22,350 research outputs found
Impact of energetic particle orbits on long range frequency chirping of BGK modes
Long range frequency chirping of Bernstein-Greene-Kruskal modes, whose
existence is determined by the fast particles, is investigated in cases where
these particles do not move freely and their motion is bounded to restricted
orbits. An equilibrium oscillating potential, which creates different orbit
topologies of energetic particles, is included into the bump-on-tail
instability problem of a plasma wave. With respect to fast particles dynamics,
the extended model captures the range of particles motion (trapped/passing)
with energy and thus represents a more realistic 1D picture of the long range
sweeping events observed for weakly damped modes, e.g. global Alfven
eigenmodes, in tokamaks. The Poisson equation is solved numerically along with
bounce averaging the Vlasov equation in the adiabatic regime. We demonstrate
that the shape and the saturation amplitude of the nonlinear mode structure
depends not only on the amount of deviation from the initial eigenfrequency but
also on the initial energy of the resonant electrons in the equilibrium
potential. Similarly, the results reveal that the resonant electrons following
different equilibrium orbits in the electrostatic potential lead to different
rates of frequency evolution. As compared to the previous model [Breizman B.N.
2010 Nucl. Fusion 50 084014], it is shown that the frequency sweeps with lower
rates. The additional physics included in the model enables a more complete 1D
description of the range of phenomena observed in experiments.Comment: Submitted to Nuclear Fusion 25/01/201
Non-consensus opinion model on directed networks
Dynamic social opinion models have been widely studied on undirected
networks, and most of them are based on spin interaction models that produce a
consensus. In reality, however, many networks such as Twitter and the World
Wide Web are directed and are composed of both unidirectional and bidirectional
links. Moreover, from choosing a coffee brand to deciding who to vote for in an
election, two or more competing opinions often coexist. In response to this
ubiquity of directed networks and the coexistence of two or more opinions in
decision-making situations, we study a non-consensus opinion model introduced
by Shao et al. \cite{shao2009dynamic} on directed networks. We define
directionality as the percentage of unidirectional links in a network,
and we use the linear correlation coefficient between the indegree and
outdegree of a node to quantify the relation between the indegree and
outdegree. We introduce two degree-preserving rewiring approaches which allow
us to construct directed networks that can have a broad range of possible
combinations of directionality and linear correlation coefficient
and to study how and impact opinion competitions. We find that, as
the directionality or the indegree and outdegree correlation
increases, the majority opinion becomes more dominant and the minority
opinion's ability to survive is lowered
Micro-displacement sensors based on plastic photonic bandgap Bragg fibers
We demonstrate an amplitude-based micro-displacement sensor that uses a
plastic photonic bandgap Bragg fiber with one end coated with a silver layer.
The reflection intensity of the Bragg fiber is characterized in response to
different displacements (or bending curvatures). We note that the Bragg
reflector of the fiber acts as an efficient mode stripper for the wavelengths
near the edge of the fiber bandgap, which makes the sensor extremely sensitive
to bending or displacements at these wavelengths. Besides, by comparison of the
Bragg fiber sensor to a sensor based on a regular multimode fiber with similar
outer diameter and length, we find that the Bragg fiber sensor is more
sensitive to bending due to presence of mode stripper in the form of the
multilayer reflector. Experimental results show that the minimum detection
limit of the Bragg fiber sensor can be smaller than 5 um for displacement
sensing
Some analysis on mobile-agent based network routing
©2004 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.Deployment of mobile agents in network-based applications has attracted lots of attentions in recent years. How to control the activities of agents is crucial for effective application of mobile agents. This paper focuses on the application of mobile agents in network routing. Two important activity properties of mobile agents are identified: the probability of success (the probability of finding the destination) and the distribution of mobile agents running in the network. To our knowledge, little work has been done on these two aspects. Our results show that the number of mobile agents can be controlled by adjusting the number of agents generated per request and the number of jumps each mobile agent can move. Thus, we can improve network performance by tuning relevant parameters.Wenyu Qu, Hong She
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