Autor: Collier, P. - Prolib Integro

Skocz do pozycji: 2.

Tytuł:: Two-dimensional hp-adaptive algorithm for continuous approximations of material data using space projection
Autorzy:: Gurgul, P.
Sieniek, M.
Paszyński, M.
Madej, Ł.
Collier, N.
Tematy:: adaptive finite element method
projection operator
digital material representation; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/305268.pdf Link otwiera się w nowym oknie
Opis:: In this paper we utilize the concept of the L 2 and H 1 projections used to adaptively generate a continuous approximation of an input material data in the finie element (FE) base.This approximation, along with a corresponding FE mesh, can be used as material data for FE solvers. We begin with abrief theoretical background, followed by description of the hp -adaptive algorithm adopted here to improve gradually quality of the projections. We investigate also a few distinct sample problems, apply the aforementioned algorithms and conclude with numerical results evaluation.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 3.

Tytuł:: Metastability exchange optical pumping of $^{3}He$ gas up to hundreds of millibars at 4.7 Tesla
Autorzy:: Pałasz, Tadeusz
Głowacz, Bartosz
Węglarz, Władysław P.
Tastevin, Geneviève
Nikiel-Osuchowska, Anna
Dohnalik, Tomasz
Nacher, Pierre-Jean
Collier, Guilhem
Olejniczak, Zbigniew
Opis:: Metastability exchange optical pumping (MEOP) is experimentally investigated in $^{3}He$ at 4.7 T, at room temperature and for gas pressures ranging from 1 to 267 mbar. The $2^{3}S-2^{3}P$ transition at 1083 nm is used for optical pumping and for detection of the laser-induced orientation of ^{3}He atoms in the rf discharge plasma. The collisional broadening rate is measured (12.0 $\pm$ 0.4 MHz $mbar^{-1}$FHWM) and taken into account for accurate absorption-based measurements of both nuclear polarization in the ground state and atom number density in the metastable $2^{3}S$ state. The results lay the ground for a comprehensive assessment of the efficiency of MEOP, by comparison with achievements at lower field (1 mT–2 T) over an extended range of operating conditions. Stronger hyperfine decoupling in the optically pumped $2^{3} S$ state is observed to systematically lead to slower build-up of $^{3}He$ orientation in the ground state, as expected. The nuclear polarizations obtained at 4.7 T still decrease at high pressure but in a less dramatic way than observed at 2 T in the same sealed glass cells. To date, thanks to the linear increase in gas density, they correspond to the highest nuclear magnetizations achieved by MEOP in pure $^{3}He$ gas. The improved efficiency puts less demanding requirements for compression stages in polarized gas production systems and makes high-field MEOP particularly attractive for magnetic resonance imaging of the lungs, for instance.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego