停机位分配的多商品网络流模型及离散粒子群算法

本文建立了停机位分配的多商品网络流模型,并以航空器总场面运行时间最小为目标,建立数学模型。将机场场面分为若干区域,建立区域—机位两级分配策略,以降低问题规模。设置机位外等待时间,以省去区域容量相关约束。在传统粒子群算法的基础上,设计离散粒子群算法,对模型进行求解。选取乌鲁木齐机场某日240架航班和109个机位进行实验,证明了与现有研究中的典型模型相比,多商品网络流模型能使运算时间减少10.1%,并能达到与典型模型相同的精度。全空域和机场模型(total airspace and airport modeller,TAAM)仿真结果表明,和现行机位分配方案相比,多商品网络流模型的机位分配结果能使航空器的场面调配运行时间减少7.49%,延误时间减少8.87%。算例结果进一步表明,提高机场场面运行效率的关键在于均衡航班的进离港滑行距离,同时避免停机位密集分布。

基于改进Dijkstra算法的滑行路径优化

为了减少大型繁忙机场场面拥堵与航班延误,对处于机场终端区的航班进行预先战术性的滑行路径动态优化。首先,对处于机场终端区的航班划分时间窗口,对航班集合进行分类,使用改进Dijkstra算法对需要路径优化的航班进行动态规划。改进Dijkstra算法是将整个时间进程分成多个连续滚动的时间片,在每个时间片中,以场面节点的时间当量长度总和最小为优化目标,采用传统Dijkstra算法思想,获得每个航班的最优滑行路径解。其次,在TAAM(total airspace and airport modeller)仿真软件中利用Matlab编程实现算法,并以实际机场为例验证算法正确性。实验结果证明:改进Dijkstra算法能有效减少滑行冲突,提高滑行效率,缩短机场航班延误时间。

低空救援实时飞行的冲突探测与解脱算法研究

航空器冲突探测和解脱的实时计算对航空救援飞行安全意义重大。基于低空目视飞行规则,构建三维空域网格,采用时间窗理论分析了两航空器同高度飞行的时空冲突判定方法。依据救援目视飞行规则和航空器飞行性能约束,建立航空器Agent的可行路径集和基于网格划分的Airspace模型,并根据航空器Agent的救援任务属性确定了优先级判定准则,对各个Agent模型在冲突顶点上的优先级进行判定。建立两航空器无冲突最优路径规划方法,计算Agent的无冲突路径。通过仿真验证,分析了飞行冲突的时间窗和区域,以及优先级下的无冲突路径,结果表明,本方法相对于非协作的冲突探测和解脱方法可以有效提高解脱效率,节约飞行时间146s。

Lung squamous cell carcinoma presenting as rare clustered cystic lesions:A case report and review of literature

BACKGROUND Lung cancer is the leading cause of cancer-related death.Early diagnosis is critical to improving a patient’s chance of survival.However,lung cancer associated with cystic airspaces is often misdiagnosed or underdiagnosed due to the absence of clinical symptoms,poor imaging specificity,and high risk of biopsy-related complications.CASE SUMMARY We report an unusual case of cancer in a 55-year-old man,in which the lesion evolved from a small solitary thin-walled cyst to lung squamous cell carcinoma(SCC)with metastases in both lungs.The SCC manifested as rare clustered cystic lesions,detected on chest computed tomography.There were air-fluid levels,compartments,and bronchial arteries in the cystic lesions.Additionally,there was no clear extrathoracic metastasis.After chemotherapy,the patient achieved a partial response,type I respiratory failure was relieved,and the lung lesions became a clustered thin-walled cyst.CONCLUSION Pulmonary cystic lesions require regular imaging follow-up.Lung SCC should be a diagnostic consideration in cases of thin-walled cysts as well as multiple clustered cystic lesions.

