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John F Shortle - One of the best experts on this subject based on the ideXlab platform.

  • rare event simulation for Potential Wake encounters
    Winter Simulation Conference, 2017
    Co-Authors: Azin Zarenoghabi, John F Shortle
    Abstract:

    A flying aircraft produces two coherent rotating vortices of air in its trail. If another aircraft flies into one of these vortices, it can experience an un-commanded roll. Because of the Potential risk, Wake separation standards exist to significantly reduce the probability of such events. Thus, Wake encounters are inherently rare. As new procedures and technologies are proposed to increase the capacity of the airspace, rare-event simulation is necessary to evaluate to the safety of proposed changes. This paper explores the performance of a rare-event splitting technique in the context of estimating probabilities of Potential Wake encounters. The goal is to identify good strategies for the splitting method while using a relatively simple model for the Wakes. Suggestions for the choice of the level function and the locations of levels are given.

  • WSC - Rare event simulation for Potential Wake encounters
    2017 Winter Simulation Conference (WSC), 2017
    Co-Authors: Azin Zare-noghabi, John F Shortle
    Abstract:

    A flying aircraft produces two coherent rotating vortices of air in its trail. If another aircraft flies into one of these vortices, it can experience an un-commanded roll. Because of the Potential risk, Wake separation standards exist to significantly reduce the probability of such events. Thus, Wake encounters are inherently rare. As new procedures and technologies are proposed to increase the capacity of the airspace, rare-event simulation is necessary to evaluate to the safety of proposed changes. This paper explores the performance of a rare-event splitting technique in the context of estimating probabilities of Potential Wake encounters. The goal is to identify good strategies for the splitting method while using a relatively simple model for the Wakes. Suggestions for the choice of the level function and the locations of levels are given.

  • Using Multilateration Data in Probabilistic Analysis of Wake Vortex Hazards for Landing Aircraft
    Transportation Research Record, 2007
    Co-Authors: John F Shortle, Babak Ghalebsaz Jeddi
    Abstract:

    Wake vortices are a safety hazard to landing aircraft. A landing aircraft that encounters a Wake may roll; this might result in a fatal crash if the roll is severe enough or if the aircraft is low enough to the ground. Therefore, aircraft are separated by a sufficient distance to ensure that Wakes have time to decay in strength. However, because of the inherent variability in Wake behavior and aircraft separation and position, there is still a possibility for a Wake encounter. To estimate the probability of such encounters, a hybrid simulation methodology is presented. The approach is hybrid in the sense that part of the simulation is conducted by using a direct data feed of flight-track data, and the other part is obtained by simulation of Wake-evolution models. The approach is demonstrated on a 1-week sample of flight tracks to predict the frequency of Potential Wake alerts. A Wake alert is defined as an event in which the trailing aircraft is in a region of space where the Wake is likely to be. The res...

  • Probabilistic Analysis of Wake Vortex Hazards for Landing Aircraft Using Multilateration Data
    2007
    Co-Authors: John F Shortle, Babak Ghalebsaz Jeddi
    Abstract:

    Wake vortices are a safety hazard to landing aircraft. A landing aircraft that encounters a Wake may roll, resulting in a fatal crash if the roll is severe enough and/or if the aircraft is low enough to the ground. Therefore, aircraft are separated by a sufficient distance to ensure that Wakes have time to decay in strength. However, because of the inherent variability in Wake behavior and aircraft separation and position, there is still a possibility for a Wake encounter. The objective of this paper is to estimate the probability of such encounters. This paper presents a hybrid simulation methodology. The approach is hybrid in the sense that part of the simulation is conducted using a direct data feed of flight-track data, while the other part is obtained by simulation of Wake-evolution models. We demonstrate the approach on a one-week sample of flight tracks to predict the frequency of Potential Wake alerts. In this paper a Wake alert is defined to be an event where the trailing aircraft is in a region of space where the Wake is likely to be. We show how the results depend on atmospheric conditions and other model parameters. TRB 2007 Annual Meeting CD-ROM Paper revised from original submittal.

Babak Ghalebsaz Jeddi - One of the best experts on this subject based on the ideXlab platform.

  • Using Multilateration Data in Probabilistic Analysis of Wake Vortex Hazards for Landing Aircraft
    Transportation Research Record, 2007
    Co-Authors: John F Shortle, Babak Ghalebsaz Jeddi
    Abstract:

    Wake vortices are a safety hazard to landing aircraft. A landing aircraft that encounters a Wake may roll; this might result in a fatal crash if the roll is severe enough or if the aircraft is low enough to the ground. Therefore, aircraft are separated by a sufficient distance to ensure that Wakes have time to decay in strength. However, because of the inherent variability in Wake behavior and aircraft separation and position, there is still a possibility for a Wake encounter. To estimate the probability of such encounters, a hybrid simulation methodology is presented. The approach is hybrid in the sense that part of the simulation is conducted by using a direct data feed of flight-track data, and the other part is obtained by simulation of Wake-evolution models. The approach is demonstrated on a 1-week sample of flight tracks to predict the frequency of Potential Wake alerts. A Wake alert is defined as an event in which the trailing aircraft is in a region of space where the Wake is likely to be. The res...

