We propose a high-performance path planning algorithm for automatic target tracking in the applications of real-time simulation and visualization of large-scale terrain datasets, with a large number of moving objects ...We propose a high-performance path planning algorithm for automatic target tracking in the applications of real-time simulation and visualization of large-scale terrain datasets, with a large number of moving objects （such as vehicles） tracking multiple moving targets. By using a modified Dijkstra＇s algorithm, an optimal path between each vehicle-target pair over a weighted grid-presented terrain is computed and updated to eliminate the problem of local minima and losing of tracking. Then, a dynamic path re-planning strategy using multi-resolution representation of a dynamic updating region is proposed to achieve high-performance by trading-off precision for efficiency, while guaranteeing accuracy. Primary experimental results showed that our algorithm successfully achieved l0 to 96 frames per second interactive path-replanning rates during a terrain simulation scenario with 10 to 100 vehicles and multiple moving targets.展开更多
This research focuses on tin whisker growth under two different environmental conditions namely hygrothermal and a salt solution. Tin coated brass coupons were used for this study to analyze the growth of tin whiskers...This research focuses on tin whisker growth under two different environmental conditions namely hygrothermal and a salt solution. Tin coated brass coupons were used for this study to analyze the growth of tin whiskers over time. Their growth rates were examined periodically using optical and scanning electron microscopy. The physical characteristics of the tin whiskers were identified for each environmental condition. It was discovered that submersion of tin coated brass substrates in 5% salt solution considerably increased the density (number of whiskers per unit area), and the length of the whiskers. In addition, it was found that the geometry and aspect ratio of tin whiskers were different for each environment.展开更多
It is well-known that equilibrium density profiles of gases and fluids in gravitational potentials have an r−1 dependence, where r is the radius. This is found in both astronomical observations and detailed ...It is well-known that equilibrium density profiles of gases and fluids in gravitational potentials have an r−1 dependence, where r is the radius. This is found in both astronomical observations and detailed simulations in spherically-symmetric geometries. It is also well-known that the standard equation for hydrostatic equilibrium does not produce such solutions. This paper utilizes a Lagrangian formulation that produces a closed-form r−1 solution and identifies the needed terms to be added to the standard equation for hydrostatic equilibrium to obtain such a solution. Variants of the r−1 solution avoid a density singularity at the origin and a total-enclosed mass singularity at infinity. The resulting solutions are shown to be in good agreement with well-established density profiles of ordinary matter in galaxies, dark matter haloes, and the atmosphere of earth. Comparisons are made to solutions based on the standard hydrostatic equation, including solutions based on the Lane-Emden equation. The origins of differences are explained.展开更多
The objective of this research is to provide an explanation of galactic haloes using established particles and forces using recent theoretical developments. Light fermions, with masses on the order of 1 eV/c<sup>...The objective of this research is to provide an explanation of galactic haloes using established particles and forces using recent theoretical developments. Light fermions, with masses on the order of 1 eV/c<sup>2</sup>, are not a leading candidate for dark matter because of their large free-streaming scale length and their violation of the Tremaine-Gunn bound. With a self-interaction of fermions, the free-streaming scaling length is reduced, and the tenets of the Tremaine-Gunn bound are not applicable. Binding of neutrinos via a feeble SU(3) force is considered as a model for such interactions. The assumed sum of masses of the three neutrino flavors is 0.07 eV/c<sup>2</sup>. The resulting form of matter for such bound neutrinos is found to be a degenerate Fermi fluid. Pressure-equilibrium approaches applied to this fluid provide cuspy solutions and match observationally-inferred profiles for galactic haloes. Such approaches also match the observed total enclosed mass for galaxies similar to the Milky Way. The computed structures are found to be stable. The hypothesis is considered in view of observationally-inferred halo-halo interactions and gives results that are consistent with the observed Bullet cluster halo interaction. The theory gives agreement with observationally-inferred properties of dark matter near earth. Questions related to interaction rates, consistency with SN1987a data, the cosmic microwave background, the issue of SU(3) interactions between neutrinos and quarks, free-streaming after neutrino decoupling, and dark-matter abundance are addressed in a companion paper.展开更多
