International tourism is highly dependent on air travel,which enhances destination countries’economic growth and living standards while causing environmental degradation.This study investigates the effect of air trav...International tourism is highly dependent on air travel,which enhances destination countries’economic growth and living standards while causing environmental degradation.This study investigates the effect of air travel on environmental degradation in BRICS nations.The study used feasible generalized least squares(FGLS)to evaluate the environmental Kuznets curve using data spanning 1995 to 2018.The study finds evidence of N-shaped EKC in the economies of the BRICS nations.We also find a positive relationship between tourism,urbanization,and environmental degradation(as measured by CO_(2) and SO_(2) emissions from civil aviation)and a negative relationship between economic development and environmental degradation.To achieve sustainable growth and environmental protection and promote green technology,the BRICS governments should devise policies that address the aviation industry’s short-and long-term needs.展开更多
Since its outbreak in December 2019 in Wuhan Province (China), the Coronavirus (COVID-19) disease quickly spread around the world in such a way that most response plans were outdated. There was an urgent need to chang...Since its outbreak in December 2019 in Wuhan Province (China), the Coronavirus (COVID-19) disease quickly spread around the world in such a way that most response plans were outdated. There was an urgent need to change and adapt response strategies as the virus globally spread. Entire firms and economies were brought to a standstill in order to reduce the virus’ capacity to spread and to limit some of the short-term impacts in order to save time and find out solutions to come back to a more or less normal way of life. Thus, most of the countries that closed their air, sea and land borders had to reopen them progressively, with travel restrictions submitted to rigid controls. In Côte d’Ivoire, as in all other countries, air travellers leaving the territory were required to provide a certificate for a negative COVID-19 test, valid for 24 to 72 hours depending on the country of destination. However, the national system implemented could not provide a result before 48 hours. The objective of this work was to develop an alternative strategy to the system for air travellers who were in a hurry and those who had a computer bug in obtaining their result. A total of 38,444 air travellers benefited from this strategy implemented by the Institut Pasteur de Côte d’Ivoire during these two years.展开更多
Demand forecasting is often difficult due to the unobservability of the applicable historical demand series. In this study, the authors propose a demand forecasting method based on stochastic frontier analysis(SFA) mo...Demand forecasting is often difficult due to the unobservability of the applicable historical demand series. In this study, the authors propose a demand forecasting method based on stochastic frontier analysis(SFA) models and a model average technique. First, considering model uncertainty,a set of alternative SFA models with various combinations of explanatory variables and distribution assumptions are constructed to estimate demands. Second, an average estimate from the estimated demand values is obtained using a model average technique. Finally, future demand forecasts are achieved, with the average estimates used as historical observations. An empirical application of air travel demand forecasting is implemented. The results of a forecasting performance comparison show that in addition to its ability to estimate demand, the proposed method outperforms other common methods in terms of forecasting passenger traffic.展开更多
Taking the input and reflected waves into account,the relationship between the acoustic impedance at the end and the input of a system were theoretically analyzed.Closed and open acoustic configurations that influence...Taking the input and reflected waves into account,the relationship between the acoustic impedance at the end and the input of a system were theoretically analyzed.Closed and open acoustic configurations that influence the pressure,volumetric velocity,impedance and acoustic work were compared in detail.Based on the above investigation,an open-air traveling-wave thermoacoustic generator was designed and fabricated.It is composed of a looped tube,a resonator open at one end,a regenerator,and hot and cold heat exchangers.It is a small scale and simple configuration.The resonant frequency is 74 Hz at 1 bar in air.The maximum acoustic pressures at the open end and 0.5 m far away from the open end are 133.4 dB and 101 dB from a reference value of 20μPa when the heating power was 210 W,respectively.Acoustic pressure is reasonable for practical application as a low-frequency acoustic source.In further work,we believe that the acoustic pressure at the open end can achieve 150 dB,which could be a solution to problems in existing acoustic generators.These problems include low acoustic pressure and system complexity.It can be used as a basic acoustic source for low frequency and long-range noise experiments,and as a supply for high acoustic pressures necessary for industrial sources.展开更多
