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
为揭示船舶在追越过程中碰撞危险演化特征,提出一种基于情景反演的碰撞风险推理方法。基于追越事故案例中记录的船舶碰撞过程的动态信息,反演船舶追越过程中碰撞危险信息;引入负指数函数,结合船舶属性,通过最近会遇距离(Distance of Clo...为揭示船舶在追越过程中碰撞危险演化特征,提出一种基于情景反演的碰撞风险推理方法。基于追越事故案例中记录的船舶碰撞过程的动态信息,反演船舶追越过程中碰撞危险信息;引入负指数函数,结合船舶属性,通过最近会遇距离(Distance of Closest Point of Approach,d_(CPA))与两船到达最近会遇距离的时间(Time to Closest Point of Approach,t_(CPA))无因次化,确立船舶会遇的碰撞危险度(Collision Risk Index,I_(CR)),运用灰云推理模型,提出时间维度下追越两船的碰撞风险推理(Potential Collision Risk,P_(CR));结合多起案例反演数据,得出船舶追越过程中P_(CR)特征。结果表明:船舶追越依次经过碰撞危险、紧迫局面和紧迫危险等3个阶段,在时间节点上有一定稳定性特征,对应的P_(CR)均值分别为0.3491、0.5575和0.7771;船舶左舷追越的P_(CR)值略大于右舷追越;让路船的P_(CR)值感知也略大于直航船。基于情景反演的碰撞风险推理方法能反映会遇过程中两船实时的碰撞风险,为驾驶员实施精细化避碰行动提供有效理论支撑。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.
文摘为揭示船舶在追越过程中碰撞危险演化特征,提出一种基于情景反演的碰撞风险推理方法。基于追越事故案例中记录的船舶碰撞过程的动态信息,反演船舶追越过程中碰撞危险信息;引入负指数函数,结合船舶属性,通过最近会遇距离(Distance of Closest Point of Approach,d_(CPA))与两船到达最近会遇距离的时间(Time to Closest Point of Approach,t_(CPA))无因次化,确立船舶会遇的碰撞危险度(Collision Risk Index,I_(CR)),运用灰云推理模型,提出时间维度下追越两船的碰撞风险推理(Potential Collision Risk,P_(CR));结合多起案例反演数据,得出船舶追越过程中P_(CR)特征。结果表明:船舶追越依次经过碰撞危险、紧迫局面和紧迫危险等3个阶段,在时间节点上有一定稳定性特征,对应的P_(CR)均值分别为0.3491、0.5575和0.7771;船舶左舷追越的P_(CR)值略大于右舷追越;让路船的P_(CR)值感知也略大于直航船。基于情景反演的碰撞风险推理方法能反映会遇过程中两船实时的碰撞风险,为驾驶员实施精细化避碰行动提供有效理论支撑。