Currently,flight delays are common and they propagate from an originating flight to connecting flights,leading to large disruptions in the overall schedule.These disruptions cause massive economic losses,affect airli...Currently,flight delays are common and they propagate from an originating flight to connecting flights,leading to large disruptions in the overall schedule.These disruptions cause massive economic losses,affect airlines’reputations,waste passengers’time and money,and directly impact the environment.This study adopts a network science approach for solving the delay propagation problem by modeling and analyzing the flight schedules and historical operational data of an airline.We aim to determine the most disruptive airports,flights,flightconnections,and connection types in an airline network.Disruptive elements are influential or critical entities in an airline network.They are the elements that can either cause(airline schedules)or have caused(historical data)the largest disturbances in the network.An airline can improve its operations by avoiding delays caused by the most disruptive elements.The proposed network science approach for disruptive element analysis was validated using a case study of an operating airline.The analysis indicates that potential disruptive elements in a schedule of an airline are also actual disruptive elements in the historical data and they should be considered to improve operations.The airline network exhibits small-world effects and delays can propagate to any part of the network with a minimum of four delayed flights.Finally,we observed that passenger connections between flights are the most disruptive connection type.Therefore,the proposed methodology provides a tool for airlines to build robust flight schedules that reduce delays and propagation.展开更多
The texture-based volume rendering is a memory-intensive algorithm.Its performance relies heavily on the performance of the texture cache.However,most existing texture-based volume rendering methods blindly map comput...The texture-based volume rendering is a memory-intensive algorithm.Its performance relies heavily on the performance of the texture cache.However,most existing texture-based volume rendering methods blindly map computational resources to texture memory and result in incoherent memory access patterns,causing low cache hit rates in certain cases.The distance between samples taken by threads of an atomic scheduling unit(e.g.a warp of 32 threads in CUDA)of the GPU is a crucial factor that affects the texture cache performance.Based on this fact,we present a new sampling strategy,called Warp Marching,for the ray-casting algorithm of texture-based volume rendering.The effects of different sample organizations and different thread-pixel mappings in the ray-casting algorithm are thoroughly analyzed.Also,a pipeline manner color blending approach is introduced and the power of warp-level GPU operations is leveraged to improve the efficiency of parallel executions on the GPU.In addition,the rendering performance of the Warp Marching is view-independent,and it outperforms existing empty space skipping techniques in scenarios that need to render large dynamic volumes in a low resolution image.Through a series of micro-benchmarking and real-life data experiments,we rigorously analyze our sampling strategies and demonstrate significant performance enhancements over existing sampling methods.展开更多
基金Project partially supported by NSF (No. CCR0306438) and theBoeing Company, USA
文摘We propose a high-performance path planning algorithm for automatic target tracking in the applications of real-time simulation and visualization of large-scale terrain datasets, with a large number of moving objects （such as vehicles） tracking multiple moving targets. By using a modified Dijkstra＇s algorithm, an optimal path between each vehicle-target pair over a weighted grid-presented terrain is computed and updated to eliminate the problem of local minima and losing of tracking. Then, a dynamic path re-planning strategy using multi-resolution representation of a dynamic updating region is proposed to achieve high-performance by trading-off precision for efficiency, while guaranteeing accuracy. Primary experimental results showed that our algorithm successfully achieved l0 to 96 frames per second interactive path-replanning rates during a terrain simulation scenario with 10 to 100 vehicles and multiple moving targets.
文摘This research focuses on tin whisker growth under two different environmental conditions namely hygrothermal and a salt solution. Tin coated brass coupons were used for this study to analyze the growth of tin whiskers over time. Their growth rates were examined periodically using optical and scanning electron microscopy. The physical characteristics of the tin whiskers were identified for each environmental condition. It was discovered that submersion of tin coated brass substrates in 5% salt solution considerably increased the density (number of whiskers per unit area), and the length of the whiskers. In addition, it was found that the geometry and aspect ratio of tin whiskers were different for each environment.
