Jurnal Edukasi
Not a member yet
4879 research outputs found
Sort by
Maximizing concave piecewise affine functions on the unitary group
No full textInternational audienceWe show that a convex relaxation, introduced by Sridharan, McEneaney, Gu and James to approximate the value function of an optimal controlproblem arising from quantum gate synthesis, is exact. This relaxation appliesto the maximization of a class of concave piecewise affine functions over theunitary grou
Reconstruction and identification of tau lepton decays to hadrons and tau neutrino at CMS
No full textSubmitted to J. Instrum ; see paper for full list of authorsInternational audienceThis paper describes the algorithms used by the CMS experiment to reconstruct and identify tau to hadrons + tau decays during Run 1 of the LHC. The performance of the algorithms is studied in proton-proton collisions recorded at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 inverse femtobarns. The algorithms achieve an identification efficiency of 50-60%, with misidentification rates for quark and gluon jets, electrons, and muons between per mille and per cent levels
A new macroscopic model for the diffusion MRI accounting for time-dependent diffusivity
No full textInternational audienceDiffusion Magnetic Resonance Imaging (dMRI) encodes water displacement due to diffusion and is a powerful tool to obtain information on the tissue micro-structure. An important quantity measured in dMRI in each voxel is the Apparent Diffusion Coefficient () and it is well-established from imaging experiments that, in the brain, {\it in-vivo}, the is dependent on the measured diffusion time. To aid in the understanding and interpretation of the , using homogenization techniques, we derived a new asymptotic model for the dMRI signal from the Bloch-Torrey equation governing the water proton magnetization under the influence of diffusion-encoding magnetic gradient pulses. Our new model was obtained using a particular choice of scaling for the time, the biological cell membrane permeability, the diffusion-encoding magnetic field gradient strength, and a periodicity length of the cellular geometry. The of the resulting model is dependent on the diffusion time. We numerically validated this model for a wide range of diffusion times for two dimensional geometrical configurations
A multi-instrument and multi-model assessment of atmospheric moisture variability over the western Mediterranean during HyMeX
No full textInternational audienceThe Hydrological cycle in the Mediterranean eXperiment (HyMeX) was held in fall 2012 during which part of the observational effort has been established on Menorca Island to characterize the upwind marine low-level flow. The ground-based Water vapour Raman Lidar (WALI), the airborne water vapour lidar LEANDRE 2 and boundary layer pressurized balloons were implemented during the first Special Observing Period and contributed to characterize water vapour variability in the vicinity of the Balearic Islands, together with the existing network of Global Positioning System receivers. Furthermore, analyses from regional and global numerical weather prediction (NWP) models (AROME-WMED, the ECMWF/IFS NWP system and the Weather Research and Forecasting (WRF) model) were also available over large domains encompassing part or the entire Western Mediterranean basin. We assess the consistency of water vapour mixing ratio (WVMR) profiles and integrated water vapour contents (IWVC) derived from the different data sets by comparing them to a common reference, the ground-based lidar WALI. We use consistency indicators such as root mean square errors, biases and correlations. Comparison between WVMR profiles from ground-based and airborne lidars (ground-based lidar and boundary layer pressurized balloons) leads to a root mean square error lower than 1.6 g kg−1 (1.3 g kg−1) when the closest possible air masses are sampled. We observed a good agreement between the vertical WVMR profiles derived from WALI and the numerical models with correlations higher than 0.7 and root mean square errors lower than 2 g kg−1. Regarding IWVCs, the models exhibit biases less than 2 kg m−2, root mean square errors lower than 2.3 g kg−1 and correlations higher than 0.86 when compared to WALI. Finally, AROME-WMED 48-h forecasts were compared with WALI data composited over eleven 48-h periods. The quality of the forecast does not visibly degrade within the 48-h period from the initial analyses
Study of B Meson Production in p+Pb Collisions at root s(NN)=5.02 TeV Using Exclusive Hadronic Decays
No full textsee paper for full list of authorsInternational audienceThe production cross sections of the B+, B0, and B0s mesons, and of their charge conjugates, are measured via exclusive hadronic decays in pPb collisions at the center-of-mass energy sqrt(s_NN) = 5.02 TeV with the CMS detector at the CERN LHC. The dataset used for this analysis corresponds to an integrated luminosity of 34.6 inverse-nanobarns. The production cross sections are measured in the transverse momentum range between 10 and 60 GeV/c. No significant modification is observed compared to proton-proton perturbative QCD calculations scaled by the number of incoherent nucleon-nucleon collisions. These results provide a baseline for the study of in-medium b quark energy loss in PbPb collisions
Short time heat diffusion in compact domains with discontinuous transmission boundary conditions
