4,582 research outputs found
Tailored electron bunches with smooth current profiles for enhanced transformer ratios in beam-driven acceleration
Collinear high-gradient beam-driven wakefield methods for
charged-particle acceleration could be critical to the realization of compact,
cost-efficient, accelerators, e.g., in support of TeV-scale lepton colliders or
multiple-user free-electron laser facilities. To make these options viable, the
high accelerating fields need to be complemented with large transformer ratios
, a parameter characterizing the efficiency of the energy transfer between
a wakefield-exciting "drive" bunch to an accelerated "witness" bunch. While
several potential current distributions have been discussed, their practical
realization appears challenging due to their often discontinuous nature. In
this paper we propose several alternative current profiles which are smooth
which also lead to enhanced transformer ratios. We especially explore a
laser-shaping method capable of generating one the suggested distributions
directly out of a photoinjector and discuss a linac concept that could possible
drive a dielectric accelerator
Analysis of a time-dependent problem of mixed migration and population dynamics
In this work, we consider a system of differential equations modeling the
dynamics of some populations of preys and predators, moving in space according
to rapidly oscillating time-dependent transport terms, and interacting with
each other through a Lotka-Volterra term. These two contributions naturally
induce two separated time-scales in the problem. A generalized center manifold
theorem is derived to handle the situation where the linear terms are depending
on the fast time in a periodic way. The resulting equations are then amenable
to averaging methods. As a product of these combined techniques, one obtains an
autonomous differential system in reduced dimension whose dynamics can be
analyzed in a much simpler way as compared to original equations. Strikingly
enough, this system is of Lotka-Volterra form with modified coefficients.
Besides, a higher order perturbation analysis allows to show that the
oscillations on the original model destabilize the cycles of the averaged
Volterra system in a way that can be explicitely computed
Estimation of Saturation of Permanent-Magnet Synchronous Motors Through an Energy-Based Model
We propose a parametric model of the saturated Permanent-Magnet Synchronous
Motor (PMSM) together with an estimation method of the magnetic parameters. The
model is based on an energy function which simply encompasses the saturation
effects. Injection of fast-varying pulsating voltages and measurements of the
resulting current ripples then permit to identify the magnetic parameters by
linear least squares. Experimental results on a surface-mounted PMSM and an
interoir magnet PMSM illustrate the relevance of the approach.Comment: IEMDC-2011 (preliminary version
Irrigated agriculture, water pricing and water savings in the Lower Jordan River Basin (in Jordan)
Farming systems / Irrigated farming / Water conservation / Groundwater / Water policy / Water rates / Water costs / Pricing / Cost recovery / Economic impact / Jordan / Lower Jordan River Basin / Jordan Valley / Amman-Zarqa Basin / Yarmouk Basin
On the Connectivity of Unions of Random Graphs
Graph-theoretic tools and techniques have seen wide use in the multi-agent
systems literature, and the unpredictable nature of some multi-agent
communications has been successfully modeled using random communication graphs.
Across both network control and network optimization, a common assumption is
that the union of agents' communication graphs is connected across any finite
interval of some prescribed length, and some convergence results explicitly
depend upon this length. Despite the prevalence of this assumption and the
prevalence of random graphs in studying multi-agent systems, to the best of our
knowledge, there has not been a study dedicated to determining how many random
graphs must be in a union before it is connected. To address this point, this
paper solves two related problems. The first bounds the number of random graphs
required in a union before its expected algebraic connectivity exceeds the
minimum needed for connectedness. The second bounds the probability that a
union of random graphs is connected. The random graph model used is the
Erd\H{o}s-R\'enyi model, and, in solving these problems, we also bound the
expectation and variance of the algebraic connectivity of unions of such
graphs. Numerical results for several use cases are given to supplement the
theoretical developments made.Comment: 16 pages, 3 tables; accepted to 2017 IEEE Conference on Decision and
Control (CDC
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