753 research outputs found
Electron emission at very low electron impact energy: experimental and Monte-Carlo results
The behaviour of electron emission under electron impact at very low energy
is of great importance in many applications such as high energy physics,
satellites, nuclear reactors, etc. However the question of the total electron
reflectivity is still in discussion. Our experimental and theoretical studies
show that the total reflectivity at very low energy is far from being an
obvious fact. Moreover, our results show that the yield is close to zero and
not equal to one for low energy incident electron.Comment: 3 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop
on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba,
Italy; CERN Yellow Report CERN-2013-002, pp.137-13
Polaron relaxation in ferroelectric thin films
We report a dielectric relaxation in ferroelectric thin films of the ABO3
family. We have compared films of different compositions with several growth
modes: sputtering (with and without magnetron) and sol-gel. The relaxation was
observed at cryogenic temperature (T<100K) for frequencies from 100Hz up to
10MHz. This relaxation activation energy is always lower than 200meV. It is
very similar to the polaron relaxation that we reported in the parent bulk
perovskites. Being independent of the materials size, morphology and texture,
this relaxation can be a useful probe of defects in actual integrated
capacitors with no need for specific shapin
Performance evaluation of several well-known and new scintillators for MeV X-ray imaging
International audienceDigital X-ray imaging systems for MeV range photon beams are based on a combination of a scintillator screen and either a camera or an amorphous silicon array. To limit dose rate on electronics and enhance imaging device lifetime, the scintillator screen is mirror-coupled to the camera. Performances of such devices are a compromise between exposure time and spatial resolution. These technical characteristics are especially scintillator dependent. In this paper, we present a performance evaluation of six different scintillators with a 9 MeV Bremsstrahlung X-ray source. The tested scintillators are composed of one micro-structured CsI(Tl) scintillator, two phosphor (GOS) screens and three transparent scintillators. These scintillators present a wide range of density, thickness and conversion efficiency. Each scintillator's performance is assessed based on the combination of light output (ADU number) and modulation transfer function (spatial resolution) obtained. The results are helpful to guide design and engineering of high energy imaging devices adapted to specific requirements
Pressure ulcer prevention in spinal cord injury subjects using the TexiSense pressure sensing textile
International audienc
Haptic guidance improves the visuo-manual tracking of trajectories
BACKGROUND: Learning to perform new movements is usually achieved by
following visual demonstrations. Haptic guidance by a force feedback device is
a recent and original technology which provides additional proprioceptive cues
during visuo-motor learning tasks. The effects of two types of haptic
guidances-control in position (HGP) or in force (HGF)-on visuo-manual tracking
("following") of trajectories are still under debate. METHODOLOGY/PRINCIPALS
FINDINGS: Three training techniques of haptic guidance (HGP, HGF or control
condition, NHG, without haptic guidance) were evaluated in two experiments.
Movements produced by adults were assessed in terms of shapes (dynamic time
warping) and kinematics criteria (number of velocity peaks and mean velocity)
before and after the training sessions. CONCLUSION/SIGNIFICANCE: These results
show that the addition of haptic information, probably encoded in force
coordinates, play a crucial role on the visuo-manual tracking of new
trajectories
Implementation of fatigue model for unidirectional laminate based on finite element analysis : theory and practice
The aim of this study is to deal with the simulation of intra-laminar fatigue damage in unidirectional composite under multi-axial and variable amplitude loadings. The variable amplitude and multi-axial loading is accounted for by using the damage hysteresis operator based on Brokate method [6]. The proposed damage model for fatigue is based on stiffness degradation laws from Van Paepegem combined with the 'damage' cycle jump approach extended to deal with unidirectional carbon fibres. The parameter identification method is here presented and parameter sensitivities are discussed. The initial static damage of the material is accounted for by using the LadevSze damage model and the permanent shear strain accumulation based on Van Paepegem's formulation. This approach is implemented into commercial software (Siemens PLM). The validation case is run on a bending test coupon (with arbitrary stacking sequence and load level) in order to minimise the risk of inter-laminar damages. This intra-laminar fatigue damage model combined efficient methods with a low number of tests to identify the parameters of the stiffness degradation law, this overall procedure for fatigue life prediction is demonstrated to be cost efficient at industrial level. This work concludes on the next challenges to be addressed (validation tests, multiple-loadings validation, failure criteria, inter-laminar damages...)
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