Considering the nuclear option: Hidden benefits and social costs of nuclear power in the U.S. since 1970

Although burning fossil fuels has environmental consequences, many countries have switched away from nuclear power in favor of fossil-fuel fired electricity production after incidents at Three Mile Island, Chernobyl, and Fukushima. This study estimates the substitution between nuclear and fossil-fuel fired electricity generation in the United States. Using an event-study framework, we leverage nuclear plant openings from 1970 to 1995 and forced nuclear plant outages from 1999 to 2014. Plant openings (nuclear outages) reduce (increase) monthly net coal-fired generation by approximately 200 GWh, implying a considerable reduction (increase) in emissions. We find that the substitution between nuclear and coal is not one-to-one, as has been assumed in prior literature. After establishing these stylized facts, we explore the potential underlying forces driving the observed substitution between coal and nuclear.     

Collaborative delay management towards demand-capacity balancing within User Driven Prioritisation Process

The concept of User Driven Prioritisation Process (UDPP) was introduced to give Airspace Users (AUs) more flexibility under demand-capacity imbalance. This paper presents two UDPP-DCB models, built on the UDPP principle, using the Selective Flight Protection (SFP) approach to minimize the total delay cost. AUs are enabled to adapt their operations in a more cost-efficient way in the presence of capacity constraints in airspace, optimizing their flights to keep the priorities track. Then, ATFM integrates the AUs’ decision to reassign the time slots and the preferred rerouting trajectories. Results suggest that the delay cost for AUs can be largely reduced through applying the UDPP-DCB models proposed in this paper, while allowing rerouting proves effective in reducing the system delay cost.     

学前儿童平板电脑导航按钮交互设计评价研究

学前儿童平板电脑导航按钮交互设计评价指标的建立,有利于交互设计在学前儿童平板电脑中的优化和改良.从学前儿童体验视角出发,创建平板电脑导航按钮交互设计的多维度多层次评价指标,该方法以创建多维度多层次评价指标为基础,根据D-S证据理论设计评价指标的决策矩阵,利用层次分析法确定评价指标权重.最后以优学派儿童平板电脑"童话故事"界面导航按钮8个优化设计方案对比分析与评价为例,验证了所提出方法的合理性与有效性.     

Analyzing passenger behavior in airport terminals based on activity preferences

Airport terminals are facilities that provide a variety of activities related to both the preparation of the passengers for their air trip (aeronautical) and their free time inside the terminal (non-aeronautical). In the last years, the number of non-aeronautical activities has substantially increased and significantly diversified both before and after the security checkpoint. The established role of non-aeronautical activities forces planners and managers to better understand passenger behavior. The potential of discrete choice models for the exploration of passenger behavior is analyzed in this paper. For the demonstration of the methodology, Lisbon Humberto Delgado International airport is used as a case study. Data is collected through a revealed and stated preference survey inside the terminal at the area before the security checkpoint. Activity-choice models are developed to identify the factors that affect the choices of the passengers over the area where they conduct non-aeronautical activities. Forecasts show that when increasing the percentage of passengers who conduct the check-in online and have planned their activities before arriving at the airport, the passengers’ preferences to conduct non-aeronautical activities only after the security checkpoint increase. This paper shows the contribution of developing discrete choice models in the better comprehension of passenger decisions over the activities they perform in an airport terminal.     

COVID-19, commuting flows,and air quality

Fossil-fuel burning transportation methods significantly contribute to air pollution. During the COVID-19 pandemic, South Korea experienced a 10-20% decline in commuting flows, even without government-mandated stay-at-home orders. This paper quantifies the impact that decreased commuting flows have on PM_2.5, PM₁₀, NO₂, CO, and SO₂, using municipality level commuting data. We find that a 1% decrease in commuting flows decreases air pollutants by 0.08-0.17%, after controlling for seasonality and time-varying local production. The effect was higher in regions with high initial pollution, and people recognized air quality improvements. These results emphasize the importance of encouraging cleaner transportation methods after the pandemic.     

