In this paper,a new method to calculate collision risk of air-routes,based on variable nominal separation,is proposed. The collision risk model of air-routes,based on the time variable and initial time interval variab...In this paper,a new method to calculate collision risk of air-routes,based on variable nominal separation,is proposed. The collision risk model of air-routes,based on the time variable and initial time interval variable,is given. Because the distance and the collision probability vary with time when the nominal relative speed between aircraft is not zero for a fixed initial time interval,the distance,the variable nominal separation,and the collision probability at any time can be expressed as functions of time and initial time interval. By the probabilistic theory,a model for calculating collision risk is acquired based on initial time interval distribution,flow rates,and the proportion of aircraft type. From the results of calculations,the collision risk can be characterized by the model when the nominal separation changes with time. As well the roles of parameters can be shown more readily.展开更多
There are standard procedures for collecting data on numbers of birds at sites being proposed for wind farm development and evaluating collision risk for each key species. However, methods do not work well for all spe...There are standard procedures for collecting data on numbers of birds at sites being proposed for wind farm development and evaluating collision risk for each key species. However, methods do not work well for all species. Where a local bird population is depleted, empirical data cannot provide estimates of likely collision mortality numbers if that population returns to satisfactory conservation status. Field survey methods are also inadequate for cryptic bird species. Both these problems can be important for evaluation of impacts of proposed wind farms on bird populations protected by the EU Birds Directive. We present an alternative method, based on energy constrained activity budgets and natural history, which permits assessment of likely collision numbers where empirical data are inadequate. Two case studies are presented where this approach has been successfully used to resolve disputed planning applications, one for a hen harrier population where numbers present are much below the population size at designation, and one for a cryptic species (greenshank). Our novel method helps reduce uncertainty in assessments constrained by difficulties in collecting suitable empirical data.展开更多
Advanced driver-assistance systems(ADASs),such as forward collision warning(FCW),are widely used and,in some countries,have been made mandatory for commercial vehicles.In practical applications,however,FCW systems pro...Advanced driver-assistance systems(ADASs),such as forward collision warning(FCW),are widely used and,in some countries,have been made mandatory for commercial vehicles.In practical applications,however,FCW systems produce many false alarms.Using scenario and driving behavior data collected from naturalistic driving study data of trucks,a variable threshold evaluation method was proposed to determine the factors correlating with false alarms.A total of 450 collision avoidance events were divided based on driving character-istics into three groups with k-means clustering.Responsibility-sensitive safety(RSS)mod-el’s parameters were calibrated with the driving behavior characteristics and scenarios to evaluate the truck FCW system’s alarm accuracy.The evaluation of the results of truck FCW system based on RSS model found 47 false alarm alarms in the 450 events,a false alarm rate of 11.19%.When the following distance was close(<7 m)or far(>20 m),the false alarm rate reached more than 30%.The minimum time to collision(TTC)in the close distance driving clusters(DCs)(5.81 s)was lower than that in long distance DCs(7.68 s and 9.46 s).Braking force in the low-speed DCs(deceleration at0.16 g and0.55 g)was lower than in high-speeded DC(deceleration=1.21 g).The FCW system does not conform to the driver’s reaction time and braking characteristics in different scenarios,and is the main reason for false alarms.This is more obviously reflected in low-speed short distance and high-speed long-distance scenarios.展开更多
基金The National Natural Science Foundations(Nos. 60776813 and 60979018)the National Air Traffic Management Research Program ( GKG200802015)the NUAA Research Funding (NS2010184)
文摘In this paper,a new method to calculate collision risk of air-routes,based on variable nominal separation,is proposed. The collision risk model of air-routes,based on the time variable and initial time interval variable,is given. Because the distance and the collision probability vary with time when the nominal relative speed between aircraft is not zero for a fixed initial time interval,the distance,the variable nominal separation,and the collision probability at any time can be expressed as functions of time and initial time interval. By the probabilistic theory,a model for calculating collision risk is acquired based on initial time interval distribution,flow rates,and the proportion of aircraft type. From the results of calculations,the collision risk can be characterized by the model when the nominal separation changes with time. As well the roles of parameters can be shown more readily.
文摘There are standard procedures for collecting data on numbers of birds at sites being proposed for wind farm development and evaluating collision risk for each key species. However, methods do not work well for all species. Where a local bird population is depleted, empirical data cannot provide estimates of likely collision mortality numbers if that population returns to satisfactory conservation status. Field survey methods are also inadequate for cryptic bird species. Both these problems can be important for evaluation of impacts of proposed wind farms on bird populations protected by the EU Birds Directive. We present an alternative method, based on energy constrained activity budgets and natural history, which permits assessment of likely collision numbers where empirical data are inadequate. Two case studies are presented where this approach has been successfully used to resolve disputed planning applications, one for a hen harrier population where numbers present are much below the population size at designation, and one for a cryptic species (greenshank). Our novel method helps reduce uncertainty in assessments constrained by difficulties in collecting suitable empirical data.
基金sponsored by the National Key R&D Program of China(2018YFB0105202).
文摘Advanced driver-assistance systems(ADASs),such as forward collision warning(FCW),are widely used and,in some countries,have been made mandatory for commercial vehicles.In practical applications,however,FCW systems produce many false alarms.Using scenario and driving behavior data collected from naturalistic driving study data of trucks,a variable threshold evaluation method was proposed to determine the factors correlating with false alarms.A total of 450 collision avoidance events were divided based on driving character-istics into three groups with k-means clustering.Responsibility-sensitive safety(RSS)mod-el’s parameters were calibrated with the driving behavior characteristics and scenarios to evaluate the truck FCW system’s alarm accuracy.The evaluation of the results of truck FCW system based on RSS model found 47 false alarm alarms in the 450 events,a false alarm rate of 11.19%.When the following distance was close(<7 m)or far(>20 m),the false alarm rate reached more than 30%.The minimum time to collision(TTC)in the close distance driving clusters(DCs)(5.81 s)was lower than that in long distance DCs(7.68 s and 9.46 s).Braking force in the low-speed DCs(deceleration at0.16 g and0.55 g)was lower than in high-speeded DC(deceleration=1.21 g).The FCW system does not conform to the driver’s reaction time and braking characteristics in different scenarios,and is the main reason for false alarms.This is more obviously reflected in low-speed short distance and high-speed long-distance scenarios.
