The dynamic behavior of a two-degree-of-freedom oblique impact system consisted of two pendulums with non-fixed impact positions is investigated. The relations between the restitution coefficient, the friction coeffic...The dynamic behavior of a two-degree-of-freedom oblique impact system consisted of two pendulums with non-fixed impact positions is investigated. The relations between the restitution coefficient, the friction coefficient, as well as other parameters of the system and the states before or after impact, are clarified in this oblique impact process. The existence criterion of single impact periodic-n subharrnonic motions is deduced based on the Poincare map method and the oblique impact relations with non-fixed impact positions. The stability of these subharrnonic periodic motions is analyzed by the Floquet theory, and the formulas to calculate the Flocluet multipliers are given. The validity of this method is shown through numerical simulation. At the same time, the probability distribution of impact positions in this oblique system with nonfixed impact positions is analyzed.展开更多
This paper discusses the time-of-arrival(TOA) based indoor visible light communication(VLC) positioning system in a non-line-of-sight environment. The propagation delay is assumed to be gamma distributed. The generali...This paper discusses the time-of-arrival(TOA) based indoor visible light communication(VLC) positioning system in a non-line-of-sight environment. The propagation delay is assumed to be gamma distributed. The generalized Cramer–Rao lower bound for multipath propagation is derived as the theoretical accuracy limitation. The performance of the positioning system is affected by the shape parameter and the scale parameter of gamma distribution.The influences on positioning accuracy of multipath effects are analyzed through discussing the physical meaning of the gamma distribution parameters. It is concluded that the lower bound of positioning accuracy is attained when variance of the non-line-of-sight propagation-induced path lengths is zero. The simulation result provesthat the theoretical positioning accuracy is in the order of centimeters with the given scenario.展开更多
The impact of the imported fire ant （IFA） is complex, in large part, because several very different species of＂Fire Ants＂ have invaded and one of these has two forms, all of which are hard to separate by the publi...The impact of the imported fire ant （IFA） is complex, in large part, because several very different species of＂Fire Ants＂ have invaded and one of these has two forms, all of which are hard to separate by the public, as well as, some investigators not focused on the ant. Each of these different ＂IFA＂ species and forms differ in their impact. Further, these ants impact a number of＂things＂ ranging from the environment and wildlife （plants and animals） as well as people, their environment and infrastructure. In addition, they can not only lead to death of living things （including people）, but they can destroy many aspects of our environment and infrastructure at the cost of millions of dollars. But there are some beneficial aspects and some people can make many thousands of dollars due to their presence. This is an attempt to look at these issues.展开更多
文摘The dynamic behavior of a two-degree-of-freedom oblique impact system consisted of two pendulums with non-fixed impact positions is investigated. The relations between the restitution coefficient, the friction coefficient, as well as other parameters of the system and the states before or after impact, are clarified in this oblique impact process. The existence criterion of single impact periodic-n subharrnonic motions is deduced based on the Poincare map method and the oblique impact relations with non-fixed impact positions. The stability of these subharrnonic periodic motions is analyzed by the Floquet theory, and the formulas to calculate the Flocluet multipliers are given. The validity of this method is shown through numerical simulation. At the same time, the probability distribution of impact positions in this oblique system with nonfixed impact positions is analyzed.
基金supported by the National Key Basic Research Program of China (973 program) under grant 2013CB32920the Natural Science Foundation of China under grant 61375083
文摘This paper discusses the time-of-arrival(TOA) based indoor visible light communication(VLC) positioning system in a non-line-of-sight environment. The propagation delay is assumed to be gamma distributed. The generalized Cramer–Rao lower bound for multipath propagation is derived as the theoretical accuracy limitation. The performance of the positioning system is affected by the shape parameter and the scale parameter of gamma distribution.The influences on positioning accuracy of multipath effects are analyzed through discussing the physical meaning of the gamma distribution parameters. It is concluded that the lower bound of positioning accuracy is attained when variance of the non-line-of-sight propagation-induced path lengths is zero. The simulation result provesthat the theoretical positioning accuracy is in the order of centimeters with the given scenario.
文摘The impact of the imported fire ant （IFA） is complex, in large part, because several very different species of＂Fire Ants＂ have invaded and one of these has two forms, all of which are hard to separate by the public, as well as, some investigators not focused on the ant. Each of these different ＂IFA＂ species and forms differ in their impact. Further, these ants impact a number of＂things＂ ranging from the environment and wildlife （plants and animals） as well as people, their environment and infrastructure. In addition, they can not only lead to death of living things （including people）, but they can destroy many aspects of our environment and infrastructure at the cost of millions of dollars. But there are some beneficial aspects and some people can make many thousands of dollars due to their presence. This is an attempt to look at these issues.
