1,873 research outputs found
Construction Status of Linac4
The civil engineering works of the Linac4 linear accelerator at CERN started in October 2008 and regular machine operation is foreseen for 2013. Linac4 will accelerate H−ions to an energy of 160 MeV for injection into the PS Booster (PSB). It will thus replace the ageing Linac2, which presently injects at 50 MeV into the PSB, and it will also represents the first step in the injector upgrade for the LHC aiming at increasing its luminosity. This paper reports on the status of the design and construction of the main machine elements, which will be installed in the linac tunnel from the beginning of 2012 onwards, on the progress of the civil engineering and on the ongoing activities at the Linac4 test stand
Investigation of the thermal stability of Mg/Co periodic multilayers for EUV applications
We present the results of the characterization of Mg/Co periodic multilayers
and their thermal stability for the EUV range. The annealing study is performed
up to a temperature of 400\degree C. Images obtained by scanning transmission
electron microscopy and electron energy loss spectroscopy clearly show the good
quality of the multilayer structure. The measurements of the EUV reflectivity
around 25 nm (~49 eV) indicate that the reflectivity decreases when the
annealing temperature increases above 300\degreeC. X-ray emission spectroscopy
is performed to determine the chemical state of the Mg atoms within the Mg/Co
multilayer. Nuclear magnetic resonance used to determine the chemical state of
the Co atoms and scanning electron microscopy images of cross sections of the
Mg/Co multilayers reveal changes in the morphology of the stack from an
annealing temperature of 305\degreee;C. This explains the observed reflectivity
loss.Comment: Published in Applied Physics A: Materials Science \& Processing
Published at
http://www.springerlink.com.chimie.gate.inist.fr/content/6v396j6m56771r61/ 21
page
Two-way multi-lane traffic model for pedestrians in corridors
We extend the Aw-Rascle macroscopic model of car traffic into a two-way
multi-lane model of pedestrian traffic. Within this model, we propose a
technique for the handling of the congestion constraint, i.e. the fact that the
pedestrian density cannot exceed a maximal density corresponding to contact
between pedestrians. In a first step, we propose a singularly perturbed
pressure relation which models the fact that the pedestrian velocity is
considerably reduced, if not blocked, at congestion. In a second step, we carry
over the singular limit into the model and show that abrupt transitions between
compressible flow (in the uncongested regions) to incompressible flow (in
congested regions) occur. We also investigate the hyperbolicity of the two-way
models and show that they can lose their hyperbolicity in some cases. We study
a diffusive correction of these models and discuss the characteristic time and
length scales of the instability
Effects of Pacing When Using Material Handling Manipulators
Common manipulator-assisted materials handling tasks were performed in a laboratory simulation at self-selected and faster (paced) speeds. The effects of pacing on peak hand forces, torso kinematics, spine moments and forces, and muscle antagonism were determined, along with any influences of several task variables on these effects. The faster trials were performed 20% more rapidly than the self-paced trials. It was found that (a) achieving this level of performance required 10% higher hand forces and 5%-10% higher torso moments, (b) consistent torso postures and motions were used for both speed conditions, and (c) the faster trials resulted in 10% higher spine forces and 15% higher levels of lumbar muscle antagonism. On whole, these results suggest a higher risk of musculoskeletal injury associated with performance of object transfers at faster than self-selected speeds with and without a manipulator. Further analysis provided evidence that the use of manipulators involves higher levels of motor coordination than do manual tasks. Several implications regarding the use of material handling manipulators in paced operations are discussed. Results from this investigation can be used in the design, evaluation, and selection of material handling manipulators.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67067/2/10.1518_001872099779591240.pd
Formation of the compact jets in the black hole GX 339-4
Galactic black hole binaries produce powerful outflows with emit over almost
the entire electromagnetic spectrum. Here, we report the first detection with
the Herschel observatory of a variable far-infrared source associated with the
compact jets of the black hole transient GX 339-4 during the decay of its
recent 2010-2011 outburst, after the transition to the hard state. We also
outline the results of very sensitive radio observations conducted with the
Australia Telescope Compact Array, along with a series of near-infrared,
optical (OIR) and X-ray observations, allowing for the first time the
re-ignition of the compact jets to be observed over a wide range of
wavelengths. The compact jets first turn on at radio frequencies with an
optically thin spectrum that later evolves to optically thick synchrotron
emission. An OIR reflare is observed about ten days after the onset of radio
and hard X-ray emission, likely reflecting the necessary time to build up
enough density, as well as to have acceleration (e.g. through shocks) along an
extended region in the jets. The Herschel measurements are consistent with an
extrapolation of the radio inverted power-law spectrum, but they highlight a
more complex radio to OIR spectral energy distribution for the jets.Comment: Accepted for publication in MNRAS Letter, 6 pages, 3 Figures + 1
online Tabl
Galactic Bulge Microlensing Optical Depth from EROS-2
We present a new EROS-2 measurement of the microlensing optical depth toward
the Galactic Bulge. Light curves of clump-giant stars
distributed over of the Bulge were monitored during seven Bulge
seasons. 120 events were found with apparent amplifications greater than 1.6
and Einstein radius crossing times in the range 5 {\rm d}.
This is the largest existing sample of clump-giant events and the first to
include northern Galactic fields. In the Galactic latitude range
1.4\degr<|b|<7.0\degr, we find with . These results are in good
agreement with our previous measurement, with recent measurements of the MACHO
and OGLE-II groups, and with predictions of Bulge models.Comment: accepted A&A, minor revision
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