No full textInternational audienceWe consider a heat problem with discontinuous diffusion coefficientsand discontinuous transmission boundary conditions with a resistancecoefficient. For all compact -domains with a -set boundary (for instance, aself-similar fractal), we find the first term of the small-timeasymptotic expansion of the heat content in the complement of, and also the second-order term in the case of a regularboundary. The asymptotic expansion is different for the cases offinite and infinite resistance of the boundary. The derived formulasrelate the heat content to the volume of the interior Minkowskisausage and present a mathematical justification to the de Gennes'approach. The accuracy of the analytical results is illustrated bysolving the heat problem on prefractal domains by a finite elementsmethod
Coherent medium-induced gluon radiation in hard forward 1→1 partonic processes
No full textInternational audienceWe revisit the medium-induced coherent radiation associated to hard and forward (small angle) scattering of an energetic parton through a nuclear medium. We consider all 1→1 hard forward processes (g→g, q→q, q→g and g→q), and derive the energy spectrum of induced coherent radiation rigorously to all orders in the opacity expansion and for the specific case of a Coulomb scattering potential. We obtain a simple general formula for the induced coherent spectrum, which encompasses the results corresponding to previously known special cases
Identifiability and non-identifiability in acoustic tomography of moving fluid
No full textInternational audienceWe consider a model time-harmonic wave equation of acoustic tomography of moving fluid in an open bounded domain in , , with variable sound speed , density , fluid velocity and absorption coefficient . We give global uniqueness results for related inverse boundary value problem for the cases of boundary measurements given for two and for three fixed frequencies. Besides, we also give a non-uniqueness result for this inverse problem for the case of boundary measurements given for all frequencies
Effect of climate change, CO<sub>2</sub> trends, nitrogen addition, and land-cover and management intensity changes on the carbon balance of European grasslands
No full textInternational audienceSeveral lines of evidence point to European managed grassland ecosystems being a sink of carbon. In this study, we apply ORCHIDEE-GM a process-based carbon cycle model that describes specific management practices of pastures and the dynamics of carbon cycling in response to changes in climatic and biogeochemical drivers. The model is used to simulate changes in the carbon balance [i.e., net biome production (NBP)] of European grasslands over 1991–2010 on a 25 km × 25 km grid. The modeled average trend in NBP is 1.8–2.0 g C m−2 yr−2 during the past two decades. Attribution of this trend suggests management intensity as the dominant driver explaining NBP trends in the model (36–43% of the trend due to all drivers). A major change in grassland management intensity has occurred across Europe resulting from reduced livestock numbers. This change has ‘inadvertently’ enhanced soil C sequestration and reduced N2O and CH4 emissions by 1.2–1.5 Gt CO2-equivalent, offsetting more than 7% of greenhouse gas emissions in the whole European agricultural sector during the period 1991–2010. Land-cover change, climate change and rising CO2 also make positive and moderate contributions to the NBP trend (between 24% and 31% of the trend due to all drivers). Changes in nitrogen addition (including fertilization and atmospheric deposition) are found to have only marginal net effect on NBP trends. However, this may not reflect reality because our model has only a very simple parameterization of nitrogen effects on photosynthesis. The sum of NBP trends from each driver is larger than the trend obtained when all drivers are varied together, leaving a residual – nonattributed – term (22–26% of the trend due to all drivers) indicating negative interactions between drivers
Adapting the Kärger model to account for finite diffusion-encoding pulses in diffusion MRI
No full textInternational audienceDiffusion magnetic resonance imaging (dMRI) is an imaging modality that probes the diffusion characteristics of a sample via the application of magnetic field gradient pulses. If the imaging voxel can be divided into different Gaussian diffusion compartments with inter-compartment exchange governed by linear kinetics, then the dMRI signal can be described by the Kärger model, which is a well-known model in Nuclear Magnetic Resonance. However, the Kärger model is limited to the case when the duration of the diffusion-encoding gradient pulses is short compared to the time delay between the start of the pulses. Under this assumption, the time at which to evaluate the Kärger model to obtain the dMRI signal is unambiguously the delay between the pulses. Recently, a new model of the dMRI signal, the Finite-Pulse Kärger (FPK) model, was derived for arbitrary diffusion gradient profiles. Relying on the FPK model, we show that when the duration of the gradient pulses is not short, the time at which to evaluate the Kärger model should be the time delay between the start of the pulses, shortened by one third of the pulse duration. With this choice, we show the sixth order convergence of the Kärger model to the FPK model in the non-dimensionalized pulse duration