Study of emerging air taxi network operation using discrete-event systems simulation approach

This research focuses on understanding the air taxi operations to determine the number of air taxis required to fulfill the demand for urban air mobility in New York City (NYC). We leverage the Define, Measure, Analyze, Design, and Verify (DMADV) framework and integrate it with the systems simulation approach. Upon investigation, we find that all the parameters linearly impact the vehicle utilization, while other measures are robust, specifically with respect to the seating capacity. It is also recommended to operate initially with 70 air taxis in NYC to achieve a trade-off between customer wait time and vehicle utilization. The proposed approach can act as a recommender system for air taxi companies.     

省直管县改革与区域空气污染——来自卫星反演数据的实证证据

从政府治理结构改革的角度探讨如何推进环境污染治理是一种有益的尝试。从理论上来说,省直管县改革作为一种重要的政府治理结构改革,能够通过简化政府治理级次来改变政府治理效率,影响诸如环保等公共产品和服务的供给。本文采用卫星反演的PM2.5数据检验了省直管县改革前后县级区域空气污染的变动趋势。发现“财政省直管县”改革能显著降低地区空气污染水平,“强县扩权”改革则显著加剧了地区空气污染。稳健性检验、进一步的分析结果均支持上述结论。机制检验发现,“财政省直管县”主要体现为财力保障水平提升导致的治理变化,而“强县扩权”则主要体现为地方政府竞争行为改变导致的空气污染治理变化。总之,单纯的政府级次减少可能并不必然利于地方公共服务的提供,良好的财力保障为地方污染治理服务提供了支撑,竞争行为变化带来的改革效应则会受到政府对环境污染重视程度的显著影响。     

The economics and geography of regional airline services in six countries

Do the determinants of service and pricing on “regional” routes – linking towns and smaller cities to main trunk routes and/or to each other – differ from the established results from the literature? We study all flights (about 3000) on all regional routes (about 250) with scheduled airline service from one of about 130 regional towns or cities, in regional airline markets in six countries: Australia, Canada, New Zealand, Norway, Sweden, and a sample of three U.S. states which closely resemble the other regions studied. For each flight we have observations on up to five prices offered at different times before flight date. We also have equipment type and social-economic data. Overall, our results give qualified support to the standard gravity model of the extent of service between city pairs, though with two interesting differences: operators on regional routes have greater flexibility in the size of aircraft they can deploy, which results in a finer-grained variability of service offerings and, the presence of competition on regional routes has a large effect on the total supply of seats. We are able to successfully estimate a well-specified airfare model, which shows strong effects of competition on prices, quite substantial intertemporal price discrimination, and interesting differences between regional and main trunk route pricing.     

The fortunes of air transport gateways

The paper explores the idea that the fortunes of some gateway cities are changing as airlines use modern aircraft to respond to new market opportunities. It uses data on inter-city journeys between Australia and Asia to identify a hierarchy of gateway cities, and then shows how the connections between them has changed over the 2000–2013 period. Results show that secondary, and smaller, gateways in both Australia and Asia have played more important roles in passenger movements over this time. In Melbourne in particular, stronger growth in the demand for international travel in that city along with more use made of the smaller long-haul aircraft by airlines, has strengthened its role as a gateway city relative to Sydney. These results confirm that the geography of inter-continental air networks are changing which may have important implications for the air transport roles of some cities in the immediate future.     

Air express network design based on express path choices – Chinese case study

Due to the shortage of cargo aircraft, Chinese express companies have to provide transportation services with a hybrid method that consists of “rented bellies and self-owned cargo aircraft”. Because the bellies are rented from air passenger companies and because the cargo aircraft are owned by the express companies, it is important for the express companies to use their cargo aircraft as effectively as possible. This paper constructs a bi-level model to optimize the flight transportation network of an express company. The upper model designs the network and allocates the transportation capacity with the objective of minimizing the total transportation cost, and the lower model calculates the link flows in user equilibrium. Data from ShunFeng (SF) Express Company (China) are used to conduct the case study. Using the model outputs, the flows on links and at nodes are analyzed to illustrate the transportation and transshipment situations.