Time to burn: Flight delay,terminal efficiency,and fuel consumption in the National Airspace System

Improved Air Traffic Management (ATM) leading to reduced en route and gate delay, greater predictability in flight planning, and reduced terminal inefficiencies has a role to play in reducing aviation fuel consumption. Air navigation service providers are working to quantify this role to help prioritize and justify ATM modernization efforts. In the following study we analyze actual flight-level fuel consumption data reported by a major U.S. based airline to study the possible fuel savings from ATM improvements that allow flights to better adhere to their planned trajectories both en route and in the terminal area. To do so we isolate the contribution of airborne delay, departure delay, excess planned flight time, and terminal area inefficiencies on fuel consumption using econometric techniques. The model results indicate that, for two commonly operated aircraft types, the system-wide averages of flight fuel consumption attributed to ATM delay and terminal inefficiencies are 1.0–1.5% and 1.5–4.5%, respectively. We quantify the fuel impact of predicted delay to be 10–20% that of unanticipated delay, reinforcing the role of flight plan predictability in reducing fuel consumption. We rank terminal areas by quantifying a Terminal Inefficiency metric based on the variation in terminal area fuel consumed across flights. Our results help prioritize ATM modernization investments by quantifying the trade-offs in planned and unplanned delays and identifying terminal areas with high potential for improvement.     

The asymmetric effects of income and fuel price on air transport demand

Forecasts of passenger demand are an important parameter for aviation planners. Air transport demand models typically assume a perfectly reversible impact of the demand drivers. However, there are reasons to believe that the impacts of some of the demand drivers such as fuel price or income on air transport demand may not be perfectly reversible. Two types of imperfect reversibility, namely asymmetry and hysteresis, are possible. Asymmetry refers to the differences in the demand impacts of a rising price or income from that of a falling price or income. Hysteresis refers to the dependence of the impacts of changing price or income on previous history, especially on previous maximum price or income. We use US time series data and decompose each of fuel price and income into three component series to develop an econometric model for air transport demand that is capable of capturing the potential imperfectly reversible relationships and test for the presence or absence of reversibility. We find statistical evidence of asymmetry and hysteresis – for both, prices and income – in air transport demand. Implications for policy and practice are then discussed.     

Does European high-speed rail affect the current level of air services? An EU-wide analysis

This paper analyses whether the current provision of air services in Europe is impacted by high-speed rail (HSR). An ex-post analysis is carried out considering 161 routes EU-wide using transnational data. We use censored regressions with special attention paid to the presence of outliers in the sample and to the potential problem of non-normality of error terms. It is found that shorter HSR travel times involve less air services, with similar impact on both airline seats and flights. This impact quickly drops between 2.0- and 2.5-h HSR travel time. The impact of HSR frequencies is much more limited. Hubbing strategies led by the airlines have the opposite effect from HSR, as hubs involve more air services. Airline/HSR integration at the airport and cities being served by both central and peripheral stations have no significant impact. Metropolitan and national spatial patterns may help to better understand intermodal effects.     

气囊模拟计算技术综述

安全气囊模拟计算技术是研究气囊与假人相互作用的有效手段。常用的计算 双压法和压力温度法等，可以采用直接折叠法或始使短阵法建立气囊的有限元模型。现在有的折叠方式如星形叠法用传统的建模方法已有能解决，而考虑气体流动的气囊欧拉模型将得到更广泛的应用。     

列车交会压力波对车体和侧窗的影响

列车交会时产生的瞬态压力冲击波对车体钢结构和侧窗均带来不利影响，严惩时将危及行车安全。文章对瞬变压力冲击载荷作用下的客车车体钢结构及侧窗，进行非线性结构瞬态冲击响应分析，考核既有线上现有车辆承受列车交会压力波的能力，为设计新型车辆和对玻璃性能的要求提供科学依据。     

基于Agent的空中交通流量管理系统结构研究

空中交通流量管理系统(ATFM)对于适应飞行量的不断增长、减少延误、充分利用空域和地面资源,具有战略性意义.多Agent具有实时性高、可扩充性好、自治能力强的特点,符合空中交通流量管理系统的要求.本文充分考虑到空中交通流量管理系统三级结构的特点,把那些具有自主性和智能性、并对系统有重要影响的实体用Agent来实现,基于Agent技术构建了空中交通流量管理系统的框架,详细阐述了系统工作方式及各分Agent系统的结构;将多Agent应用到空中交通流量管理系统,可有效提高系统的动态环境适应性和自治性,降低系统设计与实现的复杂性,为建设流量管理系统提供了新的思维模式.     

车辆空气弹簧动力学参数特性研究

在车辆动力学模拟计算中,车辆动力学性能主要取决于悬挂参数的匹配,悬挂参数的精确度直接影响车辆动力学模拟计算误差。基于热力学及流体力学理论,建立空气弹簧的统一物理模型,导出其计算的统一数学表达式,提出了确定空气弹簧参数的计算方法,并对影响空气弹簧性能的因素进行了详细的分析。结果表明,空气弹簧气囊外形及刚度、附加气室容积和流孔直径是影响空气弹簧性能的主要因素。     

客车空气压缩机皮带轮断裂失效分析

运用金相显微镜、扫描电镜和能谱仪等分析仪器，研究了某客车空气压缩机皮带轮断裂的原因。结果表明，该空气压缩机的皮带轮辐条与轮毂、轮盘连接处产生应力集中现象，是导致该处出现裂纹并发生疲劳断裂的主要原因。针对以上问题提出了改进建议。     

空气弹簧悬架托架有限元计算及力学性能试验研究

针对某大客车空气弹簧悬架托架批量断裂问题,曾采取了增加板厚、增焊U型槽等措施,但致使托架质量增加且安装工艺性差。依据有限元计算分析结果,对托架结构进行了优化。通过包括静态应力和固有频率的力学特性试验表明,优化后的托架能够满足强度要求,且质量减轻了三分之一。     

An aggregate demand model for air passenger traffic in the hub-and-spoke network

In this paper, we build an aggregate demand model for air passenger traffic in a hub-and-spoke network. This model considers the roles of airline service variables such as service frequency, aircraft size, ticket price, flight distance, and number of spokes in the network. It also takes into account the influence of local passengers and social-economic and demographic conditions in the spoke and hub metropolitan areas. The hub airport capacity, which has a significant impact on service quality in the hub airport and in the whole hub-and-spoke network, is also taken into consideration.Our demand model reveals that airlines can attract more connecting passengers in a hub-and-spoke network by increasing service frequency than by increasing aircraft size in the same percentage. Our research confirms the importance of local service to connecting passengers, and finds that, interestingly, airlines’ services in the first flight leg are more important to attract passengers than those in the second flight segment. Based on data in this study, we also find that a 1% reduction of ticket price will bring about 0.9% more connecting passengers, and a 1% increase of airport acceptance rate can bring about 0.35% more connecting passengers in the network, with all else equal. These findings are helpful for airlines to understand the effects of changing their services, and also useful for us to quantify the benefits of hub airport expansion projects.At the end of this paper, we give an example as an application to demonstrate how the developed demand model could be used to valuate passengers’ direct benefit from airport capacity expansion.