A growing number of international studies have highlighted that ambient air pollution exposures are related to different health outcomes. To do so, researchers need to estimate exposure levels to air pollution through...A growing number of international studies have highlighted that ambient air pollution exposures are related to different health outcomes. To do so, researchers need to estimate exposure levels to air pollution throughout everyday life. In the literature, the most commonly used estimate is based on home address only or taking into account, in addition, the work address. However, several studies have shown the importance of daily mobility in the estimate of exposure to air pollutants. In this context, we developed an R procedure that estimates individual exposures combining home addresses, several important places, and itineraries of the principal mobility during a week. It supplies researchers a useful tool to calculate individual daily exposition to air pollutants weighting by the time spent at each of the most frequented locations (work, shopping, residential address, etc.) and while commuting. This task requires the efficient calculation of travel time matrices or the examination of multimodal transport routes. This procedure is freely available from the Equit’Area project website: (https://www.equitarea.org). This procedure is structured in three parts: the first part is to create a network, the second allows to estimate main itineraries of the daily mobility and the last one tries to reconstitute the level of air pollution exposure. One main advantage of the tool is that the procedure can be used with different spatial scales and for any air pollutant.展开更多
The back-propagation neural network ( BPN ) is used to explore what the most influential variables are to drive business and leisure air passenger travel from Japan to Taiwan.The variables are systematically identifie...The back-propagation neural network ( BPN ) is used to explore what the most influential variables are to drive business and leisure air passenger travel from Japan to Taiwan.The variables are systematically identified , evaluated and analyzed in detail.The results reveal that some factors affect both leisure and business air passenger transport , and the others only affect one of them.Flights from Tokyo to Taipei and average hotel rate in Taiwan are the two most important factors for forecasting the demand of leisure air passenger transport , while variables related to business activities have more effect on the demand forecast of business air passenger transport.By using BPN , a forecasting model that considers actual market segments is established , and the results show that it is an accurate tool to forecast air transport demand.展开更多
This paper considers the problem of generating a flight trajectory for a single fixed-wing unmanned combat aerial vehicle （UCAV） performing an air-to-surface multi-target attack （A/SMTA） mission using satellite-gu...This paper considers the problem of generating a flight trajectory for a single fixed-wing unmanned combat aerial vehicle （UCAV） performing an air-to-surface multi-target attack （A/SMTA） mission using satellite-guided bombs. First, this problem is formulated as a variant of the traveling salesman problem （TSP）, called the dynamic-constrained TSP with neighborhoods （DCT- SPN）. Then, a hierarchical hybrid approach, which partitions the planning algorithm into a roadmap planning layer and an optimal control layer, is proposed to solve the DCTSPN. In the roadmap planning layer, a novel algorithm based on an updatable proba- bilistic roadmap （PRM） is presented, which operates by randomly sampling a finite set of vehicle states from continuous state space in order to reduce the complicated trajectory planning problem to planning on a finite directed graph. In the optimal control layer, a collision-free state-to-state trajectory planner based on the Gauss pseudospectral method is developed, which can generate both dynamically feasible and optimal flight trajectories. The entire process of solving a DCTSPN consists of two phases. First, in the offline preprocessing phase, the algorithm constructs a PRM, and then converts the original problem into a standard asymmet- ric TSP （ATSP）. Second, in the online querying phase, the costs of directed edges in PRM are updated first, and a fast heuristic searching algorithm is then used to solve the ATSP. Numerical experiments indicate that the algorithm proposed in this paper can generate both feasible and near-optimal solutions quickly for online purposes.展开更多
文摘International tourism is highly dependent on air travel,which enhances destination countries’economic growth and living standards while causing environmental degradation.This study investigates the effect of air travel on environmental degradation in BRICS nations.The study used feasible generalized least squares(FGLS)to evaluate the environmental Kuznets curve using data spanning 1995 to 2018.The study finds evidence of N-shaped EKC in the economies of the BRICS nations.We also find a positive relationship between tourism,urbanization,and environmental degradation(as measured by CO_(2) and SO_(2) emissions from civil aviation)and a negative relationship between economic development and environmental degradation.To achieve sustainable growth and environmental protection and promote green technology,the BRICS governments should devise policies that address the aviation industry’s short-and long-term needs.
文摘Since its outbreak in December 2019 in Wuhan Province (China), the Coronavirus (COVID-19) disease quickly spread around the world in such a way that most response plans were outdated. There was an urgent need to change and adapt response strategies as the virus globally spread. Entire firms and economies were brought to a standstill in order to reduce the virus’ capacity to spread and to limit some of the short-term impacts in order to save time and find out solutions to come back to a more or less normal way of life. Thus, most of the countries that closed their air, sea and land borders had to reopen them progressively, with travel restrictions submitted to rigid controls. In Côte d’Ivoire, as in all other countries, air travellers leaving the territory were required to provide a certificate for a negative COVID-19 test, valid for 24 to 72 hours depending on the country of destination. However, the national system implemented could not provide a result before 48 hours. The objective of this work was to develop an alternative strategy to the system for air travellers who were in a hurry and those who had a computer bug in obtaining their result. A total of 38,444 air travellers benefited from this strategy implemented by the Institut Pasteur de Côte d’Ivoire during these two years.
