Spoke airports,intentional and unintentional ground travel,and the air travel decision-making process

For air travelers originating from the spokes of the US hub-and-spoke air network, price, flight frequency, and aircraft type are all known factors in their travel decision-making process. Less well known, however, is the extent to which different elements of ground travel enter into these travelers’ air journeys. Based on 51 interviews at four universities at spokes surrounding O’Hare International Airport, this article describes how considerations such as vehicle availability, individual driving ability, localized weather, and unanticipated ground travel are fundamentally part of the air travel decision-making process for spoke travelers.     

Technical efficiency of automobiles – A nonparametric approach incorporating carbon dioxide emissions

We conduct an empirical analysis of the technical efficiency of cars sold 2010 in Germany. The analysis is performed using traditional data envelopment analysis (DEA) as well as directional distance functions (DDF). The approach of DDF allows incorporating the reduction of carbon dioxide emissions as an environmental goal in the efficiency analysis. A frontier separation approach is used to gain deeper insight for diesel and gasoline cars. Natural gas driven cars and sport utility vehicles are also treated as different groups. The results show that the efficiency measurement is statistically yet not economically significantly influenced by the incorporation of carbon dioxide emissions. Moreover, we find that natural gas driven cars are highly inefficient even if the reduction of emissions is accounted for in the analysis.     

Are we successful in reducing vehicle miles traveled in air quality nonattainment areas?

An important planning and policy question in the transportation, energy, and environment areas is whether or not air quality control and the associated funding preference and mitigation efforts to attain air quality conformity have indeed led to traveler behavior changes such as reduction in vehicle miles traveled (VMT) or VMT growth rates. In this research, we develop statistical models to analyze the relationship between air quality nonattainment designation and VMT between 1966 and 2004 based on observed data. These models employ different statistical methods, including hypothesis testing and simultaneous equations. Findings from these statistical models and datasets are consistent, and suggest there is a statistically significant negative correlation between nonattainment designation and VMT/VMT growth. For instance, the simultaneous equation model in this research, suggests that if a nonattainment area and an attainment area that are similar in all other aspects (population composition, socio-economics, urbanization, fuel price, vehicle stock, etc.) are compared, the VMT in the nonattainment area will be 1.80% less than that in the attainment area in the short run, and 7.61% less in the long run. While these results show strong statistical evidence that efforts in reducing VMT in nonattainment areas have been successful, future research should be conducted to attribute the VMT reduction effects to specific policy instruments for decision-making (e.g. the Congestion Management and Air Quality Improvement program, the conformity regulation in the transportation planning process, etc.).     

Rapid transit system simulation with interactive graphics display

A mathematical model of a rapid transit system has been developed. The model employs computer techniques to simulate the physical system. To further enhance the results and gain management confidence in the reliability and validity of the design of the model, a TV‐like display of the computer results enables the viewer to “see” the performance of the model as it happens. The results displayed thus include: The track layout, time (simulation), train position on the track, and the number of passengers riding on each train and waiting at each platform or station. The computer printout of results is limited to summary type data, relying on the display for detailed evaluation and analysis.     

A demand trend change early warning forecast model for the city of São Paulo multi-airport system

The need of accurate forecasts of air passenger numbers to assist managerial decision making for both short and long terms is well recognized and a central problem on both short and long term forecasting is how to handle future trend. The aim of this paper is to develop a demand trend change early warning forecast model (EWFM) for the city of São Paulo multi-airport system (SPMARs). For SPMARs the EWFM is based on the combination of leading indicators and alarms against possible occurrence of changes on trend component of the monthly number of domestic air passengers. A topdown induction procedure is employed to identify leading indicators to provide an interpretable prediction procedure to support the development of scenarios for future demand trend. Results show that changes on such demand trend are mostly associated to changes on the economic activity and six different scenarios were built combining the identified leading indicators. The EWFM was employed to assist managerial decision making for both short and long terms in order to evaluate different alternatives to prevent congestion delay occurrences and to support infrastructure planning.     

解决国Ⅲ摩托车燃油箱气压平衡的技术探讨

增加了单向阀的燃油蒸发控制技术,解决了普通燃油蒸发控制技术中由于通气管折弯或积油、炭罐板结或堵塞等原因导致的燃油箱内气压不平衡、供油不畅的问题。     

美国气垫登陆艇的技术发展及分析

基于美国气垫登陆艇(LCAC)的研制实情及其最近的延寿计划(SLEP)和其未来替代者——舰岸连接器(SSC)的发展趋势,对LCAC的快速性等总体性能进行计算和分析,并追踪LCAC有关新技术在芬兰T-2000艇与韩国LSF-II艇上的应用情况。     

重型商用汽车发动机空气滤清器的研究应用

本文介绍了重型商用汽车空气滤清器的作用,油浴式空气滤清器和干式空气滤清器的结构、工作原理以及空气滤清器的选型依据。     

通过控制过量空气系数提高注汽锅炉热效率

通过理论分析及现场测试 ,分析了过量空气系数对注汽锅炉热效率的影响 ,得出了在注汽锅炉实际运行中应加强对过量空气系数的监控 ,使过量空气系数降低 ,从而提高注汽锅炉热效率的结论     

密实型沥青抗滑磨耗层的分析研究

选择目前工程中常用的AK型沥青混合料(代表密实型沥青混合料)作为研究对象。通过15条级配曲线,比较系统地分析研究了级配对AK16型沥青混合料的体积性能(空隙率)、表面特性(构造深度)和力学性能(动稳定度)的影响。试图通过分析研究探索级配组成对混合料性质的主要影响因素并寻求最佳的级配形式,以指导实际沥青路面工程的材料设计。