Coordinated multi-aircraft 4D trajectories planning considering buffer safety distance and fuel consumption optimization via pure-strategy game

In this paper, we consider a coordinated multi-aircraft 4D (3D space plus time) trajectories planning problem which is illustrated by planning 4D trajectories for aircraft traversing an Air Traffic Control (ATC) sector. The planned 4D trajectories need to specify each aircraft’s position at any time, ensuring conflict-free and reducing fuel and delay costs, with possible aircraft maneuvers such as speed adjustment and flight level change. Different from most existing literature, the impact of buffer safety distance is also under consideration, and conflict-free is guaranteed at any given time (not only at discrete time instances). The problem is formulated as a pure-strategy game with aircraft as players and all possible 4D trajectories as strategies. An efficient maximum improvement distributed algorithm is developed to find equilibrium at which every aircraft cannot unilaterally improve further, without enumerating all possible 4D trajectories in advance. Proof of existence of the equilibrium and convergence of the algorithm are given. A case study based on real air traffic data shows that the algorithm is able to solve 4D trajectories for online application with estimated 16.7% reduction in monetary costs, and allocate abundant buffer safety distance at minimum separation point. Scalability of the algorithm is verified by computational experiments.     

西安市交通拥堵和空气污染的成因和政策研究

近年来,西安市交通拥堵和空气污染问题突出。文章旨在分析这两大问题的现状、成因以及现行政策的效果。对于改善拥堵和空气污染,限行政策在短期内有显著效果,燃煤整治明显改善了空气质量。而从长远来看,正面效果会随着机动车数量的增长而逐渐消失。文章将有助于政府进一步针对拥堵和雾霾的长期政策研究。     

基于商用车气囊减震系统的舒适性研究

随着社会的发展,商用卡车的减震系统从最初的机械减震发展到后来流行的气囊减震,全浮式、半浮式、四点悬浮气囊结构等,说明人们对商用车的舒适性要求越来越高。文章研究全浮式气囊减震系统在商用车领域中的设计应用,舒适性要求仅通过理论计算很难获得最佳状态,应通过理论、实验相结合方式持续优化。在设计验证阶段,需要对实车进行初步测量,计算出固有参数,再通过一些特殊手段计算出相应数据作为输入,经过分析筛选出有效数据,进行分析,使用初版参数样件进行装车,最后通过不断的实际路试进行验证修正原输入参数,最终确定最佳匹配参数并固化下来用于量产。     

环境因素对战时野战机场开设影响的模糊分析

分析了野战机场环境对后勤保障影响的问题。以场务保障为例,提出了影响飞行场务保障实施的因素集,从量化角度运用模糊相似优先比决策法对几个野战机场方案对场务保障实施影响情况进行了排序。在直观地看出各个野战机场方案对场务保障支持情况基础上,说明了各个方案中影响场务保障因素的利弊,从而可以针对各个方案有的放矢地制定未来应急场务保障预案,实现场务保障快速、高效的目标。经推广研究,可以得出野战机场选址对空军后勤保障的影响,增强制定战时后勤保障预案的针对性。     

航班延误统计指标体系及延误等级评估研究

针对我国现行航班统计方法存在的缺陷,基于对航班运行全过程以及在此过程中空管、航空公司、机场等单位工作职责的分析,构建了科学系统的航班延误统计指标体系,同时设计了航班延误等级综合评估的模型。上述统计指标体系及评估方法经国内某航空公司实际试用表明,与目前民航所使用的航班正常性统计标准比较,该方法能够更加真实、准确地跟踪航班整个运行阶段的延误状况,较好地反应了航班的实际运行情况,能有效地支持航空公司运行管理部门的延误控制和公司决策层的宏观管理。     

Optimal shipment decisions for an airfreight forwarder: Formulation and solution methods

We study the freight forwarder’s shipment planning problem in an airfreight forwarding network where a set of cargo shipments have to be transported to given destinations. We provide mixed integer programming formulations that use piecewise-linear cargo rates and account for volume and weight constraints, flight departure/arrival times, as well as shipment-ready times.After exploring the solution of such models using CPLEX, we devise two solution methodologies to handle large problem sizes. The first is based on Lagrangian relaxation, where the problems decompose into a set of knapsack problems and a set of network flow problems. The second is a local branching heuristic that combines branching ideas and local search. The two approaches show promising results in providing good quality heuristic solutions within reasonable computational times, for difficult and large shipment consolidation problems.     

