59,755 research outputs found
Evaluation of Includem’s intensive support services – September 2007
In 2005 Includem commissioned a two-year evaluation of its intensive support services provided to young people as part of the Intensive Support and Monitoring Service in Edinburgh, Glasgow, Dundee, East Dunbartonshire, and West Dunbartonshire. Over two years Includem’s provided intensive support, normally around 15 hours per week plus access to Includem’s 24-hour crisis helpline, to over 200 young people, including 69 young people with a Movement Restriction Condition ('electronic tag')
The effect of magnetic islands on ITG turbulence driven transport
In this work, we address the question of the influence of magnetic islands on
the perpendicular transport due to steady-state ITG turbulence on the energy
transport time scale. We demonstrate that turbulence can cross the separatrix
and enhance the perpendicular transport across magnetic islands. As the
perpendicular transport in the interior of the island sets the critical island
size needed for growth of neoclassical tearing modes, this increased transport
leads to a critical island size larger than that predicted from considering
collisional conductivities, but smaller than that using anomalous effective
conductivities.
We find that on Bohm time scales, the turbulence is able to re-establish the
temperature gradient across the island for islands widths , the turbulence correlation length. The reduction in the island
flattening is estimated by comparison with simulations retaining only the
perpendicular temperature and no turbulence. At intermediate island widths,
comparable to , turbulence is able to maintain finite
temperature gradients across the island
Plasma turbulence simulations with X-points using the flux-coordinate independent approach
In this work, the Flux-Coordinate Independent (FCI) approach to plasma
turbulence simulations is formulated for the case of generic, static magnetic
fields, including those possessing stochastic field lines. It is then
demonstrated that FCI is applicable to nonlinear turbulent problems with and
without X-point geometry. In particular, by means of simulations with the
FENICIA code, it is shown that the standard features of ITG modes are recovered
with reduced toroidal resolution. Finally, ITG turbulence under the influence
of a static island is studied on the transport timescale with ITER-like
parameters, showing the wide range of applicability of the method
Solar-cycle variation of the sound-speed asphericity from GONG and MDI data 1995-2000
We study the variation of the frequency splitting coefficients describing the
solar asphericity in both GONG and MDI data, and use these data to investigate
temporal sound-speed variations as a function of both depth and latitude during
the period from 1995-2000 and a little beyond. The temporal variations in even
splitting coefficients are found to be correlated to the corresponding
component of magnetic flux at the solar surface. We confirm that the
sound-speed variations associated with the surface magnetic field are
superficial. Temporally averaged results show a significant excess in sound
speed around 0.92 solar radii and latitude of 60 degrees.Comment: To be published in MNRAS, accepted July 200
Seismic investigation of the solar structure using GONG frequencies
Using the recently obtained GONG frequencies, we investigate the properties
of the solar interior by constructing solar models with various input physics
like opacities, equation of state, nuclear reaction rates etc. The differential
asymptotic inversion technique is then used to infer the relative difference in
sound speed between the Sun and solar models. Here we apply these results to
test equation of state and different formulation for calculating the convective
flux.Comment: Latex, 2 pages, 3 figures, To appear in the IAU Symp. # 181:
"Sounding solar and stellar interiors", eds. F.X. Schmider & J. Provos
Low-thrust chemical propulsion system propellant expulsion and thermal conditioning study
Thermal conditioning systems for satisfying engine net positive suction pressure (NPSP) requirements, and propellant expulsion systems for achieving propellant dump during a return-to-launch site (RTLS) abort were studied for LH2/LO2 and LCH4/LO2 upper stage propellant combinations. A state-of-the-art thermal conditioning system employing helium injection beneath the liquid surface shows the lowest weight penalty for LO2 and LCH4. A technology system incorporating a thermal subcooler (heat exchanger) for engine NPSP results in the lowest weight penalty for the LH2 tank. A preliminary design of two state-of-the-art and two new technology systems indicates a weight penalty difference too small to warrant development of a LH2 thermal subcooler. Analysis results showed that the LH2/LO2 propellant expulsion system is optimized for maximum dump line diameters, whereas the LCH4/LO2 system is optimized for minimum dump line diameter (LCH4) and maximum dump line diameter (LO2). The primary uncertainty is the accurate determination of two-phase flow rates through the dump system; experimentation is not recommended because this uncertainty is not considered significant
Low-thrust chemical propulsion system propellant expulsion and thermal conditioning study. Executive summary
Preferred techniques for providing abort pressurization and engine feed system net positive suction pressure (NPSP) for low thrust chemical propulsion systems (LTPS) were determined. A representative LTPS vehicle configuration is presented. Analysis tasks include: propellant heating analysis; pressurant requirements for abort propellant dump; and comparative analysis of pressurization techniques and thermal subcoolers
Dynamics of axial separation in long rotating drums
We propose a continuum description for the axial separation of granular
materials in a long rotating drum. The model, operating with two local
variables, concentration difference and the dynamic angle of repose, describes
both initial transient traveling wave dynamics and long-term segregation of the
binary mixture. Segregation proceeds through ultra-slow logarithmic coarsening.Comment: 4 pages, 3 Postscript figures; submitted to PR
Chemical abundances in LMC stellar populations. II. The bar sample
This paper compares the chemical evolution of the Large Magellanic Cloud
(LMC) to that of the Milky Way (MW) and investigates the relation between the
bar and the inner disc of the LMC in the context of the formation of the bar.
We obtained high-resolution and mid signal-to-noise ratio spectra with
FLAMES/GIRAFFE at ESO/VLT and performed a detailed chemical analysis of 106 and
58 LMC field red giant stars (mostly older than 1 Gyr), located in the bar and
the disc of the LMC respectively. We measured elemental abundances for O, Mg,
Si, Ca, Ti, Na, Sc, V, Cr, Co, Ni, Cu, Y, Zr, Ba, La and Eu. We find that the
{\alpha}-element ratios [Mg/Fe] and [O/Fe] are lower in the LMC than in the MW
while the LMC has similar [Si/Fe], [Ca/Fe], and [Ti/Fe] to the MW. As for the
heavy elements, [Ba,La/Eu] exhibit a strong increase with increasing
metallicity starting from [Fe/H]=-0.8 dex, and the LMC has lower [Y+Zr/Ba+La]
ratios than the MW. Cu is almost constant over all metallicities and about 0.5
dex lower in the LMC than in the MW. The LMC bar and inner disc exhibit
differences in their [{\alpha}/Fe] (slightly larger scatter for the bar in the
metallicity range [-1,-0.5]), their Eu (the bar trend is above the disc trend
for [Fe/H] > -0.5 dex), their Y and Zr, their Na and their V (offset between
bar and disc distributions). Our results show that the chemical history of the
LMC experienced a strong contribution from type Ia supernovae as well as a
strong s-process enrichment from metal-poor AGB winds. Massive stars made a
smaller contribution to the chemical enrichment compared to the MW. The
observed differences between the bar and the disc speak in favour of an episode
of enhanced star formation a few Gyr ago, occurring in the central parts of the
LMC and leading to the formation of the bar. This is in agreement with recently
derived star formation histories.Comment: 22 pages, 20 figures; Accepted for publication in A&
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