order to resolve the safety problem of the existing crane runway gir-ders(CRGs)with defects,the constraint-based R6 criterion is proposed to assess their structural integrity.The ex isting steel CRGs with defects at the weld joint between the upper flange and web plate,are characterized to three-dimensional finite element models with a semi-ellipse surface crack.The R6 criterion has been modified by considering the constraint effect which is represented by T-stress.The analysis results ilustrate that working condition of the cracked CRGs leads to high constraint level along the crack front.The crack aspect ratio(a/c)and run-way eccentricity(e)have significant influence on the integrity of the cracked CRGs.The integrity assessment results based on modified constraint-based R6 failure criterion enable to more effectively protect the cracked CRGs from brittle fracture failure.