文摘It is well-known that equilibrium density profiles of gases and fluids in gravitational potentials have an r−1 dependence, where r is the radius. This is found in both astronomical observations and detailed simulations in spherically-symmetric geometries. It is also well-known that the standard equation for hydrostatic equilibrium does not produce such solutions. This paper utilizes a Lagrangian formulation that produces a closed-form r−1 solution and identifies the needed terms to be added to the standard equation for hydrostatic equilibrium to obtain such a solution. Variants of the r−1 solution avoid a density singularity at the origin and a total-enclosed mass singularity at infinity. The resulting solutions are shown to be in good agreement with well-established density profiles of ordinary matter in galaxies, dark matter haloes, and the atmosphere of earth. Comparisons are made to solutions based on the standard hydrostatic equation, including solutions based on the Lane-Emden equation. The origins of differences are explained.
文摘The objective of this research is to provide an explanation of galactic haloes using established particles and forces using recent theoretical developments. Light fermions, with masses on the order of 1 eV/c<sup>2</sup>, are not a leading candidate for dark matter because of their large free-streaming scale length and their violation of the Tremaine-Gunn bound. With a self-interaction of fermions, the free-streaming scaling length is reduced, and the tenets of the Tremaine-Gunn bound are not applicable. Binding of neutrinos via a feeble SU(3) force is considered as a model for such interactions. The assumed sum of masses of the three neutrino flavors is 0.07 eV/c<sup>2</sup>. The resulting form of matter for such bound neutrinos is found to be a degenerate Fermi fluid. Pressure-equilibrium approaches applied to this fluid provide cuspy solutions and match observationally-inferred profiles for galactic haloes. Such approaches also match the observed total enclosed mass for galaxies similar to the Milky Way. The computed structures are found to be stable. The hypothesis is considered in view of observationally-inferred halo-halo interactions and gives results that are consistent with the observed Bullet cluster halo interaction. The theory gives agreement with observationally-inferred properties of dark matter near earth. Questions related to interaction rates, consistency with SN1987a data, the cosmic microwave background, the issue of SU(3) interactions between neutrinos and quarks, free-streaming after neutrino decoupling, and dark-matter abundance are addressed in a companion paper.
基金part of a BOEING project“Airline Performance and Disruption Management Across Extended Networks(APEMEN)”funded with research(Grant No.:46599).
文摘Currently,flight delays are common and they propagate from an originating flight to connecting flights,leading to large disruptions in the overall schedule.These disruptions cause massive economic losses,affect airlines’reputations,waste passengers’time and money,and directly impact the environment.This study adopts a network science approach for solving the delay propagation problem by modeling and analyzing the flight schedules and historical operational data of an airline.We aim to determine the most disruptive airports,flights,flightconnections,and connection types in an airline network.Disruptive elements are influential or critical entities in an airline network.They are the elements that can either cause(airline schedules)or have caused(historical data)the largest disturbances in the network.An airline can improve its operations by avoiding delays caused by the most disruptive elements.The proposed network science approach for disruptive element analysis was validated using a case study of an operating airline.The analysis indicates that potential disruptive elements in a schedule of an airline are also actual disruptive elements in the historical data and they should be considered to improve operations.The airline network exhibits small-world effects and delays can propagate to any part of the network with a minimum of four delayed flights.Finally,we observed that passenger connections between flights are the most disruptive connection type.Therefore,the proposed methodology provides a tool for airlines to build robust flight schedules that reduce delays and propagation.
文摘The texture-based volume rendering is a memory-intensive algorithm.Its performance relies heavily on the performance of the texture cache.However,most existing texture-based volume rendering methods blindly map computational resources to texture memory and result in incoherent memory access patterns,causing low cache hit rates in certain cases.The distance between samples taken by threads of an atomic scheduling unit(e.g.a warp of 32 threads in CUDA)of the GPU is a crucial factor that affects the texture cache performance.Based on this fact,we present a new sampling strategy,called Warp Marching,for the ray-casting algorithm of texture-based volume rendering.The effects of different sample organizations and different thread-pixel mappings in the ray-casting algorithm are thoroughly analyzed.Also,a pipeline manner color blending approach is introduced and the power of warp-level GPU operations is leveraged to improve the efficiency of parallel executions on the GPU.In addition,the rendering performance of the Warp Marching is view-independent,and it outperforms existing empty space skipping techniques in scenarios that need to render large dynamic volumes in a low resolution image.Through a series of micro-benchmarking and real-life data experiments,we rigorously analyze our sampling strategies and demonstrate significant performance enhancements over existing sampling methods.
