21,044 research outputs found
On closing for flows on 2-manifolds
For some full measure subset B of the set of iet's (i.e. interval exchange
transformations) the following is satisfied: Let X be a , , vector field, with finitely many singularities, on a compact
orientable surface M. Given a nontrivial recurrent point of X, the
holonomy map around p is semi-conjugate to an iet If
then there exists a vector field Y, arbitrarily close to X, in
the topology, such that Y has a closed trajectory passing through p.Comment: 7 pages, 1 figur
Authoring courses with rich adaptive sequencing for IMS learning design
This paper describes the process of translating an adaptive sequencing strategy designed using Sequencing Graphs to the semantics of IMS Learning Design. The relevance of this contribution is twofold. First, it combines the expressive power and flexibility of Sequencing Graphs, and the interoperability capabilities of IMS. Second, it shows some important limitations of IMS specifications (focusing on Learning Design) for the sequencing of learning activities
Nongauge bright soliton of the nonlinear Schrodinger (NLS) equation and a family of generalized NLS equations
We present an approach to the bright soliton solution of the NLS equation
from the standpoint of introducing a constant potential term in the equation.
We discuss a `nongauge' bright soliton for which both the envelope and the
phase depend only on the traveling variable. We also construct a family of
generalized NLS equations with solitonic sech^p solutions in the traveling
variable and find an exact equivalence with other nonlinear equations, such as
the Korteveg-de Vries and Benjamin-Bona-Mahony equations when p=2Comment: ~4 pages, 3 figures, 16 references, published versio
Parallel ion strings in linear multipole traps
Additional radio-frequency (rf) potentials applied to linear multipole traps
create extra field nodes in the radial plane which allow one to confine single
ions, or strings of ions, in totally rf field-free regions. The number of nodes
depends on the order of the applied multipole potentials and their relative
distance can be easily tuned by the amplitude variation of the applied
voltages. Simulations using molecular dynamics show that strings of ions can be
laser cooled down to the Doppler limit in all directions of space. Once cooled,
organized systems can be moved with very limited heating, even if the cooling
process is turned off
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