Research on Operation of UAVs in Non-isolated Airspace

In order to explore the safe operation of UAVs in non-segregated airspace,a collision risk model for cylindrical UAVs based on conflict areas was constructed and the risk of conflict between manned and unmanned aerial vehicles was researched.According to the results of risk analysis,a strategy for solving the conflict of aircraft is proposed,and the risk assessment experiment of unmanned aerial vehicle(UAV)in non-isolated airspace conflict is carried out.The results show that under the experimental conditions,large unmanned aerial vehicles equipped with ADS-B,TCAS and other airborne sensing systems will indeed interfere with other aircraft in airspace when they enter non-isolated airspace.Especially when the number of aircraft in airspace is large,the automatic avoidance system of UAV will increase the avoidance time and trigger the safety alarm,but the safety level is still acceptable.This indicates that it is relatively safe for UAVs to enter non-isolated airspace under limited conditions.The results can be used as a reference for the safe operation of unmanned aerial vehicle(UAV)in non-isolated airspace.

Modeling of 3-D Air Traffic Complexity Based on Route Structure Constraints

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.

UAV safe route planning based on PSO-BAS algorithm

In order to solve the current situation that unmanned aerial vehicles(UAVs)ignore safety indicators and cannot guarantee safe operation when operating in low-altitude airspace,a UAV route planning method that considers regional risk assessment is proposed.Firstly,the low-altitude airspace is discretized based on rasterization,and then the UAV operating characteristics and environmental characteristics are combined to quantify the risk value in the low-altitude airspace to obtain a 3D risk map.The path risk value is taken as the cost,the particle swarm optimization-beetle antennae search(PSO-BAS)algorithm is used to plan the spatial 3D route,and it effectively reduces the generated path redundancy.Finally,cubic B-spline curve is used to smooth the planned discrete path.A flyable path with continuous curvature and pitch angle is generated.The simulation results show that the generated path can exchange for a path with a lower risk value at a lower path cost.At the same time,the path redundancy is low,and the curvature and pitch angle continuously change.It is a flyable path that meets the UAV performance constraints.

Beamforming of Whole Airspace Phased Array TT&C System Based on Linear Subarrays

The whole airspace phased array telemetry,track and command(TT&C)system is regarded as the development tendency of next generation TT&C system,and the distribution of the antenna units and the beamforming technology have sparked wide interest in this field.A method for antenna distribution is proposed based on the linear subarrays technology.A symmetrical truncated cone conformal array is composed of the linear subarrays placed on the generatrix.The impact of truncated cone bottom radius and elevation angle on beamforming are studied and simulated.Simulation results verify the system design.

Three-Dimensional Planning of Arrival and Departure Route Network Based on Improved Ant-Colony Algorithm

In order to improve safety,economy efficiency and design automation degree of air route in terminal airspace,Three-dimensional(3D)planning of routes network is investigated.A waypoint probability search method is proposed to optimize individual flight path.Through updating horizontal pheromones by negative feedback factors,an antcolony algorithm of path searching in 3Dterminal airspace is implemented.The principle of optimization sequence of arrival and departure routes is analyzed.Each route is optimized successively,and the overall optimization of the whole route network is finally achieved.A case study shows that it takes about 63 sto optimize 8arrival and departure routes,and the operation efficiency can be significantly improved with desirable safety and economy.

