Jurnal Edukasi
Not a member yet
4879 research outputs found
Sort by
Global Solutions of the Boltzmann Equation over R D near Global Maxwellians with Small Mass
No full text30 pagesWe study the dynamics defined by the Boltzmann equation set in the Euclidean space RD in the vicinity of global Maxwellians with finite mass. A global Maxwellian is a special solution of the Boltzmann equation for which the collision integral vanishes identically. In this setting, the dispersion due to the advection operator quenches the dissipative effect of the Boltzmann collision integral. As a result, the large time limit of solutions of the Boltzmann equation in this regime is given by noninteracting, freely transported states and can be described with the tools of scattering theory
Modeling of the L-shell copper X-pinch plasma produced by the compact generator of Ecole polytechnique using pattern recognition
No full textInternational audiencePrincipal component analysis is applied and compared with the line ratios of special Ne-like transitions for investigating the electron beam effects on the L-shell Cu synthetic spectra. The database for the principal component extraction is created over a non Local Thermodynamic Equilibrium (non-LTE) collisional radiative L-shell Copper model. The extracted principal components are used as a database for Artificial Neural Network in order to estimate the plasma electron temperature density and beam fractions from a representative time-integrated spatially resolved L-shell Cu X-pinch plasma spectrum. The spectrum is produced by the explosion of 25-μm Cu wires on a compact LC (40 kV 200 kA and 200 ns) generator. The modeled plasma electron temperatures are about Te ∼ 150 eV and Ne = 5 × 1019 cm−3 in the presence of the fraction of the beams with f ∼ 0.05 and a centered energy of ∼10 keV
Algebraic Adaptive Multipreconditioning applied to Restricted Additive Schwarz
No full textIn 2006 the Multi-Preconditioned Conjugate Gradient (MPCG) algorithm was introduced by Bridson and Greif [4]. It is an iterative linear solver, adapted from the Preconditioned Conjugate Gradient (PCG) algorithm which can be used in cases where several preconditioners are available or the usual preconditioner is a sum of contributions. In [4] it was already pointed out that Domain Decomposition algorithms are ideal candidates to benefit from MPCG.The question posed by this work is whether an adaptive MPCG algorithm can be developed for Restricted Additive Schwarz. The goal is to design an adaptive algorithm that is robust at a minimal cost. One great feature of Additive Schwarz is that it is algebraic (all the components in the preconditioner can be computed from the knowledge of matrix A) and we will aim to preserve this property
Thickness control in structural optimization via a level set method
No full textInternational audienceIn the context of structural optimization via a level-set method we propose a framework to handle geometric constraints related to a notion of local thickness. The local thickness is calculated using the signed distance function to the shape. We formulate global constraints using integral functionals and compute their shape derivatives. We discuss diff erent strategies and possible approximations to handle the geometric constraints. We implement our approach in two and three space dimensions for a model of linearized elasticity. As can be expected, the resulting optimized shapes are strongly dependent on the initial guesses and on the speci fic treatment of the constraints since, in particular, some topological changes may be prevented by those constraints
Helical vortices generated by flappling wings of bumblebees
No full textInternational audienceno abstrac
Buffered high charge spectrally-peaked proton beams in the relativistic-transparency regime
No full textInternational audienceSpectrally-peaked proton beams of high charge (Ep ≈ 8 MeV, ΔE ≈ 4 MeV, N ≈ 50 nC) have been observed from the interaction of an intense laser ( >10^19 W cm−2) with ultrathin CH foils, as measured by spectrally-resolved full beam profiles. These beams are reproducibly generated for foil thicknesses 5–100 nm, and exhibit narrowing divergence with decreasing target thickness down to ≈8° for 5 nm. Simulations demonstrate that the narrow energy spread feature is a result of buffered acceleration of protons. The radiation pressure at the front of the target results in asymmetric sheath fields which permeate throughout the target, causing preferential forward acceleration. Due to their higher charge-to-mass ratio, the protons outrun a carbon plasma driven in the relativistic transparency regime
The Xanthate Route to Amines, Anilines, and Other Nitrogen Compounds. A Brief Account
No full textInternational audienc
The core contribution of transmission electron microscopy to functional nanomaterials engineering
No full textInternational audienceResearch on nanomaterials and nanostructured materials is burgeoning because their numerous and versatile applications contribute to solve societal needs in the domain of medicine, energy, environment and STICs. Optimizing their properties requires in-depth analysis of their structural, morphological and chemical features at the nanoscale. In a transmission electron microscope (TEM), combining tomography with electron energy loss spectroscopy and high-magnification imaging in high-angle annular dark-field mode provides access to all features of the same object. Today, TEM experiments in three dimensions are paramount to solve tough structural problems associated with nanoscale matter. This approach allowed a thorough morphological description of silica fibers. Moreover, quantitative analysis of the mesoporous network of binary metal oxide prepared by template-assisted spray-drying was performed, and the homogeneity of amino functionalized metal-organic frameworks was assessed. Besides, the morphology and internal structure of metal phosphide nanoparticles was deciphered, providing a milestone for understanding phase segregation at the nanoscale. By extrapolating to larger classes of materials, from soft matter to hard metals and/or ceramics, this approach allows probing small volumes and uncovering materials characteristics and properties at two or three dimensions. Altogether, this feature article aims at providing (nano) materials scientists with a representative set of examples that illustrates the capabilities of modern TEM and tomography, which can be transposed to their own research
Search for heavy Majorana neutrinos in e+/- e+/- plus jets and e+/- mu+/- plus jets events in proton-proton collisions at sqrt(s) = 8 TeV
No full textSubmitted to J. High Energy Phys ; see paper for full list of authorsInternational audienceA search is performed for heavy Majorana neutrinos (N) decaying into a W boson and a lepton using the CMS detector at the Large Hadron Collider. A signature of two jets and either two same sign electrons or a same sign electron-muon pair is searched for using 19.7 inverse-femtobarns of data collected during 2012 in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data are found to be consistent with the expected standard model (SM) background and, in the context of a Type-1 seesaw mechanism, upper limits are set on the cross section times branching fraction for production of heavy Majorana neutrinos in the mass range between 40 and 500 GeV. The results are additionally interpreted as limits on the mixing between the heavy Majorana neutrinos and the SM neutrinos. In the mass range considered, the upper limits range between 0.00015 - 0.72 for |V[eN]|^2 and 6.6E-5 - 0.47 for |V[eN]V*[muN]|^2 / ( |V[eN]|^2 + |V[muN]|^2 ), where V[lN] is the mixing element describing the mixing of the heavy neutrino with the SM neutrino of flavour l. These limits are the most restrictive direct limits for heavy Majorana neutrino masses above 200 GeV
