Most of the traditional taxi path planning studies assume that the aircraft is in uniform speed,and the optimization goal is the shortest taxi time.Although it is easy to solve,it does not consider the changes in the ...Most of the traditional taxi path planning studies assume that the aircraft is in uniform speed,and the optimization goal is the shortest taxi time.Although it is easy to solve,it does not consider the changes in the speed profile of the aircraft when turning,and the shortest taxi time does not necessarily bring the best taxi fuel consumption.In this paper,the number of turns is considered,and the improved A*algorithm is used to obtain the P static paths with the shortest sum of the straight-line distance and the turning distance of the aircraft as the feasible taxi paths.By balancing taxi time and fuel consumption,a set of Pareto optimal speed profiles are generated for each preselected path to predict the 4-D trajectory of the aircraft.Based on the 4-D trajectory prediction results,the conflict by the occupied time window in the taxiing area is detected.For the conflict aircraft,based on the priority comparison,the waiting or changing path is selected to solve the taxiing conflict.Finally,the conflict free aircraft taxiing path is generated and the area occupation time window on the path is updated.The experimental results show that the total taxi distance and turn time of the aircraft are reduced,and the fuel consumption is reduced.The proposed method has high practical application value and is expected to be applied in real-time air traffic control decision-making in the future.展开更多
From the point of view of urban consumption behavior, urban fresh water consumption could be classified as three types, namely, direct, indirect and induced water consumption. A calculation approach of urban flesh wat...From the point of view of urban consumption behavior, urban fresh water consumption could be classified as three types, namely, direct, indirect and induced water consumption. A calculation approach of urban flesh water consumption was presented based on the theory of urban basic material consumption and the input-output method, which was utilized to calculate urban fresh water consumption of China, and to analyze its structural change and causes. The results show that the total urban flesh water consumption increased 561.7× 10^9m^3, and the proportion to the total national flesh water resources increased by 20 percentage points from 1952 to 2005. The proportion of direct and induced water consumption had been continuously rising, and it increased by 15 and 35 percentage points separately from 1952 to 2005, while the proportion of indirect water consumption decreased by 50 percentage points. Urban indi- rect water consumption was mainly related to urban grain, beef and mutton consumption, and urban induced water consumption had a close relationship with the amount of carbon emission per capita. Finally, some countermeasures were put forward to realize sustainable utilization of urban fresh water resources in China.展开更多
Recreation and beach use constitute core aspects of coastal tourism development since they incorporate various stakeholders at different levels and diverse activities. This research investigates the economical recreat...Recreation and beach use constitute core aspects of coastal tourism development since they incorporate various stakeholders at different levels and diverse activities. This research investigates the economical recreational value of the coastal zone between Molos and Arkitsa, in prefecture of Fthiotida, in Sterea Ellada region, in Greece. The study area provides substantial benefits to host community and remains an advantageous natural setting for tourism sustainable development. An economic valuation of the benefits largely assists the efforts of the local authorities to establish viable tourism products and preferred destination attributes. The travel cost method was used to estimate recreation demand. Based on personal and on site interviews 1,433 questionnaires were collected. The consumer surplus per day enjoyed by the visitors is 22,352.28 （Euros）. The analysis assigned a considerable value to the coastal zone. Results shed light on core issues such as environmental management and proper resource allocation in view of finding areas for further improvement so as to increase consumer surplus by satisfying the needs and wants of coastal visitors.展开更多
基金supported by the National Key R&D Project(No.2020YFB1600101)National Natural Science Foundations of China(Nos.U1833103,71801215)Civil Aviation Flight Wide Area Surveillance and Safety Control Technology Key Laboratory Open Fund(No.202008)。
文摘Most of the traditional taxi path planning studies assume that the aircraft is in uniform speed,and the optimization goal is the shortest taxi time.Although it is easy to solve,it does not consider the changes in the speed profile of the aircraft when turning,and the shortest taxi time does not necessarily bring the best taxi fuel consumption.In this paper,the number of turns is considered,and the improved A*algorithm is used to obtain the P static paths with the shortest sum of the straight-line distance and the turning distance of the aircraft as the feasible taxi paths.By balancing taxi time and fuel consumption,a set of Pareto optimal speed profiles are generated for each preselected path to predict the 4-D trajectory of the aircraft.Based on the 4-D trajectory prediction results,the conflict by the occupied time window in the taxiing area is detected.For the conflict aircraft,based on the priority comparison,the waiting or changing path is selected to solve the taxiing conflict.Finally,the conflict free aircraft taxiing path is generated and the area occupation time window on the path is updated.The experimental results show that the total taxi distance and turn time of the aircraft are reduced,and the fuel consumption is reduced.The proposed method has high practical application value and is expected to be applied in real-time air traffic control decision-making in the future.
基金Under the auspices of Key Project of National Natural Science Foundation of China (No. 40535026)
文摘From the point of view of urban consumption behavior, urban fresh water consumption could be classified as three types, namely, direct, indirect and induced water consumption. A calculation approach of urban flesh water consumption was presented based on the theory of urban basic material consumption and the input-output method, which was utilized to calculate urban fresh water consumption of China, and to analyze its structural change and causes. The results show that the total urban flesh water consumption increased 561.7× 10^9m^3, and the proportion to the total national flesh water resources increased by 20 percentage points from 1952 to 2005. The proportion of direct and induced water consumption had been continuously rising, and it increased by 15 and 35 percentage points separately from 1952 to 2005, while the proportion of indirect water consumption decreased by 50 percentage points. Urban indi- rect water consumption was mainly related to urban grain, beef and mutton consumption, and urban induced water consumption had a close relationship with the amount of carbon emission per capita. Finally, some countermeasures were put forward to realize sustainable utilization of urban fresh water resources in China.
文摘Recreation and beach use constitute core aspects of coastal tourism development since they incorporate various stakeholders at different levels and diverse activities. This research investigates the economical recreational value of the coastal zone between Molos and Arkitsa, in prefecture of Fthiotida, in Sterea Ellada region, in Greece. The study area provides substantial benefits to host community and remains an advantageous natural setting for tourism sustainable development. An economic valuation of the benefits largely assists the efforts of the local authorities to establish viable tourism products and preferred destination attributes. The travel cost method was used to estimate recreation demand. Based on personal and on site interviews 1,433 questionnaires were collected. The consumer surplus per day enjoyed by the visitors is 22,352.28 （Euros）. The analysis assigned a considerable value to the coastal zone. Results shed light on core issues such as environmental management and proper resource allocation in view of finding areas for further improvement so as to increase consumer surplus by satisfying the needs and wants of coastal visitors.