Integrated Network Design and Demand Forecast for On-Demand Urban Air Mobility

Urban air mobility(UAM)is an emerging concept proposed in recent years that uses electric vertical takeoff and landing vehicles(eVTOLs).UAM is expected to offer an alternative way of transporting passengers and goods in urban areas with significantly improved mobility by making use of low-altitude airspace.In addition to other essential elements,ground infrastructure of vertiports is needed to transition UAM from concept to operation.This study examines the network design of UAM on-demand service,with a particular focus on the use of integer programming and a solution algorithm to determine the optimal locations of vertiports,user allocation to vertiports,and vertiport access-and egress-mode choices while considering the interactions between vertiport locations and potential UAM travel demand.A case study based on simulated disaggregate travel demand data of the Tampa Bay area in Florida,USA was conducted to demonstrate the effectiveness of the proposed model.Candidate vertiport locations were obtained by analyzing a three-dimensional(3D)geographic information system(GIS)map developed from lidar data of Florida and physical and regulation constraints of eVTOL operations at vertiports.Optimal locations of vertiports were determined to achieve the minimal total generalized cost;however,the modeling structure allows each user to select a better mode between ground transportation and UAM in terms of generalized cost.The outcomes of the case study reveal that although the percentage of trips that switched from ground mode to multimodal UAM was small,users choosing the UAM service benefited from significant time saving.In addition,the impact of different parameter settings on the demand for UAM service was explored from the supply side,and different pricing strategies were tested that might influence potential demand and revenue generation for UAM operators.The combined effects of the number of vertiports and pricing strategies were also analyzed.The findings from this study offer in-depth planning and managerial insights for municipal decision-makers and UAM operators.The conclusion of this paper discusses caveats to the study,ongoing efforts by the authors,and future directions in UAM research.

Analysis on Potential Conflict Frequency of Intersected Air Routes in Terminal Airspace Design

In order to obtain accurate conflict risks in terminal airspace design,the concept and calculation model of potential conflict frequency for intersected routes are proposed.Conflict frequency is represented by the product of horizontal conflict frequency and vertical conflict probability.The horizontal conflict frequency is derived from the probability density distribution of conflicts in a period of time.Based on the recorded radar trajectory data,the concept and model of ROUTE distance are proposed,and the probability density function of aircraft height at a specified ROUTE distance is deduced by kernel density estimation.Furthermore,vertical conflict probability and its horizontal distribution are achieved.Examples of three intersected arrival and departure route design schemes are studied.Compared with scheme 1,the conflict frequency values of the other two improved schemes decrease to53% and 24%,respectively.The results show that the model can quantify potential conflict frequency of intersected routes.

Dynamic airspace sectorization via improved genetic algorithm

This paper deals with dynamic airspace sectorization （DAS） problem by an improved genetic algorithm （iGA）. A graph model is first constructed that represents the airspace static structure. Then the DAS problem is formulated as a graph-partitioning problem to balance the sector workload under the premise of ensuring safety. In the iGA, multiple populations and hybrid coding are applied to determine the optimal sector number and airspace sectorization. The sector constraints are well satisfied by the improved genetic operators and protect zones. This method is validated by being applied to the airspace of North China in terms of three indexes, which are sector balancing index, coordination workload index and sector average flight time index. The improvement is obvious, as the sector balancing index is reduced by 16.5 %, the coordination workload index is reduced by 11.2 %, and the sector average flight time index is increased by 11.4 % during the peak-hour traffic.

Review on artificial intelligence techniques for improving representative air traffic management capability

The use of artificial intelligence(AI)has increased since the middle of the 20th century,as evidenced by its applications to a wide range of engineering and science problems.Air traffic management(ATM)is becoming increasingly automated and autonomous,making it lucrative for AI applications.This paper presents a systematic review of studies that employ AI techniques for improving ATM capability.A brief account of the history,structure,and advantages of these methods is provided,followed by the description of their applications to several representative ATM tasks,such as air traffic services(ATS),airspace management(AM),air traffic flow management(ATFM),and flight operations(FO).The major contribution of the current review is the professional survey of the AI application to ATM alongside with the description of their specific advantages:(i)these methods provide alternative approaches to conventional physical modeling techniques,(ii)these methods do not require knowing relevant internal system parameters,(iii)these methods are computationally more efficient,and(iv)these methods offer compact solutions to multivariable problems.In addition,this review offers a fresh outlook on future research.One is providing a clear rationale for the model type and structure selection for a given ATM mission.Another is to understand what makes a specific architecture or algorithm effective for a given ATM mission.These are among the most important issues that will continue to attract the attention of the AI research community and ATM work teams in the future.