Sound wall barriers: Near roadway dispersion under neutrally stratified boundary layer

With the passage of California Senate Bill 375, which motivates infill development near transit hubs, there is the potential to increase vehicle congestion in residential communities and increase in human exposure to toxic mobile source pollutants. Among all the mitigation strategies that protect near roadway residents from health-affecting vehicular emissions (e.g. separating sensitive receptors from high traffic roadways), this paper discusses the impact of sound wall barriers (SBs) in reducing the air pollution exposure of nearby residents. To date, there have been some studies done to understand the impact of these structures on dispersion of vehicular emissions; however, no definitive conclusion has been drawn yet. The main objective of this paper is to provide more information and details on flow and dispersion affected by barriers through a systematic laboratory simulation of plume dispersion using a water channel. Three sets of experiments were conducted: (1) plume visualizations, (2) plume concentration measurements, and (3) flow velocity measurements. Results from this study shows that the deployment of sound barriers induces a recirculating flow over the roadway which transports the surface released emissions to the upwind side of the roadway, and then shifts the plume upward through an induced updraft motion. Plume visualizations clearly demonstrate that the presence of SBs induce significant vertical mixing and updraft motion on the roadway which increases the initial plume dilution and plume height and consequently results in reduced downwind ground level concentrations. Although different SB configurations result in different localized flow patterns, the dispersion pattern does not change significantly after several SB heights downwind of the roadway.     

Light duty gasoline vehicle emission factors at high transient and constant speeds for short road segments

Vehicle emissions estimates are needed at high spatial and temporal resolution to estimate near-roadway air quality and human exposures. The MOBILE6 emission factor model is based on transient test cycles of less than 65 mph. Correction factors for high speed and constant speed are developed based on vehicle-specific power-based modal models for light duty gasoline vehicles, using data from portable emission measurement systems. At 80 mph versus 65 mph, the estimated average emission rates are greater by 30%, 20%, 80%, and 10% for NO_x, HC, CO, and CO₂. The ratio of constant to average of transient speed emission rates range from 0.49 to 0.94 for NO_x at speeds of 20 mph and 80 mph. The high speed and constant speed correction factors are applied to estimate vehicle emissions for a freeway segment that includes vehicle cruising speeds between 65 and 80 mph. The potential error for not accounting for constant speed operation on a short segment of highway could be 49% at moderate speed and 24% at high speed.     

Influence of coordinated traffic lights parameters on roadside pollutant concentrations

The paper examines the effects of coordinated traffic lights on CO and C₆H₆ roadside concentrations in an urban area of Palermo in Southern Italy. Traffic loop detectors and one pollution-monitoring are used to collect data for use in DRACULA traffic microsimulator software. CO and C₆H₆ roadside concentrations associated with varying cycle and offset times of the coordinated traffic lights are estimated using a neural network. Two functions were set up describing the relations of pollutant concentrations in term of cycle and offset time.     

大交通流量条件下分布式空管系统安全性分析

尽管分布式空中交通管理系统相比集中式系统具有容错性好的特点,但是,随着空中交通流量的增长,由于多米诺效应的影响,系统的稳定性下降,安全性降低.本文建立了大流量条件下分布式系统的安全性计算模型,分析了系统的安全性随空中流量的增长而变化的规律.仿真结果表明在大流量时分布式系统的安全性低于集中式系统.