Can stable environmental protection officials’ tenure reduce illegal emissions?

Based on the day-night PM_2.5 difference of the nearest atmospheric monitoring points to measure whether there is illegal emission, this paper explores the impact of environmental protection officials' tenure (EPLT) on illegal emissions. The results show that there is a positive correlation between EPLT and illegal emissions. Stable EPLT can reduce illegal emissions by increasing environmental information disclosure and environmental subsidies. It can increase illegal emissions by weakening public pollution reporting and media supervision, environmental law enforcement and promoting corruption. In addition, EPLT can increase illegal emissions as EPLT is less than 3.55 years, while EPLT can increase illegal emissions as EPLT exceeds 6.21 years. Further, when mayor's tenure and EPLT are both stable, the promotion effect of EPLT on illegal emission is stronger. Stable company director's tenure can also aggravate the promotion effect of EPLT on illegal emissions.     

美国空军卫星控制网的现状与发展趋势

近几年的几场局部战争部分表明了现代军事航天系统的重要性。本文主要介绍了美国最重要的一个军事航天测控网－－空军卫星控制网的情况，希望能对了解美国军事航天测控体制有所帮助。     

Modeling air flow in sanitary sewer systems: A review

Current designs of sanitary collection systems normally only consider the transport of wastewater without attention on the air movement in the sewer airspaces. Under anaerobic conditions, hydrogen sulfide (H₂S) can be generated in the liquid phase in sewer systems. H₂S is corrosive to concrete and steel structures and odorous or even toxic to human, which can cause corrosion and sewer odor issues. To develop a feasible sewer corrosion and odor control strategy, it is necessary to understand the mechanisms of air flow in sewer systems for developing practical tools to predict and control the air flow. This paper comprehensively reviewed previous efforts on modeling the air flow in sewer systems and provided recommendations on predicting the air flow for engineering applications. The air flow in a single pipe was firstly reviewed followed by the air flow in sewer structures as well as air flow models in sewer networks. Some other considerations such as temperature driven flow, transient water flow, and wind effect were also reviewed. The knowledge gaps were then identified, and recommendations on the further studies were provided.     

羰基合成法制取高纯纳米氧化铁工艺研究

纳米氧化铁是近年来研发的新型纳米材料,它具有良好的光学、磁性、催化性能,在涂料、磁性材料、医学磁介质和催化等方面有广泛的应用前景,采用传统技术生产的纳米氧化铁因其粒度分布宽,纯度低等问题无法用于生物医药等高端领域,本文通过实验的方法介绍了一种新型高纯纳米氧化铁生产技术,可为高纯纳米氧化铁的研究和生产提供参考。     

A SWOT analysis of China's air cargo sector in the context of COVID-19 pandemic

This paper discusses the situation of China's air cargo sector facing the COVID-19 pandemic. Based on the expectation that it can go out of recession more easily than China's air passenger sector, this paper analyzes four aspects that are favorable and unfavorable for its further development: (1) strengths (China's sustainable economic basis and proliferating cargo suppliers), (2) weaknesses (insufficient cargo capacity and less business internationalization), (3) opportunities (top authority support, rising e-commerce demand, and new technological momentum), and (4) challenges (uncertain trade environment and increasing profitability pressure). Then this paper suggests strategies for China's air cargo suppliers to adapt to the pandemic.     

Impact of Continuous Climb Operations in ATC workload. Case-study Palma airport

This research assesses the impact of the integration of Continuous Climb operations (CCOs) on Air Traffic Control (ATC) workload. The methodology encompasses different modules: CCO, standard departing and arriving trajectories extracted from an external database, an ad-hoc algorithm for detecting and solving conflicts, and an ATC-workload model with the inclusion of CCO-task modifications. Monte Carlo simulations evaluates different combinations of these modules. Then, a sensitivity analysis is performed to evaluate two parameters: the impact of the calibration of the maximum ATC workload and the percentage increase of the CCO tasks on the ATC workload. The methodology is applied to a case study at Palma airport in Spain. Extensive numerical simulations are executed based on the integration of CCOs into the system from 0% to 100%. The integration of CCOs implies the increase of the ATC workload in the Control Tower (TWR) and the reduction in the Approach Control Centre (APP). The sensitivity analysis shows that the decrease in the increase of CCO-task workload barely affects the number of CCOs that can be operated without exceeding the workload limits. Conversely, the reduction of the ATC workload calibration allows the integration of CCOs around 50% in the case of 90% TWR calibration and up to 100% in the case of 80%.     

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.     

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.