53,918 research outputs found
The impact of EU enlargement on migration flows
This document is a report commissioned by the Home Office in order to assess the magnitude of potential migration flows to the UK after the enlargement of the European Union (EU). The countries which are expected to join the EU on 1 May 2004 are Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia. The aim of the report is to provide extensive information that will be helpful in evaluating the migration potential from
these countries to the UK. This is done by (i) describing the socio-economic situation of the accession countries nowadays and since the early 1990s and comparing it to that of the UK and Germany, (ii) critically reviewing the existing literature that attempts to predict the effects of the current EU enlargement on migration flows, (iii) analysing the so-called Southern enlargement (the accessions of Greece, Portugal and Spain) and comparing it to the current one, and (iv) presenting a quantitative analysis of the effect of the current enlargement on migration to the UK
Analytical mode normalization and resonant state expansion for optical fibers - an efficient tool to model transverse disorder
We adapt the resonant state expansion to optical fibers such as capillary and
photonic crystal fibers. As a key requirement of the resonant state expansion
and any related perturbative approach, we derive the correct analytical
normalization for all modes of these fiber structures, including leaky modes
that radiate energy perpendicular to the direction of propagation and have
fields that grow with distance from the fiber core. Based on the normalized
fiber modes, an eigenvalue equation is derived that allows for calculating the
influence of small and large perturbations such as structural disorder on the
guiding properties. This is demonstrated for two test systems: a capillary
fiber and an endlessly single mode fiber.Comment: 10 pages, 4 figure
VHF radar measurements in the summer polar mesosphere
Measurements in the mesosphere over Andoya/Norway (69 N, 16 E) were carried out using the mobile SOUSY-VHF radar with an extended beam configuration during the MAC/SINE campaign in summer 1987. First results of a 48 h and a 3 h observational period for heights between about 83 and 91 km are presented. Zonal mean winds are characterized by a strong westward flow of up to 50/ms, whereas the equatorward directed meridional component is weaker. The dominating semidiurnal tide has amplitudes up to 30/ms and a vertical wavelength of about 55 km. The diurnal tide is less pronounced. The total upward flux of horizontal momentum takes values of -2 sq m/sq s near 84 km and increases with increasing height, reaching a maximum value of 22 sq m/sqs for both the zonal and meridional components. However, measurements of the horizontal isotropy of the wave field suggest significant anisotropy. The major contribution to the momentum flux is from the 10 min to 1 h period range below about 87 km, and from the 1 to 6 h period range above this height
Toward a numerical deshaker for PFS
The Planetary Fourier Spectrometer (PFS) onboard Mars Express (MEx) is the
instrument with the highest spectral resolution observing Mars from orbit since
January 2004. It permits studying the atmospheric structure, major and minor
compounds. The present time version of the calibration is limited by the
effects of mechanical vibration, currently not corrected. We proposed here a
new approach to correct for the vibrations based on semi-blind deconvolution of
the measurements. This new approach shows that a correction can be done
efficiently with 85% reduction of the artefacts, in a equivalent manner to the
stacking of 10 spectra. Our strategy is not fully automatic due to the
dependence on some regularisation parameters. It may be applied on the complete
PFS dataset, correcting the large-scale perturbation due to microvibrations for
each spectrum independently. This approach is validated on actual PFS data of
Short Wavelength Channel (SWC), perturbed by microvibrations. A coherence check
can be performed and also validate our approach. Unfortunately, the coherence
check can be done only on the first 310 orbits of MEx only, until the laser
line has been switch off. More generally, this work may apply to numerically
"deshake" Fourier Transform Spectrometer (FTS), widely used in space
experiments or in the laboratory.Comment: 18 pages, 8 figures, submitted to Planetary and Space Scienc
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