Search results for "Fluids"

2019

The atomic spectrum of neutral promethium has been studied extensively by laser resonance ionization spectroscopy. We report on more than 1000 atomic transitions in the blue and near infrared spectral ranges, most of them between high excited energy levels. As Rydberg convergences could not be assigned unambiguously in the dense spectrum at high excitation energies, the first ionization potential (IP) was determined via field ionization of weakly bound states within a static electric field. By applying the saddle-point model, a value of ${\mathrm{IP}}_{(\mathrm{Pm})}=45\phantom{\rule{0.16em}{0ex}}020.8(3)\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1} [5.58188(4)\phantom{\rule{0.16…

Quantum screened interactions in moderately dense plasmas and atomic contributions to thermodynamics

2017

Instabilité modulationnelle incohérente

2006

Dans cet article, nous presentons une etude theorique et experimentale de l'instabilite de modulation d'une onde partiellement coherente. Les experiences ont ete realisees dans une fibre optique standard au voisinage de 1320 nm. En particulier, et en comparaison avec le cas coherent, nous observons que l'utilisation d'une onde incoherente conduit a une augmentation significative du gain et de la frequence de modulation.

L'alignement moléculaire comme une méthode de calibration pour la détermination de probabilité d'ionisation

2006

Par le biais d'une methode originale, nous avons determine experimentalement la probabilite d'ionisation de l'azote (N 2 ) soumis a un champ laser non resonnant et ultracourt (100 fs). La technique de defocalisation croisee mis en oeuvre dans ce travail est sensible a l'alignement moleculaire post-impulsion et a l'ionisation. L'analyse du signal experimental permet d'extraire une probabilite d'ionisation calibree par une mesure d'alignement.

Statistical Methods for Parameter Identification of Temperature Dependent Viscoelastic Models

2018

A General Computational Approach for Magnetohydrodynamic Flows Using the CFX Code: Buoyant Flow through a Vertical Square Channel

2000

The buoyancy-driven magnetoconvection in the cross section of an infinitely long vertical square duct is investigated numerically using the CFX code package. The implementation of a magnetohydrodynamic (MHD) problem in CFX is discussed, with particular reference to the Lorentz forces and the electric potential boundary conditions for arbitrary electrical conductivity of the walls. The method proposed is general and applies to arbitrary geometries with an arbitrary orientation of the magnetic field. Results for fully developed flow under various thermal boundary conditions are compared with asymptotic analytical solutions. The comparison shows that the asymptotic analysis is confirmed for hi…

Numerical modeling and design of a disk-type rotating permanent magnet induction pump

2016

Abstract Electromagnetic induction pumps with rotating permanent magnets appear to be the most promising devices to transport liquid metals in high-temperature applications. Here we present a numerical methodology to simulate the operation of one particular modification of these types of pumps: a disk-type induction pump. The numerical model allows for the calculation and analysis of the flow parameters, including the pressure–flow rate characteristics of the pump. The simulations are based on an iterative fully coupled scheme for electromagnetic and hydrodynamic solvers. The developed model is verified by comparing with experimental data obtained using a Pb-Bi loop test facility, for press…

First Flight Escape Probability and Uncollided Flux of Nuclear Particles in Convex Bodies with Spherical Symmetry

2016

This paper deals with the evaluation of the first flight escape probability of nuclear particles from convex bodies with spherical symmetry by means of some geometrical arguments and very simple probability considerations. The cases of a full sphere, a one-region spherical shell with an empty central zone, a spherical shell region containing a black central zone, and a full sphere with a sourceless shell have been considered. In all the aforementioned cases, a homogeneous medium and uniform isotropic source have been taken into account. Moreover, a simple and general formula has been derived for the calculation of the uncollided flux that is presupposed to be valid for arbitrary geometries.…

Towards the time-optimal control of dissipative spin-1/2 particles in nuclear magnetic resonance

2011

International audience; We consider the time-optimal control of a spin 1/2 particle whose dynamics is governed by the Bloch equations with both longitudinal and transverse relaxation terms. We solve this control problem by using geometric optimal control techniques. We show the crucial role of singular extremals in the time-optimal synthesis. This role can mainly be attributed to the presence of dissipation. We also analyze the robustness of the optimal control sequence when both the maximum amplitude of the control field and the dissipative parameters are varied. Finally, we present an experimental implementation of the different solutions using techniques of Nuclear Magnetic Resonance.

Fourier-transform spectroscopy, relativistic electronic structure calculation, and coupled-channel deperturbation analysis of the fully mixed A1Σu+ a…

2019

The 4503 rovibronic term values belonging to the mutually perturbed $A^1\Sigma^+_u$ and $b^3\Pi_u$ states of Cs$_2$ were extracted from laser induced fluorescence (LIF) $A\sim b\rightarrow X^1\Sigma^+_g$ Fourier transform spectra with the 0.01 cm$^{-1}$ uncertainty. The experimental term values of the $A^1\Sigma^+_u\sim b^3\Pi_u$ complex covering the rotational levels $J\in [4,395]$ in the excitation energy range $[9655,13630]$ cm$^{-1}$ were involved into coupled-channel (CC) deperturbation analysis. The deperturbation model takes explicitly into account spin-orbit coupling of the $A^1\Sigma^+_u(A0^+_u)$ and $b^3\Pi^+_{0_u}(b0^+_u)$ states as well as spin-rotational interaction between the…