Optimization of a Route Network in Dakar Airspace: Surface Navigation

In this paper, the map of a network of air routes was updated by removing the non-optimal routes and replacing them with the best ones. An integer linear programming model was developed. The aim was to find optimal routes in superspace based on performance-based navigation. The optimal routes were found from a DIJKSTRA algorithm that calculates the shortest path in a graph. Simulations with python language on real traffic areas showed the improvements brought by surface navigation. In this work, the conceptual phase and the upper airspace were studied.

Design of Simulation System for Effectiveness Evaluation of Future Airspace Window Shooting

Future Airspace Window Shooting is a newly developed technology, which needs effectiveness evaluation before widely used. Future airspace window shooting technology, simulation system development principles and software chosen to develop the simulation system are introduced in the first. And then the overall design of the system, realization of the system and effectiveness evaluation through simulation are discussed in detail. Through the simulation, it is known that the FAW shooting has more superior performance when facing maneuvering targets.

Dynamic reconfiguration for en-route airspace

As the air traffic demand is anticipated to be increased significantly in the near future,dynamic and effective allocation of the airspace resource is becoming a world-wide focus in the research field of air traffic management（ATM）.Taking the U.S.targeting the en-route airsapce,a dynamic airspace configuration（DAC） algorithm to reconfigure the airspace in consideration of higher efficiency and safety is presented.First,a modeling technique based on graph theory is proposed to generate a mathematical model for the airspace,and then,the graph model is partitioned into subgraphs for the purpose of sectorizatoin.The final step generates sector configuration with desirable geometry shape.Through analysis on the Cleveland airspace center（ZOB） in the U.S.,the algorithm is proved to be robust to time-varying traffic load.

基于区域导航概念——西安仪表飞筇地程序优化方案

Describing the procession of a RNAV procedure design project;it introduced the evolution,basics and characteristics of RNAV system and also RNAV methods,operation requirements and procedures in TMA.After a series of detailed analysis and calculation based on the reality of fleet and operation environment in Xi'an,procedures design criteria and RNAV operation requirements,finally it resulted a set of sketch optimized RNAV procedures for Xi'an.

Sector Capacity Estimation Based on Differentiated Routes and Busy Levels

Sector capacity estimation plays an important role in applied research of airspace management.Previous researches manifest that sector capacity should be influenced by its standard flow,or routes in that sector.However,if air traffic controller(ATCO)workload busy levels(level of proactivity of an ATCO)are ignored,the estimated sector capacity may not be accurate.There is a need to compare the estimated sector capacity with and without busy levels consideration,both with differentiated routes consideration.This paper proposes a method for sector capacity estimation based on ATCO workload considering differentiated routes and busy levels.Firstly,the main routes in the sector are identified,and for each route,the ATCO workload per flight is determined.Secondly,the workload for each route at three busy levels is determined.Regression analysis is then applied to determine the relationship between workload and the number of flights(with and without considering busy levels)in 15 min and 1h time slices.Sector capacity is then determined on the basis of a specified workload threshold,for the two cases with and without considering busy levels.Comparing the two scenarios and following validation by ATCO survey,it is found that capacity estimation considering busy levels is a more realistic and accurate approach.The validated capacity values for the Zhengzhou approach(ZHCC AP)airspace sector accounting for the busy levels were determined accurately as 10 and 33 flights for the 15 min and 1h slices,respectively.The corresponding results without considering busy levels were 12 and 41 flights for the 15 min and 1h time slices,respectively.

Chronic airspace disease:Review of the causes and key computed tomography findings

Chronic airspace diseases are commonly encountered by chest,body or general radiologists in everyday practice.Even though there is significant overlap in the imaging findings of different causes of chronic airspace disease,some key clinical,laboratory and imaging findings can be used to guide the radiologist to the correct diagnosis.The goal of this article is to review and compare these features.