  • Probabilistic Analysis of Wake Vortex Hazards for Landing Aircraft Using Multilateration Data
    2007
    Co-Authors: John F Shortle, Babak Ghalebsaz Jeddi
    Abstract:

    Wake vortices are a safety hazard to landing aircraft. A landing aircraft that encounters a Wake may roll, resulting in a fatal crash if the roll is severe enough and/or if the aircraft is low enough to the ground. Therefore, aircraft are separated by a sufficient distance to ensure that Wakes have time to decay in strength. However, because of the inherent variability in Wake behavior and aircraft separation and position, there is still a possibility for a Wake encounter. The objective of this paper is to estimate the probability of such encounters. This paper presents a hybrid simulation methodology. The approach is hybrid in the sense that part of the simulation is conducted using a direct data feed of flight-track data, while the other part is obtained by simulation of Wake-evolution models. We demonstrate the approach on a one-week sample of flight tracks to predict the frequency of Potential Wake alerts. In this paper a Wake alert is defined to be an event where the trailing aircraft is in a region of space where the Wake is likely to be. We show how the results depend on atmospheric conditions and other model parameters. TRB 2007 Annual Meeting CD-ROM Paper revised from original submittal.

Wencong Chen - One of the best experts on this subject based on the ideXlab platform.

  • Energy levels of a heavy ion moving in dense plasmas
    Physics of Plasmas, 2013
    Co-Authors: Yongtao Zhao, Chenzhong Dong, Wencong Chen
    Abstract:

    In this paper, the Potential of a slowly moving test particle moving in collisional dense plasmas is studied. It is composed of the Debye-shielding Potential, Wake Potential, and collision term. The Ritz variational-perturbational method is developed for calculating relativistic binding energy levels of a heavy ion moving in dense plasmas. Binding energy levels of a heavy ion moving in plasmas are calculated. The results show that both non-relativistic energy levels and relativistic energy levels become more negative as the temperature becomes high. They also become more negative as the number density decreasing. Relativistic correction is important for calculating binding energy levels. Both relativistic energy levels and non-relativistic energy levels vary minutely as the speed of heavy ion varies.

F. Bell - One of the best experts on this subject based on the ideXlab platform.

  • Heavy-ion stopping in solids: Energy transfer to the target or the dragging force due to the induced Potential Wake
    Physical Review A, 2005
    Co-Authors: Florian Grüner, F. Bell
    Abstract:

    There are two different approaches for describing the slowing down of charged particles in solids, commonly used in a separate way. Either one treats the energy transfer to the target or considers the dragging force due to the induced Potential ('Wake'). We herewith present a classical many-body calculation which intrinsically allows simultaneously both descriptions. For the first time, we can follow in detail the development of the stopping power, the projectile's charge and excitation state, as well as the formation of the Wake, for ions entering into a solid. We further show that in nonequilibrium, stopping the development of the Wake contributes much stronger to the change in stopping power than one could expect from the corresponding change of the projectile's charge or excitation state. This is exemplified by the explanation of an experimentally observed surface enhancement in the stopping power, which sheds new light on analysis tools with single atomic depth resolution. We underline our findings by simulating also anti-Ni ions, which are found to form a pressure wave in contrast to trailing Wakes in the case of Ni ions.

Azin Zare-noghabi - One of the best experts on this subject based on the ideXlab platform.

  • WSC - Rare event simulation for Potential Wake encounters
    2017 Winter Simulation Conference (WSC), 2017
    Co-Authors: Azin Zare-noghabi, John F Shortle
    Abstract:

    A flying aircraft produces two coherent rotating vortices of air in its trail. If another aircraft flies into one of these vortices, it can experience an un-commanded roll. Because of the Potential risk, Wake separation standards exist to significantly reduce the probability of such events. Thus, Wake encounters are inherently rare. As new procedures and technologies are proposed to increase the capacity of the airspace, rare-event simulation is necessary to evaluate to the safety of proposed changes. This paper explores the performance of a rare-event splitting technique in the context of estimating probabilities of Potential Wake encounters. The goal is to identify good strategies for the splitting method while using a relatively simple model for the Wakes. Suggestions for the choice of the level function and the locations of levels are given.