基金supported by the National Natural Science Foundation of China under Grant Nos.71522004,11471324 and 71631008a Grant from the Ministry of Education of China under Grant No.17YJC910011
文摘Demand forecasting is often difficult due to the unobservability of the applicable historical demand series. In this study, the authors propose a demand forecasting method based on stochastic frontier analysis(SFA) models and a model average technique. First, considering model uncertainty,a set of alternative SFA models with various combinations of explanatory variables and distribution assumptions are constructed to estimate demands. Second, an average estimate from the estimated demand values is obtained using a model average technique. Finally, future demand forecasts are achieved, with the average estimates used as historical observations. An empirical application of air travel demand forecasting is implemented. The results of a forecasting performance comparison show that in addition to its ability to estimate demand, the proposed method outperforms other common methods in terms of forecasting passenger traffic.
基金supported by the National Natural Science Foundation of China(50806081)
文摘Taking the input and reflected waves into account,the relationship between the acoustic impedance at the end and the input of a system were theoretically analyzed.Closed and open acoustic configurations that influence the pressure,volumetric velocity,impedance and acoustic work were compared in detail.Based on the above investigation,an open-air traveling-wave thermoacoustic generator was designed and fabricated.It is composed of a looped tube,a resonator open at one end,a regenerator,and hot and cold heat exchangers.It is a small scale and simple configuration.The resonant frequency is 74 Hz at 1 bar in air.The maximum acoustic pressures at the open end and 0.5 m far away from the open end are 133.4 dB and 101 dB from a reference value of 20μPa when the heating power was 210 W,respectively.Acoustic pressure is reasonable for practical application as a low-frequency acoustic source.In further work,we believe that the acoustic pressure at the open end can achieve 150 dB,which could be a solution to problems in existing acoustic generators.These problems include low acoustic pressure and system complexity.It can be used as a basic acoustic source for low frequency and long-range noise experiments,and as a supply for high acoustic pressures necessary for industrial sources.
文摘A growing number of international studies have highlighted that ambient air pollution exposures are related to different health outcomes. To do so, researchers need to estimate exposure levels to air pollution throughout everyday life. In the literature, the most commonly used estimate is based on home address only or taking into account, in addition, the work address. However, several studies have shown the importance of daily mobility in the estimate of exposure to air pollutants. In this context, we developed an R procedure that estimates individual exposures combining home addresses, several important places, and itineraries of the principal mobility during a week. It supplies researchers a useful tool to calculate individual daily exposition to air pollutants weighting by the time spent at each of the most frequented locations (work, shopping, residential address, etc.) and while commuting. This task requires the efficient calculation of travel time matrices or the examination of multimodal transport routes. This procedure is freely available from the Equit’Area project website: (https://www.equitarea.org). This procedure is structured in three parts: the first part is to create a network, the second allows to estimate main itineraries of the daily mobility and the last one tries to reconstitute the level of air pollution exposure. One main advantage of the tool is that the procedure can be used with different spatial scales and for any air pollutant.
文摘The back-propagation neural network ( BPN ) is used to explore what the most influential variables are to drive business and leisure air passenger travel from Japan to Taiwan.The variables are systematically identified , evaluated and analyzed in detail.The results reveal that some factors affect both leisure and business air passenger transport , and the others only affect one of them.Flights from Tokyo to Taipei and average hotel rate in Taiwan are the two most important factors for forecasting the demand of leisure air passenger transport , while variables related to business activities have more effect on the demand forecast of business air passenger transport.By using BPN , a forecasting model that considers actual market segments is established , and the results show that it is an accurate tool to forecast air transport demand.
文摘This paper considers the problem of generating a flight trajectory for a single fixed-wing unmanned combat aerial vehicle （UCAV） performing an air-to-surface multi-target attack （A/SMTA） mission using satellite-guided bombs. First, this problem is formulated as a variant of the traveling salesman problem （TSP）, called the dynamic-constrained TSP with neighborhoods （DCT- SPN）. Then, a hierarchical hybrid approach, which partitions the planning algorithm into a roadmap planning layer and an optimal control layer, is proposed to solve the DCTSPN. In the roadmap planning layer, a novel algorithm based on an updatable proba- bilistic roadmap （PRM） is presented, which operates by randomly sampling a finite set of vehicle states from continuous state space in order to reduce the complicated trajectory planning problem to planning on a finite directed graph. In the optimal control layer, a collision-free state-to-state trajectory planner based on the Gauss pseudospectral method is developed, which can generate both dynamically feasible and optimal flight trajectories. The entire process of solving a DCTSPN consists of two phases. First, in the offline preprocessing phase, the algorithm constructs a PRM, and then converts the original problem into a standard asymmet- ric TSP （ATSP）. Second, in the online querying phase, the costs of directed edges in PRM are updated first, and a fast heuristic searching algorithm is then used to solve the ATSP. Numerical experiments indicate that the algorithm proposed in this paper can generate both feasible and near-optimal solutions quickly for online purposes.
