严寒地区高速铁路混凝土基床聚氨酯保温特性试验研究

基于严寒区京沈客专朝阳试验段路基基床的温度监测资料分析,研究不同厚度聚氨酯保温板对高速铁路路基混凝土基床温度变化特性影响.测试结果表明:①铺设聚氨酯保温板能够有效阻断严寒区环境与路基基床间的热量传递,保温效果与板厚相关;②地温大多数时间呈阳高阴低现象,同时阴、阳坡路基温差波动幅度随埋深逐渐减小;③基床表层阴、阳面各测点的温度变化起始时间一致,而阴面的冻结时间比阳面晚一个月.由此表明,保温板能够有效降低环境与混凝土道床之间的热交换,但是对路基阴、阳坡的影响存在差异.建议在严寒地区高速铁路路基阳、阴坡可以采取不同厚度的聚氨酯保温板,减小阴阳坡地温差异,保持季冻土路基温度变化稳定.     

基于动态冲击试验的通勤类飞机座椅符合性验证技术

国产某型民用通勤类飞机为了取得欧洲航空安全局(EASA)型号合格证,机上座椅需进行设计更改并补充进行应急着陆情况下的动态要求符合性验证.通过对适航条款及相应标准的解读,研究了基于动态试验的航空座椅动态要求适航验证技术,其主要包括座椅动态性能基本要求、试验构型及工况筛选、试验规划、合格判据和试验结果分析等内容.结果表明,该型机旅客座椅满足适航规章对座椅的动态性能要求.该项旅客座椅动态性能试验的成功为型号取得EASA型号合格证奠定了良好的基础,该型飞机也即将成为第一个取得欧洲型号合格证的国产飞机.     

Quantifying the impact of the COVID-19 pandemic on US airline stock prices

This paper uses data at the trading day frequency and the method of local projections to quantify the dynamic responses of U.S. airline stock prices to a COVID-19 shock. We show that airline stock prices decline immediately by 0.1 percentage point in response to a 1% COVID-19 shock. In addition, the effect of the shock persists beyond the day on which it occurs, with most airline stock prices falling by as much as 0.6 percentage points after fifteen days. This negative response of airline stock prices to a COVID-19 shock is not explained by a COVID-19-induced increase in airlines’ variable costs, but rather by a COVID-19-induced decrease in air travel, which, in turn decreases revenues, profitability, and stock prices of U.S. airlines.     

Influential factors on Chinese airlines’ profitability and forecasting methods

We establish profit models to predict the performance of airlines in the short term using the quarterly profit data collected on the three largest airlines in China together with additional recent historical data on external influencing factors. In particular, we propose the application of the LASSO estimation method to this problem and we compare its performance with a suite of other more modern state-of-the-art approaches including ridge regression, support vector regression, tree regression and neural networks. It is shown that LASSO generally outperforms the other approaches in this study. We concluded a number of findings on the oil price and other influential factors on Chinese airline profitability.     

铁路运输客货管理机制的探讨

随着我国加入WTO和铁路全面参与运输市场竞争,必须尽快构建适应市场需求的铁路客货管理的动力机制和运作机制,以激发企业和员工搞好营销的内在活力,同时要构建铁路客运和货运的服务质量评价指标,以及相应的质量监督和考核管理办法,做到各项管理活而不乱、管而不死,使铁路客货运输服务质量不断提高,以满足不断增长的经济和社会发展需要。     

新财务清算政策下提高铁路城际列车效益的思考

近年来,铁路短途城际客运得到了很大的发展,开行城际列车已成为铁路运输企业新的经济增长点。新财务清算政策实施后,开行城际列车的效益受到一定程度的影响,针对存在的问题,就如何提高其效益水平进行了讨论。提出了完善开行结构、增加营业收入、减少客运付费、降低成本支出等建议措施。     

基于灰色系统理论的旅游客源预测模型--以中国入境旅游客源为例

本文基于灰色系统理论,以中国1978年以来入境客源为例,建构了旅游客源预测的灰色模型,并与常用的线性模型的预测精度进行了定量对比。所得基本结论为:①旅游系统是灰色系统,灰色系统理论是研究旅游现象的有力工具;②中国入境客源灰色GM(1,1)模型的预测精度高于线性模型;③就灰色预测而言,如果原始数据列较长(例如21年),对原始数据进行平滑处理所得预测模型精度较高,而对原始数据进行取自然对数的处理所得模型预测精度较低;如果原始数据列较短(例如5年),对原始数据进行取自然对数的预处理所得模型预测精度较高。本文所得结论对其他旅游序列预测应该具有一定的借鉴与参考价值。     

Ratio-based design hour determination for airport passenger terminal facilities

To avoid both over-design and under-sizing of airport passenger terminal facilities such as security checkpoints, the infrastructure is designed for a specifically determined design load. As such, the design load is considered for a short period of time, usually an hour of operation, during which peak, though not necessarily maximum, demand occurs. For strategic planning applications, future design loads can be determined by either fictitious flight schedules or ratio-based models which forecast the relationship between design load and annual demand. This study presents two ratio-based methods which allow the direct determination of design hour loads (DHL) for passenger terminal facilities. The unsaturated DHL model considers the relationship between observed passenger flows in the terminal and aggregated annual demand data. The saturated DHL model includes several operational constraints which limit the actual DHL, such as limitations in the runway system or the fleet mix operating at an airport. Both models are applied to two real-world airports, for which the DHL of the security checkpoint facilities is estimated from large datasets covering multiple years. Results are significant at the 5 % level and suggest that the proposed ratio-based methods are appropriate for airport strategic planning applications.     

Identifying airline cost economies: An econometric analysis of the factors affecting aircraft operating costs

This paper provides the results of an econometric analysis of the influences of airline characteristics on the average operating costs per aircraft movement. The analysis combines a comprehensive selection of airline-output variables, airline-fleet variables, and airline-market variables. The results confirm the existence of economies of density, economies of load factor, economies of aircraft utilisation and economies of aircraft size. The paper does not provide evidence of economies of scale, economies of stage length or economies of fleet commonality. Furthermore, airlines that additionally operate full freighters, airlines that are members of a worldwide alliance and airlines that operate a multi-hub system face higher average operating costs per aircraft movement. Surprisingly, the regression results demonstrate that airlines that use newer aircraft have higher average operating costs per aircraft movement, suggesting that ownership costs (depreciation and leasing costs) of new aircraft outweigh the increasing maintenance costs of old aircraft. Finally, the results show that airlines that have a dominant position at their hubs or bases have higher operating costs per aircraft movement, implying that the absence of serious competitive pressure enables airlines to charge higher ticket prices and, with that, leads to a limited focus on cost savings.