3,200 research outputs found
EUCARD magnet development
The FP7-EuCARD work package 7 (WP7), "HFM: Superconducting High Field Magnets
for higher luminosities and energies" is a collaboration between 12 European
institutes and firms with the objective of developing high field magnet
technology. WP7 foresees to construct a 13 T dipole with a 100 mm aperture, a B
= 6 T high temperature superconductor (HTS) dipole insert, a superconducting
HTS link and a superconducting helical undulator.Comment: 5 pages, contribution to the EuCARD-AccNet-EuroLumi Workshop: The
High-Energy Large Hadron Collider, Malta, 14 -- 16 Oct 2010; CERN Yellow
Report CERN-2011-003, pp. 45-4
Modulation equations near the Eckhaus boundary: the KdV equation
We are interested in the description of small modulations in time and space
of wave-train solutions to the complex Ginzburg-Landau equation \begin{align*}
\partial_T \Psi = (1+ i \alpha) \partial_X^2 \Psi + \Psi - (1+i \beta ) \Psi
|\Psi|^2, \end{align*} near the Eckhaus boundary, that is, when the wave train
is near the threshold of its first instability. Depending on the parameters , a number of modulation equations can be derived, such as
the KdV equation, the Cahn-Hilliard equation, and a family of Ginzburg-Landau
based amplitude equations. Here we establish error estimates showing that the
KdV approximation makes correct predictions in a certain parameter regime. Our
proof is based on energy estimates and exploits the conservation law structure
of the critical mode. In order to improve linear damping we work in spaces of
analytic functions.Comment: 44 pages, 8 figure
The CERN High Field Magnet Program
With the LHC, magnets of 10 T peak flux density Nb-Ti technology were developed and this technology reached full maturity. The next step in flux density level, with a peak in the range of 15 T, will be needed for the LHC Phase II upgrade. For this upgrade the temperature margin and radiation resistance of the Nb-Ti coil technology is not sufficient. Beginning 2008 CERN started a program to develop high field magnets for LHC upgrades and other future programs. For this mostly NbSn conductors will be employed, but also HTS conductors will be considered. In this paper an overview will be presented of the projects for which this HFM technology will be needed. The program will be presented in terms of R&D chapters and work packages. The need and opportunities for collaborations with other institutes will be discussed
COMBINING TUBERCULOSIS AND LEPROSY SERVICES IN ONE PROGRAMME
ABSTRACT
Reasons are provided for considering combining the services for leprosy and tuberculosis in one programme. Advantages and disadvantages of the combination are reviewed for leprosy and for tuberculosis separately. The place of a partly integrated special programme in general services with a primary health care concept is indicated and the potentially important role of the community health agent briefly described
Nonlinear stability and asymptotic behavior of periodic wave trains in reaction-diffusion systems against -perturbations
We present a nonlinear stability theory for periodic wave trains in
reaction-diffusion systems, which relies on pure -estimates only. Our
analysis shows that localization or periodicity requirements on perturbations,
as present in the current literature, can be completely lifted. Inspired by
previous works considering localized perturbations, we decompose the semigroup
generated by the linearization about the wave train and introduce a
spatio-temporal phase modulation to capture the most critical dynamics, which
is governed by a viscous Burgers' equation. We then aim to close a nonlinear
stability argument by iterative estimates on the corresponding Duhamel
formulation, where, hampered by the lack of localization, we must rely on
diffusive smoothing to render decay of the semigroup. Yet, this decay is not
strong enough to control all terms in the Duhamel formulation. We address this
difficulty by applying the Cole-Hopf transform to eliminate the critical
Burgers'-type nonlinearities. Ultimately, we establish nonlinear stability of
diffusively spectrally stable wave trains against
-perturbations. Moreover, we show that the perturbed solution
converges to a modulated wave train, whose phase and wavenumber are
approximated by solutions to the associated viscous Hamilton-Jacobi and
Burgers' equation, respectively.Comment: 44 page
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